JP2948032B2 - Hydrogenated block copolymer elastomer composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrogenated block copolymer elastomer which is excellent in the deployability of an airbag and the splash resistance upon deployment in an airbag cover of an airbag system used as a safety device for automobiles and the like. It relates to a composition.

[0002]

2. Description of the Related Art Conventionally, urethane in which a reinforcing nylon net is inserted is used for an airbag cover. The airbag cover is ruptured at a thin portion without a reinforcing nylon-based net due to inflation and deployment of the airbag folded inside and stored. However, in the case of such an airbag cover, if there is no reinforcing nylon-based net, a crack is generated in a portion other than the thin-walled cleavage portion, or the cover is scattered. Also, when molding the airbag cover, it takes time to position the reinforcing net, and the defect rate due to the misalignment of the reinforcing nylon net is high. The disadvantage was the low production by urethane RIM molding. Many airbag covers made of a thermoplastic resin that does not require a reinforcing nylon-based net have also been studied, but as a car interior part having a hardness of 40 to 90, it is soft enough to be unpleasant for humans and has a temperature of -40C to 85C. It is very difficult for the airbag to be reliably deployed in the airbag, and it is very difficult for the airbag cover to crack other than the cleaved portion when the airbag is deployed, and for the fragments to never scatter, so the airbag at a temperature of -40 ° C to 90 ° C. Developing hardness, excellent in splash resistance during deployment
At present, the 90 airbag cover has not been developed.

[0003]

SUMMARY OF THE INVENTION The present invention relates to a JIS K630 made of a thermoplastic resin that does not require a reinforcing nylon-based net, which cannot be provided by an airbag cover of an airbag system used as a conventional safety device for automobiles and the like.
As a result of researching to obtain an airbag cover having a spring hardness (hardness) of 40 to 90, a thermoplastic elastomer comprising a hydrogenated block copolymer composition as a main component and a low-temperature-side developability of an e-component was used. Is improved by alloying, and the developability on the high-temperature side is improved by alloying the amorphous olefin resin of the component c. An airbag cover excellent in the deployability of the airbag in the range and the splash resistance during the deployment can be obtained, and based on this finding, various studies have been advanced to complete the present invention.

[0004]

That is, the present invention is a hydrogenated block copolymer elastomer composition for an airbag cover obtained by melting and kneading the following components a, b, c and e to form a pellet. (A) A block copolymer comprising at least two terminal polymer blocks A mainly composed of a vinyl aromatic compound and at least one intermediate polymer block B mainly composed of a conjugated diene compound is hydrogenated. 100 parts by weight (b) paraffinic oil 10 to 300 parts by weight (c) Amorphous olefin resin alone or amorphous olefin 5 to 250 parts by weight of a blend of a crystalline resin and a crystalline olefin resin having a temperature of 90 ° C. or higher and having a ratio of 25/75 or higher (weight) (e) Dynamically vulcanized ethylene-α · Olefin-non-conjugated diene copolymer A thermoplastic elastomer composed of a blend of rubber and a polyolefin resin, having a brittleness temperature of -50 ° C or lower 10 to 150 The amount part

[0005] The hydrogenated block copolymer of component a used in the present invention comprises at least two terminal polymer blocks A mainly composed of a vinyl aromatic compound and at least one intermediate polymer block mainly composed of a conjugated diene compound. It is obtained by hydrogenating a block copolymer composed of a polymer block B and a hydrogenated vinyl aromatic compound-conjugated diene compound block copolymer having a structure represented by the following general formula. is there. A- (BA) n 1 ≦ n ≦ 5 In order to obtain a hydrogenated block copolymer elastomer composition, a hydrogenated block copolymer having a hardness of 99 or less, preferably 90 or less is used. It is necessary to include the vinyl aromatic compound in an amount of 5 to 50% by weight, preferably 10 to 40% by weight. Further, when referring to the block structure, the terminal polymer A mainly composed of the vinyl aromatic compound is a vinyl aromatic compound. Having a structure of a polymer block or a copolymer block of a vinyl aromatic compound containing more than 50% by weight, preferably 70% by weight or more of a vinyl aromatic compound and a hydrogenated conjugated diene compound, and Further, the intermediate polymer block B mainly composed of a hydrogenated conjugated diene compound is used as a hydrogenated conjugated diene compound polymer block or a hydrogenated conjugated diene compound. The diene compound preferably exceed 50% by weight and has a structure of a copolymer block of a conjugated diene compound and a vinyl aromatic compound added hydrogen containing more than 70 wt%.
When there are two or more polymer blocks mainly composed of a vinyl aromatic compound and two or more polymer blocks mainly composed of a hydrogenated conjugated diene compound, each of the polymer blocks may have the same structure or may be different. It may have a structure.

