Fluororubber tackiness agent composition

Abstract

This fluororubber tackiness agent composition is obtained by blending an acrylic tackiness agent containing an acrylic copolymer having a glass transition temperature Tg of 20°C or lower into a modified fluororubber that has a Mooney viscosity ML1+10 (121°C) of 10-80 and that has an unsaturated bond or includes a functional group and an unsaturated bond. The acrylic tackiness agent is used at a proportion of 10-400 parts by weight with respect to 100 parts by weight of the modified fluororubber. The fluororubber tackiness agent composition exhibits excellent adhesiveness and tackiness without making any compromise to heat resistance, chemical resistance, weather resistance, flame retardancy, etc., inherent to fluororubbers.

Description

Fluororubber adhesive composition

[0001] The present invention relates to a fluororubber pressure-sensitive adhesive composition, and more particularly to a fluororubber pressure-sensitive adhesive composition that has excellent adhesiveness and pressure-sensitive adhesiveness without impairing the heat resistance, chemical resistance, weather resistance, flame retardancy, and other properties inherent to fluororubber.

[0002] Conventionally, adhesives have generally been used, such as resin-based adhesives including vinyl acetate resin, ethylene-vinyl acetate copolymer resin, vinyl chloride resin, epoxy resin, urethane resin, styrene resin, acrylic resin, polyamide resin, cyanoacrylate, cellulose resin, silane-based adhesives, and silicone-based adhesives, or rubber-based adhesives including nitrile rubber, styrene-butadiene rubber, and chloroprene rubber. Heat-resistant adhesives generally include acrylic adhesives and silicone adhesives, but acrylic adhesives have lower heat resistance than silicone adhesives, and silicone adhesives have lower adhesive strength than acrylic adhesives. While adhesives other than silicone-based adhesives are difficult to use in long-term heat-resistant applications above 175°C, silicone-based adhesives cannot be used for electronic component applications due to their tendency to contaminate.

[0003] Fluororesins and fluororubbers have excellent heat resistance, including long-term durability at temperatures above 175°C, chemical resistance, weather resistance, and abrasion and wear resistance. However, due to their poor tackiness and adhesive properties, they generally cannot be used alone as pressure-sensitive adhesives or adhesives. Fluororesins and fluororubbers exhibit slight tackiness when not crosslinked, but have poor adhesive properties. Such uncrosslinked fluororubbers can exhibit tackiness and adhesive properties by dehydrofluorinating them with alkali, but because they are not crosslinked, they lack strength, solvent resistance, chemical resistance, and other liquid resistance, pressure resistance, and adhesive strength under heat, limiting their range of use.

[0004] Furthermore, when general fluororubber is crosslinked with polyols, polyamines, peroxides, etc., it is possible to improve its strength, liquid resistance (solvent resistance, chemical resistance, etc.), pressure resistance, and adhesive strength under heat. However, even though its glass transition temperature (Tg) is below room temperature, the adhesiveness and adhesion properties become poor after crosslinking, and therefore crosslinked fluororubber generally cannot be used as an adhesive.

[0005] Furthermore, when crosslinking fluororubbers with polyols such as bisphenol AF or amines such as bifunctional polyamines, dehydrofluorination occurs without calcium hydroxide or a divalent metal oxide such as magnesium oxide, resulting in the formation of carbon-carbon unsaturated bonds. Therefore, while a divalent metal oxide such as magnesium oxide or calcium hydroxide is essential for crosslinking, the bivalent metal oxides absorb moisture, resulting in a rapid curing rate and the inability to store the material in sheet form for long periods of time. Furthermore, calcium hydroxide cures quickly, and when dissolved in an organic solvent, it gels quickly and cannot be used as an adhesive. Furthermore, adding large amounts of inorganic substances such as calcium hydroxide or magnesium oxide results in a loss of adhesiveness, further reducing the adhesiveness after crosslinking.

[0006] Furthermore, peroxide crosslinking of fluororubber requires that crosslinking be carried out in a manner that blocks oxygen, such as by pressing, and does not crosslink exposed areas or areas through which oxygen penetrates, resulting in problems such as poor adhesion and liquid resistance in the uncrosslinked areas. Furthermore, in production, crosslinking must be carried out quickly while blocking air (oxygen), and when an adhesive is prepared by dissolving the rubber composition in an organic solvent, it is difficult to use because gelation occurs quickly, and exposure to air during solvent drying deactivates the peroxide compound, preventing sufficient crosslinking.

[0007] Although general fluororubber can be crosslinked with a crosslinking agent such as an acid acceptor, it cannot be crosslinked with epoxy resin, which has excellent heat resistance and water resistance and can increase adhesive strength. Even if epoxy resin and polyamine are added to general fluororubber, the crosslink density of the fluororubber does not increase, although the epoxy resin reacts with the polyamine, and improvement in adhesiveness and liquid resistance cannot be achieved.

[0008] Patent Document 1 discloses a pressure-sensitive adhesive composition containing a fluorine-based oligomer having a weight-average molecular weight Mw of 3,500 or more, an ionic compound, and an acrylic polymer. While the inclusion of the acrylic polymer improves adhesion, the fluorine-based oligomer has poor compatibility with other polymers, such as acrylic polymers, and therefore migrates to the surface after coating or drying, resulting in reduced surface tack and adhesion. The state of migration of the fluorine-based oligomer to the surface varies depending on the standing time and environmental temperature, preventing stable adhesion. Furthermore, crosslinking further reduces adhesion.

[0009] Patent Document 2 proposes a pressure-sensitive adhesive whose main component is a fluorocopolymer obtained by copolymerizing a (meth)acrylic acid perfluoroalkyl ester monomer, a (meth)acrylic acid alkyl ester monomer, a hydroxyl group-containing acrylic monomer, and a carboxyl group-containing acrylic monomer. However, the adhesive is not particularly high in adhesiveness, and the adhesive strength is low, and the adhesive deteriorates after being exposed to high temperatures for a long period of time, resulting in problems of reduced adhesiveness.

[0010] Japanese Patent No. 7,177,581, Japanese Patent Application Laid-Open No. 2004-292529, Japanese Patent Application Laid-Open No. 2009-108287, Japanese Patent Application Laid-Open No. 2014-105268, Japanese Patent Application Laid-Open No. 3,327,447, Japanese Patent Application Laid-Open No. 3,975,249, Japanese Patent Application Laid-Open No. 2002-030263, Japanese Patent Application Laid-Open No. 59-059764, Japanese Patent Application Laid-Open No. 2-245046

[0011] An object of the present invention is to provide a fluororubber pressure-sensitive adhesive composition that has excellent adhesiveness and tackiness without impairing the heat resistance, chemical resistance, weather resistance, flame retardancy, etc. that are inherent to fluororubber.

[0012] The object of the present invention is to provide a Mooney viscosity ML 1+10 This is achieved by a fluoroelastomer adhesive composition in which a modified fluoroelastomer having a Tg (at 121°C) of 10 to 80 is blended with an acrylic adhesive containing an acrylic copolymer having a glass transition temperature Tg of 20°C or less.

[0013] In the fluororubber pressure-sensitive adhesive composition of the present invention, an acrylic pressure-sensitive adhesive is blended with a modified fluororubber having unsaturated bonds (and functional groups such as carboxyl groups), and the excellent effect of being able to exhibit tackiness that is not as great as that of commercially available acrylic pressure-sensitive adhesives or silicone pressure-sensitive adhesives when made from the fluororubber alone is achieved without impairing the excellent adhesion (heat resistance) of the modified fluororubber after long-term heating, chemical resistance, weather resistance, flame retardancy, etc. This is because the fluorocompound is not copolymerized with the acrylic compound, the adhesion level can be adjusted by adding the acrylic pressure-sensitive adhesive, and the fluororubber is compatible with the acrylic pressure-sensitive adhesive, resulting in a pressure-sensitive adhesive with better heat resistance and adhesion than an acrylic pressure-sensitive adhesive alone.

