Adhesive composition and adhesive tape

Abstract

The pressure-sensitive adhesive composition of the present invention comprises 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 comprising 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, and 5 to 18 parts by mass of a carboxyl group-containing monomer (B). The present invention can provide a pressure-sensitive adhesive composition that has high adhesive strength to poorly adhered substrates such as polypropylene resins and that suppresses deterioration of adhesive strength over time to soft polyvinyl chloride resins, and a pressure-sensitive adhesive tape using the pressure-sensitive adhesive composition.

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 adhesion to, for example, a soft polyvinyl chloride resin, and a substrate containing a plasticizer is used as the substrate of the pressure-sensitive adhesive tape, 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 purposes such as 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, and transparency, and are therefore widely used to fix components inside vehicles, houses, electronic devices, etc. Many adhesive tapes are equipped with a substrate and an adhesive layer provided on at least one surface of the substrate, and the material constituting 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 a decrease in adhesive strength over time due to migration of plasticizer when an adhesive tape having an acrylic adhesive layer is used with a soft polyvinyl chloride resin, and to solve this problem, it discloses a technology that uses an adhesive composition containing a specific acrylic copolymer and a metal chelate crosslinker. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-199843 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, components, sheets, etc. made from flexible polyvinyl chloride resins have been widely used as interior materials for vehicles, and there is a need for pressure-sensitive adhesive tapes that can be applied to such interior materials. Therefore, there is a need for a more advanced method for preventing the problem of reduced adhesive strength caused by the migration of plasticizers in the flexible polyvinyl chloride resins. In addition, adhesive tapes generally have low adhesive strength to adherends such as polypropylene resins with low polarity, which are widely used as vehicle components, and high adhesive strength is required even to such difficult-to-adhere substrates. A known method for improving adhesive strength to such difficult-to-adhere substrates is to incorporate a certain amount of tackifier resin into the adhesive layer. However, when a tackifier resin is incorporated, the tackifier resin promotes the migration of the plasticizer, resulting in a problem of a decrease in adhesive strength to soft polyvinyl chloride resins over time. Therefore, there is a need for an adhesive tape having an adhesive layer that suppresses the decrease in adhesive strength to soft polyvinyl chloride resins over time while also improving adhesiveness to difficult-to-adhere substrates such as polypropylene resins. In addition, a porous material 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 the decrease in adhesive strength resulting from the migration of the plasticizer even for such substrates.

[0005] The present invention has been made in consideration of the above-mentioned conventional problems, 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-mentioned object, and as a result have found that the above-mentioned problems can be solved by 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, 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 (meth)acrylic acid alkyl ester monomer (A) containing 60% by mass or more of (meth)acrylic acid alkyl ester monomer (a) having an alkyl group with 4 or less carbon atoms, and 5 to 18 parts by mass 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 comprises 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) contains 13 mass % or less of components having a molecular weight of 600 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 made of the pressure-sensitive adhesive composition according to any one of [1] to [6] above. [8] A pressure-sensitive adhesive tape having a substrate and a pressure-sensitive adhesive layer formed on at least one surface thereof and 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 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 antiresonant frequency in the range of 0 to 50°C, as measured by mechanical impedance measurement (MIM) in accordance with ISO 16940, and a second antiresonant frequency of 800 Hz or less in the range of 0 to 30°C.

[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 items

[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 when the rebound height is measured, the rebound coefficient (rebound height / dropped ball height) is 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 items [7] to

[17] , which is used for vehicle interiors. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a pressure-sensitive adhesive composition that has high adhesive strength to poorly adherends such as polypropylene resins and that suppresses deterioration of adhesive strength over time to soft polyvinyl chloride resins, and a pressure-sensitive adhesive tape using the pressure-sensitive adhesive composition. Furthermore, it is possible to provide a pressure-sensitive adhesive composition that can suppress 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 explanation of the drawings]

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

[0009] [Adhesive composition] The pressure-sensitive adhesive composition of the present invention comprises 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 an adherend such as a soft polyvinyl chloride resin is increased and the adhesive strength is less likely to decrease over time. The reason for this is unclear, but is presumed to be as follows. Normally, when a pressure-sensitive adhesive composition is used by being applied to the surface of a sheet formed from a 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 from the pressure-sensitive adhesive composition, which is thought to result in a decrease in adhesive strength. In contrast, the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present invention contains an acrylic polymer containing a relatively large amount of carboxyl group-containing monomer. Therefore, the acrylic polymer has a relatively high polarity and a high acid value, which is thought to easily inhibit the migration of plasticizers with relatively low polarity, thereby suppressing the decrease in adhesive strength of the pressure-sensitive adhesive layer. Furthermore, the high molecular weight of the acrylic copolymer and, in some cases, the high crosslinking density are also thought to enhance the effect of suppressing the decrease in adhesive strength through the inhibition of plasticizer migration. Furthermore, as will be described later, 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% by 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 (meth)acrylic acid alkyl ester monomer (a) having an alkyl group with 4 or less carbon atoms. If the content of (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 flexible polyvinyl chloride tends to decrease. From the viewpoint of suppressing a decrease in adhesive strength to flexible polyvinyl chloride, the content of (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 (meth)acrylic acid alkyl ester monomers (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, n-butyl (meth)acrylate is preferably used, and n-butyl (meth)acrylate is more preferably used 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 (meth)acrylic acid alkyl ester monomers (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, with (meth)acrylic acid being preferred and acrylic acid being more preferred. The carboxyl group-containing monomer (B) may be used alone or in combination of two or more.

