HK1093999B - Moisture-curing composition and hot-melt adhesive - Google Patents

Description

Moisture-curable composition and hot-melt adhesive

Cross Reference to Related Applications

The present application claims priority from german application DE 102004062653, filed 24.12.2004.

Technical Field

The present invention relates to compositions based on alkoxysilane-functional polyurethane prepolymers suitable for reactive hot-melt adhesives which are stable to storage at high temperatures.

Background

Isocyanate-functional reactive polyurethane adhesives (PU hot melt adhesives) which cure irreversibly by the action of moisture from the environment or from materials which adhere to one another are known (EP-B455400). Such prepolymers are the specific reaction products of polyester polyols and optionally polyether polyols with polyisocyanates. These reactive PU hot melt adhesives can be used universally for bonding various materials such as, for example, plastic, glass, metal, leather or wood.

The curing time of the PU hot melt adhesives, i.e.the curing time without the onset of reaction between the components, can be adjusted from a few seconds to a few minutes by modifying the mass with components which are crystalline or amorphous at room temperature. In the present application, the crystalline structure not only has a low melt viscosity and a fast curing after application, but also has good low-temperature elasticity owing to the low glass transition temperature (DE-A3827224, DE-A4114220, EP-A0354527).

In addition, components that are liquid at room temperature may also be used for property modification. Thus, EP-A0340906 describes reactive polyurethane hot melts comprising a mixture of two polyurethane prepolymers, the first prepolymer being prepared from an amorphous polyol having a glass transition temperature of greater than 20 ℃ and the second prepolymer being prepared from a polyol which is liquid at room temperature (Tg < 20 ℃).

The actual curing of the reactive PU hot-melt adhesives, i.e.the mutual crosslinking reaction between the components, takes place within a few days by reaction of the isocyanate groups with water, giving thermosetting polyureas. Thereafter, the PU hot-melt adhesive can no longer be melted or, for example, dissolved in a solvent. As such, the cured adhesive has good heat resistance, as well as chemical resistance to plasticizers, solvents, oils, or fuels.

However, these adhesives have the disadvantage that, owing to their preparation, they all have a high content of free monomeric polyisocyanates such as, for example, 4 '-diisocyanatodiphenylmethane (4, 4' -MDI) or 2, 4-diisocyanatotoluene or 2, 6-diisocyanatotoluene (TDI). These monomeric polyisocyanates have a vapor pressure that is not negligible at adhesive application temperatures of about 130 ℃ to about 180 ℃. This means that the monomer component will escape to the environment in gaseous form. Due to the cleavage of these isocyanates, corresponding industrial hygiene measures, such as the installation of suitable extraction devices, have to be taken.

Another disadvantage of these binders is the evolution of carbon dioxide gas during the reaction with water to form polyurea. The result is that the adhesive bubbles up at the bond, changing the intended position of the adhesive means.

In order to overcome the above disadvantages, silane-functional reactive hot-melt adhesives based on polyester polyols are described in the literature.

Thus, EP-A0202491 discloses moisture-curing hotmelt adhesives which are obtainable in a first embodiment by contact reaction of a polyester mixture comprising a solid polyester having a glass transition temperature of above 10 ℃ and a liquid polyester having a glass transition temperature of below-10 ℃ with a polyisocyanate, followed by reaction of the prepolymers containing free NCO groups obtained in this way with an aminosilane or mercaptosilane. In a second embodiment, an adduct is first prepared with an aminosilane or mercaptosilane and a diisocyanate, the two components being reacted in a 1: 1 molar ratio. The reaction of the addition product with the polyester mixture is then carried out in a second step. The addition of a catalyst to accelerate the curing reaction with moisture is not described. Nevertheless, dibutyltin Dilaurate (DBTL) was used as catalyst in all the examples of the embodiment for the preparation of the hot-melt adhesive. When the reaction is complete, DBTL is not deactivated and remains in the product, which in turn could theoretically act as a curing catalyst. Hot melt adhesives prepared in this manner are believed to be readily cured with ambient moisture at room temperature.

EP-A0354472 describes NCO-terminated silane compounds which can be prepared by a) reacting aminosilanes or mercaptosilanes with diisocyanates and linear alkylene glycols having from 2 to 12 carbon atoms and b) reacting the compounds with linear OH and/or NH₂Linear OH-and/or NH-chains obtained by reaction of end-capped polyesters, polyethers and/or polyurethanes with diisocyanates₂-contacting the end-capped difunctional polymer with an alkoxysilane-terminated moisture-crosslinking hotmelt adhesive obtained by the reaction. In order to accelerate the crosslinking reaction with moisture, mention may be made of the usual acidic catalysts selected, for example, from tin (II) octoate, dibutyltin dilaurate, tetrabutyltitanate, zinc acetate, zinc acetylacetonate and the like.

Nevertheless, the hotmelt adhesives described in the two publications mentioned have not been used industrially to date, since they have a significantly reduced reactivity with moisture, the alkoxysilane end groups, in comparison with the isocyanate end groups, do not cure without addition of catalysts or cure only incompletely over a long period of time, and thus build up only inadequate strength. If the above-mentioned Lewis acids are added as catalysts, the compositions lose their thermal stability during storage, since the above-mentioned catalysts also catalyze the transesterification of the polyester units present in the prepolymer with low molecular weight alcohols, such as, for example, methanol or ethanol, which split off from the alkoxy end groups. This can lead to irreversible degradation of the polymer chains, which can lead to adhesive failure. Since hot melt adhesives melt in construction ovens and remain liquid for a longer period of time, usually at least one working day, however, sufficient high temperature stability must be required for industrial applications.

The described process for preparing adducts from diisocyanates and aminosilanes in the first step entails considerable industrial disadvantages, since the two-molecule adducts of aminosilanes and diisocyanates often also form, with the result that expensive aminosilanes are lost.

EP-A0480363 describes curable compositions carrying at least two hydrolyzable silyl groups which are obtainable by reacting aliphatic polyesters containing hydroxyl groups and acryloyl groups in the molecule with isocyanatosilanes, followed by reacting the reaction product with aminosilanes and then reacting the reaction product with monofunctional isocyanates and/or with polyisocyanates. Catalysts which can be used for the curing of the compositions are mentioned as organotin compounds such as, for example, dibutyltin dilaurate or tin octoate, acid compounds such as, for example, p-toluenesulfonic acid or phosphoric esters, and amines such as 1, 2-ethylenediamine, isophoronediamine or N, N-dimethyldodecylamine.

The above compositions are obtainable only by complex multistep preparation processes and are therefore very expensive. In addition, the polyesters having hydroxyl groups and acryloyl groups in the molecule, which are necessary as raw materials, are not standard products such as those available in various forms, for example, for the preparation of reactive PU hot melts, and can be obtained only by severe restrictions. As a result, it is possible to influence the properties of hot melt adhesives in a controlled manner only to a limited extent by the mixing of amorphous, liquid and crystalline polyesters with suitable end groups. When the above-mentioned lewis acid catalyst is used, the above-described binder can be applied in terms of thermal storage stability.

EP-A0096250 discloses crosslinkable compositions based on hydroxyl-containing polymers which are liquid at temperatures below 100 ℃ and in which only certain hydroxyl groups have been replaced by alkoxysilyl end groups. Particularly suitable hydroxyl-containing polymers are, in particular, polyester polyols. Its preparation is carried out in a multi-step synthesis. In a first embodiment, an adduct is first prepared from an aminosilane or mercaptosilane and a diisocyanate, the two components being reacted in a molar ratio of 1: 1. In a second step, the reaction of the addition product with a polyol takes place, the ratio OH/NCO being less than 1: 0.9. In a second embodiment, the contact reaction of the OH-containing polymer or polymer mixture with the diisocyanate takes place in a first step, followed by the reaction of the prepolymer containing free NCO groups obtained in this way with amino groups or mercaptosilanes. The product obtained in step 2 is then mixed with an OH-containing polymer in a third step. In addition to tin and titanium compounds, amines may also be mentioned as suitable curing catalysts, but in the examples of embodiments only DBTL is employed. Nevertheless, these compositions can be cured not only by contact with moisture, but also by elevated temperatures.