[0014] Generally, when fluororubber is blended with acrylic rubber or an acrylic adhesive and dissolved in a solvent, the solution undergoes layer separation, and even if coated, the coated surface after drying is non-uniform and thickness variations occur, making it impossible to fully effectively use the resulting product as an adhesive tape or adhesive sheet. However, by alkali-modifying the fluororubber and blending it with an acrylic adhesive, layer separation of the solution can be prevented, the coated surface becomes even, and the product can be fully effectively used as an adhesive tape or adhesive sheet.

[0015] In this way, by using a modified fluororubber that has adhesiveness and bonding properties and is obtained by decomposing, lowering the molecular weight, and adding functional groups to uncrosslinked fluororubber with an inorganic or organic alkali, excellent effects are achieved, such as improved compatibility with acrylic pressure-sensitive adhesives, preventing separation even when mixed, and maintaining a good coating surface.

[0016] This modified fluororubber can be co-crosslinked with the acrylic pressure-sensitive adhesive by using a crosslinking agent commonly used in acrylic pressure-sensitive adhesives, even without the addition of a commonly used acid acceptor. This allows for higher tackiness and adhesiveness. Therefore, inorganic fillers such as acid acceptors are not necessarily required, and the addition of a filler does not deteriorate the tackiness, while the addition of a crosslinking agent can improve the tackiness. Furthermore, without the addition of an acid acceptor, there is no hardening degradation due to the acid acceptor, and the adhesiveness does not decrease significantly with heating. Furthermore, even when other pressure-sensitive adhesives are added, the adhesive has good compatibility, does not separate into layers, and remains uniform after coating and drying.

[0017] Until now, there has not been a pressure-sensitive adhesive that has better heat resistance than acrylic pressure-sensitive adhesives, higher adhesive strength than silicone pressure-sensitive adhesives, is free of silicone contamination, and is highly heat-resistant, but the fluororubber pressure-sensitive adhesive composition of the present invention can provide a pressure-sensitive adhesive that satisfies these requirements. Specifically, for example, when a steel ball with a diameter of 4.8 mm is placed on an adhesive surface formed on an inclined surface at an angle of 30 degrees, the adhesive has such adhesiveness that the steel ball does not roll off.

[0018] Such a fluororubber pressure-sensitive adhesive composition has tack at room temperature, allowing it to be laminated and bonded to a mating substrate at room temperature, and its tackiness and adhesiveness can be further enhanced by oven heating. In addition, because the fluororubber is modified to a low molecular weight, it can be embedded without gaps into the unevenness of the mating substrate, such as the unevenness of a pattern on an electronic board, resulting in high adhesive strength.

[0019] Polyamine crosslinking and polyol crosslinking of binary fluororubbers do not occur without a divalent metal oxide such as magnesium oxide, or an acid acceptor such as calcium hydroxide or hydrotalcite. However, because these particles are large, adhesives containing them may have particles larger than the coating thickness, resulting in reduced tackiness, adhesion, and heat resistance. Furthermore, the particles tend to shed from the adhesive surface, which can cause contamination in semiconductor applications, such as the detachment of inorganic filler particles. The fluororubber adhesive composition of the present invention allows the direct crosslinking reaction between the modified fluororubber and a crosslinking agent such as an epoxy resin, without the addition of a divalent metal oxide such as magnesium oxide, calcium hydroxide, or hydrotalcite, thereby preventing particle contamination from the adhesive surface.

[0020] Furthermore, even without using bisphenol AF, an environmentally hazardous substance, the modified fluororubber is crosslinked by the epoxy resin, and there is little reactive gas generated when the laminate is heated, preventing foaming of the laminate.

[0021] As the fluororubber, a highly fluorinated elastic copolymer, for example, an elastic copolymer of two or more kinds of vinylidene fluoride, hexafluoropropylene, pentafluoropropylene, trifluoroethylene, trifluorochloroethylene, tetrafluoroethylene, vinyl fluoride, perfluoro(methyl vinyl ether), perfluoro(ethyl vinyl ether), perfluoro(propyl vinyl ether), etc., is used, preferably a vinylidene fluoride-hexafluoropropylene copolymer, particularly preferably a vinylidene fluoride-hexafluoropropylene copolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, or a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene-perfluoro(alkyl vinyl ether) quaternary copolymer.

[0022] Patent Document 3 proposes an adhesive composition comprising a non-peroxide-crosslinkable fluororubber polymer, a peroxide-crosslinkable fluororubber polymer, and peroxide. However, although this adhesive composition has excellent heat resistance and solvent resistance, it is not adhesive at room temperature, and the peroxide is deactivated by oxygen in the air, preventing a sufficient crosslinking reaction. Therefore, this adhesive composition, which does not contain an acrylic adhesive, will stick to surfaces such as glass, but if a 30-degree inclined surface is formed and a 4.8 mm diameter steel ball is placed on it, the steel ball will roll away.

[0023] Fluororubber can be produced as a latex by aqueous emulsion polymerization or aqueous suspension polymerization. In aqueous emulsion polymerization, either a water-soluble peroxide alone or a redox system in which it is combined with a water-soluble reducing substance can be used as the reaction initiator system. Examples of water-soluble peroxides include ammonium persulfate, potassium persulfate, and sodium persulfate, and examples of water-soluble reducing substances include sodium sulfite and sodium bisulfite. In this case, a pH adjuster (buffer), such as sodium monohydrogen phosphate, sodium dihydrogen phosphate, potassium monohydrogen phosphate, or potassium dihydrogen phosphate, is used as a stabilizer for the aqueous emulsion.

[0024] As an emulsifier used in emulsion polymerization, a fluorinated carboxylate is generally used, preferably CF3CF2CF2O [CF(CF3)CF2O] n CF(CF3)COONH4 (n: 1 or 2) is used. These emulsifiers are used as aqueous solutions of about 1 to 30% by weight, preferably about 5 to 20% by weight. If the amount of emulsifier is less than this, the monomers and the resulting copolymer cannot be uniformly dispersed in the aqueous medium, and if the amount is too much, it is economically disadvantageous.

[0025] The copolymerization reaction is carried out at a temperature of about 20 to 80°C, preferably about 25 to 60°C. If the polymerization temperature is too high, problems such as foaming may occur during molding. The polymerization pressure is generally about 5 MPa or less.

[0026] Vinylidene fluoride, tetrafluoroethylene, and hexafluoropropylene are copolymerized in an aqueous medium in the presence of an emulsifier represented by the general formula above. Copolymerization in an aqueous medium can also be carried out as a suspension polymerization method, but emulsion polymerization is preferred to obtain the desired average emulsion particle size. The emulsion polymerization reaction is carried out using a water-soluble inorganic peroxide such as ammonium persulfate or a redox system consisting of such a peroxide and a reducing agent as a catalyst, in the presence of a surfactant, typically used at a ratio of about 0.001 to 0.2 wt.% based on the total weight of the charged water, at a pressure of about 0 to 10 MPa, preferably about 0.5 to 4 MPa, and a temperature of about 0 to 100°C, preferably about 20 to 80°C. The fluorinated olefin mixture is preferably fed in portions to maintain the reaction pressure within a constant range. To adjust the pH of the polymerization system, electrolytes with buffering capacity, such as sodium monohydrogen phosphate, sodium dihydrogen phosphate, or potassium dihydrogen phosphate, or sodium hydroxide may be added. Furthermore, if necessary, a chain transfer agent such as ethyl malonate, acetone, or isopropanol may be used appropriately.

[0027] Although the polymerization reaction depends on various polymerization conditions, it is generally completed in about 1 to 15 hours, which is not much different from when ammonium perfluorooctanoate emulsifier is used. After the reaction is complete, an aqueous solution of potassium alum, sodium chloride, calcium chloride, etc. is added to the resulting aqueous emulsion to coagulate the produced polymer, which is then washed with water and dried to obtain a fluorine-containing copolymer.

