JPH064745B2 - Thermoplastic elastomer composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thermoplastic elastomer composition.

More specifically, a selectively hydrogenated block copolymer having an ABA structure (hereinafter abbreviated as a hydrogenated block copolymer), a thermoplastic elastomer composed of a polyolefin resin and a mineral oil-based softening agent is used. The present invention relates to an antiblocking thermoplastic elastomer composition containing a fatty acid amide.

[Conventional technology]

In a thermoplastic elastomer composition comprising a hydrogenated block copolymer, a polyolefin resin and a mineral oil-based softening agent, the mineral oil-based softening agent should be blended for the purpose of adjusting the hardness of the thermoplastic elastomer, improving the processability and reducing the cost. Is already well known.

By incorporating a mineral oil-based softening agent, such an object can be sufficiently achieved, but pellets obtained by kneading the thermoplastic elastomer composition and then granulating it are packed into a bag, and when the bag is stacked and stored, pellets are obtained. Due to the tackiness of the surface, the pellets stick together and form a nodule, making it difficult to supply them to the molding machine.

When the pellets are molded by an injection molding machine, the mineral oil-based softening agent exudes over time on the surface of the molded product to form a sticky surface.

Such a phenomenon occurs when the blending ratio of the softening agent to the hydrogenated block copolymer is large, specifically, when the weight ratio of the mineral oil-based softening agent to the hydrogenated block copolymer is about 50: 100 or more. It was confirmed to be easy. Since the range of such a weight ratio is in the range of the blending ratio practically required for the thermoplastic elastomer composition, it is necessary to solve the above problems while maintaining such a blending ratio.

Conventionally, as a method for preventing the adhesion of such a thermoplastic elastomer, talc, an inorganic filler such as magnesium carbonate or a powdered polyethylene, a method of dusting a resin powder such as a powdered polypropylene on the pellet surface is generally performed, but in this method, It is difficult to uniformly attach these mutual adhesion preventive agents to the pellet surface, and the addition of an inorganic filler is liable to cause deterioration of physical properties such as deterioration of transparency and poor appearance, which is not always a satisfactory method.

Further, the method described in JP-B-57-37618, that is, 100 parts by weight of hydrogenated block copolymer, 15 to 200 parts by weight of polyolefin, hydrocarbon oil 2
Paraffin wax 5 to 75 for 0 to 150 parts by weight
As a result of additional tests conducted by the present inventors, a method of preventing bleed-out of hydrocarbon oil by adding parts by weight showed some effects, but the effect was not sufficiently satisfactory.

Further, the method described in JP-A-52-53957, that is, 100 parts by weight of the hydrogenated block copolymer, 5 to 150 parts by weight of the polyolefin, and 10 to 175 parts by weight of the oil for diluting the rubber, sterically hindered phenol and benzotriazole are used. Alternatively, the method of adding 0.2 to 5 parts by weight of a mixture of these oil exudation inhibitors also showed some improvement as a result of additional tests by the present inventors, but did not provide a sufficiently satisfactory effect.

[Problems to be solved by the invention]

As described above, the thermoplastic elastomer obtained by blending the hydrogenated block copolymer and the polyolefin resin with the mineral oil-based softening agent causes a phenomenon in which the pellets or molded articles adhere to each other due to the tackiness of the surface.

Although such a phenomenon is improved to some extent by reducing the blending ratio of the mineral oil-based softening agent to the hydrogenated block copolymer, the reduction of the softening agent causes a decrease in processability and an increase in cost, and is practically used. It is not preferable, and it is necessary to prevent tackiness while maintaining the necessary mixing ratio of the mineral oil softener.

The present invention, in a thermoplastic elastomer comprising a hydrogenated block copolymer, a polyolefin resin and a mineral oil-based softening agent, prevents stickiness on the surface of pellets or molded articles which is thought to be mainly due to leaching of the mineral oil-based softening agent. Then
It is an object of the present invention to improve the mutual sticking phenomenon of thermoplastic elastomer pellets due to the tackiness and the stickiness of the surface of molded articles.

Still another object is to provide a thermoplastic elastomer composition in which the mutual sticking phenomenon of pellets and the stickiness of the surface of molded articles are improved.

[Means for solving problems]

As a result of intensive studies to solve the above problems, the present inventors have found that by adding a higher fatty acid amide to a thermoplastic elastomer composed of a hydrogenated block copolymer, a polyolefin resin and a mineral oil softener, We have found that it is possible to effectively prevent sticking.

