Fluororubber adhesive composition

Abstract

To provide a fluororubber pressure-sensitive adhesive composition excellent in adhesion and tackiness without detriment to the heat resistance, chemical resistance, weatherability, flame retardancy, etc., inherent in fluororubber.SOLUTION: A fluororubber adhesive composition comprising a modified fluororubber containing unsaturated bonds or unsaturated bonds and functional groups and having a Mooney viscosity ML1 + 10 (121 °C) of 10 to 80, and an acrylic copolymer-containing acrylic adhesive having a glass-transition temperature Tg of 20 °C or lower. The acrylic adhesive is used at a ratio of 10 to 400 parts by weight with respect to 100 parts by weight of the modified fluororubber.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a fluororubber pressure-sensitive adhesive composition, and more specifically to a fluororubber pressure-sensitive adhesive composition that has such adhesiveness that when a steel ball having a diameter of 4.8 mm is placed on an adhesive surface formed into an inclined plane at an angle of 30 degrees, the steel ball does not roll off the adhesive surface.

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

[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 with bifunctional polyamine compounds, dehydrofluorination occurs and carbon-carbon unsaturated bonds are formed without the presence of divalent metal oxides such as magnesium oxide or calcium hydroxide. Therefore, while divalent metal oxides such as magnesium oxide or calcium hydroxide are essential for crosslinking, the curing rate of divalent metal oxides increases due to moisture absorption, making them unsuitable for long-term storage in sheet form. 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 crosslinking 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, since crosslinking must be carried out quickly in order to achieve crosslinking in a short time for production purposes while blocking air (oxygen), crosslinking must be carried out quickly, 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 problems such as 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. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Patent No. 7,177,581 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-292529 [Patent Document 3] Japanese Patent Application Laid-Open No. 2009-108287 [Patent Document 4] Japanese Patent Application Laid-Open No. 2014-105268 [Patent Document 5] Patent No. 3,327,447 [Patent Document 6] Patent No. 3,975,249 [Patent Document 7] Japanese Patent Application Laid-Open No. 2002-030263 [Patent Document 8] Japanese Patent Publication No. 59-059764 [Patent Document 9] Japanese Patent Application Publication No. 2-245046 Summary of the Invention [Problem to be solved by the invention]

[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 inherent heat resistance, chemical resistance, weather resistance, flame retardancy, etc. of fluororubber. [Means for solving the problem]

[0012] The object of the present invention is to provide a Mooney viscosity ML 1+10 This is achieved by a fluororubber adhesive composition obtained by blending a modified fluororubber having a modulus of elasticity (Tg) of 10 to 80 with an acrylic adhesive containing an acrylic copolymer having a glass transition temperature Tg of 20°C or lower. [Effects of the Invention]

[0013] In the fluororubber adhesive composition of the present invention, an acrylic 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 adhesives or silicone adhesives when used alone with the fluororubber 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 fluorine compound is not copolymerized with acrylic, so the adhesion level can be adjusted by adding an acrylic adhesive, and because the fluororubber is compatible, an adhesive with better heat resistance and adhesion than an acrylic adhesive alone can be obtained.

[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 becomes uneven after drying, resulting in thickness variations and making the product unusable 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 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, without the addition of a commonly used acid acceptor. This results in higher tackiness and adhesiveness. Therefore, inorganic fillers such as acid acceptors are not necessarily required, and the addition of fillers 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 divalent metal oxides such as magnesium oxide, calcium hydroxide, hydrotalcite, etc. However, because these particles are large, adhesives containing these particles may have particles larger than the coating thickness, resulting in reduced tackiness, adhesion, and heat resistance. Furthermore, the particles tend to fall off from the adhesive surface, which can cause contamination in semiconductor applications, such as the falloff of inorganic filler particles. The fluororubber adhesive composition of the present invention modifies and functionalizes the fluororubber, allowing the modified fluororubber to directly crosslink with a crosslinking agent such as an epoxy resin without the addition of divalent metal oxides such as magnesium oxide, calcium hydroxide, or hydrotalcite, eliminating contamination from particles on 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. DETAILED DESCRIPTION OF THE INVENTION

[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 also used to stabilize the aqueous emulsion.

