JP2001114935A - Inflating agent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide inflating agents which obtain a large expansion coefficient in the course of rising pressure and are easy to control the size of the inflating agents under the pressure used. SOLUTION: Inflating agents are composed of a material having a ratio of the average gradient of a stress-extension curve in the range of 0%-50% breaking extension of the material to that in the range of 60%-95% breaking extension of 1: not less than 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intumescent material having a characteristic of low stiffness of up to 50% of the elongation at break of a material, and thereafter rapidly increasing the stiffness so that the rupture strength exceeds a predetermined level.

[0002]

2. Description of the Related Art Materials for protecting personnel in the event of a collision include a folded bag and an exterior material for protecting the outside of the bag, for example, an SRS airbag for a front seat of an automobile, or plastic deformation of the material. Impact-absorbing materials utilizing, for example, brittle fracture materials and honeycomb structural materials.
In the former case, it is possible to fill a sufficient space (take a sufficient expansion rate) as an inflatable material, but in addition to the original intended inflated folded bag body, an exterior material that protects the outside is required There is a problem inevitably resulting in such a configuration. On the other hand, the latter has a relatively simple structure, but cannot be used as an inflating material, so that it was impossible to fill a large space. In order to solve these problems, a method using an expanding material made of a single material is conceivable.However, the internal pressure and the surface area usually have a nearly linear relationship, and a large expansion coefficient cannot be obtained at low pressure, It has been difficult to keep the internal pressure during expansion and the size of the expanding material constant. In addition, there was a disadvantage that a sufficient expansion rate could not be obtained.

[0003]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to make it possible to use a single material to obtain a large expansion coefficient in the process of increasing the pressure and to increase the size of the expandable material under the working pressure. It is an object of the present invention to provide an inflatable material that can easily control the expansion.

[0004]

According to the present invention, the ratio between the average slope of the stress-elongation curve from 0% to 50% and the average slope from 60% to 95% of the elongation at break of the material is determined. An intumescent material comprising a material that is 1: 5 or more is provided.

[0005] According to the present invention, there is further provided an inflatable material having the above-mentioned structure, wherein the elongation at break of the material at the time of a break test is 1000% or more.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, as shown in FIG.
Stress from 0% to 50% of the elongation at break of the material-
Assuming that the expansion material is made of a material in which the ratio between the average slope a of the elongation curve and the average slope b from 60% to 95% is 1: 5 or more, the pressure rising process as shown in FIG. It is possible to take a large expansion coefficient in,
It has been found that it is easy to control the size of the expanding material under working pressure so as to reduce the variation. The elastic material having such characteristics of the present invention can be effectively used as an SRS airbag made of a single material, and is also extremely effectively used in fields where shock absorbers utilizing plastic deformation are currently used. it can.

The material satisfying the requirements of the expandable material of the present invention must be a polymer material having a glass transition point at room temperature or lower and restricted by cross-links or pseudo-crosslinks such as hydrogen bonds. In the low elongation region, elongation is exhibited with low stress due to deformation of the polymer chain, and in the high elongation region,
This is because a sufficient strength can be obtained by the crosslinking point of the polymer. As such a material, specifically, a vulcanized rubber, particularly a flexible rubber such as butyl rubber or EPDM is desirable. The thermoplastic elastomers include polyurethanes having hard segments and soft segments, styrene-based elastomers, polyester-based elastomers, polyamide-based elastomers, and the like. Further, as the expanding material of the present invention, a thermoplastic elastomer composition containing a vulcanized rubber in at least a part of a thermoplastic resin material can also be used.

[0008] As the thermoplastic resin used in the thermoplastic elastomer composition of the present invention, various thermoplastic resins or compositions thereof can be used. That is, it may be a single thermoplastic resin or composition, or a composition comprising a mixture thereof. Specifically, polyolefin resin, polyamide resin, polyester resin, polystyrene resin, polynitrile resin, polymethacrylate resin, polyvinyl resin, cellulose resin, fluorine resin, imide resin, styrene resin, olefin resin And thermoplastic elastomers such as polyester, urethane and the like.

