CA1337615C - Benzophenone derivatives and their preparation - Google Patents

Abstract

UV-crosslinkable materials based on (meth)acrylate copolymers and containing special modified unsaturated benzophenone derivatives as copoly-merized units are used as hotmelt adhesives, for coating sheet-like mineral substrates and as surface coatings.

Description

._ Novel benzophenone derivatives and their preparation The present invention relates to materials which can be crosslinked with W light in the air and can be used, in particular, as hotmelt adhesives, for coating mineral substances, for example roofing tiles, and as surface coatings. The materials should have increased reactivity toward W radiation. When used as hotmelt ad-hesives, the products should have a low melt viscosity, good tack and increased heat distortion resistance.
Dutch Patent Application 6,606,711 published 23 November 1966 discloses contact adhesive tapes which are produced by coating a sheet-like substrate with a polyacrylate adhesive, one or more monomeric acrylates, eg.

2-ethylhexyl acrylate, being present and being polymerized by exposure to W light followed by heating. However, in order to obtain useful results, exposure must be carried out under an inert gas atmosphere. Furthermore, the presence of readily volatile acrylates which may irritate skin and eyes is disadvantageous.
Dutch Patent Application 7,009,629 published 4 January 1971 further discloses a process for the preparation of adhesives, in which mixtures of acrylates and methacrylates, such as 2-ethylhexyl acrylate, with organic polymers, such as cellulose derivatives, polyolefins or polyesters, as viscosity regulators and, if required, together with a tackifier, such as polyvinyl methyl ether, are applied in a thin layer to a sheet-like substrate and treated with high-energy radiation. In this process too, the presence of the monomeric (meth)acrylates, which have an irritant effect and are readily volatile, is disadvantageous, and furthermore only products whose cohesion is insufficient for many applications in the contact adhesive sector are obtained.
In the process of German Laid-Open Application DOS 2,351,S86 for the production of self-adhesive coat-ings, ionizing radiation is used for exposure, the mix-ture exposed being a mixture which is liquid at room ,~
,`,~ ~D

