JP3375684B2 - Powder processing composition - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to transparency, metal adhesion,
The present invention relates to a powder processing composition capable of forming a coating film having excellent pinhole resistance. For more details, the decorativeness of metal products,
The present invention relates to a powder processing composition which is useful as a surface coating material for improving corrosion resistance and weather resistance and has no troubles such as oxidation during baking and thermal deterioration. [0002] Ethylene / unsaturated carboxylic acid copolymers or ionomers thereof are known as resins which are transparent and have excellent pinhole resistance and metal adhesion. It can be said to be an attractive raw material for coating materials. For example, when a coating film is formed on the surface of a metal product by a fluid immersion method on a laboratory scale using a powder obtained by pulverizing the resin, a transparent anticorrosive film having excellent metal adhesion can be obtained. However, industrially, if the above resin is used as it is, there is a concern that it may be oxidized during baking or deteriorated due to heat. Therefore, it is essential to use an antioxidant. However, when the antioxidant powder and the resin powder are directly dry-blended, it is difficult to weld them in a completely mixed state because the layers are separated by a fluid immersion method or the like. The effect cannot be fully exhibited. [0003] When powder obtained by pulverizing a pellet obtained by melt-mixing a resin and an antioxidant is used, the compounding effect of the antioxidant can be sufficiently exhibited. When such a formulation is adopted for the polymer or its ionomer, the reason is not yet clear,
It was found that when viewed from diagonally above, the coating film obtained by powder coating appeared cloudy and did not become completely transparent. Accordingly, the present inventors have proposed powder coating of an ethylene / unsaturated carboxylic acid copolymer or an ionomer thereof such that a transparent coating film containing an antioxidant can be obtained. We studied to obtain powder for use. As a result, they have found that a composition obtained by the following formulation can achieve the object, and have reached the present invention. