JPH0733499B2 - Synthetic rubber adhesive composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a synthetic rubber-based pressure-sensitive adhesive composition using a thermoplastic block copolymer such as styrene-isoprene-styrene block copolymer, and more specifically. Relates to a synthetic rubber-based pressure-sensitive adhesive composition with reduced malodor.

[Conventional technology]

Thermoplastic block copolymers typified by styrene-isoprene-styrene block copolymer (SIS) and styrene-butadiene-styrene block copolymer (SBS) form a styrene domain, so they are around room temperature. Shows high cohesiveness similar to that of cross-linked polymer and flows at a temperature higher than the glass transition point (Tg) of styrene, so it is widely used as a synthetic rubber adhesive that can be applied with a hot melt coater.

In the adhesive using these thermoplastic block copolymers, the styrene block (S
Phase) and the rubber block (I phase or B phase) have different compatibility, it is important to select a tackifying resin or a softening agent in order to obtain desired adhesive properties and hot melt coatability.

For example, a tackifying resin having a good compatibility with the I phase or the B phase lowers the viscosity, increases the tack and the adhesive force, but lowers the cohesive force, and the aromatic pressure-sensitive adhesive having a good compatibility with the S phase is Tg
To improve heat resistance.

Conventionally, coumarone / indene resin is well known as a tackifying resin in a hot-melt pressure-sensitive adhesive using a thermoplastic block copolymer (see, for example, Japanese Patent Application Laid-Open No. Sho-06-26).
63-27573). This coumarone-indene resin is compatible with the S phase of the thermoplastic block copolymer and greatly increases Tg. That is, when coumarone indene resin is blended with block copolymers such as SIS and SBS, the volume fraction of S phase increases, the adhesive becomes more elastic as a whole, and the high-temperature retention performance of the adhesive increases (Foundation) Adhesive Research Laboratory, Yoji Takashima “Hot Melt Adhesive”). On the other hand, the coumarone-indene resin has almost no effect on the phase I or phase B.

In this way, an adhesive that contains a thermoplastic block copolymer such as SIS or SBS as a base polymer and contains coumarone / indene resin has an excellent adhesive function, but has a peculiar odor, so the adhesive tape Is disliked in the food market.

However, at present, no effective method for removing or reducing this malodor has been found.

[Problems to be Solved by the Invention]

An object of the present invention is a synthetic rubber-based pressure-sensitive adhesive composition containing a thermoplastic block copolymer as a base polymer and a coumarone / indene resin mixed therein, while maintaining the adhesive performance,
It is intended to provide a synthetic rubber-based pressure-sensitive adhesive composition in which a peculiar odor is significantly reduced.

As a result of intensive studies to overcome the problems of the above-mentioned conventional techniques, the present inventor has found that the cause of odor lies in the low molecular weight substance contained in the coumarone-indene resin.

The coumarone-indene resin is usually obtained by thermal polymerization of coal tar fraction containing coumarone and indene as it is or by polymerization with concentrated sulfuric acid as a catalyst. Among them, it is measured by gel permeation chromatography (GPC). In the obtained molecular weight distribution chart, about 1.5 to 2.0% of low molecular weight substances having a molecular weight of 150 or less are contained. When using the coumarone indene resin with the content of this low molecular weight substance reduced to 0.6% or less, while maintaining the adhesive performance,
It was found that a synthetic rubber-based pressure-sensitive adhesive composition in which the peculiar malodor is significantly reduced can be obtained.

The present invention has been completed based on these findings.

[Means for Solving the Problems]

Thus, according to the present invention, in a synthetic rubber-based pressure-sensitive adhesive composition containing a thermoplastic block copolymer and coumarone / indene resin, coumarone / indene resin has a low molecular weight content of 150 or less by GPC. There is provided a synthetic rubber-based pressure-sensitive adhesive composition characterized by having an area ratio of 0.6% or less with respect to the total area surrounded by a molecular weight distribution curve and a baseline in a measured molecular weight distribution chart.

Hereinafter, the present invention will be described in detail.