Such heat curing is a considerable industrial disadvantage, since hot melt adhesives melt in construction ovens and remain liquid at elevated temperatures for a longer period of time, usually at least one working day. However, these conditions result in at least partial crosslinking of the adhesive, with the result that the adhesive becomes unusable. Furthermore, it is disclosed herein that the preparation of hot melt adhesives requires a complex multi-step process. The adducts of aromatic isocyanates, such as, for example, MDI or TDI, with aminosilanes are also unstable on storage and therefore have to be reacted additionally directly, which additionally increases the difficulty of synthesis. However, such aromatic diisocyanates can be preferably used in hot melt adhesives because of their relatively high reactivity compared to aliphatic diisocyanates.

WO 2004/005420 describes moisture-curing hotmelt adhesives which are substantially free of tin for ecological reasons and are prepared from semicrystalline polyols, substantially amorphous polyols having branched primary or secondary OH groups or mixtures thereof, aminosilanes having secondary amino groups and isocyanates.

Methods for preparing these moisture-curing hotmelt adhesives are also described. In this process, in a first step, a prepolymer is prepared from a semi-crystalline polyol, a substantially amorphous polyol having branched primary or secondary OH groups, or mixtures thereof, and an isocyanate. A tin-free catalyst may optionally be used in this step. The use of 2, 2' -dimorpholinodiethylether (DMDEE) as an example of a catalyst without tin is mentioned. In a second step, the prepolymer is reacted with an aminosilane having a secondary amino group to give a moisture-curing hot-melt adhesive. In this case, both reaction steps should be carried out without addition of a tin-containing catalyst. N-alkyl-aminoalkyl-alkoxysilanes are used as aminosilanes with secondary amino groups. In addition, catalysts which accelerate moisture curing can also be mixed into the finished hot melt adhesive. By way of example, tertiary amines are mentioned. In the examples illustrating the invention, DMDEE is used as a catalyst in the preparation of the prepolymer, i.e. the reaction of the polyol with the isocyanate. However, no other curing catalyst is mixed in the finished hot melt adhesive. However, since the DMDEE remains in the hot melt adhesive, it of course also acts as a moisture cure catalyst. The examples and comparative examples clearly show that, if DMDEE is used, a bond having sufficient final strength can only be obtained if the polyol mixture used to prepare the prepolymer comprises polyether polyols having secondary OH groups or amorphous polyesters having branches along the main chain. The different comparative examples (e.g., comparative example 2) show that, by not using crystalline or unbranched polyester polyols, the DMDEE catalyzed hot melt adhesive can only obtain completely unsuitable final strength values of ≦ 4MPa after 24 hours of curing. These values are significantly lower than the final strength exhibited by products comprising polyether polyols (reaching about 9-12MPa after 24 hours of curing). However, the use of polyether polyols having secondary OH groups is not suitable in all cases, since under certain circumstances they have a negative effect on the adhesive properties.

Sealants based on alkoxysilane-terminated polyether polyols have been known for a long time (EP-A0596360 and WO 00/26271). In addition to organometallic curing catalysts such as, for example, dibutyltin dilaurate, strongly basic bicyclic tertiary amines can also be employed as catalysts in the prior art. Thus, 1, 8-diazabicyclo [5.4.0] -undec-7-ene (DBU) and 1, 5-diazabicyclo [4.3.0] -non-5-ene (DBN) described in JP 08283366 are particularly suitable. On the other hand, according to the published specification, no other tertiary amines are particularly suitable curing catalysts, since with them a relatively long curing time is required. Specifically, the compound bis (N, N' -dimethylaminoethyl) ether (catalyst a-1) is mentioned as an example of negative comparison, and the catalyst is described as being unsuitable for accelerating the curing reaction of alkoxysilane-terminated polyurethane prepolymer with moisture.

Nevertheless, strongly basic bicyclic tertiary amines such as 1, 8-diazabicyclo [5.4.0] -undec-7-ene (DBU) and 1, 5-diazabicyclo [4.3.0] -non-5-ene (DBN) cannot be used as curing catalysts in the case of alkoxy-terminated hot melt adhesives based on polyester polyols, since they lead to irreversible degradation of the polyester units of the adhesive and thus to structural destruction thereof under the effect of heat, for example during melting operations.

As can be seen from the prior art, there is a continuing need for polyester-based alkoxysilane-functional hot-melt adhesives which are storage-stable and cure very rapidly with moisture and which have high strength after complete curing with moisture.

Summary of The Invention

It is therefore an object of the present invention to provide moisture-curing alkoxysilane-functional hotmelt adhesives which are easy to prepare, have good thermal storage stability and cure quickly after contact with moisture and give high strength after curing.

This object is achieved by providing compositions and hot melt adhesives containing alkoxysilane end groups, as will be described in more detail below.

In fact, the applicant has surprisingly found that polyester-based compositions and hot-melt adhesives containing alkoxysilane end groups and comprising the catalyst bis (N, N' -dimethylaminoethyl) ether (catalyst a-1) have excellent storage stability, cure very quickly with moisture and also provide bond points with very high final strength.

The present invention therefore provides moisture-curing alkoxysilane-functional compositions suitable for hotmelt adhesives, which are obtainable by reacting A) with B) and adding C) below:

A) can pass through

i) Preferably at least one aromatic, aliphatic, araliphatic and/or cycloaliphatic diisocyanate having a free NCO group content of 5 to 60% by weight,

and

ii) a polyol component comprising at least one linear polyester polyol which is solid at room temperature, preferably at least crystalline, and optionally one or more further amorphous linear polyester polyols and/or one or more linear polyester polyols which are liquid at room temperature and optionally one or more linear polyether polyols,

wherein the ratio of i) to ii) is selected such that the molar ratio of NCO to OH is from 1.2 to 4.0, preferably from 1.3 to 3.0,

polyurethane prepolymer obtained by reaction;

B) compounds of the general formula (I) containing alkoxysilanes and amino or mercapto groups

Wherein

X, Y and Z represent identical or different linear or branched chains (C)₁-C₈) Alkyl or cyclic (C)₃-C₈) Alkyl or (C)₁-C₈) Alkoxy, provided that at least one radical is (C)₁-C₈) An alkoxy group,

r represents a linear or branched alkylene group having 1 to 8 carbon atoms, preferably 1 to 4 carbon atoms, or a cycloalkylene group having 3 to 8 carbon atoms,

w represents-SH or-NH-R'

Wherein

R' represents hydrogen, a linear or branched alkyl radical having from 1 to 8 carbon atoms, preferably from 1 to 4 carbon atoms, or a cycloalkyl or aryl radical having from 3 to 8 carbon atoms or a radical of the formula (II)

Wherein

R 'and R' represent identical or different linear or branched alkyl groups having 1 to 8 carbon atoms, preferably 1 to 4 carbon atoms, or cycloalkyl groups having 3 to 8 carbon atoms

Wherein

In formula (I), X, Y and Z preferably represent, independently of one another, methoxy or ethoxy, W preferably represents-NH-R 'and R' preferably represents a radical of formula (II)

Wherein the ratio of the amounts of A) and B) is selected such that 0.95 to 1.1mol of amino or mercapto groups from B) are used per mole of NCO groups from A),

and adding

C) Bis (N, N' -dimethylaminoethyl) ether (catalyst A-1) (curing catalyst) for catalyzing the crosslinking reaction of alkoxy end groups in contact with moisture from the environment or from substrates that are adhered to each other.

The invention also provides a hot melt adhesive comprising the composition according to the invention, and the use of the composition according to the invention as an adhesive, in particular a hot melt adhesive, or for the preparation of such an adhesive.

The invention also provides substrates bonded with a composition according to the invention and a hot melt adhesive.

Detailed description of the preferred embodiments

Unless specifically stated otherwise, all data used in the examples of this application may be read as "about", even if the term is not expressly stated. Also, any reference to data ranges herein is intended to include all sub-ranges subsumed therein.

The expression "room temperature" as used here and hereinafter is intended to mean a temperature of 25 ℃.

