JP2005082693A - Molded component for sheet belt excellent in heat resistance and sliding property - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for inexpensively producing a molded component for sheet belts having a sliding property and heat resistance, having extremely excellent heat resistance and sliding property while retaining excellent strength, impact resistance and chemical resistance of the polyamide-based resin molded component, not polluting the surface of the molded article with an oil, etc., not changing a frictional coefficient even when long-term repeated sliding is carried out. <P>SOLUTION: The polyamide molded component for sheet belts excellent in a sliding property and heat resistance is composed of a polyamide-based resin composition composed of a polyamide-based resin and containing a silicone compound. The dynamic elastic modulus E' of the polyamide molded component at 280°C by dynamic viscoelasticity measurement is ≥0.1 MPa. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention retains the excellent strength, impact resistance and chemical resistance of polyamide-based molded parts, has excellent sliding properties and heat resistance, and the coefficient of friction varies even after repeated sliding over a long period of time. The present invention relates to a molded part for seat belt made of a polyamide-based molded part having excellent slidability and heat resistance.

Usually, an automobile seat belt is made of a polyester fabric belt, a polyamide-based molded part in which a metal fitting for adjusting the length of the belt is inserted, and an anchor metal fitting that connects the body and the seat belt. With these seat belt parts, polyamide molded parts with metal fittings that adjust the length of the belt are inserted between the seat belt and this polyamide molded part for a "more natural fit" and "safety". The slipperiness is very important. That is, it is necessary to always keep good sliding characteristics between the polyester fabric of the seat belt and the polyamide-based molded part.
In general, the polyamide resin often used in the molded parts for seat belts is a crystalline resin, so that it is a resin having good slidability. However, the slidability between the polyester fabric used for the seat belt and the polyamide resin is not always sufficient, and improvement is required.

Polyamide resin has excellent slidability due to its crystallinity, but many studies have been made for a long time to obtain even better sliding properties. Solid lubricants such as molybdenum disulfide, graphite, and fluororesin Liquid lubricants such as various lubricating oils and silicone oils are being studied as major sliding improvers.
Plastic course [16] "Polyamide resin", Nikkan Kogyo Shimbun (1970)

  Of these sliding improvers, solid lubricants need to be blended with a large amount of solid lubricants in order to further improve the sliding properties of resins having inherently excellent sliding properties such as polyamide resins. When a large amount of solid lubricant is blended, the toughness of the polyamide resin is remarkably lowered, and not only the evaluation standard of molded parts for automobiles such as heat cycle cannot be cleared, but also a large amount of expensive solid lubricant is blended, which is economically undesirable.

  On the other hand, liquid lubricants can impart highly effective slidability to resins such as engineering plastics in a relatively small amount, but in many cases, the compatibility with the base resin is poor, and the surface of the molded part is the liquid lubricant. In many cases, the resin products whose sliding properties have been improved with these liquid lubricants have limited applications. In particular, it is not preferable that the surface of the molded part is contaminated with oil or the like in an application in contact with a person. For example, the solitary parameter (SP value) of nylon 66 resin is 12.7, and the SP value of silicone oil generally used as a liquid lubricant is 7.3. Thus, if the SP values of the two are greatly different, the compatibility is very poor, and the silicone-based molded part is often contaminated by silicone oil, which is not preferable.

In addition, an abnormally high load is applied to the seat belt in an accident such as a sudden brake or a collision during the operation of the automobile, and when sliding at such a high load, heat generation on the sliding surface is large, up to nearly 200 to 300 ° C. The temperature rises and the seat belt component, which is a safety device, may be damaged. In such high temperature sliding due to heat generation, studies have been made to improve the limit PV value by adding glass fiber or carbon fiber to polyamide resin.
However, there is a limit to increasing the heat resistance during sliding by adding glass fiber or carbon fiber. When the heat generated during sliding approaches the melting point of the polyamide resin, the coefficient of friction suddenly increases and the sliding performance deteriorates. And the material melts locally.
Toray technical data "Torayca pellet" (improvement of limit PV value by adding carbon fiber)

  The present invention has been made against the background of the problems of the prior art, and has excellent heat resistance and slidability while maintaining the excellent strength, impact resistance and chemical resistance of polyamide-based molded parts, and To produce molded parts for seat belts made of polyamide-based molded parts that have slidability and heat resistance that do not change the coefficient of friction even if the surface of the molded parts is not contaminated with oil, etc. Is an issue.

