HIGH Tg ACRYLATE COPOLYMERS WITH NITROGEN-CONTAINING AROMATIC HETEROCYCLIC GROUP

Abstract

The invention relates to a process for the radical polymerization for preparing a copolymer, using specific monomers A, which have a glass transition temperature Tg of at least 0° and specific monomers B, which contain an aromatic heterocyclic group that contain at least one nitrogen atom in the ring. The invention also relates to copolymers that are obtained by the radical polymerization, to the use of same as accelerators in a curing reagent for adhesive compounds, and to adhesive strips containing same.

Claims

1. A process for the radical polymerization for the preparation of a copolymer, comprising or consisting of the polymerizing of at least one monomer A which contains at least one unsaturated —C═C— double bond and has a T.sub.g≥0° C., determined from the homopolymer of the monomer A by means of DSC measurement; at least one monomer B which contains an aromatic heterocyclic group containing at least one nitrogen atom in the ring and which further contains at least one unsaturated —C═C— double bond; and optionally at least one monomer C which contains at least one unsaturated —C═C— double bond that is different from monomer A and B; in the presence of at least one radical initiator and optionally of at least one chain transfer agent; where the at least one monomer A is contained in at least 30 mol % based on the total monomers of the copolymer.

2. The process as claimed in claim 1, characterized in that i) the at least one monomer A has a molecular weight of less than 1000 g/mol; and/or ii) the at least one monomer A comprises no nitrogen-containing aromatic heterocyclic group; and/or iii) the at least one monomer A is selected from one of the following groups iiia) to iiid), iiia) acenaphthylene, maleic anhydride, N-phenylmaleimide, N-vinylpyrrolidone, 2-vinylnaphthalene, acrylamide, N-vinylcaprolactam, itaconic anhydride, tert-butyl methacrylate, dihydrodicyclopentadienyl acrylate, isobornyl methacrylate, tert-butyl acrylate, acrylic acid, methyl methacrylate, styrene and styrene derivatives, N,N-dimethylacrylamide, N-tert-butylacrylamide, N-isopropylacrylamide, isobornyl acrylate, acrylonitrile, methacrylonitrile, hydroxyethyl methacrylate, cyclohexyl methacrylate, tert-butylcyclohexyl methacrylate, 3,4-epoxycyclohexylmethyl methacrylate, glycidyl methacrylate, ethyl methacrylate, benzyl methacrylate, phenyl methacrylate, isobutyl methacrylate, stearyl acrylate, vinyl acetate, n-butyl methacrylate, methyl acrylate, 2-phenoxyethyl acrylate, 2-(3-toloidylureido)ethyl methacrylate or mixtures thereof; or iiib) acenaphthylene, maleic anhydride, N-phenylmaleimide, N-vinylpyrrolidone, 2-vinylnaphthalene, acrylamide, N-vinylcaprolactam, itaconic anhydride, tert-butyl methacrylate, dihydrodicyclopentadienyl acrylate, isobornyl methacrylate, tert-butyl acrylate, acrylic acid, methyl methacrylate, styrene and styrene derivatives, N,N-dimethylacrylamide, N-tert-butylacrylamide, N-isopropylacrylamide, isobornyl acrylate, acrylonitrile, methacrylonitrile, hydroxyethyl methacrylate, cyclohexyl methacrylate, tert-butylcyclohexyl methacrylate, 3,4-epoxycyclohexylmethyl methacrylate, glycidyl methacrylate, ethyl methacrylate, benzyl methacrylate, phenyl methacrylate, isobutyl methacrylate, 2-(3-toloidylureido)ethyl methacrylate or mixtures thereof; or iiic) acenaphthylene, maleic anhydride, N-phenylmaleimide, N-vinylpyrrolidone, 2-vinylnaphthalene, acrylamide, N-vinylcaprolactam, itaconic anhydride, tert-butyl methacrylate, dihydrodicyclopentadienyl acrylate, isobornyl methacrylate, tert-butyl acrylate, acrylic acid, methyl methacrylate, styrene and styrene derivatives, N,N-dimethylacrylamide, N-tert-butylacrylamide, N-isopropylacrylamide, isobornyl acrylate, acrylonitrile, methacrylonitrile, hydroxyethyl methacrylate, cyclohexyl methacrylate, tert-butylcyclohexyl methacrylate, phenyl methacrylate, 3,4-epoxycyclohexylmethyl methacrylate, glycidyl methacrylate, 2-(3-toloidylureido)ethyl methacrylate or mixtures thereof; or iiid) acenaphthylenes, maleic anhydride, N-phenylmaleimide, N-vinylpyrrolidone, 2-vinylnaphthalene, acrylamide, N-vinylcaprolactam, itaconic anhydride, tert-butyl methacrylate, dihydrodicyclopentadienyl acrylate, isobornyl methacrylate, tert-butyl acrylate, acrylic acid, methyl methacrylate, styrene and styrene derivatives, N,N-dimethylacrylamide, N-tert-butylacrylamide, N-isopropylacrylamide, isobornyl acrylate, acrylonitrile, methacrylonitrile, phenyl methacrylate, 2-(3-toloidylureido)ethyl methacrylate or mixtures thereof.

