Pressure-sensitive adhesive composition, pressure-sensitive adhesive layer, and adhesive sheet

Abstract

The present invention addresses the problem of providing a pressure-sensitive adhesive that can be temporarily fixed to an adherend without reducing the adhesive force of an adhesive layer. The problem is solved by a pressure-sensitive adhesive composition containing acrylonitrile butadiene rubber (A) and an aromatic resin (C) (excluding a phenol resin (B)).

Description

Pressure-sensitive adhesive composition, pressure-sensitive adhesive layer, and adhesive sheet

[0001] The present invention relates to a pressure-sensitive adhesive composition used for adhering adherends to each other, a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition, and an adhesive sheet including the pressure-sensitive adhesive layer.

[0002] Patent Documents 1 and 2 disclose an adhesive sheet for adhering a metal and an unvulcanized rubber. This adhesive sheet vulcanizes the rubber by heating and pressing the adhesive constituting the adhesive sheet, and adheres the rubber and the metal.

[0003] The adhesive sheets of Patent Documents 1 and 2 have a layer formed from a solvent-dispersed vulcanizing adhesive having reactivity with an unvulcanized rubber and a layer formed from a metal-side adhesive which is an adhesive on the side that adheres to the metal.

[0004] The solvent-dispersed vulcanizing adhesive having reactivity with an unvulcanized rubber is an adhesive containing at least one or more of, for example, chlorosulfonated polyethylene, chlorinated natural rubber, maleimide-based compounds, nitroso-based compounds, acid scavengers, crosslinking agents and crosslinking accelerators, carbon black, silica-based fillers, and the like.

[0005] Further, Patent Document 3 describes an undercoat adhesive layer formed from an adhesive having reactivity with a metal. The adhesive having reactivity with a metal is an adhesive containing at least one or more of, for example, phenol resin and phenolic derivative resin, bisphenol-based epoxy resin, polyfunctional aromatic epoxy resin, chlorinated natural rubber, chlorinated polyethylene, chlorinated polypropylene, chlorinated polyolefin, acid scavenger, amine-based curing agent, silica-based filler, carbon black, and the like.

[0006] This adhesive sheet fixes the rubber and the metal through an adhesive having reactivity with the metal and a solvent-dispersed vulcanizing adhesive having reactivity with an unvulcanized rubber by reacting the layer formed from the solvent-dispersed vulcanizing adhesive together with the vulcanization of the rubber of the adherend by heating and pressing.

[0007] Japanese Patent No. 4681634 Japanese Patent No. 5820091 Japanese Patent No. 6767964

[0008] However, the adhesive sheets disclosed in Patent Documents 1 and 2 presuppose the vulcanization of the rubber to be bonded by heating and pressurizing. In other words, before heating and pressurizing, temporary fixing on the bonded object where the adhesive sheet is initially placed is not possible, so the adhesive sheet may shift relative to the bonded object, making it impossible to stably position the adhesive sheet on the bonded object. Moreover, there was a problem in that it was difficult to transfer the adhesive sheet by peeling off only the release liner from the adhesive sheet that had been placed on the bonded object. Here, temporary fixing is defined as fixing the adhesive sheet to the bonded object to the extent that it does not move due to a slight adhesive force.

[0009] Furthermore, if a conventionally known pressure-sensitive adhesive layer (adhesive layer) is separately provided on the adhesive layer of the adhesive sheet in order to impart temporary fixation to the adhesive sheet disclosed in Patent Documents 1 and 2, the pressure-sensitive adhesive layer will inhibit the adhesion of the adhesive layer, resulting in a decrease in adhesive strength after heating and pressurizing.

[0010] Therefore, a pressure-sensitive adhesive is required that allows for temporary fixing to the object to be bonded without reducing the adhesive strength of the adhesive layer. Furthermore, an adhesive sheet is required that allows for temporary fixing to the object to be bonded and, after heating and pressurizing, provides strong adhesion to rubber and other objects to be bonded. The adhesive strength to rubber should be comparable to the interlayer strength of the rubber.

[0011] The problem is solved by a pressure-sensitive adhesive composition containing acrylonitrile butadiene rubber (A) and at least one selected from a phenolic resin (B) and an aromatic resin other than phenolic resin (C).

[0012] This adhesive sheet allows for temporary fixing to the object being bonded without hindering the adhesive strength of the adhesive layer, and its high adhesive strength enables excellent transferability.

[0013] This shows a cross-section of the adhesive sheet 10 according to one embodiment. This shows a cross-section of the adhesive sheet 10 according to one embodiment, which comprises a first release liner 4 and a second release liner 5.

[0014] (Composition of pressure-sensitive adhesive) The pressure-sensitive adhesive composition of this embodiment will be described below. The pressure-sensitive adhesive composition of this embodiment comprises acronitrile butadiene rubber (A) and at least one selected from a phenolic resin (B) and an aromatic resin other than a phenolic resin (C).

[0015] The type of acrylonitrile butadiene rubber (NBR in each table) in this embodiment is not limited, but it is sufficient if it has a sufficiently large amount of bound acrylonitrile (hereinafter, "nitrile amount" is defined as the mass percentage of nitrile groups represented by the formula -C≡N when the entire rubber molecule is considered to be 100% by mass). Preferably, it is acrylonitrile butadiene rubber with a nitrile amount of 18% to 50%, more preferably 25% to 45%, and even more preferably 31% to 43%.

[0016] Examples of acrylonitrile butadiene rubber with an extremely high nitrile content (43% or more), which is even higher than the average high nitrile content, include Nipol® DN003 manufactured by Nippon Zeon Co., Ltd. Examples of high nitrile content acrylonitrile butadiene rubber include Nipol® 1041, 1041L, DN101, DN101L, and DN4050 Examples of medium-high nitrile content acrylonitrile butadiene rubber include Nipol® 1042, 1052J, DN202, DN212, DN219, DN3335, DN3350, and DN3380 Examples of medium nitrile content acrylonitrile butadiene rubber include Nipol® 1043, DN302, DN302H, DN2850, and DN2880. Examples of low-nitrile acrylonitrile butadiene rubber include Nipol® DN401, ND401L, and DN401LL.

