JPH06192634A - Natural-rubber-based self-adhesive composition and self-adhesive tape prepared therefrom - Google Patents

Abstract

PURPOSE:To provide a compsn. which is prepd. from a latex, is excellent in film-forming properties requiring no high-temp. treatment, has self-adhesive characteristics, water resistance, electrical insulating properties. etc., equivalent to those of a solvent-based self-adhesive compsn., and is excellent in safety properties such as environmental hygiene and fire prevention, and to provide a self-adhesive tape prepd. from the compsn. CONSTITUTION:The compsn. contains a latex of a natural rubber contg. 0.1wt.% protein determined by nitrogen content. A self-adhesive tape is prepd. by applying the compsn. to at least one side of a substrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a latex-type natural rubber-based pressure-sensitive adhesive composition having excellent adhesive properties, and a pressure-sensitive adhesive tape using the same.

[0002]

2. Description of the Related Art Conventionally, as a natural rubber-based pressure-sensitive adhesive composition containing natural rubber in a latex state, a natural rubber latex which has been industrially prepared has been known. However, in order to destroy the natural rubber latex and make it compatible with tackifier and the like to develop practical adhesive properties, high temperature treatment is required and the film-forming property is poor, and an adhesive layer is attached on the support. Has a problem that a large amount of energy is required due to high temperature drying. In addition, it is inferior in various properties such as adhesive properties, water resistance, electrical insulation, etc. compared to those prepared as a solution system using a solvent, and therefore it is also excellent in safety such as environmental hygiene and disaster prevention property due to the absence of solvent. Nevertheless, it is not in practical use.

[0003]

DISCLOSURE OF THE INVENTION The present invention has excellent film-forming properties and does not require high-temperature treatment, and has performance comparable to that prepared in a solution system with respect to various properties such as adhesive properties, water resistance, and electrical insulation properties. It is an object of the present invention to develop a latex-based natural rubber-based pressure-sensitive adhesive composition excellent in safety such as environmental hygiene and disaster prevention, or its pressure-sensitive adhesive tape.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides a natural rubber-based pressure-sensitive adhesive composition characterized by containing a natural rubber in a latex state in which the content of protein is 0.1% by weight or less based on the nitrogen. And a layer comprising the natural rubber-based pressure-sensitive adhesive composition applied on one side or both sides of a support.

[0005]

The present inventors have conducted extensive studies to overcome the above-mentioned problems, and the problem of the conventional pressure-sensitive adhesive composition using a natural rubber latex is that the protein contained in the natural rubber causes the problem. Investigated. That is, a commercially available natural rubber latex obtained as a sap contains about several percent of protein, and it functions as an emulsifier to form a latex state. Such a latex is a polymer which is easily denatured by heat. Since it is a body, it was determined that high temperature is required for destruction and film forming property is deteriorated.

[0006] Therefore, by using the natural rubber from which proteins have been removed, even when it is prepared into a latex-based pressure-sensitive adhesive composition which is excellent in safety such as environmental hygiene and disaster prevention, it exhibits excellent film-forming properties and high temperature. It can be broken without requiring treatment, and it is compatible with tackifiers and the like, and exhibits various properties such as adhesive properties and water resistance comparable to those when prepared in a solution system.
Moreover, surprisingly, it is a latex, but it also has excellent electrical insulation. It is considered that this is because the protein is easily charged and is removed.

[0007]

[Exemplary constituent elements of the present invention] The natural rubber-based pressure-sensitive adhesive composition of the present invention has a protein content of 0.1% by weight or less based on the nitrogen (value when the protein content is converted into the nitrogen content). It contains the natural rubber of 1. in the form of latex.
If the protein content exceeds 0.1% by weight based on nitrogen, the improvement effect is difficult to be exhibited. The preferred protein content is 0.05% by weight or less based on the nitrogen. Above all, when the content is 0.02% by weight or less, particularly 0.01% by weight or less, the holding force (creep resistance) and the water resistance are improved in addition to the effect of improving the adhesive force and the electric insulating property. The removal of the protein from the natural rubber may be carried out by an appropriate method such as a method of treating with a proteolytic enzyme.

A surfactant is used for forming a latex of natural rubber having a predetermined protein content, and examples of the surfactant include cationic, anionic, nonionic, and zwitterionic. From the viewpoint of improving the water resistance of the obtained pressure-sensitive adhesive layer, it is preferable that the adhesive layer does not easily absorb water like proteins.

The natural rubber-based pressure-sensitive adhesive composition of the present invention can be prepared as various compositions containing natural rubber in the form of a latex. Examples thereof include emulsion-based or water-dispersed PSA compositions using natural rubber having a predetermined protein content in place of conventional natural rubber latex, and other emulsion- or water-dispersed PSA compositions. For example, a product obtained by adding natural rubber having a predetermined protein content to the product.