3. The process as claimed in claim 1, characterized in that the at least two different monomers A are polymerized; preferably one monomer A is N-phenylmaleimide and the other monomer A is selected from acenaphthylenes, maleic anhydride, N-vinylpyrrolidone, 2-vinylnaphthalene, acrylamide, N-vinylcaprolactam, itaconic anhydride, tert-butyl methacrylate, dihydrodicyclopentadienyl acrylate, isobornyl methacrylate, tert-butyl acrylate, acrylic acid, methyl methacrylate, styrene and styrene derivatives, such as 4-acetoxy styrene, alpha-methylstyrene, 3-methyl styrene, 4-methylstyrene, N,N-dimethylacrylamide, N-tert-butylacrylamide, N-isopropylacrylamide, isobornyl acrylate, acrylonitrile, methacrylonitrile, hydroxyethyl methacrylate, cyclohexyl methacrylate, tert-butylcyclohexyl methacrylate, 3,4-epoxycyclohexylmethyl methacrylate, glycidyl methacrylate, ethyl methacrylate, benzyl methacrylate, phenyl methacrylate, isobutyl methacrylate, stearyl acrylate, vinyl acetate, n-butyl methacrylate, methyl acrylate, 2-phenoxyethyl acrylate, and 2-(3-toloidylureido)ethyl methacrylate.

4. The process as claimed in claim 1, characterized in that i) the at least one monomer B has a molecular weight of less than 2000 g/mol; and/or ii) the at least one monomer B contains imidazole, pyridine or derivatives thereof as aromatic heterocyclic group containing at least one nitrogen atom in the ring; and/or iii) in that the aromatic heterocyclic group containing the at least one nitrogen atom in the ring is bonded to the polymer backbone of the resultant copolymer by a spacer group having 2 to 20 atoms; and/or iv) the at least one monomer B is contained in 20 to 70 mol %, based on the total monomers of the copolymer; and/or v) the at least one monomer B contains no —OH radical.

5. The process as claimed in claim 1, characterized in that the molar ratio of the monomers A to monomers B is from 30 to 60:40 to 70.

6. The process as claimed in claim 1, characterized in that the at least one radical initiator is a UV radical initiator or a thermal radical initiator; and/or the at least one radical initiator is contained in less than 10 mol % based on 100 mol % of the monomers A to C.

7. The process as claimed in claim 1, characterized in that the polymerizing i) is carried out in at least one organic solvent; and/or ii) is carried out under protective gas atmosphere; and/or iii) in that further at least one chain transfer agent is used.

8. The process as claimed in claim 1, characterized in that i) the polymerization is carried out with heating and/or ii) the reaction time is at least 1 h.

