JPH044280A - Pressure-sensitive adhesive composition - Google Patents

Abstract

PURPOSE:To obtain the title composition having excellent bond strength, tack (initial tack) and heat resistance, comprising a block copolymer of styrene and another monomer, a tackifier resin and superfine silica in a specific ratio. CONSTITUTION:(A) 100 pts.wt. block copolymer of styrene and a monomer (preferably butadiene) except styrene is blended with (B) 40-200 pts.wt., preferably 60-150 pts.wt. tackifier resin (e.g. rosin or polyterpene) and (C) 1-20 pts.wt., preferably 2-10 pts.wt. superfine silica having preferably <=0.3mum, preferably 0.1-0.02mum average particle diameter.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a pressure-sensitive adhesive mainly composed of a styrene block polymer that has excellent adhesive strength and tack (initial adhesive strength) as well as excellent heat resistance. The present invention relates to a drug composition.

[Conventional technology]

Pressure-sensitive adhesives are generally made by blending a tackifying resin and a crosslinking agent with a high molecular weight polymer, applying the solution to a support, and then heating it to volatilize the solvent and cause crosslinking. .

The above-mentioned crosslinking agent is used to impart holding power and heat resistance to the pressure-sensitive adhesive, and its type and amount are determined as appropriate, taking into account its own reactivity and compatibility with high molecular weight polymers. However, in many cases, improvements in holding power and heat resistance usually result in a decrease in adhesion and tack.

On the other hand, among high molecular weight polymers, styrenic block polymers are homogeneous in a molten state or solution state, but it is known that when cooled or dried, the high glass transition block portion forms domains and physically crosslinks.

According to such block polymers, if tackifiers, softeners, anti-aging agents, etc. are added to the block polymers, and the mixture is coated on a support in a molten or solution state and dried, heat resistance can be improved. A pressure-sensitive adhesive is obtained, in which case it is easy to maintain adhesive strength and tack.

[Problem to be solved by the invention]

However, the above-mentioned styrenic block polymer is not expected to have heat resistance above this temperature because the physical crosslinking is removed at a temperature above the glass transition point of styrene.

For this reason, attempts have been made to further improve heat resistance by blending this type of block polymer with a tackifier resin that has a high softening point and is compatible with the styrene phase, but in this case, the adhesive strength and tack are large. There is a problem of deterioration.

In addition, attempts have been made to improve heat resistance by applying it to a support, drying it, and then crosslinking it using electron beams, etc. However, depending on the type of tackifier, crosslinking does not proceed, and the tackifier There are significant restrictions on the selection of adhesives, and adhesive strength and tack also tend to decrease.

In view of the above circumstances, an object of the present invention is to improve the heat resistance of a pressure-sensitive adhesive containing a styrene block polymer as a main component without impairing adhesive strength or tack.

[Means for Solving the Problem] As a result of intensive studies to achieve the above object, the present inventors have found that fine powder silica of a specific particle size is added to an adhesive composition containing a styrene block polymer as a main component. The present inventors have discovered that by blending, heat resistance can be improved without impairing adhesive strength or tack, and have completed the present invention.

That is, in the present invention, 40 to 200 parts by weight of a tackifying resin and 1 to 20 parts by weight of finely divided silica having an average particle diameter of 0.3 μm or less are contained for 100 parts by weight of a block polymer of styrene and other monomers. The present invention relates to a pressure-sensitive adhesive composition.

[Structure and operation of the invention]

As the styrenic block polymer in the present invention,
For example, styrene-butadiene-styrene block polymer = (hereinafter referred to as SB
S), styrene-isoprene-styrene block polymer (hereinafter referred to as srs), styrene-ethylene-butylene-styrene block polymer (J, under I, 5
EBS), etc.

Among these block polymers, SBS in which the heptad polymer other than styrene is butadiene is particularly preferred because it has a remarkable effect of improving heat resistance according to the present invention.

Furthermore, as this type of block polymer, side chain type block polymers are more effective in improving heat resistance according to the present invention than linear type ones, and are therefore preferably used.

In such a styrenic block polymer, the styrene content is preferably in the range of 25 to 40% by weight. If the styrene content is too low, the heat resistance will not be improved even if finely divided silica is added, and if the styrene content is too high, the adhesive strength and tack will be low, which is not preferable.

