METHOD FOR PREPARING AN ADHESIVE TAPE OR MOLDING MASS

Abstract

A polymerizable composition which may be used as an adhesive mass in a method for preparing an adhesive tape or as molding mass in a method for preparing molded articles is provided. The polymerizable composition contains: A) a thermal cationic initiator, or B) a combination of a cationic photoinitiator and a thermal free-radical initiator for inducing the polymerization of the cationically polymerizable monomers in such an amount that the heat energy released during polymerization is sufficient for cleaving the thermal initiator. The adhesive mass is curable via a local impulse a) of thermal energy orb) of thermal energy and/or radiation energy through frontal polymerization; or the molding mass is initially prepared by mixing all components and then molded into the desired shape, whereafter its frontal polymerization is induced by a local impulse a) of thermal energy and/or b) of radiation energy in order to prepare a cured molded article.

Claims

1. A use of a polymerizable composition comprising cationically polymerizable monomers, at least one cationic polymerization initiator, and optionally one or more additives, as an adhesive mass in a method for preparing an adhesive tape, wherein the polymerizable composition comprises A) a thermal cationic initiator, or B) a combination of a cationic photoinitiator and a thermal free-radical initiator for inducing the polymerization of the cationically polymerizable monomers in such an amount that the heat energy released during polymerization is sufficient for causing cleavage of the thermal initiator, so that the adhesive mass is curable via a local impulse a) of thermal energy or b) of thermal energy and/or radiation energy through frontal polymerization.

2. A use of a polymerizable composition comprising cationically polymerizable monomers, at least one cationic polymerization initiator, and optionally one or more additives, in a method for preparing molded articles, wherein the polymerizable composition comprises A) a thermal cationic initiator, or B) a combination of a cationic photoinitiator and a thermal free-radical initiator for inducing the polymerization of the cationically polymerizable monomers in such an amount that the heat energy released during polymerization is sufficient in order to cause cleavage of the thermal initiator; and a molding mass is initially prepared by mixing all components contained therein and then molded into the desired shape, whereafter its frontal polymerization is induced by a local impulse of thermal energy and/or radiation energy in order to prepare a cured molded article.

3. The use according to claim 2, characterized in that the polymerizable composition used as the molding mass i) is flowable before molding and, for molding, is introduced as a casting mass or casting resin into a casting mold or is applied as a coating onto an uneven surface; or ii) is spreadable-pasty before molding and, for molding, is applied as a spackle, filler or mortar onto uneven surfaces; or iii) is solid, but plastically moldable, before molding and is used as a modelling mass or putty and molded into the desired shape manually or by means of a tool; whereafter it is frontally polymerized in this shape.

4. The use according to claim 3, characterized in that, at least in the above cases ii) and iii), one or more viscosity modifiers, thickeners and/or rheology modifiers are added to the polymerizable composition in order to adjust predefined viscosities or flow properties.

5. The use according to any one of the claims 1 to 4, characterized in that the thermal cationic initiator is selected from alkylbenzylsulfonium or alkylarylbenzylsulfonium, benzylpyridinium, methylimidazonium, benzylpyrazinium or substituted benzylphosphonium salts of non-nucleophilic bases of very strong acids, wherein the cationic photoinitiator is optionally selected from alkylbenzylsulfonium or alkyl-arylbenzylsulfonium, benzylpyridinium, methylimidazolium, benzylpyrazinium or substituted benzylphosphonium salts of B(C6F5)4-, SbF6-, AsF6-, PF6- or BF4- or the tetrakis(perfluoro-t-butyloxy)aluminate anion or mixtures thereof, wherein the thermal cationic initiator is optionally selected from alkylbenzylsulfonium or alkylarylbenzylsulfonium salts of SbF6- or the tetrakis(perfluoro-t-butyloxy)aluminate anion.

