EP1692078A1 - Deagglomerated barium sulfate - Google Patents

Abstract

The invention relates to deagglomerated barium sulfate that has a primary particle size of less than 0.5 mu m and that is coated with a dispersant. The dispersant preferably has reactive groups that can interact with the surface of the barium sulfate. Particularly preferred are dispersants that provide the barium sulfate with a hydrophilic surface and that have reactive groups for coupling to or into polymers. The invention also relates to a synthetic premix comprising the deagglomerated, coated barium sulfate.

Description

 Deagglomerated barium sulfate Description

The present invention relates to deagglomerated barium sulfate, its production, a plastic premix containing the barium sulfate, the use of the deagglomerated barium sulfate in plastics, plastics produced therewith and an intermediate product.

It is already known to use barium sulfate as a filler for plastics. International patent application WO 00/14165 discloses the production of barium sulfate, which is embedded in a finely divided form in a carrier material. The grain size is 0.01 to 10 μm; they have good matting properties. They are produced by wet grinding in the presence of the carrier material.

International patent application WO 02/30994 discloses the addition of such an inorganic barium sulfate to polymer raw materials before polymer formation. The preferred average grain size D _{50 of} the inorganic solid which is embedded in the organic substance is 0.25 to 0.45 μm. The additive compositions in polyester and polyamide are used.

International patent application WO 00/57932 discloses materials for surgical use which contain so-called "nanocomposites". The filler particles can be treated with organic compounds in order to improve their dispersibility, to reduce their tendency towards agglomeration or aggregation and to improve the uniformity of the dispersion. For this purpose, organic compounds such as the monomer of the surgical material to be produced, citrates or other compounds are used, for example. Coupling agents such as organosilanes or polymeric materials such as surfactants, for example sodium dodecyl sulfate, but also amphiphilic molecules, ie molecules which have a hydrophilic and a hydrophobic part, can also be used. Nonylphenol ethoxylates are mentioned; sulfosuccinate (2-ethylhexyl) to; Hexadecyltrimethylammoniumbromid as well Phospholipids. In the examples, either uncoated barium sulfate is used, or particles that were coated with sodium citrate after the precipitation.

It was an object of the present invention, inter alia, to provide a finely divided, deagglomerated barium sulfate which can be redispersed even after drying, in particular one which can be readily incorporated into plastics. A special task was to provide a deagglomerated barium sulfate which, especially when incorporated into plastic, does not react. These and other objects are achieved by the present invention.

The deagglomerated barium sulfate according to the invention with an average (primary) particle size <0.5 μm contains a crystallization inhibitor and a dispersant. Preferred is deagglomerated barium sulfate, which has an average (primary) particle size of <0.1 μm, in particular <0.08 μm (= 80 nm), very particularly preferably <0.05 μm (= 50 nm), even more preferably <0.03 μm (= 30 nm). Particle sizes <20 μm are outstanding, especially those with an average primary particle size of <10 nm. The lower limit for the primary particle size is, for example, 5 nm, but it can still be lower. These are medium particle sizes, determined by XRD or laser diffraction methods. A preferred barium sulfate is obtainable by precipitating barium sulfate in the presence of a crystallization inhibitor, a dispersing agent being present during the precipitation and / or the barium sulfate being deagglomerated after the precipitation in the presence of a dispersing agent.

The amount of crystallization inhibitor and dispersant in the deagglomerated barium sulfate is flexible. Up to 2 parts by weight, preferably up to 1 part by weight, of crystallization-inhibiting agent and dispersant can be present per part by weight of barium sulfate. Crystallization-inhibiting and dispersing agents are preferably present in the deagglomerated barium sulfate in an amount of 1 to 50% by weight. The barium sulfate is preferably contained in an amount of 20 to 80% by weight.

It is known that barium sulfate forms agglomerates ("secondary particles") from primary particles in conventional production. The term "deagglomerated" in this context does not mean that the secondary particles have been completely comminuted to primary particles which are present in isolation. It means that the barium sulfate secondary particles are not present as agglomerated as is usually the case with precipitation. len, but in the form of smaller agglomerates. The deagglomerated barium sulfate according to the invention preferably has agglomerates (secondary particles), of which at least 90% have a particle size of less than 2 μm, preferably less than 1 μm. At least 90% of the secondary particles are particularly preferably less than 250 nm, very particularly preferably less than 200 nm. Even more preferred are at least 90% of the secondary particles less than 130 nm, particularly preferably less than 100 nm, very particularly preferably less than 80 nm; more preferably, 90% of the secondary particles have a size of <50 nm, even <30 nm. The barium sulfate is partly or even largely completely in the form of non-agglomerated primary particles. These are medium particle sizes, determined by XRD or laser diffraction methods.

Preferred crystallization inhibitors have at least one anionic group. The crystallization inhibitor preferably contains at least one sulfate, at least one sulfonate, at least two phosphate, at least two phosphonate or at least two carboxylate groups as anionic group.

Substances known for this purpose, for example shorter-chain or longer-chain polyacrylates, usually in the form of the sodium salt, may be present as a crystallization inhibitor; Polyethers such as polyglycol ether; Ether sulfonates such as lauryl ether sulfonate in the form of the sodium salt; Esters of phthalic acid and its derivatives; Esters of polyglycerol; Amines such as triethanolamine; and esters of fatty acids such as stearic acid esters as mentioned in WO 01/92157.

A compound or a salt of the formula (I) with a carbon chain R and n substituents [A (0) OH] can also be used as the crystallization inhibitor.

wherein

R is an organic radical which has hydrophobic and / or hydrophilic partial structures and where R is a low molecular weight, oligomeric or polymeric, optionally branched and / or cyclic carbon chain which optionally contains oxygen, nitrogen, phosphorus or sulfur as heteroatoms, and / or is substituted by radicals which are bonded to the radical R via oxygen, nitrogen, phosphorus or sulfur and in which

A means C, P (OH), OP (OH), S (O) or OS (O),

and n is 1 to 10,000.

If they are monomeric or oligomeric compounds, n is preferably 1 to 5.

A corresponding barium sulfate with an average primary particle size <50 nm, preferably <30 nm, in particular <20 nm, very particularly <10 nm, is likewise new and is an object of the invention as an intermediate. The intermediate product preferably has a BET surface area of at least 30 m ² / g, in particular at least 40 m ² / g, particularly preferably of at least 45 m ² / g and very particularly preferably of at least 50 m ² / g.

Useful crystallization inhibitors of this type include hydroxy-substituted carboxylic acid compounds. For example, hydroxy substituted mono- and dicarboxylic acids with 1 to 20 carbon atoms in the chain (calculated without the carbon atoms of the COO groups), such as citric acid, malic acid (2-hydroxy-1, 4-dibutanoic acid), dihydroxysuccinic acid and 2 -Hydroxy oleic acid. Citric acid and polyacrylate are very particularly preferred as crystallization inhibitors.

Phosphonic acid compounds with an alkyl (or alkylene) radical with a chain length of 1 to 10 carbon atoms are also very useful. Compounds which have one, two or more phosphonic acid residues can be used. They can additionally be substituted by hydroxyl groups. For example, 1-hydroxyethylene diphosphonic acid, 1,1-diphosphonopropane-2,3-dicarboxylic acid, 2-phosphonobutane-1,2,2,4-tricarboxylic acid are very useful. These examples show that those compounds which have both phosphonic acid residues and carboxylic acid residues can also be used.

Compounds which have 1 to 5 or even more nitrogen atoms and 1 or more, for. B. contain up to 5 carboxylic acid or phosphonic acid residues and are optionally additionally substituted by hydroxyl groups. These include e.g. B. Compounds with an ethylenediamine or diethylenetri- amine basic structure and carboxylic acid or phosphonic acid substituents. Compounds which can be used are, for example, diethylenetriamine-pentakis (methanephosphonic acid), iminodisuccinic acid, diethylenetriaminepentaacetic acid, N- (2-hydroxyethyl) ethylenediamine-N, N, N-triacetic acid.

Polyamino acids, for example polyaspartic acid, are also very useful.

Sulfur-substituted carboxylic acids with 1 to 20 carbon atoms (calculated without the carbon atoms of the COO group) and 1 or more carboxylic acid residues, e.g. B. bis-2-ethylhexyl sulfosuccinate (dioctyl sulfosuccinate).

Mixtures of the additives, for example also with other additives such as phosphorous acid, can of course also be used.

The preparation of the barium sulfate intermediate described above with the crystallization inhibitors of the formula (I) is advantageously carried out in such a way that the barium sulfate is precipitated in the presence of the intended crystallization inhibitor. It can be advantageous if at least part of the inhibitor is deprotonated, for example by using the inhibitor at least partially or completely as an alkali metal salt, for example as a sodium salt or as an ammonium salt. Of course you can also use the acid and add an appropriate amount of the base or as an alkali.

In addition to the crystallization inhibitor, the deagglomerated barium sulfate according to the invention also contains a dispersing agent. This agent ensures that no undesirably large agglomerates form if it is already added during the precipitation. As will be described later, it can also be added in a subsequent deagglomeration step; it prevents re-agglomeration and causes agglomerates to be easily redispersed.

The dispersant preferably has one or more anionic groups which can interact with the surface of the barium sulfate. Preferred groups are the carboxylate group, the phosphate group, the phosphonate group, the bisphosphonate group, the sulfate group and the sulfonate group. Some of the agents mentioned above can be used as dispersants, which in addition to a crystallization-inhibiting action also have a dispersing action. When such agents are used, the crystallization inhibitor and dispersant may be identical. Suitable means can be determined by hand tests. Such agents with a crystallization-inhibiting and dispersing effect have the result that the precipitated barium sulfate is obtained in particularly small primary particles and forms readily redispersible agglomerates. If such an agent is used which has a crystallization-inhibiting and at the same time dispersing action, it can be added during the precipitation and, if desired, an additional deagglomeration can be carried out in its presence.

