POLYPHENYLENE SULPHIDE RESIN COMPOSITION USEFUL FOR PLATING

Abstract: A polyphenylene sulphide composition useful for plating is disclosed, comprising a polyphenylene sulphide resin, glass fibres, and potassium titanate fibres. Moulded articles of this composition, when plated after etching, provide a plated article which has a good appearance and good peel strength. Thus these plated articles can be used in outer applications, such as for electrical parts and automobile parts.

Description: The present invention relates to a polyphenylene sulphide resin (hereinafter referred to as a "PPS resin") composition useful for plating, which has good peel strength and good in appearance. PPS resins have good heat resistance, mechanical properties and chemical resistance, and thus are used, for example, in the fabrication of parts for electric equipment and automobiles, utilizing the above characteristics. Further, since plating processing which was hitherto considered to be difficult because of excessively high chemical resistance of the PPS resins has become possible, the PPS resins can also be effectively applied for reflector plates, printed circuit boards, electromagnetic shields, sheathed parts, etc. As such PPS resin compositions for plating, a PPS resin and glass fibre composition as described in Japanese Patent Application (OPI) No. 54290/84 (the term "OPI" as used herein means a "published unexamined patent application") and a PPS resin, glass fibre, and calcium carbonate composition ad described also in Japanese Patent Application (OPI) No. 54290/84 are under investigation. These compositions, however, have disadvantages in that the initial plate peel strength is low and post-treatment such as aging for a long time is needed. They thus are somewhat unsuitable for practical use. Furthermore, since PPS resins have good chemical resistance, there is no suitable etching solution available for use as a plating pre-processing solution at the etching step and, therefore, a plated article with good adhesion properties has not yet been obtained. It has therefore been desired to develop, as well as an etching solution for PPS resins, PPS resin compositions which permit the fabrication of plated articles having good plate adhesion properties and also having good surface lustre. As a result of extensive investigations to overcome the above problems and to develop a PPS resin composition which has good plate peel strength and appearance, it has been found that when a PPS resin composition containing glass fibres and potassium titanate fibres is subjected to surface treatment, even using a strongly acidic etching solution, a PPS resin composition which is excellent in both peel strength and appearance can be obtained. Thus, the present invention provides a PPS resin composition useful for plating, comprising a PPS resin, glass fibres, and potassium titanate fibres. The composition has good adhesion properties. In the PPS resin as used in the present invention, other components may be copolymerized, the resin should preferably contain at least 70 mol%, and preferably at least 90 mol%, of a repeating unit represented by formula The viscosity is not critical. In the above copolymerization case, as the other components, the following examples can be listed. In the foregoing, R represents an alkyl group (e.g. of 1-8 carbon atoms), a phenyl group, a nitro group, a carboxyl group, a nitrile group, an amino group, an alkoxyl group (e.g. of 1-8 carbon atoms), a hydroxyl group, or a sulphone group. The PPS resin as used herein is reinforced with glass fibres. The PPS resin content is from 30 to 70 wt%, and the glass fibre content is from 70 to 30 wt%. In addition, the PPS resin as used herein may contain a thermal degradation-inhibiting agent, a nucleating agent, a releasing agent, and the like. The potassium titanate fibres as used herein are preferably short fibres having an average fibre diameter of not more than 1 micron, an average fibre length of from 5 to 100 microns and an aspect ratio of at least than 10 (i.e., 10/1). The potassium titanate fibre content is from 1 to 10 wt%. If the potassium titanate fibre content is less than 1 wt%, the plate peel strength tends to be low and the appearance of the plated article tends to be poor. On the other hand, if the potassium titanate fibre content is in excess of 10 wt%, the mechanical properties of the resin composition tends to be reduced, and furthermore the plate peel strength tends to be decreased. By compounding potassium titanate fibres to a composition comprising the PPS resin and glass fibres according to the present invention, a plated article of the PPS resin composition can be obtained, which has unexpectedly good plate adhesion properties and appearance, without seriously reducing its mechanical properties. The reason for this is