Adhesive composition and adhesive tape

Abstract

To provide: an adhesive composition which has high adhesive strength to a hard-to-adhere material such as a propylene resin and has temporal deterioration of adhesive strength to a soft polyvinyl chloride resin suppressed; and an adhesive tape using the adhesive composition.SOLUTION: Provided is an adhesive composition, comprising: 100 pts.mass of an acrylic polymer (X) having a weight average molecular weight of 550,000 to 1,000,000; 3 to 9 pts.mass of a tackifier resin (Y) having a softening point of 140 to 160°C; and a crosslinking agent (Z). The acrylic polymer (X) is a polymer of monomer components including 100 pts.mass of an alkyl (meth)acrylate monomer (A) containing 60 mass% or more of an alkyl (meth)acrylate monomer (a) in which the alkyl group has a carbon number of 4 or less; and 5-18 pts.mass of a carboxylic acid-containing monomer (B).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a pressure-sensitive adhesive composition and a pressure-sensitive adhesive tape using the pressure-sensitive adhesive composition. More specifically, the present invention relates to a pressure-sensitive adhesive composition for use as an adhesive tape substrate, the substrate containing a plasticizer, and a pressure-sensitive adhesive tape using the pressure-sensitive adhesive composition. [Background technology]

[0002] Because of their excellent workability, pressure-sensitive adhesive tapes are widely used for the purposes of protection, packaging, repair, etc. For example, pressure-sensitive adhesive tapes having an acrylic pressure-sensitive adhesive layer are excellent in various physical properties such as weather resistance, durability, heat resistance, transparency, etc., and therefore are widely used for fixing members inside vehicles, houses, electronic devices, etc. Many adhesive tapes are used that have a substrate and an adhesive layer provided on at least one side of the substrate, and the material that constitutes the adhesive layer affects the adhesive strength to the adherend, so it is necessary to design it according to the type of material of the adherend. Patent Document 1 addresses the problem of the decrease in adhesive strength over time caused by the migration of plasticizer when an adhesive tape having an acrylic adhesive layer is used with soft polyvinyl chloride resin, and discloses a technology that uses an adhesive composition that contains a specific acrylic copolymer and a metal chelate crosslinking agent to solve this problem. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2006-199843 A Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, components, sheets, etc. made of soft polyvinyl chloride resin are often used as interior materials for vehicles, and there is a need for an adhesive tape that can be applied to such interior materials. Therefore, there is a demand for a more advanced method for preventing the problem of adhesive strength reduction caused by the migration of plasticizer in the soft polyvinyl chloride resin. In addition, adhesive tapes generally have low adhesion to adherends such as polypropylene resins with low polarity, which are widely used as vehicle components, and high adhesion is required even to such difficult-to-adhere substrates. As a method for improving adhesion to such difficult-to-adhere substrates, a technique of including a certain amount of tackifier resin in the adhesive layer is known, but when the tackifier resin is included, the tackifier resin promotes the migration of the plasticizer described above, resulting in a problem of a decrease in adhesion to soft polyvinyl chloride resins over time. Therefore, there is a demand for an adhesive tape having an adhesive layer that suppresses the decrease in adhesion to soft polyvinyl chloride resins over time and also improves adhesion to difficult-to-adhere substrates such as polypropylene resins. In addition, a porous body containing a thermoplastic resin and a plasticizer may be used as a substrate, and there is a demand for an adhesive tape that can suppress a decrease in adhesive strength resulting from migration of the plasticizer even for such substrates.

[0005] The present invention has been made in consideration of the above-mentioned problems in the conventional art, and aims to develop an adhesive composition that contains a certain amount of a tackifier resin and that suppresses a decrease in adhesive strength over time, and an adhesive tape using the same. [Means for solving the problem]

[0006] The present inventors have conducted extensive research to achieve the above object, and as a result have found that a pressure-sensitive adhesive composition containing an acrylic polymer, which is a polymer of a specific (meth)acrylic acid alkyl ester monomer and a specific amount of a carboxyl group-containing monomer, a specific tackifier resin, and a crosslinking agent, as well as a pressure-sensitive adhesive tape using the pressure-sensitive adhesive composition, can solve the above problems, and have thus completed the present invention. That is, the present invention relates to the following [1] to

[18] . [1] A pressure-sensitive adhesive composition comprising: 100 parts by mass of an acrylic polymer (X) having a weight-average molecular weight of 550,000 to 1,000,000; 3 to 9 parts by mass of a tackifier resin (Y) having a softening point of 140 to 160°C; and a crosslinking agent (Z); The acrylic polymer (X) is a polymer of monomer components including 100 parts by mass of a (meth)acrylic acid alkyl ester monomer (A) containing 60 mass% or more of a (meth)acrylic acid alkyl ester monomer (a) having an alkyl group with 4 or less carbon atoms, and 5 to 18 mass parts of a carboxyl group-containing monomer (B). [2] The pressure-sensitive adhesive composition according to the above [1], wherein the (meth)acrylic acid alkyl ester monomer (a) having an alkyl group with 4 or less carbon atoms contains n-butyl (meth)acrylate. [3] The pressure-sensitive adhesive composition according to the above [1] or [2], wherein the carboxyl group-containing monomer (B) is acrylic acid. [4] The pressure-sensitive adhesive composition according to any one of the above [1] to [3], wherein the tackifier resin (Y) is a rosin-based tackifier resin. [5] The pressure-sensitive adhesive composition according to any one of the above [1] to [4], wherein the tackifier resin (Y) has a content of components having a molecular weight of 600 or less of 13 mass % or less. [6] The pressure-sensitive adhesive composition according to any one of the above [1] to [5], wherein the crosslinking agent (Z) is at least one selected from the group consisting of metal chelate crosslinking agents and isocyanate crosslinking agents. [7] A pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition according to any one of the above [1] to [6]. [8] A pressure-sensitive adhesive tape comprising a substrate and a pressure-sensitive adhesive layer formed on at least one surface thereof, the pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition according to any one of the above [1] to [6]. [9] The pressure-sensitive adhesive tape according to the above [8], wherein the substrate is a pulp fiber nonwoven fabric containing 0.1 to 60% by mass of a rayon component.

[10] The adhesive tape according to the above [8], wherein the substrate contains a thermoplastic resin and a plasticizer.

[11] The pressure-sensitive adhesive tape according to the above

[10] , wherein the thermoplastic resin is polyvinyl acetal.

[12] The pressure-sensitive adhesive tape according to

[10] or

[11] above, wherein the substrate is either a nonwoven fabric made of fibers containing the thermoplastic resin and a plasticizer, or a porous body having a large number of bubbles.

[13] The substrate is a porous body containing a thermoplastic resin and a plasticizer and having a large number of bubbles, The pressure-sensitive adhesive tape according to any one of the above

[10] to

[12] , wherein the porous body has a loss factor of 0.2 or more at a first anti-resonant frequency in the range of 0 to 50°C, and a second anti-resonant frequency of 800 Hz or less in the range of 0 to 30°C, as measured by mechanical impedance measurement (MIM) in accordance with ISO 16940.

[14] The substrate is a porous body containing polyvinyl acetal and a plasticizer and having a large number of bubbles, The pressure-sensitive adhesive tape according to any one of the above

[10] to

[12] , wherein the porous body has an elongation strain of 300% or more and a 50% compressive stress of 70 kPa or less.

[15] The substrate is a nonwoven fabric made of fibers containing polyvinyl acetal and a plasticizer, The nonwoven fabric has a basis weight of 100 to 800 g / m 2 The pressure-sensitive adhesive tape according to any one of the above

[10] to

[12] , wherein a nonwoven fabric sample having a length of 10 cm, a width of 10 cm and a thickness of 4 mm is placed on an iron plate having a length of 10 cm or more, a width of 10 cm or more and a thickness of 1 cm, and a 1 / 2 inch stainless steel ball conforming to JIS B 1501 is dropped from a certain ball height toward the center of the nonwoven fabric sample, and the rebound height is measured, and the rebound coefficient (bounce height / dropped ball height) is measured to be 0.1 or less.

[16] The pressure-sensitive adhesive tape according to any one of the above [7] to

[15] , wherein the pressure-sensitive adhesive layer has a gel fraction of 30 to 50 mass %.

[17] The pressure-sensitive adhesive tape according to any one of the above [7] to

[16] , wherein a soft polyvinyl chloride resin is used as the adherend.

[18] The pressure-sensitive adhesive tape according to any one of the above [7] to

[17] , which is used for vehicle interior decoration. Effect of the Invention

[0007] According to the present invention, it is possible to provide an adhesive composition which has high adhesive strength to poorly adherends such as polypropylene resins and which inhibits deterioration of adhesive strength over time to soft polyvinyl chloride resins, and an adhesive tape using the adhesive composition. Furthermore, it is possible to provide a pressure-sensitive adhesive composition that is capable of suppressing a decrease in adhesive strength over time even when a plasticizer is contained in the substrate of the pressure-sensitive adhesive tape, and a pressure-sensitive adhesive tape using the pressure-sensitive adhesive composition. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of a method for evaluating repulsion retention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] [Adhesive composition] The pressure-sensitive adhesive composition of the present invention is a pressure-sensitive adhesive composition containing 100 parts by mass of an acrylic polymer (X) having a weight-average molecular weight of 550,000 to 1,000,000, 3 to 9 parts by mass of a tackifier resin (Y) having a softening point of 140 to 160°C, and a crosslinking agent (Z), and the acrylic polymer (X) is a polymer of specific monomer components. In the present invention, the acrylic polymer (X) is a polymer of monomer components containing 5 to 18 parts by mass of a carboxyl group-containing monomer (B) relative to 100 parts by mass of a (meth)acrylic acid alkyl ester monomer (A) containing 60% or more by mass of a (meth)acrylic acid alkyl ester monomer (a) having an alkyl group with 4 or less carbon atoms. By using the pressure-sensitive adhesive composition of the present invention, the adhesive strength to the adherend such as soft polyvinyl chloride resin is increased, and the adhesive strength is less likely to decrease over time. The reason is unclear, but it is presumed as follows. Usually, when the pressure-sensitive adhesive composition is applied to the surface of a sheet formed of soft polyvinyl chloride resin, the plasticizer contained in the soft polyvinyl chloride sheet is likely to migrate from the surface of the soft polyvinyl chloride sheet to the adhesive layer formed by the pressure-sensitive adhesive composition, which is thought to decrease the adhesive strength. In contrast, the adhesive layer formed by the adhesive composition of the present invention contains an acrylic polymer containing a relatively large amount of carboxyl group-containing monomer. Therefore, the acrylic polymer is in a state of relatively high polarity and high acid value, which is likely to inhibit the migration of plasticizers with relatively low polarity, and as a result, it is presumed that the decrease in adhesive strength of the adhesive layer is suppressed. Furthermore, the molecular weight of the acrylic copolymer is high, and in some cases, the crosslinking density is also high, which is expected to enhance the effect of inhibiting the decrease in adhesive strength through the inhibition of plasticizer migration. Furthermore, as described below, when the substrate of the adhesive tape contains a plasticizer, it is presumed that the migration of the plasticizer from the substrate to the adhesive layer is inhibited, thereby suppressing a decrease in the adhesive strength of the adhesive layer. Each component constituting the pressure-sensitive adhesive composition of the present invention will be described below.

