Pressure-sensitive adhesive composition, method for producing same, and removable sheet comprising pressure-sensitive adhesive layer

Abstract

This invention relates to an adhesive composition, a method for manufacturing the same, and a re-peeling sheet. The adhesive composition is a copolymer obtained by polymerizing at least one of the unsaturated compounds represented by formula (1) below (A) with at least one of the group of unsaturated carboxylic acids selected from unsaturated carboxylic acids and unsaturated carboxylic acid esters other than component (A). (In the formula, R1 represents a hydrocarbon group or acetyl group with 8 to 36 carbon atoms, A1 and A2 each independently represent an alkyl group with 2 to 4 carbon atoms, L represents a group represented by the general formula (2) below, z represents a number from 1 to 10, X represents a hydrogen atom or an ionic hydrophilic group, m represents a number from 0 to 100, and n represents a number from 0 to 100.) (In the formula, R2 and R3 each independently represent a hydrogen atom or a methyl group, x represents a number from 0 to 12, and y represents a number from 0 to 1.)

Description

Technical Field

[0001] The present invention relates to an adhesive composition and a method for manufacturing the same, as well as a re-peeling sheet having an adhesive layer. More specifically, it provides an adhesive composition containing a copolymer obtained by polymerizing two or more specific monomers containing unsaturated groups, and a re-peeling sheet having an adhesive layer containing the same. Prior Technology

[0002] Adhesive sheets with adhesive layers, such as labels, masking tapes or sheets, and surface protective films, naturally have excellent adhesion. However, after being applied to the substrate and after a certain period of time, they may peel off. At this point, a portion of the adhesive layer may remain on the surface of the substrate, known as "adhesive residue." Furthermore, if the substrate is paper, peeling off the adhesive sheet can cause the substrate or the substrate itself to crack. In particular, if the substrate is coated paper such as art paper or cast coated paper, the adhesive layer adheres strongly to the surface of the coated paper due to its smooth surface, frequently causing damage to the surface layer of the coated paper. To avoid the aforementioned problems and to facilitate easy peeling of the adhesive sheet from the adhered material, numerous re-peelable adhesives have been proposed, which incorporate cross-linking agents to enhance cohesion and reduce adhesion. In particular, regarding re-peelable adhesives, there has been a strong demand in recent years for solvent-free water-based adhesives from an environmental health perspective, leading to various reviews.

[0003] For example, Patent Document 1 discloses an aqueous pressure-sensitive adhesive, which is a polyoxypropylene compound blended into an aqueous copolymer emulsion having a specific monomer composition, molecular weight, glass transition temperature and particle size.

[0004] Patent document 2 discloses an acrylic emulsion adhesive, which is a specific acrylic emulsion adhesive with the addition of one or more crosslinking agents selected from polyfunctional aziridine compounds and polyfunctional carbodiimide compounds.

[0005] Patent document 3 discloses a re-peel pressure-sensitive adhesive, which is made by mixing a specific amount of a water-soluble crosslinking agent containing an oxazoline group with a specific acrylic emulsion adhesive, and the solvent soluble content is less than 40% by mass, the elastic modulus is 2~50 kg / cm 2, and the re-peel force is less than 500 g / 20 mm width.

[0006] Patent document 4 discloses a water-dispersible pressure-sensitive adhesive for re-peeling, which is formed by blending a crosslinking agent containing carbodiimide groups into a specific acrylic emulsion adhesive, wherein the ratio of carbodiimide groups to carboxyl groups contained in the above acrylic emulsion adhesive (carbodiimide groups / carboxyl groups) is 0.1 to 5.0, and the re-peelability is 500g / 20mm width or less.

[0007] Patent document 5 discloses an adhesive that uses alkyl (meth)acrylate as the main component, contains acrylic acid and methacrylic acid as functional monomers, and further incorporates water-soluble crosslinking agents and oil-soluble crosslinking agents.

[0008] Patent document 6 discloses a re-peelable adhesive sheet that uses a water-dispersible adhesive composition containing: an emulsion of a (meth)acrylate copolymer containing alkyl (meth)acrylate units with 4 to 12 carbon atoms as the main component and containing 0.1 to 2.0% by mass of carboxyl-containing unsaturated monomer units; an emulsion of an alkali-soluble or alkali-swellable (meth)acrylate copolymer containing carboxyl-containing unsaturated monomer units; and a crosslinking agent as essential components.

[0009] However, the aforementioned proposed re-peel adhesive composition, when used as a re-peel sheet with an adhesive layer, still suffers from insufficient adhesion and residue during peeling, and has not yet achieved satisfactory performance.

[0010] On the other hand, Patent Document 7 and others have proposed a specific reactive emulsifier for improving the stability of polymer emulsions by reducing coagulants during emulsification polymerization. [Previous Technical Documents] [Patent Literature]

[0011] [Patent Document 1] Japanese Patent Publication No. 5-75034 [Patent Document 2] Japanese Patent Application Publication No. 7-278233 [Patent Document 3] Japanese Patent Application Publication No. 10-114887 [Patent Document 4] Japanese Patent Application Publication No. 2001-131512 [Patent Document 5] Japanese Patent Application Publication No. 2001-152118 [Patent Document 6] Japanese Patent Application Publication No. 2009-73920 [Patent Document 7] Japanese Patent Application Publication No. 2006-75808 Summary of the Invention

[0012] [The problem that the invention aims to solve]

[0013] Therefore, the object of the present invention is to provide an adhesive composition and a method for manufacturing the same, as well as a re-peeling sheet. The adhesive composition is used as an adhesive layer in the case of a re-peeling sheet, has sufficient adhesive holding force and can be peeled from the surface of the adhered object with a moderate peeling force, and can reduce the amount of residual adhesive on the surface of the adhered object after peeling. [Methods used to solve problems]

[0014] Therefore, through careful research, the inventors discovered that an adhesive composition containing a copolymer obtained by polymerizing two or more specific monomers containing unsaturated groups can achieve the aforementioned objective, thus completing the present invention.

[0015] That is, the present invention provides an adhesive composition comprising: a copolymer obtained by polymerizing at least one of the unsaturated compounds shown in formula (1) below (A) with at least one of the unsaturated carboxylic acid ester compounds selected from the group other than unsaturated carboxylic acids and component (A).

[0016]

[0017] (In the formula, R1 represents a hydrocarbon group or acetyl group with 8 to 36 carbon atoms, A1 and A2 each independently represent an alkyl group with 2 to 4 carbon atoms, L represents the group shown in the general formula (2) below, z represents the number 1 to 10, X represents a hydrogen atom or an ionic hydrophilic group, m represents the number 0 to 100, and n represents the number 0 to 100.)

[0018]

[0019] (In the formula, R2 and R3 each independently represent a hydrogen atom or a methyl group, x represents a number from 0 to 12, and y represents a number of 0 or 1.)

[0020] Furthermore, a re-peeling sheet is provided, which has an adhesive layer containing the aforementioned adhesive composition. [Effects of the Invention]

[0021] The adhesive composition provided by the present invention has sufficient adhesive retention force and can be peeled off from the surface of the adhered object with appropriate peel force when used in the case of re-peeling sheets, and can especially reduce the residual adhesive on the surface of the adhered object. Therefore, it can provide re-peeling sheets suitable for use in adhesive labels, masking tapes, surface protective films, etc. Implementation

[0022] The adhesive composition of the present invention will be described below.

[0023] The copolymer contained in the adhesive composition of the present invention is obtained by polymerizing at least one of the unsaturated compounds shown in formula (1) below (A) with at least one of the groups of unsaturated carboxylic acids selected from unsaturated carboxylic acids and unsaturated carboxylic acid esters other than component (A). The copolymers used in the present invention do not have a consistent repeating unit, and their structures and repeating are diverse. Therefore, the structure of the copolymer contained in the adhesive composition of the present invention is very complex. Therefore, the structure of the copolymer contained in the present invention is difficult to represent using a consistent general formula. Therefore, in the present invention, the "adhesive composition" characterized by containing such a copolymer is defined by a manufacturing method called "containing a copolymer obtained by polymerizing component (A) and component (B)".