[0028] Here, fluorosurfactants are widely used as surfactants in emulsion polymerization reactions of fluorine-containing monomers. Among them, perfluorooctanoic acid CF 15COOH or its salt (PFOA) is known to be a surfactant with excellent monomer emulsification and latex stability. However, perfluorinated chemicals are difficult to decompose in the natural environment, and it has recently been discovered that perfluorinated compounds with eight carbon atoms, such as PFOA, have a significantly long-lasting effect on the human body. In addition, due to PFOA's excellent affinity for rubber, after coagulation of rubber latex obtained by emulsion polymerization, the amount of PFOA adhering to and remaining on the resulting fluororubber is high, and there is a strong demand for reducing this.

[0029] To meet such demands, it is considered that a means of imparting environmental degradability to a fluorine-containing emulsifier is to provide a hydrogenated portion in the perfluorinated hydrophobic group of the surfactant compound. In fluorine-containing rubber latex, perfluoroalkyl alkyl phosphonate C n F 2n+1 C m H 2m P(O)(OM 1 )(OM 2 ) as an emulsifier, it is possible to take measures against PFOA without using fluorine-based surfactants.

[0030] When a perfluoroalkyl alkyl phosphonate is used, perfluoroalkyl alkyl phosphonic acid C n F 2n+1 C m H 2m It can be obtained by reacting P(O)(OH)2 (n: an integer of 2 to 6, m: an integer of 1 to 3) with an alkali metal hydroxide or aqueous ammonia. When the alkali metal hydroxide or ammonia is used in an equimolar amount relative to the perfluoroalkylalkylphosphonic acid, it forms a monosalt, and when it is used in a double molar amount, it forms a di-salt. Generally, it is used in an amount equal to or greater than the theoretically required number of moles, and when it is used in an equimolar amount but less than double the molar amount, a mixture of the mono-salt and the di-salt is formed.

[0031] Since these perfluoroalkyl alkyl phosphonates have a linear fluoroalkyl group, they have better solubility in water than fluoropolyether-type emulsifier compounds having equivalent emulsifying performance, and on the other hand, they have lower adhesion to the produced fluororubber than PFOA, so that the amount of residual emulsifier in the fluororubber obtained by coagulating the fluororubber latex obtained by emulsion polymerization using various methods such as salting out, acid precipitation, mechanical stirring, etc. The emulsion polymerization reaction of fluorine-containing monomers using this emulsifier is carried out in the same manner as when a PFOA emulsifier is used.

[0032] The emulsion polymerization reaction is carried out using a water-soluble inorganic peroxide such as ammonium persulfate or a redox system of such a peroxide with a reducing agent as a catalyst, and to adjust the pH within the polymerization system, an electrolyte substance with buffer capacity such as a phosphate (NaHPO, NaHPO, KHPO, etc.) or a borate (NaBO, etc.), or NaOH, etc., may be added. The emulsion polymerization reaction is carried out under pressurized conditions at about 30 to 120°C for about 1 to 48 hours using about 0.001 to 10% by weight, preferably about 0.01 to 5% by weight, of an emulsifier relative to water.

[0033] Furthermore, for the purpose of further enhancing adhesiveness, a modified fluororubber having a weight average molecular weight Mw of 300,000 or less is preferably used. The glass transition temperature Tg is preferably 20° C. or less. When a fluororubber within this range is used, adhesiveness is exhibited by modification, as described below, and the fluororubber can be dissolved in a solvent and applied.

[0034] Patent Document 4 discloses an easy-adhesive composition containing an acrylic resin, a hydroxyl group-containing resin such as a fluororesin, a wax, and a polyisocyanate compound, and Patent Document 5 discloses an adhesive for vinylidene fluoride resins, which adhesive consists of a soft fluororesin, an acrylic resin, a vinylidene fluoride resin, a polyisocyanate, and an organic solvent. However, these compositions bond during a crosslinking reaction, but lose adhesiveness after the crosslinking reaction. Therefore, although they can be used as paints or adhesives, they cannot be used as pressure-sensitive adhesives.

[0035] The molecular weight, molecular weight distribution, and Mooney viscosity of fluororubber can be controlled by adjusting conditions such as the degree of polymerization, amount of alkali, modification temperature, time, etc. The weight average molecular weight Mw is measured by gel permeation chromatography and converted using a calibration curve prepared using standard polystyrene.

[0036] The fluororubber is used after being modified by a known modification method. The modification of fluororubber is carried out by introducing unsaturated bonds through a partial dehydrofluorination reaction by base modification, such as alkali modification using an inorganic or organic alkali, preferably an organic alkali (Patent Documents 6 and 7). This modification treatment removes HF from the fluoropolymer main chain, forming carbon-carbon unsaturated bonds, and the molecular weight of the fluoropolymer is reduced by a chain scission reaction. This allows for decomposition, low molecular weight, and functionalization in a short period of time, resulting in a modified fluororubber with adhesive properties. Inorganic alkali modification exhibits low penetration into the rubber even at room temperature or when heated, so organic alkalis that penetrate into the fluororubber latex at room temperature are preferably used. The organic alkali uniformly modifies the fluororubber, resulting in a more adhesive modified fluororubber.

[0037] Modified fluororubber has unsaturated bonds and functional groups such as carboxyl groups at its terminals. By adding a crosslinking agent, the crosslinking agent reacts with the substrate to be bonded, forming crosslinks, improving adhesion, durability, liquid resistance, solvent resistance, and adhesive strength under heat. This allows the material to be used as an adhesive that takes advantage of the characteristics of fluororubber.

[0038] Furthermore, partial dehydrofluorination forms unsaturated bonds in the main chain, and after the chain scission reaction, functional groups such as carboxyl groups are formed at the molecular chain ends by oxidation reaction, allowing crosslinking with crosslinking agents such as epoxy resins, diamine compounds, polyamine compounds, etc. without the need for an acid acceptor. The number of functional groups resulting from modification is not particularly limited.

[0039] The higher the modification temperature, the more polymeric compounds are produced, and the lower the temperature, the more low-molecular-weight compounds are produced. When using inorganic alkali, modification is not possible unless the fluororubber is heated to above 40°C. When using organic alkali, the modification is carried out at a temperature of approximately 5 to 35°C, as molecular weight control becomes difficult above 40°C. When using organic alkali, the modification takes time to stabilize at temperatures below room temperature. At room temperatures between 20 and 30°C, the modification is stable and occurs in a short time. A short modification time results in greater variation in the state of modification, while a longer modification time reduces this variation. The more modification agent used, the more low-molecular-weight compounds are produced. The modification temperature and amount of modification agent are adjusted according to the required molecular weight. The heating and drying temperature after modification washing is approximately 60 to 150°C, preferably approximately 80 to 120°C. Lower temperatures result in insufficient drying and residual solvent, which can lead to foaming and residual low-molecular-weight compounds during adhesive sheet lamination, resulting in poor adhesion. Higher temperatures result in increased crosslinking, polymerization, and reduced adhesiveness.

[0040] As the organic alkali, at least one selected from 1,8-diazabicyclo[5.4.0]undecene-7 (DBU), 1,5-diazabicyclo[4.3.0]nonene-5 (DBN), tetramethylammonium hydroxide, tetramethylammonium hydroxide, tetrabutylphosphonium hydroxide, etc. As the inorganic alkali, potassium hydroxide, sodium hydroxide, lithium hydroxide, etc. can be mentioned, which are dissolved in water and mixed with the fluororubber.

[0041] The modified fluoroelastomer conforms to Mooney viscosity ML in accordance with JIS K6300-1 (2013), which corresponds to ISO 289:12005. 1+10 (121°C) is 10 to 80, preferably 10 to 50, and the weight average molecular weight Mw is 1.0 × 10 5 ~3.0×10 5 , and the number average molecular weight Mn is 0.3 × 10 5 ~7.0×10 5A Mooney viscosity within this range is used. If the Mooney viscosity is higher than this, the adhesive will not be adhesive, and if it is lower than this, liquid substances will be contained due to decomposition during modification, which will cause staining of the adherend and will actually reduce adhesiveness. Here, Mooney viscosity is measured in accordance with JIS K6300-1 (2013), which corresponds to ISO 289:12005, using a Mooney Viscometer SMV-201 (manufactured by Shimadzu Corporation) under conditions of a temperature of 121°C, a preheating time of 1 minute, and a rotor rotation time of 10 minutes.

