SK992001A3 - MONOMER-POOR POLYURETHANE BONDING AGENT HAVING AN IMPROVEDì (54) LUBRICANT ADHESION - Google Patents

Abstract

The invention relates to a polyurethane bonding agent which has a low content of highly volatile residual monomers, which essentially forms no migrates and which has an improved lubricant adhesion. The invention also relates to a method for producing the inventive bonding agent and to an adhesive containing such a polyurethane bonding agent. In addition, the invention relates to the use of a low-viscous polyurethane bonding agent, said bonding agent carrying isocyanate groups (NCO groups), during the production of adhesives, especially adhesives containing one and two constituents, for example, provided for gluing web materials comprised of e.g. paper, plastic and/or aluminum, coatings, especially lacquers, dispersion paints, casting resins and shaped bodies.

Description

Technical field

The present invention relates to a polyurethane binder, a process for producing a low viscosity isocyanate-containing polyurethane binder having only a low content of readily volatile residual monomers, substantially non-migrating, and having improved adhesion to slippery compositions. The invention furthermore relates to the use of a low viscosity polyurethane binder containing isocyanate groups (NCO groups) in the manufacture of adhesives, in particular one-component and two-component adhesives, for example for bonding sheet materials of e.g. paper, plastics and / or aluminum, coatings, especially varnishes, dispersion paints and cast resins as well as shaped articles.

BACKGROUND OF THE INVENTION

Polyurethane prepolymers having terminal isocyanate groups have been known for a long time. These can be converted into high molecular weight compounds in a simple manner by suitable compounds - mostly polyfunctional alcohols - by chain extension or crosslinking. Polyurethane prepolymers have gained importance in many application areas, as well as in the production of adhesives, coatings, cast resins and molded articles.

In order to obtain polyurethane prepolymers having terminal isocyanate groups, it is common to react polyfunctional alcohols with an excess of polyisocyanates, generally at least predominantly diisocyanates. Thus, the molecular weight can be at least approximately controlled by the ratio of OH groups to isocyanate groups. While the ratio of OH groups to isocyanate groups of 1: 1 or almost 1: 1 results in a generally high molecular weight conversion, for example, at a ratio of about 2: 1 using diisocyanates in the statistical composition, one diisocyanate molecule is suspended per OH group. such that oligomers or chain lengthening are ideally avoided during the reaction.

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In practice, however, even in the latter case, it is not possible to completely avoid chain elongation reactions, which results in a certain amount of excess component remaining at the end of the reaction regardless of the reaction time. If, for example, diisocyanate is used as an excess component, due to the described situation, as a rule, an insignificant proportion of this component in the reaction mixture remains.

The content of such substances is particularly disturbing when they are easily volatile diisocyanates. The vapors of these diisocyanates are often harmful to health, and the use of products with a high content of such readily volatile diisocyanates requires costly measures for the user to protect the person working with the product, particularly costly measures to purify the breathing air.

As protection and cleaning measures are generally associated with high financial investment or costs, there is a need for users to have the lowest volatile diisocyanate content, depending on the isocyanate used, depending on the isocyanate used.

By "readily volatile" is meant within the present text those substances having a vapor pressure greater than about 0.097 Pa (0.0007 mmHg) or a boiling point of less than about 190 ° C (70 mPa) at about 30 ° C.

If hardly volatile diisocyanates, in particular extended bicyclic diisocyanates, such as diphenylmethane diisocyanates, are used instead of easily volatile diisocyanates, as a rule, polyurethane binders with a viscosity which are beyond the range applicable to simple processing methods are obtained. In these cases, it is possible to reduce the viscosity of the polyurethane prepolymer by the addition of a suitable solvent, but this often contradicts the required solvent free content of such binders. Another possibility of reducing the viscosity while avoiding solvents is to add an excess of monomeric polyisocyanates, which will be co-incorporated in a later hardening process (after hardener addition or moisture curing) into the coating or bonding (reactive diluent).

While the viscosity of the polyurethane prepolymers can indeed be reduced in this way, the incomplete conversion of the reactive diluent often leads to a content of free, monomeric polyisocyanates in the adhesive or coating, which can migrate, for example, in the coating or adhesive, or partially to the interior. ·

-3 ······································ Coated or glued material. Such coating or sticking ingredients are often referred to in the professional circles as "migrants". By contact with moisture, the isocyanate groups of migrants are continually converted to amino groups. Thus, the usually formed aromatic amines are suspected of having a carcinogenic effect.

In particular, in the area of packaging, migrants are often not tolerable, as migration of migrants through packaging material can cause contamination of packaged goods and the consumer would inevitably have to come into contact with migrants when using the goods.

Especially in the field of coating, especially food packaging, such migrants are therefore undesirable.

In order to avoid the disadvantages described above, EP-A 0 118 065 proposes to produce a polyurethane prepolymer in a two-stage process. Here, in the first step, the monocyclic diisocyanate first reacts with a polyfunctional alcohol in a ratio of OH groups: isocyanate groups of < In the second step, a ratio of OH groups: isocyanate groups of from 0.65 to 0.8, preferably from 0.7 to 0.75, is proposed. The prepolymers thus obtained still have a viscosity of 2500 mPas or 7150 mPas and 9260 mPas at high temperatures (75 [deg.] C. or 90 [deg.] C.), and there is no statement as to compatibility with glidants.

EP-A 0 019 120 relates to a process for the production of weather-resistant elastic sheets. Here, a two-step process is proposed in which, in a first step, toluylenediisocyanate (TDI) is reacted with at least an equimolar amount of polyol and the reaction product obtained is subsequently reacted with diphenylmethane diisocyanate (MDI) and polyol. The polyurethane binder thus obtained should be capable of curing with water or moisture. Although the described process results in relatively low viscosity products, the content of free, slightly volatile diisocyanate (TDI in the present case) is still high (0.7% by weight) and can only be reduced if time and energy are used. demanding methods to remove excess, easily volatile diisocyanate, such as thin-film distillation.

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-4 ······································ • ·· · · ·· ·

The unpublished German patent application 197 49 834.5 relates to a low monomer polyurethane binder. A two-component polyurethane binder with a low monomer content and a low proportion of migrants is disclosed.

For example, films used for food packaging often have a high content of glidants. A common lubricant is, for example, erucic acid amide (ESA), which is often present in the film in an amount greater than 400 ppm. Conventional adhesives which are used for bonding such films often have a deteriorating adhesive adhesion with an increasing proportion of glidants in the bonding film. Especially in modern, rationally operating packaging machines, an increase in productivity is achieved by significantly increasing the running speed of the packaging machine. The films used herein generally have a significantly increased content of glidants, which is often 600 ppm or higher, compared to the slow-running packaging machines. Many conventional adhesives have significant drawbacks when gluing films containing glidants in these sessions. As a result, the film composites thus produced often have insufficient bonding strength, especially after hardening has taken place.

SUMMARY OF THE INVENTION It was therefore an object of the present invention to provide a polyurethane binder having a low viscosity and low residual content of volatile diisocyanates of less than 1% by weight, with a residual volatile diisocyanate content of toluylene diisocyanate (TDI) of less than 0.1%.

