JP2758438B2 - Surface treatment method for painting polyacetal resin molded products - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a surface treatment method for coating a polyacetal resin molded product, and more particularly, to a method of chemically activating and roughening the surface of a polyacetal resin molded product by plasma treatment. And a method for improving the paintability of a molded article.

[Conventional technology and its problems]

Polyacetal resin molded products are widely used in various fields because of their excellent mechanical strength, friction and wear resistance, chemical stability and durability, and moldability. With the expansion of the field of use of polyacetal resin molded products, the molded products are often subjected to secondary processing such as painting.

However, polyacetal resin molded articles have the disadvantage that their surfaces are extremely chemically stable and their coating properties are poor.

In order to solve such a drawback, it has been conventionally proposed to treat the surface of a molded article by a method such as a corona discharge treatment, a plasma treatment, or an acid aqueous solution treatment to improve the adhesion to a coating film.

However, since the effect of the corona discharge treatment is lost with time, there is an inconvenience that the coating must be performed continuously after the treatment.

In addition, in general plasma treatment, a hydrophilic group is generated on the surface,
It is said that wettability is improved and paintability is improved. However, in the case of the polyacetal resin, even if the wettability of the surface is improved, the anchoring effect of the coating film on the polyacetal resin cannot be expected due to the good surface smoothness and solvent resistance. In the case of painting, plasma treatment is not an effective means.

Further, although the acid aqueous solution treatment has a large effect, it requires steps such as annealing, degreasing, etching, neutralization, water washing, and drying, and the work process is complicated, takes time, and cracks are generated depending on the acid treatment conditions. Product defect rate may increase.

[Means for solving the problem]

The present inventors have conducted intensive studies on a surface pretreatment method, particularly a plasma treatment method, which improves the above-mentioned disadvantages of the conventional method, and as a result, have found the following facts.

That is, it is generally said that the plasma treatment of a thermoplastic resin molded article improves the coatability by generating a hydrophilic functional group on the molded article surface, but the polyacetal resin has a chemically extremely stable surface. , Sufficient adhesion cannot be obtained.

Therefore, the present inventors have further studied and found that the polyacetal resin contains an oxygen atom in the main chain which is most easily decomposed in plasma due to its chemical structure, and this CO bond is radically cleaved. -CH of polyacetal resin
Paying attention to the fact that _2- O-units are easily decomposed and desorbed in plasma to generate minute cracks, treatment with plasma using oxygen or a compound containing oxygen or a compound containing halogen or halogen makes it easy to perform The present invention has been completed by focusing on the fact that the main chain of the polyacetal resin is cleaved, the generation of radicals is promoted, the decomposition is easily caused, and the surface of the molded article can be roughened.

That is, the present invention provides a polyacetal resin molded product surface, by performing a plasma treatment under specific conditions using oxygen or a compound containing oxygen or a halogen or a compound containing a halogen, a hydrophilic functional group on the surface of the molded product. An object of the present invention is to provide a polyacetal resin molded article having improved coatability by generating and decomposing only the surface layer of the polyacetal resin to roughen the surface.

The depth of the surface roughening by the plasma treatment of the present invention is 1 μm.
Despite the fact that it is shallower than 1 to 10 μm of the acid aqueous solution treatment, the uniformity of the roughening and the size of the distribution density of the pores, and the synergistic effect of the hydrophilic group generated by the plasma, improve the coatability. It has a sufficient effect. Further, when the surface is deeply roughened as in the case of an acid aqueous solution treatment, it may have an adverse effect such as a decrease in strength in some cases.

The polyacetal resin used in the present invention refers to all high molecular compounds in which the main structural unit in the main chain is an oxymethylene group, and is a homopolymer of formaldehyde or its cyclic oligomer, trioxane or tetraoxane, or mainly And a copolymer obtained by copolymerization with a copolymerizable component. The copolymer may be a multi-component copolymer of three or more components or a graft copolymer having a branched or cross-linked structure in the molecule.

In the present invention, oxygen or a compound containing oxygen includes oxygen, water, methanol, ethanol, propanol, isopropanol, carbon monoxide, carbon dioxide, formaldehyde, acetaldehyde, propionaldehyde, acetone, methyl ethyl ketone, diethyl ketone, formic acid, acetic acid, Propionic acid, dimethyl ether, methyl ethyl ether, diethyl ether, oxirane,
1,2-epoxypropane and the like. Of these,
Inorganic substances such as oxygen, water, carbon monoxide and carbon dioxide which do not cause a polymerization reaction during the plasma treatment are preferred.

The halogen as the halogen or the compound containing a halogen is chlorine, fluorine or the like.

Examples of chlorine or a compound containing chlorine include chlorine,
Chloromethane, dichloromethane, chloroform, carbon tetrachloride, chloroethane, 1,1-dichloroethane, 1,2-dichloroethane, 1,1,1-trichloroethane, 1,1,2-trichloroethane, 1,1,1,2-tetra Chloroethane, 1,1,2,2-
Tetrachloroethane, pentachloroethane, hexachloroethane, chloroethylene, 1,1-dichloroethylene,
Examples thereof include 1,2-dichloroethylene, trichloroethylene, and tetrachloroethylene.

Fluorine or fluorine-containing compounds include fluorine,
Fluoromethane, difluoromethane, trifluoromethane, tetrafluoromethane, fluoroethane, 1,1-difluoroethane, 1,2-difluoroethane, 1,1,1-trifluoroethane, 1,1,2-trifluoroethane, 1, 1,1,2
-Tetrafluoroethane, 1,1,2,2-tetrafluoroethane, pentafluoroethane, hexafluoroethane,
Examples thereof include fluoroethylene, 1,1-difluoroethylene, 1,2-difluoroethylene, trifluoroethylene, and tetrafluoroethylene.