~ l 33761 5 2 temperature and consists of (A) a monoolefinically unsaturated monomer which forms tacky polymers at room temperature, (B) a diolefinically or polyolefinically unsaturated compound, (C) a polymer having a softening point below 50C and a mean molecular weight of from S00 to 10,000 and (D) a conventional photoinitiator, for example benzoin, acetophenone or benzophenone, and which is likewise applied to a sheet-like substrate.
In this process too, acrylates and methacrylates of A 1 kAnolS of 4 to 12 carbon atoms can be used as monomers (A). Although the adhesive layers produced by this process have a high shear strength at room temperature and good surface tack, they have relatively great cold flow, and insufficient shear strength at elevated temperatures.
High-energy radiation is also employed by the process of European Patent 88,300, in which self-adhesive coatings are obtAinP~ by coating substrates with deriva-tives of dihydroxypropylacrylates mixed with polymers having a glass transition temperature below 0C and a R value of from 20 to 80 and/or a tackifying resin. Al-though this process gives good surface tack and good heat distortion resistance, the irritant monomers and the necessity of working under an inert gas atmosphere give rise to disadvantages.
Since photoinitiators are present in the case of materials which are to be cro slinked with W radiation, these photoinitiators should be very readily soluble in the materials and should not exude from the materials in order to enable the materials to be processed at elevated temperatures too. Furthermore, on exposure these photo-initiators should not form any degradation products which tend to exude and have a strong intrinsic odor.
Copolymerizable photoinitiators have therefore also been used in W-curable materials. Thus, EP-A-0 017 364 published 1 December 1980 describes, for example, copolymers which are suitable, inter alia, as adhesives and for sealing compounds and which contain from 0.1 to 10% by weight of allyl benzoylbenzoate as a copolymerized photoinitiator. Although these materials can be crosslinked with UV radiation, they give crosslinked products having a very high viscosity. Moreover, their reactivity to UV radiation is too low and tacky layers produced from them do not meet the requirements set for good contact adhesive. Furthermore, irritant monomers are also used in this process (Example 10).
According to German Laid-Open Application DOS
2,411,169, contact adhesives crosslinkable with ultra-violet radiation can be prepared by using copolymers of (meth)acrylates which contain monoolefinically un-saturated ether and ester derivatives of substituted benzoph~non~s as copolymerized photoinitiators. However, the copolymerized benzophenone derivatives are less reactive to W radiation and the pressure-sensitive adhesives prepared from the copolymers do not meet high requirements. Moreover, hotmelt adhesives prepared by this method have an excessively high melt viscosity, which makes them unsuitable for use in practice.
Furthermore, EP-A-0 246 848 published 19 November 1987 discloses UV-crosslinkable contact adhesives based on polyacrylates, which contain monoolefinically unsaturated benzophenone derivatives as copolymerized photoinitiators.
These contact adhesives are intended for use in the medical field, for example for plasters, and their adhesion to the skin should not increase in the course of time. However, the disadvantage of these contact adhesives is that they have only little reactivity to W radiation and a comparatively high melt viscosity.
We have found that W-crosslinkable materials based on (meth~acrylate copolymers having a K value of from 15 to 100, are particularly advantageous if they contain from 0.01 to 10% by weight, based on the -- 1 3376 1 5 4 _ copolymers, of copolymerized monomers of the general formula I
~
z c-x (I) where X is alkyl of 1 to 3 carbon atoms or is phenyl which is unsubstituted or substituted by n Y groups, Y is -H, -CF3, -O-alkyl and/or alkyl-COO-, where alkyl in each case is of 1 to 4 carbon atoms, halogen, -CN, -COOH or a non-ortho -OH group, n is from 0 to 4 and Z is a group of the general formula o o --C--N--(--A--)--O--C--f=CH 2 R R
O O
--O--C--N--~--~--)--O--C--C=C H 2 R R or o o --N--C~ --O--C--f--C H 2 R R R