[0024]

[0025] (In the formula, R1 represents a hydrocarbon group or acetyl group with 8 to 36 carbon atoms, A1 and A2 each independently represent an alkyl group with 2 to 4 carbon atoms, L represents the group shown in the general formula (2) below, z represents the number 1 to 10, X represents a hydrogen atom or an ionic hydrophilic group, m represents the number 0 to 100, and n represents the number 0 to 100.)

[0026]

[0027] (In the formula, R2 and R3 each independently represent a hydrogen atom or a methyl group, x represents a number from 0 to 12, and y represents a number of 0 or 1.)

[0028] The component (A) of the adhesive composition of the present invention is as shown in the aforementioned formula (1). In formula (1), the hydrocarbon group with 8 to 36 carbon atoms represented by R1 is preferably alkyl, alkenyl, or aryl.

[0029] Examples of alkyl groups that are straight-chain or branched include octyl, isooctyl, 2-ethylhexyl, secondary octyl, nonyl, isononyl, secondary nonyl, decyl, isodel, secondary decyl, undecyl, isoundecyl, secondary undecyl, dodecyl, isododecyl, secondary dodecyl, tridecyl, isotridecyl, secondary tridecyl, tetradecyl, isotetradecyl, secondary tetradecyl, hexadecyl, isohexadecyl, secondary hexadecyl, stearyl, isooctyl, eicosyl, 2-butyloctyl, 2-butyldecyl, 2-hexyloctyl, 2-hexyldecyl, 2-octyldecyl, 2-hexyldodecyl, 2-octyldodecyl, monomethylisostearyl, dodecyl, dodecyl, triadenyl, and hexadecyl.

[0030] Examples of alkenyl groups mentioned above include octenyl, nonenyl, decenyl, undecenyl, dodecenyl, tetradecenyl, and oleyl.

[0031] Examples of aryl groups include styryl, cumenyl, styryl, triphenylmethyl, ethylphenyl, propylphenyl, butylphenyl, pentylphenyl, hexylphenyl, heptylphenyl, octylphenyl, nonylphenyl, decylphenyl, undecylphenyl, dodecylphenyl, tridecaylphenyl, tetradecylphenyl, etc.

[0032] Furthermore, as the acetyl group with 8 to 36 carbon atoms as indicated in R 1, a branched aliphatic acetyl group is preferred. The branched aliphatic acetyl group is a residue of the fatty acid corresponding to the branch. Examples of fatty acids that can be categorized as branches include isooctanoic acid, 2-ethylhexanoic acid, neooctanoic acid, isononanoic acid, 3,4,4-trimethylhexanoic acid, neononanoic acid, isodecanic acid, 2-propylheptanoic acid, neodecanoic acid, isoundecanoic acid, isodococic acid, 2-butyloctanoic acid, isotriadecanoic acid, isotetradecanoic acid, isomyristic acid, 2-pentylnonanoic acid, isopentadecanoic acid, isohexadecanoic acid, isopramearic acid, 2-hexyldecanoic acid, isohexadecanoic acid, isostearic acid, 2-hexyldecanoic acid, isohexadecanoic acid, isostearic acid, 2-heptylundecanoic acid, isononadecanoic acid, isoeicosanoic acid, 2-octyldodecanoic acid, 2-nonyltridecanoic acid, 2-decyltetradecanoic acid, 2-undecylpentadecanoic acid, 2-dodecylhexadecanoic acid, 2-tetriadecylheptadecanoic acid, 2-tetriadecylheptadecanoic acid, 2-tetradecyloctadecanoic acid, 2-pentadecadecylheptadecanoic acid, 2-hexadecyleicosanoic acid, and isoleic acid.

[0033] The presence of aliphatic groups with such branches results in excellent polymerization stability during copolymer manufacturing, and the stability of the adhesive composition obtained from the copolymer is also excellent, which is advantageous.

[0034] As the aforementioned hydrocarbon group, alkyl groups with 8 to 36 carbon atoms are preferred, alkyl groups with 8 to 24 carbon atoms are even more preferred, alkyl groups with 10 to 14 carbon atoms are even more preferred, and alkyl groups with 11 to 13 carbon atoms and having branches are the most preferred. As component (A), the chain length of the alkyl groups shown in R 1 is preferably mixed in the range of 8 to 36 carbon atoms.

[0035] Examples of alkyl groups with 2 to 4 carbon atoms, such as ethyl, propyl, isopropyl, butyl, isobutyl, and secondary butyl groups, can be derived from A1 and A2 of the aforementioned general formula (1). The (A1O)n and (A2O)m groups can be the same or different. Furthermore, two or more alkyl groups in each (A1O)n and (A2O)m can be randomly or block-formed. m and n are each independent numbers from 0 to 100, with 1 to 80 being the best, 2 to 50 being better, and 3 to 20 being even better.

[0036] When A1O and A2O are each a separate base, or when there are two or more types of bases, it is preferable that there is an ethyl group present. When the ratio of the total molar amount of ethyl group to A1O and A2O is less than 50 molars, the stability of the polymer emulsion will decrease. Therefore, the ratio of the aforementioned ethyl group is preferably 50-100 molars, more preferably 60-100 molars, even better 80-100 molars, and best at 100 molars.

[0037] Furthermore, in the aforementioned general formula (1), L is as shown in the following general formula (2).

[0038]

[0039] (In the formula, R2 and R3 each independently represent a hydrogen atom or a methyl group, x represents a number from 0 to 12, and y represents a number of 0 or 1.)

[0040] In the aforementioned formula, x is preferably 1~8, better is 1~5, even better is 1~3, and the best is 1. Furthermore, by using y=0, the reactivity is moderately suppressed, and the copolymer is obtained efficiently. Therefore, y=0 is preferred.

[0041] In the case where the ionic hydrophilic group X in the aforementioned general formula (1) is an anionic hydrophilic group, it is preferable to use -SO 3M, -R 4-SO 3M, -R 5-COOM, -PO 3M 2, -PO 3MH or -CO-R 6-COOM (where M represents hydrogen atom, alkali metal atom, alkaline earth metal atom [but, since alkaline earth metal atom is usually divalent, 1 / 2 mole is equivalent to M], quaternary ammonium cation, R 4 and R 5 represent alkyl groups with 1 to 6 carbon atoms, and R 6 represents divalent hydrocarbon groups with 1 to 12 carbon atoms).

[0042] In the aforementioned formula representing anionic hydrophilic groups, examples of alkali metal atoms represented by M include lithium, sodium, and potassium, while examples of alkaline earth metal atoms include magnesium and calcium. Furthermore, examples of fourth-order ammonium cations include those derived from ammonia, alkylamines, and alkanolamines.

[0043] In the aforementioned formulas representing anionic hydrophilic groups, examples of alkyl groups with 1 to 6 carbon atoms, represented by R4 and R5, include methylene, ethyl, propyl, butyl, pentene, pentamethylene, and hexamethylene.

[0044] In the aforementioned formula for anionic hydrophilic groups, R6 represents a divalent hydrocarbon group with 1 to 12 carbon atoms, preferably with two carboxyl residues removed from the dicarboxylic acid. Examples of the aforementioned dicarboxylic acids include, for instance, saturated aliphatic dicarboxylic acids such as malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, octanoic acid, azelaic acid, sebacic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, and tetradecanoic acid; saturated alicyclic dicarboxylic acids such as cyclopentanedicarboxylic acid, hexahydrophthalic acid, and methylhexahydrophthalic acid; aromatic dicarboxylic acids such as isophthalic acid, p-phthalic acid, methylphenyl dicarboxylic acid, and succinic acid; unsaturated aliphatic dicarboxylic acids such as maleic acid, fumaric acid, iconic acid, citrate, and succinic acid; and unsaturated alicyclic dicarboxylic acids such as tetrahydrophthalic acid, methyltetrahydrophthalic acid, nadic acid (methylenetetrahydrophthalic acid), methylnadic acid, methylbutenyltetrahydrophthalic acid, and methylpentenyltetrahydrophthalic acid.