  As a result of intensive studies to solve the above problems, the present inventors have completed the present invention. That is, the present invention is (1) a molded part for a seat belt mainly composed of a polyamide-based resin and comprising a resin composition containing a silicone compound, and an elastic modulus at 280 ° C. by dynamic viscoelasticity measurement of the molded part. Is a molded part for a seat belt excellent in slidability and heat resistance, characterized by being 0.1 MPa or more. One of the preferred embodiments is (2) a molded component for a seat belt of a polyamide resin composition mainly composed of a polyamide resin having a melting point of 280 ° C. or less and containing a silicone compound, and the molded component is irradiated with an electron beam. By doing so, at least the surface layer portion of the molded part is crosslinked, and the elastic modulus at 280 ° C. by dynamic viscoelasticity measurement is 0.1 MPa or more. In a particularly preferred embodiment, (3) the molded part for seat belt according to (1) and (2) above, wherein (3) the silicone compound is a silicone compound in which polyoxyalkylene is introduced into the side chain or terminal The seat belt molded part according to the above (1) and (2), which is a silicone compound having a polyoxyalkylene introduced into the side chain or terminal and having an OH group at the terminal of the polyoxyalkylene. 5) The molded part for seat belts according to (1) and (2), wherein the silicone compound is a silicone graft thermoplastic resin in which a silicone structure is introduced into the thermoplastic resin by 30% by weight or more by graft polymerization; ) Silicone compounds with functional groups that allow silicone compounds to react with polyamide resins Which is the (1) described and the (2) a seat belt for molded part described is.

  The molded parts for seat belts with high heat resistance and excellent slidability according to the present invention provide a very stable friction coefficient when repeatedly sliding, and there is no melting of the molded part even when sliding at high loads, and the stable friction coefficient Is obtained. In addition, because the excellent toughness of polyamide resins is not impaired without contamination with oil, etc., it can be used for molded parts for automobile seat belts (parts such as sash guides and shoulder adjusters), contributing to the industry. It is great to do.

Hereinafter, the present invention will be described in detail.
The polyamide-based resin in the present invention has an acid amide bond (—CONH—) in the molecule, and specifically includes ε-caprolactam, 6-aminocaproic acid, ω-enantolactam, 7-aminoheptanoic acid, Polymers or copolymers or blends obtained from 11-aminoundecanoic acid, 9-aminononanoic acid, α-pyrrolidone, α-piperidone, etc., hexamethylene diamine, nonamethylene diamine, undecamethylene diamine, dodecamethylene diamine, meta Examples include polymers or copolymers or blends obtained by polycondensation of diamines such as xylylenediamine and dicarboxylic acids such as terephthalic acid, isophthalic acid, adipic acid, and sebacic acid. It is not limited.
In order to obtain a molded part having excellent slidability, the polyamide resin is preferably a crystalline polyamide resin having a melting point. Moreover, it is preferable that melting | fusing point (melting peak temperature calculated | required based on JISK7121) of the polyamide-type resin in this invention is 280 degrees C or less. When the melting point exceeds 280 ° C., it is necessary to mold at an extremely high temperature, and a special molding machine is required. Further, the resin itself is not preferable because it is expensive. The lower limit of the melting point is not particularly limited as long as the elastic modulus at 280 ° C. measured by dynamic viscoelasticity measurement of the molded part is 0.1 MPa or more. Since processing requires a long time, 100 or more is preferable. In this respect, a polyamide-based resin having nylon 6, nylon 66, and nylon MXD6 as main constituent components is particularly preferable.
In the present invention, the polyamide resin preferably has a number average molecular weight of 7,000 to 30,000. A number average molecular weight of 7,000 or less is not preferable because the toughness is lowered. Moreover, if it is 30000 or more, fluidity | liquidity falls and it is not preferable.

  In the present invention, reinforcing polyamides can be blended with the polyamide-based resin. Reinforcing inorganic materials include fiber reinforcing materials such as glass fibers, carbon fibers, ceramic fibers and various whiskers, and powdery inorganic reinforcing materials such as silica, alumina, talc, kaolin, quartz, powdered glass, mica, and graphite. Can be mentioned. These reinforcing inorganic materials may be treated with a silane coupling agent as a surface treatment agent.

Examples of the various silicone compounds contained in the polyamide resin composition in the present invention include the following (1) to (4).
(1) A silicone compound having polyoxyalkylene introduced in the side chain or terminal. Specific examples include silicone compounds represented by the chemical formulas shown below.

(2) A silicone compound having a polyoxyalkylene introduced into the side chain or terminal and having an OH group (also referred to as a hydroxy group) at the terminal of the polyoxyalkylene. Specific examples include silicone compounds in which the alkyl group R ₂ in the chemical formulas [Chemical Formula 1] and [Chemical Formula 2] has an OH group.

