JP2002105422A - Aqueous dispersion type pressure-sensitive repeelable adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a one-component aqueous dispersion type, pressure-sensitive, repeelable adhesive that can be used for adhesive labels and/or sheets that has excellent adhesion, and that can be easily peeled off the surface of an object even when it is left as it is for a long time after it has been adhered to the object. SOLUTION: This aqueous dispersion type, pressure-sensitive, repeelable adhesive comprises (A) an aqueous dispersion composed of two layers of layer (a) made of a copolymer having, as a main component, an alkyl (meth)acrylate having a 4-12C alkyl group and comprising 0-2 wt.% of a carbonyl group- containing unsaturated monomer based on 100 wt.% of the total monomer mixture in layer (a), and layer (b) made of a copolymer having, as a main component, an alkyl (meth)acrylate having a 4-12C alkyl group and comprising 0.1-5 wt.% of a carbonyl group-containing unsaturated monomer based on 100 wt.% of the total monomer mixture in layer (b), wherein the content of the carbonyl group-containing unsaturated monomer in layer (a) is <=1/2 of that in layer (b), and (B) a hydrazine derivative having at least two hydrazino groups in a molecule.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention can be used as an adhesive for adhesive labels, tapes, sheets, and surface protective films, has excellent adhesiveness, and is attached to various adherends (metal plates, plastic plates, etc.). The present invention relates to a water-dispersible pressure-sensitive adhesive for re-peeling which can be easily peeled even after being left for a long time.

[0002]

2. Description of the Related Art Adhesive labels are used for price labels, process control labels, home delivery address labels, and the like.
In many cases, after being attached to an adherend in these applications, the adhesive is peeled off from the adherend after a certain period of time. At this time, a part of the pressure-sensitive adhesive often remains on the adherend. In addition, when the base material is paper, the strength of the paper is low, so that it is often difficult to peel the paper from the adherend due to paper breakage. Conventionally, a removable pressure-sensitive adhesive has been proposed so that the adhesive can be easily peeled off from an adherend without such a problem.

[0003] Japanese Patent Publication No. 5-075034 discloses an aqueous pressure-sensitive adhesive characterized in that a polyglycidyl compound is blended in an aqueous copolymer emulsion having a specific monomer composition, molecular weight, glass transition temperature and particle size. Have been. However, when a polyglycidyl compound is blended with the emulsion in this pressure-sensitive adhesive, the cross-linking reaction between the particles of the emulsion proceeds, causing an increase in viscosity and gelation.
There is a problem of pot life after blending the polyglycidyl compound.

Japanese Patent Publication No. 58-22492 discloses an emulsion copolymerization of a monomer containing an alkyl acrylate, an ethylenically unsaturated carboxylic acid and a monomer having two vinyl groups. A pressure-sensitive adhesive in which a monovalent metal ion is added to the obtained copolymer emulsion is disclosed. Since this emulsion utilizes ionic cross-linking, it is not necessary to mix a cross-linking agent immediately before use, and it can be made into one liquid. However, if it is stored for a long time after application, the adhesive strength increases and the removability decreases. is there.

JP-A-6-158010 discloses a resin obtained by emulsion-polymerizing a monomer mixture containing 0.1 to 5% by weight of a carbonyl group-containing unsaturated monomer using a chain transfer agent. An aqueous adhesive composition comprising an aqueous dispersion and a hydrazine derivative having at least two hydrazino groups in the molecule is disclosed. This composition provides a stable performance even after the hydrazine derivative is compounded, so that it can be made into one liquid. However, the pressure-sensitive adhesive sheet using the pressure-sensitive adhesive has removability at the initial stage of application, but has a long length after application. If stored for a long period of time, there is a problem that the adhesive strength increases and the removability decreases.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to use an adhesive label which has excellent adhesiveness and can be easily peeled off from the surface of an adherend even after being left for a long time after being adhered to the adherend. It is an object of the present invention to provide a water-dispersible pressure-sensitive adhesive for one-component re-peeling.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies in order to achieve the above object, and as a result, when emulsion polymerization of an acrylic monomer was carried out, the functional group contained in the monomer composition was simply removed. Polymer particles having a two-layer composition having different monomer contents or two types of polymer particles having different functional group monomer contents in the monomer composition are formed and blended. It was found that by blending a hydrazine derivative having two hydrazino groups with the obtained aqueous dispersion, it can be easily peeled off from the surface of the adherend even after being left for a long time after pasting, to complete the present invention. Reached.

