JPH089709B2 - Method for producing solvent-based natural rubber adhesive - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a solvent-type natural rubber-based pressure-sensitive adhesive, and more specifically, the dissolution time in a solvent is significantly shortened to improve productivity. The present invention also relates to a method for producing a solvent-based natural rubber adhesive.

[Conventional technology]

The natural rubber-based pressure-sensitive adhesive is usually used as a solvent type by mixing natural rubber with various components such as a tackifying resin, a softening agent, an antiaging agent, and a filler. This solvent-based natural rubber-based pressure-sensitive adhesive is prepared by dissolving the raw material in an organic solvent such as hexane, heptane, or toluene, applying it to the base material by a coating method such as gravure, reverse, or doctor, and then scattering the solvent to form an adhesive tape. There is.

Conventionally, in the process of dissolving solvent-based natural rubber adhesive,
When dissolving raw material components such as natural rubber, tackifying resin, softening agent, etc. in a solvent, measure the specified amount of natural rubber, tackifying resin, softening agent, etc. in a solvent that has been weighed in a specified amount in advance. Then, the adhesive was applied sequentially, and after stirring for a few dozen hours to a few dozen hours, a coatable adhesive was obtained.

Thus, in the prior art, in order to obtain an adhesive solution that can be applied, that is, an adhesive solution having an adhesive solution concentration as designed and an adhesive solution viscosity suitable for the application method, a dozen hours to several hours are required. It requires a long stirring and dissolution time of 10 hours, resulting in extremely low productivity. However, heretofore, no effective method has been proposed for shortening the time for dissolving the raw material components.

[Problems to be Solved by the Invention]

An object of the present invention is to provide a production method in which the productivity of the pressure-sensitive adhesive is improved by shortening the stirring / dissolving time of the raw material components in the solvent in the production process of the solvent-type natural rubber-based pressure-sensitive adhesive. is there.

The present inventor, as a result of diligent research for overcoming the problems of the above-mentioned prior art, kneaded part or all of the tackifying resin during mastication of natural rubber, leaving the blended product as a residue. It was found that the stirring / dissolving time can be significantly shortened by dissolving it in a solvent together with the above-mentioned component, and the present invention has been completed based on the finding.

[Means for solving the problem]

Thus, according to the present invention, in the step of dissolving the raw material components constituting the solvent-type natural rubber-based pressure-sensitive adhesive in the solvent, a mixture obtained by previously kneading the natural rubber and at least a part of the tackifying resin together with the remaining raw material components Disclosed is a method for producing a solvent-based natural rubber-based pressure-sensitive adhesive, which is characterized by being dissolved in a solvent.

 Hereinafter, the present invention will be described in detail.

As described above, generally, in the stirring / dissolving step of the solvent-type natural rubber-based pressure-sensitive adhesive, the solvent is preliminarily measured in a specified quantity,
A method is used in which a specified amount of a pressure-sensitive adhesive constituent component (raw material component) such as natural rubber, a tackifying resin, and a softening agent is sequentially measured, and then stirred and dissolved.

By the way, since the molecular weight of natural rubber is usually as large as 1,000,000 or more and the coating properties and adhesive properties are insufficient as it is, it is necessary to adjust the molecular weight to an appropriate level and stabilize the molecular weight. For that purpose, mastication work is generally performed. Mastication breaks the main chain of natural rubber, destroys its network structure, lowers the molecular weight, and improves coatability and miscibility with a tackifying resin. In the present invention,
During this mastication operation, at least one part of the specified amount of tackifying resin is added and kneaded, and the obtained natural rubber-tackifying resin mixture is dissolved in the solvent together with the other remaining raw material components.

The mixing ratio of each component in the kneading work is 10% natural rubber.
With respect to 0 parts by weight, the tackifying resin is usually 1 to 100 parts by weight,
It is preferably 1 to 50 parts by weight. If the mixing ratio of the tackifying resin is too small, there is little effect of shortening the time of the stirring / dissolving step of the raw material components, and conversely, if it is too large, the plasticization of the natural rubber-tackifying resin mixture proceeds and blocking occurs. This reduces the operability.

Addition and kneading of adhesion-giving resin to natural rubber is usually
It can be carried out by a roll machine or a Banbury mixer used for mastication, but a closed Banbury mixer is preferable from the viewpoint of measurement control.

The natural rubber-tackifying resin mixture thus obtained is
Since the solubility in a solvent is higher than in the case of using natural rubber alone, it is possible to shorten the stirring / dissolving time until obtaining a coatable adhesive.

