FIBER-REINFORCED HEAT-RESISTANT POLYOLEFIN COMPOSITION

Abstract: This improved fibre-reinforced heat-resistant polyolefin composition comprises 5-85 wt.% of polyphenylene sulphide (A), 15-95 wt.% of modified polyolefin (B) and 10-60 pts. wt. of reinforcing fibres (C) to 100 pts. wt. of the sum of (A) and (B). The modified polyolefin (B) has a melting point of 200 deg. C or higher and is partly or wholly graft-modified within a range of 0.01 to 10 wt.% with an unsatd. carboxylic acid or a deriv. thereof. The basic polyolefin of (B) is specified to be poly4-methyl-1-pentene or poly3-methyl-1-butene. Oxazoline-modified polystyrene (D) is added, if necessary, to the above-mentioned compsn. to the amt. of 5-30 pts. wt. per 100 pts. wt. of the sum of (A) and (B). If necessary, additives such as heat-stabiliser, weather-stabiliser, dyes, antiraster etc. can also be added in amts. that do not interfere with the purpose of this invention.

Description: The invention relates to fiber reinforced polyolefin compositions which have excellent properties such as heat resistance, tensile strength and soldering heat resistance, the compositions containing a graft-modified polyolefin, a polyphenylene sulfide and a reinforcing fiber. It is known to improve the mechanical properties, such as tensile strength, bending strength and impact strength, and heat resistance of polyolefins by incorporating therein reinforcing materials such as glass fiber. However, the mechanical properties and heat resistance of polyolefins are not sufficiently improved merely by incorporating glass fiber therein because they do not bond together and hence it is not possible to obtain such an improvement as may be obtained when glass fiber is incorporated into unsaturated polyesters having polar groups in the molecule, or into epoxy resins. There have been various proposals for improving the bond between polyolefins and glass fiber. Japanese Patent Publn. No. 41096/1974 discloses a process in which maleic acid or maleic anhydride, a polyolefin and glass fiber which has been surface treated with an aminosilane are allowed to react at a temperature higher than the melting point of the polyolefin in the presence of organic peroxides. Japanese Patent Pubin. No. 31895/1977 discloses compositions comprising a polyolefin, a modified polyolefin having aromatic carboxylic acid anhydride units and glass fiber which has been surface treated with an aminosilane. Japanese Patent Publn. No. 10265/1976 discloses a process comprising melt kneading in an atmosphere of nitrogen a polyolefin and maleic anhydride in the presence of a glass type reinforcing material to modify the polyolefin, and optionally adding an unmodified polyolefin. More recently there has arisen a strong and growing demand for so-called engineering plastics, i.e. heat-resistant thermoplastic resins which have better heat resistance and mechanical strength than the above-mentioned compositions. Japanese Patent Publn. No. 9943/1981 discloses a polyolefin resin composition comprising (A) a polyolefin resin having added unsaturated carboxylic acid or a polyolefin resin having added unsaturated carboxylic acid diluted with a polyolefin resin, (B) a nitrogen-containing resin and (C) a filler, and it is alleged that by virtue of incorporating the nitrogen-containing resin, the resulting compositions have excellent mechanical strength, heat resistance and coatability. However, it has been found that even when ABS or nylon 6 (mentioned in the publication) is incorporated into a polyolefin having a melting point of above 200°C, for example poly-4-methyl-1-pentene, which has particularly good heat resistance among polyolefins, the heat resistance of the resulting composition is not improved at all, or rather decreases. JP-A-59/207921 discloses a composition comprising a polyphenylene sulfide resin, a graft-modified α-olefin copolymer and an epoxy resin, and optionally a reinforcing filler such as glass fiber. The graft-modified α-olefin copolymers disclosed have melting points below 200°C and without the epoxy resin the compositions have poor compatibility and low strength. Japanese Patent L-O-P Publn. No. 53549/1985 discloses that compositions comprising poly-4-methyl-1-pentene, unsaturated carboxylic acid graft modified poly-4-methyl-1-pentene, nylon 66 and inorganic fiber have excellent heat resistance and mechanical strength in comparison with fiber reinforced