where R is H or Cl-C4-alkyl and A is an alkylene, oxa-alkylene or polyoxaalkylene radical of 2 to 12 carbon atoms.
The copolymers generally contain, as principal monomers, predominant amounts of, in general, from 50 to 99.99, preferably from 70 to 97.5, % by weight of acry-lates and/or methacrylates of alkanols of 1 to 24, in particular 1 to 12, carbon atoms, such as methyl, ethyl, propyl, isoamyl, isooctyl, n-butyl, isobutyl, tert-butyl, cyclohexyl, 2-ethylhexyl, decyl, lauryl or stearyl acryl-ate and/or methacrylate as copolymerized units. Examples of suitable comonomers are vinyl esters of saturated car-boxylic acid~ of 1 to 20, in particular 2 or 3, carbon atoms, such as vinyl formate, vinyl acetate or vinyl _ - 5 -propionate, and also vinyl laurate and vinyl stearate, vinyl ethers of 3 to 22 carbon atoms, such as methyl, ethylj butyl, hexyl or octadecyl vinyl ether, vinyl-aromatics of 8 to 12 carbon atoms, in particular styrene, as well as ~-methylstyrene, vinyltoluenes, tert-butyl styrene and halostyrenes, olefins of 2 to 20 carbon atoms, in particular ethylene and propylene, and also n-butylene, isobutylene, diisobutene, triisobutene and oligopropylenes, and/or vinyl halides, in particular vinyl chloride and vinylidene chloride, and allyl ethers or allyl esters. Copolymers which contain from 0.5 to 20, preferably from 2 to 10, % by weight, based on the copolymers, of tetrahydrofurfur-2-yl acrylate or meth-acrylate and/or alkoxy-contA i n i~g monomers, such as 3-methoxybutyl (meth)acrylate, 2-methoxyethyl (meth)-acrylate, 2-butoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, N-butoxymethyl (meth)acrylamide and/or N-isobutoxymethyl (meth)acrylamide, as copolymerized units in addition to other acrylates and methacrylates are of particular interest, tetrahydrofurfur-2-yl acry-late and methacrylate and 3-methoxybutyl acrylate and methacrylate being preferred.
The copolymers also particularly advantageously contain from 0.1 to 10, preferably from 0.5 to 4, % by weight of ~,A-monoolefinically unsaturated mono- and/or dicarboxylic acids of 3 to 5 carbon atoms and/or their amides or, if desired, monoalkyl esters or anhydrides of the dicarboxylic acids as copolymerized units. Examples of these are, in psrticular, acrylic and methacrylic acid and itaconic acid, and also crotonic acid, fumaric acid, maleic acid, maleic anhydride, n-butylmaleic monoesters, monoethyl fumarate, monomethyl itaconate and monomethyl maleate. Particularly interesting amides of such car-boxylic acids are acrylamide and methacrylamide. N-methyl acrylamide and -methacrylamide, N-methylolacryl-amide and -methacrylamide, maleic acid monoamide and diamide, itaconic acid monoamide and diamide and fumaric acid monoamide and diamide are also suitable. In some cases, vinylsulfonic acid or vinylphosphonic acids are also suitable, in amounts of from 0.1 to 5% by weight, based on the copolymers.
Other suitable comonomers, in amounts of not more than 30, preferably from 0.5 to 5, % by weight, are ole-finically unsaturated tertiary amino compounds, such as N,N-dimethylaminoethyl- and N,N-diethylaminoethyl(meth)-acrylamide,N,N-diisopropyl(meth)acrylamide,N,N-dibutyl-(meth)acrylamide, N,N-dimethylaminoethyl (meth)acrylate and N,N-diethylaminoethyl (meth)acrylate, dimethyl- and diethylaminoethyl vinyl ether, N-vinylimidazole, N-vinyl-imidazoline, vinylpyridines, dialkyl(meth)acrylamides, N-vinylformamide, N-vinylpyrrolidone, N-vinylcaprolactam, p-hydroxy(meth)acrylic acid anilide, N-tert-butyl(meth)-acrylamide, diacetone(meth)acrylamide, N-(1-methylundec-yl) (meth)acrylamide, N-isobornyl(meth)acrylamide, N-adamantyl(meth)acrylamide, N-benzyl(meth)acrylamide, N-4-methylphenyl(meth)acrylamide, methyl(meth)acrylamide, N-diphenylmethylacryl~ide, phthalimidomethyl(meth)acryl-amide, (meth)acrylamidohydroxyacetic acid, (meth)acryl-amidoacetic acid, (meth)acrylamidoacetic esters, such as methyl (meth)acrylamidoacetate, 2-(meth)acrylamido-2-methylbutyric acid, N-(2,2,2-trichloro-1-hydroxy)-ethyl-(meth)acrylamide, N,N-bis-(2-cyanoethyl)-methacrylamide, N-(1,1,1-trishydroxymethyl)(meth)acrylamide, methyl-(meth)acrylamide and N-(3-hydroxy-2,2-dimethylpropyl)-(meth)acrylamide. Other examples are 2-hydroxy-3-[N,N-di-(2-hydroxyethyl)]-propyl (meth)acrylate, 2-methoxy-3-[N,N-di-(2-hydroxyethyl)]-propyl (meth)acrylate, 2-hydroxy-3-tN-hydroxyethyl-N-alkyl]-propyl (meth)acrylates and/or 2-hydroxy-3-[N,N-dialkyl]-propyl (meth)acrylate where alkyl is of 1 to 10 carbon atoms, such as 2-hyd~o~y-3-~N-hydroxyethyl-N-methyl]-propyl (meth)acrylate and2-hydroxy-3-[N-ethyl-N-methyl]-propyl(meth)acrylate.
Finally, monoolefinically unsaturated monomers such as 3-cyclohexylprop-1-yl (meth)acrylate, cyclohexyl _ - 7 -(meth)acrylate, 4-tert-butylcyclohexyl (meth)acrylate,2-N-morpholinoethyl (meth)acrylate, 2-N-morpholinohexyl (meth~acrylate and furfuryl (meth)acrylate, isobornyl (meth)acrylate, N-cyclohexyl(meth)acrylamide and N-iso-bornyl(meth)acrylamide are also suitable, in amounts of not more than 30, preferably from 0.1 to 25, particularly preferably from 0.5 to 20, % by weight. The copolymers generally have R values of from 15 to 100, determined according to DIN 53,726 in 1% strength solution in tetra-hydrofuran at 25C. The R value is preferably from 25 to 50 if the materials are to be used a~ hotmelt adhesive If the materials are to be used for coating roofing tiles, their R values are preferably from 60 to 100, and materials which are to be used for surface coatings preferably have R values of from 15 to 85.
The W-crosslinkable materials which, in the case of contact adhesives, are applied in the form of their melts, generally have Staudinger indices (viscosity numbers) of from 0.10 to 1.60, preferably from 0.2 to 0.9, very particularly preferably from 0.25 to 0.49, 100 ml/g (measured in tetrahydrofuran at 25C).
The compounds of the general formula I can be prepared by known processe~. Of particular interest are the acrylate~ and/or methacrylate~ of the compound II

