adhesive tape

Abstract

The purpose of the present invention is to provide a pressure-sensitive adhesive tape that not only has exceptional flexibility and impact resistance but also imposes a low environmental load. The present invention is a pressure-sensitive adhesive tape having a foam substrate and at least one pressure-sensitive adhesive layer, wherein the foam substrate contains a block copolymer having blocks derived from (meth)acrylic-based monomers, and the pressure-sensitive adhesive tape contains biologically derived carbon.

Description

[Technical Field]

[0001] The present invention relates to an adhesive tape. [Background technology]

[0002] Adhesive tapes are used for assembly of portable electronic devices such as mobile phones and personal digital assistants (PDAs) (for example, Patent Documents 1 and 2). Adhesive tapes are also used to fix in-vehicle electronic device components such as in-vehicle panels to the vehicle body. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-242541 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-258274 Summary of the Invention [Problem to be solved by the invention]

[0004] Adhesive tapes used to fix portable electronic device components, in-vehicle electronic device components, etc., require high adhesive strength and impact resistance so that they do not peel even when subjected to impact. Meanwhile, in recent years, portable electronic devices, in-vehicle electronic devices, etc., have tended to have more complex shapes as their functionality has increased, and adhesive tapes are sometimes applied to steps, corners, non-flat surfaces, etc. In such cases, the adhesive tape is required to have excellent flexibility so that it can conform to the shape of the adherend. However, conventional adhesive tapes have not yet fully achieved both impact resistance and flexibility, and adhesive tapes that combine higher levels of impact resistance and flexibility are desired. Furthermore, due to the recent increase in environmental awareness, products that not only have the functionality of adhesive tapes but also have a lower environmental impact are desired.

[0005] An object of the present invention is to provide a pressure-sensitive adhesive tape that has excellent flexibility and impact resistance, and also has a low environmental impact. [Means for solving the problem]

[0006] The present invention provides an adhesive tape having a foam substrate and at least one adhesive layer, wherein the foam substrate contains a block copolymer having a block derived from a (meth)acrylic monomer, and the adhesive tape contains bio-derived carbon. The present invention will be described in detail below.

[0007] The pressure-sensitive adhesive tape of the present invention has a foam substrate and at least one pressure-sensitive adhesive layer. By using a foam substrate as the substrate of the pressure-sensitive adhesive tape, the pressure-sensitive adhesive tape of the present invention can exhibit excellent flexibility and impact resistance. The foam substrate may have an open-cell structure or a closed-cell structure, but a closed-cell structure is preferred. The foam substrate may have a single-layer structure or a multi-layer structure.

[0008] The pressure-sensitive adhesive tape of the present invention contains bio-derived carbon. The use of a biologically-derived material in the pressure-sensitive adhesive tape makes it possible to produce a pressure-sensitive adhesive tape with a low environmental impact. The biologically-derived carbon may be contained in the foam substrate or the pressure-sensitive adhesive layer, or, if the pressure-sensitive adhesive tape of the present invention has a layer other than the foam substrate and the pressure-sensitive adhesive layer, it may be contained in that layer. However, it is preferable that the foam substrate contains biologically-derived carbon, as this allows the tape to exhibit excellent flexibility and impact resistance.

[0009] The foam substrate contains a block copolymer having a block derived from a (meth)acrylic monomer. By using a block copolymer having a block derived from a (meth)acrylic monomer as the foam substrate, excellent flexibility and impact resistance can be exhibited. In addition, the presence of a block derived from a (meth)acrylic monomer can impart heat resistance to the resulting pressure-sensitive adhesive tape, thereby preventing deformation and peeling of the pressure-sensitive adhesive tape even when exposed to high temperatures for a long period of time.

[0010] The block copolymer having a block derived from the (meth)acrylic monomer is not particularly limited as long as it has a block derived from the (meth)acrylic monomer. Among them, a block copolymer having a block derived from a monomer having a rigid structure (hereinafter also referred to as a hard block) and a block derived from the (meth)acrylic monomer is preferred because it can further improve flexibility and impact resistance.

[0011] In block copolymers having a hard block and a block derived from a (meth)acrylic monomer, the two blocks are poorly compatible with each other, and the copolymer may have a heterogeneous phase-separated structure in which islands of aggregated hard blocks are scattered among a sea of ​​blocks derived from the (meth)acrylic monomer. These islands act as pseudo-crosslinking points, imparting rubber elasticity to the copolymer and contributing to high flexibility and impact resistance to the resulting pressure-sensitive adhesive tape. Furthermore, introducing crosslinkable functional groups into the hard blocks is believed to contribute to further flexibility and impact resistance to the resulting pressure-sensitive adhesive tape. The block copolymer having a hard block and a block derived from a (meth)acrylic monomer may have any structure, such as a diblock structure or a triblock structure. However, a triblock structure having a block derived from a (meth)acrylic monomer between the hard blocks is preferred, as this provides improved flexibility and impact resistance. The block copolymer having a hard block and a block derived from a (meth)acrylic monomer may also be a graft copolymer. The graft copolymer may be a graft copolymer having a hard block in the side chain and a block derived from a (meth)acrylic monomer in the main chain. Examples of the graft copolymer include a styrene macromer-(meth)acrylic monomer copolymer.

[0012] The hard block is not particularly limited as long as it has a structure derived from a monomer having a rigid structure. It may be a polymer of a single monomer having a rigid structure, or a copolymer composed of multiple monomers including a monomer having a rigid structure. Examples of the monomer having a rigid structure include vinyl aromatic compounds, compounds having a cyclic structure, and compounds with short side chain substituents (e.g., compounds in which the main chain of the side chain substituent has two or less carbon atoms). The hard block may also have a structure derived from methyl methacrylate. Among these, it is more preferable for the hard block to have a structure derived from a vinyl aromatic compound monomer, as this further improves impact resistance. Examples of the vinyl aromatic compound monomer include styrene, alpha-methylstyrene, para-methylstyrene, and chlorostyrene. Among these, styrene is preferred, as it further improves impact resistance. In this specification, the structure derived from a vinyl aromatic compound monomer refers to the structures shown in the following general formulas (1) and (2).

[0013] [ka] R in formulas (1) and (2) 1 represents a substituent having an aromatic ring. 1 Examples of the phenyl group include a phenyl group, a methylphenyl group, and a chlorophenyl group.

[0014] When the block copolymer has a structure derived from the vinyl aromatic compound monomer, the content of the structure derived from the vinyl aromatic compound monomer in the block copolymer is preferably 1% by weight or more and 30% by weight or less. By setting the content of the structure derived from the vinyl aromatic compound monomer within the above range, flexibility and impact resistance can be further improved. The lower limit of the content of the structure derived from the vinyl aromatic compound monomer is more preferably 1.5 wt%, even more preferably 2 wt%, particularly preferably 2.5 wt%, and more preferably 24 wt%, even more preferably 19 wt%, particularly preferably 16 wt%, and particularly preferably 8 wt%.

[0015] The hard block preferably has a structure derived from a monomer having a crosslinkable functional group. When the hard block has a crosslinkable functional group, the crosslinking enhances the rubber elasticity of the block copolymer, thereby further improving flexibility and impact resistance. The crosslinkable functional group may be crosslinked or not. Even if the structure remains uncrosslinked, the interaction between the functional groups improves the cohesive force within the block, improving flexibility and impact resistance. However, crosslinking is more preferable. In this specification, the structure derived from a monomer having a crosslinkable functional group refers to the structure shown in the following general formulas (3) and (4).

[0016] [ka] where R 2 represents a substituent containing at least one functional group. Examples of the functional group include a carboxyl group, a hydroxyl group, an epoxy group, a double bond, a triple bond, an amino group, an amide group, and a nitrile group. 2 may contain, as its constituent elements, an alkyl group, an ether group, a carbonyl group, an ester group, a carbonate group, an amide group, a urethane group, or the like.