[0017] Acrylonitrile butadiene rubber may also be acrylonitrile butadiene isoprene rubber (NBIR) containing isoprene units as repeating units. Examples of acrylonitrile butadiene isoprene rubber include Nipol® DN1201 and DN1201L manufactured by Nippon Zeon Co., Ltd.

[0018] The acrylonitrile butadiene rubber may be carboxyl-modified acrylonitrile butadiene rubber (XNBR) that has been modified with a carboxyl group. Examples of carboxyl-modified acrylonitrile butadiene rubber include Nipol® 1072CGJ and NX775, manufactured by Nippon Zeon Co., Ltd.

[0019] The acrylonitrile butadiene rubber may be hydrogenation-modified hydrogenated nitrile rubber (HNBR). Examples of very high nitrile content hydrogenated acrylonitrile butadiene rubber include Zetpol® 0020 manufactured by Nippon Zeon Co., Ltd. Examples of high nitrile content hydrogenated acrylonitrile butadiene rubber include Zetpol® 1010 and 1020 manufactured by Nippon Zeon Co., Ltd. Examples of medium-high nitrile content hydrogenated acrylonitrile butadiene rubber include Zetpol® 2001, 2001L, 2010, 2010L, 2010H, 2010H, 2020, 2020L, and 2030L manufactured by Nippon Zeon Co., Ltd.

[0020] (Phenolic resin (B)) Examples of phenolic resin (B) in this embodiment include alkylphenol resin, terpene phenol resin, phenol novolac resin, cresol novolac resin, aromatic hydrocarbon formaldehyde resin-modified phenolic resin, dicyclopentadienephenol addition resin, phenol aralkyl resin, naphthol aralkyl resin, trimethylol methane resin, tetraphenyloleethane resin, naphthol novolac resin, naphthol-phenol co-condensed novolac resin, naphthol-cresol co-condensed novolac resin, biphenyl-modified phenolic resin, biphenyl-modified naphthol resin, aminotriazine-modified phenolic resin, and alkoxy group-containing aromatic ring-modified novolac resin. Among these, alkylphenol resins are preferred, and examples of alkylphenol resins include Showol® CKS-380A, CKS-3898, CKM-908, BKS-368, CKM-947, CKM-5254C, ADM-8000, and ADM-8200, all manufactured by Aica Kogyo Co., Ltd.

[0021] The content of phenolic resin (B) can be arbitrarily selected, but it is preferably 100 parts by weight or less, more preferably 10 parts by weight or more and 80 parts by weight or less, and particularly preferably 20 parts by weight or more and 60 parts by weight or less, per 100 parts by weight of acrylonitrile butadiene rubber (A). Furthermore, even if phenolic resin (B) is not included, the objective of the pressure-sensitive adhesive composition of this embodiment can be achieved if the content of aromatic resin (C) other than phenolic resin (B), as described later, is suitable.

[0022] By setting the content of phenolic resin (B) within this range, it becomes easier to improve the transferability of the adhesive sheet, and high adhesive strength can be obtained after heating and pressurizing.

[0023] (Aromatic resin (C)) The aromatic resin (C) in this embodiment is defined as an aromatic resin other than the phenolic resin (B), and examples include xylene resin, styrene resin, coumarone resin, aromatically modified terpene resin, aromatically modified rosin resin, novolac resin, resol resin, aromatic indene resin, etc. Hereinafter in this specification, aromatic resin (C) refers to an aromatic resin other than the phenolic resin (B).

[0024] Here, aromatic resin (C) refers to a resin that contains an aromatic ring in its structure. Examples of aromatic rings include benzene rings, naphthalene rings, anthracene rings, pyridine rings, and five-membered heterocyclic rings such as pyrrole rings and thiophene rings, with benzene rings being preferred among these. Xylene resins are particularly preferred. Xylene resins may be modified resins (for example, alkylphenol-modified xylene resins, rosin-modified xylene resins, xylene-acetylene resins, xylene-formaldehyde resins). Specific examples of xylene resins include xylene resins manufactured by Fudo Co., Ltd. (product names: Nikanol (Y-50, Y-100, Y-300, Y-1000, LLL, LL, L, H, G)), resol-type xylene resins (product names: Nikanol (PR-1440, PR-1440M)), and alkylphenol-modified xylene resins (product names: Nikanol (GHP-150, HP-120, HP-100, HP-2)). Examples include 10. HP-70), novolac-type xylene resin (product name: Nikanol (NP-100, GP-212, P-100, GP-200, HP-30)), polyol-modified xylene resin (product name: Nikanol K-100), ethylene oxide-modified xylene resin (product name: Nikanol L5), etc. Among these, Nikanol L is preferred because it can achieve both adhesive strength and transferability after heating and pressing.

[0025] The content of the aromatic resin (C) in this embodiment can be arbitrarily selected, but it is preferably 200 parts by weight or less, and more preferably 60 parts by weight or more and 160 parts by weight or less, per 100 parts by weight of acrylonitrile butadiene rubber (A). Even if the aromatic resin (C) is not included, the objective of the pressure-sensitive adhesive composition of this embodiment can be achieved by optimizing the type and amount of phenolic resin (B).

[0026] The total content of phenolic resin (B) and aromatic resin (C) is preferably 44 parts by weight or more and less than 300 parts by weight, more preferably 50 parts by weight or more and 260 parts by weight or less, and particularly preferably 60 parts by weight or more and 200 parts by weight or less, per 100 parts by weight of acrylonitrile butadiene rubber (A). By setting the total content of phenolic resin (B) and aromatic resin (C) within this range, an appropriate cohesive force can be imparted to the pressure-sensitive adhesive, thereby preventing peeling defects due to cohesive failure when peeling only the release liner from the aforementioned adhesive sheet.

