EP2999729A1

EP2999729A1 - Method for producing hot melt adhesives containing silane groups

Info

Publication number: EP2999729A1
Application number: EP13802280.1A
Authority: EP
Inventors: Urs Burckhardt; Andreas Kramer
Original assignee: Sika Technology AG
Current assignee: Sika Technology AG
Priority date: 2013-05-22
Filing date: 2013-11-25
Publication date: 2016-03-30
Also published as: US20160096983A1; WO2014187508A1; JP2016524000A; CN105408382A

Abstract

The invention relates to a method for producing a hot melt adhesive containing silane groups, in which at least one polyurethane polymer which contains isocyanate groups and is solid at room temperature is reacted with at least one hydroxysilane that is devoid of urea and thiourethane groups. The hot melt adhesive containing silane groups obtained from said method allows a low hazard classification, has a good degree of thermal resistance when melted such that, even upon application under prolonged heating, it does not tend towards premature thickening, releases no unpleasant odours, and crosslinks at room temperature without bubbles under the influence of moisture, resulting in an optically and mechanically high-quality and resistant adhesive connection.

Description

PROCESS FOR PREPARING SILANE GROUP-CONTAINING HOT-GLUE ADHESIVES

Technical area

The invention relates to moisture-curing hot-melt adhesives.

State of the art

Hotmelt adhesives (hotmelts) are solid polymer compositions at room temperature, which are melted for application and hot applied to the substrates to be bonded, which are added immediately thereafter. After application, the hot-melt adhesive, which is usually applied in a thin layer, cools rapidly, as a result of which the bond builds up strength very quickly.

Classic hot-melt adhesives are chemically non-reactive and remain thermoplastic after application. They are therefore not suitable for bonding, which are exposed to elevated temperature. In addition, they often tend to creep (cold flow) even at temperatures well below the softening point.

These disadvantages are largely eliminated in the case of the so-called reactive hot-melt adhesives, which contain reactive groups leading to moisture crosslinking of the adhesive polymers. Cooling first results in the buildup of hot melt adhesive typical early strength, followed by crosslinking of the polymers by chemical reaction, which typically occurs at room temperature and can take several hours to several days. After crosslinking, the bond can be heated without melting the adhesive. The cold flow is also prevented by the chemical crosslinking of the adhesive.

In particular, isocyanate group-containing polyurethane hot-melt adhesives are widely used. A disadvantage of these systems is that they tend to form bubbles during crosslinking, in particular in the case of amorphous polymers and at elevated humidity or temperature. The bubbles can greatly affect the aesthetic and mechanical quality as well as the resistance of the bond. Another disadvantage is their content of breathable mo- monomeric isocyanates which may outgas during application and require protective measures. This leads to a higher hazard classification of the products and thus limits their applicability.

Instead of isocyanate group-containing silane-containing systems ("STP hotmelt adhesives") can be used, which crosslink via the condensation reaction of silanol groups, which are formed by hydrolysis of the silane groups, and allow low hazard classification due to the low content of monomeric isocyanates Silane groups are most easily introduced by reacting an isocyanate group-containing polyurethane hotmelt adhesive with an aminosilane or a mercaptosilane, as described, for example, in EP 0 202 491 and EP 1 801 138. However, these systems known from the prior art have disadvantages Over prolonged heating, STP hotmelt adhesives produced via aminosilanes can suddenly thicken heavily and become unapplicable, in particular in industrial production applications in which the adhesive has melted over a certain period of time The condition remains at the application temperature, very disadvantageous. While STP hotmelt adhesives made from mercaptosilanes do not thicken in the molten state, they have the disadvantage that the attachment of the silane group, especially at elevated temperature, is reversible and, as a result, odorous mercapto compounds are released during application, which is very undesirable ,

EP 0 354 472 describes STP hot-melt adhesives obtained by means of isocyanatosilanes. The isocyanatosilanes used are obtained starting from mercapto or amino silanes by reaction with diisocyanates and dialcohols. In this process, the silane groups are also bonded to the polymer via urea or thiourethane groups, whereby the aforementioned difficulties persist.

Presentation of the invention

The object of the present invention is therefore to provide a process for the preparation of a hot-melt adhesive containing silane groups, which allows a low hazard classification and in the molten state has a good thermal resistance, so does not prone to premature thickening and releases no unpleasant odors.

Surprisingly, it has been found that the method according to claim 1 solves this problem. In this case, a hydroxysilane which is free of urea and of thiourethane groups is reacted with a solid, isocyanate group-containing polyurethane polymer at room temperature. The silane-group-containing hot-melt adhesive obtainable by the process according to the invention permits a low hazard classification because, depending on the stoichiometry used, it has little or no content of monomeric isocyanates. During the course of the application process, it has a good thermal resistance even with prolonged heating and does not tend to premature thickening; it can therefore be applied well and does not lead to emissions, since the silane groups are largely irreversibly tethered. Finally, it crosslinks at room temperature under the influence of moisture bubble-free and leads to a visually and mechanically high-quality and durable adhesive bond.

The preparation and handling of hydroxysilanes has the difficulty that they tend to self-condensation due to a rapid reaction of the hydroxyl group with the silane group and therefore are often very impure and / or poor storage stability. In particular, however, the preferred hydroxysilanes having a secondary hydroxyl group are surprisingly stable enough so that high-strength silane group-containing hot-melt adhesives are accessible.

Further aspects of the invention are the subject of further independent claims. Particularly preferred embodiments of the invention are the subject of the dependent claims.

Ways to carry out the invention

The invention relates to a process for the preparation of a hot-melt adhesive containing silane groups, in which at least one isocyanate-group-containing polyurethane polymer which is solid at room temperature and has at least a hydroxysilane which is free of urea and thiourethane groups, is reacted.

In the present document, the term "silane" or "organosilane" refers to silicon compounds which on the one hand have at least one, usually two or three, hydrolyzable substituents bonded directly to the silicon atom via Si-O bonds, and on the other hand at least one via a Si -C bond directly to the silicon atom bonded organic radical. The hydrolyzable substituents are in particular alkoxy, acetoxy, ketoximato, amido or enoxy radicals. The term "silane group" denotes the silicon-containing group bonded to the organic radical of a silane.

As "hydroxysilane", "aminosilane", "isocyanatosilane" and the like organosilanes are referred to, which have on the organic radical a corresponding functional group, ie a hydroxyl group, amino group or isocyanate group.

Substance names beginning with "poly", such as polyol or polyisocyanate, refer to substances which formally contain two or more of the functional groups occurring in their name per molecule.

The term "polyurethane polymer" encompasses all polymers which are prepared by the so-called diisocyanate-polyaddition process The term "polyurethane polymer" also encompasses polyurethane polymers containing isocyanate groups, as obtainable from the reaction of polyisocyanates and polyols, which are themselves polyisocyanates and often also called prepolymers.

The term "active hydrogen" denotes the hydrogen atoms of hydroxyl, mercapto and primary and secondary amino groups.

