DE19957351A1 - Monomer-free reactive polyurethane adhesive or sealant composition, e.g. for use as a hot melt, obtained by reacting polyol with high-mol. wt. di-isocyanate with a low monomer content - Google Patents

Abstract

Reactive polyurethane adhesive/sealant compositions based on reaction products of polyols (I) and high-mol. wt. di-isocyanates (II) obtained by reaction of diols with a number-average mol. wt. of below 2000 (III) with monomeric di-isocyanates with a mol. wt. of below 500 (IV), in which (II) contains not more than 10 wt% monomer (IV) before reaction with (I). Independent claims are also included for: (i) a method for the production of these polyurethane compositions (PUR) by: (a) reacting diol (III) with excess di-isocyanate (IV) to form high-mol. wt. di-isocyanate (II); (b) optionally precipitating (II) by adding a non-solvent; (c) removing unreacted (IV) by filtration or centrifuging; and (d) reacting (II) with polyol (I) to give an isocyanate-terminated reactive prepolymer; (ii) an alternative method in which excess monomer (IV) is removed by distillation after stage (a); (iii) an alternative method in which excess (IV) is removed by selective extraction after stage (a); (iv) a method for the production of a polyurethane adhesive composition from the PUR by adding (during formulation of the adhesive composition) an adhesion-enhancing polyisocyanate (V) which is capable of migration.

Description

The present invention relates to compositions based on polyols and high molecular diisocyanates with a low content of monomers Diisocyanates, as well as their preparation and their use as binders for reactive one or two component adhesives / sealants, reactive hot melt adhesives or solvent-based polyurethane adhesives.

Reactive polyurethane adhesives / sealants, especially one-component moisture-curing systems, usually contain at room temperature liquid polymers with urethane groups, possibly urea groups and reactive Isocyanate groups. These compositions are suitable for many applications Solvent-free and very highly viscous and / or pasty, they will be Room temperature or at a slightly elevated temperature between about 50 ° C and processed about 100 ° C.

Reactive, one-component, moisture-curing polyurethane hot melt adhesives are moisture-curing or moisture-curing adhesives that are used in Are solid at room temperature and applied in the form of their melt as an adhesive be, and their polymeric components urethane groups and reactive Contain isocyanate groups. By cooling this melt after the The substrate parts to be joined are first applied and joined rapid physical setting of the hot melt adhesive through its solidification. This is followed by a chemical reaction of those that are still present Isocyanate groups with moisture from the environment become a cross-linked infusible adhesive. Reactive hot melt adhesives based on Isocyanate-terminated polyurethane prepolymers are e.g. B. with H. F. Huber and  H. Müller in "Shaping Reactive Hotmelts Using LMW Copolyesters", Adhesives Age, November 1987, pages 32 to 35.

Laminating adhesives can either have a structure similar to that of reactive ones Hot melt adhesives or they are as one-component systems out of solution applied in organic solvents, another embodiment exists from two-component solvent-containing or solvent-free systems, in which the polymeric components of one component are urethane groups as well as reactive isocyanate groups and, in the two-component systems, the second component contains polymers or Oligomers with hydroxyl groups, amino groups, epoxy groups and / or Carboxyl groups. With these two-component systems, the Isocyanate group-containing component and the second component immediately mixed before application, usually with the help of a mixing and Dosing system.

Reactive polyurethane adhesives / sealants are characterized by a very high level Performance profile. Therefore, new ones have been increasingly available in recent years Applications for these adhesives / sealants can be developed.

Compositions for such adhesives and / or sealants are already out known to many patent applications and other publications.

In addition to many advantages, these polyurethane compositions also have some systemic disadvantages. One of the most serious disadvantages is that Residual monomer content of isocyanates, especially the more volatile diisocyanates. Adhesives / sealants and in particular the melt adhesives are increased with Temperature processed. The hot melt adhesives are, for example, between 100 ° C and 200 ° C processed, laminating adhesives between room temperature and 150 ° C. Volatile isocyanates such as TDI or IPDI already show at room temperature a not negligible vapor pressure. This noticeable vapor pressure is particularly serious in the case of a spray application, since it does so significant amounts of isocyanate vapors occur above the application object who are toxic because of their irritating and sensitizing effects.  

Therefore, protective measures to prevent health damage for the persons responsible for processing are seized. This Measures such as B. the obligation to monitor compliance with the maximum Concentration in the workplace is complex. In particular suction measures the fumes at the point of origin and exit are very expensive and also hinder some application processes, such as spraying in particular of reactive polyurethane adhesives / sealants.