Different compounds with crystallization-inhibiting or dispersing action are usually used.

The deagglomerated barium sulfate according to the invention which contains dispersants which give the barium sulfate particles an electrostatic, steric or electrostatic and steric surface which inhibits agglomeration or prevents re-agglomeration is very advantageous. If such a dispersant is already present during the precipitation, it inhibits the agglomeration of the precipitated barium sulfate, so that deagglomerated barium sulfate is obtained even during the precipitation. If such a dispersant is incorporated after the precipitation, for example in the course of wet grinding, it prevents the reagglomeration of the deagglomerated barium sulfate after the deagglomeration. Barium sulfate containing such a dispersant is most preferred because it remains in the deagglomerated state.

A particularly advantageous deagglomerated barium sulfate is characterized in that the dispersant has carboxylate, phosphate, phosphonate, bisphosphonate, sulfate or sulfonate groups which can interact with the barium sulfate surface and that it has one or more organic R ¹ has residues which have hydrophobic and / or hydrophilic partial structures.

R ¹ is preferably a low molecular weight, oligomeric or polymeric, optionally branched and / or cyclic carbon chain, the oxygen optionally, nitrogen, phosphorus or sulfur as heteroatoms and / or substituted by ^radicals' the oxygen, nitrogen, phosphorus or sulfur are bound to the radical R ¹ and the Carbon chain is optionally substituted by hydrophilic or hydrophobic radicals. An example of such substituting radicals are polyether groups. Preferred polyether groups have 3 to 50, preferably 3 to 40, in particular 3 to 30 alkyleneoxy groups. The alkyleneoxy groups are preferably selected from the group consisting of the methyleneoxy, ethyleneoxy, propyleneoxy and butyleneoxy group.

Preferred barium sulfate according to the invention contains a dispersant which has groups for coupling into or coupling into polymers. These can be groups that effect this coupling or coupling, e.g. B. OH groups or NH groups or NH2 ~ groups. The groups can also be those that bring about physical coupling or coupling.

An example of a dispersing agent which makes the surface of the barium sulfate hydrophobic are phosphoric acid derivatives in which one oxygen atom of the P (0) group is replaced by a C3-C10-alkyl or alkenyl radical and another oxygen atom of the P (0) group a polyether function is substituted. Another acidic oxygen atom of the P (0) group can interact with the barium sulfate surface.

The dispersant can be, for example, a phosphoric diester which has a polyether group and a C6-C10 alkenyl group as partial structures. Phosphoric acid esters with polyether / polyester side chains such as Disperbyk®111, phosphoric acid ester salts with polyether / alkyl side chains such as Disperbyk®102 and 106, deflocculating substances, e.g. based on high molecular copolymers with pigment-affine groups such as Disperbyk®190 or polar acidic esters of long-chain alcohols such as Disperplast®1 140 are other well-suited types of dispersants.

A barium sulfate with very particularly good properties contains, as a dispersant, a polymer which has anionic groups which can interact with the surface of the barium sulfate, for example the above-mentioned groups, and which is substituted by polar groups, for example by hydroxyl or amino groups. It preferably contains polyether groups which are terminally substituted by hydroxyl groups. As a result of this substitution, the barium sulfate particles are externally hydrophilized. Such barium sulfate according to the invention shows no tendency towards reagglomeration. It can even cause further disagglomeration when used come. The polar groups, in particular hydroxyl and amino groups, are reactive groups which are particularly suitable for coupling or coupling in epoxy resins. A barium sulfate which is coated with a dispersant which has a multiplicity of polycarboxylate groups and a multiplicity of hydro groups, and further substituents which are sterically demanding, for. B. polyether groups. A very preferred group of dispersants are polyether polycarboxylates which are terminally substituted on the polyether groups by hydroxyl groups.

Such barium sulfate, which has a crystal growth inhibitor and one of the particularly preferred dispersing agents which sterically prevent reagglomeration, in particular a dispersing agent substituted by polar groups as described above, has the great advantage that it comprises very fine primary particles and, if need be, slightly agglomerated secondary particles, because: they are easy to redisperse, are very easy to use, for example can be easily incorporated into polymers and do not tend to reagglomerate, and even further disagglomerate when used.

In one embodiment, the deagglomerated coated barium sulfate is dry. According to a further embodiment, it is in the form of a suspension in water or in the form of a suspension in an organic liquid, the organic liquid possibly also containing water. Preferred organic liquids are alcohols such as isopropanol or its mixtures with other alcohols or polyols, ketones such as acetone, cyclopentanone or methyl ethyl ketone, naphtha or mineral spirits and mixtures thereof. Plasticizers such as dioctyl phthalate or diisodecyl phthalate can be added. The deagglomerated barium sulfate is preferably present in the suspension in an amount of 0.1 to 60% by weight, for example 0.1 to 25% by weight or 1 to 20% by weight.

The deagglomerated barium sulfate according to the invention and in particular its suspension, in particular on an aqueous basis, can also have modifying agents which influence its properties. The additional modifying agent which may be present preferably has a lower hydrodynamic volume than the compound used as a dispersing agent. The modifying agent (M) is preferably of low molecular weight; in particular it contains at least one, in particular one of the anionic groups described above. Examples of particularly suitable modifiers (M) are organic acids, preferably acetic acid and propionic acid, in particular acetic acid. It has been found that suspensions of the deagglomerated barium sulfate, particularly aqueous suspensions which contain organic acid, are particularly stable to sedimentation.

The product according to the invention is also barium sulfate with an average primary particle size of <50 nm, preferably <20 nm, which is essentially free of agglomerates, in which the average secondary particle size is thus at most 30% larger than the average primary particle size.

The invention provides several variants of making the deagglomerated barium sulfate according to the invention available.

The first variant provides for the precipitation of barium sulfate in the presence of a crystallization-inhibiting agent and then for a deagglomeration. This deagglomeration is carried out in the presence of a dispersant.

The second variant provides for the precipitation of barium sulfate in the presence of a crystallization-inhibiting agent and a dispersing agent.

The first variant will now be explained further.

Barium sulfate is precipitated using conventional methods, e.g. B. by reaction of barium chloride or barium hydroxide with alkali sulfate or sulfuric acid. Methods are used in which primary particles with the fineness specified above are formed. In the precipitation, additives are used which inhibit crystallization, for example those as mentioned in WO 01/92157 or the abovementioned compounds of the formula (I) which have a crystallization-inhibiting action. If desired, the precipitated barium sulfate is dewatered to paste or even to a dry powder. A wet disagglomeration follows. Water or an organic liquid can be selected as the liquid, e.g. B. an alcohol. The deagglomeration, which is carried out, for example, in a bead mill, then takes place in the presence of a dispersant. The dispersants are mentioned above; for example, an agent of formula (I) can be used which has dispersing properties. In this case, the crystallization-inhibiting and Dispersant be the same. The crystallization-inhibiting effect is used in the case of precipitation and the dispersing effect in the case of deagglomeration. In the deagglomeration, preference is given to using those dispersants which sterically prevent the reagglomeration, in particular those dispersants which are substituted by hydroxyl groups. The grinding and thus the deagglomeration are carried out until the desired degree of deagglomeration is reached. The deagglomeration is preferably carried out until the deagglomerated barium sulfate according to the invention has secondary particles, of which 90% are less than 2 μm, preferably less than 1 μm, particularly preferably less than 250 nm, very particularly preferably less than 200 nm. It is even more preferred to deagglomerate until 90% of the secondary particles are smaller than 130 nm, particularly preferably smaller than 100 nm, very particularly preferably smaller than 80 nm, more preferably <50 nm. The barium sulfate can be partially or even largely completely in the form of non-agglomerated primary particles (average particle sizes, determined by XRD or laser diffraction methods). The suspension of the deagglomerated barium sulfate formed during wet deagglomeration and containing a crystallization-inhibiting agent and a dispersant can then be used as such, for example for incorporation into plastics. As described above, a storage-stable suspension can also be produced by adding acid.

You can also carry out drying, e.g. B. spray drying. The particles formed in this process disintegrate very easily into the deagglomerated barium sulfate. The barium sulfate according to the invention is formed from very small primary particles, the secondary particles are in the deagglomerated state, and it can be redispersed.

The second variant of the invention provides that the precipitation, for. B. by reaction of barium chloride or barium hydroxide with alkali sulfate or sulfuric acid, in the presence of a crystallization inhibitor and a dispersant; this procedure already leads to the formation of deagglomerated barium sulfate during precipitation, which is easily redispersible. Such dispersants which give the barium sulfate particles an electrostatic, steric or electrostatic and steric surface which inhibits agglomeration during precipitation and prevents re-agglomeration are explained above. In this embodiment, a barium sulfate which has been deagglomerated in the sense of the invention is formed already during the precipitation. The barium sulfate thus precipitated, containing crystallization inhibitor and dispersant, is in principle ready for use and can be used as an aqueous suspension; as described above, an additional stabilization of the suspension with acid is possible. You can also partially or completely dewater the precipitated barium sulfate, e.g. B. by spray drying. A paste or powder is then created. The powder naturally has agglomerates. However, these are not agglomerated, as in the case of barium sulfate according to the prior art, but are loose agglomerates which are redispersible in liquid media and again form deagglomerated particles. Alternatively, the powder can be converted into a suspension with the addition of water or organic liquids; again, the deagglomerated particles are obtained as they were before drying. In some applications, it is not necessary to comminute the dried aggregates or convert them into a suspension before use because they convert into the deagglomerated particles during use, for example when they are incorporated into liquid precursors. If the very particularly preferred polymeric dispersants are used which sterically prevent the reagglomeration and have polar groups for coupling or coupling into polymers, a further deagglomeration is observed.

