EP2021425A1

EP2021425A1 - Heat-activable polyurethane sheet

Info

Publication number: EP2021425A1
Application number: EP07728792A
Authority: EP
Inventors: Andre Burghardt; Oliver Hartz; Karl-Heinz Schumacher
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2006-05-09
Filing date: 2007-05-04
Publication date: 2009-02-11
Also published as: CN101432378A; WO2007128789A1; KR20090015111A; US20090104453A1; JP2009536234A

Abstract

Use of a sheet to bond two substrates adhesively, characterized in that the sheet comprises a layer composed to an extent of more than 30% by weight of a heat-activable polyurethane (PU layer for short).

Description

Heat activated polyurethane film

description

The invention relates to the use of a film for bonding two substrates, characterized in that the film contains a layer which consists of more than 30% by weight of a heat-activatable polyurethane (PU layer for short)

In the automotive and furniture industry are often molded parts with a laminate, z. As a plastic film laminated. Here, the molded part and / or the film to be laminated is coated with an adhesive and the two parts are then glued together, generally under application of pressure or at reduced pressure in a thermoforming process.

DE-A 100 00 656, DE-A 100 01 777, DE-A 103 30 748 or EP-A 1 598 382 disclose heat-activatable polyurethanes. These are carbodiimide-containing polyurethane adhesives. In the polyurethane adhesives described is already advantageous that the coating of the laminating film can not be made by the manufacturer of the laminated molding, but the manufacturer of the laminating film. The resulting polyurethane-adhesive-coated film can be transported in the form of rolls and stored by the user. In lamination, the block-resistant coating of the polyurethane adhesive is then activated by heat, i. it becomes sticky and the lamination process can be carried out.

The manufacturer of the laminated molding generally requires different laminating films for different moldings and applications, moreover, in addition to the adhesive-coated films, uncoated films are generally also required in such plants. The manufacturer therefore has to stockpile with a large number of coated and uncoated foils in order to be able to practice his processes at any time. It is therefore desirable to further simplify the process, in particular a simplification which affects the extent of storage.

The object of the present invention was therefore a simple method for laminating moldings, in particular, the laminated moldings should have good performance properties, eg. B. a very good adhesion of the laminating film on the molding.

Accordingly, the use defined above was found. Also found were films which are suitable for the process.

The film used contains a layer which consists of more than 30% by weight of a heat-activatable polyurethane (PU layer for short). To the polyurethane

The PU layer contains as its essential constituent a heat-activatable polyurethane, which may also be a mixture of different heat-activatable polyurethanes, as a binder.

A polyurethane is preferably suitable which is composed predominantly of polyisocyanates, in particular diisocyanates, and, as reactants, polyester diols, polyether diols or mixtures thereof.

Preferably, the polyurethane is at least 40 wt .-%, more preferably at least 60 wt .-% and most preferably at least 80 wt .-% of diisocyanates, polyether diols and / or polyester diols constructed.

Preferably, the polyurethane contains polyester diols in an amount of more than

10 wt .-%, particularly preferably greater than 30 wt.%, In particular greater than 40 wt.% Or greater than 50 wt.%, Very particularly preferably greater than 60 wt. %, based on the polyurethane.

In particular, polyesterdiols are used as builders; if polyesterdiols are used in admixture with polyetherdiols, they are preferably at least 50 mole%, more preferably at least 80 mole%, most preferably 100 mole% of the blend of polyester and polyether diols, polyester diols ,

Preferably, the polyurethane has a melting point greater than 30 ° C, in particular greater than 40 ° C, more preferably greater than 50 ° C or greater than 60 or greater than 70 ° C; In general, the melting point is not greater than 150 ° C, in particular not greater than 100 ° C. The melting point is therefore in particular in a range from 30 to 150.degree. C., particularly preferably from 40 to 150, and very particularly preferably from 30 to 100.degree. C. and in particular from 50 to 80.degree.

The polyurethane preferably has a melting enthalpy of more than 20 J / g.

The measurement of the melting point and the enthalpy of fusion is carried out by the method of differential scanning calorimetry.

The measurement is carried out on polyurethane films of a thickness of 200 .mu.m, which were dried before the measurement in a circulating air T rockenschrank at 40 ° C for 72 hours. To prepare the measurement, about 13 mg of the polyurethane are filled in pans. The pans are sealed, the samples heated to 120 ° C, cooled at 20 K / min and annealed at 20 ° C for 20 hours. The thus prepared samples become measured according to the DSC method according to DIN 53765, wherein the sample is heated at 20 K / min. The melting point temperature is evaluated according to DIN 53765, the enthalpy of fusion is determined as in FIG. 4 of DIN 53765.

Overall, the polyurethane is preferably composed of:

a) diisocyanates,

b) Diols, of which

b1) 10 to 100 mol%, based on the total amount of diols (b), have a molecular weight of 500 to 5000 g / mol,

b2) 0 to 90 mol%, based on the total amount of diols (b), have a molecular weight of 60 to 500 g / mol,

c) monomers other than monomers (a) and (b) having at least one isocyanate group or at least one isocyanate-reactive group which moreover bear at least one hydrophilic group or a potentially hydrophilic group, thereby causing the water dispersibility of the polyurethanes,

d) optionally other than the monomers (a) to (c) different polyvalent compounds having reactive groups which are alcoholic see hydroxyl groups, primary or secondary amino groups or isocyanate groups, and

e) optionally monovalent compounds other than the monomers (a) to (d), having a reactive group which is an alcoholic hydroxyl group, a primary or secondary amino group or an isocyanate group.