9. A copolymer obtainable by the radical polymerization according to a process of claim 1.

10. An adhesive tape comprising at least one layer of a pressure-sensitive adhesive, where the adhesive comprises a polymeric film-forming matrix and also a curable composition, where the curable composition comprises one or more epoxy resins and also at least one curing reagent for epoxy resins, characterized in that the curing reagent comprises at least one copolymer as claimed in claim 9 and at least one hardener.

11. The adhesive tape as claimed in claim 10, characterized in that at least one of the epoxy resins of the curable composition is an elastomer-modified epoxy resin and/or a fatty acid-modified epoxy resin.

12. The adhesive tape as claimed in claim 10, characterized in that the polymeric film-forming matrix used comprises wholly or partly one or more thermoplastic polyurethanes or one or more nonthermoplastic elastomers.

13. The use of the copolymer as claimed in claim 9 as an accelerator in the curing reagent for adhesives, more particularly epoxy-based adhesives.

14. The process as claimed in claim 2, characterized in that the at least two different monomers A are polymerized; preferably one monomer A is N-phenylmaleimide and the other monomer A is selected from acenaphthylenes, maleic anhydride, N-vinylpyrrolidone, 2-vinylnaphthalene, acrylamide, N-vinylcaprolactam, itaconic anhydride, tert-butyl methacrylate, dihydrodicyclopentadienyl acrylate, isobornyl methacrylate, tert-butyl acrylate, acrylic acid, methyl methacrylate, styrene and styrene derivatives, such as 4-acetoxy styrene, alpha-methylstyrene, 3-methyl styrene, 4-methylstyrene, N,N-dimethylacrylamide, N-tert-butylacrylamide, N-isopropylacrylamide, isobornyl acrylate, acrylonitrile, methacrylonitrile, hydroxyethyl methacrylate, cyclohexyl methacrylate, tert-butylcyclohexyl methacrylate, 3,4-epoxycyclohexylmethyl methacrylate, glycidyl methacrylate, ethyl methacrylate, benzyl methacrylate, phenyl methacrylate, isobutyl methacrylate, stearyl acrylate, vinyl acetate, n-butyl methacrylate, methyl acrylate, 2-phenoxyethyl acrylate, and 2-(3-toloidylureido)ethyl methacrylate.

15. The process as claimed in claim 2, characterized in that i) the at least one monomer B has a molecular weight of less than 2000 g/mol; and/or ii) the at least one monomer B contains imidazole, pyridine or derivatives thereof as aromatic heterocyclic group containing at least one nitrogen atom in the ring; and/or iii) in that the aromatic heterocyclic group containing the at least one nitrogen atom in the ring is bonded to the polymer backbone of the resultant copolymer by a spacer group having 2 to 20 atoms; and/or iv) the at least one monomer B is contained in 20 to 70 mol %, based on the total monomers of the copolymer; and/or v) the at least one monomer B contains no —OH radical.

16. The process as claimed in claim 3, characterized in that i) the at least one monomer B has a molecular weight of less than 2000 g/mol; and/or ii) the at least one monomer B contains imidazole, pyridine or derivatives thereof as aromatic heterocyclic group containing at least one nitrogen atom in the ring; and/or iii) in that the aromatic heterocyclic group containing the at least one nitrogen atom in the ring is bonded to the polymer backbone of the resultant copolymer by a spacer group having 2 to 20 atoms; and/or iv) the at least one monomer B is contained in 20 to 70 mol %, based on the total monomers of the copolymer; and/or v) the at least one monomer B contains no —OH radical.

17. The process as claimed in claim 2, characterized in that the molar ratio of the monomers A to monomers B is from 30 to 60:40 to 70.

18. The process as claimed in claim 3, characterized in that the molar ratio of the monomers A to monomers B is from 30 to 60:40 to 70.

19. The process as claimed in claim 4, characterized in that the molar ratio of the monomers A to monomers B is from 30 to 60:40 to 70.

20. The process as claimed in claim 2, characterized in that the at least one radical initiator is a UV radical initiator or a thermal radical initiator; and/or the at least one radical initiator is contained in less than 10 mol % based on 100 mol % of the monomers A to C.

