WO2004005354A1

WO2004005354A1 - Method for producing an aqueous polymer dispersion

Info

Publication number: WO2004005354A1
Application number: PCT/EP2003/006884
Authority: WO
Inventors: Markus Schmid; Mubarik Mahmood Chowdhry; Peter PREISHUBER-PFLÜGL; Xavier Sava; Horst Weiss; Marc Oliver Kristen
Original assignee: Basf Aktiengesellschaft
Priority date: 2002-07-03
Filing date: 2003-06-30
Publication date: 2004-01-15
Also published as: DE10229977A1; AU2003281347A1

Abstract

The invention relates to a method for producing an aqueous polymer dispersion by polymerizing at least one ethylenically unsaturated compound (monomer) using at least one polymerization catalyst and at least one dispersant in an aqueous medium and in the presence of wax particles.

Description

Process for the preparation of an aqueous polymer dispersion

Description 5

The present invention relates to a process for the preparation of an aqueous polymer dispersion by polymerizing at least one ethylenically unsaturated compound (monomer) using at least one polymerization catalyst and at least one dispersant in an aqueous medium, which is characterized in that the polymerization takes place in the presence of wax particles, which contain the at least one polymerization catalyst and have an average particle diameter> 0 and <1000 nm. 15

The invention further relates to the aqueous polymer dispersions obtainable by the process according to the invention and to their use as binders in adhesives, sealants, plastic plasters, paper coating slips and paints. The invention also relates to a method for producing the wax particles containing the polymerization catalysts.

Aqueous polymer dispersions (latices) are generally known. These are fluid systems which contain as disperse phase 25 in aqueous dispersion medium polymer balls consisting of several intertwined polymer chains (so-called polymer particles) in disperse distribution.

The diameter of the polymer particles is often in the range 30 from 10 nm to 5000 nm.

Just like polymer solutions when the solvent is evaporated, aqueous polymer dispersions have the potential to form polymer films when the aqueous dispersion medium is evaporated, which is why they are used in particular as binders. Because of their environmentally friendly properties, they are becoming increasingly important.

Aqueous polymer dispersions are often prepared by free-radically initiated aqueous emulsion polymerization [cf. eg Encyclopedia of Polymer Science and Engineering, Vol. 8, page 659 ff. (1987); DC Blackley, in High Polymer Latices, vol. 1, page 35 ff. (1966); H. Warson, The Applications of Synthetic Resin Emulsions, page 246 ff., Chapter 5 (1972); D. Die- 5 derich, Chemistry in our time 24, pages 135 to 142 (1990); Emulsion Polymerization, Interscience Publishers, New York (1965); DE-A 40 03 422 and dispersions of synthetic high polymer rer, F. Hölscher, Springer-Verlag, Berlin 1969]. It is characteristic of this process that so-called radical formers are used as polymerization catalysts and so-called polar monomers are generally used as main monomers. On the other hand, a large number of polymerization catalysts are known, the polymerization effect of which is based not on radical formation but on a so-called monomer insertion. So-called non-polar monomers are particularly suitable for these polymerization processes. If at all, polar monomers are only used to a minor extent to modify the polymer properties. The polymerization catalysts used for these polymerization processes are, in particular, catalytically active transition metal complexes or transition metal complexes in combination with compounds which activate the transition metal complexes, so-called activators. Due to the generally high sensitivity to hydrolysis of the transition metal complexes or transition metal complex / activator combinations, these polymerization reactions usually take the form of bulk polymerization, the monomer being simultaneously reactant and solvent or in the form of solution polymerization, a nonaqueous, frequently aprotic organic Solvent contains both the transition metal complex or the transition metal complex / activator combination, the monomer and the polymer formed in solution. The documents DE-A 10017660, DE-A 10118633, Leclerc et al. , Appl. Chem., Int. Ed. Engl. 1998 (37) 922, Ziegler, Angew. Chem., 1955 (67) 541, Natta, J. Am. Chem. Soc. 1962 (84) 1488 and Sinn and Kaminsky, Adv. Organomet. Chem. 1980 (18) 99.

Against the background of the prior art, the object of the present invention was to provide a process for the preparation of aqueous polymer dispersions in which non-radical-forming polymerization catalysts or polymerization catalyst / activator combinations are used in an aqueous medium to polymerize monomers to form aqueous polymer dispersions can.

Accordingly, the method defined at the outset was found.

Suitable ethylenically unsaturated monomers according to the invention are both pure hydrocarbon compounds and heteroatom-containing α-olefins, such as (meth) acrylic acid esters and homoallyl or allyl alcohols, ethers or halides. Among the pure hydrocarbons, C ₂ to C ₂ o-l alkenes are suitable. Among these, the low molecular weight olefins, for example ethene or α-olefins with 3 to 20 C atoms, such as propene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, are to be emphasized. Of course, NEN cyclic olefins, for example cyclopentene, cyclohexene, norbornene, aromatic olefin compounds such as styrene or α-methylstyrene or vinyl esters such as vinyl acetate can also be used. However, the C - to C ₂ rj-1-alkenes are particularly suitable. Among these, ethene, propene, 1-butene, 1-pentene, 1-hexene or 1-octene and 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene and 1-octadecene and olefin fractions of a cracker containing them are to be emphasized. It is of course possible according to the invention to use the aforementioned ethylenically unsaturated monomers individually or in a mixture. The monomers mentioned generally form the main monomers which, based on the total amount of monomers, comprise a proportion of> 50% by weight, in particular> 80% by weight or> 90% by weight. The monomer mixture to be polymerized frequently consists of 100% by weight of the aforementioned monomers.