That is, the present invention has at least two terminal polymer blocks A consisting of an aromatic monoalkenyl or mono-alkenylidene hydrocarbon polymer having a number average molecular weight of 5,000 to 125,000, and a partial number average molecular weight of 10,000 to 300,000. Selectively or fully hydrogenated block copolymers of the ABA structure having at least one intermediate polymer block B consisting of fully or fully hydrogenated aliphatic conjugated diene hydrocarbon polymers, polyolefins To 100 parts by weight of a thermoplastic elastomer consisting of a resin and a mineral oil softener,
The present invention relates to an anti-adhesion thermoplastic elastomer composition, which comprises adding about 0.03 to 2 parts by weight of a higher fatty acid amide.

The monomer constituting the aromatic monoalkenyl or monoalkenylidene hydrocarbon polymer block A of the hydrogenated block copolymer used in the present invention is styrene, α-methylstyrene or tert-butylstyrene. The monomer forming the aliphatic conjugated diene hydrocarbon polymer block B is butadiene, isoprene, or the like.

A typical example of such a hydrogenated block copolymer has a styrene-ethylene / butylene-styrene structure and is referred to by the abbreviation SEBS, which is a product name of KRATON-G from US Shell Chemical Company. It is commercially available.

The polyolefin resin used in the present invention is polypropylene, low density polyethylene, medium density polyethylene, high density polyethylene, ethylene-vinyl acetate copolymer, polybutene and the like.

The mineral oil-based softening agent used in the present invention is a paraffin having a composition of aromatic hydrocarbons of 30% or less among mineral oils called process oils or extender oils used for softening, increasing the amount of rubber and improving processability. It is a series or naphthenic hydrocarbon oil. Generally, these mineral oil-based softeners are
It is a mixture of three kinds of aromatic ring, naphthene ring and paraffin chain, and the hydrocarbon of paraffin chain is 50% of the total hydrocarbons.
Those that occupy the above are called paraffin hydrocarbon oils,
The naphthene ring-added hydrogen having a hydrogen content of 30 to 45% is called naphthene hydrocarbon oil.

Specific examples of the higher fatty acid amide added in the present invention include saturated fatty acid amides such as lauric acid amide, palmitic acid amide, atearinic acid amide, and behenic acid amide, erucic acid amide, oleic acid amide, bridic acid amide, and elaidic acid amide. Unsaturated fatty acid amide, methylenebisstearic acid amide, methylenebisoleic acid amide, ethylenebisstearic acid amide, ethylenebisoleic acid amide and other bisfatty acid amides are used.

A particularly preferable higher fatty acid amide has a melting point of about 70.
It is a compound in the range of ℃ to 110 ℃.

The higher fatty acid amide is added in an amount of about 0.03 to 2 parts by weight based on 100 parts by weight of the thermoplastic elastomer composed of SEBS, polyolefin resin and mineral oil softener.
Preferably about 0.04 to 1 part by weight is added.

If the addition ratio is higher than this, leaching of higher fatty acid amide to the surface and deterioration of physical properties of the thermoplastic elastomer occur,
Below this, the anti-adhesion effect cannot be obtained.

The thermoplastic elastomer composition of the present invention comprises 100 parts by weight of a hydrogenated block copolymer, 5 to 150 parts by weight of a polyolefin resin such as polypropylene, and a mineral oil softener 10 to 20.
It can be obtained by adding about 0.03 to 2 parts by weight of higher fatty acid amide to 100 parts by weight of the mixture to a mixture of 0 parts by weight.

The most general method for preparing the composition of the present invention is to perform melt kneading mechanically using an ordinary thermoplastic resin kneader.

As the kneading machine that can be used, a single-screw extruder, a twin-screw extruder,
There are Banbury mixer, two rolls, etc. The mixing operation of each component may be carried out simultaneously or separately.

Further, in the present invention, in addition to the above-mentioned basic components, additives such as an antioxidant, a heat stabilizer, an ultraviolet absorber and a pigment can be blended if necessary.

The composition of the present invention can maintain the original physical properties of the thermoplastic elastomer and prevent sticking of pellets and molded articles of the thermoplastic elastomer within the range of the practically necessary compounding composition. You can try to solve the problems.

〔Example〕

 The contents of the present invention will be specifically described below with reference to examples.