The isocyanate prepolymers A) employed according to the invention are prepared in a manner known per se from polyurethane chemistry, for example by reaction of a diisocyanate component i) having free NCO groups, which is described in more detail below, with a polyol component ii), the characteristics of which are described in more detail below.

Diisocyanates suitable as diisocyanate component i) are, for example, those having an isocyanate content of from 5 to 60% by weight, based on the diisocyanate, of isocyanate groups bonded aliphatically, cycloaliphatically, araliphatically and/or aromatically, such as 1, 4-diisocyanatobutane, 1, 6-diisocyanatohexane (HDI), 2-methyl-1, 5-diisocyanatopentane, 1, 5-diisocyanato-2, 2-dimethylpentane, 2, 4-or 2, 4, 4-trimethyl-1, 6-diisocyanatohexane, 1, 10-diisocyanatodecane, 1, 3-and 1, 4-diisocyanatocyclohexane, 1, 3-and 1, 4-bis (isocyanatomethyl) -cyclohexane, 1-isocyanato-3, 3, 5-trihexyl-5-isocyanatomethylcyclohexane (isophorone-diisocyanate, IPDI), 4 '-diisocyanatodicyclohexylmethane, 1-isocyanato-1-methyl-4 (3) -isocyanatomethylcyclohexane, bis (isocyanatomethyl) -norbornane, 1, 3-and 1, 4-bis (2-isocyanatoprop-2-yl) benzene (TMXDI), 2, 4-and/or 2, 6-diisocyanatotoluene (TDI), 2' -, 2, 4 '-and/or 4, 4' -diisocyanatodiphenylmethane (MDI), 1, 5-diisocyanatonaphthalene and 1, 3-and 1, 4-bis (isocyanatomethyl) benzene.

Preferred diisocyanates for the diisocyanate i) are 1, 6-diisocyanatohexane (HDI), 1-isocyanato-3, 3, 5-trimethyl-5-isocyanatomethylcyclohexane (isophorone-diisocyanate, IPDI), 4 '-diisocyanatodicyclohexylmethane, 2, 4-and/or 2, 6-diisocyanatotoluene (TDI) and 2, 2', 2, 4 '-and/or 4, 4' -diisocyanatodiphenylmethane (MDI).

For the preparation of the polyurethane prepolymers A), the diisocyanate component i) is reacted with the polyol component ii) in such a way that the molar ratio of NCO groups to OH groups is from 1.2 to 4.0, preferably from 1.3 to 3.0.

In the context of the present invention, polyester polyols as polyol component ii) are understood to mean polyesters having more than one OH group, preferably two blocked OH groups. Such polyesters are well known to those of ordinary skill in the art. They can be prepared by known routes, for example from aliphatic hydroxycarboxylic acids or from aliphatic and/or aromatic dicarboxylic acids with one or several diols. The corresponding derivatives, for example lactones, esters of lower alcohols or anhydrides, can also be used as starting materials. Examples of suitable starting materials are succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, glutaric dianhydride, phthalic acid, isophthalic acid, terephthalic acid, phthalic anhydride, ethylene glycol, diethylene glycol, 1, 4-butanediol, 1, 6-hexanediol, neopentyl glycol and epsilon-caprolactone.

Suitable partially crystalline, amorphous and liquid polyester polyols have a molecular weight of 500-10,000 g/mol. The polyester polyols preferably have a molecular weight of 1,000-8,000g/mol, and the cap polyester polyols particularly preferably have a molecular weight of 1,500-6,500 g/mol.

The polyester polyols are liquid (glass transition temperature Tg < 20 ℃) or solid at room temperature. In this context, polyester polyols which are solid at room temperature are amorphous (glass transition temperature Tg > 20 ℃) or at least partially crystalline.

The moisture-curing alkoxysilane-functional compositions and hotmelt adhesives according to the invention comprise in their polyol component ii) at least one polyester polyol which is at least difunctional and solid at room temperature and preferably at least partially crystalline.

They optionally additionally comprise in their polyol component ii) one or several at least difunctional and at least partially crystalline polyester polyols and/or one or several at least difunctional amorphous polyester polyols and/or one or several at least difunctional polyester polyols which are liquid at room temperature and optionally one or several at least difunctional polyether polyols.

"at least partially crystalline" is understood to mean polyester polyols which are not completely crystalline, but which additionally have a certain amorphous content. They are crystalline and have a crystalline melting point (Tm) and a glass transition temperature (Tg). Melting point refers to the temperature at which the crystalline content of the material melts. It can be determined, for example, by means of DSC measurement by differential calorimetric analysis of the main endothermic peak (crystal melting peak). The melting point of the at least partially crystalline polyester polyol, as determined by means of DSC during the second heating at a heating and cooling rate of 10K/min, is in the range of, for example, about 35 deg.C to about 120 deg.C. The glass transition temperature of the at least partially crystalline polyester polyols is generally, for example, well below room temperature. Suitable partially crystalline polyester polyols are well known to those of ordinary skill in the art.

Suitable at least partially crystalline, i.e. crystalline, polyester polyols are based, for example, on linear aliphatic dicarboxylic acids having from 6 to 12 carbon atoms in the molecule, such as adipic acid, azelaic acid, sebacic acid and dodecanedioic acid, preferably adipic acid and dodecanedioic acid, and also linear diols having from 4 to 8 carbon atoms in the molecule, preferably having an even number of carbon atoms, such as 1, 4-butanediol and 1, 6-hexanediol. Polycaprolactone derivatives based on bifunctional starter molecules, such as 1, 6-hexanediol, may also be mentioned as being particularly suitable.

Suitable amorphous polyester polyols are, for example, polyester polyols based on adipic acid, isophthalic acid, terephthalic acid, ethylene glycol, neopentyl glycol and 3-hydroxy-2, 2-dimethylpropyl 3-hydroxy-2, 2-dimethylpropionate.

Suitable polyester polyols which are liquid at room temperature are, for example, polyester polyols based on adipic acid, ethylene glycol, 1, 6-hexanediol and neopentyl glycol.

Polyethers customary in polyurethane chemistry are suitable as polyether polyols, for example addition compounds or mixed addition compounds of tetrahydrofuran, styrene oxide, ethylene oxide, propylene oxide, butylene oxide or epichlorohydrin, preferably of ethylene oxide and/or propylene oxide, which are prepared with difunctional to hexafunctional starter molecules such as, for example, water, ethylene glycol, 1, 2-or 1, 3-propanediol, bisphenol A, neopentyl glycol, glycerol, trimethylolpropane, pentaerythritol, sorbitol or amines having 1 to 4 NH bonds. Preference is given to difunctional propylene oxide and/or ethylene oxide adducts and polytetrahydrofuran. Such polyether polyols and processes for their preparation are well known to those skilled in the art.

Suitable polyether polyols have molecular weights of 300-20,000 g/mol. The polyether polyols preferably have molecular weights of 500-15,000g/mol, particularly preferably 500-10,000 g/mol.

One or more different polyester polyols of at least partially crystalline or amorphous and liquid nature may be employed in the compositions of the present invention. The amount of each component of the polyol can be determined by one of ordinary skill in the art according to the desired properties, and is not particularly limited. The at least partially crystalline solid polyester polyol and the solid amorphous polyester polyol are present in an amount of up to 100% by weight, in each case based on the total weight of the polyol component. Preference is given to a content of polyester polyols which are solid and at least partly crystalline at room temperature of from 10 to 100% by weight, a content of solid amorphous polyester polyols of, for example, from 0 to 70% by weight, and a content of polyester polyols which are liquid at room temperature of, for example, from 0 to 70% by weight, in each case based on the total weight of the polyol component. The polyether polyol may be present in an amount of from 0 to 50% by weight based on the total weight of the polyol component.

The polyurethane prepolymers a) can be prepared, for example, in such a way that, when a polyol which is liquid at the reaction temperature is used, it is mixed with an excess of polyisocyanate and the homogeneous mixture is stirred until a constant NCO value is obtained, which usually takes from 30 minutes to 2 hours. The reaction temperature is selected to be in the range of 80 ℃ to 150 ℃, preferably in the range of 100 ℃ to 130 ℃. The preparation of the polyurethane prepolymers A) can of course also be carried out continuously in stirred tanks arranged in series or in suitable mixing units, for example in high-speed stirrers according to the rotor-stator principle.