[0024] The emulsifier used in the emulsion polymerization method is generally a fluorinated carboxylate, 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 a surfactant 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 under conditions of 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, using a water-soluble inorganic peroxide such as ammonium persulfate or a redox system of such peroxide and a reducing agent as a catalyst, in the presence of a surfactant as an emulsifier, typically used in a proportion of about 0.001 to 0.2 wt% based on the total weight of the charged water. The reaction is carried out under conditions of 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 NaHPO, NaHPO, or KHPO, 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 the case where ammonium perfluorooctanoate emulsifier is used. After the reaction is completed, an aqueous potassium alum solution, an aqueous sodium chloride solution, an aqueous calcium chloride solution, etc. is added to the obtained 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 salts (hereinafter referred to as [PFOA]) are known to be surfactants with excellent monomer emulsification properties 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 with rubber, after coagulation of rubber latex obtained by emulsion polymerization, there is a high amount of PFOA adhering to and remaining in the resulting fluoroelastomer, and there is a strong demand for reducing this.

[0029] To meet such demands, it is conceivable to provide a fluorine-containing emulsifier with environmental degradability by providing a hydrogenated moiety 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 an alkali metal hydroxide or aqueous ammonia with P(O)(OH)2 (n: an integer of 2 to 6, m: an integer of 1 to 3). When an alkali metal hydroxide or ammonia is used in an equimolar amount relative to the perfluoroalkylalkylphosphonic acid, it forms a monosalt, and when 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 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] Because these perfluoroalkyl alkyl phosphonates have a linear fluoroalkyl group, they have better solubility in water than fluoropolyether-type emulsifier compounds with equivalent emulsifying performance, and at the same time, they adhere less to the resulting fluoroelastomer than PFOA, so they can significantly reduce the amount of emulsifier remaining in the fluoroelastomer obtained by coagulating the fluoroelastomer 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 using a PFOA emulsifier.

[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 in the polymerization system, electrolytes with buffering capacity such as phosphates (NaHPO, NaHPO, KHPO, etc.) or borates (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 is composed of a soft fluororesin, an acrylic resin, a vinylidene fluoride resin, a polyisocyanate, and an organic solvent. However, these compositions bond during the crosslinking reaction, but lose their 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 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 to form a modified fluororubber. The modification of the fluororubber is carried out by introducing unsaturated bonds through a partial dehydrofluorination reaction by base modification, such as alkali modification using an inorganic alkali or an organic alkali, preferably an organic alkali (Patent Documents 6-7). This modification treatment removes HF from the fluoropolymer main chain, resulting in carbon-carbon unsaturation, 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. In inorganic alkali modification, the permeation into the rubber is minimal even at room temperature or when heated, so an organic alkali that permeates into the fluororubber latex at room temperature is 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 the ends. 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 the rubber, and the lower the temperature, the more low-molecular-weight the rubber. When using inorganic alkali, modification is not possible unless the fluororubber is heated to 40°C or higher. When using organic alkali, molecular weight control becomes difficult at temperatures above 40°C, so the modification is carried out at approximately 5 to 35°C. When using organic alkali, it takes time for the modification to stabilize at temperatures below room temperature. However, at room temperature, 20 to 30°C, the modification can be achieved stably 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 use of a larger amount of modifier results in an increase in low-molecular-weight the rubber. The modification temperature and amount of modifier are adjusted according to the required molecular weight. The heat drying temperature after modification washing is approximately 60 to 150°C, preferably approximately 80 to 120°C. If the temperature is lower than this, insufficient drying and residual solvent can lead to foaming during adhesive sheet lamination, and residual low-molecular-weight components can cause poor adhesion. If the temperature is higher than this, crosslinking increases, resulting in 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 fluoro rubber conforms to JIS K6300-1 (2013) Mooney viscosity ML 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, the Mooney viscosity is measured in accordance with JIS K6300-1 (2013) using a Mooney Viscometer SMV-201 (manufactured by Shimadzu Corporation) at a temperature of 121°C, with 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 allows adhesiveness to be developed.

