JPH0531576B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a polyamide resin molded article coated with a thin film made of a specific polyamide resin. Polyamide 6 or polyamide 66 resin has excellent heat resistance, oil resistance, and high strength, so it has been widely used in automobile parts in recent years, and is used as so-called underhood parts, such as cooling fans, radiators, Applications are attracting attention for functional parts such as tank tops and bases, cylinder heads, covers, oil pans, gears, valves, and other exhaust gas system parts and fuel system parts, and for exterior parts such as bumpers and oil caps. There is. However, since polyamide 6 and polyamide 66 resins inherently have a strong affinity for inorganic metal salts, molded products made from these materials
It has a serious drawback that it is attacked by metal salts such as calcium chloride and zinc chloride and cracks occur within a short period of time. Especially in the winter, when antifreeze agents mainly composed of calcium chloride, which are sprayed in large quantities on roads to prevent roads from freezing, adhere to underhood parts that are exposed to high temperatures while driving, they can cause cracks in the parts. This can lead to car breakdowns and even personal injury. Therefore, a method has been adopted in which the polyamide molded product is painted to form a coating film to improve its resistance to metal chlorides. It has the disadvantage that substances can seep through the pinhole and eventually cause cracks. Therefore, the present inventors discovered that (1) polyamide 6 and polyamide 66 resins do not impair their excellent heat resistance, high strength, and high rigidity, (2) have excellent chemical resistance, and (3)
As a result of intensive research aimed at obtaining inexpensive molded products, polyamide 6 and/or polyamide 66
Injection or blow molded parts made of polyamide
It has been found that the polyamide molded article may be coated with a thin film of polyamide resin selected from at least one of polyamide 610, polyamide 612, polyamide 116, polyamide 11, and polyamide 12 and having a thickness of 10 to 750 microns. Hereinafter, the method for producing a molded product of the present invention and the effects of the molded product obtained by the method will be described. Polyamide 6 and/or polyamide 66 resin as used in the present invention refers to polyamide 6 or a homogeneous polymer consisting only of polyamide 66, a copolymer of polyamide 6 and polyamide 66, or a blend thereof. In this sense we use the word “or/and” and the symbol. Furthermore, a small amount of other polyamide components may be copolymerized or blended within a range that does not significantly impair the physical properties of polyamide 6 and polyamide 66. Next, a polyamide molded article is obtained. The molded article can be obtained by a known method, ie, injection molding or blow molding. During molding, it is preferable to add 10 to 60% of glass fiber, carbon fiber, or other inorganic filler such as wollastenite, talc, clay, glass beads, or organic fiber to the polyamide resin.
% by weight. On the other hand, a polyamide resin for coating the polyamide molded product is prepared. This resin is selected from at least one of polyamide 610, polyamide 612, polyamide 116, polyamide 11, and polyamide 12 (hereinafter referred to as high-grade polyamide resin), preferably polyamide 612, polyamide 11, or polyamide 12. The polyamide resin molded product of the present invention can be produced by (a) preparing a film made of high-grade polyamide resin in advance, pasting the film on a mold, and then injection molding polyamide 6 or/and polyamide 66 resin. (b) fixing a pre-molded polyamide molded product in a mold and forming a film on the surface of the molded product by injection molding a high-grade polyamide resin; (c) forming a film on a polyamide resin molded product by hot pressing, or (d) forming a molded product with the same shape as the desired molded product using a thin film made of high-grade polyamide resin. , a method of molding polyamide resin after making it in advance and fixing it in a mold,
or (e) using an injection molding machine with two cylinders, from each cylinder polyamide 6,
Or/and the so-called 2-way injection molding of polyamide 66 resin and high-grade polyamide resin at the same time.
There is a method of forming a film by color molding, but
Particularly preferred methods are method (a), method (b), and method (e). The thickness of the coating is 10-750μ, preferably 20-450μ
shall be. If the thickness is less than 10μ, the method of forming the thin film is that if it is a pre-prepared film, the film will tear due to the molding pressure during molding, or if it is injection molding, it will not flow during injection molding. Therefore, a film cannot be formed on the entire surface of the polyamide molded product. If the thickness exceeds 750μ, the ratio of the coating increases relative to the weight of the polyamide resin molded product coated, making it expensive and reducing the excellent heat resistance and rigidity of the molded product, which is preferable. do not have. Since the polyamide resin molded product thus obtained has an extremely thin film formed on its surface, the metal chloride resistance is significantly improved without impairing the properties of the molded product made of polyamide 6 and polyamide 66 resin. No cracks at all. Furthermore, since the weight of the thin film required to cover the molded product is small, it has the advantage of being inexpensive. Furthermore, unlike the paint film, there are no pinholes at all. Examples of the present invention will be described in detail below. The calcium chloride resistance of the molded products obtained in Examples and Comparative Examples was evaluated as follows. After pre-humidifying the molded product in hot water at 100°C for 40 hours, 0.5cc of 5% CaCl ₂ liquid was dropped onto the surface of the molded product.
Leave it in a gear oven at 100℃ for 2 hours. After repeating this process (humidity conditioning → dropping ₂ liquids of CaCl → leaving in the oven) for 10 cycles, the presence or absence of cracks on the surface of the molded product was confirmed using an optical microscope under 30x magnification. Example 1 A film made of polyamide 12 with a thickness of 20 μm was prepared, and the film was molded into a small automobile wheel cap molded product (diameter 100 mm, wall thickness 3 mm) attached to a famous injection molding machine SJ-35B (manufactured by Meiki Seisakusho). It was attached to the fixed side of the mold for a plate-shaped molded product. The temperature of the mold was adjusted to 80℃ with the film attached, and after closing the mold, the cylinder temperature was 280℃ and the injection pressure was 450℃.
