DE19701124A1 - Adhesive with high cohesion, especially pressure-sensitive or laminating adhesive - Google Patents

Abstract

Adhesive contains a free radical-polymerised polymer (I) with 0.5-90 wt.% units derived from (a) a monomer with dicyclopentadiene or dihydrodicyclopentadiene groups of formula (IIA) or (IIB); which is mono-substituted by R<1> and optionally mono- or poly-substituted by R<2>. R<1> = an organic radical with a copolymerisable, ethylenically unsaturated group; R<2> = a 1-12 carbon (C) alkyl or 5-20 C cycloalkyl, aryl or aralkyl group. Also claimed are a method of bonding substrates with the adhesive; and substrates coated with an adhesive, especially a pressure-sensitive adhesive or laminating adhesive of this type.

Description

The invention relates to an adhesive containing a radika Lisch polymerized polymer, which consists of 0.5 to 90 wt .-% a monomer a) with the base of the formula

which is represented by a radical R 1 and optionally one or more, identical or different radicals R² is substituted, where at R¹ for an organic radical with a copolymerizable, ethylenically unsaturated group and R² for a C₁-C₁₂ alkyl or is a C₅-C₂₀ cycloalkyl, aryl or aralkyl group.

In particular, the invention relates to corresponding pressure sensitive adhesives and laminating adhesives.

In addition to sufficient adhesion (adhesion to the substrates to be bonded) in particular also a high cohesion sion (cohesion in the adhesive layer). A good Cohesion can e.g. B. achieved by crosslinking polymers will. We are looking for adhesives that are easy to use, e.g. B. can be networked by irradiation with high-energy light and have good cohesion.

Good networking is particularly important at Kaschier adhesives, which are used for large-area gluing of e.g. B. foils be used. When applied to the foils, the Laminating adhesive to be low-viscosity, so that it ver can be divided and thin coatings are possible. Before the Gluing with a second film (lamination) must then Cohesion in the adhesive layer can be increased.

Solvent-free hot melt adhesives are known from EP-A-458164 Basis of radically polymerized polymers known. The Polymers contain copolymerized photoinitiators and can be networked by high-energy radiation. The so cohesion is not yet achieved for many applications satisfying.  

Special copolymers with acryloyl groups and dicyclopenta dienyl derivatives are e.g. B. is known from EP-A-237312. you will be used for the production of printed circuit boards.

The object of the present invention was therefore adhesives, adhesive adhesives and especially laminating adhesives with a high Cohesion.

Accordingly, the adhesives defined at the outset were found.

The adhesives according to the invention contain a radical poly merized polymer, which is 0.5 to 90 wt .-%, preferably 0.5 to 40 wt .-%, particularly preferably 1 to 20 wt .-% and whole particularly preferably 2 to 15% by weight of those defined at the outset Monomers a) exists.

The monomers a) preferably have a base body Formula I.

The radical R¹ is an organic radical with a copolymerizable double bond, this is preferably Molecular weight of R1 less than 500 g.

R¹ is e.g. B. a group-R³-O-CO-CHR⁴-CH₂, wherein R³ for a divalent link with preferably one mole weight less than 300 g / mol and especially for a single bond and for a C₁ to C₃₀ alkylene which, if appropriate, by Oxygen atoms can be interrupted or a C₄ to C₂₀-arylene, alkarylene or aralkylene group and R⁴ for a H atom, a methyl or ethyl group.

R 1 is preferably an acrylic, methacrylic or also ethacrylic group.

R² is preferably a C₁-C₆alkyl group. The Base bodies of the formula I or II are preferably not or maximum substituted by up to 2 radicals R².

As monomers a) z. B. called:

with n = 1 to 10

The following should be mentioned in particular:
Dihydrocyclopentadienyl acrylate,
Dihydrocyclopentadienyl methacrylate,
Dihydrocyclopentadienyl ethacrylate,
and dihydrocyclopentadienyl cinnamate.

Dihydrocyclopentadienyl acrylate and Me are particularly preferred thacrylate.

In addition to the above monomers a), the polymer contains so-called called main monomers b) and optionally copolymerized bare photoinitiators c) and other monomers d).