That is, (A) the alkyl group has 4 carbon atoms.
To 12% by weight of (meth) acrylic acid alkyl ester, and 0 to 2% by weight of a carbonyl group-containing unsaturated monomer.
(A layer composed of a copolymer containing 100% by weight of the total of the monomer mixture of the a layer) and an alkyl group having 4 to 4 carbon atoms.
12 (meth) acrylic acid alkyl ester as a main component, and 0.1 to 5% by weight of a carbonyl group-containing unsaturated monomer.
(A total of 100% by weight of the monomer mixture of the b layer) and a b layer made of a copolymer containing
An aqueous dispersion wherein the content of the carbonyl group-containing unsaturated monomer in the layer is not more than １ ／ of the content of the carbonyl group-containing unsaturated monomer in the layer b, and (B) at least two It contains a hydrazine derivative having a hydrazino group,
When the monomer mixture of the layer a constituting the aqueous dispersion is 10 to 9
0 parts by weight, the monomer mixture of the layer b is 90 to 10 parts by weight, the monomer mixture of the layer a is polymerized, and then the monomer mixture of the layer b is polymerized. Adhesive.

Further, (A) the alkyl group has 4 to 1 carbon atoms.
2 (meth) acrylic acid alkyl ester as a main component, and 0 to 2% by weight (a
(A total of the monomer mixture of the particles is 100% by weight).
12 (meth) acrylic acid alkyl ester as a main component, and 0.1 to 5% by weight of a carbonyl group-containing unsaturated monomer.
(The total of the monomer mixture of the particles b is 100% by weight.)
The copolymer is composed of two types of copolymer particles with the b particles comprising the copolymer, and the content of the carbonyl group-containing unsaturated monomer of the a particles is the content of the carbonyl group-containing unsaturated monomer of the b particles. An aqueous dispersion having a content of not more than 1/2, and (B) a particle comprising the hydrazine derivative having at least two hydrazino groups in a molecule, and the polymer particles comprising 10 to 90% by weight. Part and b particles are 90 to 10 parts by weight, a water-dispersible pressure-sensitive adhesive for re-peeling.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail. The water-dispersible pressure-sensitive adhesive for re-peeling of the present invention is an aqueous dispersion constituting two layers, and in order to obtain good re-peelability, the a layer constituting the aqueous dispersion is 10 to 90 parts by weight. ,
It is necessary that the amount is preferably 20 to 80 parts by weight, and the amount of the layer b is 90 to 10 parts by weight, preferably 80 to 20 parts by weight. When the proportion of the a layer is less than 10 parts by weight or more than 90 parts by weight, the removability is reduced.

The monomer mixture constituting the a-layer used in the present invention comprises, as a main component, an alkyl (meth) acrylate having an alkyl group having 4 to 12 carbon atoms, and a carbonyl group-containing unsaturated monomer. The copolymer contains 0 to 2% by weight (the total of the monomer mixture in the a layer is 100% by weight), and preferably has a glass transition temperature of -20 ° C or lower. Specific examples of the alkyl (meth) acrylate having 4 to 12 carbon atoms in the alkyl group include butyl (meth) acrylate,
2-ethylhexyl (meth) acrylate, isononyl (meth) acrylate, isooctyl (meth) acrylate,
Lauryl (meth) acrylate and the like can be mentioned, and at least one selected from these groups can be used. Further, a polymerizable unsaturated monomer other than the carbonyl group-containing unsaturated monomer copolymerizable with the alkyl (meth) acrylate can also be used. For example, the alkyl group such as methyl methacrylate, ethyl acrylate and isopropyl acrylate has 1 to 3 carbon atoms, and the alkyl group such as alkyl (meth) acrylate, tridecyl methacrylate, and stearyl acrylate has 13 to 13 carbon atoms. 18 hydroxyl-containing monomers such as alkyl (meth) acrylates, hydroxyalkyl (meth) acrylates, and glycerin di (meth) acrylate; and carboxyl-containing monomers such as maleic anhydride, (meth) acrylic acid, and itaconic acid. Monomer, vinyl acetate, styrene, (meth) acrylonitrile, N-vinylpyrrolidone, (meth) acryloylmorpholine, cyclohexylmaleimide, isopropylmaleimide, (meth) acrylamide, N, N-dimethyl (meth) acrylamide, (meth) acrylic acid Glycidyl, etc. Among them, at least selected from these groups 1
More than one species can be used.