[0042] Fluorine rubber Mooney viscosity ML 1+10 The temperature (121°C) is lowered by 15 to 70, preferably 20 to 70, compared to before modification due to the decomposition of the fluororubber caused by modification. This causes adhesion to develop.

[0043] After salting out or coagulation, the modified fluororubber latex liquid or solution can be washed with water to easily and inexpensively remove components other than the fluororubber, forming a non-staining adhesive that can be used for electronic components, semiconductor components, etc. This is because the fluororubber is prepolymerized (partially crosslinked) by heating and drying the water, imparting adhesiveness.

[0044] The acrylic adhesive contains, in addition to acrylic acid monomers and methacrylic acid monomers, acrylic acid ester monomers and methacrylic acid ester monomers with highly crosslinkable functional groups. For example, a copolymer of a monomer containing no functional group, such as ethyl acrylate (EA), butyl acrylate (BA), or methyl methacrylate (MMA), with at least one monomer containing a highly crosslinkable functional group, such as methacrylic acid (MAA) or monobutyl fumarate (MBF), is used.

[0045] Examples of monomers that do not contain functional groups include (meth)acrylates (excluding ethyl methacrylate and methyl methacrylate) having an alkyl group, which are components that facilitate adjusting the Tg of the entire adhesive layer to an appropriate range, such as ethyl acrylate, methyl acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, propyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, vinyl acetate, vinyl propionate, styrene, and (meth)acrylonitrile. Preferably, at least one selected from ethyl acrylate, butyl (meth)acrylate, acrylonitrile, methyl acrylate, 2-ethylhexyl (meth)acrylate, and vinyl acetate is used. By using these monomers, it is possible to more easily adjust the peel strength from the adherend and more easily adjust the Tg of the entire adhesive layer to an appropriate range.

[0046] Examples of monomers containing highly crosslinkable functional groups include monomers having a carboxyl group, a hydroxyl group, an amino group, an acetoacetoxyethyl group, an epoxy group, etc., and preferably, from the viewpoint of versatility, monomers containing at least one group selected from a carboxyl group and a hydroxyl group, and more preferably, monomers containing a carboxyl group.

[0047] Examples of monomers containing a carboxyl group include unsaturated carboxylic acids such as (meth)acrylic acid (methacrylic acid and / or acrylic acid), fumaric acid, maleic acid, itaconic acid, crotonic acid, trimellitic acid, and pyromellitic acid; unsaturated dicarboxylic acid monoesters such as monomethyl itaconate, monobutyl itaconate, monobutyl fumarate, and 2-acryloyloxyethyl phthalic acid; unsaturated tricarboxylic acid monoesters such as 2-(meth)acryloyloxyethyl trimellitic acid and 2-(meth)acryloyloxyethyl pyromellitic acid; and carboxyalkyl (meth)acrylates such as carboxyethyl (meth)acrylate and carboxypentyl (meth)acrylate.

[0048] These monomers are used in proportions of 30-95.5% by weight of monomers without highly cross-linkable functional groups and 0.5-70% by weight of monomers with highly cross-linkable functional groups, and the more low-molecular-weight monomers such as ethyl acrylate are used, the better the compatibility with modified fluororubber tends to be. The degree of cross-linking can be adjusted by copolymerizing monomers with highly cross-linkable functional groups, and increasing the degree of cross-linking increases adhesive strength and liquid resistance, but also decreases adhesion, so the copolymerization ratio is adjusted depending on the application.

[0049] The synthesis of the acrylic copolymer is carried out by polymerizing these monomers in the presence of a polymerization initiator. The polymerization method is not particularly limited, and conventionally known methods can be used, such as solution polymerization, emulsion polymerization, suspension polymerization, and bulk polymerization. Among these, solution polymerization is preferred because of its simplicity. When solution polymerization is used as the polymerization method, reaction solvents such as ethyl acetate, toluene, methyl ethyl ketone, methyl sulfoxide, ethanol, acetone, and diethyl ether are used. These reaction solvents may be used alone or in combination of two or more.

[0050] The polymerization initiator is not particularly limited, and radical polymerization initiators, anionic polymerization initiators, cationic polymerization initiators, etc. can be used. Among them, thermal radical polymerization initiators are preferably used. Examples of thermal radical polymerization initiators include organic peroxides and azo compounds. Examples of organic peroxides include 1,1-bis(tert-hexylperoxy)-3,3,5-trimethylcyclohexane, tert-hexylperoxypivalate, tert-butylperoxypivalate, 2,5-dimethyl-2,5-bis(2-ethylhexanoylperoxy)hexane, tert-hexylperoxy-2-ethylhexanoate, tert-butylperoxy-2-ethylhexanoate, tert-butylperoxyisobutyrate, tert-butylperoxy-3,3,5-trimethylhexanoate, and tert-butylperoxylaurate. Examples of azo compounds include azobisisobutyronitrile and azobiscyclohexanecarbonitrile. These polymerization initiators may be used alone or in combination of two or more.

[0051] Among the resulting acrylic copolymers, those having a Tg of 20° C. or less, preferably 0° C. or less, are used as acrylic adhesives. By using those having such a Tg, the adhesiveness at room temperature is improved.

[0052] The weight-average molecular weight Mw of the acrylic copolymer is preferably about 100,000 to 1,000,000, more preferably about 300,000 to 500,000. The weight-average molecular weight Mw can be adjusted by the polymerization conditions, such as the type or amount of polymerization initiator, polymerization temperature, and monomer concentration. If the weight-average molecular weight Mw is lower than this range, the adhesive strength will be low and foaming will occur after lamination. If the weight-average molecular weight Mw is higher than this range, the compatibility with the modified fluororubber will be poor, the liquid will undergo layer separation, and the surface will lose its adhesiveness.

[0053] The lower the weight-average molecular weight Mw of the acrylic copolymer, the better the adhesiveness, and if it exceeds 1,000,000, adhesiveness will be lost even if the Tg is below 20° C. Commercially available acrylic adhesives can be used instead of acrylic rubber, such as Arontack S-1511X, S-3403, and S-3452YKF, all manufactured by Toagosei; Saibinol AT-193, AT-D40, AT-D50, AT-D45, AT-191, AT-260NT, ATR-1, ATR-373, and ATR-347, all manufactured by Saiden Chemical; CT-5030, manufactured by DIC; and Nissetsu KP-2500, manufactured by Nippon Carbide Industries.

[0054] Patent Document 8 proposes a heat-sensitive adhesive made of a fluorine-containing thermoplastic rubber containing an acrylic polymer, etc. However, this heat-sensitive adhesive is not the type of adhesive used in commercially available adhesive tapes, and since the acrylic polymer is rubber-like, it has almost no tackiness. Therefore, while it can be used as a heat-sensitive adhesive, it cannot be used as a pressure-sensitive adhesive that is applied at room temperature. If a crosslinking agent is added to this adhesive and crosslinked before lamination, it loses its tackiness and adhesiveness. Therefore, the desired adhesiveness cannot be achieved unless the adhesive is applied to the bonding surface before crosslinking. Patent Document 9 also discloses a rubber composition comprising a specific blend of fluorine rubber and acrylic rubber, and an organic peroxide, etc. Similar to the invention described in Patent Document 8, molded articles obtained from the disclosed rubber composition are rubber-like, not the type of adhesive used in commercially available adhesive tapes, and have almost no tackiness at room temperature, making them unusable as pressure-sensitive adhesives.