[0027] By adjusting the content of phenolic resin (B) and aromatic resin (C) within the above-mentioned range, it becomes easier to improve the transferability of the adhesive sheet and obtain high adhesive strength after heating and pressurizing.

[0028] (Other Additives) The pressure-sensitive adhesive composition of this embodiment may contain other additives as needed. Specific examples of other additives include solvents, inorganic fillers, antioxidants, flame retardants, ultraviolet absorbers, light stabilizers, antistatic agents, light-shielding fillers, softeners, plasticizers, dispersants, thickeners, pigments, and foaming agents. The ratio of these additives to 100 parts by weight of acrylonitrile butadiene rubber (A) can be selected from a range of 0.1 parts by weight to 100 parts by weight.

[0029] The pressure-sensitive adhesive composition of this embodiment can be easily mixed into a uniform state by dissolving it in, for example, alcohols such as methyl ethyl ketone, toluene, xylene, and butanol, or alcohols such as ethylene glycol monobutyl ether. However, the pressure-sensitive adhesive composition of this embodiment may be an emulsion type or suspension type using water, or it may be a solid type that does not use dispersants such as organic solvents or water.

[0030] (Pressure-sensitive adhesive layer 2) The pressure-sensitive adhesive composition of this embodiment has appropriate tackiness, and by configuring the pressure-sensitive adhesive composition as a pressure-sensitive adhesive layer, it can typically be used to temporarily fix metals. Furthermore, the objects to be bonded are not limited to metals, and it is suitable for temporarily fixing various objects such as plastics, rubber, cloth, and paper. The pressure-sensitive adhesive layer of this embodiment can be used as an element constituting the adhesive sheet 10 described later, or it can be used alone or laminated on a support that supports the pressure-sensitive adhesive layer.

[0031] The thickness of the pressure-sensitive adhesive layer 2 in this embodiment can be set arbitrarily, but is preferably 0.005 mm or more and less than 0.020 mm, more preferably 0.007 mm or more and 0.017 mm or less, and particularly preferably 0.01 mm or more and 0.015 mm or less. By setting the thickness of the pressure-sensitive adhesive layer 2 to 0.005 mm or more and less than 0.02 mm, good temporary fixation can be obtained, and when the adhesive sheet 10 described later is formed, high adhesive strength after heating and pressurizing and good transferability to the object to be bonded can be achieved. When the pressure-sensitive adhesive layer 2 is used alone or laminated on the support described above, a thickness of less than 0.005 mm or 0.02 mm or more can be appropriately applied depending on the application, etc.

[0032] The method for manufacturing the pressure-sensitive adhesive layer 2 in this embodiment is not particularly limited, but it can be manufactured on a support or release liner using a known coating apparatus, such as a roll coater, comma coater, knife coater, die coater, lip coater, gravure coater, calender coater, etc.

[0033] (Adhesive Sheet 10) The pressure-sensitive adhesive composition of the present invention can be formed as a pressure-sensitive adhesive layer to form an adhesive sheet 10. The adhesive sheet 10 of this embodiment has, in this order, a pressure-sensitive adhesive layer 2, a first adhesive layer 1 that is attached to a first object to be bonded via the pressure-sensitive adhesive layer 2, and a second adhesive layer 3 that is reactive with rubber and is attached to a second object to be bonded different from the first object to be bonded. That is, the pressure-sensitive adhesive layer 2 is on one main surface side of the first adhesive layer 1, and the second adhesive layer 3 is on the main surface side of the first adhesive layer 1 opposite to the pressure-sensitive adhesive layer 2. As long as the pressure-sensitive adhesive layer 2, the first adhesive layer 1, and the second adhesive layer 3 are in this order, each layer may be in direct contact with the others, or they may be laminated with other layers in between.

[0034] (First adhesive layer 1) The first bonded object to be bonded via the pressure-sensitive adhesive layer 2 is typically metal, but other materials such as plastic, cloth, paper, wall coverings, and painted surfaces can also be bonded. Furthermore, rubber can also be bonded, as long as it is different from the second bonded object selected later.

[0035] The adhesive composition constituting the first adhesive layer 1 is typically a metal primer, but is composed of vulcanizing adhesives, other adhesives, or combinations thereof. Specifically, it contains at least two of the group selected from chlorinated rubbers such as chlorinated natural rubber, chlorinated polyethylene, chlorinated polypropylene, and chlorinated polyolefins; carbon black, phenolic resins (including derivatives), bisphenol epoxy resins, polyfunctional aromatic epoxy resins, and other epoxy resins; vulcanization accelerators, acid scavengers, vulcanizing agents, silica-based fillers, and amine-based curing agents. The adhesive composition constituting the first adhesive layer 1 may also contain other additives as needed. Specific examples of other additives include solvents, inorganic fillers, antioxidants, flame retardants, ultraviolet absorbers, light stabilizers, antistatic agents, light-shielding fillers, softeners, plasticizers, dispersants, thickeners, and pigments. The content ratio of these additives can be selected from a range of 0.1% to 10% by weight, when the entire first adhesive composition is considered to be 100% by weight.

[0036] The adhesive composition constituting the first adhesive layer 1 can typically be uniformly mixed by dissolving and dispersing it in an organic solvent, but it may also be an emulsion type or suspension type using water, or a solid type that does not use an organic solvent or a dispersant such as water.

[0037] As commercially available products corresponding to the adhesive composition constituting the first adhesive layer 1, various adhesives sold as commercially available metal primers can be used, such as: Rhode Far East Co., Ltd.'s trade names: Chemlock (205, 207, 208, 2000, 8006, 8007, 8008, 8009B, AP-133, EP5080-11), Circalock 6756, Rhode (P-1201); DuPont's trade names: Sixxon (403, 404, 520-EF, P-6-EF, P-11-EF, P-21); and Toyo Chemical Research Institute's trade names: Metalock (AS, P, PA, PC, PA-3375, PH-37, PH-50, PH-50G, PH-56).

