DE102008039679A1 - Method for laminating films - Google Patents

Abstract

Use of a solvent-free room temperature liquid one-component adhesive for bonding composite films, wherein the adhesive comprises a reaction product of low molecular weight polyether diols, polyester diols and / or polyalkylene diodes having a molecular weight of 60 to 2000 g / mol, reacted with a high molar excess of TDI and removing the unreacted monomeric TDI by distillation as well as auxiliaries and additives.

Description

The This invention relates to liquid one-component adhesives based on isocyanate-reactive prepolymers used as laminating adhesive suitable for producing composite films.

laminating adhesives based on isocyanates are general as 1K or 2K adhesive known. These adhesives are applied, the substrates glued, then the films are usually stored. The can also be done at elevated temperature. The reaction rate can be accelerated by using aromatic isocyanates. Storage is necessary to ensure adequate curing of the reactive adhesive is ensured. This should be the included Isocyanates react with polymeric moieties so as not to migrate To produce ingredients. Reacting such monomeric isocyanates with water, arise in the preferred aromatic used Isocyanates primary aromatic amines. These should not come in contact with food. That's why it's necessary to avoid the formation of these substances.

It is the EP 1241197 known. This application describes a process for removing isocyanates, in which reaction products of diols with monomeric isocyanates are freed of monomers by multistage distillation. A specific use of such prepolymers for Kaschierverklebung is not described.

Furthermore, the EP 1253159 known. This describes liquid 2K adhesives consisting of a prepolymer and a polyol component, wherein only less than 2% of monomeric isocyanates should be included. The prepoly mer is the reaction product of polyethers and diisocyanates, which is listed in a list, inter alia, TDI. As a substrate steel, aluminum, glass fiber reinforced polyester, PVC, polycarbonate wood or glass are enumerated. A disadvantage of 2K adhesives in principle, the two components that always require a complex mixture. In addition, an exact mixing ratio must be maintained in order to ensure a good bond. Otherwise unreacted isocyanates may be present, which then react to desired impurities.

Also known is the EP 0827995 , It describes a solid hot melt adhesive containing a reaction product of polyester alcohols with TDI. This product should also contain only small amounts less than 2% of monomeric diisocyanates. The application temperature 80 ° C are given in the example. Such high temperatures are not suitable for many film materials, as they can be destroyed under the kurzeitigen temperature increase. In addition, application in a thin layer by the higher viscosity of hot melt adhesives is difficult.

Furthermore, the EP 0961493 known. This describes the bonding of film substrates with 1K PU adhesives. Two different diisocyanates are reacted, TDI and MDI. Prepolymers with different isocyanate groups are formed. By the reaction, the content of monomeric isocyanates can be less than 1%, a distillation step is not described. Due to the different isocyanates is a uniform fast reaction during bonding and fast processing ability not given.

The Performing operations according to the prior art not the requirements of practice. Thus, in general, the residual monomer content the adhesives are too high. There is a requirement for Composite films for packaging that the amount of aromatic Amines should be below 10 ppb. Residual monomers of the isocyanates lead upon hydrolysis with water to avoid such aromatic amines. Furthermore, by reacting with symmetrical polycyclic diisocyanates due to the high reactivity higher molecular weight polymer content generated. This leads to increased viscosities of the products, these are therefore worse to apply. Furthermore Such aromatic nuclei can become domains store together. This leads to much worse Viscosity properties. Object of the present invention That is why it is an easy-to-apply reactive polyurethane adhesive to provide, which is suitable for film lamination is. Here, thin layers should be applied quickly. Furthermore, the bonded substrates should harden quickly, so that the composite films can be processed into packaging in a short time can be. Nevertheless, the requirements should be low levels of migratory aromatic primary amines be fulfilled.

The object is achieved by the use of a solvent-free, liquid at room temperature Einkomponentenklebstoffs for bonding composite films, wherein the adhesive comprises a reaction product prepared from low molecular weight polyether diols, polyester diols and / or polyalkylene diols with egg Nem molecular weight of 60 to 2000 g / mol, reacted with a high molar excess of TDI greater than 3: 1 and removing the unreacted monomeric TDI by distillation, which may additionally contain auxiliaries and additives.

