WO1999028388A1

WO1999028388A1 - Compositions of polyphenylene ether resin and syndiotactic polystyrene

Info

Publication number: WO1999028388A1
Application number: PCT/JP1998/005347
Authority: WO
Inventors: Takashi Ohtomo; Hiroshi Morokuma
Original assignee: Ge Plastics Japan Limited
Priority date: 1997-11-27
Filing date: 1998-11-27
Publication date: 1999-06-10
Also published as: JP4364319B2; AU1261499A; JPH11158366A; TW432095B

Abstract

The present invention provides a resin composition containing (A) a polyphenylene ether resin and (B) a syndiotactic styrene polymer, characterized in that (1) the composition also contains (C) a high-impact styrene resin; and (2) the composition contains (C) in the amount of 90-10 parts by weight with respect to 10-90 parts by weight of (A) and (B) in the amount of 5 to 60 parts by weight with respect to a total of 40 to 95 parts by weight of (A) and (C).

Description

DESCRIPTION

COMPOSITIONS OF POLYPHENYLENE ETHER RESIN AND SYNDIOTACTIC POLYSTYRENE

FIELD OF THE INVENTION

The present invention concerns a resin composition containing a polyphenylene ether (abbreviated in the following as PPE) resin, and more specifically, it concerns a resin composition of the aforementioned type which is highly useful in plastic applications requiring chemical resistance in the field of industrial and household materials such as automotive components, electrical and electronic components, household materials for the kitchen, bathroom, and construction, and lavatory products.

PRIOR ART

As non-crystalline (amorphous) resins show outstanding dimensional accuracy in injection molding due to their amorphous structural properties, their properties are taken advantage of in widespread use in large-scale molded products and industrial fields requiring precision assembly, etc . However, because of their amorphous structure, they are permeable to organic chemicals, i.e., they showpoor chemical resistance, and they therefore have the drawback of being easily attacked by substances such as oils and organic solvents. On the other hand, due to their crystalline properties, crystalline resins show highly outstanding chemical resistance and are therefore used in applications involving contact with oils, organic solvents, etc . , but when crystallization proceeds during the molding cooling process, the phenomenon of molding shrinkage occurs, resulting in poor dimensional stability and making these resins unsuitable for large-scale molded products. In order to remedy this, attempts have been made to add inorganic fillers such as glass fibers, but this causes an increase in specific gravity and a decrease in ductile impact strength, as well as discrepancies in the degree of shrinkage in the direction of injection molding flow and perpendicular to this direction, resulting in the defects of warping and deformation. Polyphenylene ether resin is a typical non-crystalline thermoplastic resin having an elevated softening point . It has balanced mechanical properties and outstanding electrical properties, its water absorption is low, and it shows favorable dimensional stability. In addition, polyphenylene ether resin shows extremely favorable compatibility with polystyrene resin, another non-crystalline thermoplastic resin, and it can easily be deformed. As resin compositions composed of PPE resin and styrene resin (referred to in the following as a PPE/PS resin composition) show outstanding molding workability and impact resistance (US Patent No. 3,383,435) , they have conventionally been widely used in applications such as automotive conponents and electrical and electronic conponents. However, this type of PPE/PS resin composition is an amorphous resin, and as mentioned above, it does not show sufficient chemical resistance, particularly resistance to aromatic hydrocarbon solvents. For example, when the solvent comes into contact with sites subjected to strain or molding residual strain, crazing and cracks may develop from these sites, resulting in failure of the component. For this reason, use of these compositions in such applications has been limited. For example, their use is avoided in external automotive components, engine room components, and cabin interiors of ships, to which waxes, machine oils/engine oils, rust-preventing agents, aromatic agents, etc., may adhere; components for office equipment, computer-related equipment, etc., to whic lubricating oils for sliding, grease, or cleaners may adhere (such as internal parts, fan motor cases, and plastic chassis) ; home electronic and commercial electrochemical product components, to which salad oil, tempura oil, or other organic solvents may adhere; and components of electrical and electronic equipment used in environments exposed to oil and smoke or organic gases (such as factory environments and construction environments) . This is considered to be a fundamental drawback derived from the fact that polyphenylene ether resin is non-crystalline.

There have been many attempts in the past to remedy this defect, but no one has as yet been successful in developing a technology for iπproving chemical resistance without impairing the properties of PPE/PS resin compositions . Examples from prior art include the methods of mixing the PPE/PS resin composition with crystalline resins such as polyolefins (e.g., polyethylene, polypropylene, EEA) , polyester, nylon, etc.; low-molecular-weight olefins (such as polybutene and ethylene oligomer) ; or rubber-like polymers (such as SEBS, SBS, or SEPS rubber) . In these technologies, however, although addition of small amounts does improve chemical resistance somewhat, when the amount added is increased in order to increase chemical resistance to the level required for practical use, this not only causes a reduction in the outstanding mechanical strength, thermal resistance, and flame resistance properties of conventional PPE/PS resin compositions, it causes the phenomenon of laminar peeling during injection molding due to insufficient compatibility and impairs dimensional accuracy during molding.