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

[0044] The acrylic adhesive contains acrylic acid monomers and methacrylic acid monomers as well as acrylic acid ester monomers and methacrylic acid ester monomers with highly crosslinkable functional groups. For example, a copolymer of a monomer without functional groups, such as ethyl acrylate (EA), butyl acrylate (BA), or methyl methacrylate (MMA), with at least one monomer with highly crosslinkable functional groups, 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 (EA), methyl acrylate, butyl (meth)acrylate (BA, BMA), 2-ethylhexyl (meth)acrylate (2-EHA, 2-EHMA), propyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, vinyl acetate (VA), vinyl propionate, styrene, and (meth)acrylonitrile. Preferred examples include at least one selected from ethyl acrylate, butyl (meth)acrylate, acrylonitrile (AN), methyl acrylate, 2-ethylhexyl (meth)acrylate, and vinyl acetate. Using these monomers makes it easier to adjust the peel strength from the adherend and 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 EA are used, the better the compatibility with modified fluoroelastomers tends to be. The degree of cross-linking can be adjusted by copolymerizing monomers with highly cross-linkable functional groups, but increasing the degree of cross-linking increases adhesive strength and liquid resistance but also reduces adhesion, so the copolymerization ratios are 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 (boiling point polymerization or constant temperature 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, examples of the reaction solvent include ethyl acetate, toluene, methyl ethyl ketone, methyl sulfoxide, ethanol, acetone, and diethyl ether. 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 as is 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. Because the acrylic polymer is rubbery, 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 adhesive properties 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, compounded with an organic peroxide, etc. Similar to the invention described in Patent Document 8, molded articles obtained from the disclosed rubber composition are rubbery, unlike the type of adhesive used in commercially available adhesive tapes. They have almost no tackiness at room temperature, and therefore cannot be used as pressure-sensitive adhesives.

[0055] In all of these inventions, the fluororubber is combined with a rubber-like acrylic polymer, and therefore the adhesiveness aimed at by the present invention cannot be obtained. 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 the modified fluororubber. If the blending amount is less than this, the adhesiveness will decrease, while if it is more than this, the heat resistance and solvent resistance will deteriorate. The degree of adhesion can be adjusted depending on the amount of acrylic adhesive. By blending an acrylic adhesive with the modified fluororubber, it is possible to adjust the desired tackiness and adhesiveness that cannot be obtained 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 fluorine with an alkali to form a latex and then mixing the emulsion acrylic adhesive, or a method of kneading a solid modified fluororubber with a solvent-free acrylic adhesive using a roll or kneader can 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 adhesives. This contributes to improved adhesion between the cured product of the adhesive composition and the modified fluororubber and acrylic 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 thereof; cresol novolac-type epoxy resins are preferred. One type of epoxy resin may be used alone, or two or more types may be mixed together.

[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 the modified fluororubber. The incorporation of the thermosetting resin improves the adhesiveness, adhesion to the substrate, solvent resistance, durability, etc. If the amount is less than this, the adhesive strength is low and the 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 about 0.1 to 5 parts by weight, preferably about 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 increased curing rate of the fluororubber will result in a decrease in the stability of the adhesive organic solvent solution over time, a decrease in adhesion due to reduced storage stability of the coated sheet, and a decrease in tackiness due to increased 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, and 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, and polyethylene glycols, all of which have 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 the like, 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 fluororesin 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 contain various additives, such as antioxidants, ultraviolet absorbers, plasticizers, pigments, dyes, and other colorants, as needed. 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 properties 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 an adherend and in peeling it from the adherend.

[0073] The adhesive is applied to a thickness of 5 to 200 μm after drying, typically with a solids concentration of 10 to 50 wt%, preferably 15 to 40 wt%. Coating methods include roll coating, die coating, and knife coating, as well as partial application by screen printing, dispenser, or inkjet. The coating solution is adjusted to a viscosity appropriate for each coating method. For example, a viscosity of 500 to 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, which is then dried at approximately 50 to 200°C for approximately 1 to 15 minutes to obtain an adhesive film. Acrylic adhesives containing low-molecular-weight components may foam upon heating after lamination. In such cases, the drying temperature after application can be increased to approximately 200°C.

[0074] Lamination conforms to JIS Z 0237 2009, Test Methods for Adhesive Tapes and Sheets, and can be performed using a roller or roll laminator at room temperature or with heating. Furthermore, when using a vacuum press or heated press to process the material with heated air at approximately 150-200°C for approximately 10 seconds to 3 hours (oven crosslinking), adhesive strength can be further improved by post-processing at approximately 150-200°C for approximately 1 minute to 15 hours. After lamination, adhesive strength can also be increased by heating the material in an oven at approximately 80-200°C for approximately 1 minute to 24 hours, even without pressing. [Example]

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

[0076] Reference example 1 [Preparation of Fluorine Rubber 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 emulsifier (Neos product FS-1110), and the internal space was then 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 it 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 a 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 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 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, after which 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 Fluororubber] 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 dried modified fluororubber 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 was not modified. 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 To 100 g of the dried unmodified fluororubber obtained in Reference Example 2, 900 g of methyl isobutyl ketone was added, and 100 g of a 20 wt % potassium hydroxide solution was poured. 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 while stirring, and then washed with water and dried 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 adhesive solution] A reactor equipped with a stirring blade, thermometer, nitrogen gas inlet tube, and condenser 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 polymerization reaction was carried out for 6 hours, yielding a 40% by weight acrylic adhesive solution. The weight average molecular weight (Mw) was 220,000, and the Tg was -43°C.