  (3) A silicone graft thermoplastic resin in which a silicone structure is introduced into the thermoplastic resin by graft polymerization in an amount of 30% by weight or more. Specifically, it can be obtained by graft polymerization of a reactive polyorganosiloxane onto a thermoplastic resin. As the thermoplastic resin, various polyethylene resins, ethylene / olefin resins and the like are preferable, but the thermoplastic resin is not limited thereto.

  (4) A silicone compound having a functional group that reacts with a polyamide resin. Specifically, it is a silicone compound in which a part of the methyl group of polyorganosiloxane is substituted with a functional group such as an amino group, a hydroxyl group, a carboxyl group, an acid anhydride group or an epoxy group that reacts with the polyamide resin. The group is not limited to this.

  The compounding quantity of these silicone compounds is 0.1-10 weight part as a silicone compound single-piece | unit with respect to 100 weight part of polyamide-type resin compositions, Preferably it is 0.2-8 weight part.

  In the present invention, a compatibilizing agent may be added in order to improve the compatibility between the thermoplastic resin grafted with the silicone compound and the polyamide resin. When the thermoplastic resin is a polyethylene resin, it is preferable to add a maleic acid-modified polyethylene resin.

  The seat belt molded part comprising the polyamide resin composition of the present invention is composed of a polyamide resin composition having a high melting point of 280 ° C. or higher, or a polyamide resin composition having a melting point of 280 ° C. or lower. The seat belt molded part is obtained by crosslinking at least the surface layer portion of the seat belt molded part by electron beam irradiation.

  In the case of a molded part for a seat belt made of a polyamide resin composition having a melting point of 280 ° C. or lower, it is necessary to crosslink at least the surface layer part of the molded part by irradiating an electron beam. In order to promote the crosslinking of the molded part during electron beam irradiation, a crosslinking aid can be blended in the polyamide resin composition. Specific examples of crosslinking aids include triallyl cyanurate (TAC), triallyl isocyanurate (TAIC), trimethylallyl isocyanurate (TMAIC), trimethylolpropane trimethacrylate (TMPTA), trishydroxyethyl. Although polyfunctional compounds, such as isocyanuric acrylate (THEICA) and N, N'-m-phenylene bismaleimide (MPBM), can be illustrated, it is not limited to these. These crosslinking assistants can be used alone or in combination of two or more. The amount of the crosslinking aid is 0.01 to 10 parts by weight, preferably 0.03 to 5 parts by weight, based on 100 parts by weight of the polyamide-based composition. If it is 0.01 parts by weight or less, the crosslinking does not proceed and the crosslinking degree is lowered. On the other hand, if it is 10 parts by weight or more, not only the efficiency as a crosslinking aid is deteriorated, but also the physical properties of the polyamide-based resin are lowered, which is not preferable.

  A heat stabilizer can be blended in the polyamide resin composition of the present invention. The heat stabilizer is blended mainly for the purpose of preventing thermal deterioration of a compound having relatively poor thermal stability, such as a crosslinking aid, when kneading a polyamide resin, a crosslinking aid and other compounding agents. The hindered phenol-based heat stabilizer is not particularly limited.

  Specifically, 2,6-di-t-butyl-4-methylphenol (BHT), tetrakis- [methylene-3- (3 ′, 5′-di-t-butyl-4-hydroxyphenyl) propionate] Methane (manufactured by Ciba Geigy, Irganox (R) 1010), triethylene glycol-bis- [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionate] (manufactured by Ciba Geigy, Irganox (R) ) 245) and the like can be exemplified, but not limited thereto. These heat stabilizers can be used alone or in combination of two or more. The blending amount of the heat stabilizer is 0.05 to 5 parts by weight, preferably 0.1 to 3 parts by weight with respect to 100 parts by weight of the polyamide-based composition. If it is 0.05 parts by weight or less, there is no effect as a heat stabilizer, and if it is 5 parts by weight or more, the efficiency as a heat stabilizer is poor and it is not economical.

  The composition constituting the molded part for seat belt of the present invention is used for ordinary polyamide resin compositions in addition to other thermoplastic resins, crosslinking aids for promoting electron beam crosslinking and thermal stabilizers. Add carbon black and copper oxide and / or alkali metal halide as weather resistance improver, phenolic antioxidant, phosphorus compound, flame retardant, antistatic agent, pigment, dye, etc. as light or heat stabilizer Also good.

  As a method for producing a polyamide-based resin composition having excellent heat resistance and slidability in the present invention and constituting the seat belt molded part, a polyamide compound is added to the polyamide resin and, if necessary, reinforcing inorganics and a crosslinking aid, It can be obtained by melt-kneading a polyamide-based resin composition containing additives such as a heat stabilizer. As the melting and kneading apparatus, there are a single screw extruder, a twin screw extruder, a pressure kneader and the like, and a twin screw extruder is particularly preferable.

  The dose of the electron beam irradiation for obtaining the seat belt molded part of the present invention by cross-linking varies depending on the type of the polyamide resin composition and the shape of the seat belt molded part, but is generally 30 to 400 kGy. The minimum dose at which a seat belt molded part is obtained is preferred.

  A molded part for seat belt made of the polyamide resin composition of the present invention has a dynamic elastic modulus E ′ at 280 ° C. of 0.1 MPa by a dynamic viscoelasticity measuring device regardless of whether the molded part for seat belt is crosslinked or not. Above, preferably 1 MPa or more. When the elastic modulus at 280 ° C. of the molded part for seat belt is 0.1 MPa or less, the friction coefficient increases remarkably when the temperature of the sliding surface approaches 280 ° C. due to sliding heat generation or other causes, and heat generation due to sliding occurs. Is further accelerated, and the temperature on the sliding surface is rapidly increased to melt the seat belt molded part.

  In general, the cross-linking by electron beam irradiation is most advanced in the surface layer portion of the molded part directly hit by the electron beam, and the degree of cross-linking gradually decreases in the inner layer portion and the back surface. For this reason, in the molded part for seat belt, it is necessary to irradiate the sliding part with an electron beam to crosslink, or to irradiate a dose necessary to sufficiently crosslink the entire molded part for seat belt.

  The present invention retains the excellent strength, impact resistance and chemical resistance of polyamide-based molded parts, has excellent sliding characteristics at high temperatures, and the surface of molded parts for seat belts is not contaminated with oil or the like. Thus, a molded part for a seat belt made of polyamide resin whose coefficient of friction does not fluctuate even after repeated sliding over a long period of time can be obtained.

EXAMPLES Next, although this invention is demonstrated concretely using an Example and a comparative example, this invention is not limited to these.
(Evaluation methods)
1. Melting point The polyamide resin sample was subjected to DSC measurement under the following conditions, and the melting point (melting peak temperature Tpm) was determined according to JIS K7121.
Device name: MacScience DSC3100
Bread: Aluminum bread (non-hermetic)
Sample weight: 4 mm
Measurement start temperature: 30 ° C
Temperature increase rate: 20 ° C./min.
Atmosphere: Argon

2. Tensile strength and tensile elongation Tensile strength and tensile elongation are measured according to ASTM D638.
3. Izod impact strength Izod impact strength is measured according to ASTM D256.

4). Coefficient of friction Evaluation of the coefficient of friction by repeated sliding was performed under the following conditions using the apparatus of FIG.
Evaluation sample: 2 mm flat plate Mating material: Delrin (R) 100 manufactured by DuPont
Opposite material shape: 1/2 inch spherical molded product Total load: 500 gf
Sliding distance: 40mm repetition 1000 times reciprocating speed: 30cm / min
Measurement temperature: room temperature (25 ° C., 65% RH)
The coefficient of friction was evaluated by the average value of the coefficient of friction every 100 times in 1000 reciprocating slides.

5). Heat resistance Evaluation of heat resistance is done by placing an evaluation sample with a thickness of 3 mm on a hot plate at 280 ° C, placing a load of 630 gf from the top, taking out the sample after 1 minute, observing the molten state of the contact surface, and the appearance of melting Was evaluated in the following four stages.
◎: No surface melting, no change in surface state ○: Very little surface melting, almost no change in surface state ×: There is surface melting, large change in surface state XX: There is considerable surface melting, and the change in surface state is severe

6). Dynamic Viscoelasticity Measurement of dynamic viscoelasticity E 'is a test of cutting a test piece of width 4.0mm and thickness 0.5mm from a 2mm thick flat plate product with "Rheogel-E4000" manufactured by Toyo Sangyo Co., Ltd. A piece was used and measured under the following test conditions. FIG. 2 shows a graph of (temperature) versus (dynamic viscoelastic modulus E ′) as a measurement example.
Frequency: 1Hz
Temperature rising rate: 3 ° C./min.
Temperature range; 30 ° C to 300 ° C

(Examples 1-3, Comparative Examples 1-3)
<Raw materials used>
NY6 (Toyobo Nylon T-850, Toyobo Nylon T-850) and NY66 (Asahi Kasei Co., Ltd., Leona 1700) are used as polyamide resins, and master pellets are thermoplastic resins in which a silicone structure is graft-polymerized as a silicone compound. SP-350 (resin is LDPE, manufactured by Multibase Asia Co., Ltd.), ether-modified silicone that is a silicone compound having a polyoxyalkylene structure introduced in the side chain or terminal (manufactured by Dow Corning Asia Co., Ltd., Paintad (R)) 54), a maleic acid-modified polyethylene resin (manufactured by Sumitomo Mitsui Polyolefin Co., Ltd., MME001) as a compatibilizer, triallyl isocyanurate (manufactured by Nippon Kasei Co., Ltd., also referred to as TAIC) as a crosslinking aid, and a heat stabilizer Hindered phenol heat stabilizer (Ciba Geigy Co., Ltd.) was used Irganox (R) B1171).

<Manufacture of evaluation samples>
In the production of the evaluation sample, each raw material was weighed at a ratio shown in Table 1 and Table 2, mixed with a tumbler, kneaded at a temperature of 270 to 290 ° C. with a twin screw extruder, pelletized, and then injected with an injection molding machine. Evaluation samples of thickness 2 mm, 3 mm and ASTM dumbbell were molded. The cylinder temperature of the injection molding machine was 270 to 310 ° C, and the mold temperature was 60 to 120 ° C. About the evaluation sample with electron beam irradiation, the injection-molded molded article was irradiated on the following electron beam irradiation conditions.

<Electron beam irradiation conditions>
Electron beam irradiation device: Dynamitron type 5 MeV electron accelerator manufactured by RDI Irradiation conditions: Voltage = 4.6 MeV, current = 20 mA
Irradiation dose: 60 kGy
The results are shown in Table 1.

  Comparative Example 1 has a relatively high coefficient of friction at room temperature and no heat resistance. In Comparative Example 2, the coefficient of friction is significantly high. In Comparative Examples 3 and 4, the friction coefficient at normal temperature is good due to the blending of the specific silicone compound. However, at a high temperature of 280 ° C., the molded part does not melt and retain its shape as indicated by the dynamic elastic modulus E ′ of 280 ° C., so when used at a high temperature, it is not used as a sliding part. On the other hand, in Examples 1 and 3, the coefficient of friction at room temperature is also excellent, and the dynamic elastic modulus E ′ at 280 ° C. becomes 2.2 to 2.3 MPa due to cross-linking of the surface layer part of the molded part by electron beam irradiation. However, since it does not lose its shape by flowing due to melting, it can be used as a sliding component for seat belts with high heat resistance. In addition, a stable friction coefficient can be obtained even after 1000 times of sliding, and there is no contamination of the molded part surface with oil or the like. Example 2 uses nylon 66, while examples 1 and 3 use nylon 6, but can be used as a sliding part having high heat resistance as in example 1. In Example 4, the molded part was not cross-linked by electron beam irradiation. However, since the molded part had a high melting point of 296 ° C., the dynamic elastic modulus E ′ at 280 ° C. was high and the slidability at high temperature was excellent.

  When the seat belt molded part having excellent heat resistance and slidability according to the present invention slides repeatedly, a very stable coefficient of friction is obtained and the molded part is not contaminated. In addition, even if a heavy load is applied to the seat belt due to sudden braking or collision during driving, stable slidability can be obtained, making it ideal for sash guides, shoulder adjustments, and buckles for molded parts for seat belts. It is important to contribute to the industry.

Schematic diagram of a friction coefficient evaluation device by repeated sliding Example of measurement result of dynamic elastic modulus E '

Explanation of symbols

1. Load 2. Sliding material 3: Evaluation target material

Claims (5)

  A molded part for a seat belt mainly composed of a polyamide-based resin and a resin composition containing a silicone compound, and the dynamic elastic modulus E ′ at 280 ° C. of the molded part measured by dynamic viscoelasticity is 0.00. A molded part for a seat belt excellent in slidability and heat resistance, characterized by being 1 MPa or more.   2. The molded part for seat belt according to claim 1, wherein the polyamide-based resin is a polyamide-based resin having a melting point of 280 [deg.] C. or less, and at least a surface layer portion is crosslinked by irradiating the molded part with an electron beam.   The molded component for a seat belt according to any one of claims 1 and 2, wherein the silicone compound is a silicone compound in which polyoxyalkylene is introduced into a side chain or a terminal.   The sheet according to any one of claims 1 and 2, wherein the silicone compound is a silicone compound having a polyoxyalkylene introduced into a side chain or a terminal, and a silicone compound having an OH group at the terminal of the polyoxyalkylene. Molded parts for belts.   The molded part for seat belts according to any one of claims 1 and 2, wherein the silicone compound is a silicone graft thermoplastic resin in which a silicone structure is introduced into the thermoplastic resin by a graft polymerization of 30% by weight or more.

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