Of the According to the invention suitable adhesive is a one-component adhesive based on reactive polyurethanes. He should only have a low salary having monomeric isocyanates and a low viscosity.

When Polyol for the preparation of PU prepolymers are the known polyether diols, polyester diols, polyalkylene diols and / or oleochemical polyols suitable. These should be thin-viscous be.

Examples for such polyols are polyester polyols. These are preferred produced by polycondensation. Such polyester polyols include the reaction products of preferably low molecular weight difunctional Alcohols and preferably difunctional and / or trifunctional Carboxylic acids. Instead of free polycarboxylic acids may also be the corresponding polycarboxylic anhydrides or corresponding polycarboxylic acid esters with alcohols with preferably 1 to 3 carbon atoms are used. For the production of such Polyester polyols are particularly suitable aliphatic alcohols, such as hexanediol, 1,4-hydroxymethylcyclohexane, 2-methyl-1,3-propanediol, Triethylene glycol, ethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, Dibutylene glycol and polybutylene glycol. The polycarboxylic acids may be aliphatic or cycloaliphatic. You can optionally substituted, for example by alkyl groups, Alkenyl groups or ether groups. As polycarboxylic acids For example, succinic acid, adipic acid, Suberic acid, azelaic acid, sebacic acid, Tetrahydrophthalic anhydride, hexahydrophthalic anhydride, Glutaric anhydride, maleic acid, maleic anhydride, Fumaric acid, dimer fatty acid or trimer fatty acid or mixtures of two or more thereof. The quantities will be chosen such that terminal OH-functional polyester diols to be obtained. In one embodiment, in particular contain no aromatic carboxylic acids.

Farther Polyalkylenediols can be used. For example, these are aliphatic Alcohols with 2 OH groups per molecule. The OH groups can both primary and secondary. To the 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 their higher homologs or isomers, as they are for the skilled person from a gradual extension the hydrocarbon chain by one CH 2 group or below Introduction of branching into the carbon chain. These can also be proportionally mixed with other polyols be used. For example, these can be up to 30 Contain C atoms.

Farther can be used as polyol component reaction products of low molecular weight polyfunctional alcohols with alkylene oxides, so-called polyether polyols, be used. The alkylene oxides preferably have 2 to 4 C atoms on. Suitable examples are the reaction products of ethylene glycol, propylene glycol, the isomeric butanediols or Hexanediols with ethylene oxide, propylene oxide or butylene oxide, or mixtures from two or more of them. Suitable polyols continue to arise by polymerization of tetrahydrofuran. Among the mentioned polyether polyols are the reaction products of polyfunctional low molecular weight Alcohols with propylene oxide under conditions where at least partially secondary hydroxyl groups are formed, especially suitable. Particularly suitable are polyether polyols having a molecular weight from about 100 to about 2000, preferably from 200 to 1200 g / mol.

Farther can also be used oleochemical polyols. Under Oleochemical polyols are understood to be polyols based on natural oils and fats, e.g. As the reaction products of epoxidized fatty substances with mono-, di- or polyfunctional alcohols or glycerol esters long-chain fatty acids that are at least partially hydroxylated are substituted.

A Group of oleochemical polyols are ring-opening and Transesterification products of epoxidized fatty acid esters lower Alcohols, ie of epoxidized fatty acid methyl, ethyl, propyl or butyl esters. Preference is given here to the ring-opening or transesterification products with alcohols of functionality 2 to 4, in particular the reaction products with ethylene glycol, Propylene glycol, oligomeric ethylene glycols, oligomeric propylene glycols, Glycerol, trimethylolpropane or pentaerythritol.

The oleochemical polyols also include the reaction products of epoxidized fatty alcohols with C ₂ -C ₈ -alcohols of functionality 1 to 10, in particular 2 to 4, in the molar ratio of the epoxide groups to the hydroxyl groups of 1: 1 to 1:10.

