JPH0757866B2 - Hot melt adhesive composition and hot melt adhesive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a hot-melt type pressure-sensitive adhesive, and more specifically,
The present invention relates to a hot-melt pressure-sensitive adhesive having improved practical adhesive performance and improved operability in a coating process, and a hot-melt pressure-sensitive adhesive composition for obtaining the same.

(Prior Art) Conventionally, as a main adhesive for hot-melt adhesives,
ABA-type block copolymers, especially styrene-isoprene-styrene (S-I-S) block copolymers in which the A block is a styrene polymer block and the B block is an isoprene polymer block are widely used. Has been. Then, in order to sufficiently satisfy the balance of the initial adhesive force, adhesive force and holding force required for the pressure-sensitive adhesive, it has been attempted to change the structure, composition or average molecular weight of the block copolymer, but it is sufficient. It cannot be said that the results have been obtained. Also, a method of mixing the S-I-S block copolymer and the styrene-isoprene (S-I) block copolymer in a specific ratio has been attempted (Japanese Patent Laid-Open Publication No. Sho.
52-140545), the balance of adhesive properties is improved by this method, but the operability in the kneading process step, which is a problem during the production of the adhesive, and the coating property of the adhesive on the substrate, and the productivity. There is a problem in the aspect and improvement is needed.

(Problems to be Solved by the Invention) In the above-mentioned circumstances, the present invention provides a hot-melt type pressure-sensitive adhesive having excellent adhesive properties, that is, a balance of initial adhesive strength, adhesive strength and holding power, and coatability, and such an adhesive. It is intended to provide a composition for hot-melt pressure-sensitive adhesive, which is excellent in kneading processability for obtaining the composition.

(Means for Solving the Problems) As a result of intensive studies to achieve such an object, the present inventors have found that a specific zinc compound and a tackifier are added to a block copolymer produced using a specific coupling agent. It was found that the composition for pressure-sensitive adhesives containing the above can be used, and the present invention has been completed.

Thus, according to the invention, (a) a general formula A-B-X-B- linked by a coupling agent consisting of an ester compound.
A block represented by A (in the formula, A is a polymer block of an aromatic vinyl monomer, B is a polymer block of a conjugated diene monomer, and X is a residue of the coupling agent). 50% by weight of the copolymer (1) or the block copolymer (1) of more than 50% by weight and the block copolymer (2) represented by the general formula AB (in the formula, A and B are the same as above). % Or less of a copolymer composition, (b) a zinc salt of dithiocarbamic acid, and (c) a tackifier resin as essential components, and a composition for a hot-melt pressure-sensitive adhesive, and the composition. A hot-melt pressure-sensitive adhesive obtained by kneading a material is provided.

The block copolymer (2) represented by the general formula AB used in the present invention can be produced by a method known in the art. Here, the polymer block A is a polymer block of an aromatic vinyl monomer. The aromatic vinyl monomer is not particularly limited, and specific examples thereof include styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, etc. Among them, styrene is preferable. Further, the polymer block B is a polymer block of a conjugated diene monomer. The conjugated diene-based monomer is not particularly limited, and specific examples thereof include
1,3-butadiene, isoprene, 2,3-dimethyl-1,3-
Examples thereof include butadiene, 1,3-pentadiene, and 2,4-hexadiene, but among them, 1,3-butadiene and
Isoprene is preferred.

The weight ratio of the polymer block A to the polymer block B in the block copolymer (2) represented by the general formula AB is preferably in the range of 10:90 to 30:70, more preferably 12:88, in view of the adhesive property. The range is from ~ 25: 75. The weight average molecular weight of the block copolymer (2) is usually in the range of 50,000 to 200,000, preferably 70,000, in view of adhesive properties and processing.
The range is ~ 180,000. The weight average molecular weight of the polymer block A is preferably in the range of 7,000 to 30,000.

The block copolymer (1) represented by the general formula A-B-X-B-A used in the present invention has the above-mentioned general formula A-B.
It is a linear copolymer obtained by binding the block copolymer represented by the above with a bifunctional coupling agent composed of an ester compound.