In addition, however, it is also possible to use the abovementioned monomers in a mixture with those ethylenically unsaturated monomers which contain at least one amide group, an acid group and / or their corresponding anion as the structural element. Examples include α, β-monoethylenically unsaturated mono- and dicarboxylic acids and their aids, such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, acrylamide, methacrylamide, and also vinylsulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, Styrene sulfonic acid, 10-undecenoic acid, 3-butenoic acid, 4-pentenoic acid, 5-hexenoic acid and their corresponding alkali metal and ammonium salts. In the normal case, the monomers containing amide or acid groups are only present as modifying monomers in amounts of <50% by weight, <10% by weight, preferably <5% by weight, based in each case on the total amount of monomers.

All those polymerization catalysts which are capable of polymerizing the aforementioned monomers without the formation of radical intermediates are suitable for the process according to the invention. In particular, these polymerization catalysts are catalytically active transition metal complexes or transition metal complexes in combination with so-called activators, which are described, for example, in the documents DE-A 10017660, DE-A 10118633, WO 01/44387, DE-A 19907999, Leclerc et al , , Appl. Chem., Int. Ed. Engl. 1998 (37) 922, Ziegler, Angew. Chem., 1955 (67) 541, Natta, J. Am. Chem. Soc. 1962 (84) 1488, Sinn and Kaminsky, Adv. Organomet. Chem. 1980 (18) 99, Wild et al. , J. Organomet. Chem. 1982 (232) 233 and Mülhaupt, Nachr. Chem. Tech. Lab. 1993 (41) 1341 are listed. Catalytically active transition metal complexes whose transition metal originates from the 4th to 8th subgroup of the periodic table of the elements are particularly preferred. Fe, Co, Ni, Ru, Rh, Pd, Pt and Ti, Zr, Hf, V or Cr complex compounds are often preferred. With loading According to the invention, such transition metal complexes or transition metal complexes are used to particular advantage in combination with activators, as described in DE-A 10017660, DE-A 10118633, WO 01/44387, DE-A 19907999, Leclerc et al. , Appl. Chem., Int. Ed. Engl. 1998 (37) 922, Ziegler, Angew. Chem., 1955 (67) 541, Natta, J. Am. Chem. Soc. 1962 (84) 1488, Sinn and Kaminsky, Adv. Organomet. Chem. 1980 (18) 99, Wild et al. , J. Organomet. Chem. 1982 (232) 233 and Mülhaupt, Nachr. Chem. Tech. Lab. 1993 (41) 1341.

In particular, bis (cyclopentadienyl) zirconium (IV) dichloride, 2,6-bis [1- (2,6-di-isopropylphenylimino) ethyl] pyridine-iron (II) dichloride, 2,3-bis (2,6-di -isopropylphenylimino) butane-nickel (II) dichloride and rac-dimethylsilyl-bis (indenyl) zirconium (IV) dichloride are used for the process according to the invention.

Under wax should in this document [based on the definition of the German Society for Fat Sciences; (DGF standard methods, Department M: Waxes and wax products, Stuttgart 1975, Scientific Publishing Company)] Substances that are understood

Kneadable at 20 ° C, hard to brittle hard, coarse to fine crystalline, translucent to opaque, but not glassy, melt at> 40 ° C without decomposition, melted in the molten state and are non-stringy and have a strongly temperature-dependent consistency and solubility and can be polished under slight pressure.

Waxes differ from chemically similar natural or synthetic products mainly in that they generally change to a molten, low-viscosity state between 50 and 90 ° C (in exceptional cases up to 200 ° C) and are practically free of ash-forming compounds. In addition, waxes form pastes or gels and usually burn with a sooty flame.

Waxes can be roughly divided into natural waxes, chemically modified natural waxes and synthetic waxes based on their origin. The natural waxes are further subdivided into vegetable waxes, such as candelilla wax, carnauba wax, Japanese wax, esparto grass wax, cork wax, guaruma wax, rice oil wax, sugar cane wax or montan wax, animal waxes, such as beeswax, shellac wax, walnut or lanolin, mineral waxes, such as, for example, ceresin or Ozokerite and petrochemical waxes such as petroleum, paraffin waxes or micro waxes. Examples of chemically modified hard waxes are montan ester waxes, sasol waxes or hydrogenated jojoba waxes. The synthetic waxes include polyalkylene waxes, their oxidates and copolymers as well as polyalkylene glycol waxes. A good overview of the different waxes, their preparation and their economic importance as well as the further reading can be found in Ullmann's Encyclopedia of Industrial Chemistry, ^5th Edition Vol. A28, pages 103 to 164, Verlag Chemie, Weinheim.

As a rule, the wax particles containing at least one polymerization catalyst are used in the form of an aqueous wax particle dispersion with wax particles which have an average particle diameter> 0 and <1000 nm. This wax particle dispersion is usually produced by under an inert gas atmosphere, for example under nitrogen or argon

a) wax is heated to a temperature which is higher than the melting temperature of the wax, then b) the polymerization catalyst is introduced into the liquid wax and homogeneously distributed, then c) optionally a compound which activates the polymerization catalyst in the liquid Wax is introduced and distributed homogeneously, then d) the liquid wax containing the polymerization catalyst is stirred into an aqueous medium which contains at least one dispersant and has a temperature which is higher than the melting temperature of the wax, then e) that obtained under d) liquid mixture is subjected to high shear forces with the formation of wax droplets with an average diameter> 0 and <1000 nm, and then f) the reaction mixture is cooled to a temperature which is below the melting point of the wax.

For this purpose, wax is usually placed in a reaction vessel at 20 to 25 ° C. (room temperature) under a dry inert gas atmosphere (relative inert gas humidity <50%, preferably <20% and in particular <10%) and melted with stirring. The polymerization catalyst is introduced into the melted liquid wax and distributed homogeneously. The polymerization catalyst can be both dissolved and dispersed in the liquid wax. It is necessary for the activity of the polymerization catalyst to be increased by adding an activator. This must, which can be the case with catalytically active transition metal complexes, this activator can also be added to the polymerization wax-containing liquid wax and distributed homogeneously.

The selection of the suitable wax depends in particular on the polymerization catalyst used and the activator optionally to be added. The wax should not have any functional chemical groups which react with the polymerization catalyst or the activator and thus can reduce their reactivity or activity. It is also a matter of course that only such polymerization catalysts or activators can be used which are temperature stable and whose reactivities or activities are retained in the molten wax. It follows from the foregoing that only such waxes are used according to the invention which have a low solubility in aqueous medium, in particular 1 1 part by weight, <0.5 part by weight, <0.2 part by weight or < 0.1 parts by weight, based in each case on 100 parts by weight of aqueous medium, formed from the amounts of deionized water and the at least one dispersant. Which waxes are suitable for which polymerization catalyst or activator is known to the person skilled in the art or can be determined by this in a few orienting experiments. In the context of the present invention, paraffin waxes or polyalkylene waxes are preferred. It is important that the organic metal compounds possibly present in the synthetic waxes from their production do not generally have a negative effect on the process according to the invention.

The amount of polymerization catalyst introduced into the wax is in particular dependent on the type and activity of the polymerization catalyst used. The amount of polymerization catalyst is generally such that the amount of metal contained in the polymerization catalyst used

0.000001 to 1 part by weight, often 0.00001 to 0.1 part by weight or 0.00005 to 0.01 part by weight and often 0.0001 to 0.001 part by weight, per 100 parts by weight Parts of wax, is. The amount of optionally used activator depends on the polymerization catalyst used and is usually chosen so that a maximum activity of the polymerization catalyst results. The amount of activator is known to the person skilled in the art, for example by means of an “optimal” polymerization catalyst / activator ratio known from the prior art, or can be determined by the latter in preliminary tests. It is important that the liquid wax containing at least one polymerization catalyst and optionally an activator in homogeneous distribution cools down again to room temperature under solidification, and the solid wax block obtained under inert gas but also under moist ambient air (relative air humidity

> 50%) can be stored for several weeks or months without loss of the polymerization catalyst and / or activator activity.

Usually, however, the liquid wax containing the polymerization catalyst is stirred into an aqueous medium which contains at least one dispersant and has a temperature which is higher than the melting temperature of the wax. As a rule, a wax emulsion is formed as a liquid mixture, the wax droplets of which contain a polymerization catalyst and have an average particle diameter of> 1000 nm up to 100 μm.

The total amount of liquid wax stirred into the aqueous medium and containing the polymerization catalyst is> 0.1 to <20 parts by weight, often> 1 to <15 parts by weight and often

> 5 to <10 parts by weight, based in each case on 100 parts by weight of aqueous medium, formed from the amounts of deionized water and the at least one dispersant.

According to the invention, at least one dispersant is used which keeps both the wax droplets and the polymer particles formed during the polymerization dispersed in the aqueous phase and thus ensures the stability of the aqueous polymer dispersion produced. Both protective colloids and emulsifiers can be considered as dispersants.

Suitable protective colloids are, for example, polyvinyl alcohols, polyalkylene glycols, alkali metal salts of polyacrylic acids and polymethacrylic acids, cellulosic, starch and gelatin derivatives or acrylic acid, methacrylic acid, maleic anhydride, 2-acrylamido-2-methylpropane sulfonate and / or their containing sulfonic acid sulfate and / but also N-vinylpyrrolidone, N-vinylcaprolactam, N-vinylcarbazole, 1-vinylimidazole, 2-vinylimidazole, 2-vinylpyridine, 4-vinylpyridine, acrylamide, methacrylamide, amine group-bearing acrylates, methacrylates, acrylamides and / or methacrylamides containing homo - and copolymers. A detailed description of other suitable protective colloids can be found in Houben-Weyl, Methods of Organic see Chemistry, Volume XIV / 1, Macromolecular Substances, Georg-Thieme-Verlag, Stuttgart, 1961, pages 411 to 420.

