JP6554922B2 - Re-peelable water pressure sensitive adhesive - Google Patents

Description

  The present invention relates to a re-peelable water-based pressure sensitive adhesive.

Pressure sensitive adhesive sheets are widely used in removable applications. And the examination of the water-based pressure-sensitive adhesive used for a pressure-sensitive-type adhesive sheet was performed for the purpose of the improvement of removability and the suppression of the contamination at the time of re-peeling.
For example, in Patent Document 1, (a1) 50 to 99.89% by weight of (meth) acrylic acid alkyl ester containing an alkyl group having 4 to 12 carbon atoms, (a2) carboxyl group-containing unsaturated monomer 0.1 to A monomer mixture comprising 10% by weight, (a3) 0.01 to 10% by weight of a carbonyl group-containing unsaturated monomer, and (a4) 0 to 49.89% by weight of another unsaturated monomer. Emulsion obtained by emulsion polymerization in the presence of a type-reactive emulsifier and having a glass fraction of -50 ° C. and less than −25 ° C. and having a gel fraction of less than 70% by weight, [B] hydrazine A re-peelable aqueous pressure-sensitive adhesive comprising a compound and a [C] phosphate ester compound is disclosed.

JP 2006-241419 A

  However, the conventional re-peelable water-based pressure-sensitive adhesive had some high-temperature performance, but it was difficult to achieve both re-peelability when used in a high-temperature atmosphere and durability at high temperatures. . Further, since the adhesiveness between the pressure-sensitive adhesive layer and the substrate is insufficient, there is a problem that contamination (glue residue) occurs when the pressure-sensitive adhesive sheet is peeled off at high speed.

  The present invention provides a pressure-sensitive adhesive sheet that is compatible with re-peelability after use at a high temperature of 100 ° C. or higher (hereinafter, high-temperature re-peelability) and durability, and that suppresses contamination during high-speed peeling. An object is to provide a re-peelable water-based pressure-sensitive adhesive obtained.

The re-peelable water-based pressure-sensitive adhesive of the present invention comprises 50 to 99% by weight of (meth) acrylic acid alkyl ester containing an alkyl group having 2 to 12 carbon atoms, and 1 to 5% by weight in total of acrylic acid and methacrylic acid. An acrylic polymer obtained by emulsion polymerization of a monomer mixture containing, and a phosphate ester compound having an alkyl group having 8 to 14 carbon atoms,
The phosphoric acid ester compound is included in an amount of 0.3 to 2 parts by weight based on 100 parts by weight of the acrylic polymer.

  According to the present invention described above, the re-peelable water-based pressure-sensitive adhesive contains a phosphate ester compound having an alkyl group having 8 to 14 carbon atoms, whereby the pressure-sensitive adhesive sheet obtained is a pressure-sensitive adhesive layer. Since the cohesive strength of the material improved, it was possible to achieve both high temperature removability and durability. Furthermore, the phosphoric acid ester-based compound is hardly compatible with the inside of the pressure-sensitive adhesive layer and has a high ratio at the interface with the adherend, so that contamination at high-speed peeling can be suppressed.

  A re-peelable water-based pressure-sensitive adhesive capable of obtaining a pressure-sensitive adhesive sheet that suppresses contamination at the time of releasability and durability after being used at a high temperature of 100 ° C. or higher according to the present invention and high-speed peeling. Can be provided.

It is a side view which shows the test method of durability.

The re-peelable water-based pressure-sensitive adhesive of the present invention is 50 to 99% by weight of a (meth) acrylic acid alkyl ester containing an alkyl group having 2 to 12 carbon atoms, and 1 to 5% by weight in total of acrylic acid and methacrylic acid. An acrylic polymer obtained by emulsion polymerization of a monomer mixture containing a phosphate ester compound having an alkyl group having 8 to 14 carbon atoms,
The phosphoric acid ester compound is included in an amount of 0.3 to 2 parts by weight based on 100 parts by weight of the acrylic polymer. The monomer is an ethylenically unsaturated monomer.
The re-peelable water-based pressure-sensitive adhesive of the present invention is preferably used as a pressure-sensitive adhesive sheet provided with a base material and a pressure-sensitive adhesive layer by coating. This pressure-sensitive adhesive sheet can be used for permanent adhesion that does not peel and for re-peeling applications, and therefore, re-peeling applications are more preferable. Sheet and tape are synonymous.