polyolefin resin composition proposed prior to the filing date of said publication. However, on studying further the compositions disclosed in said publication, we have found that the compositions have relatively high water absorption properties due to the presence of nylon 66, and the mechanical strength of the composition can decrease as a result of moisture absorption. The present invention is intended to solve the problems associated with known compositions and provides fiber reinforced polyolefin compositions which have excellent heat resistance, water resistance, moisture resistance, solderability and mechanical strength. According to the present invention there is provided a fiber reinforced heat-resistant polyolefin composition characterized by comprising: 5-85% by weight of polyphenylene sulfide (A), 15-95% by weight of a graft-modified polyolefin (B) having grafted units of an unsaturated carboxylic acid or a derivative thereof which is an acid halide, amide, imide, anhydride or ester in an amount of 0.01 to 10% by weight and having a melting point of above 200°C, and 10-60 parts by weight, based on 100 parts by weight of (A) + (B), of reinforcing fiber (C). The fiber reinforced polyolefin compositions of the invention can also comprise 5-30 parts by weight based on 100 parts by weight of (A) + (B), of an oxazoline-modified polystyrene (D). Polyphenylene sulfide (A) Polyphenylene sulfides (A) used in the present invention have as a main component a repeating unit represented by the structural formula and may further contain other copolymerizable component units, for example These polyphenylene sulfides preferably have a melt viscosity of 5 to 5000 Pas (50-50000 poises), particularly 10 to 500 Pas (100-5000 poises) as measured at 300°C for 200 sec⁻¹. Graft-modified polyolefin (B) The graft-modified polyolefins (B) used in the present invention are polyolefins which have been graft modified, either partly or wholly, with 0.01-10% by weight, preferably 0.1-5% by weight of, as graft monomer, an unsaturated carboxylic acid or derivative thereof, and which are crystalline polymers usually having an intrinsic viscosity of 0.5-15 dl/g, preferably 0.6-10 dl/g and a melting point (ASTM D 3418) of above 200°C. If the graft amount of unsaturated carboxylic acid or derivative thereof is less than 0.01% by weight, the modified polyolefins (B) obtained have poor compatibility with the polyphenylene sulfides (A) and hence the resulting compositions are liable to have poor heat resistance. On the other hand, if the graft amount exceeds 10% by weight, the resulting compositions are liable to have poor water resistance. The graft-modified polyolefin (B) must have a melting point of above 200°C, preferably above 230°C. If the graft-modified polyolefin (B) has a melting point of less than 200°C, the heat resistance is insufficient. Thus, when a modified polyolefin (B) having a melting point of less than 200°C is used in combination with a polyphenylene sulfide and reinforcing fiber, the resulting composition has low heat resistance. Furthermore, since the polyolefin composition must be heated at least to above the melting point when said composition is subjected to melt molding, the use of a graft-modified polyolefin having a melting point of less than 200°C brings about deterioration or decomposition thereof at the time of melt molding, so that it is difficult to obtain a molded article having excellent properties in all respects, such as heat resistance, water resistance, moisture resistance and mechanical strength. Accordingly, graft-modified polyolefins used in the present invention are preferably those which have, if possible, a melting point substantially equal to that of the polyphenylene sulfides used in combination therewith. Polyolefins onto which are grafted the graft monomer, referred to herein as the base polymer, are obtained by homopolymerization or copolymerization of monomers having in the molecular chain relatively bulky side chains. Poly-4-methyl-1-pentene or poly-3-methyl-1-butene are preferably used as a base polymer for the graft-modified polyolefin (B). Poly-4-methyl-1-pentene can be a homopolymer of 4-methyl-1-pentene or a copolymer of 4-methyl-1-pentene with another α-olefin of 2 to 20 carbon atoms, for example ethylene, propylene, 1-butene, 1-hexene, 1-octene, 1-decene, 1-tetradecene or 1-octadecene. Usually, there are used polymers consisting