[0055] In all of these inventions, the fluororubber is combined with a rubber-like acrylic polymer, so the adhesiveness targeted by the present invention cannot be achieved. Although the rubber will stick to surfaces such as glass, if a rubber surface is formed on a slope at an angle of 30 degrees and a steel ball with a diameter of 4.8 mm is placed on it, the steel ball will roll away.

[0056] The acrylic adhesive is blended in a ratio of 10 to 400 parts by weight, preferably 25 to 250 parts by weight, per 100 parts by weight of modified fluororubber. If the blend amount is less than this, the adhesiveness will decrease, while if the blend amount is more than this, the heat resistance and solvent resistance will deteriorate. The adhesiveness can be adjusted depending on the amount of acrylic adhesive. By blending the acrylic adhesive with the modified fluororubber, it is possible to adjust the desired adhesiveness and adhesion that cannot be achieved with the modified fluororubber alone.

[0057] The blending method is generally a method of dissolving the modified fluororubber in a solvent and blending the solution-polymerized acrylic adhesive solution with stirring. Alternatively, a method of modifying the fluororubber with alkali to form a latex and then mixing the emulsion acrylic adhesive, or a method of kneading the solid modified fluororubber with a solvent-free acrylic adhesive using a roll or kneader can also be used.

[0058] By further adding a crosslinking agent to the fluororubber composition, the terminal functional groups of the prepolymerized fluororubber react with the crosslinking agent, and the crosslinking agent further reacts with the substrate to be adhered, resulting in crosslinking, and thus improving durability, liquid resistance, chemical resistance, etc.

[0059] The crosslinking agent is not particularly limited as long as it cures upon heat treatment, and one or more of thermosetting resins such as epoxy resins, phenolic resins, xylene resins, guanamine resins, diallyl phthalate resins, vinyl ester resins, unsaturated polyester resins, furan resins, polyimide resins, polyurethane resins, cyanate resins, maleimide resins, benzocyclobutene resins, and butadiene resins, aromatic diamine compounds, and aliphatic diamine compounds can be used. Epoxy resins are preferred in terms of reactivity, heat resistance, and adhesion to substrates, while aromatic diamine compounds are preferred in terms of pot life. Epoxy resins and aromatic diamine compounds not only enhance adhesion to substrates, but are also capable of crosslinking with both modified fluororubber and acrylic pressure-sensitive adhesives. This contributes to improved adhesion between the cured product of the pressure-sensitive adhesive composition and the modified fluororubber and acrylic pressure-sensitive adhesive, compatibility in the coating solution, and solvent resistance, chemical resistance, water resistance, and water vapor resistance of the sheet after coating and drying. If a crosslinking agent such as epoxy resin is used, the crosslinking reaction will occur even in the presence of oxygen or air. Therefore, even if the crosslinking reaction does not occur by blocking air or oxygen with a press, crosslinking can occur by coating and oven drying, and the adhesive reaction can be carried out with the mating material.

[0060] Examples of epoxy resins include bisphenol-type epoxy resins such as bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, and bisphenol S-type epoxy resins, novolac-type epoxy resins such as phenol novolac-type epoxy resins, cresol novolac-type epoxy resins, and bisphenol A novolac-type epoxy resins, alicyclic epoxy resins, aliphatic chain epoxy resins, diglycidyl ethers of biphenols, diglycidyl ethers of naphthalenediol, diglycidyl ethers of phenols, diglycidyl ethers of alcohols, and alkyl-substituted and hydrogenated versions of these, with cresol novolac-type epoxy resins being preferred. One type of epoxy resin may be used alone, or two or more types may be mixed and used.

[0061] Examples of polyamine compounds that can be used include 4,4'-methylbis(2-ethyl-6-methylaniline), diaminodiphenylsulfone, diaminodiphenylmethane, m-phenylenediamine, diethylenetriamine, triethylenetetramine, isophoronediamine, etc. From the viewpoints of adhesive liquid life, adhesive sheet life, and heat resistance, aromatic diamine compounds are preferred over aliphatic ones.

[0062] The crosslinking agent is used in a ratio of 1 to 50 parts by weight, preferably 4 to 20 parts by weight, per 100 parts by weight of modified fluororubber. The addition of a thermosetting resin improves adhesiveness, adhesion to the substrate, solvent resistance, durability, etc. If the amount is less than this, the adhesive strength is low and liquid resistance and durability are reduced, while if the amount is more than this, compatibility is poor, adhesiveness is lost, and the product becomes hard.

[0063] Examples of curing catalysts for crosslinking include imidazole compounds such as 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-phenylimidazole, 1-benzylimidazole, 1-benzyl-2-methylimidazole, 2,4-diamino-6-[2-methylimidazoline-(1)]-ethyl, and s-triazine. The curing catalyst is used in a ratio of 0.1 to 5 parts by weight, preferably 0.2 to 2.5 parts by weight, per 100 parts by weight of modified fluororubber. If the curing catalyst is used in a lower ratio than this, the curing of the fluororubber will be slower and crosslinking will be reduced. Conversely, if the curing catalyst is used in a higher ratio than this, the curing rate of the fluororubber will increase, resulting in a decrease in the stability of the adhesive organic solvent solution over time, a decrease in adhesion due to a decrease in the storage stability of the coated sheet, and a decrease in adhesion due to an increase in crosslink density or residual catalyst. Depending on the type of epoxy resin and the adjustment of the curing speed, a catalyst may not be used in some cases due to heat treatment.

[0064] To the fluororubber pressure-sensitive adhesive composition, a tackifying resin, a plasticizer, a liquid rubber, a liquid resin, a filler, etc. may be appropriately added or used in combination to adjust the tackiness and adhesiveness, as long as the object of the present invention is not impaired. Here, depending on the heating temperature and heating time after lamination to the counterpart material, the adhesive strength may increase and the pressure-sensitive adhesive may be transferred to the counterpart material. To prevent such transfer, the amount of crosslinking agent may be reduced or a plasticizer, liquid rubber, liquid resin, etc. may be appropriately added or used in combination.

[0065] Examples of tackifying resins include rosin ester tackifying resins with a hydroxyl value of less than 40 mgKOH / g, terpene resins, terpene phenol resins, coumarone-indene resins, alicyclic saturated hydrocarbon resins, C5 petroleum resins, C9 petroleum resins, C ５～９ Copolymerized petroleum resins and the like are included.

[0066] Examples of the plasticizer include phthalate ester-based plasticizers, fatty acid dibasic acid ester-based plasticizers, trimellitate ester-based plasticizers, epoxy-based plasticizers, phosphate ester-based plasticizers, ether-based plasticizers, polyester-based plasticizers, and chlorine-based plasticizers.

[0067] Examples of liquid rubber include isoprene, 1,4-polybutadiene, NBR, and HNBR, each having a viscosity of 10 to 100,000 mPa·s.

[0068] Examples of liquid resins include terpene resins, epoxy resins, polyamide resins, acrylic resins, 1,2-polybutadiene, polyether polycarbonates, polyethylene glycols, and the like, all having a viscosity of 10 to 100,000 mPa·s.

[0069] Known filler materials can be used, including metal hydroxides such as aluminum hydroxide and magnesium hydroxide, metal oxides such as aluminum oxide, antimony oxide, tin oxide, titanium oxide, and manganese oxide, inorganic fillers such as silica, calcium silicate, aluminum silicate, calcium carbonate, silicon nitride, aluminum nitride, boron nitride, talc, mica, and kaolin, reinforcing materials, and various organic and inorganic flame retardants. If the maximum particle size of the filler is larger than the coating thickness of the adhesive, unevenness will occur in the coated sheet, and the adhesiveness can be adjusted by the particle size and the amount of filler added. To increase adhesiveness, it is preferable to add less than 3% or no filler at all.

[0070] The solvent used in the fluororubber pressure-sensitive adhesive composition is not particularly limited as long as the organic solvent dissolves the fluororubber. Examples include ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, di-n-propyl ketone, diisobutyl ketone, phoron, isophorone, cyclohexanone, and cyclohexanone, aromatic hydrocarbon solvents such as toluene and xylene, ester solvents such as ethyl acetate and butyl acetate, and alcohol solvents such as ethanol, 2-propanol, n-butanol, amyl alcohol, and heptanol, and these can also be used as a mixed solvent of two or more of them.

