US-12624253-B2 - Method for preparing an adhesive tape or molding mass

US12624253B2US 12624253 B2US12624253 B2US 12624253B2US-12624253-B2

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.

Inventors

Christoph SCHNÖLL
Robert Liska
Patrick KNAACK
Moritz Mitterbauer
Daniel GRUNENBERG

Assignees

TECHNISCHE UNIVERSITÄT WIEN

Dates

Publication Date: 20260512
Application Date: 20210122
Priority Date: 20200123

Claims (17)

1 . A method of preparing an adhesive tape comprising using a polymerizable composition comprising cationically polymerizable monomers, at least one cationic polymerization initiator, and optionally one or more additives, as an adhesive mass, wherein the polymerizable composition comprises as the at least one cationic polymerization initiator: 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, wherein the polymerizable composition is prepared by mixing all components contained therein, whereafter it is, as an adhesive mass, applied in the form of a layer a) onto a carrier or b) onto a release sheet to form a transfer adhesive tape; whereafter optionally the exposed surface of the layer is covered with a) a release sheet or b) another release sheet.
2 . A method for preparing molded articles comprising using a polymerizable composition comprising cationically polymerizable monomers, at least one cationic polymerization initiator, and optionally one or more additives, wherein the polymerizable composition comprises as the at least one cationic polymerization initiator: 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; wherein the polymerizable composition used as the molding mass is spreadable-pasty before molding and, for molding, is applied as a spackle, filler or mortar onto uneven surfaces or 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; and optionally wherein, before molding, 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.
3 . The method according to claim 1 , wherein 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 as anions, wherein the cationic photoinitiator is optionally selected from alkylbenzylsulfonium or alkylarylbenzylsulfonium, benzylpyridinium, methylimidazolium, benzylpyrazinium or substituted benzylphosphonium salts of B(C 6 F 5 )4-, SbF 6 − , AsF 6 —, PF 6 — or BF 4 — or the tetrakis(perfluoro-t-butyloxy)aluminate anion or mixtures thereof, and wherein the thermal cationic initiator is optionally selected from alkylbenzylsulfonium or alkylarylbenzylsulfonium salts of SbF 6 — or the tetrakis(perfluoro-t-butyloxy)aluminate anion.
4 . The method according to claim 1 , wherein: 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 as anions and mixtures thereof, wherein the cationic photoinitiator is optionally selected from diaryliodonium salts of B(C 6 F 5 )4-, SbF 6 —, AsF 6 —, PF 6 —, BF 4 — 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.
5 . The method according to claim 1 , wherein the cationic photoinitiator is selected from (4-octyloxyphenyl)(phenyl)iodonium hexafluoroantimonate, bis(4-dodecylphenyl)iodonium hexafluoroantimonate, (4-isopropylphenyl)(4′-methylphenyl)iodonium tetrakis(pentafluorophenyl)borate, or iodonium salts of the tetrakis(perfluoro-t-butyloxy)-aluminate anion.
6 . The method according to claim 1 , wherein the cationic polymerizable monomers are selected from monovalent or multivalent epoxides (oxiranes), thiiranes (episulfides), oxetanes, lactams, lactones, lactides, glycolides, tetrahydrofuran or mixtures thereof.
7 . The method according to claim 1 , wherein in the polymerizable composition, a) the thermal cationic initiator is present in a proportion of 0.5 to 6 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; and/or b2) the initiator combination is present in a proportion of 0.5 to 12 wt. % based on the total weight of the cationic polymerizable monomers.
8 . The method according to claim 1 , wherein the polymerizable composition further comprises additives selected from the group consisting of 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.
9 . The method according to claim 1 , wherein the adhesive mass is applied in the form of a layer onto a carrier selected from paper, fabrics, non-woven materials, plastic foils, metal foils, foams, or combinations thereof, wherein the carrier is optionally fiber-reinforced.
10 . An adhesive tape prepared by to the method according to claim 1 .
11 . A cured molded article prepared by to the method of claim 2 .
12 . The method according to claim 2 , wherein 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 as anions, wherein the cationic photoinitiator is optionally selected from alkylbenzylsulfonium or alkylarylbenzylsulfonium, benzylpyridinium, methylimidazolium, benzylpyrazinium or substituted benzylphosphonium salts of B(C 6 F 5 )4-, SbF 6 − , AsF 6 —, PF 6 — or BF 4 — or the tetrakis(perfluoro-t-butyloxy)aluminate anion or mixtures thereof, and wherein the thermal cationic initiator is optionally selected from alkylbenzylsulfonium or alkylarylbenzylsulfonium salts of SbF 6 — or the tetrakis(perfluoro-t-butyloxy)aluminate anion.
13 . The method according to claim 1 , wherein: 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 as anions and mixtures thereof, wherein the cationic photoinitiator is optionally selected from diaryliodonium salts of B(C 6 F 5 )4-, SbF 6 —, AsF 6 —, PF 6 —, BF 4 — 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.
14 . The method according to claim 2 , wherein the cationic photoinitiator is selected from (4-octyloxyphenyl)(phenyl)iodonium hexafluoroantimonate, bis(4-dodecyl-phenyl)iodonium hexafluoroantimonate, (4-isopropylphenyl)(4′-methylphenyl) iodonium tetrakis-(pentafluorophenyl)borate, or iodonium salts of the tetrakis(perfluoro-t-butyloxy)aluminate anion.
