JPH0925468A - Grafted natural rubber adhesive and its adhesive tape - Google Patents

Abstract

(57) [Summary] [Purpose] Various properties such as adhesive properties, water resistance, electrical insulation properties, etc., without compromising the modifying effect of grafting with vinyl-based monomers, excellent film-forming properties, and without the need for high-temperature treatment. To obtain a latex-based graft natural rubber-based pressure-sensitive adhesive exhibiting excellent performance. A graft natural rubber-based pressure-sensitive adhesive containing a copolymer obtained by graft-polymerizing a vinyl-based polymer on a natural rubber having a protein content of 0.1% by weight or less based on the nitrogen, and a support. An adhesive tape having a layer formed by coating the graft natural rubber-based adhesive on one or both sides. [Effect] It is possible to obtain a latex type natural rubber-based pressure-sensitive adhesive that is excellent in safety such as environmental hygiene and disaster prevention while achieving improvement in adhesive property modification by grafting natural rubber.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a graft natural rubber-based pressure-sensitive adhesive in a latex state having excellent pressure-sensitive adhesive properties, and a pressure-sensitive adhesive tape using the same.

[0002]

BACKGROUND ART Conventionally, a latex type natural rubber-based pressure-sensitive adhesive using a natural rubber latex whose concentration is adjusted has been known. However, in addition to the fact that the film-forming property is poor, and that a high-temperature destructive treatment of the latex is required in order to exhibit practical adhesive properties, and a large amount of energy is required for attaching the adhesive layer on the support due to high-temperature drying, Compared to the solution type of natural rubber dissolved in an organic solvent, there are problems that it is inferior in various properties such as adhesive property, water resistance, electric insulation, etc. Therefore, although there is an advantage of the solvent removal type, it is not in practical use Is.

On the other hand, as the solution-type natural rubber-based pressure-sensitive adhesive, there has been known one using a natural rubber obtained by graft-polymerizing a vinyl-based monomer. The purpose of graft copolymerization of natural rubber is to improve the adhesive properties such as adhesive strength and adherend selectivity, for example, by graft-polymerizing methyl methacrylate to obtain cohesive strength and adhesion to polar substances such as metals. The adhesive strength is improved, the adhesive residue during re-peeling is prevented, and the strong adhesion between the rubber plate and the metal is achieved, and the performance as a surface protection sheet for metal plates and fixing plate with good revisionability is achieved. improves. However, as described above, it is a solution type, and the lack of safety such as environmental hygiene and disaster prevention has not been overcome.

[0004]

Technical Problem of the Invention The present invention is excellent in film-forming property without impairing the modification effect by grafting with a vinyl-based monomer, does not require high temperature treatment, and has excellent adhesive properties, water resistance, electrical insulation properties, etc. The objective is to develop a latex-based graft natural rubber-based pressure-sensitive adhesive that exhibits excellent properties.

[0005]

Means for Solving the Problems The present invention is characterized in that a natural rubber having a protein content of 0.1% by weight or less based on its nitrogen content is copolymerized with a vinyl polymer graft-polymerized in a latex state. Grafted natural rubber adhesive,
And a pressure-sensitive adhesive tape having a layer formed by coating the graft natural rubber-based pressure-sensitive adhesive on one or both sides of a support.

[0006]

Industrial Applicability According to the present invention, a latex type natural rubber-based pressure-sensitive adhesive having excellent safety such as environmental hygiene and disaster prevention while achieving improvement in adhesive property modification by grafting natural rubber is obtained. Thus, a coating film can be formed without the need for high-temperature treatment, and various properties such as excellent adhesive properties, water resistance, and electrical insulation properties can be exhibited.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The grafted natural rubber-based pressure-sensitive adhesive of the present invention is a latex of a copolymer obtained by graft-polymerizing a vinyl-based polymer on a natural rubber having a protein content of 0.1% by weight or less based on its nitrogen. It is contained in. The natural rubber can be prepared by, for example, a method of deproteinizing the natural rubber latex and graft-polymerizing it with a vinyl monomer.

The deproteinization method is not particularly limited, for example, a method of degrading a protein by adding a proteolytic enzyme or bacteria to natural rubber latex, a method of repeatedly washing by adding a surfactant, and the like. It can be performed by an appropriate method such as a method of using together. As the natural rubber latex to be treated, field latex and industrial latex such as ammonia-treated or concentration-adjusted latex can be used.

By the deproteinization treatment, the protein that highly stabilizes the natural rubber latex by the emulsifying action is removed,
A latex system that can be destroyed without the need for high-temperature treatment, exhibits good coating film-forming properties, and can be obtained as a natural rubber latex that is well compatible with tackifiers, etc., and has excellent safety such as environmental hygiene and disaster prevention. The adhesive can be prepared.

The content of protein in the natural rubber latex obtained by the deproteinization treatment is 0.1% by weight or less based on nitrogen. That is, the protein is deproteinized so that the value when the protein content is converted into the nitrogen content is 0.1% by weight or less. When the content exceeds 0.1% by weight, the effect of improving film-forming property, high temperature treatment unnecessary property, water resistance and electric insulation becomes poor, and the adhesive property and water resistance are comparable to those of solution type adhesive. Etc. are difficult to develop.

The preferable protein content based on the nitrogen conversion is 0.05% by weight or less, and particularly when it is 0.02% by weight or less, especially 0.01% by weight or less, the adhesive strength and the electric insulation Retention effect (creep resistance)
Also improves. It is considered that the characteristic of the natural rubber latex type, which is excellent in electric insulation, is that the protein, which is easily charged, is removed.

[0012] The above-described method for deproteinizing with a proteolytic enzyme has the advantage that proteins can be removed with high precision, but the proteolytic enzyme used is not particularly limited. Any of bacteria-derived products, filamentous fungi-derived products, yeast-derived products and the like can be used. Proteolytic enzymes that can be preferably used are bacterial proteases.

The treatment conditions, that is, the amount and method of addition of the proteolytic enzyme, the treatment temperature and the treatment time, may be appropriately determined. By the way, the proteolytic enzyme is added to the field latex in a proportion of 0.001 to 10% by weight, and if necessary, under temperature control of 5 to 90 ° C, especially 20 to 60 ° C,
After standing or stirring for several minutes to 1 week, it is diluted with water or an aqueous solution of a surfactant and the protein is separated and removed by an appropriate separation method such as a centrifuge or a separation membrane, and the latex is washed and purified. And so on.

As the above-mentioned detergent for cleaning and purification, an appropriate one such as cation type, anion type, nonion type and zwitterionic type can be used. Preferably, it has an excellent emulsifying action and hardly absorbs water. Such emulsifying action,
It is related to the stability of the latex during the graft polymerization treatment and to the pressure sensitive adhesive, and the non-absorption of water is related to the water resistance of the pressure sensitive adhesive.

On the other hand, the deproteinization treatment method using a surfactant is one in which the natural rubber latex is washed and purified with a surfactant in accordance with the above-mentioned washing and purification method to deproteinize. As the surfactant, An appropriate one can be used. For the same reason as above, it is preferable that it has an excellent emulsifying action and hardly absorbs water.

Incidentally, examples of the above-mentioned surfactant for deproteinization treatment include anionic surfactants such as carboxylic acid type, sulfonic acid type, sulfuric acid ester type and phosphoric acid ester type, and POA (polyoxyalkylene). Ether and PO
Nonionic surfactants such as A-ester type, polyhydric alcohol ester type and POA polyhydric alcohol ester type, glucoside type and POA glucoside type, amphoteric surfactants such as amino acid type and betaine type, imidazoline type and amine oxide type Can be given.

Specific examples of the above-mentioned anionic surfactants include metal salts such as fatty acids, alkylbenzene sulfonic acids, alkyl sulfates and alkylphenol phosphates, ammonium salts, alkanolamine salts and the like. Specific examples of the nonionic surfactant include POA alkyl ether, POA fatty acid ester, sorbitol fatty acid ester and fatty acid ester of polysaccharide, POA polysaccharide fatty acid ester and alkyl (poly).
Examples include glucoside and POA alkylamine.
Specific examples of the amphoteric surfactant include an acylamino acid salt, alkyldimethylbetaine, alkylcarboxymethylhydroxyethylimidazolium betaine, alkyldimethylamine oxide and the like.

