JPH08218039A - Biodegradable adhesive sheet - Google Patents

Abstract

(57) [Summary] [Purpose] A biodegradable adhesive sheet that easily decays in the natural environment especially when used products and defective products are buried in the soil or dumped in the ocean. A biodegradable pressure-sensitive adhesive sheet that is hydrolyzed. [Structure] A biodegradable pressure-sensitive adhesive sheet comprising a release sheet, a pressure-sensitive adhesive layer, and a surface base material laminated, wherein the pressure-sensitive adhesive and the surface base material constituting the pressure-sensitive adhesive layer are biodegradable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biodegradable pressure-sensitive adhesive sheet, which is easily biodegradable in a natural environment when used products, defective products, etc. are buried or dumped in the ocean. Regarding adhesive sheet.

[0002]

2. Description of the Related Art Adhesive sheets are used for labels, stickers, stickers, etc.
It is used after being processed into patches. The constitution of a general pressure-sensitive adhesive sheet is one in which a pressure-sensitive adhesive layer is formed between a surface base material and a release sheet, and the surface base material is paper, film,
A metal foil or the like is used, and as the release sheet, high-density base paper such as glassine paper, clay-coated paper, polyethylene laminated base paper or the like coated with a release agent such as a silicone compound or a fluorine compound is used.

As the pressure-sensitive adhesive, various types of rubber-based, acrylic-based, vinyl ether-based emulsion, solvent or solventless pressure-sensitive adhesives are used. Such an adhesive sheet is a permanent adhesive type that is permanently used while being attached to an adherend after being attached to a product, etc. Some are removable types.

Conventionally, a plastic film of polyethylene, polypropylene, polyvinyl chloride, polystyrene or the like has been used for an adhesive sheet using a film as a surface base material. Due to the water resistance and transparency of the film, these pressure-sensitive adhesive sheets are often used for display labels of contents in containers such as shampoo and drinking water and for decoration of windows and the like. Further, these adhesive sheets are used for a certain period of time and then disposed of due to the nature of their intended use.

However, the above-mentioned plastic film containing a polyethylene resin does not hydrolyze in a natural environment, or has a very low hydrolysis rate, and therefore, when used, for example, when it is buried, It will remain in the soil semipermanently. Alternatively, in the case of dumping into the ocean, the landscape may be damaged or the living environment of marine organisms may be destroyed, and the disposal of these is a major problem from the viewpoint of conservation of the natural environment.

Further, as the pressure-sensitive adhesive used in the conventional pressure-sensitive adhesive sheet, as described above, the rubber-based pressure-sensitive adhesive containing natural rubber and synthetic rubber as the main component, the acrylic resin-based and the silicone resin-based as the main components. There is an adhesive that does. By the way, these pressure-sensitive adhesives generally have no biodegradability or have a very slow biodegradation rate, and are not practical as biodegradable pressure-sensitive adhesives. On the other hand, as a biodegradable pressure-sensitive adhesive, it is known that a polymer having a urethane bond is susceptible to deterioration by microorganisms, and it was sometimes used as a pressure-sensitive adhesive. Then, there was a problem that the adhesive property was inferior.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above problems and provides a biodegradable pressure-sensitive adhesive sheet which is easily hydrolyzed in a natural environment.

[0008]

The present invention provides a release sheet,
A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer and a surface base material laminated, wherein the pressure-sensitive adhesive and the surface base material constituting the pressure-sensitive adhesive layer have biodegradability.

[0009]

Specific examples of the biodegradable surface substrate used in the present invention include paper, a natural or water-soluble polymer such as polyvinyl alcohol, a blend of starch and modified poval, polypropylene, polystyrene and the like, Examples thereof include polyhydroxybutyric acid, a copolymer of hydroxybutyric acid and hydroxyvaleric acid, poly (3-hydroxyalkanoate), polybutylene succinate, polyethylene succinate, and polylactic acid.

On the other hand, in the case of blending starch and resin, there arises a problem that the starch is decomposed but the resin remains as it is to pollute the environment, or the decomposition rate of the resin is so slow that a large amount of it cannot be discarded. Further, in the case of a polymer of hydroxycarboxylic acid such as polyhydroxybutyric acid or a copolymer of hydroxybutyric acid and hydroxyvaleric acid, the film is opaque and elastic, and there is a risk that wrinkles may occur due to stretching during adhesive processing. is there.

On the other hand, polylactic acid and lactic acid-hydroxycarboxylic acid copolymer are known to have appropriate strength and to be easily hydrolyzed, and further, they can be easily hydrolyzed by an alkali treatment carried out when recycling used paper or the like. There are advantages such as From the above viewpoint, the biodegradable film used in the present invention is preferably a lactic acid-based polymer.

Incidentally, in the present invention, biodegradability means the property of being easily decomposed or eluted in soil or water.

Specific examples of the lactic acid type polymer include:
Polylactic acid, lactic acid or lactide and glycolic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxypentanoic acid,
Examples thereof include copolymers with hydroxycarboxylic acids such as hydroxycaproic acid and hydroxyheptanoic acid. The constituent units of polylactic acid include poly (L-lactic acid) consisting only of L-lactic acid, poly (D-lactic acid) consisting only of D-lactic acid, and poly (LD consisting of both in various proportions.
-Lactic acid) can be preferably used.

The lactic acid-based polymer used in the biodegradable pressure-sensitive adhesive sheet of the present invention is obtained by dehydration condensation of raw material monomers, or lactide, glycolide, which is a cyclic dimer of lactic acid,
Caprolactone, propiolactone, butyrolactone,
And cyclic ester such as valerolactone can be obtained by ring-opening polymerization.

In the present invention, 5 to 4 of all the monomer components are used as the monomer components constituting the copolymer which becomes the adhesive.
Particularly preferred is one in which 0 wt% consists of polyethylene glycol (meth) acrylate monomers. And
The polyethylene glycol (meth) acrylate monomer is a compound represented by the following general formula (1).

[0016]

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Here, R ₁ is a methyl group or a hydrogen atom,
R ₂ represents a methyl group or a phenyl group, respectively.
In addition, n is an integer of 1-10.

The blending ratio of the polyethylene glycol (meth) acrylate monomer is 5 to 40% by weight.
When the amount is less than 5% by weight, the biodegradability becomes insufficient, while when it exceeds 40% by weight, the cohesive force of the pressure-sensitive adhesive decreases and the function as a pressure-sensitive adhesive sheet tends to decrease. This is because.

In the present invention, the monomer composition of the pressure-sensitive adhesive used in addition to the polyethylene glycol (meth) acrylate monomer is (meth) acrylic acid C _14-
Examples thereof include C ₁₈ alkyl ester monomers and ethylenically unsaturated carboxylic acid-containing monomers. here,
Specific examples of the C ₁₄ -C ₁₈ alkyl ester monomer of (meth) acrylic acid include butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, and (meth) acrylic acid-2- Ethylhexyl,
Stearyl (meth) acrylate and the like can be mentioned.

Specific 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, etc. Is mentioned.

Furthermore, the above-mentioned polyethylene glycol (meth) acrylate monomer, C ₁₄ -C ₁₈ alkyl ester monomer of (meth) acrylic acid, and other monomer copolymerizable with the ethylenically unsaturated carboxylic acid-containing monomer may be added. it can. Specific examples of these other copolymerizable monomers include, for example, carboxylic acid-modified rosin ester monomers represented by the following general formula (2), methyl (meth) acrylate, ethyl (meth) acrylate, Propyl (meth) acrylate, cyclohexyl (meth) acrylate, methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, (meth) Examples thereof include glycidyl acrylate, vinyl acetate, vinyl propionate, ethylene, (meth) acrylonitrile, (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N, N′-methylenebis (meth) acrylamide.

Among these other copolymerizable monomers, carboxylic acid-modified rosin ester is particularly preferable in terms of biodegradability.

[0023]

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R ₁ represents a hydrogen atom or a methyl group, and n represents an integer of 1-8.

The method for producing the above-mentioned copolymer is not particularly limited, and for example, a method of emulsion polymerization in an aqueous system in the presence of water, a solvent, a chain transfer agent, a polymerization initiator, a dispersant and the like. Manufactured by. The monomer concentration during polymerization is usually 30 to 70% by weight, preferably 40.
About 60% by weight is suitable. Examples of the polymerization initiator used during the polymerization include persulfates such as potassium persulfate and ammonium persulfate, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4). -Dimethyl compounds such as dimethyl valeronitrile), hydrogen peroxide,
Examples thereof include so-called redox-based polymerization initiators composed of a combination of peroxides such as benzoyl peroxide and lauryl peroxide, ammonium persulfate and sodium sulfite, acidic sodium sulfite and the like.

The amount of the above-mentioned polymerization initiator to be used is usually adjusted in the range of 0.2 to 2% by weight, more preferably 0.3 to 1% by weight, based on the total amount of the monomers used for the polymerization.