[0038] The thickness of the first adhesive layer 1 can be set arbitrarily, but is preferably 0.001 mm or more and 0.100 mm or less, more preferably 0.005 mm or more and 0.050 mm or less, and particularly preferably 0.010 mm or more and 0.020 mm or less. The thickness of the first adhesive layer 1 being 0.001 mm or more and 0.100 mm or less contributes to obtaining high adhesive strength after heating and pressurizing.

[0039] (Second adhesive layer 3) The second bonding target to which the second adhesive layer 3, which has reactivity with rubber, is applied is typically unvulcanized rubber, but it may also be vulcanized rubber. In addition, bonding targets other than rubber, such as plastics, cloth, paper, wall materials, and painted surfaces, can also be selected. Furthermore, metals can also be used as bonding targets, as long as they are different from those selected as the first bonding target.

[0040] The adhesive composition constituting the second adhesive layer 3 is typically a vulcanizing adhesive, but is composed of a metal primer, other adhesives, or a combination thereof. Specifically, it contains at least two of the group selected from chlorosulfonated polyethylene, chlorinated rubber such as chlorinated natural rubber, carbon black, acid scavenger, vulcanizing agent, vulcanization accelerator, maleimide compounds, and nitroso compounds. The adhesive composition constituting the second adhesive layer 3 may also contain other additives as needed. Specific examples of other additives include solvents, inorganic fillers, antioxidants, flame retardants, ultraviolet absorbers, light stabilizers, antistatic agents, light-shielding fillers, softeners, plasticizers, dispersants, thickeners, and pigments. The content ratio of these additives can be selected from a range of 0.1% to 10% by weight, when the total adhesive composition constituting the second adhesive layer 3 is considered to be 100% by weight.

[0041] The adhesive composition constituting the second adhesive layer 3 can typically be uniformly mixed by dissolving and dispersing it in an organic solvent, but it may also be an emulsion type or suspension type using water, or a solid type that does not use an organic solvent or a dispersant such as water.

[0042] The thickness of the second adhesive layer 3 can be set arbitrarily, but is preferably 0.001 mm or more and 0.100 mm or less, more preferably 0.005 mm or more and 0.050 mm or less, and particularly preferably 0.010 mm or more and 0.020 mm or less. The thickness of the second adhesive layer 3 being 0.001 mm or more and 0.100 mm or less contributes to obtaining high adhesive strength after heating and pressurizing.

[0043] As commercially available products corresponding to the adhesive composition constituting the second adhesive layer 3, there are products manufactured by Lord Corporation, trade names: Chemglue (236X, 238 (NW), 238ID, 259, 286, 289, 290, 320, 310 - B, 402, 402X - HS, 481, 487, 489, 456, 6016, 607, 608, 610, 6108, 8110, 8210, Y - 4310, 2332, 234B, 234X, 236A, 855 - 1, 8560D - 1, 8560S - 1), products manufactured by DuPont, trade names: Zyxone (2001 - EF, 422, 423, 511 - EF, 516 - EF, 520 - EF, 520 - P - EF, 526, 532 - A - EF, 550, 560, OSN - 2 - EF, OSN - 2 - EF - VV, OSN - 2 - S), products manufactured by Toyo Chemical Research Institute, trade names: Metalock (B, F - 112, F - 116, F - 142, G - 25, G - 165, G - 166, J - 11, J - 21, R - 17, R - 141, R - 146), etc. Various adhesives sold as for unvulcanized rubber, vulcanized rubber, etc. can be used.

[0044] (Release Liner) The adhesive sheet 10 of the present embodiment may have a first release liner 4 or a second release liner 5 as necessary. The first release liner 4 and the second release liner 5 are a general term for release films, release papers, and other release sheets, and are typically release films. By using the first release liner 4 or the second release liner 5, blocking when the adhesive sheet is wound around a winding core such as a paper tube can be prevented. In particular, since the adhesive sheet 10 of the present embodiment has a pressure - sensitive adhesive layer 2 having adhesiveness, by protecting the side of the pressure - sensitive adhesive layer 2 with the first release liner 4, the workability during processing into a specific punching shape can be improved. The thickness of the first release liner 4 of the present embodiment is not limited, but is preferably 0.010 mm or more and 0.500 mm or less, more preferably 0.020 mm or more and 0.300 mm or less, and particularly preferably 0.023 mm or more and 0.200 mm or less.

[0045] Furthermore, in addition to the first release liner 4 positioned on the pressure-sensitive adhesive layer 2 side, a second release liner 5 may be positioned on the second adhesive layer 3 side of the adhesive sheet 10 in this embodiment. In this case, it is preferable that the peeling force between the first release liner 4 and the pressure-sensitive adhesive layer 2 is lower than the peeling force between the second release liner 5 and the second adhesive layer 3. This allows the first object to be temporarily fixed after the first release liner 4 has been peeled off from the pressure-sensitive adhesive layer 2. After temporary fixing, the adhesive sheet 10 can be transferred to the first object to be bonded (e.g., metal) by peeling off the second release liner 5 from the second adhesive layer 3. After the transfer, the second adhesive layer 3, from which the second release liner 5 has been peeled off, is placed on the second object to be bonded (e.g., unvulcanized rubber) and temporarily fixed, making it possible to heat and pressurize the adhesive sheet 10 positioned between the first and second objects to be bonded.

[0046] (Thickness of the adhesive sheet 10) The thickness of the adhesive sheet 10 in this embodiment, excluding the first release liner 4 and the second release liner 5, can be set arbitrarily, but is preferably 0.007 mm or more and 0.220 mm or less, more preferably 0.017 mm or more and 0.177 mm or less, and particularly preferably greater than 0.035 mm and less than 0.050 mm.

[0047] (Method for manufacturing the adhesive sheet 10) Next, referring to FIGS. 1 and 2, the adhesive sheet 10 and its manufacturing method according to the present embodiment will be described. FIG. 1 shows the adhesive sheet 10 according to the present embodiment. FIG. 2 shows the adhesive sheet 10 provided with the first release liner 4 and the second release liner 5. The manufacturing method of the adhesive sheet 10 according to the present embodiment is, for example, sequentially forming the second adhesive layer 3, the first adhesive layer 1, and the pressure-sensitive adhesive layer 2 on the release surface of the second release liner 5 using the above-described coating apparatus, and, if necessary, laminating the first release liner 4 on the pressure-sensitive adhesive layer 2, whereby an adhesive sheet 10 having the first release liner 4 and the second release liner 5 on both sides can be obtained. On the contrary, it is also possible to manufacture the adhesive sheet 10 according to the present embodiment by sequentially forming the pressure-sensitive adhesive layer 2, the first adhesive layer 1, and the second adhesive layer 3 on the release surface of the first release liner 4 and laminating the second release liner 5 on the second adhesive layer 3 if necessary. Further, the second adhesive layer 3 and the first adhesive layer 1 are sequentially formed on the release surface of the second release liner 5 using the above-described coating apparatus, and a pressure-sensitive adhesive layer 2 formed separately on the release surface of the first release liner 4 is laminated on the first adhesive layer 1 side, whereby the adhesive sheet 10 can be obtained.

[0048] As described above, the embodiments of the present invention have been described, but the present invention is not limited to the above embodiments and various modifications can be made.

[0049] Hereinafter, the effects of the present invention will be made clearer by way of examples and comparative examples. Note that the present invention is not limited only to the following examples and can be implemented with appropriate modifications without changing the gist thereof.

[0050] (Preparation of the pressure-sensitive adhesive composition) With respect to 100 parts by weight of acrylonitrile-butadiene rubber (A), a phenol resin (B) and an aromatic resin (C) were added in the amounts shown in the table and mixed by a stirrer to prepare the pressure-sensitive adhesive compositions of Examples 1 to 18 and Comparative Examples 1 to 6. Note that the amounts shown in the table are all amounts of parts other than the solvent, and were diluted with an organic solvent such as methyl ethyl ketone or ethylene glycol monobutyl ether so as to have a viscosity suitable for coating and then mixed.

[0051] The correspondence between each symbol of each component listed in the table is as follows (in no particular order): 1041L (High Nitrile): Manufactured by Nippon Zeon Co., Ltd., product name "Nipol 1041L" (Acrylonitrile Butadiene Rubber (NBR)) CKS-3898: Manufactured by Aica Kogyo Co., Ltd., product name "Shounol CKS-3898" (Phenolic Resin) Nikanol L: Manufactured by Fudo Co., Ltd., product name "Nikanol L" (Xylene Resin) AST-8850: Manufactured by Nippon Shokubai Co., Ltd., product name "AST-8850E" (Acrylic Adhesive) ATR-340: Manufactured by Saiden Chemical Co., Ltd., product name "ATR-340" (Acrylic Adhesive) D-101: Manufactured by Mitsui Chemicals, Ltd., product name "Takenate D-101E" (Isocyanate Crosslinking Agent) 1010 (HNBR): Manufactured by Nippon Zeon Co., Ltd., product name "Zetpol 1010" (Hydrogenated Acrylonitrile Butadiene Rubber) BKS-368: Manufactured by Aica Kogyo Co., Ltd., product name "BKS-368" (alkylphenol resin) EQ715F: Manufactured by Aica Kogyo Co., Ltd., product name "EQ715F" (phenol resin) 003 (Extra High Nitrile): Manufactured by Nippon Zeon Co., Ltd., product name "Nipol DN003" (nitrile content 50%) 1043 (Medium Nitrile): Manufactured by Nippon Zeon Co., Ltd., product name "Nipol 1043" (nitrile content 29%) 401 (Low Nitrile): Manufactured by Nippon Zeon Co., Ltd., product name "Nipol DN401" (nitrile content 18%)

[0052] (Preparation of adhesive sheet) Chemlock 6108 manufactured by Rhode Far East Co., Ltd. (referred to as "Rhode" in each table) was applied to the release surface of Toyobo Co., Ltd.'s separator TN100 (second release liner 5, thickness 0.038 mm) so that the thickness after drying was as indicated in each table. Next, the solvent was removed by heating at 65°C for 3 minutes to obtain a laminate 5 / 3 in which the second release liner 5 and the second adhesive layer 3 were laminated. Next, Chemlock 205 manufactured by Rhode Far East Co., Ltd. (referred to as "Rhode" in each table) was applied to the second adhesive layer 3 side of the laminate 5 / 3 so that the thickness after drying was as indicated in each table. Next, the solvent was removed by heating at 65°C for 3 minutes to obtain a laminate 5 / 3 / 1 in which the second release liner 5, the second adhesive layer 3 and the first adhesive layer 1 were laminated. Separately, the pressure-sensitive adhesive composition prepared as described above was applied to the release surface of a separator MA (first release liner 4, thickness 0.025 mm) manufactured by Nakamoto Pax Co., Ltd., so that the thickness after drying was as indicated in each table. Next, the solvent was removed by heating at 85°C for 2 minutes and then at 100°C for 1 minute to obtain laminate 2 / 4 in which the pressure-sensitive adhesive layer 2 and the first release liner 4 were laminated. Then, the side of the first adhesive layer 1 in laminate 5 / 3 / 1 and the side of the pressure-sensitive adhesive layer 2 in laminate 2 / 4 were bonded together using two rolls (except for Comparative Example 1, which did not have a pressure-sensitive adhesive layer 2). The resulting laminates 5 / 3 / 1 / 2 / 4 were used as the adhesive sheet 10 in each example and comparative example (only Comparative Example 1, which did not have a pressure-sensitive adhesive layer 2, had the configuration of laminate 4 / 3 / 1).

[0053] The adhesive sheet 10 obtained in this manner was evaluated using the measurement method shown below, and the evaluation results are shown in Tables 1 to 7.

[0054] (Measurement Method) (Excluding the peelability of the first release liner 4 and Comparative Example 1) An adhesive sheet 10 (width 25 mm, length 100 mm) for each example and comparative example was prepared. The first release liner 4 and the adhesive sheet 10 excluding the first release liner 4 were grasped by hand and pulled at a speed of approximately 300 mm / min to perform the peeling operation. The following criteria were used for evaluation, and are shown in Tables 1 to 7. ◎: No residue (adhesive residue) of the pressure-sensitive adhesive layer 2 remained on the release surface, and no lifting occurred on the second release liner 5, allowing the first release liner 4 to be peeled off from the pressure-sensitive adhesive layer 2 first. ○: Some residue of the pressure-sensitive adhesive layer 2 was observed on part of the release surface, or some lifting was observed on part of the second release liner 5, but it was still possible to peel it off first (at a level that does not interfere with use). ×: Residue of the pressure-sensitive adhesive layer 2 remained on the entire release surface, or lifting occurred on the second release liner 5, making it impossible to peel it off first.

[0055] (Adhesion after heating and pressurizing) The first release liner 4 was peeled off from each example and comparative example sample (adhesive sheet 10) cut to a width of 10 mm and a length of 100 mm, and the exposed pressure-sensitive adhesive layer 2 was temporarily fixed to the metal plate as the first bonding target (the test surface side of a cold-rolled steel plate (SPCC-SD) specified in JIS G 3141 was polished with brown fused alumina abrasive (SKTC Alundum: grit #100) to an arithmetic surface roughness Ra (measured in accordance with JIS B 0601:1982) of 2.7 ± 0.5 and a ten-point average roughness Rz (measured in accordance with JIS B 0601:1982) of 20 ± 5). Next, the second release liner 5 is peeled off from the temporarily fixed adhesive sheet 10, and an unvulcanized rubber sheet with a thickness of 35 μm, a width of 10 mm, and a length of 90 mm is placed on the second adhesive layer 3 side as the second bonding target (manufacturing method: 100 parts by weight of natural rubber (RSS#3), 15 parts by weight of calcium carbonate (heavy calcium carbonate manufactured by Maruo Calcium Co., Ltd.), 70 parts by weight of carbon black (Seist 116 [MAF] manufactured by Tokai Carbon Co., Ltd.), 5 parts by weight of zinc oxide (zinc oxide type 2 manufactured by Mitsui Mining & Smelting Co., Ltd.), 1 part by weight of stearic acid (Lunac S-50V manufactured by Kao Corporation), 1 part by weight of antioxidant (Nocrac 6C manufactured by Ouchi Shinko Co., Ltd.), and anti-scorch agent (Bullcurrent manufactured by Lanxess). 1.5 parts by weight of E / C was placed in a pressurized kneader (Moriyama Co., Ltd., 2.5 liter capacity, WDS2.5-10MWA-E type kneader) until the total weight was 2.0 kg, and kneading was carried out for 20 minutes while passing cooling water through to keep the removal temperature below 130°C. Subsequently, using an 8-inch roll, 0.15 parts by weight of vulcanization accelerator (Noxellar TT, Ouchi Shinko Co., Ltd.), 1 part by weight of vulcanization accelerator (Noxellar CZ, Ouchi Shinko Co., Ltd.), and 2 parts by weight of sulfur (Fine Powdered Sulfur 200Mesh, Hosoi Chemical Industry Co., Ltd.) corresponding to the total weight were added and a final kneading was performed, followed by sheeting to obtain an unvulcanized rubber sheet with a thickness of 2 mm. The sheet was then pressed by one back-and-forth motion with a 2 kg roller at a speed of 300 mm / min, and then pressed using a heated press machine at a temperature of 170°C and a pressure of 26 kg / cm² applied to the entire test piece. ２The unvulcanized rubber sheet was subjected to vulcanization by pressurizing for 20 minutes, resulting in a vulcanized rubber sheet with a rubber hardness (JIS K 6253, durometer type A) of 70. After allowing the sample to cool at 23°C for more than 24 hours, a test was conducted in accordance with JIS K 6256-2:2013, using a Strograph (manufactured by Toyo Seiki Co., Ltd., device name: Strograph EL) to peel off the vulcanized rubber sheet (second bonding target) at a peeling angle of 90° and peeling speed of 50 mm / min in an environment of 23°C and 50% RH. The following criteria were used for evaluation, and the results of the adhesive strength are shown in Tables 1 to 7. ◎: The vulcanized rubber sheet (second bonding target) was destroyed, indicating excellent adhesive strength in all cases. ○: The vulcanized rubber (second bonding target) was not destroyed, indicating that an adhesive strength of a usable level was obtained depending on the application. ×: Only extremely low adhesive strength was obtained. If no numerical value is listed, it indicates that measurement was not possible, meaning the peeling force was less than 0.5 N / 25 mm.

[0056] (Transferability) For each example and comparative example, an adhesive sheet 10 (width 25 mm, length 100 mm) was prepared. The first release liner 4 was peeled off the pressure-sensitive adhesive layer 2, and the pressure-sensitive adhesive side was temporarily fixed to the same cold-rolled steel plate (first bonding target) as described above. After temporary fixing, the second release liner 5 was peeled off the second adhesive layer 3. The following criteria were used for evaluation, and the results are shown in Tables 1 to 7. ◎: The temporarily fixed adhesive sheet 10 remained on the metal plate (first bonding target), and only the second release liner 5 could be peeled off. In other words, it was possible to transfer the adhesive sheet 10 to the metal plate (first bonding target). ○: When peeling off the second release liner 5, a part of the temporarily fixed adhesive sheet 10 lifted from the metal plate, but it was still possible to peel off the second release liner 5 itself. In other words, although the transferability was somewhat inferior, it was still possible to transfer the adhesive sheet. ×: When peeling off the second release liner 5, the temporarily fixed adhesive sheet 10 peeled off from the metal plate, making it impossible to peel off only the second release liner 5. In other words, the transferability was poor.