The surfactant to be used may contain one or more of the above-mentioned surfactants for deproteinization as an active ingredient, and the addition amount thereof may be stability of the formed latex, adhesive property and the like. From the point of, the natural rubber latex of 0.
001-10 weight% is preferable. The surfactant for deproteinization described above can also be used for the purification treatment of a solution deproteinized with a protease.

The copolymer of natural rubber graft-polymerized with a vinyl polymer, that is, a latex of grafted natural rubber is prepared, for example, by adding a vinyl monomer and a polymerization initiator to the natural rubber latex before or after deproteinization. It can be carried out by a method such as emulsion polymerization treatment. Therefore, either the deproteinization treatment or the graft polymerization treatment of the natural rubber latex may precede.

As the vinyl-based monomer, an appropriate one can be used depending on the purpose of modification by grafting,
Any vinyl-based monomer can be graft-polymerized. Examples thereof include a carboxyl group-containing substance such as (meth) acrylic acid or itaconic acid, an alkyl group such as a methyl group or an isopropyl group, a butyl group or an isooctyl group, and particularly an alkyl group having 20 or less carbon atoms. (Meta)
Examples thereof include acrylic monomers such as alkyl esters of acrylic acid, hydroxyalkyl esters of (meth) acrylic acid having a hydroxyalkyl group such as hydroxyethyl group and hydroxypropyl group, and hydroxyl group-containing substances such as glycerin dimethacrylate.

Further, vinyl acetate, styrene, (meth) acrylonitrile, (meth) acrylamide, isopropylmaleimide, cyclohexylmaleimide, N-vinylpyrrolidone, (meth) acryloylmorpholine, N, N
-Vinyl-based monomers such as dimethyl acrylamide and glycidyl methacrylate are also included.

A vinyl-based monomer which can be preferably used from the viewpoint of adhesive properties is a polar group-containing one such as methyl methacrylate or styrene which forms a homopolymer having a high glass transition temperature. As the vinyl-based monomer, one kind or two or more kinds can be used, and the addition amount thereof is not particularly limited and can be appropriately determined. Generally, from the viewpoint of the reactivity of graft polymerization and the effect of modification, natural rubber 1
5 to 100 parts by weight, especially 10 to 50 parts by weight of the vinyl-based monomer is used per 00 parts by weight.

Graft polymerization of the vinyl-based monomer by emulsion polymerization is carried out by a suitable method such as a method of adding an emulsifier to natural rubber latex and adding the vinyl-based monomer, or a method of emulsifying and adding the vinyl-based monomer with an emulsifier. Can be taken. Examples of the emulsifier include a surfactant for deproteinization and an amine-based surfactant exemplified above.
Those containing one or more reactive surfactants as active ingredients are used.

Specific examples of the above-mentioned amine-based surfactants include acid salts or quaternary ammonium salts of (mono-, di-, tri-) alkylamines and their alkylene oxide adducts. Specific examples of reactive surfactants include anionic or cationic ones such as POA alkylpropenyl phenyl ether sulfate ester salt, POA (meth) acrylic acid ester, and dimethylalkylallyloxyhydroxypropyl ammonium chloride, and nonionic ones. Can be given.

On the other hand, the graft polymerization initiator is not particularly limited, and various vinyl polymerization initiators can be used, and the addition method thereof is also not particularly limited. Examples of commonly used polymerization initiators include 2,
Azo compounds such as 2'-azobisisobutyronitrile and 2,2'-azobis (2-diaminopropane) dihydrochloride, persulfates such as potassium persulfate and ammonium persulfate, benzoyl peroxide and t-butylhydro. Examples thereof include peroxides such as peroxides and cumene hydroperoxides, redox initiators such as combinations of persulfates and sodium bisulfite, and combinations of peroxides and amines.

The method of adding the polymerization initiator may be, for example, a method of adding the whole amount before the polymerization treatment, a method of dividing at the time of heating of the polymerization reaction, or a method of adding all at once, by mixing two or more kinds of initiators or Another method or a method of adding with a time lag is included. A preferred method is a method in which the entire amount of a redox type initiator using a peroxide is added in advance to start the polymerization.

