Adhesive, method for producing adhesive, and adhesive sheet

Abstract

Provided is a polyester-based adhesive which can contribute to the reduction of environmental burden and which has excellent coatability. A polyester adhesive according to one embodiment of the present invention contains a polyester resin and a surfactant, the weight-average molecular weight of the polyester resin being 0.2 * 104 to 2.0 * 104, and the viscosity of the polyester adhesive being 1 Pa.s to 50 Pa.s. The polyester-based adhesive can substantially contain no organic solvent.

Description

Technical Field

[0001] The present invention relates to an adhesive, a method for producing the adhesive, and an adhesive sheet. Background Art

[0002] Adhesives have been used in various technical fields. In addition to acrylic adhesives, polyester adhesives have been studied for use from the viewpoint of optimizing adhesive strength.

[0003] On the other hand, demands for reduction of environmental load are increasing year by year, and adhesives are also required to reduce environmental load during production and use.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2020-056006

[0007] Patent Document 2: Japanese Patent Application Laid-Open No. 2003-238930 Summary of the Invention

[0008] Problems to be solved by the invention

[0009] One method for reducing environmental impact is to reduce the amount of solvent used. However, when preparing an adhesive with a low solvent content, the molecular weight of the base polymer (e.g., polyester resin) in the adhesive must be reduced. This may result in poor coating properties due to the low molecular weight of the base polymer.

[0010] The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a polyester-based adhesive that can contribute to reducing environmental load and has excellent coating properties.

[0011] Solutions for solving problems

[0012] [1] The polyester adhesive of one embodiment of the present invention comprises a polyester resin and a surfactant, wherein the weight average molecular weight of the polyester resin is 0.2×10 4 ~2.0×10 4 The viscosity of the polyester adhesive is 1 Pa·s to 50 Pa·s.

[0013] [2] The polyester-based adhesive described in [1] above may contain substantially no organic solvent.

[0014] [3] In the polyester adhesive described in [1] or [2] above, the surface tension of the polyester adhesive may be 30 mN / m or less.

[0015] [4] In the polyester adhesive described in any one of [1] to [3] above, the polyester resin may be a biopolyester resin.

[0016] [5] In the polyester adhesive described in any one of [1] to [4] above, the surfactant may be a silicone surfactant.

[0017] [6] A method for producing a polyester-based adhesive according to one embodiment of the present invention includes mixing a polyester-based resin and a surfactant to prepare a mixture, wherein the mixture contains substantially no organic solvent.

[0018] [7] A pressure-sensitive adhesive sheet according to one embodiment of the present invention comprises a pressure-sensitive adhesive layer comprising the polyester pressure-sensitive adhesive according to any one of [1] to [5] above.

[0019] [8] The adhesive layer of the adhesive sheet described in [7] may have an adhesive strength of 5 N / 20 mm or more at 23°C when bonded to a SUS304 plate.

[0020] [9] The haze value of the adhesive layer of the adhesive sheet described in [7] or [8] may be 0.1% to 5%.

[0021] Effects of the Invention

[0022] According to the present invention, a polyester-based adhesive can be provided that can contribute to reducing environmental load and has excellent coating properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 (a) and (b) are schematic cross-sectional views of a pressure-sensitive adhesive sheet according to one embodiment of the present invention. DETAILED DESCRIPTION

[0024] A. Polyester adhesive

[0025] The polyester adhesive according to the embodiment of the present invention contains a polyester having a weight average molecular weight of 0.2×10 4 ~2.0×10 4 The polyester resin and surfactant. The viscosity of the polyester adhesive is 1 Pa·s to 50 Pa·s.

[0026] In the embodiment of the present invention, by adding a surfactant to adjust the viscosity to the above range, the surface tension of the adhesive can be preferably adjusted. As a result, a polyester adhesive having excellent coating properties can be provided while using a low molecular weight polyester resin. When a low molecular weight polyester resin is used, the amount of organic solvent added can be reduced, thereby making it possible to produce a polyester adhesive with a low environmental impact.

[0027] The polyester adhesive preferably contains substantially no organic solvent. By containing substantially no organic solvent, a polyester adhesive with less environmental impact can be provided. The concept of "substantially containing no organic solvent" (hereinafter sometimes also referred to as "solvent-free") may also include a method in which a small amount of organic solvent inevitably present in the raw materials or an organic solvent accidentally mixed in during production is contained. However, the amount of the organic solvent accidentally contained is preferably 3 parts by weight or less, preferably 1 part by weight or less, more preferably 0.5 parts by weight or less, and particularly preferably 0.1 parts by weight or less per 100 parts by weight of the polyester adhesive.

[0028] As mentioned above, the viscosity of the polyester adhesive at 25°C is 1 Pa·s to 50 Pa·s, more preferably 2 Pa·s to 40 Pa·s, and even more preferably 2.5 Pa·s to 20 Pa·s. Within this range, a polyester adhesive with significantly excellent coating properties can be obtained. In this specification, viscosity refers to the viscosity measured using a rheometer at 0.1 to 1000 (1 / s).