The rubber used as the domain phase dispersed in the thermoplastic resin is at least partially crosslinked. Various rubbers can be used as the rubber component constituting the rubber particles. For example, diene rubbers and hydrogenated products thereof (for example, NR,
IR, epoxidized natural rubber, SBR, BR (high cis BR
And low cis BR), NBR, hydrogenated NBR, hydrogenated S
BR), olefin rubbers (for example, ethylene propylene rubber (EPDM, EPM), maleic acid-modified ethylene propylene rubber (M-EPM), IIR, isobutylene and aromatic vinyl or diene monomer copolymer, acrylic rubber ( ACM), ionomers), halogen-containing rubbers (for example, bromide of Br-IIR, Cl-IIR, isobutylene paramethylstyrene copolymer (BIM
S), CR, hydrin rubber (CHR), chlorosulfonated polyethylene (CSM), chlorinated polyethylene (C
M), maleic acid-modified chlorinated polyethylene (MC
M), silicone rubber (eg, methyl vinyl silicone rubber, methyl phenyl vinyl silicone rubber), sulfur-containing rubber (eg, polysulfide rubber), fluorine rubber (eg, vinylidene fluoride rubber, fluorine-containing vinyl ether rubber, fluorine-containing phosphazene) Rubber) and thermoplastic elastomers (eg, styrene-based elastomers, olefin-based elastomers, ester-based elastomers, urethane-based elastomers, and polyamide-based elastomers).

The ratio of the thermoplastic resin forming the thermoplastic resin matrix phase to the rubber composition forming the domain phase rubber particles in the thermoplastic elastomer composition used in the present invention is not particularly limited. The weight ratio between the thermoplastic resin and the rubber composition is preferably 20/80 to 90/10. When the blending amount of the thermoplastic resin is large, the flexibility of the obtained thermoplastic elastomer composition decreases. Conversely, if the amount is too small, the melt fluidity of the thermoplastic elastomer composition decreases, and molding processing becomes difficult.If the amount is excessively small, the thermoplastic resin as the continuous phase physically removes the rubber particles as the domain phase. They tend to be unwrapped and difficult to knead.

The thermoplastic elastomer composition used in the present invention contains, in addition to the essential components described above, a plasticizer, a compatibilizer, a vulcanization accelerator, an antioxidant, an oxidizing agent, as long as the object of the present invention is not impaired. Additives such as inhibitors, ultraviolet absorbers, colorants such as pigments and dyes, and processing aids can be added.

[0012] The thermoplastic elastomer composition used in the present invention is a thermoplastic elastomer produced by dynamic crosslinking in which the crosslinking of the rubber proceeds while kneading the thermoplastic resin and the rubber component. It is preferably a plastic elastomer composition. By utilizing such a manufacturing method, the obtained thermoplastic elastomer composition has a crosslinked rubber phase at least partially discontinuous finely dispersed in a thermoplastic resin phase at least partially continuous. Since the obtained thermoplastic elastomer composition exhibits the same behavior as the crosslinked rubber, and at least the continuous phase is a thermoplastic resin,
Processing according to thermoplastic resin is possible. In the production of the thermoplastic elastomer composition of the present invention, the type used for kneading is not particularly limited, and examples thereof include a screw extruder, a kneader, a Banbury mixer, and a twin-screw kneading extruder. Above all, it is preferable to use a twin-screw kneading extruder in consideration of kneading and dynamic crosslinking. Further, two or more types of kneaders may be used to knead sequentially.

The rubber particles, which are domain phases of the thermoplastic elastomer composition used in the present invention, are at least partially crosslinked. In such a thermoplastic elastomer composition, an additive is kneaded in advance with a rubber component that forms rubber particles, and this rubber component, a thermoplastic resin component, and other additives as necessary, are kneaded with two axes. Melt-kneading with an extruder, etc., while dispersing the rubber particles in the thermoplastic resin matrix phase, adding a cross-linking agent that cross-links the rubber particles, and dynamically cross-linking during kneading. Can be. In addition, as dynamic crosslinking, crosslinking can be performed while kneading at a temperature of 150 to 300 ° C. using a crosslinking agent such as a sulfur-based, organic peroxide-based, metal oxide-based, phenolic resin, or quinone dioxime. .