[0010] <Acrylic polymer (X)> The acrylic polymer (X) contained in the pressure-sensitive adhesive composition of the present invention is a polymer of monomer components containing 5 to 18 parts by mass of a carboxyl group-containing monomer (B) relative to 100 parts by mass of a (meth)acrylic acid alkyl ester monomer (A) containing 60 mass% or more of a (meth)acrylic acid alkyl ester monomer (a) having an alkyl group with 4 or less carbon atoms. In this specification, (meth)acrylic acid refers to acrylic acid or methacrylic acid, and (meth)acrylate refers to acrylate or methacrylate.

[0011] ((Meth)acrylic acid alkyl ester monomer (A)) The (meth)acrylic acid alkyl ester monomer (A) contains 60% by mass or more of the (meth)acrylic acid alkyl ester monomer (a) having an alkyl group with 4 or less carbon atoms. If the content of the (meth)acrylic acid alkyl ester monomer (a) having an alkyl group with 4 or less carbon atoms is less than 60% by mass, the adhesive strength of the adhesive layer formed from the adhesive composition to an adherend such as soft polyvinyl chloride tends to decrease. From the viewpoint of suppressing a decrease in adhesive strength to soft polyvinyl chloride, the content of the (meth)acrylic acid alkyl ester monomer (a) having an alkyl group with 4 or less carbon atoms in the (meth)acrylic acid alkyl ester monomer (A) is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 100% by mass. Examples of the (meth)acrylic acid alkyl ester monomer (a) having an alkyl group with 4 or less carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, and t-butyl (meth)acrylate. These (meth)acrylic acid alkyl ester monomers can be used alone or in combination of two or more. Among the above, it is preferable to use n-butyl (meth)acrylate, and it is more preferable to use n-butyl (meth)acrylate alone. The content of n-butyl (meth)acrylate is preferably 60% by mass or more, more preferably 80% by mass or more, and particularly preferably 100% by mass, based on the total amount of the (meth)acrylic acid alkyl ester monomer (a) having an alkyl group with 4 or less carbon atoms.

[0012] The (meth)acrylic acid alkyl ester monomer (A) may contain a (meth)acrylic acid alkyl ester monomer (b) having an alkyl group with 5 or more carbon atoms. Examples of the (meth)acrylic acid alkyl ester monomer (b) include 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, and lauryl (meth)acrylate. The content of the (meth)acrylic acid alkyl ester monomer (b) having an alkyl group with 5 or more carbon atoms in the (meth)acrylic acid alkyl ester monomer (A) is preferably 20 mass% or less, and more preferably 10 mass% or less.

[0013] (Carboxyl Group-Containing Monomer (B)) The carboxyl group-containing monomer (B) is a polymerizable monomer containing a carboxyl group in the molecule, and is preferably a vinyl monomer containing a carboxyl group. Examples of the carboxyl group-containing monomer (B) include (meth)acrylic acid, itaconic acid, maleic acid, fumaric acid, and crotonic acid, and (meth)acrylic acid is preferred, and acrylic acid is more preferred. The carboxyl group-containing monomer (B) may be used alone or in combination of two or more kinds.

[0014] The monomer components for obtaining the acrylic polymer (X) contain 5 to 18 parts by mass of a carboxyl group-containing monomer (B) relative to 100 parts by mass of the (meth)acrylic acid alkyl ester monomer (A). If the amount of the carboxyl group-containing monomer (B) is less than 5 parts by mass, the reactivity with the crosslinking agent described below is reduced, and the adhesive strength of the adhesive composition to an adherend such as soft polyvinyl chloride is likely to decrease. This is because, if the amount of the carboxyl group-containing monomer (B) is small, the polarity of the acrylic polymer (X) is reduced, and migration from the soft polyvinyl chloride of the plasticizer, which is a compound with relatively low polarity, or the substrate of the adhesive tape to the adhesive composition is likely to occur. On the other hand, when the amount of the carboxyl group-containing monomer (B) exceeds 18 parts by mass, the adhesive layer formed from the adhesive composition tends to become hard as the crosslinking proceeds, and the adhesive strength to adherends such as soft polyvinyl chloride tends to decrease. Also, when the amount of the carboxyl group-containing monomer (B) exceeds 18 parts by mass, the adhesive property to low-energy surfaces such as polypropylene resin tends to decrease. The amount of the carboxyl group-containing monomer (B) is preferably 5 to 17 parts by mass, more preferably 6 to 15 parts by mass, and further preferably 10 to 15 parts by mass, based on 100 parts by mass of the (meth)acrylic acid alkyl ester monomer (A). The monomer component may contain other monomers in addition to the (meth)acrylic acid alkyl ester monomer (A) and the carboxyl group-containing monomer (B). Examples of other monomers include monomers containing a polar group other than a carboxyl group, and styrene-based monomers such as styrene, α-methylstyrene, o-methylstyrene, and p-methylstyrene.

[0015] (Weight average molecular weight of acrylic polymer (X)) The weight average molecular weight of the acrylic polymer (X) used in the pressure-sensitive adhesive composition of the present invention is 550,000 to 1,000,000. If the weight average molecular weight is less than 550,000, the adhesive strength to adherends such as soft polyvinyl chloride tends to decrease over time. On the other hand, if the weight average molecular weight exceeds 1,000,000, the adhesive layer tends to become hard, so that the adhesive strength to adherends with complex shapes tends to decrease, and the adhesiveness to low-energy surfaces such as polypropylene resin tends to decrease. The weight average molecular weight of the acrylic polymer (X) is preferably 600,000 to 800,000, more preferably 650,000 to 750,000.

[0016] <Method for producing acrylic polymer (X)> The method for producing the acrylic polymer (X) is not particularly limited, and may be, for example, a method of radically polymerizing a monomer component in the presence of a polymerization initiator. As the polymerization method, a known method may be adopted, and may be, for example, solution polymerization, emulsion polymerization, suspension polymerization, bulk polymerization, etc. The polymerization initiator is not particularly limited, but examples thereof include organic peroxide-based polymerization initiators and azo-based polymerization initiators.

[0017] Examples of the organic peroxide polymerization initiator include cumene hydroperoxide, benzoyl peroxide, lauroyl peroxide, octanoyl peroxide, stearoyl peroxide, o-chlorobenzoyl peroxide, acetyl peroxide, t-butyl hydroperoxide, t-butyl peroxyacetate, t-butyl peroxyisobutyrate, 3,5,5-trimethylhexanoyl peroxide, t-butylperoxy-2-ethylhexanoate, and di-t-butyl peroxide.

[0018] The azo-based polymerization initiator is not particularly limited, and examples thereof include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), 4,4'-azobis(4-cyanopentanoic acid), 2,2'-azobis(2-methylbutyronitrile), and the like. Among the above-mentioned polymerization initiators, lauroyl peroxide, octanoyl peroxide, stearoyl peroxide, and 3,5,5-trimethylhexanoyl peroxide are preferably used from the viewpoint of reducing the odor of the acrylic polymer (X). The polymerization initiators may be used alone or in combination of two or more kinds. The amount of the polymerization initiator is not particularly limited, but is preferably 0.01 to 10 parts by mass, and more preferably 0.05 to 2 parts by mass, relative to 100 parts by mass of the monomer component.

[0019] <Tackifier resin (Y)> The softening point of the tackifier resin (Y) contained in the pressure-sensitive adhesive composition of the present invention is 140 to 160° C. If the softening point is outside the above range, the adhesive strength of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition to an adherend such as soft polyvinyl chloride is likely to decrease over time. From the viewpoint of increasing the adhesive strength of the pressure-sensitive adhesive layer to an adherend such as soft polyvinyl chloride and suppressing the decrease in adhesive strength over time, the softening point of the tackifier resin (Y) is preferably 140 to 150° C. The softening point can be measured in accordance with JIS K2207. Examples of the type of tackifier resin (Y) include rosin-based resins such as petroleum resin-based tackifier resins, hydrogenated petroleum resin-based tackifier resins, rosin diol-based tackifier resins, and rosin ester-based tackifier resins, terpene resins, phenol resins, xylene resins, coumarone resins, ketone resins, and modified resins thereof, etc. Among these, from the viewpoints of increasing the adhesive strength to adherends such as soft polyvinyl chloride and suppressing the adhesive strength over time, rosin-based tackifier resins are preferred, and rosin ester-based tackifier resins are more preferred. Examples of rosin ester-based tackifying resins include disproportionated rosin ester, polymerized rosin ester, hydrogenated rosin ester, and rosin phenol-based tackifying resins.

[0020] The amount of the tackifier resin (Y) in the adhesive composition is 3 to 9 parts by mass relative to 100 parts by mass of the acrylic polymer (X). If the amount of the tackifier resin is less than 3 parts by mass, the adhesive strength to a difficult adherend such as polypropylene is likely to decrease, and it is difficult to hold the adhesive layer when the adherend is deformed. If the amount of the tackifier resin is more than 9 parts by mass, in a state in which the adhesive layer is laminated on a soft polyvinyl chloride or a substrate, the migration of the plasticizer from the soft polyvinyl chloride or the substrate to the adhesive layer is likely to be promoted, and the adhesive strength is likely to decrease over time. From the viewpoint of increasing the adhesive strength to a difficult adherend such as polypropylene resin and maintaining the adhesive strength to a soft polyvinyl chloride or other adherend, the amount of the tackifier resin (Y) in the adhesive composition is preferably 3 to 8 parts by mass, more preferably 4 to 7 parts by mass, relative to 100 parts by mass of the acrylic polymer (X).

[0021] The tackifier resin (Y) preferably contains 13% by mass or less of components with a molecular weight of 600 or less. By using such a tackifier resin, it is possible to maintain adhesion while suppressing the amount of volatile components generated by the tackifier resin to a low level. Furthermore, the small amount of low molecular weight components makes it possible to relatively increase the viscosity of the adhesive layer, and when the adhesive layer is laminated on a soft polyvinyl chloride or a substrate, the movement of the plasticizer from the soft polyvinyl chloride or substrate to the adhesive layer is easily inhibited, making it difficult for the adhesive strength to decrease over time. The molecular weight and content of the tackifier resin can be measured by gel permeation chromatography (GPC) and calculated from the polystyrene equivalent value and area ratio. Methods for removing components having a molecular weight of 600 or less from the tackifier resin include, for example, a method of heating and melting the tackifier resin to a temperature above its softening point, a method of blowing in water vapor, and the like.

[0022] <Crosslinking agent (Z)> The pressure-sensitive adhesive composition of the present invention contains a crosslinking agent. By using the crosslinking agent, the cohesive force of the pressure-sensitive adhesive layer formed is increased, and the physical properties of the pressure-sensitive adhesive tape are improved. The crosslinking agent is not particularly limited, and examples thereof include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, aziridine-based crosslinking agents, and metal chelate-based crosslinking agents. Among these, isocyanate-based crosslinking agents and metal chelate-based crosslinking agents are preferred. Examples of isocyanate crosslinking agents include tolylene diisocyanate, naphthylene-1,5-diisocyanate, and diphenylmethane diisocyanate, and examples of commercially available products include Coronate L manufactured by Nippon Polyurethane Co., Ltd. Examples of metal chelate crosslinking agents include chelate compounds whose metal atoms are aluminum, zirconium, titanium, zinc, iron, tin, etc., and aluminum chelates whose central metal is aluminum are preferred. Examples of commercially available products include Aluminum Chelate A and Aluminum Chelate M manufactured by Kawaken Fine Chemical Co., Ltd. The content of the crosslinking agent in the pressure-sensitive adhesive composition is not particularly limited, but is preferably 0.005 to 5 parts by mass, more preferably 0.01 to 1 part by mass, and even more preferably 0.02 to 0.1 part by mass, relative to 100 parts by mass of the acrylic polymer (X).

[0023] <Other ingredients> The pressure-sensitive adhesive composition of the present invention may contain, in addition to the acrylic polymer (X), the tackifier resin (Y), and the crosslinking agent (Z), a solvent such as ethyl acetate, dimethyl sulfoxide, ethanol, acetone, diethyl ether, etc., and among the solvents, ethyl acetate is preferred from the viewpoint of keeping the volatile components low. The pressure-sensitive adhesive composition of the present invention may contain additives such as a filler, a pigment, a dye, and an antioxidant.

[0024] <Gel fraction> The adhesive composition of the present invention can be applied to a substrate or the like and dried to form an adhesive layer, as described below. The gel fraction of the adhesive layer formed from the adhesive composition of the present invention is preferably 30 to 50% by mass, more preferably 35 to 45% by mass, from the viewpoint of inhibiting migration of the plasticizer from the soft polyvinyl chloride or substrate to the adhesive layer and suppressing a decrease in adhesive strength over time. The gel fraction can be measured by the method described in the Examples.

[0025] [Adhesive tape] The pressure-sensitive adhesive tape of the present invention includes a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition described above. The pressure-sensitive adhesive tape may be a non-support type made of only a pressure-sensitive adhesive layer, or may be a type in which a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition is laminated on at least one side of a substrate. Among these, a double-sided pressure-sensitive adhesive tape in which pressure-sensitive adhesive layers are laminated on both sides of a substrate is preferred. The method for producing the pressure-sensitive adhesive tape is not particularly limited, but for example, the pressure-sensitive adhesive composition containing the above-mentioned acrylic polymer (X), tackifier resin (Y), crosslinking agent (Z) and other components such as a solvent as necessary is applied to a substrate or the like, and then dried to form a pressure-sensitive adhesive layer on the substrate, thereby producing the pressure-sensitive adhesive tape. As a drying method, for example, a method of drying in a drying furnace such as an IR heater or an oven can be mentioned.

[0026] The substrate is not particularly limited, and examples that can be used include Japanese paper, nonwoven fabric, plastic films such as polyethylene, polyethylene terephthalate, polypropylene, and polyurethane, metal foil, porous bodies, etc. Among these substrates, nonwoven fabric is preferably used as the substrate from the viewpoints of workability and conformability to adherends such as soft polyvinyl chloride, and among nonwoven fabrics, pulp fiber nonwoven fabric is more preferably used from the viewpoints of environmental conservation and retention performance for the pressure-sensitive adhesive layer.

[0027] The basis weight of the pulp fiber nonwoven fabric is not particularly limited, but is preferably 8 to 25 g / m 2 , more preferably 10 to 18 g / m 2 By setting the basis weight within this range, the permeability and applicability of the pressure-sensitive adhesive composition can be improved. The thickness of the pulp fiber nonwoven fabric is not particularly limited, but is preferably 5 to 50 μm, and more preferably 10 to 40 μm. When a pulp fiber nonwoven fabric is used as a substrate, it is preferable to use a pulp fiber nonwoven fabric containing a rayon component. The amount of the rayon component in the pulp fiber nonwoven fabric containing a rayon component is preferably 0.1 to 60 mass%, more preferably 1 to 50 mass%, and the amount of the pulp fiber component is preferably 40 to 99.9 mass%, more preferably 50 to 99 mass%. In addition to the rayon component, the pulp fiber nonwoven fabric may contain other fibers such as Manila hemp, nylon, polyester, acrylonitrile, polypropylene, and polyvinyl alcohol as necessary, but the content of the other fibers is preferably 20 mass% or less, more preferably 5 mass% or less. The use of a pulp fiber nonwoven fabric containing a rayon component is not only excellent in terms of workability and environmental conservation, but also when the pressure-sensitive adhesive composition of the present invention is applied to the pulp fiber nonwoven fabric to form an adhesive layer, the pressure-sensitive adhesive layer is less likely to separate from the pulp fiber nonwoven fabric, improving performance as an adhesive tape.

[0028] It is also preferable to use a porous body as the substrate. The porous body has a large number of bubbles and is made of a resin foam.

[0029] Furthermore, in the present invention, the substrate may contain a thermoplastic resin and a plasticizer. Even when a substrate containing a plasticizer is used in this way, the use of the pressure-sensitive adhesive composition prevents the plasticizer from migrating from the substrate to the pressure-sensitive adhesive layer, and suppresses the adhesive strength of the pressure-sensitive adhesive layer from decreasing over time. Examples of the thermoplastic resin include polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-propylene hexafluoride copolymer, polytrifluoroethylene, acrylonitrile-butadiene-styrene copolymer, polyester, polyether, polyamide, polycarbonate, polyacrylate, polymethacrylate, polyvinyl chloride, polyethylene, polypropylene, polystyrene, polyvinyl acetal, ethylene-vinyl acetate copolymer, etc. Among these, polyvinyl acetal or ethylene-vinyl acetate copolymer is preferable, and polyvinyl acetal is more preferable.

[0030] When the substrate contains a thermoplastic resin and a plasticizer, the substrate is preferably a nonwoven fabric or a porous body. That is, the substrate is preferably a polyvinyl acetal nonwoven fabric made of fibers containing polyvinyl acetal and a plasticizer, or a porous body containing polyvinyl acetal and a plasticizer, and among these, a porous body is more preferable. By making the substrate a porous body, it becomes easier to improve at least one of the impact absorption properties, vibration damping properties, shapeability, and sound insulation properties of the substrate, as described below. Therefore, the porous body is suitably used in applications where the substrate requires any one of these properties.

[0031] The polyvinyl acetal is not particularly limited as long as it is a polyvinyl acetal obtained by acetalizing polyvinyl alcohol with an aldehyde, but polyvinyl butyral is preferred. If necessary, two or more kinds of polyvinyl acetals may be used in combination.

[0032] The lower limit of the degree of acetalization of the polyvinyl acetal is preferably 40 mol % and the upper limit is preferably 85 mol %, more preferably 60 mol % and more preferably 75 mol %. The polyvinyl acetal has a hydroxyl group content of preferably 15 mol % (lower limit) and 40 mol % (upper limit). When the hydroxyl group content is within this range, the compatibility with plasticizers is increased. The degree of acetalization and the amount of hydroxyl groups can be measured, for example, in accordance with JIS K 6728 "Testing methods for polyvinyl butyral".

[0033] The polyvinyl acetal can be prepared by acetalizing polyvinyl alcohol with an aldehyde. The polyvinyl alcohol is usually obtained by saponifying polyvinyl acetate, and polyvinyl alcohol having a saponification degree of 70 to 99.8 mol % is generally used. The saponification degree of the polyvinyl alcohol is preferably 80 to 99.8 mol %. The preferred lower limit of the degree of polymerization of the polyvinyl alcohol is 500, and the preferred upper limit is 4000. When the degree of polymerization of the polyvinyl alcohol is 500 or more, the handleability of the resulting porous body is excellent. When the degree of polymerization of the polyvinyl alcohol is 4000 or less, the molding of the porous body is easy. The more preferred lower limit of the degree of polymerization of the polyvinyl alcohol is 1000, and the more preferred upper limit is 3600.

[0034] The aldehyde is not particularly limited, but generally, an aldehyde having 1 to 10 carbon atoms is preferably used. The aldehyde having 1 to 10 carbon atoms is not particularly limited, and examples thereof include n-butyl aldehyde, isobutyl aldehyde, n-valeraldehyde, 2-ethylbutyraldehyde, n-hexyl aldehyde, n-octyl aldehyde, n-nonyl aldehyde, n-decyl aldehyde, formaldehyde, acetaldehyde, and benzaldehyde. Among these, n-butyl aldehyde, n-hexyl aldehyde, and n-valeraldehyde are preferred, and n-butyl aldehyde is more preferred. These aldehydes may be used alone or in combination of two or more.

[0035] The plasticizer is not particularly limited, and examples thereof include organic ester plasticizers such as monobasic organic acid esters and polybasic organic acid esters, and phosphate plasticizers such as organic phosphate plasticizers and organic phosphite plasticizers. Among these, organic ester plasticizers are preferred. The plasticizer is preferably a liquid plasticizer. The liquid plasticizer is a plasticizer that is liquid at room temperature (23°C) and normal pressure (1 atm).