6. The use according to any one of the claims 1 to 4, characterized in that i) the cationic photoinitiator is selected from aryl-substituted iodonium, phosphonium, sulfonium, pyridinium or diazonium salts, wherein the cationic photoinitiator is optionally selected from diaryliodonium salts of non-nucleophilic bases of very strong acids and mixtures thereof, wherein the cationic photoinitiator is optionally selected from diaryliodonium salts of B(C6F5)4-, SbF6-, AsF6-, PF6-, BF4- or the tetrakis(perfluoro-t-butyloxy)aluminate anion or mixtures thereof; and/or ii) the thermal free-radical initiator is selected from benzopinacol or derivatives thereof, peroxides or azo compounds, wherein the thermal free-radical initiator is optionally selected from benzopinacol, dibenzoylperoxide or azobis(isobutyronitrile), wherein the thermal free-radical initiator is optionally benzopinacol.

7. The use according to claim 6, characterized in that the cationic photoinitiator is selected from (4-octyloxyphenyl)(phenyl)iodonium hexafluoroantimonate, bis(4-dodecyl-phenyl)iodonium hexafluoroantimonate, (4-isopropylphenyl)(4′-methylphenyl)iodonium tetra-kis(pentafluorophenyl)borate or iodonium salts of the tetrakis(perfluoro-t-butyloxy)aluminate anion.

8. The use according to any one of the claims 1 to 7, characterized in that the cationic polymerizable monomers are selected from monovalent or multivalent epoxides (oxiranes), thiiranes (episulfides), oxetanes, lactams, lactones, lactides, glycolides, tetrahydrofuran or mixtures thereof, preferably epoxides, in particular epoxy novolak prepolymers.

9. The use according to any one of the claims 1 to 8, characterized in that, in the polymerizable composition, a) the thermal cationic initiator is present in a proportion of 0.5 to 6 wt. %, optionally 1 to 4 wt. %, optionally 1.5 to 2 wt. %, based on the total weight of the cationic polymerizable monomers; or b1) the cationic photoinitiator and the thermal free-radical initiator of the initiator combination are present in a molar ratio of 1:0.5 to 1:45, optionally 1:2 to 1:10; and/or b2) the initiator combination is present in a proportion of 0.5 to 12 wt. %, optionally 1 to 6 wt. %, optionally 2 to 4 wt. %, based on the total weight of the cationic polymerizable monomers.

10. The use according to any one of the claims 1 to 9, characterized in that the polymerizable composition further comprises additives, selected from, optionally further, thickeners and rheology modifiers, coupling agents, tackifiers, network, impact strength and surface modifiers, film-forming agents, wetting agents, pigments, coloring agents, stabilizers, control agents, flame retardants or fillers, and/or radically polymerizable monomers, optionally selected from acrylates, methacrylates, or acrylamides.

11. The use according to any one of claim 1 and the claims 5 to 10 depending on claim 1, characterized in that, first, the polymerizable composition is prepared by mixing all components contained therein, whereafter it is, as an adhesive mass, i) formed into a transfer adhesive tape, or ii) applied in the form of a layer onto a carrier, wherein the carrier is preferably selected from paper, fabrics, non-woven materials, plastic foils, metal foils, foams or combinations thereof, which are each optionally fiber-reinforced, and more preferably selected from glass-fiber non-wovens and meshes.

12. The use according to any one of claim 1 and the claims 5 to 11 depending on claim 1, characterized in that at least one surface of the adhesive mass is provided with a release sheet.

13. An adhesive tape prepared according to any one of claim 1 and the claims 5 to 12 depending on claim 1.

14. A cured molded article prepared according to any one of the claims 2 to 4 and 5 to 10 depending on claim 2.

Description

EXAMPLES

[0055] In the following, the present invention is described in further detail by means of non-limiting exemplary embodiments that are only provided for illustrative purposes.

Examples 1 to 3— Adhesive Tapes with Carrier

[0056] From each of the following formulations comprising a combination of a cationic photoinitiator and a thermal free-radical initiator, an adhesive mass was prepared and then applied onto a carrier, whereafter the side of the mass facing away from the carrier was surface-modified with a melt polymer filler powder.

