JPH0132854B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for surface treatment of plastics,
More specifically, the present invention relates to a surface treatment method for polyacetal resin. Polyacetal resin has excellent mechanical properties, particularly extremely excellent wear resistance and fatigue resistance, and has been widely used as a functional resin. In other words, in recent years, the uses of plastics have been expanding in various fields, and along with the tendency to emphasize weight reduction and decorativeness, the use of plastics, which are lighter and easier to process than metals, has expanded. be. Particularly in the automobile industry, weight reduction is being promoted as a measure to reduce fuel consumption, and metals are being replaced with plastics. Polyacetal resins have also been used in place of metals in various fields. The surface of this polyacetal resin molded product is extremely smooth and has excellent surface gloss, and there seems to be no particular problem with the aesthetic appearance.
Like other plastics, it can be touched to varying degrees and exposed to light, heat, and wind and rain.
This results in a decrease in surface gloss, discoloration, and deterioration of physical properties, making it unable to match the excellent durability of metal. In the past, polyacetal resin was often used as functional parts, especially inside devices, and there were no major problems such as weather resistance or discoloration, but in recent years polyacetal resin has been used not only inside devices, but also in external parts and exterior Furthermore, the use of products for outdoor use is being considered, and weather resistance and durability are becoming serious issues.Furthermore, there is also the issue of human taste, so printing and painting of complex decorative patterns, Metal coating etc. are increasingly required. However, since polyacetal resin itself has a smooth surface and excellent solvent resistance, it cannot be printed, painted, or coated with metal by plating in its original state. For this reason, several attempts have been made to roughen the surface of polyacetal resin by some method and then apply painting, printing, or metal plating to the surface. For example, there is a method of roughening the surface of polyacetal resin with acid or oxide (Japanese Patent Publication No. 47-19876), in order to reduce the amorphous portion on the surface of polyacetal resin molded products and make it easier to roughen the surface with acid. There is a method of molding using a high mold temperature (Japanese Patent Application Laid-Open No. 54-83066). These methods focus on directly roughening the polyacetal resin, but this is not easy with polyacetal resins that have poor surface activity, and if the surface is roughened to a level sufficient for printing or plating, the entire resin will be roughened. The deterioration of the material has become so severe that it cannot be put to practical use at all. On the other hand, as a new surface treatment method for polyacetal resin, metal carbonates or carbonates, phosphates, and acetates of group metals in the periodic table are blended with polyacetal resin, and then the metal salts are dissolved and extracted with acid. Therefore, attempts have been made to roughen the surface of polyacetal resin compositions (Japanese Unexamined Patent Application Publication No. 1983-1999).
78023, 56−28237). However, this method has the disadvantage that unless a certain amount of metal salt is mixed in, an etched surface with an anchoring effect cannot be obtained, and if a large amount of metal salt is mixed in, discoloration occurs during extrusion manufacturing or molding. The present inventors conducted intensive research to obtain a polyacetal resin composition that can be easily surface-roughened without impairing the excellent properties of polyacetal resin. The surface of a resin composition containing one or more metal hydroxides selected from the group consisting of magnesium oxide and aluminum hydroxide can be easily roughened by contacting with an acid aqueous solution. Heading, we arrived at the present invention. That is, the present invention uses 97 to 80 parts by weight of a polyacetal resin and an average particle diameter of 0.01 to 30μ, preferably 0.1 to 30μ.
A resin composition containing 3 to 20 parts by weight of one or more metal hydroxides selected from the group consisting of calcium hydroxide, magnesium hydroxide, and aluminum hydroxide in the form of fine powder in the range of 10μ. This is a surface treatment method for polyacetal resin, which is characterized by bringing the polyacetal resin into contact with an acid aqueous solution by means such as dipping or coating. If the metal hydroxide is less than 3 parts by weight, it will be difficult to obtain an etched surface with excellent anchoring effect, and if it is more than 20 parts by weight, the surface will become rough and physical properties will deteriorate due to excessive etching, so the mixing ratio is as follows:
Must be well managed. In addition, if the average particle size of the metal hydroxide is larger than 30μ, the surface after painting or plating will be difficult to become a so-called mirror surface, and the adhesion will be insufficient. In order to obtain this, it is more preferable that the average particle diameter is 10 μm or less. On the other hand, ultrafine powder with an average particle diameter of 0.01 or less has an anchoring effect, but is not practical in terms of operability, and when considering ease of blending with resin, dispersibility, anchoring effect, etc. , the average particle size is 0.1μ
The above is more preferable. The polyacetal resin used in the present invention may be either an oxymethylene homopolymer or a copolymer having an oxymethylene group and an oxyethylene group. The method for producing the resin composition used in the present invention is not particularly limited, but may include a kneader, roll mill,
The metal hydroxide can be blended into the resin while the resin is melted using a device such as an extruder. In particular, it is preferable to manufacture using an extruder in terms of operability. The resin composition used in the present invention contains various additives that can be normally added to polyacetal resin, such as