thought to be that the PPS resin layer is corroded by a strongly acidic etching solution and the potassium titanate fibres themselves present in the vicinity of the surface are partly dissolved. This leads to formation of irregularities greatly contributing to the plate adhesion properties on the surface layer of the moulded article, as a result of which there can be obtained good plate peel strength. In etching of the PPS resin composition of the present invention, a mixed solution of a chromic acid compound, sulphuric acid, and phosphoric acid is used as an etching solution. In a case where higher plate peel strength is needed, surface abrasion, for example, by sand blasting, is applied before the etching treatment, or a mixed solution of a hydrofluoric acid salt, a mineral acid, and hydrofluoric acid is used as an etching solution. The treatment temperature is in a range of from room temperature to about 70°C, and the treatment time is in a range of from about 1 to 30 minutes. After etching, chemical plating and subsequently electroplating which are conventionally employed for plating are applied, whereupon there can be obtained a plated moulded article. The above chemical plating step comprises sensitization, activation, and chemical plating. The sensitization is a step wherein a reducing metal salt, such as stannous chloride, is adsorbed on the surface of the moulded article. The activation is a step wherein a metal having a catalytic activity, such as palladium, gold, silver, or rhodium is adsorbed, and the noble metal is deposited and absorbed from the treatment solution by the action of the reducing substance used at the preceding step. Onto the moulded article thus treated, chemical plating such as chemical copper plating and chemical nickel plating is applied. This chemical plating is applied to impart electro-­ conductivity to the moulded article. As a result of the chemical plating, therefore, suitable electroplating can be subsequently applied. Using a moulded article of the PPS resin composition of the present invention, comprising the PPS resin, glass fibres, and potassium titanate fibres, there can be obtained a plated article with good peel strength and appearance, without causing a serious reduction in mechanical properties. Thus the PPS resin composition of the present invention is useful in production of electric parts to be used for outer equipment parts, automobile parts, exterior surfaces, printed circuit boards, moulded plates having electro-­ conductivity, and boxes having complex structures. The present invention is described in greater detail with reference to the following examples, although the invention is not intended to be limited thereto. The characteristics values in the examples were measured by the following methods. (1) Peel Strength Parallel lines were cut in the plated surface at 1 cm intervals. The cut plated layer was pulled in a direction vertical to the line cut direction at 20 mm/min, and the force (minimum value) needed therefor was measured. (2) Appearance The test surface was visually examined for smoothness at a distance of 60 cm under a light source of at least 150 lux. The rating was as follows: a: Excellent b: Good c: Bad (3) Flexural Strength An injection moulded article (1/2 in. x 5 in. x 1/8 in.) before plating was measured for breaking strength by bending at a rate of 1.5 mm/min according to ASTM D-790. EXAMPLE 1 A resin composition of 50 wt% of a PPS resin (trade name: Ryton® P-4; produced by Phillips Petroleum Co.), 45 wt% of glass fibres (chopped strand having a fibre diameter of 13 µm and a cut length of 3mm), and 5 wt% (based on the total weight of the first two components, as previously noted) of potassium titanate fibres (high-strength short crystal whiskers produced by Otsuka Chemical Co., Ltd.; trade name: Tismo D (average fibre diameter: 0.2 to 0.5 micron; average fibre length: 10 to 20 microns; aspect ratio: 20 to 100)) was injection moulded using a moulding apparatus, Sumitomo Netstal PROMAT 165.75 (mould clamping force: 75 tonf (metric), injection volume (max): 68 cm³), to produce a plate. This plate was used as a sample. This sample was previously degreased by washing in a neutral detergent heated to 60°C for 10 minutes. The previously degreased sample was soaked for 30 minutes in a mixed solution of 10 wt% of potassium dichromate, 35 wt% of sulphuric acid, and 10 wt% of phosphoric acid maintained at 60°C to perform etching and, thereafter, the sample was washed with water. Then the above etched sample was soaked at room temperature for 10 minutes in a mixed solution of 150 ml/litre of Catalyst A-­ 30 (produced by Okuno Seiyaku Kogyo K.K.) and 150 ml/litre of hydrochloric acid to perform sensitization. After washing with water, the sample was soaked in a 8 ml/litre solution of sulphuric acid for 3 