essentially of at least 85 mol%, preferably at least 91 mol% of 4-methyl-1-pentene. Such poly-4-methyl-1-pentenes preferably have a melt flow rate (load: 5 kg, temperature: 260 o C) of 5-500 g/min, more preferably 25-150 g/min. If the poly-4-methyl-1-pentene used has a melt flow rate of less than 5 g/min, the graft-modified polyolefin containing the same has an excessively high melt viscosity, showing a strong tendency to become poor in moldability, whereas if said melt flow rate exceeds 500 g/min, the graft-modified polyolefin has an excessively low melt viscosity, showing a strong tendency to become poor in moldability. Poly-3-methyl-1-butene can be a homopolymer of 3-methyl-1-butene or a copolymer of 3-methyl-1-butene with an other α-olefin having 2 to 20 carbon atoms as aforesaid. Usually, there are used polymers consisting essentially of at least 85 mol%, preferably at least 91 mol%, of 3-methyl-1-butene. Such poly-3-methyl-1-butenes as mentioned above have preferably a melt flow rate (load: 2.16 kg, temperature: 340 o C) of 5-500 g/min, more preferably 25-150 g/min, for the same reasons as in the case of poly-4-methyl-1-pentene. Unsaturated carboxylic acids or derivatives thereof used for graft modifying such the polyolefins used as a base of the modified polyolefins include unsaturated carboxylic acids such as acrylic acid, maleic acid, fumaric acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, isocrotonic acid and nadic acid® (endocis-bicyclo [2,2,1] hept-5-ene-2,3-dicarboxylic acid) or, as derivatives thereof, their acid halides, amides, imides, anhydrides or esters, for example malenyl chloride, maleimide, maleic anhydride, citraconic anhydride, monomethyl maleate, dimethyl maleate and glycidyl maleate. Among these, preferrred are unsaturated dicarboxylic acids or acid anhydrides thereof, particularly preferable are maleic acid, nadic acid® or acid anhydrides thereof. To prepare modified polyolefins by graft copolymerization of polyolefins used as a base of the modified polyolefins with a graft monomer selected from among the above-exemplified unsaturated carboxylic acids or derivatives thereof, there may be adopted various processes, per se, known. For instance, there is a process which comprises dissolving the base polyolefin and adding to the molten base polyolefin a graft monomer, thereby effecting graft copolymerization, or a process which comprises dissolving the base polyolefin in a solvent and adding to the resulting solution a graft monomer, thereby effecting graft copolymerization. In either case, it is preferable to carry out the reaction in the presence of radical initiators in order to efficiently effect the graft copolymerization of the graft monomer with the base polyolefin. The graft reaction is carried out usually at a temperature of 60-350 o C, and the proportion of the radical initiator used is usually 0.001-1 part by weight based on 100 parts by weight of the base polyolefin. Useful radical initiators include organic peroxides, organic peresters, and azo-compounds. Of these radical initiators, preferred are dialkyl peroxides such as dicumyl peroxides di-tert-butyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexine-3, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane and 1,4-bis(tert-butylperoxyisopropyl) benzene. The modified polyolefins (B) used in the present invention may be such polyolefins as have wholly been modified with unsaturated carboxylic acids or derivatives thereof, so long as the graft amount of said unsaturated carboxylic acids or derivatives thereof used in within the aforementioned range, or the modified polyolefins (B) may be such polyolefins as have partly been modified, that is, said modified polyolefins (B) are mixtures comprising modified polyolefin and unmodified polyolefin. In the case where a mixture comprising modified polyolefin and unmodified polyolefin is used as the modified polyolefin (B), it is also possible to use said modified polyolefin in the mixture with the graft monomer at a slightly higher concentration, usually about 25% by weight, so long as the graft amount in said mixture is within the aforementioned range. Reinforcing fiber (C) The reinforcing fibers (C) used in the present invention are inorganic substances such as glass fiber, carbon fiber, boron fiber, potassium titanate fiber, wollastonite and asbestos fiber, or fibrous substances consisting of organic substances