  The acrylic polymer used in the present invention is 50 to 99% by weight of (meth) acrylic acid alkyl ester (hereinafter referred to as “(meth) acrylic acid alkyl ester”) containing an alkyl group having 2 to 12 carbon atoms, acrylic acid. And a monomer mixture containing 1.0 to 5% by weight of methacrylic acid is obtained by emulsion polymerization. For example, (meth) acrylate is meant to include methyl acrylate and methyl methacrylate.

  The (meth) acrylic acid alkyl ester is preferably contained in an amount of 50 to 99% by weight, more preferably 70 to 99% by weight, in 100% by weight of the monomer mixture. By including 50 to 99% by weight, it becomes easy to obtain adhesive strength, heat resistance and removability.

  (Meth) acrylic acid alkyl ester is, for example, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, iso-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl ( Examples include meth) acrylate, iso-octyl (meth) acrylate, lauryl (meth) acrylate, iso-nonyl (meth) acrylate, cyclohexyl (meth) acrylate, and benzyl (meth) acrylate.

  The (meth) acrylic acid alkyl ester may be a monomer having an alkoxy group in the side chain of the alkyl group (also referred to as an alkoxy group-containing monomer). Specific examples include 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, 2-phenoxyethyl (meth) acrylate, and methoxypolyethylene glycol (meth) acrylate.

  Moreover, it is preferable that a monomer mixture contains 1 to 5 weight% in total of acrylic acid and methacrylic acid, and 2 to 4 weight% is more preferable. When the content is 1% by weight or more, the removability is further improved. Further, when the content is 5% by weight or less, the durability is further improved.

  The monomer mixture more preferably contains 0.5 to 2% by weight of methacrylic acid. When 0.5% by weight or more of methacrylic acid is contained, high temperature suitability and removability are further improved. Further, when methacrylic acid is contained in an amount of 2.0% by weight or less, the adhesion of the pressure-sensitive adhesive layer to the substrate is improved, and the durability is further improved.

  In addition to acrylic acid and methacrylic acid, acidic monomers such as carboxyl group-containing monomers and acid anhydride group-containing monomers can be used in combination with the monomer mixture.

  Examples of the acidic monomer include β-carboxyethyl acrylate, itaconic acid, crotonic acid, fumaric acid, fumaric anhydride, maleic anhydride, butyl maleate and the like.

  Other monomers that can be included in the monomer mixture include, for example, aminomethyl (meth) acrylate, dimethylaminomethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, (meth) acrylamide, Diacetone (meth) acrylamide, (meth) acrylonitrile, N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, N-phenylmaleimide, N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, N-laurylitaconimide, N- (meth) acryloyloxymethylene succin And N- (meth) acryloyl-6-oxyhexamethylene succinimide, N- (meth) acryloyl-8-oxyoctamethylene succinimide, glycidyl (meth) acrylate, vinyl acetate, styrene, methylstyrene, vinyltoluene and the like. .

  Among the other unsaturated monomers, an acetoacetoxy group-containing monomer is preferably used in combination, and acetoacetoxyethyl (meth) acrylate is preferred because it can further improve removability and heat resistance. The amount used is preferably 0.1 to 0.6% by weight, more preferably 0.2 to 0.5% by weight, in 100% by weight of the monomer mixture. By using 0.1 part by weight to 0.6% by weight, removability, durability and adhesion are further improved.

  In the present invention, the acrylic polymer is obtained by emulsion polymerization of the monomer mixture. The emulsifier used in the emulsion polymerization is preferably appropriately selected from an anionic emulsifier and a nonionic emulsifier. The emulsifier may be a reactive emulsifier having a radical polymerizable functional group, a non-reactive emulsifier having no radical polymerizable functional group, or a combination of both.

Among the emulsifiers in the present invention, the reactive anionic emulsifier is an anionic emulsifier having one or more unsaturated double bonds capable of radical polymerization in the molecule.
Examples of reactive anionic emulsifiers include sulfosuccinic acid ester emulsifiers and alkylphenol ether emulsifiers.

  Non-reactive anionic emulsifiers include, for example, polyoxyethylene polycyclic phenyl ether sulfates, higher fatty acid salts such as sodium stearate, alkylaryl sulfonates such as sodium dodecylbenzenesulfonate, and alkyl sulfate esters such as sodium lauryl sulfate. And polyoxyethylene alkyl ether sulfate salts such as sodium polyoxyethylene lauryl ether sulfate and polyoxyethylene alkyl aryl ether sulfate salts such as sodium polyoxyethylene nonylphenyl ether sulfate.

