Fluororubber binder composition

Abstract

A fluororubber binder composition in which an acrylic binder containing an acrylic copolymer having a glass transition temperature Tg of 20 DEG C or less is blended in a modified fluororubber having an unsaturated bond or having an unsaturated bond and a functional group and having a Mooney viscosity ML1 + 10 (121 DEG C) of 10-80. The acrylic binder is used in a ratio of 10 parts by weight to 400 parts by weight with respect to 100 parts by weight of the modified fluororubber. The fluororubber adhesive composition does not damage the heat resistance, chemical reagent resistance, weather resistance, flame retardancy and the like of fluororubber, and shows excellent adhesion and cohesiveness.

Description

Technical Field

[0001] This invention relates to fluororubber adhesive compositions. More specifically, it relates to a fluororubber adhesive composition that exhibits excellent adhesion and tackiness without compromising the inherent heat resistance, chemical resistance, weather resistance, flame retardancy, etc., of fluororubber. Background Technology

[0002] Traditionally, adhesives have been made from resins such as vinyl acetate, ethylene-vinyl acetate copolymer, vinyl chloride, epoxy, polyurethane, styrene, acrylic, polyamide, cyanoacrylate, cellulose, silane, and silicone, or rubber-based adhesives such as nitrile rubber, styrene-butadiene rubber, and neoprene rubber. For heat-resistant adhesives, acrylic and silicone adhesives are commonly used, but acrylic adhesives have inferior heat resistance compared to silicone adhesives, while silicone adhesives have lower bond strength. While adhesives other than silicone are difficult to use for long-term heat resistance applications above 175°C, silicone adhesives are unsuitable for electronic component applications due to their potential for contamination.

[0003] Fluoropolymers or fluororubbers, while exhibiting excellent heat resistance, long-term resistance to chemical reagents, weather resistance, and abrasion resistance above 175°C, generally cannot be used alone as adhesives due to their lack of bonding properties. Uncrosslinked fluororubber, although considered to have slight tackiness, lacks bonding properties. This uncrosslinked fluororubber can develop adhesive properties through defluorination and hydrogenation with alkali, but due to its lack of crosslinking, it lacks strength, solvent resistance, chemical resistance, liquid resistance, pressure resistance, and bonding strength under heat, thus limiting its applications.

[0004] In addition, while crosslinking with polyols, polyamines, peroxides and other substances can improve strength, solvent resistance, chemical resistance, liquid resistance, pressure resistance, and bonding strength under heating, crosslinked fluororubber lacks adhesiveness and bonding properties when the glass transition temperature (Tg) is below room temperature. Therefore, crosslinked fluororubber is generally not suitable for use as an adhesive.

[0005] Furthermore, in the crosslinking of fluororubber using polyols such as bisphenol AF, or amine crosslinking using difunctional polyamine compounds, defluorination and hydrogenation occur without divalent metal oxides such as magnesium oxide or calcium hydroxide, resulting in the formation of carbon-carbon unsaturated bonds. Therefore, divalent metal oxides such as magnesium oxide or calcium hydroxide are essential for crosslinking. However, divalent metal oxides are hygroscopic, leading to faster curing speeds and making long-term storage in sheet form impossible. In addition, calcium hydroxide cures quickly, and when dissolved in organic solvents to form adhesives, it gels rapidly, rendering it unusable. Moreover, the addition of large amounts of inorganic substances such as calcium hydroxide and magnesium oxide can lead to a loss of adhesiveness, resulting in even poorer adhesion after crosslinking.

[0006] Furthermore, peroxide crosslinking of fluororubber requires pressure or other methods to isolate oxygen during crosslinking. Since exposed or oxygen-permeable portions do not crosslink, there are issues with poor adhesion and / or liquid resistance in the uncrosslinked areas. Consequently, in production, rapid crosslinking is necessary to isolate air (oxygen) and achieve crosslinking within a short time. However, when preparing adhesives by dissolving rubber compositions in organic solvents, rapid gelation makes them difficult to use, and the deactivation of peroxides due to air exposure during solvent drying results in insufficient crosslinking.

[0007] While conventional fluororubber can be crosslinked using acid-resistant agents and other crosslinking agents, it cannot be crosslinked with epoxy resins, which offer superior heat and water resistance and improve adhesive strength. Even when epoxy resin and polyamine are added to conventional fluororubber, although the epoxy resin reacts with the polyamine, the crosslinking density of the fluororubber does not increase, thus failing to improve adhesion and liquid resistance.

[0008] Patent Document 1 discloses an adhesive composition containing a fluorinated oligomer with a weight-average molecular weight (Mw) of 3500 or higher, an ionic compound, and an acrylic polymer. While the inclusion of the acrylic polymer improves adhesion, the poor compatibility between the fluorinated oligomer and other polymers, such as acrylic polymers, leads to the migration of the fluorinated oligomer to the surface after coating or drying, reducing surface adhesion and bonding strength. The migration state of the fluorinated oligomer to the surface varies with storage time and ambient temperature, resulting in unstable adhesion. Furthermore, crosslinking further reduces adhesion.

[0009] Patent document 2 proposes an adhesive with a fluorinated copolymer as the main component, which is copolymerized from (meth)acrylate perfluoroalkyl ester monomers, (meth)acrylate alkyl ester monomers, hydroxyl-containing acrylic monomers, and carboxyl-containing acrylic monomers. However, the adhesiveness is not high, and the bonding strength is also low, with problems of deterioration and reduced adhesion after prolonged exposure to high temperatures.

[0010] Existing technical documents Patent documents Patent Document 1: Japanese Patent No. 7,177,581 Patent Document 2: Japanese Patent Application Publication No. 2004-292529 Patent Document 3: Japanese Patent Application Publication No. 2009-108287 Patent Document 4: Japanese Patent Application Publication No. 2014-105268 Patent Document 5: Japanese Patent No. 3,327,447 Patent Document 6: Japanese Patent No. 3,975,249 Patent Document 7: Japanese Patent Application Publication No. 2002-030263 Patent Document 8: Japanese Patent Application Publication No. 59-059764 Patent Document 9: Japanese Patent Application Publication No. 2-245046 Summary of the Invention Technical problems to be solved The purpose of this invention is to provide a fluororubber adhesive composition that exhibits excellent adhesion and bonding properties without compromising the inherent heat resistance, chemical resistance, weather resistance, and flame retardancy of fluororubber.

[0011] Problem-solving methods The above-mentioned objective of the present invention is achieved by a fluororubber adhesive composition having a Mooney viscosity of ML with unsaturated bonds or functional groups such as unsaturated bonds and carboxyl groups. 1+10 An acrylic binder is blended into a modified fluororubber with a (121℃) value of 10-80, the acrylic binder containing an acrylic copolymer with a glass transition temperature (Tg) below 20℃.

