JPH0142295B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a polyacetal resin molded article having novel surface properties particularly suitable for surface decoration by printing, painting, metal vapor deposition, etc., adhesion with adhesives, surface coating such as metal plating, etc. In general, plastics, especially polyacetal resins, are chemically stable and the surface of molded products made by injection molding etc. is smooth, so they have poor surface activity, and can be used for surface decoration by printing, painting, vapor deposition, adhesion with adhesives, metal plating, etc. surface coating is difficult to apply. Several attempts have been made to improve the surface coverage of these materials. For example, there is a method of treating the surface of the molded product with phosphoric acid, a method of treating it with chromium sulfuric acid, etc.
No. 19876, etc.). However, the surface properties of polyacetal resin molded products obtained by implementing these treatment methods also
It cannot be said that it is sufficiently suitable for the above-mentioned surface decoration and surface coating, and, for example, it has not been possible to provide a metal-plated product with a beautiful appearance and high plating peel strength. Later, as an improved invention of the above-mentioned U.S. Patent No. 3,554,880, a method was discovered in which the surface of the molded product was immersed in an aqueous solution of Picgin, quinoline, γ-butyrolactone, etc. before being treated with phosphoric acid for the purpose of more uniform surface roughening. (U.S. Pat. No. 3,905,877,
No. 3963590). However, when surface roughening a polyacetal resin molded product, for example, by metal plating, it is still not possible to industrially easily achieve a surface roughness that is sufficient and uniform for practical use using the above-mentioned conventional techniques. Non-uniform roughening phenomenon is observed in each part of the product, which is thought to be mainly caused by variations in wall thickness. This uneven roughening phenomenon is an undesirable phenomenon, such as causing "blisters" in areas where roughening is insufficient, for example, in cold-heat cycle tests of plated products. Therefore, in order to obtain a good plated product, there is a need for a method that can further improve the level of plating adhesion and its uniformity, and that can be easily implemented industrially. The present inventors have discovered a method that is simpler than the method disclosed in U.S. Pat. No. 3,905,877 and U.S. Pat.
As a result of intensive research in order to solve the above problems with a method that can be easily implemented industrially from the viewpoint of toxicity, the method shown below was invented. That is, the present invention provides (a) polyacetal resin
100 parts by weight, (b) 2 to 35 parts by weight of carbonates, phosphates, acetates or mixtures thereof of metals of Group Group of the Periodic Table, and (c) unsaturated polyesters, alkyl esters of acrylic acid or methacrylic acid. , amides of acrylic acid or methacrylic acid, triallyl cyanurate, diallyl phthalate, vinyl acetate and divinylbenzene, polymers, copolymers or mixtures thereof0.01
A polyacetal resin composition consisting of ~20 parts by weight is molded into a predetermined shape, and then, before surface roughening with an acidic aqueous solution, it is molded within a range of conditions that satisfy the following formulas (1) and (2). Improved surface treatment method for polyacetal resin compositions consisting of immersion in hot water Formula (1) x≦90, y≦60 Formula (2) logy≧−1/19x+74/19 where x is the temperature of the hot water (℃ ) y relates to the immersion time in warm water (minutes). In the present invention, the purpose of incorporating various salts of group metals in the periodic table into the polyacetal resin is to easily form a roughened surface suitable for surface processing. In other words, when various salts of Group Group metals of the periodic table are dispersed and dotted in the polyacetal continuous phase, they are easily decomposed and removed by an appropriate acid, leaving traces of the roughening on the surface. In various salts of group metals of the periodic table used in the present invention,
Examples of preferred carbonates include calcium carbonate,
Examples include magnesium carbonate, zinc carbonate, barium carbonate, and calcium carbonate is particularly preferred. Further, the content of the above-mentioned various salts is preferably 2 to 35 parts by weight based on 100 parts by weight of the polyacetal resin, taking into consideration the balance between the effect of improving the roughening properties and the decrease in mechanical properties and thermal stability. In the present invention, the above-mentioned polyester such as unsaturated polyester
The purpose of containing component (c) is to improve the thermal stability of the resin composition and to prevent cracking during surface roughening. Its content is determined by the balance between the desired effect and the mechanical strength of the resin.
The amount is preferably 0.01 to 20 parts by weight per 100 parts by weight. The polyacetal resin used in the present invention may be a homopolymer, that is, a polymer obtained by polymerizing formaldehyde or trioxane (including those whose terminals have been stabilized), or a polymer obtained by polymerizing formaldehyde or trioxane, or a polymer obtained by polymerizing trioxane and a cyclic ether, a cyclic It may be a binary, ternary or more copolymer obtained by copolymerizing comonomers such as acetal. The composition of the present invention includes various additives normally added to polyacetal resins, such as heat stabilizers, antioxidants, ultraviolet absorbers, antistatic agents, crystal nucleating agents,
There is no problem even if pigments are added. In order to obtain the composition of the present invention, it is preferable to mix the constituent components using a device, such as a kneader, roll mill, or extruder, which is normally used for kneading resin melts. An extruder is most preferable from the viewpoint of blocking oxygen and working environment. The mixing temperature is above the melting point of the polyacetal resin used. This is determined by the need to uniformly mix the polyacetal resin in its molten state. The upper temperature limit is generally limited by the thermal decomposition stability of the polyacetal resin used;
Mixing is usually carried out at a temperature below 250°C, preferably below 230°C. Further, a polymerization initiator may be added to the composition. A polymer such as an unsaturated polyester for thermal stability and crack prevention may be mixed as a polymer as it is, or may be added in the form of a monomer or prepolymer and polymerized in an extruder. In the case of thermosetting polymers, the latter is preferred. In addition, it is preferable to pre-mix each component using a tumbler or Henschel mixer in order to make a homogeneous composition, and it is preferable to use the polyacetal resin in a powdered state for stable supply to the extruder. Although preferred, these are not required. In addition, in the case of the method of adding the above-mentioned monomer or prepolymer, it is preferable to maintain a temperature at which a polymerization reaction does not occur during premixing. In the case of the above method of adding monomers or prepolymers, the heating conditions for polymerizing them depend on the type of monomer or prepolymer, but for example, 190°C x 1 to 10 minutes is required. It is.