The carbonyl group-containing unsaturated monomer constituting the a layer used in the present invention is, for example, acrolein, diacetone acrylamide or formylstyrene, preferably a vinyl alkyl ketone having 4 to 7 carbon atoms. For example, vinyl methyl ketone, vinyl ethyl ketone,
Acetoacetoxyethyl (meth) acrylate, diacetone (meth) acrylate, acetonyl acrylate, 2-hydroxypropyl acrylate-acetyl acetate, butanediol-
Examples include 1,4-acrylate-acetyl acetate, and at least one selected from these groups can be used.

In the monomer mixture constituting the layer a, alkyl (meth) acrylate having an alkyl group of 4 to 12 carbon atoms, a carbonyl group-containing monomer and other polymerizable unsaturated monomers are used. Each amount can be selected so that the glass transition point of the copolymer is usually -20 ° C or lower. The alkyl (meth) acrylate having 4 to 12 carbon atoms in the alkyl group is used as a main component at a ratio of 80% by weight or more of all monomers, and the carbonyl group-containing monomer is Among them, it is used in a ratio of 0 to 2% by weight. The content of the carbonyl group-containing unsaturated monomer used in the a layer needs to be １ ／ or less of the content of the carbonyl group containing unsaturated monomer in the b layer. If the amount used exceeds １ ／, the removability will decrease.

The monomer mixture constituting the layer b used in the present invention comprises, as a main component, an alkyl (meth) acrylate having an alkyl group having 4 to 12 carbon atoms, The same ones as the alkyl (meth) acrylate having a number of 4 to 12 can be used. As a main component, it is used in a proportion of 80% by weight or more of all monomers.

The carbonyl group-containing unsaturated monomer constituting the layer b used in the present invention may be the same as the above-mentioned layer a. 0.1 to 5% by weight. Outside of these ranges, any of the properties, such as adhesive strength and removability, deteriorate.

As the polymerizable unsaturated monomer other than the carbonyl group-containing unsaturated monomer copolymerizable with the alkyl (meth) acrylate, the same as the above-mentioned layer a can be used.

The removable water-dispersible pressure-sensitive adhesive of the present invention is prepared by first emulsion-polymerizing a monomer mixture constituting one layer, and then, in the polymerization system, a monomer constituting the other layer. By a two-stage polymerization method in which a mixture is added and emulsion polymerization is performed, an aqueous dispersion in which polymer particles having a two-layer structure are emulsified and dispersed in water is obtained. Preferably, it can be obtained by a two-stage emulsion polymerization method in which the monomer mixture constituting the layer a is emulsion-polymerized, and then the monomer mixture constituting the layer b is added to the polymerization system and emulsion-polymerized. It is obtained from an aqueous dispersion in which polymer particles having a two-layer structure of a layer and b layer are emulsified and dispersed. The ratio of the monomer mixture constituting the a layer and the monomer mixture constituting the b layer is such that the monomer mixture constituting the a layer is 10 to 90 parts by weight, preferably 20 to 80 parts by weight, Is 90 to 10 parts by weight, preferably 80 to 20 parts by weight.

In the two-stage polymerization method, a monomer mixture constituting one component and at least water, a surfactant and a polymerization initiator are charged into a reaction vessel at once, and emulsion polymerization is carried out. A water-based surfactant mixture and a polymerization initiator, if necessary, in a single reaction vessel to carry out emulsion polymerization (A polymerization method); After the emulsion polymerization is carried out by dropping the mixture into a reaction vessel charged with an initiator and a polymerization initiator, the other monomer mixture is continuously mixed with water, a surfactant and a polymerization initiator, if necessary. Emulsion polymerization by dropping into a container (B polymerization method) or a method in which a monomer mixture constituting one of them is emulsified in advance with water and a surfactant is mixed with water and, if necessary, a surfactant or a polymer. Reaction vessel charged with initiator After the emulsion polymerization by dropping, the other monomer mixture was previously emulsified with water and a surfactant in advance, and the same reaction was conducted, where necessary, water, a surfactant and a polymerization initiator were charged. There is a method in which emulsion polymerization is carried out by dropping the mixture into a container (C polymerization method), or a method using a combination of these methods. The water-dispersible pressure-sensitive adhesive for re-peeling of the present invention can be produced by any of these methods, but the C polymerization method is suitable because of the reaction stability at the time of polymerization and the like.

In the emulsion polymerization of the aqueous dispersion of the present invention, 2,2'-azobis (2-
Methylpropionamidine) dihydrochloride, azo compounds such as 2,2'-azobis (2-amidinopropane) dihydrochloride, persulfates such as potassium persulfate and ammonium persulfate, benzoyl peroxide, t-butyl hydroperoxide And peroxides such as hydrogen peroxide. Further, a redox initiator comprising a combination of a persulfate and sodium bisulfite or a combination of a peroxide and sodium ascorbate can also be used. Usually, a predetermined amount of these polymerization initiators may be added at each stage of the emulsion polymerization to carry out the polymerization reaction.

In the emulsion polymerization of the aqueous dispersion of the present invention, an appropriate amount of an anionic or nonionic emulsifier is used in order to secure polymerization stability. Specific examples of the anionic emulsifier include sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkyl phenyl ether sulfate, and the like. Examples of the nonionic emulsifier include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, and the like, and at least one or more selected from these groups can be used. Further, a radical polymerizable emulsifier into which a propenyl group or the like has been introduced can also be used. These emulsifiers can be used alone or in combination.

The hydrazine derivative having at least two hydrazino groups in the molecule used in the present invention is 2 to 10
Dihydrazide, which is a dehydration condensate of a dicarboxylic acid having preferably 4 to 6 carbon atoms with hydrazine, such as oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, sebacine Acid dihydrazide, maleic acid dihydrazide, fumaric acid dihydrazide,
Itaconic dihydrazide and the like; aliphatic water-soluble dihydrazine having 2 to 4 carbon atoms, for example, ethylene-1,2
-Dihydrazine, propylene-1,3-dihydrazine,
Butylene-1,4-dihydrazine and the like, and at least one or more selected from this group can be used.

The proportion of the hydrazine derivative used in the present invention is 0.05 to 5 mol, preferably 0.2 to 3 mol of the hydrazino group per mol of the carbonyl group in the component (A).
Is a mole. Outside of these ranges, the adhesive strength and the removability are reduced.

The removable water-dispersible pressure-sensitive adhesive of the present invention may be an aqueous dispersion composed of two kinds of polymer particles. The a particles constituting the aqueous dispersion are 10 to 90 parts by weight, preferably 20 to 80 parts by weight, and the b particles are 9 to 90 parts by weight.
It is necessary to be 0 to 10 parts by weight, preferably 80 to 20 parts by weight. When the proportion of the particles a is less than 10 parts by weight or more than 90 parts by weight, the removability after being left for a long time after application is reduced.

The water-dispersible pressure-sensitive adhesive for re-peeling of the present invention is obtained by emulsion polymerization of a monomer mixture constituting the a particles to obtain an aqueous dispersion in which the a particles are emulsified and dispersed in water. The emulsion mixture of the monomer mixture constituting the b particles is subjected to emulsion polymerization to obtain an aqueous dispersion in which the b particles are emulsified and dispersed in water. 90% by weight, preferably 20 to 80% by weight;
It is obtained by blending so as to be 10 to 10% by weight, preferably 80 to 20% by weight. The monomer mixture constituting the particles a has an alkyl group having 4 to 12 carbon atoms.
(Meth) acrylic acid alkyl ester as a main component,
The unsaturated monomer having a carbonyl group is contained in an amount of 0 to 2% by weight (total of the monomer mixture of the a particles is 100% by weight). Used. In addition, the monomer mixture constituting the b particles is mainly composed of an alkyl (meth) acrylate having an alkyl group of 4 to 12 carbon atoms and a carbonyl group-containing unsaturated monomer of 0.1 to 5 carbon atoms. % By weight (total of the monomer mixture of the b particles is 100% by weight), and the content of the carbonyl group-containing unsaturated monomer in the a particles is the content of the carbonyl group-containing unsaturated monomer in the b particles. Less than 1/2 of the rate.
The same monomers as those described above for the layer b are used. As the polymerization initiator and the emulsifier, the same ones as in the above-described two-stage polymerization can be used. A removable water-dispersible pressure-sensitive adhesive comprising the obtained aqueous dispersion and a hydrazine derivative having at least two hydrazino groups in the molecule.

