JP6674303B2 - Adhesive composition - Google Patents

Description

  The present invention relates to a pressure-sensitive adhesive composition, more specifically, does not significantly increase the peel strength even when used at high temperatures, leaving adhesive on the substrate or breaking the substrate during peeling The present invention relates to a pressure-sensitive adhesive composition having excellent removability without the use of the same.

  Adhesives have been used for various applications, but adhesives having removability such as office sticky notes have been used so that they can be repeatedly peeled and reused. The re-peelable pressure-sensitive adhesive is required to be able to be easily peeled without changing its adhesive force even when it is stuck for a long period of time. It tended to be too high to be able to peel off smoothly again.

Patent Document 1 discloses an adhesive removable sheet containing adhesive microspheres and non-adhesive microspheres. Removability when used below has not been studied.
JP 11-21524 A

  The problem of the present invention is that the peel strength does not significantly increase even when used under high temperature, and the adhesive does not remain on the base material or the base material is not broken at the time of peeling, and the re-peelability is excellent. It is to provide an adhesive composition.

  The present invention includes, as constituent monomers, acrylic resin particles (A) containing at least 2-ethylhexyl acrylate and a silicon group-containing acrylic monomer, having an average particle diameter of 15 to 30 μm, and a glass transition temperature (Tg). An adhesive composition containing an acrylic resin emulsion (B) having a temperature of -40 ° C or lower.

The pressure-sensitive adhesive composition of the present invention does not significantly increase the peel strength even when used at high temperatures, does not leave adhesive on the base material or breaks the base material during peeling, and has a re-peeling property. Excellent. Therefore, Especially suitable for the use of.

  The pressure-sensitive adhesive composition of the present invention contains, as constituent monomers, acrylic resin particles (A) containing at least 2-ethylhexyl acrylate and a silicon group-containing acrylic monomer and having an average particle diameter of 15 to 30 μm. . In the pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition of the present invention, it is presumed that each acrylic resin particle comes out of the head of the pressure-sensitive adhesive layer, and that re-peelability can be ensured by spot bonding with the substrate.

Since the acrylic resin particles themselves need to have tackiness, it is necessary to contain 2-ethylhexyl acrylate as a constituent monomer, and it is preferable to contain 90% by weight or more. Further, by including the silicon group-containing acrylic monomer, the time of re-peeling can be improved, so that it is preferably contained in an amount of 0.1 to 5% by weight.
Specific examples of the silicon group-containing acrylic monomer include 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropyltriethoxysilane. And so-called silane coupling agents, but those having a siloxane structure may also be used.

  In addition, known acrylic monomers can be used. For example, alkyl acrylate monomers such as methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, n-octyl acrylate, isononyl acrylate, lauryl acrylate, stearyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl Alkyl methacrylate monomers such as methacrylate, 2-ethylhexyl methacrylate, and stearyl methacrylate; aromatic vinyl monomers such as styrene, α-methylstyrene, vinyltoluene, and ethylvinylbenzene; vinyl acetate; vinyl propionate; Saturated fatty acid vinyl monomers such as vinyl acrylate, vinyl cyanide monomers such as acronitrile and methacrylonitrile, ethylene, propylene, butadiene Olefinic monomers such as styrene, hydroxyl-containing monomers such as 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate and 2-hydroxy methacrylate, acrylic acid, methacrylic acid, crotonic acid, citraconic acid, itaconic acid, and maleic acid , Carboxyl group-containing monomers such as fumaric acid, ethylene carboxylic anhydrides such as maleic anhydride, monoalkyl esters of ethylene dicarboxylic acids such as monobutyl maleic acid, and ammonium salts or alkali metal salts thereof. Ethylene carboxylic acid acid amides such as ethylene carboxylate, methacrylamide and diacetone acrylamide; ethylene carboxylic acid such as dimethylaminoethyl methacrylate and diethylaminoethyl methacrylate; Esters with alcohol, polyfunctional monomers such as divinylbenzene, ethylene glycol dimethacrylate, and diallyl phthalate.

  As a method for producing acrylic resin particles, water and monomer in which a surfactant and a water-soluble polymer are dissolved are mixed and stirred to disperse the monomer, and then a polymerization initiator is added and heated. A method of polymerizing a monomer may be used. Examples of the surfactant include nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyalkylene alkylphenol ethers, and polyoxyethylene / polyoxypropylene block polymers, sodium alkylbenzene sulfonate, sodium lauryl sulfate, and alkyl sulfosuccinic acid. Anionic surfactants such as ester salts and derivatives thereof, polyoxyalkylene alkyl ether sulfates, polyoxyalkylene alkyl allyl ether sulfates, and cationic surfactants such as alkylamine salts and polyoxyethylalkylamine. And an amphoteric surfactant such as alkyl betaine. Examples of the water-soluble polymer include polyvinyl alcohol.

As the polymerization initiator, a persulfate such as ammonium persulfate or sodium persulfate, an aqueous radical polymerization initiator such as aqueous hydrogen peroxide or t-butyl hydroperoxide, or a mixture thereof can be used. The amount of the polymerization initiator to be used is generally 0.1 to 5 parts by weight, preferably 0.1 to 2 parts by weight, based on 100 parts by weight of the monomer.
Further, by using a polymerization initiator in the presence of a reducing agent, a redox system can be formed. Examples of such a reducing agent include alkali metal salts such as sulfites, hydrogen sulfites, and pyrosulfites, ammonium salts, and carboxylic acids such as L-ascorbic acid and tartaric acid. The amount of the reducing agent to be used is 0.1 to 5 parts by weight, preferably 0.1 to 2 parts by weight, based on 100 parts by weight of the monomer.

  The average particle size of the acrylic resin particles needs to be 15 to 30 μm. When the average particle size is 15 μm or more, the removability is improved, and when the average particle size is 30 μm or less, the adhesive strength during use is excellent. The average particle size can be adjusted by the dispersion state of the monomer. That is, the average particle size can be reduced by increasing the amount of the surfactant or the water-soluble polymer, increasing the stirring speed, or increasing the stirring time. In addition, the average particle diameter in the present invention is a weight average particle diameter measured using Multisizer III (trade name, manufactured by Beckman Coulter, Inc.).

The pressure-sensitive adhesive composition of the present invention contains an acrylic resin emulsion (B) having a glass transition temperature (Tg) of −40 ° C. or lower. The acrylic resin emulsion is obtained by emulsion polymerization of the above-mentioned acrylic monomer. When the glass transition temperature is −40 ° C. or lower, the adhesive strength can be secured.
In addition, as long as the performance is not impaired, an acrylic resin emulsion having a glass transition temperature exceeding −40 ° C. may be used in addition to an acrylic resin emulsion having a glass transition temperature of −40 ° C. or less.

The pressure-sensitive adhesive composition of the present invention preferably contains 100 to 900 parts by weight of acrylic resin particles (A) based on 100 parts by weight of acrylic resin emulsion (B). When the acrylic resin particles (A) are contained in an amount of 100 parts by weight or more, removability is remarkably improved, and when it is 900 parts by weight or less, adhesive strength during use can be secured.

The acrylic resin emulsion of the present invention may further contain, if necessary, a plasticizer, a film-forming aid, a wettability improver, and the like. Examples of the plasticizer include phthalic esters such as dibutyl phthalate and dioctyl phthalate, phosphates such as tributoxyethyl phosphate, and adipic esters such as dimethyladipic acid. Examples of the film-forming auxiliary include alcohols and glycol ethers. In addition to the above various components, an antifoaming agent and a preservative can be included.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but it shows specific examples and is not particularly limited thereto. All parts mean parts by weight.

Preparation of acrylic resin particles 200 parts ion-exchanged water, 1.5 parts sodium dodecylbenzenesulfonate as anionic surfactant, partially saponified polyvinyl alcohol (degree of saponification 87-89 mol /%, degree of polymerization) 2400), and 1 part of the solution was charged and sufficiently stirred under heating to be uniformly dissolved to prepare an aqueous solution.
Next, in another container, 93 parts of 2-ethylhexyl acrylate, 5 parts of acrylonitrile, 1.5 parts of methacrylic acid, 0.5 part of 3-methacryloxypropyltrimethoxysilane which is a silicon group-containing acrylic monomer, and Niper as a polymerization initiator A mixed solution was prepared by charging 0.6 parts of BW (manufactured by NOF CORPORATION, benzoyl peroxide, trade name) and sufficiently stirring. This mixed solution was added to the aqueous solution, and dispersed with a stirrer at a stirring speed of 300 rpm for 10 minutes. A thermometer, a stirrer, a nitrogen inlet tube and a reflux condenser were attached, and nitrogen replacement and temperature rise were started. The reaction started at 65-70 ° C and exothermed violently. This was cooled and maintained at 70 ° C., and a reaction was performed for 3 hours. After the reaction, the mixture was cooled to 40 ° C., and an alkali thickener and aqueous ammonia were sequentially added to obtain an acrylic resin particle dispersion 1 having a viscosity of 700 mPa · s, a pH of 8.0, and an average particle diameter of 30 μm.

Further, the same procedure as in the acrylic resin particle dispersion 1 was performed except that the addition amounts of the surfactant and the polyvinyl alcohol and the dispersion conditions of the mixture were changed as shown in Table 1, and the acrylic resin particle dispersions having different average particle diameters were used. 2 to 4 were obtained.

Further, the preparation of the acrylic resin particle dispersion 1 was carried out in the same manner as the preparation of the acrylic resin particle dispersion 1, except that 0.5 part of ethylene glycol dimethacrylate was added instead of 3-methacryloxypropyltrimethoxysilane. Was 30 μm.