15 . The method according to claim 2 , wherein the cationic polymerizable monomers are selected from monovalent or multivalent epoxides (oxiranes), thiiranes (episulfides), oxetanes, lactams, lactones, lactides, glycolides, tetrahydrofuran or mixtures thereof.
16 . The method according to claim 2 , wherein in the polymerizable composition, a) the thermal cationic initiator is present in a proportion of 0.5 to 6 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; and/or b2) the initiator combination is present in a proportion of 0.5 to 12 wt. % based on the total weight of the cationic polymerizable monomers.
17 . The method according to claim 2 , wherein the polymerizable composition further comprises additives selected from the group consisting of 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.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a Section 371 of International Application No. PCT/EP2021/051447, filed Jan. 22, 2021, which was published in the German language on Jul. 29, 2021 under International Publication No. WO 2021/148602 A1, which claims priority under 35 U.S.C. § 119(b) to Austrian Application No. A 19/2020, filed Jan. 23, 2020, and Austrian Application No. A 20/2020, filed Jan. 23, 2020, the disclosures of which are incorporated herein by reference in their entireties. The invention relates to the preparation of adhesive tapes and molded articles using special polymerizable compositions, as well as adhesive tapes and molded articles thus prepared. STATE OF THE ART Adhesive masses curable via polymerization have been known for various types of resin compositions for a long time, curing of which can be induced in many different ways such as thermically, photochemically or by absorption of humidity. However, all embodiments have the common disadvantage that the surface of the adhesive mass entering into contact with the adhesion partners to be bonded always has to be completely activated, for example, heated or irradiated, in order to induce polymerization in the entire adhesive mass. Additionally, if large areas of the surfaces of two adhesion partners are to be bonded, where sometimes a transfer adhesive tape is used, i.e., a carrier-free adhesive tape that is protected on both sides with a release sheet before use, the adhesion process is particularly cumbersome because often, depending on the nature of the adhesive mass, both adhesive surfaces of the transfer adhesive tape have to be completely activated. For this purpose, a release sheet has to be removed, the adhesive tape has to be activated on one side and then adhered to one of the bonding partners, whereafter the opposite adhesive surface also has to be activated after removing the other release sheet, before it is brought into contact with the second bonding partner, which usually has to be pressed on. However, depending on the speed of the polymerization induced by the activation, time frames for these processes are strongly limited, often to only a few seconds, or it takes a very long time, after the two bonding partners have been bonded, for the adhesive mass to harden sufficiently in order to guarantee a stable connection between the bonding partners, for example, several hours up to 1 to 2 days. Herein, the term of “adhesive tape” includes, in addition to the common embodiments of carrier tapes adhesively coated on one or both sides and carrier-free transfer adhesive tapes, also fixing tapes or repair wrapping tapes as disclosed in, for example, US 2015/047769 A1. These are mostly porous or perforated or foamed carrier tapes that are impregnated or soaked with a polymerizable composition and are, during use, wrapped around a location to be repaired and then cured in order to prepare a dimensionally stable, cured composition. According to US 2015/047769 A1 such a porous carrier tape is, for example, impregnated with a composition curable by reaction with water, wherein the water is to be added immediately before using the composition, which thus constitutes a two-component system. Subsequently, the tape is once or twice wrapped around a defective workpiece, for example, around a location around a hole in a pipe, or around two pieces to be bonded to each other, for example, around a fracture of a broken bar or a broken pipe, and allowed to cure, which usually takes a few minutes. In such cases, the adhesive strength of the polymerizable composition as “adhesive mass” of such tapes is rather low because they only serve to prevent slipping off from the application site before the curing process starts, while fixing or repairing is achieved by the formation of a dimensionally stable sheath around the workpiece(s) during curing. The embodiments disclosed in US 2015/047769 A1 specifically have the general disadvantage of two-component polymerization systems, i.e., that there is only a relatively short pot life after mixing of the two components of the curable composition in order to move the tape to the desired position before curing reaches a point after which the mass cannot be firmly wrapped around the workpiece(s) anymore. For various types of resin compositions, molding masses curable by polymerization have also been known for a long time, the curing of which can be induced in many different ways such as thermically, photochemically or by absorption of humidity. The latter are, for example, disclosed in WO 2008/065406 A1, which describes a silicone elastomer mass vulcanizable by H2O absorption at room temperature. However, all these embodiments have the common disadvantage that either only relatively thin layers or bodies of the molding mass can be provided because the penetration depth of irradiation or water molecules is rather low, i.e., in the range of millimeters or a few centimeters, or the masses have