Main monomers b) are selected from C₁-C₂₀ alkyl (meth) acrylates, Vinyl esters of carboxylic acids containing up to 20 carbon atoms, Vinyl aromatics with up to 20 carbon atoms, ethylenically unsaturated Nitriles, vinyl halides, vinyl ethers of 1 to 10 carbon atoms ent holding alcohols, aliphatic hydrocarbons with 2 to 8 carbon atoms and 1 or 2 double bonds or mixtures of these Monomers.

To mention are z. B. (meth) acrylic acid alkyl ester with a C₁-C₁₀ alkyl radical, such as methyl methacrylate, methyl acrylate, n-butyl acrylate, ethyl acrylate and 2-ethylhexyl acrylate.

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

Vinyl esters of carboxylic acids with 1 to 20 carbon atoms are e.g. B. Vinyl laurate, stearate, vinyl propionate, vinyl versatic acid and vinyl acetate.

The vinyl aromatic compounds are vinyl toluene a and p-methylstyrene, a-butylstyrene, 4-n-butylstyrene, 4-n-decylstyrene and preferably styrene. Examples of nitriles are Acrylonitrile and methacrylonitrile.

The vinyl halides are substituted with chlorine, fluorine or bromine ethylenically unsaturated compounds, preferably vinyl chloride and Vinylidene chloride.

Examples of vinyl ethers include B. vinyl methyl ether or vinyl isobutyl ether. Vinyl ether of 1 to 4 carbon atoms is preferred keeping alcohols.  

As hydrocarbons with 2 to 8 carbon atoms and two olefinic Double bonds are butadiene, isoprene and chloroprene.

Suitable copolymerizable photoinitiators c) are e.g. B. 3 derivatives of thioxanthone or preferably acetophenone or Benzophenone derivatives, as z. B. in EP-A-246848 or DE-A-38 44 445 are described.

The following compounds III are listed as examples up to XLIII.

Other monomers d) are, for. B. containing hydroxyl groups Monomers, in particular C₁-C₁ Hydrox hydroxyalkyl (meth) acrylates, (Meth) acrylamide, ethylenically unsaturated acids, in particular Carboxylic acids, such as (meth) acrylic acid or itaconic acid, dicarbon acids and their anhydrides or half esters, e.g. B. maleic acid, Fumaric acid and maleic anhydride.

Phenyloxyethyl glycol are also further monomers d) mono- (meth) acrylate, glycidyl acrylate, glycidyl methacrylate, Amino (meth) acrylates such as 2-aminoethyl (meth) acrylate called.

Monomers d) which, in addition to the double bond, have further functions wear small groups, e.g. B. isocyanate, amino, hydroxy, amide, Glycidyl or carboxyl groups, e.g. B. liability on sub improve straten.

By monomers b) or d), the easily abstractable water contain types of material, the sensitivity to light, d. H. the Cross-linkability can be further increased by exposure to radiation.

Particularly noteworthy are isobornyl acrylate and isobornyl meth acrylate, isobornyl ethacrylate, isobornyl cinnamate, adamantane acrylate, adamantane methacrylate, adamantane ethacrylate and adamane tancinnamate, and monomer with the following groups: isoalkyl groups with 3 to 12 carbon atoms, such as isopropyl, isobutyl or ethylhexyl groups, aminoisooalky groups with 3 to 12 carbon atoms, such as Diiso propylaminoethyl, N-isobutylisopropylaminoalkyl, cycloisoalky groups with 5 to 8 carbon atoms such as methylcyclohexyl, isopropylcy clohexyl, cycloalkyl, furfuryl and tetrahydrofurfuryl groups, further furfuryl, tetrahydrofur furyl, p-menthyl, terpin and Thymol groups, or groupings of the following formulas:

wherein
n = 2 or 3
and
R⁵ = H, straight-chain alkyl having 1 to 15 carbon atoms, branched alkyl having 1 to 15 carbon atoms, by halogen, such as. B. Cl, F, Br, substituted straight-chain or branched alkyl, such as. B. -C- (CF₃) or isopropyl,
R⁶ = alkyl having 1 to 15 carbon atoms, such as. B. isopropyl, isobutyl or isoamyl, aryl, such as. B. isoamylphenyl, by halogen, such as. B. F, Cl or Br, substituted alkyl having 1 to 15 carbon atoms, by halogen, such as. B. F, Cl, Br substituted aryl.

Overall, the polymer is preferably composed of:
0.5 to 40% by weight, particularly preferably 1 to 20% by weight and very particularly preferably 2 to 15% by weight of monomers a)
20 to 99.5% by weight, particularly preferably 40 to 99% by weight and very particularly preferably 60 to 98% by weight of monomers b)
0 to 30% by weight, particularly preferably 0 to 20% by weight and very particularly preferably 0 to 10% by weight of monomer c)
0 to 40% by weight, particularly preferably 0 to 30% by weight and very particularly preferably 0 to 20% by weight.

The monomers can preferably be free radical or as far as possible can also be anionically polymerized. Both the radical as Anionic polymerization is also common methods known to the expert.

The radical polymerization can e.g. B. in solution, e.g. B. one organic solvent (solution polymerization) in aqueous Dispersion (emulsion polymerization, suspension polymerization) or in bulk, d. H. essentially in the absence of water or organic solvents (bulk polymerization) be performed.

The emulsion polymerization can e.g. B. discontinuously, with or without the use of seed latices, with presentation of all or individually ner components of the reaction mixture, or preferably below partial submission and replenishment of the or individual stock parts of the reaction mixture, or according to the dosing process without Template.  

The monomers can be used as usual in emulsion polymerization in the presence of a water-soluble initiator and one Emulsifier can be polymerized at preferably 30 to 95 ° C.

Suitable initiators are e.g. B. sodium, potassium and ammonium persulfate, tert-butyl hydroperoxides, water-soluble azo compounds or redox initiators such as H₂O₂ / ascorbic acid.

As emulsifiers z. B. Alkaline salts of longer chain fat acids, alkyl sulfates, alkyl sulfonates, alkylated aryl sulfonates or alkylated biphenyl ether sulfonates. Furthermore come as Emulsifiers Reaction products of alkylene oxides, in particular Ethylene or propylene oxide with fatty alcohols, acids or Phenol, or alkylphenols into consideration.

In the case of aqueous secondary dispersions, the copolymer first by solution polymerization in an organic Solvent produced and then with the addition of salt formers, e.g. B. from ammonia to carboxylic acid groups Copolymers, in water without the use of an emulsifier or Dispersing aid dispersed. The organic solvent can be distilled off. The production of aqueous secondary dispersions is known to the skilled worker and z. B. in the DE-A 37 20 860.

To adjust the molecular weight in the Polymerisa tion controller can be used. Are suitable for. B. -SH containing Compounds such as mercaptoethanol, mercaptopropanol, thiophenol, Thioglycerin, thioglycolic acid ethyl ester, thioglycolic acid methyl ester and tert-dodecyl mercaptan.

The solids content of the polymer dispersions obtained is preferably 40 to 80% by weight, particularly preferably 45 to 75 % By weight. High polymer solids can e.g. B. by method, which in German patent application P 4 307 683.1 or the EP 37 923 are described can be set.

The most preferred method of polymerization is solution polymerization. Solution polymerization can be carried out continuously, discontinuously as a batch process or preferably half be carried out continuously in the feed process. In the last one Ren case is presented a portion of the monomers on the polymer sation temperature heated and the rest of the monomers continuously Lich fed.  

As a solvent for radical solution polymerization, see above as for any subsequent implementations in Solution z. B. alcohols such as i-butanol, i-propanol, aromatics such as toluene or xylene, ethers such as dioxane or tetrahydrofuran, Ketones such as acetone, cyclohexanone or esters such as ethyl acetate or n-Butyl acetate can be used.

Preferred initiators are dibenzoyl peroxide, tert-butyl perpivalate, tert-butyl per-2-ethylhexanoate, tert-amuyl-2-ethyl hexyl peroxide, di-tert-butyl peroxide, tert-butyl hydroperoxide, Cumene hydroperoxide, dilauroyl peroxide, didecanoyl peroxide, methyl ethyl ketone peroxide, 2,2'-azobis- (2,4-dimethylvaleronitrile), 2,2'-azobis (2,3-dimethylbutyronitrile) and 2,2'-azobisisobutyro to call nitrile.