[0036] The monobasic organic acid ester is not particularly limited, and examples thereof include glycol esters obtained by reacting glycols such as triethylene glycol, tetraethylene glycol, and tripropylene glycol with monobasic organic acids such as butyric acid, isobutyric acid, caproic acid, 2-ethylbutyric acid, heptyl acid, n-octylic acid, 2-ethylhexyl acid, pelargonic acid (n-nonylic acid), and decylic acid. Among these, triethylene glycol dicaproic acid ester, triethylene glycol di-2-ethylbutyric acid ester, triethylene glycol di-n-octylic acid ester, and triethylene glycol di-2-ethylhexyl acid ester are preferred.

[0037] The polybasic organic acid ester is not particularly limited, but examples thereof include ester compounds of polybasic organic acids such as adipic acid, sebacic acid, and azelaic acid with alcohols having a straight-chain or branched structure having 4 to 8 carbon atoms. Among these, dibutyl sebacate, dioctyl azelate, dibutyl carbitol adipate, and the like are preferred.

[0038] The organic ester plasticizer is not particularly limited, and examples thereof include triethylene glycol di-2-ethyl butyrate, triethylene glycol di-2-ethylhexanoate, triethylene glycol dicaprylate, triethylene glycol di-n-octanoate, triethylene glycol di-n-heptanoate, tetraethylene glycol di-n-heptanoate, tetraethylene glycol di-2-ethylhexanoate, dibutyl sebacate, dioctyl azelate, dibutyl carbitol adipate, ethylene glycol di-2-ethyl butyrate, 1,3-propylene glycol di-2-ethyl butyrate, 1,4-butylene glycol di-2-ethyl butyrate, diethylene ... Examples of the polyalkylene glycol include ethylene glycol di-2-ethylhexanoate, dipropylene glycol di-2-ethylbutyrate, triethylene glycol di-2-ethylpentanoate, tetraethylene glycol di-2-ethylbutyrate, diethylene glycol dicapryate, dihexyl adipate, dioctyl adipate, hexylcyclohexyl adipate, diisononyl adipate, heptylnonyl adipate, dibutyl sebacate, oil-modified alkyd sebacic acid, a mixture of a phosphate ester and an adipate ester, an adipate ester, a mixed adipate ester made from an alkyl alcohol having 4 to 9 carbon atoms and a cyclic alcohol having 4 to 9 carbon atoms, and an adipate ester having 6 to 8 carbon atoms such as hexyl adipate. The organic phosphoric acid plasticizer is not particularly limited, and examples thereof include tributoxyethyl phosphate, isodecylphenyl phosphate, and triisopropyl phosphate.

[0039] Furthermore, as the plasticizer, it is preferable that the plasticizer contains triethylene glycol di-2-ethylhexanoate (3GO), triethylene glycol di-2-ethylbutyrate (3GH), tetraethylene glycol di-2-ethylhexanoate (4GO), or dihexyl adipate (DHA), it is more preferable that the plasticizer contains tetraethylene glycol di-2-ethylhexanoate (4GO) or triethylene glycol di-2-ethylhexanoate (3GO), and it is particularly preferable that the plasticizer contains triethylene glycol di-2-ethylhexanoate (3GO).

[0040] The content of the plasticizer is not particularly limited, but the preferred lower limit is 5 parts by mass and the preferred upper limit is 60 parts by mass relative to 100 parts by mass of the thermoplastic resin. When the content of the plasticizer is within this range, it is easy to improve at least one of sound insulation, impact absorption, vibration damping, and formability. In addition, the plasticizer does not bleed out from the porous body. The more preferred lower limit of the content of the plasticizer is 20 parts by mass, and the more preferred upper limit is 55 parts by mass. In most interlayer films for laminated glass, the content of plasticizer per 100 parts by mass of thermoplastic resin such as polyvinyl acetal is about 20 to 55 parts by mass. Therefore, for example, discarded interlayer films for laminated glass can be used as they are as the raw material for the substrate of the present invention. The above-mentioned thermoplastic resin and plasticizer are preferably the main components in the substrate, and the total amount of the thermoplastic resin and plasticizer is usually 70 mass % or more, preferably 80 mass % or more, and more preferably 90 mass % or more, based on the total amount of the substrate.

[0041] In addition to the above-mentioned thermoplastic resin and plasticizer, the substrate may contain additives such as an adhesion regulator, a heat ray absorber, an ultraviolet shielding agent, an antioxidant, a light stabilizer, an antistatic agent, etc. Furthermore, in order to adjust the appearance of the obtained substrate, the substrate may contain a pigment such as carbon black or a dye, etc.

[0042] The open cell ratio of the porous body is, for example, 10% or more, preferably 14% or more, more preferably 20% or more, even more preferably 30% or more, even more preferably 40% or more, and particularly preferably 50% or more. The upper limit of the open cell ratio is not particularly limited, but about 98% is a practical upper limit. In this way, by increasing the open cell ratio, it becomes easier to improve at least one of the impact absorption properties, vibration damping properties, shapeability, and sound insulation properties of the substrate, and it also becomes easier to obtain the porous bodies of the first and second embodiments described below. In this specification, the term "open cells" means that the cells forming the porous body are interconnected. The open cell ratio is defined as the volume ratio of cells that are connected to the outside of a porous body to the apparent volume of the porous body obtained by dimensional measurement, and can be measured by the pycnometer method described in JIS K7138.

[0043] The porous body has a preferred lower limit of an average cell diameter of 100 μm and a preferred upper limit of 1000 μm. A more preferred lower limit of the average cell diameter is 120 μm, a more preferred upper limit is 500 μm, and a further more preferred lower limit is 200 μm. By setting the average cell diameter within this range, at least one of the impact absorption, vibration damping, shaping, and sound insulation performance of the substrate can be further improved. In addition, the porous body of the first and second embodiments described below can be easily obtained.

[0044] The porous body preferably has an average aspect ratio of bubbles of 2 or less. When the average aspect ratio of the bubbles is 2 or less, it becomes easier to further improve at least one of the impact absorption, vibration damping, shapeability, and sound insulation performance of the substrate. In addition, it becomes easier to obtain the porous body of the first and second embodiments described below. It is more preferable that the average aspect ratio of the bubbles is 1.5 or less.

[0045] The average cell diameter can be measured by observing the cell walls and voids in a cross-sectional photograph of the cells and measuring the size of the voids. Specifically, first, a porous body sample for measurement is cut to 50 mm length and 50 mm width, immersed in liquid nitrogen for 1 minute, and then cut along a plane parallel to the thickness direction with a razor blade. Then, a 200x magnified photograph is taken using a digital microscope (Keyence Corporation, product name VHX-900), and the bubble diameters of all bubbles present on a cut surface 2 mm long in the thickness direction are measured. If the thickness of the porous body is less than 2 mm, it is recommended to prepare multiple samples. The above procedure is repeated five times at different measurement points, and the average of all the observed bubble diameters is taken as the average bubble diameter. The bubble diameter of each bubble is taken as the diameter of the largest inscribed circle when an inscribed circle is drawn around the observed bubble.

[0046] The average aspect ratio of the bubbles can be measured by measuring the major axis and minor axis of the voids in a cross-sectional photograph of the bubbles and calculating the ratio. Specifically, when measuring the average bubble diameter, the major axis and minor axis of an ellipse inscribed in each observed bubble are measured, and the aspect ratio is calculated by dividing the major axis by the minor axis. The aspect ratios are then calculated for all observed bubbles, and the average aspect ratio is calculated.

[0047] The porous body has an apparent density of 500 kg / m 3 It is preferable that the apparent density is 500 kg / m or less. 3 By setting the apparent density to 300 kg / m or less, excellent shaping properties can be exhibited, and for example, the porous body of the second embodiment described later can be easily obtained. 3 It is preferable that the apparent density is 300 kg / m or less. 3 By setting the apparent density to 260 kg / m or less, it becomes easy to improve the impact absorption, vibration damping, shapeability, low flowability, etc. of the substrate. And it becomes easy to obtain the porous body of the first and second embodiments described later. 3 More preferably, it is 200 kg / m or less. 3 It is even more preferable that: The lower limit of the apparent density is not particularly limited, but the apparent density is preferably 50 kg / m 3 It is preferable that the apparent density is 50 kg / m or more. 3 If the apparent density is more than 60 kg / m, the elongation strain can be easily adjusted to within a predetermined range shown in the second embodiment described later, the formability is good, and the porous body of the second embodiment described later can be easily obtained. 3 More preferably, it is 80 kg / m or more. 3 More preferably, it is 100 kg / m or more. 3 More preferably, it is equal to or greater than this. The apparent density can be measured by a method of calculation from the measured weight and the apparent volume obtained by dimensional measurement.

[0048] Moreover, the porous body preferably has a specific gravity of 0.3 or less. By having a specific gravity of 0.3 or less, higher impact absorption properties can be exhibited. The specific gravity is more preferably 0.2 or less. There is no particular restriction on the lower limit of the specific gravity, but the practical lower limit is about 0.05. By setting the specific gravity of the porous body within this range, the impact absorption properties of the resulting porous body are improved. The specific gravity of a porous body does not refer to the density of the porous body relative to the density of water, but for example, in the case of a foamed body, it means the ratio of the density after foaming to the density before foaming, that is, "density after foaming / density before foaming". Specifically, "specific gravity = density after foaming / density before foaming" can be calculated from the measured weight and the apparent volume obtained by dimensional measurement as "density after foaming = measured weight after foaming / apparent volume after foaming" and "density before foaming = measured weight before foaming / apparent volume before foaming". In addition, when the measured weight before foaming and the apparent volume before foaming are unknown, it can also be calculated as specific gravity = 1 / expansion ratio.

[0049] The thickness of the porous body used in the present invention is preferably 10 mm or less. If the upper limit of the thickness of the porous body is within the above range, the obtained porous body is less likely to break in shear. The thickness of the porous body used in the present invention is preferably 50 μm or more. If the lower limit of the thickness of the porous body is within the above preferred range, at least one of the shock absorption, vibration damping, shapeability, and sound insulation performance of the obtained porous body is more easily improved. In addition, if the thickness of the porous body is within the above range, the porous body can be suitably used as a substrate for an adhesive tape.