[0012] Invention Effects The fluororubber adhesive composition of the present invention, in which an acrylic adhesive is blended into a modified fluororubber having unsaturated bonds (and functional groups such as carboxyl groups), achieves the following excellent effects: it does not impair the excellent long-term adhesion (heat resistance), chemical resistance, weather resistance, and flame retardancy of the modified fluororubber, and the fluororubber, when used alone, does not exhibit the same level of tackiness as commercially available acrylic adhesives and / or silicone adhesives. This is because the fluorinated compound is not copolymerized with the acrylic compound; by adding the acrylic adhesive, the degree of adhesion can be adjusted. Since the fluororubber is compatible with the acrylic adhesive, an adhesive with superior heat resistance and adhesion compared to the acrylic adhesive alone can be obtained.

[0013] Generally, when acrylic rubber and / or acrylic adhesive are blended into fluororubber and dissolved in a solvent, the solution will separate into layers. Therefore, even if coated, the coating surface will be uneven after drying, resulting in uneven thickness. This makes it unsuitable for use as adhesive tape or adhesive sheet. However, by alkali-modifying fluororubber and blending it with acrylic adhesive, the separation of the solution can be prevented, the unevenness of the coating surface can be eliminated, and it can be used as adhesive tape and / or adhesive sheet.

[0014] In this way, by decomposing, reducing the molecular weight, and imparting functional groups to the uncrosslinked fluororubber using inorganic and / or organic bases, modified fluororubber with adhesive and bonding properties is used, thereby improving its compatibility with acrylic adhesives. Even when mixed, it will not separate, resulting in an excellent effect that allows the coated surface to be in good condition.

[0015] This modified fluororubber, even without the addition of commonly used acid-receptor agents, can be co-crosslinked with acrylic adhesives using crosslinking agents commonly found in acrylic adhesives, resulting in superior adhesion and bonding strength. Therefore, since inorganic fillers such as acid-receptors are not necessarily required, the addition of fillers does not lead to deterioration of adhesion; instead, the addition of crosslinking agents improves adhesion. Furthermore, without the addition of acid-receptors, there is no curing degradation caused by acid-receptors, and adhesion does not decrease significantly with heating. Moreover, even with the addition of other adhesives, compatibility is good, delamination does not occur, and the coating remains uniform after drying.

[0016] To date, no adhesive has been found that offers better heat resistance than acrylic adhesives, higher bond strength than silicone adhesives, and is free of silicone contamination while maintaining high heat resistance. However, the fluororubber adhesive composition of the present invention provides an adhesive that meets these requirements. Specifically, it exhibits adhesion to the extent that, for example, a steel ball with a diameter of 4.8 mm is not rolled when placed on the bonding surface (formed on an inclined plane at a 30-degree angle).

[0017] This fluororubber adhesive composition is tacky at room temperature, allowing it to be laminated and bonded to the substrate at room temperature. Oven heating treatment can further improve its adhesion and bonding strength. Furthermore, because the fluororubber is modified to a lower molecular weight, it can be seamlessly embedded into the irregularities of the substrate, such as the irregularities in patterns on electronic substrates, resulting in high bonding strength.

[0018] The polyamine and polyol crosslinking of binary fluororubbers will not crosslink without the presence of divalent metal oxides such as magnesium oxide or acid-sensitive agents such as calcium hydroxide and hydrotalcite. However, due to the large size of these particles, the binders containing them sometimes become particles larger than the coating thickness, leading to reduced adhesion, bonding, and heat resistance. Furthermore, these particles easily detach from the binder surface, causing contamination such as particle shedding from inorganic fillers (fillers) in semiconductor applications. The fluororubber binder composition of this invention, by modifying the fluororubber and imparting functional groups, eliminates the need for adding divalent metal oxides such as magnesium oxide or calcium hydroxide and hydrotalcite. Crosslinking agents such as epoxy resin can directly crosslink with the modified fluororubber, eliminating contamination caused by particles from the binder surface.

[0019] Furthermore, even without using bisphenol AF, which is an environmentally burdensome substance, modified fluororubber can be cross-linked with epoxy resin, resulting in fewer reactive gases during lamination heating and preventing foaming of the laminate. Detailed Implementation

[0020] As fluororubber, highly fluorinated elastic copolymers can be used, such as two or more elastic copolymers of 1,1-difluoroethylene, hexafluoropropylene, pentafluoropropylene, trifluoroethylene, trifluorochloroethylene, tetrafluoroethylene, fluoroethylene, perfluoro(methyl vinyl ether), perfluoro(ethyl vinyl ether), perfluoro(propyl vinyl ether), etc. 1,1-difluoroethylene-hexafluoropropylene copolymers are preferred, and 1,1-difluoroethylene-hexafluoropropylene copolymers, 1,1-difluoroethylene-hexafluoropropylene-tetrafluoroethylene terpolymers, and 1,1-difluoroethylene-hexafluoropropylene-tetrafluoroethylene-perfluoro(alkyl vinyl ether) terpolymers are particularly preferred.

[0021] It should be noted that Patent Document 3 discloses an adhesive composition consisting of a fluororubber polymer that cannot be cross-linked by peroxide, a fluororubber polymer that can be cross-linked by peroxide, and a peroxide. However, although this adhesive composition has excellent heat resistance and solvent resistance, it has no adhesive properties at room temperature, and the peroxide is deactivated by oxygen in the air, thus failing to undergo a sufficient cross-linking reaction. Therefore, although the aforementioned adhesive composition without the blended acrylic adhesive can adhere to surfaces such as glass, for example, if a steel ball with a diameter of 4.8 mm is placed on a 30-degree inclined plane, the steel ball will roll.

[0022] Fluororubber can be manufactured as a latex using either aqueous emulsion polymerization or aqueous suspension polymerization. In aqueous emulsion polymerization, water-soluble peroxides can be used alone as the reaction initiator system, or a redox system combining them with water-soluble reducing agents can be used as the reaction initiator system. Examples of water-soluble peroxides include ammonium persulfate, potassium persulfate, and sodium persulfate, while examples of water-soluble reducing agents include sodium sulfite and sodium bisulfite. In this case, pH adjusters (buffers) such as sodium monohydrogen phosphate, sodium dihydrogen phosphate, potassium monohydrogen phosphate, and potassium dihydrogen phosphate can be used as stabilizers in the aqueous emulsion.

[0023] Fluorinated carboxylates are commonly used as emulsifiers in emulsion polymerization, with CF3CF2CF2O [CF(CF3)CF2O] being preferred. n CF(CF3)COONH4 (n: 1 or 2). These emulsifiers can be used in the form of an aqueous solution of about 1% to 30% by weight, preferably about 5% to 20% by weight. If the amount of emulsifier is less than this, the monomer and the resulting copolymer cannot be uniformly dispersed in the aqueous medium, while if the amount is too much, it is economically disadvantageous.