A polyamide 66 resin (CM3001G-30) reinforced with 30% glass fiber was molded under the conditions of Kg/cm ² and a molding cycle of 10 seconds for injection and 12 seconds for cooling. A molded product with no film tearing, uniform appearance, and good film adhesion was obtained. The calcium chloride resistance of the molded product thus obtained was examined by the method described above, and it was found to be extremely excellent, with no cracks occurring even after 10 cycles. Comparative Example 1 Using the same mold as used in Example 1 and under the same molding conditions, a small wheel cap molded product (without coating) made only of CM3001G-30 of Example 1 (diameter
A dish-shaped molded product (100 mm long and 3 mm thick) was obtained. As a result of evaluating the calcium chloride resistance of the molded product, it was only 1.
During the cycle treatment, cracks with a depth of about 0.2 mm were generated on the entire surface where the calcium chloride aqueous solution was dropped. Example 2 A film with a thickness of 30μ made of polyamide 11 was prepared, and the film was used for a box-shaped molded product (width 50 mm x length 80 mm) attached to the famous injection molding machine SJ-35B.
x height 20 mm, wall thickness 2.5 mm) on the fixed side of a mold, and after mold temperature control (80℃) as in Example 1, using non-reinforced polyamide 66 resin ((CM3001N),
Injection molding was performed at a cylinder temperature of 280℃, an injection pressure of 400Kg/cm ² , a molding cycle of 12 seconds for injection, and 15 seconds for cooling.
A box-shaped molding covered with polyamide 11 film was obtained. The obtained molded product had no film tearing, good film adhesion, and a uniform appearance. The molded product obtained in this way is made of polyamide 11.
The calcium chloride resistance was examined by dropping an aqueous calcium chloride solution onto the film-covered surface, and the results showed that the molded product did not show any cracks even after 10 cycles of treatment. Comparative Example 2 Using the same mold as in Example 2 and under the same molding conditions, a box-shaped molded product was obtained using only CM3001N without pasting the polyamide 11 film. As a result of examining the calcium chloride resistance of the box-shaped molded product, large cracks with a depth of 1.5 mm were formed in just one cycle. Example 3 A polyamide 612 film with a thickness of 40 μm was used for injection molding.The material was non-reinforced polyamide 6 resin (CM1017) and the material was coated with a polyamide 612 film in the same manner as in Example 1.It had a uniform appearance and had a uniform appearance. A small wheel cap molded product with good adhesion was obtained. The calcium chloride resistance was examined by dropping an aqueous calcium chloride solution onto the film-coated surface, and the results showed that the molded product did not show any cracks even after 10 cycles of treatment. Comparative Example 3 Using the mold used in Example 3 and under the same molding conditions, without attaching polyamide 612 film,
Only CM1017 was injection molded to obtain a small wheel cap molded product. As a result of investigating the calcium chloride resistance of the molded product,
After just one cycle of treatment, a large crack with a depth of approximately 1.6 mm was generated over the entire area where the calcium chloride aqueous solution was dropped. Example 4 Using the famous SJ-35B injection molding machine, cylinder temperature 280℃, mold temperature 90℃, injection pressure 350Kg/cm ² , injection 10sec, cooling 10sec cycle, CM3001G-30
was injection molded to obtain a disc molded product with a diameter of 50 mm and a thickness of 4.0 mm. The molded product was fixed in a cavity carved with a disc shape of 50.1 mm in diameter and 4.4 mm in thickness,
After controlling the temperature of the mold to 90℃, the thickness is 0.8mm, the width is 15mm,
Polyamide 12 resin was injection molded using a film gate with a length of 2 mm under the conditions of a cylinder temperature of 275°C, an injection cycle of 10 seconds, and a cooling cycle of 10 seconds. The obtained molded product was a molded product in which the surface of a CM3001G-30 disk molded product with a thickness of 4.0 mm was coated with polyamide 12 resin with a thickness of 420 μm. The calcium chloride resistance of the molded product was examined by dropping an aqueous calcium chloride solution onto the surface coated with polyamide 12, and the molded product did not show any cracks even after 10 cycles of treatment. Example 5 Polyamide 11 films having thicknesses of 12 μm, 20 μm, and 28 μm were prepared, and each film was attached to the fixed side of a mold for a small automobile wheel cap molded product in the same manner as in Example 1. After that, in the same manner as in Example 1, after closing the mold, the glass fiber was molded under the conditions of cylinder temperature 260℃, injection pressure 450Kg/cm ² , and molding cycle injection 10sec/cooling 12sec.
A 30% reinforced polyamide 6 resin (CM1011G-30) was molded. As shown in Table 1, in the wheel cap molded products coated with films having various thicknesses, molded products with no film tearing, uniform appearance, and good film adhesion were obtained. As a result of examining the calcium chloride resistance of the thus obtained molded product, as shown in the table, it was found to be extremely excellent, with no cracks occurring even after 10 cycles of treatment. Comparative Example 4 When a polyamide 11 film with a thickness of 7μ was prepared and an attempt was made to coat a CM1011G-30 wheel cap molded product with the polyamide 11 film in the same manner as in Example 5, the film was torn during molding and the appearance was poor. It was not possible to obtain a good molded product.

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Claims (1)

[Claims] 1 Polyamide 6 or/and polyamide 66
Polyamide injection or blow molded products made of
polyamide 610, polyamide 612, polyamide 116,
A polyamide resin molded article coated with a thin film of polyamide resin selected from at least one of polyamide 11 and polyamide 12 and having a thickness of 10 to 750 μm.