JPH04328150A - Thermoplastic elastomer composition - Google Patents

Abstract

PURPOSE:To obtain a thermoplastic elastomer composition, excellent in rubber elasticity, flexibility and weather resistance and having improved properties such as unrecognized oil bleeding even in ozone atmospheres. CONSTITUTION:A thermoplastic elastomer composition is obtained by blending (A) 100 pts.wt. thermoplastic elastomer composed of (A1) 25-50wt.%, preferably 35-45wt.% hydrogenated block copolymer, composed of >=2 polymer blocks consisting essentially of styrene and >=1 polymer blocks composed of a conjugated diene compound and having 5000-1000000, preferably 30000-500000 number- average molecular weight and (A2) 75-50wt.%, preferably 65-55wt.% softener for hydrocarbon-based rubbers with (B) 2-20 pts.wt., preferably 5-10 pts.wt. polyethylene-based wax and (C) 0.05-0.3 pt.wt., preferably 0.1-0.2 pt.wt. heterocyclic hindered amine-based additive.

Description

[Detailed description of the invention]

0001

TECHNICAL FIELD The present invention relates to a thermoplastic elastomer that has excellent rubber elasticity, flexibility, weather resistance, and moldability, and exhibits little oil bleed in an ozone atmosphere.

0002

BACKGROUND ART In recent years, thermoplastic elastomers (hereinafter simply referred to as "TPE") are a rubber-like soft material that does not require a vulcanization process and have moldability similar to that of thermoplastic resins. has come to be widely used in automobile parts, home appliance parts, electric wire coatings, etc. In such fields, durability such as weather resistance and ozone resistance has become an important performance, especially for products intended for outdoor use. Such TPE
Currently, various types of polymers such as polyolefins, polyurethanes, polystyrenes, and polyesters have been developed and are commercially available. Among these TPEs, polystyrene-based TPEs, especially those based on hydrogenated derivatives of block copolymers consisting of styrene and conjugated diene, contain hydrocarbon rubber softeners in the block copolymer.
Products containing olefin resins, styrene resins, inorganic fillers, etc. not only have excellent rubber elasticity and flexibility, but also have double bonds saturated by hydrogenation.
It basically has good potential in terms of weather resistance and ozone resistance. On the other hand, in specific applications such as automobile parts, weather resistance, such as accelerated weathering test of 2,000 hours or more, is generally required, and in order to satisfy this requirement, oxidation prevention It is common to add agents, light stabilizers, ultraviolet absorbers, etc.

0003

[Problems to be Solved by the Invention] However, such additive-containing products have long-term weather resistance and the softener for hydrocarbon rubber blended in an ozone atmosphere bleeds out, resulting in a noticeable change in product appearance. There were problems such as damage to the Improvements in bleed-out of such softeners for hydrocarbon rubber have already been reported in Japanese Patent Publication No. 57-3761.
No. 8 proposes a method of adding petroleum hydrocarbon wax. The technology described in this publication is for a short period of time of 360 hours of exposure in a weather tester, and in order to withstand even longer weather tests, antioxidants and light stabilizers as mentioned above are required. It was necessary to add UV absorbers, etc.

0004

[Means for Solving the Problems] [Summary of the Invention] In order to solve the above-mentioned problems, the present inventors have devised a material that has excellent rubber elasticity, flexibility, weather resistance, and moldability, and that is suitable for use in oil under an ozone atmosphere. As a result of extensive research to develop a thermoplastic elastomer composition that does not bleed, we have identified a thermoplastic elastomer component whose main components are a hydrogenated product of styrene/conjugated diene block copolymer and a softener for hydrocarbon rubber. A thermoplastic elastomer that solves the above-mentioned problems by incorporating a specific amount of compounding agents, which has excellent rubber elasticity, flexibility, and weather resistance, and has excellent performance such that no oil bleed is observed in an ozone atmosphere. The present inventors have discovered that a composition can be obtained and have completed the present invention. That is, the thermoplastic elastomer composition of the present invention is produced by hydrogenation of a block copolymer consisting of a polymer block (A) having at least two styrenes and a polymer block (B) comprising at least one conjugated diene compound. To 100 parts by weight of a thermoplastic elastomer consisting of 25 to 50% by weight of a polyethylene wax and 75 to 50% by weight of a softener for hydrocarbon rubber, 2 to 5% of a polyethylene wax is added.
It is characterized by containing 20 parts by weight and 0.05 to 0.3 parts by weight of a heterocyclic hindered amine additive.