The water-dispersible pressure-sensitive adhesive for re-peeling of the present invention is an aqueous dispersion containing two-layered polymer particles of the a layer and the b layer prepared as described above, or the a particle and the b particle. In any type of the aqueous dispersion containing the two types of polymer particles of the above, in the aqueous dispersion, various additives as long as the effect of the present invention is not affected if necessary, for example,
Tackifying resins, crosslinking agents, plasticizers, softeners, fillers, pigments, dyes, antioxidants, thickeners, defoamers, preservatives, and the like can be added.

The water-dispersible pressure-sensitive adhesive for re-peeling of the present invention can be directly coated on a suitable support such as plastic film, paper, metal foil, etc., and dried by a usual method for producing pressure-sensitive adhesive sheets. Or after being coated on a separator and dried, and then transferred onto an appropriate support, it is possible to obtain a pressure-sensitive adhesive sheet for re-peeling in the form of a sheet or a tape. .

[0027]

The present invention will be described below in more detail with reference to examples. Note that the present invention is not limited only to the following examples. In the following, “parts” or “%” means “parts by weight” or “% by weight”.

Example 1 Separately, 48.8 parts of 2-ethylhexyl acrylate, 1 part of acrylic acid, 0.2 parts of diacetone acrylamide, sodium polyoxyethylene alkylphenyl ether sulfate (48.8 parts of a monomer mixture emulsion for layer a) A product emulsified with 1.5 parts of Kao Corporation (trade name: Revenol WZ) and 28 parts of ion-exchanged water is prepared. Separately, 48 parts of 2-ethylhexyl acrylate, 1 part of acrylic acid, 1 part of diacetone acrylamide as a monomer mixed emulsion for the layer b, sodium polyoxyethylene alkylphenyl ether sulfate (trade name Revenol WZ, manufactured by Kao Corporation) 1 .5 copies,
A solution emulsified with 28 parts of ion-exchanged water is prepared. 28 parts of ion-exchanged water and nitrogen were sealed in a reactor equipped with a thermometer, a stirrer, a dropping device, a reflux condenser, and a nitrogen inlet tube. While maintaining the internal temperature of the reactor at 80 ° C., 2 parts of a 5% strength aqueous solution of potassium persulfate was added, and the monomer-mixed emulsion for layer a was immediately dropped continuously over 2 hours. %
Emulsion polymerization was carried out while dropping 2 parts of concentrated potassium persulfate aqueous solution. Immediately after the completion of the dropwise addition of the monomer mixture emulsion for layer a, b.
The monomer mixture emulsion for layer is continuously dropped over 2 hours,
Similarly, emulsion polymerization was carried out while 2 parts of a 5% aqueous solution of potassium persulfate was added dropwise in parallel. After completion of the dropwise addition, the mixture was aged for 2 hours while maintaining the internal temperature at 80 ° C. Then, it cooled to room temperature. Neutralized with aqueous ammonia, adjusted to 50% solids, viscosity 2
An aqueous dispersion having a two-layer structure of 00 mPa · s and pH 8.0 was obtained. Further, a polyacrylic acid-based thickener (made by Rohm and Haas Co., Ltd., trade name: ASE-60) was added to add 1
Viscosity was increased to 000 mPa · s (B-type viscometer), and 0.3 parts of adipic dihydrazide dissolved in 10% of ion-exchanged water with respect to 100 parts of solid content was added and mixed well. A water-dispersible pressure-sensitive adhesive for re-peeling was prepared. The adhesive is applied to a release paper so as to have a thickness of 25 μm after drying, and after drying at 100 ° C. for 1 minute, high-quality paper (64 g / m ² )
After leaving for 7 days in an atmosphere of 23 ° C. and 65% RH, an adhesive label for re-peeling was obtained. The test results showed that the removability and the stability over time were all good. The results are shown in Table 1.

Examples 2 to 6 Examples 2, 3, 4, 5, and 6 were prepared in the same manner as in Example 1 except that the types and amounts of monomers were changed as shown in Table 1. A pressure-sensitive adhesive was obtained, and a crosslinking agent was added in the same manner as in Example 1 to obtain a re-peelable pressure-sensitive adhesive label. The test results showed that the removability and the stability over time were all good. The results are shown in Tables 1 and 2.