  Examples of the reactive nonionic emulsifier include polyoxyethylene nonylpropenyl phenyl ether.

Non-reactive nonionic emulsifiers include, for example, polyoxyethylene alkylphenyl ethers such as polyoxyethylene nonylphenyl ether and polyoxyethylene octylphenyl ether; polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether and the like Polyoxyethylene alkyl ethers of the following: polyoxypolycyclic phenyl ethers such as polyoxyethylene distyrenated phenyl ether; polyoxyethylene sorbitan fatty acid esters and the like.
The emulsifier can be used alone or in combination of two or more.

  The emulsifier is preferably used in an amount of 0.5 to 3 parts by weight based on 100 parts by weight of the monomer mixture. By using in the said range, superposition | polymerization stability and removability are improved more.

  The emulsifier is preferably a non-reactive anionic emulsifier because of its good adhesion to the substrate. Among the anionic emulsifiers, polyoxyethylene alkyl ether sulfate is more preferred, and the alkyl chain has 11 to 14 carbon atoms. The polyoxyethylene alkyl ether sulfate ester salt is more preferred.

  The polymerization initiator used for the emulsion polymerization is not particularly limited, and can be appropriately selected from a water-soluble polymerization initiator and an oil-soluble polymerization initiator.

  Examples of the water-soluble polymerization initiator include potassium persulfate, sodium persulfate, ammonium persulfate, hydrogen peroxide, and an ammonium (amine) salt of 4,4'-azobis-4-cyanovaleric acid.

  Examples of oil-soluble polymerization initiators include alkyl peroxides, t-butyl hydroperoxide, cumene hydroperoxide, p-methane hydroperoxide, lauroyl peroxide, 3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, t -Butyl cumyl peroxide, benzoyl peroxide, dichlorobenzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, 3,3,5-trimethylcyclohexanone peroxide, methylcyclohexanone peroxide, di-isobutyl peroxy dicarbonate, di-2-ethylhexyl peroxy dicarbonate, t-butyl peroxy Organic peroxides such as isobutyrate, 2,2′-azobisisobutyronitrile, dimethyl-2,2′-azobisisobutyrate, 2,2′-azobis (2,4-dimethylvaleronitrile), 2 , 2′-azobis (2-methylbutyronitrile), 2,2′-azobis (2-methylamidooxime) dihydrochloride, 2,2′-azobis (2-methylbutanamidoxime) dihydrochloride tetrahydrate, 2,2′-azobis {2-methyl-N- [1,1-bis (hydroxymethyl) -2-hydroxyethyl] -propionamide}, 2,2′-azobis [2-methyl-N- (2- Hydroxyethyl) -propionamide] and the like.

Moreover, the redox initiator which used the oxidizing agent and the reducing agent together as a polymerization initiator is also preferable.
Examples of the oxidizing agent include ammonium persulfate, potassium persulfate, sodium persulfate, hydrogen peroxide, t-butyl hydroperoxide, benzoyl peroxide, and the like.
Examples of the reducing agent include sodium sulfite, acidic sodium sulfite, Rongalite, ascorbic acid and the like.

  The polymerization initiator is preferably used in an amount of 0.01 to 0.5 parts by weight, more preferably 0.05 to 0.4 parts by weight, based on 100 parts by weight of the monomer mixture. By using 0.01-0.5 weight part, the copolymerization property of a monomer improves and re-peelability improves more.

In the present invention, a buffer may be used to adjust the pH as necessary during emulsion polymerization. The buffer is not particularly limited as long as it has a pH buffering action of a reaction solution for emulsion polymerization. Buffering agents include, for example, sodium bicarbonate, potassium bicarbonate, monosodium phosphate, monopotassium phosphate, disodium phosphate, trisodium phosphate, sodium acetate, ammonium acetate, sodium formate, ammonium formate, trisodium citrate, etc. Is mentioned.
The buffer is preferably used in an amount of less than 5 parts by weight and more preferably less than 3 parts by weight with respect to 100 parts by weight of the monomer mixture.

  In the present invention, the emulsion polymerization is preferably, for example, a method in which a monomer is prepared into an emulsion and then synthesized (pre-emulsion method). Emulsion polymerization is a method in which the entire amount of the pre-emulsion is charged in the emulsion polymerization field, or a method in which a part of the pre-emulsion is charged in the emulsion polymerization field and the remaining amount of the pre-emulsion is added or dropped after the reaction is started. It can react by a well-known method.