The addition amount of the polymerization initiator is preferably about 0.001 to 1% based on the molar ratio with respect to the vinyl monomer from the viewpoints of the progress of graft polymerization and the inhibition of rubber crosslinking. In addition, the polymerization treatment should be performed under nitrogen substitution at 10 to 80 ° C. for 2 to 100 hours from the viewpoint of stable progress of graft polymerization, completion of polymerization, and suppression of formation of aggregates due to destabilization of latex. Is preferred.

The graft natural rubber-based pressure-sensitive adhesive of the present invention can be prepared in various forms containing the deproteinized graft natural rubber in the form of a latex. As an example thereof, an emulsion-based or water-dispersed pressure-sensitive adhesive using a grafted natural rubber having a predetermined protein content in place of the conventional natural rubber latex, and other emulsion-based or water-dispersed pressure-sensitive adhesives are prescribed. Examples include those to which the grafted natural rubber having the protein content of is added.

A typical graft natural rubber-based pressure-sensitive adhesive according to the present invention has, for example, a solid content concentration of the graft natural rubber of a predetermined protein content of 30 to 80% by weight, especially 45 to 7%.
0% by weight latex and tackifier (tackifier)
It is a dispersion liquid type in which a grafted natural rubber and a tackifier are mixed by mixing the emulsion of (1). At that time, for example, a softener or a plasticizer, an antiaging agent, a filler,
Appropriate additives such as pigments and colorants may be added.

Examples of the tackifier include rosin ester, hydrogenated rosin ester, rosin-based resin such as disproportionated rosin ester and polymerized rosin ester, coumarone indene resin, hydrogenated coumarone indene resin, and phenol-modified coumarone indene. Resin or coumarone indene resin such as epoxy modified coumarone indene resin, polyterpene resin or styrene modified terpene resin, terpene resin such as phenol modified terpene resin, aliphatic petroleum resin or aromatic petroleum resin, aromatic modified fat Appropriate materials such as petroleum-based resins such as group-based petroleum resins and aromatic pure monomer resins can be used. The compounding amount of the tackifier is generally 10 to 200 parts by weight per 100 parts by weight of the graft natural rubber, but is not limited to this.

The pressure-sensitive adhesive tape of the present invention has a layer formed by coating the above-mentioned grafted natural rubber-based pressure-sensitive adhesive on one side or both sides of the support. The pressure-sensitive adhesive layer may be fixed to the support or may be peelable from the support. The peelable type can be formed by, for example, a method using a support treated with a release agent. As the support, for example, a suitable material such as plastic film, paper, non-woven fabric, foam, metal foil or a laminate thereof can be used. The thickness of the pressure-sensitive adhesive layer provided on the support is generally 1 to 500 μm, but is not limited to this and may be an appropriate thickness.

[0032]

【Example】

Example 1 Pure water was added to HA type natural rubber latex (commercial product, rubber solid content 60% by weight) produced in Malaysia to make the rubber solid content concentration 30% by weight, and 2% by weight nonionic anion complex type surfactant. , Proteolytic treatment was carried out by adding bacterial-derived proteolytic enzyme to a concentration of 0.02% by weight and leaving it at 40 ° C. for 24 hours, and then adding pure water to the natural rubber latex to obtain a rubber solid content concentration. To 10% by weight,
The operation of washing and concentrating the concentration to 60% by weight with a DeLaval continuous centrifuge was repeated three times, and the protein content was 0.01 based on the nitrogen as measured by the Kjeldahl method.
A weight percent deproteinized natural rubber latex was obtained.

Then, pure water was added to the above-mentioned deproteinized natural rubber latex to make the rubber solid content concentration 50% by weight, and a nonionic surfactant was added thereto to make the concentration 2% by weight, and then the atmosphere was replaced with nitrogen. 30% by weight of methyl methacrylate and 0.3% by weight of aromatic peroxide with respect to the rubber solid content, and 0.1% by weight of the rubber solid content under stirring. The amine compound of 1 was gradually added dropwise as a dilute aqueous solution, and after completion of the dropping, the graft polymerization treatment was continued for about 2 hours to lower the heating, and a latex of grafted natural rubber was obtained.