The development of reactive is therefore necessary for the fields of application mentioned Polyurethane compositions with a drastically reduced proportion of monomeric diisocyanates highly desirable since the latter in part it is only possible to use them in many applications in which the use of the occupational hygiene problems explained above was not possible until now.

According to the Schulz-Flory statistics, is involved in the implementation of diisocyanates Isocyanate groups of approximately the same reactivity with hydroxyl groups Compounds the remaining content of monomeric diisocyanate in the Reaction product of the NCO / OH ratio of the reactants in the prepolymer Synthesis dependent. At an NCQ / OH ratio of 2, as is common for the Prepolymer composition is necessary, about 25% of the remaining monomeric diisocyanates used as a monomer in the prepolymer. Become at a prepolymer synthesis z. B. 10 wt .-% diphenylmethane diisocyanate (MDI) an NCO / OH ratio of 2 is used, it is found in agreement with the above-mentioned statistical estimate in the order of magnitude about 2% by weight monomeric MDI in prepolymers. At 150 ° C the pure MDI already has a vapor pressure of 0.8 mbar, in compositions this vapor pressure is Although lower according to Raoult's law, it is still above the hygienically safe area. Among the above described application conditions, especially for a large area Application as a hot melt adhesive in a thin layer, so get considerable Amounts of residual monomer in the airspace above and must be removed by suction. A significant reduction in the Monomer content by a power of ten by reducing the NCO / OH  Relationship is usually not feasible in practice because that average molecular weight would then increase exponentially and that resulting polyurethane compositions extremely high viscosity would and could no longer be processed. In practice, therefore hence other approaches to prepolymer synthesis. For example synthesized with a sufficiently high NCO / OH ratio and that monomeric diisocyanate after prepolymerization in a second step removed, for example by distilling off the unreacted monomeric diisocyanates in a vacuum or by subsequent chemical binding of the monomeric diisocyanate. This is how EP-A- 316738 a process for the production of urethane groups Polyisocyanates with a starting diisocyanate free of urethane groups a maximum of 0.4% by weight by reacting aromatic diisocyanates with polyhydric alcohols and subsequent removal of the unreacted, excess starting diisocyanate, the distillative removal of the excess starting diisocyanate in the presence of an isocyanate group having aliphatic polyisocyanate is carried out.

EP-A-0393903 describes a process for the preparation of prepolymers, in which in a first step monomeric diisocyanate with a polyol is implemented. Then a catalyst in sufficient quantity added so that a significant part of the remaining isocyanate functionality in Allophanat functionality is transferred. After reaching the theoretical NCO content is the reaction by rapid cooling and addition of Stopped salicylic acid.

WO-95/06124 describes polyurethane compositions with a low proportion of monomeric diisocyanates by the reaction of polyols with trifunctional isocyanates and possibly addition of monofunctional Chain breakers are manufactured. The disadvantage of this method is that low availability of trifunctional, low molecular weight isocyanates, especially the trifunctional homologues of diphenylmethane diisocyanate are not commercially available in pure form.  

The work of V. A. Kudishina and E. F. Morgunova, Sin. Fiz.-Khim. Polim. (1970), No. 7, 125-129 are cold-curing polyurethane adhesives based on hydroxy-functional polyesters or polyethers and isocyanate-containing hardeners described. The isocyanate-containing hardeners are Reaction products of toluene diisocyanate (TDI) or diphenylmethane diisocyanates (MDI) ethylene glycol or glycerin. It is stated that this Hardener components to significantly reduce the toxicity of the Adhesives, although this still contains 1.7% isocyanate in the airspace the corresponding test chamber. Such Workplace concentrations of isocyanates are according to today's Industrial hygiene standards no longer apply in western industrialized countries tolerable.

Despite the aforementioned prior art, there is still a need improved polyurethane compositions with a low proportion of monomeric diisocyanates that are suitable for use as adhesives / sealants, particularly suitable for reactive hot melt adhesives. In particular, the raw materials used are easily and inexpensively accessible and easy to grasp.

The achievement of the task is according to the claims remove. It essentially consists in the provision of Reaction products made from polyols and high-molecular diisocyanates.

High molecular weight diisocyanates in the sense of this invention are such Diisocyanates made by reacting diols with a molecular weight smaller than 1000 with monomeric diisocyanates with a molecular weight less than 500 will be obtained. The high molecular weight diisocyanates are said to be Reaction with one or more polyols at most 10 mol% of monomers Contain diisocyanate based on the high molecular weight diisocyanate.  

