JPH0841436A - Adhesive composition and adhesive tape - Google Patents

Abstract

PURPOSE:To obtain the odorless adhesive free from a malodor and excellent in high temperature characteristics and obtain the adhesive tape. CONSTITUTION:The adhesive composition comprises a thermoplastic block copolymer and a tackifying resin, wherein the tackifying resin is the copolymer of a vinyl-substituted aromatic hydrocarbon with an unsaturated aromatic hydrocarbon whose ring has 8-10 carbon atoms (copolymers containing dicyclopentadiene in an amount of >=5 pts.wt. therein are excluded), impurities having mol.wts. of <=100 being contained in the copolymer in an amount of <=0.5wt.%. And the adhesive tape has the adhesive layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot-melt type pressure-sensitive adhesive for pressure-sensitive adhesive tape used for packaging and a pressure-sensitive adhesive tape using the same.

[0002]

2. Description of the Related Art Hot-melt type pressure-sensitive adhesives used as pressure-sensitive adhesive tapes have a high coating speed during production, do not require solvent drying and recovery, do not worry about fire, and do not pollute the atmosphere or work environment. It is becoming popular because it is not available.
The hot-melt type pressure-sensitive adhesive is usually composed of a thermoplastic block copolymer and a tackifying resin. JP 63
-27573 gazette, a thermoplastic block copolymer,
And a number of tackifying resins are listed.

As a result of research conducted by the inventor, the best combination was a combination of a styrene-butadiene block copolymer and a coumarone-indene resin. Similar performance was also observed for the combination of styrene-isoprene block copolymer and coumarone-indene resin. When coumarone / indene resin is used as a tackifying resin, the high temperature characteristics are improved, and it is particularly suitable for corrugated cardboard packaging and the like which requires high temperature characteristics. However, when the coumarone-indene resin is used as a hot-melt type pressure-sensitive adhesive, it gives off a peculiar odor, so that the tape using this pressure-sensitive adhesive has a drawback that it is not suitable for food-related use. For this reason, the inventors of the present invention have disclosed that, as shown in Japanese Patent Application No. 5-157063, an unsaturated alicyclic group having 8 to 10 carbon atoms constituting a ring with a vinyl-substituted aromatic hydrocarbon instead of the coumarone-indene resin. By using a copolymer with a hydrocarbon group, a pressure-sensitive adhesive composition having excellent high-temperature properties and having no bad odor to the extent that it can be used for food packaging was obtained. However, some foods are required to have a particularly strong odorless property, and even in the above case, a slight odor remains. Therefore, it cannot be applied to the use where such an odorless property is particularly required.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems and has odorlessness to the extent that it can be used in applications where odorlessness is particularly strongly required, and coumarone indene. It is an object of the present invention to provide a hot-melt adhesive having the same adhesive performance as that using a resin and an adhesive tape using the hot-melt adhesive.

[0005]

The present invention relates to a pressure-sensitive adhesive composition comprising a thermoplastic block copolymer and a tackifying resin, wherein the tackifying resin comprises a vinyl-substituted aromatic hydrocarbon and the number of carbon atoms constituting a ring. Is a copolymer with an unsaturated alicyclic hydrocarbon of 8 to 10 (excluding those in which dicyclopentadiene is contained in the copolymer in an amount of 5 parts by weight or more), and the molecular weight in the copolymer is 100 or less. It is intended to solve the above problems by providing a pressure-sensitive adhesive composition having an impurity content of 0.5% by weight or less, and a pressure-sensitive adhesive tape using the pressure-sensitive adhesive composition. It was found and completed.