In bulk polymerization, part of the Submitted polymerization approach to the polymerization temperature heated, after which the rest is continuous is fed.

The polymer is selected depending on the poly merization method in the form of an aqueous dispersion of the poly meren, a solution in an organic solvent or in obtained essentially free of water and solvents.

The polymer is particularly preferably essentially water- and used solvent-free. For this, the polymer is preferred by solution polymerization with subsequent removal of the Solvent or water or by bulk polymerization poses.

The glass transition temperature of the polymer is preferably -50 to + 40 ° C, particularly preferably -40 to + 10 ° C.

The glass transition temperature of the polymer can be adjusted according to the usual Methods such as differential thermal analysis or differential scanning Calorimetry (see e.g. ASTM 3418/82, so-called "midpoint temperature") determine.

The polymer preferably has a K value (measure of the molecule Lar weight, determined according to Fikentscher, on a 1 wt .-% Solution of the polymer in tetrahydrofuran at 20 ° C, s. Encyclopedia of Chemical Technology, Vol 23, page 967 (1983)).  

The adhesives according to the invention preferably contain the poly mer and beyond, if necessary, only conventional additives for adhesives such as B. Takifier, especially rosins, Thickener or rheology aid.

The adhesives according to the invention are preferably essentially free of monomers and solvents.

The adhesives according to the invention can be of the most varied types Substrates e.g. B. on textile fabrics, papers, plastic films Polyvinyl chloride, polyester, polyethylene or polypropylene, Cellulose acetate, on metals, especially metal foils will wear.

After application, the coating obtained is preferred irradiated with high-energy light, especially UV light, and so on to increase cohesion through networking.

The addition of a photo initiator is not necessary, but before partial. Even without a photo initiator, just by the present of the monomers a) is an increase in cohesion by irradiation effect.

However, the adhesive is preferably 0.1 to 30 wt .-%, particularly preferably 0.5 to 10% by weight of photoinitiators added to the polymer.

These photo initiators are, in particular, those which cause a hydrogen release.

May be mentioned for. B. acetophenone, thiaxanthone or benzophenone derivatives.

It is particularly preferred to insert the photo initiators directly into the To incorporate polymer in the form of monomers c). The minimum amount of Monomers c) is then preferably 0.1, particularly preferably 0.5% by weight.

Lowered in the stated compositions of the polymer then the maximum content of the monomers b) accordingly 0.1 or 0.5% by weight.

Irradiation with high-energy, preferably ultraviolet Light, e.g. B. immediately after application, after Ent removal of the solvent (application from the solution) or after Passing through a heating, tempering and / or cooling section (ins especially when applied from the melt). To the  Commercial UV lamps, preferably in a wavelength range of 250 to 400 mm radiation emits ren, are used. Mercury, for example, is suitable medium pressure radiator with a radiation power of 80 to 240 W / cm.

In this way, pressure sensitive adhesive coated with adhesive can be used items such as labels or tapes can be obtained.

In the case of the manufacture of pressure sensitive adhesive articles, it concerns in the adhesive according to the invention a pressure sensitive adhesive and the glass transition temperature of the polymer is preferably from -20 to -50 and the K value of the polymer is preferably from 30 to 70.

Laminating adhesives are used to make flat substrates, in particular ver the above-mentioned plastic films with each other over a large area be stuck. It is particularly important here that the adhesive is free of water and solvents, and (preferably at Room temperature well distributed on the substrate. The polymer has there forth in this case preferably a glass transition temperature of -35 to +5 and a K value of 10 to 50.

After applying the adhesives and then UV exposure Then the coated film with a second flat Substrate, d. H. generally laminated to a second film and so on Composite, here received a film composite.