In recent years, moreover, there have been numerous attempts involving the technology of alloying a crystalline resin with a non-crystalline thermoplastic resin, with a commercial example being the method of producing an alloy of polyphenylene ether resin and nylon resin during extrusion using a compatibilizer. In this method, the polyphenylene ether resin is finely mechanically dispersed in the nylon matrix, with this dispersion status controlled by means of the compatibilizer. The resulting product is referred to as a non- compatible alloy. Specifically, by covering the polyphenylene ether resin with a nylon matrix, the chemical permeability of the polyphenylene ether resin is dihibited, and its chemical resistance is improved. Looking at this from the nylon side, by dispersing the polyphenylene ether resin in the nylon, the poor dimensional stability resulting from shrinkage of the nylon during molding is improved, with this improvement increasing as an increasing amount of polyphenylene ether resin is mixed in. In this technology, however, the effect of improving dimensional stability resulting from the ciystallinity of the nylon is insufficient.

In light of the above, a new technology allowing full coπpatibilization with polyphenylene ether resin and improved chemical resistance has been eagerly awaited. Along with ground-breaking technological developments in recent years, crystalline styrene polymers having a syndiotactic stereostrueture (referred to in the following as syndiotactic styrene polymers) have been developed and manufactured commercially (Japanese Unexamined Patent Application No. S62-10481) . As a natural result, there have been attempts to blend such syndiotactic styrene polymers with various resins. There are known blended compositions of polyphenylene ether resins and syndiotactic styrene polymer which, because syndiotactic styrene resin is crystalline and has a styrene skeleton as the main component of its molecular structure, are expected to show favorable compatibility with polyphenylene ether resin in the same manner as conventional atactic styrene polymers. Examples are presented in publications such as Japanese Unexamined Patent Applications Hl-182344, Hl-82350, H2-64140, H2-92948, H2-218724, H3-126743, H5-86296, H5-209098, H5-279530, H6-93151, H6-93153, H7-53815, H7-62175, H7-138433, H7-292184, H7-331003, H8-143699, H8-311196, H9-52958, and H9-52959. Among the above publications, however, many of the compositions are simple alloys of syndiotactic styrene polymers and polyphenylene ether resins, and there are few concrete examples which clearly show an improvement in chemical resistance and a synergistic effect of the composition. The only publications in which an improvement in chemical resistance is described are H2-64140,

H2-92948, H9-52958, and H9-52959. In these publications, one siirply adds a syndiotactic styrene polymer and an addition-type rubber-like elastic body to polyphenylene ether resin and attempts to increase chemical resistance by increasing the crystalline component, but as the problem of maintaining the dimensional accuracywhich is characteristic of amorphous polyphenylene ether resin is not taken into consideration, these compositions are ill-suited for practical application. Furthermore, in all of these cases, chemical resistance is evaluated by the solvent immersion method, inwhich a molded test piece is immersed in a solvent and its external appearance is visually evaluated after a specified period of time, which is not an outstanding method from the standpoint of quantitative determination. As we have mentioned above, however, from the standpoint of the environment of use of polyphenylene ether resin, there are no applications in which the resin is constantly immersed in or in contact with a solvent . Due to the fact that conponents such as peripheral automotive engine parts and peripheral driving components of electrical and electronic devices are subject to adhesion of solvents, oils, etc . , during use for several reasons, with fastening conponents, which are subjected to tightening strain, being particularly vulnerable to the problem of breakage, there are limitations on the use of these compositions in such applications, and in view of this fact, there is a demand for a polyphenylene ether resin which shows outstanding chemical resistance at sites subject to strain, i.e., does not develop crazing or cracks .

BRIEF DESCRIPTION OF THE INVENTION The purpose of the present invention is to provide a PPE resin composition which has the chemical resistance required for practical applications while maintaining the high dimensional accuracy and other outstanding properties characteristic of polyphenylene ether resin.