[0045] Among the aforementioned anionic hydrophilic groups, those represented by -SO3M, -PO3M2, or -PO3MH are preferred, with -SO3M being the most preferred. Furthermore, M-groups are preferably alkali metals or grade 4 ammonium, with grade 4 ammonium being the most preferred.

[0046] In the general formula (1), z represents 1 to 10, but depending on the manufacturing method of component (A), there may be a mixture of dissimilar compounds with z as z. In the case of a mixture, z represents the average value. A z value of 1 to 8 is preferred, a z value of 1 to 5 is particularly preferred, and a z value of 1 to 3 is optimal.

[0047] The method of manufacturing component (A) of the present invention is not particularly limited. For example, as a method of synthesizing a compound in general formula (1) where X is a hydrogen atom, it can be obtained by adding an alkylene oxide to a reactant of an unsaturated hydrocarbon ether and an alcohol or an alcohol alkoxylate using a known method.

[0048] For example, glycidyl ethers with unsaturated hydrocarbon groups used in the manufacture of component (A) include, for example, allyl glycidyl ether, acryloxypropyl ether, and methacryloxypropyl ether; and alcohols include, for example, straight-chain and branched octanol, 2-ethylhexanol, secondary octanol, straight-chain and branched nonyl alcohol, secondary nonyl alcohol, straight-chain and branched decanol, secondary decanol, straight-chain and branched undecyl alcohol, secondary undecyl alcohol, and straight-chain and branched undecyl alcohol. Branched dodecyl alcohol, secondary dodecyl alcohol, straight-chain and branched tridecyl alcohol, secondary tridecyl alcohol, straight-chain and branched tetradecyl alcohol, secondary tetradecyl alcohol, straight-chain and branched hexadecyl alcohol, secondary hexadecyl alcohol, straight-chain and branched stearyl alcohol, straight-chain and branched eicosyl alcohol, 2-butyloctyl alcohol, 2-butyldecyl alcohol, 2-hexyloctyl alcohol, 2-hexyldecyl alcohol, 2-octyldecyl alcohol, 2-hexyldodecyl alcohol, 2-octyldodecyl alcohol, monomethyl branched-isostearyl alcohol, etc.

[0049] Furthermore, the ring-opening reaction of glycidyl ether (epoxy group) can be carried out using a catalyst as necessary. The catalysts that can be used are not particularly limited as long as they involve ring-opening reactions of epoxy groups, such as tertiary amines, quaternary ammonium salts, boron trifluoride or its ether salts, aluminum chloride, barium oxide, sodium hydroxide, potassium hydroxide, etc.

[0050] Furthermore, the method of manufacturing compounds in general formula (1) that are represented by -SO 3M, -R 4-SO 3M, -R 5-COOM, -PO 3M 2, and -CO-R 6-COOM is not limited. They can be manufactured by reacting compounds in general formula (1) where X is equivalent to a hydrogen atom with an ionic hydrophilic agent. There are no particular limitations on the reaction conditions. Typically, the temperature is between room temperature and 150°C, the pressure is between atmospheric pressure and 0.5 MPa, and the reaction time is between 1 and 10 hours. If necessary, catalysts such as urea can also be used. Furthermore, when M is a hydrogen atom, it can also be neutralized using bases such as sodium hydroxide and potassium hydroxide, or alkanolamines such as ammonia, alkylamines, monoethanolamine, and diethanolamine.

[0051] Examples of ionic hydrophilizing agents that introduce anionic hydrophilic groups such as -SO3M into X include sulfanilic acid, sulfuric acid, anhydrous sulfuric acid, fuming sulfuric acid, and chlorosulfonic acid.

[0052] Examples of ionic hydrophilizing agents that introduce anionic hydrophilic groups with X represented as -R 4-SO 3M include propane sultone and butane sultone.

[0053] As an ionic hydrophilizing agent that introduces an anionic hydrophilic group represented by X as -R 5-COOM, examples include chloroacetic acid (R 5 is equivalent to methylene), chloropropionic acid (R 5 is equivalent to ethyl) or salts thereof.

[0054] As an ionic hydrophilizing agent that introduces an anionic hydrophilic group represented by X as -CO-R 6-COOM, for example, maleic acid, phthalic acid, or salts thereof can be used.

[0055] As an ionic hydrophilizing agent that introduces an anionic hydrophilic group such as -PO 3M 2 or -PO 3MH into X, examples include phosphorus pentoxide, polyphosphoric acid, orthophosphoric acid, and phosphorus oxychloride. In the case of phosphorylation, the monoester type compound and the diester type compound are obtained as a mixture. These systems can also be separated, and if separation is difficult, they can be used directly as a mixture.

[0056] When the ionic hydrophilic group represented by X in the aforementioned general formula (1) is a cationic hydrophilic group, examples include groups such as -R7-NR8R9R10·Y or -Z-NR8R9R10·Y. In the formulas representing cationic hydrophilic groups, Y represents a halogen atom or a methyl sulfate group (-CH3SO4). Examples of halogen atoms include chlorine atoms, bromine atoms, and iodine atoms. Furthermore, R7 represents an alkyl group having 1 to 6 carbon atoms. Examples of alkyl groups having 1 to 6 carbon atoms include the same alkyl group as those exemplified in R4 of the aforementioned anionic hydrophilic groups.

[0057] R8, R9, and R10 each independently represent an alkyl group having 1 to 4 carbon atoms, an alkanol group having 2 to 4 carbon atoms, or a benzyl group. Examples of alkyl groups having 1 to 4 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, secondary butyl, and tertiary butyl. Examples of alkanol groups having 2 to 4 carbon atoms include 2-hydroxyethyl, 2-hydroxypropyl, and 2-hydroxybutyl. Furthermore, Z represents a group indicated by -CH2CH(OH)CH2- or -CH(CH2OH)CH2-.

[0058] When introducing a cationic hydrophilic group such as -R 7-NR 8R 9R 10·Y, the hydroxyl group of the compound with X as a hydrogen atom in the general formula (1) is first halogenated by a halogenating agent such as thionyl chloride, thionyl bromide, or phosgene. Then, a tertiary amine compound is reacted to introduce the hydroxyl group. Alternatively, a secondary amine compound can be reacted by replacing the tertiary amine compound, followed by the reaction of a alkyl halide, dimethyl sulfate, etc. The reaction conditions for halogenating the hydroxyl group are not particularly limited; generally, the temperature is room temperature to 100°C, the pressure is atmospheric pressure to 0.5 MPa, and the reaction time is 1 to 10 hours. Similarly, the reaction conditions for amination are not particularly limited; generally, the temperature is room temperature to 150°C, the pressure is atmospheric pressure to 0.5 MPa, and the reaction time is 1 to 10 hours. If necessary, alkalis such as sodium hydroxide and potassium hydroxide can also be used as catalysts.

[0059] When introducing a cationic hydrophilic group such as -Z-NR 8R 9R 10·Y, epihalohydrins such as epichlorohydrins and epibromohydrins are first reacted with compounds of the general formula (1) where X is a hydrogen atom. Then, a tertiary amine compound is reacted to introduce the substance. Alternatively, a secondary amine compound can be reacted instead of a tertiary amine compound, followed by the reaction of a alkyl halide, dimethyl sulfate, etc. There are no particular limitations on the reaction conditions for epihalohydrins; generally, the temperature is room temperature to 100°C, the pressure is atmospheric pressure to 0.3 MPa, and the reaction time is 1 to 10 hours. If necessary, alkaline catalysts such as sodium hydroxide and potassium hydroxide, or acid catalysts such as sulfuric acid, phosphoric acid, ferric chloride, boron fluoride, and tin chloride can also be used. Furthermore, there are no particular limitations on the reaction conditions for amination. Typically, the temperature is between room temperature and 150°C, the pressure is between atmospheric pressure and 0.5 MPa, and the reaction time is between 1 and 10 hours. If necessary, alkalis such as sodium hydroxide or potassium hydroxide can also be used as catalysts.

[0060] In this invention, component (B) of the adhesive composition is at least one selected from the group consisting of unsaturated carboxylic acid esters other than component (A). Examples of unsaturated carboxylic acids include, for example, vinyl unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid; vinyl unsaturated dicarboxylic acids such as fumaric acid, iconic acid, maleic acid, and citralic acid; and 2-carboxyethyl acrylate and 2-carboxyethyl methacrylate.

[0061] Furthermore, ester compounds of unsaturated carboxylic acids are compounds having a structure obtained by reacting the aforementioned unsaturated carboxylic acids with alcohols. Examples of the aforementioned alcohols include, for example, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, dibutanol, tributanol, pentanol, hexanol, heptanol, octanol, 2-ethylhexanol, nonanol, decanol, undecyl alcohol, dodecanol, tridecanol, tetradecanol, pentadecyl alcohol, hexadecyl alcohol, heptadecanol, hexadecyl alcohol, vinyl alcohol, allyl alcohol, benzyl alcohol, etc.

[0062] While the aforementioned unsaturated carboxylic acids or their ester compounds can be used individually, the adhesiveness can also be adjusted by combining two or more of them.

[0063] From the viewpoint of improving the initial adhesion of the adhesive composition, it is preferable to use at least one selected from the group consisting of acrylic acid, methacrylic acid, and ester compounds of the like. Specifically, butyl acrylate, butyl methacrylate, pentyl acrylate, pentyl methacrylate, hexyl acrylate, hexyl methacrylate, heptyl acrylate, heptyl methacrylate, 2-ethylhexyl acrylate, and 2-ethylhexyl methacrylate are preferred, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, and 2-ethylhexyl methacrylate are more preferred, and 2-ethylhexyl acrylate and 2-ethylhexyl methacrylate are even more preferred.

[0064] The mixing ratio of component (A) and component (B) is not particularly limited as long as it achieves the effect of the present invention. It is preferred to mix 10 to 200 parts by mass relative to 1 part by mass of component (A), more preferably 20 to 150 parts by mass, and especially preferably 30 to 100 parts by mass.

[0065] Furthermore, by using an unsaturated carboxylic acid ester with two or more unsaturated bonds, obtained from polyhydric alcohols and unsaturated carboxylic acids, as an internal crosslinking agent to enhance the cohesiveness of the adhesive composition, and in the case of re-peeling sheets, it is possible to peel off from the surface of the adhered object with appropriate peeling force. Examples of unsaturated carboxylic acid esters having two or more unsaturated bonds include (poly)ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, methylenebisacrylamide, and divinylbenzene.

[0066] The present invention comprises an adhesive composition containing a copolymer obtained by polymerizing the aforementioned component (A) and component (B), but other reactive unsaturated compounds may also be used as monomer components of the copolymer.

[0067] Other unsaturated compounds mentioned above include, for example, styrene, dichlorostyrene, chloromethylstyrene, methylstyrene, acrylamide, acrylonitrile, butadiene, and maleinitrile. When using the aforementioned other unsaturated compounds, it is preferable to use 0 to 100 parts by mass relative to 100 parts by mass of the copolymer used in this invention, and even more preferably 0 to 70 parts by mass.

[0068] Furthermore, the glass transition temperature (Tg) of the copolymer of the present invention is preferably below 0°C, and more preferably between -20°C and -60°C. When the glass transition temperature (Tg) is too high, excellent adhesive properties cannot be obtained, and when used as an adhesive layer in the re-peeling of sheets, the penetration into the sheet substrate will also decrease, raising concerns about the inability to achieve good peelability. On the other hand, when the glass transition temperature is too low, there is a tendency for reduced adhesive strength.

[0069] Furthermore, in this invention, the glass transition temperature (Tg) of the copolymer is a theoretically calculated value obtained by the following FOX formula. (In the formula, Tg is the glass transition temperature (K) of the copolymer obtained from component (A) and component (B) of the present invention, W1, W2, ..., Wn are the weight fractions of each monomer, and Tg1, Tg2, ..., Tgn are the glass transition temperatures of the homopolymers of each monomer.) The glass transition temperature of the homopolymer used in the above calculations can be the value recorded in the literature, for example, the acrylate catalogue (1997 edition) of Mitsubishi Rayon Co., Ltd., or Kyozo Kitaoka, "New Polymer Library 7: Introduction to Synthetic Resins for Coatings", Polymer Journal, pp. 168-169, etc.

[0070] The method for manufacturing the copolymer obtained from components (A) and (B) can be carried out by adding water, a polymerization initiator, and an emulsifier as needed to the monomer mixture (hereinafter also referred to as the "monomer mixture") and conducting a polymerization reaction. Furthermore, since the compound shown in general formula (1) may act as an emulsifier, there may be cases where no other emulsifier is needed.

[0071] From the viewpoint of improving the stability of the emulsion and ensuring good stability during the manufacturing and coating of the adhesive composition, anionic or nonionic emulsifiers are preferred, with anionic emulsifiers being more preferable. Examples of anionic emulsifiers include sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium polyoxyethylene alkyl ether sulfate, and sodium polyoxyethylene alkylphenyl ether sulfate. Examples of nonionic emulsifiers include polyoxyethylene alkyl ethers and polyoxyethylene alkylphenyl ethers.

[0072] In the adhesive composition of this invention, the unsaturated compound represented by formula (1) acts as an emulsifier. Therefore, the emulsifier is not necessary but optional. In use, its addition amount is preferably 0 to 12 parts by mass relative to 100 parts by mass of the monomer mixture, more preferably 0 to 8 parts by mass, and even more preferably 0 to 6 parts by mass. Even if the amount of emulsifier added is 0 parts by mass, the emulsion polymerization can still proceed stably. On the other hand, when more than 12 parts by mass are used, there is a concern that unreacted emulsifier residues may lead to reduced adhesion or water whitening resistance, and deterioration of peelability. Furthermore, the emulsifier can be added directly to the solution prepared by adding water to the monomer mixture, or it can be added to the reaction vessel in advance, or both can be used together.

[0073] There are no particular limitations on the polymerization initiator that can be used here; it can be either water-soluble or oil-soluble. Specific polymerization initiators include, for example, azo compounds such as 2,2'-azobis(2-methylpropane) dihydrochloride and 2,2'-azobis(2-amidinopropane) dihydrochloride; persulfates such as potassium persulfate, sodium persulfate, and ammonium persulfate; and peroxides such as benzoyl peroxide, t-butyl hydroperoxide, and hydrogen peroxide. Furthermore, redox initiators composed of combinations of persulfates and sodium bisulfite, or combinations of peroxides and sodium ascorbate, can also be used. These polymerization initiators can be used alone or in combination of two or more. Of these, persulfate or redox initiators are preferred from the viewpoint of excellent polymerization stability.

[0074] From the viewpoint of accelerating polymerization, the amount of polymerization initiator added relative to 100 parts by mass of the monomer mixture is preferably 0.01 to 6 parts by mass, more preferably 0.03 to 4 parts by mass, and even more preferably 0.1 to 2 parts by mass.

[0075] The polymerization initiator can be added to the reaction vessel in advance, either immediately before polymerization begins or in multiple additions after polymerization has started. Alternatively, it can be added to the monomer mixture in advance. When adding the polymerization initiator, it can be dissolved separately in a solvent or monomer mixture before addition, or the dissolved polymerization initiator can be emulsified before addition.