Preference is given to the use of castor oil or dimerdiols obtained by complete ring opening of epoxidized triglycerides of an at least partially olefinically unsaturated fatty acid-containing fat mixture with one or more alcohols having 1 to 12 carbon atoms and subsequent partial transesterification of the triglyceride derivatives to alkyl ester polyols having 1 to 12 carbon atoms in the alkyl radical.

The Oleochemical polyols can have hydroxyl numbers from 50 to 400 (mg KOH / g solids), preferably 100 to 300. These polyols can have a functionality between 2 and 3 have.

The polyols can be used individually or in a mixture. They should have a molecular weight of 60 to 2000 g / mol, in particular from 200 to 1200 g / mol. It should preferably be at temperatures up to 30 ° C liquid polyols. Particularly preferred are polyether polyols, optionally also in a mixture with oleochemical polyols (number average molecular weight, M _N , as determined by GPC). The polyols can be mixed and reacted together with the isocyanates, but no other procedure, the polyols converts separately, wherein in a later step, the two prepolymers are mixed.

When Isocyanate for the preparation of the prepolymers are toluene diisocyanate (TDI), its isomers or oligomers are used. It can optionally also added to other diisocyanates be, for example, the known in urethane chemistry aromatic Polyisocyanates such as MDI. Preference is given to technical mixtures of TDI used.

A another embodiment sets the above-mentioned Polyol separately with the other aromatic isocyanates, in particular MDI, to polymers, which then also by distillation in the monomer content be reduced. The prepolymers are then mixed later, However, the amounts should be below 25 wt .-% based on the amount of TDI polymer be.

The Prepolymers are prepared by processes known per se. The isocyanates and the polyols are mixed and reacted. If necessary, the reaction can be accelerated by heating. The amount of isocyanates is chosen so that a molar excess is used on diisocyanate. The ratio should be NCO: OH more than 3: 1 to 10: 1, in particular to 5: 1. By a higher isocyanate content may have a molecular weight structure of the prepolymer are reduced.

To the preparation of the prepolymer, this is not unreacted TDI freed. The purification step can be carried out according to known methods, such as extraction, chromatography or crystallization methods individually or optionally in combination of the listed methods respectively. However, preference is given to a distillation, if appropriate also in several Stages, under vacuum. Such apparatus and procedures are known to the skilled person. The concentration of monomeric isocyanates is below 0.1 wt .-%, preferably below 0.05 wt .-%, based on the prepolymer amount.

To The prepolymer may optionally be used to formulate the adhesive Additives and additives are added. It can work for example, plasticizers, stabilizers, antioxidants, adhesion promoters, Resins, polymers, dyes or fillers act.

In an embodiment contains the invention suitable Adhesive at least one tackifying resin. The resin causes an additional stickiness. It can basically all resins are used which are compatible, d. H. form a largely homogeneous mixture.

These are, in particular, resins which have a low softening point below 100 ° C. (ring-ball method, DIN 52011 ). These are, for example, aromatic, aliphatic or cycloaliphatic hydrocarbon resins, as well as modified or hydrogenated versions thereof. The resins generally have a low molecular weight below 1500 g / mol, in particular below 1000 g / mol. They should be chemically inert so that any functional groups present do not react with the PU prepolymer. Preference is also given to using liquid resins. The resin can be used in an amount of 0 to 50 wt .-%, preferably up to 25 wt .-% based on the adhesive.

When Plasticizers can be, for example, medicinal white oils, naphthenic mineral oils, paraffinic hydrocarbon oils, Polypropylene, polybutene, polyisoprene oligomers, hydrogenated polyisoprene and / or Polybutadiene oligomers, phthalates, adipates, benzoate esters, herbal or animal oils and their derivatives. As usable stabilizers or antioxidants can Phenols, hindered high molecular weight phenols, polyfunctional Phenols, sulfur and phosphorus phenols or amines selected become.

It is possible, the 1K PU adhesive silane compounds as Add adhesive. As adhesion promoters are preferably organofunctional silanes such as hydroxyfunctional, (meth) acryloxyfunctional, mercapto-functional, amino-functional or epoxy-functional silanes used.

