JP2001089722A - Pressure-sensitive adhesive label - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a pressure-sensitive adhesive label capable of exhibiting an excellent water washing property even pasted on a printed surface of a plastic container without receiving an influence from the printed surface and capable of easily peeling off in the case of pasting a label having incorrect information printed on it. SOLUTION: The pressure-sensitive adhesive label for managing plastic container uses a pressure-sensitive adhesive having easily peeling off property by water comprising 100 pts.wt of a water redispersion type pressure-sensitive adhesive comprising an acrylic copolymer including 5-15 wt.% of an ethylenic unsaturated carboxylic acid monomer and 0.1-1.5 pts.wt of a cross-linking agent, and the label has 40-500 N/m of adhesive strength to a polypropylene plate measured in conformity to JIS-Z-0237 method for dry adhesive strength measurement.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adhesive label used for managing a plastic container used as a return box in various distribution departments. More specifically, the present invention relates to an adhesive label which can be easily peeled off from a plastic container by washing water when the plastic container is washed when reused.

[0002]

2. Description of the Related Art Adhesive labels are used in a very wide range such as for commercial use, office work, process control, distribution control, and home use. In general, an adhesive sheet in which an adhesive is applied to one surface of a surface substrate and an adhesive is sandwiched between the surface substrate and a release sheet is widely used. Recently, there has been developed an article without a release paper in which a release agent or a release agent is applied to one of the surface base materials, and an adhesive layer is provided on the opposite surface and laminated.

[0003] Paper, film, metal foil or the like is used as the surface substrate. A release agent or a release agent such as a silicone compound or a fluorine compound is applied to the release sheet substrate. The base material for the release sheet may be a high-density base paper such as glassine paper, a clay-coated paper, a kraft paper, a laminated paper obtained by laminating a resin film such as polyethylene on a high-quality paper, or a kraft paper or a high-quality paper. Resin-coated paper provided with a coating layer containing a water-soluble polymer such as polyvinyl alcohol or starch and a pigment as main components can be used. Above all, laminated paper obtained by laminating polyethylene is generally widely used. As the pressure-sensitive adhesive, various types of pressure-sensitive adhesives such as rubber-based, acrylic-based, and vinyl ether-based emulsions, solvents, and non-solvents are used.

One use of such an adhesive label is as follows.
There are management applications for plastic containers used as return boxes in various logistics departments. At this time, the plastic container is generally made of a polypropylene resin or a polyethylene resin in terms of ease of molding, durability, chemical resistance, and the like. Labels printed or printed with information necessary for logistics management are affixed to one or more surfaces of these plastic containers, and they are not peeled off until they are transported to the destination, that is, the surface of the adherend It has been basically required to have strong adhesive performance.

On the other hand, from the viewpoints of recent effects of waste pollution on the environment and reduction of distribution costs, reuse of plastic containers used as return boxes in various distribution divisions has been studied. In the case of self-adhesive labels, information necessary for management is printed with a bar code, etc., and a new management label etc. is placed on top of the previous label when reusing a plastic container so that the information can be read by a computer. There was a problem such as misreading of the computer occurred when pasting. Therefore, simple removal of these labels is a major challenge.

In order to solve the above-mentioned problem, a removable adhesive label has been proposed, but there is a disadvantage that removing the adhesive label by hand requires cost and time. Recently, an adhesive containing an excessive emulsifier has been proposed so that it can be easily peeled off when washed with water. There is a problem that the cleaning workability is reduced due to re-adhesion to a container made of glass.

[0007] Labels using a water-soluble adhesive or a water-redispersible adhesive have also been proposed. These labels are printed on a plastic container, for example, by printing the name and address of the owner. When this is applied, the adhesive strength is remarkably increased, and not only does the label become less likely to be peeled off during washing, but also there is a problem that the pressure-sensitive adhesive remains on the printed portion, which is not suitable for actual use. This is because screen printing is generally used when printing company names etc. on plastic containers, but it seems that epoxy-based resin is widely used as the screen ink resin used at that time . Further, it has been pointed out that the adhesive is dissolved or dispersed in water and contaminates washing water.

[0008]

SUMMARY OF THE INVENTION The present invention provides a water-redispersible pressure-sensitive adhesive which comprises a cross-linking agent, thereby maintaining the hydrophilicity of the water-redispersible pressure-sensitive adhesive while preventing the pressure-sensitive adhesive film from being dispersed.
When washing with water to reuse plastic containers used as return boxes in various logistics departments,
The adhesive label can be easily peeled off from the plastic container without being manually peeled off, and the peeled label adhesive provides a label that does not contaminate the washing water, and can be attached to the printed surface of the plastic container. ,
To provide an adhesive label that can exhibit good water washability without being affected by a printing surface and that can be easily peeled off even when a label on which incorrect information is printed is attached. It is in.