Mixtures of emulsifiers and / or 5 protective colloids can of course also be used. Often only emulsifiers are used as dispersants, the relative molecular weights of which, in contrast to the protective colloids, are usually below 1500. They can be of anionic, cationic or nonionic nature. Of course,

10 εen if the use of mixtures of surface-active substances the individual components are compatible with one another, which in case of doubt can be checked by means of a few preliminary tests. In general, anionic emulsifiers are compatible with one another and with nonionic emulsifiers. The same applies

15 also for cationic emulsifiers, whereas anionic and cationic emulsifiers are usually not compatible with one another. An overview of suitable emulsifiers can be found in Houben-Weyl, Methods of Organic Chemistry, Volume XIV / 1, Macromolecular Substances, Georg-Thieme-Verlag, Stuttgart, 1961, pages 192 to 208.

20

Common nonionic emulsifiers are, for example, ethoxylated mono-, di- and tri-alkylphenols (EO degree: 3 to 50, alkyl radical: C to Cχ ₂ ) and ethoxylated fatty alcohols (EO degree: 3 to 80; alkyl radical: Cβ to C ₃₆ ) • Examples of this are the Lutensol® A-

25 brands (Cχ ₂ Cι fatty alcohol ethoxylates, EO grade: 3 to 8), Lutensol® AO brands (Cι ₃ Ci ₅ oxo alcohol ethoxylates, EO grade: 3 to 30), Lutensol® AT brands (C ₁₆ Cι ₈ -Fatty alcohol ethoxylates, EO grade: 11 to 80), Lutensol® ON brands (Cι ₀ -Oxoalcohol ethoxylates, EO grade: 3 to 11) and the Lutensol® TO brands (Cι -Oxoalcohol ethoxylates, E0-

30 degrees: 3 to 20) from BASF AG.

Typical anionic emulsifiers are, for example, alkali metal and ammonium salts of alkyl sulfates (alkyl radical: Cβ to Cχ), of sulfuric acid half-esters of ethoxylated alkanols (EO degree: 4 to 35 50, alkyl radical: Cχ ₂ to Ci ₈ ) and ethoxylated alkylphenols (EO degree: 3 to 50, alkyl radical: C to Cι ₂ ) of alkyl sulfonic acids (alkyl radical: Cι ₂ to Ciβ) and of alkylarylsulfonic acids (alkyl radical: C ₉ to C ₁₈ ).

40 Other anionic emulsifiers are also compounds of the general formula I.

45

S0 ₃ A S0 ₃ B

in which R ¹ and R ^{2 are} H atoms or C ₄ - to C ₂₄ -alkyl and are not simultaneously H atoms, and A and B can be alkali metal ions and / or ammonium ions. In the general formula I, R ¹ and R ^{2 are} preferably linear or branched alkyl radicals having 6 to 18 C atoms, in particular 6, 12 and 16 C atoms or -H, where R ¹ and R ^{2 are} not both H atoms at the same time εind. A and B are preferably sodium, potassium or ammonium, sodium being particularly preferred. Compounds I in which A and B are sodium, R ^{1 is} a branched alkyl radical having 12 C atoms and R ^{2 is} an H atom or R ¹ are particularly advantageous. Technical mixtures are frequently used which have a proportion of 50 to 90% by weight of the monoalkylated product, such as Dowfax 2A1 (brand of the Dow Chemical Company). The compounds I are generally known, for example from US Pat. No. 4,269,749, and are commercially available.

Suitable cationic emulsifiers are usually a Ce to C ~ ₈ alkyl, aralkyl or heterocyclyl-containing primary, secondary, tertiary or quaternary ammonium salts, alkanols lammoniumsalze, pyridinium salts, Imidazoliniumεalze, oxazolinium salts, morpholinium salts, thiazolinium salts εowie of amine oxides, quinolinium salts, isoquinolinium salts, tropylium salts, sulfonium salts and phosphonium salts. Examples include dodecylammonium acetate or the corresponding hydrochloride, the chlorides or acetates of the various 2- (N, N, N-trimethylammonium) ethyl paraffinic acid esters, N-cetylpyridinium chloride, N-laurylpyridinium sulfate and N-cetyl-N, N, N- trimethylammonium bromide, N-dodecyl-N, N, N-trimethylammonium bromide, N-octyl-N, N, N-trimethlyammonium bromide, N, N-distearyl-N, N-dimethylammonium chloride and the gemini surfactant N, N '- ( Lauryldimethyl) ethylenediamine dibromide. Numerous further examples can be found in H. Stche, Tenεid-Taschenbuch, Carl-Hanser-Verlag, Munich, Vienna, 1981 and in McCutcheon'ε, Emulsifiers & Detergents, MC Publishing Company, Glen Rock, 1989.

However, nonionic and / or anionic emulsifiers are particularly suitable. As a rule, a total of 0.05 to 10 parts by weight, frequently 0.1 to 7 parts by weight and often 1 to 5 parts by weight of dispersant, based in each case on 100 parts by weight of aqueous medium, are formed from the amounts of deionized water and the at least one dispersant used.