The coupling agent comprising an ester compound used in the present invention is an ester of a monovalent carboxylic acid and a monovalent alcohol or a phenol ester of a monovalent carboxylic acid and a monovalent phenol. The monovalent carboxylic acid may be any monovalent aliphatic carboxylic acid, monovalent alicyclic carboxylic acid or monovalent aromatic carboxylic acid, for example, formic acid, acetic acid, propionic acid, Examples thereof include cyclohexanecarboxylic acid, cyclopentanecarboxylic acid, benzoic acid, naphthoic acid and toluic acid. The monohydric alcohol is not particularly limited, and examples thereof include methanol, ethanol and butanol. further,
The monohydric phenol is not particularly limited, and examples thereof include phenol and cresol. Specific examples of such coupling agents include ethyl formate, ethyl acetate,
Examples thereof include butyl acetate, methyl propionate, phenyl acetate, methyl benzoate, ethyl benzoate, phenyl benzoate, cresyl naphthoate, and phenyl toluate.

In the present invention, it is essential to bond the active end of the block copolymer represented by the general formula AB by using a bifunctional coupling agent composed of an ester compound, and other bifunctional coupling agents. With the block copolymer obtained using the coupling agent, it is not possible to suppress the viscosity during production of the pressure-sensitive adhesive to a low level, and it is possible to achieve the object of the present invention of obtaining a pressure-sensitive adhesive having an excellent balance of pressure-sensitive adhesive properties. Can not.

The copolymer composition (a) in the present invention may be the block copolymer (1) represented by the above general formula A-B-X-B-A, or the block copolymer (1) and the general formula. A
A block copolymer (2) represented by -B,
The content of (1) in the composition (a) is more than 50% by weight, preferably 50 to
90% by weight, (2) is 50% by weight or less, preferably 50 to 10% by weight. When the proportion of the copolymer (1) is 50% by weight or less, the composition for pressure-sensitive adhesive is too soft, which causes a problem in operability during pressure-sensitive adhesive production.

The method for producing the copolymer composition (a) in the present invention is not particularly limited, and the general formula A-B-X-B separately prepared in advance is used.
The block copolymer (1) represented by -A and the general formula A-
Even if the block copolymer (2) represented by B is mixed in a predetermined ratio, the block copolymer (2) represented by the general formula AB is mixed in a predetermined ratio. The product produced by controlling the coupling reaction may be used. Further, a part of the block copolymer (1) represented by the general formula A-B-X-B-A may be decoupled by a shearing force or the like, or a combination of these methods may be used. Good.

Use of such a copolymer composition (a) realizes advantages such as balance of adhesive properties, easy preparation of an adhesive having excellent corrugated board sealing property, and easy application of the adhesive to a substrate. Is.

Zinc salt of dithiocarbamic acid used in the present invention (b)
Examples include zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, zinc pentamethylenedithiocarbamate, zinc dimethylpentamethylenedithiocarbamate, zinc ethylphenyldithiocarbamate, zinc dibenzyldithiocarbamate, and the like. It is not limited to these. These zinc salts of dithiocarbamic acid can be used alone or in combination of two or more. The zinc salt of dithiocarbamic acid is preferably used in an amount of 0.1 to 10 parts by weight, preferably 0.2 to 8 parts by weight, based on 100 parts by weight of the copolymer composition. If the amount is less than 0.1 part by weight, the viscosity of the pressure-sensitive adhesive is not sufficiently reduced when it is manufactured, and the adhesiveness of the pressure-sensitive adhesive is inferior. In the present invention, it is necessary to use a zinc salt of dithiocarbamic acid, and the effect of the present invention cannot be obtained even if another metal salt of dithiocarbamic acid or another zinc compound that is not a dithiocarbamate salt is used.