[0009]

The present invention provides (1) a water-redispersible pressure-sensitive adhesive comprising an acrylic copolymer containing 5 to 15% by weight of an ethylenically unsaturated carboxylic acid-containing monomer.
A water-peelable pressure-sensitive adhesive obtained by adding 0.1 to 1.5 parts by weight of a crosslinking agent to 00 parts by weight, and JIS-Z-0
An adhesive label for managing a plastic container, wherein the adhesive force to a polypropylene plate measured according to the measuring method of normal adhesive force of No. 237 is 40 to 500 N / m.

The present invention also provides the pressure-sensitive adhesive label according to (1), wherein (2) the crosslinking agent is an epoxy-based crosslinking agent. The present invention further provides (3) the pressure-sensitive adhesive label according to (1) or (2), wherein the pressure-sensitive adhesive layer has a contact angle with water of 70 ° or less after 60 seconds. Furthermore, the present invention provides (4) the water-redispersible pressure-sensitive adhesive composition,
100% by weight of a hydrophilic plasticizing substance in the pressure-sensitive adhesive copolymer
(1)
An adhesive label according to any one of (1) to (3). A fifth aspect of the present invention is the adhesive label according to any one of (1) to (4), wherein (5) the water-redispersible pressure-sensitive adhesive composition contains an alkoxyalkyl (meth) acrylate. is there.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The term "adhesive strength to a polypropylene plate" used in the present invention refers to a value obtained by measuring only an adherend as a polypropylene plate in accordance with the method for measuring the normal adhesive force of JIS-Z-0237 ( (Unit: N / m). Further, the polypropylene plate used as the adherend is not particularly limited, and it is more preferable that the plate is cut out from an actual container. However, there is no problem in evaluating a commercially available injection molded product. The contact angle is defined as a value obtained by dropping water from a micro syringe onto the surface of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive label,
This is a value obtained by measuring the angle of a water droplet after a lapse of seconds, and indicates the ease with which the pressure-sensitive adhesive layer adapts to water. By the way, if the measurement is performed immediately after dropping, it is impossible to accurately evaluate the familiarity with water.

According to the present invention, as described above, by adding a crosslinking agent to a water-redispersible pressure-sensitive adhesive, the hydrophilicity of the water-redispersible pressure-sensitive adhesive is maintained while the pressure-sensitive adhesive film is not dispersed, thereby enabling various physical distribution. When washing a plastic container used as a return box in water for reuse, the adhesive label can be easily peeled off from the plastic container without manually peeling it off, and the adhesive on the peeled label is washed Along with providing a label that does not contaminate water, even when affixed to the printed surface of a plastic container, the adhesive is not affected by the printed surface, and can exhibit good water washability, Another object of the present invention is to provide an adhesive label that can be easily re-peeled even when a label on which incorrect information is printed is attached.

In order to obtain such an adhesive label, a water redispersible adhesive comprising an acrylic copolymer containing 5 to 15% by weight of an ethylenically unsaturated carboxylic acid-containing monomer in the adhesive composition. And a crosslinking agent such that the adhesive strength to the polypropylene plate is 40 to 500 N / m.
It is characterized by using an easily water-peelable pressure-sensitive adhesive to which about 1.5 parts by weight is added. By the way, when the adhesive strength to the polypropylene plate is less than 40 N / m, sufficient adhesiveness cannot be obtained, and the label is not practically used because the label does not fall off or adhere during use. On the other hand, if it exceeds 500 N / m, removability is impaired.

The water-releasable pressure-sensitive adhesive used in the pressure-sensitive adhesive sheet of the present invention is a water-redispersible pressure-sensitive adhesive comprising an acrylic copolymer containing 5 to 15% by weight of an ethylenically unsaturated carboxylic acid-containing monomer. It is an adhesive obtained by adding 0.1 to 1.5 parts by weight of a crosslinking agent. Examples of the ethylenically unsaturated carboxylic acid-containing monomer include acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, monoalkyl maleic acid, monoalkyl itaconic acid, monoalkyl fumaric acid, and the like. This monomer must be polymerized so as to account for 5 to 15% by weight of the copolymer. If the amount is less than 5% by weight, the water redispersibility of the pressure-sensitive adhesive will be insufficient, and if it exceeds 15% by weight, the adhesive force will be insufficient, and the pressure-sensitive adhesive will easily deteriorate with time.