The deagglomerated barium sulfate according to the invention, which is present as an easily redispersible powder, if desired also in the form of an aqueous suspension or in the form of a suspension in an organic liquid, can be used for all purposes for which barium sulfate is usually used, e.g. in plastics such as plastomers and elastomers. It is particularly well suited as an additive in curable compositions and hardened compositions, which also include adhesives and sealants.

Curable compositions which contain nanoparticles, in particular nanoparticles based on silicon dioxide or aluminum oxide, have long been known. Reference is made, for example, to patent applications EP 1 179 575 A 2, WO 00/35599 A, WO 99/52964 A, WO 99/54412 A, W099 / 52964 A, DE 197 26 829 A1 or DE 195 40 623 A1. They are used in particular for the production of highly scratch-resistant coatings, the chemical stability of which, however, leaves something to be desired. From European patent application EP 0 943 664 A 2, transparent paint binders containing nanoparticles are known which, based on the paint solid, contain 0.5 to 25% by weight of primarily nanoscale particles incorporated as a solid and by jet-jet dispersion of the nanoscale particles in the Binders are made. The simpler incorporation of the nanoparticles increases the scratch resistance of the hardened masses produced from the hardened lacquer binders. In addition to numerous other species, barium sulfate nanoparticles can also be used. The European patent application does not state whether these are surface-modified or not and what influence they have on gloss, transparency, clarity, flow, surface quality, scratch resistance and chemical resistance.

The new, curable compositions have at least one curable constituent (A) selected from the group consisting of low molecular weight compounds, oligomers and polymers, and the deagglomerated barium sulfate according to the invention.

A new process for the preparation of the curable compositions according to the invention provides that

(1) at least one curable constituent (A) selected from the group consisting of low molecular weight compounds, oligomers and polymers with

(2) a suspension of

(2.1) deagglomerated barium sulfate nanoparticles (2.2) according to the invention in an aqueous phase

mixed and the resulting mixture homogenized.

The curable compositions obtained in this way are very easy to transport and stable in storage, even with a high content of deagglomerated barium sulfate and a solids content of more than 30%, and can be processed very well. This makes them very easy to apply to substrates. The curable compositions can be used in a wide variety of areas of application, in particular as coating materials, adhesives, sealing compounds, as starting products for molded parts and freely slides. The hardened masses produced from the hardenable masses, which contain the deagglomerated barium sulfate according to the invention, have a high gloss, a very good flow, even with layer thicknesses> 40 μm, no stress cracks, a surface which is free from surface defects, such as craters, specks, Microbubbles and pinpricks, is, and high scratch resistance. If the new, hardened materials are not optically opaque, they are particularly transparent, clear and brilliant. In addition, they have very good chemical resistance. Last but not least, they effectively shield all types of substrates against high-energy radiation, especially X-rays. Furthermore, the new, curable compositions can be produced in a simple manner.

The solids content of the curable compositions according to the invention, i. H. the content of constituents which build up the hardened masses according to the invention produced from the hardenable masses according to the invention can vary very widely and depend on the requirements of the individual case. The solids content is preferably 20 to 80, preferably 30 to 70 and in particular 30 to 60% by weight, in each case based on the curable composition according to the invention.

The content of the above-mentioned constituents (A) in the curable compositions according to the invention can likewise vary very widely and also depends on the requirements of the individual case. The content is preferably 50 to 99.9, preferably 60 to 99.9 and in particular 70 to 99.9% by weight, in each case based on the solid of the curable composition according to the invention.

Likewise, the content of surface-modified barium sulfate nanoparticles (N) in the curable compositions according to the invention varies very widely and depends on the requirements of the individual case. The content is preferably 0.05 to 10, preferably 0.05 to 8 and in particular 0.05 to 6% by weight, in each case based on the solids of the curable compositions according to the invention.

The curable low molecular weight constituents (A) are preferably epoxy-functional silanes, such as those used for. B. from the patent applications EP 1 179 575 A 2, WO 00/35599 A, WO 99/52964 A, WO 99/54412 A, DE 197 26 829 A 1 or DE 195 40 623 A 1, are known, in particular G lycidyloxypropyltrimethoxysilane or glycidyloxypropyltriethoxysilane, and / or around silanes which have at least one olefinically unsaturated group, in particular a vinyl group or a methacrylate or Contain acrylate group, as z. B. from the patent applications WO 00/22052 A, WO 99/54412 A, DE 199 10 876 A 1 or DE 197 19 948 A 1 are known, in particular the monomers (a2) described below.

In addition, the hydrolyzates and / or condensates of these low molecular weight compounds can be used as constituents (A).

The hydrolysates and / or condensates (A) can be prepared by condensing the low molecular weight compounds (A), preferably in the so-called sol-gel process. Its basic reactions can be explained using the tetraorthosilicates. If appropriate, these are hydrolyzed and condensed in the presence of a co-solvent:

Hydrolysis:

Si (OR ') ₄ + H ₂ 0 → (R'0) ₃ Si-OH + ROH

Condensation:

-Si-OH + HO-Si- → -Si-O-Si- + H ₂ 0

-Si-OH + R'O-Si- → -Si-O-Si- + ROH,

where R 'can be an alkyl group such as methyl or ethyl. Acids, bases or fluoride ions are used to catalyze the reactions.

The curable polymers and oligomers (A) contain at least one reactive functional group (a1) and preferably at least two and in particular at least three reactive functional groups (a1) which make the oligomers and polymers (A) thermally and / or curable with actinic radiation , Examples of suitable reactive functional groups (a1) are known from international patent application WO 03/01641 1A, page 10, line 20, to page 12, line 2, and page 20, line 1, to page 22, line 16. In particular, epoxy groups (a1) are used.

The oligomers and polymers (A) are preferably hydrolysates and / or condensates which can be prepared by hydrolyzing and / or condensing oligomers and / or polymers (A) which contain epoxy groups (a1) and hydrolyzable silane groups (a2). The oligomers and / or polymers (A) which contain epoxy groups (a1) and hydrolyzable silane groups (a2) can, however, also be used as curable constituents (A).

The hydrolyzates and / or condensates (A) can be prepared by condensing oligomers and / or polymers (A) containing epoxide groups and hydrolyzable silane groups (a2), preferably in the so-called sol-gel process, the basic reactions of which are described above.

The statistical average of the oligomers (A) contains more than 2 and not more than 15 built-in monomer units. In general, the polymers (A) contain more than 10, preferably more than 15, built-in monomer units.

The hydrolysates and / or condensates (A) can each be prepared from at least one, in particular one, oligomer (A) or polymer (A) containing hydrolyzable silane groups (a2). For special applications, however, mixtures of at least two different hydrolyzable Si long groups (a2) containing oligomers (A), polymers (A) or oligomers and polymers (A) can also be used.

The hydrolyzable silane groups (a2) containing oligomers and polymers (A) each contain at least one epoxy group (a1) and at least one in the above. Meaning hydrolyzable silane group (a2). On statistical average, they preferably contain at least two, in particular at least three, epoxy groups (a1) and at least two, in particular at least three, hydrolyzable silane groups (a2). These can be terminal and / or lateral epoxy groups (a1) and hydrolyzable silane groups (a2).

The hydrolyzable silane groups (a2) containing oligomers and polymers (A) can have a linear, star-shaped or dendrimeric branched or comb-like structure. These structures can be combined with one another within an oligomer or polymer (A) containing hydrolyzable silane groups (a2). The monomer units can be distributed randomly, alternatingly or in blocks, it being possible for these distributions to be present in combination with one another within an oligomer or polymer (A) containing hydrolysable silane groups (a2). The number average and mass average molecular weights and the non-uniformity of the molecular weight of the oligomers and polymers (A ¹ ) can vary widely and depend on the requirements of the individual case. The number average molecular weight (determined by gel permeation chromatography with polystyrene as the internal standard) is preferably 800 to 3,000, preferably 1,000 to 2,000 and in particular 1,000 to 2,000 Daltons. The mass average molecular weight is preferably 1,000 to 8,000, preferably 1,500 to 6,500 and in particular 1,500 to 6,000 Daltons. Non-uniformity is preferably <10, preferably <8 and in particular <5.

The oligomers and polymers (A) containing hydrolyzable silane groups (a2) can originate from all the polymer classes in which the epoxy groups (a1) and the hydrolyzable silane groups (a2) are not reacted during their preparation and thereafter. The person skilled in the art can therefore easily select the suitable polymer classes on the basis of his general specialist knowledge. The hydrolyzable silane groups (a2) containing oligomers and polymers (A) are addition polymers, in particular copolymers of olefinically unsaturated monomers.

The epoxy groups (a1) are covalently linked to the main chain or the main chains of the hydrolyzable silane groups (a2) containing oligomers and polymers (A) via linking organic groups (G1). An epoxy group (a1) can be linked to the main chain via a double-bonded, linking organic group (G1) or at least two epoxy groups (a1) can be linked to the main chain via an at least three-link, linking organic group (G1). An epoxy group (a1) is preferably linked to the main chain via a double-bonded, linking organic group (G1).