The authors of the present invention studied the problem of how to inhibit crazing and cracking of polyphenylene ether resin at the aforementioned sites subjected to strain. The test method they used was to investigate chemical resistance by applying a solvent to a molded product subjected to forced strain of 1% or more (a molded test piece was fixed in place on a die subjected to forced strain, the portion under strain was covered with a piece of gauze, etc., soaked in a solvent, and the extent of attack due to the solvent was evaluated) , while simultaneously observing the polyphenylene ether resin from the twin standpoints of mechanical properties and stable dimensional accuracy. Surprisingly, they found that when a conventional crystalline polymer (syndiotactic styrene polymer) was added to a polyphenylene ether resin, it was not true that the effect of improving chemical resistance became greater as an increasing amount was added. Within a particular specified range, however, and when the combination included a high- impact styrene, an effect of improving chemical resistance was obtained while retaining the inherent properties of polyphenylene ether resin of outstanding dimensional accuracy and mechanical strength. In this manner, they arrived at the present invention.

The present invention provides a resin composition containing (A) a polyphenylene ether resin and (B) a syndiotactic styrene polymer, characterized in that

(1) the composition also contains (C) a high-impact styrene resin; and

(2) the composition contains (C) in the amount of 90-10 parts by weight with respect to 10-90 parts byweight of (A) and (B) in the amount of 5 to 60 parts by weight with respect to a total of 40 to 95 parts by weight of (A) and (C) . Conventionally, high-ijτpact styrene resin has been blended in order to improve impact resistance, but when this styrene resin alone is added to polyphenylene ether resin, it has not had the effect of improving the chemical resistance of the polyphenylene ether resin. Surprisingly, when high-impact styrene resin is blended into a system containing a syndiotactic styrene polymer and a polyphenylene ether resin, chemical resistance is further improved. Moreover, the fact that syndiotactic styrene polymers cause a decrease in dimensional accuracy in systems in which the above range is exceeded and the fact that opacity and a decrease in physical properties of the composition occur due to excessive crystallinity were also not predicted based on prior art. Specifically, it was discovered that only when a syndiotactic styrene polymer is blended with a polyphenylene ether in amounts exceeding the above range and a high-impact styrene resin is also blended into the composition is it possible to obtain a composition having both high dimensional accuracy and outstanding chemical resistance.

DESCRIPTION OF THE DRAWINGS

Fig. 1

Forced 1.5% bending strain die used in chemical resistance testing.

Fig. 2 Flat plate test piece measuring 100 mm x 100 mm x 3 mm used in measurement of molding shrinkage.

Explanation of Symbols a. Molding shrinkage flow direction b. Perpendicular to molding shrinkage flow direction 1. Gauze

2. Solvent

3. Specimen 4. Bent portion

5. Gate

DETAILED DESCRIPTION OF THE INVENTION

The (A) polyphenylene ether resin used in the resin composition of the present invention is known in and of itself, with this being a general term for a polymer having General Formula (I) below:

In the formula, R¹, R², R³, and R⁴ are independent hydrogen atoms, halogen atoms, hydrocarbon groups, substituted hydrocarbon groups, alkoxy groups, cyano groups, phenoxy groups, or nitro groups, and n is an integer indicating the degree of polymerization) , and polymers having the above general formula may be used either individually or in combinations of two or more in copolymers.

Specific examples of R¹, R², R³, and R⁴ are chlorine atoms, bromine atoms, iodine atoms, or methyl, ethyl, propyl, allyl, phenyl, benzyl, methylbenzyl, chloromethyl, bromomethyl, cyanoethyl, cyano, methoxy, ethoxy, phenoxy, or nitro groups.

A preferred PPE resin is a polymer in which R¹ and R² in Formula (I) above are alkyl groups having 1-4 carbon atoms, and R³ and R⁴ are hydrogen or alkyl groups having 1-4 carbon atoms . n should preferably be 50 or a higher integer. Specific examples include poly(2, 6-dimethyl-l,4- phenylene) ether, poly(2 , 6-diethyl-l, 4-phenylene) ether, poly(2- methyl-6-ethyl-l, 4-phenylene) ether, poly(2-methyl-6-propyl-1, 4- phenylene) ether, poly(2 , 6-dipropyl-1,4-phenylene) ether, poly(2- ethyl-6-propyl-l, 4-phenylene) ether, poly(2 , 6-dimethoxy-l, 4- phenylene) ether, poly(2 , 6-dichloromethyl-l, 4-phenylene) ether, poly(2, 6-dibromomethyl-1,4-phenylene) ether, poly(2 , 6-diphenyl-1,4- phenylene) ether, poly(2,6-ditolyl-l, 4-phenylene) ether, poly(2,6- dichloro-1, 4-phenylene) ether, poly(2 , 6-dibenzyl-l, 4-phenylene) ether, and poly(2,5-dimethyl-l, 4-phenylene) ether. Among these, a particularly preferred PPE is poly(2, 6-dimethyl-1,4-phenylene) ether. Moreover, an example of a PPE copolymer is a copolymer containing a portion of an alkyl tri-substituted phenol such as 2,3,6- trimethylphenol in the aforementioned polyphenylene ether repeating unit.