[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 a (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 decreases, and the adhesive strength of the pressure-sensitive adhesive composition to an adherend such as soft polyvinyl chloride tends to decrease. This is thought to be because when the amount of the carboxyl group-containing monomer (B) is small, the polarity of the acrylic polymer (X) decreases, and the plasticizer, which is a relatively low-polarity compound, tends to migrate from the soft polyvinyl chloride or the substrate of the pressure-sensitive adhesive tape to the pressure-sensitive adhesive composition. On the other hand, if the amount of the carboxyl group-containing monomer (B) exceeds 18 parts by mass, the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition itself tends to harden as crosslinking proceeds, and the adhesive strength to adherends such as soft polyvinyl chloride tends to decrease. Furthermore, if the amount of the carboxyl group-containing monomer (B) exceeds 18 parts by mass, the adhesive strength 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 even more preferably 10 to 15 parts by mass, relative to 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 polar groups other than carboxyl groups, 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, which tends to decrease the adhesive strength to adherends with complex shapes and also tends to decrease the adhesiveness to low-energy surfaces such as polypropylene resin. 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 examples thereof include a method of radically polymerizing a monomer component in the presence of a polymerization initiator. As the polymerization method, known methods can be used, such as solution polymerization, emulsion polymerization, suspension polymerization, and bulk polymerization. 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 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), and 2,2'-azobis(2-methylbutyronitrile). 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. 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] <Tackifying 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 this 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 a 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 types 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, as well as terpene resins, phenol resins, xylene resins, coumarone resins, ketone resins, and modified resins thereof. Among these, from the viewpoints of increasing adhesive strength to adherends such as soft polyvinyl chloride and suppressing 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 tackifier resin (Y) in the pressure-sensitive adhesive composition is 3 to 9 parts by mass per 100 parts by mass of acrylic polymer (X). If the amount of tackifier resin is less than 3 parts by mass, the adhesive strength to poorly adherends such as polypropylene tends to decrease, and the adhesive layer becomes difficult to maintain when the adherend is deformed. If the amount of tackifier resin is more than 9 parts by mass, when the adhesive layer is laminated on a flexible polyvinyl chloride or a substrate, migration of plasticizer from the flexible polyvinyl chloride or the substrate to the adhesive layer tends to be promoted, resulting in a decrease in adhesive strength over time. From the viewpoint of increasing adhesive strength to poorly adherends such as polypropylene resin and maintaining adhesive strength to flexible polyvinyl chloride or other adherends, the amount of tackifier resin (Y) in the pressure-sensitive adhesive composition is preferably 3 to 8 parts by mass, more preferably 4 to 7 parts by mass, per 100 parts by mass of 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. Use of such a tackifier resin allows the amount of volatile components emitted from the tackifier resin to be kept low while maintaining adhesion. Furthermore, the low content of low-molecular-weight components allows the adhesive layer to have a relatively high viscosity, which, when the adhesive layer is laminated on a flexible polyvinyl chloride or a substrate, tends to inhibit the migration of plasticizer from the flexible polyvinyl chloride or the substrate to the adhesive layer, making it less likely for 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. Examples of methods for removing components having a molecular weight of 600 or less from a tackifier resin include a method of heating and melting the tackifier resin to a temperature above its softening point, and a method of blowing water vapor into the tackifier resin.

[0022] <Crosslinking agent (Z)> The pressure-sensitive adhesive composition of the present invention contains a crosslinking agent. The use of the crosslinking agent increases the cohesive strength of the pressure-sensitive adhesive layer formed, improving the physical properties of the pressure-sensitive adhesive tape. 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 a commercially available product thereof is, for example, 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., with aluminum chelates whose central metal is aluminum being preferred. Examples of commercially available products include Aluminum Chelate A and Aluminum Chelate M manufactured by Kawaken Fine Chemicals 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 parts 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, or diethyl ether, 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 also contain additives such as a filler, a pigment, a dye, or an antioxidant.

[0024] <Gel fraction> The pressure-sensitive adhesive composition of the present invention can be applied to a substrate or the like and dried to form a pressure-sensitive adhesive layer, as described below. The gel fraction of the pressure-sensitive adhesive layer formed from the pressure-sensitive 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 plasticizer from the soft polyvinyl chloride or substrate to the pressure-sensitive 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 consisting 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 the pressure-sensitive adhesive tape can be produced, for example, by applying a pressure-sensitive adhesive composition containing the above-mentioned acrylic polymer (X), tackifier resin (Y), crosslinking agent (Z), and optionally other components such as a solvent to a substrate or the like, and drying the composition to form a pressure-sensitive adhesive layer on the substrate. Examples of drying methods include drying in a drying furnace such as an IR heater or an oven.

[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 penetration and application properties 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 the substrate, it is preferable to use a pulp fiber nonwoven fabric containing a rayon component. The amount of rayon 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 pulp fiber 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 needed, but the content of 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 from the viewpoints 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 a pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer is less likely to separate from the pulp fiber nonwoven fabric, improving the performance of the pressure-sensitive adhesive tape.

[0028] It is also preferable to use a porous body as the substrate. The porous body has a large number of cells 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 such a plasticizer is used, the use of the above-mentioned pressure-sensitive adhesive composition prevents the plasticizer from migrating from the substrate to the pressure-sensitive adhesive layer, and suppresses a decrease in the adhesive strength of the pressure-sensitive adhesive layer over time. Examples of the thermoplastic resin include polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-hexafluoropropylene 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 preferred, and polyvinyl acetal is more preferred.

[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 preferred. By using a porous substrate, it becomes easier to improve at least one of the impact absorption, vibration damping, shapeability, and sound insulation performance of the substrate, as will be described later. Therefore, the porous substrate is suitably used in applications where any one of these properties is required in the substrate.

[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 types 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 %, the upper limit is preferably 85 mol %, the more preferable lower limit is 60 mol %, and the more preferable upper limit is 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, 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 facilitated. 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 suitably used. The aldehyde having 1 to 10 carbon atoms is not particularly limited, and examples thereof include n-butylaldehyde, isobutyraldehyde, n-valeraldehyde, 2-ethylbutyraldehyde, n-hexylaldehyde, n-octylaldehyde, n-nonylaldehyde, n-decylaldehyde, formaldehyde, acetaldehyde, and benzaldehyde. Among these, n-butylaldehyde, n-hexylaldehyde, and n-valeraldehyde are preferred, and n-butylaldehyde 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. A liquid plasticizer is a plasticizer that is liquid at room temperature (23°C) and normal pressure (1 atmosphere).

[0036] The monobasic organic acid ester is not particularly limited, but 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-ethylhexylic 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 linear or branched structure and 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-ethylbutyrate, 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-ethylbutyrate, 1,3-propylene glycol di-2-ethylbutyrate, 1,4-butylene glycol di-2-ethylbutyrate, diethylene ... Examples of the alkyl acrylate copolymer include ethylene glycol di-2-ethylhexanoate, dipropylene glycol di-2-ethylbutyrate, triethylene glycol di-2-ethylpentanoate, tetraethylene glycol di-2-ethylbutyrate, diethylene glycol dicaprylate, dihexyl adipate, dioctyl adipate, hexylcyclohexyl adipate, diisononyl adipate, heptylnonyl adipate, dibutyl sebacate, oil-modified alkyd sebacate, a mixture of a phosphate ester and an adipate ester, an adipate, a mixed adipate made from an alkyl alcohol having 4 to 9 carbon atoms and a cyclic alcohol having 4 to 9 carbon atoms, and an adipate 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, the plasticizer preferably contains triethylene glycol di-2-ethylhexanoate (3GO), triethylene glycol di-2-ethylbutyrate (3GH), tetraethylene glycol di-2-ethylhexanoate (4GO), or dihexyl adipate (DHA), more preferably tetraethylene glycol di-2-ethylhexanoate (4GO) or triethylene glycol di-2-ethylhexanoate (3GO), and particularly preferably triethylene glycol di-2-ethylhexanoate (3GO).

[0040] The content of the plasticizer is not particularly limited, but a preferred lower limit is 5 parts by mass and a preferred upper limit is 60 parts by mass per 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. Furthermore, the plasticizer does not bleed out from the porous body. A more preferred lower limit of the content of the plasticizer is 20 parts by mass and a more preferred upper limit is 55 parts by mass. In many interlayer films for laminated glass, the content of plasticizer per 100 parts by mass of thermoplastic resin such as polyvinyl acetal is approximately 20 to 55 parts by mass. Therefore, for example, discarded interlayer films for laminated glass can be used as they are as a raw material for the substrate of the present invention. The thermoplastic resin and plasticizer are preferably the main components of the substrate, and the total amount of the thermoplastic resin and plasticizer is usually 70% by mass or more, preferably 80% by mass or more, and more preferably 90% by mass or more, based on the total amount of the substrate.

[0041] In addition to the thermoplastic resin and plasticizer, the substrate may contain additives such as an adhesion modifier, a heat ray absorber, an ultraviolet light 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 pigments such as carbon black, dyes, 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. There is no particular upper limit to the open cell ratio, but a practical upper limit is about 98%. Increasing the open cell ratio in this way makes it easier to improve at least one of the impact absorption, vibration damping, shaping, and sound insulation properties of the substrate, and also makes it 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 the porous body relative 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 an average cell diameter with a preferred lower limit of 100 μm and a preferred upper limit of 1000 μm. The average cell diameter is more preferably 120 μm, more preferably 500 μm, and even more preferably 200 μm. By setting the average cell diameter within this range, it becomes easier to further improve at least one of the impact absorption, vibration damping, shaping ability, and sound insulation performance of the substrate. In addition, it becomes easier to obtain the porous bodies of the first and second embodiments described below.

[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, shaping ability, and sound insulation performance of the substrate. It also becomes easier to obtain the porous bodies 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 sample for measurement is cut into a length of 50 mm and a width of 50 mm, 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 magnification photograph is taken using a digital microscope (Keyence Corporation, product name VHX-900), and the bubble diameters of all bubbles present on a 2mm-long cut surface in the thickness direction are measured. If the thickness of the porous sample is less than 2mm, 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 and minor diameters of the voids in a cross-sectional photograph of the bubbles and calculating the ratio. Specifically, when measuring the average bubble diameter, the major and minor axes 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 by averaging the obtained aspect ratios.

[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 ensuring that the apparent density is 260 kg / m or less, it becomes easier to improve the impact absorption, vibration damping, shaping properties, low flowability, etc. of the substrate. This also makes it easier to obtain the porous bodies of the first and second embodiments described below. 3 More preferably, it is 200 kg / m or less. 3 It is 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 a predetermined range shown in the second embodiment described later, the shapeability is improved, 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 measuring the dimensions.

[0048] Furthermore, the porous body preferably has a specific gravity of 0.3 or less. A specific gravity of 0.3 or less allows the porous body to exhibit higher impact absorption properties. The specific gravity is more preferably 0.2 or less. There are no particular restrictions on the lower limit of the specific gravity, but a 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 foam, it refers to the ratio of the density after foaming to the density before foaming, i.e., "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." Furthermore, if the measured weight before foaming and the apparent volume before foaming are unknown, the calculation can also be performed 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 susceptible to shear rupture. 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, it becomes easier to further improve at least one of the impact absorption, vibration damping, shapeability, and sound insulation performance of the obtained porous body. Furthermore, 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 with 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, or the like contained in the side chain of the polyvinyl acetal can be used as the crosslinking agent. Specific examples include epoxy compounds, isocyanate compounds, and boric acid compounds. Furthermore, a polyfunctional (meth)acrylate compound such as trimethylolpropane triacrylate (TMPTA) can also be used as the crosslinking agent. When a polyfunctional (meth)acrylate compound is used as a crosslinking agent in a 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 first anti-resonant frequency in the range of 0 to 50°C, measured by mechanical impedance measurement (MIM) in accordance with ISO 16940, and a second 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 dissipating sound energy. The loss factor is preferably 0.3 or more. When the second anti-resonance frequency is 800 Hz or less, sound generated from the adherend can be made less perceptible to the human ear as noise. Therefore, the porous body of the first embodiment can exhibit high sound-insulating 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-insulating material or soundproofing material. The loss factor of the first antiresonant frequency and the second antiresonant frequency can be measured using the central excitation method and are determined as the maximum value of the loss factor in the temperature range of 0 to 50°C and the maximum value of the second antiresonant frequency in the temperature range of 0 to 30°C. The sample used is a laminated sample in which a porous body is fixed between two glass plates measuring 25 mm wide, 305 mm long, and 2 mm thick with double-sided tape (Sekisui Chemical Co., Ltd., #5782). Before applying the double-sided tape for measurement, the porous body is either pre-attached to the tape or, if the porous body has an adhesive layer, the double-sided tape (Sekisui Chemical Co., Ltd., #5782) is applied only to the side without the double-sided tape or the side without the adhesive layer.