Description

EXPERIMENTAL SECTION

[0228] Shelf Life

[0229] The shelf life (SL) of the (uncured) copolymers was determined via DSC. For this purpose the heat of reaction of a fresh mixture of Epikote828LVEL with 7.03% of dicyandiamide (Dyhard 100SF) and, unless otherwise noted, 5 phr of the copolymer under test is determined (ΔH.sub.fresh) and compared with the residual heat of reaction of the storage at 60° C. for 10 d (ΔH.sub.10d60).

SL=ΔH.sub.10d60/ΔH.sub.fresh

[0230] Shelf life is satisfactory in the sense of the invention at SL>85%, more particularly >95%, and is denoted in the experiments by “pass”.

[0231] Tpeak

[0232] T.sub.peak is the temperature of the curing curve, determined by DSC, from the shelf life measurement that is achieved at the maximum of the exothermic reaction signal.

[0233] Raw materials used:

[0234] List of monomers used in preparing the illustrative polymers

[0235] a) High-Tg Monomers

[0236] “TUEMA” 2-(3-toloidylureido)ethyl methacrylate (homopolymer Tg˜137° C.)

[0237] “PhMal” n-phenylmaleimide (homopolymer Tg˜325° C.)

[0238] “MMA” methyl methacrylate (homopolymer Tg˜105° C.)

[0239] “S” styrene (homopolymer Tg˜100° C.)

[0240] b) Monomers having tertiary aromatic amine side groups

[0241] “Vlm” vinylimidazole (homopolymer Tg˜131° C.)

[0242] “ImEMA” imidazoleethyl methacrylate (homopolymer Tg˜60° C.)

[0243] “ImEUr-M” imidazoleethylurethane methacrylate (homopolymer Tg˜32° C.)

[0244] “2M-ImEMA” 2-methylimidazoleethyl methacrylate (homopolymer Tg˜76° C.)

[0245] “DMAP-M” N-methyl-N-(4-pyridylamino)ethyl methacrylate (homopolymer Tg˜29° C.)

[0246] PMI (TCI Chemicals, not purified before use), MMA (Sigma Aldrich, distilled before use), S (Merck, distilled before use) and Vim (Sigma-Aldrich, not purified before use).

[0247] Preparation of the Noncommercial Monomers p-Toluidineureaethyl Methacrylate (TUEMA)

##STR00005##

[0248] A two-neck flask was charged under a nitrogen atmosphere with 0.760 g (7.09 mmol) of p-toluidine and 0.0365 g (0.325 mmol) of 1,4-diazabicyclo[2.2.2]octane in 10 ml of tetrahydrofuran. The solution was admixed dropwise with 1.00 ml (7.08 mmol) of 2-isocyanatoethyl methacrylate. The reaction mixture was subsequently stirred at 60° C. for 3 h and the solvent was removed under reduced pressure. The resulting crude product was dissolved in DCM, washed once with water and twice with saturated sodium chloride solution, the solution was dried using magnesium sulfate, and the solvent was subsequently removed under reduced pressure. Purification by column chromatography (silica gel; nH:EE 2:1 to 1:1) gave 1.60 g (6.10 mmol; 86%) of a beige solid.

[0249] Imidazoleethyl Methacrylate (ImEMA)

[0250] 1)

##STR00006##

[0251] In a two-neck flask with reflux condenser, 8.01 g (0.118 mol) of imidazole and 16.0 g of ethylene carbonate (0.182 mol) were dissolved in 30 ml of toluene and heated under reflux for 6 h. After cooling to room temperature, the toluene phase was taken off and 11 ml of concentrated hydrochloric acid were added with water-bath cooling. The solution was washed three times with DCM and the aqueous phase was adjusted to a pH of 12 by addition of potassium carbonate. The aqueous phase was extracted with dichloromethane and the solution obtained was dried using magnesium sulfate, and the solvent was subsequently removed under reduced pressure. This gave 6.14 g (0.0548 mol; 47%) of the product in the form of an oily brown liquid.

[0252] 2)

##STR00007##

[0253] In a two-neck flask under a nitrogen atmosphere, a solution of 1.92 g (17.1 mmol) of hydroxyethylimidazole, 2.80 ml of triethylamine (20.2 mmol) and 10 mg of phenothiazine in 8 ml of THF was admixed slowly dropwise in an ice bath with a solution of 2.00 ml (20.5 mmol) of methacryloyl chloride in 4 ml of THF. The solution was allowed to warm to room temperature overnight and the solid form was subsequently removed by filtration. The solvent was subsequently removed under reduced pressure. Purification by column chromatography (silica gel) using DCM:MeOH 100:3 gave 2.15 g (11.9 mmol; 70%) of a yellowish liquid.

[0254] 2-Methylimidazoleethyl Methacrylate (2M-ImEMA)

[0255] 1)

##STR00008##

[0256] In a two-neck flask with reflux condenser, 5.00 g (0.0609 mol) of 2-methylimidazole and 8.34 g of ethylene carbonate (0.0947 mol) were dissolved in 20 ml of toluene and heated under reflux for 5 h 30 min. After cooling to room temperature, the toluene phase was taken off and 11 ml of concentrated hydrochloric acid were added with water-bath cooling. The solution was washed three times with DCM and the aqueous phase was adjusted to a pH of 12 by addition of potassium carbonate. The aqueous phase was extracted with dichloromethane and the solution obtained was dried using magnesium sulfate, and the solvent was subsequently removed under reduced pressure. This gave 4.58 g (0.0363 mol; 60%) of the product in the form of an oily brown liquid.

[0257] 2)

##STR00009##

[0258] In a two-neck flask under a nitrogen atmosphere, a solution of 3.21 g (25.4 mmol) of PRO40, 4.30 ml of triethylamine (31.0 mmol) and 10 mg of phenothiazine in 13 ml of THF was admixed slowly dropwise in an ice bath with a solution of 3.03 ml (31.0 mmol) of methacryloyl chloride in 7 ml of THF. The solution was allowed to warm to room temperature overnight and the solid form was subsequently removed by filtration. The solvent was subsequently removed under reduced pressure. Purification by column chromatography (silica gel) using DCM:MeOH 100:3 gave 1.25 g (6.04 mmol; 24%) of a yellowish liquid.

[0259] Methylaminopyridineethyl Methacrylate (DMAP-M)

[0260] 1)

##STR00010##

[0261] In a two-neck flask under a nitrogen atmosphere, 7.51 g (50.1 mmol) of 4-chloropyridine hydrochloride were dissolved in 50.0 ml (622 mmol) of 2-methylaminoethanol and stirred at 120° C. for 14 h. The 2-methylaminoethanol was subsequently distilled off and the residue remaining was dissolved in ethyl acetate and washed three times with saturated sodium chloride solution. Sodium hydroxide was added to the collective aqueous phases, which were extracted three times with ethyl acetate. The collected organic phases were dried using magnesium sulfate, the solvent was removed under reduced pressure, and the crude product was purified by column chromatography (silica gel, DCM:MeOH 10:1 to 10:2). This gave 5.14 g (33.6 mmol; 67%) of a yellow crystalline solid.

[0262] 2)

##STR00011##

[0263] In a two-neck flask under a nitrogen atmosphere, a solution of 2.01 g (13.2 mmol) of PR065, 2.20 ml of triethylamine (15.9 mmol) and 10 mg of phenothiazine in 15 ml of THF was admixed slowly dropwise in an ice bath with a solution of 1.54 ml (15.8 mmol) of methacryloyl chloride in 10 ml of THF. The solution was allowed to warm to room temperature overnight and the solid form was subsequently removed by filtration. The solvent was subsequently removed under reduced pressure. Purification by column chromatography (silica gel; DCM:MeOH 100:1) gave 1.62 g (7.35 mmol; 55%) of a yellowish liquid.

