JPS6124468B2 - - 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 their surface coverage. 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. The present inventors have conducted various studies on surface treatment methods for polyacetal resin molded articles, and have also made intensive research on specifying the surface condition obtained by these methods. It is believed that the surface coverage of not only polyacetal resin molded products but also plastic molded products in general is influenced by the chemical properties of the surface, such as the polar groups, and especially the physical properties, such as the shape of the unevenness and its distribution state. It will be done. Figure 1 shows Tenatsuku 5010 (polyacetal homopolymer manufactured by Asahi Kasei Corporation), 85
This is a micrograph (magnification: 1000) of a polyacetal resin surface treated product by the conventional method, which was immersed in % phosphoric acid (40 minutes at room temperature). Of course, it would be extremely difficult to quantify the chemical properties of such a treated surface, but the shape of the unevenness itself as a physical property can be measured by the size of the unevenness (e.g. width, width, etc.).
depth, diameter, etc.) and its distribution,
Moreover, it is extremely difficult to express it quantitatively. As a result of various studies on how to appropriately quantify the unevenness of these surfaces, rather than using them as numerical values that directly represent the shape, the present inventors first introduced the chemical nickel precipitation amount as a value that represents the roughened surface area. did. This value is determined by the following method. A sample of ASTM D790 tanzak polyacetal resin was injection molded _, subjected to a specified surface roughening treatment, then neutralized, washed with hot water, and air _- dried.
Add water to 20g of 2H ₂ O and 200ml of 35% HCl to make a total of 1. Dip at 25℃ for 4 minutes, wash with water, and then add 12% HCl.
Immerse in an aqueous solution for 5 minutes at 25°C, and finally immerse for 10 minutes at 40°C in a chemical nickel solution consisting of 1 volume part of Nyco SP type manufactured by Kizai Co., Ltd. and 1 volume part of Nyco SP type manufactured by Kizai Co., Ltd. Water. death,
Chemical nickel is deposited on the surface of the tanzak sample. Next, the precipitated chemical nickel is completely eluted by treating it with an ammonium persulfate aqueous solution at 100°C for 10 to 30 minutes, and the eluted nickel is quantified by chelate titration with ethylenediaminetetraacetic acid (EDTA). do. This nickel weight is divided by the surface area of the tanzak sample (the surface area calculated by multiplying the vertical and horizontal lengths) to obtain the chemical nickel precipitation amount (mg/dm ² ). It has been revealed that this chemical nickel precipitation occurs almost uniformly on the uneven surface of the polyacetal resin to a thickness of about 1 μm, and therefore, this quantitative value is a characteristic value that accurately represents the surface area of the uneven resin surface. However, the surface coverage of the resin surface cannot be determined simply by the size of the surface area. That is, even if surfaces exhibit the same surface area value (mg/dm ² ), the surface coverage, that is, the adhesion of a plating film or the like (due to the anchor effect), will vary greatly depending on the shape of the unevenness. For example, as shown in a model, even if the surface areas of the uneven surfaces shown in FIG. Furthermore, the adhesion of plating films, etc. should also differ depending on differences in surface chemical affinity (for example, amount of polar groups, etc.). The present inventors adopted the following plating peel strength as a value that linearly and concisely represents the physical properties (related to the anchor effect) and chemical properties of these irregularities on the resin surface. This plating peel strength is a value determined as follows. A 3 mm thick flat plate of polyacetal resin was created by injection molding, this flat plate was degreased with 1,1,1,-trichloroethane, the surface was subjected to a specified chemical treatment, and then the flat plate was neutralized, washed with water, and air-dried.
Chemically plated using the above method, immediately subjected to electrolytic copper plating to give an average plating film thickness of about 40μ, make parallel cuts of 10 mm width on the plating surface, and apply the plating layer between the cuts to the flat plate surface. The stress required for this is determined by pulling in the perpendicular direction, and this is determined as the plating peel strength (Kg/cm). In the present invention, the surface condition of a polyacetal resin molded article is defined by the amount of chemical nickel precipitated and the plating peel strength.