[Detailed Description of the Invention] [I] Thermoplastic elastomer composition (1) Constituent component (a) Hydrogenated block copolymer consisting of a styrene polymer block and a conjugated diene compound polymer block From a polymer block (B) consisting of at least two styrene-based polymer blocks (A) and at least one conjugated diene compound, which are one component of the thermoplastic elastomer component constituting the thermoplastic elastomer composition. The hydrogenated block copolymer (hereinafter simply referred to as hydrogenated block copolymer) has the general formula A-(-B
-A)n or AB-(-A-B)n [However, A in the formula represents a polymer block mainly composed of styrene, and B represents a polymer block mainly composed of a conjugated diene compound. Moreover, n represents an integer of 1 to 5. ] This is a hydrogenated derivative of a block copolymer represented by: The polymer block mainly composed of styrene in the A block is a styrene homopolymer block, or a copolymer block of styrene and a comonomer that can be copolymerized with styrene in an amount of 50% by weight or less based on the styrene. The A block is composed of at least two blocks sandwiching at least one of the B blocks described below. In addition, the conjugated diene used in the polymer consisting of the conjugated diene of the B block is as follows:
Butadiene, isoprene, etc. can be mentioned. In addition, the number average molecular weight of the hydrogenated block copolymer is 5,000~
1,000,000, preferably 10,000-500
,000, more preferably from 30,000 to
500,000 range. The molecular structure of the copolymer may be linear, branched, radial, or any combination thereof. These hydrogenated block copolymers may be produced by any method as long as they have the above structure. For example, a styrene/conjugated diene block copolymer is synthesized in an inert solvent using a method described in Japanese Patent Publication No. 40-23798, specifically, using a lithium catalyst or the like, and then, Kosho 42-870
Publication No. 4, Japanese Patent Publication No. 43-6636, Japanese Patent Application Publication No. 1987-
The hydrogenated block copolymer used in the present invention can be synthesized by hydrogenation in the presence of a hydrogenation catalyst in an inert solvent by the methods described in JP-A No. 133203 and JP-A-60-79005. can. It is preferable that at least 50%, preferably 80% or more of the olefin type double bonds in the polymer block B are hydrogenated in the hydrogenation during its production. Examples of such hydrogenated block copolymers include commercially available polymers such as "Krayton-G" manufactured by Shell Chemical Co., Ltd., "Septon" manufactured by Kuraray Co., Ltd., and "Tuftec" manufactured by Asahi Kasei Corporation.

(b) Softener component for hydrocarbon rubber The softener for hydrocarbon rubber, which is the other component of the thermoplastic elastomer component constituting the thermoplastic elastomer composition of the present invention, may be mineral oil-based or A synthetic resin-based rubber softener is suitable. Mineral oil-based softeners are a mixture of aromatic rings, naphthenic rings, and paraffin chains, and those in which the paraffin chain carbon number accounts for 50% or more of the total carbon are called paraffinic softeners. Those with a carbon number of 30 to 45% are called naphthenic, and those with an aromatic carbon number of more than 30% are called aromatic. Mineral oil softeners suitable as softener components for hydrocarbon rubber include naphthenic and paraffinic softeners, particularly those having an aromatic carbon number of 30% or less. Aromatic compounds are preferably not contained in large amounts because their dispersion with the naphthenic and paraffinic components used in the present invention is not very favorable. In terms of properties, it has a kinematic viscosity of 20 to 500 cst at 37.8°C, a pour point of -10 to -15°C, and a flash point (COC) of 170 to 300°C. In addition, as synthetic resin softeners, polybutene,
Although low molecular weight polybutadiene and the like can be used, mineral oil-based softeners are preferred.

(c) Polyethylene wax component In the present invention, the polyethylene wax to be blended with the thermoplastic elastomer component is obtained by polymerization of ethylene and has a melting point of 100 to 130°C by DSC method or according to ASTM-D-3104. Dropping point 90-120℃, 1
Brookfield viscosity at 40℃ is 407,000 cps
I can name some things. A specific example of polyethylene wax is Mitsui Petrochemical's "Hiwax".
, "Sunwax" by Sanyo Chemical Co., Ltd., "AC Polyethylene" by Allied Signal Co., Ltd., and the like.