The wax emulsion usually obtained after the liquid wax wax has been stirred into the aqueous medium, the wax droplets containing the polymerization catalyst having an average particle diameter of> 1000 nm up to 100 μm (macroemulsion) is, according to the invention, exposed to high shear forces until the wax droplets have an average diameter> 0 and <1000 nm (miniemulsion). After the reaction mixture has cooled to a temperature which is below the melting point of the wax, usually to room temperature, the aqueous wax particle dispersion according to the invention is obtained with an average wax particle diameter> 0 and <1000 nm.

The general production of aqueous mini-emulsions from aqueous macroemulsions is known to the person skilled in the art (cf. PL Tang, ED Sudol, CA. Silebi and MS El-Aaεεer in Journal of Applied Polymer Science, Vol. 43, p. 1059 to 1066 [1991 ]).

To this end, in particular high-speed stirrers such as Ultra-Turrax ^® T25 Fa. Janke and Kunkel GmbH & Co. KG, IKA laboratory technology, or high pressure homogenizer can be used. The fine distribution of the components is achieved in these machines by a high local energy input. Two variants have proven particularly useful in this regard.

In the first variant, the aqueous macroemulsion is compressed to over 1000 bar using a piston pump and then expanded through a narrow gap. The effect here is based on an interaction of high shear and pressure gradients and cavitation in the gap. An example of a high pressure homogenizer that works on this principle is the Niro-Soavi high pressure homogenizer type NS1001L Panda.

In the second variant, the compressed aqueous macroemulsion is expanded into a mixing chamber via two oppositely directed nozzles. The fine distribution effect is primarily dependent on the hydrodynamic conditions in the mixing chamber. An example of this type of homogenizer is the microfluidizer type M 120 E from Microfluidicε Corp. In this high-pressure homogenizer, the aqueous macroemulsion is applied to a pressure of up to 1200 atm by means of a pneumatically operated piston pump compressed and relaxed via a so-called "interaction chamber". In the "interaction chamber", the emulsion jet is divided into two jets in a microchannel system, which are brought together at an angle of 180 °. Another example of a homogenizer working according to this type of homogenization is the Nanojet type Expo from Nanojet Engineering GmbH. However, instead of a fixed duct system, two homogenizing valves are installed in the Nanojet, which can be adjusted mechanically.

In addition to the principles explained above, homogenization can e.g. also by using ultrasound (e.g. Branson Sonifier II 450). The fine distribution here is based on cavitation mechanisms. In principle, the devices described in GB-A 22 50 930 and US-A 5,108,654 are also suitable for homogenization by means of ultrasound. The quality of the aqueous miniemulsion generated in the sound field depends not only on the sound power introduced, but also on other factors such as e.g. B. the intensity distribution of the ultrasound in the mixing chamber, the residence time, the temperature and the physical properties of the substances to be emulsified, for example on the toughness, the interfacial tension and the vapor pressure. The resulting droplet size depends, among other things. on the concentration of the dispersant as well as on the energy introduced during the homogenization and is therefore e.g. selectively adjustable by changing the homogenization pressure or the corresponding ultrasonic energy.

The device described in the older German patent application DE 197 56 874 has proven particularly useful for producing the aqueous mini-emulsion from conventional macroemulsions using ultrasound. This is a device which has a reaction space or a flow-through reaction channel and at least one means for transmitting ultrasound waves to the reaction space or the flow-through reaction channel, the means for transmitting ultrasound waves being designed in such a way that the entire reaction space or Flow reaction channel in one section, can be irradiated evenly with ultrasonic waves. For this purpose, the radiation surface of the means for transmitting ultrasound waves is designed such that it essentially corresponds to the surface of the reaction space or, if the reaction space is a partial section of a flow-through reaction channel, extends essentially over the entire width of the channel , and that the essentially to the radiation surface perpendicular depth of the reaction space is less than the maximum depth of action of the ultrasound transmission means.

The term "depth of the reaction space" is understood here to mean essentially the distance between the emitting surface of the ultrasound transmission means and the floor of the reaction space.

Reaction chamber depths of up to 100 mm are preferred. The depth of the reaction space should advantageously be no more than 70 mm and particularly advantageously no more than 50 mm. In principle, the reaction spaces can also have a very small depth, but in view of the lowest possible risk of clogging and easy cleanability and a high product throughput, reaction space depths are preferred, which are considerably larger than, for example, the usual gap heights in high-pressure homogenizers and are usually over 10 mm , The depth of the reaction space can advantageously be changed, for example by means of ultrasound transmission means which are immersed at different depths in the housing.

According to a first embodiment of this device, the radiation area of the means for transmitting ultrasound essentially corresponds to the surface of the reaction space. This embodiment serves to manufacture the mini-emulsions used according to the invention. With this device, ultrasound can act on the entire reaction space. A turbulent flow is generated in the reaction chamber by the axial sound radiation pressure, which causes intensive cross-mixing.

