JPH0573139B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention is a heat treatment agent that has good resistance to road surface antifreeze agents based on metal halides such as calcium chloride and zinc chloride, and has excellent mechanical properties such as impact resistance and tensile strength. This invention relates to underhood parts for automobiles made of plastic resin. (Prior Art) In recent years, there has been a noticeable trend in the automobile industry to replace conventional metal parts with resin for the purpose of reducing weight to improve fuel efficiency, rust prevention, sound insulation, and the like. Among them, reinforced polyamide resins containing reinforcing agents such as glass fibers have excellent mechanical properties such as impact resistance, tensile strength, and flexural modulus, as well as good heat resistance, chemical resistance, abrasion resistance, and dimensional stability. By taking advantage of its characteristics, such as underhood parts of automobiles, such as cooling fans, radiator tank tops and bases, cylinder head covers, oil pans, gears, pulp, brake piping, fuel piping tubes, and other exhaust gas systems. Applications to various functional parts such as parts and electrical system parts such as connectors are attracting attention. (Problems to be Solved by the Invention) However, reinforced aliphatic polyamides with a relatively high concentration of amide groups, such as reinforced nylon 6 and reinforced nylon 66, which are commonly used among reinforced polyamide resins, cannot be used with inorganic metal salts. Because it inherently has a strong affinity for metals, it has the serious drawback that under harsh conditions, it will be attacked by metal salts such as calcium chloride, magnesium chloride, zinc chloride, etc., and cracks will occur in a short period of time. are doing. In general, large amounts of antifreeze agents containing calcium chloride, magnesium chloride, etc. are sprayed on roads in cold regions to prevent road surfaces from freezing, especially in winter. If it adheres to the underhood parts of a car, it will cause cracks in the parts, and there is a high risk of causing a car accident. Therefore, automotive underhood parts made of reinforced nylon 6, reinforced nylon 66, etc. have excellent toughness and heat resistance.
Although they are inexpensive, they do not have sufficient resistance to road antifreeze agents, which limits the expansion of their use. On the other hand, reinforced aliphatic polyamides with a low concentration of amide groups, such as reinforced nylon 11 and reinforced nylon 12, have excellent metal halide resistance and chemical resistance, so they can be used for special functional parts. However, it lacks the mechanical properties such as tensile density and flexural modulus as well as heat resistance as a metal substitute material, and the material price is high, so it can only be used in extremely limited applications. . (Means for solving the problem) From the above, it has metal halide resistance equivalent to or higher than reinforced nylon 11 or reinforced nylon 12, and equivalent or higher than reinforced nylon 6 or reinforced nylon 66. At present, there is a desire for the emergence of materials with mechanical properties. Therefore, the present inventors conducted studies aimed at obtaining a reinforced thermoplastic resin underhood part for automobiles that satisfies the required performance as described above, and as a result, they finally completed the present invention. That is, the present invention relates to (A) a polyamide that is nylon 6 and/or nylon 6,6, and (B) a hydrogenated product of a block copolymer consisting of a monovinyl aromatic compound polymer segment and a conjugated diene polymer segment, or a combination of this and butyl rubber. This is an underhood part for an automobile mainly comprising a composition containing a modified block copolymer obtained by modifying a blend with maleic anhydride in the presence of a radical generator. In the present invention, the polyamide that is nylon 6 and/or nylon 6,6 usually has a relative viscosity (measured in 98% sulfuric acid according to JIS K6810-1970).
It is preferably 1.8 or more, and more preferably 2.0 or more. In order to further improve chemical resistance, oil resistance, etc., the relative viscosity of the polyamide is 2.8 to 4.0, preferably 3.0 to 4.0, and the number of amino terminal groups is about 2.0 to 4.0 × 10 ^-5 equivalent/g, especially 2.2 to 3.7×10 ⁻⁵ equivalent/g is preferred. In the present invention, the copolymer blended into the polyamide is composed of a vinyl aromatic compound polymer block and an olefin compound polymer block,
It is a copolymer that has a functional group that binds or interacts with the thermoplastic resin, and optionally has a radically decomposable polymer as a graft portion. First, a vinyl aromatic compound polymer block and an olefin compound polymer are combined. A block copolymer composed of blocks can be obtained by hydrogenating a block copolymer composed of polymer blocks mainly composed of a vinyl aromatic compound polymer and a conjugated diene compound. Vinyl aromatic compounds constituting the block copolymer before hydrogenation include styrene, α-
Among methylstyrene, vinyltoluene, etc., styrene is particularly preferred. Further, as the conjugated diene compound, among butadiene, isoprene, 1,3-pentadiene, etc., butadiene and isoprene are particularly preferred. Further, in the hydrogenation of the conjugated diene compound, the degree of unsaturation is 20% or less, preferably 10% or less. The copolymerization ratio of the vinyl aromatic compound and the conjugated diene compound before hydrogenation is 5/95-60/40, especially 10/90.
A weight ratio of ~30/70 is preferred. Next, in the present invention, in order to improve fluidity during molding, a block/graft copolymer can be used in which the above-mentioned block copolymer is used as a backbone part and a radically decomposable polymer is used as a graft part. A collapsible polymer is a polymer that has the property that in the presence of radicals, the disintegration reaction (molecular scission) takes precedence over the recombination reaction and crosslinking reaction, resulting in lower molecular weight. Homopolymers such as isobutylene, polypropylene, polyα-methylstyrene, polymethacrylate, polymethacrylamide, polyvinylidene chloride, cellulose, cellulose derivatives, polytetrafluoroethylene, polytrifluorochloroethylene, or polyisobutylene and 1 to 3% isobutylene Examples include copolymers such as butyl rubber obtained by copolymerization with ethylene and propylene, and butyl rubber is preferred in the present invention. The mixing ratio of the block copolymer and the radically decomposable polymer