Heat stabilizers, antioxidants, ultraviolet absorbers, antistatic agents, crystal nucleating agents, lubricants, pigments, dyes, etc. may be included within the range that does not impair the effects of the present invention. The acid aqueous solution used in the present invention is preferably a sulfuric acid aqueous solution or a sulfuric acid-phosphoric acid aqueous solution for the purpose of obtaining a rough surface with an excellent anchoring effect, and the acid concentration is preferably 40 to 70% by weight. In the case of a sulfuric acid-phosphoric acid aqueous solution, it is further preferable that the sulfuric acid concentration is 15% by weight or more. An acid aqueous solution with an acid concentration of less than 40% by weight will not sufficiently roughen the surface, and an acid aqueous solution with a concentration higher than 70% by weight will rapidly roughen the surface, resulting in an over-etched state, resulting in a so-called mirror surface. In addition, it is difficult to control surface roughening during operation. A particularly preferred acid concentration is 45-55% by weight. As a method for plating metal on the roughened polyacetal resin molded article obtained by the method of the present invention, a method generally employed for plastic plating can be employed. An extremely common method is shown below.
The roughened molded product is immersed in an activating solution, and then electroless plating is applied to form a thin nickel or copper film, followed by electroplating to coat the desired metal. According to the present invention, a polyacetal resin molded product has the inherent mechanical properties of polyacetal resin such as abrasion resistance and fatigue resistance, and has a rough surface suitable for printing, painting, metal plating, etc. can be obtained. The present invention will be explained in more detail below with reference to Examples and Comparative Examples. There are various methods for evaluating the effect of surface roughening, but here we will use the most common method, which is the adhesive strength (adhesion) between the coated metal film and the base resin, on a coated metal surface with a width of 10 mm. A method was used in which the strength (peel strength in kg/cm) that occurs when peeled off at a right angle to the base material was used. It is said that a peel strength of 1.0 Kg/cm or more is sufficient for practical use. Another problem with metal-plated resins is that because the thermal expansion coefficients of the resin and metal are different, rapid temperature changes can cause blisters and cracks. Therefore, thermal cycle tests are conducted between high and low temperatures. It is common practice to do so. The temperature conditions for the thermal cycle test vary depending on the base resin, and in the case of ABS resin, which is a typical plastic plating resin, it seems to be carried out between -30℃ and 80℃, but here it is -40℃ A method was adopted in which three cycles of heating and cooling thermal cycle tests were conducted at 110°C for 30 minutes and at 110°C for 30 minutes to observe the occurrence of abnormalities in the sample. In addition, the average particle diameter was measured by a light transmission centrifugal sedimentation method. Examples 1-3 Diuracon M90- as polyacetal resin
02 (Acetal copolymer general grade manufactured by Polyplastics Co., Ltd.) 95 parts by weight and 5 parts by weight of the various metal hydroxides shown in Table 1 were preliminarily mixed in a tumbler, and then mixed in an extruder set at 200°C. The mixture was kneaded and pelletized. After drying this pellet, a test piece (12.5 mm x 125 mm x 3 mm thick) was made using an injection molding machine.
It was created. This test piece was degreased and placed in a 55% by weight sulfuric acid aqueous solution.
It was immersed at 30°C for 15 minutes and etched. Next, the etched test piece was immersed in an activating solution for plastics (catalyst manufactured by Okuno Pharmaceutical Co., Ltd.) and an accelerator for a predetermined period of time, and then subjected to electroless nickel plating (MTP chemical nickel plating liquid manufactured by Okuno Pharmaceutical Co., Ltd.).
It was chemically plated. Furthermore, the chemically plated test piece was subjected to electroplating. The electroplating process uses copper sulfate plating solution (composition: CuSO ₄ 5H ₂ O210
g/, H ₂ SO ₄ 60 g/, HCl 0.012 g/, dextrin 0.01 g/, urea 0.01 g/).
The test was carried out under the conditions of 3.5A and 90 minutes, and after washing with water, it was dried at 100°C for 1 hour to obtain a metal-coated test piece.
Table 1 shows the results of measuring the peel strength of these test pieces.
It was shown to. Examples 4 to 6 Using Tenac 5010 (acetal homopolymer, general grade, manufactured by Asahi Kasei Industries, Ltd.) as the polyacetal resin, the surface was roughened in the same manner as in Examples 1 to 3, electroplated, and peel strength was measured. The results shown in Table 1 were obtained. Comparative Example 1 Using Tenatsuku 5010 (acetal homopolymer manufactured by Asahi Kasei Corporation, general grade), 7 parts of calcium carbonate with an average particle size of 1.0μ was added to 93 parts by weight of the polymer.
After adding parts by weight and preliminarily mixing in a tumbler,
The mixture was kneaded using an extruder and pelletized. This pellet was molded into the same test piece as in the example, and the test piece was mixed with a sulfuric acid-phosphoric acid mixed aqueous solution (composition: 98% sulfuric acid).
720g, 85% phosphoric acid 450g, water 630g) at 40℃, 15
After being immersed for a minute, it was electroplated in the same manner as above and the peel strength was measured.The results are shown in Table 1 as Comparative Example 1. Examples 7-9 Diuracon M90- as polyacetal resin
88 parts by weight of 02 (general grade acetal copolymer manufactured by Polyplastics Co., Ltd.) and 12 parts by weight of various metal hydroxides shown in Table 1 were preliminarily mixed in a tumbler, and then mixed in an extruder set at 200℃. The mixture was kneaded and pelletized. After drying this pellet, test pieces (12.5 mm x 125 mm x 3 mm thick) were made by injection molding.
It was created. Thereafter, the peel strength was measured after metal coating in the same manner as in Examples 1 to 3, and the results are shown in Table 1.