[0029] The surface tension of the above-mentioned polyester adhesive is preferably 50mN / m or less, more preferably 30mN / m or less, and further preferably 10mN / m to 25mN / m. If it is within such a range, a polyester adhesive that can form an adhesive layer without poor coating can be obtained. In one embodiment, the surface tension of the polyester adhesive is 5mN / m to 28mN / m (preferably 10mN / m to 25mN / m). By using a silicone surfactant as a surfactant and setting the surface tension to the above-mentioned range, a polyester adhesive that has a significant effect in preventing poor coating (for example, shrinkage) can be obtained. In addition, when the viscosity of the polyester adhesive at 25°C is 1Pa·s to 20Pa·s, by setting the surface tension of the polyester adhesive to 5mN / m to 28mN / m (preferably 10mN / m to 25mN / m), a polyester adhesive that has a significant effect in preventing poor coating (for example, shrinkage) can be obtained. The surface tension of the polyester adhesive can be measured by the pendant drop method.

[0030] The contact angle of the polyester adhesive on polyethylene terephthalate is preferably 50° or less, more preferably 40° or less, and further preferably 10° to 40°. If it is within such a range, a polyester adhesive that can form an adhesive layer without poor coating can be obtained. In one embodiment, the contact angle of the polyester adhesive on polyethylene terephthalate is set to 10° to 45° (preferably 15° to 40°). By using a silicone surfactant as a surfactant and setting the contact angle to the above range, a polyester adhesive that has a significant effect in preventing poor coating (for example, shrinkage) can be obtained. In addition, when the viscosity of the polyester adhesive at 25°C is 1Pa·s to 50Pa·s (preferably 2.5Pa·s to 20Pa·s), by setting the above contact angle to 10° to 45° (preferably 15° to 40°), a polyester adhesive that has a significant effect in preventing poor coating (for example, shrinkage) can be obtained.

[0031] (Polyester resin)

[0032] Typically, polyester resins can be obtained by reacting a polycarboxylic acid component with a polyol component. The polycarboxylic acid component includes one or more compounds selected from polycarboxylic acids having two or more carboxyl groups in one molecule and their derivatives. Furthermore, the polyol component includes one or more compounds selected from polyols having two or more hydroxyl groups in one molecule.

[0033] In one embodiment, the polyester resin is a biopolyester resin. As used herein, a biopolyester resin refers to a polyester resin in which at least one of the polycarboxylic acid component and the polyol component is derived from a plant. By using these renewable, plant-derived materials, a polyester adhesive can be obtained that contributes to reducing environmental impact as a countermeasure to the depletion of fossil resources and global warming.

[0034] Examples of the polycarboxylic acid include aliphatic or alicyclic dibasic acids. Specific examples include adipic acid, azelaic acid, dimer acid, sebacic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 4-methyl-1,2-cyclohexanedicarboxylic acid, dodecenylsuccinic anhydride, fumaric acid, succinic acid, dodecanedioic acid, hexahydrophthalic anhydride, tetrahydrophthalic anhydride, maleic acid, maleic anhydride, itaconic acid, and citraconic acid. Furthermore, aromatic dibasic acids may also be used. Specific examples of aromatic dibasic acids include terephthalic acid, isophthalic acid, phthalic acid, 1,5-naphthalene dicarboxylic acid, 2,6-naphthalene dicarboxylic acid, 4,4'-biphenyl dicarboxylic acid, 2,2'-biphenyl dicarboxylic acid, and 4,4'-diphenyl ether dicarboxylic acid. As the polycarboxylic acid derivatives, anhydrides and alkyl esters (for example, monoesters and diesters, preferably monoalcohols having 1 to 3 carbon atoms) of the carboxylic acids mentioned above can be used.

[0035] In one embodiment, a plant-derived polycarboxylic acid is used. Examples of plant-derived polycarboxylic acids include dimer acid, sebacic acid, succinic acid, and glutaric acid. Here, "dimer acid" refers to a dicarboxylic acid having a structure formed by dimerization of unsaturated fatty acids. A typical example of such dimer acids is a dicarboxylic acid having a structure formed by dimerization of unsaturated fatty acids having 18 carbon atoms (such as oleic acid, linoleic acid, and linolenic acid).

[0036] When the above-mentioned polycarboxylic acid component contains a polycarboxylic acid derived from a plant, the content ratio of the polycarboxylic acid derived from a plant is preferably 10 mol% or more, preferably 50 mol% or more, more preferably 75 mol% or more, further preferably 90 mol% or more, and most preferably 100 mol% relative to the entire polycarboxylic acid in the polycarboxylic acid component.