It is of course also possible to modify the polyester polyols and/or polyether polyols or parts thereof with insufficient amounts of diisocyanates, preferably 1, 6-diisocyanatohexane (HDI), 2, 4-and/or 2, 6-diisocyanatotoluene (TDI) and/or 2, 4 '-and/or 4, 4' -diisocyanatodiphenylmethane (MDI), and to react the urea group-containing polyols with excess diisocyanate at the end of the reaction to give polyurethane prepolymers A).

It is also possible to react the polyol with the diisocyanate in the presence of up to 5% by weight of a trimer of, for example, an aliphatic diisocyanate, for example hexamethylene diisocyanate, or to add this trimer at the end of the prepolymerization.

In the second stage of the process according to the invention, the polyurethane prepolymers A) which can be employed according to the invention are reacted with compounds B) of the general formula (I) defined above.

Suitable examples of compounds B) of the general formula (I) are gamma-aminopropyltrimethoxysilane, gamma-aminopropyltriethoxysilane, N-butyl-gamma-aminopropyltrimethoxysilane, N-propyl-gamma-aminopropyltrimethoxysilane, N-phenyl-gamma-aminopropyltrimethoxysilane, 4-amino-3, 3-dimethylbutyltrimethoxysilane, 4-amino-3, 3-dimethylbutylmethyldimethoxysilane, gamma-mercaptopropyltrimethoxysilane and gamma-mercaptopropyltriethoxysilane.

Preference is given to using compounds B of the formula (I) which contain alkoxysilanes and amino groups, i.e.in which the radical W corresponds to the radical-NH-R '), in which the radical R' preferably corresponds to the formula (II). The preparation of such compounds is carried out, for example, as described in EP-A0596360.

Specific examples of such preferred compounds B) which may be mentioned are diethyl N- (3-triethoxysilylpropyl) aspartate, dimethyl N- (3-triethoxysilylpropyl) aspartate, di-N-butyl N- (3-triethoxysilylpropyl) aspartate, dimethyl N- (3-trimethoxysilylpropyl) aspartate and diethyl N- (3-trimethoxysilylpropyl) aspartate.

In the process according to the invention, the reaction of the NCO prepolymer with the compounds of the formula (I) containing alkoxysilanes and amino or mercapto groups is carried out, for example, at temperatures in the range from 80 to 150 ℃ and preferably in the range from 100 ℃ to 130 ℃ and the proportions are generally chosen so that from 0.95 to 1.1mol of aminosilane or mercaptosilane compound are used per mol of NCO groups employed. Preferably, 1mol of aminosilane or mercaptosilane compound is used per mol of NCO groups used.

If aspartates are used as compounds of the general formula (I) containing alkoxysilanes and amino groups, a cyclocondensation reaction takes place according to the teaching of EP-A0807649 if higher reaction temperatures are used, but this is not troublesome and sometimes even advantageous.

Bis (N, N' -dimethylaminoethyl) ether (catalyst A-1) is added to the polyurethane prepolymer which contains alkoxysilane end groups and can be used according to the invention as a catalyst for the curing reaction of the hotmelt adhesive according to the invention with moisture from the environment or from substrates which are bonded to one another. The addition reaction can be carried out as the next processing step after the preparation of the polyurethane prepolymer containing alkoxysilane end groups. The bis (N, N' -dimethylaminoethyl) ether (catalyst A-1) functioning as a catalyst may optionally also be added at an earlier time, for example during the preparation of prepolymer A), although this is not preferred.

The catalyst is used, for example, in an amount of 0.1 to 1.5% by weight based on the polyurethane prepolymer having alkoxysilane terminal groups.

The catalyst is preferably used in an amount of 0.2 to 1.0% by weight based on the polyurethane prepolymer having alkoxysilane terminal groups.

The catalysts are particularly preferably used in amounts of from 0.25 to 0.8% by weight, based on the polyurethane prepolymer containing alkoxysilane end groups.

The alkoxysilane-functional hot melt adhesives according to the invention may also contain one or more of the usual additives for hot melt adhesives. For example, they may be modified in a customary manner with inorganic or organic fillers, dyes, resins and/or extender oils.

Further desiccants may be added to the alkoxysilane-functional hot-melt adhesives according to the invention, examples which may be mentioned being in particular alkoxysilyl compounds such as vinyltrimethoxysilane, methyltrimethoxysilane, isobutyltrimethoxysilane and hexadecyltrimethoxysilane.

In addition, known functional silanes can be added as adhesion promoters to the alkoxysilane-functional hot-melt adhesives according to the invention, for example aminosilanes of the type mentioned above, and also N-aminoethyl-3-aminopropyltrimethoxy-and/or N-aminoethyl-3-aminopropylmethyldimethoxysilane, epoxysilanes and/or mercaptosilanes.

The compositions according to the invention can be employed in the opposite way as adhesives, for example as structural adhesives for the temporary fixing of structural parts, as bookbinding adhesives or adhesives for the preparation of cross-bottom valve covers (cross bottom valve covers), composite films or laminate films, or as edge strips and as adhesives in the automotive industry for bonding metal sheets to one another or, for example, to glass and plastics.

The invention therefore also provides for the use of the moisture-reactive, alkoxysilane-functional polyurethane prepolymers according to the invention as adhesives. The invention also provides substrates that have been bonded with a composition or adhesive according to the invention.

The moisture-curing alkoxysilane-functional polyurethane hot-melt adhesive is processed in a manner known to those skilled in the art. They are preferably applied at elevated temperature, the reactive hot-melt adhesive is melted continuously or discontinuously, for example at temperatures of 80 to 180 ℃ and the melt is brought into contact with the substrate by, for example, spraying or roller coating. In this context, the moisture-curing alkoxysilane-functional polyurethane hot-melt adhesive is applied to at least one surface of the substrates to be bonded. The parts to be bonded can then be immediately bonded together under pressure.

Examples

Polyester a (polyester polyol which is solid at room temperature and at least partially crystalline):

adipic acid and 1, 6-hexanediol-based polyester polyols having a hydroxyl number of about 30mg KOH/g and an acid value of about 0.5mg KOH/g. Their preparation is carried out in a manner known to the person skilled in the art and described, for example, in Ullmanns Enzyklopadie der technischen Chemie, "Polyester", 4 th edition, Verlag Chemie, Weinheim, 1980.

Polyester B (polyester polyol which is solid at room temperature and at least partially crystalline):

polyester polyols based on dodecanedioic acid and 1, 6-hexanediol having a hydroxyl number of about 30mg KOH/g and an acid value of about 0.8mg KOH/g. Their preparation is carried out in a manner known to the person skilled in the art and described, for example, in Ullmanns Enzyklopadie der technischen Chemie, "Polyester", 4 th edition, Verlag Chemie, Weinheim, 1980.

Polyester C (polyester polyol which is solid and amorphous at room temperature):

has the following formula:

content in polyester (wt.)

Ethylene glycol about 15.3

Neopentyl glycol about 10.3

3-hydroxy-2, 2-dimethylpropionic acid 3-hydroxy-2, 2-dimethylpropyl ester about 21.0

Adipic acid about 6.0

Isophthalic acid about 20.7

Terephthalic acid about 26.7

And a hydroxyl number of about 34.7mg KOH/g and an acid number of about 1.2mg KOH/g. The preparation thereof is carried out in a manner known to the person skilled in the art and described, for example, in Ullmanns Enzyklopadie der technischen Chemie, "Polyester", 4 th edition, VerlagChemie, Weinheim, 1980.

Polyester D (polyester polyol which is liquid at room temperature):

has the following formula:

content in polyester (wt.)

Ethylene glycol about 17.0

1, 6-hexanediol of about 19.5

Neopentyl glycol about 8.1

Adipic acid about 55.4

And a hydroxyl number of about 22mg KOH/g and an acid value of about 1.5mg KOH/g. The preparation thereof is carried out in a manner known to the person skilled in the art and described, for example, in Ullmanns Enzyklopadie der technischen Chemie, "Polyester", 4 th edition, VerlagChemie, Weinheim, 1980.

Polyether E:

polypropylene oxide having a hydroxyl number of about 56mg KOH/g.

Such Polyethers are prepared in a generally known manner by means of KOH catalysis, for example by means of L.E.St.Pierre, Polyethers Part I, polyallylene Oxide and other Polyethers, editor: norman g.gaylord; high Polymers vol.xiii; interscience Publishers; newark 1963; p.130 and the following, etc.

Catalyst A-1:

bis (N, N' -dimethylaminoethyl) ether, available, for example, from Huntsman Belgium BVBA, Everberg under the trade nameZF-20 was obtained.

DMDEE：

2, 2' -dimorpholinodiethyl ether available, for example, from Air Products Nederland B.V., Urrecht under the trade nameDMDEE was obtained.

DBTL：

Dibutyltin dilaurate, available for example from OSi Specialties under the trade nameSUL-4 was obtained.

DBU：

1, 8-diazabicyclo [5.4.0] undec-7-ene, available from Merck KGaA, Darmstadt.

DBN：

1, 5-diazabicyclo [4.3.0] non-5-ene, available from Merck KGaA, Darmstadt.

Example 1 (according to the invention):

790.34g (0.219mol) of polyester A were initially introduced into a 2 l ground sealed beaker, melted at 130 ℃ and subsequently dewatered for 1 hour at a reduced pressure of 30mbar (+ -10 mbar) and 130 ℃. 109.5g (0.438mol) of 4, 4' -diisocyanatodiphenylmethane (f) (I) are then added44M, Bayer AG, Leverkusen). After stirring for 30 minutes, the NCO content was determined to be 1.99% (theoretical value: 2.04%). 148.46g (0.422mol) of diethyl N- (3-trimethoxysilylpropyl) aspartate (prepared according to example 5 of EP-A596360) corresponding to the NCO content were slowly added dropwise to the apparatus and purged with nitrogen, the temperature rise not exceeding 10 ℃ being as far as possible. When the total amount of diethyl N- (3-trimethoxysilylpropyl) aspartate was added completely, the mixture was stirred at 130 ℃ for about a further half an hour. Then, 0.5% by weight of catalyst A-1 was added as a curing catalyst. The mixture was thoroughly homogenized and then poured into aluminum cartridges, each having a filling amount of about 150g, and these aluminum cartridges were hermetically sealed. One of these aluminum cartridges was stored in each case in a circulating air drying cabinet at 100 ℃ for 4 hours, 24 hours, 48 hours and 72 hours. The viscosity of these samples after heated storage was measured. The remaining aluminum cylinder was aged in a circulating air drying oven at 100 ℃ for 4 hours. The remaining tests were performed on these samples.

Example 2 (according to the invention):

790.34g (0.219mol) of polyester A were initially introduced into a 2 l ground sealed beaker, melted at 130 ℃ and subsequently dewatered for 1 hour at a reduced pressure of 30mbar (+ -10 mbar) and 130 ℃. 109.5g (0.438mol) of 4, 4' -diisocyanatodiphenylmethane (f) (I) are then added44M, Bayer AG, Leverkusen). After stirring for 30 minutes, the NCO content was determined to be 2.00% (theoretical value: 2.04%). 76.28g (0.425mol) of 3- (trimethoxysilyl) propylamine (Merck KGaA, Darmstadt) corresponding to the NCO content were slowly added dropwise to the apparatus and purged with nitrogen, the temperature rise not exceeding 10 ℃ being as far as possible. When the entire amount of 3- (trimethoxysilyl) propylamine was added dropwise, the mixture was then stirred at 130 ℃ for about another half hour. Then, 0.5% by weight of catalyst A-1 was added as a curing catalyst. The mixture was thoroughly homogenized and then poured into aluminum cartridges, each having a filling amount of about 150g, and these aluminum cartridges were hermetically sealed. One of these aluminum cartridges was stored in each case in a circulating air drying cabinet at 100 ℃ for 4 hours, 24 hours, 48 hours and 72 hours. The viscosity of these samples after heated storage was measured. The remaining aluminum cylinder was aged in a circulating air drying oven at 100 ℃ for 4 hours. The remaining tests were performed on these samples.

Example 3 (according to the invention):

738.78g (0.191mol) of polyester A and 316.62g (0.098mol) of polyester C were initially introduced into a 2 l ground-sealed beaker, melted at 130 ℃ and then dewatered for 1 hour at a reduced pressure of 30mbar (+ -10 mbar) and 130 ℃. 144.6g (0.578mol) of 4, 4' -diisocyanatodiphenylmethane (I) are then added44M, Bayer AG, Leverkusen). After stirring for 30 minutes, the NCO content was determined to be 1.95% (theoretical value: 2.02%). 145.38g (0.414mol) of diethyl N- (3-trimethoxysilylpropyl) aspartate (prepared according to example 5 of EP-A0596360) corresponding to the NCO content were slowly added dropwise to the apparatus and purged with nitrogen, the temperature rise not exceeding 10 ℃ being as far as possible. When the total amount of diethyl N- (3-trimethoxysilylpropyl) aspartate was added completely, the mixture was stirred at 130 ℃ for about a further half an hour. Then, 0.5% by weight of catalyst A-1 was added as a curing catalyst. Thoroughly homogenizing the mixture, and thenPoured into aluminum cylinders, each filled in an amount of about 150g, and hermetically sealed. The aluminum cylinder was aged in a circulating air drying oven at 100 ℃ for 4 hours.

Example 4 (according to the invention):

425.67g (0.110mol) of polyester A, 319.25g (0.099mol) of polyester C and 319.25g (0.063mol) of polyester D were initially introduced into a 2 l ground-sealed beaker, melted at 130 ℃ and then dewatered for 1 hour at a reduced pressure of 30mbar (+ -10 mbar) and 130 ℃. 135.83g (0.543mol) of 4, 4' -diisocyanatodiphenylmethane (b)44M, Bayer AG, Leverkusen). After stirring for 30 minutes, the NCO content was determined to be 1.90% (theoretical value: 1.90%). 141.12g (0.402mol) of diethyl N- (3-trimethoxysilylpropyl) aspartate (prepared according to example 5 of EP-A596360) corresponding to the NCO content were slowly added dropwise to the apparatus and purged with nitrogen, the temperature rise not exceeding 10 ℃ being as far as possible. When the total amount of diethyl N- (3-trimethoxysilylpropyl) aspartate was added completely, the mixture was stirred at 130 ℃ for about a further half an hour. Then, 0.5% by weight of catalyst A-1 was added as a curing catalyst. The mixture was thoroughly homogenized and then poured into aluminum cartridges, each having a filling amount of about 150g, and these aluminum cartridges were hermetically sealed. The aluminum cylinder was aged in a circulating air drying oven at 100 ℃ for 4 hours.

Example 5 (according to the invention):

831.82g (0.215mol) of polyester A and 207.95g (0.105mol) of polyether E were initially introduced into a 2 l ground sealed beaker, melted at 130 ℃ and then dehydrated for 1 hour at a reduced pressure of 30mbar (+ -10 mbar) and 130 ℃. 160.23g (0.640mol) of 4, 4' -diisocyanatodiphenylmethane (I) are then added44M, Bayer AG, Leverkusen). Determination of the NCO content after 30 minutes of stirringIt was 2.26% (theoretical value: 2.24%). 168.77g (0.480mol) of diethyl N- (3-trimethoxysilylpropyl) aspartate (prepared according to example 5 of EP-A0596360) corresponding to the NCO content were slowly added dropwise to the apparatus and purged with nitrogen, the temperature rise not exceeding 10 ℃ being as far as possible. When the total amount of diethyl N- (3-trimethoxysilylpropyl) aspartate was added completely, the mixture was stirred at 130 ℃ for about a further half an hour. Then, 0.5% by weight of catalyst A-1 was added as a curing catalyst. The mixture was thoroughly homogenized and then poured into aluminum cartridges, each having a filling amount of about 150g, and these aluminum cartridges were hermetically sealed. The aluminum cylinder was aged in a circulating air drying oven at 100 ℃ for 4 hours.