such as aramide fiber known as Kevlar®. Further, there may be used also such reinforcing fibers treated on the fiber surface thereof with silane type compounds, for example, vinyl triethoxysilane, γ-aminopropyl triethoxysilane, γ-aminopropyl trimethoxysilane, N-(β-aminoethyl)-γ-aminopropyl trimethoxysilane and γ-glycidoxypropyl trimethoxysilane. Oxazoline-modified polystyrene (D) In the fiber reinforced polyolefin compositions of the present invention, there may be used, if necessary, oxazoline-modified polystyrene (D) in addition to the components (A), (B) and (C) as mentioned previously. The oxazoline-modified polystyrene (D) as referred to above has an oxazoline ring attached to the polystyrene along its polystyrene chain, as shown in the following formula wherein is a polystyrene chain. Such oxazoline-modified polystyrene may be prepared by addition polymerization of polystyrene with oxazoline substituted at an unsaturated portion in the 2-position. In this connection, such oxazoline-modified polystyrene as illustrated above is commercially available as a product of The Dow Chemical Co. under a trade name of RPS. By virtue of incorporating the above-mentioned oxazoline-modified polystyrene into the fiber reinforced heat-resistant polyolefin compositions of the present invention, said compositions are improved in mechanical strength, particularly strength at the time when high temperatures are applied thereto, and moreover a thermal deformation temperature of the compositions is improved. Blending proportions A first type of composition of the present invention comprises polyphenylene sulfide (A), graft-modified polyolefin (B) and reinforcing fibers (C). In the composition, there are present the polyphenylene sulfide (A) in an amount of 5-85% by weight, preferably 10-80% by weight, the graft-modified polyolefin (B) in an amount of 15-95% by weight, preferably 30-80% by weight and the reinforcing fiber (C) in an amount of 10-60 parts by weight, preferably 15-50 parts by weight, based on (A)+(B) = 100 parts by weight . If the amount of the polyphenylene sulfide (A) used is less than 5% by weight, it becomes difficult to obtain a composition having excellent heat resistance, mechanical strength and solderability while if said amount exceeds 85% by weight there is no further improvement in heat resistance, mechanical strength and solderability but there is a disadvantage from the standpoint of material costs. If the amount of the graft-modified polyolefin (B) used is less than 15% by weight, it becomes difficult to obtain a composition having excellent impact strength while if said amount exceeds 95% by weight there is no further improvement in impact strength but there is a disadvantage from the standpoint of material costs. If the amount of the reinforcing fiber (C) used is less than 10 parts by weight based on (A) + (B) = 100 parts by weight , it becomes difficult to obtain a composition having excellent heat resistance and mechanical strength while if said amount exceeds 60 parts by weight, there is a tendency for the reinforcing fiber to rise to the surface of a product resulting from the composition, thereby markedly marring the appearance of the product and reducing the value of said product as an article of commerce. A second type of composition of the present invention further comprises an oxazoline-modified polystyrene (D) in addition to the components (A), (B) and (C) as defined above, the oxazoline-modified polystyrene (D) being present in an amount of 5-30 parts by weight, preferably 10-25 parts by weight based on (A)+(B) = 100 parts by weight . When the oxazoline-modified polystyrene (D) is used the resulting composition has improved mechanical strength, particularly the strength at the time when high temperatures are applied thereto and, at the same time, the thermal deformation temperature of the composition is also improved. Other components The fiber reinforced heat-resistant polyolefin compositions of the present invention may incorporate various additives which can be usually used in and mixed with polyolefins, such as thermal stabilizers, weathering agents, flame-retardants, nucleating agents, pigments, dyes, lubricants and rust preventives, in such ranges that the object of the present invention is not hindered thereby. For instance, useful flame retardants include phosphoric acid esters such as tricresyl phosphate, cresyldiphenyl