It is a further object of the invention to provide a polyurethane binder with as low a migrate content as possible, i.e., a low binder content. with a low content of monomeric polyisocyanates.

Another object of the present invention was to provide a process for the production of a polyurethane binder with the above properties.

Another object of the invention was to find a polyurethane binder and an adhesive which, in addition to the properties already mentioned, due to its content of readily volatile diisocyanates and, as far as possible, a low proportion of migrants, also has an additionally improved compatibility with glidants, i. for example, improved bond adhesion or improved bond cohesion when bonding films with a high content of glidants.

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-5-Summary of the invention

The present invention relates to a polyurethane binder having a low content of isocyanate-containing, easily volatile monomers containing at least components A, B and C, wherein

(a) a polyurethane prepolymer containing at least two isocyanate groups is present, or a mixture of two or more polyurethane prepolymers containing at least two isocyanate groups, at least one polyurethane prepolymer having isocyanate groups bound by at least two different methods or at least two different polyurethane prepolymers in two different ways, of which at least one species has lower activity to the isocyanate-reactive group than the other species or the other species, and

(b) contains as component B at least one bifunctional isocyanate containing no nitrogen atom not belonging to the NCO group or a mixture of two or more of these; and

(c) component C is one of at least a bifunctional isocyanate or a mixture of two or more isocyanates with an average functionality of at least two and having at least one nitrogen atom per isocyanate molecule that is not part of the NCO or urethane group.

The term "low-viscosity" in the context of the present invention means a viscosity (measured according to Brookfield) that is below 5000 mPas at 50 ° C.

As used herein, the term "polyurethane binder" refers to a mixture of molecules containing at least two isocyanate groups in which the proportion of molecules having a molecular weight greater than 500 is at least 50% by weight, more preferably at least 60% by weight. % or at least about 70 wt.

As component A, a polyurethane prepolymer containing at least two isocyanate groups or a mixture of two or more polyurethane prepolymers containing at least two isocyanate groups which can be used may be used.

Preferably obtained by reaction of the polyol component and at least one bifunctional isocyanate.

As used herein, the term "polyurethane prepolymer" refers to a compound such as formed by reacting a polyol component with at least a bifunctional isocyanate. Thus, the term "polyurethane prepolymer" also encompasses relatively low molecular weight compounds, for example formed by reaction of a polyol with an excess of polyisocyanate, but also oligomeric or polymeric compounds are also included. Also delimited by the term "polyurethane prepolymer" are compounds, such as formed, for example, in the reaction of a tri or quaternary polyol with a molar excess of diisocyanates relative to the polyol. In this case, one molecule of the resulting compound contains multiple isocyanate groups.

Molecular weight data relating to the polymeric compounds refer, unless otherwise stated, the average molecular weight (M _n).

Typically, the polymer prepolymers used in the present invention have a molecular weight of from about 150 to about 15,000, or from about 500 to about 10,000, for example, about 5,000, especially from 700 to about 2,500.

In a preferred embodiment of the present invention, the polyurethane prepolymer has two isocyanate groups, or at least one of a mixture of two or more isocyanate-containing polyurethane prepolymers having isocyanate groups bound by at least two different methods, one species having a lower reactivity to the other or isocyanate-reactive group. other isocyanate groups. Isocyanate groups with a relatively lower reactivity over isocyanates with more reactive groups (as compared to at least one other isocyanate group present in the polyurethane binder) will hereinafter be referred to as "less reactive isocyanate groups", corresponding to isocyanate reactive groups with isocyanate groups will also be referred to as "reactive isocyanate groups".

Thus, for example, a bifunctional polyurethane prepolymer containing two different bonded polymers may be used as component A in the present invention. isocyanate groups, one of these isocyanate groups having a higher reactivity to the isocyanate-reactive group than the other isocyanate group. Such a polyurethane prepolymer can be obtained, for example, by reacting a bifunctional alcohol with a compound containing two different, for example bifunctional, isocyanate groups, the reaction being carried out, for example, by reacting each molecule of the bifunctional alcohol with one molecule of compound containing different isocyanate groups.

It is also possible to use a three- or more-functional polyurethane prepolymer in component A, whereby one polyurethane prepolymer molecule contains, for example, a different number of less reactive and reactive isocyanate groups.

In a further preferred embodiment, mixtures of two or more polyurethane prepolymers are usable as component A. The mixtures may be polyurethane prepolymers in which the individual polyurethane molecule always contains identically bonded isocyanate groups. There must therefore be at least two different types of polyurethane molecules in the mixture which differ at least by the kind of isocyanate group they contain. Overall, in this embodiment, at least one more reactive and one less reactive species of the isocyanate group must be present in such a mixture, i. one polyurethane molecule with at least two reactive and a polyurethane molecule with at least two less reactive isocyanate groups. It is also possible for the composition to contain, in addition to molecules having one or more identically linked isocyanate groups, another molecule which also contains one or more identically linked isocyanate groups as well as one or more differently bound isocyanate groups.

Also suitable as component A or at least as part of component A are reaction products of bivalent or multifunctional alcohols with at least an equimolar amount (based on the OH groups of the bivalent or more functional alcohol) of lower molecular diisocyanates having a molecular weight of up to about 400.

In a preferred embodiment, the polyurethane prepolymer or the mixture of two or more polyurethane prepolymers used as component A in the molecule comprises at least one urethane group.

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-8 · · ·

In a preferred embodiment of the invention, component A is produced by at least a two-step reaction in which

(a) in the first stage, a polyurethane prepolymer is produced from at least a bifunctional isocyanate and at least a first polyol component, wherein the NCO / OH ratio is less than 2 and the polyurethane prepolymer still contains free OH groups; and

b) reacting in the second step another at least two-functional isocyanate with the polyurethane prepolymer of the first step, wherein the isocyanate groups of the isocyanate added in the second stage have a higher reactivity to the isocyanate-reactive compounds than the minimum prevailing isocyanate groups of the first stage.

In a further preferred embodiment, additional, at least bifunctional isocyanate, in a molar excess, based on the free OH groups of component A, is added.

In another preferred embodiment, component A is produced by at least a two-step reaction in which

(a) in the first stage, a polyurethane prepolymer is produced from at least a bifunctional isocyanate and at least a first polyol component, wherein the NCO / OH ratio is less than 2 and the polyurethane prepolymer still contains free OH groups; and

b) reacting in the second stage another at least two-functional isocyanate and another polyol component with the polyurethane prepolymer of the first stage, wherein the isocyanate groups of the isocyanate added in the second stage have a higher reactivity to the isocyanate-reactive compounds than the minimally degree.

Within the scope of the present invention, it is preferred that in the second stage production of component A, the OH: NCO ratio is from about 0.001 to less than 1, more preferably from 0.005 to about 0.8.

In a preferred embodiment of the present invention, the ratio of OH: NCO in the second stage is from about 0.2 to 0.6.

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In a further preferred embodiment of the invention, the OH: NCO ratio in the first stage is less than 1, more preferably from 0.5 to 0.7, wherein the possible described ratios in the second stage can also be observed.