As the vinyl aromatic compound constituting the hydrogenated block copolymer, for example, one or more of styrene, α-methylstyrene, vinyltoluene, p-tert-butylstyrene and the like can be selected. Among them, styrene is preferred. As the conjugated diene compound before hydrogenation constituting the hydrogenated conjugated diene compound, for example, one or more selected from butadiene, isoprene, 2.3-dimethyl-1.3-butadiene and the like are selected. Among them, butadiene, isoprene and a combination thereof are preferred. The hydrogenated block copolymer used in the present invention has a number average molecular weight (Mn) of 5,000 to 1,000,000, preferably 10,000 to 800,000, more preferably 3 to 100,000.
000 to 500,000, and the molecular weight distribution Mw
/ Mn is 10 or less (Mw: weight average molecular weight). Further, the molecular structure of the hydrogenated block copolymer may be linear, branched, radial, or any combination thereof. Further, the dynamic storage modulus G ′ of the above-mentioned type hydrogenated block copolymer at 23 ° C. is 5 × 102 MPa or less.

[0007] The paraffinic oil of the component b used in the present invention is an essential component having an effect of adjusting the hardness of the resulting composition and imparting flexibility. Generally, rubber softening, volume expansion,
The mineral oil-based rubber softener called process oil or extender oil used for improving processability is a mixture of an aromatic ring, a naphthene ring, and a paraffin chain. Those occupying 50% or more of the number are called paraffinic, those having 30 to 45% naphthenic ring carbon are naphthenic, and those having more than 30% aromatic ring carbon are aromatic. The oil used as the component b in the present invention is preferably a paraffinic oil in the above category, and a naphthenic or aromatic oil is not preferred in terms of dispersibility and solubility. The paraffin rubber softener has a kinematic viscosity at 37.8 ° C. of 20 to 50.
0 cst, pour point -10 to -15 ° C and flash point 1
The amount of the component b paraffinic oil exhibiting 70 to 300 ° C is 10 to 300 parts by weight, preferably 20 to 250 parts by weight, per 100 parts by weight of the component a. 30
If the amount exceeds 0 parts by weight, the softener tends to bleed out, which may cause tackiness in the final product, and deteriorates the mechanical properties. If the amount is less than 10 parts, the composition obtained is close to the resin composition, the hardness is increased, the flexibility is lost, and it is not preferable from an economic viewpoint.

Next, the amorphous olefin-based resin used as the component c of the present invention is not only an essential component for improving the airbag deployability at 85 ° C. It is effective in improving processability and heat resistance, and is a polymer having a cyclic olefin structure alone or a copolymer of a cyclic olefin and an α-olefin, and can be said to be an amorphous polyolefin from its structure and properties. Examples of the amorphous olefin-based resin include the following.
For example, a ring-opened polymer of dicyclopentadiene represented by the general formula (1) or a hydrogenated product thereof.

[0009]

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The ring-opened polymer can be produced by a known ring-opening polymerization method of a cyclic olefin using dicyclopentadiene as a monomer. The hydrogenated product of the ring-opened polymer can also be obtained by using a usual hydrogenation reaction method. And also, at least one compound selected from the group consisting of unsaturated monomers represented by the general formula (2) or (3) is included. These are easily produced by condensing cyclopentadiene with the corresponding olefin and cyclic olefin by a Diels-Alder reaction.