Further, as the chain transfer agent added in the copolymerization, alkyl mercaptans such as octyl mercaptan, nonimercaptan, decyl mercaptan and dodecyl mercaptan, octyl thioglycolate, nonyl thioglycolate, 2-ethylhexyl thioglycolate, Examples thereof include thioglycolic acid esters such as 2-ethylhexyl β-mercaptopropionate, 2,4-diphenyl-4-methyl-1-pentene, 1-methyl-4-isopropylidene-1-cyclohexene and the like. In particular, 1-methyl-4-isopropylidene-1-
When cyclohexene is used, the resulting copolymer has a low odor and is more preferable. The amount of the chain transfer agent used is adjusted within the range of about 0.001 to 3% by weight of all the monomers to be polymerized. The polymerization reaction is usually 60 to
It is carried out at a temperature of 100 ° C. for 2 to 8 hours.
Further, the pressure-sensitive adhesive may contain a plasticizer, an emulsifier, a thickener, a defoaming agent, a dispersant and the like within a range that does not lose its adhesive performance and biodegradability.

The base material of the release sheet having biodegradability is, for example, high-density base paper such as glassine paper, clay-coated paper, kraft paper, or high-quality paper such as casein, dextrin, starch, carboxymethyl cellulose, methyl cellulose, ethyl cellulose. It is possible to use a release base material provided with a sealing layer mainly composed of a natural resin such as hydroxyethyl cellulose, polyvinyl alcohol and the like and a pigment. Moreover, you may use what laminated | stacked the biodegradable polymer like a lactic acid type polymer, or the biodegradable polymer film itself.

There is no particular limitation on the method for constructing the pressure-sensitive adhesive sheet, and the pressure-sensitive adhesive layer is formed by coating the pressure-sensitive adhesive on the surface of the release agent layer of the release sheet and drying according to a conventional method, and the surface substrate is attached. It is finished together. Examples of the release sheet include high-density base paper such as glassine paper, clay-coated paper, kraft paper, and high-quality paper, and natural resins such as casein, dextrin, starch, carboxymethyl cellulose, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, etc. Water-, solvent- or solvent-free fluororesin or silicone on the release base material such as one with a sealing layer mainly composed of pigment and pigment, one laminated with biodegradable polymer, or biodegradable polymer film Resin weight is 0.05 ~
It is used in which a release agent layer is formed by coating at about 3 g / m ² and thermally curing, curing by irradiation with ionizing radiation, or the like.

As the coating apparatus in this case, for example, a multi-stage roll coater, an air knife coater, a bar coater, an offset gravure coater, a direct gravure coater or the like is used. The pressure-sensitive adhesive is usually applied to the release sheet after adjusting the viscosity to about 3,000 to 8,000 centipoise by adjusting the molecular weight, diluting with water, or increasing the viscosity. As the coating device in this case, for example, a reverse roll coater, a knife coater, an air knife coater, a bar coater, a slot die coater, a lip coater, a reverse gravure coater, or the like is used, and the coating amount is 5 to 50 g / dry weight. m ²
It is adjusted within a range.

[0031]

The present invention will be specifically described below with reference to examples, but of course the present invention is not limited to these examples. Further, all parts, ratios, coating amounts, etc. in the examples are shown by solid content weight unless otherwise specified.

Example 1 (Synthesis of carboxylic acid-modified rosin ester) 70 g of methacrylic acid and 90 g of epichlorohydrin were placed in a flask equipped with a stirrer, an exhaust pipe, a dropping funnel, a nitrogen suction pipe and a thermometer.
Was charged, the temperature was raised to 100 ° C. under nitrogen gas, and the temperature was maintained for 2 hours. Then, 300 g of fully dissolved rosin abietic acid was added, and the mixture was kept at 230 ° C. for 2 hours. Further, 125 g of glutaric anhydride was added, and the mixture was kept at 230 ° C. for 2 hours to synthesize a carboxylic acid-modified rosin ester represented by the following general formula (3).

[0033]

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(Production of pressure-sensitive adhesive) First, as an emulsified monomer mixture liquid, a carboxylic acid-modified rosin ester represented by the general formula (3): 60 parts methoxydiethylene glycol methacrylate: 60
Parts Butyl acrylate: 100 parts 2-Ethylhexyl acrylate: 100 parts Acrylic acid: 40 parts Dimethylaminoethyl methacrylate: 40 parts Anionic emulsifier (trade name: Emal NC-35 / Kao Corporation): 6 parts Ions Exchanged water: Prepared by mixing 150 parts.

Next, a flask equipped with a stirrer, a cooler, a dropping funnel, a nitrogen suction tube, and a thermometer was charged with 150 parts of ion-exchanged water, 3 parts of potassium peroxide, and 3 parts of octyl mercaptan, and the mixture was replaced with nitrogen at 80 ° C. After heating to
The emulsified monomer mixture liquid was dropped ⅙. Reaction rate is 9
When it reached 0%, the remaining monomer mixture was added dropwise over 3 hours to carry out polymerization. After the dropping was completed, the reaction was completed by aging at 80 ° C. for 3 hours. Next, put the contents of the flask at 40 ° C.
After cooling to room temperature, ammonia water was added to carry out a neutralization reaction, and after completion of the reaction, vigorous stirring was carried out to produce an adhesive for use in the present invention.

(Preparation of Adhesive Sheet) Commercially available clay-coated release paper was coated with the above adhesive at a dry weight of 22 g / m ² and dried, and the adhesive layer surface and a commercially available polylactic acid film ( Product name: Lacty / manufactured by Shimadzu Corporation) The back surface was pasted to create an adhesive sheet.

Example 2 A pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1 except that the surface base material was changed to a polyester biodegradable plastic film (trade name: Biopol / manufactured by Zeneca UK). Created.

Example 3 A pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1 except that the surface base material was changed to high-quality paper having a weight of 64 g / m ² of rice.

Example 4 A pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1 except that the addition amount of methoxydiethylene glycol methacrylate in the monomer composition of the pressure-sensitive adhesive was changed to 10% by weight.

Example 5 A pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1 except that the amount of methoxydiethylene glycol methacrylate in the monomer composition of the pressure-sensitive adhesive was changed to 35% by weight.

Example 6 A pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1 except that the base material of the release sheet was changed to a commercially available polylactic acid film.

Example 7 A pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1 except that the addition amount of methoxydiethylene glycol methacrylate in the monomer composition of the pressure-sensitive adhesive was changed to 0.

Example 8 A pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1 except that the addition amount of methoxydiethylene glycol methacrylate in the monomer composition of the pressure-sensitive adhesive was changed to 50% by weight.

Example 9 A pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1 except that the commercially available polyethylene laminated release paper was used as the release sheet.

Comparative Example 1 An adhesive sheet was prepared in the same manner as in Example 1 except that the commercially available polyethylene terephthalate film was used as the surface substrate.

Comparative Example 2 In the same manner as in Example 1, except that the pressure-sensitive adhesive was changed to a commercially available general-purpose type (trade name: Nikasol L-145 / Nippon Carbide Industry Co., Ltd.). An adhesive sheet was created.

Comparative Example 3 A pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1 except that the commercially available polyethylene terephthalate film was used as the surface substrate and the commercially available general-purpose adhesive was used. .

Comparative Example 4 In Example 1, except that the surface substrate was changed to a commercially available polyethylene terephthalate film, the adhesive was changed to a commercially available general type, and the release sheet was changed to a commercially available polyethylene terephthalate film release paper. A pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1.

The adhesive sheet obtained as described above was subjected to the following evaluation test, and the obtained results are shown in Table 1.

[Evaluation Test Items] (Adhesive Strength) The adhesive strength to the SUS plate and the glass plate was measured according to the method for measuring the normal adhesive strength of JISZ-0237 (unit: g / 25 mm).

(Biodegradability) The shape of the pressure-sensitive adhesive sheet was visually observed after the pressure-sensitive adhesive sheet was buried in the soil (about 50 cm below the ground) on the premises of Shin-Oji Paper Co., Ltd. and Osaka Commodity Research Institute for 12 months. The evaluation was performed according to the following criteria. A: The sheet itself is almost in its original form and is disassembled. B: About 2/3 of the sheet is disassembled. C: About 1/3 of the sheet is decomposed. D: The shape of the sheet is maintained, but it is partially decomposed (decomposition less than 1/3 of the sheet) E: Almost not decomposed.

[0052]

[Table 1]

[0053]

As is clear from Table 1, the biodegradable pressure-sensitive adhesive sheet of the present invention exhibits the necessary adhesive strength when applied, and when it is discarded after use and buried in the soil, microorganisms in the soil are present. The pressure-sensitive adhesive sheet was extremely easily decomposed by the above.

Claims (4)

[Claims] 1. A pressure-sensitive adhesive sheet obtained by laminating a release sheet, a pressure-sensitive adhesive layer, and a surface base material, wherein the pressure-sensitive adhesive and the surface base material constituting the pressure-sensitive adhesive layer are biodegradable. Adhesive sheet. 2. A monomer composition constituting a copolymer which is an adhesive agent, wherein 5 to 40% of the total weight thereof is a polyethylene glycol (meth) acrylate monomer.
The biodegradable adhesive sheet described. 3. The biodegradable pressure-sensitive adhesive sheet according to claim 1, wherein the surface substrate is a lactic acid-based polymer film. 4. The biodegradable pressure-sensitive adhesive sheet according to claim 1, wherein the release sheet is made of a base material having biodegradability.