Examples of the thermoplastic block copolymer used as the base polymer in the present invention include SIS, SBS, styrene-ethylene-butylene-styrene-block copolymer (SEBS), and the like.

The coumarone-indene resin used in the present invention has a much lower content of low molecular weight substances than conventional ones.

That is, the content of the low molecular weight product having a molecular weight of 150 or less is 0 in terms of the area ratio with respect to the total area surrounded by the molecular weight distribution curve and the baseline in the molecular weight distribution map measured by GPC.
6% or less, preferably 0.5% or less, more preferably 0.3%
The following coumarone indene resin.

When a coumarone-indene resin containing a low molecular weight substance having a molecular weight of 150 or less in excess of 0.6% is used, the effect of reducing the odor peculiar to the synthetic rubber adhesive composition is small.

In the present invention, to measure the content of low molecular weight substances,
Known ordinary methods are used. For example, an appropriate method for normal GPC may be used as follows.

1. Measurement conditions Temperature: 25 ° C Solvent: Tetrahydrofuran (THF) Flow rate: 1 ml / min Sample concentration: 8 mg / ml THF solution Sample injection amount: 0.5 ml 2. Column A commercially available polystyrene column is used to measure the molecular weight region properly. use. For example, Showa Denko's trade name Sh
It is appropriate to use a combination of multiple odex GPC KF series.

3. Calibration curve Standard polystyrene is used to prepare the calibration curve. As the standard polystyrene, for example, those having a molecular weight of 6000, 3000, 1000, 300 manufactured by Asahi Kasei are used.

4. Detector An RI (refractive index) detector is used as the detector.

From the obtained GPC chart (distribution amount distribution chart), the total area surrounded by the molecular weight distribution curve and the baseline and the area of the portion having a molecular weight of 150 or less are obtained, and the area ratio occupied by the latter is calculated.

To reduce the content of low-molecular-weight substances with a molecular weight of 150 or less in the coumarone / indene resin to 0.6% or less, for example, in the decoloring step before polymerization, the removal of impurities at the bottom of the polymerization tank should be increased more than before, and purification to a higher degree. Polymerization may be performed after the obtained monomer is obtained.

The synthetic rubber-based pressure-sensitive adhesive composition of the present invention contains, in addition to the thermoplastic block copolymer and the coumarone-indene resin, various commonly used tackifying resins, softening agents, antioxidants, fillers, and the like. You can leave.

The general compounding recipe of the synthetic rubber-based pressure-sensitive adhesive composition using the thermoplastic block copolymer is, for example, as follows.

Thermoplastic block copolymer 100 parts by weight Tackifying resin 40 to 200 parts by weight Softener 10 to 100 parts by weight Anti-aging agent 1 to 10 parts by weight Coumaron indene resin is usually used as at least one part of the tackifying resin. However, it is preferable to use it in a proportion of 3 to 25% by weight with respect to the total weight of the synthetic rubber-based pressure-sensitive adhesive composition in terms of the adhesive performance and the odor suppressing effect.

〔Example〕

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

Example 1 A SIS-based pressure-sensitive adhesive composition was prepared according to the following formulation.

SIS block copolymer (* 1) 100 parts by weight Tackifying resin (* 2) 100 parts by weight Coumaron indene resin 50 parts by weight Naphthenic oil (* 3) 50 parts by weight Anti-aging agent (* 4) 1 part by weight (* 1) Product name TR-1107 manufactured by Shell Chemical Co., Ltd. (* 2) Aliphatic tackifier resin Product name Eskoletz 4401 manufactured by Tonex Co., Ltd. (* 3) Product name Sunsen Oil manufactured by SUNOCO (* 4) Product manufactured by Yoshitomi Pharmaceutical Name Yoshinox 425 Here, when the content of a low molecular weight substance having a molecular weight of 150 or less as a coumarone / indene resin is expressed as an area ratio with respect to the entire area surrounded by the molecular weight distribution curve and the baseline in the GPC chart. , 5 different resins were used as follows.

Coumaron indene resin (resin code) (content of low molecular weight substances) A ... Approx. 2.0% (conventional product) B .... Approx. 1.0% C .... Approx. 0.6% D .... Approx. 0.3% E .. About 0.2% The above formulation was placed in a mixer maintained at about 180 ° C and mixed under a nitrogen atmosphere. About the thickness of the obtained pressure-sensitive adhesive composition
It was applied on a 120 μm adhesive tape kraft so that the adhesive thickness would be about 40 μm. The blending ratio of the coumarone / indene resin in the pressure-sensitive adhesive composition is about 16.6% by weight.

Various physical properties of the obtained adhesive tape were measured.

<Physical property measurement method> SP Adhesive strength: JIS Z 0237-8 Tack: JIS-Z-0237 (Inclined ball tack method, 1/32 ~
32/32 inch diameter steel balls are used and indicated by the ball number.) K method retention: JIS Z 0237-11 Odor: 10 panelists conducted a sensory test.
Specifically, the presence or absence of odor peculiar to each panel and the degree of odor were evaluated according to the following three levels, and 7 or more people indicated the same evaluation points.

X: A peculiar odor is strong.

◯: Almost no odor.

A: There is no odor.

The results are shown in Table 1.

As is clear from Table 1, in the molecular weight distribution measured by GPC, the adhesive composition containing the coumarone-indene resin containing less than 0.6% of low molecular weight substances with a molecular weight of 150 or less has a peculiar odor. Significantly reduced, yet retains a high degree of adhesive performance. Especially, when the content of the low molecular weight substance is 0.3% or less, the effect of improving the odor is remarkable.

[Example 2] In Example 1, resin code C (ratio of low-molecular-weight substances: 0.
A pressure-sensitive adhesive composition was prepared in the same manner as in Example 1 except that 6%) of coumarone-indene resin was used in the ratio shown in Table 2, and a pressure-sensitive adhesive tape was prepared and evaluated in the same manner.

The results are shown in Table 2.

From Table 2, when the ratio of coumarone / indene resin in the pressure-sensitive adhesive composition is as low as 2.0% by weight, the holding power tends to decrease, and conversely, when it is as high as 28.4% by weight, the odor becomes worse. There is a tendency. Therefore, it is preferable that the coumarone / indene resin is used in a proportion of 3 to 25% by weight based on the pressure-sensitive adhesive composition in terms of the adhesive performance and the odor suppressing effect.

[Example 3] In Example 1, S was used instead of the SIS block copolymer.
A BS block copolymer was used, a coumarone / indene resin having a resin code shown in Table 3 was blended to prepare an adhesive composition in the same manner as in Example 1, and an adhesive tape was prepared and evaluated in the same manner. did.

The results are shown in Table 3.

SBS block copolymer (* 1) 100 parts by weight Tackifying resin (* 2) 100 parts by weight Coumaron indene resin 50 parts by weight Naphthenic oil (* 3) 50 parts by weight Anti-aging agent (* 4) 1 part by weight (* 1) Product name TR1102 manufactured by Shell Chemical Co., Ltd. (* 2) Same as Example 1 (* 3) Same as Example 1 (* 4) Same as Example 1 As shown in Table 3, SBS is used. Even in the case where it is present, the pressure-sensitive adhesive composition of the present invention similarly has a good odor suppressing effect and adhesive performance.

[Effects of the Invention] According to the present invention, a thermoplastic rubber block copolymer is used as a base polymer, and there is a synthetic rubber-based pressure-sensitive adhesive composition containing a coumarone / indene resin.
It is possible to obtain a synthetic rubber-based pressure-sensitive adhesive composition in which the characteristic odor is significantly reduced. Therefore, the market value of the present invention is extremely high, and it can be expected to be used in the field of foods and the like, which have been disliked because of a bad odor.

Claims (1)

[Claims] 1. A synthetic rubber-based pressure-sensitive adhesive composition containing a thermoplastic block copolymer and a coumarone-indene resin, wherein the coumarone-indene resin is a low-molecular-weight substance having a molecular weight of 150 or less and gel permeation chromatography. A synthetic rubber-based pressure-sensitive adhesive composition characterized by having an area ratio of 0.6% or less with respect to the entire area surrounded by the molecular weight distribution curve and the baseline in the molecular weight distribution chart measured by.