Next, water 140 containing 50 parts of terpene-based tackifying resin (parts by weight, the same applies hereinafter), 50 parts of polybutene-based softening agent, 100 parts of toluene, and 1 part of antioxidant and 2 parts of nonionic surfactant. To 200 parts of the graft natural rubber latex having a rubber solid content of 50% by weight, to obtain a graft natural rubber-based pressure-sensitive adhesive having a thickness of 30 μm. Was coated on the polyester film of No. 1 and dried at 100 ° C. for 5 minutes to obtain an adhesive tape having an adhesive layer with a thickness of about 40 μm.

Comparative Example 1 Grafted natural rubber was prepared in the same manner as in Example 1 except that HA type natural rubber latex (nitrogen-based protein content: about 0.25% by weight) was subjected to a graft polymerization treatment without being subjected to a proteolytic treatment. A system adhesive and an adhesive tape were obtained.

Comparative Example 2 A grafted natural rubber-based pressure-sensitive adhesive and a pressure-sensitive adhesive tape were obtained in the same manner as in Example 1 except that the proteolytically-treated natural rubber latex was used without being graft-polymerized.

Evaluation Test The adhesive tapes obtained in Examples and Comparative Examples were examined for the following characteristics. Film-forming property The adhesive layer in the adhesive tape immediately after drying was observed, and when the film-forming property was good, it was evaluated as ◯, and when it was poor, it was evaluated as x.
The goodness and poorness of the film forming property of the pressure-sensitive adhesive layer is based on the electron micrograph. That is, when the film-forming property is good, the emulsion is satisfactorily destroyed by heat and the components are compatible with each other. In this case, the pressure-sensitive adhesive layer is visually excellent in transparency. On the other hand, when the film-forming property is poor, the emulsion is not sufficiently destroyed by heat and the mutual compatibility of the components is poor. In this case, the pressure-sensitive adhesive layer is visually clouded.

Adhesive Strength A 2 mm thick adhesive tape was applied to a 2 mm thick stainless steel plate surface-polished with a No. 280 water-resistant abrasive paper by reciprocating a 2 kg rubber roller once for 30 minutes to examine the adhesive strength ( 180 degree peeling, pulling speed 300mm / min, 23 ℃,
65% RH).

Holding power: At 23 ° C., an adhesive tape having a width of 5 mm was applied to a bake plate as described above.
C. An area of 20 mm in length was crimped and drooped, a uniform load of 500 g was applied to the free end of the adhesive tape, the temperature was kept at 40 ° C., and the time until the adhesive tape peeled off was measured with a creep tester. .

Water resistance: According to the above adhesive strength measurement test, an adhesive tape was pressure-bonded to a stainless steel plate, immersed in water at 23 ° C. for 72 hours to be taken out, and after the surface water was wiped off for 30 minutes, its adhesive strength was examined. It was

Insulating property The surface resistivity of the pressure-sensitive adhesive layer in the pressure-sensitive adhesive tape was examined according to JIS K 6911.

The above results are shown in the following table.

It can be seen from Table 1 that the grafted natural rubber-based pressure-sensitive adhesives of Examples are excellent in film-forming property, adhesive force, cohesiveness (holding power), water resistance, and electrical insulating property and are excellent in practicality.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yasuyuki Tanaka 1481-184 Uchikoshi-cho, Hachioji-shi, Tokyo (72) Inventor Kazuhiko Shibata 1-2-1, Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation (72) Inventor Shoji Hayashi 1334 Minato Minato, Wakayama, Wakayama Kao Stock Company Wakayama Research Institute (72) Inventor Shinichi Nakade 3-31 Kasugaoka, Itami, Hyogo (72) Inventor Eiji Kanemaru 2917 Asahi, Sano, Tochigi -1

Claims (3)

[Claims] 1. A protein content of 0.
A grafted natural rubber-based pressure-sensitive adhesive, comprising a copolymer of 1% by weight or less of natural rubber graft-polymerized with a vinyl-based polymer in a latex state. 2. The graft natural rubber-based pressure-sensitive adhesive according to claim 1, wherein the vinyl-based polymer contains one or both of methyl methacrylate and styrene as a component. 3. The support according to claim 1 or 2 on one side or both sides of the support.
A pressure-sensitive adhesive tape having a layer formed by coating the graft natural rubber-based pressure-sensitive adhesive as described in 1.