This condition can be achieved in most cases by a combination of temperature and time (determined by extrusion speed) commonly used when mixing polyacetal resin compositions using conventional extruders; However, the present invention does not impose any limitations on the heating method itself. There are various ways to confirm that the polymerization of the added monomer or prepolymer is completed by the above heating and that no unreacted materials remain. There are methods for checking by odor, and further checking by immersing pellets in a solvent and checking whether unreacted substances are extracted using infrared spectrophotometry. The polyacetal resin composition of the present invention produced by the above method is usually molded into a molded product using an injection molding machine, and the molded product is further roughened with a suitable acid. In this way, a polyacetal resin molded product with excellent surface workability can be obtained. In the present invention, it has been discovered that by immersing the molded product in hot water at a predetermined temperature for a predetermined period of time before roughening treatment with an acid, the roughening state of each part of the molded product becomes uniform. The hot water immersion conditions that satisfy the effects of the present invention are within a range that satisfies the following equations (1) and (2). Equation (1) x≦90, y≦60 Equation (2) logy≧−1/19x+74/19 Here, x is the temperature of hot water (℃) y is the immersion time in hot water (minutes) Above (1), ( Area A in Figure 2 is a graph that shows the range that satisfies formula 2). In Figure 2,
The reason for excluding areas B, C, and D is as follows. B: The conditions are too weak and the desired effect of the present invention cannot be obtained. C: It is necessary to considerably lengthen the immersion time, which is not preferable from an industrial point of view. D: Due to the high temperature, the liquid evaporates rapidly, making it difficult to manage the liquid, which is not desirable from an industrial perspective. When selecting specific immersion conditions within the range that satisfies Equations (1) and (2), it is necessary to take into account the shape of the molded product and the mold temperature during molding. In other words, in terms of the shape of the polyacetal molded product shown in FIG. 1, the larger the t/T and the lower the mold temperature, the higher the immersion conditions need to be at a higher temperature and for a longer time. Some examples are shown in the Examples. As described above, the object of the present invention can be achieved by immersing the molded article in hot water under predetermined conditions before etching. The principle of its operation is that the A part of the molded product is relatively difficult to etch (see Figure 1).
It is presumed that one of the reasons is that hydrogen ions in the etching solution can easily approach the upper part of the rib due to the presence of water. As a result of studying embodiments of the present invention with the aim of creating even more rational industrial processes, the present inventors found that
It has been confirmed that the effects of the present invention are not impaired at all even when various chemicals are added to hot water. Some of these chemicals include acids and alkalis such as sulfuric acid, phosphoric acid, hydrochloric acid, acetic acid, caustic soda, caustic potash, and ammonium hydroxide (however, these are preferably used at low concentrations that do not etch the surface of the molded product). , salts such as sodium phosphate and sodium carbonate, surfactants, and plastic degreasers. Therefore, in the case of an actual industrial process, it is preferable not to make the hot water immersion process an independent process, but to combine it with processes such as dilute acid treatment and degreasing. Next, the molded article subjected to the above treatment is etched with acid. Suitable acids for use in etching the polyacetal resin composition of the present invention include any acidic or oxidizing liquid that can decompose the various salts of Group Group metals of the periodic table blended as described above. However, acidic or oxidizing liquids with low volatility, such as sulfuric acid aqueous solution, sulfuric acid-phosphoric acid mixed aqueous solution, sulfuric acid-chromic acid mixed aqueous solution, phosphoric acid aqueous solution, etc. are preferred from the viewpoint of workability. . The thus etched polyacetal resin molded product with excellent surface workability has a peel strength (Kg/cm) of the plating layer of 1 when plated with metal.
Kg/cm or more, usually 1.5 to 2.5 Kg/cm, and has a uniform adhesion force on each part of the molded product (meaning that it does not blister locally in a cold/heat cycle test), and is coated with paint other than metal plating or adhesive. It also showed surprising effects in terms of adhesion, demonstrating how useful the polyacetal resin composition of the present invention is. The present invention will be explained in more detail below with reference to Examples. Examples 1-2, Comparative Examples 1-2 "Tenatsuku 5010" as polyacetal resin
(Manufactured by Asahi Kasei Corporation, acetal homopolymer,
General purpose grade) 100 parts by weight, 8.7 parts by weight of fine powder calcium carbonate (Whiten SSB Red, manufactured by Shiraishi Calcium Co., Ltd., average particle size 1.25 microns) and 0.87 parts by weight of unsaturated polyester (manufactured by Nippon U-Pica Co., Ltd., U-Pica 5834P) Parts by weight were mixed in a tumbler and then kneaded in an extruder set at 190°C to form pellets. Using this pellet, a test piece having the shape shown in Figure 1 (T = 4 mm, t = 4 mm) was made by injection molding.
mm) was molded (mold surface temperature 115°C) and used as a test material. After immersing this test material in hot water under each condition listed in Table 1, it was immersed in a solution consisting of 96% sulfuric acid/85% phosphoric acid/water = 40/25/35 (parts by weight) at 40°C for a specified period of time (see Table 1). and (see notes)) and etching was performed by immersion. Next, the etched plate was plated using a conventional method. In other words, as is generally done, after catalyst addition and activation, chemical nickel plating is carried out.
Bright copper sulfate plating (40μ) was quickly applied. The performance of the plated product is shown in Table 1. The method for measuring the performance of plated products is as follows. Peeling strength of plated products: Make parallel cuts of 10 mm width on the plated surface, pull the plated film between the cuts in a direction perpendicular to the flat plate surface, and calculate the stress required for peeling. A and B in Table 1 are A in Figure 1.
(upper part of the rib, thick part) and B (upper part other than the rib, thin part) (the same applies to the tables below).