~ C ~ O--C--N--(--cH2--cH2--O)2H II

Other very suitable benzophenone derivatives to be copolymerized are the acrylates and methacrylate~ of the compound~ III and IV
O H
o O - c - N - cH2 - cH2 - oH
~ c ~ III

~ c ~ o--lcl--I c H 2--C H 2--O H IV

and examples of suitable acetophenone derivatives are the compounds V and VI

C H 3--C~O I _N--C H 2--C H 2-- H V
O H

CH3--C ~ O--C--N--(--CH2--CH2--O)2H VI
O H
These compounds are acrylates and methacrylates of acetophenone and benzophenone derivatives which have an N-hydroxyalkylcarbamic ester group at the ortho or para position of a phenyl group of the acetophenone or of the benzophenone, the alkyl group of the said ester group being of 2 to 4 carbon atoms which may be bonded to one another via an ether bridge.
Finally, the copolymers may contain further co-polymerized monomers having functional groups, in amounts of not more than 20% by weight, for example hydroxyalkyl (meth)acrylates, ~uch a~ 2-hydroxypropyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)-acrylate and glycidyl acrylate and methacrylate. Mono-acrylates and monomethacrylates of polyetherols or of oxypropylated fatty alcohols, for example having a mole-cular weight of from 200 to 10,000, or of polyoxyeth-ylated Al~Anols and/or phenols, in amounts of from 0.5 to 10% by weight, may also be advantageous comonomers in some cases.
If the copolymers are to be used as contact adhesives, the acrylates and/or methacrylates used as principal monomers are preferably those whose homopoly-mers have glass transition temperatures below 0C, in particular below -10C, in particular n- and isobutyl acrylate and methacrylate, isoamyl and isooctyl acrylate and methacrylate and 2-ethylhexyl acrylate and meth-acrylate, a~ well as decyl acrylate and lauryl acrylate and methacrylate. The amount of these principal monomers is then preferably more than 60% of the total monomers.
The copolymers generally contain from 0.1 to 10%
by weight of copolymerized monomers of the general formula I, although amounts of from 0.01 to 5% by weight, based on the copolymers, are frequently sufficient. Co-polymers which contain from 0.5 to 25, in particular from 5 to 15, % by weight of tetrahydrofurfur-2-yl (meth)-acrylate in addition to other acrylates and monomers of the general formula I as copolymerized units often have a very low molecular weight and a low viscosity.
The novel W-crosslinkable (meth)acrylate copoly-mers can be prepared by copolymerization of the monomeric components using the conventional polymerization in-itiators and, if required, regulators, polymerization being carried out at the conventional temperatures in the form of mass polymerization, emulsion polymerization, for example in water or liquid hydrocarbons, or solution polymerization. The novel copolymers are preferably prepared by polymerization of the monomers in solventæ, in particular in solvents boiling within a range from 50 to 150C, preferably from 60 to 120C, using the conven-tional amount of polymerization initiators, which in general is from 0.01 to 10, in particular from 0.1 to 4, % by weight, based on the total weight of the monomers.
Particularly suitable solvents are alcohols, such as methanol, ethanol, n-propanol, isopropanol, n-butanol and isobutanol, preferably isopropanol and/or isobutanol, and hydrocarbons, such as toluene and, in particular, gaso-lines boiling within a range from 60 to 120C. Retones, such as acetone and methyl ethyl ketone, and esters, such as ethyl acetate, and mixtures of solvents of the stated type can also be used, mixtures which contain isopropanol and/or isobutanol in amounts of from 5 to 95, in par-ticular from 10 to 80, preferably from 25 to 60, % by weight, based on the solvent mixture used, being preferred.
Suitable polymerization initiators in the , -- 10 --solution polymerization are, for example, 2,2'-azobisiso-butyronitrile, acyl peroxides, such as benzoyl peroxide, dilauroyl peroxide, didecanoyl peroxide and isononanoyl peroxide, alkyl peresters, such as tert-butyl perpiva-late, tert-butyl per-2-ethyl~eY~noate, tert-butyl per-maleate, tert-butyl perisononanoate and tert-butyl per-benzoate, dialkyl peroxides, such as dicumyl peroxide, tert-butyl peroxide, di-tert-butyl peroxide and peroxy-dicarbonates, such as dimyristyl peroxydicarbonate, bicetyl peroxydicarbonate, bis-(4-tert-butylcyclohexyl) peroxydicarbonate, dicyclohexyl peroxydicarbonate and di-2-ethylhexyl peroxydicarbonate, hydroperoxides, such as cumene hydroperoxide and tert-butyl hydroperoxide, and polymerization initiators such as 3,4-dimethyl-3,4-diphenylhexane and 2,3-dimethyl-2,3-diphenylbutane. Par-ticularly preferred polymerization initiators are ketone peroxides, such as methyl ethyl ketone peroxide, acetyl-acetone peroxide, cyclohexanone peroxide and methyl iso-butyl ketone peroxide.
After the solution polymerization, the solvents can, if required, be separated off under reduced pressure and at elevated temperatures, for example from 100 to 150C. The novel copolymers can then be used in the solvent-free state, ie. as a melt, in particular as a hotmelt adhesive, but also for coating mineral sub-stances, in particular roofing tiles, and as surface coatings. In some cases, it is also advantageous to pre-pare the novel, W -crosslinkable copolymers by mass poly-merization, ie. in the absence of a solvent; the pro-cedure can be carried out batchwise or continuously, for example as described in U.S. Patent 4,042,768.
If the novel copolymers are used in the form of solutions, for example for surface coatings or for coat-ing roofing tiles, the mixtures of the copolymers and solvents generally contain from 10 to 900, preferably - from 20 to 200, in particular from 25 to 150, % by weight of solvents. Preferably, however, the copolymers are used in solvent-free form.
In some cases, for example if the novel copoly-mers are prepared in aqueous emulsion by emulsion poly-merization, conventional regulators in the usual amounts, for example of from 0.1 to 15, preferably from 2 to 10, % by weight, based on the monomers, may also be used.
Examples of regulators of this type are mercapto com-pounds, such as 2-mercaptoethanol, methyl 3-mercaptoprop-ionate, 3-mercaptopropionic acid, 1,6-dimercaptohexane or 1,9-dimercaptononane, hydrocarbons, such as cumene, alcohols, such as isopropanol or isobutanol, and halo-hydrocarbons, such as carbon tetrachloride, tetrabromo-methanol, chloroform or bromoform. Preferred regulators are compounds such as 3-mercaptopropionic acid, 3-mercapto-1,2-propAne~iol, 2-mercaptoethanol, glycerol and di- and triglycerides. Ether~, such as dioxane and tetrahydrofuran can also be used as regulators.
When the novel materials are used, they may be modified and/or compounded in a conventional manner. For example, conventional tackifying resins, eg. hydrocarbon resins, unmodified or modified rosins, terpene/phenol resins, ketone resin~, aldehyde resins or homopolymers, such as poly-2-ethylhexyl acrylate and poly-n-butyl acrylate, plasticizers, such a~ those based on mono-, di-or polyester compounds, polychlorinated hydrocarbons or liquid paraffins, dyes and pigments, or stabilizers or elastomeric substances, such as natural or synthetic rubber, polyvinyl ethers and polybutadiene oils may be added. Modification may also be carried out using rela-tively high molecular weight monoolefinically or poly-olefinically unsaturated compounds, such as polyesterols and polyetherols esterified with acrylic acid, eg. tri-propylene glycol acrylate, tetraethylene glycol acrylate, polyethylene glycol diacrylate and polytetrahydrofuran.
Diacrylates and dimethacrylates of polytetrahydrofuran having number average molecular weight~ of in general from 250 to 2,000 are also suitable. Such diolefinically or polyolefinically unsaturated compounds can advan-tageously be used in amounts of from 0.1 to 10% by weight, based on the novel copolymer, diolefinically unsaturated compound~ of this type having a number average molecular weight of not less than 500 being of particular interest.
