JPH0225984B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a surface brightening treatment method, such as a sputtering method or a vacuum deposition method, for obtaining polybutylene terephthalate molded products that are suitably used as automobile parts, electrical parts, and other various industrial parts. .

When polybutylene terephthalate is subjected to surface brightening treatment, it is desirable that the surface of the molded product after treatment exhibits a mirror finish, and the brightening coating (metallized coat) must not crack. The degree of adhesion must also be good. By the way, as a method for surface brightening treatment of polybutylene terephthalate, there are two methods:
Along with ion plating and the like, mention may be made of sputtering and vacuum evaporation. However, when a polybutylene terephthalate molded product is brightened by these methods, there is a large difference in linear expansion coefficient between the molded product and the brightened coating.
Cracks often occur in the brightening coating. In addition, since polybutylene terephthalate resin is a crystalline resin, it may undergo post-shrinkage after long-term use, which may also cause cracks in the brightening coating, and as a result, the adhesion may become insufficient. To prevent this, glass fibers, glass flakes, mica, etc. are blended with polybutylene terephthalate resin and sputtered or vacuum-deposited. However, in such cases, cracks do not occur in the brightening coating, but An undulating pattern appears on the surface of the treated product, impairing its specularity, and making it impossible to achieve the intended purpose of the brightening treatment. By the way, the occurrence of the undulating pattern in the molded article is caused by anisotropy during mold shrinkage of the matrix resin caused by the filler added to the polybutylene terephthalate resin. Taking the example of polybutylene terephthalate resin reinforced with glass fibers, the difference in molding shrinkage between the resin near the glass fibers and the resin elsewhere during molding and solidification causes unevenness on the surface, creating an undulating pattern. It turns out. The degree of this waviness is influenced by the shape, especially the size, of the filler to be mixed.

As a result of various studies on brightening treatment methods that do not have the above-mentioned drawbacks, the present inventors have found that by sputtering or vacuum deposition using polybutylene terephthalate filled with potassium titanate fibers, the surface can be made into a mirror-like state. The present invention was achieved based on the discovery that a treated product can be obtained that exhibits the same properties and does not cause cracks in the brightening coating due to changes in temperature or the like. The present invention also has the effect of increasing the adhesion of the coating.

That is, in the present invention, when a polybutylene terephthalate molded product is subjected to a brightening treatment, a molded product mainly composed of a polybutylene terephthalate resin composition containing 2 to 40% by weight of potassium titanate fibers based on the total composition. This is a surface brightening treatment method characterized by forming a brightening film by sputtering or vacuum evaporation treatment.

The potassium titanate fiber used in the present invention is a white acicular single crystal fiber whose chemical composition is K ₂ O.nTiO ₂ (n is 1 or more). It is desirable that the fiber length is on average 5 to 50μ, preferably 10 to 20μ, and the fiber diameter is on average 0.1 to 0.8μ, preferably 0.2 to 0.5μ. The amount of potassium titanate fiber added to polybutylene terephthalate is 2 to 40% by weight based on the total composition, and in particular, 3% to 40% by weight based on the total composition.
An amount of ~30% by weight is preferred. Potassium titanate fibers have conventionally been used simply for white coloring of resins. However, when polybutylene terephthalate containing potassium titanate fibers is subjected to a brightening treatment method such as sputtering or vacuum evaporation according to the present invention, improvements in film adhesion, surface specularity, crack prevention, etc. It has been discovered that it can produce excellent effects. Furthermore, depending on the amount added, it is of course possible to simultaneously strengthen the polybutylene terephthalate resin. In addition, in order to improve the adhesiveness between the potassium titanate fiber and the resin, a treatment can be performed using a known surface treatment agent. Examples of surface treatment agents used here include silane type surface treatment agents such as aminosilane type and epoxy silane type, titanate type surface treatment agents, etc., and silane type surface treatment agents are particularly suitable.

In the method of the present invention, other fillers may be mixed with the potassium titanate fibers. For example, calcium carbonate with an average particle size of 4μ or less, kaolin or kaolin groups (kaolinite, sericite, etc.) with hexagonal plate-shaped crystals with an average particle size of about 0.1 to 0.3μ, block-like wollastonite with an average particle size of 10μ or less , average fiber length 4-6μ and aspect ratio 40
~60 Processed Mineral Fiber (composition example:
Composition consisting of 43% _SiO2 , 39% CaO, ₈ % _Al2O3 )
etc.

As the polybutylene terephthalate used in the present invention, in addition to polybutylene terephthalate, copolymers mainly composed of polybutylene terephthalate and other thermoplastic resins can be mixed and used. For example, polyolefins such as polyethylene and polypropylene, ethylene-carboxylic acid ester copolymers such as ethylene-alkyl acrylate copolymers, vinyl compounds such as polystyrene, styrene-butadiene-acrylonitrile copolymers, and polyesters such as polyethylene terephthalate and polycarbonate. , rubber-like substances such as polybutadiene, and derivatives thereof can be used in combination. In addition, various elastomers such as multistage polymers made of polyacrylate resins, segmented copolyesters, stabilizers, surfactants, etc. can also be contained.

