JPS5928236B2 - Isoprene salt - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to a cis l.4-
The present invention relates to a polyisoprene pressure-sensitive adhesive composition.

The basic properties required of pressure-sensitive adhesives are cohesive force and adhesive force (tack), and it is important that the two are well balanced.

Generally, pressure sensitive adhesives using cis-1.4 polyisoprene rubber have a satisfactory level of adhesive strength, but often have insufficient cohesive strength. Here, cohesive force refers to creep resistance, which is a problem for pressure-sensitive adhesives, especially in areas with high temperatures in the summer. Natural rubber is a synthetic rubber
- Although it has a slightly higher cohesive force than 4-polyisoprene rubber, it still often poses a problem when the temperature is high. To improve the cohesive strength of pressure sensitive adhesives,
There are methods of partially cross-linking rubber and methods of blending thermoplastic resins, but cross-linking methods have the disadvantage of complicating the manufacturing process, and blending thermoplastic resins significantly reduces adhesive strength. This causes drawbacks, and furthermore, it is not always possible to obtain a satisfactory improvement in cohesive force. The object of the present invention is to provide a pressure-sensitive adhesive composition containing cis-1,4-polyisoprene as a rubber component and having a well-balanced cohesive force and adhesive force. It has been found that this can be achieved by blending a block copolymer with a cis-1.4-polyisoprene rubber in a specific proportion.

That is, the isoprene-based pressure-sensitive adhesive composition according to the present invention comprises 20 to 65% by weight of cis-1,4-polyisoprene rubber and an isoprene-based block copolymer I-A (where A is a vinyl aromatic hydrocarbon polymer block). , I
-The content of A in A is 5 to 75% by weight. I represents an isoprene polymer block, and the number average molecular weight of I-A is 30,000 to 700,000) 80 to 35% by weight of a blend a) and 10 to 250 parts by weight of a tackifier per 100 parts by weight of the blend It has a good balance of cohesive force and adhesive force, and has extremely excellent performance as a pressure-sensitive stone remover.
Isoprene-based block copolymer 1-A, which is a component of the pressure-sensitive adhesive composition according to the present invention, refers to a vinyl aromatic hydrocarbon-isoprene block copolymer; Prok has a glass transition temperature of 2
As the vinyl aromatic hydrocarbon, styrene is the most suitable as the vinyl aromatic hydrocarbon, as long as it has a temperature of 0° C. or higher and can be obtained industrially at low cost and easily.

Examples of other vinyl aromatic hydrocarbons are alphamethylstyrene, vinyltoluene, vinylnaphthalene, vinylxylene, ethylvinylxylene, vinylbiphenyl, and the like. The polymer block to be combined with the vinyl aromatic hydrocarbon polymer block of the block copolymer is limited to an isoprene polymer block. For diene polymer block other than isoprene (e.g. butadiene polymer block),
It is not possible to obtain satisfactory adhesive strength as an isoprene-based pressure-sensitive adhesive composition. The isoprene-based block copolymer used in the present invention includes, for example, metallic lithium as a catalyst,
It can be produced by a known method of polymerizing each monomer in an appropriate solvent in the presence of an organolithium. Most preferred solvents are inert hydrocarbons. Examples of organolithium include methyllithium, ethyllithium, propyllithium, butyllithium, allyllithium, alphanaphthyllithium, methylene dilithium, trimethylene dilithium, dibutadienyl dilithium, distyrenyl dilithium, etc. . Vinyl aromatic hydrocarbon monomer and isoprene monomer are polymerized separately, and then both polymer blocks are combined with a suitable coupling agent (e.g. dilogenoalkane, divinylbenzene) to obtain the desired block copolymer. Alternatively, after polymerizing either the vinyl aromatic monomer or the isoprene monomer, the desired block copolymer can be obtained by adding another monomer to the same polymerization system and continuing the polymerization. can. Even if both monomers coexist in the initial stage of polymerization, due to their copolymerization properties, isoprene monomer polymerization will substantially precede the polymerization of the isoprene monomer. Copolymers are also included in the block copolymers of the present invention. The content of vinyl aromatic hydrocarbon in the isoprene-based block copolymer is 5 to 75% by weight, but 15 to 60% by weight.
is more desirable.