  In the present invention, the molecular weight of the acrylic polymer can be appropriately adjusted using a chain transfer agent during emulsion polymerization. The chain transfer agent is preferably a thiol compound such as a mercaptan compound, a thioglycol compound, or β-mercaptopropionic acid.

  The chain transfer agent is preferably used in an amount of 0.03 to 0.1 parts by weight, more preferably 0.04 to 0.08 parts by weight, based on 100 parts by weight of the monomer mixture. When 0.03 to 0.1 part by weight is used, the balance between adhesion and removability is further improved.

  The re-peelable water-based pressure-sensitive adhesive of the present invention contains a phosphoric ester compound having an alkyl group having 8 to 14 carbon atoms (hereinafter referred to as a phosphoric ester compound) and thus has good cohesive force and removability. It is. Since the phosphate ester compound has low affinity with the acrylic polymer, it easily shifts to the interface between the pressure-sensitive adhesive layer and the adherend and changes the surface polarity of the pressure-sensitive adhesive layer. Therefore, when left in a high-temperature atmosphere, the cohesive force of the pressure-sensitive adhesive layer is not lowered, and the pressure-sensitive adhesive layer and the adherend are not excessively adhered while the adhesive force is good, and thus the removability is excellent. Further, when a phosphoric ester compound is included, an unexpected effect of good durability can be obtained despite the presence at the interface of the pressure-sensitive adhesive layer. The phosphate ester compound is a compound that does not substantially function as an emulsifier.

  Phosphate ester compounds include, for example, ethyl hexyl diphenyl phosphate, ethyl hexyl acid phosphate, bis (2-ethylhexyl) phosphate, isodecyl acid phosphate, tridecyl phosphite, isotridecyl acid phosphate, oleyl acid phosphate, etc. Is mentioned.

  The phosphate ester compound is more preferably a compound that does not have an alkylene oxide structure and has an alkyl group having a branched structure. Due to the branched structure, the phosphate ester-based compound can further improve the removability. Such a compound is preferably, for example, isodecyl acid phosphate, isotridecyl acid phosphate or the like.

  The phosphate ester compound is preferably used in an amount of 0.3 to 2 parts by weight, more preferably 0.5 to 1.5 parts by weight, based on 100 parts by weight of the acrylic polymer. Use of 0.3 to 2 parts by weight facilitates coexistence of cohesive force and removability.

  The method for producing a re-peelable water-based pressure-sensitive adhesive is (meth) acrylic acid alkyl ester 50 to 99.9% by weight containing an alkyl group having 2 to 12 carbon atoms in the presence of a phosphoric ester compound. A step of emulsion polymerization of a monomer mixture containing 1 to 5% by weight of an acid and methacrylic acid to obtain an acrylic polymer, and 0.3 to 2 phosphoric acid ester compounds with respect to 100 parts by weight of the acrylic polymer. It is preferable to include parts by weight.

  The method of using a phosphate ester compound in the above production method is (1) a method of adding a phosphate ester compound after synthesizing an acrylic polymer. (2) A method of synthesizing an acrylic polymer in the presence of a phosphate ester compound is preferred. Among these, the method (2) is preferable because the removability can be further improved. The method (2) is preferably a pre-emulsion method, that is, emulsion polymerization is carried out after preparing a pre-emulsion by mixing a phosphate ester compound and a monomer.

The re-peelable water-based pressure sensitive adhesive of the present invention can further contain a crosslinking agent.
Examples of the crosslinking agent include a metal crosslinking agent, a zirconium crosslinking agent, an aziridine crosslinking agent, a carbodiimide crosslinking agent, an isocyanate crosslinking agent, an oxazoline crosslinking agent, a hydrazide crosslinking agent, and an epoxy crosslinking agent.

The metal-based crosslinking agent is preferably a zinc-based crosslinking agent, and more preferably zinc oxide.
Among the above crosslinking agents, epoxy-based crosslinking agents are preferable. Among the commercially available products, “TETRAD-C” and “TETRAD-X” manufactured by Mitsubishi Gas Chemical Company are particularly preferable because removability and adhesion are improved.

  The re-peelable water-based pressure sensitive adhesive of the present invention can further contain additives such as leveling agents, preservatives, antifoaming agents, thickeners, and pigment dispersions as optional components.