[0017] The monomer having a crosslinkable functional group is not particularly limited, and examples thereof include carboxyl group-containing monomers, hydroxyl group-containing monomers, epoxy group-containing monomers, double bond-containing monomers, triple bond-containing monomers, amino group-containing monomers, amide group-containing monomers, and nitrile group-containing monomers. Among these, at least one selected from the group consisting of hydroxyl group-containing monomers, carboxyl group-containing monomers, epoxy group-containing monomers, amide group-containing monomers, double bond-containing monomers, and triple bond-containing monomers is preferred, as it provides improved flexibility and impact resistance. Examples of the hydroxyl group-containing monomer include 4-hydroxybutyl (meth)acrylate and 2-hydroxyethyl (meth)acrylate. Examples of the carboxyl group-containing monomer include (meth)acrylic acid. Examples of the epoxy group-containing monomer include glycidyl (meth)acrylate. Examples of the amide group-containing monomer include (meth)acrylamide. Examples of the double bond-containing monomer include allyl (meth)acrylate and hexanediol di(meth)acrylate. Examples of the triple bond-containing monomer include propargyl (meth)acrylate. Among these, carboxyl group-containing monomers are preferred, (meth)acrylic acid-based monomers are more preferred, and acrylic acid is even more preferred, as they can impart superior flexibility and impact resistance to the adhesive tape.

[0018] When the hard block is a copolymer of the monomer having the rigid structure and the monomer having the crosslinkable functional group, the hard block preferably contains 0.1% by weight or more and 30% by weight or less of the structure derived from the monomer having the crosslinkable functional group. When the content of the structure derived from the monomer having a crosslinkable functional group in the hard block is within the above range, flexibility and impact resistance can be further improved. The lower limit of the content of the structure derived from the monomer having a crosslinkable functional group is more preferably 0.5 wt %, even more preferably 1 wt %, and more preferably 25 wt %, even more preferably 20 wt %.

[0019] The (meth)acrylic monomer used as a raw material for the block derived from the (meth)acrylic monomer is not particularly limited as long as it has flexibility exhibiting rubber elasticity, and examples thereof include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, lauryl (meth)acrylate, isostearyl (meth)acrylate, etc. Among these, methyl acrylate, ethyl acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate are preferred because they easily achieve both heat resistance and flexibility, and methyl acrylate, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate are more preferred. The (meth)acrylic monomers may be used alone or in combination.

[0020] The (meth)acrylic monomer preferably contains a (meth)acrylic monomer containing bio-derived carbon. By using a (meth)acrylic monomer containing bio-derived carbon, it is possible to create an adhesive tape with a lower environmental impact. Biogenic carbon contains a certain percentage of the radioactive isotope C-14, whereas petroleum-derived carbon contains almost no C-14. Therefore, the content of biogenic carbon can be calculated by measuring the concentration of C-14 in the target material. Specifically, this can be measured in accordance with ASTM D6866, a standard used in many bioplastic industries.

[0021] Examples of the (meth)acrylic monomer containing bio-derived carbon, that is, the (meth)acrylic monomer that can be produced from a bio-derived raw material, include butyl (meth)acrylate, n-heptyl (meth)acrylate, 1-methylheptyl (meth)acrylate, n-octyl (meth)acrylate, lauryl (meth)acrylate, n-stearyl (meth)acrylate, isostearyl (meth)acrylate, behenyl (meth)acrylate, isobornyl (meth)acrylate, and tetrahydrofurfuryl (meth)acrylate. Among these, the (meth)acrylic monomer containing bio-derived carbon is preferably a (meth)acrylic monomer having an alkyl group having 7 to 12 carbon atoms, since this can further improve heat resistance and impact resistance. It is believed that the use of such a monomer results in a relatively large molecular weight between entanglement points of the polymer, which makes the polymer more likely to elongate when the pressure-sensitive adhesive tape is subjected to an impact, thereby absorbing the impact. Examples of the (meth)acrylic monomer having an alkyl group having 7 to 12 carbon atoms include n-heptyl acrylate, 1-methylheptyl acrylate, n-octyl acrylate, lauryl acrylate, lauryl methacrylate, and isobornyl acrylate. Among these, n-heptyl acrylate or n-octyl acrylate is preferred because it allows the pressure-sensitive adhesive tape to have better heat resistance and impact resistance. The (meth)acrylic monomer containing bio-derived carbon may be used alone or in combination.

[0022] The (meth)acrylic monomer containing bio-derived carbon is preferably a (meth)acrylic monomer having a homopolymer glass transition temperature Tg of −40° C. or lower. When the (meth)acrylic monomer containing bio-derived carbon is made into a homopolymer, the impact resistance can be further improved by having the Tg within the above range. The glass transition temperature can be determined by measuring a homopolymer of the (meth)acrylic monomer containing bio-derived carbon having a weight-average molecular weight of 100,000 to 1,000,000 in air using a differential scanning calorimeter (e.g., 220C manufactured by Seiko Instruments Inc.) at a temperature rise rate of 10°C / min. The glass transition temperature can be adjusted by the type of (meth)acrylic monomer. Examples of (meth)acrylic monomers containing bio-derived carbon that satisfy the above Tg include n-heptyl acrylate, n-octyl acrylate, and lauryl methacrylate.

[0023] The block derived from the (meth)acrylic monomer may contain a monomer other than the (meth)acrylic monomer, as long as the effect of the present invention is not lost.

[0024] The block copolymer preferably contains 1% by weight or more and 40% by weight or less of the hard block. By setting the content of the hard block within the above range, a foam substrate having excellent flexibility, impact resistance, and heat resistance can be formed. From the viewpoint of further improving flexibility, impact resistance, and heat resistance, the lower limit of the hard block content is more preferably 2% by weight, even more preferably 2.5% by weight, and particularly preferably 3% by weight, and the upper limit is more preferably 35% by weight, even more preferably 30% by weight, still more preferably 26% by weight, particularly preferably 20% by weight, especially preferably 17% by weight, and particularly preferably 8% by weight.

[0025] The weight average molecular weight of the block copolymer is preferably 50,000 to 800,000. When the weight-average molecular weight of the block copolymer is within the above range, flexibility, impact resistance, and heat resistance can be further improved. A more preferred lower limit of the weight-average molecular weight of the block copolymer is 75,000, and a more preferred upper limit is 600,000. The weight-average molecular weight can be measured, for example, by GPC using a Waters "2690 Separations Module" as a measuring instrument, a Showa Denko "GPC KF-806L" column, ethyl acetate as a solvent, a sample flow rate of 1 mL / min, and a column temperature of 40°C.

[0026] A method for obtaining the block copolymer includes a method in which raw material monomers for the hard block and the block derived from a (meth)acrylic monomer are respectively subjected to a radical reaction in the presence of a polymerization initiator to obtain a hard block and a block derived from a (meth)acrylic monomer, and then the two are reacted. Another method includes a method in which, after obtaining a hard block by the above method, raw material monomers for the block derived from a (meth)acrylic monomer are subsequently added and copolymerized. The radical reaction method, i.e., the polymerization method, can be any conventionally known method, such as solution polymerization (boiling point polymerization or constant temperature polymerization), emulsion polymerization, suspension polymerization, or bulk polymerization.

[0027] The foam substrate may contain additives such as antistatic agents, release agents, antioxidants, weathering agents, and crystal nucleating agents, and resin modifiers such as polyolefins, polyesters, polyamides, and elastomers.

[0028] The foam substrate has an apparent density of 0.3 g / cm 3 More than 0.95g / cm 3 It is preferable that: By setting the apparent density of the foam substrate within the above range, it is possible to obtain a pressure-sensitive adhesive tape that is more excellent in flexibility and impact resistance while maintaining strength. From the viewpoint of further improving the strength, flexibility and impact resistance of the pressure-sensitive adhesive tape, a more preferable lower limit of the foam substrate is 0.33 g / cm 3 , and a more preferable upper limit is 0.9 g / cm 3and a more preferable lower limit is 0.35 g / cm 3 , and a more preferable upper limit is 0.88 g / cm 3 is. The apparent density can be measured in accordance with JIS K 7222 using an electronic densimeter (for example, "ED120T" manufactured by Mirage).