The type of the crosslinking agent, the conditions for the dynamic crosslinking (temperature, time) and the like may be appropriately determined according to the composition of the rubber composition, and are not particularly limited. As the crosslinking agent, those described above can be used.More specifically, as the sulfur-based crosslinking agent, powdered sulfur, precipitated sulfur, highly dispersible sulfur, surface-treated sulfur, insoluble sulfur, dimorpholine disulfide, Examples thereof include alkylphenol disulfide and the like. The addition amount may be, for example, about 0.5 to 4 parts by weight based on 100 parts by weight of rubber. In addition, as the organic peroxide-based crosslinking agent, benzoyl peroxide,
t-butyl hydroperoxide, 2,4-dichlorobenzoyl peroxide, 2,5-dimethyl-2,5-
Di (t-butylperoxy) hexane, 2,5-dimethylhexane-2,5-di (peroxylbenzoate)
For example, for 100 parts by weight of rubber, 1
About 15 parts by weight may be used. Examples of the phenolic resin-based cross-linking agent include brominated alkylphenol resins, and mixed cross-linking systems containing a halogen donor such as tin chloride or chloroprene and an alkylphenol resin. About 20 parts by weight may be used.

Others include zinc white (about 5 parts by weight),
Magnesium oxide (about 4 parts by weight), litharge (10 to 10 parts by weight)
About 20 parts by weight), p-quinone dioxime, p-dibenzoylquinone dioxime, tetrachloro-p-benzoquinone, poly-p-dinitrosobenzene (about 2 to 10 parts by weight), methylene dianiline (0.2 To about 10 parts by weight). Moreover, you may add a crosslinking promoter as needed.

In addition to the above constitution, for example, when the thermoplastic resin component and the rubber component have different compatibility in the thermoplastic elastomer composition used in the present invention, they can be made compatible with each other using a compatibilizer. Good. By mixing the compatibilizer into the system, the interfacial tension between the thermoplastic resin component and the rubber component is reduced, and as a result, the particles of the rubber dispersed phase become finer, so that the properties of both components are more effectively expressed. Will be. Such a compatibilizer is generally a copolymer having a structure of both or one of a thermoplastic resin component and a rubber component, or an epoxy group, a carbonyl group, a halogen group, an amino group capable of reacting with the thermoplastic resin component or the rubber component. The copolymer may have a structure having a group, an oxazoline group, a hydroxyl group and the like. These may be selected according to the type of the thermoplastic resin component or the rubber component to be mixed, and commonly used ones include styrene / ethylene / butylene block copolymer (SEBS) and its modified maleic acid, EPM and EPDM. Maleic acid modified product, EPDM / styrene or EPDM / acrylonitrile graft copolymer and its maleic acid modified product, styrene / maleic acid copolymer, reactive phenoxy resin and the like.

As the above-mentioned thermoplastic elastomer, Tg
A block (A) made of a polymer having a temperature above room temperature;
A block copolymer with a block (B) made of a polymer having a temperature of room temperature or lower is preferable. When the block copolymer contains the above-mentioned blocks (A) and (B) made of a polymer having a Tg in a different temperature range, the temperature range of Tg or lower between the blocks (A) made of a polymer having a high Tg. In the above, a crystal phase is formed, whereby a pseudo-crosslinked structure is formed, and the resulting composition of the present invention becomes a composition having high breaking strength. The block copolymer is a diblock or triblock as long as it has a structure having a block (A) composed of a polymer whose Tg is higher than normal temperature and a block (B) composed of a polymer whose Tg is lower than normal temperature. Or multi-block. Diblock and triblock are preferred from the viewpoint of easy production.

Tg of the polymer constituting the block (A)
Is higher than room temperature, that is, higher than 20 ° C., preferably higher than 40 ° C. This is because, within the above temperature range, the obtained composition of the present invention has high breaking strength at ordinary temperature. As such a polymer, various polymers having a property that Tg is higher than ordinary temperature can be used. For example, a polystyrene resin, a polyester resin, a polyacrylate resin, a polymethacrylate resin,
Polyamide resins and the like can be mentioned. Among them, polystyrene resins are preferable because they are inexpensive, and the resulting composition of the present invention has high breaking strength and high flexibility. As the polystyrene resin, for example, styrene homopolymer, or a substituted styrene in which one or more alkyl groups, alkoxy groups, halo groups and the like are bonded to an aromatic ring, for example, α-methylstyrene, p-methylstyrene, Copolymers containing butylstyrene, p-hydroxystyrene, bromostyrene and the like can be mentioned, and among these, a styrene homopolymer is preferable because of its high cohesiveness and high strength.