As the tackifier resin in the present invention, any commonly used tackifier resin can be used, such as rosin or its derivatives, polyterpene, 05 petroleum resin,
Examples include hydrogenated petroleum resins and cyclopentadiene petroleum resins. One or more of these may be selected and used depending on the type of block polymer used.

The amount of the tackifying resin used is 40 to 200 parts by weight, preferably 60 to 15 parts by weight, based on 100 parts by weight of the block polymer.
It is 0 parts by weight. If it is less than 40 parts by weight, the adhesive force and tack will be poor, and if it is more than 200 parts by weight, the effect of improving heat resistance will be reduced. Note that tackifier resins that are compatible with the styrene phase, such as coumaron indene resin, tend to reduce tack, so when using such resins, use as much as possible within the range that can improve adhesive strength. Less is better. - The fine powder silica in the present invention has an average particle diameter of 0°3 μm
Hereinafter, it is preferably 0.1 μm or less, and usually up to about 0.02 μm. If the average particle diameter is larger than 0.3 μm, the effect of improving heat resistance will be small, and furthermore, when coated on a support, the surface smoothness will be poor. The amount used is 1 to 20 parts by weight, preferably 2 to 10 parts by weight, based on 100 parts by weight of the block polymer.

If it is less than 1 part by weight, there will be no effect of improving heat resistance, and if it is more than 20 parts by weight, the tack will decrease.

When blending this finely divided silica into an adhesive composition, the finely divided silica is uniformly dispersed in a solvent or softener using a sand mill, ball mill, colloid mill, etc., and then mixed with a styrene block polymer and a tackifying resin. It is best to mix it into a formulation with. If the fine powder silica aggregates during blending and good uniform dispersion cannot be obtained, the surface smoothness of the adhesive will be impaired when it is applied to a support and dried, which is not preferable.

In the present invention, the reason why the heat resistance of the adhesive improves when finely divided silica is blended as described above is not clear at present. It is speculated that the heat resistance improvement effect is expressed only when a styrene-based block polymer is used, and since no decrease in adhesive strength is observed at that time, it is assumed that the silica in fine powder form acts on the styrene phase. This seems to be to make the physical crosslinking stronger.

The pressure-sensitive adhesive composition of the present invention contains the above-mentioned styrenic block polymer, tackifying resin, and finely divided silica as essential components, and also requires various known softeners such as naphthene-based softeners for the purpose of improving tack. May be used accordingly. The amount used is preferably up to 80 parts by weight per 100 parts by weight of the styrene block polymer; if too much is used, heat resistance will be impaired, which is not preferable.

Furthermore, the pressure-sensitive adhesive composition of the present invention may contain an anti-aging agent such as a polyphenol type or an imidazole type, and may further contain various other known additives within a range that does not impede the effects of the present invention. It can also be mixed within.

〔Effect of the invention〕

According to the present invention, heat resistance can be improved without impairing adhesive strength or tack by blending fine powder silica with a specific particle size into a pressure-sensitive adhesive composition containing a styrenic block polymer as a main component. Therefore, when this adhesive composition is used for holding articles, for example, it can be used at temperatures about 10 degrees or more higher than conventional holding temperatures, which is a great effect.

〔Example〕

Next, examples of the present invention will be described in more detail. In the following, parts mean parts by weight.

Example 1 Cariflex TR1102 manufactured by Shell (linear SBS; styrene content 28% by weight) was used as a styrenic block polymer, and 100 parts of this polymer was uniformly dissolved in 200 parts of toluene. Superester A-75 (rosin derivative) 12 manufactured by Arayo Kagaku Co., Ltd.
A solution of 5 parts dissolved in 125 parts of toluene was added and mixed uniformly. In addition, Shell Flex 37 manufactured by Shell
1 (naphthenic softener) and 2 parts of Irganox 1010 (antiaging agent) manufactured by Ciba Geigy were added and mixed uniformly to obtain a rubber compounding solution.

On the other hand, as fine silica powder, 10 parts of Aerosil 200 (manufactured by Nippon Aerosil Co., Ltd.) was dispersed in 20 parts of toluene and 20 parts of butanol, and treated three times with a colloid mill to obtain a dispersion of fine silica powder. The average particle size of the finely divided silica in this dispersion was measured using Nanosizer Model N-10 manufactured by Coulter, and was found to be 0.06 μm.