[Table] Examples 3 to 4 Test materials similar to Examples 1 to 2 (only the test piece shape is different as shown in Table 2. Mold temperature is 115°C)
After immersion in hot water under the conditions listed in Table 2, electroplating was carried out in the same manner as in Examples 1 and 2. The performance of the plated product is shown in Table 2.

[Table] Examples 5 to 8 Test materials similar to Example 3 (only the mold temperature was
After immersion in hot water under the conditions listed in Table 3, electroplating was performed in the same manner as in Example 3. Table 3 shows the performance of the plated products.

[Table] Examples 9 to 13 Using the same test materials as in Examples 1 to 2, they were immersed in hot water containing the substances shown in Table 4 at 65°C for 10 minutes. Thereafter, electroplating was performed under the same conditions as in Examples 1 and 2. Table 4 shows the performance of the plated products.

[Table] Examples 14 to 29 The same experiments as in Example 1 were carried out using pellets prepared by kneading the substances shown in Tables 5 and 6 in place of the calcium carbonate or unsaturated polyester in Example 1. The performance of the plated product is shown in Tables 5 and 6.

【table】

[Table] Examples 30 to 31, Comparative Example 3 An experiment similar to Example 1 was conducted using an oxymethylene copolymer (melt index 9
g/10 minutes, 190°C), and the amount of calcium carbonate was changed as shown in Table 7. The hot water immersion was at 65°C for 10 minutes, and the etching was at 40°C for 10 minutes. The results are shown in Table 7.

【table】 [Brief explanation of drawings]

FIG. 1 is a perspective view schematically showing the shape of a polyacetal molded product used in Examples. FIG. 2 is a diagram showing the range of conditions for hot water immersion in the present invention.

Claims (1)

[Scope of Claims] 1 (a) 100 parts by weight of a polyacetal resin, (b) 2 to 35 parts by weight of a carbonate, phosphate, acetate or a mixture thereof of a group metal of the periodic table, and (c) Polymers, copolymers or mixtures thereof of compounds selected from the group of saturated polyesters, alkyl esters of acrylic acid or methacrylic acid, amides of acrylic acid or methacrylic acid, triallyl cyanurate, diallyl phthalate, vinyl acetate and divinylbenzene. A polyacetal resin composition consisting of 0.01 to 20 parts by weight is molded into a predetermined shape, and then, before surface roughening with an acidic aqueous solution, the following conditions are satisfied: (1) and (2). An improved method for surface treatment of polyacetal resin compositions comprising immersion in hot water at (℃) y is the immersion time in warm water (minutes).