Example 7 (a) Preparation of Aqueous Dispersion for Particles A reactor equipped with a thermometer, a stirrer, a dropping device, a reflux condenser, and a nitrogen inlet tube was charged with 14 parts of ion-exchanged water and nitrogen. While maintaining the temperature at 80 ° C., 1 part of a 5% strength aqueous potassium persulfate solution was added, and immediately 48.8 parts of separately prepared 2-ethylhexyl acrylate and 1 part of acrylic acid
Parts, 0.2 parts of diacetone acrylamide, 1.5 parts of sodium polyoxyethylene alkylphenyl ether sulfate (trade name: Revenol WZ, manufactured by Kao Corporation) and 28 parts of ion-exchanged water were continuously emulsified over 4 hours. 5% aqueous potassium persulfate solution 2
The mixture was added dropwise to carry out emulsion polymerization. After completion of the dropwise addition, the mixture was aged at 80 ° C. for 2 hours and cooled to room temperature to obtain an aqueous dispersion for a particles. Production of b-particle aqueous dispersion In a separate reactor equipped with a thermometer, a stirrer, a dropping device, a reflux cooling pipe, and a nitrogen introduction pipe, 14 parts of ion-exchanged water and Nitrogen was sealed, and while maintaining the internal temperature of the reactor at 80 ° C., 1 part of a 5% strength aqueous solution of potassium persulfate was added, and 48 parts of separately prepared 2-ethylhexyl acrylate, 1 part of acrylic acid, and diacetone acrylamide 1 part Sodium polyoxyethylene alkylphenyl ether sulfate (trade name: Revenol WZ, manufactured by Kao Corporation) 1.5 parts, emulsified with 28 parts of ion-exchanged water, while maintaining the internal temperature of the reactor at 80 ° C., 4 parts
The solution was continuously dropped over a period of time, and 2 parts of a 5% strength aqueous solution of potassium persulfate was dropped in parallel to carry out emulsion polymerization. After completion of the dropwise addition, the mixture was aged at 80 ° C. for 2 hours and cooled to room temperature to obtain an aqueous dispersion for b particles. The aqueous dispersion of the particle a and the aqueous dispersion of the particle b
The mixture was mixed at a ratio of 0:50, neutralized with aqueous ammonia, adjusted to a solid content of 50%, a viscosity of 200 mPa · s, and a pH of 8.
An aqueous dispersion composed of two types of particles was obtained. A polyacrylic acid-based thickener (manufactured by Rohm and Haas Co., Ltd., trade name: ASE-60) was added to the aqueous dispersion to obtain 11,000 mP.
a.s (B-type viscometer), and a solution obtained by dissolving 0.3 parts of adipic dihydrazide in 10% of ion-exchanged water with respect to 100 parts of the solid content of the mixture was added and mixed well.
A water-dispersible pressure-sensitive adhesive for peeling was prepared. An adhesive label for re-peeling was obtained in the same manner as in Example 1. The test results showed that the removability and the stability over time were all good. The results are shown in Table 2. In Example 7, when mixing the aqueous dispersions a and b, the mixing ratio of the aqueous dispersion b was further increased. For example, 5 parts by weight of the polymer particles of the aqueous dispersion a were added to the aqueous dispersion b.
When the polymer particles were mixed at a ratio of 95 parts by weight, the adhesiveness tended to decrease. Conversely, the mixing ratio of the aqueous dispersion a is further increased, for example, 95 parts by weight of the polymer particles of the aqueous dispersion a and 5 parts by weight of the polymer particles of the aqueous dispersion b.
When it was blended in the ratio of parts by weight, there was a tendency that the removability was reduced. From these results, it was confirmed that it is preferable to mix the two dispersions a and b so that the former polymer particles are 10 to 90 parts by weight and the latter polymer particles are 90 to 10 parts by weight. Was done.

