GB2164046A

GB2164046A - Resin compositions for electroplating

Info

Publication number: GB2164046A
Application number: GB08518977A
Authority: GB
Inventors: Kihachiro Nishiuchi; Kenichi Wada; Masayoshi Suzue; Minoru Takenaka; Yukiya Hareyama
Original assignee: Otsuka Chemical Co Ltd
Current assignee: Otsuka Chemical Co Ltd
Priority date: 1984-07-30
Filing date: 1985-07-26
Publication date: 1986-03-12
Also published as: DE3527131A1; JPS6137991A; GB8518977D0; JPH0635675B2; FR2568260A1; FR2568260B1

Abstract

A resin composition for electroplating capable of giving moldings having smooth surface, good durability in a heating/cooling cycle and a high dimensional stability comprises a thermoplastic resin and a conductive alkali metal titanate.

Description

SPECIFICATION Resin compositions for electroplating The present invention relates to a resin composition for electroplating, more particularly, a resin composition for electroplating which is applicable, for example, to electrical machinery and apparatus, automobile and the like.

Recently, research and development on plastic materials as substitutes for various metallic products are enthusiastically carried out. Especially in the field of electrical or electronic machinery and apparatus or of automobiles, many plastic materials have been developed in response to the needs for lightness, thinness, shortness and smallness, However, those plastic materials still have many defects in respect of chemical resistance, heat resistance, weather resistance, etc. Therefore, there are many instances where these plastic materials are used after offsetting such defects by applying metallic coating on their surface.

The methods of applying metallic coating on the surface of plastic products can be broadly advided into the wet method and the dry method. Between the two methods, the dry method has made a great progress recently. There are well known dry methods such as the chemical vapour deposition method (CVD), the physical vapour deposition method (PVD), the ionic plating method, etc. All these dry methods, however, are of batch production system and necessitate expensive machinery and apparatus. Thus, the dry method is still not so developed as the wet method.

The wet method is a metallic coating method by the so-called metal plating. Usual plastic materials hitherto known are per se electrical insulators and accordingly exhibit no electric conduction. Therefore, non-electrolytic plating is popular for such plastic materials. However, non-electrolytic plating of plastic materials involved many problems such as a high cost for the treatment, an insufficient adherence to the plastic materials, and the like. Then, by giving electric conductivity to plastic materials by kneading them together with conductive substances and electrically plating the resulting conductive plastic materials, the existing defects have been improved greatly. As said conductive substances, conductive carbon black, conductive carbon fiber, various metal fibers, and the like have been used practically.However, there exist still various defects in these known conductive plastic materials. Conductive plastic materials suitable for plating are requested in general to have the following characteristic properties: 1 a high conductivity of 5 x 101flcm or more, 2 smooth surface of moldings prepared from the resin composition, 3 a good durability or endurance in a heating/cooling cycle, and 4 a high dimensional stability of moldings prepared from the resin composition.

Compositions to which electric conductivity is given by conductive carbon black satisfy the above condition 1. However, they are not always best with respect to the conditions 3 and 4, because physical properties of plastics are largely lowered by filling them with a large amount of said carbon black.

Compositions to which electric conductivity is given by conductive carbon fiber satisfy the condition 1 to some extent and offer no problem with respect to the conditions 3 and 4, as they are filled with a large amount of said carbon fiber. However, they are insufficient in respect of the condition 2, and moreover they are requested to be filled with an extremely large amount of said carbon fiber, in order to satisfy the condition 1 Therefore, the use of such compositions containing a large amount of expensive carbon fiber is extremely limited from economical point.

Compositions to which electric conductivity is given by metal fibers also satisfythe conditions 1,3 and 4 to some extent, as they are filled with a large amount of said metal fibers. However, they are very inferior in respect of the condition 2, and moreover the characteristic property of plastics of being freely molded or shaped is lost by filling with a large amount of metal fibers. Thus, they are nowadays scarcely used in practice.