minutes, and then washed with water. Then the sample was soaked in a mixed solution of 100 ml/litre of a chemical copper plating solution #100A and 100 ml/litre of #100B (both produced by Okuno Seiyaku Kogyo K.K.) at room temperature for 20 minutes to perform chemical copper plating. In a mixed solution of 220 g of copper sulphate, 34 ml of sulphuric acid, 6 ml of a gloss agent, and 1,000 ml of water with the above chemical copper-plated molded article as a cathode and a copper plate as an anode, 4 A/dm² of current was passed to perform electric copper plating at room temperature for 120 minutes. The plated mould article thus obtained was evaluated for appearance and peel strength. The results are shown in Table 1 along with the flextural strength of the moulded article before plating. EXAMPLE 2 In addition, a sample was produced in the same manner as in Example 1, except that surface abrasion using a sand paper #400 was applied before degreasing and washing. This sample was subjected to plating pre­ treatment and plating in the same manner as in Example 1. The results of evaluation of the plated moulded article are shown in Table 1. EXAMPLE 3 A sample was produced in the same manner as in Example 1, except that the etching treatment after the degreasing treatment was conducted by soaking in a mixed solution of 20 wt% of ammonium hydrogenfluoride, 70 wt% of nitric acid, and 10 wt% of hydrofluoric acid at 40°C for 10 minutes. This sample was plated under the same plating conditions as in Example 1. The results of evaluation of the plated moulded article thus obtained are shown in Table 1. EXAMPLE 4 Plating pre-treatment and plating were performed in the same manner as in Example 3, except that the potassium titanate fibre content was changed to 10 wt% and that the glass fibre content was changed to 40 wt%. The results of evaluation of the plated moulded article thus obtained are shown in Table 1. COMPARATIVE EXAMPLE 1 A plate was produced in the same manner as in Example 2, except that a PPS resin composition containing only 50 wt% of glass fibres was used. This plate was subjected to the same plating pre-treatment and plating in the same manner as in Example 2. The results of evaluation of the plated molded article are shown in Table 1. COMPARATIVE EXAMPLE 2 Using a composition containing 50 wt% of a PPS resin and 50 wt% of glass fibres, the plating was carried out in the same manner as in Example 3. The results of evaluation are shown in Table 1. COMPARATIVE EXAMPLE 3 Using a composition containing 70 wt% of a PPS resin and 30 wt% of potassium titanate fibres, the plating was carried out in the same manner as in Example 3. The results of evaluation are shown in Table 1. COMPARATIVE EXAMPLE 4 The same procedures as in Example 3 were repeated except that the glass fibre content was changed to 20 wt% and that the potassium titanate fibre content was changed to 30 wt%. The results of evaluation are shown in Table 1. COMPARATIVE EXAMPLES 5 AND 6 The same procedures as in Example 3 were repeated except that the potassium titanate fibres were changed to 5 wt% of calcium carbonate (in Comparative Example 5) or 5 wt% of talc (in Comparative Example 6). The results of evaluation are shown in Table 1. *: "A" means the etching treatment with a potassium dichromate/sulphuric acid mixture, and "B" means the etching treatment with an ammonium hydrogen-­ fluoride/nitric acid/hydrofluoric acid mixture. As shown by the Examples in Table 1, incorporation of potassium titanate fibres into a resin composition comprising a PPS resin and glass fibres permits the production of a plated moulded article of the PPS resin composition which is excellent in appearance and peel strength, without causing a serious reduction in the mechanical properties. This plated moulded article is sufficiently satisfactory for practical use. While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.

Claims: 1. A polyphenylene sulphide resin composition comprising from 30 to 70% by weight of a polyphenylene sulphide resin, from 70 to 30% by weight of glass fibres, and from 1 to 10% by weight of potassium titanate fibres. 2. A composition as in claim 1, wherein the polyphenylene sulphide resin contains at least 70 mol% of a repeating unit represented by formula 3. A composition as in claim 1 wherein the polyphenylene sulphide resin contains at least 90 mol% of a repeating unit represented by formula 4. A composition as in claim 1,2 or 3 wherein the potassium titanate fibres have an average fibre diameter of not more than 1 micron, an average fibre length of from 5 to 100 microns, and an aspect ratio of at least than 10.

Inventors: EMURA, NORIAKI, OGAWARA, KENSUKE, SATO, MASATOSHI
Applicants: HODOGAYA CHEMICAL CO., LTD., TOSOH CORPORATION
Application year: 1986
Main classification: C08L81
IPC codes: C08K7, H05K1, C08L81