[0011]

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[0012]

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(Wherein n and m are each 0 or a positive integer, l is an integer of 3 or more, and R ₁ to R
₁₀ represents a hydrogen atom, a halogen atom or a carbon-hydrogen group, respectively. ) And the general formula (4) (wherein, R1 represents a hydrogen atom or a methyl group, R ₂ is a hydrocarbon group of C ₁ -C _20.) And (5) (R ₃ to R ₆ is , A hydrogen atom or a C ₁ -C ₁₀ alkylidene group composed of R ₃ and R ₄ ), and a ring-opened polymer of a tetracyclododecene derivative or a hydrogenated product thereof. These can be used as a mixture of two or more kinds.

[0014]

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[0015]

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The amount of component c is 5 to 250 parts by weight, preferably 10 to 150 parts by weight, per 100 parts by weight of component a.
Parts by weight. If the amount exceeds 250 parts by weight, the resulting elastomeric composition will have too high a hardness to lose flexibility, and not only will not be able to obtain a rubber-like product, but also have a high elasticity (compression set) at high temperatures. ) Gets worse,
Unsatisfactory airbag deployment at 85 ° C. Also, 5
If the amount of the component (c) is less than 85 parts by weight,
It can only exhibit airbag deployment at ℃, workability and heat resistance. Here, the amorphous olefin-based resin and the crystalline olefin-based resin of the component c can be used in combination as the component c. The crystalline olefin-based resin used is, for example, polyethylene, isotactic polypropylene or a random or block copolymer of propylene and a small amount of other α-olefin, specifically polypropylene-
Examples include ethylene copolymer, propylene-1-hexene copolymer, propylene-4-methyl-1pentene copolymer, poly-4-methyl-1-pentene, polybutene-1 and the like. It is effective to use a cyclic olefin-based resin. Further, two or more crystalline olefin resins such as polyethylene and polypropylene may be used in combination. MFR (ASTM-D-1238L conditions, when using isotactic polypropylene or a copolymer thereof as a crystalline olefin resin,
230 ° C) is 0.1 to 50 g / 10 min, especially 0.5 to 30 g
/ 10 minutes can be suitably used. In addition, the reason why the heat distortion temperature (JIS K72074.6 kgf / cm ² ) is limited to 90 ° C. or higher is that if it is lower than 90 ° C., there is no effect on improving heat resistance. When the component c is a blend of an amorphous olefin-based resin and a crystalline olefin-based resin having a heat distortion temperature of 90 ° C. or more, the ratio is specified to be 25/75 or more (by weight). In the case of (1), the effect of adding the amorphous olefin-based resin (improvement of the airbag deployability at 85 ° C.) is not exhibited.

Further, the thermoplastic elastomer used as the component e in the present invention is an essential component for improving the expandability of the airbag at -40 ° C., and the α-olefin in the copolymer rubber has 3 to 15 carbon atoms. Are suitable. As the non-conjugated diene, dicyclopentadiene, 1,4-hexadiene, ethylidene norbornene, methylene norbornene and the like can be used. In the present invention, polypropylene is suitable as the α-olefin from the viewpoint of easy availability and improvement of impact resistance. Therefore, the ethylene in component e
So-called EPDM is suitable as the α-olefin-non-conjugated diene copolymer rubber. Ethylene of copolymer rubber /
α / olefin ratio is 50/50 to 90/10 by weight,
More preferably, 60/40 to 80/20 is suitable. As the vulcanizing agent, an ordinary vulcanizing agent for rubber can be used. In particular, an organic peroxide such as alkylphenol / formaldehyde resin and dicumyl peroxide is particularly preferably used in addition to sulfur. In addition to the vulcanizing agent, a vulcanizing aid, an antioxidant and the like may be used in combination. The addition amount of the alkylphenol-formaldehyde resin is preferably in the range of 0.5 to 15 parts by weight based on 100 parts by weight of the copolymer rubber in view of the balance between strength and processability. In the case of an organic peroxide, the range of 0.05 to 1 part by weight based on 100 parts by weight of the copolymer rubber is preferable from the viewpoint of balance between strength and processability. It is indispensable to contain 5 parts by weight or more of the polyolefin resin with respect to 100 parts by weight of the copolymer rubber in order to maintain processability. While dynamically blending and kneading the blend of the copolymer rubber and the polyolefin-based resin, a vulcanizing agent is added and vulcanized to obtain the component f. As a method of obtaining the component e, there is a method of obtaining a commercially available product. However, since these components may be added in advance with the component b of the present invention in order to improve processability, the amount of the component b added may be reduced. Correction is required.
Here, the reason why the embrittlement temperature of the thermoplastic elastomer is specified to be -50 ° C or lower is that the thermoplastic elastomer having a higher embrittlement temperature is -4 ° C.
This is because the deployability of the airbag at 0 ° C. cannot be improved. The amount of the component e is 10 to 15 with respect to 100 parts by weight of the component a.
It can be suitably selected in the range of 0 parts by weight. Component e is 1
If the amount is more than 50 parts by weight, not only the rubber elasticity at high temperature of the obtained elastomeric composition is inferior, but also the airbag expandability at 90 ° C. is not favorable, but also the heat-resistant shape retention at high temperature is remarkably deteriorated, resulting in a molded article. Does not stand use. In addition, when the component e is less than 10 parts by weight, the improvement of the airbag expandability at −40 ° C. as an effect of adding the copolymer rubber is not recognized, which is not preferable.