To be mentioned in particular as monomers (a) diisocyanates X (NCO) 2, wherein X is an aliphatic hydrocarbon radical having 4 to 15 carbon atoms, a cycloaliphatic or aromatic hydrocarbon radical having 6 to 15 carbon atoms or an araliphatic hydrocarbon radical having 7 to 15 carbon atoms , Examples of such diisocyanates are tetramethylene diisocyanate, hexamethylene diisocyanate, dodecamethylene diisocyanate, 1,4-diisocyanatocyclohexane, 1-isocyanato-S.δ.δ-trimethyl-S-isocyanatomethylcyclohexane (IPDI), 2,2-bis (4-isocyanatocyclohexyl) propane , Trimethylhexandiisocyanat, 1, 4-diisocyanatobenzene, 2,4-diisocyanatotoluene, 2,6-diisocyanatotoluene, 4,4'-diisocyanato-diphenylmethane, 2,4'-diisocyanato-diphenylmethane, p-xylylene diisocyanate, tetramethylxylylene diisocyanate (TMXDI), the Isomers of bis (4-isocyanatocyclohexyl) methane (HMDI) such as the trans / trans, the cis / cis and the cis / trans isomers and mixtures consisting of these compounds.

Such diisocyanates are available commercially.

Particularly suitable mixtures of these isocyanates are the mixtures of the respective structural isomers of diisocyanatotoluene and diisocyanato-diphenylmethane; in particular, the mixture of 80 mol% of 2,4-diisocyanatotoluene and 20 mol% of 2,6-diisocyanatotoluene is suitable. Furthermore, the mixtures of aromatic isocyanates such as 2,4-diisocyanatotoluene and / or 2,6-diisocyanatotoluene with aliphatic or cycloaliphatic isocyanates such as hexamethylene diisocyanate or IPDI are particularly advantageous, the preferred mixing ratio of aliphatic to aromatic isocyanates being 4: 1 to 1: 4 is.

To build up the polyurethanes can be used as compounds except the aforementioned also isocyanates, in addition to the free isocyanate groups further blocked isocyanate groups, eg. B. wear uretdione groups.

With regard to good film formation and elasticity, suitable diols (b) are primarily relatively high molecular weight diols (b1) which have a molecular weight of about 500 to 5000, preferably about 1000 to 3000 g / mol. This is the number average molecular weight Mn. Mn is determined by determining the number of end groups (OH number).

The diols (b1) may be polyester polyols, the z. B. from Ullmann's Encyclopedia of Industrial Chemistry, 4th Edition, Volume 19, pp 62 to 65 are known. Preference is given to using polyesterpolyols which are obtained by reacting dihydric alcohols with dibasic carboxylic acids. Instead of the free polycarboxylic acids, it is also possible to use the corresponding polycarboxylic acid anhydrides or corresponding polycarboxylic acid esters of lower alcohols or mixtures thereof to prepare the polyesterpolyols. The polycarboxylic acids may be aliphatic, cycloaliphatic, araliphatic, aromatic or heterocyclic and optionally, for. B. by halogen atoms, substituted and / or unsaturated. Examples of these are: suberic acid, azelaic acid, phthalic acid, isophthalic acid, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, tetrachlorophthalic anhydride, endomethylenetetrahydrophthalic anhydride, glutaric anhydride, maleic acid, maleic anhydride, fumaric acid, dimer fatty acids. Preference is given to dicarboxylic acids of the general formula HOOC- (CH 2) y -COOH, where y is a number from 1 to 20, preferably an even number from 2 to 20, for example succinic acid, adipic acid, sebacic acid and dodecanedicarboxylic acid. As polyhydric alcohols come z. Ethylene glycol, propane-1, 2-diol, propane-1, 3-diol, butane-1, 3-diol, butene-1, 4-diol, butyne-1, 4-diol, pentane-1, 5 diol, neopentyl glycol, bis (hydroxymethyl) cyclohexanes, such as 1,4-bis (hydroxymethyl) cyclohexane, 2-methylpropane-1,3-diol, methylpentanediols, furthermore diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, Polypropylene glycol, dibutylene glycol and polybutylene glycols into consideration. Alcohols of the general formula HO- (CH 2) x -OH are preferred, where x is a number from 1 to 20, preferably an even number from 2 to 20. Examples of these are ethylene glycol, butane-1, 4-diol, hexane-1, 6-diol, octane-1, 8-diol and dodecane-1, 12-diol. Further preferred is neopentyl glycol.

Furthermore, if appropriate, polycarbonate diols, as they are, for. B. can be obtained by reacting phosgene with an excess of the mentioned as synthesis components for the polyester polyols low molecular weight alcohols into consideration.

Optionally, it is also possible to use polyester-based lactone-based sols, which are homopolymers or copolymers of lactones, preferably hydroxyl-terminated addition products of lactones to suitable difunctional starter molecules. Preferred lactones are those which are derived from compounds of the general formula HO- (CH 2) z -COOH, where z is a number from 1 to 20 and an H atom of a methylene unit is also a C 1 - to C 4 -alkyl radical may be substituted. Examples are e-caprolactone, β-propiolactone, g-butyrolactone and / or methyl-e-caprolactone and mixtures thereof. Suitable starter components are for. As the above-mentioned as a structural component for the polyester polyols low molecular weight dihydric alcohols. The corresponding polymers of e-caprolactone are particularly preferred. Lower polyester diols or polyether diols can also be used as starters for the preparation of the lactone polymers. Instead of the polymers of lactones, it is also possible to use the corresponding, chemically equivalent polycondensates of the hydroxycarboxylic acids corresponding to the lactones.