【table】

[Table] Examples 10 to 12 and Comparative Example 2 Figures 1 to 2 were obtained by injection molding using three types of pellets obtained in the same manner as in Examples 1 to 3 except that the average particle size of the metal oxide was changed. A test piece was prepared as shown in . FIG. 1 is a plan view, and FIG. 2 is a sectional view taken along the line A--A in FIG. 1. 1 is a plate-shaped part with a length of 97 mm, a width of 68 mm, and a thickness of 3 mm, and a missing part 2 with a length of 48 mm and a width of 17 mm.
It has cylindrical protruding parts 3 and 4 with an outer diameter of 9 mm, an inner diameter of 3 mm, and a height of 9 mm. After subjecting this test piece to the same etching treatment and chemical plating treatment as in Examples 1 to 3, the following steps were performed:
It was subjected to electroplating under the following conditions. The resulting plated product was subjected to a thermal cycle test to observe the occurrence of abnormalities in the plated layer. The results are shown in Table-2. For comparison, the shape of the test piece was
~2 The test pieces were subjected to the process up to surface roughening in exactly the same manner as in Comparative Example 1, except for those shown in Figure 2.The test pieces were chemically plated and electroplated in the same manner as in Examples 10 to 12, and then subjected to a thermal cycle test. Comparative example 2
It is shown in Table 2. (1) Electrolytic copper plating Liquid composition Copper sulfate sulfate chloride ion brightener (Kotaku manufactured by Daiwa Tokushu Kagaku Kogyo Co., Ltd.) 200g/ 60g/ 40mg/ A-1 0.5cc/ A-2 0.5cc/ Conditions 20℃, 4A/ ^dm2 , 45 minutes (2) Electric nickel plating Liquid composition Nickel sulfate Nickel chloride Boric acid brightener (naphthalene-1,5-sodium disulfonate) Formalin 240g/ 45g/ 30g/ 5g/ 1.5cc/ Conditions 40℃, 4A/dm2, ¹⁰ Minutes (3) Electrochromic plating Liquid composition Chromium trioxide sulfuric acid 250g/2.5g/45℃, 25A/dm ² , 3 minutes

【table】 [Brief explanation of drawings]

FIG. 1 is a plan view showing an example of a test piece for measuring the effects of the present invention, and FIG.
It is an A-line sectional view. In the figure 1... plate-like part, 2... missing part, 3...
Cylindrical protrusion.

Claims (1)

[Claims] 1 97 to 80 parts by weight of polyacetal resin and one or more metals selected from the group consisting of finely powdered calcium hydroxide, magnesium hydroxide, and aluminum hydroxide with an average particle size in the range of 0.01 to 30.0μ. A method for surface treatment of polyacetal resin, which comprises bringing a polyacetal resin composition containing 3 to 20 parts by weight of a hydroxide into contact with an aqueous acid solution.