These PPE resins may also be copolymers with styrene compounds grafted on. An example of a styrene compound-grafted polyphenylene ether is a copolymer obtained by grafting a styrene compound such as styrene, α-methylmethylstyrene, vinyl toluene, or chlorostyrene onto the aforementioned PPE resin and then carrying out graft polymerization.

Furthermore, the PPE resin may also be modified using a modifier having a polar group. Examples of polar groups include acid hydrides, carbonyl groups, acid anhydrides, acid amides, carboxylic esters, acid azides, sulfone groups, nitrile groups, cyano groups, isocyanate esters, amino groups, imide groups, hydroxyl groups, epoxy groups, oxazoline groups, and thiol groups. The syndiotactic styrene polymer of component (B) of the present invention is a styrene polymer having a highly syndiotactic structure. A syndiotactic structure refers to a stereostructure in which phenyl groups or substituted phenyl groups are configured in mutually opposite directions with respect to a main chain composed of carbon-carbon bonds, and the tacticity thereof is determined by nuclear magnetic resonance using isotopic carbon (^UC-NMR) . Tacticity as measured by ¹³C-NMR can be expressed by the number of multiple contiguous structural units, e.g., diad in the case of 2 , triad in the case of 3 , and pentad in the case of 5. In the present invention, the syndiotacticity of the styrene polymer is ordinarily characterized by a diad ratio of 75% or more, and preferably 85% or more, and a racemic pentad ratio of 30% or more, and preferably 50% or more. Examples of styrene polymers include polystyrene, poly(alkylstyrene) , poly(halostyrene) , poly(alkoxystyrene) , poly(vinylbenzoic acid ester) , mixtures thereof, or copolymers having these as their main components . Moreover, the term poly(alkylstyrene) used here includes poly(methlystyrene) , poly(ethylstyrene) , poly(isopropylstyrene) , poly(tert-butylstyrene) , etc. , and examples of poly(halostyrenes) include poly(chlorostyrene) , poly(bromostyrene) , and poly(fluorostyrene) . Furthermore, examples of poly(alkoxystyrenes) include poly(methoxystyrene) and poly(ethoxystyrene) . Among these substances, particularly preferred styrene polymers are polystyrene, poly(p-methylstyrene) , poly(m- methylstyrene) , poly(p-tert-butylstyrene) , poly(p-chlorostyrene) , poly(m-chlorostyrene) , poly(p-fluorostyrene) , and copolymers of styrene and p-methylstyrene. Moreover, there are no particular restrictions on the molecular weight of the syndiotactic styrene polymer, but its weight average molecular weight should be 10,000 or above, and preferably 50,000 or above. If this weight average molecular weight is less than 10,000, chemical resistance will tend to be insufficient. Moreover, there are also no restrictions on the range of molecular weight distribution, and various ranges may be used. The syndiotactic styrene polymer has a melting point of 200-310°C, and its thermal resistance is outstanding compared with that of conventional styrene polymers having an atactic structure.

For example, this type of syndiotactic styrene polymer may be manufactured by polymerization of a styrene monomer (a monomer corresponding to the aforementioned styrene polymer) , either in an inactive hydrocarbon solvent or without a solvent, using titanium or a condensation product of water and trialkyl aluminum as a catalyst (cf . Japanese Unexamined Patent Applications S62-104818, S63-268709) , and commercial substances may also be used.

Furthermore, the syndiotactic styrene polymer may be modified using a modifier having a polar group. Examples include an acidhydride, carbonyl group, acid anhydride, acid amide, carboxylic ester, acid azide, sulfone group, nitrile group, cyano group, isocyanate ester, amino group, imide group, hydroxyl group, epoxy group, oxazoline group, or thiol group. Particularly preferred polar groups are acid anhydrides and epoxy groups, with a maleic anhydride group being preferred as an acid anhydride.

The high-impact styrene resin of component (C) used in the present invention is known in and of itself, and is obtained by graft polymerization of an elastic body (rubber-like substance) and a portion of a styrene polymer. This [elastic body (rubber-like substance) /styrene resin] graft component is distributed in a stable manner when bothmolten and solid in the styrene resin in a form commonly referred to as a "salami" structure, with a size of approximately 0.1-4.0 μ . High-impact styrene resin does not temporarily melt and disperse in molten plastic, unlike addition-type thermoplastic elastomer such as styrene-butadiene-styrene copolymer (SBS) and hydrogenated styrene-butadiene-styrene block copolymer (SEBS) . This high-mpact styrene resin may be manufactured by any desired known polymerization method, such as that of dissolving an elastic body (rubber-like substance) in a styrene monomer. Polymerization may be carried out by the batch method or continuous method. Examples of polymerization methods include emulsion polymerization, bulk polymerization, and bulk suspension two-stage polymerization.