Polyetherdiols are in particular by polymerization of ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran, styrene oxide or epichlorohydrin with itself, z. B. in the presence of BF3 or by addition of these compounds, optionally in admixture or in succession, to starting components with reactive hydrogen atoms, such as alcohols or amines, for. For example, water, ethylene glycol, propane-1, 2-diol, propane-1, 3-diol, 2,2-bis (4-hydroxyphenyl) propane or aniline available. Particularly preferred are polypropylene oxide, polytetrahydrofuran having a molecular weight of 240 to 5000, and especially 500 to 4500. Under b1) fall only polyether diols, which consist of less than 20 wt .-% of ethylene oxide. Polyether diols containing at least 20% by weight are hydrophilic polyether diols which belong to monomers c).

Optionally, polyhydroxyolefins may also be included, preferably those having 2 terminal hydroxyl groups, e.g. α, -ω-Dihydroxypolybutadien, α, -ω- Dihydroxypolymethacrylester or α, -ω-Dihydroxypolyacrylester as monomers (c1). Such compounds are known, for example, from EP-A 622 378. Further suitable polyols are polyacetals, polysiloxanes and alkyd resins.

Preferably, at least 30 mol%, more preferably at least 70 mol% of the diols b1) are polyesterdiols. Particular preference is given to using diols b1) exclusively polyesterdiols.

The hardness and modulus of elasticity of the polyurethanes can be increased if, as diols (b), low molecular weight diols (b2) having a molecular weight of from about 60 to 500, preferably from 62 to 200, g / mol are used in addition to the diols (b1).

The monomers (b2) used are in particular the synthesis components of the short-chain alkanediols mentioned for the preparation of polyester polyols, the unbranched diols having 2 to 12 carbon atoms and an even number of carbon atoms and pentane-1, 5-diol and neopentyl glycol to be favoured.

As diols b2) come z. As ethylene glycol, propane-1, 2-diol, propane-1, 3-diol, butane-1, 3-diol, butene-1, 4-diol, butyne-1, 4-diol, pentane-1, 5 diol, neopentyl glycol, bis (hydroxymethyl) cyclohexanes, such as 1,4-bis (hydroxymethyl) cyclohexane, 2-methylpropane-1,3-diol, methylpentanediols, furthermore diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, Polypropylene glycol, dibutylene glycol and polybutylene glycols into consideration. Alcohols of the general formula HO- (CH 2) x -OH are preferred, where x is a number from 1 to 20, preferably an even number from 2 to 20. Examples of these are ethylene glycol, butane-1, 4-diol, hexane-1, 6-diol, octane-1, 8-diol and dodecane-1, 12-diol. Further preferred is neopentyl glycol.

Preferably, the proportion of the diols (b1), based on the total amount of the diols (b) is 10 to 100 mol% and the proportion of the monomers (b2), based on the total amount of the diols (b) 0 to 90 mol%. The ratio of the diols (b1) to the monomers (b2) is particularly preferably 0.1: 1 to 5: 1, particularly preferably 0.2: 1 to 2: 1.

In order to achieve the water-dispersibility of the polyurethanes, the polyurethanes preferably contain components (a), (b) and (d) which are different from the monomers (c) which contain at least one isocyanate group or at least one isocyanate group. natgruppen reactive group and moreover, at least one hydrophilic group or a group which can be converted into a hydrophilic group wear, as a building component. In the following text, the term "hydrophilic groups or potentially hydrophilic groups" is abbreviated to "(potentially) hydrophilic groups". The (potentially) hydrophilic groups react much more slowly with isocyanates than the functional groups of the monomers used to build up the main polymer chain.

The proportion of components having (potentially) hydrophilic groups in the total amount of components (a), (b), (c), (d) and (e) is generally such that the molar amount of (potentially) hydrophilic groups, based on the amount by weight of all monomers (a) to (e), 30 to 1000, preferably 50 to 500 and particularly preferably 80 to 300 mmol / kg.

The (potentially) hydrophilic groups may be nonionic or, preferably, (potentially) ionic hydrophilic groups.

Suitable nonionic hydrophilic groups are, in particular, polyethylene glycol ethers of preferably 5 to 100, preferably 10 to 80, ethylene oxide repeat units. The content of polyethylene oxide units is generally 0 to 10, preferably 0 to 6 wt .-%, based on the amount by weight of all monomers (a) to (e).

Preferred monomers having nonionic hydrophilic groups are polyethylene oxide diols containing at least 20% by weight of ethylene oxide, polyethylene oxide monools and the reaction products of a polyethylene glycol and a diisocyanate which carry a terminally etherified polyethylene glycol radical. Such diisocyanates and processes for their preparation are given in the patents US-A 3,905,929 and US-A 3,920,598.

Ionic hydrophilic groups are especially anionic groups such as the sulfonate, the carboxylate and the phosphate group in the form of their alkali metal or ammonium salts and cationic groups such as ammonium groups, in particular protonated tertiary amino groups or quaternary ammonium groups.

Potentially ionic hydrophilic groups are especially those which can be converted by simple neutralization, hydrolysis or quaternization into the above-mentioned ionic hydrophilic groups, ie, for. As carboxylic acid groups or tertiary amino groups.

(Potentially) ionic monomers (c) are e.g. For example, in Ullmann's Encyclopedia of technical chemistry, 4th edition, volume 19, p.31 1-313 and described for example in DE-A 1 495 745 in detail. As (potentially) cationic monomers (c), especially monomers having tertiary amino groups are of particular practical importance, for example: tris (hydroxyalkyl) amines, N, N'-bis (hydroxyalkyl) alkylamines, N-hydroxyalkyl-dialkylamines , Tris (aminoalkyl) -amines, N, N'-bis (aminoalkyl) -alkylamines, N-aminoalkyl-dialkylamines, wherein the alkyl radicals and alkanediyl moieties of these tertiary amines independently of one another consist of 1 to 6 carbon atoms. Furthermore, tertiary nitrogen atoms containing polyether having preferably two terminal hydroxyl groups, such as, for example, by alkoxylation of two on Am in nitrogen-bonded hydrogen atoms containing amines, such as methylamine, aniline or N, N'-dimethylhydrazine, are accessible per se in a conventional manner, into consideration , Such polyethers generally have a molecular weight between 500 and 6000 g / mol.

These tertiary amines are either with acids, preferably strong mineral acids such as phosphoric acid, sulfuric acid, hydrohalic acids or strong organic see acids or by reaction with suitable quaternizing agents such as C1 to C6 alkyl halides or benzyl halides, eg. As bromides or chlorides, transferred to the ammonium salts.

Suitable monomers having (potentially) anionic groups are usually aliphatic, cycloaliphatic, araliphatic or aromatic carboxylic acids and sulfonic acids which carry at least one alcoholic hydroxyl group or at least one primary or secondary amino group. Preference is given to dihydroxyalkyls, especially those having 3 to 10 carbon atoms, as are also described in US Pat. No. 3,412,054. In particular, compounds of the general formula (d)

R ³

HO-R ¹ ^ R-OH (C ₁ )

COOH

in which R1 and R2 is a C1 to C4 alkanediyl (unit) and R3 is a C1 to C4 alkyl (unit) and, in particular, dimethylolpropionic acid (DMPA) is preferred.

Also suitable are corresponding dihydroxysulfonic acids and dihydroxyphosphonic acids, such as 2,3-dihydroxypropanephosphonic acid.

Otherwise suitable are dihydroxyl compounds having a molecular weight above

500 to 10,000 g / mol with at least 2 carboxylate groups, which are known from DE-A 39 11 827. They are obtainable by reacting dihydroxyl compounds with tetracarboxylic acid dianhydrides such as pyromellitic dianhydride or cyclopentanetetracarboxylic dianhydride in a molar ratio of 2: 1 to 1:05 in a polyaddition reaction. Particularly suitable dihydroxyl compounds are the monomers (b2) listed as chain extenders and also the diols (b1).

Suitable monomers (c) with isocyanate-reactive amino groups are amino carboxylic acids such as lysine, β-alanine or the adducts of aliphatic diprimary diamines mentioned in DE-A 20 34 479 to α, β-unsaturated carboxylic or sulfonic acids into consideration.

Such compounds obey, for example, the formula (c2)

H2N-R4-NH-R5-X (c2)

in the

R4 and R5 independently represent a C1 to C6 alkanediyl unit, preferably ethylene

and X is COOH or SO3H.

Particularly preferred compounds of the formula (c2) are N- (2-aminoethyl) -2-aminoethanecarboxylic acid and also N- (2-aminoethyl) -2-aminoethanesulfonic acid or the corresponding alkali metal salts, Na being particularly preferred as the counterion.

Also particularly preferred are the adducts of the abovementioned aliphatic diprimary diamines with 2-acrylamido-2-methylpropanesulfonic acid, as described, for example, in US Pat. B. in DE-B 1 954 090 are described.

If monomers having potentially ionic groups are used, their conversion into the ionic form may take place before, during, but preferably after the isocyanate polyaddition, since the ionic monomers are often difficult to dissolve in the reaction mixture. Neutralizing agents are z. As ammonia, NaOH, triethanolamine (TEA) triisopropylamine (TIPA) or morpholine, bze its derivatives. The sulfonate or carboxylate groups are particularly preferably in the form of their salts with an alkali ion or an ammonium ion as the counterion.

The monomers (d), which are different from the monomers (a) to (c) and which are optionally also constituents of the polyurethane, generally serve for crosslinking or chain extension. They are generally more than dihydric non-phenolic alcohols, amines having 2 or more primary and / or secondary amino groups and compounds which carry one or more primary and / or secondary amino groups in addition to one or more alcoholic hydroxyl groups. Alcohols with a value higher than 2, which can serve to set a certain degree of branching or crosslinking, z. B. trimethylolpropane, glycerol or sugar.

Also suitable are monoalcohols which, in addition to the hydroxyl group, carry a further isocyanate-reactive group, such as monoalcohols having one or more primary and / or secondary amino groups, eg. B. monoethanolamine.

Polyamines having 2 or more primary and / or secondary amino groups are used especially when the chain extension or crosslinking is to take place in the presence of water, since amines usually react faster than alcohols or water with isocyanates. This is often required when aqueous dispersions of high molecular weight crosslinked polyurethanes or polyurethanes are desired. In such cases, the procedure is to prepare prepolymers with isocyanate groups, to rapidly disperse them in water and then to chain extend or crosslink them by adding compounds containing several isocyanate-reactive amino groups.

Suitable amines for this purpose are generally polyfunctional amines of the molecular weight range from 32 to 500 g / mol, preferably from 60 to 300 g / mol, which contain at least two amino groups selected from the group of primary and secondary amino groups. Examples of these are diamines such as diaminoethane, diamopropanes, diaminobutanes, diaminohexanes, piperazine, 2,5-dimethylpiperazine, amino-3-aminomethyl-3,5,5-trimethylcyclohexane (isophoronediamine, IPDA), 4,4'-diaminodicyclohexylmethane , 1, 4-diaminocyclohexane, aminoethylethanolamine, hydrazine, hydrazine hydrate or triamines such as diethylenetriamine or 1, 8-diamino-4-aminomethyloctane.