Preparation of acrylic resin emulsion Charge 40 parts of ion-exchanged water, 0.2 parts of diammonium phosphate, 0.07 parts of polyoxyethylene nonylphenyl ether sulfate ammonium ester into a reactor, thermometer, stirrer, nitrogen inlet tube and reflux cooling. The apparatus was attached, and nitrogen replacement and heating were started while stirring.
Next, 26 parts of ion-exchanged water, 0.8 part of dialkyl sulfosuccinate, 2 parts of ammonium polyoxyethylene nonylphenyl ether sulfate and 0.7 part of acrylamide were charged into another container, and the aqueous solution was prepared by sufficiently stirring.
In a separate container, 45.4 parts of 2-ethylhexyl acrylate, 45.4 parts of butyl acrylate, 5 parts of vinyl acetate, 1.5 parts of 2-hydroxyethyl methacrylate, 2 parts of acrylic acid, and 0.03 part of dodecyl mercaptan were prepared to prepare a monomer solution. The prepared aqueous solution was added and stirred to prepare an emulsified monomer liquid.
Further, 0.5 part of ammonium persulfate was dissolved in 5 parts of ion-exchanged water to prepare a polymerization initiator solution.
3.7% of the emulsified monomer solution was added to the reactor, and after 10 minutes, 12% of the polymerization initiator solution was added, and seed polymerization was performed for 30 minutes from the start of heat generation. Next, the remaining emulsified monomer solution and polymerization initiator solution were added dropwise over 4 hours while maintaining the reaction system at 80 ° C. ± 3 ° C. After the completion of the dropwise addition, the temperature was further maintained at 80 ° C. ± 3 ° C. for 2 hours. After completion of the polymerization, the mixture was cooled to 40 ° C., and an antifoaming agent and a preservative were added to obtain an acrylic resin emulsion 1.

Preparation of pressure-sensitive adhesive composition On the basis of solid content, 100 parts of acrylic resin particles and 100 parts of acrylic resin particles and carbodilite, a carbodiimide-based cross-linking agent, based on 100 parts of the acrylic resin emulsion (trade name, manufactured by Nisshinbo Chemical Inc.) By mixing 0.5 part, the pressure-sensitive adhesive composition of Example 1 was obtained.

Evaluation method Each pressure-sensitive adhesive composition was applied on a coated paper using a bar coater so that the film thickness after drying was 10 μm, and dried under a 110 ° C. atmosphere for 1 minute, and then bonded with another coated paper. Was. By pressing back and forth by two reciprocations with a roller, leaving it in an atmosphere of 23 ° C. for 24 hours, the width becomes A test specimen measuring 25 mm was prepared.
The test piece was peeled in a 180 ° direction at a pulling speed of 300 mm / min, and the adhesive strength was measured. Those having an adhesive strength of 1 N / 25 mm or more were evaluated as ○, and those having an adhesive strength of less than 1 N / 25 mm were evaluated as x.
In addition, the peeling property was evaluated by confirming whether the adherend was broken at the time of peeling. Those in which the adherend did not break were evaluated as ○, and those in which the adherend broke were evaluated as x.
In addition, it was confirmed whether or not the pressure-sensitive adhesive was adhered to the adherend after peeling, and adhesive residue was confirmed. The sample to which no adhesive was attached was evaluated as ○, and the sample to which the adhesive was attached was evaluated as ×.

After the test specimen was further left for 7 days in an atmosphere of 40 ° C., the adhesive strength was measured in the same manner. Compared to the adhesive strength before standing for 7 days in an atmosphere of 40 ° C., those with an increase in adhesive strength of 20% or less were evaluated as ○, and those with more than 20% were evaluated as x.

Each of the pressure-sensitive adhesive compositions of the examples had sufficient adhesive strength and good releasability, and maintained releasability even when exposed to high temperatures. On the other hand, in each of the pressure-sensitive adhesive compositions of Comparative Examples, one of the performances was insufficient.

Claims (4)

Acrylic resin particles (A) containing at least 2-ethylhexyl acrylate and a silicon group-containing acrylic monomer having an average particle diameter of 15 to 30 μm as constituent monomers, and having a glass transition temperature (Tg) of −40 ° C. or less acrylic resin containing emulsion (B), pressure-sensitive adhesive composition constituting ratio of the silicon group-containing acrylic monomer in the (a) is characterized by 0.1 to 5 wt% der Rukoto is.   2. The pressure-sensitive adhesive composition according to claim 1, wherein 2-ethylhexyl acrylate is 90% by weight or more as a ratio of a constituent monomer of the acrylic resin particles (A).   The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the acrylic resin particles (A) are contained in an amount of 100 to 900 parts by weight based on 100 parts by weight of the acrylic resin emulsion (B). An adhesive layer, wherein the adhesive composition according to any one of claims 1 to 3 is formed to a thickness of 5 to 20 µm.