A) pressure sensitive adhesives example 1 (B1) UV-crosslinkable pressure-sensitive adhesive with polymerized in Photo initiator

In a stirring flask (capacity 2 liters) with an inlet funnel ter, thermometer, reflux condenser and light nitrogen purge were

Submitted 300 g of ethyl acetate and heated to reflux; a mixture of was then added with stirring at constant speed in 3 hours
348 g of 2-ethylhexyl acrylate
12 g dihydrodicyclopentadienyl acrylate (DCPA)
28 g acrylic acid and
12 g of the compound of structural formula (XVII) with R 1 = H, n = 4 and a solution from a further feed vessel
50 g of ethyl acetate and
4 g of 2,2′-azobis (2-methylbutyronitrile) (Wako V 59, Wako Chemicals)
after the end of the feed, cooking was continued for an hour and then a solution of
50 g of ethyl acetate and
2 g of 2,2'-azobis (2-methylbutyronitrile) were added dropwise and the mixture was re-polymerized at reflux for one hour and then cooled. A viscous solution was created. The polymer has a K value of 56 (measured as a 1% solution in ethyl acetate).

Example 2 (B2) UV-crosslinkable pressure sensitive adhesive with admixed Photo initiator

In the same manner as in Example 1, one was changed Polymerized monomer composition.

360 g of 2-ethylhexyl acrylate
12 g dihydrodicyclopentadienyl acrylate (DCPA)
28 g acrylic acid.

At the end of the polymerization, the mixture was cooled,
20 g of benzophenone were added and the mixture was stirred until dissolved.

The polymer has a K value of 51 (measured as a 1% solution in Ethyl acetate, before adding the benzophenone).

Example 3 Pressure sensitive adhesive without DCPA (not according to the invention)

The preparation was carried out as in Example 2, except that the addition of the monomer DCPA is dispensed with.

Application test of the pressure sensitive adhesives

The heat-flowable polymers of Examples 1-3 wer as a melt at 120 ° C using a heatable doctor blade knife-coated onto polyester films (40 µm thick). Layer thickness 20 g / m².

Then the polyester film was at a speed of 20 m / min under a standard mercury pressure spotlights (120 W / cm). From the thus obtained itself  adhesive film were strips 2 cm wide and 5 cm long cut out.

= Testing the shear strength

The test strips were applied over a length of 2.5 cm Weight of the mass 2.5 kg, on a chromed steel Sheet (V2A) rolled up and stored under normal conditions for 24 hours. Then the unaffected end of the steel sheet fixed between 2 clamping jaws and the opposite one above standing adhesive tape hanging freely at temperatures of 25 ° C a mass of 2 kg and at 70 ° C with a weight of Weight 1 kg. The benchmark for the shear strength is Time until the adhesive film breaks open. For comparison the test was repeated with self-adhesive films had not been irradiated. The results are shown in Table 1.

Testing the peel strength

To determine the peel strength of the test strips (a) on the Surface of a substrate, these were made to a length of 2.5 cm, using a weight of mass 2.5 kg, on a Chromed steel sheet (V2A) rolled up. 24 hours later Force determined to the test strips in a tensile test device temperature at a peeling angle of 180 ° C at one speed deducted from 300 mm / min backwards. The results contain if table 1.

Table 1

B) Laminating adhesives Example 4 (B4) UV-crosslinkable film laminating adhesive with a poly merized photo initiator

In a stirring flask (capacity 2 liters) with an inlet funnel ter, thermometer, reflux condenser and light nitrogen purge were

300 g of toluene are introduced and heated to reflux; with stirring was then in an hour with constant speed added a mixture of

212 g n-butyl acrylate
60 g styrene
80 g dihydrodicyclopentadienyl acrylate
8 g acrylic acid and
40 g of the compound of structural formula (XVII) with R 1 = H, n = 4 and a solution from a further feed vessel
50 g of toluene and
12 g of tert-butyl peroctoate
after the end of the feed, cooking was continued for an hour and then a solution of
50 g of toluene and
12 g of tert-butyl peroctoate

further polymerized at reflux for 2 hours and then from chilled. A viscous solution was created. The polymer has a K value of 28 (measured as a 1% solution in toluene).

Example 5 (B5) UV-crosslinkable film laminating adhesive with a mixed photo initiator

In the same manner as in Example 3, one was changed Polymerized monomer composition.