An example of the aforementioned styrene monomer is a monomer of General Formula (II) below:

in the above formula, R is a hydrogen atom or an alkyl group having 1-4 carbon atoms, Z is a halogen atom or a substituent which is an alkyl group having 1-4 carbon atoms, and p is an integer from 0 to 5. Examples of the aforementioned elastic body (rubber-like substance) include polybutadiene, polyisoprene, butyl rubber, EPEM, ethylene-propylene copolymer, natural rubbers, and natural or synthetic elastomers such as epichlorohydrin, with polybutadiene being preferred.

The high-impact styrene resin of component (C) should preferably be high-impact polystyrene (using styrene and polybutadiene) . The high-impact styrene resin of component (C) maybe commercially obtained, with examples including the Dialex HT series marketed by Mitsubishi Kagaku K.K. and the Topalex series marketed by Mitsui Toatsu K.K.

The aforementioned (A) PPE resin and (C) high-impact styrene resin should be blended in in the amounts of 90-10 parts by weight of (C) with respect to 10-90 parts by weight of (A) , and preferably 80-10 parts by weight of (C) with respect to 20-90 parts byweight of (A) . If the amount of (C) is too low, the effect of improving chemical resistance will not be achieved. Moreover, if the amount of (A) is too low, the outstanding properties of PPE resin will not be displayed.

Moreover, the syndiotactic styrene polymer of component (B) is mixed in in an amount of 5 to 60 parts by weight with respect to a total of 40 to 95 parts by weight of (A) and (C) . Preferably, 10-50 parts by weight of (B) should be blended in with respect to a total of 90-50 parts byweight (A) and (C) . Even more preferably, 15-50 parts byweight of (B) should be blended in with respect to a total of 85-50 parts by weight of (A) and (C) . If the amount of the syndiotactic styrene polymer of component (B) is too high, dimensional accuracy and mechanical strength will decrease, and if it is too low, the effect of improving chemical resistance will not be achieved. In addition to the above components, (D) a styrene resin may also be blended into the resin composition of the present invention as desired.

The styrene resin is known in and of itself, and this must be a compound of General Formula (III) below:

in the formula, RYs a hydrogen atom or an alkyl group having 1-4 carbon atoms, Z' is a halogen atom or a substituent which is an alkyl group having 1-4 carbon atoms, and q is an integer from 0 to 5 in which repeating structural units derived from vinyl aromatic compounds account for at least 25% by weight of the polymer. Examples of such styrene resins include homopolystyrene, styrene-containing copolymers such as styrene-methylstyrene copolymer, styrene-butadiene copolymer, styrene-acrylonitrile copolymer (SAN) , styrene-maleic anhydride copolymer, and styrene-acrylonitrile-butadiene copolymer (ABS) .

Homopolystyrenes include substances having an atactic or isotactic structure. Examples of styrene-class elastomers include styrene- butadiene copolymer (SBR) , styrene-butadiene-styrene copolymer (SBS) , hydrogenated styrene-butadiene-styrene block copolymer (SEBS) , styrene-isoprene copolymer (SIR) , styrene-isoprene-styrene copolymer (SIS) , and hydrogenated styrene-isoprene-styrene copolymer (SEPS) . These styrene resins may be used either individually or in combinations of two or more. They may also be modified either partly or completely using a modifier having a polar group. The styrene resin of component (D) should be blended in in an amount of 50 parts by weight or less with respect to a total of 100 parts by weight of conponents (A) , (B) , and (C) , and more preferably, 5-50 parts by weight. In order to achieve the effect of the present invention, the resin composition should be such that ΔE, which indicates the total degree of crystallization, satisfies the condition ΔE < 54. More preferably, this should be ΔE < 50. ΔE is indicated by the Equation (i) below:

ΔE (%) = Ec/(Esps x W) x 100 (i) in the above equation, Ec is the crystallization energy (unit: mJ/mg) of the resin composition measured with a differential scanning calorimeter; Esps is the crystallization energy (unit: mJ/mg) of the syndiotactic styrene polymer alone measured under the same conditions as Ec above; and W is the weight ratio of the syndiotactic styrene polymer in the resin composition. Thus ΔE indicates the proportion of crystallization energy, which is a measure of the total degree of crystallization. Here, Ec is the crystallization energy (unit: mJ/mg) of the resin composition measured with a differential scanning calorimeter) . The value of Ec is determined as follows : The molten resin composition cools at a rate of -20°C/min. in an inert gas atmosphere, its crystallization behavior is plotted, the area of the crystallization peaks obtained is determined, and this is taken as the crystallization energy (Ec) . Esps is the crystallization energy (unit: mJ/mg) measured with the syndiotactic styrene polymer alone, and it is measured under the same conditions as Ec . W is the weight ratio of the syndiotactic styrene polymer in the resin composition. Moreover, in cases where a peak crystallization energy of the polymer composition cannot be obtained, i.e., cases in which the Ec value cannot be measured, Ec = 0, and the ΔE value is also 0.