[0053] The loss factor and second anti-resonance frequency can be achieved by, for example, adjusting the foaming state of the porous body. Specifically, the open cell rate of the porous body is preferably 20% or more. Furthermore, by further increasing the open cell rate, it becomes easier to adjust the loss factor and second anti-resonance frequency to suitable values while exhibiting high sound insulation properties. In this embodiment, it is preferable to use polyvinyl acetal as the thermoplastic resin as described above. By using polyvinyl acetal, it is easier to adjust the loss factor of the first antiresonant frequency and the second antiresonant frequency within a predetermined range. Furthermore, it is better to adjust the average cell diameter, average aspect ratio of the cells, 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 and 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 term "extensional strain" refers to a value indicating the degree of deformation applied to a sheet-like porous body when the porous body is subjected to extensional deformation in one axial direction. When the extensional strain is 300% or more, the porous body can exhibit excellent impact resistance while remaining flexible. The extensional strain is preferably 400% or more, and more preferably 500% or more. There are no particular limitations on the upper limit of the extensional strain, but the upper limit is practically about 800%. In this specification, the 50% compressive stress refers to a value indicating the stress applied to a sheet-like porous body when it is compressed by 50% in the thickness direction. When the 50% compressive stress is 70 kPa or less, the porous body of this 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. There are no particular restrictions on the lower limit of the 50% compressive stress, but the lower limit 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 using a sample punched into a No. 1 dumbbell shape as specified in JIS K 6251 and pulling it at a tensile speed of 500 mm / min using a universal testing machine. Alternatively, a sample cut into a square shape with a side length of 50 mm can be stacked to a thickness of 25 mm or more, and the stacked sample can be compressed at a compression speed of 10 mm / min using a universal testing machine to measure the 50% compressive stress.

[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 adjusting the open cell ratio to 20% or more, the 50% compressive stress of the resulting porous body can be adjusted to a predetermined range, allowing it to exhibit extremely high flexibility. From this perspective, the higher the open cell ratio, as described above, the better. Furthermore, 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 preferable to adjust the average cell diameter, the average aspect ratio of the cells, 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 a suitable method is, for example, to prepare a resin composition by blending a thermally decomposable foaming agent with the thermoplastic resin, plasticizer, and optional additives, and then heating the resin composition to a foaming temperature to decompose the thermally decomposable foaming agent. Furthermore, when crosslinking the porous body, a crosslinking agent may be blended into the resin composition. Furthermore, crosslinking is preferably carried out before foaming. For example, when crosslinking the porous body by irradiating it with light such as ultraviolet light, light irradiation may be carried out before heating for foaming.

[0058] Here, in order to obtain the porous body of the first or second embodiment with the open cell ratio and other properties within the above ranges, it is important to select the thermoplastic resin and plasticizer, as well as the type and amount of the thermal decomposition type foaming agent used during production and to set the foaming temperature. In particular, setting the foaming temperature is important for achieving a high open cell ratio. Specifically, the foaming temperature is preferably 180°C or higher. At temperatures of 180°C or higher, the resin composition is sufficiently softened during foaming, making it easier for the cells to communicate with each other, which is thought to facilitate the generation of open cells. In particular, since such an increase in the open cell ratio is observed when a resin composition containing polyvinyl acetal and a plasticizer is used, the porous body containing polyvinyl acetal and a plasticizer can easily increase the open cell ratio.

[0059] The thermally decomposable foaming agent is not particularly limited as long as it has a decomposition temperature of about 120 to 240°C, and conventionally known foaming agents can be used. Since this allows for a higher open cell ratio, it is preferable to set the foaming temperature to 180°C or higher and to select a thermally decomposable foaming agent whose foaming temperature is higher than the decomposition temperature of the thermally decomposable foaming agent. More specifically, foaming temperatures higher than the decomposition temperature of the thermally decomposable foaming agent are preferably 20°C or higher, 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, commercially available ones include, for example, the Cellmic series (manufactured by Sankyo Kasei Co., Ltd.), the Vinihole series, the Cellular series, and the Neo Cellbon 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 a preferred lower limit is 2 parts by mass and a preferred upper limit is 20 parts by mass per 100 parts by mass of the thermoplastic resin. When 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. Furthermore, from the viewpoint of easily achieving a high open cell ratio (e.g., 20% or more), a more preferred lower limit of the amount of the thermally decomposable foaming agent is 4 parts by mass, an even more preferred lower limit is 5 parts by mass, and an even 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 preferably the nonwoven fabric of the third embodiment described below.

[0063] (Third embodiment) The nonwoven fabric of the third embodiment uses polyvinyl acetal as the 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 rebound coefficient (rebound height / drop 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 pressure-sensitive adhesive tapes that require impact absorption properties, and more specifically, is suitable when the substrate is used as a sound-insulating 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 then dropping a 1 / 2-inch SUS ball conforming to JIS B 1501 from a certain height toward the center of the nonwoven fabric sample, and measuring the height of the rebound.