[0024] The copolymerization reaction is carried out at a temperature of approximately 20°C to 80°C, preferably approximately 25°C to 60°C. If the polymerization temperature is too high, problems such as foaming may occur during molding and processing. In addition, the polymerization pressure is usually below approximately 5 MPa.

[0025] 1,1-Difluoroethylene, tetrafluoroethylene, and hexafluoropropylene are copolymerized in an aqueous medium in the presence of an emulsifier represented by the above general formula. The copolymerization in the aqueous medium can also be carried out by suspension polymerization, 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 its redox system with a reducing agent as a catalyst, in the presence of a surfactant as an emulsifier (usually used at a ratio of about 0.001% to 0.2% by weight relative to the total weight of the added water), typically under conditions of pressure about 0 MPa to 10 MPa, preferably about 0.5 MPa to 4 MPa, and temperature about 0°C to 100°C, preferably about 20°C to 80°C. At this time, in order to maintain the reaction pressure within a certain range, it is preferable to supply the fluorinated olefin mixture by partial addition. Furthermore, to adjust the pH within the polymerization system, electrolytes with buffering capacity such as sodium monohydrogen phosphate, sodium dihydrogen phosphate, potassium dihydrogen phosphate, or sodium hydroxide can be added. Furthermore, depending on the needs, chain transfer agents such as diethyl malonate, acetone, and isopropanol can be appropriately used.

[0026] Although the polymerization reaction is also affected by various polymerization conditions, it usually completes in about 1 to 15 hours, which is not much different from the case when using ammonium perfluorooctanoate emulsifier. After the reaction is completed, potassium alum aqueous solution, sodium chloride aqueous solution, calcium chloride aqueous solution, etc. are added to the resulting aqueous emulsion to cause the polymer to coagulate. After washing with water and drying, the fluorinated copolymer can be obtained.

[0027] Here, fluorinated surfactants are widely used as surfactants in the emulsion polymerization of fluorinated monomers. Among them, perfluorooctanoic acid (PFOA) C7F is known to be a good example. 15 COOH or its salts (PFOA) are surfactants with excellent monomer emulsifying and / or latex stability. However, perfluorinated chemicals are difficult to decompose in the natural environment, and recent studies have shown that 8-carbon perfluorinated compounds, represented by PFOA, have extremely high residual levels in the human body. Furthermore, due to its excellent affinity for rubber, PFOA results in high levels of PFOA adhering to and / or remaining on the fluororubber formed after the latex obtained by emulsion polymerization coagulates, making it strongly desirable to reduce its content.

[0028] To address this requirement, as a means of imparting environmental degradability to fluorinated emulsifiers, a hydrogenated portion can be incorporated into the perfluorinated hydrophobic group of the surfactant compound. In fluororubber latexes, this can be achieved by using perfluoroalkylalkylphosphonates (C... n F 2n+1 C m H 2m P(O)(OM 1 (OM) 2 As an emulsifier, it can address PFOA issues even without using fluorinated surfactants.

[0029] In the case of using perfluoroalkyl alkyl phosphonates, by making perfluoroalkyl alkyl phosphonate C n F 2n+1 C m H 2m P(O)(OH)₂ (n: an integer from 2 to 6, m: an integer from 1 to 3) is obtained by reacting with alkali metal hydroxides or ammonia. With alkali metal hydroxides or ammonia, a single salt is formed when used in equimolar amounts relative to perfluoroalkylalkylphosphonic acids, and a disalt is formed when used in twice the molar amounts. Generally, a mixture of single and disalts can be formed when used in amounts greater than the necessary theoretical molar number and in amounts greater than equimolar amounts but less than twice the molar amounts.

[0030] These perfluoroalkyl phosphonates, due to their linear fluoroalkyl groups, exhibit better water solubility compared to fluoropolyether emulsifiers with equivalent emulsifying properties. Furthermore, they show lower adhesion to the resulting fluororubber compared to PFOA, thus significantly reducing the residual emulsifier content in fluororubber obtained by coagulating fluororubber latex through emulsion polymerization using methods such as salting out, acid precipitation, and mechanical stirring. The emulsion polymerization reaction of the fluorinated monomers using this emulsifier is carried out in the same manner as when using PFOA emulsifier.

[0031] For emulsion polymerization, water-soluble inorganic peroxides such as ammonium persulfate or their redox systems with reducing agents are used as catalysts. To adjust the pH of the polymerization system, buffering electrolytes such as phosphates (Na₂HPO₄, NaH₂PO₄, KH₂PO₄, etc.) or borates (Na₂B₂O₇, etc.) or NaOH can be added. The emulsion polymerization reaction uses an emulsifier at approximately 0.001% to 10% by weight, preferably approximately 0.01% to 5% by weight, relative to water, and is carried out under pressure at approximately 30°C to 120°C for approximately 1 hour to 48 hours.

[0032] Furthermore, to further improve adhesion, modified fluororubber with a weight-average molecular weight (Mw) of 300,000 or less is preferred. Additionally, the glass transition temperature (Tg) is preferably 20°C or less. If fluororubber within the above range is used, adhesion will be exhibited through the modification described later, and it will be soluble in solvents for coating.

[0033] It should be noted that Patent Document 4 discloses an easy-to-adhesive composition containing hydroxyl-containing resins such as acrylic resin and fluororesin, wax and polyisocyanate compound, and Patent Document 5 discloses an adhesive for 1,1-difluoroethylene resin composed of soft fluororesin, acrylic resin, 1,1-difluoroethylene resin, polyisocyanate and organic solvent. However, although these compositions adhere during the crosslinking reaction, they do not have adhesive properties after the crosslinking reaction. Therefore, although they can be used in coatings and / or adhesives, they cannot be used as adhesives.

[0034] The molecular weight, molecular weight distribution, and Mooney viscosity of fluororubber can be controlled by adjusting conditions such as the degree of polymerization, alkali content, modification temperature, and time. The weight-average molecular weight (Mw) is determined by gel permeation chromatography and is a value obtained by converting a calibration curve made using standard polystyrene.

[0035] Fluororubber is used after being modified using known modification methods. The modification of fluororubber is carried out through alkali modification (using inorganic or organic alkalis, preferably organic alkalis) via a partial defluorination-hydrogenation reaction based on alkali modification, introducing unsaturated bonds (Patent Documents 6-7). This modification process removes HF from the fluoropolymer backbone to form carbon-carbon unsaturated bonds, and reduces the molecular weight of the fluoropolymer through chain scission reactions. This allows for rapid decomposition, molecular weight reduction, and the introduction of functional groups, resulting in a modified fluororubber with adhesive and bonding properties. In inorganic alkali modification, even at room temperature or under heating, the penetration into the rubber is minimal; therefore, organic alkalis that penetrate into the fluororubber latex at room temperature are preferred. With organic alkalis, the fluororubber is uniformly modified, resulting in a more adhesive modified fluororubber.