When the amount of the syndiotactic styrene polymer of component (B) blended in exceeds 60 parts by weight, ΔE becomes 54% or higher, crystallization proceeds to an excessive degree during fabrication, adversely affecting dimensional accuracy due to molding shrinkage, and the coπposition becomes brittle, not only resulting in a decrease in mechanical properties such as impact strength, but bringing about a decrease in chemical resistance, despite the fact that there is a high proportion of crystal components. Moreover, in this type of mixing in an excess range, crystallization is accompanied by turbidity and opacity of the composition, causing the transparent amorphous properties of conventional modified polyphenylene ether resin to be lost.

Accordingly, when component (B) is present in the above-mentioned component range, i.e., when the condition of an ΔE value < 54 is satisfied, it is possible to achieve a sufficient improvement in chemical resistance for practical use without harming the properties of the polyphenylene ether resin composition, which is an amorphous resin, namely its high dimensional accuracy and other outstanding properties .

Moreover, in the present invention, various flame retardants may also be used. Examples include phosphoric ester flame retardants and halogen flame retardants. Among these, phosphoric ester flame retardants are preferred for safety reasons. Examples of phosphoric ester flame retardants include trimethylphosphate, triethylphosphate, tributylphosphate, trioctylphosphate, tributoxyethylphosphate, triphenylphosphate, tricresylphosphate, cresylphenylphosphate, octyldiphenylphosphate, diisopropylphenylphosphate, tris (chloroethyl)phosphate, tris (chloropropyl)phosphate, tris (dichloropropyl)phosphate, bis (2,3-dibromopropyl) -2 , 3- dichloropropylphosphate, tris (2,3-dibromopropyl)phosphate, and polyphosphates such as (chloropropyl)monooctylphosphate, bisphenol A bisphosphate, hydroquinone bisphosphate, resorcinol bisphosphate, and trioxybenzene triphosphate, with triphenylphosphate and various polyphosphates being preferred.

In the resin composition of the present invention, moreover, in addition to the above components, one may add during mixing or molding of the resin, in amounts which do not impair the purpose of the invention, other resins, rubber-like substances (such as polybutadiene and polyisoprene; however, excluding styrene elastomers) , common additives such as pigments, dyes, strengtheners (glass fibers, carbon fibers, etc.), fillers (carbon black, mica, talc, silica, titanium oxide, etc.), heat-resistance agents, antioxidants, weather-proofing agents, lubricants, mold-releasing agents, crystal nucleating agents, plasticizers, fluidity-improving agents, antistatic agents, and antibacterial and antifungal agents.

There are no particular restrictions on the method used for manufacturing the resin composition of the present invention, and any ordinary method may be used as appropriate. Generally speaking, the melt kneading method is preferred. Specific examples of equipment which may be used include extruders, Banbury mixers, rollers, and kneaders, and these may operate by either batch or continuous operation. The resin coπposition of the present invention may be used to obtain the desired molded product in any desired form using any desired molding method, such as injection molding, extrusion molding, or blow molding. The resin coπposition of the present invention should preferably meet the following conditions:

(i) In a chemical resistance crack test carried out under strain conditions of 1% or above, it does not undergo cracking failure even when exposed to an organic substance selected from among fats and oils, grease, and organic solvents for 24 hours or more, and

(ii) the molding shrinkage of a square plate test piece formed by injection molding (100 mm x 100 mm x 3 mm in thickness) is 0.8% or less in the flow direction and 0.8% or less in a direction perpendicular to the flow. Specific examples of the organic substance used in the 1.5% strain chemical resistance cracking test include tempura oil, salad oil, epoxy hardening agents, engine oil, gasoline, lubricating oil, wax remover solution, and rust-preventing agents. EXAMPLES

The following is an explanation of the present invention in greater detail by means of working exanples, but the present invention is not limited to these exanples.

Moreover, in the working exanples and comparison examples, the components used were as follows.

(A) Polyphenylene ether resin: PPE: Poly(2,6-dimethyl-l, 4-phenylene) ether having an intrinsic viscosity (chloroform, 25°C) of 0.48 dl/g manufactured by Nihon G.E. Plastics K.K. (B) Syndiotactic polystyrene: S-PS: trademark; Zarek 70Z (molecular weight 250,000, syndiotacticity indicated by racemic pentad ratio according to C-NMR analysis: 97%), manufactured by Shukko Sekiyu Kagaku Kogyo K.K.) (C) High-impact styrene resin:

HIPS: High-mpact polystyrene (trademark; HT644, manufactured by Mitsubishi Kasei K.K.)