[0076] Furthermore, chain transfer agents or pH buffers can be added during polymerization. Examples of chain transfer agents mentioned above include decyl mercaptan, lauryl mercaptan, epichlorohydrin, mercaptoacetic acid, 2-mercaptoethanol, mercaptoacetic acid, 2-ethylhexyl mercaptoacetic acid ester, and 2,3-dimercapto-1-propanol. As for the aforementioned pH buffers, there are no particular restrictions as long as they are compounds with pH buffering properties. Examples include sodium bicarbonate, potassium bicarbonate, sodium dihydrogen phosphate, potassium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium acetate, ammonium acetate, sodium formate, and ammonium formate.

[0077] When polymerizing, ion-exchanged water is preferred for use. The amount of water used relative to 100 parts by weight of the monomer mixture is preferably 30 to 400 parts by weight, more preferably 35 to 200 parts by weight, and even more preferably 40 to 150 parts by weight. If the amount of water used is 30 parts by weight or more, the viscosity of the resulting copolymer emulsion can be made within an appropriate range. Furthermore, the polymerization stability also becomes better. On the other hand, if it is 400 parts by weight or less, the solid content concentration of the resulting copolymer emulsion can be made within an appropriate range, and the coating film formation properties when coated onto a substrate constituting a re-peeling sheet become better.

[0078] The copolymer constituting the adhesive composition of the present invention can be synthesized by adding a polymerization initiator to the aforementioned monomer mixture as necessary in the presence of an emulsifier, and by performing emulsification polymerization. As for the order of operations when carrying out this emulsion polymerization, the following methods (1) to (3) can be cited. From the viewpoint of easy control of polymerization temperature, method (2) or (3) is preferred, and method (3) is better. (1) Place the monomer mixture into a reaction vessel and heat it up. Add the polymerization initiator dissolved in water or solvent dropwise or in portions, and then carry out polymerization. (2) After placing a portion of the monomer mixture into the reaction vessel and heating it, add the polymerization initiator dissolved in water or solvent dropwise or in portions to allow the polymerization reaction to proceed. Then, add the remaining monomer mixture dropwise or in portions and continue the polymerization. (3) After pre-placing the polymerization initiator dissolved in water or solvent into the reaction vessel and heating it, the emulsion or solution composed of monomer mixture and water or solvent is dripped or added in portions to carry out polymerization.

[0079] There are no particular limitations on the polymerization conditions for the above polymerization method, but it is preferable to carry out the polymerization under the following conditions. (1) The preferred temperature range is 40~100℃, and the preferred time for polymerization reaction is 1~8 hours. (2) The method is to polymerize 1 to 50% by mass of the monomer mixture at 40 to 90°C for 0.1 to 4 hours, then spend 1 to 5 hours dripping or adding the remaining monomer mixture in portions, and then mature at the same temperature for 1 to 3 hours. (3) The method involves heating the polymerization initiator dissolved in water to 40-90°C, and then dripping or adding the emulsion composed of the monomer mixture and water in batches over a period of 2-5 hours. Afterward, it is preferable to mature the emulsion at the same temperature for 1-5 hours.

[0080] In the above polymerization method, from the viewpoint of polymerization stability, it is preferable that the monomer mixture is pre-dissolved in the emulsifier (or a portion thereof) or pre-formed into an O / W type emulsion state.

[0081] The emulsion of the copolymer obtained by the above polymerization method can be further adjusted to pH 5-9 by adding alkaline aqueous solutions such as ammonia, various water-soluble amines, sodium hydroxide aqueous solution, and potassium hydroxide aqueous solution, preferably to pH 6-8.5. The emulsion of the copolymer is preferably prepared by adding the above-mentioned alkaline aqueous solution to adjust the pH to the above-mentioned range. The above-mentioned alkaline aqueous solution can be added during or after polymerization. From the viewpoint of polymerization stability and the viscosity stability of the obtained emulsion over time, it is preferable to add a portion or the total amount after cooling to room temperature during the maturation stage of polymerization.

[0082] The concentration of solid components in the emulsion or solution of the copolymer obtained from the aforementioned components (A) and (B) and other unsaturated compounds is preferably 10-80% by mass, and more preferably 25-70% by mass.

[0083] The viscosity of the emulsion of the aforementioned copolymer at 25°C is preferably 30~400 mPa·s, and more preferably 50~300 mPa·s.

[0084] The average particle size of the emulsion of the aforementioned copolymer is preferably 100-900 nm, and more preferably 200-600 nm. The average particle size referred to herein is measured by dynamic light scattering method.

[0085] The adhesive composition of the present invention may also include the aforementioned copolymer and crosslinking agent. The crosslinking agent refers to a compound that can react with the carboxyl groups present in the copolymer to crosslink. Examples of crosslinking agents include, for example, epoxy compounds, oxazoline compounds, carbodiimide compounds, aziridine compounds, polyisocyanate compounds, melamine compounds, metal complex compounds, amine compounds, hexamethylenedihydrazine, sebadecylhydrazine, and their derivatives. These crosslinking agents can be used alone or in combination of two or more.

[0086] Among the aforementioned crosslinking agents, from the perspectives of adhesion between the substrate and the adhesive layer when used for re-peeling sheets, peelability of the adhered object, inhibition of the increase in adhesion over time after being applied to the adhered object, and improvement of stain resistance, it is preferable to select at least one of the group consisting of epoxy compounds, oxazoline compounds, and carbodiimide compounds, with epoxy compounds being more preferred.

[0087] As an epoxy compound, it is preferred to have two or more epoxy groups or glycidyl groups in the molecule. Examples of the aforementioned epoxy compounds include, for instance, polyoxypropylene ether compounds of mononuclear polyvalent phenolic compounds such as hydroquinone, resorcinol, pyrocatechol, and phloroglucinol; dihydroxynaphthalene, biphenol, methylene bisphenol (bisphenol F), methylene bis(o-cresol), ethyl bisphenol, isopropylidene bisphenol (bisphenol A), isopropylidene bis(o-cresol), tetrabromobisphenol A, 1,3-bis(4-hydroxyisopropylphenylbenzene), 1,4-bis(4-hydroxyisopropylphenylbenzene), 1,1,3-tris(4-hydroxyphenyl)butane, 1,1,2,2-tetra(4-hydroxyphenyl)ethane, thiobisphenol, sulfobisphenol, oxybisphenol, phenolic aldehyde, o-cresol aldehyde, and ethylphenol aldehyde. Polyoxypropyl ether compounds of polynuclear polyvalent phenolic compounds such as butylphenol phenolic aldehyde, octylphenol phenolic aldehyde, resorcinol phenolic aldehyde, and terpene phenols; polyoxypropyl ether compounds of polyvalent alcohol compounds such as ethylene glycol, propylene glycol, butanediol, hexanediol, polyethylene glycol, polypropylene glycol, thioglycol, dicyclopentadiene dimethylethanol, 2,2-bis(4-hydroxycyclohexyl)propane (hydrogenated bisphenol A), glycerol, trimethylolpropane, pentaerythritol, sorbitol, and bisphenol A-epoxide adducts; polyoxypropyl ether compounds of maleic acid, fumaric acid, iconic acid, succinic acid, glutaric acid, succinic acid, adipic acid, azelaic acid, sebacic acid, dimer acid, trimer acid, phthalic acid, isophthalic acid, p-phthalic acid, trimellitic acid, pyromellitic acid, benzopyrophthalic acid, tetrahydrophthalic acid, and endomethylene tetrahydrophthalic acid. The following are homopolymers or copolymers of aliphatic, aromatic, or alicyclic polyacids: glycidyl esters of acids such as acetic acid and glycidyl methacrylate; N,N-diepoxypropylaniline, bis(4-(N-methyl-N-epoxypropylamino)phenyl)methane, diepoxypropyl o-toluidine, N,N-bis(2,3-epoxypropyl)-4-(2,3-epoxypropoxy)-2-methylaniline, N,N-bis(2,3-epoxypropyl)-4-(2,3-epoxypropoxy)aniline, N,N,N',N'-tetra(2,3-epoxypropyl)-4,4 Epoxides of cyclic olefins such as diaminodiphenylmethane and others containing glycidylamine groups; epoxides of cyclic olefins such as diepoxide vinylcyclohexene, diepoxide cyclopentadiene, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate, 3,4-epoxy-6-methylcyclohexylmethyl-6-methylcyclohexane carboxylate, and bis(3,4-epoxy-6-methylcyclohexylmethyl) adipate; epoxide conjugated diene polymers such as epoxide polybutadiene and epoxide styrene-butadiene copolymers; and heterocyclic compounds such as triepoxide isocyanurate.Furthermore, these epoxy resins can also be internally cross-linked via prepolymers with terminal isocyanates, or they can be molecularly upgraded using polyvalent active hydrogen compounds (polyphenols, polyamines, carbonyl compounds, polyphosphates, etc.).