The amines may also be in blocked form, for. In the form of the corresponding ketimines (see, for example, CA-A 1 129 128), ketazines (see, for example, US-A 4,269,748) or amine salts (see US-A 4,292,226). Also oxazolidines, as used for example in US Pat. No. 4,192,937, are capped polyamines which can be used for the preparation of the polyurethanes according to the invention for chain extension of the prepolymers. When such capped polyamines are used, they are generally mixed with the prepolymers in the absence of water, and this mixture is then mixed with the dispersion water or part of the dispersion water, so that the corresponding polyamines are released hydrolytically.

Preference is given to using mixtures of di- and triamines, particularly preferably mixtures of isophoronediamine (IPDA) and diethylenetriamine (DETA). The polyurethanes preferably contain from 1 to 30, particularly preferably from 4 to 25, mol%, based on the total amount of components (b) and (d), of a polyamine having at least 2 isocyanate-reactive amino groups as monomers (d).

For the same purpose higher than divalent isocyanates can also be used as monomers (d). Commercially available compounds are, for example, the isocyanurate or the biuret of hexamethylene diisocyanate.

Monomers (e), which are optionally used, are monoisocyanates, monohydric alcohols and monoprimary and secondary amines. In general, their proportion is at most 10 mol%, based on the total molar amount of the monomers. These monofunctional compounds usually carry further functional groups, such as olefinic groups or carbonyl groups, and serve to introduce functional groups into the polyurethane, which make possible the dispersion or crosslinking or further polymer-analogous reaction of the polyurethane. Suitable for this purpose are monomers such as isopropenyl-α, α-dimethylbenzyl isocyanate (TMI) and esters of acrylic or methacrylic acid such as hydroxyethyl acrylate or hydroxyethyl methacrylate.

In the field of polyurethane chemistry, it is generally known how the molecular weight of the polyurethanes can be adjusted by selecting the proportions of the monomers which are reactive with one another and the arithmetic mean of the number of reactive functional groups per molecule.

Normally, the components (a) to (e) and their respective molar amounts are chosen so that the ratio A: B with

A is the molar amount of isocyanate groups and

B is the sum of the molar amount of the hydroxyl groups and the molar amount of the functional groups which can react with isocyanates in an addition reaction

0.5: 1 to 2: 1, preferably 0.8: 1 to 1, 5, more preferably 0.9: 1 to 1, 2: 1. Most preferably, the ratio A: B is as close as possible to 1: 1.

The monomers (a) to (e) used carry on average usually 1.5 to 2.5, preferably 1.9 to 2.1, particularly preferably 2.0 isocyanate groups or functional groups which can react with isocyanates in an addition reaction ,

The polyaddition of components (a) to (e) for the preparation of the polyurethane is preferably carried out at reaction temperatures of up to 180 ° C, preferably up to 150 ° C under atmospheric pressure or under autogenous pressure. The preparation of polyurethanes or of aqueous polyurethane dispersions is known to the person skilled in the art.

To further components of the PU layer

In addition to the heat-activatable polyurethane or the various heat-activatable polyurethanes, the PU layer may contain further constituents.

In addition to the heat-activatable polyurethane, the PU layer may contain other polymers as binders.

The further polymer may in particular be a polymer obtainable by radical polymerization of ethylenically unsaturated compounds (monomers).

The polymer is preferably at least 40 wt .-%, preferably at least 60 wt .-%, more preferably at least 80 wt .-% of so-called main monomers.

The main monomers are selected from C1-C20-alkyl (meth) acrylates, vinyl esters of carboxylic acids containing up to 20 carbon atoms, vinylaromatics having up to 20 carbon atoms, ethylenically unsaturated nitriles, vinyl halides, vinyl ethers having from 1 to 10 carbon atoms Alcohols, aliphatic hydrocarbons having 2 to 8 carbon atoms and one or two double bonds or mixtures of these monomers.

To name a few are z. B. (meth) acrylic acid alkyl ester having a C 1 -C 10 -alkyl radical, such as methyl methacrylate, methyl acrylate, n-butyl acrylate, ethyl acrylate and 2-ethylhexyl acrylate.

In particular, mixtures of (meth) acrylic acid alkyl esters are also suitable.

Vinyl esters of carboxylic acids having 1 to 20 carbon atoms are e.g. Vinyl laurate, stearate, vinyl propionate, vinyl versatate and vinyl acetate.

Suitable vinylaromatic compounds are vinyltoluene, α- and p-methylstyrene, α-butylstyrene, 4-n-butylstyrene, 4-n-decylstyrene and preferably styrene. Examples of nitriles are acrylonitrile and methacrylonitrile.

The vinyl halides are chloro, fluoro or bromo substituted ethylenically unsaturated compounds, preferably vinyl chloride and vinylidene chloride.

Vinyl ethers include, for example, vinyl methyl ether or vinyl isobutyl ether. Vinyl ether is preferably from 1 to 4 C-containing alcohols. As hydrocarbons having 2 to 8 carbon atoms and one or two olefinic double bonds may be mentioned ethylene, propylene, butadiene, isoprene and chloroprene.

Preferred main monomers are the C 1 - to C 10 -alkyl acrylates and -methacrylates, in particular C 1 - to C 8 -alkyl acrylates and -methacrylates and vinylaromatics, in particular styrene and mixtures thereof.

Very particular preference is given to methyl acrylate, methyl methacrylate, ethyl acrylate, n-butyl acrylate, n-hexyl acrylate, octyl acrylate and 2-ethylhexyl acrylate, styrene and mixtures of these monomers.

In addition to the main monomers, the polymer may contain other monomers, for. As monomers with carboxylic acid, sulfonic acid or phosphonic acid groups. Preferred are carboxylic acid groups. Called z. For example, acrylic acid, methacrylic acid, itaconic acid, maleic acid or fumaric acid.