Examples of the crosslinking agent include ethylene glycol diglycidyl ether, diglycerol polyglycidyl ether, glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether,
Epoxy crosslinking agent such as pentaerythritol polyglycidyl ether, 1,2-ethylene diisocyanate,
Isocyanate-based cross-linking agents such as 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 2,2,4-trimethyl-1,6-hexamethylene diisocyanate, aluminum tris (acetyl acetate), aluminum tris (ethyl acetoacetate) Acetate), aluminum acetoacetate aluminum diisopropylate, aluminum monoacetylacetonate bis (ethylacetoacetate), and other aluminum metal chelate-based crosslinking agents.

These crosslinking agents need to be added in the range of 0.1 to 1.5 parts by weight based on 100% by weight of the copolymer. By the way, when the amount is less than 0.1 parts by weight, when the adhesive is applied to the printed surface of the plastic container, the obtained adhesive has an excessively strong adhesive force to the adherend and is hardly peeled off by washing with water, and paste is printed. Remain in the department. On the other hand, when the amount exceeds 1.5 parts by weight, the crosslinking density becomes too high, and the adhesive strength of the obtained pressure-sensitive adhesive is weakened, resulting in poor practicality. Among these crosslinking agents, an epoxy crosslinking agent is more preferable because the pressure-sensitive adhesive film after crosslinking is hardly dispersed and does not contaminate the washing water.

Here, the role of the above-mentioned monomer and cross-linking agent with respect to the easily water-peelable pressure-sensitive adhesive of the present invention will be briefly described. In the water-redispersible pressure-sensitive adhesive, a certain amount of ethylene is contained in the acrylic copolymer composition. It is important to include the unsaturated carboxylic acid containing monomer. Furthermore, when an epoxy-based cross-linking agent is used to develop the easily water-removable and re-peelable properties of these copolymers, the copolymer can be re-peeled while maintaining the hydrophilicity of the water-redispersible pressure-sensitive adhesive, In addition, even when affixed to the printing portion of a plastic container, good water-peeling properties can be imparted without being affected by the printing surface.

Further, in order to adjust the physical properties of the pressure-sensitive adhesive and to prevent discoloration and deterioration of the pressure-sensitive adhesive with the lapse of time, a hydrophilic plasticizing agent is used for the water-redispersible pressure-sensitive adhesive used in the water-releasable pressure-sensitive adhesive. Substances can also be added. Examples of the hydrophilic plasticizing substance include triethanolamine, tripropanolamine, triisopropanolamine, N-
Alkanolamines such as methyldiethanolamine and N, N-dibutylethanolamine, sugar alcohols such as glycerin, sorbit, mannitol, dursit, idit, erythritol, arabbit, adnit, polyethylene oxide or polypropylene oxide and glycerin, xylitol trioxyisobutane , Copolymers with polyhydric alcohols such as sorbitol, polyether polyols such as polyethylene glycol and polypropylene glycol, copolymers of ethylene oxide and propylene oxide, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, poly Nonionic surfactants such as oxyethylene polyoxypropylene glycol are exemplified.

This substance is added in an amount of 10% by weight or less, more preferably 0.5 to 10% by weight, based on 100% by weight of the copolymer, in consideration of tackiness and water redispersibility. Added. In addition, among these hydrophilic plasticizing substances, in particular, alkanolamines and nonionic surfactants are
It is preferable because a pressure-sensitive adhesive having good adhesiveness and storage stability can be finished.

Further, an alkoxyalkyl (meth) acrylate can be copolymerized with the water-redispersible pressure-sensitive adhesive used for the water-releasable pressure-sensitive adhesive in order to improve the hydrophilicity of the pressure-sensitive adhesive. The alkoxyalkyl (meth) acrylate is a compound represented by the following general formula (1).

[0021]

Embedded image [Wherein, R ¹ represents a methyl group or a hydrogen atom, and R ² represents a methyl group or an ethyl group. ]

The alkoxyalkyl (meth) acrylate is preferably copolymerized in a range of 2 to 20% by weight of the copolymer.

Accordingly, in order to obtain a water-releasable pressure-sensitive adhesive having good detergency during water washing as a label for managing plastic containers used in the present invention, it is necessary to use an ethylenically unsaturated carboxylic acid-containing monomer. A water-redispersible pressure-sensitive adhesive made of an acrylic copolymer having a certain amount, which can be re-peeled while maintaining the hydrophilicity of the water-redispersible pressure-sensitive adhesive, and affixed to a printing portion of a plastic container. Even in such a case, it is extremely important to balance the blending of the cross-linking agent in order to develop good water releasability without being affected by the printing surface.

The method for producing the acrylic copolymer of the water-redispersible pressure-sensitive adhesive used in the above-mentioned easily water-peelable pressure-sensitive adhesive is not particularly limited. It is manufactured by a known method such as a method of performing solution polymerization in the presence of an agent, a polymerization initiator, and the like, and a method of performing emulsion polymerization in an aqueous system in the presence of an emulsifier, a chain transfer agent, a polymerization initiator, a dispersant, and the like.