These may have reactive groups with NCO groups, or they do not react with isocyanates. It may be dialkoxy or Trialkoxysilane act, especially with methoxy, ethoxy, propoxy or Butoxy. Particularly suitable are amino or epoxy silanes. In a preferred embodiment, the adhesive 0.1 to 3 wt .-% of such silanes added.

It is also possible, the adhesive mixture up to 25% aliphatic Add diisocyanates as a monomer or oligomer. This can be the Adhesion to the substrate can be improved, also the Viscosity of the adhesive can be reduced.

When optionally additionally present additive can According to the invention suitable adhesive also catalysts contain. Examples of such catalysts are organometallic Compounds such as iron or tin compounds, for example 1,3-dicarbonyl compounds of iron or tin, or tin (II) carboxylates or dialkyltin (4) dicarboxylates. Likewise are alkyl titanates or alkaline catalysts based cyclic, aliphatic amines suitable, in particular special tertiary Amines such as 1,4-diazabicyclo [2.2] octane (DABCO) or 1,8-diazabicyclo-ene (DBU). The amount of catalysts can be between 0.01 to 1% by weight. another embodiment operates without a catalyst.

The viscosity of these suitable laminating adhesives should be between 200 and 5000 mPas at the application temperature, preferably 500 to 3000 mPas, in particular at 20 to 50 ° C. (measured by Brookfield viscometer, according to US Pat ISO 2555 ). Since rapid further processing is necessary, the adhesives should be solvent-free.

When Film materials for producing the multilayer films can the known flexible films are used. It is about while substrates of thermoplastic plastics in film form, for example, polyolefins such as polyethylene (PE) or polypropylene (PP, CPP, OPP), polyvinyl chloride (PVC), polystyrene (PS), polyesters, such as PET, polyamide, organic polymers, such as cellophane, it is too Metal foils or paper as substrates possible. It could the film materials also be modified, for. By modifying the polymers with functional groups, or it can additional components, for example pigments, dyes, or foamed layers may be contained in the film. It can be colored, printed, colorless or transparent Act slides.

The inventive method sticks two or several, identical or in particular different films together. In one embodiment of the invention, the Outer foil before application of Kaschierklebstoffs already colored be printed. On the thus treated outer film is then a liquid suitable according to the invention Laminating adhesive applied. This can be done by printing methods known per se, z. As with anilox rollers, burnishing, done, the adhesive is sprinkled over nozzles, or it will be the Adhesive applied via slot nozzles. The order procedure is dependent on the viscosity of the adhesive select.

By the selection of the inventively suitable 1-component PU adhesives and its additives, it is possible to have a low application viscosity to obtain. In this case, the invention suitable Adhesive has a low viscosity, so is a Application in thin layer thickness of 1 to 25 μm, in particular from 2 to 15 microns possible.

The Production of the multilayer film takes place by joining a coated with the adhesive outer layer and a second slide. The bonding can be under pressure and elevated Temperature done. Optionally, several can Foils are glued together. Such laminating methods are known to the skilled person.

To The multi-layer films can be glued directly be wound up and stored. This is a good bond achieved. Furthermore, should also be a complete reaction from individual residual reactive groups to be done rapidly. The can be due to increased temperature, increased humidity or catalysis of the isocyanate groups can be achieved. Mostly after 48 hours, especially after 24 hours, the slides can be further processed. Then the levels of migratory are also Constituents of the adhesive, e.g. As isocyanates or reaction products of the adhesive, as primary aromatic amines lowered so far, that the requirements for the content of such ingredients are met become.

By the laminating of thin, flexible films, with one According to the invention suitable 1K PU adhesive it is possible to make a strong bond between the films. Due to the high reactivity of the isocyanate groups is a ensures rapid bonding as well as quick reaction of all reactive groups. By the use of low-viscosity 1K PU adhesives make it possible to apply the glue quickly Apply in thin layers to the substrates. there no elevated temperature must be used so that a thermal load of the films can be avoided.

By the selection of polyols from non-aromatic polyols becomes a high flexibility of the composite film achieved. Furthermore It is possible by using prepolymers with a Functionality bigger two a good one Ensuring networking of the adhesives and at the same time a to allow rapid buildup of cohesion. Furthermore, the adhesion to the various film substrates very well. This is also evident in the mechanical stability the laminating-bonded substrates.