Other monomers are z. B. also hydroxyl-containing monomers, in particular C 1 -C 10 -hydroxyalkyl (meth) acrylates, (meth) acrylamide.

Phenyloxyethylglycol mono (meth) acrylate, glycidyl acrylate, glycidyl methacrylate, amino (meth) acrylates such as 2-aminoethyl (meth) acrylate may also be mentioned as further monomers.

Other monomers which may also be mentioned are crosslinking monomers.

Preferred polymers consist of at least 40 wt .-%, in particular at least 60 wt .-% and most preferably at least 80 wt .-% of C1-C20-, in particular C1-C10Alkyl (meth) acrylates, or of vinyl esters, in particular vinyl - Acetate, or mixtures of vinyl esters, in particular vinyl acetate, with ethylene.

Preferred polymers which are optionally used in admixture with the heat-activatable polyurethane in the PU layer are therefore polyacrylates, polyvinyl acetate or ethylene / vinyl acetate copolymers or other non-heat-activatable polyurethanes.

The polymers are produced in a preferred embodiment by emulsion polymerization, which is therefore an emulsion polymer.

However, the production can z. B. also be carried out by solution polymerization and subsequent dispersing in water. The PU layer consists overall of at least 30% by weight, preferably at least 40% by weight, more preferably at least 50% by weight. %, in particular at least 70% by weight, or at least 90% by weight, of heat-activatable polyurethane, based on the sum of all constituents.

In a particular embodiment, the PU layer contains, in addition to the polyurethane no further polymer as a binder.

The further constituents of the PU layer may in particular be crosslinkers.

Preferably, the PU layer contains at least one crosslinker for the polyurethane.

Suitable crosslinkers are, in particular, chemically blocked isocyanates, compounds containing silicon groups, in particular encapsulated silane-group-containing compounds, encapsulated isocyanates, encapsulated uretdiones, biurets or allophanates or particularly preferably compounds having carbodiimide groups.

The crosslinker can be bound to the polyurethane, then it is a self-crosslinking polyurethane, but it can also be a compound that is dissolved or distributed in the polyurethane.

The PU layer preferably contains 0.0001 to 0.1 mol, preferably 0.0005 to 0.1 mol, particularly preferably 0.001 to 0.1 mol of carbodiimide groups per 100 g of polyurethane. In particular, the content of carbodiimide groups is not higher than 0.05 mol / 100 g of polyurethane.

Carbodiimide groups have the general structural formula -N = C = N-.

Suitable compounds with carbodiimide groups (carbodiimides for short) generally contain on average 1 to 20, preferably 1 to 15, particularly preferably 2 to 10 carbodiimide groups.

The number average molecular weight Mn of the carbodiimides is preferably 100 to 10,000, more preferably 200 to 5,000, and most preferably 500 to 2,000 g / mol.

The number-average molecular weight is determined by end-group analysis of the diisocyanates (ie consumption of the isocyanate groups by carbodiimide formation, see below) or, if end-group analysis is not possible, by gel permeation chromatography (polystyrene standard, THF as eluent). Carbodiimide groups are readily available from two isocyanate groups with elimination of carbon dioxide:

-R-N = C = O + O = C = N-R

-RN = C = NR + ^C0 2

Starting from polyisocyanates or diisocyanates, carbodiimides having a plurality of carbodiimide groups and optionally isocyanate groups, in particular terminal isocyanate groups, are thus obtainable.

Suitable diisocyanates z. B. Diisocyanates X (NCO) 2, wherein X is an aliphatic hydrocarbon radical having 4 to 12 carbon atoms, a cycloaliphatic or aromatic hydrocarbon radical having 6 to 15 carbon atoms or an araliphatic hydrocarbon radical having 7 to 15 carbon atoms. Examples of such diisocyanates are tetramethylene diisocyanate, hexamethylene diisocyanate, dodecamethylene diisocyanate, 1,4-diisocyanatocyclohexane, 1-isocyanato-3,5,5-trimethyl-5-isocyanatomethylcyclohexane (IPDI), 2,2-bis (4-isocyanatocyclohexyl) propane , Trimethylhexandiisocyanat, 1, 4-diisocyanatobenzene, 2,4-diisocyanatotoluene, 2,6-diisocyanatotoluene, 4,4'-diisocyanato-diphenylmethane, 2,4'-diisocyanato-diphenylmethane, p-xylylene diisocyanate, tetramethylxylylene diisocyanate (TMXDI), the isomers of bis (4-isocyanatocyclohexyl) methane (HMDI) such as the trans / trans, the cis / cis and the cis / trans isomers, and mixtures consisting of these compounds.

Particularly preferred is TMXDI.

Due to the terminal isocyanate group, the carbodiimides slightly hydrophilic, z. B. by reaction with amino or hydroxy acids are modified. Hydrophilically modified carbodiimides can of course be mixed more easily with aqueous adhesives or adhesives based on hydrophilic polymers.

Just as easily, the carbodiimides can be attached to polymers in which the isocyanate group with a reactive group of the polymer, for. B. an amino group or hydroxyl group is reacted.

The PU layer, the carbodiimides therefore z. As an additive or in bound form, e.g. by attachment to a polyurethane or a free-radically polymerized polymer.

The PU layer preferably contains further reactive groups which can undergo a crosslinking reaction with one another or with the carbodiimide groups. Suitable examples are carboxyl or carboxylate groups. These reactive groups are preferably present in an amount of from 0.0001 to 0.5 mol, more preferably from 0.0005 to 0.5 mol / 100 g of polyurethane.

Carboxyl groups are also formed by transesterification reactions, so that even without an initial content of carboxyl groups in the polyurethane crosslinking occurs.