The novel W-crosslinkable materials are par-ticularly suitable in the form of melts or as solutions or in the form of aqueous dispersions for the production of coatings and for impregnation, in particular in the form of contact adhesives, pressure-sensitive adhesive films and pressure-sensitive adhesive labels, and block-ing foils. The materials can be applied in a conven-tional r-nn~r by brushing, spraying, roller-coating, knife coating or pouring, if necessary at elevated tem-peratures, generally at from 20 to 150C, to conventional substrates, for example to paper, board, wood, metals and plastic films, for example films of plasticized PVC, polyethylene, polyamides or polyethylene glycol tereph-thalate, or aluminum or poly~ o~ylene.
If solvents are present, they can readily be evaporated off from the coatings, if required, at room temperature or ~lightly elevated temperatures, in general at from 20 to 150C, preferably from 50 to 80C, radiant heaters or hot air circulation apparatuses being used in a conventional manner. The coatings, which may be dried or predried, can then be crosslinked by exposure to W
light to give coatings which have good tack, high cohe-sion and good peeling strength in combination with excellent aging resistance. Exposure need not be carried out under an inert gas atmosphere but may be effected in the air. The W lamps used may be the usual lamps, for example low pressure, medium pressure and high pressure mercury vapor lamps, which can have powers of, for example, from 80 to 160 watt/cm. Lamps having a higher power generally permit faster crosslinking. In some cases, residual solvent or water can be removed simultaneously by the IR component of the lamps during exposure to effect crosslinking.
The adhesive properties of sheet-like substrates which have a contact adhesive layer can be determined by S measuring the shear strength as a measure of the cohesion and the peeling strength as an overall measure of cohes-ion and surface tack.
For the test, films of polyethylene glycol terephthalate are coated with the novel materials so that the resulting dry layer is 25 ~m in thickness.
The solvents are evaporated off for 1 minute at 70C and under 1 bar. The coated and dried films are exposed to light from medium pressure mercury lamps.
Exposure is effected using two medium pressure mercury lamps which are arranged one h~hin~ the other and each of which has a power of 80 watt/cm. The coated and dried films are placed on a continuous moving belt, so that the coated films pass below the lamps at a distance of 15 cm and at a speed of 10 m/min.
Exposure is effected in the air.
The films thus produced are cut into 2 cm wide strips and these strips are applied to a chromium-plated brass plate. The plate with the strips is stored for 24 hours at 23C and 65% relative humidity.
To measure the peeling strength, the test strips are pulled off backward, parallel to the adhesive layer, at a speed of 300 mm/min. The force required for this purpose is measured.
In the measurement of the shear strength, an adhesively bonded area of 20 x 25 mm i~ cut out, the plate is clamped vertically and the pro~ecting part of the adhesive strip is sub~ected to a weight of 1 kg. The time taken to break the adhesive bond is determined. The measurement is carried out at 23C and 50C. All measure-ments are carried out in triplicate.
In the Examples which follow, parts and percent-ages are by weight. The K values are determined accord-ing to DIN 53,726, in 1~ strength solution in tetrahydrofuran at 25C. The melt viscosities are measured in a plate-and-cone rheometer, for example a Rotovisko RV 20 with measuring unit PR 100 (from Haake, Rarlsruhe).
The Staudinger index (viscosity number) is deter-m; ~ in tetrahydrofuran at 25C by a known method (eg.
G.V. Schulz and H.-J. Cantow in Houben-Weyl, Methoden der organischen Chemie, G. Thieme Verlag, 1955, Vol. 3/1, page~ 431-445, and B. Vollmert: Grundriss der makro-molekularen Chemie, Volume III, page 55 et seq.).
EXAMPLES
Copolymer solution P1 320 parts of a mixture of 400 parts of 2-ethyl-hexyl acrylate, 470 parts of n-butyl acrylate, 30 parts of acrylic acid, 100 parts of tetrahydrofurfur-2-yl acrylate and 50 parts of a benzophenone derivative of the general formula VII