Examples of the polymerization initiator used in the polymerization include persulfates such as potassium persulfate and ammonium persulfate; 2,2'-azobisisobutyronitrile;
From azo compounds such as 2′-azobis (2,4-dimethylvaleronitrile), peroxides such as hydrogen peroxide, benzoyl peroxide, lauryl peroxide, and combinations of ammonium persulfate with sodium sulfite, acidic sodium sulfite, etc. , A so-called redox-based polymerization initiator. The amount of the polymerization initiator to be used is generally about 0.2 to 2% by weight, more preferably about 0.3 to 1% by weight, based on the total amount of the monomers commonly used for polymerization.

Examples of the chain transfer agent to be added in the copolymerization include alkyl mercaptans such as octyl mercaptan, nonyl mercaptan, decyl mercaptan, dodecyl mercaptan, octyl thioglycolate, nonyl thioglycolate, 2-ethylhexyl thioglycolate, β Thioglycolic acid esters such as 2-ethylhexyl mercaptopropionate; 2,4-diphenyl-4-methyl-1-pentene; 1-methyl-4-isopropylidene-1-cyclohexene; In particular, thioglycolic acid esters, 2,4-diphenyl-4-methyl-1-pentene, 1-methyl-4-pentene
When isopropylidene-1-cyclohexene is used, the obtained copolymer has a low odor, which is preferable. The amount of the chain transfer agent is adjusted to about 0.001 to 3% by weight of all monomers to be polymerized.

The monomer concentration during the polymerization is usually 30 to 70
% By weight, preferably about 40 to 60% by weight. The polymerization reaction is usually carried out at a temperature of 60 to 100 ° C. for 2 to 8 hours. In addition, wetting agents,
Leveling agents, thickeners, defoamers, preservatives and the like can be added as appropriate. If particularly desired, an ethylene-vinyl acetate copolymer, an ethylene-vinyl acetate-acrylic copolymer may be used for the purpose of improving the properties of the pressure-sensitive adhesive, in particular, the physical properties such as adhesion to a polyolefin-based adherend and cohesion. Coalescence can also be added. These substances are desirably added in an amount of 3 to 30% by weight based on 100% by weight of the copolymer in consideration of the balance between tackiness and water redispersibility.

In the copolymer obtained by the above method, a carboxyl group in the copolymer can be neutralized with an alkaline substance for improving mechanical stability and adjusting viscosity. However, if ammonia or a lower amine is used for neutralizing the carboxyl group in the copolymer, the volatilization of these and the water redispersibility of the pressure-sensitive adhesive deteriorate. In the case of neutralization, it exhibits a function as a plasticizer of the copolymer and has a boiling point to prevent a change in adhesive performance due to volatilization over time after processing into an adhesive sheet and a deterioration in water redispersibility. 220 ゜ C
The use of the above alkanolamines is preferred.

The above-mentioned copolymer has a glass transition temperature of -7.
It is in the range of 0 to -10 ° C, and is appropriately selected according to the purpose. Incidentally, the glass transition temperature of the copolymer is -7.
If the temperature is lower than 0 ° C, the obtained film has insufficient cohesive strength. On the other hand, if the temperature exceeds -10 ° C, the obtained copolymer film tends to be too hard, resulting in poor practicality.

The present invention maintains the hydrophilicity of the water-redispersible pressure-sensitive adhesive by adding a crosslinking agent to the water-redispersible pressure-sensitive adhesive comprising such a copolymer and using it as an easily water-removable pressure-sensitive adhesive. The adhesive label is not dispersed while the plastic container used as a return box in various logistics departments is easily washed from water without having to peel off the adhesive label manually when washing it with water to reuse it. It provides a label that can be peeled off and the peeled-off adhesive of the label does not contaminate the washing water, and the adhesive is not affected by the printing surface even when applied to the printed surface of a plastic container. , Which can exhibit good water-cleaning properties, and can provide an adhesive label which can be easily peeled off even when a label on which incorrect information is printed is attached.

Next, as the surface base material used for the adhesive label, high-quality paper, art paper, coated paper, cast paper, kraft paper, thermal paper, inkjet paper, impregnated paper, low-size paper, water-soluble paper, kraft paper, Or on high-quality paper, for example, casein, dextrin, starch and derivatives thereof, carboxymethylcellulose, methylcellulose, ethylcellulose, hydroxyethylcellulose, polyvinyl alcohol, styrene-butadiene copolymer, methylmethacrylate-butadiene copolymer, ethylene-vinyl chloride copolymer Paper such as a base material provided with a sealing layer mainly composed of a natural or synthetic resin and / or a pigment such as a copolymer, an ethylene-vinyl acetate copolymer, an acrylate ester copolymer, etc .; Methyl cellulose, methyl cellulose A water-soluble film formed from a water-soluble polymer such as, or a copolymer of lactic acid or lactide with a glycolic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxypentanoic acid, hydroxycaproic acid, hydroxyheptanoic acid or other hydroxycarboxylic acid. A film that is easily hydrolyzed with an aqueous alkali solution formed from a lactic acid-based polymer such as polylactic acid can be used.