is preferably 20:1 to 1:2. In the present invention, the block copolymer or block-graft copolymer is modified by bonding a molecular unit (hereinafter referred to as a modifier) containing a functional group that binds or interacts with the polyamide. Alternatively, the functional group may be substituted with a monomer such as styrene as a starting material for obtaining the copolymer. (hereinafter referred to as modified block copolymer or modified block/graft copolymer). Specifically, the modifier is a molecular unit containing a carboxylic acid group, a sulfonic acid group, an amino group, etc., or a derivative group thereof, and is modified by, for example, addition reaction with an unsaturated carboxylic acid or a derivative thereof. . Examples of unsaturated carboxylic acids or derivatives thereof include maleic acid, acrylic acid, methacrylic acid, α-ethyl acrylic acid, fumaric acid, itaconic acid, citraconic acid, crotonic acid, tetrahydrophthalic acid, methyltetrahydrophthalic acid, and cis-4- Unsaturated dicarboxylic acids such as cyclohexene-1,2-dicarboxylic acid, endo-cis-bicyclo[2.2.1]-5-heptene-2,3-dicarboxylic acid, their acid halides, amides, imides, acid anhydrides, Examples include derivatives such as esters. The modifier is blended in an amount of 0.02% by weight or more, preferably 0.1 to 2% by weight, based on the total amount of the block copolymer and radically decomposable polymer. In the present invention, the modified block/graft copolymer can be obtained by melt-kneading the block copolymer, the radically decomposable polymer, and the modifier, or by melt-kneading the mixture together with a radical generator. You can get it. In addition, examples of the radical generator include known organic peroxides, diazo compounds, etc. Specific examples include benzoyl peroxide, dicumyl peroxide,
Examples include di-t-butyl peroxide, t-butylcumyl peroxide, t-butyl hydroperoxide, cumene hydroperoxide, and azobiisobutyronitrile. The amount of radical generator used is 0.05% by weight based on the total amount of block copolymer and radically decomposable polymer.
Above, preferably 0.1 to 1.5% by weight. In the present invention, the polyamide (A) and the copolymer (B) preferably contain 5 to 95% by weight of (A) and 95 to 5% by weight of (B) based on the total composition. For example, when polyamide is used as (A), it is preferably 25% by weight or more, especially 40% by weight or more in order to obtain heat resistance, oil resistance, and gasoline resistance, and in order to obtain durability against metal halides ( B) The copolymer content is preferably 5% by weight or more. In the automotive underhood part of the present invention,
For parts that require strength, an inorganic reinforcing agent may be added in an amount of 5 to 200 parts by weight, preferably 20 to 100 parts by weight, based on the total of 100 parts by weight of (A) and (B). . Inorganic reinforcement materials include glass fiber, carbon fiber, alumina fiber, silicon carbide fiber,
Fibrous reinforcement materials such as boron fibers, zirconia fibers, asbestos fibers, potassium titanate whiskers,
Alternatively, filler-like reinforcing materials such as wollastenite, talc, mica, and quartz, or spherical glass can be used, but glass fibers, carbon fibers, etc. have particularly large reinforcing effects, so they are not suitable for use as reinforcing materials in the present invention. is the most suitable. These reinforcing materials may be left untreated or may be surface-treated with a silane coupling agent having good thermal stability, or two or more reinforcing materials may be used in combination. The method of mixing the reinforcing material is not particularly limited, and any commonly known method can be employed. For example, after uniformly mixing resin pellets, powder, pieces, etc. of (A) and (B) with the reinforcing material in a known mixer,
A suitable method is to melt-knead the mixture using an extruder with sufficient kneading capacity and then mold it. There is also a method of uniformly mixing pellets, powder, and pieces of both resins in a mixer, and then melting and kneading the pellets and reinforcing material in an extruder, and pellets, powder, and pieces of each resin. etc. and the reinforcing material are uniformly mixed in a mixer, and then separately melt-mixed in an extruder, the pellets are melt-kneaded directly into the material to be molded in the molding machine, and then molded. Methods such as direct mixing in the molding machine can be adopted without causing any oxidation. The underhood parts for automobiles of the present invention are molded by subjecting the above-mentioned compound to molding methods generally known for thermoplastic resins such as injection molding, extrusion molding, blow molding, and vacuum molding, but particularly injection molding,
Or cooling fans, radiator tanks, cylinder head covers, oil pans, gears, pulp, brake piping, etc. obtained by extrusion molding,
Useful items include fuel lines, other tubes, pipes, other exhaust gas system parts, electrical system parts such as connectors and switches, seats, housings, etc.
In addition, the molded parts obtained in this way are painted,
Secondary processing such as vapor deposition and adhesion can also be performed. In addition, the automotive underhood parts of the present invention may contain other ingredients, such as pigments, dyes, heat resistant agents, antioxidants, weathering agents, lubricants, crystal nucleating agents, electrostatic charges, as long as they do not impair its moldability or physical properties. Inhibitors, plasticizers, other polymers, etc. can be added and introduced. (Example) The present invention will be described in more detail with reference to Examples below. The physical properties of the test pieces described in Examples and Comparative Examples were measured in accordance with the following method. (1) Tensile test: ASTM D 638 (2) Bending test: ASTM D 790 (3) Izod impact test: ASTM D 250 (4) Metal halide resistance test: No. 3 dumbbell immersed in warm water at 90°C for 24 hours After that, the molded product was left in a gear oven at 100° C., and 50% calcium chloride solution was sprayed in the form of water droplets every hour as one cycle, and the number of cycles until cracks appeared in the molded product was measured. Reference Example 1 In order to obtain a copolymer as component (B), SEBS (Krayton G-1657: manufactured by Showa Shell Chemical Co., Ltd.) and butyl rubber (butyl
065: manufactured by Japan Synthetic Rubber Co., Ltd.), maleic anhydride, and dicumyl peroxide in the amounts shown in Table 1 and dry blended, using a 40 mmφ single screw extruder set at a cylinder temperature of 200 to 220 ° C. Copolymer () ~ () by melt-kneading reaction
I got it.