Example 6 (according to the invention):

422.76g (0.109mol) of polyester A, 317.07g (0.098mol) of polyester C and 317.07g (0.079mol) of polyester B were initially introduced into a 2 l ground-sealed beaker, melted at 130 ℃ and dewatered for 1 hour at a reduced pressure of 30mbar (+ -10 mbar) and 130 ℃. 143.11g (0.572mol) of 4, 4' -diisocyanatodiphenylmethane (b)44M, Bayer AG, Leverkusen). After stirring for 30 minutes, the NCO content was determined to be 2.02% (theoretical value: 2.00%). 149.32g (0.425mol) of diethyl N- (3-trimethoxysilylpropyl) aspartate (prepared according to example 5 of EP-A0596360) corresponding to the NCO content were slowly added dropwise to the apparatus and purged with nitrogen, the temperature rise not exceeding 10 ℃ being as far as possible. When the total amount of diethyl N- (3-trimethoxysilylpropyl) aspartate was added completely, the mixture was stirred at 130 ℃ for about a further half an hour. Then, 0.5% by weight of catalyst A-1 was added as a curing catalyst. The mixture was thoroughly homogenized and then poured into aluminum cartridges, each having a filling amount of about 150g, and these aluminum cartridges were hermetically sealed. The aluminum cylinder was aged in a circulating air drying oven at 100 ℃ for 4 hours.

Comparative example 1 (not according to the invention):

790.34g (0.219mol) of polyester A were initially introduced into a 2 l ground sealed beaker, melted at 130 ℃ and subsequently dewatered for 1 hour at a reduced pressure of 30mbar (+ -10 mbar) and 130 ℃. 109.5g (0.438mol) of 4, 4' -diisocyanatodiphenylmethane (f) (I) are then added44M, Bayer AG, Leverkusen). After stirring for 30 minutes, the NCO content was determined to be 1.98% (theoretical value: 2.04%). 147.27g (0.419mol) of diethyl N- (3-trimethoxysilylpropyl) aspartate (prepared according to example 5 of EP-A596360) corresponding to the NCO content were slowly added dropwise to the apparatus and purged with nitrogen, the temperature rise not exceeding 10 ℃ being as far as possible. When the total amount of diethyl N- (3-trimethoxysilylpropyl) aspartate was added completely, the mixture was stirred at 130 ℃ for about a further half an hour. The mixture was then poured into aluminum cylinders, approximately 150g per pour, and the cylinders were hermetically sealed. One of these aluminum cartridges was stored in each case in a circulating air drying cabinet at 100 ℃ for 4 hours, 24 hours, 48 hours and 72 hours. The viscosity of these samples after heated storage was measured. The remaining aluminum cylinder was aged in a circulating air drying oven at 100 ℃ for 4 hours. The remaining tests were performed on these samples.

Comparative example 2 (according to the invention):

790.34g (0.219mol) of polyester A were initially introduced into a 2 l ground sealed beaker, melted at 130 ℃ and subsequently dewatered for 1 hour at a reduced pressure of 30mbar (+ -10 mbar) and 130 ℃. 109.5g (0.438mol) of 4, 4' -diisocyanatodiphenylmethane (f) (I) are then added44M, Bayer AG, Leverkusen). After stirring for 30 minutes, the NCO content was determined to be 1.99% (theoretical value: 2.04%). 75.67g (0.422mol) of 3- (trimethoxysilyl) propylamine (Merck KGaA, Darmstadt) corresponding to the NCO content were slowly added dropwise to the apparatus and blown with nitrogenSweeping to make the temperature rise not exceed 10 ℃ as much as possible. When the entire amount of 3- (trimethoxysilyl) propylamine was added dropwise, the mixture was then stirred at 130 ℃ for about another half hour. The mixture was then poured into aluminum cylinders, approximately 150g per pour, and these aluminum cylinders were hermetically sealed. One of these aluminum cartridges was stored in each case in a circulating air drying cabinet at 100 ℃ for 4 hours, 24 hours, 48 hours and 72 hours. The viscosity of these samples after heated storage was measured. The remaining aluminum cylinder was aged in a circulating air drying oven at 100 ℃ for 4 hours. The remaining tests were performed on these samples.

Comparative example 3 (not according to the invention):

1062.53g (0.275mol) of polyester A were initially introduced into a 2 l ground sealed beaker, melted at 130 ℃ and subsequently dewatered for 1 hour at a reduced pressure of 30mbar (+ -10 mbar) and 130 ℃. 137.47g (0.549mol) of 4, 4' -diisocyanatodiphenylmethane (f) (I) are then added44M, Bayer AG, Leverkusen). After stirring for 30 minutes, the NCO content was determined to be 1.86% (theoretical value: 1.92%). 138.89g (0.395mol) of diethyl N- (3-trimethoxysilylpropyl) aspartate (prepared according to example 5 of EP-A0596360) corresponding to the NCO content were slowly added dropwise to the apparatus and purged with nitrogen, the temperature rise not exceeding 10 ℃ being as far as possible. When the total amount of diethyl N- (3-trimethoxysilylpropyl) aspartate was added completely, the mixture was stirred at 130 ℃ for about a further half an hour. Thereafter 0.5% by weight of DBTL was added as curing catalyst. The mixture was then homogenized well and poured into aluminium cylinders, approximately 150g per pour, and these aluminium cylinders were sealed in a gas-tight manner. One of these aluminum cartridges was stored in each case in a circulating air drying cabinet at 100 ℃ for 4 hours, 24 hours, 48 hours and 72 hours. The viscosity of these samples after heated storage was measured. The remaining aluminum cylinder was aged in a circulating air drying oven at 100 ℃ for 4 hours. The remaining tests were performed on these samples.

Comparative example 4 (not according to the invention):

790.34g (0.219mol) of polyester A were initially introduced into a 2 l ground sealed beaker, melted at 130 ℃ and subsequently dewatered for 1 hour at a reduced pressure of 30mbar (+ -10 mbar) and 130 ℃. 109.5g (0.438mol) of 4, 4' -diisocyanatodiphenylmethane (f) (I) are then added44M, Bayer AG, Leverkusen). After stirring for 30 minutes, the NCO content was determined to be 1.91% (theoretical value: 2.04%). 142.46g (0.406mol) of diethyl N- (3-trimethoxysilylpropyl) aspartate (prepared according to example 5 of EP-A596360) corresponding to the NCO content were slowly added dropwise to the apparatus and purged with nitrogen, the temperature rise not exceeding 10 ℃ being as far as possible. When the total amount of diethyl N- (3-trimethoxysilylpropyl) aspartate was added completely, the mixture was stirred at 130 ℃ for about a further half an hour. Thereafter 0.5% by weight of DBU (50% in ethyl acetate) was added as curing catalyst. The mixture was homogenized well and poured into aluminum cylinders, approximately 150g per pour, and the cylinders were hermetically sealed. One of these aluminum cartridges was stored in each case in a circulating air drying cabinet at 100 ℃ for 4 hours, 24 hours, 48 hours and 72 hours. The viscosity of these samples after heated storage was measured. The remaining aluminum cylinder was aged in a circulating air drying oven at 100 ℃ for 4 hours. The remaining tests were performed on these samples.