The purpose of the present invention resides in providing resin compositions for electroplating, which have a high conductivity and are capable of giving moldings having smooth surface, good durability in a heating/cooling cycle and a high dimensional stability.

Thus, the present invention relates to a resin composition for electroplating which comprises a thermoplastic resin and a conductive alkali metal titanate and is highly conductive having a specific volume resistivity of 5 x 1 0cm or less.

The characteristic feature of the present invention resides in employing a conductive alkali metal titanate as the conductive substance in a resin composition for electroplating. The conductive alkali metal titanate according to the present invention denotes the followings: 1) A conductive alkali metal titanate (I) which is represented by the general formu a M2O.aTiOx.bH2O (wherein M is an alkali metal such as Li, Na, K, etc. and a, band x are each a real number of O < a < 8,0 ~ b ~ 4 and 0 < 'x < 2, respectively) and is generally called "reductive alkali metal titanate" or "bronze alkali metal titanate";; 2) A conductive alkali metal titanate (Il) which is represented by the general formula M2O.aTiOy.bH2O (wherein M, a and b have the same meanings as described above and 0 < y - 2) and comprises an alkali metal titanate and a hetero metal compound sticked or solid dissolved on its surface; 3) A conductive alkali metal titanate (Ill) which is obtained by further reducing the conductive alkali metal titanate (ill); or The like; or A mixture of two or more of these various conductive alkali metal titanates.

The above conductive alkali metal titanates used according to the present invention are differentiated from alkali metal titanates (IV) which are represented by the general formula M20.aTi02.bH2O (wherein M, a and b have the same meanings as described above).

Alkali metal titanates (IV) are obtained generally as fibrous single crystal and are excellent as heat-resisting and reinforcing filler. However, they are electrical insulator and any conductive composition cannot be obtained from an alkali metal titanate (IV) only.

As regards the conductive alkali metal titanates used according to the present invention, the inventors of the present invention have already developed a process for the preparation of conductive alkali metal titanates (I) from alkali metal titanates (IV), a process for the preparation of conductive alkali metal titanates (Il) from alkali metal titanates (IV) or conductive alkali metal titanates (I) and a process for the preparation of conductive alkali metal titanates (Ill) from conductive alkali metal titanates (II), and filed patent applications concerning each process. However, the conductive alkali metal titanates of the present invention shall never be limited to those described in the specifications of such patent applications.

The conductive alkali metal titanates used in the present invention are conductive materials having excellent reinforcing property and heat-resisting property.

Hereinafter, a process for the preparation of conductive alkali metal titanates (I) is illustrated.

Conductive alkali metal titanates (l) are obtained by a process wherein an alkali metal titanate (IV) is heated in a reductive gaseous atmosphere, or in a non-oxidative atmosphere in the presence of a reducing agent such as a carbonaceous substance or the like, at a temperature of 500"C or higher, or also by maintaining, on preparing an alkali metal titanate (IV), the alkali metal titanate (IV) directly in a reductive atmosphere or in a non-oxidative atmosphere in the presence of a reducing agent.An alkali metal titanate of the general formula M2O.aTiOx.bH20 wherein M is potassium and a, b and x have the same meanings as described above, i.e. a reductive potassium titanate, changes its colortintfrom white purple, purple, black, black purple, gold to silberwhite, as x changes. As the conductive alkali metal titanates of the present invention, however, those reductive potassium titanates which are reduced up to a tint of pale purple-blackorfurther, or wherein x ' 1.99, preferably x < 1.95, are preferred from the view-point of conductivity.

The conductive alkali metal titanate of the present invention includes each of conductive alkali metal titanates (I), (Il) and (Ill), a mixture of two or more of them, and also all of reinforcing or non-reinforcing conductive alkali metal titanates. However, it is preferred from the view-point of practical use that they are fine fibrous ones. Usually, those having a fiber diameter of 0.1-1 and an aspect ratio of 10 or more but below 1000 are preferably because they give a good surface smoothness along with a good reinforcing effect.