In addition to the above-mentioned components (a) to (e), the composition of the present invention may further contain an inexpensive resin such as an inorganic filler and a polystyrene resin, if necessary. . These not only have the benefit of reducing product costs as extenders, but also have a positive effect on quality improvement (inorganic fillers: heat-resistant shape retention, flame retardancy, etc. Polystyrene resins: processability improvement, etc.) There are also advantages to give. Examples of inorganic fillers include calcium carbonate, carbon black, talc, magnesium hydroxide, mica, barium sulfate, natural silicic acid, synthetic silicic acid (white carbon),
There are titanium oxide and the like, and as the carbon black, channel black, furnace black and the like can be used. Of these inorganic fillers, talc and calcium carbonate are economically advantageous and preferred. Further, as the polystyrene resin usable for this purpose, those obtained by a radical polymerization method or an ionic polymerization method can be suitably used, and the number average molecular weight thereof is 5,000 to 500,000, preferably 1,000.
The molecular weight distribution Mw can be selected from the range of 0 to 200,000.
/ Mn is preferably 5 or less. Further, if necessary, a nucleating agent, an outer lubricant, an inner lubricant, a hindered amine light stabilizer, a hindered phenol antioxidant, a coloring agent, a silicone oil, and the like may be added. As a method for producing the composition of the present invention, all general methods used for producing ordinary resin compositions and rubber compositions can be employed. Basically, it is a mechanical melt kneading method, such as a single screw extruder, a twin screw extruder, a Banbury mixer, various kneaders,
Brabender, rolls and the like are used. At this time, the order of addition of each component is not limited.For example, all components are pre-mixed by a mixer such as a Henschel mixer or a blender and melt-kneaded by the above-described kneader, or any component is pre-mixed by master batch. It is possible to employ an addition method in which the components are melt-kneaded, the remaining components are added, and the mixture is melt-kneaded. At this time, the temperature for melt-kneading can be suitably selected from 180 ° C to 300 ° C. The hydrogenated block copolymer composition obtained here is further supplied to an injection molding machine equipped with a mold for an airbag cover, and injection molded in a short time to obtain an airbag cover. In addition, unnecessary burrs of injection molded products,
Since the composition of the present invention is thermoplastic, the runner portion and the spool portion can be recycled and can be reused as a material for an airbag cover. Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

[0019]