Another object of the present invention is a method for Production of such reaction products from polyols and high molecular weight Diisocyanates. In a first step, the diol component with a Molecular weight less than 1000 with a large stoichiometric excess of monomeric diisocyanate with a molecular weight less than 500 to one high molecular diisocyanate implemented. After this implementation, if necessary Add a non-solvent, the high molecular weight diisocyanate from the Reaction mixture precipitated and not by filtration or centrifugation implemented diisocyanate freed. In a subsequent second step implemented this high molecular weight diisocyanate with a polyol, so that a reactive prepolymer with isocyanate end groups is formed, which is a very low Content of monomeric diisocyanates with a molecular weight less than 500 having.

Another method of making such compositions is in that after the first writing the implementation of the diol component with the monomeric diisocyanate, the excess monomeric diisocyanate by distillation the reaction mixture is removed or by selective extraction from the Reaction mixture is removed and then also in a second step this high molecular diisocyanate with a polyol to a reactive Prepolymer with isocyanate end groups is implemented.

For the purposes of this invention, monomeric diisocyanates are aromatic, aliphatic or cycloaliphatic diisocyanates whose molecular weight is less than 500. Examples of suitable aromatic diisocyanates are all isomers of tolylene diisocyanate (TDI) either in isomerically pure form or as a mixture of several isomers, naphthalene-1,5-diisocyanate (NDI), naphthalene-1,4-diisocyanate (NDI) and diphenylmethane-4,4 'diisocyanate (MDI), diphenylmethane-2,4'-diisocyanate and mixtures of 4,4'-diphenylmethane diisocyanate with the 2,4'-isomer, xylylene diisocyanate (XDI), 4,4'-diphenyldimethylmethane diisocyanate, di- and tetraalkyl diphenylmethane diisocyanate, 4,4'-di benzyl diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate. Examples of suitable cycloaliphatic diisocyanates are the hydrogenation products of the aforementioned aromatic diisocyanates such as. B. the 4,4'-dicyclohexylmethane diisocyanate (H ₁₂ MDI), 1-isocyanatomethyl-3-isocyanato-1,5,5-trimethyl-cyclohexane (isophorone diisocyanate, IPDI), cyclohexane-1,4-diisocyanate, hydrogenated xylylene diisocyanate (H ₆ XDI), 1-methyl-2,4-diisocyanatocyclohexane, m- or p-tetramethylxylene diisocyanate (m-TMXDI, p-TMXDI) and dimer fatty acid diisocyanate. Examples of aliphatic diisocyanates are tetramethoxybutane-1,4-diisocyanate, butane-1,4-diisocyanate, hexane-1,6-diisocyanate (HDI), 1,6-diisocyanato-2,2,4-trimethylhexane, 1,6- Diisocyanato-2,4,4-trimethylhexane, lysine diisocyanate and 1,12-dodecane diisocyanate (C ₁₂ DI).

These monomeric diisocyanates are used in a first reaction step low molecular weight diols converted to high molecular weight diisocyanates. The diols used for this have a molecular weight of less than 1000. In principle, all linear or weakly branched C2-C18- Alkanediols can be used. Furthermore, the low molecular weight polyethers are used as well as low molecular weight alkoxylation products from aromatic dihydroxy compounds (diphenols).

Specific examples of the diols to be used according to the invention are Ethylene glycol, 1,2-propanediol, 1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 2- Methyl propanediol, 1,6-hexanediol, 2,4,4-trimethylhexanediol-1,6, 2,2,4- Trimethylhexanedioi-1,6, 1,4-cyclohexanedimethanol, diethylene glycol, Triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, Tetrapropyfenglycol, poly (oxytetramethylene) glycol with a molecular weight up to to 650, alkoxylation products of bisphenol A, alkoxylation products of Bisphenols F, the isomeric dihydroxyanthracenes, the isomeric Dihydroxynaphthalenes, catechol, resorcinol, hydroquinone with up to 8 alkoxy units per aromatic hydroxy group or mixtures of the aforementioned diols.

The reaction of the monomeric diisocyanates with the diols takes place in known manner, possibly with the addition of aprotic solvents. To the Avoiding the formation of higher oligomers is expedient for this high stoichiometric excess of diisocyanates in relation to the  Diols used applied. Possibly. can be known catalysts to accelerate the reaction between the isocyanate group and the Alcohol group can be used. The reaction and the stoichiometric ratio of monomeric diisocyanate and diol chosen be that as far as possible a 2: 1 adduct of monomeric diisocyanate and diol is formed and the formation of higher oligomers is largely suppressed becomes.