Example 1

[0057]

TABLE-US-00001 Component Name Amount (wt. %) Cationic Bis(4-tert-butylphenyl)iodonium 2 photoinitiator tetrakis-(perfluoro-t- butyloxy)aluminate Thermal free- 1,1,2,2-Tetraphenyl-1,2- 2 radical initiator ethanediol (benzopinacol) Monomer Epoxy novolak resin 80 epoxy functionality: 3.8 Monomer Bisphenol A diglycidyl ether 16 Σ 100

Example 2

[0058]

TABLE-US-00002 Component Name Amount (wt. %) Cationic (4-Isopropylphenyl)(4′- 3 photoinitiator methylphenyl)iodonium tetrakis(pentafluorophenyl)borate Thermal free- 1,1,2,2-Tetraphenyl-1,2- 3 radical initiator ethanediol (Benzopinacol) Monomer Epoxy novolak resin 75 epoxy functionality: 3.8 Monomer Bisphenol A diglycidyl ether 19 Σ 100

Example 3

[0059]

TABLE-US-00003 Component Name Amount (wt. %) Cationic Bis(4-tert-butylphenyl)iodonium 3 photoinitiator tetrakis-(perfluoro-t- butyloxy)aluminate Thermal free- 2,2,7,7-Tetramethyl-4,4,5,5- 3 radical initiator tetraphenyl-3,6-dioxa-2,7- disilaoctane (Benzopinacol- bis(trimethylsilyl ether) Monomer Epoxy novolak resin 75 epoxy functionality: 3.8 Monomer Bisphenol A diglycidyl ether 19 Σ 100

[0060] Preparation of Adhesive Masses

[0061] From each the three formulations above, 200 g of adhesive mass were prepared by weighing in the thermal free-radical initiator, the cationic photoinitiator and the monomers in the given proportions and stirring them in a dissolver (e.g., IKA Ultra-Turrax) until a clear homogeneous solution was obtained.

[0062] Preparation of Adhesive Tapes

[0063] For preparing the carrier, a glass-fiber nonwoven tape having a width of 50 mm and a thickness of 0.5 mm plus a glass-fiber mesh tape self-adhesive on one side having a width of also 50 mm and a thickness of 0.25 mm were bonded to each other, whereafter one of the adhesive masses prepared above was applied to a nonwoven side of the carrier tape at a temperature of 50° C. and uniformly distributed on the carrier using a spatula so that a uniform thickness of the adhesive mass of 2 mm and a weight ratio of adhesive mass and carrier of 10:1 were obtained. Then, ethylene-vinyl acetate (EVA) copolymer powder was sprinkled as a melt polymer filler onto the mass in an amount of 5 parts per weight per 100 parts per weight of adhesive mass, on the surface of which it fused with the formulation. During cooling, the viscosity of the adhesive mass thus obtained increased until it was not flowable anymore, which resulted in an adhesive tape that was compact and flexible at room temperature.

[0064] Bonding of Bonding Partners

[0065] The adhesive tapes prepared as described above were each cut to a length of 10 cm and twice wrapped around a wooden bar, wherein the adhesive mass showed good initial bonding in all cases. Subsequently, the wrapping of the adhesive mass was, at one location, heated for 3 s using a lighter (Examples 1 and 3) or irradiated for 3 s using an LED UV lamp Omnicure Series 2000 (Example 2), with the flame or the lamp being kept at a distance of approximately 2 cm from the side of the adhesive tape. In all three cases, the polymerization reaction thus initiated travelled through the entire adhesive mass of the adhesive tape in the form of a “curing front”. In this way, the adhesive masses of the three adhesive tapes cured completely within 30 s to 1 min, which corresponds to curing rates of approximately 10 to 20 cm/min.

Examples 4 to 6— Molding Mass

[0066] From the following formulations, each comprising a combination of a cationic photoinitiator and a thermal free-radical initiator, a flowable composition was prepared by mixing the polymerizable components (in amounts that together result in 100 wt. % of the composition), to which various additives were added (in wt. % amounts based on 100 wt. % of the composition without additives) in order to prepare a plastically moldable modelling mass as a molding mass, from which a molded article was subsequently prepared and cured by frontal polymerization according to the present invention.