[0064] If the thickness of the nonwoven fabric to be measured is less than 4 mm, the nonwoven fabric sample can be prepared by stacking the nonwoven fabric in the thickness direction until the thickness exceeds 4 mm, and then shaving it to a thickness of 4 mm. If the thickness of the nonwoven fabric to be measured exceeds 4 mm, the nonwoven fabric sample can be prepared by shaving it to a thickness of 4 mm. If it is difficult to shave it to an exact thickness of 4 mm, an average thickness of 4 mm ± 0.1 mm is acceptable. The thickness of the nonwoven fabric sample can be adjusted using an appropriate mechanical device. The environment when measuring the above-mentioned rebound coefficient is a temperature of 23°C and a humidity of 50% Rh. Furthermore, a certain falling ball 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 a specified range in any one of these cases, but it is better that it be within a specified range in all cases.

[0065] The polyvinyl acetal, plasticizer, additives, etc. 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 is. Furthermore, the average diameter (average fiber diameter) of the fibers constituting the nonwoven fabric of this embodiment preferably has a lower limit of 50 μm and an upper limit of 2 mm. 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 and an upper limit of 1 mm.

[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 preferred value, higher impact absorption properties can be exhibited.

[0068] From the viewpoint of improving the handleability of the pressure-sensitive adhesive tape, the upper limit of the thickness of the nonwoven fabric used as the substrate is preferably 10 mm, more preferably 4 mm, particularly preferably 0.5 mm, and most preferably 0.3 mm. The lower limit of the thickness is preferably 20 μm. A thickness of 20 μm or more further improves the impact absorption of the nonwoven fabric. The lower limit of the thickness of the nonwoven fabric of this embodiment is more preferably 50 μm, even more preferably 100 μm, particularly preferably 150 μm, and most preferably 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, and then laminating the resulting laminate using a press. In this process, the basis weight of the resulting nonwoven fabric can be adjusted by adjusting the diameter and length of the strands and the thermal compression conditions.

[0070] The uses of the pressure-sensitive adhesive tape of the present invention are not particularly limited, and it can be used for a wide variety of purposes, including vehicle components for automobiles, aircraft, ships, etc., building components, electronic components, household components such as carpet backings, and electrical appliances for home and commercial use. Among these, it is preferably used inside vehicles, homes, and electronic devices, more preferably for vehicle components, and even more preferably for vehicle interiors.

[0071] In the present invention, it is also preferable to use a flexible polyvinyl chloride resin as the adherend. The flexible 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 entire flexible polyvinyl chloride resin. The type of plasticizer contained in the flexible polyvinyl chloride resin is not particularly limited, and examples 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). Furthermore, since the pressure-sensitive adhesive tape of the present invention also has good adhesive strength to polyolefin resins such as polyethylene resin and polypropylene resin, a suitable mode of use may also be to make it into a double-sided pressure-sensitive adhesive tape in which the adherend on one side is a polyolefin resin such as polyethylene resin or polypropylene resin and the adherend on the other side is a soft polyvinyl chloride resin. [Example]

[0072] The present invention will be explained in more detail by way of 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. The mixture was refluxed at 70°C for 5 hours to obtain a solution of an acrylic polymer with a weight average molecular weight of 720,000. <Production of Pressure-Sensitive Adhesive Composition and Pressure-Sensitive Adhesive Tape> To the obtained acrylic polymer solution, 6.3 parts by mass of a polymerized rosin ester tackifying resin (softening point 140) containing 13% by mass of components with a molecular weight of 600 or less, and 0.054 parts by mass of aluminum chelate, a metal chelate crosslinking agent, were added relative to 100 parts by mass of the acrylic polymer, which is the nonvolatile content of the acrylic polymer solution. The mixture was then uniformly mixed to obtain a pressure-sensitive adhesive composition. Next, the adhesive composition was 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 a phthalate ester-containing adherend (soft polyvinyl chloride sheet), the rebound holding power, and the adhesive strength to 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. Next, a double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 1, except that the type and amount of tackifier resin and the type and amount of crosslinking agent were changed as shown in Table 1 or 2. The adhesive tape was evaluated for adhesive strength retention (%) to a phthalate ester-containing adherend (soft polyvinyl chloride sheet), rebound holding power, 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 Resin> Polymerized rosin ester tackifying 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 tackifying resin (rosin-based (standard product)) - Softening point 160°C, molecular weight of 600 or less: 33% by mass Terpene phenolic tackifying resin...Softening point 150℃ <Crosslinking agent> Metal chelate crosslinking agent: Aluminum chelate, "M-A5DT" manufactured by Soken Chemical & Engineering Co., Ltd. Isocyanate crosslinking agent: "Coronate L" manufactured by Nippon Polyurethane Co., Ltd. Epoxy crosslinking agent: "E-AX" manufactured by Soken Chemical & Engineering Co., 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> Measurement was carried out 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 netting. The residue on the wire netting was dried by heating at 110°C, and the weight W2 (g) of the obtained 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] <Adhesion retention rate (%) to 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 each double-sided adhesive tape of each Example and Comparative Example, without allowing 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% 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 25 mm width 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) Adhesion strength over time A 23 μm thick PET film was attached to one side of each double-sided adhesive tape of each Example and Comparative Example, ensuring that no air was trapped. The adhesive layer side of the double-sided adhesive tape attached to the PET film, which was not attached to the PET film, was then 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% using a 2 kg pressure-bonding rubber roller at a speed of 30 mm / min. The tape was then left at 60° C. for 72 hours, and then left at room temperature for 30 minutes. The 180° peel strength at a 25 mm width was measured at a speed of 3 mm / min according to the method of JIS Z0237, and this was recorded as the adhesive strength over time (N / 25 mm).