[0029] The foam substrate preferably has a gel fraction of 90% or less. When the gel fraction of the foam substrate is within the above range, the impact resistance of the resulting pressure-sensitive adhesive tape can be further improved. From the viewpoint of further improving the impact resistance of the pressure-sensitive adhesive tape, the upper limit of the gel fraction is more preferably 85%, and even more preferably 80%. The lower limit of the gel fraction is not particularly limited, but is, for example, 10% or more, particularly 20% or more, and particularly 35% or more. The gel fraction can be adjusted by crosslinking the hard block with at least one of the blocks derived from the (meth)acrylic monomer. The gel fraction can be measured by the following method. 0.1 g of the foam substrate alone was removed from the resulting adhesive tape, immersed in 50 ml of ethyl acetate, and shaken in a shaker at 23°C and 120 rpm for 24 hours. After shaking, the ethyl acetate and the foam substrate that had absorbed the ethyl acetate and swollen were separated using a metal mesh (opening #200 mesh). The separated foam substrate was dried at 110°C for 1 hour. The weight of the foam substrate including the metal mesh after drying was measured, and the gel fraction of the foam substrate was calculated using the following formula. Gel fraction (wt%) = 100 × (W1 - W2) / W0 (W0: initial foam substrate weight, W1: foam substrate weight including metal mesh after drying, W2: initial weight of metal mesh)

[0030] The foam substrate preferably contains a crosslinking agent to form a crosslinked structure between the main chains of the resin constituting the foam substrate. Forming a crosslinked structure between the main chains of the resin constituting the foam substrate can disperse intermittently applied peel stress, thereby further improving the heat resistance and impact resistance of the pressure-sensitive adhesive tape. The crosslinking agent is not particularly limited and can be appropriately selected depending on the functional groups possessed by the resin constituting the foam substrate. Specific examples include isocyanate-based crosslinking agents, aziridine-based crosslinking agents, epoxy-based crosslinking agents, and metal chelate-type crosslinking agents. Among these, epoxy-based crosslinking agents and isocyanate-based crosslinking agents are preferred because they can crosslink resins containing alcoholic hydroxyl groups or carboxyl groups, which can further improve flexibility and impact resistance. The isocyanate-based crosslinking agent crosslinks between the alcoholic hydroxyl groups or carboxyl groups in the resin constituting the foam substrate and the isocyanate groups of the crosslinking agent. The epoxy-based crosslinking agent crosslinks between the carboxyl groups in the resin constituting the foam substrate and the epoxy groups of the crosslinking agent. The amount of the crosslinking agent added is preferably 0.01 to 10 parts by weight, more preferably 0.1 to 7 parts by weight, per 100 parts by weight of the resin that is the main component of the foam substrate.

[0031] The foam substrate preferably has bubbles with an average diameter of 80 μm or less. When the average cell diameter of the foam substrate is within the above range, the balance between strength, flexibility and impact resistance of the resulting pressure-sensitive adhesive tape can be further improved. The average cell diameter of the foam substrate is more preferably 60 μm or less, and even more preferably 55 μm or less. There is no particular lower limit to the average cell diameter of the foam substrate, but from the viewpoint of ensuring tape flexibility, it is preferably 20 μm or more, and more preferably 30 μm or more. The average cell diameter can be measured by the following method. First, the foam substrate was cut into 50 mm squares and immersed in liquid nitrogen for 1 minute. Then, a razor blade was used to cut the foam substrate along a plane perpendicular to its thickness. Next, a digital microscope (e.g., Keyence VHX-900) was used to take a magnified photograph of the cut surface at 200x magnification, and the longest cell diameter (cell diameter) of all cells present within a thickness x 2 mm area was measured. This procedure was repeated five times, and the average cell diameter was calculated by averaging all the obtained cell diameters.

[0032] The thickness of the foam substrate is not particularly limited, but a preferred lower limit is 40 μm and a preferred upper limit is 2900 μm. By setting the thickness of the foam substrate within the above range, the pressure-sensitive adhesive tape of the present invention can be suitably used for fixing portable electronic device components, in-vehicle electronic device components, etc. From the viewpoint of being more suitably used for fixing the above components, the more preferred lower limit of the thickness of the foam substrate is 60 μm, a more preferred upper limit is 1900 μm, an even more preferred lower limit is 80 μm, an even more preferred upper limit is 1400 μm, a particularly preferred lower limit is 100 μm, and a particularly preferred upper limit is 1000 μm.

[0033] The foam substrate may have a cellular structure, and the manufacturing method is not particularly limited. Examples of manufacturing methods include a method of manufacturing the foam substrate by the action of a foaming gas or a method of blending hollow spheres into a raw material matrix. Foams manufactured by the latter method are called syntactic foams, and are preferred for the foam substrate because they have superior impact resistance and heat resistance. Using a syntactic foam as the foam substrate results in a closed-cell foam with a uniform size distribution of the foamed bubbles, thereby making the density of the entire foam substrate more consistent and improving impact resistance. Furthermore, syntactic foams are less likely to irreversibly collapse under high temperatures and pressures than other foams, and therefore exhibit higher heat resistance. Syntactic foams include those having a foam structure composed of hollow inorganic particles and those having a foam structure composed of hollow organic particles. From the perspective of flexibility, syntactic foams having a foam structure composed of hollow organic particles are preferred.

[0034] Examples of the hollow organic fine particles include the Expancel DU series (manufactured by Nippon Phillite Co., Ltd.) and the Advancel EM series (manufactured by Sekisui Chemical Co., Ltd.) Among these, Expancel 461-20 (average cell diameter after foaming under optimal conditions: 20 μm), Expancel 461-40 (average cell diameter after foaming under optimal conditions: 40 μm), Expancel 043-80 (average cell diameter after foaming under optimal conditions: 80 μm), and Advancel EML101 (average cell diameter after foaming under optimal conditions: 50 μm) are preferred because the cell diameter after foaming can be easily designed to a more effective range.

[0035] When the foam substrate is made of a foam other than the syntactic foam, the foaming agent is not particularly limited, and any conventionally known foaming agent such as a thermal decomposition type foaming agent can be used.

[0036] The pressure-sensitive adhesive layer is not particularly limited, and examples thereof include an acrylic pressure-sensitive adhesive layer, a rubber-based pressure-sensitive adhesive layer, a urethane pressure-sensitive adhesive layer, a silicone-based pressure-sensitive adhesive layer, etc. Among these, an acrylic pressure-sensitive adhesive layer containing an acrylic copolymer is preferred because it has excellent heat resistance and can be adhered to a wide variety of adherends.

[0037] The acrylic copolymer constituting the acrylic pressure-sensitive adhesive layer is preferably obtained by copolymerizing a monomer mixture containing butyl acrylate and / or 2-ethylhexyl acrylate, from the viewpoint of improving initial tack and thereby improving ease of application at low temperatures. Among these, it is more preferable to obtain it by copolymerizing a monomer mixture containing butyl acrylate and 2-ethylhexyl acrylate. That is, a copolymer having structural units derived from butyl acrylate and / or structural units derived from 2-ethylhexyl acrylate is preferred, and a copolymer having structural units derived from butyl acrylate and structural units derived from 2-ethylhexyl acrylate is more preferred.

[0038] Furthermore, from the viewpoint of enabling the production of an adhesive tape with a lower environmental impact, the acrylic copolymer is preferably obtained by copolymerizing a mixture of (meth)acrylic monomers containing bio-derived carbon. Particularly preferred examples of the (meth)acrylic monomers containing bio-derived carbon include butyl acrylate, n-heptyl acrylate, 1-methylheptyl acrylate, n-octyl acrylate, and lauryl methacrylate.

[0039] The preferred lower limit of the content of the butyl acrylate in the total monomer mixture is 40% by weight, and the preferred upper limit is 80% by weight. That is, the preferred lower limit of the content of the structural units derived from the butyl acrylate in the acrylic copolymer is 40% by weight, and the preferred upper limit is 80% by weight. By setting the content of the butyl acrylate in the above range, it is possible to achieve both high adhesive strength and tackiness.

[0040] The preferred lower limit of the content of the 2-ethylhexyl acrylate in the total monomer mixture is 10% by weight, the preferred upper limit is 100% by weight, the more preferred lower limit is 30% by weight, the more preferred upper limit is 80% by weight, the even more preferred lower limit is 50% by weight, and the even more preferred upper limit is 60% by weight. That is, the content of the structural unit derived from the 2-ethylhexyl acrylate in the acrylic copolymer is preferably 10% by weight at the lower limit, 100% by weight at the upper limit, 30% by weight at the lower limit, 80% by weight at the upper limit, 50% by weight at the lower limit, and 60% by weight at the upper limit. By setting the content of the 2-ethylhexyl acrylate within the above range, high adhesive strength can be exhibited.

[0041] The preferred lower limit of the content of the bio-derived carbon-containing n-heptyl acrylate in the total monomer mixture is 25 wt %, and the preferred upper limit is 100 wt %. That is, the preferred lower limit of the content of the bio-derived carbon-containing structural unit derived from n-heptyl acrylate in the acrylic copolymer is 25 wt %, and the preferred upper limit is 100 wt %. The lower limit of the content of the structural units derived from n-heptyl acrylate is more preferably 48% by weight, even more preferably 50% by weight, even more preferably 60% by weight, even more preferably 70% by weight, and even more preferably 80% by weight. The upper limit of the content of the structural units derived from n-heptyl acrylate is not particularly limited and may be 100% by weight, but since it is preferable that the acrylic copolymer also contains structural units derived from monomers having crosslinkable functional groups, the upper limit is preferably 99% by weight, and more preferably 97% by weight.

[0042] The content of the (meth)acrylic monomer containing bio-derived carbon in the total monomer mixture is preferably 50% by weight at its lower limit, 100% by weight at its upper limit, 80% by weight at its lower limit, and 98% by weight at its upper limit. That is, the content of the structural units derived from the (meth)acrylic monomer containing bio-derived carbon in the acrylic copolymer is preferably 50% by weight at its lower limit, 100% by weight at its upper limit, 80% by weight at its lower limit, and 98% by weight at its upper limit. By setting the content of the (meth)acrylic monomer containing bio-derived carbon within the above range, it is possible to achieve both high adhesive strength and reduced environmental impact.

[0043] The monomer mixture may contain other copolymerizable polymerizable monomers other than butyl acrylate and 2-ethylhexyl acrylate, as needed. Examples of the other copolymerizable polymerizable monomers include (meth)acrylic acid alkyl esters having an alkyl group with 1 to 18 carbon atoms, functional monomers, and the like. Examples of the (meth)acrylic acid alkyl esters having an alkyl group having 1 to 18 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, tridecyl methacrylate, stearyl (meth)acrylate, etc. Examples of the functional monomers include hydroxyalkyl (meth)acrylate, glycerin dimethacrylate, glycidyl (meth)acrylate, 2-methacryloyloxyethyl isocyanate, (meth)acrylic acid, itaconic acid, maleic anhydride, crotonic acid, maleic acid, fumaric acid, etc.

[0044] To obtain the acrylic copolymer by copolymerizing the monomer mixture, the monomer mixture may be subjected to a radical reaction in the presence of a polymerization initiator. As a method for radically reacting the monomer mixture, i.e., a polymerization method, a conventionally known method may be used, such as solution polymerization (boiling point polymerization or constant temperature polymerization), emulsion polymerization, suspension polymerization, bulk polymerization, etc.

[0045] The weight-average molecular weight (Mw) of the acrylic copolymer is preferably 400,000 at its lower limit and 1,500,000 at its upper limit. By setting the weight-average molecular weight of the acrylic copolymer within the above range, high adhesive strength can be exhibited. From the viewpoint of further improving adhesive strength, the weight-average molecular weight is more preferably 500,000 at its lower limit and 1,400,000 at its upper limit. The weight average molecular weight (Mw) is the weight average molecular weight determined by GPC (Gel Permeation Chromatography) in terms of standard polystyrene.

[0046] The upper limit of the ratio (Mw / Mn) of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) of the acrylic copolymer is preferably 10.0. When Mw / Mn is 10.0 or less, the proportion of low-molecular-weight components is suppressed, and the pressure-sensitive adhesive layer is prevented from softening at high temperatures, resulting in a decrease in bulk strength and a decrease in adhesive strength. From the same viewpoint, the upper limit of Mw / Mn is more preferably 5.0, and even more preferably 3.0.

[0047] The pressure-sensitive adhesive layer may contain a tackifying resin. Examples of the tackifying resin include rosin ester resins, hydrogenated rosin resins, terpene resins, terpene phenol resins, coumarone-indene resins, alicyclic saturated hydrocarbon resins, C5 petroleum resins, C9 petroleum resins, C5-C9 copolymer petroleum resins, etc. These tackifying resins may be used alone or in combination of two or more.

[0048] The content of the tackifier resin is not particularly limited, but a preferred lower limit is 10 parts by weight and a preferred upper limit is 60 parts by weight per 100 parts by weight of the resin (e.g., acrylic copolymer) that is the main component of the pressure-sensitive adhesive layer. When the content of the tackifier resin is 10 parts by weight or more, a decrease in the adhesive strength of the pressure-sensitive adhesive layer can be suppressed. When the content of the tackifier resin is 60 parts by weight or less, a decrease in adhesive strength or tackiness due to hardening of the pressure-sensitive adhesive layer can be suppressed.

[0049] The pressure-sensitive adhesive layer preferably contains a crosslinking agent, which forms a crosslinked structure between the main chains of the resins (e.g., the acrylic copolymer, the tackifier resin, etc.) that constitute the pressure-sensitive adhesive layer. The crosslinking agent is not particularly limited, and examples include isocyanate-based crosslinking agents, aziridine-based crosslinking agents, epoxy-based crosslinking agents, and metal chelate-type crosslinking agents. Of these, isocyanate-based crosslinking agents are preferred. Adding an isocyanate-based crosslinking agent to the pressure-sensitive adhesive layer causes the isocyanate groups of the isocyanate-based crosslinking agent to react with alcoholic hydroxyl groups in the resins (e.g., the acrylic copolymer, the tackifier resin, etc.) that constitute the pressure-sensitive adhesive layer, thereby crosslinking the pressure-sensitive adhesive layer. Formation of a crosslinked structure between the main chains of the resins that constitute the pressure-sensitive adhesive layer allows the pressure-sensitive adhesive layer to disperse intermittently applied peel stress, further improving the adhesive strength of the pressure-sensitive adhesive tape. The amount of the crosslinking agent added is preferably 0.01 to 10 parts by weight, more preferably 0.1 to 7 parts by weight, per 100 parts by weight of the resin (for example, the acrylic copolymer) that is the main component of the pressure-sensitive adhesive layer.

[0050] The pressure-sensitive adhesive layer may contain a silane coupling agent to improve adhesive strength. The silane coupling agent is not particularly limited, and examples thereof include epoxy silanes, acrylic silanes, methacrylic silanes, amino silanes, and isocyanate silanes.

[0051] The pressure-sensitive adhesive layer may contain a colorant to impart light-blocking properties. The colorant is not particularly limited, and examples thereof include carbon black, aniline black, titanium oxide, etc. Among these, carbon black is preferred because it is relatively inexpensive and chemically stable. The pressure-sensitive adhesive layer may contain conventionally known fine particles and additives, such as inorganic fine particles, conductive fine particles, antioxidants, foaming agents, organic fillers, and inorganic fillers, as needed.

[0052] The thickness of the pressure-sensitive adhesive layer is not particularly limited, but a preferred lower limit is 0.01 mm and a preferred upper limit is 0.1 mm. By setting the thickness of the pressure-sensitive adhesive layer within the above range, the pressure-sensitive adhesive tape of the present invention can be suitably used for fixing portable electronic device components, in-vehicle electronic device components, etc. From the viewpoint of being more suitably used for fixing the above components, a more preferred lower limit of the thickness of the pressure-sensitive adhesive layer is 0.015 mm and a more preferred upper limit is 0.09 mm.

[0053] The pressure-sensitive adhesive tape of the present invention may have a resin layer on at least one surface of the foam substrate. The presence of the resin layer improves the strength of the resulting pressure-sensitive adhesive tape, thereby further increasing impact resistance, and in particular improving durability (tumble resistance) when repeatedly subjected to impacts. The resin layer may be formed on one or both sides of the foam substrate, but is preferably formed on one side of the foam substrate.

[0054] The resin constituting the resin layer preferably has heat resistance. Examples of the heat-resistant resin constituting the resin layer include polyester resins such as polyethylene terephthalate, acrylic resins, silicone resins, phenolic resins, polyimides, polycarbonates, etc. Among these, acrylic resins and polyester resins are preferred, and polyethylene terephthalate is more preferred, as they provide a pressure-sensitive adhesive tape with excellent flexibility.

[0055] The resin layer may be colored. By coloring the resin layer, it is possible to impart light-blocking properties to the pressure-sensitive adhesive tape. The method for coloring the resin layer is not particularly limited, and examples thereof include a method of kneading particles of carbon black, titanium oxide, or the like, or fine bubbles into the resin constituting the resin layer, and a method of applying ink to the surface of the resin layer.

[0056] The resin layer may contain conventionally known fine particles and additives, such as inorganic fine particles, conductive fine particles, plasticizers, tackifiers, ultraviolet absorbers, antioxidants, foaming agents, organic fillers, and inorganic fillers, as needed.

[0057] The thickness of the resin layer is not particularly limited, but a preferred lower limit is 5 μm and a preferred upper limit is 100 μm. By setting the thickness of the resin layer within the above range, it is possible to achieve both handleability and impact resistance of the pressure-sensitive adhesive tape. From the viewpoint of further achieving both handleability and impact resistance, a more preferred lower limit of the thickness of the resin layer is 10 μm and a more preferred upper limit is 70 μm.

[0058] The pressure-sensitive adhesive tape of the present invention may have layers other than the foam substrate and the pressure-sensitive adhesive layer, if necessary.

[0059] In the pressure-sensitive adhesive tape of the present invention, the ratio of the thickness of the pressure-sensitive adhesive layer to the thickness of the foam substrate (pressure-sensitive adhesive layer thickness / foam substrate thickness) is preferably 0.1 or more and 2 or less. When the thickness ratio of the pressure-sensitive adhesive layer to the foam substrate is within the above range, the strength of the entire pressure-sensitive adhesive tape obtained is improved, and therefore impact resistance can be further enhanced. The ratio of the thickness of the pressure-sensitive adhesive layer to the thickness of the foam substrate is more preferably 0.15 or more and more preferably 1.2 or less. The thickness of the pressure-sensitive adhesive layer refers to the sum of the thicknesses of the pressure-sensitive adhesive layers on both sides.

[0060] The thickness of the pressure-sensitive adhesive tape of the present invention is not particularly limited, but the lower limit is preferably 0.04 mm, more preferably 0.05 mm, and the upper limit is preferably 2 mm, more preferably 1.5 mm. By setting the thickness of the pressure-sensitive adhesive tape of the present invention within the above range, the pressure-sensitive adhesive tape can be made to have excellent handleability.

[0061] The adhesive tape of the present invention preferably has a bio-derived carbon content of 10% by weight or more. A bio-derived carbon content of 10% by weight or more is an indicator of a "bio-based product." By setting the content of bio-derived carbon in the pressure-sensitive adhesive tape of the present invention to 10% by weight or more, it is possible to obtain a pressure-sensitive adhesive tape with a lower environmental impact from the viewpoints of saving petroleum resources and reducing carbon dioxide emissions. A more preferred lower limit of the content of bio-derived carbon is 20% by weight or more, an even more preferred lower limit is 40% by weight, an even more preferred lower limit is 50% by weight, and an even more preferred lower limit is 60% by weight. There is no particular limitation on the upper limit of the content of bio-derived carbon, and it may be 100% by weight. In particular, it is more preferable that the content of bio-derived carbon in the foam substrate is 50% by weight or more, and it is preferable that the content of bio-derived carbon in the block copolymer is 40% by weight or more, and even more preferably 50% by weight or more.

[0062] The method for producing the pressure-sensitive adhesive tape of the present invention is not particularly limited, and examples thereof include the following methods. First, a pressure-sensitive adhesive solution is applied to a release film and dried to form a pressure-sensitive adhesive layer, and a second pressure-sensitive adhesive layer is formed in the same manner. Next, an unfoamed substrate is produced by the above method, and the resin layer is laminated on the unfoamed substrate to form a laminate. Thereafter, the pressure-sensitive adhesive layers obtained are bonded to both sides of the obtained laminate, and the unfoamed substrate is foamed by heating, thereby producing a pressure-sensitive adhesive tape.

[0063] The shape of the pressure-sensitive adhesive tape of the present invention is not particularly limited, but examples thereof include a rectangular, frame-like, circular, oval, and doughnut-like shape.

[0064] The pressure-sensitive adhesive tape of the present invention can exhibit excellent flexibility and impact resistance by using the above-mentioned block copolymer as a foam substrate. Meanwhile, the inventors have furthered their research and found that when a foam substrate contains a copolymer including a structure derived from the above-mentioned vinyl aromatic compound monomer and a structure derived from the above-mentioned (meth)acrylic monomer, even a random copolymer can exhibit excellent flexibility, impact resistance, and heat resistance. This is thought to be due to the fact that interactions similar to those of the above-mentioned phase-separated structure are at work on an extremely small scale, such as the nano or molecular level. In this specification, the structure derived from the (meth)acrylic monomer refers to the structure shown in the following general formulas (5) and (6).

[0065] [ka] where R 3 represents a side chain. Side chain R 3 Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a 2-ethylhexyl group, a nonyl group, a decyl group, a dodecyl group, a lauryl group, and an isostearyl group.

[0066] The present invention also provides an adhesive tape having such a foam substrate and at least one adhesive layer, wherein the foam substrate contains a copolymer, the copolymer having a structure derived from a vinyl aromatic compound monomer and a structure derived from a (meth)acrylic monomer, and the adhesive tape contains bio-derived carbon (hereinafter referred to as an adhesive tape containing a copolymer).

[0067] The copolymer is not particularly limited, and may be a random copolymer or a graft polymer.

[0068] The vinyl aromatic compound monomer and the (meth)acrylic monomer may be the same as those used in the block copolymer.

[0069] The copolymer preferably contains 1% by weight or more of the structure derived from the vinyl aromatic compound monomer, more preferably 2% by weight or more, and even more preferably 5% by weight or more, and preferably 30% by weight or less, more preferably 19% by weight or less, even more preferably 15% by weight or less, and even more preferably 10% by weight or less.

[0070] The copolymer preferably contains 70% by weight or more, more preferably 81% by weight or more, of the structure derived from the (meth)acrylic monomer, and preferably 99% by weight or less, more preferably 98% by weight or less.

[0071] The copolymer preferably has a structure derived from a monomer having a crosslinkable functional group. When the copolymer has a crosslinkable functional group, the rubber elasticity of the copolymer is increased by crosslinking or interactions between the functional groups, thereby further improving flexibility and impact resistance. The crosslinkable functional group may be crosslinked or not, and even if it remains an uncrosslinked structure, the cohesive force is improved by interactions between the functional groups, improving flexibility and impact resistance, but crosslinking is more preferable. In this specification, the structure derived from a monomer having a crosslinkable functional group refers to the structure shown in the following general formulas (3) and (4).

[0072] [ka] where R 2 represents a substituent containing at least one functional group. Examples of the functional group include a carboxyl group, a hydroxyl group, an epoxy group, a double bond, a triple bond, an amino group, an amide group, and a nitrile group. 2 may contain, as its constituent elements, an alkyl group, an ether group, a carbonyl group, an ester group, a carbonate group, an amide group, a urethane group, or the like.

[0073] The monomer having a crosslinkable functional group is not particularly limited, and examples thereof include carboxyl group-containing monomers, hydroxyl group-containing monomers, epoxy group-containing monomers, double bond-containing monomers, triple bond-containing monomers, amino group-containing monomers, amide group-containing monomers, and nitrile group-containing monomers. Among these, at least one selected from the group consisting of hydroxyl group-containing monomers, carboxyl group-containing monomers, epoxy group-containing monomers, amide group-containing monomers, double bond-containing monomers, and triple bond-containing monomers is preferred, as it provides improved flexibility and impact resistance. Examples of the hydroxyl group-containing monomer include 4-hydroxybutyl (meth)acrylate and 2-hydroxyethyl (meth)acrylate. Examples of the carboxyl group-containing monomer include (meth)acrylic acid. Examples of the epoxy group-containing monomer include glycidyl (meth)acrylate. Examples of the amide group-containing monomer include (meth)acrylamide. Examples of the double bond-containing monomer include allyl (meth)acrylate and hexanediol di(meth)acrylate. Examples of the triple bond-containing monomer include propargyl (meth)acrylate. Among these, carboxyl group-containing monomers are preferred, (meth)acrylic acid-based monomers are more preferred, and acrylic acid is even more preferred, as they can impart superior flexibility and impact resistance to the adhesive tape.

[0074] The copolymer preferably contains 0.1% by weight or more and 30% by weight or less of the structure derived from the monomer having the crosslinkable functional group. When the content of the structure derived from the monomer having a crosslinkable functional group in the copolymer is within the above range, flexibility and impact resistance can be further improved. The lower limit of the content of the structure derived from the monomer having a crosslinkable functional group is more preferably 0.5 wt %, even more preferably 1 wt %, and more preferably 20 wt %, even more preferably 10 wt %.

[0075] The copolymer can be produced, for example, by subjecting a solution containing a vinyl aromatic compound monomer, a (meth)acrylic monomer, and optionally a monomer having a crosslinkable functional group and other monomers to a radical reaction in the presence of a polymerization initiator. The radical reaction can be carried out by a conventionally known method, such as solution polymerization (boiling point polymerization or constant temperature polymerization), emulsion polymerization, suspension polymerization, or bulk polymerization.

[0076] The adhesive tape containing the copolymer of the present invention preferably has a bio-derived carbon content of 10% by weight or more. A bio-derived carbon content of 10% by weight or more is an indicator of a "bio-based product." By setting the content of bio-derived carbon in the pressure-sensitive adhesive tape containing the copolymer of the present invention to 10% by weight or more, it is possible to produce a pressure-sensitive adhesive tape with a lower environmental impact from the viewpoints of saving petroleum resources and reducing carbon dioxide emissions. A more preferred lower limit for the content of bio-derived carbon is 20% by weight or more, an even more preferred lower limit is 40% by weight, an even more preferred lower limit is 50% by weight, and an even more preferred lower limit is 60% by weight. There is no particular limitation on the upper limit of the content of bio-derived carbon, and it may be 100% by weight. In particular, it is more preferable that the content of bio-derived carbon in the foam base material is 50% by weight or more, and it is even more preferable that the content of bio-derived carbon in the copolymer is 50% by weight or more.

[0077] The pressure-sensitive adhesive tape containing the copolymer of the present invention can use the same foam substrate materials other than the copolymer, their contents, apparent density, gel fraction, average cell diameter, thickness, and production method as those for the pressure-sensitive adhesive tape using the above-mentioned block copolymer.

[0078] In the pressure-sensitive adhesive tape containing the copolymer of the present invention, the pressure-sensitive adhesive layer can be the same as the pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape using the above-mentioned block copolymer.

[0079] The pressure-sensitive adhesive tape containing the copolymer of the present invention can be similar to the pressure-sensitive adhesive tape using the block copolymer described above, except for the foam substrate and the pressure-sensitive adhesive layer. [Effects of the Invention]

[0080] According to the present invention, it is possible to provide a pressure-sensitive adhesive tape that has excellent flexibility and impact resistance, and also has a low environmental impact. [Brief explanation of the drawings]

[0081] [Figure 1] Fig. 1(a) is a front view showing the state of the adhesive tape holding power test, and Fig. 1(b) is a side view showing the state of the adhesive tape holding power test. DETAILED DESCRIPTION OF THE INVENTION

[0082] The following examples will explain the present invention in more detail, but the present invention is not limited to these examples.

[0083] Example 1 (1) Manufacturing of unfoamed substrate 0.902 g of 1,6-hexanedithiol, 1.83 g of carbon disulfide, and 11 mL of dimethylformamide were added to a two-neck flask and stirred at 25°C. 2.49 g of triethylamine was added dropwise over 15 minutes and the mixture was stirred at 25°C for 3 hours. 2.75 g of methyl-α-bromophenylacetate was then added dropwise over 15 minutes and stirred at 25°C for 4 hours. The reaction mixture was then extracted with 100 mL of extraction solvent (n-hexane:ethyl acetate = 50:50) and 50 mL of water. The organic layers obtained from the first and second extractions were combined and washed sequentially with 50 mL of 1 M hydrochloric acid, 50 mL of water, and 50 mL of saturated saline. The washed organic layer was dried over sodium sulfate, filtered, and the filtrate was concentrated using an evaporator to remove the organic solvent. The resulting concentrate was purified by silica gel column chromatography to obtain the RAFT agent.

[0084] 87 parts by weight of styrene (St), 12 parts by weight of acrylic acid (AAc), 1 part by weight of hydroxyethyl acrylate (HEA), 1.9 parts by weight of a RAFT agent, and 0.2 parts by weight of 2,2'-azobis(2-methylbutyronitrile) (ABN-E) were placed in a two-neck flask, and the flask was heated to 85°C while being purged with nitrogen gas. The mixture was then stirred at 85°C for 6 hours to carry out a polymerization reaction (first-stage reaction). After the reaction was completed, 4,000 parts by weight of n-hexane was added to the flask and stirred to precipitate the reaction product. The unreacted monomers (St, AA, HEA) and RAFT agent were then filtered off, and the reaction product was dried under reduced pressure at 70°C to obtain a copolymer (hard block).

[0085] A mixture containing 50 parts by weight of butyl acrylate (BA, non-biologically derived), 50 parts by weight of n-heptyl acrylate (nHPA, biologically derived), 0.058 parts by weight of ABN-E, and 50 parts by weight of ethyl acetate was placed in a two-neck flask, and the temperature was raised to 85°C while the atmosphere in the flask was replaced with nitrogen gas. The mixture was then stirred at 85°C for 6 hours to carry out a polymerization reaction (second-stage reaction), yielding a reaction solution containing a block copolymer formed from a hard block and a block derived from a (meth)acrylic monomer (soft block). The blending amounts of the mixture (block derived from a (meth)acrylic monomer and hard block) were such that the hard block content in the resulting block copolymer was 17% by weight. A portion of the reaction mixture was collected, 4,000 parts by weight of n-hexane was added, and the mixture was stirred to precipitate the reaction product. The unreacted monomers (BA, nHPA) and solvent were then filtered, and the reaction product was dried under reduced pressure at 70°C to isolate the block copolymer. The weight-average molecular weight of the resulting block copolymer was measured by GPC, which was found to be 250,000. The weight-average molecular weight was measured using a Waters 2690 Separations Module, a Showa Denko GPC KF-806L column, ethyl acetate as the solvent, at a sample flow rate of 1 mL / min and a column temperature of 40°C.

[0086] The resulting block copolymer was dissolved in ethyl acetate to a solids content of 35%. To 100 parts by weight of the block copolymer, 0.30 parts by weight of Expancel 461-40 (manufactured by Nippon Phillite Co., Ltd., referred to as DU40 in the table) as a blowing agent and 0.2 parts by weight of Tetrad C (manufactured by Mitsubishi Gas Chemical Company, Inc.) as a crosslinking agent were added and further stirred thoroughly to obtain a substrate solution. The resulting substrate solution was applied to the release-treated surface of a 50 μm polyethylene terephthalate (PET) film with a release treatment on one side and dried at 90 °C for 7 minutes to obtain an unfoamed substrate. The thickness of the unfoamed substrate was adjusted to 100 μm when the unfoamed substrate was heated at 130 °C for 1 minute.

[0087] (2) Preparation of adhesive solution A reactor equipped with a thermometer, stirrer, and condenser was charged with 52 parts by weight of ethyl acetate. After purging with nitrogen, the reactor was heated to begin reflux. Thirty minutes after the ethyl acetate boiled, 0.08 parts by weight of azobisisobutyronitrile was added as a polymerization initiator. A monomer mixture consisting of 70 parts by weight of butyl acrylate, 27 parts by weight of 2-ethylhexyl acrylate, 3 parts by weight of acrylic acid, and 0.2 parts by weight of 2-hydroxyethyl acrylate was added dropwise evenly and gradually over 1 hour and 30 minutes, allowing the reaction to proceed. Thirty minutes after the addition was complete, 0.1 parts by weight of azobisisobutyronitrile was added, and the polymerization reaction continued for an additional 5 hours. The reactor was then cooled while being diluted with ethyl acetate, yielding an acrylic random copolymer solution with a solids content of 40% by weight. The weight-average molecular weight of the obtained acrylic random copolymer was measured by GPC and found to be 710,000. The ratio (Mw / Mn) of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) was 5.5. The weight-average molecular weight and number-average molecular weight were measured using a Waters "2690 Separations Module" as the measuring instrument, a Showa Denko "GPC KF-806L" column, and ethyl acetate as the solvent under the conditions of a sample flow rate of 1 mL / min and a column temperature of 40°C. To 100 parts by weight of the solid content of the obtained acrylic random copolymer, 15 parts by weight of polymerized rosin ester with a softening point of 150° C., 10 parts by weight of terpene phenol with a softening point of 145° C., and 10 parts by weight of rosin ester with a softening point of 70° C. were added. Furthermore, 30 parts by weight of ethyl acetate (manufactured by Fuji Chemicals Co., Ltd.) and 3.0 parts by weight of an isocyanate-based crosslinking agent (Coronate L45, manufactured by Tosoh Corporation) were added and stirred to obtain a pressure-sensitive adhesive solution.

[0088] (3) Manufacture of adhesive tapes The resulting adhesive solution was applied to the release-treated surface of a 50 μm polyethylene terephthalate (PET) film with one side treated with a release agent using a doctor knife to a dry film thickness of 50 μm. The coating solution was then dried by heating at 110 ° C for 5 minutes to obtain an adhesive layer. Next, another adhesive layer was produced using the same procedure, yielding two adhesive layers. The release film was then peeled off from the unfoamed substrate obtained above, and the two adhesive layers obtained were bonded to both sides of the unfoamed substrate. The resulting adhesive layer was then left to stand in a 40 ° C environment for 48 hours. After 48 hours, the substrate was removed from the 40 ° C environment and heated at 130 ° C for 1 minute to foam the substrate, yielding an adhesive tape.

[0089] (4) Measuring tape density The density of the obtained adhesive tape was measured using an electronic densimeter (manufactured by Mirage, ED120T).

[0090] (5) Measurement of apparent density of foam substrate The density of the obtained foam base material was measured in accordance with JIS K 7222 using an electronic densimeter (manufactured by Mirage, ED120T).

[0091] (6) Measurement of gel fraction of foam substrate 0.1 g of the foam substrate alone was removed from the obtained adhesive tape, immersed in 50 ml of ethyl acetate, and shaken in a shaker at 23°C and 120 rpm for 24 hours. After shaking, the ethyl acetate and the foam substrate that had absorbed the ethyl acetate and swollen were separated using a metal mesh (opening #200 mesh). The separated foam substrate was dried at 110°C for 1 hour. The weight of the foam substrate including the metal mesh after drying was measured, and the gel fraction of the foam substrate was calculated using the following formula. Gel fraction (wt%) = 100 × (W1 - W2) / W0 (W0: initial foam substrate weight, W1: foam substrate weight including metal mesh after drying, W2: initial weight of metal mesh)

[0092] (7) Measurement of the biocarbon content of adhesive tape and its substrate The obtained adhesive tape and foam substrate were analyzed using a radioactive isotope of carbon ( 14 The biocarbon content of the adhesive tape and substrate was measured by measuring the concentration of α-tocopherol (C).

[0093] (Examples 2 to 15, Comparative Examples 1 to 3) Pressure-sensitive adhesive tapes were obtained in the same manner as in Example 1, except that the composition, apparent density, thickness, and amount of foaming agent of the foam substrate were as shown in Table 1. Comparative Examples 1 and 3 did not contain a foaming agent, and therefore remained unfoamed even after heating at 130°C for 1 minute. The obtained pressure-sensitive adhesive tapes and foam substrates (unfoamed substrates in Comparative Examples 1 and 3) were subjected to the same measurements as in Example 1. In Comparative Example 2, SIS (styrene-isoprene block copolymer, manufactured by Zeon Corporation, Quintac 3421) was used as the block copolymer constituting the foam substrate. The raw materials in the table are as follows. nOA: n-octyl acrylate (biologically derived) 1-MHA: 1-methylheptyl acrylate (biologically derived) LA: Lauryl acrylate (biologically derived) LMA: Lauryl methacrylate (biologically derived) IBOA: Isobornyl acrylate (biologically derived) Isoprene: Non-(meth)acrylic monomer (non-biologically derived)

[0094] (Examples 16 and 17) (1) Manufacturing of unfoamed substrate An unfoamed substrate was obtained in the same manner as in Example 1, except that the composition was as shown in Table 1.

[0095] (2) Preparation of adhesive solution Ethyl acetate was added to the reaction vessel as the polymerization solvent, and nitrogen was bubbled through. The reaction vessel was then heated while nitrogen was flowing in to initiate reflux. Next, a polymerization initiator solution prepared by diluting 0.1 parts by weight of azobisisobutyronitrile 10 times with ethyl acetate was added to the reaction vessel, and 96.9 parts by weight of n-heptyl acrylate (biologically derived), 2.9 parts by weight of acrylic acid, and 0.1 parts by weight of 2-hydroxyethyl acrylate were added dropwise over two hours. After the dropwise addition, a polymerization initiator solution prepared by diluting 0.1 parts by weight of azobisisobutyronitrile 10 times with ethyl acetate was added again to the reaction vessel, and the polymerization reaction was carried out for four hours to obtain an acrylic random copolymer-containing solution. The weight-average molecular weight of the obtained acrylic random copolymer was measured by GPC and found to be 1,000,000. The ratio (Mw / Mn) of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) was 5.5. The weight-average molecular weight and number-average molecular weight were measured using a Waters "2690 Separations Module" as the measuring instrument, a Showa Denko "GPC KF-806L" column, and ethyl acetate as the solvent under the conditions of a sample flow rate of 1 mL / min and a column temperature of 40°C. To 100 parts by weight of the solid content of the obtained acrylic random copolymer, 15 parts by weight of polymerized rosin ester with a softening point of 150° C., 10 parts by weight of terpene phenol with a softening point of 145° C., and 10 parts by weight of rosin ester with a softening point of 100° C. were added. Furthermore, 30 parts by weight of ethyl acetate (manufactured by Fuji Chemicals Co., Ltd.) and 0.2 parts by weight of an isocyanate-based crosslinking agent (Coronate L45, manufactured by Tosoh Corporation) were added and stirred to obtain a pressure-sensitive adhesive solution.

[0096] (3) Manufacture of adhesive tapes Except for using the obtained unfoamed base material and adhesive solution, a pressure-sensitive adhesive tape was obtained in the same manner as in Example 1. The obtained pressure-sensitive adhesive tape was subjected to various measurements in the same manner as in Example 1.