As the tackifier resin, a general-purpose resin can be used and is not particularly limited, and examples thereof include rosin-based, coumarone-indene-based, terpene-based, petroleum-based, styrene-based, phenol-based, and xylene-based resins. Among these, a natural rosin-based or terpene-based compound having high compatibility in combination with natural rubber is preferable.

Examples of the softening agent include polybutene, polyisobutylene, polyisoprene, process oil, and naphthenic oil.

As the antiaging agent, general-purpose phenol-based and amine-based stabilizers are preferable.

Examples of the filler include titanium white, zinc white, calcium carbonate, clay, talc, pigment, carbon black and the like.

As the cross-linking agent, thiuram-based, phenol-based, isocyanate-based, etc. can be used.

These raw material components are appropriately selected and used according to the purpose of use. However, in the solvent-based natural rubber-based pressure-sensitive adhesive of the present invention, it is necessary to contain natural rubber and tackifying resin as essential components.

Here, a standard configuration example of the adhesive is as follows.

Natural rubber: 100 parts by weight Tackifying resin: 60 to 120 parts by weight Softener: 0 to 30 parts by weight Anti-aging agent: 1 to 3 parts by weight As a solvent, normal hexane, heptane, toluene, trichlene, rubber An organic solvent such as volatile oil is used.

For stirring and dissolving, the raw material components are put into a solvent and dissolved with stirring by various types of mixers such as a propeller type, an inversion type and a kneader type. Whether or not the uniform dissolution is completed can be determined by whether or not the concentration and solution viscosity of the solution have reached a certain value (equilibrium value).

〔Example〕

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

[Example 1] 10 parts by weight of tackifying resin (YS resin PX # 1150: made by Yasuhara Resin) was added to 100 parts by weight of natural rubber (TPC 1X: international standard of natural rubber) in an open roll of 30 cm x 61 cm. The natural rubber obtained by kneading and kneading was mixed with a natural rubber-tackifying resin mixture having a weight average molecular weight of 930,000 and a number average molecular weight of 430,000 and 70 parts by weight of a tackifying resin (YS resin PX1150: Yasuhara resin). It was dissolved in 720 parts by weight of a solvent (normal hexane).

Stirring / dissolving was carried out in a 200-tank tank manufactured by Satake Co., using a stirrer A-540, 0.2B manufactured by Satake Co. under stirring conditions of 150 rpm (the same applies hereinafter).

[Example 2] To 100 parts by weight of natural rubber (TPC 1X), 50 parts by weight of a tackifying resin (YS resin PX # 1150: made by Yasuhara Resin) was added to a volume of 70.
Natural rubber obtained by kneading with a Banbury mixer of 950,000 having a weight average molecular weight of 950,000 and a number average molecular weight of 440,000-a tackifying resin mixture and a tackifying resin (YS resin
30 parts by weight of PX1150: Yasuhara resin) was dissolved in 720 parts by weight of a solvent (normal hexane).

Comparative Example 1 100 parts by weight of natural rubber (TPC 1X) and 80 parts by weight of tackifying resin (YS resin PX # 1150: made by Yasuhara Resin) were dissolved in 720 parts by weight of a solvent (normal hexane). The weight average molecular weight of natural rubber was 940,000 and the number average molecular weight was 440,000.

 The results are shown in Table 1.

From the results shown in Table 1, the concentration and viscosity of the pressure-sensitive adhesive solution reach the equilibrium value in 12 hours in Example 1 and reach the equilibrium value in 8 hours in Example 2.

On the other hand, in Comparative Example 1 in which the raw material components were dissolved in the solvent, about 16 hours of stirring and dissolving time were required.

As described above, compared with Comparative Example 1, the stirring / dissolving time was 2/3 in the case of Example 1 and 1/2 in the case of Example 2, and the productivity was improved by 1.5 times and 2 times, respectively. There is.

〔The invention's effect〕

According to the present invention, the stirring / dissolving time of the solvent-type natural rubber-based pressure-sensitive adhesive can be significantly shortened, and the productivity of the pressure-sensitive adhesive can be improved.

Claims (1)

[Claims] 1. In a step of dissolving a raw material component constituting a solvent-type natural rubber-based pressure-sensitive adhesive in a solvent, a mixture obtained by previously kneading natural rubber and at least a part of a tackifier resin is used as a solvent together with the remaining pigment component. A method for producing a solvent-based natural rubber-based pressure-sensitive adhesive, which comprises dissolving.