The term "molecular weight" as used herein refers to the molar mass (in grams per mole) of a molecule. "Average molecular weight" refers to the number average M _{n of} an oligomeric or polymeric mixture of molecules, which is usually determined by GPC versus polystyrene as a standard , A dashed line in the formulas in this document represents the bond between a substituent and the associated moiety. As the "primary hydroxyl group" is meant an OH group bonded to a C atom with two hydrogens, as a "secondary hydroxyl group "denotes an OH group which is bonded to a C atom with a hydrogen.

The term "storage stable" refers to the property of a substance or composition that it can be stored at room temperature in a suitable container for several weeks to 6 months and more, without being limited in its application or use properties by storage in a for their use relevant extent changed.

The term "room temperature" refers to a temperature of about 23 ° C. The reaction of the isocyanate group-containing polyurethane polymer with the hydroxysilane which is solid at room temperature is advantageously carried out with exclusion of moisture and at elevated temperature, in particular at a temperature at which the polyurethane polymer The reaction is preferably carried out by reacting the isocyanate group-containing polyurethane polymer and the hydroxysilane at a temperature in the range from 60 to 180 ° C., in particular from 80 to 160 ° C., hydroxyl groups of the hydroxysilane being present As a result, the silane groups are covalently bonded to the polyurethane polymer, in which case a catalyst can be used, in particular a bismuth (III), zinc (II), zirconium (IV) or tin (II) Compound or an organotin (IV) compound.

The bonding of the silane groups via urethane groups has the great advantage that the hot-melt adhesive obtained has a very good thermal resistance both in the non-crosslinked and in the crosslinked state. The thermal stability of the uncrosslinked adhesive is important for its good applicability. Hot-melt adhesives whose silane groups are bonded to the polymer via urea or thiourethane groups show weaknesses here. In particular, the thiourethane group is thermal easily fissile, releasing sulfur-containing substances that cause odor emissions. Also in the case of urea groups, instability is observed which, presumably due to catalytic processes, leads to excessive thickening until gelation of the adhesive in the molten state.

In one embodiment of the invention, the polyurethane polymer and the hydroxysilane are used in such an amount that the OH groups of the hydroxysilane are substoichiometrically present in relation to the isocyanate groups of the polyurethane polymer, that is, the OH / NCO ratio is less than 1. From this reaction, a hot-melt adhesive containing silane groups is obtained, which additionally has isocyanate groups. In such a hotmelt adhesive, both the silane and the isocyanate groups contribute to crosslinking under the influence of moisture. Such a hotmelt adhesive has a significantly reduced content of monomeric isocyanates compared to the isocyanate group-containing polyurethane polymer which was used for the method described. Preferred is an OH / NCO ratio in the range of 0.1 to 0.9, particularly preferably 0.2 to 0.8, in particular 0.3 to 0.7. Such a hotmelt adhesive has, in particular, a content of monomeric isocyanates of <2% by weight, in particular <1% by weight. Due to labeling regulations, such a hotmelt adhesive has in particular a content of monomeric MDI of <1% by weight, or a content of monomeric IPDI of <2% by weight, in particular <0.5% by weight, where the abbreviation "MDI" stands for " 4,4'-, 2,4'- and / or 2,2'-diphenylmethane diisocyanate and any mixtures of these isomers ", and the abbreviation" IPDI "stands for" isophorone diisoyanate ".

In a preferred embodiment of the invention, the polyurethane polymer and the hydroxysilane are used in such an amount that the OH groups of the hydroxysilane are at least stoichiometrically present in relation to the isocyanate groups of the polyurethane polymer

OH / NCO ratio is therefore at least 1. This implementation will be a Silane group-containing hotmelt adhesive which is free of isocyanate groups. Such an isocyanate group-free hot-melt adhesive is particularly advantageous from a toxicological point of view. An isocyanate group-free hotmelt adhesive is accordingly also free of monomeric isocyanates. Preferred is an OH / NCO ratio in the range of 1 to 2, particularly preferably 1 to 1 .8, in particular 1 to 1 .5.

In the process described, at least one isocyanate group-containing polyurethane polymer which is solid at room temperature is used. This may be crystalline, partially crystalline or amorphous at room temperature. For a partially crystalline or amorphous polyurethane polymer is valid that it is not or only slightly flowable at room temperature. This means in particular that it has a viscosity of more than 5Ό00 Pa s at 20 ° C. The isocyanate group-containing polyurethane polymer preferably has an average molecular weight M _n in the range from 2Ό00 to 20Ό00 g / mol, preferably 2Ό00 to 15Ό00 g / mol, in particular 2Ό00 to 10Ό00 g / mol.

Preferably, the isocyanate group-containing polyurethane polymer 1 to 3, more preferably 2, isocyanate groups per molecule.

Such a polyurethane polymer allows a suitable processing viscosity and in the crosslinked state good mechanical properties.

A suitable isocyanate group-containing polyurethane polymer which is solid at room temperature is obtained, in particular, by the reaction of at least one polyol with at least one diisocyanate, the diisocyanate being present in a stoichiometric excess.

Preference is given to a ratio between isocyanate and hydroxyl groups in the range from 1.5 to 5, more preferably from 1.8 to 4, in particular from 2 to 3.

The reaction is advantageously carried out at elevated temperature, in particular at a temperature at which the polyols, diisocyanates and polyurethane polymer used are present in liquid form. Optionally, a suitable catalyst is present. In the reaction of polyols with diisocyanates to a polyurethane polymer containing isocyanate groups, a residual content of unreacted monomeric diisocyanates remains in the resulting polymer due to the statistical distribution of the possible reaction products. These monomeric diisocyanates, also referred to for short as "monomeric isocyanates", are volatile compounds and may be hazardous to health due to their irritant, allergenic and / or toxic effect.

Particularly suitable as polyol are polyols which are solid at room temperature. Amorphous or partially crystalline or crystalline polyols, in particular polyester polyols and polycarbonate polyols, are particularly suitable at room temperature.

Suitable polyester polyols are, in particular, those which are prepared from dihydric to trihydric, preferably dihydric, alcohols, such as, in particular, 1,2-ethanediol, diethylene glycol, 1,2-propanediol, dipropylene glycol, 1,4-butanediol, 1 , 5-pentanediol, 1, 6-hexanediol, neopentyl glycol, glycerol, 1, 1, 1-trimethylolpropane or mixtures of the abovementioned alcohols, with organic dicarboxylic acids or their anhydrides or esters, in particular succinic acid, glutaric acid, adipic acid, suberic acid , Sebacic acid, dodecanedicarboxylic acid, maleic acid, fumaric acid, phthalic acid, isophthalic acid, terephthalic acid and hexahydrophthalic acid or mixtures of the abovementioned acids, as well as polyester polyols from lactones such as ε-caprolactone. Particularly suitable polyester polyols are polyester polyols of adipic acid, sebacic acid or dodecanedicarboxylic acid as dicarboxylic acid and of hexanediol or neopentyl glycol as dihydric alcohol. The polyesterpolyols preferably have an average molecular weight M _n in the range from 1'500 to 15Ό00 g / mol, preferably 1'500 to 8000 g / mol, in particular 2Ό00 to 5'500 g / mol.