EXAMPLES The components blended in the following examples and comparative examples are as follows. <Component a> Tuftec H1041 manufactured by Asahi Kasei having a structure of polystyrene-hydrogenated polybutadiene-polystyrene having an amount of bound styrene of 30% [hardness: 86] <Component b> Diana Process Oil PW-380 manufactured by Idemitsu Kosan [paraffin type] Process oil, kinematic viscosity: 381.6 cst
(40 ° C), 30.1 (100 ° C), average molecular weight 74
6. Ring analysis value: CA = 0%, CN = 27%, CP = 73
%] <Component c (1)> Amorphous olefin resin manufactured by Mitsui Petrochemical, Apel 13
0A [Heat deformation temperature: 130 ° C] <Component c (2)> Amorphous olefin resin made of Japan Synthetic Rubber, ARTON
I [Heat deformation temperature: 165 ° C] <Component c (3)> Amorphous olefin resin manufactured by Zeon, ZEONEX
280 [Heat deformation temperature: 150 ° C.] <Component c (5)> Sumitomo Chemical polypropylene resin, AV664B [MFR (230 ° C.) = 5 g / 10 min Heat deformation temperature: 122 ° C.] <Component e (1)> Monsanto Santoprene 201-80 [vulcanizing agent: alkylphenol-formaldehyde resin Embrittlement temperature:
−60 ° C.>] <Component e (2)> Sumitomo TPE821 manufactured by Sumitomo Chemical [vulcanizing agent: organic peroxide]
Embrittlement temperature: -60 ° C>]

<< Examples 1 to 8 and Comparative Examples 1 to 5 >> After sufficiently dry-blending those having the mixing ratios shown in the table, the resin temperature was adjusted to 260 to 275 ° C. using a twin-screw kneader. The mixture was melt-kneaded and extruded into pellets. The following evaluation was performed using this pellet. (1) Hardness (JIS K6301): A press sheet was prepared and measured. (2) Appearance: Using an injection molding machine, a molded product of the airbag cover having a thickness of 0.5 mm at the cleavage portion of the airbag cover and a thickness of 2 to 5 mm other than the cleavage portion of the airbag cover is produced.
The appearance such as flow mark and gloss was visually observed. Good was evaluated as O, slightly poor as Δ, and poor as X. (3) Heat-resistant shape retention: This airbag cover molded product is heated at a temperature of 9
A heat-resistant shape retention test was performed in an environment of 0 ° C. After 24 hours, the sample having good shape retention and no sagging, etc. was evaluated as ○, and the sample having sagging, etc. was evaluated as ×. (4) Deployment test: The airbag cover molded product was subjected to an airbag deployment test at ambient temperatures of 85 ° C, 23 ° C and -40 ° C. The sample that satisfactorily expanded from the cleaved portion of the airbag cover was rated as ○, and the sample that cracked or scattered the cover other than the cleaved portion of the airbag cover, and the sample that did not deploy the airbag satisfactorily was rated as x. The results are shown in Tables 1 and 2 as examples, and in Table 3 as comparative examples. From these results, it can be seen that the airbag cover formed from the composition obtained in the present invention has a hardness of 40 to 90 and is excellent in airbag deployability at -40 ° C to 85 ° C.

[0021]

[Table 1]

[0022]

[Table 2]

[0023]

[Table 3]

[0024]

The airbag cover molded from the composition of the present invention has a good airbag development without cracking or scatter of the cover other than at the cracked portion when the airbag is deployed between -40 ° C and 90 ° C. Is obtained. In addition, since it has good light aging resistance and heat aging resistance, it has excellent long-term reliability. Moreover, compared to conventional urethane and nylon nets for reinforcement, there is good molding workability, good productivity,
The utility value is very large, such as simple color matching and low cost.

Continuation of the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C08L 53/02 C08L 23/00-23/26 C08L 23/16 C08L 91/00

Claims (1)

(57) [Claims] 1. A hydrogenated block copolymer elastomer composition comprising the following components a to c and e. (A) A hydrogenated block copolymer consisting of at least two terminal polymer blocks A mainly composed of a vinyl aromatic compound and at least one intermediate polymer block B mainly composed of a conjugated diene compound The obtained hydrogenated block copolymer having a spring hardness (JIS K6301) of 99 or less 100 parts by weight (b) Paraffin oil 10 to 300 parts by weight (c) Amorphous olefin resin alone or amorphous olefin resin A blend of a resin and a crystalline olefin resin having a heat distortion temperature of 90 ° C. or more and having a ratio of 25/75 or more (by weight) 5 to 250 parts by weight (e) Dynamically vulcanized ethylene-α · A thermoplastic elastomer comprising a blend of an olefin-non-conjugated diene copolymer rubber and a polyolefin resin, having a brittleness temperature of -50 ° C or lower 10 to 150 weights Quantity