(d) Heterocyclic hindered amine additive component In the present invention, the heterocyclic hindered amine additive blended into the thermoplastic elastomer component includes a hindered amine nitrogen atom and optionally other heteroatoms, preferably is a 6-membered heterocycle containing nitrogen or oxygen. Specifically, G-(2, 2, 6, 6-
Tetramethyl-4-piperidyl) sebacate, Tetrakis(2,2,6,6-tetramethyl-4-piperidyl)
-1,2,3,4-butanetetracarboxylate, [
{6-(1,1,3,3-tetramethylbutyl)-imino-1,3,5-triazine-2,4-diyl}{2.
2,6,6tetramethyl-4-piperidyl)imino}hexamethylene-{(2,2,6,6-tetramethyl-4
-piperidyl)imino} and the like are preferred.

(e) Other blended components The present invention is characterized in that predetermined amounts of these essential components are blended when obtaining the above TPE composition.
Other olefin polymers, styrenic polymers, and especially polypropylene resins can be blended within the range that does not impair the basic performance of the TPE composition of the present invention. In addition to inorganic fillers such as calcium carbonate, talc, mica, and carbon black, and the heterocyclic hindered amine additives used in the present invention, phenol-based, sulfur-based antioxidants, ultraviolet absorbers, benzotriazole-based, and phenylbenzoate-based Additives such as light stabilizers, metal soaps, fatty acid amide-based slip agents, silicon-based slip agents, and fluidity improvers can be added.

(2) Amount Ratio The thermoplastic elastomer component composed of the hydrogenated block copolymer component (a) and the hydrocarbon rubber softener component (b) is a styrene/conjugated diene block copolymer component. The blending ratio of the hydrogenated block copolymer component obtained by hydrogenating the polymer and the softener component for hydrocarbon rubber is such that the hydrogenated block copolymer component in the total thermoplastic elastomer is 25 to 5.
0% by weight, preferably 35-45% by weight, relative to which the softener component is in the range 75-50% by weight, preferably 65-55% by weight. If the hydrogenated block copolymer is less than 25% by weight, the resulting molded product will have poor weather resistance.
It becomes noticeably more sticky than before the ozone resistance test. Moreover, if it exceeds 45% by weight, it is not preferable from the viewpoint of not only moldability but also material cost. The blending ratio of the polyethylene wax component is based on 100 parts by weight of the hydrogenated block copolymer obtained by hydrogenating the styrene/conjugated diene block copolymer and the hydrocarbon rubber softener. , in the range of 2 to 20 parts by weight, preferably 5 to 10 parts by weight. If the amount of polyethylene wax is less than 2 parts by weight, oil bleed will worsen in the ozone resistance test, and if it exceeds 20 parts by weight, the rubber elasticity (as an elastomer, the compression set at 70°C for 22 hours will be 50% or less) It is desirable that there be.)
Flexibility deteriorates. The amount of the heterocyclic hindered amine additive added is 0.05 to 0.3 parts by weight, assuming that the total amount of the hydrogenated block copolymer and the hydrocarbon rubber softener is 100 parts by weight. Part by weight, preferably 0.1 to 0.2 part by weight. If it is less than the above range, there will be a problem in terms of weather resistance, and if it exceeds the above range, oil bleed will be significantly worsened in the ozone resistance test.

(3) Compounding As a method for producing the TPE of the present invention, a method using mechanical melt-kneading can be adopted. Specifically, general melt kneading machines such as a Banbury mixer, various kneaders, and a single-screw or twin-screw extruder can be used. The compounding conditions are generally 180 to 230°C, preferably 190 to 210°C.

[II] Molding Furthermore, thermoplastic resin molding methods such as injection molding, extrusion molding, and blow molding can be applied to the TPE of the present invention.

[IV] Applications The TPE of the present invention can be used for automobile parts, home appliance parts, electric wire coatings, etc.