[0037] Examples of the polyol include aliphatic and alicyclic diols. Specific examples include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 2-methyl-1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, 2,2,4-trimethyl-1,5-pentanediol, 2-ethyl-2-butylpropanediol, 1,9-nonanediol, 2-methyloctanediol, and 1,10-decanediol.

[0038] In one embodiment, a polyol derived from a plant is used. Examples of polyols derived from a plant include dimer diol, 1,3-propylene glycol, 1,4-butanediol, ethylene glycol, and polyoxytetramethylene glycol. Here, "dimer diol" refers to a diol having a structure in which the carboxyl group in the dicarboxylic acid formed by dimerization of unsaturated fatty acids is converted (hydrogenated) to a hydroxyl group. A typical example of the dimer diol is a diol having 36 carbon atoms, which corresponds to a dimer of an unsaturated fatty acid having 18 carbon atoms (such as oleic acid, linoleic acid, and linolenic acid).

[0039] When the polyol component contains a plant-derived polyol, the content ratio of the plant-derived polyol relative to the total polyol in the polyol component is preferably 50 mol% or more, more preferably 75 mol% or more, further preferably 90 mol% or more, and most preferably 100 mol%.

[0040] The polyester resin can be obtained by polycondensation of a polycarboxylic acid component and a polyol component. More specifically, for example, the polyester resin can be produced (synthesized) by removing water (condensation water) generated by the condensation reaction to the outside of the reaction system while carrying out a condensation reaction between the carboxyl group of the polycarboxylic acid component and the hydroxyl group of the polyol component. As a method for removing the condensation water to the outside of the reaction system, there are: a method of blowing an inert gas into the reaction system to remove the condensation water together with the inert gas to the outside of the reaction system; a method of distilling the condensation water from the reaction system under reduced pressure (decompression method), etc. In terms of being easy to shorten the polymerization time and being suitable for improving productivity, the decompression method can be preferably adopted.

[0041] The reaction conditions for the condensation reaction, such as the reaction temperature and the degree of reduced pressure (pressure within the reaction system) when a reduced pressure method is used, can be any appropriate conditions. The reaction temperature is, for example, 180°C to 260°C, preferably 200°C to 220°C. The degree of reduced pressure is, for example, 10 kPa or less, preferably 0.1 kPa to 10 kPa, and more preferably 0.1 kPa to 4 kPa.

[0042] During the condensation reaction, any appropriate polymerization catalyst may be used. Examples of the polymerization catalyst include titanium-based catalysts such as tetraisopropyl titanate and tetrabutyl titanate, antimony-based catalysts such as antimony trioxide, germanium-based catalysts such as germanium dioxide, and catalysts such as zinc acetate, manganese acetate, and dibutyltin oxide. These catalysts may be used alone or in combination. Among them, antimony trioxide, tetrabutyl titanate, germanium dioxide, and zinc acetate are preferably used.

[0043] The amount of the polymerization catalyst may be any appropriate amount. For example, the amount of the catalyst is preferably 0.001 to 5 mol%, more preferably 0.01 to 3 mol%, and even more preferably 0.1 to 2 mol%, relative to the total amount of the polycarboxylic acid component and the polyol component.

[0044] In one embodiment, the polyester resin may be synthesized without using an organic solvent.

[0045] The content of the polyester resin is preferably 60 parts by weight or more, more preferably 70 parts by weight or more, and even more preferably 80 parts by weight or more, based on 100 parts by weight of the polyester binder.

[0046] As mentioned above, the weight average molecular weight of the polyester resin is 0.2×10 4 ~2.0×10 4If it is within such a range, a polyester adhesive that can exhibit appropriate adhesive strength can be preferably prepared even without containing a solvent. In the present invention, although a polyester resin with a low weight average molecular weight is used as described above, it is advantageous in terms of excellent coating properties. Details will be described later. The weight average molecular weight of the polyester resin is preferably 0.25×10 4 ~1.5×10 4 , more preferably 0.3×10 4 ~1.0×10 4 If it is within such a range, the above-mentioned effect will become remarkable. In this specification, the weight average molecular weight refers to the value measured by gel permeation chromatography (GPC) in terms of polystyrene.

[0047] (Surfactant)

[0048] As mentioned above, the polyester adhesive contains a surfactant. In embodiments of the present invention, although a polyester resin with a low molecular weight is used, the addition of a surfactant can provide a polyester adhesive with excellent coating properties. More specifically, when a low molecular weight polyester resin is used for solvent-free preparation, coating defects such as so-called shrinkage may occur when the adhesive is applied to a substrate (e.g., a release liner). However, in the present invention, the addition of a surfactant can prevent such coating defects.