In other words, the amount of chemical nickel precipitated indicates the degree of increase in surface area due to surface irregularities, and the plating peel strength comprehensively indicates the shape of the irregularities, their distribution state, and the chemical properties of the irregular surface. Therefore, it is considered that the surface coverage of a polyacetal resin molded article can be expressed by these two characteristic values. Based on the above considerations, the present inventors investigated various methods for surface treatment of polyacetal resin molded products, and were able to obtain a polyacetal resin molded product that has improved surface properties that are completely different from conventional products. Thus, the present invention has no surface cracks perceptible to the naked eye and a chemical nickel deposition amount of 85 to 150 (mg/
dm ² ), and the plating peel strength is 1.2Kg/
The present invention relates to a polyacetal resin molded product characterized by having surface characteristics of cm or more. The present invention will be explained in detail below. The polyacetal resin of the present invention is a homopolymer, that is, a polymer obtained by polymerizing formaldehyde or trioxane (including a polymer obtained by stabilizing the terminals), or a comonomer such as trioxane and a cyclic ether or cyclic acetal. The main ingredient is a binary or tertiary or more copolymer copolymerized with polymers, and various additives that are usually added, such as heat stabilizers, antioxidants, ultraviolet absorbers, antistatic agents, crystal nucleating agents, There is no problem even if it contains pigments, etc. Further, it may contain an inorganic powder such as calcium carbonate or magnesium carbonate that promotes surface roughening, or may further contain unsaturated polyester or the like. As described above, the polyacetal resin of the present invention is not particularly limited in its component composition. Conventional polyacetal resin molded products with the surface condition shown in Figure 1 (micrograph) all have a chemical nickel precipitation amount of 80%, as shown in the comparative example below.
(mg/dm ² ) or less, plating peel strength is 1.0Kg/cm
These are as follows. Conventionally known surface treatment systems (including both polyacetal resin and surface treatment conditions) can be used within a treatment time that can be used industrially and without causing cracks that can be recognized with the naked eye on the treated surface. Even after severe treatment, it has not been possible to obtain a material with a chemical nickel precipitation amount and plating peel strength greater than the above values. In addition, when the surface of the polyacetal resin molded product is roughened by mechanical treatment such as sandpaper, the amount of chemical nickel precipitated exceeds 85 (mg/dm ² ), which falls within the scope of the present invention. This can be achieved relatively easily, but in this case, the surface unevenness is simply an increase in surface area, and is not a type of unevenness that can enhance the anchoring effect, and the plating peel strength is still less than 1.0 kg/cm. Far below. On the other hand, the surface of the novel polyacetal resin molded product of the present invention is shown in the micrograph shown in Fig. 2 (magnification
1000), the chemical nickel precipitation amount is 85 to 150 (mg/dm ² ), preferably 95 to 130 (mg/dm ² ), and the plating peel strength is 1.2 kg/dm 2 . significantly more than cm, e.g. 2.5
It is around Kg/cm. Moreover, this thing is
It may not have any surface cracks that are perceptible to the naked eye. The polyacetal resin molded product of the present invention, which has such surface characteristics, can be formed into a variety of strongly bonded, robust and beautiful shapes that have never been seen in conventional polyacetal resin molded products through plating, printing, painting, or adhesion. A variety of products of value can be provided with coatings. The novel polyacetal resin molded product of the present invention is
It is defined by a state quantity that represents surface characteristics unrelated to its manufacturing method, and can include products obtained by various manufacturing methods. An example of its production method is a composition in which calcium carbonate powder is uniformly mixed with the homopolymer or copolymer having the above-mentioned oxymethylene repeating unit, with or without the addition of unsaturated polyester. It is obtained by surface treating an injection molded product with a mixed acid of phosphoric acid and sulfuric acid. For the reasons mentioned above, it goes without saying that the present invention is not limited by these manufacturing methods. Next, examples and comparative examples will be shown. Examples 