The double-bonded, linking organic groups (G1) preferably contain at least one, in particular one, at least double-bonded, in particular double-bonded, group (G11) selected from the group consisting of substituted and unsubstituted, preferably unsubstituted, branched and unbranched, preferably unbranched, cyclic and non-cyclic, preferably non-cyclic, alkyl, alkenyl and alkynyl groups, in particular alkyl groups, and also substituted and unsubstituted, preferably unsubstituted, aryl groups, or they consist thereof. In particular, the divalent group (G11) is an unbranched, non-cyclic, unsubstituted, divalent alkyl group with 1 to 10, preferably 2 to 6 and in particular 1 to 4 carbon atoms, such as a methylene, ethylene, trimethylene or tetramethylene group.

The double-bonded, linking organic groups (G1) preferably also contain at least one, in particular one, at least double-bonded, in particular double-bonded, linking, functional group (G12), preferably selected from the group consisting of ether, thioether and carboxylic acid esters -, thiocarboxylic acid ester, carbonate, thiocarbonate, phosphoric acid ester, thio-phosphoric acid ester, phosphonic acid ester, thiophosphonic acid ester, phosphite, thiophosphite, sulfonic acid ester, amide, amine, thioamide, phosphoric acid amide, thiophosphoric acid amide, phosphonic acid -, Thiophosphonsäureamid-, sulfonic acid amide, imide, hydrazide, urethane, urea, thiourea, carbonyl, thiocarbonyl, sulfone or sulfoxide groups, especially carboxylic acid ester groups.

Examples of suitable substituents are halogen atoms, in particular fluorine atoms and chlorine atoms, nitrile groups, nitro groups or alkoxy groups. The groups (G1) and (G1 1) described above are preferably unsubstituted.

The epoxy groups (a1) are preferred via a group (G11) and these in turn via a group (G12), particularly preferably according to the general formula I:

- (- G12 -) - (G11 -) - epoxy (I),

connected to the main chain. In particular, as a group of the general formula I

-C (0) -0-CH ₂ epoxide (11)

used.

The hydrolyzable silane groups (a2) can have different structures. They are preferably selected from the group consisting of hydrolyzable silane groups (a2) of the general formula II: -SiR _m R ¹ _n (II),

selected.

In the general formula II, the indices and the variables have the following meaning:

R monovalent, hydrolyzable atom or monovalent, hydrolyzable group;

R ¹ monovalent, non-hydrolyzable radical; m is an integer from 1 to 3, preferably 3, and n is 0 or 1 or 2, preferably 0 or 1,

with the proviso that m + n = 3.

Examples of suitable, single-bonded, hydrolyzable atoms R are hydrogen, fluorine, chlorine, bromine and iodine.

Examples of suitable, monovalent, hydrolyzable radicals R are hydroxyl groups, amino groups -NH ₂ and groups of the general formula III:

R ¹ -X- (III),

where the variables have the following meaning:

X oxygen atom, sulfur atom, carbonyl group, thiocarbonyl group, carboxyl group, thiocarboxylic acid S-ester group, thiocarboxylic acid O-ester group or amino group -NH- or -NR ¹ -, preferably oxygen atom; and

R ¹ monovalent organic residue.

The monovalent organic radical R ¹ contains at least one group (G2) selected from the group consisting of substituted and unsubstituted, preferably unsubstituted, branched and unbranched, preferably unbranched, cyclic and non-cyclic, preferably non-cyclic, alkyl, alkenyl, and alkynyl groups, preferably alkyl groups, and substituted and unsubstituted aryl groups; especially unsubstituted, unbranched, non-cyclic alkyl groups; or it consists of this. Examples of suitable substituents are those mentioned above.

If the rest R consists of a group (G2), this is one-membered.

If the radical R ^{1 contains} a group (G2), this is at least double-bonded, especially. special two-column, and directly linked with -X-. In addition, the radical R ^{1 may} also contain at least one, in particular one, of the groups (G12) described above.

If the radical R ^{1 contains} at least two groups (G2), at least one of them is at least double-bonded, in particular double-bonded, and is directly linked to -X-. This group (G2) linked directly to -X- is linked to at least one further group (G2). This group (G2) linked directly to -X- is preferably linked to the further group (G2) via a group (G12) or the further groups (G2) via at least two groups (G12).

The radical R ¹ preferably consists of a group (G2). In particular, the radical R ^{1 is selected} from the group consisting of methyl, ethyl, propyl and butyl.

In particular, the hydrolyzable silane groups (a2) are selected from the group consisting of trimethoxysilyl, triethoxysilyl, tripropoxysilyl and tributoxysilyl, in particular trimethoxysilyl and triethoxysilyl.

The hydrolyzable silane groups (a2) are preferably covalently linked to the main chain or the main chains of the oligomers and polymers (A) via the linking organic groups (G1) described above. A hydrolyzable silane group (a2) can be linked to the main chain via a double-bonded, linking organic group (G1) or at least two hydrolyzable silane groups (a2) can be linked to the main chain via an at least three-linked, linking organic group (G1). A hydrolyzable silane group (a2) is preferably linked to the main chain via a double-bonded, linking organic group (G1).

Here, too, the monovalent, linking organic groups (G1) preferably contain at least one, in particular one, of the above-described, at least double-bonded, in particular double-bonded, groups (G11) or they from here. The double-bonded, linking organic groups (G1) preferably also contain at least one, in particular one, of the above-described at least double-bonded, in particular double-bonded, linking functional group (G12).

The silane groups (a2) are preferred via a double-bonded, linking group (G11) and these in turn via a double-bonded, linking, functional group (G12) according to the general formula (IV):

- (- G12 -) - (G11 -) - SiR _m R ¹ _n (IV),

wherein the indices and the variables have the meaning given above, linked to the main chain of the oligomers and polymers (A). The following groups of the general formula IV are very particularly preferably used:

-C (O) -0 - (- CH ₂ -) ₂ -Si (OCH ₃ ) ₃ (IV1),

-C (0) -0 - (- CH ₂ -) ₃ -Si (OCH ₃ ) ₃ (IV2),

-C (0) -0 - (- CH ₂ -) ₂ -Si (OC ₂ H ₅ ) ₃ (IV3),

-C (0) -0 - (- CH ₂ -) ₃ -Si (OC ₂ H ₅ ) ₃ (IV4),

-C (0) -0-CH ₂ -Si (OC ₂ H ₅ ) ₃ (IV5)

and

-C (0) -0-CH ₂ -SiCH ₃ (OC ₂ H ₅ ) ₂ (IV6),

especially (IV4).

The molar ratio of epoxy groups (a1) to hydrolyzable silane groups (a2) in the oligomers and polymers (A ') can vary widely. It is preferably 1.5: 1 to 1: 1.5, preferably 1.3: 1 to 1: 1, 3 and in particular 1.1: 1 to 1: 1.1. The (meth) acrylate copolymers (A), the lateral and / or terminal epoxy groups (a1) and lateral and / or terminal, hydrolyzable silane groups (a2) of the general formula II are very particularly advantageous:

-SiR _m R ¹ _n (II),

in which the indices and the variables have the meaning given above, in the molar ratio of (a1) :( a2) = 1.5: 1 to 1: 1.5, preferably 1.3: 1 to 1: 1, 3 and in particular 1 , 1: 1 to 1: 1, 1, included. These (meth) acrylate copolymers (A ') according to the invention provide very particularly advantageous hydrolyzates and / or condensates (A).

In addition to the epoxy groups (a1) and silane groups (a2) described above, the oligomers and polymers (A) can also contain further lateral and / or terminal groups (a3). It is essential that the groups (a3) neither react with the epoxy groups (a1) and silane groups (a2) nor interfere with the course of the condensation. Examples of suitable groups (a3) are fluorine atoms, chlorine atoms, nitrile groups, nitro groups, alkoxy groups, polyoxyalkylene groups or the monovalent organic radicals R ¹ described above, in particular aryl groups, alkyl groups and cycloalkyl groups. With the help of these groups (a3), the profile of properties of the hydrolyzable silane groups (a2) containing oligomers and polymers (A) and thus the hydrolyzates and / or condensates (A) can be varied widely in an advantageous manner.

The hydrolyzable silane groups (a2) containing oligomers and polymers (A) are obtained by copolymerization of at least one, especially one, at least one, especially one, epoxy group (a1) containing monomers (a1) with at least one, especially one, at least one, especially one, Monomers (a2) containing silane group (a2) can be prepared. The monomers (a2) and (a3) can also be copolymerized with at least one monomer (a3) which contains at least one group (a3).

Particular advantages result if the monomers (a1) and (a2) in a molar ratio of (a1) :( a2) = 1.5: 1 to 1: 1.5, preferably 1.3: 1 to 1: 1.3 and in particular 1.1: 1 to 1: 1, 1 are copolymerized with one another. Very special advantages are obtained if the molar ratio of epo oxide groups (a1) to hydrolyzable silane groups (a2) in the oligomers and polymers (A ') results.

Monomers (a1), (a2) and (a3) preferably contain at least one, in particular one, olefinically unsaturated group.

Examples of suitable, olefinically unsaturated groups are (meth) acrylate, ethacrylate, crotonate, cinnamate, vinyl ether, vinyl ester, dicyclopentadienyl, norbornenyl, isoprenyl, isopropenyl, allyl or butenyl groups; Dicyclopentadienyl, norbornenyl, isoprenyl, isopropenyl, allyl or butenyl ether groups or dicyclopentadienyl, norbornenyl, isoprenyl, isopropenyl, allyl or butenyl ester groups, preferably methacrylate groups and acrylate groups, especially methacrylate groups.