[0050] The porous body may be crosslinked by a crosslinking agent. For example, when polyvinyl acetal is used as the thermoplastic resin, a compound capable of crosslinking between polyvinyl acetals by reacting with a hydroxyl group, an acetyl group, an acetal group, etc. contained in the side chain of the polyvinyl acetal can be used as the crosslinking agent. Specific examples of the crosslinking agent include epoxy compounds, isocyanate compounds, and boric acid compounds. In addition, for example, a polyfunctional (meth)acrylate compound such as trimethylolpropane triacrylate (TMPTA) can also be used as the crosslinking agent. In the case where a polyfunctional (meth)acrylate compound is used as a crosslinking agent in the porous body, it is preferable to use a photopolymerization initiator in combination. By using a photopolymerization initiator in combination, the porous body can be crosslinked uniformly and reliably. As the photopolymerization initiator, for example, a conventionally known compound such as benzophenone can be used.

[0051] The substrate used in the pressure-sensitive adhesive tape of the present invention is preferably a porous body as described above, and the porous body is more preferably any one of the porous bodies of the following first and second embodiments.

[0052] (First embodiment) The porous body of the first embodiment of the present invention has a loss factor (hereinafter simply referred to as "loss factor") of 0.2 or more at a primary anti-resonant frequency in the range of 0 to 50°C, as measured by mechanical impedance measurement (MIM) in accordance with ISO 16940, and a secondary anti-resonant frequency of 800 Hz or less in the range of 0 to 30°C. When the loss factor is 0.2 or more, the porous body exhibits high vibration absorption properties and can exhibit high sound insulation performance by losing sound energy. The loss factor is preferably 0.3 or more. When the secondary anti-resonance frequency is 800 Hz or less, the sound generated from the adherend is less likely to be perceived as noise by the human ear. Therefore, the porous body of the first embodiment can exhibit high sound insulation performance, and an adhesive tape using the porous body of the first embodiment as a substrate is suitable for applications in which the substrate is used as a sound insulation material or soundproofing material. The loss factor of the first anti-resonant frequency and the second anti-resonant frequency can be measured by the central excitation method, and are obtained as the maximum value of the loss factor in the range of 0 to 50°C and the maximum value of the second anti-resonant frequency in the range of 0 to 30°C. At that time, a laminated sample in which a porous body is fixed with double-sided tape (manufactured by Sekisui Chemical Co., Ltd., #5782) between two glass plates with a width of 25 mm, a length of 305 mm, and a thickness of 2 mm is used as a sample. Before applying the double-sided tape for measurement, the double-sided tape is applied to the porous body in advance, or if the porous body has an adhesive layer, the double-sided tape (manufactured by Sekisui Chemical Co., Ltd., #5782) is applied only to the side to which the double-sided tape is not applied or the side that does not have an adhesive layer.

[0053] The loss factor and the second anti-resonant frequency can be achieved, for example, by adjusting the foaming state of the porous body. Specifically, the open cell rate of the porous body is preferably 20% or more, and by further increasing the open cell rate, the loss factor and the second anti-resonant frequency can be easily adjusted to suitable values ​​while exhibiting high sound insulation. In this embodiment, it is preferable to use polyvinyl acetal as the thermoplastic resin as described above, and by using polyvinyl acetal, it is easy to adjust the loss factor of the first anti-resonant frequency and the second anti-resonant frequency within a predetermined range. Furthermore, it is better to adjust the average bubble diameter, the average aspect ratio of the bubbles, the apparent density, etc. within the desired range as described above.

[0054] Second Embodiment The porous body of the second embodiment of the present invention contains polyvinyl acetal and a plasticizer, has a large number of bubbles, and has an elongation strain of 300% or more and a 50% compressive stress of 70 kPa or less. The porous body of the second embodiment is flexible and has excellent formability. Therefore, the adhesive tape can be easily formed into various shapes by embossing or the like.

[0055] In this specification, the extensional strain means a value indicating the degree of deformation applied to a sheet-like porous body when the porous body is subjected to an extensional deformation in one axial direction. When the extensional strain is 300% or more, the porous body can exhibit excellent impact resistance while being flexible. The extensional strain is preferably 400% or more, and more preferably 500% or more. The upper limit of the extensional strain is not particularly limited, but is practically about 800%. In this specification, the 50% compressive stress means a value indicating the stress applied to the porous body when the sheet-like porous body is compressed by 50% in the thickness direction. When the 50% compressive stress is 70 kPa or less, the porous body of the present embodiment becomes flexible and can exhibit excellent shapeability. The 50% compressive stress is preferably 30 kPa or less, and more preferably 20 kPa or less. The lower limit of the 50% compressive stress is not particularly limited, but is substantially about 5 kPa. The elongation strain and 50% compression stress can be measured by a method in accordance with JIS K 6767. Specifically, the elongation strain can be measured by pulling a sample punched into a dumbbell No. 1 shape as specified in JIS K 6251 at a tensile speed of 500 mm / min using a universal testing machine. Also, the 50% compressive stress can be measured by stacking a sample cut into a square shape with a side length of 50 mm to a thickness of 25 mm or more using a universal testing machine at a compression speed of 10 mm / min.

[0056] The above-mentioned elongation strain and 50% compressive stress can be achieved by adjusting the foaming state of the porous body. Specifically, it is preferable that the open cell ratio of the porous body is 20% or more. By making the open cell ratio 20% or more, the 50% compressive stress of the obtained porous body can be adjusted to a predetermined range, and extremely high flexibility can be exhibited. From this viewpoint, the higher the open cell ratio, the better, as described above. In addition, by adjusting the apparent density and the like to a desired range as described above, it becomes easier to adjust the elongation strain and the like of the porous body to a predetermined range, and flexibility and shapeability can be imparted. Furthermore, in this embodiment, it is also better to adjust the average bubble diameter, the average aspect ratio of the bubbles, and the like to within the desired range as described above.

[0057] In the present invention, the method for producing the porous body is not particularly limited, but for example, a method is suitable in which a thermally decomposable foaming agent is mixed with the above-mentioned thermoplastic resin, plasticizer, and additives added as necessary to prepare a resin composition, and the resin composition is heated to a foaming temperature to decompose the thermally decomposable foaming agent. In addition, when the porous body is crosslinked, a crosslinking agent may be mixed with the above-mentioned resin composition. Furthermore, crosslinking is preferably performed before foaming. For example, when the crosslinking of the porous body is performed by irradiating light such as ultraviolet light, light irradiation may be performed before heating for foaming.

[0058] Here, in order to obtain the porous body of the first and second embodiments, for example, with the open cell ratio within the above range, in addition to the selection of the thermoplastic resin and plasticizer, the type and amount of the thermal decomposition type foaming agent during production and the setting of the foaming temperature are important. In particular, the setting of the foaming temperature is important for achieving a high open cell ratio. Specifically, the foaming temperature is preferably 180° C. or higher. At a temperature of 180° C. or higher, the resin composition is sufficiently softened during foaming, and the air bubbles are likely to communicate with each other, so that open air bubbles are likely to be generated. In particular, since such an increase in the open air bubble ratio is observed by using a resin composition containing polyvinyl acetal and a plasticizer, the porous body containing polyvinyl acetal and a plasticizer can easily increase the open air bubble ratio.

[0059] The thermal decomposition type foaming agent is not particularly limited as long as it has a decomposition temperature of about 120 to 240° C., and a conventionally known foaming agent can be used. Since the open cell ratio can be increased, it is preferable to select a foaming agent having a foaming temperature of 180° C. or higher and a foaming temperature higher than the decomposition temperature of the thermal decomposition type foaming agent. More specifically, the foaming temperature is preferably 20° C. or higher than the decomposition temperature of the thermal decomposition type foaming agent, more preferably 50° C. or higher, and even more preferably 80° C. or higher.

[0060] Specific examples of the thermal decomposition type foaming agent include azodicarbonamide, N,N'-dinitrosopentamethylenetetramine, 4,4'-oxybis(benzenesulfonylhydrazide), urea, sodium hydrogen carbonate, and mixtures thereof. Among the above-mentioned thermal decomposition type foaming agents, examples of commercially available ones include the Cellmic series (manufactured by Sankyo Kasei Co., Ltd.), the Vinihole series, the Cellular series, and the Neo Cellvon series (all manufactured by Eiwa Kasei Kogyo Co., Ltd.).

[0061] The amount of the thermally decomposable foaming agent in the resin composition is not particularly limited, but the preferred lower limit is 2 parts by mass and the preferred upper limit is 20 parts by mass relative to 100 parts by mass of the thermoplastic resin. If the amount of the thermally decomposable foaming agent is within this range, a foam having an open cell ratio of 10% or more can be easily produced. In addition, from the viewpoint of easily increasing the open cell ratio (for example, 20% or more), the more preferred lower limit of the amount of the thermally decomposable foaming agent is 4 parts by mass, the even more preferred lower limit is 5 parts by mass, and the more preferred upper limit is 15 parts by mass.

[0062] In the present invention, when the substrate is made of a material containing a thermoplastic resin and a plasticizer and is a nonwoven fabric, it is preferable that the substrate is a nonwoven fabric of the following third embodiment.

[0063] (Third embodiment) The nonwoven fabric of the third embodiment uses polyvinyl acetal as a thermoplastic resin, and is a polyvinyl acetal nonwoven fabric made of fibers containing polyvinyl acetal and a plasticizer. The nonwoven fabric of the third embodiment has a basis weight of 100 to 800 g / m 2 and the bounce coefficient (bounce height / falling ball height) is 0.1 or less. By setting the basis weight and rebound coefficient within the above ranges, the nonwoven fabric of this embodiment has high impact absorption properties and is suitable for use in adhesive tapes that require impact absorption properties, and more specifically, is suitable when the substrate is used as a soundproofing material, impact absorbing material, or vibration absorbing material. The rebound coefficient is obtained by placing a nonwoven fabric sample 10 cm long, 10 cm wide, and 4 mm thick on an iron plate that is at least 10 cm long, 10 cm wide, and 1 cm thick, and measuring the rebound height when a 1 / 2 inch stainless steel ball conforming to JIS B 1501 is dropped from a certain ball height toward the center of the nonwoven fabric sample.

[0064] When the thickness of the nonwoven fabric to be measured is less than 4 mm, the nonwoven fabric sample may be prepared by stacking the nonwoven fabric in the thickness direction until the thickness exceeds 4 mm, and then shaving the nonwoven fabric to a thickness of 4 mm. When the thickness of the nonwoven fabric to be measured exceeds 4 mm, the nonwoven fabric sample may be prepared by shaving the nonwoven fabric to a thickness of 4 mm. If it is difficult to shave the nonwoven fabric to a thickness of 4 mm exactly, an average thickness of 4 mm ± 0.1 mm is acceptable. The thickness of the nonwoven fabric sample may be adjusted using an appropriate mechanical device. The above-mentioned rebound coefficient is measured in an environment of temperature 23°C and humidity 50%Rh. In addition, the certain ball falling height is, for example, 10 cm, 20 cm, or 30 cm, and in the present invention, it is preferable that the rebound coefficient be within the specified range in any one of these cases, but it is better that it be within the specified range in all cases.

[0065] The polyvinyl acetal, plasticizer, additives, and the like used in the nonwoven fabric of this embodiment may be the same as those described above. As described above, the nonwoven fabric uses polyvinyl acetal as the thermoplastic resin, contains polyvinyl acetal and a plasticizer, and by appropriately adjusting the basis weight, average diameter, etc. of the nonwoven fabric, it is possible to make the rebound coefficient 0.1 or less.

[0066] The preferred lower limit of the basis weight of the nonwoven fabric of this embodiment is 150 g / m 2 , the preferred upper limit is 660 g / m 2 and a more preferable lower limit is 200 g / m 2 , and a more preferable upper limit is 500 g / m 2 It is. The average diameter (average fiber diameter) of the fibers constituting the nonwoven fabric of this embodiment is preferably 50 μm in lower limit and 2 mm in upper limit. When the average diameter (average fiber diameter) of the fibers is within this range, higher impact absorption properties can be exhibited. The average diameter (average fiber diameter) of the fibers is more preferably 100 μm in lower limit and 1 mm in upper limit.

[0067] In this embodiment, the average diameter (average fiber diameter) of the fibers constituting the nonwoven fabric is preferably 1 / 2 or less, more preferably 1 / 3 or less, and even more preferably 1 / 4 or less, of the thickness of the nonwoven fabric. Also, the average diameter (average fiber diameter) of the fibers constituting the nonwoven fabric is preferably 1 / 100 or more, more preferably 1 / 50 or more, and even more preferably 1 / 10 or more, of the thickness of the nonwoven fabric. When the ratio of the average diameter of the fibers constituting the nonwoven fabric to the thickness of the nonwoven fabric is equal to or less than the above-mentioned preferable value, higher impact absorption properties can be exhibited.

[0068] From the viewpoint of improving the handling property of the adhesive tape, the preferred upper limit of the thickness of the nonwoven fabric used as the substrate is 10 mm, the more preferred upper limit is 4 mm, the particularly preferred upper limit is 0.5 mm, and the most preferred upper limit is 0.3 mm. The preferred lower limit of the thickness is 20 μm. If the thickness is 20 μm or more, the impact absorption property of the nonwoven fabric is further improved. The more preferred lower limit of the thickness of the nonwoven fabric of this embodiment is 50 μm, the more preferred lower limit is 100 μm, the particularly preferred lower limit is 150 μm, and the most preferred lower limit is 500 μm.

[0069] The nonwoven fabric of the third embodiment can be produced, for example, by extruding a resin composition containing polyvinyl acetal, a plasticizer, an additive, etc., into strands using an extruder, cutting the strands to an appropriate length, laminating the resulting laminate, and then thermocompressing the laminate using a press. In this case, the basis weight of the resulting nonwoven fabric can be adjusted by adjusting the diameter and length of the strands and the thermocompression conditions.

[0070] The applications of the pressure-sensitive adhesive tape of the present invention are not particularly limited, and it can be used for all applications, such as vehicle components for automobiles, aircraft, ships, etc., building components, electronic components, lifestyle components such as carpet backings, household and commercial electrical appliances, etc. Among these, it is preferably used inside vehicles, houses, electronic devices, etc., more preferably used for vehicle components, and even more preferably used for vehicle interiors.

[0071] In the present invention, it is also preferable to use a soft polyvinyl chloride resin as the adherend. The soft polyvinyl chloride resin means polyvinyl chloride containing a plasticizer, and the content of the plasticizer is usually 5% by mass or more, preferably 10 to 80% by mass, and more preferably 10 to 50% by mass of the whole soft polyvinyl chloride resin. The type of plasticizer contained in the flexible polyvinyl chloride resin is not particularly limited, and examples of the plasticizer that can be used include those contained in typical flexible polyvinyl chloride resins, such as phthalate ester plasticizers such as dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), di-2-ethylhexyl phthalate (DOP), di-n-octyl phthalate (N-DOP), diheptyl phthalate (DHP), diisodecyl phthalate (DIDP), butyl benzyl phthalate (BBP), and diisononyl phthalate (DINP), and fatty acid ester plasticizers such as di-2-ethylhexyl adipate (DOA), diisobutyl adipate (DIBA), dibutyl adipate (DBA), diisodecyl adipate (DIDA), and butyl oleate (BO). In addition, since the adhesive tape of the present invention has good adhesive strength to polyolefin resins such as polyethylene resin, polypropylene resin, etc., a suitable embodiment of use can be a double-sided adhesive tape in which the adherend on one side is a polyolefin resin such as polyethylene resin, polypropylene resin, etc., and the adherend on the other side is a soft polyvinyl chloride resin. EXAMPLES

[0072] The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples in any way.

[0073] Example 1 <Production of Acrylic Polymer> 100 parts by mass of n-butyl acrylate and 11 parts by mass of acrylic acid were introduced into a reaction vessel to obtain a monomer component. The monomer component was dissolved in ethyl acetate, and 0.1 parts by mass of lauroyl peroxide was added as a polymerization initiator at the reflux point, and the mixture was refluxed at 70°C for 5 hours to obtain a solution of an acrylic polymer having a weight average molecular weight of 720,000. <Production of Adhesive Composition and Adhesive Tape> To the obtained acrylic polymer solution, 6.3 parts by mass of polymerized rosin ester tackifier resin (softening point 140) containing 13% by mass of components with molecular weight of 600 or less, and 0.054 parts by mass of aluminum chelate, which is a metal chelate crosslinking agent, were added relative to 100 parts by mass of the acrylic polymer, which is the non-volatile content of the acrylic polymer solution. Then, they were mixed uniformly to obtain a pressure-sensitive adhesive composition. The adhesive composition was then applied to both sides of a 50 μm-thick polyethylene terephthalate film and dried at 120° C. for 5 minutes to obtain a double-sided adhesive tape in which a 60 μm-thick adhesive layer was laminated on each side of the polyethylene terephthalate film. The weight average molecular weight of the acrylic polymer, the gel fraction of the adhesive layer, the adhesive strength retention rate (%) of the double-sided adhesive tape to an adherend (soft polyvinyl chloride sheet) containing a phthalate ester, the rebound retention, and the adhesive strength to a polypropylene resin were evaluated as follows. The results are shown in Table 1.

[0074] (Examples 2 to 8, Comparative Examples 1 to 9) An acrylic polymer was obtained in the same manner as in Example 1, except that the monomer composition was changed as shown in Table 1 or 2. Then, a double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 1, except that the type and amount of the tackifier resin and the type and amount of the crosslinking agent were changed as shown in Table 1 or 2. The adhesive tape was evaluated for adhesive strength retention (%) to a phthalate-containing substrate (soft polyvinyl chloride sheet), rebound retention, and adhesive strength to polypropylene resin by the methods described below. The results are shown in Tables 1 and 2. The types of tackifier resins and crosslinking agents used in Tables 1 and 2 are as follows: <Adhesive-imparting resin> Polymerized rosin ester tackifier resin (rosin type (low molecular weight cut)) ···Softening point 140°C, content of components with molecular weight of 600 or less is 13% by mass Polymerized rosin ester tackifier resin (rosin type (standard product)) ···Softening point 160°C, content of components with molecular weight of 600 or less is 33% by mass Terpene phenol tackifier resin...Softening point 150℃ <Crosslinking agent> Metal chelate crosslinking agent: Aluminum chelate, "M-A5DT" manufactured by Soken Chemical & Engineering Co., Ltd. Isocyanate-based crosslinking agent: "Coronate L" manufactured by Nippon Polyurethane Co., Ltd. Epoxy crosslinking agent: "E-AX" manufactured by Soken Chemical Industries, Ltd.

[0075] [Measurement and evaluation methods] <Molecular weight of (meth)acrylic polymer> The weight average molecular weight of the (meth)acrylic polymer was calculated as a polystyrene equivalent value by gel permeation chromatography (GPC) using the (meth)acrylic polymer before crosslinking as a measurement sample. The GPC measurement was performed using a GPC device, HLC-8220GPC, manufactured by Tosoh Corporation. <Softening point of tackifier resin> Measurements were performed in accordance with JIS K2207.

[0076] <Gel fraction> W1 (g) was collected from the adhesive layer of the double-sided adhesive tape, and the collected adhesive component was immersed in ethyl acetate at 23°C for 24 hours, and the insoluble matter was filtered through a 200-mesh wire screen. The residue on the wire screen was heated and dried at 110°C, and the weight W2 (g) of the resulting dried residue was measured, and the gel fraction (degree of cross-linking) was calculated using the following formula. Gel fraction (mass%) = 100 × W2 / W1

[0077] <Adhesive strength retention rate (%) for adherends containing phthalate esters (soft polyvinyl chloride sheet)> The adhesive strength retention rate was calculated using the following formula. Adhesive strength retention rate (%) = 100 x (adhesive strength over time / initial adhesive strength) (1)Initial adhesive strength A 23 μm thick PET film was attached to one side of the double-sided adhesive tape of each Example and Comparative Example in a manner that did not allow air to get in. Next, the adhesive layer side of the double-sided adhesive tape attached to the PET film, which was not attached to the PET film, was attached to the surface of a 300 μm thick soft polyvinyl chloride sheet (containing 30% by mass of DINP as a plasticizer) at room temperature (23° C.) and a relative humidity of 50% at a speed of 30 mm / min using a 2 kg pressure rubber roller. After leaving it in this environment for 30 minutes, the 180 degree peel strength in a width of 25 mm was measured at a speed of 3 mm / min according to the method of JIS Z0237, and this was taken as the initial adhesive strength (N / 25 mm). (2) Adhesive strength over time A 23 μm thick PET film was attached to one side of the double-sided adhesive tape of each Example and Comparative Example so that air would not enter. Next, the adhesive layer side of the double-sided adhesive tape attached to the PET film that was not attached to the PET film was attached to the surface of a 300 μm thick soft polyvinyl chloride sheet (containing 30% by mass of DINP as a plasticizer) at room temperature (23° C.) and a relative humidity of 50% at a speed of 30 mm / min using a 2 kg pressure-bonding rubber roller. After that, it was left in a 60° C. environment for 72 hours, and then left at room temperature for 30 minutes, and then the 180° peel strength at a width of 25 mm was measured at a speed of 3 mm / min according to the method of JIS Z0237, and this was taken as the adhesive strength over time (N / 25 mm).