Next, this dispersion of finely divided silica was added to the rubber compounding solution and mixed uniformly to obtain a solution of a pressure sensitive adhesive composition.

Comparative Example 1 The rubber compounding solution in Example 1, which did not contain the dispersion of finely divided silica, was used alone as a solution of a pressure-sensitive adhesive composition.

Comparative Example 2 A solution of a pressure-sensitive adhesive composition was obtained in the same manner as in Example 1, except that the finely divided silica of Example 1 was directly blended into the rubber compounding solution without being treated with a colloid mill. The average particle diameter of the finely divided silica in this composition was 2 μm, and the particle size distribution was also wide.

Example 2 Cariflex TR1184 manufactured by Shell Co., Ltd. (side chain type SBS: styrene content 30% by weight) was used as a styrenic block polymer, and 100 parts of this polymer was uniformly dissolved in 200 parts of toluene. Quinton U-185 (C5 petroleum resin) manufactured by Nippon Zeon Co., Ltd.
A solution prepared by dissolving 0 part in 100 parts of toluene was added and mixed uniformly. Further, 5 parts of the same naphthenic softener as in Example 1 and 2 parts of the anti-aging agent as in Example 1 were added and mixed uniformly to obtain a rubber compounding solution.

Next, a dispersion of finely divided silica was prepared in the same manner as in Example 1, and this was blended with the above rubber compounding solution so that the amount of finely divided silica was 5 parts per 100 parts of the styrene block polymer. , and mixed uniformly to obtain a solution of the pressure sensitive adhesive composition.

Comparative Example 3 The rubber compounding solution in Example 2 without blending the finely divided silica dispersion was used alone as a solution of a pressure-sensitive adhesive composition.

The solutions of the pressure-sensitive adhesive compositions of Examples 1 and 2 and Comparative Examples 1 to 3 above were applied to a polyester film with a thickness of 508 parts so that the thickness after drying was 50 II m, and 10
It was dried at 0° C. for 5 minutes to obtain a uniform pressure-sensitive adhesive sheet.

The adhesive strength and heat resistance of this sheet were measured and evaluated as follows. The results were as shown in Table 1 below.

<Adhesive Strength> The 180 degree peel adhesive strength (g/20 m width) was measured according to JIS Z-1528.

Heat resistance〉 A sheet was pasted on a stainless steel 304 plate with an adhesive area of 20w x 20m, a load of 1 kg was applied, and the sheet was heated at 40℃ for 3 hours.
After being left for 0 minutes, heating was continued at a temperature increase rate of 1° C./1 minute, and the temperature when the sheet fell was measured.

Table 1 As is clear from the comparison between Example 1 and Comparative Example 1゜2 and the comparison between Example 2 and Comparative Example 3 in Table 1 above, it is clear that the pressure-sensitive adhesive composition of the present invention According to the results, it can be seen that heat resistance can be improved without reducing adhesive strength.

Although tack test data was omitted, as in the case of the adhesive strength described above, almost no decrease in tack was observed due to the addition of finely divided silica.

In addition, in the solutions of the pressure-sensitive adhesive compositions of Example 2 and Comparative Example 3, as the styrene block polymer, Cariflex TR116 manufactured by Shell Co., Ltd. (side chain type SBS, styrene) was used instead of Cariflex TR1184. A solution of a pressure-sensitive adhesive composition was obtained in exactly the same manner as in Example 2 and Comparative Example 3, and the adhesive strength and heat resistance tests were conducted on these in the same manner as described above. As a result, almost no changes in characteristics were observed between the two.

From this test result, it was found that the effect of improving heat resistance due to the blending of finely divided silica depends on the styrene phase of the styrenic block polymer, and the above effect is significantly expressed when the styrene phase reaches a predetermined content. That is understood.

Claims (1)

[Claims] (1) For 100 parts by weight of a block polymer of styrene and other monomers, 40 to 200 parts by weight of tackifier resin and 1 to 20 parts by weight of finely divided silica with an average particle diameter of 0.3 μm or less
A pressure sensitive adhesive composition comprising parts by weight.