[0088] The aforementioned epoxy compounds can also be commercially available products. Examples of such commercially available products include, for instance, bisphenol A-epioclonal epoxy resins, sorbitol polyoxypropylene ether (commercially available products, such as those manufactured by Nagase Chemical Co., Ltd. under the trade names "Denacol EX-611", "Denacol EX-612", "Denacol EX-614", "Denacol EX-614B", "Denacol EX-622", etc.), polyglycerol polyoxypropylene ether (commercially available products, such as those manufactured by Nagase Chemical Co., Ltd. under the trade names "Denacol EX-512", "Denacol EX-521", etc.), pentaerythritol polyoxypropylene ether (commercially available products, such as those manufactured by Nagase Chemical Co., Ltd. under the trade name "Denacol EX-411", etc.), diglycerol polyoxypropylene ether (commercially available products, such as those manufactured by Nagase Chemical Co., Ltd. under the trade name "Denacol EX-411"), and diglycerol polyoxypropylene ether (commercially available products, such as those manufactured by Nagase Chemical Co., Ltd. under the trade name "Denacol EX-611"). Glycerol polyoxypropyl ether (commercially available, such as "Denacol EX-313" and "Denacol EX-314" manufactured by Nagase Chemical Co., Ltd.), trimethylolpropane polyoxypropyl ether (commercially available, such as "Denacol EX-321" manufactured by Nagase Chemical Co., Ltd.), neopentyl glycol dioxypropyl ether (commercially available, such as "Denacol EX-211" manufactured by Nagase Chemical Co., Ltd.), 1,6-hexanediol dioxypropyl ether (commercially available, such as "Denacol EX-212" manufactured by Nagase Chemical Co., Ltd.), ethylene glycol dioxypropyl ether (commercially available, such as "Denacol EX-810" and "Denacol EX-421" manufactured by Nagase Chemical Co., Ltd.) (Examples of products mentioned: "EX-811", etc.), diethylene glycol diglycidyl ether (commercially available, such as "Denacol EX-850", "Denacol EX-851", etc. manufactured by Nagase Chemical Co., Ltd.), polyethylene glycol diglycidyl ether (commercially available, such as "Denacol EX-821", "Denacol EX-830", "Denacol EX-832", "Denacol EX-841", "Denacol EX-861", etc. manufactured by Nagase Chemical Co., Ltd.), propylene glycol diglycidyl ether (commercially available, such as "Denacol EX-911", etc. manufactured by Nagase Chemical Co., Ltd.), polypropylene glycol diglycidyl ether (commercially available, such as "Denacol EX-941", "Denacol EX-920", "Denacol EX-861", etc. manufactured by Nagase Chemical Co., Ltd.), propylene glycol diglycidyl ether (commercially available, such as "Denacol EX-911", "Denacol EX-941", "Denacol EX-920", etc. manufactured by Nagase Chemical Co., Ltd.), polypropylene glycol diglycidyl ether (commercially available, such as "Denacol EX-941", "Denacol EX-920", etc. manufactured by Nagase Chemical Co., Ltd.), etc.) EX-931, etc.), dicyclooxypropylaniline, N,N,N',N'-tetracyclooxypropyl-m-diamine, 1,3-bis(N,N'-dicyclooxypropylaminomethyl)cyclohexane, etc. Among these, water-based crosslinking agents are preferred, with glycerol polyoxypropylene ether being the most suitable.

[0089] As an oxazoline compound, a compound having two or more oxazoline groups in its molecule is preferred. Examples of such oxazoline compounds include, for instance, addition polymerizable 2-oxazoline (e.g., 2-isopropenyl-2-oxazoline) copolymers with other unsaturated monomers having a substituent having an unsaturated carbon-carbon bond at the 2-carbon position. Examples of the aforementioned copolymers include, for example, "Epocros WS-500", "Epocros WS-700", "Epocros K-2010E", "Epocros K-2020E", and "Epocros K-2030E" (all trade names, manufactured by Nippon Shokubai Co., Ltd.).

[0090] As a carbodiimide compound, it is preferred to have compounds with two or more carbodiimide groups in the molecule. Examples of such carbodiimide compounds include "Carbodilite V-02", "Carbodilite V-02-L2", "Carbodilite V-04", "Carbodilite V-06", "Carbodilite E-01", "Carbodilite E-02", and "Carbodilite E-04" (all trade names, manufactured by Nisshinbo Co., Ltd.).

[0091] The adhesive composition of the present invention may also contain other additives without compromising the effectiveness of the present invention. Other additives include, for example, adhesive resins such as (polymerized) rosin resins, (polymerized) rosin ester resins, terpene resins, and terpene phenol resins; plasticizers such as adipate diesters, fumarate diesters, and sebacic acid diesters; wetting agents, softeners, fillers, pigments, dyes, anti-aging agents, thickeners, defoamers, and preservatives such as silicate surfactants, fluorine surfactants, and acetylene glycol surfactants.

[0092] The suitable range of physical property values ​​for the adhesive composition of the present invention is as described below. Furthermore, the following physical property values ​​refer to values ​​measured by the methods described in the examples.

[0093] From the viewpoint of the peel strength of the adhesive composition, after the adhesive composition of the present invention is applied to a substrate and dried, the gel fraction after dissolving in acetone is 20-90% by mass, preferably 30-70% by mass.

[0094] From the viewpoint of high-speed coating, the viscosity of the adhesive composition of the present invention at 25°C is preferably below 500 mPa·s, more preferably 100~500 mPa·s, more preferably 130~400 mPa·s, even more preferably 160~350 mPa·s, and even more preferably 180~320 mPa·s. If the viscosity is below 500 mPa·s, it can support high-speed coating. However, if the viscosity is below 100 mPa·s, there is a possibility of cissing on the coated film.

[0095] Secondly, the re-peeling sheet of the present invention will be explained.

[0096] The re-peeling sheet of the present invention is, for example, having an adhesive layer composed of the aforementioned adhesive composition of the present invention on one or both sides of a sheet-like substrate.

[0097] Here, "repeating sheet" refers to a sheet that can be peeled off after a certain period of time after being attached to the surface of an adhesive such as paper, plastic, or metal, and also includes reusable repeating sheets. Furthermore, re-peeling sheets also include re-peeling tape, re-peeling labels, etc. Furthermore, this description pertains to a re-peeling sheet having an adhesive layer on one side of a sheet-like substrate, but adhesive layers may be present on both sides of the sheet-like substrate, and the adhesive layer itself may be used as a re-peeling sheet, which is also included within the scope of this invention.