As used herein, the term "polyol component" includes a single polyol or a mixture of two or more polyols that can be used to produce polyurethanes. By polyol is meant a polyfunctional alcohol, i. a compound with more than one OH group per molecule.

A large number of polyols can be used as the polyol component for the production of component A. For example, they are aliphatic alcohols having from 2 to 4 OH groups per molecule. OH groups may be primary or secondary linked. Suitable aliphatic alcohols include, for example, ethylene glycol, propylene glycol, butanediol-1,4, pentanediol-1,5, hexanediol-1,6, heptanediol-1,7, octanediol-1,8, and higher homologues or isomers thereof, as will be apparent to those skilled in the art. by gradually extending the hydrocarbon chain by a Chh group or by introducing a branching into the hydrocarbon chain. Multifunctional alcohols such as glycerol, trimethylolpropane, pentaerythritol as well as oligomeric ethers of the aforementioned substances on their own or in a mixture of two or more of said ethers are also suitable.

Furthermore, the reaction products of low molecular weight multifunctional alcohols with alkylene oxides, the so-called polyethers, can be used as the polyol component for the production of component A. The alkylene oxides preferably have 2 to 4 carbon atoms. Suitable reaction products are, for example, ethylene glycol, propylene glycol, isomeric butanedioles or hexanedioles with ethylene oxide, propylene oxide and / or butylene oxide. It is also possible to use reaction products of polyfunctional alcohols, such as glycerol, trimethylolethane and / or trimethylolpropane, pentaerythritol or sugar alcohols, with said alkylene oxides to form polyether polyols. Polyether polyols having a molecular weight of from about 100 to about 10,000, more preferably from about 200 to about 5,000 are particularly suitable. Polypropylene glycol having a molecular weight of from about 300 to about 2500 is particularly preferred in the present invention. polyether polyols such as those formed by the polymerization of tetrahydrofuran.

The polyethers are prepared in a manner known to the person skilled in the art by reacting the starting compound with a reactive hydrogen atom and alkylene oxides such as ethylene oxide, e.g.

Propylene oxide, butylene oxide, styrene oxide, tetrahydrofuran or epichlorohydrin or a mixture of two or more thereof.

Suitable starting compounds are, for example, water, ethylene glycol, propylene glycol-

1,2, or -1,3, butylene glycol-1,4 or -1,3, hexanediol-1,6, octanediol-1,8, neopentyl glycol, 1,4-hydroxymethylcyclohexane, 2-methyl-1,3-propanediol , glycerin, trimethylolpropane, hexanetriol-1,2,6, butanetriol-1,2,4, trimethylolethane, pentaerythritol, mannitol, sorbitol, methylglycosides, sugars, phenol, isononylphenol, resorcinol, hydroquinone,

1,2,2- or 1,1,2-tris- (hydroxyphenyl) ethane, ammonia, methylamine, ethylenediamine, tetra or hexamethyleneamine, triethanolamine, aniline, phenylenediamine, 2,4- and 2,6-diaminotoluene and polyphenylpolymethylenepolyamines such as are obtained by aniline-formaldehyde condensation.

Also suitable for use as a polyol component are polyethers that have been modified with vinyl polymers. Such products can be obtained, for example, by polymerizing styrene nitrile and / or acrylonitrile in the presence of polyethers.

Also suitable as the polyol component for the production of component A are polyester polyols having a molecular weight of from about 200 to about 10,000. Thus, for example, polyester polyols formed by reaction of lower molecular alcohols, especially ethylene glycol, diethylene glycol, neopentyl glycol, hexanediol, butanediol, propylene glycol, trimethylolpropane with caprolactone. Also suitable as polyfunctional alcohols for the production of polyester polyols are 1,4-hydroxymethylcyclohexane, 2-methyl-1,3-propanediol, butanetriol-1,2,4, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, dibutylene glycol and polybutylene glycol.

Other suitable polyester polyols can be made by polycondensation. Thus, dicarboxylic and / or tricarboxylic acid-deficient bifunctional and / or tri-functional alcohols, or reactive derivatives thereof, can condense to form polyester polyols. Suitable dicarboxylic groups are, for example, succinic acid and its higher homologues with up to 16 carbon atoms, further unsaturated dicarboxylic acids such as maleic or fumaric acid and aromatic dicarboxylic acids, in particular isomeric phthalic acids such as phthalic acid, isophthalic acid or terephthalic acid. Suitable tricarboxylic acids are, for example, citric acid or trimellitic acid. The following are particularly suitable within the scope of the invention:

-11 ·········· · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · Polyester polyols from at least one of said dicarboxylic acids and glycerin having a residual OH group content. Particularly suitable alcohols are hexanediol, ethylene glycol, diethylene glycol and neopentyl glycol or mixtures of two or more thereof. Particularly suitable acids are isophthalic acid or adipic acid or a mixture thereof.

Particularly preferred polyols used in the present invention for the production of component A are, for example, dipropylene glycol and / or polypropylene glycol having a molecular weight of from about 400 to about 2500, as well as polyester polyols, more preferably polyester polyols obtained by polycondensation of hexanediol, ethylene glycol, diethylene glycol or neopentylglycol. or more, and isophthalic acid or adipic acid or mixtures thereof. Higher molecular weight polyester polyols include, for example, the reaction products of polyfunctional, preferably bifunctional alcohols (optionally together with a small amount of trifunctional alcohols) and polyfunctional, more preferably bifunctional, carboxylic acids. Instead of the free polycarboxylic acids, the corresponding polycarboxylic anhydrides or corresponding polycarboxylic acid esters with alcohols having preferably 1 to 3 carbon atoms can also be used, if possible. The polycarboxylic acids may be aliphatic, cycloaliphatic, aromatic and / or heterocyclic. They may optionally also be substituted, for example by alkyl groups, alkenyl groups, ether groups or halogens. Suitable polycarboxylic acids are, for example, succinic acid, adipic acid, corkic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, tetrachlorophthalic anhydride, anhydride endomethylenetetrahydrophthalic acid, glutaric anhydride, maleic acid, maleic anhydride, fumaric acid, dimeric fatty acid or trimeric fatty acid or mixtures of two or more thereof. Optionally, minor amounts of monofunctional fatty acids may be present in the reaction mixture.

The polyesters may optionally contain a small proportion of terminal carboxyl groups. It is also possible to use polyesters obtained from lactones, for example from ε-kapro ·· ····

The lactone or hydroxycarboxylic acids, for example ω-hydroxycaproic acid, may be used.

Polyacetals are likewise suitable as the polyol component. Polyacetals are compounds that are obtainable from glycols, for example, diethylene glycol or hexanediol with formaldehyde. Polyacetals useful in the invention may also be obtained by the polymerization of cyclic acetals.

Polycarbonates are furthermore suitable as polyols for the production of component A. Polycarbonates can be obtained, for example, by reaction of diols such as propylene glycol, butanediol-1,4 or hexanediol-1,6, diethylene glycol, triethylene glycol or tetraethylene glycol, or mixtures of two or more thereof with diaryl carbonates, for example diphenyl carbonate or phosgene.