[0071] Examples of substrates to which the fluororubber pressure-sensitive adhesive composition can be applied include reinforcing films such as polyimide films, polyether ether ketone films, polyphenylene sulfide films, aramid films, polyethylene naphthalate films, liquid crystal polymer films, polyethylene terephthalate films, polyethylene films, polypropylene films, TPX films, and fluorine-based resin films, as well as copper, silver, gold, tin, aluminum, indium, and alloys thereof. In some cases, the composition is applied to metals, release films, peeling films, release papers, etc., and then attached to a reinforcing film or metal for transfer.

[0072] The resin material constituting the substrate film may optionally contain antioxidants, ultraviolet absorbers, plasticizers, colorants such as pigments and dyes, and various additives. For example, the substrate may be subjected to known or conventional surface treatments such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, or application of a primer. Such surface treatments may be intended to enhance the adhesion between the substrate film and the pressure-sensitive adhesive layer (the anchoring ability of the pressure-sensitive adhesive layer). The thickness of the substrate film is typically 5 to 200 μm, preferably about 10 to 100 μm. A substrate film having a thickness within this range is preferred because it provides excellent workability in laminating the film to and peeling it from the adherend.

[0073] The adhesive is applied to a thickness of 5-200 μm after drying, typically with a solids concentration of 10-50 wt%, preferably 15-40 wt%. Coating methods include roll coating, die coating, and knife coating, as well as screen printing and partial application using a dispenser or inkjet printer. The viscosity of the coating solution is adjusted to suit each coating method. For example, a viscosity of 500-5,000 mPa·s is preferred for roll coating, and the solids concentration is adjusted appropriately depending on the ambient and liquid temperatures. For example, an organic solvent solution of the adhesive composition is prepared and applied to a resin film layer such as polyimide to form an adhesive layer. This is then dried at approximately 50-200°C for approximately 1-15 minutes to obtain an adhesive film. Acrylic adhesives containing low-molecular-weight substances may foam upon heating after lamination. In such cases, the drying temperature after coating can be increased to approximately 200°C.

[0074] Lamination conforms to JIS Z0237 2009, Test Methods for Adhesive Tapes and Sheets, which corresponds to ISO 29862:2007, 29863:2007, and 29864:2007. The tapes can be laminated and bonded using a roller or roll laminator at room temperature or with heating. Furthermore, when using a vacuum press or heated press to heat the tapes at approximately 150-200°C for 10 seconds to 3 hours (oven crosslinking), adhesive strength can be further improved by post-processing at approximately 150-200°C for 1 minute to 15 hours. After lamination, adhesive strength can also be increased by heating the tapes in an oven at approximately 80-200°C for 1 minute to 24 hours, even without pressing.

[0075] Next, the present invention will be described with reference to examples.

[0076] Reference Example 1 [Preparation of fluororubber latex liquid] A 30 L stainless steel pressure vessel equipped with a stirrer was charged with 15 kg of water and 2.5 g of an emulsifier (Neos product FS-1110), and then the internal space was thoroughly purged with nitrogen gas. Then, 1,285 g of vinylidene fluoride [VdF] and 1,831 g of hexafluoropropene [HFP] were introduced, and the temperature inside the reactor was raised to 70° C. The pressure inside the reactor when the temperature reached 70° C. was 3.09 MPa.

[0077] The VdF / HFP mixed gas with the same weight ratio as that used at the time of charging was used as the initial charging gas, and the internal pressure was 24 kgf / cm 2The autoclave was pressurized until the internal pressure reached 2.94 MPa. Subsequently, 10 g of diethyl malonate was pressurized, and the internal temperature was raised to 80°C. An aqueous polymerization initiator solution prepared by dissolving 5 g of ammonium persulfate in 150 g of water was pressurized into the autoclave to initiate the polymerization reaction. When the internal pressure dropped to 2.842 MPa, the same VdF / HFP mixed gas was pressurized until the internal pressure reached 2.94 MPa. Each time the internal pressure dropped to 2.842 MPa, the same VdF / HFP mixed gas was pressurized until the internal pressure reached 2.94 MPa. This procedure was repeated. Three hours after the first addition of the mixed gas after the start of the polymerization reaction, the addition of a VdF / HFP mixed gas with the same composition was completed. Immediately thereafter, the unreacted gas in the autoclave was purged to terminate the reaction, yielding an aqueous emulsion (fluororubber latex liquid). The fluororubber latex liquid weighed 23 kg (solid content concentration 32%, solid fluororubber 7,310 g).

[0078] [Fluororubber Modification] While stirring 1 kg of fluororubber latex liquid at a liquid temperature of 25°C, 40 g of a 10 wt % aqueous solution of sodium laurate at a liquid temperature of 25°C was added dropwise, and while stirring the latex liquid at 100 rpm, 119.2 g of an aqueous solution of DBU containing 19.2 g of DBU at a liquid temperature of 25°C was added, and the mixture was further stirred at 100 rpm at room temperature for 5 hours to modify the fluororubber.

[0079] [Salting-out of fluororubber] The modified fluororubber latex liquid was added dropwise to 3 kg of 20 wt % NaCl aqueous solution stirred at 400 rpm and finely dispersed by stirring for 5 minutes. Five liters of water was further added, and after stirring for 5 minutes, the mixture was left to stand for 3 minutes to allow the fluororubber to settle. The upper layer was removed, and the fluororubber-modified latex liquid was salted out.

[0080] [Washing of fluororubber with water] Five liters of water was added, the mixture was stirred at 400 rpm for five minutes, and then allowed to stand for two minutes. The modified fluororubber was washed with water, allowed to settle, and the upper layer was removed. This process was repeated five times, and then five liters of water was added, the mixture was stirred at 400 rpm for 30 minutes, and similarly allowed to stand for two minutes. The modified fluororubber was washed with water, allowed to settle, and the upper layer was removed. This process was repeated five times.

[0081] [Drying of Fluorine Rubber] The resulting washed modified fluororubber was placed on a net at a height of 30 mm or less and dried in an oven at 80°C for 15 hours. The Mooney viscosity ML of the modified fluororubber after drying was 1+10 (121°C) was 10, and the weight average molecular weight Mw was 200,000.

[0082] Reference Example 2 In Reference Example 1, the fluororubber modification step was not carried out. Mooney viscosity ML of unmodified fluororubber after drying 1+10 (121°C) was 50, and the weight average molecular weight Mw was 500,000.

[0083] Reference Example 3: 900 g of methyl isobutyl ketone was added to 100 g of the dried unmodified fluororubber obtained in Reference Example 2, and 100 g of a 20 wt % potassium hydroxide solution was poured in. The mixture was stirred at 100 rpm at a liquid temperature of 60°C for 8 hours, and then 9 wt % sulfuric acid was added dropwise until the pH reached 3, thereby modifying the fluororubber. The modified fluororubber solution was added dropwise to ethanol with stirring, followed by washing with water and drying in the same manner as in Reference Example 1. The Mooney viscosity ML of the dried fluororubber was 1+10 (121°C) was 30, and the weight average molecular weight Mw was 300,000.

[0084] Reference Example 4 [Preparation of Acrylic Pressure-Sensitive Adhesive Solution] A reaction vessel equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a cooler was charged with 49 parts by weight of ethyl acrylate, 49 parts by weight of butyl acrylate, 1 part by weight of monobutyl fumarate, and 150 parts by weight of ethyl acetate. The mixture was stirred at 150 rpm and purged with nitrogen gas for 30 minutes. Then, 0.2 parts by weight of 2,2'-azobisisobutyronitrile was added as a polymerization initiator. The liquid temperature was maintained at around 65°C, and a polymerization reaction was carried out for 6 hours to prepare an acrylic pressure-sensitive adhesive solution with a solids concentration of 40% by weight. The weight-average molecular weight Mw was 220,000, and Tg was -43°C.