[0264] Imidazoleethylurethane Methacrylate (ImEUr-M)

[0265] 1)

##STR00012##

[0266] In a two-neck flask with reflux condenser, 8.01 g (0.118 mol) of imidazole and 16.0 g of ethylene carbonate (0.182 mol) were dissolved in 30 ml of toluene and heated under reflux for 6 h. After cooling to room temperature, the toluene phase was taken off and 11 ml of concentrated hydrochloric acid were added with water-bath cooling. The solution was washed three times with DCM and the aqueous phase was adjusted to a pH of 12 by addition of potassium carbonate. The aqueous phase was extracted with dichloromethane and the solution obtained was dried using magnesium sulfate, and the solvent was subsequently removed under reduced pressure. This gave 6.14 g (0.0548 mol; 47%) of the product in the form of an oily brown liquid.

[0267] 2)

##STR00013##

[0268] A two-neck flask was charged under a nitrogen atmosphere with 1.59 g (14.2 mmol) of hydroxethylimidazole and 0.0801 g (0.714 mmol) of 1,4-diazabicyclo[2.2.2]octane in 30 ml of tetrahydrofuran. The solution was admixed dropwise with 2 ml (14.2 mmol) of 2-isocyanatoethyl methacrylate. The reaction mixture was subsequently stirred at 65° C. for 6 h and the solvent was removed under reduced pressure. Purification by column chromatography (silica gel) DCM:MeOH 100:1 to 100:5) gave 2.89 g (11.1 mmol; 86%) of a beige solid.

[0269] Polymerization

[0270] General protocol:

[0271] The respective monomer compositions, 5 mol % of AIBN and chain transfer agent (mercaptoethanol, where used) were dissolved in DMF (30% strength solution) and the solutions were each flushed with argon for 3 min. the polymerization was carried out subsequently in an oil bath at 65° C. for 22 h. Polymers obtained were precipitated from diethyl ether and dried under reduced pressure at 60° C.

[0272] List of Illustrative Polymers

TABLE-US-00001 Monomer Mercaptoethanol/ Mn, Tg/ Monomers Composition feed mol % Mw ° C. B1 TUEMA:Vlm 52:48 1:1 2 5500, 135 10800 B2 TUEMA:ImEMA 56:44 1:1 84000, 117 115000 B3 TUEMA:ImEMA 54:46 1:1 5 1700, 83 2100 B4 TUEMA:ImEMA:PhMal 30:60:10 27:63:10 1500, 114 1800 B5 TUEMA:ImEMA:PhMal 36:54:10 36:54:10 3500, 119 9600 B6 TUEMA:ImEMA:PhMal 47:43:10 45:45:10 5 4200, 116 12600 B7 TUEMA:ImEMA 80:20 4:1 2 n.b. 119 B8 MMA:ImEMA:PhMal 21:49:30 20:50:30 1500, 113 1700 B9 MMA:ImEMA 51:49 1:1 91 B10 TUEMA:2M-ImEMA 50:50 1:1 129 B11 TUEMA:DMAP-M 56:44 1:1 2200, 118 4800 V3 ImEMA 100 1 <1000 60

TABLE-US-00002 TABLE 1 Name SL T peak B1 pass 166 B2 pass 156 B3 pass 155 B4 pass 152 B5 pass 152 B6 pass 153 B7 pass 167 B8 pass 154 B9 pass 151 B10 pass 156 B11 pass 171 V1 pass 172

[0273] Table 1 reports the Tpeak temperatures of the respective polymers, along with an indication of whether they gained a pass or a fail in the storage test.

[0274] The activating effect of the nitrogen-containing aromatic heterocyclic group is particularly effective, surprisingly, when it is not bonded directly on the polymer backbone. This becomes clear in the comparison of B1 and B2. In fact both accelerators are storage-stable and exhibit an accelerating effect. The peak temperature of B2, however, is 10° C. lower. Without being tied to any theory, it is assumed that the decoupling from the polymer backbone by at least 2, preferably 4, atoms means that on exceedance of the Tg the amino groups are more readily accessible for the reactive resin.