[0098] The thickness of the adhesive layer for peeling off the sheet is preferably 5-100 μm, more preferably 10-60 μm, and even more preferably 15-40 μm. If the thickness of the adhesive layer is 5 μm or more, sufficient adhesive performance can be obtained, and if it is less than 100 μm, the overflow of the adhesive layer can be prevented.

[0099] The sheet-like substrate used in the aforementioned re-peeling sheet is not particularly limited, as long as it is a material that can strongly adhere to the adhesive layer composed of the adhesive composition of the present invention. Examples include polyesters such as polyethylene terephthalate, polyethylene terephthalate, and polyethylene naphthalate; polyimide, polyetherimide, polyaramide, polyetherketone, polyetheretherketone, polyphenylene sulfide, poly(4-methylpentene-1) polyethylene, polyethylene, polypropylene, polybutene, polybutadiene, and polymethylpentene. Resin films and their laminates or foams made of polyvinyl chloride, vinyl chloride copolymer, polyurethane, ethylene-vinyl acetate copolymer, ionomer resin, ethylene (meth)acrylic acid copolymer, polystyrene, polycarbonate, fluororesin, low-density polyethylene, linear low-density polyethylene, triacetyl cellulose, etc.; paper substrates such as synthetic paper, metal vapor deposits, coated paper, coated paper, and cellophane made of polyolefin resins, etc.; and laminated paper on such paper substrates with thermoplastic resins such as polyethylene, etc.

[0100] The thickness of the sheet-like substrate should be selected according to the type of substrate used, preferably 5~300μm, and more preferably 10~150μm.

[0101] There is no particular limitation on the thickness of the re-peeled sheet, but 5~300μm is preferred, and 10~200μm is even better. Furthermore, when using polyethylene terephthalate film as the substrate for the sheet, the thickness of the re-peeled sheet is preferably 10~100μm.

[0102] The re-peeling sheet of the present invention can be obtained by coating the adhesive composition of the present invention onto the surface of a sheet-like substrate and drying it to form an adhesive layer. As a method for coating the adhesive composition of the present invention onto the surface of a sheet substrate, known methods can be used, such as gravure coating, bar coating, spray coating, roller coating, die coating, doctor blade coating, air knife coating, lip coating, curtain coating, etc.

[0103] The drying conditions for the formed coated film vary depending on the drying capacity of the coating machine, but it is best to dry it at a temperature of 80°C to 150°C for 5 seconds to 10 minutes. After this drying step, an adhesive layer is formed on the surface of the sheet-like substrate. [Example]

[0104] The adhesive composition and re-peeling sheet of the present invention are specifically illustrated by the following embodiments, but the present invention is not limited to the following embodiments.

[0105] [Example 1] As a monomer of component (B), 80g of 2-ethylhexyl acrylate, 116g of butyl acrylate and 4g of acrylic acid were mixed to prepare a mixed monomer solution. A mixed monomer emulsion (monomer mixture) for dripping was prepared by mixing 200g of mixed monomer liquid, 3.4g of the following compound (a) as component (A) and 56g of ion-exchanged water and 0.4g of ammonium persulfate as polymerization initiator by vibration. In contrast, 100.4 g of deionized water was added to a reaction vessel equipped with a stirrer, reflux cooler, thermometer, nitrogen inlet tube, and dropping funnel, and the temperature was raised to 80°C. Once stable at 80°C, a solution was added to dissolve 0.4 g of ammonium persulfate, the polymerization initiator, in 3.6 g of deionized water. Subsequently, 15 minutes after adding the polymerization initiator, 259.8 g of the mixed monomer emulsion was dropped over 3 hours to induce polymerization. After maturation for 1 hour, the emulsion was cooled and the pH was adjusted to 7-8 using ammonia water to obtain the copolymer emulsion used in the evaluation experiments of this invention.

[0106]

[0107] [Examples 2 and 3] After adding the amount (g) of decyl mercaptan shown in Table 1 as a chain transfer agent to the mixed monomer emulsion from the dropping funnel side, the synthesis was carried out under the same conditions as in Example 1, except for the dropping.

[0108] [Example 4] Except for replacing compound (a) with compound (b), all other compounds were synthesized under the same conditions as in Example 2 with the addition of a chain transfer agent.

[0109]

[0110] [Example 5] Except for replacing compound (a) with compound (c), all other compounds were synthesized under the same conditions as in Example 2 with the addition of a chain transfer agent.

[0111]

[0112] [Comparative Example 1] Except for replacing compound (a) with the following compound (x), all other compounds were synthesized under the same conditions as in Example 1.

[0113]

[0114] [Comparative Example 2] Except for replacing compound (a) with the above-mentioned compound (x), all other compounds were synthesized under the same conditions as in Example 3 with the addition of a chain transfer agent.

[0115] [Comparative Example 3] Except for replacing compound (a) with the following compound (y), all other compounds were synthesized under the same conditions as in Example 1.

[0116]

[0117] [Comparative Example 4] Except for replacing compound (a) with the above-mentioned compound (y), all other compounds were synthesized under the same conditions as in Example 3 with the addition of a chain transfer agent.

[0118] The following evaluation was performed using the obtained adhesive composition. The results are shown in [Table 1].

[0119] [Polymerization Stability] The coagulants generated during the emulsification polymerization step were filtered through a 200-mesh filter cloth. After washing the filter residue with water, the mixture was dried at room temperature for one night. The mass of this coagulant was expressed as a percentage of the mass of the adhesive composition. Furthermore, a lower amount of coagulant in this measurement indicates higher polymerization stability during the emulsification polymerization step, and amounts less than 0.1% by mass were evaluated as high polymerization stability.

[0120] [Average Particle Diameter] A portion of the adhesive composition was removed, and the particle size was measured using a dynamic light scattering-based potentiometric particle size and molecular weight measurement system (manufactured by Otsuka Electronics Co., Ltd., product name ELSZ-1000).

[0121] [Adhesion retention force test] A coating film was applied to the surface of a 25mm × 150mm sheet of 38µm thick PET film using a 4mil coating machine. The film was then dried at 105°C for 3 minutes to form an adhesive layer. Using a 2kg pressure roller, the 25mm × 25mm adhesive side was attached to an SUS board and cured for 24 hours. A 1kg load was then applied, and the time until the test piece fell was measured. The evaluation criteria are as follows. 0: 48 hours or more △: More than 24 hours but less than 48 hours ×: Less than 24 hours

[0122] [Peel force test] Similar to the aforementioned adhesion retention test, an adhesive layer was formed on the surface of the PET film. The adhesive side was then attached to the SUS board using a pressing roller. After curing for 24 hours, the peel force at a 180° angle was measured at a speed of 300 mm / min. The evaluation criteria are as follows: a peel force of 5 N or more but less than 10 N is considered moderate. 〇: 5N or more but less than 10N ×: 10N or more but less than 5N

[0123] [Residual Adhesive Evaluation] After the peel strength test, the residual resin in the SUS plates was colored with pigment and evaluated visually. The evaluation criteria are as follows. 5. The percentage of residual adhesive after peeling off the adhesive is less than 20%. 4. The residual adhesive after peeling off the adhesive is more than 20% but less than 40%. 3. The residual adhesive after peeling off the adhesive is more than 40% but less than 60%. 2. The residual adhesive percentage after peeling off the adhesive is 61% or more but less than 80%. Point 1: The residual adhesive content after peeling off the adhesive is 80% or more.