Particularly suitable crystalline or partially crystalline polyester polyols are adipic acid / hexanediol polyester and dodecanedicarboxylic acid / hexanediol polyester.

Suitable polycarbonate polyols are those which, in particular, are used by reacting the abovementioned ones - used to prepare the polyesterpolyols - Alcohols are accessible with dialkyl carbonates, diaryl carbonates or phosgene.

Preferred as a polyol is a mixture of at least one amorphous polyester estiol and at least one further polyester diol.

Particularly preferred as polyol are mixtures of amorphous and / or crystalline and / or partially crystalline polyester diols. Most preferably, the polyol is a mixture of an amorphous and a polyester diol which is liquid at room temperature. As a result, for example, transparent adhesives can be produced.

Also preferably, the polyol is a crystalline or a partially crystalline polyester diol.

Particularly suitable diisocyanates are commercially available aliphatic, cycloaliphatic, arylaliphatic and aromatic, preferably cycloaliphatic and aromatic, diisocyanates.

Preferred diisocyanates are 1, 6-hexamethylene diisocyanate (HDI), 2,2,4- and 2,4,4-trimethyl-1, 6-hexamethylene diisocyanate (TMDI), cyclohexane-1, 3- and - 1, 4-diisocyanate and any mixtures of these isomers, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane (= isophorone diisocyanate or IPDI), perhydro-2,4'- and -4,4'-diphenylmethane diisocyanate (HMDI), m- and p-xylylene diisocyanate (m- and p-XDI), m- and p-tetramethyl-1, 3- and -1,4-xylylene diisocyanate (m- and p-TMXDI), 2,4- and 2 , 6-tolylene diisocyanate (TDI) and any mixtures of these isomers, 4,4'-, 2,4'- and 2,2'-diphenylmethane diisocyanate and any mixtures of these isomers (MDI).

The diisocyanate is particularly preferably selected from the group consisting of IPDI, MDI and TDI. These diisocyanates are particularly easy to obtain.

Of these, preferred is MDI. Hotmelt adhesives based thereon have particularly good mechanical properties and rapid crosslinking.

Of these, preference is still IPDI. Hot-melt adhesives based thereon have a particularly good light stability and stability to discoloration on. This is particularly advantageous for the bonding of transparent substrates.

In the process described, at least one hydroxysilane, which is free of urea and thiourethane groups, is furthermore used.

The difficulty in the preparation and storage of hydroxysilanes is basically that a hydroxyl group can react with a silane group to release a hydrolyzable group ("self-condensation"), which is principally possible both intramolecular and intermolecular, with either cyclic silanes or higher condensed or oligomeric silane compounds having a plurality of silicon atoms, such impurities may already be formed during the preparation of hydroxysilanes or during storage.

The hydroxysilane preferably has two or three hydrolyzable substituents on the silicon atom, preferably two or three alkoxy groups, in particular ethoxy or methoxy groups. The hydroxysilane particularly preferably has two or three, in particular three, ethoxy groups. Ethoxy-containing hydroxysilanes are particularly stable to self-condensation.

The hydroxysilane is preferably a hydroxysilane which contains a secondary hydroxyl group. Surprisingly, these hydroxysilanes are stable enough, so that high-strength silane-containing hotmelt adhesives are obtained. In the process according to the invention, in particular a hydroxysilane of the formula (I) is used

in which

A is either a divalent aliphatic or cycloaliphatic hydrocarbon radical having 2 to 30 carbon atoms, optionally with aromatic moieties and optionally with one or more heteroatoms which is free of active hydrogen, or together with B-CH, a divalent cycloaliphatic hydrocarbon radical having 6 to 20 carbon atoms, optionally with aromatic moieties and optionally with one or more heteroatoms which is free of active hydrogen;

B is a monovalent aliphatic or cycloaliphatic hydrocarbon radical having 1 to 12 C atoms, optionally with one or more heteroatoms which is free of active hydrogen,

or together with CH-A is a divalent cycloaliphatic hydrocarbon radical having 6 to 20 C atoms, optionally with one or more heteroatoms which is free of active hydrogen;

R ^{4 is} an alkyl group having 1 to 8 C atoms;

R ^{5 is} an alkyl group having 1 to 10 C atoms, optionally with one or more ether oxygens; and

x stands for 0 or 1 or 2.

The hydroxysilane of the formula (I) has a secondary hydroxyl group and is particularly advantageous in the use according to the invention, since it can be prepared in high purity and has good storage stability and thus enables very clean functionalization of the isocyanate group-containing polyurethane polymer with silane groups, whereby a silane group-containing hot melt adhesive with high strength is available.

Preferably, A is either a divalent aliphatic or cycloaliphatic hydrocarbon radical having 4 to 30 carbon atoms, which optionally contains ether oxygen, a tertiary amino group, an amido group or a urethane group, or together with B-CH for a divalent cycloaliphatic Hydrocarbon radical having 6 to 20 carbon atoms, which optionally contains ether groups and / or tertiary amino groups.

B is preferably an alkyl group having 1 to 12 C atoms, which optionally contains ether groups and / or tertiary amino groups, or together with CH-A is a divalent cycloaliphatic hydrocarbon radical having 6 to 20 C atoms, which optionally contains ether groups and / or tertiary amino groups. Preferably, R ^{4 is} an alkyl group having 1 to 4 carbon atoms, in particular methyl.

Preferably, R ^{5 is} an alkyl group having 1 to 4 carbon atoms, in particular methyl or ethyl.

Hydroxysilanes having these preferred radicals A, B, R ⁴ and R ⁵ are particularly readily available.

R ⁵ is in particular a methyl group. This silane-containing hot melt adhesives are accessible with particularly fast networking with moisture.

In addition, R ⁵ is in particular an ethyl group. This silane-containing hot melt adhesives are accessible, which do not split off methanol when crosslinked with moisture, which is advantageous for toxicological reasons.

Preferably, x is 1 or 0, in particular 0. These hot-melt adhesives are accessible with these hydroxysilanes which, on contact with moisture, crosslink particularly rapidly and have particularly good mechanical properties.

The hydroxysilane of the formula (I) is preferably a hydroxysilane which was not obtained from the addition of an aminosilane to a methyl-substituted cyclic carbonate, in particular propylene carbonate. This addition is not very selective, with the result that the reaction product contains a relatively high content of hydroxysilane with primary OH group in addition to the secondary OH group hydroxysilane. As a result, a complex purification of the reaction product is necessary and / or the storage stability and purity of the silane is greatly reduced, whereby the strength of the resulting hot melt adhesive in the crosslinked state is only mediocre.