[0085] Reference example 5 In Reference Example 4, butyl acrylate was not used, and the amount of ethyl acrylate was changed to 99 parts by weight to prepare a 40% by weight acrylic adhesive solution. The weight average molecular weight Mw was 110,000, and Tg was -18°C.

[0086] Example 1 100 parts by weight of the modified fluororubber obtained in Reference Example 1 Acrylic adhesive solution obtained in Reference Example 4 250 (equivalent to 100 parts by weight in terms of solid content) o-Cresol novolac epoxy resin (DIC product N-695) 8 Same as above Imidazole curing catalyst (Shikoku Kasei product Curesol 2E4MZ) 0.5 〃 Butyl acetate 684 〃 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 acrylic adhesive solution was changed to 500 parts by weight (equivalent to 200 parts by weight of solid content), the amount of 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 3 100 parts by weight of unmodified fluororubber obtained in Reference Example 2 Calcium hydroxide (Omi Chemical Industry Products Caldic♯1000) 3 〃 Magnesium oxide (Kyowa Chemical Industry Products MgO♯30) 6 〃 Vulcanizing agent (DuPont Curative #30) 6 Crosslinking accelerator (Hokko Chemical Industry Products BTPPC; 0.4 〃 benzyltriphenylphosphonium chloride) Butyl acetate 461 〃 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, adhesion evaluations, initial adhesion evaluations, and adhesion tests after heat resistance tests. For the solvent resistance tests, adhesion evaluations, initial adhesion evaluations, and adhesion tests after heat resistance tests, the fluororubber compositions were coated onto 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 remove the solvent, resulting in an adhesive sheet with a coating thickness of 50 μm. Adhesive solution solubility test: After dissolving each component of the composition, the solution was left at room temperature for 3 hours and then the state of dissolution was observed. Visually check for layer separation. If no layer separation is observed, it is judged to be compatible and marked with a circle. If layer separation is observed, it is judged as incompatible and marked with ×. evaluation Curing test: Fluorine rubber composition is applied to a release film (Nitto Denko product Nitoflon No. 900UL) After drying the solvent at 140°C for 5 minutes, the thickness was 50 μm and the coating was left at room temperature for 1 After vacuum drying for 1 hour, peel off the release film and stack 5 sheets to a thickness of 250 mm. The adhesive sheet with a thickness of μm was measured using a Curelastometer manufactured by ENEOS Materials. Vulcanization was carried out at 170°C using a torsional vibration parallel die in accordance with JIS K 6300-2. Test and measure torque change The torque value increases as the crosslinking progresses. If an increase in the torque value is observed, it is judged to be cross-linked and marked with a circle. If no increase is observed, it is judged that no cross-linking has occurred and is evaluated as ×. Solvent resistance test: The adhesive sheet was immersed in methyl ethyl ketone at room temperature for 5 minutes. Visually check whether the adhesive has dissolved in methyl ethyl ketone. If it does not dissolve, it is judged that the fluororubber is crosslinked and marked with a circle. If it dissolves, it is determined that the fluororubber is not cross-linked and is marked as ×. evaluation Adhesion evaluation: Compliant with JIS Z0237 (inclined ball tack test) The film surface of the adhesive sheet is placed on a 30-degree slope. The No. 5 (diameter 4.8 mm) and No. 13 (diameter 10.3mm), No.19 (15.1mm diameter), No.25 (19.8mm diameter), No.32 (diameter Place steel balls (25.4 mm) on the test piece and check whether they roll. If it doesn't roll, it's evaluated as ○, and if it does roll, it's evaluated as ×. The larger the non-rolling steel ball, the greater the adhesiveness. Initial adhesion evaluation: JIS Z0237 compliant 25 μm thick polyimide film (Kapton EN), 0.2 mm thick SUS430 plate and 0.2 mm thick aluminum plate were After degreasing with ketone, the roll laminate was laminated at room temperature. 