[0078] <Repulsive force against adherends containing phthalate esters> Figure 1 shows a schematic diagram of the method for evaluating the resilience. 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% by weight of DINP as a plasticizer) using a 2 kg pressure roller at a speed of 30 mm / min to produce a polyvinyl chloride sheet with double-sided adhesive tape. The polyvinyl chloride sheet with double-sided adhesive tape was cut into 15 mm x 40 mm pieces and attached to a 5 mm-thick polypropylene plate 13 at a speed of 30 mm / min from a portion (10 mm) of the top surface to a portion (25 mm) of the side surface, forming a roughly U-shaped cross section (Figure 1). The pieces were left in this state at 60°C and 90% relative humidity for two weeks, and the resilience of the double-sided adhesive tape was evaluated by checking whether the soft polyvinyl chloride sheet peeled off from the portion (10 mm) of the top surface or the portion (25 mm) of the bottom surface of the polypropylene plate 13. The samples in which the soft polyvinyl chloride sheet did not peel off were rated 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 B, and those in which the polyvinyl chloride sheet peeled off were rated C.

[0079] <Adhesion 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, so as to prevent air from getting 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 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 over a 25 mm width was measured at a rate 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 prepared. 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 containing no 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 ) was used. The adhesive tape was evaluated for adhesive release from the nonwoven fabric by the method described below.

[0084] <Evaluation of adhesive layer detachment from nonwoven fabric> A 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 edge of a test plate (soft polyvinyl chloride sheet) and pressed back and forth with a 1 kg roller. After pressing, the test piece was left at a temperature of 80±2°C for 1 hour, after which a weight applying a load of 9.8±0.049 N was hung from the bottom end of the test piece, and it was confirmed whether the weight fell off within 4 hours. If the weight fell off, it meant that the adhesive layer had detached from the nonwoven fabric. The separation of the adhesive layer from the nonwoven fabric was evaluated based on the following criteria. A: The adhesive layer did not separate from the nonwoven fabric. B: The adhesive layer was confirmed to have separated from the nonwoven fabric.

[0085] [Table 3]

[0086] As is clear from the results of Examples 1 to 8, adhesive tapes using the adhesive composition of the present invention containing a specific type of acrylic polymer and a specific amount of tackifier resin exhibited good adhesive strength retention and rebound holding power against soft polyvinyl chloride sheets. Furthermore, the results of Examples 9 and 10 showed that when a nonwoven fabric containing a rayon component was used as a substrate, the adhesive was less likely to detach from the substrate. In contrast, the adhesive tapes using 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 soft polyvinyl chloride sheets. Furthermore, the pressure-sensitive adhesive tapes containing a certain amount of tackifier resin in the pressure-sensitive adhesive layer used in Examples 1 to 8 also had good adhesive strength to polypropylene resin. On the other hand, the pressure-sensitive adhesive tapes containing no tackifier resin used in Comparative Examples 5 to 7 were easily peeled off from the polypropylene plate and did not receive a good evaluation in the evaluation of rebound holding strength.

[0087] <Adhesive tape having porous body of 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 resulting resin composition was thoroughly mixed with a mixing roll at 110°C and then extruded using an extruder to obtain a sheet. PVB1 had a hydroxyl group content of 34 mol%, an acetylation degree of 1.0 mol%, a butyralization degree of 65 mol%, and an average degree of polymerization of 1650. The resulting sheet was then heated in an oven at a foaming temperature of 220°C to decompose the thermal decomposition type foaming agent, yielding a porous resin foam. The resulting porous body had a thickness of 4 mm. (2) Manufacturing 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 at the first anti-resonance frequency and the second anti-resonance frequency were measured by the methods 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) Sound transmission loss was measured using the sound intensity method in accordance with JIS A 1441. The measurement temperature was 20°C, and the frequency range was 100 to 10,000 Hz, covering 1 / 3 octave bands. The sample was prepared by sandwiching a resin foam sample (approximately 4 mm thick) between 2 mm thick glass plates and fixing it with double-sided tape (Sekisui Chemical Co., Ltd., #5782). Double-sided tape (Sekisui Chemical Co., Ltd., #5782) was attached only to the non-adhesive side, not to the adhesive side. The size (opening) was 500 mm x 500 mm. Incident power was calculated from the average sound pressure level at five points in the reverberation chamber, and transmitted power was calculated from the sound intensity at 5 x 5 = 25 points within 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 an evaluation was given of "A" when the difference in transmission loss between the first maximum value on the low frequency side and the adjacent minimum value was sufficiently small, and "B" when the difference in transmission loss was large.