Conductivity of these conductive alkali metal titanates is selected in accordance with the purpose of use. The conductivity of the conductive alkali metal titanates in the present invention is preferably a volume resistivity of 10 -10Qcm.

The thermoplastic resin in the present invention means a thermoplastic resin which is capable of substituting for metal as it is incorporated with a fibrous filler, i.e. the so-called engineering plastics.

Although fiber-reinforced resin compositions for general use, such as fiber-reinforced polypropylene, fiber-reinforced ABS resin, etc. are called engineering plastics and included in the thermoplastic resin of the present invention, there can be mentioned further polyacetal, polycarbonate, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide, polyphenylene oxide, polyamide, etc., as the thermoplastic resin. Further, polyimide, polyamide imide, bismaleimide triazine resin, polyallylate, etc., which are called super-engineering plastics, may also be employed as the thermoplastic resin.

The resin composition of the present invention which comprises the above thermoplastic resin incorporated with the above conductive alkali metal titanate is merely requested to have a specific volume resistivity of 5 x 101 flcm or less. The amount of the conductive alkali metal titanate incorporated with the thermoplastic resin may vary to some extent, depending on the sort of the thermoplastic resin. However, the conductive alkali metal titanate is incorporated in an amout of usually 20 - 50 % by weight, preferably 30 - 40 % by weight. When the conductive alkali metal titanate is incorporated in an amount of less than 20 % by weight, a conductivity necessary for electroplating cannot be obtained.When the amount of the conductive alkali metal titanate incorporated exceeds 50 % by weight, problems arise in the workability, the molding property and also the appearance of the products. Thus, incorporation of the conductive alkali metal titanate in -an amount of less than 20 % by weight or more than 50 % by weight does not meet the purpose of the present invention.

According to the present invention, any other inorganic filler such as glass fiber, carbon fiber, asbestos, carbon black, etc. may further be incorporated within the range of not lowering the adherence, the appearance and other properties.

The compositions of the present invention are obtained by incorporating a conductive alkali metal titanate with a thermoplastic resin and any publicly known method using extruder, mixing roll, kneader or the like can be employed for the incorporation. Among the known methods, however, the most suitable method is that by means of a biaxial kneading extruder. The resin compositions for electroplating of the present invention thus obtained are molded or shaped into moldings of the desired shape, by a conventional molding method such as injection molding, compression molding, extrusion molding or the like.

For application of electroplating to the corresponding moldings, any publicly known method can be employed without necessitating any special apparatus or chemicals.

The present invention is further explained concretely by giving Examples. However, the invention shall never be limited to these Examples. By the way, "part" and "%" appearing in the Examples mean "part by weight" and "% by weight", respectively, unless special notice is made.

Example 1 A resin composition for electroplating of the present invention was prepared by kneading conductive potassium titanate (I) fibers having a volume resistivity of 1 02flcm (fiber diameter: 0.2 - 0.5 > m, fiber length: 10 - 15Am, a product of Otsuka Chemical Co., Ltd. having a trade name "TISMO BK-300") together with a thermoplastic resin shown in Table 1 by means of a biaxial kneader (45). Dumbbell specinens were prepared from the resin composition thus obtained, by means of an injection molder having a power of 150 tons, and various mechanical properties and thermal properties were measured.On the other hand, test samples for determining electrical properties were prepared by supplying the same resin composition to a press, and electrical properties were measured according to the following process. Namely, sheet-shaped test samples having a thickness of 6mm, a width of 2.0cm and a length of 10.0cm were prepared by press molding using a molding box set on a teflon sheet. The thickness was measured by a micrometer having an accuracy of 0.01 mm. On both terminal sections of the test sample silver foils were adhered by pressing, silver electrodes were adhered to the surface of the silver foils, and the interval between the two electrodes was set at 10.0cm.Electric resistance between the two electrodes was measured by means of digital multimeter TR-6841 (from Takeda Riken Limited), and the volume resistivity was calculated according to the following equation: Thickness of sheet x Length of electrode x Electric resista Volume resistivity = Interval between electrodes Under the above conditions for measurement, the length of electrode and the interval between electrodes were 2.0 cm and 10.0cm respectively.