Example 4

[0067]

TABLE-US-00004 Component Name Amount (wt. %) Cationic Bis(4-tert-butylphenyl)iodonium 1 photoinitiator tetrakis-(perfluoro-t- butyloxy)aluminate Thermal free- 1,1,2,2-T etraphenyl-1,2- 3 radical initiator ethanediol (Benzopinacol) Monomer Epoxy novolak resin 80 epoxy functionality: 3.8 Monomer Bisphenol A diglycidyl ether 16 Σ 100 Additives Thixotropic agent Fumed silica 8 (hydrophobic) Aerosil ® R 812 S Filler Talc 30

Example 5

[0068]

TABLE-US-00005 Component Name Amount (wt. %) Cationic Bis(4-tert-butylphenyl)iodonium 3 photoinitiator tetrakis-(perfluoro-t- butyloxy)aluminate Thermal free- 1,1,2,2-Tetraphenyl-1,2- 3 radical initiator ethanediol (Benzopinacol) Monomer Epoxy novolak resin 75 epoxy functionality: 3.8 Monomer Bisphenol A diglycidyl ether 19 Σ 100 Additives Thixotropic agent Fumed silica 8.5 (hydrophobic) Aerosil ® R 812 S Filler Talc 21.5 Filler Silica sand 8.5

Example 6

[0069]

TABLE-US-00006 Component Name Amount (wt. %) Cationic Bis(4-tert-butylphenyl)iodonium 3 photoinitiator tetrakis-(perfluoro-t- butyloxy)aluminate Thermal free- 1,1,2,2-Tetraphenyl-1,2- 3 radical initiator ethanediol (Benzopinacol) Monomer Epoxy novolak resin 75 epoxy functionality: 3.8 Monomer Bisphenol A diglycidyl ether 19 Σ 100 Additives Thixotropic agent Fumed silica 8 (hydrophobic) Aerosil ® R 812 S Filler Sodium alumosilicate 30

[0070] Preparation of the Polymerizable Compositions

[0071] From each the three formulations above, a flowable polymerizable composition was prepared by weighing in the thermal free-radical initiator, the cationic photoinitiator and the monomers in the given proportions and stirring them in a dissolver (e.g., IKA Ultra-Turrax) until a clear homogeneous solution was obtained.

[0072] Preparation of the Molding Masses

[0073] To the flowable mixtures obtained as described above, the given amount of thixotropic agent was initially added at room temperature, whereafter the other additives were added under constant kneading until a homogeneous mass with Plasticine-like consistency was obtained that was easily moldable by hand and dimensionally stable thereafter.

[0074] In an identical manner as described above, with a suitable selection of the amounts of the components contained, i.e., of the polymerizable components as well as the additives, it is possible to prepare, rather than plastic molding masses, flowable masses, which can be used as casting masses or coatings, or spreadable, paste-like masses, which can be used as a spackle, filler or mortar. The ratios of monomers and additives is of particular importance in this regard, in particular those of viscosity modifiers, thickeners and rheology modifiers, which may optionally be omitted entirely in order to adjust a relatively low viscosity of the molding masses.

[0075] Preparation of Cured Molded Articles

[0076] Each of the molding masses obtained as described above was used to close a hole having a diameter of 1 cm that was previously formed in a PVC pipe having a diameter of 10 cm and to seal the pipe by means of frontal polymerization of the molding mass. Here, an amount of approximately 10 g of the molding mass was formed by hand to obtain a disc having a thickness of 3 cm and a diameter of 3 cm, which was put and pressed onto the hole to be closed and the outer perimeter of which was strongly pressed against the pipe. In all three cases, the modelling masses showed very good initial bonding to the PVC surface. Subsequently, the respective molded article was, at one location, heated for 3 s using a lighter (Examples 1 and 3) or irradiated for 3 s using an LED UV lamp Omnicure Series 2000 (Example 2), with the flame or the lamp being kept at a distance of approximately 2 cm from the side of the adhesive tape. In all three cases, the polymerization reaction thus initiated travelled through the entire adhesive mass of the adhesive tape in the form of a “curing front”. In this way, the molded articles cured completely within 10-12 s, which corresponds to curing rates of approximately 15 cm/min.

[0077] The present invention thus provides a new method for preparing adhesive tapes as well as adhesive tapes thus prepared, by means of which bonding partners can be bonded with each other within a short time and in a very simple manner. Also, it provides a new method for preparing molded articles as well as molded articles thus prepared, by which method articles having different shapes can be formed and cured within a short time and in a very simple manner.