[0049] As the surfactant, any suitable surfactant can be used as long as the effects of the present invention are achieved. Silicone-based surfactants are preferably used as the surfactant. By using silicone-based surfactants to control the surface tension of the polyester adhesive, a polyester adhesive can be obtained that can form an adhesive layer without coating defects. Silicone-based surfactants are compounds containing structural units having siloxane bonds in the main chain, and can contain a hydrophobic portion and a hydrophilic portion within the molecule. Silicone-based surfactants are preferably compounds that do not contain fluorine atoms. The use of such silicone-based surfactants significantly enhances the aforementioned effects.

[0050] In one embodiment, the organosilicon surfactant is preferably a modified organosilicon compound. Examples of the modified organosilicon compound include compounds having a structure in which an organic group is introduced into the side chain and / or terminal of a polysiloxane. Examples of the organic group include groups containing a functional group selected from amino, epoxy, alicyclic epoxy, carbinol, mercapto, carboxyl, fatty acid ester, and fatty acid amide groups; and groups containing a polyether chain.

[0051] In one embodiment, a polyether-modified organosilicon compound is used as the organosilicon-based surfactant. If a polyether-modified organosilicon compound is used, the above-mentioned effect will become more significant. Examples of polyether-modified organosilicon compounds include polyether-modified polydimethylsiloxane and polyether-modified polymethylalkylsiloxane in which one of the dimethyl groups of polydimethylsiloxane is partially or entirely substituted with a long-chain alkyl group. Specific examples thereof include polydimethylsiloxane modified with polyethylene oxide, polypropylene oxide, polybutylene oxide, or a mixture thereof. These polyether-modified polydimethylsiloxanes can be obtained by appropriately varying the amount or mixing ratio of polyethylene oxide, polypropylene oxide, or polybutylene oxide.

[0052] As the polyether-modified silicone compound, commercially available products can be used, and examples thereof include BYK-333, BYK-378, BYK-3760, BYK-330, and BYK-329 manufactured by BYK-Chemie Japan Co., Ltd.

[0053] The surfactant content is preferably 0.1 to 15 parts by weight, more preferably 0.2 to 10 parts by weight, and even more preferably 0.3 to 8 parts by weight relative to 100 parts by weight of the polyester resin. Within this range, a polyester adhesive capable of forming an adhesive layer without coating defects can be obtained.

[0054] (Other additives)

[0055] The polyester adhesive may further contain any appropriate additives as needed. Examples of additives include crosslinking agents, inorganic particles, tackifiers, plasticizers (e.g., trimellitic acid ester plasticizers, pyromellitic acid ester plasticizers, etc.), pigments, dyes, fillers, anti-aging agents, conductive materials, antistatic agents, ultraviolet absorbers, light stabilizers, release modifiers, softeners, flame retardants, antioxidants, etc. Furthermore, the polyester adhesive may further contain other resins such as acrylic resins, natural rubber resins, synthetic rubber resins, and silicone resins.

[0056] In one embodiment, the polyester adhesive contains a crosslinking agent. In one embodiment, an isocyanate crosslinking agent and / or an epoxy crosslinking agent is used as the crosslinking agent. In one embodiment, the crosslinking agent is contained in an amount of 3 parts by weight or more relative to 100 parts by weight of the polyester resin.

[0057] The above-mentioned isocyanate-based crosslinking agent is a compound having an isocyanate group, and specific examples thereof include: lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate; alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate, and isophorone diisocyanate; aromatic isocyanates such as 2,4-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, and xylylene diisocyanate; isocyanate adducts such as trimethylolpropane / toluene diisocyanate trimer adduct (manufactured by Nippon Polyurethane Industries, Ltd., trade name "Coronate L"), trimethylolpropane / hexamethylene diisocyanate trimer adduct (manufactured by Nippon Polyurethane Industries, Ltd., trade name "Coronate HL"), and isocyanurate of hexamethylene diisocyanate (manufactured by Nippon Polyurethane Industries, Ltd., trade name "Coronate HX"); and the like. When the polyester adhesive contains an isocyanate crosslinking agent, the content of the isocyanate crosslinking agent can be set to any appropriate amount according to the required adhesive strength, and is preferably 3 to 30 parts by weight, more preferably 10 to 20 parts by weight, relative to 100 parts by weight of the polyester resin.