After the reaction has ended, the reaction product becomes as large as possible freed from monomeric diisocyanate, the high molecular weight thus formed For the purposes of this invention, diisocyanate should have a maximum of 10 mol% of monomer Diisocyanate, based on the high molecular weight diisocyanate. The Cleaning step can be carried out according to methods known per se. In the Use of lower alkanediols has proven to be of low solubility the high molecular weight diisocyanate in some solvents, in which after the completion of the diol / diisocyanate reaction is a non-solvent for the high molecular diisocyanate is added, which is also a solvent for the is monomeric diisocyanate. As a result, the high molecular weight diisocyanate is formed the reaction mixture precipitated and by filtration or by centrifugation freed from unreacted monomeric diisocyanate. This procedure is especially applicable when the more volatile monomers Diisocyanates such as the MDI are to be used.

Non-solvents are in particular non-polar aprotic organic solvents such as B. ethyl acetate, chlorobenzene, xylenes, toluene, or in particular Border gasoline.

When using volatile monomeric diisocyanates such. B. TDI, TMXDI, IPDI, XDI can also distill the excess monomeric diisocyanate be removed from the reaction mixture. The distillation is carried out for this purpose preferably in vacuo using a thin film evaporator or Thin film evaporator. Such distillation processes are e.g. B. in plastic  Handbook Volume 7, "Polyurethanes", G. W. Becker (Editor), Hanser-Verlag, Munich, 3rd edition 1993, page 425.

Another way of removing the monomeric diisocyanate from the The reaction mixture is the selective extraction of the monomeric diisocyanate, for example using supercritical carbon dioxide or others supercritical aprotic solvents. This extraction process is known for example from WO-97/46603.

The monomer-free or low-monomer high molecular weight thus produced In a second reaction step, diisocyanate is added in a manner known per se Polyofen converted to prepolymers. The NCO / OH ratio is 1.2: 1-5: 1. Since the high molecular weight diisocyanate is already largely is free of monomers, higher NCO / OH Ratios up to 10: 1 can be used.

A large number of higher molecular weight polyols can be used Polyhydroxy compounds are used. Are suitable as polyols preferably the glassy solid amorphous or liquid at room temperature crystalline polyhydroxy compounds with two or three hydroxyl groups per Molecule in the molecular weight range from 400 to 20,000, preferably in Range from 1000 to 6000. Examples are di- and / or trifunctional Polypropylene glycols, statistical and / or block copolymers of the Ethylene oxide and propylene oxide can be used. Another group of polyethers which are preferably used are the polytetramethylene glycols (Poly (oxytetramethylene) glycol, poly-THF), e.g. B. by acidic polymerization of tetrahydrofuran, the molecular weight is Range of polytetramethylene glycols between 600 and 6000, preferably in Range from 800 to 5000.

Furthermore, the liquid, glassy amorphous or crystalline are polyols Suitable polyester, which by condensation of di- or tricarboxylic acids, such as e.g. B. adipic acid, sebacic acid, glutaric acid, azelaic acid, suberic acid, Undecanedioic acid, dodecanedioic acid, 3,3-dimethylglutaric acid, terephthalic acid,  Isophthalic acid, hexahydrophthalic acid, dimer fatty acid or mixtures thereof with low molecular weight diols or triols such. B. ethylene glycol, propylene glycol, Diethylene glycol, triethylene glycol, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol, dimer fatty alcohol, glycerin, Trimethylolpropane or mixtures thereof can be produced.

Another group of the polyols to be used according to the invention are Polyester based on ε-caprolactone, also called "polycaprolactone". However, polyester polyols of oleochemical origin can also be used become. Such polyester polyols can, for example, by complete Ring opening of epoxidized triglycerides of an at least partially olefinic unsaturated fatty acid-containing fat mixture with one or more Alcohols with 1 to 12 carbon atoms and subsequent partial transesterification of the Triglyceride derivatives to alkyl ester polyols with 1 to 12 carbon atoms in the alkyl radical getting produced. Other suitable polyols are polycarbonate polyols and Dimer diols (from Henkel) as well as castor oil and its derivatives. Even the hydroxy functional polybutadienes such as z. B. under the trade name "Poly-bd" are available for the compositions according to the invention as Polyols are used.