1 to 4, Comparative Examples 1 to 8 90 parts by weight of "Tenatsuku 5010" (manufactured by Asahi Kasei Corporation, acetal homopolymer, general grade) as polyacetal, 10 parts by weight of calcium carbonate with various average particle sizes shown in Table 1 3 parts by weight and 1 part by weight of unsaturated polyester (unsaturated polyester with an average degree of polymerization of 10 synthesized from isophthalic acid/furyic anhydride/diethylene glycol = 1 mol/1 mol/2 mol and containing styrene as a crosslinking agent) The ingredients were premixed in a tumbler and then kneaded in an extruder set at 190°C to form pellets. Using these pellets, a 3 mm thick tanzak was made by injection molding and used as a test material. This tanzak was annealed in a hot air dryer at 150°C for 30 minutes (specimen A), and then 96% sulfuric acid/
It was immersed in a solution consisting of 85% phosphoric acid/water = 40/25/35 (weight ratio) at 40°C for a predetermined time. As a comparative example, "Tenatsuku 5010" was pelletized under the same conditions as above, and then a 3 mm thick tanzak pellet obtained by injection molding was annealed at 150°C for 30 minutes (referred to as sample B), and it was treated with the following etching solution. Soaked. (1) Immersed in 85% (weight) orthophosphoric acid at 25°C for a specified time. (2) 96% sulfuric acid/potassium dichromate/water = 100/
It was immersed in a 15/50 (weight ratio) chromium sulfuric acid solution at 60°C for a specified period of time. (3) Physically treated the surface with sandpaper. After the etching process, each of the samples of Examples and Comparative Examples above was immersed in a 3% caustic soda aqueous solution at room temperature for several seconds, and then immersed in warm water at 80°C for 10 minutes to complete the etching process (for sample B,
After washing with warm water, it was further dried with hot air at 150°C for 30 minutes). Next, using the sample, the glossiness was measured by the method described in the specification (the results are shown in Table 1). Further, using the sample, chemical nickel was precipitated by the method described above, and the amount of the precipitated amount was quantified (the results are shown in Table 1). Further, after chemical nickel deposition, the plating peel strength was measured by the method described above, and electrolytic copper, nickel, and chrome plating were separately performed. The average plating film thickness is Cu/Ni/Cr=approximately 25μ/10μ/0.1μ,
The plated product was evaluated for appearance and heat cycle test (results are shown in Table 1). In addition, in Table 1 (same in Table 2), the glossiness is
The samples were injection molded from ASTM D790 tanzak, subjected to the specified surface roughening treatment, neutralized, washed with warm water, and air-dried.
Kogyo Co., Ltd.) gloss meter (Gloss
This is the value obtained by measuring three points per sample and calculating the average value. The angle of incidence and detection angle of the light beam used for measurement shall be 75°. Before measurement, the surface of the measurement sample should be wiped clean with gauze to remove dust. The appearance of the glazed product was visually inspected under a light source of 300 lux or more at a distance of 60 cm from the sample surface. shall mean the following. The heat cycle test for plated products was performed by testing the plated products at [-30℃, 60 minutes] → room temperature 15 minutes] → [90℃,
The condition of blisters on the plating surface was observed and evaluated after 4 cycles of treatment, one cycle being 60 minutes → 15 minutes at room temperature. This means the occurrence of blisters.

[Table] Examples 5 and 6 Examples 1 to 4, a mixture of magnesium carbonate with an average particle size of 2 to 3μ in place of sample A's calcium carbonate (sample C), and sample A's "Tenatsuku 5010". The same treatment as in Example 2 was carried out using a mixture of polyacetal resin ``DURACON M90-02'' (manufactured by Polyplastics Co., Ltd., acetal copolymer, general grade) instead of ``Sample D''. . The results are shown in Table 2.

【table】

【table】 [Brief explanation of the drawing]

FIG. 1 is a micrograph (magnification: 1000) of a polyacetal resin surface treated product by a conventional method. Second
The figure is a micrograph (magnification: 1000) of a polyacetal resin surface-treated product of the present invention. FIGS. 3A and 3B are cross-sectional views showing models of the types of surface irregularities.

Claims (1)

[Claims] 1 There are no surface cracks that can be recognized with the naked eye,
The chemical nickel precipitation amount specified in the text is 85 to 150.
1. A polyacetal resin molded product characterized by having a surface property of 1.2 mg/dm ² or more and a plating peel strength specified in the text of 1.2 mg/dm ² or more.