phosphate, diphenyloctyl phosphate and tributyl phosphate; halogen containing phosphoric acid esters such as tris(β-chloroethyl)phosphate, tris (dichloropropyl)phosphate and tris(2,3-dibromopropyl) phosphate; halogen compounds such as chlorinated paraffin, chlorinated polyethylene, brominated polyphenyl, chlorinated polyphenyl, dechloranephus, tetrabromoethane, tetrabromobutane, 1,2-dibromo-3-chloropropane, 1,2,3-tribromopropane, hexabromocyclododecane, tetrabromobenzene, chlorinated diphenyl, decabromodiphenyl oxide, N,N'-ethylenebis-tetrabromophthalimide, tribromopolystylen , polydibromobenzene oxide and bistribromophenoxyethane; antimony type compounds such as antimony trioxide, antimony potassium tartarate and triphenyl stibine; boron type compounds such as borax, zinc borate and barium metaborate; and metallic hydroxides such as magnesium hydroxide, aluminum hydroxide, calcium hydroxide and barium hydroxide. Of these compounds as illustrated above, preferably used are halogen compounds, particularly decrolan, decabromodiphenyl oxide, N,N'-ethylenebis-tetrabromophthalimide and brominated epoxy, when used in combination with antimony trioxide, or magnesium hydroxide since this is capable of imparting flame retardant properties without bringing about lowering in heat resistance and mechanical strength. Processes for the preparation of the compositions and uses thereof The fiber reinforced heat-resistant compositions of the present invention may be prepared by mixing together the aforementioned components in their respective amounts as defined in accordance with the present invention. For the mixing of these components, there may be employed methods, per se, known, for example, a mixing method which comprises mixing said components together by means of a Henschel mixer, V-blender, ribbon blender or tumbler blender, and a method of mixing said components in the same manner as above, melt kneading the mixture by means of a single screw extruder, twin screw extruder or kneader, followed by granulation or pulverization. The fiber reinforced heat-resistant polyolefin compositions of the present invention thus prepared have markedly high heat resistance and thermal deformation temperatures and also improved mechanical strengths, as compared with conventional glass fiber reinforced polyolefins. Therefore, the present fiber reinforced heat-resistant polyolefin compositions are applicable to household electrical appliances, electronic parts and automotive parts which all require heat resisting properties, such as connectors, tuners, switches, heater ducts, radiator fans, coil bobbins, IC sealants and print substrates. The present invention is illustrated below in more detail with reference to examples, but it should be construed that the invention is in no way limited to those examples. Preparative Example 1 (Preparation of modified polyolefin) A graft reaction of maleic anhydride with 4-methyl-1-pentene homopolymer ([η] 1.7 dl/g, M w/ M n 7.5, melting point 241 o C, crystallinity index 42%, DSC parameter 3.0) was carried out with dicumyl peroxide at 145 o C in toluene solvent. The reaction product obtained was charged with large excess of acetone to precipitate a polymer which was then collected by filtration, and the precipitate thus collected was repeatedly washed with acetone to obtain maleic anhydride graft-modified poly-4-methyl-1-pentene A [hereinafter called modified TPX(A)]. The modified polymer thus obtained had 4.0% by weight of the maleic anhydride unit as grafted, [η] 0.95 dl/g, melting point 210 o C, crystallinity index 18%, Mw/Mn 4.5 and DSC parameter 2.8. Preparative Example 2 (Preparation of modified polyolefin) To 4-methyl-1-pentene homopolymer ([η] 3.8 dl/g, M w/ M n 7.3, melting point 240 o C, crystallinity index 41% and DSC parameter 3.2) were added maleic anhydride and 2,5-dimethyl-2,5-di-tert-butyl peroxide, and the mixture was then fed in an N₂ atmosphere to a single screw extruder kept at 260 o C and melt kneaded to obtain maleic anhydride graft-modified poly-4-methyl-1-pentene B [hereinafter called modified TPX (B)]. The modified polymer thus obtained had 1.4% by weight of the maleic anhydride unit as grafted, [η] 0.15 dl/g, melting point 212 o C, crystallinity index 14%, M w/ M n 5.2 and DSC parameter 4.3. Examples 1 and 2 Polyphenylene sulfide (PSS) (R-4 produced and sold by Philips Co.), TPX (A) obtained in Preparative Example 1, unmodified