According to a second embodiment, such a device has a flow-through cell. The housing is designed as a flow-through reaction channel, which has an inflow and an outflow, the reaction space being a partial section of the flow-through reaction channel. The width of the channel is the channel extension which is essentially perpendicular to the direction of flow. The radiation area covers the entire width of the flow channel transverse to the flow direction. The length of the radiation surface perpendicular to this width, that is to say the length of the radiation surface in the direction of flow, defines the effective range of the ultrasound. According to an advantageous variant of this second embodiment, the flow-through reaction channel has an essentially rectangular cross section. If a likewise rectangular ultrasound transmission medium with corresponding dimensions is installed in one side of the rectangle, a particularly effective and uniform sound system is guaranteed. Due to the turbulent prevailing in the ultrasonic field Flow conditions, however, a round transmission means can also be used, for example, without disadvantages. In addition, instead of a single ultrasound transmission means, several separate transmission means can be arranged, which are connected in series as seen in the direction of flow. Both the radiation surfaces and the depth of the reaction space, ie the distance between the radiation surface and the bottom of the flow channel, can vary.

Particularly advantageously, the means for transmitting ultrasound waves is designed as a sonotrode, whose end facing away from the free radiation surface is coupled to an ultrasound transducer. The ultrasonic waves can be generated, for example, by using the reverse piezoelectric effect. With the help of generators, high-frequency electrical vibrations (usually in the range from 10 to 100 kHz, preferably between 20 and 40 kHz) are generated, converted into mechanical vibrations of the same frequency by means of a piezoelectric transducer, and coupled into the medium to be insulated with the sonotrode as a transmission element ,

The sonotrode is particularly preferably designed as a rod-shaped, axially radiating λ / 2 (or multiple of λ / 2) longitudinal oscillators. Such a sonotrode can, for example, be fastened in an opening in the housing by means of a flange provided on one of its vibration nodes. The passage of the sonotrode into the housing can thus be made pressure-tight, so that the sonication can also be carried out under increased pressure in the reaction space. The oscillation amplitude of the sonotrode can preferably be regulated, that is to say the respectively set one

Vibration amplitude is checked online and, if necessary, automatically adjusted. The current vibration amplitude can be checked, for example, by a piezoelectric transducer mounted on the sonotrode or a strain gauge with downstream evaluation electronics.

According to a further advantageous embodiment of devices of this type, baffles are provided in the reaction space for improving the flow-through and the mixing behavior. These internals can be, for example, simple baffles or a wide variety of porous bodies.

If necessary, the mixing can also be further intensified by an additional agitator. It is essential that the reaction space is designed for temperature control. According to a preferred embodiment, the wax particles containing the polymerization catalyst are prepared with an average particle diameter> 0 and <1000 nm in an aqueous medium in the presence of the ethylenically unsaturated monomer (s) used for the polymerization reaction. It is particularly advantageous if the actual polymerization reaction also takes place under conditions under which macroemulsions are converted into mini emulsions.

The average size of the wax droplets or wax particles contained in the aqueous medium can be determined according to the principle of quasi-light scattering according to ISO standard 13 321 (the so-called z-average droplet or particle diameter d _{2 of} the unimodal analysis of the autocorrelation function) To play this font, an Autosizer IIC from Malvern Instruments, England was used. The average particle diameter of the wax particles and of the polymer particles was determined by dynamic light scattering on a 0.01% by weight aqueous dispersion at 23 ° C.

According to the invention, the values for d _z determined in this way for the aforementioned wax mini emulsions are normally <700 nm, frequently <500 nm. According to the invention, the d _z range from 100 nm to 400 nm or from 100 nm to 300 nm is favorable. carries d _{z of} the aqueous miniemulsion to be used according to the invention> 40 nm. Corresponding particle diameters also contain the wax particles which contain or contain the polymerization catalyst after cooling to room temperature according to the invention.

It should also be noted that the aqueous wax particle dispersions obtainable according to the invention can be easily dried into redispersible wax powders (e.g. freeze drying or spray drying). This is particularly true when the melting temperature of the wax particles is> 50 ° C, preferably> 60 ° C, particularly preferably> 70 ° C, very particularly preferably> 80 ° C and particularly preferably> 90 ° C.

The process according to the invention for producing an aqueous polymer dispersion by polymerizing at least one ethylenically unsaturated monomer can be carried out in such a way that

a) the wax particles which contain at least one polymerization catalyst or optional polymerization catalyst / activator combination and which have an average particle diameter> 0 and <1000 nm in the presence of at least one Dispersants are initially introduced into the reaction vessel in an aqueous medium at a temperature which is lower than the melting temperature of the wax, then b) at least a portion of the at least one monomer is fed to the reaction vessel, then c) the aqueous reaction mixture is heated to reaction temperature which is higher than is the melting temperature of the wax and then d) the possibly remaining amount of the at least one monomer is fed to the reaction vessel.

The formation of the aqueous dispersion of the wax particles containing the polymerization catalyst required for the preparation of the aqueous polymer dispersion can be carried out in such a way that corresponding wax particle powders are redispersed in an aqueous medium with the aid of at least one dispersant. However, it is also possible to use the aforementioned aqueous wax particle dispersions according to the invention directly.

The total amount of the wax particles contained in the aqueous medium is> 0.1 to <20 parts by weight, often> 1 to <15 parts by weight and often> 5 to <10 parts by weight (calculated as solids), in each case based to 100 parts by weight of aqueous medium, formed from the amounts of deionized water and the at least one dispersant. The amount of dispersant corresponds to the values given for the corresponding aqueous wax particle dispersions.