An example of a particularly suitable monomer (a1) is glycidyl methacrylate.

An example of a particularly suitable monomer (a2) is methacryloxypropyltrimethoxysilane (MPTS), which is sold by Degussa under the Dynasilan ^® MEMO brand, or methacryloxymethyltriethoxysilane or methacryloxymethylmethyldiethoxysilane, which is sold under the Geniosil ^® XL 34 brands and Geniosil ^® XL 36 are sold by Wacker.

Examples of suitable monomers (a3) are described in international patent application WO 03/016411, page 24, lines 9 to page 28, line 8.

The oligomers and polymers (A ¹ ) can preferably be prepared in a manner known per se by radical copolymerization of the monomers (a1) and (a2) and, if appropriate, (a3), preferably in bulk or in solution, in particular in solution.

The hydrolyzates and / or condensates (A) are preferably prepared by condensing the above-described hydrolyzable silane groups (a2) containing oligomers and / or polymers (A), preferably at a pH <7. The hydrolysis and / or condensation is carried out in a sol-gel process by reaction with water in the presence of an organic or inorganic acid, preferably an organic acid, in particular formic acid or Acetic acid. The condensation is preferably carried out at -10 to +80, preferably 0 to +80 and in particular +10 to +75 ° C.

The hydrolysis and / or condensation can be carried out in the presence of customary and known hydrolyzable, low molecular weight silanes, which are different from the low molecular weight compounds (A), and / or hydrolyzable metal alkoxides, as described, for example, in German patent application DE 199 40 857 A1 be described, be carried out from the surface-modified barium sulfate nanoparticles (N) and / or from different nanoparticles.

The hydrolyzates and / or condensates (A) can be processed further as a solution or dispersion or used directly as curable compositions according to the invention. Preferably, they are largely freed of water and / or organic solvents before they are further processed into the curable compositions according to the invention.

As catalysts, compounds of metals with at least one organic, preferably non-aromatic compound capable of forming chelate ligands can be added as catalysts to the hydrolyzates and / or condensates (A) or the curable compositions according to the invention. The compounds which form the chelate ligands are organic compounds with at least two functional groups which can coordinate with metal atoms or ions. These functional groups are usually electron donors, which donate electrons to metal atoms or ions as electron acceptors. In principle, all organic compounds of the type mentioned are suitable as long as they do not adversely affect or even completely prevent the crosslinking of the curable compositions according to the invention to cured compositions according to the invention. Examples of suitable organic compounds are dimethylglyoxime or compounds which contain carbonyl groups in the 1,3-position, such as acetylacetone or ethyl acetoacetate. In addition, reference is made to Römpp Chemie Lexikon, Georg Thieme Verlag, Stuttgart, 1989, Volume 1, page 634. In particular, aluminum chelate complexes are used as catalysts.

Furthermore, the hydrolyzates and / or condensates (A) or the curable compositions according to the invention can be customary and known catalysts for crosslinking the epoxy groups, such as Lewis acids, aluminum or tin compounds Amines or heterocycles can be added, as described for example in the book by Bryan Ellis, "Chemistry and Technology of Epoxy Resins", University of Sheffield, Mackie Academic & Professional.

In addition, customary and known, paint-typical components can be added to them. Examples of suitable constituents are described in international patent application WO 03/01641 1, page 14, line 9, to page 35, line 31, for example.

The preparation of the curable compositions according to the invention has no special features in terms of method, but can be carried out using the methods and devices described in international patent application WO 03/01641 1, page 36, lines 13 to 20.

The curable compositions according to the invention contain customary and known organic solvents (cf. international patent application WO 03/01641 1, page 35, lines 12 to 14) and preferably water. This is a particular advantage of the liquid curable compositions according to the invention in that they can have a solids content> 30% by weight, without thereby affecting their very good transportability, storage stability and processability, in particular their applicability.

The curable compositions according to the invention serve to produce the cured compositions according to the invention. They are preferably used as pigmented and unpigmented coating materials, in particular clearcoats, and as starting products for moldings, in particular optical moldings, and self-supporting films.

The cured compositions according to the invention are preferably highly scratch-resistant, pigmented and unpigmented coatings and coatings, preferably transparent, in particular clear, clear coatings, moldings, in particular optical moldings, and self-supporting films. The cured compositions according to the invention are very particularly preferably highly scratch-resistant clearcoats and highly scratch-resistant clearcoats in the context of color and / or effect multi-layer coatings on customary and known substrates (cf. the international patent application in this regard WO 03/01641 1, page 41, line 6, to page 43, line 6, i. V. m. Page 44, line 6, to page 45, line 6).

The preparation of the hardened compositions according to the invention from the hardenable compositions according to the invention has no special features in terms of method, but is carried out with the aid of customary and known methods and devices which are typical of the respective hardened composition according to the invention.

In particular, the curable coating materials according to the invention are applied to substrates using the customary and known methods and devices described in international patent application WO 03/01641 1, page 37, lines 4 to 24.

The hardenable compositions according to the invention can be hardened as described in international patent application WO 03/016411, page 38, line 1, to page 41, line 4.

The curable compositions according to the invention provide new cured compositions, in particular coatings and coatings, especially clearcoats, moldings, especially optical moldings, and self-supporting films that are highly scratch-resistant and chemical-stable. In particular, the coatings and varnishes according to the invention, especially the clearcoats, can also be produced in layer thicknesses> 40 μm without stress cracks occurring.

The hardened compositions according to the invention are therefore outstandingly suitable as highly scratch-resistant, decorative, protective and / or effect-imparting coatings and coatings for vehicle bodies of all kinds of means of transportation (in particular means of transportation powered by muscle power, such as bicycles, carriages or trolleys; aircraft, such as airplanes, helicopters or zeppelins ; Floats, such as ships or buoys; rail vehicles and motor vehicles, such as locomotives, railcars, railway wagons, motorcycles, buses, trucks or cars) or parts thereof; of buildings indoors and outdoors; of furniture, windows and doors; of molded plastic parts, especially of polycarbonate, in particular CDs and windows, especially windows in the automotive sector; of small industrial parts, of coils, containers and packaging; of white goods; of foils; of optical, electrotechnical African and mechanical components as well as of hollow glass bodies and everyday objects.

In particular, the coatings and paints according to the invention, in particular clearcoats, can be used in the technologically and aesthetically particularly demanding field of automotive OEM painting. They are characterized above all by their particularly high resistance to car washes and scratch resistance.

The deagglomerated barium sulfate according to the invention is suitable not only as an additive for the curable compositions described above, but generally as an additive for. B. for plastics, e.g. Phenolic resins, acrylic resins, alkyd resins, epoxy resins, saturated and unsaturated polyesters, polyurethanes, silicone resins, urea and melamine resins, polycarbonate and polyamide resins. Plastics with added modified barium sulfate according to the invention are also the subject of the invention.

As mentioned, the barium sulfate according to the invention is suitable as an additive for adhesives. For example, barium sulfate, which had been precipitated with citric acid or Na polyacrylate as a crystallization inhibitor and had been dispersed with a high-molecular copolymer with pigment-affine groups (Disperbyk®190), was added to an acrylate-based adhesive, which improved the adhesive so that the Kohe- sion was improved without changing the adhesion. Resin-based adhesives achieved a low viscosity with high hardness by adding modified barium sulfate, which was prepared with barium sulfate precipitated by citric acid and then dispersed using a salt of a phosphoric acid ester with polyether / alkyl side chains (Disperbyk®102) in mineral spirits / acetone. Such citric acid-precipitated barium sulfate, produced with Disperbyk®102 in boiling point petrol with the addition of dioctyl phthalate, resulted in improved cohesion and chemical resistance in silicones. The modified barium sulfate, this time with dicetyl phthalate as an additive, was also used in polyurethane / epoxy resins.

It was also found that barium sulfate according to the invention, especially that which, in addition to the crystallization inhibitor, contains a polymeric polyether polycarboxylate as the dispersant and is terminally substituted on the ether groups by hydroxyl groups and is therefore hydrophilized, is particularly suitable for use in molded epoxy articles or Epoxy resins can be used. It gives these plastics good impact resistance and elongation at break.

Organic, generally oligomeric compounds with more than one epoxy group per molecule are referred to as epoxy resins. These oligomeric compounds can be converted into thermosets with suitable hardeners. Epoxy resins are used, for example, as casting resins or as laminates (for example in aircraft, vehicle or boat construction).

Monoepoxide compounds which are used as starting material for the production of epoxy resins are, in particular, epichlorohydrin, but also glycidol, styrene oxide, cyclohexene oxide and acrylic acid or methacrylic acid glycidyl esters. Resin formation takes place by reaction in particular with bisphenol-A. Other polyols such as aliphatic glycols are also suitable for special resins. Liquid resins can be extended by the "advancemenf" method. Dicarboxylic acid anhydrides or amine hardeners are suitable as hardening agents. An explanation of the basics can be found, for example, in Ullmann's Encyclopedia of Technical Chemistry, 4th edition, vol. 10, pages 563-580 and in Kirk-Othmer, Encyclopedia of Chemical Technology, 4th edition, vol. 9, pages 730-755.