As the tackifier resin (c) used in the present invention, known tackifiers used in conventional pressure-sensitive adhesives using block copolymers can be used. Specific examples thereof include rosins: modified rosins such as disproportionated rosins and dimerized rosins: esterified products of polyhydric alcohols such as glycol, glycerin and pentaerythritol with rosins or modified rosins: terpene-based resins: fats Group, aromatic, alicyclic or aliphatic-
Aromatic copolymer hydrocarbon resins or their hydrides:
Phenol resin: coumarone-indene resin and the like can be mentioned. Of these, aliphatic or aliphatic-aromatic copolymer hydrocarbon resins are preferable from the viewpoint of compatibility with the copolymer composition of the present invention. The amount of the tackifier resin (c) used in the present invention is usually 10 to 200 parts by weight per 100 parts by weight of the copolymer composition (a).

A softening agent (plasticizer) and an antioxidant can be added to the composition for pressure-sensitive adhesives of the present invention, if necessary.

As the softening agent, conventionally known aromatic type, paraffin type or naphthene type extending oils (extender oils), liquid polymers such as polybutene and polyisobutylene, which are used for adhesives, can be used. The amount of the softening agent used is usually 100 parts by weight or less per 100 parts by weight of the copolymer composition (a).

Examples of the antioxidant include 2,6-di-t-butyl-p
-Hindered phenol compounds such as cresol and di-t-butyl-4-methylphenol, thiodicarboxylate esters such as dilaurylthiopropionate, and phosphorous acid such as tris (nonylphenyl) phosphite Salts or the like may be used alone or as a mixture.

The method for obtaining the pressure-sensitive adhesive composition of the present invention is not particularly limited, and it can be obtained by blending the components of each composition by a conventionally known method. Upon blending, a mixer such as a tumbling type blender, a stirring blade mixer, a kneader mixer and a planetary motion paddle mixer may be used, and for example, the mixture may be mixed at a temperature of room temperature to 180 ° C. for 5 to 60 minutes. .

Furthermore, the pressure-sensitive adhesive of the present invention can be obtained by kneading the above-mentioned pressure-sensitive adhesive composition by a conventional method. The kneading conditions are not particularly limited, and a known method can be adopted.

As the kneading machine, for example, a single-screw extruder, a twin-screw extruder or a stirring blade mixer, a kneader mixer, a planetary motion paddle mixer, etc. are used, and usually in a temperature range of 130 ° C to 200 ° C, usually for 20 to 120 minutes. Is performed.

It is also possible to employ a method of continuously kneading the pressure-sensitive adhesive composition obtained by blending each component of the pressure-sensitive adhesive composition without once taking it out of the mixer to obtain a pressure-sensitive adhesive. Is.

(Effects of the Invention) Thus, according to the present invention, a hot melt type adhesive excellent in corrugated board sealing property as a practical performance and coating property to a substrate while maintaining the balance of adhesive properties as compared with the prior art. It is possible to obtain a pressure-sensitive adhesive and a pressure-sensitive adhesive composition which is excellent in operability in a kneading process step which is a problem during the production of the pressure-sensitive adhesive.

(Example) Hereinafter, the present invention will be described more specifically with reference to Examples. In addition, parts and% in Examples, Reference Examples and Comparative Examples
Is weight basis unless otherwise specified.

Example 1 Styrene (S) and isoprene (I) were subjected to a sequential polymerization method using n-butyllithium as a catalyst by a usual solution polymerization method, and the weight ratio of the styrene polymer block and the isoprene polymer block was 15 : 85, the SI block copolymer having a weight average molecular weight of 125,000 was obtained. Then, the copolymer was coupled using various coupling agents shown in Table 1, and the S-I-X-I-S type block copolymer (1) having a composition ratio shown in Table 1 was used. To obtain a copolymer composition consisting of the S-I type block copolymer (2). 100 parts of this copolymer composition, 2 parts of a zinc compound (zinc dibutyldithiocarbamate), 100 parts of a tackifier resin (Quinton M100, made by Nippon Zeon), naphthene-based process oil (Shelflex 371, Shell Chemical Co., Ltd.) 30 Parts and 1 part of an antioxidant (Irganox 1010, manufactured by Ciba Geigy) were put into a kneader type kneader maintained at 170 ° C. and kneaded for 40 minutes under a nitrogen atmosphere to obtain an adhesive. The apparent melt viscosity of this adhesive was measured with a flow tester (CFT-500 manufactured by Shimadzu Corporation). Further, the above-mentioned pressure-sensitive adhesive was applied onto a polyester film having a thickness of 25 μm so as to have a paste thickness of 30 μm to prepare a pressure-sensitive adhesive tape, and its initial adhesive force, adhesive force, holding force and corrugated board sealing property were measured.