A suitable hydroxysilane of formula (I) is a hydroxysilane having a tertiary amino group. Such hydroxysilanes are particularly obtainable from the reaction of at least one epoxysilane with at least one secondary amine. A hydroxysilane having a tertiary amino group especially suitable for reaction with a polyurethane polymer based on aliphatic isocyanates, in particular IPDI. Hotmelt adhesives derived therefrom have a good thermal stability in the undiluted state and good light stability.

A preferred hydroxysilane having a tertiary amino group is a hydroxysilane of the formula (I a)

in which

either R 'is a radical of formula (II) and R "is hydrogen

or R 'is hydrogen and R "is a radical of formula (II);

(R ⁴ ) _x

R ^3a -Si (OR ⁵ ) _3-x ^(M)

R ^1a and R ^2a either individually each represent an alkyl radical having 1 to 12 C atoms, which optionally has heteroatoms in the form of ether oxygen, thio ether sulfur or tertiary amine nitrogen, or together for an alkylene radical having 2 to 12 C atoms, which optionally hetero atoms in the form of ether oxygen, thioether sulfur or tertiary amine nitrogen, are;

R ^{3a is} a linear or branched alkylene or cycloalkylene radical having 1 to 20 C atoms, optionally with aromatic moieties, and optionally with one or more heteroatoms;

and R ⁴ , R ⁵ and x have the meanings already mentioned.

The hydroxysilane of the formula (I a) corresponds to either the formula (I a ') or the formula (I a ").

(I a ') (I a ")

In the formulas (I a ') and (I a "), R ^1a , R ^2a , R ^3a , R ⁴ , R ⁵ and x have the meanings already mentioned.

The formulas (I a ') and (I a ") include all possible for the respective structure diastereomers.

R ^1a and R ^2a are preferred

either individually in each case for an alkyl radical having 3 to 10 C atoms, which optionally has one or two ether oxygens,

or together for an alkylene radical having 4 to 8 C atoms, which in particular has a heteroatom in the form of ether oxygen, thioether sulfur or tertiary amine nitrogen and form a 5 or 6 or 7 with the inclusion of the nitrogen atom Ring, in particular a 5- or 6-ring.

R ^1a and R ^2a are particularly preferred

either individually for 2-methoxyethyl, 2-ethoxyethyl, 3-methoxypropyl, 3-

Ethoxypropyl, 2- (2-methoxyethoxy) ethyl, 2-octyloxyethyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, 2-ethylhexyl, or N, N-dimethylaminopropyl,

or together with the inclusion of the nitrogen atom for a, optionally substituted, pyrrolidine, piperidine, hexamethyleneimine, morpholine, thiomorpholine or 4-methylpiperazine ring.

Most preferably, R ^1a and R ^2a each individually represent 2-methoxyethyl, butyl or isopropyl, or together with the inclusion of the nitrogen atom for morpholine, 2,6-dimethylmorpholine, thiomorpholine, pyrrolidine or 4-methylpiperazine.

Most preferably, R ^1a and R ^2a are inclusive of the nitrogen atom for morpholine or pyrrolidine. These hydroxysilanes can be produced in a particularly pure quality and are particularly stable on storage. They allow silane-containing hotmelt adhesives of high strength. R ^3a is preferably a linear or branched alkylene radical having 1 to 6 C atoms, particularly preferably a 1, 2-ethylene radical.

A preferred hydroxysilane of the formula (Ia) is in particular selected from the group consisting of 2-bis (2-methoxyethyl) amino-4- (2-triethoxysilyl-ethyl) cyclohexan-1-ol, 2-dibutylamino-4- (2 triethoxysilylethyl) cyclohexan-1-ol, 2-diisopropylamino-4- (2-triethoxysilylethyl) cyclohexan-1-ol, 2-morpholino-4- (2-triethoxysilylethyl) cyclohexan-1-ol, 2- (2,6- Dimethylmorpholino) -4- (2-triethoxysilylethyl) cyclohexan-1-ol, 2-thiomorpholino-4- (2-triethoxysilylethyl) cyclohexan-1-ol, 2-pyrrolidino-4- (2-triethoxysilylethyl) cyclohexane 1 -ol, 2- (4-methylpiperazino) -4- (2-triethoxysilylethyl) cyclohexan-1-ol, and the corresponding compounds in which the silane radical is in the 5-position rather than in the 4-position, and the corresponding Compounds with methoxy groups instead of ethoxy groups on the silane.

Preferred are 2-morpholino-4- (2-trimethoxysilylethyl) cyclohexan-1-ol, 2-morpholino-4- (2-triethoxysilylethyl) cyclohexan-1-ol, 2-pyrrolidino-4- (2-trimethoxysilylethyl) cyclohexane-1-ol, 2-pyrrolidino-4- (2-triethoxysilylethyl) cyclohexan-1-ol and the corresponding compounds in which the silane radical is in the 5-position instead of the 4-position.

With these hydroxysilanes, hot-melt adhesives containing silane groups having good processing viscosity and good storage stability are obtained, which cure with moisture quickly to crosslinked adhesives of high strength.

Particularly preferred in each case is a mixture of the two molecules in which the silane radical is in the 4- and 5-position. Such mixtures are also represented by the notation "4 (5)".

Preferably, a hydroxysilane of the formula (Ia) is reacted with a polyurethane polymer having aliphatic isocyanate groups. The resulting hot Melt adhesives have a good thermal stability in the uncrosslinked state and good light stability.

Another preferred hydroxysilane having a tertiary amino group is a hydroxysilane of the formula (I b)

in which

R ^1b and R ^2b either individually each represent an alkyl radical having 1 to 12 C atoms, which optionally has heteroatoms in the form of ether oxygen, thio ether sulfur or tertiary amine nitrogen, or together for an alkylene radical having 2 to 12 C atoms optionally having heteroatoms in the form of ether oxygen, thioether sulfur or tertiary amine nitrogen;

R ^{3b is} a linear or branched alkylene or cycloalkylene radical with 1 to

20 C atoms, optionally with aromatic moieties, and optionally with one or more heteroatoms;

and R ⁴ , R ⁵ and x have the meanings already mentioned.

R ^1b and R ^2b are preferred

or together for an alkylene radical having 4 to 8 C atoms, which in particular has a heteroatom in the form of ether oxygen, thioether sulfur or tertiary amine nitrogen, forming a 5- or 6- or 7-ring with the inclusion of the nitrogen atom, in particular a 5 or 6 ring.

R ^1b and R ^2b are particularly preferred

either individually for 2-methoxyethyl, 2-ethoxyethyl, 3-methoxypropyl, 3-ethoxypropyl, 2- (2-methoxyethoxy) ethyl, 2-octyloxyethyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, 2- Ethylhexyl, or N, N-dimethylaminopropyl, or together with the inclusion of the nitrogen atom for an optionally substituted pyrrolidine, piperidine, hexamethyleneimine, morpholine, thiomorpholine or 4-methylpiperazine ring.

Most preferably, R ^1b and R ^2b are each individually 2-methoxy-ethyl, butyl or isopropyl, or together with the inclusion of the nitrogen atom for morpholine, 2,6-dimethylmorpholine, thiomorpholine, pyrrolidine or 4-methylpiperazine.

Most preferably, R ^1b and R ^2b are inclusive of the nitrogen atom for morpholine or pyrrolidine.

These hydroxysilanes can be produced in a particularly pure quality and are particularly stable on storage. They allow silane-containing hotmelt adhesives of high strength.

R ^3b is preferably a linear or branched alkylene radical having 1 to 6 C atoms, in particular a 1, 3-propylene radical. These hydroxysilanes are particularly accessible.

A preferred hydroxysilane of the formula (I b) is in particular selected from the group consisting of 1-morpholino-3- (3- (triethoxysilyl) propoxy) propan-2-ol, 1- (2,6-dimethylmorpholino) -3 (3- (triethoxysilyl) propoxy) propan-2-ol, bis (2-methoxyethyl) amino-3- (3- (triethoxysilyl) propoxy) propan-2-ol, 1-pyrrolino-dino-3- (3- (triethoxysilyl) propoxy) propan-2-ol, 1-piperidino-3- (3- (triethoxysilyl) propoxy) propan-2-ol, 1- (2-methylpiperidino) -3- (3- (triethoxysilyl) propoxy) Propan-2-ol, dibutylamino-3- (3- (triethoxysilyl) propoxy) propan-2-ol, diisopropylamino-3- (3- (triethoxysilyl) propoxy) propan-2-ol and the corresponding compounds Methoxy groups instead of ethoxy groups on the silane.

Of these, preferred is 1-morpholino-3- (3- (triethoxysilyl) propoxy) propan-2-ol. With these hydroxysilanes, hot-melt adhesives containing silane groups having a low processing viscosity and good storage stability are obtained, which cure with moisture rapidly to crosslinked adhesives, which have good mechanical properties. Preferably, a hydroxysilane of formula (I b) is reacted with a polyurethane polymer having aliphatic isocyanate groups. The hotmelt adhesives obtained in this way have good thermal stability in the uncrosslinked state and good light stability.

Another suitable hydroxysilane of the formula (I) is a hydroxysilane which is free of tertiary amino groups. These hydroxysilanes are particularly suitable for reaction with a polyurethane polymer based on very reactive aromatic isocyanates, in particular MDI. Hot-melt adhesives derived therefrom have good thermal stability in the uncrosslinked state and particularly good mechanical properties.

Such hydroxysilane in one embodiment is a hydroxysilane having a urethane group. Such is obtained in particular from the reaction of at least one isocyanatosilane with at least one diol, in particular a diol having at least one secondary hydroxyl group. Particularly suitable are reaction products of isocyanatosilanes such as 3-isocyanatopropyltriethoxysilane and diols such as 1, 2- or 1, 3-butanediol, 1, 2-pentanediol, 1, 2-hexanediol, 1, 2-octanediol, 2-ethyl-1, 3-hexanediol or 2,2,4-trimethyl-1,3-pentanediol in a molar ratio of about 1: 1.

A suitable hydroxysilane of the formula (I) which is free of tertiary amino groups is furthermore a hydroxysilane having an amido group. Such is obtained, in particular, from the reaction of at least one amino silane with at least one lactone, in particular with a lactone substituted in alpha position relative to the ring oxygen.

A preferred hydroxysilane having an amido group is a hydroxysilane of the formula (I c)

in which

R ^{1c is} an alkyl group having 1 to 12 C atoms;

R ^{2c is} a hydrogen atom or an alkyl group having 1 to 12 C atoms, which optionally has ether oxygen or amine nitrogen;

R ^{3c is} a linear or branched alkylene or cycloalkylene radical having 1 to 20 C atoms, optionally with aromatic moieties, and optionally with one or more heteroatoms;

n is 2 or 3 or 4;

and R ⁴ , R ⁵ and x have the meanings already mentioned.

R ^1c preferably represents a linear alkyl group having 1 to 8 C atoms, in particular methyl, n-butyl, n-pentyl, n-hexyl, n-heptyl or n-octyl.

R ^2c is preferably a hydrogen atom.

N is preferably 2 or 3, in particular 2.

These hydroxysilanes can be produced in a particularly pure quality and are particularly stable on storage. They enable high-strength silane-containing hotmelt adhesives with particularly good thermal stability in the un-wetted state, in particular also those based on aromatic isocyanates, in particular MDI.

R ^3c is preferably a linear or branched alkylene radical having 1 to 6 C atoms; in particular a radical selected from the group consisting of 1, 3-propylene, 2-methyl-1, 3-propylene, 1, 4-butylene, 3-methyl-1, 4-butylene and 3,3-dimethyl-1, 4-butylene, preferably for 1, 3-propylene and 3,3-dimethyl-1, 4-butylene, in particular for 1, 3-propylene. These hydroxysilanes are particularly accessible.

A preferred hydroxysilane of the formula (Ic) is in particular selected from the group consisting of N- (3-triethoxysilylpropyl) -4-hydroxypentanamide, N- (3-triethoxysilylpropyl) -4-hydroxyoctanamide, N- (3-triethoxysilylpropyl) -4 -hydroxynonanamide, N- (3-triethoxysilylpropyl) -4-hydroxydecanamide, N- (3-triethoxysilylpropyl) -4-hydroxyundecanamide, N- (3-triethoxysilylpropyl) -4-hydroxydoamide decanamide, N- (3-triethoxysilylpropyl) -5-hydroxyhexanannide, N- (3-triethoxysilylpropyl) -5-hydroxynonanamide, N- (3-triethoxysilylpropyl) -5-hydroxydecaneamide, N- (3-triethoxysilylpropyl) - 5-hydroxyundecanamide, N- (3-triethoxysilylpropyl) -5-hydroxydodecanamide, and the corresponding compounds having methoxy groups instead of ethoxy groups on the silane.

Of these, preferred are N- (3-triethoxysilylpropyl) -4-hydroxypentanamide, N- (3-triethoxysilylpropyl) -4-hydroxyoctanamide.

With these hydroxysilanes, hot-melt adhesives containing silane groups having good storage stability are obtained, which in the uncrosslinked state have good thermal stability-also in the case of hot-melt adhesives based on aromatic isocyanates-curing adhesives which are rapidly crosslinked with moisture and have good mechanical properties. Particularly preferred in the process described are the hydroxysilanes of the formula (Ia). These hydroxysilanes are particularly storage-stable, which simplifies their handling in the process described.

Most preferred in the described process are the hydroxysilanes of the formula (I c). They allow hot-melt adhesives based on aromatic isocyanates containing silane groups with good thermal stability in the uncrosslinked state.