Epoxy resin is u. a. used for composite materials. These composite materials are made up of matrix material and reinforcements. Epoxy resins are predominantly used as the matrix material. Reinforcing material is preferably fibrous; preferred materials are glass fibers, carbon fibers and aramid fibers. Basic information on this can be found in Kirk-Othmer, Encyclopedia of Chemical Technology, 4th edition, vol. 7, pages 1-40. Composite materials with an epoxy matrix are used, for example, in aircraft construction, in spaceship construction, for satellites, vehicles, in railway construction, in boat construction, usable for building components, flywheels, pressure vessels, see for example published US patent application 2003/0064228 A1 and EP-A-1 094 087. Another area of application is rotors for wind turbines, see plastics, issue 1 1 (2002), pages 1 19-124 ,

The barium sulfate according to the invention is preferably contained in an amount of 1 to 50% by weight, preferably 1 to 25% by weight, in the cured epoxy resin. A hardened epoxy resin can be obtained by dispersing the barium sulfate according to the invention in a precursor of the hardened epoxy resin, preferably in the hardener and / or in the resin (not yet mixed with hardener, that is to say not yet hardened). For example, you can use a high-speed stirrer.

Epoxides based on bisphenol-A and epichlorohydrin are particularly suitable. They can also contain admixtures, for example reaction products of bisphenol-F and epichlorohydrin or glycidyl ether, e.g. B. 1,6-hexanediol diglycidyl ether. Epoxides with 50 to 100% by weight bisphenol-A / epichlorohydrin, 0 to 50% by weight, preferably 10 to 25% by weight bisphenol-F / epichlorohydrin and 0 to 50% by weight, preferably 10, are very useful up to 25% by weight 1,6-hexanediol glycidyl ether. A commercial product of such a composition is Epilox resin M730®.

Well suited hardeners are e.g. B. those based on polyoxyalkylene amines. Mixtures can also be used, e.g. B. Mixtures of polyoxyalkylene amines with cyclohexanediamines or piperazinylethylamines. For example, a hardener with 50 to 100% by weight of polyoxyalkylene amine, 0 to 50% by weight, preferably 10 to 25% by weight of 1,2-cyclohexanediamine (also as a mixture of isomers) and 0 to 50% by weight is very useful. %, preferably 10 to 25% by weight of 2-piperazin-1-ylethylamine. A commercial product with such a composition is Epilox M888®.

The cured epoxy resins can have other conventional components such as curing accelerators or pigments.

A method for producing the epoxy resins according to the invention is described below. It provides that barium sulfate of the abovementioned particle size <0.5 μm, in particular <0.1 μm, is deagglomerated in a precursor of the hardened epoxy resin. The deagglomeration of the barium sulfate is preferably carried out in the hardener, the epoxy resin not yet mixed with the hardener, or both. By mixing the starting materials, at least one of which contains the disagglomerated, distributed barium sulfate, e.g. B. of resin and hardener, or mixing the barium sulfate-containing component with non-barium sulfate-containing hardener or resin, hardened epoxy resin is produced.

A composite material can be produced by means of the hardened epoxy resin, which contains the hardened epoxy resin. This can be, for example Trade composites that contain fibers such as glass fibers, carbon fibers or aramid fibers in the matrix. They can also be laminates, in which fibers or a fabric are assembled in individual layers in a polymer matrix.

The composites are produced by known methods, for example by wet lamination, by infusion or by means of prepregs.

For example, a mixture of a precursor of the epoxy resin, preferably hardener, and deagglomerated barium sulfate according to the invention is produced with a particle size <0.5 μm, in particular <0.1 μm. The amount of barium sulfate in this mixture is preferably 0.1 to 50% by weight. Dispersant is preferably contained in an amount of 0.5 to 50% by weight.

It is also possible to produce a mixture of hardener-free epoxy resin and deagglomerated barium sulfate with a particle size <0.5 μm, in particular <0.1 μm. Preferred particle sizes of the barium sulfate are given above. The amount of barium sulfate in this mixture is preferably 0.1 to 50% by weight. Dispersant is preferably contained in an amount of 0.5 to 50% by weight.

The composite material can be used as a construction material, for example in boat building, in wind turbines, for pipe construction, for containers, in aircraft construction, in vehicle construction.

It has the advantage that the impact resistance and elongation at break are desirably increased, which is particularly advantageous in the case of laminates since the risk of delamination is reduced.

The following examples are intended to illustrate the invention without restricting its scope.

Examples

Example 1 :

Production of finely divided barium sulfate as an intermediate by precipitation in the presence of crystallization-inhibiting agents General test instructions:

a) Manual test: In a tall 600 ml beaker, 20O ml additive solution (containing 2.3 g citric acid and 7.5 g Melpers ^® 0030) and 50 ml sodium sulfate solution with a concentration of 0.4 mol / l were introduced. The stirring was carried out using an Ultraturrax stirrer as a dispersing aid at 5,000 rpm in the center of the solution. In the suction area of the Ultraturrax, the barium chloride solution (concentration: 0.4 mol / l) was fed in using Dosimat.

b) Plant (V): an apparatus was used as described in WO 01/92157, in which shear, shear and frictional forces act on the reaction mixture; the additive was added to the initial charge of the sulfuric acid solution.

Example 2:

Production of deagglomerated barium sulfate

The barium sulfate prepared according to Example 1 and containing citric acid as the crystallization-inhibiting agent was dried and wet-ground in a bead mill with the addition of a dispersant. A polyether polycarboxylate was used as the dispersant, which was terminally substituted on the polyether groups by hydroxyl groups (Melpers type from SKW, molecular weight approx. 20,000, side chain 5800). Another dispersant that was used was a phosphoric acid ester with a free hydroxy group.

The citric acid-containing barium sulfate which is deagglomerated with the polyether polycarboxylate which is terminally substituted by hydroxyl groups has proven particularly useful for use in epoxy resin. It was found that the deagglomerated product (secondary particle size <80 nm) deagglomerated even further during processing.

Example 3:

Production of barium sulfate by precipitation in the presence of crystallization-inhibiting agents and polymeric dispersants during the precipitation

Barium chloride and sodium sulfate were used as starting materials. 3.1. Beaker experiments:

In a 200 ml volumetric flask, 7.77 g of the polyether polycarboxylate of the Melpers type (Melpers®0030) from SKW, which is substituted by hydroxyl groups, were weighed out and made up to 200 ml with water. This amount corresponded to 50% Melpers (w = 30%) based on the max. resulting amount of BaS0 ₄ (= 4.67 g).

50 ml of a 0.4 m BaCI ₂ solution were placed in a 600 ml high beaker, which was mixed with 200 ml of the Melpers solution. An Ultraturrax immersed in the middle of the beaker as a dispersing aid, which ran at 5,000 rpm. was operated. In the suction area of the Ultraturrax, 50 ml of a 0.4 m Na ₂ S0 ₄ solution were added to the tube using Dosimat, and citric acid was added (50% citric acid based on the maximum BaS0 = 2.33 g per 50 ml / Na ₂ S0 ₄ ), too. Both the BaCI ₂ / Melpers solution and the Na ₂ S0 ₄ / citric acid solution were made alkaline using NaOH before the precipitation; the pH was approx. 11-12.

The barium sulfate obtained in a deagglomerated manner had a primary particle size of about 10 to 20 nm; the secondary particle size was in the same range, so that it was considered to be largely free of agglomerates. It could be used as a filler for the production of curable compositions and for epoxy resins.

3.2. Production of the deagglomerated barium sulfate on a laboratory scale

51 of a 0.4 m BaCI ₂ solution were placed in a 30 I barrel. 780 g of the Melpers product were added with stirring (50% based on the maximum BaS0 ₄ = 467 g). This solution was mixed with 20 i demineralized water. An Ultraturrax was operated in the barrel, in the suction area of which a 5 m solution of 0.4 m Na ₂ SO _{4 was} added via a stainless steel tube using a peristaltic pump. The Na ₂ S0 ₄ solution was previously mixed with citric acid (233 g / 5 I Na ₂ S0 ₄ = 50% citric acid based on the maximum BaS0 _{4 produced} ). As with the beaker experiments, both solutions were made alkaline using NaOH before the precipitation in these experiments. The properties with regard to primary particle size and usability corresponded to those of the barium sulfate from Example 3.1. It was also largely free of agglomerates. 3.3. Production of the deagglomerated barium sulfate with higher-dose reactant concentrations

Example 3.2. was repeated. This time 1 molar solutions were used. The barium sulfate obtained corresponded to that of Example 3.2.

Example 4:

Preparation of a stabilized suspension containing 16% by weight of barium sulfate

An approximately 1% aqueous suspension (colloidal solution) of the deagglomerated barium sulfate prepared according to Example 3.2 was first adjusted to pH 6 with 0.5 N acetic acid. 10% by weight of a 0.5% strength ammonia solution were then added, so that the resulting pH was 10. The preparation was then further concentrated on a rotary evaporator until a solids content of 16% by weight was reached. The solution thus obtained was stable at room temperature for more than a week and could be used for the preparation of curable compositions.

Example 5:

Preparation of a stabilized suspension containing 10% by weight of barium sulfate

Example 4 was repeated analogously, but only up to a content of

Concentrated 10 wt .-% barium sulfate. The suspension was stable for three weeks.

Example 6:

Production of barium sulfate with grinding

6.1. Production of chemically dispersed barium sulfate by precipitation in the presence of crystallization-inhibiting agents and subsequent grinding in the presence of polymeric dispersants

Barium chloride and sodium sulfate were used as starting materials. Barium chloride solution and sodium sulfate solution were reacted in the presence of citric acid as a crystallization inhibitor to precipitate barium sulfate. The precipitated barium sulfate was dried, suspended in isopropanol, and a dispersing agent which was substituted on the polyether groups by hydroxyl groups was used as the dispersant Polyether polycarboxylate (Melpers®0030) added and deagglomerated in a bead mill. The isopropanol was evaporated. The barium sulfate contained about 7.5% by weight of citric acid and about 25% by weight of the polyether polycarboxylate.