Some of such gas bodies may be in a liquid state at normal temperature and normal pressure, but the vapor may be introduced into the processing under reduced pressure. At this time, in the case of a compound having a low vapor pressure, it is desirable to increase the vapor pressure by heating.

When an organic compound, particularly a halogen-containing compound, is used among the above-mentioned gas bodies, it is necessary to treat the exhaust gas. Therefore, it is practically preferable to use an oxygen-containing inorganic gas which is easy to treat with exhaust gas.

The plasma processing conditions of the present invention are slightly different depending on the type of equipment used, but the discharge output (W) / pressure (Torr)
Is 12 for oxygen or gas containing oxygen.
00 or more, preferably 1500 to 5000, and in the case of halogen or a gas containing halogen, 100 or more,
It is necessary to adjust so as to be preferably 120 to 2000, particularly preferably 150 to 500. If the value of (discharge output (W) / pressure (Torr)) is out of the above range, a desired surface roughening effect cannot be obtained.

Further, other plasma treatment conditions are not particularly limited, but in the case of an internal electrode machine, discharge output (W) / electrode area (cm)
^It is preferable that the value of ² ) is 0.2 or more, preferably 0.3 or more from the viewpoint of uniform surface roughening.

Further, the time of the plasma treatment may be appropriately determined depending on the pressure, the electrode area, the treatment conditions, and the like.

The apparatus used in the plasma processing of the present invention is not particularly limited. For example, as shown in FIG.
A plasma generator, an exhaust device, a general high-frequency power supply basically composed of a gas supply device, for example, an internal electrode type device equipped with 13.56 MHz is preferable, but the external electrode is not particularly limited thereto. A method, a low-frequency power supply, or a microwave power supply may be used.

The procedure of the present invention will be specifically described based on FIG.
First, a polyacetal resin molded product base 2 is set in one processing chamber, and the inside of the processing chamber 1 is evacuated to 0.001 Torr or less using a rotary pump 3 and a diffusion pump 4. Next, a gas body flows from the gas container 5 into the processing chamber 1. At this time, a plurality of gas containers 5 may be provided as shown in FIG. These flow rates can be freely controlled by the flow controller 6 and the flow meter 7. As described above, a high frequency power is applied between the electrodes 9 and 10 by the high frequency power supply 8 while flowing a certain amount of gas, so that the plasma processing proceeds on the base 2. At this time, if the substrate needs to be cooled, it may be water-cooled by the water cooling tube 11.

The polyacetal resin used in the present invention may be a polymer blended with another thermoplastic resin within a range that does not impair the intended purpose of the present invention.

The thermoplastic resin used in this case is not particularly limited, but examples thereof include polyethylene, polyolefins such as polypropylene, polyethylene terephthalate, aromatic dicarboxylic acids such as polybutylene terephthalate and aromatic polyesters such as diols or oxycarboxylic acids. , Polystyrene, polyvinyl chloride, polyamide, polycarbonate, ABS, polyphenylene oxide, polyphenylene sulfide, various polyurethane resins, and fluororesins. These thermoplastic resins can be used as a mixture of two or more kinds.

In addition, known substances added to general thermoplastic resins and thermosetting resins, that is, plasticizers, stabilizers such as antioxidants, antistatic agents, surface treatment agents, surfactants, inorganic and organic fibers Shape, powder, plate-like fillers, flame retardants, coloring agents such as dyes and pigments and lubricants for improving fluidity and mold release properties,
Lubricants, crystallization accelerators (nucleating agents), and the like can also be used as appropriate according to the required performance.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

Examples 1 to 6 and Comparative Examples 1 to 5 A molded article of polyacetal resin (manufactured by Polyplastics Co., Ltd., trade name: Duracon) was subjected to plasma treatment under the conditions shown in Table 1 to roughen the surface of the molded article. The apparatus used was a bell jar type internal electrode type having an electrode area of 200 cm ² , and the discharge frequency was a high frequency of 13.56 MHz. Table 1 shows the conditions of the plasma treatment and the evaluation results of the paintability after the treatment.

The evaluation was performed according to the following procedure. First, a melamine alkyd paint was applied to the molded article after the plasma treatment, and baking and drying were performed at 140 ° C. for 30 minutes. Then, according to JIS K5400, a grid was inserted and a cellophane tape was applied, and the number of peeled grids per 100 pieces was checked.

[Effects of the Invention] A polyacetal resin molded product whose surface is subjected to plasma treatment by the specific method of the present invention has a roughened surface, has excellent adhesion to a coating film, and is suitably used as a molded product for coating.

Also, according to this method, unlike other treatment methods, there is no need for special pre-treatment, post-treatment such as drying and washing, and there is an effect that the number of steps can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a plasma processing apparatus used in the present invention. DESCRIPTION OF SYMBOLS 1 ... Processing chamber 2 ... Substrate 3 ... Rotary pump 4 ... Diffusion pump 5 ... Gas container 6 ... Flow controller 7 ... Flow meter 8 ... High frequency power supply 9 ... Electrode 10 ... Electrode 11 ... Water cooling tube

Continuation of the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) B05D 3/04 B05D 7/02 C08J 7/00 C08L 59/00

Claims (2)

(57) [Claims] 1. The surface of a polyacetal resin molded article is formed by using oxygen or a compound containing oxygen under plasma conditions in which the value of discharge output (W) / pressure (Torr) is 1200 or more, or containing halogen or halogen. A surface treatment method for coating a polyacetal resin molded article, wherein the surface is roughened by performing a plasma treatment using a compound having a discharge power (W) / pressure (Torr) value of 100 or more under plasma conditions. 2. The method according to claim 1, wherein the halogen or the compound containing halogen is chlorine or a compound containing chlorine or a compound containing fluorine or fluorine.