[0057] (Peeling force of the second release liner 5) An adhesive sheet 10 (width 25 mm, length 100 mm) was prepared for each example and comparative example. The first release liner 4 was peeled off from the pressure-sensitive adhesive layer 2, and the pressure-sensitive adhesive side was temporarily fixed to the same metal plate (first bonding target) as described above. After temporary fixing, in accordance with JIS Z 0237:2000, the peeling force was measured by peeling off the second release liner 5 at a peeling angle of 180° and peeling speed of 300 mm / min using a Strograph (manufactured by Toyo Seiki Co., Ltd., device name: Strograph EL) in an environment of 23°C and 50% RH. The evaluation was performed based on the following criteria, and the evaluations are shown in Tables 1 to 7. ◎: The peeling force was less than 0.5 N / 25 mm, indicating good peelability. ×: The peeling force was 0.5 N / 25 mm or more, making it difficult to peel off.

[0058] (Comparison between cases with and without a pressure-sensitive adhesive layer and cases with a conventional pressure-sensitive adhesive layer)

[0059]

[0060] In Table 1, ◎ indicates a good result, and × indicates an unfavorable result. As shown in Table 1, the embodiment with the pressure-sensitive adhesive layer 2 exhibited good release properties of the first release liner 4, achieving an extremely high adhesive strength of 16.3 N / 25 mm after heating and pressing, and a light release force of 0.04 N / 25 mm for the second release liner 5, indicating good transferability. On the other hand, Comparative Example 1, which did not have a pressure-sensitive adhesive layer, could not temporarily fix the first adhesive layer to the metal plate (first bonding target), and therefore could not be transferred. Furthermore, Comparative Examples 2 and 3, which used a conventional pressure-sensitive adhesive layer (acrylic adhesive) instead of the pressure-sensitive adhesive layer of this embodiment, showed extremely low adhesive strengths of 0.5 and 2.7 N / 25 mm after heating and pressing, possibly because it inhibited the adhesive strength of the first adhesive layer 1 in the adhesive sheet 10.

[0061] (Comparison of the thickness of pressure-sensitive adhesive layer 2)

[0062]

[0063] In Table 2, ◎ indicates a very good result, ○ indicates a good result with some shortcomings compared to ◎, and × indicates an unfavorable result. As shown in Table 2, Example 2, in which the pressure-sensitive adhesive layer 2 was 0.005 mm thick, had slightly inferior transferability, but the peelability of the first release liner 4 was good, similar to Example 1 in Table 1. Furthermore, a high adhesive strength of 14.5 N / 25 mm was obtained after heating and pressing, and the second release liner 5 could be peeled off with a low peeling force of 0.06 N / 25 mm. On the other hand, Comparative Example 4, in which the pressure-sensitive adhesive layer 2 was thicker at 0.02 mm, resulted in peeling off from the metal side (the side to be bonded first), possibly because it inhibited the adhesive strength of the first adhesive layer. These results indicate that when used as an adhesive sheet 10, it is preferable for the thickness of the pressure-sensitive adhesive layer to be 0.005 mm or more and less than 0.02 mm.

[0064] (Consideration of the amount of phenolic resin (B))

[0065]

[0066] In Table 3, ◎ indicates a very good result, and ○ indicates a good result, although it is inferior to ◎ in some aspects. As shown in Table 3, good results were obtained in all evaluation items when the phenol resin (B) content was 0 parts by weight (Example 7), 10 parts by weight (Example 8), 40 parts by weight (Example 9), 60 parts by weight (Example 10), and 100 parts by weight (Example 11) per 100 parts by weight of acrylonitrile butadiene rubber (A). This indicates that it is preferable for the phenol resin (B) content to be 100 parts by weight or less per 100 parts by weight of acrylonitrile butadiene rubber (A).

[0067] (Consideration of the amount of aromatic resin (C))

[0068]

[0069] In Table 4, ◎ indicates a very good result, and ○ indicates a good result, although it is inferior to ◎ in some aspects. As shown in Table 4, good results were obtained in all evaluation items when the amount of aromatic resin was 60 parts by weight (Example 3), 80 parts by weight (Example 4), 120 parts by weight (Example 5), and 160 parts by weight (Example 6) per 100 parts by weight of acrylonitrile butadiene rubber (A). Furthermore, as shown in Table 5, in Example 12, where the amount of aromatic resin (C) was 200 parts by weight per 100 parts by weight of acrylonitrile butadiene rubber (A), although the peelability of the first release liner 4 was slightly inferior, a high adhesive strength of 10.8 N / 25 mm was obtained after heating and pressing, and the peel strength of the second release liner 5 was a low value of 0.09 N / 25 mm, so transfer was possible. These results indicate that it is preferable to have 200 parts by weight or less per 100 parts by weight of acrylonitrile butadiene rubber (A).

[0070] (Comparison of the amounts of both aromatic resin (C) and phenolic resin (B))

[0071]

[0072] Next, we conducted tests when both the amounts of phenolic resin (B) and aromatic resin (C) were changed. In Table 5, ◎ indicates a very good result, ○ indicates a good result, although it is inferior to ◎ in some aspects, and × indicates an unfavorable result. As shown in Table 5, in Example 12, where the content of phenolic resin (B) was within the aforementioned range and the amount of aromatic resin (C) was 200 parts by weight per 100 parts by weight of acrylonitrile butadiene rubber (A), although the peelability of the first release liner 4 was slightly inferior, a high adhesive strength of 10.8 N / 25 mm was obtained after heating and pressing, and the peel strength of the second release liner 5 showed a low value of 0.09 N / 25 mm, so transfer was possible.