The blending and extrusion method of potassium titanate fiber and polybutylene terephthalate resin may be any commonly used method. Further, as the method of sputtering or vacuum deposition, the method used for resins with good paintability such as ABS can be applied as is. That is, after degreasing the molded product with a suitable solvent, a base coat such as urethane paint, acrylic-urethane paint or acrylic ester paint is applied and dried. After that, in the case of the sputtering method, chromium alloy, aluminum, etc. are heated using a sputtering device at 1× argon gas pressure.
A metal thin film of about 300 to 1000 Å is produced under a pressure of 10 ^-3 to 2×10 ^-4 Torr to give the molded product a metallic luster. In addition, in the case of vacuum evaporation, a vacuum evaporation device is used to reduce the temperature of 1×10 ^-3 to 1×10 ^-4 Torr
A thin metal film with a thickness of about 200 to 500 Å is produced under the pressure of In general applications, it is common to further apply a top coat to protect the metal film. The treated product thus obtained has extremely excellent properties such as a mirror-like surface, good adhesion of the brightening coating, and no cracking of the coating due to temperature changes, etc. It can be effectively used as various industrial parts.

Example 1 Potassium titanate fibers were added to polybutylene terephthalate [manufactured by Polyplastics Co., Ltd., trade name: Diuranetx] in an amount of 15% by weight based on the total composition, and injection molded using a molding machine to form a flat plate. It was created. After degreasing, base coat EXP1474U/EXP1475C (weight cost 100/30) manufactured by Fujikura Kasei Co., Ltd. was applied and forced drying was performed at 140°C for 60 minutes.

Then, using a sputtering device, the chromium alloy was heated to 400 ^~
After sputtering to a film thickness of 500 Å,
Apply Topcoat EXP1380 manufactured by Fujikura Kasei Co., Ltd.
Force drying was performed at 70°C for 30 minutes. Visual evaluation of the appearance of the molded product subjected to brightening treatment in this manner revealed that the surface had a mirror surface and good gloss, and no cracks were formed in the brightening coating. The adhesion of the brightening coating to the base material was determined by using a knife to score 11 lines vertically and horizontally at 1 mm intervals on the coating.
When the squares of 100 frames were forcibly peeled off using JIS cellophane tape and the number of remaining squares was evaluated, the number of remaining squares was 100.

Example 2 The amount of potassium titanate fiber added to the total composition
After creating a molded article with 7.5% by weight, Example 1
Sputtering was carried out in the same manner as above, and brightening treatment was performed. In this case as well, the molded product had a mirror-like surface with good gloss, and no cracking occurred in the brightening coating. In addition, when a forced peeling test was conducted in the same manner as in Example 1 to evaluate the adhesion, the number of remaining stitches was 100.

Example 3 The amount of potassium titanate fiber added to the total composition was
It was molded at 4.3% by weight, sputtered and brightened in the same manner as in Example 1, and evaluated in the same manner. In this case as well, good results were obtained in terms of specular appearance, no cracking, and film adhesion (100 remaining goblets).

Example 4 The amount of potassium titanate fiber added to the total composition
30% by weight, and after molding, sputtering and brightening treatment were performed in the same manner as in Example 1, and evaluation was performed in the same manner.
This also showed good results in terms of specular appearance, no cracking, and film adhesion (100 remaining goblets).

Example 5 15% by weight of potassium titanate fiber in the total composition
A molded article containing 5% by weight of polycarbonate was sputtered and brightened in the same manner as in Example 1. As a result of the same evaluation as in implementation Χ1,
Good results were obtained in terms of specularity, no cracking, and film adhesion (number of remaining goblets: 100).

Example 6 In Examples 1 to 5, vacuum evaporation treatment of aluminum was performed instead of sputtering treatment, and evaluations were conducted in the same manner in all other respects. Vacuum deposition was performed using a vacuum evaporation apparatus at a vacuum degree of 5×10 ^-3 Torr so that the aluminum film thickness was 3 to 400 Å.
The molded product thus obtained had a mirror surface appearance, no cracking, and good film adhesion (number of remaining goblets: 100).

Comparative Example 1 A molded flat plate of polybutylene terephthalate that does not contain potassium titanate fibers was sputtered and brightened in the same manner as in Example 1. The treated product had a mirror-like appearance and had good gloss, but the brightening film was not present. A crack appeared.

Comparative Example 2 When glass fiber was added in place of potassium titanate fiber in an amount of 30% by weight of the total composition and sputtered in the same manner as in Example 1, no cracks were formed in the coating, but the specular luster in appearance was I couldn't get it.

Comparative Example 3 Although the amount of glass fiber added in Comparative Example 2 was 17% by weight of the total composition and sputtering was performed in the same manner as in Example 1, a mirror-like gloss was not obtained in terms of appearance and the surface condition was not good. Ta.

Comparative Example 4 In Example 5, the same amount of glass fiber was added instead of the potassium titanate fiber, and the same amount was added and molded, and sputtering was performed in the same manner as in Example 1. In this case as well, specular gloss was not obtained in appearance and the surface condition was It wasn't good.

Comparative Example 5 In Comparative Examples 1 to 4, vacuum evaporation treatment of aluminum was performed instead of sputtering and the same evaluation was performed, but only the same results as in Comparative Examples 1 to 4 were obtained.

Claims (1)

[Claims] 1. When brightening a polybutylene terephthalate molded product, a molded product mainly composed of a polybutylene terephthalate resin composition containing 2 to 40% by weight of potassium titanate fibers based on the total composition is used. A surface brightening treatment method characterized by forming a brightening film by sputtering or vacuum evaporation treatment.