[Table] Examples 1 to 3, Comparative Examples 1 to 3 Copolymer obtained in Reference Example 1, nylon 6 shown in Table 2 (relative viscosity 2.53, 0.2% by weight of magnesium stearate added as a mold release agent) and inorganic materials Each reinforcing agent was blended and melt-kneaded using a 30 mmφ twin-screw extruder set at a cylinder temperature of 260°C for a residence time of 1 minute to form pellets. 80% of the resulting pellets
Polymer temperature after drying for 16 hours in a vacuum dryer at °C
ASTM test pieces were made at 280℃ and mold temperature 80℃. The characteristics obtained with these test pieces are also listed in Table 2.

【table】

[Table] In Table 2 *1: Glass fiber
*2: Clay
NB: No breakage As is clear from Table 2, the compositions used in the present invention (Examples 1 to 10) have excellent Izot impact strength and calcium chloride resistance.
When only nylon 6 (Comparative Examples 2 and 3) or a copolymer not modified with maleic anhydride was used (Comparative Examples 1 and 4 to 6), the Izot impact strength was 8.3.
It can be seen that the resistance to calcium chloride is very low, below 3 kg/cm/cm, and the resistance to calcium chloride is below 3 times. Furthermore, the underhood parts for automobiles of the present invention are
Although the molded products were treated in hot water at 100°C for 500 hours, there were no abnormalities on the surface or inner layer of the molded products, and they had good hot water resistance. (Effects of the Invention) The underhood parts for automobiles of the present invention having the above-mentioned structure have the characteristics of excellent heat resistance, oil resistance, moldability, etc. possessed by original thermoplastic resins, and also have excellent properties at room and low temperatures. It has excellent impact strength and metal salt resistance, and is particularly resistant to the adhesion of anti-freeze agents containing calcium chloride, magnesium chloride, etc. to prevent road surfaces from freezing in winter, and the impact caused by small stones while driving. As an underhood part for automobiles that requires
The present invention satisfies these requirements as a component that can withstand a wide range of temperature conditions, from -40°C to about 150°C on the high temperature side.

Claims (1)

[Claims] 1 (A) Nylon 6 and/or nylon 6,6
Polyamide and (B) a hydrogenated block copolymer consisting of a monovinyl aromatic compound polymer segment and a conjugated diene polymer segment, or a blend of this and butyl rubber, were modified with maleic anhydride in the presence of a radical generator. An underhood part for an automobile mainly comprising a composition containing a modified block copolymer obtained by