Also suitable as the polyol component for the production of component A are polyacrylates containing OH groups. These polyacrylates can be obtained, for example, by polymerizing ethylenically unsaturated monomers containing an OH group. Such monomers can be obtained, for example, by esterification of ethylenically unsaturated carboxylic acids and bifunctional alcohols, the alcohol being generally in a slight excess. Suitable ethylenically unsaturated carboxylic acids are, for example, acrylic acid, methacrylic acid, crotonic acid or maleic acid. Corresponding OH-containing esters are, for example, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl acrylate or 3-hydroxypropyl methacrylate or mixtures of two or more thereof.

For the production of component A, the respective polyol component is always reacted with at least a bifunctional isocyanate. Basically any isocyanate having at least two isocyanate groups is suitable as the at least bifunctional isocyanate for the preparation of component A, however, compounds having 2 to 4 isocyanate groups, in particular two isocyanate groups, are generally preferred in the present invention.

Subsequently, at least two-functional isocyanates which are suitable as at least two-functional isocyanates for the production of component A will be described.

Examples are: ethylenediisocyanate, 1,4-tetramethylenediisocyanate, 1,6hexamethylenediisocyanate (HDI), cyclobutane-1,3-diisocyanate, cyclohexane-1,3 ················· · ··· ··· · · ··························································

-13-diisocyanate, cyclohexane-1,4-diisocyanate and mixtures of two or more thereof, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate, IPDI), 2,4- and 2,6-hexahydrotoluylene diisocyanate , tetramethylxylylenediisocyanate (TMXDI), 1,3- and 1,4-phenylenediisocyanate, 2,4- or 2,6-toluylenediisocyanate, diphenylmethane-2,4'-diisocyanate, diphenylmethane-2,2'-diisocyanate or diphenylmethane-4, 4'-diisocyanate or mixtures of two or more of said diisocyanates.

Equally suitable as isocyanates for the production of component A within the meaning of the present invention are trivalent or polyvalent isocyanates which can be obtained, for example, by oligomerization of diisocyanates. Examples of such trivalent and polyvalent polyisocyanates are triisocyanurates from HDI or IPDI or mixtures thereof or mixed triisocyanurates thereof.

In a more preferred embodiment of the invention, diisocyanates having two isocyanate groups with different reactivity are used to produce component A. Examples of such diisocyanates are 2,4- and 2,6-toluylenediisocyanate (TDI) and isophorone diisocyanate (IPDI). In such unsymmetrical diisocyanates, as a rule, one isocyanate group reacts significantly more rapidly with isocyanate-reactive groups, for example OH groups, while the remaining isocyanate group is relatively low reactive. Therefore, in a preferred embodiment, a monocyclic, unsymmetrical diisocyanate which contains two isocyanate groups of the described, different reactivity is used to produce component A.

Especially preferred is the use of 2,4- or 2,6-toluylenediisocyanate (TDI) or a mixture of the two isomers, but most preferably pure 2,4-TDI.

The polyurethane binder according to the invention contains as component B at least a bifunctional isocyanate which contains no nitrogen atom which is not part of the NCO group or a mixture of two or more thereof.

Suitable component B is, for example, at least two-functional isocyanates or a mixture of two or more such isocyanates having an average functionality of at least about two.

In a preferred embodiment of the invention, component B comprises at least one bifunctional isocyanate, the NCO groups of which are more reactive to the compounds.

-14 reacting with NCO groups, for example in the formation of urethane, thiourethane, biuret or allophan, as less reactive isocyanate groups of polyurethane prepolymers contained in component A.

The isocyanate groups of the bifunctional isocyanates contained in component B may have different or substantially the same reactivity. In a preferred embodiment of the invention, it is also possible to use at least bifunctional isocyanates as component B whose isocyanate groups have the same reactivity.

Generally, component B has a molecular weight up to about 2000, but more preferably the molecular weight is lower, for example less than about 1000, less than about 700, or less than about 400 g / mol.

For example, 4,4'-diphenylmethane diisocyanate (MDI), 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate as well as HDI, IPDI or TMXDI are suitable for use as component B in the present invention.

In a preferred embodiment, 4,4'-diphenylmethane diisocyanate (MDI), 2,2'-diphenylmethane diisocyanate or 2,4-diphenylmethane diisocyanate is used.

The polyurethane binder of the invention comprises at least about 3 wt. component B, based on the total polyurethane binder. In a preferred embodiment, the polyurethane binder comprises from about 5 to about 25 wt. component B.

The polyurethane binder according to the invention preferably contains a proportion of easily volatile monomers containing isocyanate groups lower than 2% by weight. % or less than 1 wt. % or more preferably less than 0.5 wt. These limits apply in particular to lightly volatile isocyanate compounds which have only a limited hazard potential for those working with them, for example isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), tetramethylxylylene diisocyanate (TMXDI) or cyclohexane diisocyanate (TMXDI) or cyclohexane diisocyanate. In the case of certain readily volatile isocyanate compounds, in particular those having a high risk potential for the processors, their content in the polyurethane binder according to the invention is preferably less than 0.3% by weight. % and more preferably less than 0.1 wt. The latter isocyanate compounds include, for example, toluylenediisocyanate (TDI). In another, advantageous ·· ····

In an embodiment of the invention, the TDI and HDI content of the polyurethane binder is less than 0.05% by weight.

The polyurethane binder according to the invention contains as component C at least one bifunctional isocyanate or a mixture of two or more isocyanates having an average functionality of at least two and containing at least one nitrogen atom per isocyanate which is not part of the NCO or urethane group.

Thus, for example, NCO-containing carbodiimides which are obtained by reaction of diisocyanates under suitable conditions and catalysis are suitable for use in component C.

Isocyanates suitable for the preparation of carbodiimides are, for example, compounds of the general structure O = C = N-X-N = C = O, wherein X is an aliphatic, alicyclic or aromatic radical, more preferably an aliphatic or alicyclic radical having 4 to 18 carbon atoms.

For example, suitable isocyanates of 1,5-naphthylenediisocyanate, 4,4'-diphenylmethane diisocyanate (MDI), hydrogenated MDI (H 2 MDI), xylylene diisocyanate (XDI), tetramethylxylylenediisocyanate methanesulfate (TMXDI), 4,4'-diphenylmethane, diisocyanate, diphenylmethane diisocyanate, diphenylene diisocyanate. 4,4'-dibenzyldiisocyanate, 1,3-phenylenediisocyanate, 1,4-phenylenediisocyanate, isomers of toluylenediisocyanate (TDI), 1-methyl-2,4-diisocyanato-cyclohexane, 1,6-diisocyanato-2,2,4-trimethylhexane 6-diisocyanato-2,4,4-trimethylhexane, 1-isocyanatomethyl-3-isocyanato-1,5,5-trimethylcyclohexane (IPDI), chlorinated and brominated diisocyanates, phosphorus-containing diisocyanates, 4,4'-diisocyanato-phenylperfluoroethane, tetramethoxybutane-1,4-diisocyanate, butane-1,4-diisocyanate, hexane-1,6-diisocyanate (HDI), dicyclohexylmethane diisocyanate, cyclohexane-1,4-diisocyanate, ethylene diisocyanate, phthalocyanate, h / s-isocyanate diisocyanates with a reactive halogen atom, and co-1-chloromethylphenyl-2,4-diisocyanate, 1-bromomethylphenyl-2,6-diisocyanate, S, N-s-chloromethylethyl N, N'-diphenyldiisocyanate.

Other useful diisocyanates are, for example, trimethylhexamethylenediisocyanate, 1,4-diisocyanatobutane, 1,12-diisocyanatododecane and dimeric acid diisocyanate. Particularly suitable are tetramethylenediisocyanate, hexamethylenediisocyanate, undecanediisocyanate, dodacanethylenediisocyanate, 2,2,4-trimethyl-16, β-trimethyl-16. Hexanediisocyanate, 1,3-cyclohexanediisocyanate, 1,4-cyclohexanediisocyanate, 1,3- or 1,4-tetramethylxyloldiisocyanate, isophorone diisocyanate, 4,4-dicyclohexylmethane diisocyanate, diisocyanate, diisocyanate and diisocyanate.

Particularly suitable herein are the reaction products of carbodiimide formation from MDI, TDI, HDI or IPDI, or mixtures of two or more thereof.

Further suitable are tri- or oligomerization products of polyisocyanates which are obtainable in the formation of isocyanurate rings by a suitable reaction of polyisocyanates, more preferably diisocyanates. If oligomerization products are used, they are particularly suitable having an average oligomerization degree of from about 3 to about 5.

Isocyanates suitable for the reaction are already mentioned above, with HDI, MDI or IPDI isocyanate trimerization products being particularly suitable.

Also suitable for use as component C are polymeric isocyanates formed as a distillation residue in the distillation of diisocyanates. Particularly suitable herein is a &quot; polymeric MDI &quot; which is obtainable in the distillation of MDI from a distillation residue and which contains at least one nitrogen atom per isocyanate which is not part of any NCO or urethane group.

Component C is added to the polyurethane binder of the invention in an amount such that the total polyurethane binder contains from about 1 to 40 wt. In a preferred embodiment of the invention, the polyurethane binder comprises from about 5 to 30 wt. % and most preferably from 10 to 22 wt. Component C.

The polyurethane binder with the advantages according to the invention can in principle be produced in any manner. However, it has proved to be particularly advantageous to have two methods which will be described hereinafter.

It is possible, for example, to produce the polyurethane binder by direct production of component A with an additional successive or simultaneous addition of components B and C. The addition of component B can optionally be carried out together with another polyol component.

Further, the invention provides a process for producing a polyurethane binder containing isocyanate groups, comprising at least three steps, in which:

·· ····

(h) in a first step, a polyurethane prepolymer is produced from at least one of a bifunctional isocyanate and at least one polyol component; and

(i) in the second stage, one additional minimum bifunctional isocyanate containing no nitrogen atom not belonging to the NCO group or a mixture of two or more thereof is added; and

(j) in the third step, add at least one divalent isocyanate or a mixture of two or more isocyanates with an average functionality of at least two, at least one isocyanate containing at least one non-NCO nitrogen atom, the major proportion of isocyanate groups existing after completion The first stage has a lower reactivity to the isocyanate-reactive groups, in particular to the OH groups, than the isocyanate groups of the bifunctional isocyanate added in the second stage.

As a further polyol component, all of the polyol components already mentioned herein can in principle be used.

It is preferred that in the first stage of the process of the invention the ratio of OH: NCO is less than 1. In a preferred embodiment, the ratio of OH groups to isocyanate groups is from 0.4 to 0.7, more preferably more than 0.5 to 0.7.

The reaction of the polyol component with the at least bifunctional isocyanate in the first step can be carried out by any method known to those skilled in the art according to the general rules of polyurethane production. For example, the reaction may be carried out in the presence of solvents. In principle, all solvents used in polyurethane chemistry, in particular esters, ketones, halogenated hydrocarbons, alkanes, alkenes and aromatic hydrocarbons, can be used as solvents. Examples of such solvents are methylene chloride, trichlorethylene, toluene, xylene, butyl acetate, amylacetate, isobutyl acetate, methyl isobutyl ketone, methoxybutyl acetate, cyclohexane, cyclohexanone, dichlorobenzene, diethyl ketone, diisobutyl ketone, dioxane, ethyl acetate, ethylene glycol acetate, ethylene glycol, isobutyl acetate, isooctane, isopropyl acetate, methyl ethyl ketone, tetrahydrofuran or tetrachlorethylene or mixtures of two or more of the aforementioned solvents.

-18 ·········································· ·· ··

If the reactants themselves are liquid or if at least one or more of the reactants form a solution or dispersion of another insufficiently liquid reactant, it is not necessary to use solvents. Such a solvent-free reaction is more preferred in the present invention.

To carry out the first step of the process according to the invention, the polyol, optionally together with a suitable solvent, is introduced and mixed in a suitable container. Subsequently at least two-functional isocyanate is added under constant stirring. The temperature is usually raised to accelerate the reaction. Typically, it is heated to a temperature of about 40 to 80 ° C. The incipient exothermic reaction subsequently causes a temperature rise. The batch temperature is maintained at a temperature of from 70 to 110 ° C, for example at a temperature of from about 85 to 95 ° C or most preferably from 75 to 85 ° C, optionally adjusting the temperature by suitable external measures such as heating or cooling.

Optionally, catalysts customary in polyurethane chemistry may be added to the reaction mixture to accelerate the reaction. The addition of dibutyltin dilaurane or diazabicyclooctane (DABCO) is preferred. If a catalyst addition is desired, the catalyst is generally added to the reaction mixture in an amount of about 0.005% by weight. or from about 0.01 wt. % to 0.2 wt. relative to the total charge.

The reaction time of the first stage depends on the polyol component used, the minimum bifunctional isocyanate used, the reaction temperature as well as any catalyst present. Typically, the total reaction time is about 30 minutes to 20 hours.

Preferably, in the first step, isophorone diisocyanate (IPDI), tetramethylxylylene diisocyanate (TMXDI), hydrogenated diphenylmethane diisocyanate (MDIH12) or toluylene diisocyanate (TDI) or a mixture of two or more thereof is used as the minimum bifunctional isocyanate in the first step.

In order to carry out the second step of the process according to the invention, one further at least two-functional isocyanate which contains no nitrogen atom, which is not part of the NCO group, or a mixture of two or more such isocyanates, optionally together with another polyol component. Any polyol from the group of polyols mentioned above may be used as part of an optional other polyol component in the course of this process.

-19text or a mixture of two or more thereof. However, it is preferred in the second stage of the process according to the invention to use as the polyol component a polypropylene glycol having a molecular weight of 400 to 2500, or a polyester polyol with at least a higher, most preferably predominant proportion of aliphatic dicarboxylic acids or a mixture thereof.

As the at least bifunctional isocyanate, which contains no nitrogen atom not part of the NCO group, at least one polyisocyanate having isocyanate groups having a higher reactivity than the lower reactivity isocyanate groups found in the prepolymers is used in the second step of the process of the invention. That is, the prepolymers may still have reactive isocyanate groups that originate from at least the bifunctional isocyanate used initially for the production of prepolymer A. The only essential aspect of the invention in this connection is that at least a small proportion, more preferably a predominant proportion of isocyanate groups present. The prepolymers of component A have lower reactivity than the isocyanate groups of another minimally bifunctional diisocyanate which contains no nitrogen atom that is not part of the NCO group added in the second step of the process of the invention.

As a further minimally bifunctional isocyanate which contains no nitrogen atom which is not part of the NCO group, a bicyclic, aromatic, symmetrical diisocyanate is preferably used. Bicyclic isocyanates include, for example, diisocyanates of the diphenylmethane series, especially 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate and 4,4'-diphenylmethane diisocyanate. Among these diisocyanates, the use of diphenylmethane diisocyanate, in particular 4,4'-diphenylmethane diisocyanate, as a further at least bifunctional isocyanate in the second step of the process according to the invention is particularly preferred.

This further minimally bifunctional isocyanate, which contains no nitrogen atom and which is not part of the NCO group, is used in the second stage in an amount of from 1 to 50% by weight, more preferably from 10 to 30% by weight. and most preferably in an amount of from 15 to 25% by weight, based on the total amount of polyisocyanates used in all steps of the process according to the invention.

In a preferred embodiment, the ratio of OH.NCO in the second step is from about 0.2 to 0.6, more preferably to 0.5. Here, for OH: NCO ratio, components added ·· ····

In the second step, isocyanate groups derived from prepolymer A are not considered here.

However, the polyurethane binder with the advantages according to the invention can also be produced by mixing the individual components D, E, F and G.

Further, the invention relates to a process for the production of a low viscosity polyurethane binder containing isocyanate groups having a low content of isocyanate-containing, easily volatile monomers, comprising mixing the four components D, E, F, and G, in which

(k) as component D, a polyurethane prepolymer containing isocyanate groups obtained by reacting a polyol component with at least a bifunctional isocyanate;

(l) as component E, another polyurethane prepolymer containing isocyanate groups obtained by reacting the polyol component with another at least bifunctional isocyanate, the isocyanate groups having a higher reactivity to the isocyanate-reactive group than the isocyanate groups of component D

(m) as component F, at least a bifunctional isocyanate containing at least two nitrogen atoms which is not part of the NCO group or a mixture of two or more of these; and

(n) as component G, a further minimum bifunctional isocyanate or a mixture of two or more isocyanates with an average functionality of at least two, at least one isocyanate having at least one non-NCO nitrogen atom, the quantity of component G being measured so that at least 5% by weight, more preferably at least 10% by weight, is left in the polyurethane binder at the end of the mixing process and after completion of any reactions possibly occurring between components D, E, F and G. component G, based on the total polyurethane binder.

The polyurethane binders of the invention and the polyurethane binders produced according to the invention preferably have a viscosity of less than 5000 mPas (measured by Brookfield RT DVII (Thermosell), spindle 27, 20 rpm, 50 ° C).

In the context of the present invention, "all reactions possibly occurring between components D, E, F and G" are understood to mean reactions of isocyanate groups with functional groups containing isocyanate-reactive hydrogen atoms. ··· ··· · ··· · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · In particular, if, for example, components D or E, or D and E, still contain free OH groups, the addition of component F generally leads to the reaction of the isocyanate groups of component F with the free OH groups. This has the effect of reducing the content of component F. Therefore, if reactions that can cause a reduction in the proportion of component F can be expected, addition of component F is necessary in such an amount that the required minimum quantity of component F remains in the polyurethane binder.

All of the polyols described above and mixtures of two or more of the aforementioned polyols can be used as the polyol component for the production of components D and E. In particular, the polyol components which have been shown to be particularly preferred for the production of component A within the scope of the present invention are preferably also used in the process according to the invention.

For at least the bifunctional isocyanate used as component F, which contains no nitrogen atom that is not part of the NCO group, or a mixture of two or more such isocyanates, the explanations analogous to component B apply.

For at least a bifunctional isocyanate or a mixture of two or more isocyanates used as component G, with an average functionality of at least two, with at least one isocyanate containing at least one nitrogen atom that is not part of the NCO group, the explanations analogous to component C apply.

The polyurethane binder according to the invention and the polyurethane binders produced according to the invention are characterized in that they contain an extremely low proportion of easily volatile isocyanate-containing monomers which is less than 2% by weight. or less than 1 wt.%, less than 0.5 wt. % and in particular less than about 0.1 wt. In this connection, it should be pointed out in particular that the process according to the invention can be carried out without separate separation steps to remove the easily volatile diisocyanate components.

A further advantage of the polyurethane binders produced by the process according to the invention is that they have a viscosity which is to a very advantageous extent for processing. The viscosity of the polyurethane binders produced by the process of the invention is particularly lower than 5000 mPas (measured with Brookfield RT DVII (Thermosell), spindle 27, 20 rpm, 50 ° C).

The polyurethane binders according to the invention are suitable in substances or as solutions in organic solvents, for example in solvents as previously described, for coating articles, in particular for gluing articles.

The invention therefore also relates to the use of the polyurethane binder according to the invention or the polyurethane binder produced by the process according to the invention in the production of adhesives, in particular one-component and two-component adhesives, coatings, in particular varnishes, dispersion paints and casting resins. coating and in particular for bonding objects, in particular for bonding films and for the production of film composites.

The polyurethane binder according to the invention or the polyurethane binder produced by the process according to the invention are used in particular for gluing plastics and particularly preferably for laminating plastic foils, plastic foils with a steamed metal or metal oxide, as well as metal foils, in particular aluminum foils.

Curing, i. crosslinking of the individual polyurethane binder molecules by means of free isocyanate groups can be achieved without the addition of further compounds, for example hardeners, only by means of atmospheric moisture. However, it is preferred that polyfunctional crosslinkers such as amines or more preferably polyfunctional alcohols (two-component systems) are added as hardening polyfunctional crosslinkers.

The foil composites produced by the products produced according to the invention have a high degree of safety in heat-adhesive processing. This is due to the reduced proportion of migratory low molecular weight products in the polyurethane binder. The preferred processing temperature for adhesives made according to the invention is in such methods from about 30 to 90 ° C.

The invention further provides an adhesive comprising two Hal components, wherein:

o) As component H, a polyurethane binder containing the isocyanate groups according to the invention or a polyurethane binder containing the isocyanate groups according to any of the methods described above is used; and

(p) as component I, a compound containing at least two isocyanate-reactive functional groups of component H with a molecular weight of up to 50,000 or a mixture of two or more of such compounds is used.

·································

Any polyurethane binder according to the invention as described above can be used as component H.

Component I is preferably a compound having at least two functional groups reactive with the isocyanate groups of component F having a molecular weight of up to 2500, or a mixture of two or more of such compounds. Suitable at least two functional groups reactive with the isocyanate groups of component F are amino, mercaptan or OH groups, wherein the compounds which are useful as component G can always contain amino, mercaptan or OH groups exclusively or in a mixture.

The functionality of the compounds useful as component I is generally about 2. More preferably, component I contains a proportion of the higher functional compounds, for example having a functionality of three, four or more. The total (average) functionality of component I is, for example, about two (for example, when only bifunctional compounds are used as component I) or more, for example, 2,1, 2,2, 2,5, 2,7 or 3. Alternatively, the component may have Even greater functionality, for example, about four or more.

More preferably, component I comprises a polyol containing at least two OH groups. All polyols mentioned above are suitable for use in component I as long as they meet the upper molecular weight limiting criterion.

As a rule, component I is used in an amount such that the ratio of the isocyanate groups of component H to the functional groups reactive with the isocyanate groups of component H in component I is from about 5: 1 to 1: 1, more preferably from 2: 1 to 1: 1.

The adhesive of the invention typically has a viscosity of from 250 to 10,000 mPas, more preferably from 500 to 8,000 or up to 5,000 mPas (Brookfield RVT DVII, spindle 27, 20 rpm, 40 ° C).

Optionally, the adhesive according to the invention may also contain additives. Additives may comprise up to about 30% by weight of the total adhesive.

Additives useful in the present invention include, for example, plasticizers, stabilizers, antioxidants, colorants, photostabilizers, or fillers.

As plasticizers, for example, phthalic acid plasticizers, in particular dialkyl phthalanes, are used, the phthalic acid esters esterified with a linear alkanol containing from about 6 to 12 carbon atoms being preferred as plasticizers. Dioctylphthalate is particularly preferred herein.

-24 «··········································

Likewise suitable as plasticizers are benzoic plasticizers, for example sucrose benzoate, diethylene glycol dibenzoate and / or diethylene glycol benzoate, in which from 50 to 95% of all hydroxyl groups are esterified, phosphate plasticizers, for example tert-butylphenyldiphenylphosphate, polyethylene glycol derivatives, polyethylene ether , for example, methyl ester of hydrogenated resin, vegetable and animal oils, for example glycerol ester of fatty acids and their polymerization products.

The stabilizers or antioxidants usable as additives in the present invention include sterically hindered phenols of high molecular weight (M _n), polyfunctional phenols and phenol containing sulfur and phosphorus. Phenols useful as an additive in the present invention are, for example, 1.3 _{L of} 5-trimethyl-2 _{L of} 4,6-trans (3,5-tert-butyl-4-hydroxybenzyl) benzene; pentaerythritol tetrakis-3- (3,5-d / N-tert-butyl-4-hydroxyphenyl) propionate; n-octadecyl-3,5-/ tert-butyl-4-hydroxyphenyl) propionate; 4,4-methylene-bis- (2,6-c // - tert-butylphenol); 4,4-thio-bis- (6-tert-butyl-o-cresol); 2,6-D / N-tert-butylphenol; 6- (4-hydroxyphenoxy) -2,4-bis (n-octyl thio) -1,3,5-triazine; d-n-octadecyl 3,5-a / N-tert-butyl-4-hydroxybenzylfosfonáty; 2- (n-octyl) -ethyl-3,5-/ N-tert-butyl-4-hydroxybenzoate; and sorbithexa [3- (3,5-tert-butyl-4-hydroxyphenyl) propionate].

Suitable photostabilizers are, for example, those obtainable under the trade name Thinuvin® (manufacturer: Ciba Geigy).

Additional additives may be added to the adhesives of the invention to alter certain properties. These may include, for example, dyes such as titanium dioxide, fillers such as talc, clay and the like. Optionally, the adhesives of the invention may contain small amounts of thermoplastic polymers, such as ethylene vinyl acetate (EVA), ethylene acrylic acid, ethylene methacrylate, and ethylene-n-butyl acrylate copolymers which impart additional flexibility, strength and strength to the adhesive. It is also possible and within the scope of the present invention to add certain hydrophilic polymers, for example polyvinyl alcohol, hydroxyethylcellulose, hydroxypropylcellulose, polyvinylmethyl ether, polyethylene oxide, polyvinylpyrrolidone, polyethylenexazoline or starches or cellulose esters, in particular acetates having a degree of substitution less than 2.5.

The invention will be further elucidated by means of examples, which are not intended to be limiting.

-25 ··············································

DETAILED DESCRIPTION OF THE INVENTION

Explanation of raw materials and abbreviations in Table 1:

K1-K5

H

PE1

PE2

DEG

THE DOG

PI3

MDI-C

HDI-T

HDI-0

MDI-P

ADV-1

ADV-G

IN

MC m-TDI m-MDI

SEZ

NCO-value

NCO-F adhesive formulations 1 to 5 hardener (polyol blend), base number = 138.8 propylene glycol polyether propylene glycol polyether diethylene glycol polyester based on adipic acid, diethylene glycol, phthalic acid and dipropylene glycol propylene glycol polyethers

MD1-carbodiimide dimer

HDI-trimer HDI-oligomer polymer MDI (distillation residue) OH / NCO addition ratio for component A and component B OH / NCO addition ratio total viscosity (Brookfield RVTD, 40 ° C) monomer content in wt. (based on total formulation) monomeric TDI monomeric MDI basicity number [mg KOH / g]

NCO value in% wt. (based on the overall formulation) final NCO value

-26Table 1

Adhesive formulations (all values are in% by weight unless otherwise stated above)

raw materials OHZ or NCO value K1 K2 K3 K4 K5 H PE1 111 29.4 29.4 29.4 29.4 29.4 PE2 267 9.8 9.8 9.8 9.8 9.8 DEG 1056 4.9 4.9 4.9 4.9 4.9 1.8 THE DOG 108 93.0 PI3 373 5.2 TDI 48.3 25.6 24.9 24.9 24.9 24.9 MDI 33.4 30.9 20.0 20.0 20.0 20.0 MDI-C 33 13.1 HDI-T 21 20.6 HDI-0 21.9 19.8 MDI-P 31 14.0 NCO-F 14.0 13.5 13.3 13.1 14.3 ADV-1 1.6 1.6 1.6 1.6 1.6 ADV-G 2.76 2.76 2.76 2.76 2.76 V [m Passport] Deň: 32 ° C 2700 4450 6000 5300 4320 Deň: 32 ° C 1200 1800 2550 1970 1790 60 ° C 550 956 1200 950 790 m-TDI 0.03 0.03 0.07 0.07 0.09 m-MDI 30 24 16 14 20

• · · · · · ·· ···· · · • • · • · · • · • · • • · • 9 · 9 · • • · • · · · · • · · · · · ·· ·· · · • ·

B1-8

V1-2

VA

F1

F2

F3 (ESA) VH

SNH koh. KS adh. alt.

Explanations and shortcuts in Table 2:

EXAMPLES 1 TO 8 COMPARATIVE EXAMPLES 1 AND 2 Construction of a composite of polyethylene terephthalate (PETP) film with a thickness of 12 μ polyethylene (PE) film with a thickness of 70 μ and a plasticizer content of 400 ppm erucic amide (ESA) film of polyethylene (PE) thickness 60 μ and a plasticizer content of 800 ppm erucic amide Adhesion of the composite Adhesion of the glued joint Cohesive distribution of adhesive alternating adhesion, the adhesive break is alternately in both composites.

The mixing ratio of the adhesive / hardener formulation was 1/1 for B1 to B8, 100 to 70 for V1 and V3.