As the polymer constituting the other block (B) of the block copolymer, a polymer having a Tg of room temperature or lower is used. Tg of polymer constituting block (B)
Is room temperature or lower, preferably 0 ° C. or lower. This is because, within this temperature range, the obtained composition of the present invention has high flexibility at room temperature. As such a polymer, various polymers having a property that Tg is equal to or lower than room temperature can be used. For example, conjugated diene-based polymers such as polybutadiene and polyisoprene having the above properties, polymers that are mixtures thereof, and polytetrafluoroethylene Amorphous polyethers such as methylene ether glycol, polyethylene glycol, polypropylene glycol and polybutylene glycol, olefin polymers such as polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-α-olefin copolymer, polyisobutylene, and halogen-containing Polymer, silicone polymer, and fluorine polymer. Among these, polybutadiene and polyisoprene are preferred because they exhibit high flexibility and high elongation. The block (B) may contain a residual unsaturated site, but is preferably saturated by hydrogenation, since the obtained composition of the present invention shows characteristics excellent in weather resistance and heat resistance.

Specific examples of the block copolymer that can be used in the present invention include polystyrene-polybutadiene block copolymer, polystyrene-polybutadiene-polystyrene block copolymer (SBS), and polystyrene-polyisoprene-polystyrene block copolymer. Coalescing (S
IS), and styrene-based thermoplastic elastomers such as modified products thereof, and hydrogenated copolymers thereof, for example, polystyrene- (ethylene-butylene) -polystyrene block copolymer (hydrogenated product of SEBS, SBS) , Polystyrene- (ethylene-propylene) -polystyrene block copolymer (hydrogenated product of SEPS, SIS), or PBT-PTMG copolymer, PET
Polyester-based thermoplastic elastomers such as -PPG copolymers; and polyamide-based thermoplastic elastomers such as N6-PTMG copolymers. Among them, the composition of the present invention obtained has high breaking strength, and flexibility,
SEBS, SEPS because of excellent weather resistance and heat resistance
Hydrogenated styrenic thermoplastic elastomers such as These block copolymers can be produced by a known production method.

The expanding material of the present invention includes a hydrogenated styrene-based block polymer having a number average molecular weight of 50,000 or more. If the number average molecular weight is less than 50,000, tensile strength is insufficient and sufficient expansion cannot be obtained. The styrene block polymer has a styrene content of 20 to 50 wt.
%, More preferably 25 to 40 wt%. Within this range, flexibility and strength can be obtained in a well-balanced manner. Commercially available products can be used as such a hydrogenated styrene-based block polymer, and examples thereof include Tuftec K2181 (hydrogenated product of SEBS and SBS, number average molecular weight of 50,000, manufactured by Asahi Kasei Corporation), and Septon 4033 (SEPS). ,
SIS hydrogenated product, number average molecular weight 100,000, manufactured by Kuraray)
Septon 2023 (SEPS, number average molecular weight 80,000, manufactured by Kuraray Co., Ltd.) and the like.

In order to further increase the coefficient of expansion of the expandable material of the present invention, the elongation at break of the material at the time of a break test is set to 1
As an expanding material effective as such a material, a rubber obtained by at least partially vulcanizing the hydrogenated styrene-based block polymer as a domain phase may be used to increase flexibility. . The rubber material, vulcanizing agent and production method used for this are the same as those used for the thermoplastic elastomer composition described above.

[0023]

The present invention will be further described below with reference to Examples and Comparative Examples, but it goes without saying that the scope of the present invention is not limited to these Examples.

Examples 1 and 2 and Comparative Examples 1 and 2 The thermoplastic resins shown in Table 1 were charged into a single screw extruder set at 180.degree.
It was formed into a sheet having a thickness of mm. This sheet is JIS K625
Perform a tensile test in accordance with No. 1, 0 to 50% of the elongation at break
The ratio between the average slope of the stress-elongation curve up to and the average slope from 60 to 95% was measured. Further, the sheet was inserted into a test jig shown in FIG. 8 and air was injected at 7 kg / cm ² to perform an expansion test. This behavior was photographed with a high-speed video, and the internal pressure and the surface area increase rate were measured. At this time, the variation in the surface area at the working internal pressure is calculated by calculating the surface area at the working internal pressure when the above-mentioned expansion test is repeated 10 times, and the difference between the maximum value and the minimum value of 15% or less is small. Variations of 25% or more were determined to be large.