[0036] Modified fluororubber has unsaturated bonds and functional groups such as carboxyl groups at the ends. Therefore, by adding crosslinking agents, the crosslinking agents react and crosslink with the substrate to be bonded, thereby improving the adhesion, durability, liquid resistance, solvent resistance, and bonding strength under heating. It can be used as an adhesive that brings out the characteristics of fluororubber.

[0037] Furthermore, through partial defluorination of hydrogen, unsaturated bonds are formed in the main chain. After the chain-breaking reaction, functional groups such as carboxyl groups are formed at the ends of the molecular chain through oxidation. This allows for crosslinking with epoxy resins and / or crosslinking agents such as diamine compounds and polyamine compounds without the need for an acid-receiving agent. The number of modified functional groups is not particularly limited.

[0038] Higher modification temperatures result in more polymers, while lower temperatures result in more low-molecular-weight compounds. When using inorganic alkalis for modification, fluororubber will not modify unless heated above 40°C. However, with organic alkalis, controlling the molecular weight becomes difficult above 40°C, so the modification is typically carried out at approximately 5°C to 35°C. With organic alkalis, if the modification temperature is below room temperature, it takes time to stabilize the modification. Modification can be carried out stably in a short time within the range of 20°C to 30°C, which is considered room temperature. Shorter modification times result in greater deviations in the modified state, while longer times result in smaller deviations. More modifier leads to more low-molecular-weight compounds; the modification temperature and amount of modifier can be adjusted according to the required molecular weight. The heating and drying temperature after modification and cleaning is about 60°C to 150°C, preferably about 80°C to 120°C. If it is lower than this, foaming will occur during adhesive sheet lamination due to insufficient drying and solvent residue. The adhesion will deteriorate due to the residue of low molecular weight substances. If it is higher than this, cross-linking will increase, and the material will become polymerized, resulting in reduced adhesion.

[0039] As an organic base, at least one of the following is used: 1,8-diazabicyclo[5.4.0]undecene-7 (DBU), 1,5-diazabicyclo[4.3.0]nonene-5 (DBN), tetramethylammonium hydroxide, tetramethylammonium hydroxide, tetrabutylphosphine hydroxide, etc. As an inorganic base, potassium hydroxide, sodium hydroxide, lithium hydroxide, etc., can be listed; these are soluble in water and mixed in fluororubber.

[0040] Modified fluororubber uses Mooney viscosity (ML) based on JIS K6300-1 (2013) corresponding to ISO 289:12005. 1+10 The molecular weight (at 121℃) is 10–80, preferably 10–50, and the weight-average molecular weight (Mw) is 1.0 × 10⁻⁶. 5 ~3.0×10 5 The number-average molecular weight Mn is 0.3 × 10⁻⁶. 5 ~7.0×10 5 Rubber within this range. If the Mooney viscosity is higher than this, there is no adhesiveness; if it is lower, it contains liquid substances due to decomposition during modification, which may contaminate the adhered material and / or impair the adhesiveness. Here, the Mooney viscosity is measured according to JIS K6300-1 (2013) corresponding to ISO 289:12005, using a Mooney viscometer SMV-201 (manufactured by Shimadzu Corporation), under the conditions of a temperature of 121°C, a preheating time of 1 minute, and a rotor rotation time of 10 minutes.

[0041] Mooney viscosity ML of fluororubber 1+10 (121℃) Due to the decomposition of fluororubber caused by modification, the concentration is reduced by 15-70%, preferably by 20-70%, compared to before modification. As a result, adhesion is improved.

[0042] Modified fluororubber latex or solutions, after salting out or condensing, can be easily and cost-effectively washed with water to remove components other than fluororubber, forming a non-polluting adhesive suitable for electronic components, semiconductor components, etc. This is because the fluororubber is prepolymerized (partially crosslinked) by heating and drying the water, which imparts adhesive properties.

[0043] As an acrylic adhesive, an adhesive is used that contains acrylate monomers and methacrylate monomers with highly crosslinkable functional groups in addition to acrylic monomers and methacrylate monomers. For example, an adhesive is made by copolymerizing at least one of monomers without functional groups, such as ethyl acrylate (EA) and / or butyl acrylate (BA) and methyl methacrylate (MMA), and monomers with highly crosslinkable functional groups, such as methacrylic acid (MAA) and / or monobutyl fumarate (MBF).

[0044] Specifically, examples of monomers without functional groups include alkyl (meth)acrylates (excluding ethyl methacrylate and methyl methacrylate), such as ethyl acrylate, methyl acrylate, butyl methacrylate, 2-ethylhexyl methacrylate, propyl methacrylate, pentyl methacrylate, hexyl methacrylate, vinyl acetate, vinyl propionate, styrene, and (meth)acrylonitrile, preferably selected from at least one of ethyl acrylate, butyl methacrylate, acrylonitrile, methyl acrylate, 2-ethylhexyl methacrylate, and vinyl acetate, which facilitate adjustment of the overall Tg of the adhesive layer to an appropriate range. By using these, the peel force from the adhered material can be adjusted more easily, and the overall Tg of the adhesive layer can be adjusted to an appropriate range more readily.

[0045] Monomers containing highly crosslinkable functional groups include, for example, monomers having carboxyl, hydroxyl, amino, acetyl acetoxy ethyl, epoxy, etc. From a general viewpoint, monomers containing at least one of carboxyl and hydroxyl groups are preferred, and monomers containing carboxyl groups are even more preferred.

[0046] As monomers containing carboxyl groups, examples 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 itaconic acid monomethyl ester, itaconic acid monobutyl ester, fumaric acid monobutyl ester, and phthalic acid 2-acryloyloxyethyl ester; and unsaturated tricarboxylic acid monoesters such as trimellitic acid 2-(meth)acryloyloxyethyl ester and pyromellitic acid 2-(meth)acryloyloxyethyl ester; and (meth)acrylic acid carboxylalkyl esters such as (meth)acrylic acid carboxyl ethyl ester and (meth)acrylic acid carboxyl pentyl ester.

[0047] For these monomers, the ratio of monomers without highly crosslinkable functional groups is 30% to 95.5% by weight, and monomers with highly crosslinkable functional groups is 0.5% to 70% by weight. The more low molecular weight monomers such as ethyl acrylate are used, the better the compatibility with modified fluororubber tends to be. By copolymerizing monomers with highly crosslinkable functional groups, the degree of crosslinking can be adjusted. While increasing the degree of crosslinking can lead to increased adhesive strength and improved liquid resistance, it can also reduce adhesion. Therefore, the above copolymerization ratios are adjusted according to the application.

[0048] The synthesis of acrylic copolymers 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. Solution polymerization is preferred for its simplicity. When solution polymerization is used, reaction solvents such as ethyl acetate, toluene, methyl ethyl ketone, methyl sulfoxide, ethanol, acetone, and diethyl ether can be used. These reaction solvents can be used alone or in combination of two or more.