If the hydrocarbon content is too low, sufficient improvement in cohesive force as a pressure-sensitive adhesive will not be observed, while if it is too high, the adhesive force will drop significantly, making it impractical. Furthermore, if the molecular weight of the block copolymer is too low, there will be little improvement in cohesive force, while if it is too high, the viscosity of the adhesive will increase and the workability will deteriorate, so the molecular weight should be in the range of 30,000 to 700,000. . The term "molecular weight" as used herein refers to a number average molecular weight, which is measured by a conventional method such as an osmotic pressure method or a gel permeation chromatography method. In the present invention, in addition to using the specific isoprene-based block copolymer itself, it is necessary to blend the block copolymer with cis-1,4-polyisoprene rubber in a specific range of proportions. It is.

That is, in order to obtain an excellent pressure-sensitive adhesive with a well-balanced cohesive force and adhesive force, the above-mentioned block copolymer and polyisoprene rubber should be mixed in a weight ratio of 35/65 to 80/20, preferably 40/20. It is necessary to use them by blending them at a ratio of /60 to 75/25. If the blending ratio of the protox copolymer is lower than the above range, a satisfactory improvement in cohesive force cannot be achieved, and if it is higher than the above range, the adhesive force will decrease too much, resulting in an extremely poor balance between cohesive force and adhesive force. do. The cis-1,4-polyisoprene rubber used in the present invention includes synthetic cis-1,4-polyisoprene rubber obtained with a Ziegler catalyst or an anionic polymerization catalyst and natural rubber.

In order for the pressure sensitive adhesive composition of the present invention to exhibit excellent performance, it is necessary to have a cis-1.4 content of 85% or more, preferably 95% or more.
Synthetic polyisoprene rubber is preferred. Sith 1.
The tackifiers constituting the composition of the present invention together with 4-polyisoprene rubber and isoprene block copolymer include rosin, dammar, modified rosin, derivatives of rosin and modified rosin, polyterpene resin, cyclopentadiene resin, petroleum resin, It can be appropriately selected and used from phenolic resins, aliphatic hydrocarbon shelf coumaron indene resins, and the like.

These may be used alone or in combination. If the amount of tackifier used is too small, the tackifying effect will be poor, while if it is too large, the cohesive force will be unsatisfactory. , 10 to 250 parts by weight, preferably 20 to 200 parts by weight. - Appropriate amounts of anti-aging agents, fillers, plasticizers, softeners, etc. are added to the composition of the present invention, if necessary. These additives are dissolved in a suitable solvent and mixed in the form of a solution, or mixed in a kneader, an internal mixer, etc. 1 according to a conventional method for producing pressure-sensitive adhesives. As the substrate for the pressure-sensitive adhesive, zero paper, kraft paper, Japanese paper, cloth, polyvinyl chloride, polypropylene, aluminum foil, etc. are used.
Next, the present invention will be specifically explained with reference to Examples. Example
Styrene was polymerized using a No. 1151 pressure reactor in a cyclohexane solvent in the presence of an n-butyllithium catalyst at 50'C with stirring for 2 hours, followed by adding a predetermined amount of isoprene monomer and stirring for 3 hours.