6.2. Preparation using different starting compounds and a different crystallization inhibitor

Example 6.1. was repeated. Instead of barium chloride, barium hydroxide solution was used and sulfuric acid was used instead of sodium sulfate. Instead of citric acid, 3% by weight Dispex® N40 (a sodium polyacrylate) was used. Melpers®0030 was used in an amount of 8.5% by weight.

Example 7:

Preparation of the premix containing the deagglomerated barium sulfate chemically dispersed

That according to example 6.2. prepared deagglomerated barium sulfate was suspended in the hardener. A deagglomeration was observed.

Example 8:

Use of the barium sulfate according to the invention in the production of epoxy resin

Deagglomerated barium sulfate, prepared as in Example 6.2. described using citrate and the polyether carboxylate of the Melpers type substituted with hydroxyl groups was used as the spray-dried powder. This powder was found to be easily redispersible in the epoxy resin precursors mentioned below, and even further deagglomeration was observed. It was dispersed in the hardener according to Example 7.

Epilox M730® from Leuna-Harze GmbH was used as the epoxy resin. Epilox M888® was used as the hardener, also from Leuna-Harze GmbH.

The cured epoxy resin consisted of 100 parts by weight of Epilox M730®, 24 parts by weight of Epilox M880® and 31 parts by weight of filler (in Use of the barium sulfate according to the invention including crystallization inhibitor and dispersant)

The filler was dispersed in the resin or hardener.

Test panels for determining the properties were produced, the procedure being as follows:

If a filler-hardener or filler-resin (dispersant) mixture was used, it was prepared in advance as follows:

1. The filler, the filler-hardener (dispersant) mixture or the filler-resin (dispersant) mixture was weighed into a dispersing vessel. The dispersing vessel is a vacuum dissolver with a mechanical stirrer at a very high speed.

2. The dissolver vessel was evacuated to about 0.1 bar absolute pressure.

3. The resin-hardener mixture or the resin was weighed into a receptacle and injected into the vacuum dissolver via a hose with a hose clamp.

4. The mixture in a vacuum dissolver was 5 min. dispersed.

5. If necessary, missing hardener or resin components were then injected.

6. After switching off the dissolver drive, at least 2 min. Waiting time inserted and then the dissolver is aerated.

7. The resin-hardener-filler mixture was taken out and injected into an evacuated, closed plate tool to form a plate with a thickness of 4 mm.

8. Hardening (if necessary with heating)

9. Demolding 0. Heat treatment of the test plate (12 h at 80 ° C). The samples were sawn and examined.

In the tests, the resin without filler addition was referred to as plate # 1. Plate No. 2 was the resin with the addition of 20% Blanc Fixe Brillant®, from Solvay Barium Strontium GmbH. Brillant has an average particle size of approx. 0.8 μm. This filler was dispersed directly into the resin. Plate No. 3 is a resin in which 20% by weight of high-grade barium sulfate was directly dispersed in the resin without the addition of a dispersant. This barium sulfate had an average particle size of 0.15 μm.

Plate No. 4 contained the resin with 20% by weight of ultra-fine barium sulfate which had been chemically dispersed; its preparation and further processing for premixing is described in Examples 7 and 8. This means that the barium sulfate with a particle size in the range of 10 to 30 nm (primary particles) has been previously dispersed in the hardener. The mixture of dispersed barium sulfate and hardener was then mixed in the epoxy resin in a vacuum dissolver as described above.

The test panels were then subjected to the following tests:

1. Tensile test according to DIN EN ISO 527

The test was carried out on shoulder bars with a nominal cross section of 10 x 4 mm ² . The parallel length was 60 mm.

The test was carried out under the boundary conditions according to Table 1:

Table 1: Test parameters tensile test

Table 2: Test results tensile test

2. Bending test according to DIN EN ISO 178

The test was carried out on flat bars with a nominal cross section of 15 x 4 mm ² .

The test was carried out under the boundary conditions according to Table 3.

Table 3: Test parameters bending test

Table 4: Test results bending test

3rd impact bending test according to EN ISO 179 (Charpy notched)

The impact bending test was carried out in the loading directions on the broad and narrow sides on a pendulum impact tester with a span of 62 mm.

Table 5: Results of the broadside impact test

The experiments show that the resin filled with nanofine barium sulfate has better properties than the material filled with the coarser product brilliant. Particularly noteworthy is the high impact resistance of plate 4 with nanofine barium sulfate containing crystallization inhibitor and dispersing agent, which has been dispersed in the hardener beforehand. The impact resistance of this material is even greater than the impact resistance of the unfilled resin. Thus, the barium sulfate according to the invention is not only advantageous in terms of application technology, but it can also impart outstanding properties to the application products.

Examples for the production of a clear lacquer

General:

The surface-modified barium sulfate prepared according to Example 3 was used in a 1% by weight suspension or as a stabilized solution of Example 5.

Example 9:

The production of a condensate (A)

534.63 parts by weight of ethoxypropanol and 59.37 parts by weight of propylglycol were placed in a three-necked flask made of glass, equipped with a stirrer, reflux condenser, gas inlet and two feed vessels. The initial charge was heated to 133 ° C. with nitrogen and with stirring. Subsequently, the first feed consisting of 380.26 parts by weight of glycidyl methacrylate and 664.27 parts by weight of methacryloxypropyltrimethoxysilane and the second feed consisting of 169.64 parts by weight of tert-butyl peroxy-2-ethylhexanoate, 172.64 parts by weight of ethoxypropanol and 19.18 Parts by weight of propylglycol are slowly metered in simultaneously, starting with stirring, to be introduced. The first feed was metered in over two hours and the second feed over five hours. The resulting reaction mixture was postpolymerized for 1.5 hours at 130 ° C. with stirring. The resulting methacrylate copolymer (A ¹ ) had a residual monomer content below the gas chromatographic detection limit.

102.8 parts by weight of the methacrylate copolymer (A ') were mixed with 184.3 parts by weight of isopropanol, 171.3 parts by weight of 2N formic acid and 46.3 parts by weight of deionized water. The resulting reaction mixture was stirred at 70 ° C. for one hour and then 95.4 parts by weight of ethoxypropanol were added. The low-boiling constituents were then distilled off in vacuo at a maximum temperature of 70.degree. Examples 10:

1 to 10.3 and comparative experiment V 1

The production of clear coats 10.1 to 10.3 and V 1 and clear coats 1 to 3 and V 1

The clear coats 10.1 to 10.3 and V 1 were prepared by mixing the constituents listed in Table 1 and homogenizing the resulting mixtures. All four clear coats were transparent and clear, transportable and stable in storage.

The clear coats 10.1 to 10.3 and V 1 were knife-coated on glass panels and thermally cured at 140 ° C. for 22 minutes. For the thermal hardening, convection ovens from Heraeus were used.

High-gloss, clear clearcoats 710.1 to 10.3 and V 1 were obtained which had a very good flow and were free from stress cracks and surface defects such as craters. Their scratch resistance was determined using the steel wool scratch test.

A hammer according to DIN 1041 (weight without handle: 800 g; handle length: 35 cm) was used to carry out the steel wool scratch test. The test panels were stored at room temperature for 24 hours prior to testing.

The flat side of the hammer was covered with a layer of steel wool and attached to the folded-up sides with tape. The hammer was placed on the clear coats at a right angle. The weight of the hammer was guided in a track over the surface of the clear varnish without being jammed and without additional physical strength.

In each test, 10 double strokes were carried out by hand. The steel wool was replaced after each of these individual tests.

After the load, the test areas were cleaned of the steel wool residues with a soft cloth. The test areas were visually evaluated under artificial light and graded as follows: Note damage image

1 not available

2 low

3 moderate

4 moderate to medium

5 strong

6 very strong

The evaluation was carried out immediately after the end of the test. The results can also be found in Table 1.

Table 6: The composition and scratch resistance of clear coats 1 to 3 and VI

a) Barium sulfate nanoparticles with a primary particle size of 20 nm, modified with a polymer with lateral polyoxyethylene groups and carboxylate groups (Melpers®0030 from SKW)

The results substantiate the high scratch resistance of the clearcoats 10.1 to 10.3. It is surprising that the high scratch resistance could be achieved with very small amounts of surface-modified barium sulfate nanoparticles (N) in the order of 0.1 to 0.15% by weight, based on the solid. Example 11:

Clear coat using a stabilized barium sulfate suspension; and comparative experiment V2

11.1: The manufacture of clearcoats 11 and V2 and clearcoats 11 and V2

The clearcoats 11 and V 2 were prepared by mixing the constituents listed in Table 2 and homogenizing the resulting mixtures. The two clear coats were transparent and clear, transportable and stable in storage.

To produce the clearcoats 11 and V2, the 1% by weight solution of the surface-modified barium sulfate nanoparticles (N) (see Table 1) was concentrated in vacuo, so that a 10% by weight solution resulted. The solution was adjusted to pH 6 with 0.5 N acetic acid. Then 10% by weight of a 0.5% ammonia solution was added, so that a pH of 9 resulted. As a result, the concentrated solution was stable in storage at room temperature for a period of more than 4 weeks. Dynamic light scattering (PCS) was used to determine the hydrodynamic volume of the surface-modified barium sulfate nanoparticles (N). The result was a hydrodynamic radius of 24 nm. Taking into account the influence of the surface modification and the hydration shell, the particle size of the actual barium sulfate nanoparticles was 20 nm.