It is essential that the temperature of the aqueous wax particle dispersion is lower than the melting temperature of the wax used. At this temperature, at least a portion of the at least one monomer is added to the reaction vessel with stirring. The reaction mixture is then heated to a reaction temperature which is higher than the melting temperature of the wax and then the remaining amount, if any, of at least one monomer is fed to the reaction vessel. The polymerization of at least one monomer can take place in the presence or in the absence of an inert gas. To avoid ignitable gas mixtures, however, in particular when using the gaseous monomers ethene, propene, 1-butene, 1-pentene or 1-hexene, the process is carried out under an inert gas atmosphere, for example under nitrogen or argon. The monomers are often fed in such a way that at least one gaseous monomer is fed to the reaction vessel at room temperature under a certain pressure, and the aqueous wax particle dispersion is then stirred up to the reaction temperature. heats and the pressure of the at least one monomer is kept constant during the polymerization reaction in the reaction vessel. Depending on the monomers used, the reaction pressure can range from 1 bar (absolute) to 1000 bar. The reaction temperature is strongly dependent on the wax melting point of the wax particles used and the activity of the polymerization catalyst or the polymerization catalyst / activator combination. Usually it is in the range of> 40 to 200 ° C, often 50 to 150 ° C and often 50 to 100 ° C or 60 to 90 ° C.

The aqueous polymer dispersion can, however, also be prepared by presenting deionized water at room temperature, at least one dispersant and the required amount of the wax containing the polymerization catalyst or polymerization catalyst / activator combination, followed by the mixture under the conditions for production a miniemulsion (for example high-speed stirrer) mixed with at least one ethylenically unsaturated monomer, heated to the reaction temperature and left with the supply of further ethylenically unsaturated monomers until the end of the reaction at this temperature.

So-called regulators known to the person skilled in the art, such as, for example, hydrogen or triphenylphosphine, can be added to regulate the average polymer molecular weight. The regulator amounts are in the range from 0.01 to 10 parts by weight and often from 0.1 to 1 part by weight, in each case based on 100 parts by weight of aqueous medium, formed from the amounts of deionized water and the at least one dispersant.

The polymerization is generally ended by cooling the reaction mixture to room temperature. Unreacted monomer is usually removed from the aqueous polymer dispersion by decompression, phase separation, water vapor or inert gas stripping or distillation.

The aqueous polymer dispersions accessible according to the invention have polymer content of 0.1 to 60% by weight, often 1 to 55% by weight and often 5 to 50% by weight, based in each case on the total amount of the aqueous polymer dispersion.

The average particle sizes (ISO standard 13 321), likewise determined by quasi-dynamic light scattering, of the polymer particles (polymer / wax) obtained in the aqueous polymer dispersions obtained are usually in the range Range from 50 to 2000 nm, often from 100 to 1000 nm and often from 150 to 700 nm.

Polymer particles whose minimum film-forming temperatures are MFT are also accessible by the process according to the invention

<100 ° C, often <60 ° C and often <20 ° C. The MFT determination can be carried out in accordance with DIN 53 787 using a film image bank (= metal plate to which a temperature gradient is applied), usually with a wet layer thickness of 1 mm. The MFT is the temperature at which the polymer film begins to crack.

The aqueous polymer dispersions accessible according to the invention are particularly suitable as binders in adhesives, sealants, plastic plasters, paper coating slips and paints.

The process according to the invention makes aqueous polymer dispersions accessible in aqueous medium by direct polymerization of monomers with polymerization catalysts which do not form free radicals, frequently hydrolysis-labile catalytically active transition metal complexes or transition metal complex / activator combinations, and thus have process engineering advantages over indirect secondary dispersion processes (for example preparation of a solution polymer / introduction of the polymer Solvent mixture in the aqueous dispersion medium and removal of the organic solvent). Due to the presence of wax / polymer mixtures, the aqueous polymer dispersions accessible according to the invention usually have novel product properties, which is why they can be used in particular as binders in adhesives, sealants, plastic plasters, paper coating slips and paints.

The invention is illustrated by the following non-limiting examples.

example

analytics

The average particle diameter of the wax particles and the polymer particles (TG) was determined by dynamic light scattering on a 0.01% by weight aqueous dispersion at 23 ° C. using an Autosizer IIC from Malvern Instruments, England. The average diameter of the cumulative Evaluation (cumulative z-average) of the measured autocorrelation function (ISO standard 13321).

The polymer solids content (FG) was determined by drying an aliquot in the drying cabinet at 140 ° C. for 6 hours. Two separate measurements were carried out. The specified value represents the average of the two measurement results.

The weight-average or number-average molecular weights (M _w ) or (M _n ) were determined by means of gel permeation chromatography in accordance with DIN 55672.

The melting point (T _m ) of the polyolefin formed was determined by the DSC method (differential scanning calometry, 20 K / min, idpoint measurement, DIN 53765).