[0078] <Repulsive force against adherends containing phthalate esters> FIG. 1 shows a schematic diagram of the method for evaluating the repulsive holding force. One side of the double-sided adhesive tape 11 of each Example and Comparative Example was attached to the surface of a 300 μm thick soft polyvinyl chloride sheet 12 (containing 30 mass % DINP as a plasticizer) using a 2 kg pressure rubber roller at a speed of 30 mm / min to prepare a polyvinyl chloride sheet with double-sided adhesive tape. The polyvinyl chloride sheet with double-sided adhesive tape was cut to 15 mm x 40 mm, and attached to a 5 mm thick polypropylene plate 13 at a speed of 30 mm / min from a part of the upper surface (10 mm) through the side to a part of the lower surface (25 mm) in an approximately U-shaped manner using a 2 kg pressure rubber roller (FIG. 1). In this state, the sheet was left to stand for 2 weeks under conditions of 60° C. and 90% relative humidity, and the resilience of the double-sided adhesive tape was evaluated by checking whether peeling occurred on the part of the upper surface (10 mm) or the part of the lower surface (25 mm) of the polypropylene plate 13. The samples in which the soft polyvinyl chloride sheet did not peel off were rated as A, those in which the soft polyvinyl chloride sheet did not peel off but some parts of the sheet were found to have lifted or had weak adhesive strength were rated as B, and those in which the polyvinyl chloride sheet peeled off were rated as C.

[0079] <Adhesive strength to polypropylene resin> A 23 μm thick PET film was attached to one side of the double-sided adhesive tape of each Example and Comparative Example in a manner that did not allow air to get in. Next, the adhesive layer side of the double-sided adhesive tape attached to the PET film that was not attached to the PET film was attached to the surface of a 300 μm thick polypropylene resin sheet at room temperature (23° C.) and a relative humidity of 50% using a 2 kg pressure rubber roller at a speed of 30 mm / min. After leaving it in this environment for 30 minutes, the 180 degree peel strength in a width of 25 mm was measured at a speed of 3 mm / min according to the method of JIS Z0237, and this was taken as the adhesive strength to polypropylene resin (N / 25 mm).

[0080] [Table 1]

[0081] [Table 2]

[0082] Example 9 A pressure-sensitive adhesive composition was obtained in the same manner as in Example 1. A pulp fiber nonwoven fabric (thickness 30 μm, basis weight 14 g / m) containing 10±2 mass% of a rayon component and 86±3 mass% of pulp fiber was used. 2 The pressure-sensitive adhesive composition was applied to both sides of the nonwoven fabric and dried at 120° C. for 5 minutes to obtain a double-sided pressure-sensitive adhesive tape in which a 60 μm-thick pressure-sensitive adhesive layer was laminated on each side of the nonwoven fabric. The adhesive tape was evaluated for release of the adhesive from the nonwoven fabric.

[0083] Example 10 Pulp fiber nonwoven fabric that does not contain rayon components (thickness 30 μm, basis weight 14 g / m 2 A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 9, except that the above-mentioned 1,2-dichlorophenyl ether was used instead of the above-mentioned 1,2-dichlorophenyl ether. The adhesive tape was evaluated for release of the adhesive from the nonwoven fabric by the method described below.

[0084] <Evaluation of adhesive layer detachment from nonwoven fabric> The double-sided adhesive tape of Example 6 or 7 cut to a width of 25 mm and a length of 130 mm was attached to one end of a test plate (soft polyvinyl chloride sheet) and reciprocally pressed with a 1 kg roller. After pressing, the test piece was left at a temperature of 80±2°C for 1 hour, and then a weight with a load of 9.8±0.049 N was hung from the lower end of the test piece, and it was confirmed whether the weight fell within 4 hours. If the weight fell, it meant that the adhesive layer had detached from the nonwoven fabric. The separation of the pressure-sensitive adhesive layer from the nonwoven fabric was evaluated based on the following criteria. A: The adhesive layer did not come off from the nonwoven fabric. B: The adhesive layer was observed to have detached from the nonwoven fabric.

[0085] [Table 3]

[0086] As is clear from the results of Examples 1 to 8, the adhesive tape using the adhesive composition of the present invention containing a specific type of acrylic polymer and a specific amount of a tackifier resin had good adhesive strength retention and rebound retention against a soft polyvinyl chloride sheet. Furthermore, the results of Examples 9 to 10 showed that when a nonwoven fabric containing a rayon component is used as a substrate, the adhesive is less likely to detach from the substrate. In contrast, the pressure-sensitive adhesive tapes using pressure-sensitive adhesive compositions not satisfying the requirements of the present invention shown in Comparative Examples 1 to 9 had insufficient adhesive strength retention rate and / or rebound retention force against a soft polyvinyl chloride sheet. Moreover, the adhesive tapes containing a certain amount of tackifier resin in the adhesive layer used in Examples 1 to 8 had good adhesive strength even to polypropylene resin. On the other hand, the adhesive tapes not containing tackifier resin used in Comparative Examples 5 to 7 were easily peeled off from the polypropylene plate and did not obtain a good evaluation in the evaluation of rebound retention strength.

[0087] <Adhesive tape having porous body according to the first embodiment> Example 11 (1) Manufacturing of porous bodies A resin composition was obtained by adding 40 parts by mass of triethylene glycol di-2-ethylhexanoate (3GO) as a plasticizer and 4 parts by mass of Cellmic CE (manufactured by Sankyo Kasei Co., Ltd., decomposition temperature 208°C) as a thermal decomposition type foaming agent to 100 parts by mass of polyvinyl butyral (PVB1). The obtained resin composition was thoroughly kneaded with a mixing roll at 110°C, and then extruded with an extruder to obtain a sheet-like body. Note that PVB1 has a hydroxyl group content of 34 mol%, an acetylation degree of 1.0 mol%, a butyralization degree of 65 mol%, and an average polymerization degree of 1650. The obtained sheet-like body was heated in an oven at a foaming temperature of 220°C to decompose the thermal decomposition type foaming agent, thereby obtaining a porous body made of a resin foam. The thickness of the obtained porous body was 4 mm. (2) Manufacture of adhesive tapes The same adhesive composition as in Example 1 was applied to one side of a porous body (substrate) and dried at 120°C for 5 minutes to obtain a single-sided adhesive tape in which a 60 μm-thick adhesive layer was laminated on one side of the substrate.

[0088] Example 12 A porous body having a thickness of 4 mm was produced in the same manner as in Example 11, except that the amount of the thermally decomposable foaming agent was changed as shown in Table 4. A single-sided adhesive tape was produced using the porous body in the same manner as in Example 11.

[0089] Comparative Example 10 A 4 mm thick porous body and a single-sided adhesive tape were produced in the same manner as in Example 11, except that the adhesive composition used was changed from the same adhesive composition as in Example 1 to the same adhesive composition as in Comparative Example 4.

[0090] Comparative Example 11 A 4 mm thick porous body and a single-sided adhesive tape were produced in the same manner as in Example 12, except that the adhesive composition used was changed from the same adhesive composition as in Example 1 to the same adhesive composition as in Comparative Example 4.

[0091] For the porous bodies produced in Examples 11 and 12 and Comparative Examples 10 and 11, the loss factor of the first anti-resonant frequency and the second anti-resonant frequency were measured by the method described in the specification, and the sound insulation performance was evaluated according to the following evaluation criteria. The results are shown in Table 4.

[0092] (Sound insulation performance evaluation) The sound transmission loss was measured by the sound intensity method according to JIS A 1441. The measurement temperature was 20°C, and the frequency range was 100 to 10,000 Hz for each 1 / 3 octave band. The sample was a resin foam sample (thickness about 4 mm) sandwiched between 2 mm thick glass and fixed with double-sided tape (Sekisui Chemical Co., Ltd., #5782). At that time, the double-sided tape was not attached to the surface having the adhesive layer, and the double-sided tape (Sekisui Chemical Co., Ltd., #5782) was attached only to the surface not having the adhesive layer. The size (opening surface) was 500 mm x 500 mm. The incident power was calculated from the average sound pressure level at five points in the reverberation chamber, and the transmitted power was calculated from the sound intensity at 5 x 5 = 25 points in the measurement area (500 mm x 500 mm). The sound insulation performance was evaluated according to the following criteria. A frequency-transmission loss graph was created, and cases in which the difference in transmission loss between the first maximum value on the low frequency side and the adjacent minimum value was sufficiently small were rated as "A," and cases in which the difference in transmission loss was large were rated as "B."

[0093] (Plasticizer resistance evaluation) The single-sided pressure-sensitive adhesive tapes of Examples 11 and 12 and Comparative Examples 10 and 11 were evaluated by the following evaluation methods. The evaluation results are shown in Table 4. (Test specimen preparation) The single-sided adhesive tapes obtained in each of the Examples and Comparative Examples were cut to a width of 25 mm and a length of 150 mm, and were pressed onto SUS304 (surface BA finish) as specified in JIS G4305 by rolling a 2 kg rubber roller back and forth once at a speed of 10 mm / sec in accordance with JIS Z0237. (Initial adhesive strength) The single-sided adhesive tape obtained by the above test specimen preparation was left at 23°C and 50% RH for 20 minutes after application, and then a 90-degree peel test was carried out in 3 tests according to JIS Z0237, and the average value was taken as the initial adhesive strength (N / 25 mm). The peel speed was 300 mm / min. (Adhesive strength over time) The test specimens obtained by the above test specimen preparation were left in an atmosphere of 60°C for 72 hours, and then left at 23°C 50% RH for 30 minutes. Then, a 90-degree peel test was carried out in accordance with JIS Z0237 for three tests, and the average value was taken as the adhesion strength over time (N / 25 mm). (Adhesion maintenance rate) Using the initial adhesive strength and adhesive strength over time obtained above, the adhesive strength retention rate (%) was calculated according to the following formula. Adhesive strength retention rate (%) = 100 x (adhesive strength over time / initial adhesive strength) The adhesive strength retention rate of the single-sided adhesive tape using the same adhesive composition as in Example 1 was rated as A if it was significantly improved compared to the adhesive strength retention rate of the single-sided adhesive tape using the same adhesive composition as in Comparative Example 4, and was rated as B if there was no change.