Comparative example 5 (not according to the invention):

790.34g (0.219mol) of polyester A were initially introduced into a 2 l ground sealed beaker, melted at 130 ℃ and subsequently dewatered for 1 hour at a reduced pressure of 30mbar (+ -10 mbar) and 130 ℃. 109.5g (0.438mol) of 4, 4' -diisocyanatodiphenylmethane (f) (I) are then added44M, Bayer AG, Leverkusen). After stirring for 30 minutes, the NCO content was determined to be 1.99% (theoretical value: 2.04%). Will be provided with148.46g (0.422mol) of diethyl N- (3-trimethoxysilylpropyl) aspartate (prepared according to example 5 of EP-A0596360) corresponding to the NCO content were slowly added dropwise to the apparatus and purged with nitrogen, the temperature rise not exceeding 10 ℃ being as far as possible. When the total amount of diethyl N- (3-trimethoxysilylpropyl) aspartate was added completely, the mixture was stirred at 130 ℃ for about a further half an hour. Thereafter, 0.5% by weight of DBN was added as a curing catalyst. The mixture was homogenized well and poured into aluminum cylinders, approximately 150g per pour, and the cylinders were hermetically sealed. One of these aluminum cartridges was stored in each case in a circulating air drying cabinet at 100 ℃ for 4 hours, 24 hours, 48 hours and 72 hours. The viscosity of these samples after heated storage was measured. The remaining aluminum cylinder was aged in a circulating air drying oven at 100 ℃ for 4 hours. The remaining tests were performed on these samples.

Comparative example 6 (not according to the invention):

1053.78g (0.292mol) of polyester A were initially introduced into a 2 l ground sealed beaker, melted at 130 ℃ and subsequently dewatered for 1 hour at a reduced pressure of 30mbar (+ -10 mbar) and 130 ℃. 146.22g (0.584mol) of 4, 4' -diisocyanatodiphenylmethane (I) are then added44M, Bayer AG, Leverkusen). After stirring for 30 minutes, the NCO content was determined to be 1.95% (theoretical value: 2.04%). The product was poured into aluminum cylinders, each having a filling amount of about 150g, and these aluminum cylinders were hermetically sealed. The aluminum cylinder was aged in a circulating air drying oven at 100 ℃ for 4 hours.

Comparative example 7 (not according to the invention):

790.34g (0.219mol) of polyester A were initially introduced into a 2 l ground sealed beaker, melted at 130 ℃ and subsequently dewatered for 1 hour at a reduced pressure of 30mbar (+ -10 mbar) and 130 ℃. 109.5g (0.438mol) of 4, 4' -diisocyanatodiphenylmethane (f) (I) are then added44M, Bayer AG, Leverkusen). After stirring for 30 minutes, the NCO content was determined to be 1.99% (theoretical value: 2.04%). 148.46g (0.422mol) of diethyl N- (3-trimethoxysilylpropyl) aspartate (prepared according to example 5 of EP-A596360) corresponding to the NCO content were slowly added dropwise to the apparatus and purged with nitrogen, the temperature rise not exceeding 10 ℃ being as far as possible. When the total amount of diethyl N- (3-trimethoxysilylpropyl) aspartate was added completely, the mixture was stirred at 130 ℃ for about a further half an hour. Thereafter, 0.5% by weight of DMDEE was added as curing catalyst. The mixture was homogenized well and poured into aluminum cylinders, approximately 150g per pour, and the cylinders were hermetically sealed. One of these aluminum cartridges was stored in each case in a circulating air drying cabinet at 100 ℃ for 4 hours, 24 hours, 48 hours and 72 hours. The viscosity of these samples after heated storage was measured. The remaining aluminum cylinder was aged in a circulating air drying oven at 100 ℃ for 4 hours. The remaining tests were performed on these samples.

Determination of the storage stability of the silane-functional moisture-curing PU hot melts:

after storage in airtight aluminum cartridges for 4 hours, 24 hours, 48 hours and 72 hours, they were taken out of the drying oven and the viscosity of the mixture was measured at a measuring temperature of 100 ℃ using a viskotest VT 550 rotary viscometer provided with an SV measuring cup and an SV DIN 2 measuring device and supplied by Haake. The results are shown in Table 1.

The results show that the prior art hot melt adhesive formulation based on polyester polyol and containing lewis acid organometallic catalysts (comparative example 3) is not thermally stable. After 24 hours of storage at 100 ℃, the viscosity had decreased to about half the viscosity of uncatalyzed comparative example 1. After 48 and 72 hours, the viscosity was only about 25% of that of the uncatalyzed sample. This viscosity reduction can be attributed to irreversible degradation of the polyester chain by transesterification with the alcohol (in this case methanol) which cleaves off at the end of the alkoxysilane. The prior art hot melt adhesives (comparative examples 4 and 5) prepared with strongly basic bicyclic tertiary amine catalysts (DBU and DBN) are also thermally unstable. The viscosity of these formulations decreased to half that of the comparative product without catalyst (comparative example 1) even when exposed to heat at 100 ℃ for a short period of 4 hours. The reduction in viscosity is even more dramatic during longer heat exposure. The reduction in viscosity here is likewise due to irreversible degradation of the polyester chain of the polyurethane prepolymers containing alkoxysilane end groups, with the result that the hotmelt adhesives become unusable.

On the other hand, the hot melt adhesive with the tertiary amine catalyst a-1 according to the present invention (example 1) showed excellent storage stability under a hot environment. The viscosity was only insignificantly reduced compared with uncatalyzed comparative example 1, even after storage at 100 ℃ for 72 hours. Excellent adhesive spots can be prepared with these hot melt adhesives even when stored under hot environment.

And (3) measuring heat resistance:

test samples were prepared from beech boards of 40X 20X 5mm size, stored at 23 ℃ and 50% relative humidity. The cartridges containing the product to be characterized were placed in a circulating air drying cabinet at 120 ℃ for 45 minutes to melt, and the molten product was then applied in a twist by means of a cartridge gun to the wooden test specimens held in a special mold. The mold is then closed firmly. The die ensures an overlap length of 10mm, 2cm²And a bond point thickness of 0.8 mm. After 24 hours of storage at 23 ℃ and 50% relative humidity, the test specimens were removed from the molds and stored for a further 14 days at 23 ℃ and 50% relative humidity. The heat resistance measurements were then carried out on 5 test specimens in each case. For this purpose, the test specimens were suspended in a drying cabinet and loaded with a weight of 2500 g. The initial temperature was 40 ℃. After 20 minutes, the temperature was raised to 200 ℃ at a constant rate of 0.5 ℃/min. When the bond point composition became completely detached, the temperature in the oven at break was recorded. The results are shown in Table 2.

The data in Table 2 show that the hot-melt adhesive containing alkoxysilane terminal groups according to example 1 of the invention has excellent heat resistance compared with conventional reactive polyurethane hot-melts (comparative example 6).

Heat resistance measurements also showed that the prior art hot melt adhesive based on polyester polyol and containing lewis acid organometallic catalyst (comparative example 3) was not stable. The heat resistance of the product containing DBTL as curing catalyst (comparative example 3) is only 100 ℃, which can be attributed to the irreversible degradation of the polyester chain by transesterification with the alcohol cleaved from the alkoxysilane end groups, in this case methanol. On the other hand, the hot melt adhesive according to example 1 of the present invention has a heat resistance higher than 200 ℃ because no transesterification reaction occurs and the adhesive is not irreversibly damaged.

Determination of tensile shear strength of Fagus crenata (beech wood) cementite (gums):

test samples were prepared from beech boards of 40X 20X 5mm size, stored at 23 ℃ and 50% relative humidity. The cartridges containing the product to be characterized were placed in a circulating air drying cabinet at 120 ℃ for 45 minutes to melt, and the molten product was then applied in a twist by means of a cartridge gun to the wooden test specimens held in a special mold. The mold is then closed firmly. The die ensures an overlap length of 10mm, 2cm²And a bond point thickness of 0.8 mm. After about 30 minutes, the test specimens were removed from the molds and then stored at 23 ℃ and 50% relative humidity until testing. The tests were performed after 1 hour, 2 hours, 1 day, 7 days, 14 days and 28 days. 5 test samples were prepared and measured for each product, and an average value of each result was obtained. The results are shown in Table 3.