[0058] The epoxy crosslinking agent is a compound having an epoxy group, and specific examples thereof include N,N,N',N'-tetraglycidyl-m-xylylenediamine, diglycidyl aniline, 1,3-bis(N,N-glycidylaminomethyl)cyclohexane (manufactured by Mitsubishi Gas Chemical Co., Ltd., trade name "Tetrad C"), 1,6-hexanediol diglycidyl ether (manufactured by Kyoeisha Chemical Co., Ltd., trade name "Epolight 1600"), neopentyl glycol diglycidyl ether (manufactured by Kyoeisha Chemical Co., Ltd., trade name "Epolight 1500NP"), ethylene glycol diglycidyl ether (manufactured by Kyoeisha Chemical Co., Ltd., trade name "Epolight 40E"), propylene glycol diglycidyl ether (manufactured by Kyoeisha Chemical Co., Ltd., trade name "Epolight 70P"), polyethylene glycol diglycidyl ether (manufactured by NOF Corporation, trade name "EPIOL E-400”), polypropylene glycol diglycidyl ether (manufactured by NOF Corporation, trade name “EPIOLP-200”), sorbitol polyglycidyl ether (manufactured by Nagase ChemteX Corporation, trade name “DENACOL EX-611”), glycerol polyglycidyl ether (manufactured by Nagase ChemteX Corporation, trade name “DENACOL EX-314”), pentaerythritol polyglycidyl ether, polyglycerol polyglycidyl ether (manufactured by Nagase ChemteX Corporation, trade name “DENACOL EX-512”), sorbitan polyglycidyl ether, trimethylolpropane polyglycidyl ether, diglycidyl adipate, diglycidyl phthalate, triglycidyl-tris(2-hydroxyethyl)isocyanurate, resorcinol diglycidyl ether, bisphenol-S-diglycidyl ether, epoxy resins having two or more epoxy groups in the molecule, and the like. When the polyester adhesive contains an epoxy crosslinking agent, the content of the epoxy crosslinking agent can be set to any appropriate amount depending on the required adhesive strength, and is typically 0.01 to 10 parts by weight, more preferably 3 to 5 parts by weight, relative to 100 parts by weight of the polyester resin.

[0059] In one embodiment, the polyester-based adhesive contains a crosslinking catalyst. Examples of the crosslinking catalyst include metal complexes such as aluminum triacetylacetonate, iron triacetylacetonate, manganese tetraacetylacetonate, nickel tetraacetylacetonate, chromium hexaacetylacetonate, titanium tetraacetylacetonate, and cobalt tetraacetylacetonate; metal alkoxides such as aluminum ethoxide, aluminum propoxide, aluminum butoxide, titanium ethoxide, titanium propoxide, and titanium butoxide; sodium acetate, tin octoate, lead octoate, cobalt octoate, zinc octoate, calcium octoate, lead naphthenate, cobalt naphthenate, dibutyltin dioctoate, dibutyltin dilaurate, dibutyltin maleate, and dibutyltin di(2-ethylhexanoate); formic acid, acetic acid, propionic acid, p-toluenesulfonic acid, trichloroacetic acid, phosphoric acid, and monoalkyl phosphate. Acidic compounds such as esters, dialkyl phosphates, phosphate esters of β-hydroxyethyl (meth)acrylate, monoalkyl phosphites, dialkyl phosphites, p-toluenesulfonic acid, phthalic anhydride, benzoic acid, benzenesulfonic acid, dodecylbenzenesulfonic acid, formic acid, acetic acid, itaconic acid, oxalic acid, maleic acid, and their ammonium salts, lower amine salts, polybasic metal salts, sodium hydroxide, lithium chloride, diethylzinc, tetra(n-butoxy)titanium, and other organometallic compounds; amines such as dicyclohexylamine, triethylamine, N,N-dimethylbenzylamine, N,N,N',N'-tetramethyl-1,3-butanediamine, diethanolamine, triethanolamine, and cyclohexylethylamine.

[0060] The content of the crosslinking catalyst is preferably 0.01 to 1 part by weight, more preferably 0.05 to 0.8 parts by weight, and even more preferably 0.08 to 0.5 parts by weight per 100 parts by weight of the polyester resin. Within this range, a polyester adhesive can be obtained that prevents coating defects.

[0061] In one embodiment, the polyester-based adhesive contains inorganic particles. The inorganic particles can impart thixotropy to the polyester-based adhesive.

[0062] Examples of the inorganic particles include silica, titanium dioxide, bentonite, zinc oxide, talc, kaolin, mica, vermiculite, magnesium carbonate, calcium carbonate, aluminum silicate, barium silicate, calcium silicate, magnesium silicate, strontium silicate, metal tungstates, magnesium, zeolite, barium sulfate, calcined calcium sulfate, calcium phosphate, fluorapatite, hydroxyapatite, and metal soaps. Furthermore, composite particles obtained by coating particles with metal oxides or modified particles obtained by treating the particle surfaces with compounds or the like may also be used. Silicon dioxide particles are preferably used, and fumed silica is more preferably used.

[0063] The content of the inorganic particles is preferably 1 to 30 parts by weight, more preferably 3 to 20 parts by weight, and even more preferably 3 to 10 parts by weight relative to 100 parts by weight of the polyester resin. Within this range, a polyester adhesive can be obtained that prevents coating defects.

[0064] B. Method for producing polyester adhesive

[0065] The method for producing a polyester-based adhesive according to an embodiment of the present invention is characterized by including mixing a polyester-based resin and a surfactant to prepare a mixture, wherein the mixture contains substantially no organic solvent.

[0066] In one embodiment, the polyester resin used in the above production method is the polyester resin described in the above item A. In the above production method, the weight average molecular weight of the polyester resin may be 0.2×10 4 ~2.0×10 4 As long as the effects of the present invention can be obtained, a polyester resin having a molecular weight outside this range may be used instead of this polyester resin.

[0067] As the surfactant, the surfactant described in the above section A can be used. The mixture may further contain the additives described in the above section A (for example, a cross-linking agent, etc.).

[0068] Any appropriate method may be used to prepare the mixture.

[0069] C. Adhesive sheet

[0070] In one embodiment, a pressure-sensitive adhesive sheet including a pressure-sensitive adhesive layer comprising the polyester-based pressure-sensitive adhesive is provided. Figure 1 FIG. 1 is a schematic cross-sectional view of an adhesive sheet according to an embodiment of the present invention. Figure 1 As shown in (a), it is composed only of the adhesive layer 10, or it can be as shown in Figure 1 As shown in (b) of FIG. 1 , the adhesive layer 10 is composed of a substrate 20 and a pressure-sensitive adhesive layer 10 disposed on at least one side of the substrate 20 .

[0071] The thickness of the pressure-sensitive adhesive sheet is preferably 3 μm to 300 μm, more preferably 5 μm to 150 μm, and even more preferably 10 μm to 100 μm.

[0072] The adhesive force at 23°C when the adhesive layer of the adhesive sheet is attached to a SUS304 plate is not particularly limited and can be adjusted to an appropriate range according to the purpose or use. The above-mentioned adhesive force can be, for example, 0.5N / 20mm or more, or 0.8N / 20mm or more. An adhesive sheet showing an adhesive force above a specific value can be well bonded to an adherend. Based on this viewpoint, in a plurality of ways, the above-mentioned adhesive force is preferably 1.0N / 20mm or more, more preferably 1.5N / 20mm or more, further preferably 2.0N / 20mm or more, 2.5N / 20mm or more, 3.0N / 20mm or more, 3.5N / 20mm or more, 4.0N / 20mm or more, 4.5N / 20mm or more, or 5N / 20mm or more. The upper limit of the adhesive strength is not particularly limited, and may be, for example, less than 30 N / 20 mm. To balance this with other properties, it may be 25 N / 20 mm or less, 20 N / 20 mm or less, or even 15 N / 20 mm or less. Adhesive strength refers to the adhesive strength measured by a method in accordance with JIS Z 0237:2009 (lamination conditions: 2 kg roller reciprocating once, peel speed (tension speed): 300 mm / min, peel angle 180°).

[0073] (Base material)

[0074] The above-mentioned substrate can be made of any appropriate material. Regarding the substrate, for example, in addition to using plastic film and plastic sheet, various sheet-like objects such as paper, cloth, non-woven fabric, metal foil, or their plastic laminates, and plastic laminates can also be used. Among them, from the perspective of operability or cost, plastic film or plastic sheet (hereinafter referred to as plastic film) is most preferably used. As the raw material of the plastic film, it can be selected as needed from the perspectives of strength, heat resistance, etc. For example, olefin resins with α-olefin as monomer component such as polyethylene (PE), polypropylene (PP), ethylene-propylene copolymer, ethylene-vinyl acetate copolymer (EVA) can be listed; polyesters such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT); polyvinyl chloride (PVC); polyphenylene sulfide (PPS); amide resins such as polyamide (nylon) and wholly aromatic polyamide (aramid); polyetheretherketone (PEEK), polyimide, polyetherimide, polystyrene, acrylic resin, etc. These raw materials may be used alone or in combination of two or more. Furthermore, as the plastic film, any of unstretched films, uniaxially oriented films, and biaxially oriented films may be used. Furthermore, these films may be laminated films comprising two or more film layers. From the perspective of operability, films to which lubricants such as inactive particles are appropriately added may also be used.

[0075] In one embodiment, the substrate may function as a release liner.

[0076] The thickness of the substrate is preferably 200 μm or less, more preferably 1 μm to 200 μm, further preferably 5 μm to 200 μm, particularly preferably 10 μm to 200 μm, particularly preferably 20 μm to 200 μm, and most preferably 30 μm to 200 μm.

[0077] The substrate may be subjected to a surface treatment, such as corona treatment, chromic acid treatment, ozone exposure, flame exposure, high voltage electric shock exposure, ionizing radiation treatment, and primer coating.

[0078] (Adhesive layer)

[0079] In one embodiment, the adhesive layer can be formed by coating the polyester adhesive on a substrate and curing the coated layer. That is, the adhesive layer can be a cured product of the polyester adhesive. Typically, the curing treatment is a cross-linking treatment. The curing treatment can be performed by heating or by active energy rays (e.g., ultraviolet rays). The curing conditions can be any appropriate conditions depending on the composition of the polyester adhesive.