(D) Styrene resin: A-PS: General-purpose atactic polystyrene (trademark; CR3500, manufactured by Dainippon Inc. K.K.)

SBS: Styrene-butadiene-styrene copolymer, Kraton D1101CU (manufactured by Shell)

Working Examples 1-4 and Coπparison Examples 1-11 (1) Extrusion process The various components were mixed in the proportions (weight ratio) shown in Tables 1-2, and after being blended in a Henschel mixer, the mixture was melt-kneaded in a 30 mm biaxial extruder under conditions of set kneading teπperature of 300°C and rotation speed of 300 rpm to obtain pellets. (2) Molding process

Pellets obtained as described were injection-molded using an inection molding machine (manufactured by Toyo Kikai Kinzoku K.K. , 80 tons) under conditions of set cylinder teπperature of 300°C and mold temperature of 80°C to obtain test pieces. Using the test pieces obtained, the following tests were conducted. The results are shown in Tables 1-2. a: Chemical resistance test: An extrusion-molded test piece measuring 3.2 mmx 12.7 mmx 63.5 mm was fixed in place on the forced 1.5% bending strain die shown in Fig. 1, and a chemical resistance test was conducted.

The following solvents were used: * Wax remover solution: Manufactured by Yushiro Kagaku Kogyo K.K. , ST-7

* Epoxy hardening agent : Manufactured by Toshida Co . , TCG1672

* Grease: Manufactured by Kycdo Yushi K.K. , Multemp SRL

* Tempura oil: Manufactured by Showa K.K.

* Engine oil: Manufactured by Shell Premium, 5W30 * Gasoline: Manufactured by Nihon Sekiyu K.K. , regular gasoline

* Rust-preventing agent: Manufactured by Kure Kogyo K.K. , CRC556

The test method was as follows:

The test piece (3) was fixed in place on the bent portion of the 1.5% bending strain die (4) , the surface of the curved portion of the test piece was covered with gauze measuring 12.7 mmx 12.7 mm (1), a solvent (2) was dripped onto this gauze so as to saturate it, the time after dripping required for the test piece to rupture completely was measured, and this time was taken as a measure of chemical resistance. Test pieces which did not rupture after 24 hours were assessed as "No break," and the test was concluded at that time. The reason is that in actual use, there are no applications which are subjected to the high strain of 1.5%, and a test duration of longer than 24 hours is considered unnecessary from a practical standpoint. Moreover, in cases where the solvent was grease, measurement was carried out after directly applying the grease to the surface of the test piece.

The tests were conducted at the following temperatures: In the case of grease, tempura oil, and engine oil, measurements were conducted in an air oven at 85°C, and in the case of wax remover solution, gasoline, the rust-preventing agent, and the epoxy hardening agent, because of the risk of fire due to the volatility of these substances, testing was conducted in a room teπperature draft. b: Measurement of molding shrinkage (evaluation of dimensional accuracy) :

The flat plate test piece shown in Fig. 2, measuring 100 mm x 100 mmx 3 mm, was moldedwith a film gate (5) using the FAS-T100D molding machine manufactured by Fanac Co. (100 tons) under the same conditions as above (set cylinder temperature of 300°C and mold teπperature of 80°C) . The test pieces were first left standing for 24 hours at room teπperature of 23°C and humidity of 50°C, they were then measured five times in direction a and five times in direction b using a three- dimensional measuring device (AF211, manufactured by Mitsutoyo) , and the average values were taken as the molding shrinkage flow direction (indicated by a in Fig. 2) and the direction parallel to the molding shrinkage flow (indicated by b in Fig. 2) respectively. Moreover, concerning the mold teπperature for nylon molding, 60°C was selected as the general optimum condition in the case of non-addition, and for PPE/nylon alloy (Noryl GTX600) , 80°C was selected as the general optimum condition in the case of non-addition, c: Izod impact strength test: A test piece obtained by injection molding measuring 3.2 mm x 12.7 mm x 63.5 mm was measured for Izod impact strength using a notched test piece according to ASTM D-256. d: HDT (heat distortion temperature) : A test piece obtained by injection molding measuring 6.4 mm x 12.7 mm x 63.5 mm was heated with a teπperature increase rate of 2°C/min. in an oil tank according to ASTM D648 with a load of 18.6 kg, and heat distortion teπperature was measured, e: MI (melt flow index)

Measurements were conducted with a load of 10 kg at 250°C using a melt indexer manufactured by Takara K.K.