[0049] There are no particular restrictions on polymerization initiators; free radical polymerization initiators, anionic polymerization initiators, and cationic polymerization initiators can be used. Thermal free radical polymerization initiators can be appropriately used. Examples of thermal free radical polymerization initiators include organic peroxides and azo compounds. Examples of organic peroxides include 1,1-bis(tert-hexylperoxide)-3,3,5-trimethylcyclohexane, tert-hexyl peroxypentanoate, tert-butyl peroxypentanoate, 2,5-dimethyl-2,5-bis(2-ethylhexanoylperoxide)hexane, tert-hexyl peroxy-2-ethylhexanoate, tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxyisobutyrate, tert-butyl peroxy-3,3,5-trimethylhexanoate, and tert-butyl peroxylaurate. Examples of azo compounds include azobisisobutyronitrile and azobiscyclohexaneformitrile. These polymerization initiators can be used alone or in combination of two or more.

[0050] In the obtained acrylic copolymer, an acrylic adhesive with a Tg of 20°C or lower, preferably 0°C or lower, is used as the acrylic adhesive. By using an acrylic adhesive with this Tg, the adhesion at room temperature is improved.

[0051] Furthermore, 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 according to polymerization conditions, such as the type or amount of polymerization initiator, polymerization temperature, and monomer concentration. If it is below this range, the adhesive strength decreases, and foaming occurs after bonding. If it is above this range, the compatibility with the modified fluororubber deteriorates, liquid layer separation occurs, and the surface loses its adhesiveness.

[0052] It should be noted that the lower the weight-average molecular weight (Mw) of the acrylic copolymer, the better the adhesion. If it exceeds 1,000,000, the adhesion will be lost even at a Tg below 20°C. If it is not acrylic rubber but acrylic adhesive, commercially available products can be used directly. For example, products such as Arontack S-1511X, S-3403, and S-3452YKF from Toa Synthetic, Cybinol AT-193, AT-D40, AT-D50, AT-D45, AT-191, AT-260NT, ATR-1, ATR-373, and ATR-347 from Saiden Chemicals, CT-5030 from DIC, and Nissetsu KP-2500 from Carbide Industries, Japan, can be used.

[0053] It should be noted that Patent Document 8 discloses a heat-sensitive adhesive composed of a fluorinated thermoplastic rubber including acrylic polymers, but this heat-sensitive adhesive is not the same type of adhesive used in commercially available adhesive tapes. Since acrylic polymers are rubbery, they have almost no adhesive properties. Although it can be used as a heat-sensitive adhesive, it cannot be used as a pressure-sensitive adhesive for pressing at room temperature. With this adhesive, if a crosslinking agent is added and crosslinked before bonding, the adhesiveness and bonding properties are lost. Therefore, if it is not bonded to the bonding surface before crosslinking, the desired adhesive properties cannot be obtained. Furthermore, Patent Document 9 discloses a rubber composition in which organic peroxides are incorporated into a specific blend of fluororubber and acrylic rubber. Similar to the invention described in Patent Document 8, the molded article obtained from the disclosed rubber composition is rubbery and is not the same type of adhesive used in commercially available adhesive tapes. It has almost no tack at room temperature and cannot be used as a pressure-sensitive adhesive.

[0054] These inventions all combine rubber-like acrylic polymers into fluororubber, thus failing to achieve the adhesive properties targeted by this invention. Although they may adhere to surfaces such as glass, for example, if a rubber surface is formed on a 30-degree inclined plane and a steel ball with a diameter of 4.8 mm is placed there, the steel ball will roll.

[0055] For acrylic adhesives, they are blended in proportions of 10 to 400 parts by weight, preferably 25 to 250 parts by weight, relative to 100 parts by weight of modified fluororubber. If the blending amount is less than this, the adhesion decreases; conversely, if it is more, the heat resistance and / or solvent resistance deteriorate. The degree of adhesion can be adjusted according to the amount of acrylic adhesive. By blending the acrylic adhesive into the modified fluororubber, the desired adhesion and bonding properties that cannot be obtained by using modified fluororubber alone can be adjusted.

[0056] As a blending method, the following steps are commonly used: dissolving modified fluororubber in a solvent and blending it with a solution-polymerized acrylic binder solution by stirring. Alternatively, methods can be used such as: latex modification of fluororubber with alkali followed by mixing with an acrylic binder emulsion, and mixing solvent-free acrylic binder into solid modified fluororubber using rollers and / or a kneader.

[0057] In fluororubber compositions, by further adding a crosslinking agent, the terminal functional groups of the prepolymerized fluororubber react with the crosslinking agent, and then the crosslinking agent reacts and crosslinks with the substrate to be bonded, thereby improving durability, liquid resistance, and chemical resistance.

[0058] As a crosslinking agent, there are no particular limitations on the material that is cured by heat treatment. The following thermosetting resins can be used: epoxy resin, phenolic resin, xylene resin, guanidine resin, diallyl phthalate resin, vinyl ester resin, unsaturated polyester resin, furan resin, polyimide resin, polyurethane resin, cyanate ester resin, maleimide resin, benzocyclobutene resin, butadiene resin, etc., as well as one or more of aromatic diamine compounds and aliphatic diamine compounds. From the viewpoints of reactivity, heat resistance, and adhesion to the substrate, epoxy resin is preferred. From the viewpoint of pot life, aromatic diamine compounds are preferred. In addition to improving adhesion to the substrate, epoxy resins and aromatic diamine compounds can undergo cross-linking reactions with modified fluororubber and acrylic adhesives. Therefore, in the cured adhesive composition, they contribute to improved adhesion to modified fluororubber and acrylic adhesives, compatibility in the coating solution, and the solvent resistance, chemical resistance, water resistance, and water vapor resistance of the coated and dried sheet. If cross-linking agents such as epoxy resins are used, the cross-linking reaction occurs even in the presence of oxygen and air. Therefore, even if the cross-linking reaction is prevented by isolating air and oxygen through a press, coating and cross-linking can still be performed, allowing it to bond with the target material.

[0059] Examples of epoxy resins include bisphenol-type epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, and bisphenol S type epoxy resin; phenolic varnish-type epoxy resins such as phenol, cresol, and bisphenol A varnish-type epoxy resin; alicyclic epoxy resins; aliphatic chain epoxy resins; diglycidyl ethers of biphenol; diglycidyl ethers of naphthalene glycol; diglycidyl ethers of phenols; diglycidyl ethers of alcohols; and their alkyl-substituted derivatives and hydrides, etc. Cresol varnish-type epoxy resins are preferred. Epoxy resins can be used alone or in combination with two or more other types.

[0060] As polyamine compounds, 4,4'-methylenebis(2-ethyl-6-methylaniline), diaminodiphenyl sulfone, diaminodiphenylmethane, m-phenylenediamine, diethylenetriamine, triethylenetetramine, isophorone diamine, etc., are used. From the viewpoints of adhesive liquid lifespan, adhesive sheet lifespan, and heat resistance, aromatic diamine compounds are preferred over aliphatic compounds.