  The pressure-sensitive adhesive sheet of the present invention comprises a substrate and a pressure-sensitive adhesive layer formed from a re-peelable water-based pressure-sensitive adhesive. Examples of methods for producing pressure-sensitive adhesive sheets include: (1) A re-peelable water-type pressure-sensitive adhesive is applied to a peelable sheet and dried to form a pressure-sensitive adhesive layer, and a substrate is further applied. How to put on. (2) A known method such as a method of forming a pressure-sensitive adhesive layer by applying a re-peelable water-based pressure-sensitive adhesive to a substrate and drying, and further attaching a peelable sheet.

  Examples of the coating method include known methods such as a Mayer bar, an applicator, a brush, a spray, a roller, a gravure coater, a die coater, a lip coater, a comma coater, a knife coater, a river coater, and a spin coater. . There is no restriction | limiting in particular in a drying method, Hot air drying, infrared rays, a pressure reduction method, etc. can be used. The drying temperature is usually preferably about 60 to 180 ° C.

  The thickness of the pressure-sensitive adhesive layer is generally preferably 5 μm to 100 μm, and more preferably 10 μm to 50 μm.

  The substrate is, for example, a sheet material or sheet such as optical film such as paper, cellophane, plastic sheet, rubber, foam, cloth, rubber cloth, resin-impregnated cloth, glass plate, metal plate, wood, polarizing plate. Is mentioned. The substrate may be a single body or a laminate. Further, the base material can be subjected to a peeling treatment or an antistatic treatment on the back surface (the surface opposite to the surface where the pressure-sensitive adhesive layer is directly bonded). Moreover, the said base material can improve adhesiveness with a pressure-sensitive type adhesive layer by coating with a well-known anchor agent.

  The pressure-sensitive adhesive sheet of the present invention can be widely used as an adherend, such as metal, glass, plastic, rubber, wood, and painted surface.

  The use of the pressure-sensitive adhesive sheet of the present invention is not particularly limited, but can be suitably used for various labels, masking tapes, protect films, and the like.

  Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. In the following description, “part” means “part by weight” and “%” means “% by weight”.

(Synthesis Example 1)
96.26 parts 2-ethylhexyl acrylate, 1.75 parts acrylic acid, 1.49 parts methacrylic acid, 0.5 parts acetoacetoxyethyl methacrylate, 0.03 parts octyl thioglycolate as chain transfer agent, phosphate ester As a compound, 1.5 parts of “JP-513” (isotridecyl acid phosphate, manufactured by Johoku Chemical Industry Co., Ltd.) was added and mixed and dissolved. Further, 5.0 parts of RA-9607 (polyoxyethylene alkyl ether sulfate ammonium salt diluted with 24% water (alkyl chain carbon number 12-13) manufactured by Nippon Emulsifier Co., Ltd.) was added as an anionic emulsifier. 23.6 parts of ionic water was added and stirred to obtain an emulsion. The obtained emulsion was put in a dropping funnel.
A four-necked flask equipped with a stirrer, condenser, thermometer and dropping funnel was charged with 46.6 parts of deionized water and 1.0 part of the resulting emulsion, and the remaining emulsion. The amount was charged into a dropping funnel. Next, the inside of the flask was replaced with nitrogen gas, and the internal temperature was raised to 80 ° C. while stirring. 0.6 parts of 10% aqueous ammonium persulfate solution was added. Ten minutes later, while maintaining the internal temperature at 80 ° C., the rest of the emulsion and 2.4 parts of a 10% aqueous ammonium persulfate solution were added dropwise from the dropping funnel over 180 minutes. After completion of the dropwise addition, the reaction was further continued at 80 ° C. for 1 hour, the internal temperature was then cooled to 65 ° C., 0.1 part of 10% aqueous solution of “Perbutyl H-69” (manufactured by NOF Corporation), "0.3 parts of a 10% aqueous solution (manufactured by Fuso Chemical Industry Co., Ltd.) was added three times every 15 minutes, and the reaction was continued for another 60 minutes. Thereafter, the mixture was cooled and neutralized by adding 25% aqueous ammonia at 30 ° C. to obtain an acrylic polymer emulsion having a nonvolatile content of 55% and a pH of 7.5.

(Synthesis Examples 1-6, Comparative Synthesis Examples 1-7)
An acrylic polymer emulsion was obtained by carrying out emulsion polymerization in the same manner as in Synthesis Example 1 except that the raw materials of Synthesis Example 1 and the blending amounts thereof were changed as described in Table 1 or Table 2.