Comparative Example 1 In a reactor equipped with a thermometer, a stirrer, a dropping device, a reflux condenser, and a nitrogen inlet tube, 28 parts of ion-exchanged water and nitrogen were sealed, and the internal temperature of the reactor was maintained at 80 ° C. Immediately after adding 2 parts of a 5% strength aqueous solution of potassium persulfate, 98 parts of separately prepared 2-ethylhexyl acrylate, 1 part of acrylic acid, and 1 part of diacetone acrylamide sodium polyoxyethylene alkylphenyl ether sulfate (manufactured by Kao Corporation) Levenol WZ) 1.5 parts, ion-exchanged water 56
The emulsified mixture was continuously dropped over 4 hours, and in parallel, 4 parts of a 5% strength aqueous solution of potassium persulfate was dropped to carry out emulsion polymerization. After completion of the dropwise addition, the mixture was aged at 80 ° C. for 2 hours, and then cooled to room temperature. It was neutralized and adjusted with ammonia water to obtain an aqueous dispersion having a solid content of 50% and a viscosity of 170 mPa · s.
To the aqueous dispersion, a polyacrylic acid-based thickener (manufactured by Rohm and Haas Company, trade name: ASE-60) was added, and 10,
000, and 0.3 parts of adipic acid dihydrazide dissolved in 10% of ion-exchanged water with respect to 100 parts of the solid content are added and mixed well. A pressure-sensitive adhesive was prepared. An adhesive label for re-peeling was obtained in the same manner as in Example 1. As a result of the test, the removability of the stainless steel plate was poor. The results are shown in Table 2.

Comparative Examples 2 to 4 In Comparative Example 2, except that the amount of diacetone acrylamide which is a carbonyl group-containing unsaturated monomer used in the layer b was outside the scope of the present invention, In Comparative Example 4, except that the amount of diacetone acrylamide, which is a carbonyl group-containing unsaturated monomer used in the a layer, is out of the range of the present invention, the ratio of monomers in the a layer and the b layer is A water-dispersed pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive was out of the range of the present invention. A crosslinking agent was added in the same manner as in Example 1 to obtain a re-peelable pressure-sensitive adhesive label. Comparative Example 2,
Both 3 and 4 had poor removability. The results are shown in Table 3.

Comparative Example 5 In a reactor equipped with a thermometer, a stirrer, a dropping device, a reflux condenser, and a nitrogen inlet tube, 28 parts of ion-exchanged water and nitrogen were sealed, and the internal temperature of the reactor was maintained at 80 ° C. 2 parts of a 5% strength aqueous solution of potassium persulfate were added, and 99 parts of 2-ethylhexyl acrylate, 1 part of acrylic acid, and sodium polyoxyethylene alkylphenyl ether sulfate (trade name: Revenol WZ, manufactured by Kao Corporation) were immediately prepared. 5
And emulsified with 56 parts of ion-exchanged water were continuously dropped over 4 hours, and 4 parts of a 5% strength aqueous solution of potassium persulfate was dropped in parallel to carry out emulsion polymerization. After completion of the dropwise addition, the mixture was aged at 80 ° C. for 2 hours and cooled to room temperature. Thereafter, the mixture was neutralized and adjusted with aqueous ammonia to obtain a solid content of 50% and a viscosity of 170 mPa ·
An aqueous dispersion having a pH of s and a pH of 7.8 was obtained. A polyacrylic acid-based thickener (Rohm and Haas,
Trade name: ASE-60) 11,000 mPa · s
, And 1 part of a water-soluble epoxy resin (manufactured by Nagase Kasei Kogyo Co., Ltd., trade name: Denacol EX-810) is added to 100 parts of the solid content and mixed well.
A water-dispersible pressure-sensitive adhesive for peeling was prepared. A re-peelable adhesive label was obtained in the same manner as in Example 1. The test results showed poor stability over time. Table 3 shows the results.

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

[Table 3]

In Tables 1, 2 and 3, the types of monomers and compounds are indicated by the following abbreviations. 2EHA: 2-ethylhexyl acrylate AA: acrylic acid DAAM: diacetone acrylamide AAEM: acetoacetoxyethyl methacrylate ADH: adipic acid dihydrazide EX-810: water-soluble epoxy resin manufactured by Nagase Kasei Kogyo Co., Ltd.

Test Method 1. Test sample The obtained water-dispersible pressure-sensitive adhesive for re-peeling was applied to a release paper so as to have a thickness of 25 μm after drying, dried at 100 ° C. for 1 minute, and then coated with a high-quality paper (64 g / m 2). ² ) Transfer to 23 ° C, 6
After standing for 7 days in an atmosphere of 5% RH, a re-peelable adhesive label was obtained.