The amount applied was 2 g / m ² in all examples.

-28Table 2: Evaluation of composites

Claims (21)

PATENT CLAIMS A low volatile monomer polyurethane binder comprising isocyanate groups comprising at least components A, B, C, wherein: a) a component is a polyurethane prepolymer comprising at least two isocyanate groups or a mixture of two or more » polyurethane prepolymers containing at least two isocyanate groups, wherein at least one polyurethane prepolymer has isocyanate groups bonded by at least two different methods or two different polyurethane prepolymers have in a pair of isocyanate groups bonded by at least two different methods, of which at least one species has an isocyanate group as a second species or other species, and (b) contains as component B at least one bifunctional isocyanate containing no nitrogen atom not belonging to the NCO group or a mixture of two or more of these; and (c) Component C is one of at least a bifunctional isocyanate or a mixture of two or more isocyanates with an average functionality of at least two and having at least one nitrogen atom per isocyanate molecule that is not part of the NCO or urethane group. • Polyurethane binder according to claim 1, characterized in that at least 5 wt. component C, based on the total polyurethane binder. Polyurethane binder according to claim 1 or 2, characterized in that the content of the easily volatile isocyanate-containing monomers is less than 1% by weight, wherein the toluylene diisocyanate (TDI) content is less than 0.1% by weight. Polyurethane binder according to any one of claims 1 to 3, characterized in that component A is produced in at least a two-step reaction in which: d) in the first step, a polyurethane prepolymer is produced from the at least bifunctional isocyanate and at least the first polyol component, wherein the NCO / OH ratio is less than 2 and the polyurethane prepolymer still contains free OH groups; and e) reacting in the second stage another at least two-functional isocyanate with the polyurethane prepolymer of the first stage, wherein the isocyanate groups of the isocyanate added in the second stage have a higher reactivity to the isocyanate-reactive compounds than the minimum prevailing proportion of the isocyanate groups of the first stage. Polyurethane binder according to claim 4, characterized in that a further minimum bifunctional isocyanate is added in a molar excess, based on the free OH groups of component A. Polyurethane binder according to any one of claims 1 to 3, characterized in that component A is produced in at least a two-step reaction in which: f) in the first stage, a polyurethane prepolymer is produced from the at least bifunctional isocyanate and at least the first polyol component, wherein the NCO / OH ratio is less than 2 and the polyurethane prepolymer still contains free OH groups, and g) reacting in the second step a further at least two-functional isocyanate and a further polyol component with the polyurethane prepolymer of the first step, wherein the isocyanate groups of the isocyanate added in the second step have a higher reactivity to the isocyanate-reactive compounds than the degree. ·· ···· -31 ····························· Polyurethane binder according to claim 6, characterized in that a further minimum bifunctional isocyanate is added in a molar excess, based on the free OH groups of component A and the other polyol component. Polyurethane binder according to any one of claims 4 to 7, characterized in that the OH: NCO ratio in the second step is from 0.1 to 1 and more preferably from 0.2 to 0.6. T Polyurethane binder according to any one of claims 4 to 8, characterized in that the OH: NCO ratio in the first stage is less than 1, more preferably from 0.5 to 0.7. 10. A method for producing a polyurethane binder containing isocyanate groups, comprising at least three steps, wherein: (h) in a first step, a polyurethane prepolymer is produced from at least one of a bifunctional isocyanate and at least one polyol component; and (i) in the second step, one or more at least bifunctional isocyanate or another at least bifunctional isocyanate and another polyol component are added; and (j) in the third stage, add at least one divalent isocyanate or a mixture of two or more isocyanates with an average functionality of at least two, at least one isocyanate containing at least one non-NCO nitrogen atom, the major proportion of isocyanate groups existing after The first stage has a lower reactivity to isocyanate-reactive compounds, in particular OH groups, than the isocyanate groups of the bifunctional isocyanate added in the second stage. The method of claim 10, wherein in the second step the OH: NCO ratio is from 0.2 to 0.6. ·· ···· -32 ··························· Process according to claim 10 or 11, characterized in that in the first step the OH: NCO ratio is less than 1, more preferably from 0.4 to 0.7. 13. The method of any of claims 10 to 12, characterized in characterized in that as the at least difunctional isocyanate in the first stage is used much isophorone diisocyanate (IPDI), tetramethyl xylene diisocyanate (TMXDI), hydrogenated diphenyl methane diisocyanate (MDI _H 12) or toluene diisocyanate (TDI) . A process according to any one of claims 10 to 13, characterized in that diphenylmethane diisocyanate (MDI) is used as the second minimum bifunctional isocyanate in the second step. A process for the production of a low viscosity polyurethane binder containing isocyanate groups having a low content of isocyanate-containing, easily volatile monomers, comprising mixing the four components D, E, F, and G, using (k) as component D, a polyurethane prepolymer containing isocyanate groups obtained by reacting a polyol component with at least a bifunctional isocyanate; (l) as component E, another isocyanate-containing polyurethane prepolymer obtained by reacting the polyol component with another at least bifunctional isocyanate, the isocyanate groups of which have a higher reactivity to the isocyanate-reactive group than the isocyanate groups of component D (m) as component F, at least a bifunctional isocyanate containing at least two nitrogen atoms which is not part of the NCO group or a mixture of two or more of these; and (n) as component G, a further minimum bifunctional isocyanate or a mixture of two or more isocyanates with an average functionality of at least two and having at least one nitrogen atom per non-NCO isocyanate molecule; ······ are measured so that at least 5% by weight, more preferably at least 10% by weight, is left in the polyurethane binder after the mixing process has been completed and all the reactions, if any, between components D, E, F and G are completed. component G, based on the total polyurethane binder. T Method according to any one of claims 10 to 15, characterized in that the polyurethane binder has a viscosity of less than 5000 mPas (measured by Brookfield RT DVII (Thermosell), spindle 27, 20 rpm, 50 ° C). Use of a polyurethane binder according to any one of claims 1 to 9, or produced according to any one of claims 10 to 16, in the manufacture of adhesives, in particular one-component and two-component adhesives, coatings, in particular varnishes, dispersion paints and casting resins, for coating and in particular for bonding objects, in particular for bonding films and for the production of film composites. 18. An adhesive comprising two components H and I, wherein: o) As component H, a polyurethane binder containing isocyanate groups according to claims 1 to 9 or a polyurethane binder containing isocyanate groups produced according to any one of claims 10 to 16 is used; and (p) as component I, a compound containing at least two isocyanate-reactive functional groups of component H with a molecular weight of up to 50,000 or a mixture of two or more of such compounds is used. Glue according to claim 18, characterized in that a polyol containing at least two OH groups is used as component I. ·· ···· -34 ·························· Adhesive according to claim 18 or 19, characterized in that component I is used in an amount such that the ratio of the isocyanate groups of component H to the functional groups in component I reactive with the isocyanate groups of component H is from about 5: 1 to 1: 1 more preferably from 2: 1 to 1: 1. An adhesive according to any one of claims 18 to 20 having a viscosity of from 500 to 6500 mPas (Brookfield, RVTD, 40 ° C).