The silane-containing hotmelt adhesive obtained by the process described may contain further constituents, in particular the following auxiliaries and additives:

- Other crosslinkable polymers, in particular silane groups and / or isocyanate groups having polymers;

- Non-reactive thermoplastic polymers, in particular homo- or copolymers of unsaturated monomers, in particular from the group comprising ethylene, propylene, butylene, isobutylene, isoprene, vinyl acetate and alkyl (meth) acrylate, in particular polyethylene (PE), polypropylene (PP), polyisobutylene, ethylene-vinyl acetate copolymers (EVA) and atactic poly (a) Olefins (APAO); furthermore polyesters, polyacrylates, polymethacrylates, polyacrylamides, polyacrylonitriles, polyimides, polyamides, polyvinyl chlorides, polysiloxanes, polyurethanes, polystyrenes, and combinations thereof, in particular polyetheramide copolymers, styrene-butadiene-styrene copolymers, styrene-isoprene-styrene copolymers, styrene-ethylene Butylene-Styrene Coplymers, Styrene-Ethylene-Propylene-Styrene Coplymers; and furthermore butyl rubber, polyisobutylene and combinations thereof, further asphalt, bitumen, raw rubber, fluorinated rubber and cellulose resins;

Tackifier resins, in particular a hydrocarbon resin, in particular coumarone-indene resins, terpene resins, phenol-modified terpene resins, natural, optionally modified, resins, in particular rosin, root resin or tall oil resin, furthermore a-methyl-styrene resins and polymeric lactic acid;

Plasticizers, especially carboxylic acid esters such as phthalates or adipates, polyols, organic phosphoric and sulfonic acid esters or polybutenes;

Catalysts for the crosslinking reactions, in particular metal catalysts and / or nitrogen-containing compounds, in particular organotin compounds, organotitanates, amines, amidines, guanidines and imidazoles; Stabilizers against oxidation, heat, hydrolysis, light and UV radiation, biocides, fungicides and flame retardants;

Desiccants, in particular tetraethoxysilane, vinyltrimethoxy- or vinyltriethoxysilane and organoalkoxysilanes which have a functional group in the α-position relative to the silane group, in particular N- (methyldimethoxysilylmethyl) -O-methyl-carbamate, (methacryloxymethyl) silanes, methoxy methylsilanes, orthoformic acid esters, as well as calcium oxide or molecular sieves;

Adhesion promoters and / or crosslinkers, in particular silanes, such as aminosilanes, mercaptosilanes, epoxysilanes, (meth) acrylosilanes, anhydridosilanes, carbamosilanes, alkylsilanes and iminosilanes;

inorganic and organic fillers, in particular mineral fillers, molecular sieves, silicic acids including highly dispersed silicas from pyrolysis processes, industrially produced carbon black, graphite, metal powder, PVC powder or hollow spheres; - dyes;

and other commonly used in reactive hot melt adhesives substances.

It may be useful to dry certain ingredients chemically or physically prior to addition.

Such auxiliaries and additives can already be present before carrying out the described process, in particular as a constituent of the isocyanate group-containing polyurethane polymer which is solid at room temperature. However, such auxiliaries and additives can also be added to the resulting hot-melt adhesive containing silane groups only after carrying out the process described.

From the process described, a hot-melt adhesive containing silane groups is obtained.

The silane group-containing hot-melt adhesive preferably has a content of room-temperature-stable silane-containing polyurethane polymer in the range of 5 to 100% by weight, in particular 15 to 95% by weight, particularly preferably 30 to 90% by weight, most preferably 50 to 80 Weight%, up.

The silane group-containing hot-melt adhesive preferably contains at least one further polymer selected from the group consisting of non-reactive thermoplastic polymers and tackifier resins.

The silane-group-containing hot-melt adhesive preferably has a content of polymers including the room temperature silane-containing polyurethane polymer in the range of 70 to 100% by weight, particularly preferably 80 to 100% by weight, in particular 90 to 100% by weight.

The silane-containing hotmelt adhesive is in a preferred embodiment free of organotin compounds. This can be advantageous for ecological and / or toxicological reasons. The silane group-containing hotmelt adhesive does not release methanol when it is crosslinked in a further preferred embodiment. This can be advantageous for ecological and / or toxicological reasons. In the event that the described process was carried out with a substoichiometric amount of hydroxysilane, the silane group-containing hotmelt adhesive contains an isocyanate- as well as silane-containing polyurethane polymer. Such a hot-melt adhesive contains a significantly reduced content of monomeric isocyanates in comparison to prior to carrying out the method described. This is advantageous for toxicological reasons.

In the event that the described process was carried out with an at least stoichiometric amount of hydroxysilane, the silane group-containing hotmelt adhesive is finally free of isocyanates. Such a hotmelt adhesive is particularly advantageous for toxicological reasons.

The silane-containing hotmelt adhesive is very stable in storage, excluding moisture. It may be stored in a suitable package or arrangement for a period of several months to a year and longer before being used.

Upon contact with moisture, the silane groups hydrolyze, eventually leading to crosslinking of the adhesive. In this case, silanol groups can condense with, for example, hydroxyl groups of the substrate to which the adhesive is applied, whereby an additional improvement in the adhesion of the adhesive to the substrate can take place during crosslinking. In the event that the hotmelt adhesive contains not only the silane groups but also isocyanate groups, these also react with moisture, which additionally contributes to crosslinking of the adhesive.

The moisture needed for crosslinking can either come from the air (humidity), or the adhesive can be contacted with a component containing water, for example by painting or spraying. The silane-containing hotmelt adhesive is applied to at least one substrate when applied in the liquid state. For this purpose, the adhesive is previously heated at least to the extent that it is liquid. The application of the adhesive typically takes place at a temperature in the range from 80 to 200.degree. C., in particular from 100 to 180.degree.

During processing, the uncrosslinked adhesive has good thermal resistance. This manifests itself in the fact that the adhesive can be left in a liquid hot state for a sufficient time for the proper application, in particular for up to several hours, without its viscosity rising excessively, in particular without gelling, and without Odor immissions occur.

The applied adhesive is advantageously added to a second substrate to a bond before it is excessively solidified by cooling.

But it can also solidify in the applied state and remelted at a later time and joined with a second substrate to a bond. In this case, care must be taken that the remelting of the adhesive takes place before the crosslinking of its reactive groups interferes with the melting. For this purpose, it may be advantageous to protect the applied adhesive against solidification prior to solidification, in particular by covering with a protective film.

The solidification of the adhesive by cooling causes a very fast strength build-up and a high initial adhesion strength of the bond. In addition to this physical adhesive curing, the crosslinking takes place in the adhesive, even after solidification, via silane groups and optionally isocyanate groups by means of moisture, as described above. This chemical crosslinking finally leads to a cured crosslinked adhesive, which can not be remelted by renewed heating to the application temperature.

Preferred substrates which can be adhered to the silane-containing hotmelt adhesive from the process described are - glass, glass ceramic, concrete, mortar, brick, brick, plaster and natural stones such as granite or marble;

- Metals and alloys, such as aluminum, iron, steel and non-ferrous metals, as well as surface-treated metals and alloys, such as galvanized or chromium-plated metals;

- leather, textiles, paper, wood, with resins, for example phenolic, melamine or epoxy resins, bonded wood-based materials, resin-textile composites and other so-called polymer composites;

- Plastics, such as polyvinyl chloride (hard and soft PVC), acrylonitrile-butadiene-styrene copolymers (ABS), polycarbonate (PC), polyamide (PA), polyester, poly (methyl methacrylate) (PMMA), epoxy resins, polyurethanes (PUR), polyoxymethylene (POM), polyolefins (PO), polyethylene (PE) or polypropylene (PP), ethylene / propylene copolymers (EPM) and ethylene / propylene / diene terpolymers (EPDM), as well as fiber-reinforced plastics such as Carbon fiber reinforced plastics (CFRP), glass fiber reinforced plastics (GRP) and

Sheet molding compounds (SMC), wherein the plastics may preferably be surface treated by means of plasma, corona or flame;

coated substrates, such as powder-coated metals or alloys;

- paints and varnishes, in particular automotive finishes.

Of these, particularly preferred are plastics, textiles, leather, wood, wood-based materials, polymer composites, paper, metals, paints and varnishes.

The substrates may be pretreated prior to application of the adhesive, for example by physical and / or chemical cleaning or by the application of an adhesion promoter, a primer solution or a primer.

Two similar substrates or two different substrates can be bonded. The adhesive is either applied to one of the two substrates and joined with the other to a bond, or it can be applied to both substrates to be bonded.

Preference is given to the bonding of two different substrates. The silane-containing hotmelt adhesive from the process described can be used in particular for construction and industrial applications, in particular as laminating adhesive, laminate adhesive, packaging adhesive, textile adhesive or wood adhesive. It is particularly suitable for adhesions in which the bonding site is visible, in particular for gluing glass, for example in vehicle and window construction, as well as for gluing transparent packaging.

From the use of the silane-containing hotmelt adhesive from the described method results in an article.

Preferred articles are automotive interior trim parts such as in particular headliner, sun visor, instrument panel, door side panel, parcel shelf and the like, wood fiber materials from the shower and bathing area, furniture decorative films, membrane films with textiles such as in particular cotton, polyester films in the clothing sector, composites of textiles and foams for car equipment, as well as transparent packaging.

The silane-containing hot-melt adhesive obtained from the process described has a number of advantages.

It allows a low hazard classification since it has little or no content of monomeric isocyanates, depending on the stoichiometry used. It can be stored in a suitable moisture-proof container over a period of several months to a year before use without losing its good applicability. When heated to a temperature in the range of 80 to 200 ° C, in particular 100 to 180 ° C, it has a viscosity at which it is easy to apply, and it has good resistance in the liquid hot state, in contrast to aminosilanes and mercaptosilanes based silane-containing hot melt adhesives from the prior art, which tend to strong Vis- cositätserhöhungen up to gelation or odor nuisance. The adhesive cross-links at room temperature under the influence of moisture bubbles and leads to a visually and mechanically high-quality adhesive composite with excellent adhesion and good resistance to environmental influences.

Examples

In the following, exemplary embodiments are listed which are intended to explain the described invention in more detail. Of course, the invention is not limited to these described embodiments.

The term "standard climate" refers to a temperature of 23 + 1 ° C and a relative humidity of 50 + 5%.

Viscosities were determined on a Rheostec RC30 thermostated plate-plate viscometer (plate diameter 25 mm, distance 1 mm, shear rate 10 s ^-1 ) at a temperature of 160 ° C.

1 . Preparation of isocyanate group-containing polyurethane polymer

Polymer P1

A mixture of 1 '200.0 g solid at room temperature, amorphous polyester estiol (Dynacoll ^® 7150 from Evonik, OH number 43 mg KOH / g) and 1' 200.0 g at room temperature liquid polyester diol (Dynacoll ^® 7250 from Evonik, OH number 22 mg KOH / g) was dried for 2 h at 120 ° C under vacuum and degassed, then 348.4 g of 4,4'-methylene diphenyl diisocyanate (Desmodur ^® 44 MC L from Bayer), stirred for 2 h at 130 ° C under vacuum and then cooled and stored in the absence of moisture. The polyurethane polymer obtained was solid at room temperature and had a content of free isocyanate groups of 2.15% by weight.

2. Preparation of Hvdroxysilane

Hydroxysilane S-1: N- (3-triethoxysilylpropyl) -4-hydroxypentanamide

In a round-bottomed flask, 100.0 g (452 mmol) of 3-aminopropyltriethoxysilane and 54.3 g (542 mmol) of γ-valerolactone were stirred under nitrogen atmosphere for about 8 h at 140 ° C until no further reaction progress was detected by means of IR. The crude product was at 80 ° C for 30 minutes and about 2 mbar treated. A liquid product with a theoretical OH equivalent weight of 321 .5 g was obtained.

3. Reaction of the Isocvanatqruppenhaltiqen Polvurethanpolymers

Example 1: hotmelt adhesive K-1

A mixture of 200.0 g (about 102.4 mmol NCO) molten polymer P1 and 36.2 g (about 1 12.6 mmol) of hydroxysilane S-1 was stirred for 2 h at 120 ° C under nitrogen until no isocyanate was detectable by IR spectroscopy , Subsequently, 40 mg of dibutyltin dilaurate were added and the resulting silane-containing polymer was cooled and stored in the absence of moisture.

The hotmelt adhesive K-1 is free of isocyanate groups.

Example 2 Hotmelt Adhesive K-2

A mixture of 200.0 g (about 102.4 mmol NCO) molten polymer P1 and 16.45 g (about 51 .2 mmol) of hydroxysilane S-1 was stirred for 2 h at 120 ° C under nitrogen until the Isocyanatbande no decrease by IR spectroscopy showed more. Subsequently, 40 mg of dibutyltin dilaurate were added and the resulting silane-containing polymer was cooled and stored in the absence of moisture.

The hot-melt adhesive K-2 contains not only the silane groups but also isocyanate groups.

Comparative Example 1 Hotmelt Adhesive Ref-1

A mixture of 200.0 g (about 102.4 mmol NCO) molten polymer P1 and 26.85 g (about 1 12.6 mmol) of 3-mercaptopropyltriethoxysilane was stirred for 2 h at 120 ° C under nitrogen until the Isocyanatbande showed no decrease by IR spectroscopy , Subsequently, 40 mg of dibutyltin dilaurate were added and the resulting silane-containing polymer was cooled and stored in the absence of moisture.

From Comparative Example 1, the silane-containing hotmelt adhesive Ref-1 was obtained. It has been observed that this adhesive smells only slightly of mercaptosilane at room temperature and, according to IR spectroscopic Copy is free of isocyanate groups. In the molten state at 120 ° C, a very strong odor of mercaptosilane perceptible and according to IR spectroscopy are again isocyanate groups present. This is an indication that the thiourethane bond is thermally so volatile that part of the mercaptosilane is released in the heat.