[0073] On the other hand, when the amount of phenolic resin (B) was at the upper limit (100 parts by weight) and the amount of aromatic resin (C) was at the upper limit (200 parts by weight), the release properties of the first release liner 4 were poor. This indicates that it is preferable for the total content of phenolic resin (B) and aromatic resin (C) to be less than 300 parts by weight per 100 parts by weight of acrylonitrile butadiene rubber (A).

[0074] (Verification of the types of acrylonitrile butadiene rubber (A), phenolic resin (B), and the case without aromatic resin (C))

[0075]

[0076] In Table 6, ◎ indicates very good results, and ○ indicates good results, although they are inferior to ◎ in some aspects. As shown in Table 6, in Example 13, where the acrylonitrile butadiene rubber was changed to a hydrogenated type, although the peelability of the first release liner 4 was slightly inferior, a high adhesive strength of 11.59 N / 25 mm was obtained after heating and pressurizing, and the second release film could be easily peeled off at 0.06 N / 25 mm, so the transferability was at a level that was not a problem for practical use. Furthermore, in Examples 14 to 16, in which the type of phenolic resin was added, good results were obtained in all evaluation items even when aromatic resin (C) was not included. This shows that the type of acrylonitrile butadiene rubber (A) does not matter. It also shows that the pressure-sensitive adhesive composition of this embodiment can obtain favorable results by including only phenolic resin (B) in addition to acrylonitrile butadiene rubber (A), provided that the amount and type are suitable.

[0077] (Verification of the nitrile content of acrylonitrile butadiene rubber (A))

[0078]

[0079] In Table 7, ◎ indicates very good results, and ○ indicates good results, although they are inferior to ◎ in some aspects. As shown in Table 7, in Example 16, which used acrylonitrile butadiene rubber (A) with an extremely high nitrile content (approximately 50.0%), Example 17, which used acrylonitrile butadiene rubber (A) with a medium nitrile content (29.0%), and Example 18, which used acrylonitrile butadiene rubber (A) with a low nitrile content (18%), good results were obtained in all evaluation items.

[0080] This indicates that it is preferable for the nitrile content of acrylonitrile butadiene rubber (A) to be 18% by mass or more and less than 50% by mass.

[0081] Although embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents.

[0082] (Industrial Applicability) According to the embodiment, it is possible to obtain a high level of adhesive strength after heating and pressurizing while maintaining temporary fixation to the object to be bonded, and moreover, the release liner can be easily peeled off in the intended order. Therefore, it can be suitably used mainly for bonding unvulcanized rubber to metal, for example, for fixing rubber components such as tire components, vibration damping rubber, hoses, rubber rolls (for conveying, pressing, etc.), conveyor belts, vibration damping materials, vibration isolation materials, and sealing members to metal such as metal fittings and reinforcing plates. However, the objects to be bonded are not limited to these and can be broadly selected as described above. Therefore, it can be widely used for structural bonding in the automotive, aerospace, electrical and electronic, and civil engineering and construction fields. It can also be widely used as a valve for pumps, a home appliance, and office automation equipment (rubber rollers).

[0083] 1. First adhesive layer 2. Pressure-sensitive adhesive layer 3. Second adhesive layer 4. First release liner 5. Second release liner 10. Adhesive sheet

Claims

1. A pressure-sensitive adhesive composition containing acrylonitrile butadiene rubber (A) and at least one selected from a phenolic resin (B) and an aromatic resin other than the phenolic resin (C).

2. The pressure-sensitive adhesive composition according to claim 1, wherein the content of the phenolic resin (B) is 100 parts by weight or less per 100 parts by weight of the acrylonitrile butadiene rubber (A).

3. The pressure-sensitive adhesive composition according to claim 1, wherein the content of the aromatic resin (C) is 200 parts by weight or less per 100 parts by weight of the acrylonitrile butadiene rubber (A).

4. The pressure-sensitive adhesive composition according to claim 1, wherein the total content of the phenolic resin (B) and the aromatic resin (C) is 44 parts by weight or more and less than 300 parts by weight per 100 parts by weight of the acrylonitrile butadiene rubber (A).

5. The pressure-sensitive adhesive composition according to claim 1, wherein the aromatic resin (C) is a xylene resin.

6. The pressure-sensitive adhesive composition according to claim 1, wherein the nitrile content of the acrylonitrile butadiene rubber (A) is 18% or more and 50% or less.

7. A pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of claims 1 to 6, having temporary fixing properties.

8. An adhesive sheet comprising: a pressure-sensitive adhesive layer according to claim 7; a first adhesive layer disposed on the pressure-sensitive adhesive layer and attached to a first object to be bonded via the pressure-sensitive adhesive layer; and a second adhesive layer having reactivity with rubber, disposed on the first adhesive layer and attached to a second object to be bonded different from the first object to be bonded.

9. The adhesive sheet according to claim 8, wherein the first object to be bonded is metal and the second object to be bonded is rubber.

10. The adhesive sheet according to claim 9, wherein the first adhesive layer is a layer formed from an adhesive composition comprising at least two or more selected from the group consisting of chlorinated rubber, carbon black, phenolic resin, epoxy resin, vulcanization accelerator, acid scavenger, vulcanizing agent, silica-based filler, and amine-based curing agent.

11. The adhesive sheet according to claim 9, wherein the second adhesive layer is a layer formed from a first adhesive composition comprising at least two or more compounds selected from the group consisting of chlorinated rubber, carbon black, acid scavenger, vulcanizing agent, vulcanization accelerator, maleimide compound, and nitroso compound.

12. The adhesive sheet according to claim 10 or 11, wherein the chlorinated rubber is at least one selected from chlorinated natural rubber, chlorinated polyethylene, chlorinated polypropylene, chlorinated polyolefin, chlorinated sulfonated polyethylene, and chloroprene.

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