232 g of n-butyl acrylate
80 g styrene
80 g dihydrodicyclopentadienyl acrylate
8 g acrylic acid and

The polymer has a K value of 31 (measured as a 1% solution in toluene).  

After cooling
20 g of benzophenone were added and the mixture was stirred until dissolved.

Example 6 Laminating adhesive without DCPA (not according to the invention)

The preparation was carried out as in Example 5, except that No addition of DCPA.

Application test

The toluene solution of the polymers was made using a doctor table (Example 4-6) min a dry layer thickness of 2-3 g / m² on ver different foils heated to 50 ° C (polyethylene terephthalate: PETP; Polyamide: PA; Polypropylene (corona treated): PP, aluminum: (corona treated) laminated.

However, UV radiation was carried out as in Examples 1-3 through the film composite. The top is the UV-permeable PE film.

Belt speed: 2.5 m / min.

The film composites obtained were then left for 7 days Store room temperature and normal climate and then in 2 cm wide Strips cut. These strips were then at 23 ° C in the win of 180 ° C at a speed of 100 m / min. The peeling force in N was determined for the 15 mm wide strips Right. Results can be found in Table 1.

Table 1

Claims (16)

1. Adhesive containing a radically polymerized poly mer, which is 0.5 to 90 wt .-% of a monomer a) with a base of the formula which is substituted by a radical R¹ and optionally one or more identical or different radicals R², where R¹ is an organic radical with a copolymerizable, ethylenically unsaturated group and R² is a C₁-C₁₂-alkyl or a C₅-C₂₀- Cycloalkyl, aryl or aralkyl group. 2. The adhesive of claim 1, wherein the polymer is 0.5 to 40 wt .-% consists of the monomers a). 3. The adhesive of claim 2, wherein the polymer is made of
0.5 to 40% by weight of monomers a)
20 to 99.5% by weight of so-called main monomers b)
selected from
C₁-C₂₀-alkyl (meth) acrylates, vinyl esters of up to 20 carbon atoms containing carboxylic acids, vinyl aromatics with up to 20 carbon atoms, ethylenically unsaturated nitriles, vinyl halides, vinyl ethers of 1 to 10 carbon atoms and alcohols and aliphatic hydrocarbons with 2 to 8 carbon atoms and 1 or 2 double bonds
0 to 30% by weight of copolymerized photoinitiators c) and
0 to 40% by weight of further monomers d)
is constructed. 4. Adhesive according to one of claims 1 to 3, containing 0.1 up to 30 wt .-%, based on the polymer, of a non copoly merized photo initiators.   5. Adhesive according to claim 3, wherein the polymer at least 0.1% by weight of the copolymerizable photoinitiator c), and correspondingly only a maximum of 99.4% by weight of monomers b) holds. 6. Adhesive according to one of claims 1 to 5, wherein it is monomers a)
Dihydrodicyclopentadienyl acrylate,
Dihydrodicyclopentadienyl methacrylate,
Dihydrodicyclopentadienyl ethacrylate,
Dihydrodicyclopentadienyl cinnamate
or their mixtures. 7. Adhesive according to one of claims 4 to 6, wherein it is in the non-copolymerized photoinitiator or copolymerizable photoinitiator c) around an acetophenone, Benzophenone or thioxanthone derivative. 8. Adhesive according to one of claims 1 to 7, wherein the Polymer was made by solution polymerization. 9. Adhesive according to one of claims 1 to 8, wherein the Polymer has a glass transition temperature of -50 to + 40 ° C points. 10. Adhesive according to one of claims 1 to 9, wherein the poly always has a K value of 10 to 70. 11. pressure sensitive adhesive according to one of claims 1 to 10. 12. Pressure sensitive adhesive according to claim 11, wherein the K value of the Polymer is from 30 to 70. 13. Laminating adhesive according to one of claims 1 to 10. 14. Laminating adhesive according to claim 13, wherein the K value of the Polymer is from 10 to 50. 15. Process for bonding substrates, characterized records that an adhesive according to any one of claims 1 to 14 applied to a substrate with high-energy light radiates and is then glued to a second substrate.   16. With an adhesive, in particular pressure sensitive adhesive or Laminating adhesive, according to one of claims 1 to 14 layered substrates.