90° peel test (Test environment: 23°C ± 2°C, 50% RH ± 10% RH, test piece Shape: Width 10mm) and measure peel strength The higher the peel strength, the higher the adhesiveness, and 0.3 N / mm or more is preferable. Adhesion evaluation after heat resistance test: JIS Z0237 compliant 25 μm thick polyimide film (Kapton EN) and Laminate the Lurami at 100℃, then at 150℃ or 200℃. A 90° peel test was performed after 250 hours, 500 hours, and 1,000 hours. Measure the peel strength The higher the peel strength, the higher the heat resistance, and 0.3 N / mm or more 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 Fruit 1 Fruit 2 Fruit 3 Fruit 4 Fruit 5 Fruit 6 Fruit 7 Fruit 8 Adhesive solution solubility test ○ ○ ○ ○ ○ ○ ○ ○ ○ Curing test 〇 〇 〇 〇 〇 〇 × 〇 Solvent resistance test 〇 〇 〇 〇 〇 〇 × 〇 [Adhesion Evaluation] No.5 Steel ball, angle 5 degrees 〇 〇 〇 〇 〇 〇 〇 〇 No.5 Steel ball, angle 30 degrees 〇 〇 〇 〇 〇 〇 〇 〇 No.13 steel ball, angle 30 degrees 〇 × 〇 〇 〇 〇 × × No.19 steel ball, angle 30 degrees 〇 × 〇 × × × × × No.25 steel ball, angle 30 degrees × × 〇 × × × × × 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℃, 250 hours (N / mm) 0.82 0.76 0.69 0.62 0.66 0.72 0.40 1.73 150℃, 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℃, 500 hours (N / mm) 1.29 1.13 0.55 1.39 1.10 1.35 0.50 0.78 200℃, 1000 hours (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 〇 × 〇 × 〇 Curing test 〇 × 〇 〇 〇 Solvent resistance test 〇 × 〇 〇 〇 [Adhesion Evaluation] No.5 Steel ball, angle 5 degrees 〇 〇 × × 〇 No.5 Steel ball, angle 30 degrees 〇 × × × × No.13 steel ball, angle 30 degrees 〇 × × × × No.19 steel ball, angle 30 degrees 〇 × × × × No.25 steel ball, angle 30 degrees 〇 × × × × No.32 steel ball, 30 degree angle × × × × × [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 following can be said from the above examples and comparative examples. (1) In each example in which modified fluororubber was used, the tackiness, adhesiveness, and heat resistance were high, and the tackiness and adhesiveness tended to increase as the amount of acrylic adhesive increased (Examples 1 to 3). (2) When a fluororubber modified with an organic alkali is used, higher tackiness and adhesiveness are obtained than when a fluororubber modified with an inorganic alkali is used (Examples 1 and 4). (3) The lower the glass transition temperature of the acrylic adhesive, the higher the adhesiveness tends to be (Examples 1 and 5). (4) When a diamine compound is further added, the adhesiveness is slightly reduced, but the heat resistance is improved (Examples 1 and 6). (5) When no crosslinking agent is used or when the amount of the crosslinking agent is large, the adhesiveness tends to decrease (Examples 1, 7 to 8). (6) In the case of an acrylic adhesive that does not contain fluororubber, although adhesiveness is observed, the adhesive strength after the heat resistance test is low (Comparative Example 1). (7) When unmodified fluororubber is used, the initial adhesive strength and tackiness are low, and the solvent resistance is poor (Comparative Example 2). (8) When components having compositions generally used as fluororubber compositions are used, crosslinking occurs, but the initial adhesive strength is low and the adhesiveness is also low (Comparative Example 3). (9) When acrylic rubber was used instead of acrylic as the adhesive, the initial adhesive strength was low and no adhesiveness was observed (Comparative Example 4). (10) If an acrylic adhesive is not used, the initial adhesive 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. [Industrial Applicability]

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

Claims

1. Mooney viscosity ML with unsaturated bonds or unsaturated bonds and functional groups 1+10 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.

2. 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 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. 2. 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. 2. The fluororubber pressure-sensitive adhesive composition according to claim 1, wherein the acrylic copolymer has a weight average molecular weight Mw of 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. 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 0.1 to 5 parts by weight of imidazole as a curing catalyst for crosslinking per 100 parts by weight of the modified fluororubber.

10. A pressure-sensitive adhesive sheet comprising a substrate and the fluororubber composition according to claim 1 laminated on one or both sides thereof.

11. 10. A laminated sheet comprising a substrate having a fluororubber composition according to claim 1 laminated on both sides thereof and a release film or release paper laminated on one or both sides thereof.

12. 2. 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 an adhesive surface formed on an inclined surface at an angle of 30 degrees, the steel ball does not roll off.