[0094] [Table 4]

[0095] <Adhesive tape having porous body according to the second embodiment> (Example 13) (1) Manufacturing of porous bodies To 100 parts by mass of polyvinyl butyral (PVB2), 40 parts by mass of triethylene glycol di-2-ethylhexanoate (3GO) as a plasticizer, 3 parts by mass of Vinihol AC#3 (manufactured by Eiwa Kasei Kogyo Co., Ltd., decomposition temperature 208°C) as a thermal decomposition type foaming agent, and 0.8 parts by mass of carbon black (manufactured by Tokai Carbon Co., Ltd., Seast SP) were added to obtain a resin composition. The obtained resin composition was thoroughly kneaded with a mixing roll at 110°C, and then extruded with an extruder to obtain a sheet-like body. Note that PVB2 has a hydroxyl group content of 31 mol%, an acetylation degree of 0.7 mol%, a butyralization degree of 68.3 mol%, and an average polymerization degree of 1800. The resulting sheet-like body was placed in an oven at a foaming temperature of 230° C. to decompose the thermal decomposition type foaming agent, thereby obtaining a porous body made of a resin foam having a thickness of 4 mm. (2) Manufacture of adhesive tapes The same adhesive composition as in Example 1 was applied to one side of a porous body (substrate) and dried at 120°C for 5 minutes to obtain a single-sided adhesive tape in which a 60 μm-thick adhesive layer was laminated on one side of the substrate.

[0096] Example 14 A porous body having a thickness of 4 mm was produced in the same manner as in Example 13, except that the amount of the thermally decomposable foaming agent was changed as shown in Table 5, and a single-sided adhesive tape was produced using the porous body in the same manner as in Example 13.

[0097] Comparative Example 12 A 4 mm thick porous body and a single-sided adhesive tape were produced in the same manner as in Example 13, except that the adhesive composition used was changed from the same adhesive composition as in Example 1 to the same adhesive composition as in Comparative Example 4.

[0098] Comparative Example 13 A 4 mm thick porous body and a single-sided adhesive tape were produced in the same manner as in Example 14, except that the adhesive composition used was changed from the same adhesive composition as in Example 1 to the same adhesive composition as in Comparative Example 4.

[0099] The elongation strain and 50% compressive stress were measured for the porous bodies produced in Examples 13 and 14 and Comparative Examples 12 and 13 by the methods described in the specification. In addition, the formability and flexibility of the pressure-sensitive adhesive tapes obtained in Examples 13 and 14 and Comparative Examples 12 and 13 were evaluated according to the following evaluation criteria. In addition, the plasticizer resistance was evaluated by the same method as in Examples 11 and 12 and Comparative Examples 10 and 11. The results are shown in Table 5.

[0100] (Evaluation of formability) The adhesive tape was placed on a polycarbonate corrugated plate with a pitch of 32 mm and a valley depth of 9 mm so that only the crests of the corrugated plate were in contact, and the parts of the tape that were not in contact were stretched and pressed against the valleys to be attached. The substrate was then observed for tears or localized thinning, and the formability was evaluated according to the following criteria. A: No tears or thinning are observed. B: Breaking or thinning was observed.

[0101] (Flexibility assessment) A 1 / 2 inch diameter stainless steel ball was left for 1 minute in the valley of a corrugated pressure-sensitive adhesive tape. When the stainless steel ball was removed, it was observed whether there was any trace of the stainless steel ball having sunk therein, and the flexibility was evaluated according to the following criteria. A: Traces of the SUS ball sinking were visible. B: No traces were found.

[0102] [Table 5]

[0103] <Adhesive tape having nonwoven fabric of the third embodiment> Example 15 (1) Nonwoven fabric manufacturing A resin composition was obtained by adding 40 parts by mass of triethylene glycol di-2-ethylhexanoate (3GO) as a plasticizer to 100 parts by mass of polyvinyl butyral (PVB1). The obtained resin composition was thoroughly kneaded with a mixing roll and then extruded into a strand-like body with a diameter of 1 mm using an extruder. The resulting strand-like body was cut to a length of 10 cm, and then heat-pressed to a weight of 400 g / m 2 The resulting laminate was heat-pressed using a press to heat-seal the contacting portions of the strand-like bodies to obtain a nonwoven fabric. The average diameter of the fibers constituting the obtained nonwoven fabric (average fiber diameter) was 1 mm, the same as the diameter of the strand-like body. The conditions for the thermocompression bonding were a distance between the press plates of 4 mm, a press temperature of 130°C, and a press time of 3 minutes. (2) Manufacture of adhesive tapes The same adhesive composition as in Example 1 was applied to one side of a nonwoven fabric and dried at 120°C for 5 minutes to obtain a single-sided adhesive tape in which a 60 µm-thick adhesive layer was laminated on one side of the substrate.

[0104] Example 16 The strand-shaped body is heat-pressed to a weight of 300 g / m 2A nonwoven fabric was produced in the same manner as in Example 12, except that the layers were laminated so as to form a single-sided adhesive tape in the same manner as in Example 15, using the nonwoven fabric.

[0105] Comparative Example 14 A nonwoven fabric and a single-sided adhesive tape were produced in the same manner as in Example 15, except that the adhesive composition used was changed from the same adhesive composition as in Example 1 to the same adhesive composition as in Comparative Example 4.

[0106] Comparative Example 15 A nonwoven fabric and a single-sided adhesive tape were produced in the same manner as in Example 16, except that the adhesive composition used was changed from the same adhesive composition as in Example 1 to the same adhesive composition as in Comparative Example 4.

[0107] For the nonwoven fabrics produced in Examples 15 and 16 and Comparative Examples 14 and 15, various physical properties, as well as rebound heights and rebound coefficients at ball drop heights of 10 cm, 20 cm, and 30 cm were measured by the methods described in the specification. In addition, plasticizer resistance was evaluated by the same method as in Examples 11 and 12 and Comparative Examples 10 and 11. The results are shown in Table 6.

[0108] [Table 6] [Explanation of symbols]

[0109] 11 Double-sided adhesive tape 12 Soft polyvinyl chloride sheet 13 Polypropylene plate

Claims

1. A pressure-sensitive adhesive composition comprising: 100 parts by mass of an acrylic polymer (X) having a weight-average molecular weight of 550,000 to 1,000,000; 3 to 9 parts by mass of a tackifier resin (Y) having a softening point of 140 to 160° C.; and a crosslinking agent (Z); The acrylic polymer (X) is a polymer of monomer components consisting of 100 parts by mass of a (meth)acrylic acid alkyl ester monomer (A) consisting solely of a (meth)acrylic acid alkyl ester monomer (a) having an alkyl group with 4 or less carbon atoms, and 10 to 18 parts by mass of a carboxyl group-containing monomer (B).

2. The acrylic pressure-sensitive adhesive composition according to claim 1 , wherein the carboxyl group-containing monomer (B) is acrylic acid.

3. 3. The acrylic pressure-sensitive adhesive composition according to claim 1, wherein the crosslinking agent (Z) is at least one selected from the group consisting of metal chelate crosslinking agents and isocyanate crosslinking agents.

4. A pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer comprising the acrylic pressure-sensitive adhesive composition according to any one of claims 1 to 3.

5. 4. A pressure-sensitive adhesive tape comprising a substrate and a pressure-sensitive adhesive layer formed on at least one surface thereof, the pressure-sensitive adhesive layer comprising the acrylic pressure-sensitive adhesive composition according to claim 1.

6. The pressure-sensitive adhesive tape according to claim 5, wherein the substrate is a pulp fiber nonwoven fabric containing 0.1 to 60% by mass of a rayon component.

7. The pressure-sensitive adhesive tape according to claim 5 , wherein the substrate contains a thermoplastic resin and a plasticizer.

8. The pressure-sensitive adhesive tape according to claim 7, wherein the thermoplastic resin is polyvinyl acetal.

9. 9. The pressure-sensitive adhesive tape according to claim 7, wherein the substrate is either a nonwoven fabric made of fibers containing the thermoplastic resin and a plasticizer, or a porous body having a large number of bubbles.

10. The substrate is a porous body containing a thermoplastic resin and a plasticizer and having a large number of bubbles, The pressure-sensitive adhesive tape according to any one of claims 7 to 9, wherein the porous body has a loss factor of 0.2 or more at a primary antiresonant frequency in the range of 0 to 50 ° C., as measured by mechanical impedance measurement (MIM) in accordance with ISO 16940, and a secondary antiresonant frequency of 800 Hz or less in the range of 0 to 30 ° C.

11. The substrate is a porous body containing polyvinyl acetal and a plasticizer and having a large number of bubbles, The pressure-sensitive adhesive tape according to any one of claims 7 to 10, wherein the porous body has an elongation strain of 300% or more and a 50% compressive stress of 70 kPa or less.

12. The substrate is a nonwoven fabric made of fibers containing polyvinyl acetal and a plasticizer, The nonwoven fabric has a basis weight of 100 to 800 g / m ２ a nonwoven fabric sample having a length of 10 cm, a width of 10 cm and a thickness of 4 mm is placed on an iron plate having a length of 10 cm or more, a width of 10 cm or more and a thickness of 1 cm, and a ½ inch SUS ball in accordance with JIS B 1501 is dropped from a certain ball drop height toward the center of the nonwoven fabric sample, and the rebound height is measured, the rebound coefficient (bounce height / dropped ball height) being 0.1 or less.

13. The pressure-sensitive adhesive tape according to any one of claims 4 to 12, wherein the pressure-sensitive adhesive layer has a gel fraction of 30 to 50 mass %.

14. The pressure-sensitive adhesive tape according to any one of claims 4 to 13, wherein a soft polyvinyl chloride resin is used as the adherend.

15. The pressure-sensitive adhesive tape according to any one of claims 4 to 14, which is used for vehicle interiors.

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