poly-4-methyl-1-pentene (TPX ® RT18, produced and sold by Mitsui Petrochemical Industries, Ltd.) and glass fiber (GF) were mixed together in the proportions as indicated in Table 1. The mixture was then melt kneaded at a molding temperature of 290 o C by means of a twin screw extruder and injection molded at that temperature by means of an injection molding machine (IS 50 manufactured and sold by Toshiba Machine Co., Ltd.) to prepare a test specimen. The test specimens thus obtained were subjected to tests in the following manner. The results obtained are shown in Table 1. Tensile strength (TS: kg/cm²): The measurement was conducted in accordance with ASTM D 638. Izod impact strength (IZ: kg cm/cm): The measurement was conducted in accordance with ASTM D 256. Heat deformation temperature (HDT: o C): The measurement was conducted in accordance with ASTM D 678 (load: 18.6 kg/cm²). Solderability: The measurement was conducted in accordance with JIS C 5034, wherein a plate of the specimen of 2 mm in thickness was immersed for 10 seconds in molten solder kept at 260 o C to visually check whether the plate was deformed or not. The result was represented by ○ when no deformation was observed and by ▵ when deformation was slightly observed. Example 3 The same procedure as described in Example 1 was carried out except that TPX (B) obtained in Preparative Example 2 was used in place of the TPX and TPX (A) used in Example 1. The results obtained are shown in Table 1. Example 4 PPS, TPX, TPX (A), GF and oxazoline-modified polystyrene (RPS produced and sold by the Dow Chemical Co.) were mixed together in the same manner as in Example 1, and the molded article obtained was evaluated in the same manner as in Example 1. The results obtained are shown in Table 1. Comparative Example 1 The same procedure as in Example 1 was carried out except that the PPS was excluded and the amount of TPX used was increased to 69% by weight. The results obtained are shown in Table 1. Comparative Example 2 The same procedure as in Example 1 was carried out except that the TPX (A) was excluded and the amount of TPX used increased to 35% by weight. The results obtained are shown in Table 1. Comparative Example 3 The same procedure as in Example 1 was carried out except that the TPX and TPX (A) were not used, and the amount of the PRS used was increased to 70% by weight. The results obtained are shown in Table 1. EX.1 EX.2 EX.3 EX.4 Compar. EX.1 Compar. EX.2 Compar. EX.3 Composition (wt%) PPS 35 35 35 31 35 70 TPX(A) 1 5 1 1 TPX(B) 35 TPX 34 30 30 69 35 GF 30 30 30 30 30 30 30 RPS 8 TS(Tensile Strength) 850 900 950 1050 550 550 1200 IZ(Izod impact strength) 9 10 10 10 12 6 6 HDT(Heat Deformation Temperature) 190 200 190 205 180 120 235≦ Solderability ○ ○ ○ ○ ▵ ○ ○ It can be seen from Table 1 that the composition of Comparative Example 1 comprising modified and unmodified polyolefins and reinforcing fiber (C) only has poor tensile strength (TS), low heat deformation temperature (HDT) and, moreover, poor solderability, that the composition of Comparative Example 2 comprising only polyphenylene sulfide (A), unmodified polyolefin and reinforcing fiber (C) has poor tensile strength (TS), and further that the composition of Comparative Example 3 comprising polyphenylene sulfide (A) and reinforcing fiber (C) has poor Izod impact strength (IZ).

Claims: A fiber reinforced heat-resistant polyolefin composition characterized by comprising: 5-85% by weight of polyphenylene sulfide (A), 15-95% by weight of a graft-modified polyolefin (B) having grafted units of an unsaturated carboxylic acid or a derivative thereof which is an acid halide, amide, imide, anhydride or ester in an amount of 0.01 to 10% by weight and having a melting point of above 200°C, and 10-60 parts by weight, based on 100 parts by weight of (A) + (B), of reinforcing fiber (C). A composition according to claim 1 wherein the polyolefin onto which the unsaturated carboxylic acid or derivative is grafted to provide the graft-modified polyolefin (B) is poly-4-methyl-1-pentene or poly-3-methyl-1-butene. A composition according to claim 1 or 2 which also comprises 5-30 parts by weight based on 100 parts by weight of (A) + (B) of an oxazoline-modified polystyrene (D).

Inventors: YOKOYAMA, AKIRA
Applicants: MITSUI PETROCHEMICAL INDUSTRIES, LTD.
Application year: 1988
Main classification: C08L23
IPC codes: C08L23, C08L51, C08L81, C08L25, H05K1, C08K7