(Comparative Synthesis Example 8)
83.0 parts of n-butyl acrylate, 2.0 parts of acrylic acid, 0.5 part of diacetone acrylamide, 14.5 parts of methyl methacrylate, 0.05 part of 1-dodecanethiol as a chain transfer agent, and Sanyo as an anionic emulsifier 3.16 parts "Eleminol JS-2" manufactured by Kasei Kogyo Co., Ltd. and 41.4 parts of water were mixed and stirred to obtain an emulsion, which was put into a dropping funnel.
In a four-necked flask equipped with a stirrer, a condenser, a thermometer, and the dropping funnel, 31.7 parts of deionized water, 0.26 parts of the above-mentioned “Eleminol JS-2”, sodium acetate trihydrate After 41 parts were charged and heated to 75 ° C. with stirring, 5% (7.23 parts) of the above emulsion was added. Further, after raising the temperature to 80 ° C., 0.8 part of 3% potassium persulfate aqueous solution was added, and then 15 minutes later, the remaining 95% (137.38 parts) of the above emulsion and 3% potassium persulfate aqueous solution 3 .2 parts of the mixed solution was added dropwise over 3.5 hours. After completion of the dropping, the reaction was continued for 2 hours while maintaining the temperature at 80 ° C., then the internal temperature was cooled to 65 ° C., and 2.4 parts of 10% aqueous ammonia solution was added for neutralization. Then, it cooled to 55 degreeC, and after adding 0.5 part of 10% aqueous solution and 0.5 part of 10% L-ascorbic acid aqueous solution made from NOF Corporation "Perbutyl H-69", and making it react for 15 minutes, again , 0.5 part of a 10% aqueous solution of “Perbutyl H-69” and 0.5 part of a 10% L-ascorbic acid aqueous solution were added and reacted for 15 minutes. Then, after cooling to 30 ° C., pH was adjusted to 8.0 using a 10% aqueous ammonia solution, and butyl acid phosphate (“AP-4” manufactured by Daihachi Chemical Industry Co., Ltd.) as a phosphate ester compound. 0.5 part was added to obtain an emulsion. In addition, when the dry coating film of this emulsion was immersed in toluene at 20 ° C. for 24 hours and dried, the ratio of the remaining coating film weight after immersion to the coating film weight before immersion was 50%. The glass transition temperature of the copolymer calculated from the calculation method described in Patent Document 1 was −37.2 ° C.

Abbreviations in Table 1 and Table 2 are as follows.
EHA: 2-ethylhexyl acrylate BA: butyl acrylate AA: acrylic acid MAA: methacrylic acid AAEM: acetoacetoxyethyl methacrylate MMA: methyl methacrylate A: 1-dodecanethiol DAAM: diacetone acrylamide RA-9607: polyoxyethylene alkyl ether 24% water-diluted ammonium tersulfate (manufactured by Nippon Emulsifier Co., Ltd.)
KH-1025: 25% water-diluted product of polyoxyethylene-1- (allyloxymethyl) alkyl ether sulfate ammonium (Daiichi Kogyo Seiyaku Co., Ltd.)
JP-513: Isotridecyl acid phosphate (manufactured by Johoku Chemical Industry Co., Ltd.)
RS-710: polyoxyethylene alkyl ether phosphate (non-volatile content 90%, alkyl chain is a mixture of 12 to 15 manufactured by Toho Chemical Industry Co., Ltd.)
AP-4: Butyl acid phosphate (manufactured by Daihachi Chemical Industry Co., Ltd.)
JS-2: Eleminor JS-2

Example 1
For 100 parts of the acrylic polymer emulsion obtained in Synthesis Example 1, 0.1 part of Adekane B-940 (ADEKA) was used as an antifoaming agent, and Unichem Flex BN-202 (Union) was used as a preservative. (Chemical Co., Ltd.) 0.05 parts, wetting agent Pelex OT-P (Kao Co., Ltd., nonvolatile content 70%) 0.2 parts, further thickened with an alkali thickener (nonvolatile content 28%), A peelable water-based pressure sensitive adhesive was obtained. This is coated on the peelable sheet with a comma coater so that the thickness after drying is 20 g / m ² , dried with a drying oven at 100 ° C. for 120 seconds, and a commercially available high-quality paper is laminated. A pressure sensitive adhesive sheet was obtained.