Also suitable as polyols are linear and / or weakly branched acrylic ester Copolymer polyols, for example, by radical copolymerization of acrylic acid esters or methacrylic acid esters with hydroxy functional groups Acrylic acid and / or methacrylic acid compounds such as Hydroxyethyl (meth) acrylate or hydroxypropyl (meth) acrylate can be produced can. Because of this method of preparation, the hydroxyl groups are with them Polyols are usually distributed statistically, so that this is either linear or slightly branched polyols with an average OH Functionality. Although for the polyols the difunctional compounds are preferred, can also, at least in minor amounts, higher functional polyols are used.

The selection of the polyol or polyols depends on the Use of this adhesive / sealant composition. With highly viscous  or pasty liquid adhesives / sealants are preferably at least predominantly liquid polyols used. With two-component adhesives / sealants the one component can be a prepolymer with reactive Isocyanate end groups from the polyols contain and the second component a hydroxy-functional polyol or hydroxy-functional polyurethane. It can but also the high-molecular diisocyanate as a hardener for a hydroxy-functional one Component are used, the hydroxy-functional component either one or more of the aforementioned polyols or one contains hydroxyl-containing polyurethane prepolymer.

When using the polyurethane compositions according to the invention the polyol components are selected as reactive hot-melt adhesives, that the composition is solid at room temperature. On the one hand, this can happen that solid amorphous and / or solid crystalline Polyhydroxy compounds can be used, but it can also do so happen that a significant proportion of short chain polyhydroxy compounds is used because of the high concentration of urethane groups these compositions are also solid at room temperature. Selection criteria for the polyols can be found e.g. B. in the aforementioned article by H. F. Huber and H. Müller.

The compositions according to the invention can optionally additionally Contain catalysts that prevent the formation of the polyurethane prepolymer Accelerate production and / or moisture crosslinking after Accelerate application of the adhesive / sealant. As according to the invention usable catalysts are suitable for. B. the organometallic compounds of tin, iron, titanium or bismuth such as tin (II) salts of carboxylic acids, e.g. B. Tin II acetate, ethylhexoate and diethylhexoate can be used. Another The class of compounds are the dialkyltin (IV) carboxylates. The carboxylic acids have 2, preferably at least 10, in particular 14 to 32 carbon atoms. It dicarboxylic acids can also be used. As acids are express called: adipic acid, maleic acid, fumaric acid, malonic acid, succinic acid, Pimelic acid, terephthalic acid, phenylacetic acid, benzoic acid, acetic acid,  Propionic acid and 2-ethylhexane, caprylic, capric, lauric, myristic, palmitic and stearic acid. Specific compounds are dibutyl and dioctyl tin diacetate, -maleate, -bis- (2-ethylhexoate), -dilaurate, tributyltin acetate, bis (β-methoxycarbonyl ethyl) tin dilaurate and bis (β-acetyl-ethyl) tin dilaurate.

Tin oxides and sulfides and thiolates can also be used. Specific compounds are: bis (tributyltin) oxide, bis (trioctyltin) oxide, dibutyl and diocytyltin bis (2-ethylhexyl thiolate) dibutyl and dioctyltin didodecyl thiolate, bis (β methoxycarbonyl-ethyl) tin dididodecyl thiolate, bis (β-acetyl) tin bis (2-ethyl hexylthiolate), dibutyl and dioctyltin didodecyl thiolate, butyl and octyltin tris (thioglycolic acid 2-ethylhexoate), dibutyl and dioctyltin bis (thioglycolic acid 2-ethylhexoate), tributyl- and di-tri-benzoic acid ethylhexoate) as well as butyl and octyltin tris (thioethylene glycol 2-ethylhexoate), dibutyl and dioctyltin bis (thioethylene glycol 2-ethylhexoate), tributyl and trioctyltin (thioethylene glycol 2-ethylhexoate) with the general formula R _{n + 1} Sn ( SCH ₂ CH ₂ OCOC ₈ H ₁₇ ) _3-n , where R is an alkyl group with 4 to 8 C atoms, bis (β-methoxycarbonyl-ethyl) tin bis (thioethylene glycol 2-ethylhexoate), bis (β-methoxycarbonyl- ethyl) -tin bis (thioglycolic acid 2-ethylhexoate), and bis (β-acetyl-ethyl) tin-bis (thioethylenglycol-2-et hylhexoate) and bis (β-acetyl-ethyl) tin-bis (thioglycolic acid 2-ethyl hexoate.