[0275] B4-B7 are examples of the invention with different amounts of monomers B in the polymer (20%-60%). The examples are storable and exhibit highly activating properties (B4-B6 T.sub.peak=152/153° C., B7 T.sub.peak=167° C.). The activating property of B7, with only 20% of monomer B, appears initially to be relatively weak. In the DSC experiment, however, the same amount of accelerator (5 phr) was used. Owing to the lower amount in the copolymer, therefore, there are fewer accelerating groups present in the curing tests. This can be counteracted by simply increasing the amount of accelerator. Surprisingly the activating effect does not rise in line with the rising amount of monomer B, as is readily apparent not only in the range of the invention between 45% and 60% (B4-B6) but also in the counter—example V1, which consists 100% of ImEMA. Without being tied to any theory, it is assumed that where the fractions of ImEMA are too high, there is a sharp reduction in the solubility, which is introduced by way of the high-Tg monomers (monomers A), and so the accelerating monomers B are not available in sufficient form.

[0276] With commercially available high-Tg monomers as well, such as MMA and n-Phenylmalimide, accelerator polymers of the invention can be obtained. This is shown with B8 and B9.

[0277] Imidazoles have emerged as being particularly reactive and at the same time highly storable (B2 unsubstituted imidazole, B10 methylimidazole). Other tertiary aromatic amino groups as well, however, have an accelerating effect and can nevertheless be used for highly storable epoxy resin adhesives. This is shown illustratively in B11 with a tertiary aromatic amine comparable to DMAP.

[0278] Use in Reactive Pressure-Sensitive Adhesive

[0279] Raw Materials Used

[0280] Breon N41H80 Hot-polymerized nitrile-butadiene rubber with an acrylonitrile fraction of 41 wt % from Zeon Chemicals (London, UK). Mooney viscosity as per technical datasheet 70-95.

[0281] PolyDis PD3611 Nitrile rubber-modified epoxy resin based on bisphenol-F diglycidyl ether with an elastomer content of 40 wt % and a weight per epoxide of 550 g/eq from Schill+Seilacher “Struktol”. Viscosity at 25° C. of 10000 Pa s.

[0282] PolyDis PD3691 Nitrile rubber-modified epoxy resin based on bisphenol-A diglycidyl ether with an elastomer content of 5 wt % and a weight per epoxide of 205 g/eq from Schill+Seilacher “Struktol”. Viscosity at 25° C. of 300 Pa s.

[0283] Dyhard 100S Latent hardener from AlzChem for epoxy systems, consisting of micronized dicyandiamide in which 98% of the particles are smaller than 10 μm.

[0284] Dyhard UR500 Latent, dimethylurea-based accelerator for epoxy systems, in which 98% of the particles are smaller than 10 μm.

[0285] Adhesives

[0286] Adhesive composition K1 Adhesive composition KV1

TABLE-US-00003 K1 KV1 Parts by Parts by weight Raw material weight Raw material 15 Breon N41H80 15 Breon N41H80 60 PD3611 60 PD3611 22 PD3691 22 PD3691 3 Aerosil R202 3 Aerosil R202 4.14 Dyhard 100S 4.14 Dyhard 100S 0.82 Polymer B2 0.41 Dyhard UR500 K1 KV1 Peel adhesion 15 16 (steel)/N cm.sup.−1 Bond strength/ 15.3 17.2 MPa (15 min 180° C.) 30 min 180° C. 20.4 19.6 40 min 180° C. 21.9 22.7 SL.sub.40/% 100 41 SL.sub.80/% 99 0

[0287] K1 in comparison to KV1 with the commercial dimethylurea accelerator Dyhard UR500 shows that the accelerators of the invention (polymer B2) achieve comparable bond strengths on curing. However, the shelf life of the two adhesives is very different. K1 shows no change in the DSC heat of reaction (SL.sub.40=SL.sub.60=100%) both on storage of 40° C. to 10 d and at 60° C. for 10 d.

[0288] In contrast to this, the adhesive with the commercial urea accelerator KV1 has already undergone 59% reaction (SL.sub.40=41%) after storage at 40° C. for 10 d, and on storage of 60° C. is completely cured after 10 d.