The initial adhesive strength is in accordance with JIS Z-0237, and an adhesive tape with a length of 10 cm is attached to the slope on a stainless steel plate with an inclination angle of 30 degrees at 23 ° C, with the adhesive side facing up, and the position 10 cm above the slope. 30 types of steel balls with a diameter of 3/32 inch to 1 inch are rolled at an initial speed of 0 and displayed on the adhesive tape in the size of the maximum diameter, and the adhesive strength is JIS Z-0237.
Adhere to a stainless steel plate polished with No. 280 water-resistant abrasive paper in accordance with the above, and attach an adhesive tape with a width of 10 mm and a length of 100 mm at 23 ° C.
Measured by peeling in a direction of 180 degrees at a speed of 200 mm / min, the holding power is in accordance with JIS Z-0237, and an adhesive tape is attached so that an area of 25 mm × 10 mm contacts a stainless plate treated in the same manner, A load of 1 kg was applied at 50 ° C, and the time required for the adhesive tape to fall off the stainless steel plate was measured.

The corrugated board sealing property is according to Japanese Utility Model Laid-Open No. 58-37549. Two corrugated board are arranged in parallel at a slight interval, and an adhesive tape is attached to the corrugated board so that the interval is at the center. The time required for the adhesive tape to break at the interface when the distance between the two corrugated board was increased.
The above results are shown in Table 1.

From the results shown in Table 1, it can be seen that the effect of the present invention cannot be obtained when a coupling agent other than the coupling agent comprising the ester compound of the present invention is used.

On the other hand, a copolymer composition having a (1) / (2) ratio of 35/65 was obtained in the same manner as in Experiment No. 7, and an attempt was made in the same manner to prepare a pressure-sensitive adhesive using the copolymer composition. The composition had strong tackiness and poor operability in pelletization and preparative weighing, resulting in low work efficiency.

Example 2 Using butyl acetate as a coupling agent (1) /
(2) A copolymer composition having a ratio of 60/40 was obtained, and the same measurement was performed as in Example 1 except that various zinc compounds shown in Table 2 were used. The results are shown in Table 2. From the results in Table 2, it can be seen that the effects of the present invention cannot be obtained even if a zinc compound other than zinc dithiocarbamate is used.

Example 3 Example 2 using phenylacetate as coupling agent
A copolymer composition similar to the above was obtained, and the same measurement was performed as in Example 2 except that various metal salts of dithiocarbamic acid or barium stearate shown in Table 3 were used.
The results are shown in Table 3. From the results in Table 3, it can be seen that the effects of the present invention cannot be obtained by using various metal salts other than the zinc salt of dithiocarbamic acid.

Claims (2)

[Claims] 1. A compound represented by the general formula A-B-X-B-A (in the formula, A), which is bound with a coupling agent composed of an ester compound (a).
Represents a polymer block of an aromatic vinyl monomer, B represents a polymer block of a conjugated diene monomer, and X represents a residue of the coupling agent. Block copolymer (1) represented by the formula (1) or a block copolymer represented by the general formula AB (wherein A and B are the same as above) with more than 50% by weight of the block copolymer (1). (2) A hot-melt pressure-sensitive adhesive characterized by containing 50% by weight or less of a copolymer composition, (b) a zinc salt of dithiocarbamic acid, and (c) a tackifier resin as essential components. Composition. 2. A hot-melt pressure-sensitive adhesive obtained by kneading the composition for hot-melt pressure-sensitive adhesive according to claim 1.