2. Test Method The adhesive strength and removability of each removable adhesive label were examined by the following methods. Adhesive strength A test adhesive label was cut to a width of 25 mm on a stainless steel plate and a polypropylene plate according to JIS Z 0237 180 ° peeling adhesive strength measurement, and then reciprocated with a 2 kg roller, followed by pressure bonding at 23 ° C and 65 ° C. After leaving for 20 minutes in% RH, the adhesive strength was measured at that temperature at a peeling speed of 300 mm / min using a tensile tester. The measurement unit is N /
25 mm. Removability The test adhesive label was cut to a width of 25 mm and bonded to a stainless steel plate, a PVC plate, and a polypropylene plate at room temperature.
After being left in an atmosphere of 65% RH for 30 days, the film was peeled off at a peeling speed of 300 mm / min using a tensile tester, and the state of the adherend surface after peeling was visually determined. ：: Peeling can be performed neatly without glue residue or paper breakage. Δ: Adhesive residue and paper tear are partially present. ×: Adhesive residue or paper tear on the entire surface. Stability over time The state after leaving the water-dispersible pressure-sensitive adhesive for re-peeling at 25 ° C. for 30 days was observed. ：: No change from initial stage. Δ: The viscosity is slightly high. X: Gelation occurs.

[0040]

According to the present invention, polymer particles having a two-layer constitution having different monomer compositions are produced, or two-layer polymer particles having different monomer compositions are produced.
More specifically, by producing and blending various kinds of polymer particles, one of the monomer compositions contains 0.1 to 5% by weight of a carbonyl group-containing monomer and the other contains a carbonyl group. By having a content of the contained monomer of 1/2 or less of one side, it has excellent adhesiveness and easily peels off from the surface of the adherend even after being left for a long time after pasting to the adherend. Because it can be used, it is useful as a water-dispersible pressure-sensitive adhesive for re-peeling used in pressure-sensitive adhesive labels and sheets.

Claims (5)

[Claims] 1. A method according to claim 1, wherein (A) alkyl (meth) acrylate having 4 to 12 carbon atoms in the alkyl group as a main component and 0 to 2% by weight of a carbonyl group-containing unsaturated monomer (a A) consisting of a copolymer containing a total of 100% by weight of a terpolymer mixture and an alkyl (meth) acrylate having 4 to 12 carbon atoms of an alkyl group as a main component, and a carbonyl group-containing unsaturated monomer. And a layer b composed of a copolymer containing 0.1 to 5% by weight of the polymer (the total of the monomer mixture in the layer b is 100% by weight). An aqueous dispersion wherein the content of unsaturated monomer is 1/2 or less of the content of carbonyl group-containing unsaturated monomer in layer b, and (B) hydrazine having at least two hydrazino groups in the molecule A water-dispersible pressure-sensitive adhesive for re-peeling containing a derivative. 2. An aqueous dispersion comprising 10 to 90 parts by weight of the monomer mixture of layer a and 90 to 1 part by weight of the monomer mixture of layer b.
The water-dispersible pressure-sensitive adhesive for re-peeling according to claim 1, which is 0 parts by weight. 3. The removable water-dispersible pressure-sensitive adhesive according to claim 1, wherein the monomer mixture of the layer a is continuously polymerized after polymerization of the monomer mixture of the layer a. 4. The method according to claim 1, wherein (A) an alkyl (meth) acrylate having an alkyl group having 4 to 12 carbon atoms as a main component and 0 to 2% by weight of a carbonyl group-containing unsaturated monomer (a A) composed of a copolymer containing a copolymer having a total of 100% by weight) and an alkyl (meth) acrylate having 4 to 12 carbon atoms of an alkyl group as a main component, and a carbonyl group-containing unsaturated monomer. B) consisting of a copolymer containing 0.1 to 5% by weight (the total of the monomer mixture of b particles is 100% by weight) and b particles comprising a copolymer; An aqueous dispersion in which the content of the carbonyl group-containing unsaturated monomer in the particles is 1/2 or less of the content of the carbonyl group-containing unsaturated monomer in the particle b; and (B) at least two Re-stripping comprising a hydrazine derivative having a hydrazino group Water-dispersible pressure sensitive adhesive. 5. The polymer according to claim 1, wherein the a particles constitute 10 to 9 particles.
The removable water-dispersible pressure-sensitive adhesive according to claim 4, wherein 0 parts by weight and b particles are 90 to 10 parts by weight.