[0061] The crosslinking agent is used in a ratio of 1 to 50 parts by weight, preferably 4 to 20 parts by weight, relative to 100 parts by weight of modified fluororubber. By combining it with a thermosetting resin, the adhesion, bonding to the substrate, solvent resistance, and durability are increased. If the amount is less than this, the bonding strength is low, and the liquid resistance and durability are reduced; if the amount is more than this, the compatibility deteriorates, the adhesion is lost, and the material hardens.

[0062] As a curing catalyst for crosslinking, imidazole compounds such as 2-methylimidazolium, 2-ethyl-4-methylimidazolium, 2-undecylimidazolium, 2-heptadecylimidazolium, 2-phenylimidazolium, 1-benzylimidazolium, 1-benzyl-2-methylimidazolium, 2,4-diamino-6-[2-methylimidazoline-(1)]-ethyl, and triazine can be used. The curing catalyst is used at a ratio of 0.1 to 5 parts by weight, preferably 0.2 to 2.5 parts by weight, relative to 100 parts by weight of the modified fluororubber. If the proportion of the curing catalyst is less than this, the curing of the fluororubber is slow and crosslinking is reduced; conversely, if the curing catalyst is used at a higher proportion, the curing speed of the fluororubber may increase, leading to decreased stability of the adhesive's organic solvent solution over time, decreased adhesion due to reduced storage stability of the coated sheet, increased crosslinking density, and / or catalyst residue, resulting in decreased adhesion. Depending on the type of epoxy resin and / or the curing speed, heat treatment may sometimes be used without the catalyst.

[0063] In fluororubber adhesive compositions, without prejudice to the purpose of this invention, tackifying resins, plasticizers, liquid rubbers, liquid resins, fillers, etc., may be appropriately added or used to adjust adhesion and bonding properties. Here, depending on the heating temperature and heating time after bonding to the target material, the adhesive strength may sometimes increase, and the adhesive may transfer onto the target material. Therefore, to prevent this transfer, the amount of crosslinking agent may be reduced, or plasticizers, liquid rubbers, liquid resins, etc., may be appropriately added or used.

[0064] Examples of tackifying resins include rosin ester-based resins with a hydroxyl value less than 40 mg KOH / g, terpene-based resins, terpene phenol-based resins, coumarone-indene-based resins, alicyclic saturated hydrocarbon resins, C5-based petroleum resins, C9-based petroleum resins, and C... 5～9 Copolymerized petroleum resins, etc.

[0065] Examples of plasticizers include phthalate plasticizers, fatty acid diester plasticizers, trimellitate plasticizers, epoxy plasticizers, phosphate plasticizers, ether plasticizers, polyester plasticizers, and chlorine plasticizers.

[0066] Examples of liquid rubbers include isoprene, 1,4-polybutadiene, NBR, and HNBR, which have viscosities ranging from 10 mPa·s to 100,000 mPa·s.

[0067] Examples of liquid resins include terpene resins, epoxy resins, polyamide resins, acrylic resins, 1,2-polybutadiene, polyether polycarbonate, and polyethylene glycol, which have viscosities ranging from 10 mPa·s to 100,000 mPa·s.

[0068] As fillers, known materials can be used, including, for example, metal hydroxides such as aluminum hydroxide and magnesium hydroxide, and / or 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. When the maximum particle size of the filler is larger than the coating thickness of the binder, the coated sheet will have unevenness; therefore, the adhesion can be adjusted by its particle size and filler dosage. To improve adhesion, the filler addition amount is less than 3%, or preferably none.

[0069] As a solvent that can be used in fluororubber adhesive compositions, any organic solvent capable of dissolving fluororubber is acceptable, without particular limitations. Examples include ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, di-n-propyl ketone, diisobutyl ketone, phorone, isophorone, 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, pentanol, and heptanol. These solvents can also be used in the form of mixtures of two or more solvents.

[0070] Examples of suitable substrates for fluororubber adhesive compositions include polyimide films, polyetheretherketone films, polyphenylene sulfide films, aramid films, polyethylene naphthalate films, liquid crystal polymer films, polyethylene terephthalate films, polyethylene films, polypropylene films, TPX films, fluoropolymer films, and reinforcing films such as copper, silver, gold, tin, aluminum, indium, and their alloys. There are also cases where the substrate is coated onto metals, release films, peel films, or release papers, and then attached to the reinforcing film and / or metal for transfer printing.

[0071] The resin material constituting the substrate film may, as needed, contain antioxidants, ultraviolet absorbers, plasticizers, pigments, dyes, and various additives. For example, known or conventional surface treatments such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, and primer coating can be performed. Such surface treatments can, for example, be used to improve the adhesion between the substrate film and the adhesive layer (the anchoring of the adhesive layer). As for the thickness of the substrate film, a film thickness of 5 μm to 200 μm is typically used, preferably around 10 μm to 100 μm. When the thickness of the substrate film is within this range, it provides excellent adhesion to and peelability from the adhered object, and is therefore preferred.

[0072] As an adhesive coating method, it can be performed as follows: after adjusting the concentration of the solid component to 10% to 50% by weight, preferably 15% to 40% by weight, coating is performed to achieve a thickness of 5 μm to 200 μm after drying. As a coating method, in addition to roller coating, die coating, and doctor blade coating, screen printing, partial coating using a dispenser, and / or inkjet printing can also be used. The coating liquid is adjusted to a viscosity suitable for each coating method. For example, in roller coating, the viscosity is preferably 500 mPa·s to 5,000 mPa·s, and the concentration of the solid component is adjusted appropriately according to the air temperature and / or liquid temperature. For example, an organic solvent solution of the above-mentioned adhesive composition is prepared, coated onto a resin film layer such as polyimide to form an adhesive layer, and then dried at approximately 50°C to 200°C for approximately 1 minute to 15 minutes to obtain an adhesive film. When acrylic adhesives contain low molecular weight compounds, foaming may occur when heated after lamination. Therefore, in such cases, the drying temperature after coating can be increased to around 200°C.

[0073] The bonding is performed according to JIS Z 0237 2009 Test Methods for Adhesive Tapes and Sheets, corresponding to ISO 29862:2007, 29863:2007, and 29864:2007, using a roller press and / or roller laminator, at room temperature or with heating. Furthermore, by further post-treatment at approximately 150°C to 200°C for approximately 1 minute to 15 hours using a vacuum press and / or a heated press with heated air at approximately 150°C to 200°C for approximately 10 seconds to 3 hours (oven crosslinking), the adhesion can be further improved. After bonding, even without a press, the bond strength can be improved by heating in an oven or similar environment at approximately 80°C to 200°C for approximately 1 minute to 24 hours.

[0074] Example The present invention will now be described based on embodiments.