~C~30--C--N--( C H 2--C H 2-- ~ 2--C--C--C H 2 are added to a mixture of 200 parts of isopropanol and 6 parts of methyl ethyl ketone peroxide.
The mixture is polymerized at 95C for 20 minutes.
The remainder of the monomer mixture and a solution of 8 parts of methyl ethyl ketone peroxide in 30 parts of isopropanol are added to this prepolymerized mixture in the course of 2 hours, and polymerization is carried out for a further 4 hours at 100C. A colorless clear solu-tion of a copolymer Pl which has a R value of 24 is ob-tained. The copolymer P1 freed from ~olvent and volatile constituents has a melt viscosity of 35 Pa.s at 25C.
Copolymer P2 The procedure described for copolymer solution P1 is followed, except that the tetrahydrofurfur-2-yl acry-late is replaced with the same amount of 3-ethoxybutyl acrylate, and furthermore 17 parts of the n-butyl acrylate are replaced with 17 parts of methyl methacryl-ate. In this case, a colorless clear solution of a co-polymer P2 having a R value of 28 is obtained; after removal of the solvent and of volatile constituents, the s said copolymer has a melt viscosity of 15 Pa.s at SO~C.
Mixture Ml 3.5 parts of polytetrahydrofuran diacrylate (molecular weight 6S0) and 5 parts of an abietic acid resin (Fora ~ 85 from Hercules) are added to 100 parts of the copolymer P2. The resulting mixture exhibits good flow at room temperature.
Mixture M2 S parts of polytetrahydrofuran dimethacrylate (molecular weight 1,000) and 10 parts of an abietic acid resin (Fora ~ 85 from Hercules) are added to 100 parts of the copolymer Pl. A mixture which exhibits good flow at room temperature is obtained.
Copolymer solution P3 The procedure described for copolymer solution P1 is followed, except that the benzophenone derivative VII
is replaced with 44.4 parts of the benzophenone deriva-tive VIII