[0085] Reference Example 5: In Reference Example 4, 99 parts by weight of ethyl acrylate was used instead of butyl acrylate to prepare an acrylic adhesive solution with a solid content of 40% by weight. The weight-average molecular weight Mw was 110,000 and Tg was -18°C.

[0086] Example 1 Modified fluororubber obtained in Reference Example 1 100 parts by weight Acrylic adhesive solution obtained in Reference Example 4 250 parts by weight (equivalent to 100 parts by weight of solid content) o-Cresol novolac epoxy resin 8 parts by weight (DIC Corporation product N-695) Imidazole curing catalyst 0.5 parts by weight (Shikoku Chemicals product Curesol 2E4MZ) Butyl acetate 684 parts by weight The above components were dissolved to obtain a fluororubber composition.

[0087] Example 2 In Example 1, the amount of the acrylic adhesive solution was changed to 125 parts by weight (equivalent to 50 parts by weight in terms of solid content), and the amount of butyl acetate was changed to 559 parts by weight.

[0088] Example 3 In Example 1, the amount of the acrylic adhesive solution was changed to 1000 parts by weight (equivalent to 400 parts by weight in terms of solid content), and the amount of butyl acetate was changed to 1430 parts by weight.

[0089] Example 4 In Example 1, the same amount (100 parts by weight) of the modified fluororubber obtained in Reference Example 3 was used as the fluororubber.

[0090] Example 5 In Example 1, the same amount (250 parts by weight, equivalent to 100 parts by weight of solid content) of the acrylic adhesive solution obtained in Reference Example 5 was used as the acrylic adhesive solution, and the amount of butyl acetate was changed to 684 parts by weight.

[0091] Example 6 In Example 1, 1.4 parts by weight of 4,4'-methylenebis(2-ethyl-6-methylaniline) (Curehard MED-J, a product of Kumiai Chemical Industry Co., Ltd.) was further used, and the amount of butyl acetate was changed to 690 parts by weight.

[0092] Example 7 In Example 2, the o-cresol novolac epoxy resin and the imidazole curing catalyst were not used, and the amount of butyl acetate was changed to 750 parts by weight.

[0093] Example 8 In Example 1, the amount of the acrylic adhesive solution was changed to 500 parts by weight (equivalent to 200 parts by weight in terms of solid content), the amount of the o-cresol novolac epoxy resin was changed to 20 parts by weight, and the amount of butyl acetate was changed to 982 parts by weight.

[0094] Comparative Example 1 In Example 1, the modified fluororubber was not used, and the amount of butyl acetate was changed to 552 parts by weight.

[0095] Comparative Example 2 In Example 1, the same amount (250 parts by weight; 100 parts by weight in terms of solid content) of the unmodified fluororubber obtained in Reference Example 1 was used in place of the modified fluororubber.

[0096] Comparative Example 3 Unmodified fluororubber obtained in Reference Example 2 100 parts by weight Calcium hydroxide (Caldic #1000, manufactured by Omi Chemical Industry Co., Ltd.) 3 parts by weight Magnesium oxide (MgO #30, manufactured by Kyowa Chemical Industry Co., Ltd.) 6 parts by weight Vulcanizing agent (Curative #30, manufactured by DuPont) 6 parts by weight Crosslinking accelerator (BTPPC, manufactured by Hokko Chemical Industry Co., Ltd.; 0.4 parts by weight benzyltriphenylphosphonium chloride) Butyl acetate 461 parts by weight The above components were dissolved to obtain a fluororubber composition.

[0097] Comparative Example 4 In Example 1, the same amount (100 parts by weight) of acrylic rubber (Unimatec product PA522HF) was used instead of the acrylic adhesive solution, and the amount of butyl acetate was changed to 834 parts by weight.

[0098] Comparative Example 5 In Example 1, the acrylic adhesive solution was not used, and the amount of butyl acetate was changed to 434 parts by weight.

[0099] The fluororubber compositions obtained in the above Examples and Comparative Examples were used as adhesives to conduct adhesive solution solubility tests, curing tests, solvent resistance tests, adhesive evaluations, initial adhesion evaluations, and adhesion tests after heat resistance tests. For the solvent resistance tests, adhesive evaluations, initial adhesion evaluations, and adhesion tests after heat resistance tests, the fluororubber compositions were coated on a 25 μm thick polyimide film (Kapton EN, a product of Toray DuPont), and the solvent was dried at 140°C for 5 minutes to produce an adhesive sheet with a coating thickness of 50 μm. Adhesive solution solubility test: After dissolving each component of the composition, the film was left to stand at room temperature for 3 hours, and the state of dissolution was visually inspected to confirm the presence or absence of layer separation. If no layer separation was observed, compatibility was judged to exist and rated as ○; if layer separation was observed, compatibility was judged to exist and rated as ×. Curing test: The fluororubber composition was applied to a release film (NITOFLON No. 1, a product of Nitto Denko) and then coated with a 50 μm thick adhesive sheet.900UL), and the solvent was dried at 140°C for 5 minutes, leaving a thickness of 50μm. After vacuum drying at room temperature for 1 hour, the release film was removed and five sheets were stacked to a thickness of 250μm. Using an ENEOS Materials Curelastometer, a torsional vibration parallel die vulcanization test was carried out at 170°C in accordance with JIS K 6300-2, which corresponds to ISO 6502-2:2018, and the change in torque was measured. Since the torque value increases as crosslinking progresses, if there is an increase in the torque value after 100 minutes, it is judged to have been crosslinked and rated as ○, and if there is no increase in torque, it is judged to have not been crosslinked and rated as ×. Solvent resistance test: The adhesive sheet was immersed in methyl ethyl ketone at room temperature for 5 minutes and visually confirmed to see if the adhesive had dissolved in the methyl ethyl ketone. If it did not dissolve, it was judged that the fluororubber had been crosslinked and rated as ○, and if it dissolved, it was judged that the fluororubber had not been crosslinked and rated as ×. Adhesion evaluation: Compliant with JIS Z0237 (inclined ball tack test) corresponding to ASTM D3121. The film surface of the adhesive sheet was attached to a 30-degree inclined surface using double-sided tape. Steel balls No. 5 (4.8 mm diameter), No. 13 (10.3 mm diameter), No. 19 (15.1 mm diameter), No. 25 (19.8 mm diameter), and No. 32 (25.4 mm diameter) were placed on the adhesive sheet and checked to see if they would roll. If they did not roll, they were rated as ○; if they did roll, they were rated ×. The larger the non-rolling steel ball, the higher the adhesion. Initial adhesion evaluation: Compliant with JIS Z0237 corresponding to ISO 29862:2007. Tests were conducted on a 25 μm thick polyimide film (Kapton EN), a 0.2 mm thick SUS430 plate, and a 0.After degreasing a 2mm aluminum plate with methyl ethyl ketone, the plate was laminated with roll laminate at room temperature and subjected to a 90° peel test (test environment: 23°C ± 2°C, 50% RH ± 10% RH, test piece width: 10mm) to measure the peel strength. The higher the peel strength, the better the adhesion; a value of 0.3N / mm or greater is preferable. Adhesion evaluation after heat resistance test: Compliant with JIS Z0237, which corresponds to ISO 29862:2007. A 25μm thick polyimide film (Kapton EN) was laminated to the roll laminate at 100°C, and a 90° peel test was performed at 150°C or 200°C after 250, 500, and 1,000 hours, and the peel strength was measured. The higher the peel strength, the better the heat resistance; a value of 0.3N / mm or greater is preferable.