[0097] Example 18 (1) Manufacturing of unfoamed substrate A reactor equipped with a thermometer, stirrer, and condenser was charged with 52 parts by weight of ethyl acetate. After purging with nitrogen, the reactor was heated to initiate reflux. Thirty minutes after the ethyl acetate boiled, 0.08 parts by weight of azobisisobutyronitrile was added as a polymerization initiator. A monomer mixture consisting of 90 parts by weight of n-heptyl acrylate, 9 parts by weight of styrene (St, non-biologically derived), and 1 part by weight of acrylic acid (AAc, non-biologically derived) was added dropwise evenly and gradually over 1 hour and 30 minutes, allowing the reaction to proceed. Thirty minutes after the addition was complete, 0.1 parts by weight of azobisisobutyronitrile was added, and the polymerization reaction continued for an additional 5 hours. The reactor was then cooled while being diluted with ethyl acetate, yielding a random copolymer solution with a solids content of 40% by weight. The weight-average molecular weight of the resulting random copolymer was measured by GPC and found to be 350,000. The weight-average molecular weight was measured using a Waters 2690 Separations Module as the measuring instrument, a Showa Denko GPC KF-806L column, ethyl acetate as the solvent, at a sample flow rate of 1 mL / min and a column temperature of 40°C.

[0098] The resulting random copolymer was dissolved in ethyl acetate to a solids content of 35%, and 0.3 parts by weight of Expancel 461-40 as a foaming agent and 0.2 parts by weight of Tetrad C as a crosslinking agent were added to 100 parts by weight of the random copolymer, followed by thorough stirring to obtain a substrate solution. The resulting substrate solution was applied to the release-treated surface of a 50 μm polyethylene terephthalate (PET) film with a release treatment on one side, and dried at 90 ° C for 7 minutes to obtain an unfoamed substrate made of a graft copolymer. The thickness of the unfoamed substrate was adjusted to 100 μm when the unfoamed substrate was heated at 130 ° C for 1 minute.

[0099] (2) Manufacturing of adhesive tapes Except for using the unfoamed substrate made of the obtained random copolymer, a pressure-sensitive adhesive tape was obtained in the same manner as in Example 1. The obtained pressure-sensitive adhesive tape was subjected to the various measurements in the same manner as in Example 1.

[0100] (Examples 19 to 21, Comparative Example 4) An adhesive tape was obtained in the same manner as in Example 18, except that the foam substrate had a composition as shown in Table 2. The obtained adhesive tape was subjected to the various measurements in the same manner as in Example 1.

[0101] <Evaluation> The pressure-sensitive adhesive tapes obtained in the examples and comparative examples were evaluated as follows, and the results are shown in Tables 1 and 2.

[0102] (Impact resistance evaluation) The resulting adhesive tape was punched into a 45mm x 60mm, 1mm wide square shape. One side of the punched adhesive tape was attached to the center of a 2mm thick, 80mm x 115mm square stainless steel plate with a 40mm x 40mm hole in the center. A 50mm x 70mm, 4mm thick tempered glass plate was then attached to the other side of the adhesive tape, pressed with a 5kg weight for 10 seconds, and allowed to stand at 23°C for 24 hours to obtain a laminate for testing. The resulting laminate was fixed to a stainless steel frame (inner diameter 60mm x 90mm) with the tempered glass plate facing downward. A 150g iron ball was then dropped onto the center of the tempered glass plate. The height from which the iron ball was dropped was gradually increased, and the height from which the iron ball fell when the tempered glass plate peeled off from the stainless steel plate was measured. Impact resistance was evaluated as follows: if the height of the iron ball when the tempered glass plate peeled off from the stainless steel plate was 50 cm or more, it was marked "◎"; if it was 40 cm or more but less than 50 cm, it was marked "○"; if it was less than 40 cm, it was marked "×".

[0103] (Evaluation of holding power) Figure 1 shows a schematic diagram illustrating a holding power test for adhesive tape. First, one side (front side) of a 25 mm x 25 mm adhesive tape test piece 1 was attached to a SUS plate 2, and a 2 kg rubber roller was rolled back and forth from the other side (back side) of the test piece 1 at a speed of 300 mm / min. Next, an aluminum plate 3 was attached to the back side of the test piece 1, and a 0.5 kg weight was applied from the aluminum plate 3 side for 10 seconds to compress the test piece. The test piece was then left in an environment of 23°C and 50% relative humidity for 24 hours to prepare a holding power test sample. This holding power test sample was then heated to 100°C, and a 0.5 kg or 1.0 kg weight 4 was attached to one end of the aluminum plate 3 so that a horizontal load was applied to the test piece 1 and the aluminum plate 3. The displacement length of the weight after 1 hour was measured. The displacement length after 2 hours with the 1.0 kg weight 4 attached was also measured. The holding power of the measurement results was evaluated as follows: when the slippage length was 0 (no slippage), it was marked as "◎", when the slippage length was greater than 0 but less than 1 mm, it was marked as "○", and when the slippage length was 1 mm or more or the adhesive tape peeled off and fell off, it was marked as "×".

[0104] (Compression strength evaluation) The 25% compressive strength of the obtained double-sided adhesive tape was calculated in accordance with JIS K-6767. A value of 50 kPa or less was evaluated as "◎", a value of more than 50 kPa and less than 80 kPa was evaluated as "○", and a value of more than 80 kPa was evaluated as "×".

[0105] [Table 1]

[0106] [Table 2] [Industrial Applicability]

[0107] According to the present invention, it is possible to provide a pressure-sensitive adhesive tape that has excellent flexibility and impact resistance, and also has a low environmental impact. [Explanation of symbols]

[0108] 1 adhesive tape test piece measuring 25mm x 25mm 2 SUS board 3 Aluminum Plate 4 weights (0.5kg or 1.0kg)

Claims

1. A pressure-sensitive adhesive tape having a foam substrate and at least one pressure-sensitive adhesive layer, the foam substrate contains a block copolymer having a block derived from a (meth)acrylic monomer, The block copolymer has at least one hard block, the hard block has a structure derived from a vinyl aromatic compound monomer, The adhesive tape contains bio-derived carbon.

2. 2. The pressure-sensitive adhesive tape according to claim 1, wherein the block copolymer contains the hard block in an amount of 1% by weight to 40% by weight.

3. The pressure-sensitive adhesive tape according to claim 1 or 2, wherein the hard block has a structure derived from a monomer having a crosslinkable functional group.

4. A pressure-sensitive adhesive tape having a foam substrate and at least one pressure-sensitive adhesive layer, The foam substrate contains a copolymer, The copolymer has a structure derived from a vinyl aromatic compound monomer and a structure derived from a (meth)acrylic monomer, The adhesive tape contains bio-derived carbon, The (meth)acrylic monomer contains a (meth)acrylic monomer containing bio-derived carbon, An adhesive tape, wherein the (meth)acrylic monomer containing bio-derived carbon has an alkyl group having 7 to 12 carbon atoms.

5. An adhesive tape having a foam substrate and at least one adhesive layer, The foam substrate contains a copolymer, The copolymer has a structure derived from a vinyl aromatic compound monomer and a structure derived from a (meth)acrylic monomer, The adhesive tape contains bio-derived carbon, The (meth)acrylic monomer contains a (meth)acrylic monomer containing bio-derived carbon, An adhesive tape, wherein the (meth)acrylic monomer containing bio-derived carbon is n-heptyl acrylate or n-octyl acrylate.

6. The pressure-sensitive adhesive tape according to claim 4 , wherein the copolymer has a structure derived from a monomer having a crosslinkable functional group.

7. The pressure-sensitive adhesive tape according to any one of claims 4 to 6, wherein the content of the structure derived from the (meth)acrylic monomer in the copolymer is 70% by weight or more and 98% by weight or less.

8. The pressure-sensitive adhesive tape according to any one of claims 1 to 3, wherein the foam substrate contains bio-derived carbon.

9. The pressure-sensitive adhesive tape according to any one of claims 4 to 7, wherein the (meth)acrylic monomer containing biocarbon is a (meth)acrylic monomer having a homopolymer glass transition temperature Tg of -40°C or lower.

10. The adhesive tape according to any one of claims 1 to 9, wherein the adhesive tape has a bio-derived carbon content of 50% by weight or more.

11. The pressure-sensitive adhesive tape according to any one of claims 1 to 10, wherein the foam substrate has a bio-derived carbon content of 50% by weight or more.

12. The pressure-sensitive adhesive tape according to any one of claims 1 to 11, wherein the block copolymer or the copolymer has a bio-derived carbon content of 50% by weight or more.

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