O O H O CH~
~C H 2--C H ~C--C=C H 2 VI I I

which is prepared according to Example 1 of C~n~ n Patent Application 602,428. Asolution of a copolymer P3 having a K value of 25 is obtained;
after removal of the solvent and of the volatile con-stituents, the said copolymer has a melt viscosity of 36 Pa.s at 25~C.
Mixture M3 100 parts of the copolymer P3 are mixed with S parts of a commercial oligoester acrylate (DYNACO ~ A, Type 2530 VP from Dynamit Nobel) and a mixture exhibiting good flow at room temperature is obtained.

The shear strengths, peeling strengths and tacks measured for the polymers and their mixtures are sum-marized in the Table below, mixtures Ml and M2 being ex-posed using a speed of the continuous belt of 10 m/min.

Results of the performance tests on the contact adhesives Sample Shear strength Peeling strength Tack thours] at [N/2 cm]
23C 50C Immediately After 24 hours P1 >100 >10 4.1 7.5 Good P2 >100 >10 3.5 7.0 Good Ml > 80 > 5 5.0 8.0 Good M2 > 70 > 5 4.0 7.8 Good P3 > 50 > 2 4.0 8.2 Good M3 > 50 ~ 4 3.0 6.0 Good Copolymer solution P4 A mixture of 200 parts of ethyl acetate, 50 parts of tetrahydrofuran, 7.5 parts of dimethyl 2,2'-azobisiso-butyrate and 200 parts of a monomer mixture of 600 parts of n-butyl acrylate, 230 parts of isooctyl acrylate, 150 parts of methyl methacrylate, 20 parts of acrylic acid and 7.5 parts of the benzophenone derivative of the general formula VII is prepolymerized at 96C for 20 minutes.
The remainder of the monomer mixture is added to the reaction mixture in the course of 2 hours. After the addition is complete, the mixture is stirred under reflux for 2 hours, after which a solution of 2 parts of tert-butyl per-2-ethylheYAnoate in 83 g of ethyl acetate is added under reflux and refluxing i~ continued for a further 4 hours.
A solution of a copolymer having a R value of 39 and a Staudinger index (viscosity number) of 0.38 [100 ml/g] is obtAine~.
- 35 After the solvent and volatile constituents have been distilled off and the residue sub~ected to subsequent distillation at 135C under reduced pressure, a resin exhibiting good flow at room temperature is obt~ine~.
The melt viscosity at 120C is 15 Pa.s (D =
500 l/s).
Polyester films are coated with the resin on a heatable coating table at 95C in an amount of 25 g/m2.
The coated films are placed on the running con-tinuou~ belt of a W exposure apparatus and are passed once at a speed of from 15 to 25 m/min below a medium pressure mercury lamp having a radiant power of 80 watt/cm.
The adhesive-coated paper is applied to the exposed films. After ~torage for 24 hours, the adhesion tests are carried out.

Results of the performance tests on the copolymer P4 as a contact adhesive Belt speed Shear strength Peeling strength Tack [m/min] [hours] [N/2 cm]
23C 50C Immediately After 24 hours >24 >24 3.3 7.3 Good >24 >24 3.5 7.6 Good >24 >24 4.5 7.5 Good

Claims (2)

1. A UV-crosslinkable material based on a (meth)-acrylate copolymer having a K value of from 15 to 100 and containing from 0.01 to 10% by weight, based on the co-polymer, of copolymerized monomers of the formula I

(I) where X is alkyl of 1 to 3 carbon atoms or is phenyl which is unsubstituted or substituted by n Y groups, Y is -H, -CF3, -O-alkyl and/or alkyl-COO-, where alkyl in each case is of 1 to 4 carbon atoms, halogen, -CN, -COOH or a non-ortho -OH group, n is from 0 to 4 and Z is a group of the formula or where R is H or C1-C4-alkyl and A is an alkylene, oxa-alkylene or polyoxaalkylene radical of 2 to 12 carbon atoms.

2. A UV-crosslinkable material as claimed in claim 1, which contains an acrylate and/or methacrylate of the compound II

as copolymerized monomers of the formula I.