[0100] The results obtained are shown in the following Tables 1 and 2. For each comparative example, an adhesiveness evaluation test was also conducted in which the film surface of the adhesive sheet was attached to a sloped surface at an angle of 5 degrees using double-sided tape, and a No. 5 steel ball (diameter 4.8 mm) was placed on it to check whether it would roll. Table 1 Test and evaluation results Experiment 1 Experiment 2 Experiment 3 Experiment 4 Experiment 5 Experiment 6 Experiment 7 Experiment 8 Adhesive solution solubility test ○ ○ ○ ○ ○ ○ ○ ○ ○ Curing test ○ ○ ○ ○ ○ ○ ○ × ○ Solvent resistance test ○ ○ ○ ○ ○ ○ ○ × ○ [Adhesion evaluation] No. 5 steel ball, 5 degree angle ○ ○ ○ ○ ○ ○ ○ ○ No. 5 steel ball, 30 degree angle ○ ○ ○ ○ ○ ○ ○ ○ No. 13 steel ball, 30 degree angle ○ × ○ ○ ○ ○ × × No. 19 steel ball, 30 degree angle ○ × ○ × × × × × No. 25 steel ball, 30 degree angle × × ○ × × × × × No. 32 steel ball, 30 degree angle × × × × × × × × [Initial adhesion] PI (N / mm) 0.55 0.38 0.84 0.31 0.46 0.31 0.30 0.35 Al (N / mm) 0.37 0.30 0.72 0.32 0.42 0.33 0.29 0.37 SUS (N / mm) 0.36 0.31 0.69 0.31 0.38 0.32 0.27 0.31 [Adhesion evaluation after heat resistance test] 150°C, 250 hours (N / mm) 0.82 0.76 0.69 0.62 0.66 0.72 0.40 1.73 150°C, 500 hours (N / mm) 1.27 0.82 0.75 0.98 1.10 1.07 0.45 1.51 150℃, 1000 hours (N / mm) 1.20 0.89 0.96 1.04 1.15 1.10 0.48 1.35 200℃, 250 hours (N / mm) 1.41 0.80 0.62 1.51 1.21 1.24 0.48 0.96 200℃、500hrs (N / mm) 1.29 1.13 0.55 1.39 1.10 1.35 0.50 0.78 200℃、1000hrs (N / mm) 1.00 0.74 0.45 1.20 0.90 1.23 0.55 0.54 Table 2 Test and evaluation results Ratio 1 Ratio 2 Ratio 3 Ratio 4 Ratio 5 Adhesive solution solubility test ○ × ○ × ○ Curing test ○ × ○ ○ ○ Solvent resistance test ○ × ○ ○ ○ [Adhesion evaluation] No.5 steel ball, angle 5 degrees ○ ○ × × ○ No.5 steel ball, angle 30 degrees ○ × × × × No.13 steel ball, angle 30 degrees ○ × × × × No.19 steel ball, angle of 30 degrees 〇 × × × × No.25 steel ball, angle of 30 degrees 〇 × × × × No.32 steel ball, angle of 30 degrees × × × × × [Initial adhesion] PI (N / mm) 0.60 0.25 0.05 0.05 0.08 Al (N / mm) 0.55 0.15 0.02 0.03 0.05 SUS (N / mm) 0.53 0.12 0.03 0.02 0.04 [Adhesion evaluation after heat resistance test] 150℃, 250 hours (N / mm) 0.52 0.72 0.10 1.20 0.81 150℃, 500 hours (N / mm) 0.38 0.97 0.12 0.70 1.06 150℃, 1000 hours (N / mm) 0.28 1.10 0.14 1.20 1.25 200℃, 250 hours (N / mm) 0.13 1.21 0.15 1.30 1.25 200℃, 500 hours (N / mm) 0.05 1.10 0.17 0.50 1.15 200℃, 1000 hours (N / mm) 0.02 0.95 0.19 0.20 1.05 .

[0101] The results of the above examples and comparative examples reveal the following: (1) In each example using modified fluororubber, the tackiness, adhesiveness, and heat resistance were high, and the tackiness and adhesiveness tended to increase with the amount of acrylic adhesive (Examples 1 to 3). (2) When fluororubber modified with an organic alkali was used, higher tackiness and adhesiveness were obtained than when fluororubber modified with an inorganic alkali was used (Examples 1 and 4). (3) The lower the glass transition temperature of the acrylic adhesive, the higher the tackiness (Examples 1 and 5). (4) When a diamine compound was further added, the tackiness was slightly reduced, but the heat resistance was improved (Examples 1 and 6). (5) When a crosslinking agent was not used or the amount was increased, the tackiness tended to decrease (Examples 1 to 2, 7 and 8). (6) When an acrylic adhesive without fluororubber was used, tackiness was observed, but the adhesive strength after the heat resistance test was low (Comparative Example 1). (7) When unmodified fluororubber was used, the initial adhesive strength and tackiness were low. In addition, the solvent resistance is poor (Comparative Example 2). (8) When components consisting of a composition commonly used for fluororubber compositions are used, crosslinking occurs, but the initial bond strength is low and the adhesiveness is also low (Comparative Example 3). (9) When acrylic rubber is used instead of acrylic as the adhesive, the initial bond strength is low and no adhesiveness is observed (Comparative Example 4). (10) When an acrylic adhesive is not used, the initial bond strength is low and the adhesiveness is also low (Comparative Example 5).

[0102] As shown in the above results, in each comparative example, there are cases where the adhesiveness is low, the adhesive strength is small when attached at room temperature, and the heat resistance is poor, and it can be said that the adhesive cannot be used as an adhesive that exhibits heat resistance.

[0103] The fluororubber pressure-sensitive adhesive composition according to the present invention is effectively used in tapes, adhesives, electronic parts, automobile parts, industrial parts, etc., as well as in chemical plants, vibration dampers, vibration-proof plates, heat insulating materials, solar cell panels, etc.

Claims

1. Mooney viscosity ML having unsaturated bonds or unsaturated bonds and functional groups 1+10 A fluororubber adhesive composition in which a modified fluororubber having a Tg (at 121°C) of 10 to 80 is blended with an acrylic adhesive containing an acrylic copolymer having a glass transition temperature Tg of 20°C or less.

2. The fluororubber pressure-sensitive adhesive composition according to claim 1, wherein the functional group of the modified fluororubber is a carboxyl group.

3. The fluoroelastomer is an alkali-modified fluoroelastomer, and the Mooney viscosity after alkali modification is ML 1+10 3. The fluororubber pressure-sensitive adhesive composition according to claim 1, wherein the alkali-modified fluororubber has a hardness (121°C) that is 15 to 70°C lower than that before alkali-modification.

4. The fluororubber pressure-sensitive adhesive composition according to claim 1, wherein the weight-average molecular weight Mw of the modified fluororubber is 300,000 or less.

5. The fluororubber pressure-sensitive adhesive composition according to claim 1, wherein the weight-average molecular weight Mw of the acrylic copolymer is 100,000 to 1,000,000.

6. The fluororubber adhesive composition according to any one of claims 1 to 5, wherein 100 parts by weight of the modified fluororubber is blended with 10 to 400 parts by weight of an acrylic adhesive.

7. The fluororubber pressure-sensitive adhesive composition according to claim 1, further comprising 1 to 50 parts by weight of a crosslinking agent per 100 parts by weight of the modified fluororubber.

8. The fluororubber pressure-sensitive adhesive composition according to claim 7, wherein the crosslinking agent is a curable resin and / or an aromatic polyamine.

9. The fluororubber pressure-sensitive adhesive composition according to claim 7 or 8, further comprising imidazole as a crosslinking curing catalyst in an amount of 0.1 to 5 parts by weight per 100 parts by weight of the modified fluororubber.

10. The fluororubber pressure-sensitive adhesive composition according to claim 7, 8 or 9, which does not contain an acid acceptor.

11. A pressure-sensitive adhesive sheet in which the fluororubber composition according to claim 1 is laminated on one or both sides of a substrate.

12. The fluororubber adhesive composition according to claim 1, which has such adhesiveness that when a steel ball having a diameter of 4.8 mm is placed on the adhesive surface formed on an inclined plane at an angle of 30 degrees, the steel ball does not roll off.