Determination of the peeling strength of beech/PVC bonds:

test specimens were prepared from beech boards of 300X 120X 4.0mm size, stored at 23 ℃ and 50% relative humidity, and rigid PVC laminate films (Benolit RTF films) of dimensions 30X 210X 0.4 mm. The cartridge containing the product to be characterized was placed in a 120 ℃ circulating air drying cabinet for 45 minutes to melt it and the molten product was then applied in a twist to the upper end of the wooden test specimen by means of a cartridge gun. The adhesive was then dispersed on the beech test specimens by means of a doctor blade (groove doctor blade, 150 μm). The bonding area is about 30 x 90 mm. After cooling at room temperature for 2 minutes, the PVC film was laid on the beech test specimens with the unstructured side of the rigid PVC laminate film in contact with the beech test specimens coated with the adhesive. An effective pressure of about 1.5bar is applied at a temperature of 105 ℃ to press the composite material with the beech board side down to the film (membranes) for 10 seconds. 3 test samples were prepared and measured for each product, and an average value of each result was obtained. The tests were performed after 1 hour, 2 hours, 1 day, 7 days, 14 days and 28 days. The results are shown in Table 4.

The results of the beech and beech/rigid PVC bonds shown in tables 3 and 4 show that the uncatalyzed silane-functional hot-melt adhesives cure very slowly and develop a bond strength after several weeks (comparative examples 1 and 2). Nevertheless, the ultimate strength achievable is still significantly lower than the level achievable with conventional isocyanate-functional polyurethane hot melts (comparative example 6). On the other hand, the hot-melt adhesives according to the invention based on crystalline polyester polyols and containing catalyst A-1 (examples 1 and 2) have sufficient initial strength after 1 hour in the case of beech wood bonding. In the case of beech/rigid PVC bonding, sufficient initial strength is achieved after 1 day. The strength which can be achieved can be greatly increased by modifying the hot-melt adhesives according to the invention by using together further crystalline or amorphous polyesters or polyesters which are liquid at room temperature and mixing polyether polyols, so that sufficient initial strength is achieved after 1 hour in the case of beech/rigid PVC bonds.

The final strength of the bond prepared with the polyurethane hot melt adhesive according to the invention having alkoxysilane end groups and containing catalyst A-1 (measured after 7 to 28 days) is at the same level as that achieved with the conventional isocyanate-functional polyurethane hot melt (comparative example 6).

The tensile shear strength of beech wood bonds also indicates that lewis acid organometallic compounds such as, for example, DBTL, are unsuitable for use as curing catalysts for hot melt adhesives based on polyester polyols and containing alkoxysilane end groups (comparative example 3). The initial strength is significantly lower than the composition according to the invention. Furthermore, it has been found that after storage for a longer time in a hot environment, the achievable strength is significantly reduced, which can be attributed to irreversible degradation of the polyester chains by transesterification with the alcohol (in this case methanol) which has split off from the alkoxysilane end groups.

If DMDEE is used as curing catalyst (comparative example 7), a higher initial strength (measured after 1 or 2 hours) is indeed obtained than for the uncatalyzed hot melt adhesive, but the final strength (measured after 7 to 28 days) is still at the same level as for the uncatalyzed hot melt adhesive (comparative example 1) and is therefore significantly lower than the value obtained with the alkoxysilane-functional hot melt adhesive according to the invention comprising catalyst A-1 (examples 1 and 2).

Table 1:the viscosity in the different examples and comparative examples was mpa.s, measured at 100 ℃ after storage in a circulating air drying cabinet at 100 ℃ for a specified period of time.

Table 2:heat resistance of silane-functional moisture-curing PU hotmelts (example 1) with catalyst A-1 as curing catalyst, isocyanate-functional reactive PU hotmelts (comparative example 6) and silane-functional moisture-curing PU hotmelts (comparative example 3) with DBTL as curing catalyst.

Examples	Heat resistance
		Example 1	＞200℃
Comparative example 6	180℃
		Comparative example 3	100℃

Table 3:tensile shear strength (N/mm) of Fagus cement after curing at 23 ℃ and 50% relative humidity for various curing times²)

Table 4:peel Strength (N/mm) of Fagus/PVC bonds after curing at 23 ℃ and 50% relative humidity for various curing times

Although the invention has been described in detail in the foregoing for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be limited by the claims.

Claims (10)

1. Alkoxysilane-functional compositions which are obtainable by reacting A) with B) and adding C) below:

A) by passing

i) At least one aromatic, aliphatic, araliphatic and/or cycloaliphatic diisocyanate

And

ii) at least one polyol comprising at least one linear polyester polyol which is solid at room temperature,

wherein the ratio of the amounts of i) and ii) is selected such that the molar ratio of NCO to OH is from 1.2 to 4.0,

polyurethane prepolymer obtained by reaction;

B) compounds of the general formula (I) containing alkoxysilanes and amino or mercapto groups

Wherein

X, Y and Z represent identical or different linear or branched chains (C)₁-C₈) Alkyl or cyclic (C)₃-C₈) Alkyl or (C)₁-C₈) Alkoxy, provided that at least one radical is (C)₁-C₈) An alkoxy group,

r represents a linear or branched alkylene group having 1 to 8 carbon atoms, or a cycloalkylene group having 3 to 8 carbon atoms,

w represents-SH or-NH-R'

Wherein

R' represents hydrogen, a linear or branched alkyl radical having from 1 to 8 carbon atoms, or a cycloalkyl or aryl radical having from 3 to 8 carbon atoms or a radical of the formula (II)

Wherein

R 'and R' represent the same or different linear or branched alkyl groups having 1 to 8 carbon atoms, or cycloalkyl groups having 3 to 8 carbon atoms

Wherein the ratio of the amounts of A) and B) is selected such that 0.95 to 1.1mol of amino or mercapto groups from B) are used per mole of NCO groups from A),

C) bis (N, N' -dimethylaminoethyl) ether.

2. The composition of claim 1 wherein the bis (N, N' -dimethylaminoethyl) ether is used in an amount of 0.1 to 1.5% by weight based on the reaction product of A) and B).

3. The composition of claim 1, wherein the polyol ii) used to prepare component a) comprises at least one solid, at least partially crystalline polyester polyol.

4. The composition of claim 1, wherein the polyol component comprises at least one solid amorphous linear polyester polyol.

5. The composition of claim 1, wherein the polyol ii) used to prepare component a) further comprises one or more linear polyester polyols which are liquid at room temperature and/or one or more linear polyether polyols.

6. A process for the preparation of an alkoxysilane-functional composition obtained by reacting A) with B) and subsequently adding C) as follows:

A) by passing

i) At least one aromatic, aliphatic, araliphatic and/or cycloaliphatic diisocyanate

And

ii) at least one polyol comprising at least one linear polyester polyol which is solid at room temperature,

wherein the ratio of i) to ii) is selected such that the molar ratio of NCO to OH is from 1.2 to 4.0,

polyurethane prepolymer obtained by reaction;

and the reaction of the polyurethane prepolymer obtained under A) with B) below:

B) compounds of the general formula (I) containing alkoxysilanes and amino or mercapto groups

Wherein

X, Y and Z represent identical or different linear or branched chains (C)₁-C₈) Alkyl or cyclic (C)₃-C₈) Alkyl or (C)₁-C₈) Alkoxy, provided that at least one radical is (C)₁-C₈) An alkoxy group,

r represents a linear or branched alkylene group having 1 to 8 carbon atoms, or a cycloalkylene group having 3 to 8 carbon atoms,

w represents-SH or-NH-R'

Wherein

R' represents hydrogen, a linear or branched alkyl radical having from 1 to 8 carbon atoms, or a cycloalkyl radical having from 3 to 8 carbon atoms, an aryl radical or a radical of the formula (II)

Wherein

R 'and R' represent the same or different linear or branched alkyl groups having 1 to 8 carbon atoms, or cycloalkyl groups having 3 to 8 carbon atoms

Wherein the ratio of the amounts of A) and B) is selected such that 0.95 to 1.1mol of amino or mercapto groups from B) are used per mole of NCO groups from A),

and then adding:

C) bis (N, N' -dimethylaminoethyl) ether.

7. Moisture-curing alkoxysilane-functional hot-melt adhesive compositions comprising a composition prepared according to claim 6, optionally containing one or more customary additives for hot-melt adhesives.

8. An adhesive composition comprising the composition of claim 1.

9. Substrates bonded with the moisture-curable hot melt adhesive composition of claim 7.

10. Substrates bonded with the composition of claim 1.