As a form of the pressure-sensitive adhesive label, a pressure-sensitive adhesive sheet is generally used in which a pressure-sensitive adhesive is applied to one surface of the surface substrate and the pressure-sensitive adhesive is sandwiched between the surface substrate and a release sheet. However, for example, a release agent is applied to the heat-sensitive layer side of the heat-sensitive paper, or a release printing layer is provided on the printing surface of printing paper such as art paper or coated paper, and an adhesive layer is provided on the opposite surface. It may be a tape-like material that does not use a release paper to be laminated.

Next, as a release sheet base material in the case of an adhesive sheet, high-density base paper such as glassine paper, clay-coated paper, kraft paper or high-quality paper may be used, for example, casein, dextrin, starch and derivatives thereof, carboxymethyl cellulose. , Such as methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer, ethylene-vinyl chloride copolymer, ethylene-vinyl acetate copolymer, acrylate ester copolymer and the like A film base such as a base material provided with a filler layer containing a natural or synthetic resin and a pigment as a main component, a polyethylene laminate paper obtained by laminating polyethylene or the like on kraft paper or woodfree paper, or a polypropylene can be used.

The filler layer containing a resin and / or a pigment as a main component is not particularly limited. For example, casein, dextrin, starch and its derivatives,
Natural or synthetic resins such as carboxymethylcellulose, methylcellulose, ethylcellulose, hydroxyethylcellulose, polyvinyl alcohol, styrene-butadiene copolymer, methylmethacrylate-butadiene copolymer, ethylene-vinyl chloride copolymer, acrylate copolymer and / or Or kaolin, calcium carbonate, clay, talc, calcined kaolin, deramikaolin,
Inorganic pigments such as titanium dioxide, aluminum hydroxide, silica, and white carbon, or organic synthetic pigments such as polystyrene resin fine particles, urea-formalin resin fine particles, and fine hollow particles can be used.

In addition to the base material provided with the filler layer, a base material provided with a pigment coating layer containing a pigment as a main component on the surface of paper such as art paper, coated paper, cast coated paper, etc. May be used.

When the pigment coating layer is provided,
An adhesive is used in the pigment coating liquid in order to fix the pigments and the pigment and the surface of the substrate in addition to the pigment. Examples of such an adhesive include casein, dextrin, starch and derivatives thereof, carboxymethyl cellulose, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer, and ethylene-vinyl chloride copolymer. Natural or synthetic adhesives, such as coalesce, ethylene-vinyl acetate copolymer, acrylate copolymer, etc., are used in the form of an aqueous solution or dispersion (emulsion). In addition, besides these pigments and adhesives, the pigment coating liquids do not impair their properties.
Various auxiliaries such as an antifoaming agent, a dispersant, a preservative, and a dye can be added as necessary.

The coating liquid for the filling layer containing such a resin and / or a pigment as a main component can be used in a usual coating solution such as a blade coater, a bar coater, an air knife coater, a gravure coater, a roll coater, a die coater, and a lip coater. Coated on the device to be coated. In this case, the coating amount is adjusted to ² g / m ² or more, preferably 4 to 30 g / m ^{2 in} terms of the weight of the solid content.

Next, when the pressure-sensitive adhesive label of the present invention is used as a pressure-sensitive adhesive sheet, the release agent or release agent used for the release agent layer formed on one surface of the release sheet substrate is not particularly limited, and is commonly used in aqueous dispersion. Dry, solvent-free or solvent-free silicone resin, fluororesin, etc.
After the application of about g / m ² , a release layer formed by heat curing, ionizing radiation curing or the like is used. Above all, solventless silicone is more preferably used because it does not use a harmful solvent at the time of forming the release layer and has excellent drying efficiency as compared with the water dispersion type.

When the adhesive label is used as an adhesive sheet, the adhesive is usually coated on the release agent surface of the release sheet, dried to form an adhesive layer, and then bonded to a surface substrate to finish. However, the pressure-sensitive adhesive layer may be provided by directly coating the pressure-sensitive adhesive on the surface substrate.

When forming an adhesive sheet, the adhesive is a molecule
Volume, dilution with water, or thickening.
To a viscosity of about 10 to 9,000 centipoise.
Knots are applied to the release sheet. In this case,
For example, reverse roll coater, knife coater
ー, air knife coater, bar coater, slotter
Equalor, lip coater, reverse gravure coater
-Etc. are used. Pressure-sensitive adhesive sheet and pressure-sensitive adhesive tape of the present invention
There is no particular limitation on the coating device in
It is manufactured by a general method. The coating amount of the adhesive is 5 to 50
g / m ^TwoIt is adjusted within a range. By the way, 5 g / m^TwoNot yet
At full, the adhesive performance of the resulting pressure-sensitive adhesive sheet is insufficient.
50g / m^TwoOver the time of production of the adhesive sheet
The adhesive may protrude or cause cohesive failure during peeling.
There is a risk that.

[0041]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but of course, the present invention is not limited to these examples. Unless otherwise specified, all parts, ratios, coating amounts, and the like in the examples are indicated by solid content weight.

Example 1 (Production of pressure-sensitive adhesive) First, methoxyethyl acrylate: 75 parts Caprolactone acrylate adduct (trade name: Aronix M-5300 / Toagosei Co., Ltd.): 20 parts Acrylic acid -2-Ethylhexyl: 220 parts Acrylic acid: 45 parts Vinyl acetate: 20 parts Methyl (meth) acrylate: 20 parts Anionic emulsifier (trade name: Emal NC-35 / Kao Corporation): 6 parts Ion-exchanged water: 150 Parts were mixed and prepared.

Next, 150 parts of ion-exchanged water, 3 parts of potassium peroxide, and 3 parts of octyl mercaptan were charged into a flask equipped with a stirrer, a cooler, a dropping funnel, a nitrogen suction pipe, and a thermometer. After heating to
The emulsified monomer mixture was dropped by 1/6. Reaction rate 9
When it reached 0%, the remaining monomer mixture was dropped over 3 hours to carry out polymerization. After completion of the dropwise addition, the mixture was aged at 80 ° C. for 3 hours to complete the reaction. Next, the copolymer 100
Parts, triethanolamine: 2 parts, nonionic surfactant (trade name: Emulgen 810 / Kao Soap Co., Ltd.): 4 parts, ethylene-vinyl acetate-acrylic copolymer (trade name: Sumikaflex S) -3110 / Sumitomo Chemical Co., Ltd.): 27 parts were added, and the mixture was vigorously stirred to obtain a water redispersible pressure-sensitive adhesive. 0.3 parts of diglycerol polyglycidyl ether (trade name: Denacol EX-421 / Nagase Kasei) was added as a crosslinking agent to 100 parts of the water-redispersible pressure-sensitive adhesive obtained by the above method to produce a pressure-sensitive adhesive. did.

(Preparation of pressure-sensitive adhesive sheet) The obtained pressure-sensitive adhesive was applied to a commercially available polyethylene laminate release paper in an amount of 25% by dry weight.
g / m ² and dried and then bonded to a commercially available high quality paper of 64 g / m ² to obtain a removable adhesive sheet.

Example 2 First, a mixed solution of emulsified monomers was prepared as follows: methoxyethyl acrylate: 55 parts Caprolactone acrylate adduct (trade name: Aronix M-5300 / Toagosei Co., Ltd.): 20 parts 2-ethylhexyl acrylate: 225 Part Acrylic acid: 60 parts Vinyl acetate: 20 parts Methyl (meth) acrylate: 20 parts Anionic emulsifier (trade name: Emar NC-35 / Kao Corporation): 6 parts Ion-exchanged water: 150 parts Prepared. Then, an adhesive was produced in the same manner as in Example 1.

A removable adhesive sheet was prepared in the same manner as in Example 1 except that the above-mentioned adhesive was used.

Example 3 (Production of adhesive) First, as a mixture of emulsified monomers, methoxyethyl acrylate: 90 parts Caprolactone acrylate adduct (trade name: Aronix M-5300 / Toagosei Co., Ltd.): 20 parts Acrylic acid 2-Ethylhexyl: 225 parts Acrylic acid: 25 parts Vinyl acetate: 20 parts Methyl (meth) acrylate: 20 parts Anionic emulsifier (trade name: Emal NC-35 / Kao Corporation): 6 parts Ion-exchanged water: 150 Parts were mixed and prepared. Then, an adhesive was produced in the same manner as in Example 1.

A removable adhesive sheet was prepared in the same manner as in Example 1 except that the above-mentioned adhesive was used.

Example 4 (Production of pressure-sensitive adhesive) To 100 parts of the water-redispersible pressure-sensitive adhesive prepared in Example 1, ethylene glycol diglycidyl ether (trade name: EX-811 / Nagase Kasei) was used as a crosslinking agent. 1.5 parts were added to produce an adhesive.

A removable pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1 except that the above-mentioned pressure-sensitive adhesive was used.

Example 5 (Production of pressure-sensitive adhesive) Diglycerol polyglycidyl ether (trade name: EX-421 / Nagase Kasei) was used as a crosslinking agent for 100 parts of the water-redispersible pressure-sensitive adhesive prepared in Example 1. Was added to produce an adhesive.

A removable adhesive sheet was prepared in the same manner as in Example 1 except that the above-mentioned adhesive was used.

Example 6 (Production of pressure-sensitive adhesive) First, a caprolactone acrylate adduct (trade name: Aronix M-5300 / manufactured by Toagosei Co., Ltd.): 40 parts as an emulsified monomer mixture, 2-ethylhexyl acrylate: 270 parts Acrylic acid: 50 parts Vinyl acetate: 20 parts Methyl (meth) acrylate: 20 parts Anionic emulsifier (trade name: Emal NC-35 / Kao Corporation): 6 parts Ion-exchanged water: 150 parts did. Then, an adhesive was produced in the same manner as in Example 1.

A removable pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1 except that the above-mentioned pressure-sensitive adhesive was used.

Example 7 (Production of pressure-sensitive adhesive) A 10% aqueous solution of potassium hydroxide: 25 parts, an ethylene-vinyl acetate-acrylic copolymer (trade name: 100 parts) based on 100 parts of the copolymer produced in Example 1 Sumikaflex S-3110 / Sumitomo Chemical Co., Ltd.): An adhesive was produced in the same manner as in Example 1 except that 27 parts was added and the mixture was vigorously stirred to obtain a water redispersible adhesive.

A removable pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1 except that the above-mentioned pressure-sensitive adhesive was used.

Comparative Example 1 An adhesive sheet was produced in the same manner as in Example 1 except that no crosslinking agent was added.

Comparative Example 2 Except that 2 parts of diglycerol polyglycidyl ether (trade name: EX-421 / Nagase Kasei) was added as a crosslinking agent to 100 parts of the water redispersible pressure-sensitive adhesive prepared in Example 1. In the same manner as in Example 1, a removable adhesive sheet was produced.

Comparative Example 3 (Production of adhesive) As an emulsified monomer mixture, methoxyethyl acrylate: 35 parts Caprolactone acrylate adduct (trade name: Aronix M-5300 / Toagosei Co., Ltd.): 40 parts Acrylic acid 2-ethylhexyl: 215 parts Acrylic acid: 70 parts Vinyl acetate: 20 parts Methyl (meth) acrylate: 20 parts Anionic emulsifier (trade name: Emar NC-35 / Kao Corporation): 6 parts Ion-exchanged water: 150 parts Was prepared by mixing. Then, an adhesive was produced in the same manner as in Example 1.

A removable pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1 except that the above-mentioned pressure-sensitive adhesive was used.

Comparative Example 4 (Production of adhesive) As an emulsified monomer mixture, methoxyethyl acrylate: 75 parts Caprolactone acrylate adduct (trade name: Aronix M-5300 / Toagosei Co., Ltd.): 20 parts Acrylic acid 2-ethylhexyl: 250 parts Acrylic acid: 15 parts Vinyl acetate: 20 parts Methyl (meth) acrylate: 20 parts Anionic emulsifier (trade name: Emal NC-35 / Kao Corporation): 6 parts Ion-exchanged water: 150 parts Was prepared by mixing. Then, an adhesive was produced in the same manner as in Example 1.

A re-peelable pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1 except that the above-mentioned pressure-sensitive adhesive was used.

Comparative Example 5 Diglycerol polyglycidyl ether (trade name: EX-421 / Nagase Kasei) as a cross-linking agent was added to 0.0 part of the water-redispersible pressure-sensitive adhesive prepared in Example 1 for 0.0 part.
Five parts were added to produce an adhesive.

A removable pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1 except that the above-mentioned pressure-sensitive adhesive was used.

Comparative Example 6 A diglycerol polyglycidyl ether (trade name: Denacol EX-) was used as a cross-linking agent for 100 parts of a commercially available acrylic re-peelable pressure-sensitive adhesive (trade name: AE279 / JSR). 421 / Nagase Kasei Co., Ltd.) was prepared in the same manner as in Example 1 except that 0.3 parts of 421 / Nagase Kasei) was added.

The pressure-sensitive adhesive sheet thus obtained was evaluated as follows, and the results are shown in Table 1.

(Evaluation Test Items) [Adhesive Strength] After the pressure-sensitive adhesive sheet was manufactured, it was stored for 14 days in an atmosphere at a temperature of 23 ± 2 ° C. and a relative humidity of 65 ± 5%, and then subjected to JI.
A plain polypropylene plate and a polypropylene plate whose surface is screen-printed (trade name: 5-000 Screen Ink / Teikoku Ink) are used as adherends in accordance with the method for measuring the normal adhesive force of SZ-0237. Then, the adhesive strength (unit: N / m) was measured.

[Contact Angle] After the production of the pressure-sensitive adhesive sheet, the temperature was 23
After storing for 14 days in an atmosphere of ± 2 ° C and a relative humidity of 65 ± 5%, the adhesive sheet was fixed on a glass plate with the surface substrate facing downward, excluding the release paper, exposing the adhesive layer, and using a micro syringe. The angle (unit: ゜) of the water droplet 60 seconds after water was dropped was measured.

[Removability] After the production of the pressure-sensitive adhesive sheet, the temperature was 23
Stored in an atmosphere of ± 2 ° C and a relative humidity of 65 ± 5% for 14 days to prepare a measurement sample, and affixed the sample to a plain polypropylene plate and a polypropylene plate whose surface was silk-printed as the adherend. After a day, the sample was peeled off. The removability at that time was evaluated according to the following criteria. ：: The adhesive label was peeled off without the adhesive remaining on the adherend. ×: When peeling, the base material of the pressure-sensitive adhesive label is broken or the pressure-sensitive adhesive remains on the adherend.

[Water washability] After the production of the pressure-sensitive adhesive sheet, the temperature was 23
The sample was stored for 14 days under an atmosphere of ± 2 ° C. and a relative humidity of 65 ± 5% to obtain a measurement sample. The samples were attached to a plain polypropylene plate and a polypropylene plate with silk printing on the surface as adherends, immersed in hot water at 65 ° C after 7 days, and the time until the sample was peeled and the degree of peeling were based on the following criteria. Was evaluated. ：: The adhesive label falls off without the adhesive remaining on the adherend. Δ: The label substrate is peeled off, but the adhesive remains on the adherend. ×: The adhesive label does not fall off even when immersed in warm water for 30 minutes or more.

[Comprehensive Evaluation] Based on the above evaluations, the performance of the plastic container of the present invention as a management label was evaluated. ：: The adhesive exhibits sufficient adhesive strength in the adhesive performance as well as excellent removability, and the label can be safely removed in a short time regardless of the presence or absence of printing on the adherend in water washability. Δ: Sufficient adhesive strength is exhibited in the adhesive performance of the pressure-sensitive adhesive,
The removability is poor, or the adhesive is contaminated with the washing water in the water washability, and it is difficult to remove the label from the printed portion. X: Poor practicality due to insufficient adhesive strength in the adhesive performance of the adhesive or lack of water washability.

[0072]

[Table 1] * In the table, recyclability is the result of evaluation for each case of pressure-sensitive adhesive label / pressure-sensitive adhesive sheet.

[0073]

As shown in Table 1, the adhesive label for managing plastic containers of the present invention exhibits a necessary adhesive strength at the time of application, regardless of the presence or absence of printing on the adherend, and has excellent removability. In addition, the pressure-sensitive adhesive label provided with good water washability without contaminating the wash water by suppressing the dispersion of the pressure-sensitive adhesive film while maintaining the hydrophilicity of the pressure-sensitive adhesive.

Claims (5)

[Claims] 1. A crosslinking agent is added in an amount of 0.1 to 100 parts by weight of a water-redispersible pressure-sensitive adhesive comprising an acrylic copolymer containing 5 to 15% by weight of an ethylenically unsaturated carboxylic acid-containing monomer.
The adhesive strength to a polypropylene plate measured using a water-peelable pressure-sensitive adhesive to which 1.5 parts by weight has been added and measured according to the method for measuring the normal pressure-sensitive adhesive strength of JIS-Z-0237 is 40 to 500.
N / m is an adhesive label for plastic container management. 2. The pressure-sensitive adhesive label according to claim 1, wherein the crosslinking agent is an epoxy-based crosslinking agent. 3. The pressure-sensitive adhesive label according to claim 1, wherein the pressure-sensitive adhesive layer has a contact angle with water of 70 ° or less after 60 seconds. 4. The pressure-sensitive adhesive composition according to claim 1, wherein the water-redispersible pressure-sensitive adhesive composition contains a hydrophilic plasticizing substance in an amount of 10% by weight or less based on 100% by weight of the pressure-sensitive adhesive copolymer. Item 4. The pressure-sensitive adhesive label according to any one of Items 3. 5. The pressure-sensitive adhesive label according to claim 1, wherein the water-redispersible pressure-sensitive adhesive composition contains an alkoxyalkyl (meth) acrylate.