The PU layer may contain further additives, such as wetting agents, defoamers, film-forming auxiliaries, thickeners, thixotropic agents (for example fumed silicas) or plasticizers or other auxiliaries.

To the entire slide

In a preferred embodiment, the film according to the invention can consist solely of the PU layer. In this case, the PU layer must have sufficient thickness to form self-supporting, tear-resistant films. To produce the film, the polyurethane, if appropriate together with other binders or excipients in a known manner be filmed. For this purpose, it is possible to start from aqueous polyurethanes, which are stirred in by the further binders and additives, and the aqueous composition is knife-coated onto a substrate which is provided with a non-stick coating (silicone paper or silicone-coated film) and dried. The resulting film is self-supporting and can be removed from the substrate.

The film according to the invention can also be constructed in multiple layers. In particular, the film may consist of two PU layers and an intermediate carrier layer. The PU layers are on the outside and, when used, stick to one of the two substrates, so that the substrates to be bonded in turn adhere to one another via the film.

As a carrier film are any films into consideration, for. As textile carrier, such as textile fabric or leather, polymer films are preferred.

The film according to the invention may, in each of the above embodiments, optionally be provided on one or both sides with an adhesive, e.g. B. with a conventional pressure sensitive adhesive, also a polyurethane pressure-sensitive adhesive coated.

The film of the invention can also be on one or optionally on both sides with a (removable) release liner, ie non-stick layer, z. As a siliconized paper or a siliconized film. The release -iner will be deducted before use. The coating with a pressure-sensitive adhesive has the advantage that the film in its later use, even before the heat activation of the polyurethane has an initial adhesion and can be fixed in a desired position.

In the heat activation of the polyurethane, the polyurethane melts and mixes with the pressure-sensitive adhesive, so that in this case too a connection of the substrates takes place via the polyurethane.

However, an adhesive coating is not essential for the purposes of the present invention.

The thickness of the film is in particular 1 μm to 3 mm, particularly preferably 10 μm to 500 μm, very particularly preferably 10 μm to 200 μm and in a particularly preferred embodiment 30 μm to 80 μm.

The film preferably has a tensile strength (at 21 ° C.) of> 0.3 N / mm ² , preferably> 1 N / mm ² , particularly preferably> 10 N / mm ² .

The film is heat-activated. By heat-activatability is meant the property that the film is block-solid at 20 ° C, i. not sticky. Only when heated to higher temperatures, especially temperatures above the melting point, does the film become tacky, i. The polyurethane melts and acts as an adhesive.

For use

The film according to the invention is used in particular as an adhesive, particularly preferably as a laminating adhesive. The film can be used as an adhesive for any substrates, e.g. B. also for textiles, shoe soles etc.

Laminating adhesives connect large-area substrates with each other, for. As laminates with other laminates or laminates with moldings.

Laminate is understood to mean any large-area substrate having a thickness of less than 10 mm, in particular less than 5 mm, particularly preferably less than 0.5 mm, very particularly preferably less than 3 mm.

In particular, it may be polymeric films, metal foils, nonwovens made of synthetic or natural fibers, coated or uncoated paper or even veneers made of wood or imitation wood. Particularly preferred are polymer films, for. B. films of polyester, such as polyethylene terephthalate, polyolefins such as polyethylene, polypropylene or polyvinyl chloride, from acetate or polyurethane films (non-heat-activatable polyurethane).

The molding may be any molding, for. B. a car interior, such as dashboard, door interior trim or hat rack, or a piece of furniture or furniture act. the molding can in particular made of wood or plastic, for. For example, be ABS (acrylonitrile-butadiene-styrene). It can be z. B. act solid wood or plywood.

In particular, it may be molded parts, which consist of synthetic or natural fibers or chips, which are solidified by a binder into a molding.

The film of the invention is preferably used for laminating moldings with any desired laminates, wherein

a) the film and the laminate are placed on the molding so that the film is between the molding and the laminate

b) the film is heat activated, z. B. by infrared radiation, and

c) the molding is glued to the laminate

to a) The film and the laminate to be laminated can be prepared and cut separately. The film can also be cut to length (cut to length), deformed or punched before bonding.

Foil and laminate can also be previously bonded together to form a composite. It is essential that the film according to the invention is positioned towards the molded part, so that it is located between the laminate and the molded part.

Alternatively, the film can be previously merged with the molding, or the film can already be adapted to the molding or glued. The laminate is then fed at any later time and deposited on the film.

To b)

The heat activation can z. Optionally, the molded part can be heated accordingly, the heat is then transferred upon contact with the film. The film of the invention is preferably heated to temperatures above the melting point of the polyurethane (see above), more preferably at temperatures of 40 to 150 ° C. The temperature in the film according to the invention is preferably 20 to 200 ° C, particularly preferably 30 to 180 ° C and in particular 40 to 150 ⁰ C.

to c)

The bonding is preferably carried out under pressure, this can, for. B. the parts to be bonded are pressed together with a pressure of 0.05 to 5 N / mm2.

Alternatively, the bonding can also take place under reduced pressure (vacuum) in a deep-drawing process.

Simultaneously with the bonding, the laminate to be bonded is optionally brought into the desired shape so that it is adapted to the shape of the molded parts.

In particular, the above method can also be carried out continuously; For this purpose, in process step a), the film and the laminate can be unrolled continuously from a supply roll, optionally combined and optionally cut or otherwise prepared in a continuously configured process and then placed on the molding and glued.

The above method can also be done in two steps. In the first working step, the film of the invention is z. B. by means of a heated roller or plate, applied to one of the substrates to be bonded. In the second step, which can be carried out directly afterwards or much later (film is stable on storage), the bonding or lamination with the second substrate is carried out by heat activation of the polyurethane.

The process according to the invention is a simple process for bonding substrates to one another, in particular for laminating molded parts with laminates; the stockpiling of different films can be reduced, since the adhesive, in the form of the film according to the invention, can be used in any desired manner. A previous coating and storage of different films is no longer necessary.

The products obtained have high strength and good mechanical properties. Examples

50 μm thick films were produced. The films were obtained by filming the following mixtures (parts by weight of titanium, ie with water):

Example A: 200 TIe. Luphen® D DS 3585 X, a polyester-based polyurethane Example B: 150 TIe. Luphen D DS 3585 X / 50 TIe. Acronal DS 3502, a polyacrylate dispersion

Example C: 150 TIe. Luphen D DS 3585 X / 50 TIe. Airflex EP 17, an ethylene / vinyl acetate copolymer

Example D: 200 TIe. Luphen D DS 3585 X / 7 TIe. Basonat DS 3582 (a carbodiimide crosslinker)

Example E: 150 TIe. Luphen D DS 3585 X / 50 TIe. Acronal DS 3502/5 TIe. Basonat DS 3582 Example F: 150 TIe. Luphen D DS 3585 X / 50 TIe. Airflex EP 17/5 TIe. Basonat DS 3582

Using these carrier-less polyurethane films, composites were produced from an MDF board with a PVC laminating film, the PU films according to the invention being placed on the MDF boards and then the PVC films in a commercial caulking press, and then at 45 sec 95 ° C (temperature of the upper die) laminated.

In order to examine the quality of the bonds obtained, the cooled laminations were tested in the ascending heat test. To do this, place the MDF / PVC laminates vertically in a warming cabinet, hang a 1 kg weight onto the upper free end of the PVC sheet to give a 180 ° C angle and then heat the oven in 30 min / 5 ° C increments. It is assessed how far the PVC foil separates from the MDF board under the weight and increasing heat load (the drainage path). Indicated is the temperature at which the discharge distance is a maximum of 20 mm.

Example A: 40 ° C

Example B: 50 ° C

Example C: 60 ° C

Example D: 55 ° C

Example E: 55 ° C

Example F: 75 ° C

In all cases, a true bonding of the PVC film with the MDF board was obtained. The positive effect of carbodiimide crosslinking can be seen. Furthermore, soft PVC films, as used for lamination in automotive interiors, bonded with ABS test specimens. ABS is a typical plastic for the production of door side parts. The activation temperature in a flat press was around 80 ° C. The laminating pressure at 0.5 bar. The pressing time was 1 min. The ABS specimens were preheated to a temperature of about 70 ° C, the film of the invention was placed between ABS and the soft PVC film and then pressed with the above-mentioned pressing conditions.

In the corresponding peel test, which was carried out at a peel angle of the soft PVC film of 90 and at 90 ° C, we have determined the following values:

Example D: 15 N / 5 cm Example E: 18 N / 5 cm Example F: 21 N / 5 cm

These values are in the range that is also achieved by conventional laminating adhesives.

Claims

claims

1. Use of a film for bonding two substrates, characterized in that the film contains a layer which consists of more than 30% by weight of a heat-activatable polyurethane (PU layer for short)

2. Use according to claim 1, characterized in that the polyurethane to more than 60 wt.% Of structural components selected from diisocyanates, polyester diols, polyether diols or mixtures thereof is constructed

3. Use according to claim 1 or 2, characterized in that the polyurethane is composed of more than 10 wt.% Of polyester diols

4. Use according to any one of claims 1 to 3, characterized in that the polyurethane has a melting point in the range of 30 to 150 ° C.

5. Use according to any one of claims 1 to 4, characterized in that the PU layer contains a crosslinker for the polyurethane.

6. Use according to any one of claims 1 to 5, characterized in that the PU layer contains 0.0001 to 0.1 mol of carbodiimide groups per 100 g of polyurethane.

7. Use according to any one of claims 1 to 6, characterized in that the PU layer in addition to the polyurethane optionally further polymers

Binders, e.g. B. by free-radical polymerization available polymers, and auxiliaries, eg. Wetting agent containing

8. Use according to any one of claims 1 to 7, characterized in that the film consists of the PU layer and the PU layer is optionally coated on one or both sides with a pressure-sensitive adhesive or primer or both.

9. Use according to one of claims 1 to 8, characterized in that the film consists of two PU layers and an intermediate carrier layer and the outer PU layers ggb. With adhesive or a primer are coated.

10. Use according to one of claims 1 to 9, characterized in that the thickness of the film is 1 micron to 3 mm.

1 1. Use according to any one of claims 1 to 10, characterized in that the film is used as Kaschierklebstoff.

12. A method for laminating moldings with any desired laminates, characterized in that

a) a film according to any one of claims 1 to 10 and a laminate aufzukaschie- to be placed on the molding, so that the film between the molding and the laminate is b) the film is heat activated, z. B. by infrared radiation, and c) the molding is glued to the laminate

13. The method according to claim 12, characterized in that the method is carried out continuously

14. The method according to any one of claims 1 1 to 13, characterized in that the method under reduced pressure, for. B. in a deep drawing process, or under increased pressure is performed.

15. Products, in particular laminated moldings, obtainable by a use or a method according to one of claims 1 to 14.

16. A film, characterized in that it consists of a PU layer according to one of claims 1 to 7 and the PU layer is optionally coated on one or both sides with a pressure-sensitive adhesive or primer or both.

17. A film, characterized in that it consists of two PU layers according to one of claims 1 to 7 and an intermediate carrier layer and the outer PU layers ggb. With pressure-sensitive adhesive or a primer or both are coated.