In the Table, PP, ABS, POM and PBT denote polypropylene, acrylonitrile/butadiene/styrene copolymer, polyoxymethylene (including modifications) and polybutylene terephthalate, respectively. More specifically, as PP, ABS, POM and PBT, there were used Noblen H50 (Sumitomo Chemical Co. Ltd. Japan), Stylac XA 980 (Asahi Chemical Industry Co., Ltd. Japan), Deuracon N25 (Polyplastic Co. Ltd. Japan) and PBT-1401 (Toray Industries, Inc. Japan) respectively.Izod impact values were measured using notch, and thermal deformation temperatures were measured under such load as giving a bending stress of 18.5 kg/cm2. TABLE 1 Test method Unit PP ABS POM PBT Content of conductive Ash measurement % 35 35 30 30 TISMO Specific gravity JISK-7112 1.35 1.40 1.58 1.61 Molding contraction - % 1.0 0.2 1.0 0.5 Tensile strength JISK-7113 kg/cm2 450 400 930 1,100 Bending strength JISK-7203 kg/cm2 750 710 1,620 1,840 Bending elasticity JISK-7203 kg/cm2 51,000 50,000 63,000 96,000 Izod impact value JISK-7110 kg.cm/cm 9.0 7.0 4.5 4.5 Rockwell hardness JISK-7202 - R90 R105 R120 R119 Thermal deformation temperature JISK-7207 C 90 92 150 207 Coefficient of linear Flexible gauge expansion method 10-5cm/cm/ C 3.0 2.0 4.5 2.7 Specific volume resistivity ASTM D-257 ##cm 30.0 25.0 2.0 10.0 Conditions Molding temperature C 220-240 220-240 190-220 230-250 for injection molding Metal mold temperature C 50-60 50-60 60-80 60-80 Injection pressure kg/cm2 700-1,000 700-1,000 700-1,000 700-1,000 Injection velocity m/min low- lowmiddle middle 1.5 1.5 Time cycle second 30-40 30-40 30-50 30-40 Example 2 The resin compositions for electroplating obtained in Example 1 were molded into rectangular test pieces having a thickness of 3 mm, a length of 65 mm and a width of 50 mm, using an injection molding machine of screw-in-line type, at a molding temperature of 190 - 250 "C, and electroplating was applied to the test pieces according to an ordinary method. Namely, the test pieces were degreased with alkali according to an ordinary method at 50 C for 3 minutes, and then washed with water at normal temperature.The neutral test pieces so obtained were subjected to Ni-Co strike plating (pH 4.2, liquid temperature 50 - 60 C,1V minute, 2V 3 - 6 minutes, 3A/dm2 3 - 5 minutes) to form a plating of about 3 p.m thickness thereon, and then treated by a plating process similar to the general ABS plating process (copper sulfate plating - gloss nickei plating - chromium plating) to obtain the final products. The four sorts of molded test pieces obtained were moldings provided with very smooth plating, in external appearance.

Evaluation of plating on a molding was effected according to the following methods, and the results obtained are shown in the following Table 2: 1) Hardness of the surface of plating layer; Hardness of the surface of plating layer was measured by means of Microhickers' hardness tester under a load of 20 g.

2) Gloss of the surface of plating layer; Gloss of the surface of plating layer was measured by means of a variable-angle photoelectric glossmeter (made by Tokyo Photoelectric Limited, TC-105) at an angle of incidence or reception of 20 C, and indicated by the refiection factor (%) against the surface mirror.