The present invention will be described in detail below. The thermoplastic block copolymer used in the present invention includes styrene-
Examples include isoprene-styrene block copolymer (hereinafter abbreviated as SIS), styrene-butadiene-styrene block copolymer (hereinafter abbreviated as SBS), styrene-ethylene-butadiene-styrene block copolymer (hereinafter abbreviated as SEBS), and the like. To be

The tackifying resin imparts tackiness to the thermoplastic block copolymer. In the present invention, one or more vinyl-substituted aromatic hydrocarbons,
A copolymer with one or a plurality of unsaturated alicyclic hydrocarbons having 8 to 10 carbon atoms constituting the ring is used. The vinyl-substituted aromatic hydrocarbon referred to herein is one having an aromatic ring as a main skeleton and having an ethylenically unsaturated group as a substituent in the aromatic skeleton. For example, styrene, α-methylstyrene,
Examples include vinyltoluene. Further, the unsaturated alicyclic hydrocarbon having 8 to 10 carbon atoms constituting the ring as referred to herein is a monocyclic or polycyclic hydrocarbon compound having 8 to 10 carbon atoms constituting the ring. 10 refers to one having at least one double bond in the ring. For example inden,
Examples include 4,5-dimethylindene. However, although dicyclopentadiene is effective in increasing the softening point, it is empirically likely to cause odor and is not preferable, so vinyl-substituted aromatic hydrocarbons and unsaturated alicyclic groups having 8 to 10 carbon atoms are used. Excluding those containing 5 parts by weight or more of dicyclopentadiene in the copolymer with a hydrocarbon group.

The vinyl-substituted aromatic hydrocarbon and the unsaturated alicyclic hydrocarbon having 8 to 10 carbon atoms constituting the ring are bonded by their respective unsaturated bonds to form a binary or ternary or more multi-element. It becomes a copolymer, and the desired aromatic tackifying resin is obtained through purification. The tackifier resin should not contain small molecules related to odor. That is, the content of impurities having a molecular weight of 100 or less must be 0.5% by weight or less. The low molecular weight product is derived from the polymerization residue or impurities or decomposition products or by-products in the monomer. If the content of impurities having a molecular weight of 100 or less is more than 0.5% by weight, odor is generated. Further, the softening point of the tackifying resin is 100 to 150 in order to satisfy both the heat activation temperature and the use environment temperature in view of suitability for use as a hot melt pressure sensitive adhesive.
C is preferred. If the temperature is 100 ° C. or lower, the adhesive property at high temperature may be poor, and it may be difficult to remove impurities having a molecular weight of 100 or less. On the other hand, when the temperature is 150 ° C. or higher, the step becomes difficult in the step of pelletizing the tackifying resin, and when the adhesive composition is blended with the thermoplastic block copolymer, the viscosity at the time of stirring is increased and stirring is difficult. It will be difficult. When the pressure-sensitive adhesive composition is applied, streaks may occur and the thickness accuracy tends to deteriorate.

In the present invention, as the tackifying resin, in addition to the above tackifying resins, a conventionally used aliphatic hydrocarbon resin, alicyclic hydrocarbon resin or the like can be partially used in combination. . In addition, a softening agent such as naphthenic oil, an antiaging agent, and other additives may be added if necessary. However, these various additives must not contain impurities that cause odor.

A hot-melt type pressure-sensitive adhesive composition can be obtained by blending a thermoplastic block copolymer, a tackifying resin and other additives and mixing them by melting. A pressure-sensitive adhesive tape can be produced by applying the composition to a tape base material such as paper or film by extrusion coating, curtain flow coating or the like at a high temperature according to a conventional method for coating a hot-melt adhesive.

[0011]

In the present invention, as the tackifying resin, a copolymer of vinyl-substituted aromatic hydrocarbon and unsaturated alicyclic hydrocarbon having 8 to 10 carbon atoms constituting the ring (dicyclopentadiene And a content of impurities having a molecular weight of 100 or less in the copolymer is 0.5% by weight or less. Therefore, the compatibility with the thermoplastic block copolymer is excellent, the pressure-sensitive adhesive composition has excellent high-temperature characteristics, exhibits well-balanced pressure-sensitive adhesive properties, is difficult to decompose, and does not contain low-molecular impurities, thus giving off a bad odor. Do not emit.