[0014]

[Example] The following test methods and raw materials were used for various evaluations in the Examples and Comparative Examples. (1) Measurement method (a) Manufacture of measurement sample sheets All measurement samples were molded in a 5-ounce in-line screw type injection molding machine at an injection pressure of 500 kg/cm2, an injection speed of 220°C, and a mold temperature of 40°C, with a width of 80 mm and a length of 80 mm. The material used was produced by transverse punching of a sheet with a length of 120 mm and a thickness of 2 mm. (b) JIS-A hardness [-] According to JIS-K-6301 (c) Compression set [%] According to JIS-K-6301 (measured by stacking 6 sheets). Measurement conditions: 70°C x 22 hours (d) Weather resistant sunshine weather meter (black panel temperature:
An accelerated weathering test was conducted for 2,000 hours at 63° C. and a spray/dry cycle of 18 minutes/102 minutes to check for any abnormalities in appearance such as cracks on the surface. Those in which no abnormality was observed were indicated as ○, and those in which any abnormality was observed were indicated as ×. (e) Ozone resistance According to JIS-K-6301. Measurement conditions: ozone concentration 5
Evaluation was made based on the occurrence of cracks and stickiness (bleeding of oil, etc.) at 0 PPhm, 20% elongation, 40° C., and 500 hours. When present, it is indicated as ×, and when it is absent, it is indicated as ○. (f) Molding processability 15 oz, in-line screw type injection molding machine, injection pressure 500 kg/cm2, injection temperature 220
It was molded at a mold temperature of 40°C using a mold having a width of 100 mm, a length of 350 mm, a thickness of 2 mm, and a two-point pin gate. The obtained injection molded sheet is judged to have good moldability when there are no short shots and no significant appearance defects (flow marks, delamination near the gate), and is indicated as ○. If a defect in appearance was observed, it was judged as defective and marked with an "×".

(2) Raw materials used (a) Hydrogenated block copolymer of styrene/conjugated diene block copolymer Hydrogenated block copolymer of styrene/butadiene block copolymer, manufactured by Shell Chemical Co., Ltd. "Krayton G165"
1''; A-B-A type, styrene content of 33% by weight, number average molecular weight of 170,000 was used. (b) Paraffin oil “PW380” manufactured by Idemitsu Kosan, a softener for hydrocarbon rubber (4
A kinematic viscosity of 381.6 cst at 0°C was used. (c) Polyethylene wax “AC polyethylene; AC-
8", dropping point 116°C, Brookfield viscosity 140°C
, 400 cps was used. (d) A heterocyclic hindered amine additive di-(2,2,6,6-tetramethyl-4-piperidyl) sebacate was used. (e) Olefin resin Mitsubishi polypropylene "BC-1" MF manufactured by Mitsubishi Yuka Co., Ltd.
R30g/10min (f) Antioxidant A phenolic antioxidant (Irganox 1010, manufactured by Ciba Geigy) was used.

Examples 1 to 2 and Comparative Examples 1 to 5 The ingredients were mixed at the proportions shown in Table 1, and these components were first mixed for 5 minutes in a Henschel type mixer, and then L/D=3.
3. 220℃ in a twin-screw extruder with a cylinder diameter of 45mmφ
The mixture was melt-kneaded with the following settings to obtain TPE pellets. Next, a sample sheet for measurement having a thickness of 2 mm was formed by injection molding using this pellet. Table 1 shows the results of various evaluations performed on the obtained sheet.

[0017]

[Table 1]

From Table 1, the examples have superior rubber elasticity, flexibility, weather resistance, and moldability compared to the comparative examples.
It can also be seen that this is a thermoplastic elastomer that does not bleed oil under an ozone atmosphere.

[0019]

[Effect of the invention] By blending a polyethylene wax and a heterocyclic hindered amine additive with a thermoplastic elastomer component containing a hydrogenated styrene/conjugated diene block copolymer and a softener for hydrocarbon rubber. The obtained thermoplastic elastomer composition is a material with excellent rubber elasticity, flexibility, weather resistance, and no oil bleed even in an ozone atmosphere, making it extremely useful industrially. be.

Claims (1)

[Claims] Claim 1: Hydrogenated block copolymer consisting of at least two styrene-based polymer blocks (A) and at least one conjugated diene compound polymer block (B) 25-50% by weight % and 75 to 50 weight % of a hydrocarbon rubber softener, 2 to 20 parts by weight of polyethylene wax and 0.05 to 0.3 parts by weight of a heterocyclic hindered amine additive. A thermoplastic elastomer composition comprising: