JP2002371257A - Wet-surface-adhering pressure-sensitive adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aqueous-dispersion-type pressure-sensitive adhesive which adheres well even to a surface wetted with water. SOLUTION: This adhesive is an emulsion-type acrylic pressure-sensitive adhesive which is prepared by the emulsion polymerization of 100 pts.wt. monomer mixture comprising 50-98 wt.% alkyl (meth)acrylate having a 4-12C alkyl, 2-40 wt.% (alkoxy)polyalkylene glycol (meth)acrylate, and 0-10 wt.% other copolymerizable monomer in an aqueous medium in the presence of 1-20 pts.wt. protective colloid comprising a polyvinyl alcohol resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-dispersed pressure-sensitive adhesive which adheres well to a surface to which moisture has adhered, and a pressure-sensitive adhesive tape or sheet obtained using the same.

[0002]

2. Description of the Related Art Adhesive tapes, sheets, labels, and other adhesive products provided with an adhesive layer on at least one surface of a base material such as paper, cloth, plastic film, etc. are widely used for temporary fixing, fixing, protection, display, etc. It is widely used in homes, offices and industrially. When such an adhesive product is used, the adherend may be a wet surface. For example, when returning frozen food from low temperature to room temperature, the surface of the product will condense, but if you stick a price tag label or binding tape on the product on such a surface, or at a construction site, it will be wet by rainwater or condensation This is the case where an adhesive tape for masking is applied to apply a coating or a sealing material to the surface of a building material, or the case where an adhesive sheet for curing is applied to protect the surface of a building material or the like.

[0003] However, under such conditions that moisture adheres to the surface of the adherend, a general adhesive tape using a pressure-sensitive adhesive, whether rubber-based or acrylic, can be used. Since moisture remains as a thin film between the adhesive and the surface of the pressure-sensitive adhesive, there has been a problem that the adhesive force is significantly reduced, and the operation is seriously hindered. Therefore, it is necessary to wipe off the water, but it is troublesome and it is difficult to completely wipe off the water. In order to solve such a problem, pressure-sensitive adhesives to which a water-absorbing resin or porous fine particles are added have been conventionally proposed, but these have insufficient tackiness or have insufficient adhesion to a wet surface. However, there is a practical problem that the adherend is contaminated when peeled off.

On the other hand, there has been proposed a method of copolymerizing a hydrophilic monomer in an acrylic pressure-sensitive adhesive mainly containing an alkyl (meth) acrylate having a long-chain alkyl group having 4 to 12 carbon atoms as a main monomer. These solutions use a large amount of organic solvents such as toluene in the case of solution polymerization.Therefore, there are problems such as fire and environmental pollution in the manufacturing process. It is suitably used for tape production. However, in these water-dispersed pressure-sensitive adhesives, a surfactant is used in order to stably polymerize in water, but during storage as an adhesive tape or during a period of sticking to an adherend, the surfactant is used as an adhesive. There has been a problem that migration from the inside to the surface causes instability of the adhesive performance. Further, when a hydrophilic monomer is copolymerized at a high ratio, there is a problem that the polymerization stability tends to be poor.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to overcome the above-mentioned drawbacks of the conventional pressure-sensitive adhesive, and to improve the inherent properties of the pressure-sensitive adhesive such as adhesion to a dry surface and non-staining property when peeled off. It is to provide a pressure-sensitive adhesive excellent in adhesion to a wet surface and removability thereafter without lowering the adhesive strength.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies to solve these problems, and as a result, obtained a vinyl polymerizable monomer having a specific composition by emulsion polymerization using a specific protective colloid. It has been found that the above problem can be solved by using the pressure-sensitive adhesive obtained in this way, and the present invention has been completed.

That is, in the present invention (1), 50 to 98% by weight of a (meth) acrylic acid alkyl ester having an alkyl group having 4 to 12 carbon atoms and (meth) acrylic acid (alkoxy) polyalkylene glycol ester Emulsion polymerization was conducted in an aqueous medium using 1 to 20 parts by weight of a polyvinyl alcohol resin as a protective colloid with respect to 100 parts by weight of a mixed monomer containing 40% by weight and 0 to 10% by weight of other copolymerizable monomers as components. This is an emulsion-type acrylic pressure-sensitive adhesive obtained by the above method.

Further, the present invention (2) provides the pressure-sensitive adhesive (1)
Is a pressure-sensitive adhesive tape or sheet obtained by laminating on at least one surface of a substrate.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The term “(meth) acrylic acid” in this specification is meant to include both methacrylic acid and acrylic acid.

The alkyl (meth) acrylate having 4 to 12 carbon atoms in the alkyl group is an ester of (meth) acrylic acid and an alcohol having 4 to 12 carbon atoms.
Here, the alcohol may be linear or branched. Examples of the ester include butyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, isononyl acrylate, decyl acrylate, and the like. Further, one kind or a combination of two or more kinds may be used. This monomer is used in an amount of 50 to 98% by weight based on all monomers used for copolymerization.

The (meth) acrylic acid (alkoxy) polyalkylene glycol ester has the structural formula:

[0012]

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Wherein R ₁ and R ₂ are each independently a hydrogen atom or a methyl group, R ₃ is a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, and n is an integer of 2 to 30. Or (meth) acrylic acid polyalkylene glycol ester or (meth) acrylic acid (alkoxy) polyalkylene glycol ester. Examples of the ester include (meth) diethylene glycol acrylate, (meth) dipropylene glycol acrylate, (meth) triethylene glycol acrylate, (meth) tripropylene glycol acrylate, (meth) polyethylene glycol (meth) acrylate, (Meth) acrylic acid polypropylene glycol, (meth) acrylic acid methoxydiethylene glycol, (meth) acrylic acid methoxydipropylene glycol, (meth) acrylic acid ethoxydiethylene glycol, (meth) acrylic acid ethoxydipropylene glycol, (meth) acrylic acid methoxytrimethyl Examples include ethylene glycol, methoxytripropylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, and methoxypolypropylene glycol (meth) acrylate. Further, one kind or a combination of two or more kinds may be used. This monomer is used in an amount of 2 to 40% by weight based on all monomers used for copolymerization.

The other copolymerizable monomer is not particularly limited as long as it is copolymerizable and does not contradict the purpose, and known monomers can be used. For example, (meth) acrylic acid,
Carboxyl group-containing monomers such as maleic acid, itaconic acid, 2-carboxyethyl acrylate, 2-acyloxyethylsuccinic acid, ω-carboxypolycaprolactone acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, etc. Hydroxyl-containing monomers, amide-based monomers such as (meth) acrylamide and N-methylolacrylamide, vinyl-based monomers such as styrene and vinyl acetate, epoxy-containing monomers such as glycidyl (meth) acrylate, and (meth) acrylonitrile and the like. Other alkyl nitrate (meth) acrylates such as nitrile monomers, methyl acrylate, ethyl acrylate, isopropyl acrylate, stearyl acrylate, etc., triethylene glycol diacrylate, neopentyl glycol dia Relate, mention may be made of polyfunctional monomers such as trimethylolpropane triacrylate. This monomer may be used alone or in combination of two or more. Among all monomers used for copolymerization,
It is appropriately used in the range of 0 to 10% by weight.

The polyvinyl alcohol resin is used as a protective colloid when the above-mentioned mixed monomer is subjected to emulsion polymerization, and has a saponification degree of 70 to 100 mol% and a viscosity of 4% at 20 ° C.
The% aqueous solution viscosity is preferably 100 mPa · s or less.
Among them, a partially saponified type having a low degree of polymerization is particularly preferably used. Most preferably, the degree of saponification is 70-95%, 20
The viscosity of a 4% aqueous solution at 25 ° C. is 25 mPa · s or less. In addition, the saponification degree and the viscosity mentioned here are JISK6726.
It is a value measured according to the “polyvinyl alcohol test method”.

Further, depending on the constitution of the monomer, those having mercapto modification, hydrophobic modification, anion modification, etc. are preferably used. The polyvinyl alcohol resin is used in an amount of 1 to 20 parts by weight based on 100 parts by weight of all monomers.

The emulsion polymerization is not particularly limited except that the above-mentioned emulsion stabilizing means is employed, and known methods and conditions can be applied. For example, a mixed monomer, a polymerization initiator, and the like are added to ion-exchanged water in which a polyvinyl alcohol resin is dissolved, and dispersed and emulsified by a high-speed stirrer. In addition, a method in which a part of the emulsion is polymerized, and the remaining part is continuously or intermittently dropped and polymerized. The concentration of the polyvinyl alcohol resin in the whole emulsion is 0.3 to 12% by weight, and the concentration of all the monomers in the whole emulsion is 30 to 70% by weight. Examples of the polymerization initiator include persulfates such as ammonium persulfate and potassium persulfate, and water-soluble azo compounds such as azobiscyanovaleric acid. The polymerization initiator is suitably used in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of all monomers. Furthermore,
If necessary, additives such as an antifoaming agent, a thickener, and a preservative, a chain transfer agent such as butyl mercaptan and dodecyl mercaptan, and a tackifier resin may be added. Further, if necessary, a polyfunctional compound can be added later to the emulsion pressure-sensitive adhesive liquid as a crosslinking agent. The final solids concentration is
Preferably, it is 30 to 70% by weight.

As described above, various properties such as adhesive strength, cohesive strength, initial tack and the like are designed in accordance with the use and purpose of the final adhesive product by selecting the monomers and additives described above, the amount of the additive, and the like.

The emulsion-type pressure-sensitive adhesive obtained in this manner is an emulsion liquid containing almost no agglomerates, having a milky appearance and having a Newtonian viscosity.

The emulsion-type acrylic pressure-sensitive adhesive liquid thus obtained is coated on at least one surface of a substrate, dried to form a pressure-sensitive adhesive layer, and then cut to form a pressure-sensitive adhesive tape or sheet. it can. Alternatively, a pressure-sensitive adhesive liquid may be applied onto a release paper treated with a release agent such as a silicone resin, dried, and the pressure-sensitive adhesive layer may be transferred to the base material to form a pressure-sensitive adhesive tape or the like. . In this case, the release paper may be wound while being laminated on the substrate / pressure-sensitive adhesive layer, or the substrate / pressure-sensitive adhesive layer may be wound while removing the release paper after transfer.

The base material may be a porous base material such as Japanese paper, kraft paper, coated paper, woodfree paper, crepe paper, synthetic paper, cloth, non-woven fabric, a plastic film such as polypropylene or vinyl chloride, a foam or paper. A composite substrate such as a film may be used. The thickness of the substrate is usually 30 to 200 μm, preferably 50 to 150 μm. When the substrate is in a rolled state, a release agent such as a long-chain alkyl-modified polymer or a silicone compound can be applied to the back surface of the pressure-sensitive adhesive applied surface in advance so that the unraveling does not become too heavy. In addition, when the adhesiveness between the adhesive and the base material is poor, various resins such as acrylic resin are applied in advance as a primer to the adhesive-coated surface to prevent adhesive residue on the adherend during peeling. You can keep it.

The application of the pressure-sensitive adhesive liquid to the base material or the release paper is carried out by a commonly used method, for example, a reverse coater, a comma coater, a lip coater, a die coater, a knife coater, a bar coater, a roll coater and the like.
Drying methods are also commonly used methods, for example, hot air,
(Far) Infrared drying method may be used. The thickness of the pressure-sensitive adhesive layer after drying is generally 5 to 200 μm, preferably 10 to 200 μm.
１００100 μm. When a crosslinking agent is added later, aging is performed at room temperature to 40 ° C. for about 1 to 7 days after drying. The cutting method is also a commonly used method, for example, a method in which the raw material wound into a roll after coating and drying is unwound, cut in a width direction with a slitter and wound into a fixed length on a paper tube or the like,
There is a method in which a roll obtained by rewinding a raw material into a fixed length around a paper tube or the like is cut into a predetermined width by a core cutter.

The pressure-sensitive adhesive tapes and sheets thus obtained, and the labels obtained by punching them into a mold, are widely used for temporary fixing, fixing, protection, display and the like. Among them,
Labels for frozen foods where the adherend may be a wet surface,
It is suitably used for a masking adhesive tape and a curing sheet at a construction site.

[0024]

Example 1 A reaction vessel equipped with a stirrer, a dropping funnel, a nitrogen gas inlet tube, a thermometer and a reflux condenser was charged with 450 parts by weight of ion-exchanged water (hereinafter, parts by weight are simply referred to as parts), polyvinyl alcohol. PVA-217 (manufactured by Kuraray, saponification degree: 88mole%, viscosity of 4% aqueous solution at 20 ° C 22.5 ± 2.0mP
as) was added, and the mixture was heated to 70 ° C. and dissolved by stirring under nitrogen gas water. On the other hand, n-butyl acrylate: 195 parts, methoxy polyethylene glycol # 400
A solution prepared by dissolving 0.9 part of ammonium persulfate in 10 parts of ion-exchanged water and a liquid obtained by mixing 90 parts of methacrylate and 15 parts of acrylic acid (total of 300 parts of monomer) was prepared. And the whole amount of the initiator solution were added to the reaction vessel and reacted for 1 hour. Thereafter, the remaining amount of the monomer mixture was continuously dropped into the container over 2.5 hours. After completion, a solution prepared by dissolving 0.1 part of ammonium persulfate in 10 parts of ion-exchanged water was added, and the mixture was kept in the same state for 2 hours. The reaction was performed to prepare an emulsion type acrylic pressure-sensitive adhesive liquid.

(Examples 2 to 8, Comparative Example 1) Polymerization was carried out in the same manner as in Example 1 at the component mixing ratios shown in Table 1.

[0026]

[Table 1]

Comparative Examples 2 and 3 Polymerization was carried out in the same manner as in the Example except that sodium lauryl sulfate was used as an emulsifier instead of polyvinyl alcohol.

(Preparation of Sample) Using a Japanese paper as a base material as an adhesive support, the coated thickness after drying with a hand applicator was 30 mm.
After coating each with a thickness of μm and drying in a dryer at 105 ° C. for 2 minutes, the pressure-sensitive adhesive surface was covered with release paper coated with a silicone resin, and cut into strips having a width of 15 mm to obtain pressure-sensitive adhesive tape samples.

(Evaluation method) These samples were heated at 23 ° C. and 65%
The specimen was left for one day in an atmosphere of relative humidity and subjected to the tests of the following items.・ Normal adhesive strength JISZ0237 (Adhesive tape / adhesive sheet test method)
Was carried out in accordance with the adhesive strength test method (180 ° peeling method) described above. -Condensation surface adhesive strength After adjusting the temperature of the glass panel as an adherend in a 5 ° C atmosphere for 3 hours or more, the glass panel is heated to about 30 ° C in an atmosphere of 23 ° C and 65% relative humidity.
Immediately after exposure for 2 seconds and dew condensation on the surface, the sample was pressure-bonded with a 2 kg rubber roller and immediately measured for 180 ° adhesive force in the same manner as in the normal adhesive force test.・ Removability: Contamination on the glass surface after leaving it for 1 hour in a state where it is stuck to the glass condensation surface in the same manner as the measurement of adhesion on the condensation surface, grasping the end by hand, and rapidly peeling it off in the 180 ° direction (Glue residue) was visually observed.汚染 indicates no contamination, and × indicates contamination.

(Results) As shown in Table 1, the embodiment of the present invention
In contrast, Comparative Example 1 had no tackiness and lacked basic properties as a pressure-sensitive adhesive, while the normal pressure, the dew surface pressure, and the removability were all good. Comparative Example 2 lacked polymerization stability. Comparative Example 3 had good normal-state adhesive strength, but lacked dew-side adhesive strength.

[0031]

The emulsion-type acrylic pressure-sensitive adhesive of the present invention can be polymerized stably, and has excellent adhesiveness to a wet surface in addition to the original adhesive properties. Because of these effects, the use of the pressure-sensitive adhesive of the present invention makes it possible to suitably obtain, in particular, pressure-sensitive adhesive labels and tapes for frozen foods, masking tapes for wet surfaces, and pressure-sensitive adhesive sheets for curing.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J004 AA08 AA10 AA15 CA02 CA04 CA05 CB01 CB02 CB04 CC02 CC03 DA01 DA04 DB01 EA01 FA01 FA04 FA08 4J040 DD022 DF031 EC232 ED001 FA09 FA10 FA11 FA13 FA18 FA23 FA26 KA38 LA11 NA05 NA06 NA12

Claims (2)

[Claims] 1. The alkyl group has 4 to 12 carbon atoms.
(Meth) acrylic acid alkyl ester 50 to 98% by weight,
Mixed monomer 100 containing 2 to 40% by weight of (meth) acrylic acid (alkoxy) polyalkylene glycol ester and 0 to 10% by weight of other copolymerizable monomers
An emulsion-type acrylic pressure-sensitive adhesive obtained by emulsion polymerization in an aqueous medium using 1 to 20 parts by weight of a polyvinyl alcohol-based resin as a protective colloid with respect to parts by weight. 2. A pressure-sensitive adhesive tape or sheet obtained by laminating the pressure-sensitive adhesive according to claim 1 on at least one surface of a substrate.