Metal complexes used

Ml: bis (cyclopentadienyl) zirconium (IV) dichloride; Strem Chemicals Inc .; Kehl, Germany

M2: 2,6-bis [1- (2,6-di-isopropylphenylimino) ethyl] pyridine-iron (II) dichloride; Synthesis analogous to Small et al. , J. Am. Chem. Soc. 1998 (120) 4049

M3: 2,3-bis (2,6-di-isopropylphenylimino) butane-nickel (II) dichloride; Syntheεe analog Johnson et al. , J. Am. Chem. Soc. 1995 (117) 6414

M4: rac-dimethyl-silyl-bis (indenyl) zirconium (IV) dichloride; Strem Chemicals Inc .; Kehl, Germany

Production of the catalyst / wax mixture

In a Schlenk tube, 5 g of Rubitherm RT 40 (paraffin wax; Rubitherm GmbH, Hamburg, Germany) were heated to 50 ° C. with argon protective gas and stirred with a magnetic stirrer. First 10 mg of one of the aforementioned metal complexes Ml, M2, M3 or M4 and then 5 g of a 10% strength by weight solution of methylaluminoxane in toluene (Aldrich-Chemie GmbH, Co. KG, Steinheim, Germany) were added to the stirred liquid wax. metered. This mixture was stirred for a further 5 minutes at 50 ° C. and then cooled to room temperature (storage in an air atmosphere possible for several weeks and months). Polymerization reaction using the aforementioned catalyst / wax mixture containing Ml, M2, M3 or M4.

30 g of a 2% strength by weight solution of Na-dodecylbenzenesulfonate in deionized water were placed in a Schlenk tube at room temperature and then 2.0 g of one of the solid catalyst / wax mixtures prepared beforehand, containing Ml, M2, M3 or M4 , admitted. The aqueous mixture obtained was heated to 55 ° C. and homogenized with a high-speed stirrer (10,000 revolutions per minute; Ultra-Turrax® T25 from Janke and Kunkel GmbH & Co. KG, IKA-Labortechnik, Stauten, Germany), with liquid wax particles with an average particle size <1000 nm were obtained. Already during the heating and the homogenization phase, ethene or propene was introduced into the aqueous mixture with a dip tube and passed through the aqueous mixture, the pressure above the aqueous mixture being kept at atmospheric pressure. 60 minutes after the reaction temperature of 55 ° C. had been reached, the ethene or propene feed was interrupted, the high-speed stirrer was switched off and the aqueous polymer dispersion formed was cooled to room temperature. The aqueous polymer dispersions formed were characterized; the results are given in the following table:

Metal complex olefin obtained aqueous polymer dispersion

TG FG T _m M _w M _n nm% by weight ° C kσ / mol kσ / mol

Ml Ethen 220 20 130 76 25 M2 Ethen 250 23 112 50 17 M3 Ethen 200 19 140 89 11 M4 Proüen 230 22 160 45 10

Claims

claims

1. A process for the preparation of an aqueous polymer dispersion by polymerizing at least one ethylenically unsaturated compound (monomer) using at least one polymerization catalyst and at least one dispersant in an aqueous medium, characterized in that the polymerization takes place in the presence of wax particles which cause the at least one polymerization - Contain lyεator and have an average particle diameter> 0 and <1000 nm.

2. The method according to claim 1, characterized in that the at least one polymerization catalyst is a catalytically active transition metal complex.

3. The method according to claim 2, characterized in that the wax particles additionally contain at least one compound which activates the catalytically active transition metal complex (activator).

4. The method according to any one of claims 1 to 3, characterized in that the polymerization takes place at a temperature which is higher than the melting temperature of the wax.

5. The method according to any one of claims 1 to 4, characterized in that

a) the wax particles in the presence of at least one

Dispersant in aqueous medium in the reaction vessel, then b) at least a portion of at least one monomer is fed to the reaction vessel, then c) the aqueous reaction mixture is heated to the reaction temperature and then d) the remaining amount of the at least one monomer, if any, is added to the reaction vessel ,

6. The method according to any one of claims 1 to 5, characterized in that the total amount of the wax particles is <20 parts by weight based on 100 parts by weight of aqueous medium, formed from the amounts of deionized water and the at least one dispersant ,

7. The method according to any one of claims 1 to 6, characterized in that the wax particles are used in the form of an aqueous wax particle dispersion.

8. Aqueous polymer dispersion, produced by a process according to one of claims 1 to 7.

9. Use of a polymer dispersion according to claim 8 as a binder in adhesives, sealants, plastic plasters, paper coating slips and paints.

10. A process for producing an aqueous wax particle dispersion with wax particles which contain at least one polymerization catalyst and have an average particle diameter> 0 and <1000 nm, characterized in that under an inert gas atmosphere

a) wax is heated to a temperature which is higher than the melting temperature of the wax, then b) the polymerization catalyst is introduced into the liquid wax and homogeneously distributed, then c) optionally a compound which activates the polymerization catalyst into the liquid Wax is introduced and homogeneously distributed, then d) the liquid wax containing the polymerization catalyst is stirred into an aqueous medium which contains at least one dispersant and has a temperature which is higher than the melting temperature of the wax, then e) that obtained under d) liquid mixture is exposed to high shear forces with the formation of wax droplets with an average diameter> 0 and <1000 nm, and then f) the reaction mixture is cooled to a temperature which is below the melting point of the wax.

11. wax particle powder obtainable from an aqueous wax particle dispersion according to claim 10.