Examples

Example 1:

100 g of a diol (PPG, about 800 g / mol) are mixed with 100 g of TDI and admixed with 0.5 g of DBTL and reacted at the reaction temperature which is established. After 2 hours, the batch is freed from monomeric TDI in vacuo. The prepolymer has a viscosity of 2290 mPas at 40 ° C.
NCO: OH = 4.5: 1

Example 2:

It 100 g of a polyol (castor oil, F = 2.7) with 290 g TDI mixed and reacted at 40 ° C. After 2 hours reaction time the approach is freed from monomeric TDI in vacuo.

The prepolymer has a viscosity of 2120 mPas at 60 ° C.
NCO: OH = 5.5: 1

Example 3:

66.5 Parts of the prepolymer of Example 1 and 33.5 parts of prepolymer according to Example 2 are mixed and 0.5 parts UL 28 (catalyst) with rapid stirring together with 0.5 part of aminopropyltrimethoxysilane was added and homogenized.

Example gluing:

On a PET film at 50 ° C with the doctor blade 15 microns an adhesive mixture according to Example 1 or 3 and immediately applied glued with a CPP film.

• Instron, Reißdehnung, N/15 mm bei RT gemessen.

The films are stored for 48 hours, after which a packaging can be produced. 4d 14d example 1 3.1 3.0 Example 3 4.6 4.7

• Instron, elongation at break, N / 15 mm measured at RT.

The Bonding is cured after 4 days.

• CPP-Folie Casted Polypropylen (Nordenia), Typ PP0946.080 (Dicke 50 µm) PE-Folie Polyethylenfolie (Dicke 12 µm).

A correspondingly stored film is extracted according to RiLi 2002/72 EC and investigated for primary aromatic amines. 1d 2d example 1 0.08 ppb 0.07 ppb Example 2 0.09 0.05

• CPP film Casted polypropylene (Nordenia), type PP0946.080 (thickness 50 μm) PE film Polyethylene film (thickness 12 μm).

The Formation of the primary aromatic amines is low, and in principle completed after days.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - EP 1241197 [0003]
• - EP 1253159 [0004]
• - EP 0827995 [0005]
• - EP 0961493 [0006]

Cited non-patent literature

• - DIN 52011 [0026]
• - ISO 2555 [0032]

Claims (9)

Use of a solvent-free, at Room temperature liquid one-component adhesive for bonding of composite films wherein the adhesive comprises a) a reaction product from low molecular weight polyether diols, polyester diols and / or Polyalkylene diols having a molecular weight of 60 to 2000 g / mol, reacted with a molar excess of TDI larger 3: 1 and removing the unreacted monomeric TDI by distillation, b) as well as auxiliaries and additives. Use according to claim 1, characterized that the adhesive has a viscosity at 50 ° C of less than 5000 mPas. Use according to claim 2, characterized that the adhesive after distillation less than 0.1 wt .-% monomeric TDI contains. Use according to one of claims 1 to 3, characterized in that flexible films selected as substrates from polyesters, polyvinyl chloride, polyamides, polyolefins, polyacrylates, Paper or metal foils to be glued. Use according to one of claims 1 to 4, characterized in that the adhesive up to 3 wt .-% of a Adhesive chosen from di-, tri- or tetraalkoxysilanes contains, in particular containing an alkyl group, the contains another functional group. Use according to one of claims 1 to 5, characterized in that polyether polyols are used, in particular having a molecular weight (M _N ) of 200 to 1200 g / mol. Use according to claim 6, characterized that additionally up to 50 wt .-% of a reaction product of TDI with trivalent alcohol, in particular an oleochemical Polyols, are included. Use according to one of claims 1 to 6, characterized in that additionally up to 25 wt .-% of a low-monomer prepolymer prepared from polyether diols having a molecular weight (M _N ) of 200 to 1200 g / mol and 4,4'-MDI is. Use according to one of claims 1 to 7, characterized in that the bonded substrates according to 48 Hours less than 10 ppb of extractable aromatic amines (measured according to VO 1935/2004 / EC, RiLi 2002/72 EC).