3) Abrasion test; For the determination of resistance against abrasion of a plating layer, an abrasion tester according to ASTM-D1242A method (JISK-7205) was used and the ratio of chipped (abraded) plating layer was measured.

4) Tensile strength of the adhesion; For the determination of bonding strength between a plating layer and the substrate material, the plating layer of a test piece was adhered to a clamp of the tester with an epoxy resin adhesives and the tensile stress (tensile strength of the adhesion) as the peeling was caused by a tensile stress right-angled to the plating layer was measured.

5) Thermal cycle test; For the test of peeling conditions by shearing caused by the difference in thermal expansion between a plating layer and the substrate material, a heating/cooling thermal cycle test of 80 C x 120 min - room temperature x 30 min - 20"C x 60 min - room temperature x 30 min was effected for 5 cycles for each plated product, and occurrence of abnormality in the plating layer of the test piece was observed.

TABLE 2 Item oftest PP ABS POM PBT Hardness 250 250 250 250 Gloss (%) 95 90 95 95 Abrasion (%) 80 80 85 80 Tensile strength 130 130 150 145 of adhesion (kg/cm2) Thermal cycle test noab- noab- noab- noab- normality normality normality normality The resin compositions for electroplating of the present invention have the following excellent characteristics: 1. Electric conductivity of the compositions of the present invention is very stable, and so the control of the plating bath is very easy.

2. The surface of moldings prepared from the oompositions of the present invention is very smooth, and so it is easy to gloss the plating layer.

3. The compositions of the present invention have excellent physical and mechanical properties, and so the plated products have also good properties and are excellent in adhesiveness and durability.

4. Accordingly, they are useful in a wide range of use to prepare plated plastics products.

Claims

1. - A resin composition for electroplating which comprises a thermoplastic resin and a conductive alkali metal titanate and is highly conductive having a specific volume resistivity of 5 x 101 flcm or less.

2. A resin composition as claimed in claim 1, wherein the specific volume resistivity is 2.0 - 30 flcm.

3. A resin composition as claimed in claim 1, wherein the conductive alkali metal titanate has a specific volume resistivity of 10-1 flcm or less.

4. A resin composition as claimed in claim 3, wherein the conductive alkali metal titanate has a specific volume resistivity of 10- - 10-2 flcm.

5. A resin composition as claimed in claim 1, wherein the conductive alkali metal titanate is contained in an amount of 20 - 50 % by weight.

6. A resin composition as claimed in claim 5, wherein the conductive alkali metal titanate is contained in an amount of 30 - 40 % by weight.

7. A resin composition as claimed in claim 1'wherein the conductive alkali metal titanate has an aspect ratio of 10 or more.

8. A resin composition as claimed in claim 1, wherein the conductive alkali metal titanate is a conductive alkali metal titanate (I) which is represented by the general formula M2O.aTiOx.bH2O (wherein M is an- alkali metal such as Li, Na, K, etc, and a, b and x are each a real number of 0 < a#8,0#b#4 and 0 < x < 2, respectively); and is generally called "reductive alkali metal titanate" or "bronze alkali metal titanate"; a conductive alkali metal titanate (II) which is represented by the general formula M2O.aTioy.bH2O (wherein M, a and b have the same meanings as described above and 0 < y# 2) and comprises an alkali metal titanate and a hetero metal compound sticked or solid dissolved on its surface; a conductive alkali metal titanate (III) which is obtained by further reducing the conductive alkali metal titanate (II); or a mixture thereof.

9. A resin composition as claimed in claim 1, wherein the thermoplastic resin is a thermoplastic resin which is capable of substituting for metal as it is incorporated with a fibrous filler.

10. A resin composition as claimed in claim 1, wherein the thermoplastic resin is polypropylene, acrylonitrile/butadiene/stryrene copolymer, polyoxymethylene or polybutylene terephalate.

11. Resin compositions according to Claim 1, substantially as hereinbefore described and exemplified.