[0093] (Plasticizer resistance evaluation) The single-coated pressure-sensitive adhesive tapes of Examples 11 and 12 and Comparative Examples 10 and 11 were evaluated by the following evaluation methods. Table 4 shows the evaluation results. (Test specimen preparation) The single-sided adhesive tape obtained in each Example and Comparative Example was cut into a piece 25 mm wide x 150 mm long, and was pressed onto SUS304 (surface BA finish) specified in JIS G4305 by using a 2 kg rubber roller that was moved 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 accordance with JIS Z0237 for three tests, and the average value was recorded 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. After that, a 90-degree peel test was conducted in accordance with JIS Z0237, with three tests, and the average value was taken as the adhesive strength over time (N / 25 mm). (Adhesive force 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 evaluated 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 evaluated as B if there was no change.

[0094] [Table 4]

[0095] <Adhesive tape having porous body according to second embodiment> Example 13 (1) Manufacturing of porous bodies To 100 parts by weight of polyvinyl butyral (PVB2), 40 parts by weight of triethylene glycol di-2-ethylhexanoate (3GO) as a plasticizer, 3 parts by weight of Vinihol AC#3 (manufactured by Eiwa Chemical Industry Co., Ltd., decomposition temperature 208°C) as a thermal decomposition type foaming agent, and 0.8 parts by weight of carbon black (manufactured by Tokai Carbon Co., Ltd., Seast SP) were added to obtain a resin composition. The resulting resin composition was thoroughly kneaded with a mixing roll at 110°C and then extruded with an extruder to obtain a sheet. The PVB2 had a hydroxyl group content of 31 mol%, a degree of acetylation of 0.7 mol%, a degree of butyralization of 68.3 mol%, and an average degree of polymerization of 1800. The thermal decomposition type foaming agent in the obtained sheet was decomposed at a foaming temperature of 230° C. in an oven to obtain a porous body made of a resin foam having a thickness of 4 mm. (2) Manufacturing 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 of the porous bodies produced in Examples 13 and 14 and Comparative Examples 12 and 13 were measured by the methods described in the specification. Furthermore, 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. Furthermore, 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 tape was stretched and attached so that the parts that were not in contact were pressed against the valleys. At this time, the substrate was observed for any tears or localized thinning, and the formability was evaluated according to the following criteria. A: No tearing or thinning is observed B: Breakage or thinning was observed

[0101] (Flexibility assessment) A 1 / 2 inch diameter stainless steel ball was left standing in the valley of a corrugated adhesive tape for 1 minute. 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 SUS balls 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 resulting resin composition was thoroughly mixed using 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 into 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 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) Manufacturing 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 that the thickness was 1 / 4 of the thickness of the nonwoven fabric. A single-sided adhesive tape was obtained 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] The nonwoven fabrics produced in Examples 15 and 16 and Comparative Examples 14 and 15 were measured for various physical properties, as well as for the rebound height and rebound coefficient when the ball was dropped from heights of 10 cm, 20 cm, and 30 cm, according to the methods described in the specifications. Furthermore, the plasticizer resistance was evaluated according to 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 board

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 metal chelate crosslinking agent as 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 95 to 100 mass% of a (meth)acrylic acid alkyl ester monomer (a) having an alkyl group with 4 or less carbon atoms, and 5 to 18 parts by mass of a carboxyl group-containing monomer (B), the acrylic polymer (X) contains only the (meth)acrylic acid alkyl ester monomer (A) and the carboxyl group-containing monomer (B); the tackifier resin (Y) is a rosin-based tackifier resin, The acrylic pressure-sensitive adhesive composition, wherein the tackifier resin (Y) contains 13 mass % or less of components having a molecular weight of 600 or less.

2. 2. The acrylic pressure-sensitive adhesive composition according to claim 1, wherein the (meth)acrylic acid alkyl ester monomer (a) in which the alkyl group has 4 or less carbon atoms comprises n-butyl(meth)acrylate.

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

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. 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 any one of claims 1 to 3.

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 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 first antiresonant frequency in the range of 0 to 50°C, as measured by mechanical impedance measurement (MIM) in accordance with ISO 16940, and a second 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 9, wherein the porous body has an elongation strain of 300% or more and a 50% compression 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 height toward the center of the nonwoven fabric sample, and the rebound height is measured, the rebound coefficient (rebound 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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