[0075] Reference Example 1 [Preparation of fluororubber latex] 15 kg of water and 2.5 g of emulsifier (Neos product FS-1110) were added to a 30 L stainless steel pressure vessel equipped with a stirrer. After fully purging the internal space with nitrogen, 1,285 g of 1,1-difluoroethylene (VdF) and 1,831 g of hexafluoropropylene (HFP) were introduced, raising the temperature inside the reaction vessel to 70 °C. The pressure inside the reactor at 70 °C was 3.09 MPa.

[0076] Use the same weight ratio of VdF / HFP mixed gas as during initial loading as the initial loading gas, pressurizing until the internal pressure reaches 24 kgf / cm². 2 G. Subsequently, 10g of diethyl malonate was injected to raise the internal temperature to 80°C. An aqueous solution of polymerization initiator, obtained by dissolving 5g of ammonium persulfate in 150g of water, was injected into the autoclave to initiate the polymerization reaction. At the point when the internal pressure decreased to 2.842MPa, the same VdF / HFP mixed gas was injected as a feed gas until the internal pressure became 2.94MPa. This process was repeated whenever the internal pressure decreased to 2.842MPa. Three hours after the first injection of the mixed gas following the start of the polymerization reaction, the injection of the same VdF / HFP mixed gas was stopped. Immediately afterwards, unreacted gas in the autoclave was purged to stop the reaction, yielding an aqueous emulsion (fluororubber latex). The fluororubber latex yielded 23kg (32% solids concentration, 7,310g solid fluororubber).

[0077] [Modification of fluororubber] While stirring 1 kg of fluororubber latex at a liquid temperature of 25°C, 40 g of a 10% sodium laurate aqueous solution at a liquid temperature of 25°C was added dropwise. While stirring the latex at 100 rpm, 119.2 g of a DBU aqueous solution containing 19.2 g of DBU at a liquid temperature of 25°C was added. Then, the mixture was stirred at 100 rpm for 5 hours at room temperature to modify the fluororubber.

[0078] Salting out of fluororubber The modified fluororubber latex was added dropwise while stirring at 400 rpm with 3 kg of a 20% by weight NaCl aqueous solution. The mixture was stirred for 5 minutes to achieve micro-dispersion. Then, 5 L of water was added, and the mixture was stirred for another 5 minutes. After standing for 3 minutes to allow the fluororubber to settle, the supernatant was removed, and salting out of the modified fluororubber latex was performed.

[0079] [Water washing of fluororubber] Add 5L of water, stir at 400rpm for 5 minutes, let stand for 2 minutes, wash the modified fluororubber with water and let it settle, remove the upper layer, repeat this operation 5 times, add 5L of water, stir at 400rpm for 30 minutes, let stand for 2 minutes, wash the modified fluororubber with water, let it settle, remove the upper layer, repeat this operation 5 times.

[0080] [Drying of fluororubber] The resulting modified fluororubber was washed and placed on a wire mesh at a height of 30 mm and dried in an oven at 80°C for 15 hours. The Mooney viscosity (ML) of the dried modified fluororubber was determined. 1+10 (121℃) is 10, and the weight-average molecular weight Mw is 200,000.

[0081] See Example 2 In Reference Example 1, no modification process was performed on the fluororubber. The Mooney viscosity (ML) of the dried, unmodified fluororubber is... 1+10 (121℃) is 50, and the weight-average molecular weight Mw is 500,000.

[0082] See Example 3 900g of methyl isobutyl ketone was added to 100g of the dried, unmodified fluororubber obtained in Reference Example 2, followed by 100g of a 20% by weight potassium hydroxide solution. The mixture was stirred at 60°C and 100 rpm for 8 hours. Then, 9% by weight sulfuric acid was added dropwise until the pH reached 3, thus modifying the fluororubber. The modified fluororubber solution was then added dropwise to ethanol while stirring, followed by washing with water and drying as in Reference Example 1. The Mooney viscosity (ML) of the dried fluororubber was... 1+10 (121℃) is 30, and the weight-average molecular weight Mw is 300,000.

[0083] See Example 4 [Preparation of acrylic adhesive solution] In a reaction vessel equipped with stirring blades, a thermometer, a nitrogen inlet pipe, and a condenser, 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 were added. After nitrogen purging for 30 minutes while stirring at 150 rpm, 0.2 parts by weight of 2,2'-azobisisobutyronitrile (2,2'-Azobisisobutyronitrile) were added as a polymerization initiator. The polymerization reaction was carried out at a temperature of approximately 65°C for 6 hours, yielding an acrylic adhesive solution with a solid content of 40% by weight. The weight-average molecular weight (Mw) was 220,000, and the Tg was -43°C.

[0084] See Example 5 In Reference Example 4, an acrylic adhesive solution with a solid content of 40% by weight was prepared by replacing butyl acrylate with 99 parts by weight of ethyl acrylate. The weight-average molecular weight (Mw) was 110,000, and the Tg was -18°C.

[0085] Example 1

[0086] The above components were dissolved to obtain a fluororubber composition.

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

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

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

[0090] Example 5 In Example 1, the same amount (250 parts by weight; equivalent to 100 parts by weight of solids) 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) (Kumiai Chemical Industry product CUREHARD MED-J) was further used, and the amount of butyl acetate was changed to 690 parts by weight.

[0092] Example 7 In Example 2, o-cresol phenolic varnish-type epoxy resin and 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 components), the amount of o-cresol phenolic varnish 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, 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, instead of modified fluororubber, the same amount (250 parts by weight; 100 parts by weight of solids) of unmodified fluororubber obtained in Reference Example 1 was used.

[0096] Comparative Example 3

[0097] The above components were dissolved to obtain a fluororubber composition.

[0098] Comparative Example 4 In Example 1, instead of the acrylic adhesive solution, the same amount (100 parts by weight) of acrylic rubber (Unimatec product PA522HF) was used, and the amount of butyl acetate was changed to 834 parts by weight.

[0099] Comparative Example 5 In Example 1, acrylic adhesive solution was not used, and the amount of butyl acetate was changed to 434 parts by weight.

[0100] The fluororubber compositions obtained in the above examples and comparative examples were used as adhesives, and adhesive solution solubility tests, curing tests, solvent resistance tests, adhesive evaluation, initial tack evaluation, and adhesion tests after heat resistance tests were conducted. In the solvent resistance test, adhesive evaluation, initial tack evaluation, and adhesion tests after heat resistance tests, an adhesive sheet with a thickness of 50 μm was coated on a 25 μm thick polyimide film (Toray-DuPont product Kapton EN), dried in solvent at 140°C for 5 minutes, and then coated.

[0101] Adhesive solution solubility test: After dissolving each component of the composition, visually observe the dissolution status after standing at room temperature for 3 hours to confirm whether there is any layer separation.

[0102] If layer separation is not confirmed, the compatibility is assessed as ○; if layer separation is confirmed, the compatibility is assessed as ×.