Example 1 A block copolymer (SEBS) having an ABA structure consisting of a polystyrene block A having a number average molecular weight of 31,000 and a completely hydrogenated butadiene block B having a number average molecular weight of 130,000.
-1. ) 100 parts by weight, melt flow rate (J
According to ISK-7210, 230 ° C) 20g / 10 minutes, density
0.91 g / cm ³ polypropylene (referred to as PP-1) 35
(2) By weight, 120 parts by weight of paraffinic process oil and 0.1 part by weight of erucic acid amide were kneaded in a Banbury mixer at 180 ° C. for 5 minutes, passed through a sheeting roll, and pelletized by a sheet pelletizer.

No mutual adhesion was observed between the pellets. 190 pellets of the thermoplastic elastomer composition thus obtained were
A sheet having a thickness of 0.5 mm was formed by a press forming machine. Two sheets of this sheet are piled up, each 25mm x 150mm x 0.5mm
Punch out the test piece of No.2, and make two pieces of this test piece adhere to each other.
After applying a load for 10 minutes, use a tensile tester to speed 50 mm /
T peel test was carried out in minutes to measure the peel strength.
It was lightly peeled off under g and no tackiness was observed.

Comparative Example 1 As a result of repeating the operation of Example 1 except that the higher fatty acid amide, erucic acid amide, was not used in Example 1, the peel strength was 85 g, and a considerably strong adhesion was observed.

Comparative Example 2 As a result of repeating the operation of Example 1 except that 0.02 parts by weight of erucic acid amide was used in Example 1, the peel strength was 55.
It was g and was quite sticky.

Comparative Example 3 As a result of repeating the operation of Example 1 except that 3 parts by weight of erucic acid amide was used in Example 1, the peel strength was 10 g.
Although almost no tackiness was observed below, erucic acid amide leached to the surface of the sheet, and surface contamination was severe.

Example 2 As a result of repeating the operation of Example 1 except that 0.1 part by weight of oleic acid amide was used in place of erucic acid amide in Example 1, the peel strength was 10 g or less.

Example 3 The number average molecular weight as SEBS in Example 1 was 9,00.
0 polystyrene block A, number average molecular weight 60,000
Block copolymer having an ABA structure consisting of the completely hydrogenated butadiene block B (referred to as SEBS-2).
100 parts by weight, melt flow rate 12, density 0.91 g / c
19 parts by weight of m ³ polypropylene (referred to as PP-2),
Other than using 70 parts by weight of naphthene-based process oil,
As a result of performing the same method as in Example 1, the peel strength was 10 g or less.

The results obtained in the above Examples and Comparative Examples are shown in Table 1.

〔The invention's effect〕

As described above, according to the present invention, it is possible to provide a thermoplastic elastomer composition in which the mutual sticking phenomenon of pellets and the stickiness of the surface of a molded article are improved.

Claims (6)

[Claims] 1. A partial polymer having at least two terminal polymer blocks A consisting of an aromatic monoalkenyl or mono-alkenylidene hydrocarbon polymer having a number average molecular weight of 5,000 to 125,000 and having a number average molecular weight of 10,000 to 300,000. A-having at least one intermediate polymer block B consisting of a fully or fully hydrogenated aliphatic conjugated diene hydrocarbon polymer
About 0.03 to 2 parts by weight of a higher fatty acid amide is added to 100 parts by weight of a thermoplastic elastomer consisting of a selectively hydrogenated block copolymer having a BA structure, a polyolefin resin and a mineral oil softener. A characteristic anti-adhesion thermoplastic elastomer composition. 2. The thermoplastic elastomer composition according to claim 1, wherein the terminal polymer block A comprising an aromatic monoalkenyl hydrocarbon polymer is polystyrene. 3. The thermoplastic elastomer according to claim 1, wherein the terminal polymer block A comprising an aromatic mono-alkenylidene hydrocarbon polymer is poly-α-methylstyrene or poly-tert-butylstyrene. Composition. 4. The thermoplastic elastomer composition according to claim 1, wherein the intermediate polymer block B is a block copolymer obtained by hydrogenating polybutadiene. 5. The thermoplastic elastomer composition according to claim 1, wherein the mineral oil-based softening agent is a paraffin-based or naphthene-based hydrocarbon oil. 6. The melting point of higher fatty acid amide is about 70 ° C. to 11 ° C.
The thermoplastic elastomer composition according to claim 1, which has a temperature of 0 ° C.