The clear coats 1 1 and V 2 were knife-coated on glass plates and thermally cured at 140 ° C. for 22 minutes. For the thermal hardening, convection ovens from Heraeus were used.

High-gloss, clear clearcoats 11 and V 2 were obtained which had a very good flow and were free from stress cracks and surface defects such as craters. Their scratch resistance was determined with the help of the steel wool scratch test and the relative elastic depth springback (Fischerscope), which correlates very well with the car wash resistance.

The results can also be found in Table 2. They confirm once again that the use of the surface-modified barium sulfate nanoparticles (N) even in wrestle amounts lead to a significant increase in scratch resistance and washability

Table 7 The material composition and scratch resistance of clear coats 11 and V2

Claims

claims

1. Deagglomerated, a dispersant-containing barium sulfate comprising crystallization inhibitor-containing primary particles of an average primary particle size <0.5 μm, preferably <0.1 μm, particularly <80 nm, particularly preferably <50 nm, particularly preferably <20 nm, very particularly preferably <10 nm.

2. Deagglomerated barium sulfate according to claim 1, characterized in that 90% of the barium sulfate secondary particles are smaller than 2 μm, preferably <250 nm, particularly preferably <200 nm, very particularly preferably <130 nm, even more preferably <100 nm, particularly preferably Are <50 nm.

3. Deagglomerated barium sulfate according to claim 1, characterized in that the crystallization inhibitor is selected from compounds which have at least one anionic group.

4. Deagglomerated barium sulfate according to claim 3, characterized in that the crystallization inhibitor as anionic group has at least one sulfate, at least one sulfonate, at least two phosphate, at least two phosphonate or at least two carboxylate groups.

5. Deagglomerated barium sulfate according to claim 1, 2 or 3, characterized in that the crystallization inhibitor corresponds to a compound of formula (I) or a salt thereof with a carbon chain R and n substituents [A (0) OH], wherein R is an organic radical is, which has hydrophobic and / or hydrophilic partial structures, and wherein R is a low molecular weight, oligomeric or polymeric, optionally branched and / or cyclic carbon chain, which optionally contains oxygen, nitrogen, phosphorus or sulfur as heteroatoms, and / or by residues is substituted, which are bonded to the radical R via oxygen, nitrogen, phosphorus or sulfur, and wherein

A means C, P (OH), OP (OH), S (O) or OS (O),

and n is 1 to 10,000, preferably 1 to 5.

6. deagglomerated barium sulfate according to any one of claims 1 to 5, characterized in that the crystallization inhibitor is a carboxylic acid with at least two carboxylate groups and at least one hydroxy group, an alkyl sulfate, an alkylbenzenesulfonate, a polyacrylic acid or an optionally hydroxy-substituted diphosphonic acid.

7. Deagglomerated barium sulfate according to claim 1, characterized in that the dispersant has anionic groups which can interact with the surface of the barium sulfate, preferably carboxylate, phosphate, phosphonate, bisphosphonate, sulfate or sulfonate groups.

8. Deagglomerated barium sulfate according to claim 1, characterized in that the dispersant gives the barium sulfate particles an electrostatic, steric or electrostatic and steric surface which inhibits agglomeration or prevents re-agglomeration.

9. Deagglomerated barium sulfate according to claim 8, characterized in that the dispersant has carboxylate, phosphate, phosphonate, bisphosphonate, sulfate or sulfonate groups which can interact with the barium sulfate surface, and one or more organic radicals R ^ Have the hydrophobic and / or hydrophilic substructures.

10. Deagglomerated barium sulfate according to claim 9, characterized in that R ^{1 is} a low molecular weight, oligomeric or polymeric, optionally branched and / or cyclic carbon chain, which optionally contains oxygen, nitrogen, phosphorus or sulfur as heteroatoms, and / or by residues is substituted, which are bonded to the radical R ¹ via oxygen, nitrogen, phosphorus or sulfur and the carbon chain is optionally substituted by hydrophilic or hydrophobic radicals.

1 1. Deagglomerated barium sulfate according to claim 9, characterized in that the dispersant is a phosphoric diester which has a polyether group and a C6-C10 alkenyl group as partial structures.

12. Deagglomerated barium sulfate according to claims 9 to 11, characterized in that the dispersant has groups for coupling or coupling in polymers.

13. deagglomerated barium sulfate according to claim 1 2, characterized in that the sterically preventing the re-agglomeration dispersant is a polymer which by polar groups, for. B. hydroxyl groups or amino groups, is substituted and thereby the barium sulfate particles are externally hydrophilized.

14. Deagglomerated barium sulfate according to claim 1 3, characterized in that the dispersant has polyether groups substituted by hydroxyl groups or amino groups.

15. Deagglomerated barium sulfate according to claim 14, characterized in that the hydroxy groups and amino groups act as reactive groups for coupling or coupling in polyepoxy resins.

16. deagglomerated, further deagglomeratable barium sulfate according to claim 15, characterized in that the dispersant is a polyether polycarboxylate which is terminally substituted on the polyether groups by hydroxyl groups.

17. Deagglomerated barium sulfate according to one of the preceding claims, characterized in that the crystallization-inhibiting agent and the dispersant in an amount of up to 2 parts by weight per part by weight of barium sulfate, preferably up to 1 part by weight per part by weight of barium sulfate, in particular in an amount of 1 up to 50% by weight is contained in the deagglomerated barium sulfate.

18. Deagglomerated barium sulfate according to one of the preceding claims, characterized in that it is obtainable a) by wet grinding a barium sulfate precipitated using a crystallization inhibitor, the wet grinding being carried out in the presence of the dispersant, with the proviso that the crystallization inhibitor and the dispersant are also the same can be, or b) by precipitation of barium sulfate in the presence of a crystallization inhibitor and a, electrostatically, sterically or electrostatically and sterically dispersing agent which inhibits agglomeration or prevents re-agglomeration.

19. Deagglomerated barium sulfate according to claim 1, characterized in that it is in the form of a suspension in water, in an organic liquid, a mixture of water and organic liquid or as a suspension in a plastic premix, which, if desired, may contain stabilizing additives, preferably acids , especially carboxylic acids, especially acetic acid ..

20. Deagglomerated barium sulfate in the form of a suspension according to claim 19, characterized in that it is in the suspension in an amount of 0.1 to

70 wt .-% is included.

21. Dry powder redispersible to deagglomerated barium sulfate, obtainable by drying deagglomerated barium sulfate according to one of Claims 1 to 20.

22. A process for the preparation of deagglomerated barium sulfate according to claim 1, characterized in that a) precipitated barium sulfate with a primary particle size of <0.5 microns in the presence of a dispersant and water or an organic liquid or a mixture thereof deagglomerated and optionally dried, wherein one starts from barium sulfate which has been precipitated in the presence of a crystallization inhibitor, or b) barium sulfate with a primary particle size of <0.5 μm is precipitated in the presence of a crystallization inhibitor and a dispersant which inhibits agglomeration or prevents reagglomeration, and optionally dries.

23. The method according to claim 22, characterized in that barium sulfate of a primary particle size <0.5 μm, preferably <100 nm, particularly preferably <80 nm, particularly preferably <50 nm, very particularly preferably <20 nm, even more preferably <10 nm falls or is used and the barium sulfate optionally deagglomerates as long as necessary, up to 90% of the secondary particles preferably <1 μm, in particular <250 nm, particularly preferably <200 nm, particularly preferably <130 nm, very particularly preferably <100 nm, more preferably <50 nm are.

24. The method according to claim 22 or 23, characterized in that the deagglomerated barium sulfate is dried and / or, optionally with the addition or removal of water, an organic liquid or a mixture of the two to a suspension which contains water or an optionally water has organic liquid.

25. Plastic premix, preferably for resin systems, containing deagglomerated barium sulfate according to one of claims 1 to 21.

26. Use of deagglomerated barium sulfate according to one of claims 1 to 21 for the production of plastics and adhesives.

27. Plastics and adhesives containing deagglomerated barium sulfate according to one of claims 1 to 21.

28. Curable compositions containing at least one curable component (A) selected from the group consisting of low molecular weight, oligomeric and polymeric compounds, and deagglomerated barium sulfate according to one of claims 1 to 21.

29. As an intermediate, barium sulfate with a medium primary particle size

<50 nm with precipitated crystallization inhibitor, wherein the crystallization inhibitor has at least one sulfate, at least one sulfonate, at least two phosphate, at least two phosphonate or at least two carboxylate groups and corresponds to a compound of formula (I) or a salt thereof

R- [A (0) OH] _n (I),

wherein

R is an organic radical which has hydrophobic and / or hydrophilic partial structures, and where R preferably represents a C1-C20-alkyl group or a C1-C2-alkyl group which is substituted by oxygen, nitrogen, phosphorus or sulfur or by radicals is substituted, which are bonded to the radical R via oxygen, nitrogen, phosphorus or sulfur, and wherein

Means AC, P (OH), OP (OH), S (O) or OS (O), and n is 1 to 10,000, preferably 1 to 5.

30. Barium sulfate according to claim 29, characterized by a particle size of <30 nm, in particular <20 nm, very particularly preferably <10 nm.

31. Barium sulfate according to claim 29, characterized by a BET surface area of at least 30 m ² / g, preferably at least 40 m ² / g, in particular at least 45 m ² / g, very particularly at least 50 m ² / g.

32. barium sulfate according to claim 29 to 31, characterized in that citric acid is precipitated as a crystallization inhibitor.