[0103] Curing test: A fluororubber composition was coated onto a release film (Nitoflon No. 900UL, Nitto Denko product). After drying the solvent at 140°C for 5 minutes to a thickness of 50 μm, the film was vacuum dried at room temperature for 1 hour. The release film was then peeled off, and five sheets were overlapped to form an adhesive sheet with a thickness of 250 μm. A torsional vibration parallel mold vulcanization test was conducted at 170°C using a Curelastometer manufactured by ENEOS Material Co., Ltd., according to JIS K 6300-2, which corresponds to ISO 6502-2:2018, to measure the change in torque.

[0104] The torque value increases as cross-linking progresses. Therefore, if an increase in torque value is observed after 100 minutes, it is considered that cross-linking has been completed and is rated as ○. If no increase in torque value is observed, it is considered that cross-linking has not been completed and is rated as ×.

[0105] Solvent resistance test: Immerse the adhesive sheet in methyl ethyl ketone (MEK) at room temperature for 5 minutes and visually confirm whether the adhesive has been dissolved by MEK.

[0106] If the fluororubber remains undissolved, it indicates that the fluororubber has cross-linked, and the rating is ○. If the fluororubber is dissolved, it indicates that the fluororubber has not cross-linked, and the rating is ×.

[0107] Adhesion evaluation: Based on JIS Z0237 (tilting ball viscosity test), which corresponds to ASTM D3121. Attach the film surface of the adhesive sheet to a 30-degree inclined plane using double-sided tape, and place steel balls No.5 (4.8mm in diameter), No.13 (10.3mm in diameter), No.19 (15.1mm in diameter), No.25 (19.8mm in diameter), and No.32 (25.4mm in diameter) on it to check if they roll.

[0108] A non-rolling ball is rated ○, and a rolling ball is rated ×. The larger the non-rolling steel ball, the higher the adhesion. Initial adhesion evaluation: According to JIS Z0237, which corresponds to ISO 29862:2007, a 25 μm thick polyimide film (KaptonEN), a 0.2 mm thick SUS430 plate, and a 0.2 mm thick aluminum plate were degreased with methyl ethyl ketone and then bonded to a roll laminate at room temperature. A 90° peel test was then conducted (test environment: 23℃±2℃, 50%RH±10%RH, sample shape: 10 mm wide) to determine the peel strength.

[0109] The higher the peel strength, the better the adhesion; preferably above 0.3 N / mm.

[0110] Evaluation of adhesion after heat resistance test: According to JIS Z0237, which corresponds to ISO 29862:2007, a 25 μm thick polyimide film (Kapton EN) was laminated to a roll laminate at 100°C, and a 90° peel test was performed at 150°C or 200°C for 250 hours, 500 hours, and 1,000 hours to determine the peel strength.

[0111] The higher the peel strength, the higher the heat resistance; preferably above 0.3 N / mm.

[0112] The results are shown in Tables 1 and 2 below. It should be noted that, for each comparative example, as an adhesion evaluation test, the following test was further conducted: the film surface of the adhesive sheet was attached to an inclined plane with a 5-degree angle using double-sided tape, and a No. 5 (diameter 4.8 mm) steel ball was placed to check whether it rolled.

[0113]

[0114]

[0115] Based on the results of the above embodiments and comparative examples, the following conclusions can be drawn: (1) In the various embodiments using modified fluororubber, the adhesion, bonding and heat resistance are high, and the more acrylic adhesive there is, the higher the adhesion and bonding are (Examples 1 to 3).

[0116] (2) When using fluororubber modified with organic alkali, higher adhesion and bonding properties can be obtained compared with those of fluororubber modified with inorganic alkali (Examples 1 and 4).

[0117] (3) It shows that the lower the glass transition temperature of the acrylic adhesive, the higher the adhesion (Examples 1 and 5).

[0118] (4) When diamine compounds are added, although the adhesion is slightly reduced, the heat resistance is improved (Examples 1 and 6).

[0119] (5) When no crosslinking agent is used or its amount increases, the adhesion tends to decrease (Examples 1-2, 7-8).

[0120] (6) In the case of acrylic adhesives without fluororubber, although adhesion was confirmed, the bond strength after heat resistance test was lower (Comparative Example 1).

[0121] (7) When using unmodified fluororubber, the initial bond strength and / or adhesion are reduced. In addition, the solvent resistance is poor (Comparative Example 2).

[0122] (8) When using components that are commonly used in fluororubber compositions, although crosslinking occurs, the initial bond strength is low and the adhesion is reduced (Comparative Example 3).

[0123] (9) When acrylic rubber is used instead of acrylic adhesive, the initial bond strength is low and no adhesion is observed (Comparative Example 4).

[0124] (10) When acrylic adhesive is not used, the initial bond strength is low and the adhesion is reduced (Comparative Example 5).

[0125] As the results above show, in each comparative example, there are issues such as low adhesion, low bond strength at room temperature, and poor heat resistance, making it unsuitable as an adhesive to demonstrate heat resistance.

[0126] Industrial availability The fluororubber adhesive composition of the present invention can be effectively used in tapes, adhesives, electronic components, automotive parts, industrial components, as well as in chemical plants, vibration damping plates, anti-vibration plates, heat insulation materials, solar panels, etc.

Claims

1. A fluororubber adhesive composition having unsaturated bonds or having both unsaturated bonds and functional groups, and a Mooney viscosity (ML). 1+10 An acrylic binder is blended into a modified fluororubber with a (121℃) value of 10-80, wherein the acrylic binder contains an acrylic copolymer with a glass transition temperature (Tg) below 20℃.

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

3. The fluororubber adhesive composition according to claim 1 or 2, wherein, Fluororubber is alkali-modified fluororubber, and specifically, the Mooney viscosity (ML) after alkali modification. 1+10 Alkali-modified fluororubber (121℃) has a temperature 15-70℃ lower than that before alkali modification.

4. The fluororubber adhesive composition according to claim 1, wherein, The weight-average molecular weight (Mw) of the modified fluororubber is below 300,000.

5. The fluororubber 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, The mixture contains 10 to 400 parts by weight of acrylic binder relative to 100 parts by weight of modified fluororubber.

7. The fluororubber adhesive composition according to claim 1, wherein, Relative to 100 parts by weight of modified fluororubber, it also contains 1 to 50 parts by weight of crosslinking agent.

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

9. The fluororubber adhesive composition according to claim 7 or 8, wherein, Imidazole is also used as a crosslinking and curing catalyst, and contains 0.1 to 5 parts by weight relative to 100 parts by weight of modified fluororubber.

10. The fluororubber adhesive composition according to claim 7, 8 or 9, wherein, No acid-receiving agent was added.

11. An adhesive sheet, wherein, The fluororubber adhesive composition of claim 1 is laminated on one or both sides of the substrate.

12. The fluororubber adhesive composition according to claim 1, having adhesive properties such that a steel ball with a diameter of 4.8 mm is not rolled when placed on the bonding surface, said bonding surface being formed on an inclined surface at an angle of 30 degrees.

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