(Examples 2 to 10, Comparative Examples 1 to 9)
A pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 except that the formulation of Example 1 was changed as described in Tables 3 and 4.
However, Examples 4-7 and 10 are reference examples.

[Test method]
(1) Adhesive strength (JIS Z-0237)
The obtained pressure-sensitive adhesive sheet was prepared as a sample having a length of 100 mm and a width of 25 mm. The peelable sheet was peeled off from the sample in an environment of 23 ° C. and 50% RH, and the exposed pressure-sensitive adhesive layer was attached to a stainless steel plate whose surface was polished, followed by one reciprocation with a 2 kg roll. Immediately after that, the adhesive force was measured to determine the adhesive force immediately after the press bonding. Further, the sample pressed in the same manner as described above was allowed to stand for 78 hours in a 70 ° C. atmosphere, and then further left for 1 hour in a 23 ° C. atmosphere, and then the adhesive strength was measured to obtain the adhesive strength after thermal aging. In addition, the measurement of adhesive force was performed at a peeling angle of 180 ° at a peeling speed of 300 mm / min according to JIS Z-0237. The adhesive force change rate was calculated by the following calculation method. If the adhesive force change rate is within 20%, there is no practical problem.
Adhesive force change rate (%): [(Adhesive force after heat aging) / (Adhesive force immediately after pressure bonding)] × 100 Absolute value is evaluated.

(2) Removability The obtained pressure-sensitive adhesive sheet was prepared as a sample having a shape of length 100 mm × width 25 mm. The peelable sheet is peeled off from the sample in an environment of 23 ° C. and 50% RH, and the exposed pressure-sensitive adhesive layer is attached to a polished stainless steel plate (SUS plate). did. Next, after leaving the sample in a 120 ° C. atmosphere for 24 hours and then in a 23 ° C. atmosphere for 1 hour, the sample was peeled off under the same conditions as in (1) above, and the contamination of the SUS plate was visually observed according to the following criteria. evaluated.
A: No contamination can be confirmed on the SUS plate. Particularly good ○: Contamination is hardly confirmed on the SUS plate. Good Δ: The SUS plate was slightly contaminated. No problem in practical use ×: Remarkable contamination remained on the SUS plate. Impractical

(3) High-speed removability The obtained pressure-sensitive adhesive sheet was prepared as a sample having a length of 100 mm and a width of 25 mm. The peelable sheet was peeled off from the sample in an environment of 23 ° C. and 50% RH, and the exposed pressure-sensitive adhesive layer was attached to a commercially available veneer plate, followed by one reciprocation with a 2 kg roll. Further, after standing in a 40 ° C. atmosphere for 78 hours and then in a 23 ° C. atmosphere for 1 hour, the sample was peeled off in a 180 ° direction at a speed of 1500 mm / min. I commented on.
A: No contamination can be confirmed on the veneer plate. Particularly good ○: Almost no contamination was observed on the veneer board. Good Δ: The veneer plate was slightly contaminated. No problem in practical use ×: Significant contamination remained on the veneer plate. Impractical

(4) Durability The obtained pressure-sensitive adhesive sheet was prepared as a sample having a length of 100 mm and a width of 10 mm.
The peelable sheet was peeled from the sample by 80 mm, and according to FIG. 1, the exposed pressure-sensitive adhesive layer of sample 2 was applied to the polished stainless steel plate 1 and reciprocated once with a 2 kg roll. Further, after leaving Sample 2 in an atmosphere of 80 ° C. for 30 minutes, the 20 mm portion of the pressure-sensitive adhesive layer that is not exposed to the stainless steel plate exposed by completely peeling off the peelable sheet as shown in FIG. By lowering the weight 3, the load 4 was applied in the 90 ° direction of the pressure-sensitive adhesive sheet, and the durability in a high temperature atmosphere (80 ° C.) was evaluated. The evaluation was performed for 10 minutes, and when the pressure-sensitive adhesive sheet was peeled off and dropped, the dropping time was recorded. When the pressure-sensitive adhesive sheet did not fall, the length of the 80 mm portion where the pressure-sensitive adhesive sheet was initially bonded to the stainless steel plate was recorded from the stainless steel plate. In addition, when the sample falls, it is not practical.