[0124] [Gel fraction measurement] Similar to the aforementioned adhesion retention test, an adhesive layer was formed on the surface of the PET film. The film was then immersed in acetone for 24 hours, and the gel fraction was calculated from the weight change before and after immersion. The evaluation criteria are as follows, with larger values ​​being considered good. 0:30% or more of the quality △:21-29% of mass ×: 20% or less in mass

[0125]

[0126] It was confirmed that the peelable sheet obtained by using the adhesive composition provided in this embodiment has sufficient adhesive retention force and can be peeled from the adhered object with appropriate peel force, and the residual adhesive on the surface of the adhered object after peeling is small, and the peeling performance is excellent. On the other hand, it was confirmed that when using the adhesive composition provided by the comparative example, the adhesive holding power was not only insufficient, but also residual adhesive was produced, resulting in poor peelability. [Industrial Applicability]

[0127] The adhesive composition of the present invention has excellent adhesion properties to the surface of the adhered object and excellent peelability, so it is suitable for use as an adhesive for re-peeling sheets called adhesive labels and masking tapes.

Claims

1. An adhesive composition comprising a copolymer obtained by polymerizing a monomer mixture for forming repeating structural units with a chain transfer agent, the monomer mixture being composed of at least one unsaturated compound of formula (1) below (A), at least one unsaturated carboxylic acid (B-1), and at least two unsaturated carboxylic acid ester compounds other than component (A); wherein, The aforementioned unsaturated carboxylic acid ester compound is a compound having a structure obtained by reacting an unsaturated carboxylic acid with an alcohol. The unsaturated carboxylic acid in the aforementioned unsaturated carboxylic acid ester compound is selected from acrylic acid, methacrylic acid, crotonic acid, fumaric acid, iconic acid, maleic acid, citrate, 2-carboxyethyl acrylate, or 2-carboxyethyl methacrylate. The aforementioned alcohol is selected from ethanol, propanol, isopropanol, butanol, isobutanol, dibutanol, tributanol, pentabutanol, pentabutanol, pentaethanol, 2-ethylhexanol, nonanol, decanol, undecyl alcohol, dodecanol, tridecanol, tetradecanol, pentadecyl alcohol, vinyl alcohol, allyl alcohol, or benzyl alcohol. In the formula, R1 represents a hydrocarbon group or acetyl group with 8 to 36 carbon atoms, A1 and A2 each independently represent an alkyl group with 2 to 4 carbon atoms, L is the group shown in the general formula (2) below, z represents a number from 1 to 10, X represents a hydrogen atom or an ionic hydrophilic group, m represents a number from 0 to 100, and n represents a number from 0 to 100; In the formula, R2 and R3 each independently represent a hydrogen atom or a methyl group, x represents a number from 0 to 12, and y represents a number of 0 or 1.

2. The adhesive composition of claim 1, wherein in the aforementioned general formula (1), R1 is a branched aliphatic hydrocarbon group or a branched aliphatic acetyl group having 8 to 36 carbon atoms.

3. An adhesive composition as claimed in claim 1 or 2, wherein in the aforementioned general formula (1), X is an anionic hydrophilic group.

4. The adhesive composition of claim 3, wherein in the aforementioned general formula (1), X is an anionic hydrophilic group represented by -SO3M, -R4-SO3M, -R5-COOM, -PO3M2, -PO3MH or -CO-R6-COOM; wherein M represents a hydrogen atom, an alkali metal atom, an alkaline earth metal atom [however, since alkaline earth metal atoms are usually divalent, 1 / 2 mole is equivalent to M], a fourth-order ammonium cation, R4 and R5 represent alkyl groups having 1 to 6 carbon atoms, and R6 represents a divalent hydrocarbon group having 1 to 12 carbon atoms.

5. An adhesive composition as claimed in claim 1 or 2, wherein X in the aforementioned general formula (1) is a cationic hydrophilic group.

6. The adhesive composition of claim 5, wherein in the aforementioned general formula (1), X is a cationic hydrophilic group represented by -R7-NR8R9R10・Y or -Z-NR8R9R10・Y; wherein R7 represents an alkyl group having 1 to 6 carbon atoms, R8 to R10 are each independently represented by an alkyl group having 1 to 4 carbon atoms, an alkyl group having 2 to 4 carbon atoms, or a benzyl group, Y represents a halogen atom or a methyl sulfate group, and Z represents a group represented by -CH2CH(OH)CH2- or -CH(CH2OH)CH2-.

7. An adhesive composition as claimed in claim 1 or 2, wherein in the aforementioned general formula (1), z is a number from 1 to 5.

8. An adhesive composition as claimed in claim 1 or 2, wherein component (B-1) is acrylic acid or methacrylic acid, and component (B-2) is at least two of the group consisting of ester compounds selected from acrylic acid or methacrylic acid.

9. A re-peeling sheet having an adhesive layer composed of an adhesive composition as claimed in any one of claims 1 to 8.

10. A method for manufacturing an adhesive composition, comprising polymerizing a monomer mixture for forming repeating structural units with a chain transfer agent to obtain a copolymer, wherein the monomer mixture is composed of at least one unsaturated compound of formula (1) below (A), at least one unsaturated carboxylic acid (B-1), and at least two unsaturated carboxylic acid ester compounds other than component (A) (B-2); wherein, The aforementioned unsaturated carboxylic acid ester compound is a compound having a structure obtained by reacting an unsaturated carboxylic acid with an alcohol. The unsaturated carboxylic acid in the aforementioned unsaturated carboxylic acid ester compound is selected from acrylic acid, methacrylic acid, crotonic acid, fumaric acid, iconic acid, maleic acid, citrate, 2-carboxyethyl acrylate, or 2-carboxyethyl methacrylate. The aforementioned alcohol is selected from ethanol, propanol, isopropanol, butanol, isobutanol, dibutanol, tributanol, pentabutanol, pentabutanol, pentaethanol, 2-ethylhexanol, nonanol, decanol, undecyl alcohol, dodecanol, tridecanol, tetradecanol, pentadecyl alcohol, vinyl alcohol, allyl alcohol, or benzyl alcohol. In the formula, R1 represents a hydrocarbon group or acetyl group with 8 to 36 carbon atoms, A1 and A2 each independently represent an alkyl group with 2 to 4 carbon atoms, L represents the group shown in the general formula (2) below, z represents a number from 1 to 10, X represents a hydrogen atom or an ionic hydrophilic group, m represents a number from 0 to 100, and n represents a number from 0 to 100; In the formula, R2 and R3 each independently represent a hydrogen atom or a methyl group, x represents a number from 0 to 12, and y represents a number of 0 or 1.

11. Use of a copolymer for manufacturing an adhesive composition, wherein the copolymer is obtained by polymerizing a monomer mixture for forming repeating structural units with a chain transfer agent, the monomer mixture being composed of at least one unsaturated compound of formula (1) below (A), at least one unsaturated carboxylic acid (B-1), and at least two unsaturated carboxylic acid ester compounds other than component (A); wherein, The aforementioned unsaturated carboxylic acid ester compound is a compound having a structure obtained by reacting an unsaturated carboxylic acid with an alcohol. The unsaturated carboxylic acid in the aforementioned unsaturated carboxylic acid ester compound is selected from acrylic acid, methacrylic acid, crotonic acid, fumaric acid, iconic acid, maleic acid, citrate, 2-carboxyethyl acrylate, or 2-carboxyethyl methacrylate. The aforementioned alcohol is selected from ethanol, propanol, isopropanol, butanol, isobutanol, dibutanol, tributanol, pentabutanol, pentabutanol, pentaethanol, 2-ethylhexanol, nonanol, decanol, undecyl alcohol, dodecanol, tridecanol, tetradecanol, pentadecyl alcohol, vinyl alcohol, allyl alcohol, or benzyl alcohol. In the formula, R1 represents a hydrocarbon group or acetyl group with 8 to 36 carbon atoms, A1 and A2 each independently represent an alkyl group with 2 to 4 carbon atoms, L represents the group shown in the general formula (2) below, z represents a number from 1 to 10, X represents a hydrogen atom or an ionic hydrophilic group, m represents a number from 0 to 100, and n represents a number from 0 to 100; In the formula, R2 and R3 each independently represent a hydrogen atom or a methyl group, x represents a number from 0 to 12, and y represents a number of 0 or 1.

Images