Comparative Example 2 Hotmelt Adhesive Ref-2

To 200.0 g (about 102.4 mmol NCO) molten polymer P1 were added at 120 ° C 25.0 g (about 1 12.9 mmol) of 3-aminopropyltriethoxysilane (Dynasylan ^® AMEO Evonik) and the mixture was stirred under nitrogen. The mixture gelled during manufacture.

4. Properties of the hotmelt adhesives obtained

Content of monomeric 4,4'-methylenediphenyl diisocyanate:

The content of monomeric isocyanate was determined by HPLC.

The polymer P1 contained 2.60% by weight of 4,4'-methylene diphenyl diisocyanate. The hot-melt adhesive K-2 contained 0.63% by weight of 4,4'-methylene diphenyl diisocyanate, ie a significantly reduced content. Thermal stability in uncrosslinked state:

Several aluminum tubes were filled with freshly prepared, molten hot-melt adhesive and sealed in a convection oven at 160 ° C stored. The viscosity was determined in each case from fresh material ("0 h") and after 2 h, 4 h and 6 h of storage at 160 ° C. The results are given in Table 1.

Table 1: Viscosity of the novel hot-melt adhesives K-1 and K-2 and Comparative Adhesive Ref-1.

Mechanical properties:

To determine the mechanical properties of the respective hot melt adhesive was pressed in a heated press between two PTFE-coated films to a film of 1 mm thickness, cooled, removed with PTFE-coated films and dumbbell-shaped test specimens with a length of 75 mm punched at a web length of 30 mm and a web width of 4 mm from the film. Three test specimens of each hotmelt adhesive were measured 3 hours after fabrication (marked "fresh" in Table 2) and three more after storage under standard conditions for 10 days (indicated in the table as "10d NK"). Tensile strength (breaking strength), elongation at break and modulus of elasticity (in the specified strain range) in accordance with DIN EN 53504 at a tensile speed of 200 mm / min were determined. The results are shown in Table 2.

Table 2: Mechanical properties of the novel hotmelt adhesives K-1 and K-2 and of the polymer P1.

Claims

claims:

1 . A process for the preparation of a hot-melt adhesive containing silane groups, in which at least one isocyanate group-containing polyurethane polymer solid at room temperature is reacted with at least one hydroxysilane which is free of urea and thiourethane groups.

A process according to claim 1, wherein the OH groups of the hydroxysilane are substoichiometrically present in relation to the isocyanate groups of the polyurethane polymer and the hot-melt adhesive obtained therefrom preferably has a content of monomeric isocyanates of <2% by weight, in particular <1

% By weight.

A process according to claim 1, characterized in that the OH groups of the hydroxysilane are at least stoichiometrically present in relation to the isocyanate groups of the polyurethane polymer and the hot-melt adhesive obtained therefrom is in particular free from

Isocyanates.

Method according to one of claims 1 to 3, characterized in that the isocyanate group-containing polyurethane polymer has an average molecular weight M _n in the range of 2Ό00 to 20Ό00 g / mol.

Method according to one of the preceding claims, characterized in that the isocyanate group-containing polyurethane polymer has 1 to 3 isocyanate groups per molecule.

Method according to one of the preceding claims, characterized in that for the preparation of the isocyanate group-containing polyurethane polymer, a mixture of at least one amorphous polyester diol and at least one other polyester diol has been used Method according to one of the preceding claims, characterized in that for the preparation of the isocyanate group-containing polyurethane polymer, a diisocyanate selected from the group consisting of 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane (IPDI), 4.4 ', 2,4'- and 2,2'-diphenylmethane diisocyanate and any mixtures of these isomers (MDI) and 2,4- and 2,6-toluene diisocyanate and any mixtures of these isomers (TDI) was used.

Method according to one of the preceding claims, characterized in that the hydroxysilane contains a secondary hydroxyl group.

A process according to claim 8, characterized in that the hydroxysilane is a hydroxysilane of the formula (I),

in which

A is either a divalent aliphatic or cycloaliphatic hydrocarbon radical having 2 to 30 carbon atoms, optionally with aromatic moieties and optionally with one or more heteroatoms which is free of active hydrogen,

or together with B-CH for a bivalent Cydoaliphatic hydrocarbon radical having 6 to 20 carbon atoms, optionally with aromatic moieties and optionally with one or more heteroatoms which is free of active hydrogen;

B is a monovalent aliphatic or cydoaliphatic hydrocarbon radical having 1 to 12 C atoms, optionally with one or more heteroatoms, which is free of active hydrogen, or together with CH-A for a bivalent Cydoaliphatic hydrocarbon radical having 6 to 20 carbon atoms, optionally with one or more heteroatoms which is free of active hydrogen;

R ^{4 is} an alkyl group having 1 to 8 C atoms; R ^{5 is} an alkyl group having 1 to 10 C atoms, optionally with one or more ether oxygens; and

x stands for 0 or 1 or 2.

A process according to claim 8 or 9, characterized in that the hydroxysilane is a hydroxysilane of the formula (I a),

in which

either R 'is a radical of formula (II) and R "is hydrogen or R' is hydrogen and R" is a radical of formula (II);

(R ⁴ ) _x

R ^3a -Si (OR ⁵ ) _3-x ^(M)

R ^1a and R ^2a either individually each represent an alkyl radical having 1 to 12 C

Atoms which optionally heteroatoms in the form of ether oxygen, thioether sulfur or tertiary Am in nitrogen, or together for an alkylene radical having 2 to 12 C-atoms, which optionally heteroatoms in the form of ether oxygen, thioether sulfur or tertiary amine nitrogen;

R ^{3a represents} a linear or branched alkylene or cycloalkylene radical having 1 to 20 C atoms, optionally with aromatic moieties, and optionally with one or more heteroatoms. A process according to claim 8 or 9, characterized in that the hydroxysilane is a hydroxysilane of the formula (I b),

where R ^1b and R ^2b either individually each represent an alkyl radical having 1 to 12 C atoms which optionally contains heteroatoms in the form of ether Oxygen, thioether sulfur or tertiary amine nitrogen, or together represent an alkylene radical having 2 to 12 C atoms, which optionally has heteroatoms in the form of ether oxygen, thioether sulfur or tertiary amine nitrogen;

R ^{3b is} a linear or branched alkylene or cycloalkylene radical having 1 to 20 carbon atoms, optionally with aromatic moieties, and optionally with one or more heteroatoms.

12. The method according to claim 8 or 9, characterized in that the hydroxysilane is a hydroxysilane of the formula (I c),

in which

R ^{1c is} an alkyl group having 1 to 12 C atoms;

R ^{3c is} a linear or branched alkylene or cycloalkylene radical having 1 to 20 C atoms, optionally with aromatic moieties, and optionally with one or more heteroatoms; and n is 2 or 3 or 4.

13. Silane group-containing hotmelt adhesive, characterized in that it was obtained from a process according to one of claims 1 to 12. 14. Use of a silane-containing hotmelt adhesive according to claim 13 as Kaschierklebstoff, laminate adhesive, packaging adhesive, textile adhesive or wood adhesive.

Article obtained from a use according to claim 14.