Also suitable are aliphatic tertiary amines, especially with cy clical structure. Among the tertiary amines, those which are suitable are also suitable additionally carry groups reactive towards the isocyanates, in particular Hydroxyl and / or amino groups. Specifically: Dimethylmonoethanolamine, diethylmonoethanolamine, methylethylmonoethanola min. Triethanolamine, trimethanolamine, tripropanolamine, tributanolamine, trihexa nolamine, tripentanolamine, tricyclohexanolamine, diethanolmethylamine, diethano methylamine, diethanolpropylamine, diethanolbutylamine, diethanolpentylamine, diet hanohexylamine, diethanolcyclohexylamine, diethanolphenylamine and their Ethoxylation and propoxylation products, diaza-bicyclo-octane (DABCO), Triethylamine, dimethylbenzylamine (Desmorapid DB, BAYER), Bis dimethylaminoethyl ether (Calalyst A 1, UCC), tetramethylguanidine, bis  dimethylaminomethylphenol, 2- (2-dimethylaminoethoxy) ethanol, 2-dimethyiami noethyl-3-dimethylaminopropyl ether, bis (2-dimethylaminoethyl) ether, N, N-dime thylpiperazine, N- (2-hydroxyethoxyethyl) -2-azanorbornane, or unsaturated bicyclic amines, e.g. B. Diazabicycloundecen (DBU) and Texacat DP-914 (Texaco Chemical), N, N, N, N-tetramethylbutane-1,3-diamine, N, N, N, N-tetra methylpropane-1,3-diamine and N, N, N, N-tetramethylhexane-1,6-diamine. The Catalysts can also exist in oligomerized or polymerized form lie, e.g. B. as N-methylated polyethyleneimine.

However, very particularly preferred catalysts are the derivatives of Morpholins. Specific examples of suitable morpholino compounds are Bis (2- (2,6-dimethyl-4-morpholino) ethyl) - (2- (4-morpholino) ethyl) amine, bis (2- (2,6- dimethyl-4-morpholino) ethyl) - (2- (2,6-diethyl-4-morpholino) ethyl) amine, tris (2- (4- morpholino) ethyl) amine, tris (2- (4-morpholino) propyl) amine, tris (2- (4-morpholino) butyl) amine, tris (2- (2,6-dimethyl-4-morpholino) ethyl) amine, tris (2- (2,6-diethyl-4- morpholino) ethyl) amine, tris (2- (2-methyl-4-morpholino) ethyl) amine or tris (2- (2- ethyl-4-morpholino) ethyl) amine, dimethylaminopropylmorpholine, bis- (morpholinopropyl) methylamine, diethylaminopropylmorpholine, bis (morpholinopropyl) ethylamine, bis (morpholinopropyl) propylamine, Morpholinopropylpyrrolidone or N-morpholinopropyl-N'-methyl-piperazine, Dimorpholinodiethyl ether (DMDEE) or di-2,6-dimethylmorpholinoethyl) ether.

Furthermore, the composition according to the invention can optionally additionally Stabilizers, adhesion-promoting additives such as tackifying resins, fillers, Contain pigments, plasticizers and / or solvents.

On the one hand, "stabilizers" in the sense of this invention are stabilizers understand the viscosity stability of the polyurethane prepolymer during the manufacture, storage or application. For this, z. B. monofunctional carboxylic acid chlorides, monofunctional highly reactive isocyanates, but also non-corrosive inorganic acids are suitable, for example called benzoyl chloride, toluenesulfonyl isocyanate, phosphoric acid or phosphorous acid. Furthermore, are used as stabilizers in the sense of this invention To understand antioxidants, UV stabilizers or hydrolysis stabilizers. The The selection of these stabilizers depends on the one hand on the main components the composition and the other according to the application conditions and the expected loads on the cured product. If that  Polyurethane prepolymer is composed predominantly of polyether building blocks mainly antioxidants, possibly in combination with UV protection agents, necessary. Examples of this are the commercially sterically hindered Phenols and / or thioethers and / or substituted benzotriazoles or the sterically hindered amines of the HALS type ("Hindered Amine Light Stabilizer ").

They consist of essential components of the polyurethane prepolymer Polyester building blocks are preferably hydrolysis stabilizers, e.g. B. from Carbodiimide type used.