[0080] The gel fraction of the adhesive layer (cured polyester adhesive) is preferably 50% to 95%, more preferably 60% to 90%, and even more preferably 70% to 80%. Within this range, an adhesive layer exhibits excellent coating and adhesive properties. The method for measuring the gel fraction is described below.

[0081] The glass transition temperature (Tg) of the above-mentioned adhesive layer (polyester adhesive after curing treatment) is preferably -100°C to 0°C, more preferably -70°C to -10°C, and further preferably -60°C to -20°C. If it is within such a range, an adhesive layer with excellent coating properties and adhesion can be made. Typically, in the dynamic viscoelasticity measurement carried out at a frequency of 1 Hz, the above-mentioned Tg can be determined as the temperature corresponding to the peak top of the loss elastic modulus G". Specifically, the measurement method is described later.

[0082] The thickness of the adhesive layer is preferably 5 μm to 200 μm, more preferably 10 μm to 100 μm.

[0083] The haze value of the pressure-sensitive adhesive layer is preferably 0.1% to 5%, more preferably 0.2% to 3%. Within this range, the transparency of the pressure-sensitive adhesive layer can be maintained.

[0084] (Method for producing adhesive sheet)

[0085] The adhesive sheet can be produced by any appropriate method, for example, by directly coating the adhesive on a substrate or by transferring a coating layer formed by coating the adhesive on any appropriate base onto the substrate.

[0086] Examples of a method for applying the adhesive include a method using a die coater, a comma coater, a gravure coater, and the like.

[0087] Example

[0088] The present invention will be described in detail below by way of examples, but the present invention is not limited to these examples. In the examples, "parts" and "%" are by weight unless otherwise specified. The evaluation methods are as follows.

[0089] (1) Weight average molecular weight

[0090] A sample (polyester resin) was prepared as a 0.2 wt% tetrahydrofuran (THF) solution, which was left at room temperature for 20 hours, then filtered through a 0.45 μm membrane filter, and the filtrate was subjected to GPC measurement.

[0091] Analytical equipment: Waters, Alliance

[0092] Column: Made by Tosoh, G7000HXL+GMHXL+GMHXL

[0093] Column temperature: 40°C

[0094] Eluent: THF

[0095] Flow rate: 0.8 mL / min

[0096] Injection volume: 100uL

[0097] Detector: Differential Refractometer (RI)

[0098] Standard sample: Agilent, polystyrene (PS)

[0099] (2) Viscosity

[0100] The viscosity of the polyester-based adhesive was measured under the following conditions.

[0101] Measuring device: HAAKE rheometer

[0102] Cone plate: 35mm diameter, 1°, titanium

[0103] Shear speed: 0.1~1000 1 / s

[0104] Temperature: 25℃

[0105] Gap: 0.025 μm

[0106] (3) Contact angle

[0107] 2.0 μL of a polyester adhesive (a formulation excluding crosslinking agents and catalysts) was added dropwise to the release-treated surface of a polyethylene terephthalate (PET) film. The contact angle was measured 60 seconds later. Contact angle measurements were performed using a contact angle meter (manufactured by Kyowa Interface Co., Ltd., trade name "CX-A") at 23°C and 50% RH.

[0108] (4) Surface tension

[0109] A polyester adhesive (a formulation excluding a crosslinking agent and catalyst) was filled into a syringe and placed on a contact angle meter (trade name "CX-A" manufactured by Kyowa Interface Co., Ltd.). In an atmosphere of 23°C and 50% RH, droplets were formed to a size that prevented them from falling, and the surface tension was evaluated using the pendant drop method.

[0110] (5) Adhesion

[0111] A sheet of 100 mm in length and 20 mm in width was cut from the adhesive sheet obtained in the examples and comparative examples. Next, one of the PET films of the adhesive sheet that had been subjected to a peeling treatment was peeled off, and the exposed adhesive surface was attached (backing) to a PET film (trade name "Lumirror S10#25", manufactured by Toray Industries, Ltd.). Next, the other PET film that had been subjected to a peeling treatment was peeled off and pressed onto a SUS304 plate serving as a test plate under the conditions of a 2 kg roller reciprocating once, and left for 72 hours in an atmosphere of 23°C and 50% RH. Afterwards, a tensile testing machine (device name "EZ Test / Ez-S", manufactured by Shimadzu Corporation) was used in accordance with JIS Z0237, at an atmosphere of 23°C and 50% RH, at a tensile speed of 300 mm / min and a peeling angle of 180°, to peel the adhesive sheet (adhesive layer / PET film) from the test plate and measure the adhesive strength (N / 20 mm).

[0112] (6) Coating properties

[0113] The appearance of the PSA sheets obtained in Examples and Comparative Examples was visually observed, and the coating properties were evaluated.