The monomer concentration in the reaction system was 15% by weight in total of styrene and isoprene, and the weight ratio of styrene monomer/isoprene monomer was 30/70. Pour the solution after polymerization into a large amount of methanol to collect the product by precipitation.
A styrene-isoprene block copolymer (abbreviated as S-1) was obtained. The polymerization yield 5 was 99.6%, and the styrene content in SI-1 analyzed by infrared absorption spectroscopy was 30.2% by weight. The molecular weight evaluated by gel permeation chromatography was 32,300.
It was 0.
, cis-1 obtained by polymerizing isoprene with Ziegler-catalyst
・Cis-1,4-polyisoprene rubber with 98% 4 content (
(abbreviated as R) and the above SI-1 in various proportions,
A toluene solution of a pressure sensitive adhesive was prepared according to the formulation in Table 1. j The above solution was aged at room temperature for one day and night, then coated on ordinary cellophane (thickness: 30 microns) and dried at 70° C. for 10 minutes to produce a cellophane adhesive tape. Table 2 shows the results of evaluating the performance of these adhesive tapes (sample numbers 1 to 9) using the following method. (1) Adhesive force (tack): Place the adhesive layer on top of a smooth slope with an inclination angle of 302 and a length of 10? From the position, the diameter is l/32
Roll a steel ball in 1/32 inch increments (these are ball numbers 1 to 32) up to 1 inch, and the ball number when it stops without falling on the tape is taken as the adhesive strength.
The higher the number, the greater the tack. (2) Cohesive force (creep resistance performance): stainless steel plate, width 15 mm, height 1
0m77! At the bottom edge of the tape with the size of 1
A creep test was carried out in an atmosphere of 40° C. with a load of 1 kg, and the time required for the tape to fall was measured.

The longer the time, the greater the cohesive force. As is clear from Table 2, the blend ratio of SI-1/IR is 35/65 to 80/
Within the range of 20, a pressure-sensitive adhesive with good performance and well-balanced adhesive force and cohesive force can be obtained.

In particular, extremely excellent performance can be obtained when the SI-1/IR is in the range of 40/60 to 75/25. Example 2 51? ．． S in a cyclohexane solvent using a pressure-resistant container.
Styrene was polymerized under stirring at 50° C. for 1.5 hours in the presence of an ec-butyllithium catalyst, followed by addition of isoprene monomer and stirring for 2 hours.

The total amount of added monomers is 15% by weight, and the weight ratio of styrene monomer/isoprene monomer is 45/55.
The solution after polymerization is poured into a large amount of methanol, the product is precipitated and collected, and a styrene-isoprene block copolymer (S
(abbreviated as I-2) was obtained. The styrene content of SI-2 is 44
．． 7% by weight, and the molecular weight was 184,000. The styrene-isoprene copolymer and cis-1,4-polyisoprene rubber (IR) polymerized with a Ziegler catalyst and having a cis-1,4 bond content of 98% were blended in various proportions, and the following compositions were prepared in Table 3. A toluene solution of the pressure-sensitive adhesive composition having the formulation shown in Example 1 was prepared, and cellophane adhesive tapes (sample numbers 10 to 17) were prepared in the same manner as in Example 1. {( (1
) Table 4 shows the performance measurement results of adhesive tapes made of cheap crude oil (YS resin PXll5O), and it is clear that the adhesive tapes with a blend ratio of SI-2 and IR of 35/65 to 80/20 have lower adhesive strength and cohesive strength. It has excellent balanced properties.

Example 3 According to the polymerization method of Example 1, the monomers shown in Table 5 were polymerized to obtain a styrene-isoprene block copolymer (abbreviated as S-3) and a styrene-butadiene block copolymer (SI-1). ) was obtained.

Adhesive tapes similar to those in Example 1 were prepared using a blend ratio of each block copolymer and IR of 60/40 (by weight), and their performance was evaluated.

As shown in Table 6, the adhesive tape containing the blend of styrene-isoprene block copolymer and IR has adhesive strength,
Although the cohesive force is well balanced, when a styrene-butadiene block copolymer is used, a satisfactory adhesive force cannot be obtained. Example 4 According to the polymerization method of Example 1, styrene-isoprene block copolymers (SI-4 to SI-6) having different styrene contents as shown in Table 7 were obtained.

Claims (1)

[Scope of Claims] 1 20 to 65% by weight of cis-1,4-polyisoprene rubber and isoprene block copolymer IA (where A represents a vinyl aromatic hydrocarbon polymer block, I
-The content of A in A is 5 to 75% by weight. I represents an isoprene polymer block, and the number average molecular weight of IA is 30,000 to 700,000) 80 to 3
An isoprene-based pressure-sensitive adhesive composition comprising 5% by weight of a blend (a) and 10 to 250 parts by weight of a tackifier (b) per 100 parts by weight of the blend (a).