If the compositions according to the invention are used as hot melt adhesives, Laminating adhesives or adhesives / sealants are used, so they can still tackifying resins, such as. B. abietic acid, abietic acid ester, terpene resins, Terpene phenol resins or hydrocarbon resins and fillers (e.g. silicates, Talc, calcium carbonate, clays or soot), plasticizers (e.g. phthalates) or Thixotropic agents (e.g. bentones, pyrogenic silicas, urea derivatives, fibril gelled or pulp short fibers) or color pastes or pigments.

When used as a laminating adhesive it can be used to achieve certain additional properties, such as thermal and chemical resistance an addition of epoxy resins, phenolic resins, novolaks, resols or Melamine resins and the like may be necessary. In addition, in this case the prepolymers are also prepared in solution, preferably in polar, aprotic solvents. The preferred solvents have one Boiling range from about 50 ° C to 140 ° C. Although halogenated too Hydrocarbons are suitable, especially ethyl acetate, Methyl ethyl ketone (MEK) or acetone preferred.

The adhesive / sealant compositions according to the invention can be like that Use the usual known polyurethane adhesives / sealants as a reactive one or two-component adhesive / sealant, as a reactive hot melt adhesive or as Solvent-based adhesive in one or two components. More essential Advantage compared to the well-known polyurethane adhesives / sealants low proportion of monomeric diisocyanates, which are hazardous to occupational hygiene a molecular weight below 500.  

The invention is illustrated below using some preferred exemplary embodiments explained in more detail, the selection of the examples being no limitation of the To represent the scope of the subject matter of the invention. The quantities in The examples are parts by weight or percentages by weight, if not different specified.

Examples 1. Production of high molecular weight diisocyanates

The monomeric diisocyanates were placed in ethyl acetate and heated to 50 ° C. The heating was then switched off and the corresponding diol was metered in within 10 minutes. Due to the heat of reaction, the reaction mixture heated up to approx. 60 ° C. After a reaction time of 15 minutes, the batch was heated to 80.degree. The catalyst was added a further 15 minutes later and the reaction continued for a further 30 minutes. As a precipitant for the high molecular weight diisocyanate, ethyl acetate, chlorobenzene, gasoline, acetone, and n-heptane were used. The properties of the high molecular weight diisocyanates are listed in the table below:

Notes on the table

1) NPG: neopentyl glycol, HPN: hydroxypivalic acid neopentyl glycol ester
2) Tr .: drops, DBTL: dibutyltin dilaurate
3) Refurbishment process:
A1: Isolation after precipitation of the reaction mixture during synthesis
A2: as A1, then crystallization in the refrigerator to complete the precipitation
A3: like A1, filtrate precipitated with hexane
A4: Crystallization in the refrigerator, precipitation with hexane
A5: as A1, then filtrate treated with hexane
A6: precipitated and washed with petrol
A7: Precipitated and washed with gasoline and washed with chlorobenzene

As can be seen from the table, Recrystallize / wash the high molecular weight diisocyanate in aprotic Solvents reduce the monomer residues to less than 0.5% by weight.

2. Implementation of the high molecular weight diisocyanates with polyols Example 13

The high molecular weight diisocyanate of Example 11 was also known the hydroxy-functional polyester Dynacoll 7380 (from Creanova, polyester from Dodecanedioic acid and 1,6-hexanediol, OH number 30) implemented (code number 2.2). The the resulting PU prepolymer had an NCO content of 1.97% by weight (theoretically 2.01% by weight) and a viscosity of 24.8 Pa.s at 130 ° C. The Residual monomer content was <0.1% by weight. This product showed good ones Properties as a reactive hot melt adhesive.

Example 14

Analogously to Example 13, the high molecular weight diisocyanate from Example 12 was used Dynacoll 7380 implemented (key figure 2.2). NCO content 2.1% by weight (theoretical  2.16% by weight) viscosity 9.6 Pa.s at 130 ° C. The residual monomer content was <0.1% by weight. This product also showed good properties as a reactive Hot melt adhesive.

Example 15 (comparison)

For comparison, a standard prepolymer for a PU hot melt adhesive was made 4,4'-Diphenylmethane diisocyanate reacted with Dynacoll 7380 (index 2.2). NCO content 2.31% by weight (theoretically 2.35% by weight) viscosity 4.5 Pa.s at 130 ° C. The residual monomer content was determined to be 2.8% by weight.

The compositions of the invention have compared to Comparative product a slightly higher melt viscosity, but this affects not your use as a hot melt adhesive. The main advantage over that State of the art is the significantly reduced content of monomeric Diisocyanate in the hot melt adhesive according to the invention.

Claims (9)

1. Reactive polyurethane adhesive / sealant composition based on reaction products of polyols and high molecular weight diisocyanates, which by reacting diols with a molecular weight less than 1000 with monomeric diisocyanates with a molecular weight less than 500, characterized in that the high molecular weight used Diisocyanates contain a maximum of 10 mol% of monomeric diisocyanate before they are reacted with the polyol (s). 2. Composition according to claim 1, characterized in that the monomeric diisocyanate is selected from the group of all isomers of tolylene diisocyanate (TDI), either in isomerically pure form or as a mixture of several isomers, naphthalene-1,5-diisocyanate, 4,4'- Diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate and mixtures thereof, xylene diisocyanate (XDI), 4,4'-dicyclohexylmethane diisocyanate (H ₁₂ MDI), 1-isocyanatomethyl-3-isocyanato-1,5,5-trimethyl-diisocyanate (isophorone diisocyanate , IPDI), cyclohexane, 1,4-diisocyanate, hydrogenated xylylene diisocyanate (H ₆ XDI), 1-methyl-2,4-diisocyanatocyclohexane, hexane-1,6-diisocyanate (HDI), m- or p-tetramethylxylene diisocyanate (m-TMXDI, p-TMXDI) or mixtures of the aforementioned diisocyanates. 3. Composition according to claim 1, characterized in that the diols are selected from the group of C2 to C18 alkanediols including the isomers such as B. ethylene glycol, 1,2-propanediol, 1,3-propanediol, 2,2- Dimethyl-1,3-propanediol, 2-methylpropanediol, 1,6-hexanediol, 2,4,4- Trimethylhexanediol-1,6,2,2,4-trimethylhexanediol-1,6,1,4- Cyclohexane dimethanol, diethylene glycol, triethylene glycol, tetraethylene glycol, Dipropylene glycol, tripropylene glycol, tetrapropylene glycol, Poly (oxytetramethylene) glycol with a molecular weight up to 650, Alkoxylation products of bisphenol A, alkoxylation products of Bisphenols F, the isomeric dihydroxyanthracenes, the isomeric Dihydroxynaphthalenes, catechol, resorcinol, hydroquinone  with up to 8 alkoxy units per aromatic hydroxyl group or Mixtures of the aforementioned diols. 4. Composition according to claim 1 to 3, characterized in that as Polyol one or more di- or trifunctional polyethylene glycols, Polypropylene glycols, statistical or block copolymers of ethylene oxide and Propylene oxide, poly (oxytetramethylene) glycols, linear or branched Polyester polyols, poly-ε-caprolactones, hydroxy-functional polybutadienes or their hydrogenation products, hydroxy-functional poly (meth) acrylates or Mixtures of the aforementioned polyols is used, the number average the molecular weight of the polyol (s) 400 to 20,000, preferably 1000 to 6000 is. 5. A method for producing a composition according to any one of the preceding claims, characterized in that

• a) in a first step the diol component is converted to a high molecular weight diisocyanate with a stoichiometric excess of monomeric diisocyanate,
• b) if appropriate, by adding a non-solvent for the high molecular weight diisocyanate which is precipitated from the reaction mixture,
• c) is freed of unreacted monomeric diisocyanate by filtration or centrifugation and
• d) in a second step, this high molecular weight diisocyanate is reacted with a polyol, so that a reactive prepolymer with isocyanate end groups is formed.

6. A method for producing a composition according to any one of the preceding claims, characterized in that

• a) in a first step the diol component is converted to a high molecular weight diisocyanate with a stoichiometric excess of monomeric diisocyanate,
• b) the excess monomeric diisocyanate is removed from the reaction mixture by distillation, and
• c) in a second step, this high molecular weight diisocyanate is reacted with a polyol, so that a reactive prepolymer with isocyanate end groups is formed.

7. A method for producing a composition according to any one of the preceding claims, characterized in that

• a) in a first step the diol component is converted to a high molecular weight diisocyanate with a stoichiometric excess of monomeric diisocyanate,
• b) the excess monomeric diisocyanate is removed from the reaction mixture by selective extraction, and
• c) in a second step, this high molecular weight diisocyanate is reacted with a polyol, so that a reactive prepolymer with isocyanate end groups is formed.

8. The method according to claim 5 to 7, characterized in that in the second Step the NCO / OH ratio is 1.2: 1 to 5: 1. 9. Use of a composition according to claim 5 to 8 as a binder for a reactive one or two component adhesive / sealant, reactive Hot melt adhesive or solvent-based adhesive.