[0114] ○: No shrinkage

[0115] Δ: There are multiple shrinkages (allowable range)

[0116] ×: Shrinkage on the entire surface

[0117] [Manufacturing Example 1] Manufacture of Polyester Resin A-1

[0118] Into a reaction system equipped with a stirrer, a thermometer, and an outlet cooler were added 1 mol of bis(2-hydroxyethyl)terephthalate (manufactured by TCI) as a dicarboxylic acid component, 1.4 mol of dimer diol (trade name "Pripol 2033", molecular weight 534, manufactured by Croda Japan Co., Ltd.) as a diol component, 0.4 mol of polytetramethylene ether glycol (trade name "BioPTMG650", molecular weight 650), and 0.025 wt% of tetrabutyl titanate as a catalyst. The mixture was then decompressed to 3 kPa and polycondensed at 210° C. for 4 hours to obtain polyester resin A-1.

[0119] The polyester resin A-1 had a weight average molecular weight Mw of 4,400 and a viscosity of 10 Pa·s. The dicarboxylic acid component and the diol component were used in such a ratio that 1.8 mol of hydroxyl groups were present in the diol component per 1.0 mol of carboxyl groups in the dicarboxylic acid component.

[0120] [Manufacturing Example 2] Manufacture of Polyester Resin A-2

[0121] Into a reaction system equipped with a stirrer, a thermometer, and an outlet cooler were added 1 mol of dimer acid (trade name "Pripol 1009", molecular weight 565, manufactured by Croda Japan Co., Ltd.) as a dicarboxylic acid component, 2 mol of polytetramethylene ether glycol (trade name "BioPTMG650", molecular weight 650) as a diol component, and 0.025 wt% of tetrabutyl titanate as a catalyst. The pressure was reduced to 3 kPa, and polycondensation was carried out at 210° C. for 4 hours to obtain polyester resin A-2.

[0122] The polyester resin A-2 had a weight average molecular weight Mw of 6,260 and a viscosity of 2.5 Pa·s. The dicarboxylic acid component and the diol component were used in such a ratio that 1.8 mol of hydroxyl groups were present in the diol component per 1.0 mol of carboxyl groups in the dicarboxylic acid component.

[0123] [Example 1]

[0124] An adhesive prepared by blending 12 parts by weight of a diisocyanate (trade name "DURANATE D101", manufactured by Asahi Kasei) as a crosslinking agent, 8 parts by weight of a polyisocyanate (trade name "Coronate HX", manufactured by Tosoh) with 100 parts by weight of the polyester resin (A-1), 0.1 parts by weight of titanium tetraacetylacetonate as a catalyst, and 0.5 parts by weight of a silicone surfactant (trade name "BYK-329", manufactured by BYK-Chemie Japan Co., Ltd.) as a surfactant was applied to the release-treated surface of a non-silicone release liner (trade name "PJ31", manufactured by Toray Industries, Ltd.) to a thickness of 20 μm after drying. The mixture was heated at 130° C. for 1 minute and then allowed to stand in an atmosphere at 50° C. for 3 days to obtain a pressure-sensitive adhesive sheet.

[0125] [Example 2]

[0126] A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that the amount of the silicone-based surfactant added was 1 part by weight.

[0127] [Example 3]

[0128] A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that the amount of the silicone surfactant added was 3 parts by weight.

[0129] [Example 4]

[0130] A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that polyester resin (A-2) was used instead of polyester resin (A-1).

[0131] [Comparative Example 1]

[0132] A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that the silicone-based surfactant was not added.

[0133] [Table 1]

[0134]

[0135] Description of Reference Numerals

[0136] 10: Adhesive layer

[0137] 20: Base material

[0138] 100: Adhesive sheet

Claims

1. A polyester adhesive comprising a polyester resin and a surfactant, The weight average molecular weight of the polyester resin is 0.2×10 4 ~2.0×10 4 , The viscosity of the polyester-based adhesive is 1 Pa·s to 50 Pa·s.

2. The polyester-based adhesive according to claim 1, which contains substantially no organic solvent.

3. The polyester adhesive according to claim 1, wherein The surface tension of the polyester-based adhesive is 30 mN / m or less.

4. The polyester adhesive according to claim 1, wherein The polyester resin is a bio-polyester resin.

5. The polyester adhesive according to claim 1, wherein The surfactant is an organosilicon surfactant.

6. A method for producing a polyester adhesive, comprising mixing a polyester resin and a surfactant to prepare a mixture, The mixture is substantially free of organic solvent. 7 . A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer comprising the polyester pressure-sensitive adhesive according to claim 1 . 8 . The adhesive sheet according to claim 7 , wherein the adhesive strength at 23° C. when the adhesive layer of the adhesive sheet is bonded to a SUS304 plate is 5 N / 20 mm or more.

9. The adhesive sheet according to claim 7, wherein The haze value of the adhesive layer is 0.1% to 5%.

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