Examples 3 and 4 First, rubber (EPDM) was pelletized with a rubber pelletizer. Next, the thermoplastic resin and the rubber were dry-blended at a ratio of 90/10, and charged from the first feeder of a twin-screw kneader set at 180 ° C. Paraffin oil was injected from the second feeder with a liquid injection pump at the composition shown in Table 1, and after sufficiently kneading the resin, rubber and oil, a vulcanizing system was introduced from the third feeder to vulcanize the rubber portion. . The material extruded from the twin-screw kneader was water-cooled and pelletized with a strand cutter. Thereafter, the material was formed into a sheet in the same manner as in Example 1 and subjected to the same evaluation.

The resins, rubbers and compounding agents used in each of the examples in Table 1 are as follows. SEPS-1: Hydrogenated product of SIS, Septon 2002, molecular weight 15,000, (manufactured by Kuraray) SEBS: Hydrogenated product of SBS, Tuftec K2181, molecular weight 50,000, (manufactured by Asahi Kasei) SEPS-2: SIS Hydrogenated product, septon 2023, molecular weight 80,000 (manufactured by Kuraray) SEPS-3: SIS hydrogenated product, septon 4033, molecular weight 100,000 (manufactured by Kuraray) ethylene-propylene copolymer: PER-R110E
Molecular weight 50,000 (manufactured by Tokuyama Corporation) EPDM: ethylene propylene diene rubber, Esplen 600F (manufactured by Sumitomo Chemical Co., Ltd.) Zinc flower: zinc flower No. 3 (manufactured by Seido Chemical Co., Ltd.) Stearic acid: Bead stearic acid (manufactured by NOF CORPORATION) Anti-aging agent: Nocrack 224 (manufactured by Ouchi Shinko Chemical Co., Ltd.) Brominated phenol resin: Tackilol 250-I (manufactured by Taoka Chemical Co., Ltd.) Paraffin oil: machine oil 22 (manufactured by Showa Shell Sekiyu KK)

The above results are shown in Table 1 below.

[Table 1]

[0028]

From the results shown in FIGS. 3 to 7 and Table 1, in the case of the expandable material of the present invention, a large expansion coefficient was obtained in the process of increasing the pressure, and the controllability of the internal pressure during expansion and the size of the expandable material. (Small variation in surface area at use internal pressure) is good. Particularly, in the case of the expandable material of the present invention (Example 4) composed of a thermoplastic elastomer composition, the elongation at break is extremely large, and the surface area at break is further large. Because the rate of increase is large,
It can be seen that this material can be used effectively for current SRS airbags.

[Brief description of the drawings]

FIG. 1 shows a tensile stress-elongation curve of a material having material properties used for the expansion material of the present invention.

FIG. 2 shows characteristic curves of an internal pressure and a surface area expansion rate of a product of the present invention and a comparative product.

FIG. 3 shows tensile stress-elongation curves of Examples 1 and 2 and Comparative Example 1.

FIG. 4 shows tensile stress-elongation curves of Examples 3 and 4.

5 shows an internal pressure-surface area increase rate curve of Comparative Example 1. FIG.

FIG. 6 shows an internal pressure-surface area increase rate curve of Examples 1 and 3.

FIG. 7 shows an internal pressure-surface area increase rate curve of Example 4.

FIG. 8 shows a test jig used for an expansion test.

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Claims (4)

[Claims] 1. A material having an elongation at break of 0% to 50%
An inflatable material composed of a material having a ratio of the average slope of the stress-elongation curve up to% to the average slope from 60% to 95% of 1: 5 or more. 2. The expandable material according to claim 1, wherein the material is a thermoplastic elastomer composition having at least a part of a vulcanized rubber as a dispersed phase and a thermoplastic resin as a continuous phase. 3. The expansion material according to claim 1, wherein the material is a hydrogenated styrene-based block polymer having a molecular weight of 50,000 or more. 4. The breaking elongation of a material at the time of a breaking test is 1000.
% Or more.