A typical natural rubber-based pressure-sensitive adhesive composition according to the present invention is adhered to natural rubber by, for example, mixing a latex of natural rubber having a predetermined protein content with an emulsion of a tackifier (tackifier). It is of a dispersion type that contains an imparting agent. At that time, for example, suitable additives such as a softening agent or a plasticizer, an antiaging agent, a filler, a pigment, a coloring agent and the like can be added.

Examples of the tackifier include rosin ester, hydrogenated rosin ester, disproportionated rosin ester, rosin-based resin such as polymerized rosin ester, coumarone indene resin, hydrogenated coumarone indene resin, and phenol-modified coumarone indene. Resin, coumarone indene resin such as epoxy modified coumarone indene resin, polyterpene resin, styrene modified terpene resin, terpene resin such as phenol modified terpene resin, aliphatic petroleum resin, 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 tackifier content is generally 10 to 200 parts by weight per 100 parts by weight of 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 natural rubber-based pressure-sensitive adhesive composition on one side or both sides of a 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, and metal foil can be used. The thickness of the pressure-sensitive adhesive layer provided on the support is 1 to 500 μm.
m is generally used, but the thickness is not limited to this and may be an appropriate thickness.

[0013]

EFFECTS OF THE INVENTION The natural rubber-based pressure-sensitive adhesive composition of the present invention exhibits various characteristics such as excellent adhesive properties, water resistance, and electrical insulation without the need for high temperature treatment, and is safe for environmental hygiene and disaster prevention. It has excellent properties.

[0014]

【Example】

Example 1 50 parts of terpene-based tackifying resin (parts by weight, the same applies hereinafter),
An emulsion obtained by adding 50 parts of a softening agent, 100 parts of toluene, and 1 part of an anti-aging agent to 140 parts of water containing 2 parts of a nonionic surfactant and stirring the mixture, and the content of protein based on the nitrogen thereof was about 0. A latex prepared by dispersing 100 parts of 03% by weight of natural rubber in water using a nonionic surfactant was mixed to prepare a natural rubber-based pressure-sensitive adhesive composition. Then, the natural rubber-based pressure-sensitive adhesive composition was applied onto a polyester film having a thickness of 25 μm and dried at 70 ° C. for 8 minutes to obtain a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer having a thickness of about 30 μm.

Example 2 A natural rubber-based pressure-sensitive adhesive composition and a pressure-sensitive adhesive tape were obtained in the same manner as in Example 1 except that natural rubber having a protein content of about 0.02% by weight based on the nitrogen was used.

Example 3 A natural rubber-based pressure-sensitive adhesive composition and pressure-sensitive adhesive tape were obtained in the same manner as in Example 1 except that natural rubber having a protein content of about 0.01% by weight based on the nitrogen was used.

Comparative Example A natural rubber-based pressure-sensitive adhesive composition and a pressure-sensitive adhesive tape were obtained in the same manner as in Example 1 except that a natural rubber having a protein content of about 0.25% by weight based on the nitrogen was used.

Evaluation Test The following tests were conducted on the pressure-sensitive adhesive tapes obtained in Examples and Comparative Examples. 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 steel plate surface-polished with water-resistant abrasive paper No. 280 was pressure-bonded with an adhesive tape having a width of 20 mm by reciprocating a 2 kg rubber roller once, and after 30 minutes, the adhesive strength was examined (180 Degree peel, pulling speed 300 mm / min, 23 ° C, 65% R.
H.).

Water resistance In accordance with the above, after the pressure-sensitive adhesive tape was pressure-bonded to a steel plate, it was placed in water at 23 ° C for 7
Dip for 2 hours to remove, wipe off surface moisture and remove
After a lapse of minutes, the adhesive strength was examined.

Holding power: 23 ° C., the adhesive tape was applied to a bake plate in a width of 5 mm as described above.
C. A length of 20 mm was crimped and hung down, 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. .

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 Table 1.

[Table 1]

It can be seen from Table 1 that the natural rubber-based pressure-sensitive adhesive composition of the present invention is excellent in film-forming property, pressure-sensitive adhesive property, water resistance and electric insulation property and is excellent in practicality.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Yasuyuki Tanaka 1481-184 Uchikoshi-cho, Hachioji-shi, Tokyo

Claims (2)

[Claims] 1. A protein content of 0.
A natural rubber-based pressure-sensitive adhesive composition comprising 1% by weight or less of natural rubber in a latex state. 2. A pressure-sensitive adhesive tape comprising a support and a layer formed by coating the natural rubber-based pressure-sensitive adhesive composition according to claim 1 on one side or both sides of the support.