Table 1

)

Table 2

As can be seen from Table 1, in Conparison Exanple 1, the amount of syndiotactic polystyrene (S-PS) blended in was the same as in Working

Example 1, but the PPE coπposition did not have high-mpact polystyrene

(HIPS) blended in. One can see that chemical resistance is extremely poor compared to Working Example 1.

Next, comparing Working Exanple 1 and Comparison Examples 2 and 3 , in Conparison Exanple 2 (PPE/A-PS) , in which the resin did not contain S-PS or HIPS, one can see that chemical resistance is markedly inferior. Moreover, in Comparison Example 3 (PPE/S-PS/A-PS) , in which A-PS was blended in instead of HIPS, the effect of improving chemical resistance was superior to Comparison Example 2 , but it was still markedly inferior to Working Example 1 (PPE/S-PS/HIPS) . The same can be said for the coπparisons of Working Example 2 with Conparison Examples 5 and 6, the coπparisons of Working Example 3 with Conparison Exanples 8 and 9 (Table 2) , and the coπparisons of Working Exanple 4 with Conparison Exanples 10 and 11 (Table 2) . Thus it was found that by mixing S-PS with PPE, one can obtain an effect of improving chemical resistance, and when HIPS is included in the blend, one obtains a marked effect of improving chemical resistance. This effect is not obtained with a mixture of A-PS and S-PS. It is surprising that this chemical resistance-improving effect was obtained by blending in HIPS, which is used for improving impact resistance and is not thought to have anything to do with chemical resistance. Moreover, in all of the compositions of all of the working examples, characteristics such as mechanical strength and molding shrinkage (dimensional accuracy) were identical to PPE/A-PS.

Furthermore, in Comparison Examples 4 and 7, it can be seen that excessive amounts of S-PS were added, with chemical resistance being observed which was identical to Working Examples 1 and 2 respectively, but the molding shrinkage was extremely high and dimensional accuracy was poor.

One can see that from the above that only when HIPS is combined with a specified amount of S-PS can one achieve a PPE resin coπposition showing outstanding chemical resistance while maintaining high dimensional accuracy.

The resin coπposition of the present invention makes it possible to markedly increase chemical resistance without impairing the inherent properties (particularly dimensional stability) of conventional polyphenylene ether resin (amorphous resin) . Moreover, this advantage is not adversely affected by adding flame retardants or fillers (such as glass fibers and mica) . Accordingly, the resin coπposition of the present invention is well-suited for applications in wzhich such resins were previously limited, such as external automotive components, engine room conponents, and cabin interiors of ships, to which waxes, machine oils/engine oils, rust-preventing agents, aromatic agents, etc., may adhere, conponents for office equipment, computer-related equipment, etc., to which lύbrieating oils for sliding, grease, or cleaners may adhere (such as internal parts, fan motor cases, and plastic chassis) ; home electronic and commercial electrochemical product components, to which salad oil, tempura oil, or other organic solvents may adhere; and conponents of electrical and electronic equipment used in environments exposed to oil and smoke or organic gases (such as factory environments and construction environments) . It is particularly well-suited for use in conponents subject to strain, and it is therefore extremely useful from an industrial standpoint.

Claims

1. A resin co╧Çposition containing (A) a polyphenylene ether resin and (B) a syndiotactic styrene polymer, characterized in that

(1) the co╧Çposition also contains (C) a high-impact styrene resin; and (2) the co╧Çposition contains (C) in the amount of 90-10 parts by weight with respect to 10-90 parts by weight of (A) and (B) in the amount of 5 to 60 parts by weight with respect to a total of 40 to 95 parts by weight of (A) and (C) .

2. Resin co╧Çposition according to Claim 1, characterized by containing 80-20 parts by weight of (C) with respect to 20-80 parts by weight of (A).

3. Resin co╧Çposition according to Claims 1 or 2 , characterized by containing 10-50 parts by weight of (B) with respect to a total of 50-90 parts by weight of (A) and (C) .

4. Resin co╧Çposition according to any of Claims 1-3 , characterized by also containing 50 parts by weight or less of (D) a styrene resin with respect to a total of 100 parts by weight of (A) , (B) , and (C) .

5. Resin composition of any of Claims 1-4, characterized by simultaneously meeting the following conditions:

(i) in a chemical resistance crack test carried out under strain conditions of 1% or above, it does not undergo cracking failure even when exposed to an organic substance selected from among fats and oils, grease, and organic solvents for 24 hours or more, and (ii) the molding shrinkage of a square plate test piece formed by injection molding (100 mm x 100 mm x 3 mm in thickness) is 0.8% or less in the flow direction and 0.8% or less in a direction perpendicular to the flow.