[0012]

The present invention will be described in detail with reference to the following examples. 1. Examples 1, 2, 3 Styrene, indene, vinyltoluene, α-methylstyrene, 4,5-dimethylindene, dicyclopentadiene were copolymerized in a weight ratio using a catalyst to give a resin. Five kinds of resins 1 to 5 were obtained. Further, in the purification of the polymerized resin, different precisions were applied to the resins 1 and 3 with high precision, and the resins 2, 4, and 5 were refined with lower precision than the resins 1 and 3. The molecular weight and softening point of the obtained resin were measured by a conventional method. The results are shown in Table 1.

[0013]

[Table 1]

As the SIS block copolymer, 100 parts by weight of TR-1107 manufactured by Shell Chemical Co., Ltd. and 25 parts by weight of the above resins 1 to 4 are used as an aliphatic adhesive resin in combination with Nippon Zeon Co., Ltd. 100 parts by weight of Quinton A-100 manufactured by Co., Ltd., as a naphthenic oil for softening agent, Shell Chemical Co., Ltd.
50 parts by weight of Shelf Rex 371 manufactured by the company and 1 part by weight of Irganox 1010 manufactured by Ciba-Geigy Co., Ltd. as an anti-aging agent are mixed and put into a mixer kept at 180 ° C.,
The mixture was melted and mixed under a nitrogen atmosphere to obtain a hot melt type pressure sensitive adhesive. The obtained pressure-sensitive adhesive was applied by extrusion coating to a 120-micron-thick adhesive tape kraft paper having a back surface subjected to a release treatment so that the adhesive thickness would be 40 microns and cut to obtain a pressure-sensitive adhesive tape.

The adhesive thickness of the obtained tape was measured by a conventional method. In addition, SP adhesion, tack, and SP retention were measured according to JIS-Z-0237. Regarding the odor, the degree of the odor was determined by 10 inspectors, and a sensory test was conducted to assume that the odor is particularly severe in food packaging and packaging applications. Those having a strong odor and being unusable were evaluated on a three-point scale of X, and 7 or more people asked for a consistent evaluation. Table 2 shows the results.

2. Comparative Examples 1 and 2 Instead of Resins 1 to 3 in Examples 1 to 3, Resin 4,
5 was blended, and the other components were similarly produced and evaluated. Table 2 shows the results. 3. Comparative Example 3 In place of Resins 1 to 3 in Examples 1 to 3, a coumarone indene resin (trade name: Esclon V-120) manufactured by Nippon Steel Chemical Co., Ltd. was blended, and other trials were made and evaluated in the same manner.
Table 2 shows the results.

[0017]

[Table 2]

It can be seen from Table 2 that those using resins 1 to 3 have tape properties comparable to those using coumarone-indene resin, and there is no odor problem.

[0019]

According to the present invention, as described in detail above,
As a tackifying resin for hot-melt pressure-sensitive adhesive composition, by using a specific tackifying resin, it has excellent adhesive performance in high-temperature characteristics similar to the case of using coumarone / indene resin, and especially foods with strict odor. It is possible to obtain an adhesive composition having no odor problem even in the case of packaging. The adhesive tape using this is suitable for packaging foods and the like with strict odor.

Claims (2)

[Claims] 1. A pressure-sensitive adhesive composition comprising a thermoplastic block copolymer and a tackifying resin, wherein the tackifying resin is
Copolymers of vinyl-substituted aromatic hydrocarbons and unsaturated alicyclic hydrocarbons having 8 to 10 carbon atoms constituting the ring (excluding dicyclopentadiene in an amount of 5 parts by weight or more in the copolymer) ), Wherein the content of impurities having a molecular weight of 100 or less in the copolymer is 0.5% by weight or less. 2. A pressure-sensitive adhesive tape comprising the pressure-sensitive adhesive composition according to claim 1 as a pressure-sensitive adhesive.