(5) Substrate adhesion The obtained pressure-sensitive adhesive sheet was prepared as a sample having a length of 100 mm and a width of 25 mm. The peelable sheet was peeled from the sample in an environment of 23 ° C. and 50% RH, the exposed pressure-sensitive adhesive layer was rubbed with a finger, and the number of times until the substrate was exposed was measured. The test was conducted by five testers, and the average value was evaluated according to the following criteria.
(Double-circle): A base material is not exposed even if it rubs 15 times or more. Especially good: The substrate was exposed 10 times or more and less than 15 times. Good Δ: The base material was exposed 5 times or more and less than 10 times. There is no problem in practical use.
X: The base material was exposed by less than 5 times. Impractical

The symbols in Tables 3 and 4 are as follows.
・ Crosslinking agent A: TETRAD-X (epoxy crosslinking agent, manufactured by Mitsubishi Gas Chemical Company)
B: Zinc Oxide Solution No. 1 (carbonic acid / ammonium / zinc salt 2: 2: 1 30% aqueous solution manufactured by BASF Japan)
C: 5% aqueous solution of adipic acid dihydrazide

  From the results shown in Tables 3 and 4, Examples 1 to 1 which are the re-peelable water-based pressure-sensitive adhesive of the present invention have a small change in adhesive strength after aging, re-peelability, high-speed re-peelability, durability, and substrate. The adhesiveness was satisfied. On the other hand, the pressure-sensitive adhesives of Comparative Examples 1 were poor in any of removability, high-speed removability, durability, and substrate adhesion, and could not satisfy all the characteristics.

1: Stainless steel plate 2: Sample 3: Weight of 50 g 4: Load direction 5: String

Claims (8)

Containing alkyl group having 2 to 12 carbon atoms (meth) acrylic acid alkyl esters, acrylic acid, an acrylic polymer obtained by emulsion polymerization of a monomer mixture containing a main Taakuriru acid and acetoacetoxy group-containing monomer, carbon A phosphate ester compound having an alkyl group having a number of 8 to 14,
In the monomer mixture, the (meth) acrylic acid alkyl ester containing an alkyl group having 2 to 12 carbon atoms is 50 to 96.80 % by weight, the total of acrylic acid and methacrylic acid is 1 to 5% by weight , an acetoacetoxy group The contained monomer is 0.2 to 0.6% by weight ,
The phosphate ester compound does not have an alkylene oxide structure, and an alkyl group has a branched structure,
A re-peelable water-based pressure-sensitive adhesive containing 0.3 to 2 parts by weight of the phosphoric ester compound with respect to 100 parts by weight of the acrylic polymer. The re-peelable water-based pressure-sensitive adhesive according to claim 1, wherein the content of methacrylic acid in the monomer mixture is 0.5 to 2% by weight.   The detachable aqueous pressure-sensitive adhesive according to claim 1 or 2, wherein the acrylic polymer is obtained by emulsion polymerization of a monomer mixture in the presence of the phosphate ester compound. Agent.   The re-peelable water-based pressure sensitive adhesive according to any one of claims 1 to 3, further comprising a crosslinking agent.   The re-peelable water-based pressure-sensitive adhesive according to claim 4, wherein the crosslinking agent is an epoxy-based crosslinking agent. The re-peelable water-based pressure sensitive adhesive according to any one of claims 1 to 5, wherein the acetoacetoxy group-containing monomer is acetoacetoxyethyl (meth) acrylate.   A pressure-sensitive adhesive sheet comprising a substrate and a pressure-sensitive adhesive layer formed from the re-peelable water-based pressure-sensitive adhesive according to any one of claims 1 to 6. In the presence of a phosphoric ester compound having an alkyl group of 8 to 14 carbon atoms, containing alkyl group having 2 to 12 carbon atoms (meth) acrylic acid alkyl esters, acrylic acid, main Taakuriru acid, and acetoacetoxy Including emulsion polymerization of a monomer mixture containing a group-containing monomer to obtain an acrylic polymer,
In the monomer mixture, the (meth) acrylic acid alkyl ester containing an alkyl group having 2 to 12 carbon atoms is 50 to 96.80 % by weight, the total of acrylic acid and methacrylic acid is 1 to 5% by weight , an acetoacetoxy group The contained monomer is 0.2 to 0.6% by weight ,
The phosphate ester compound does not have an alkylene oxide structure, and an alkyl group has a branched structure,
A method for producing a releasable water-based pressure-sensitive adhesive, comprising 0.3 to 2 parts by weight of the phosphoric ester compound relative to 100 parts by weight of the acrylic polymer.

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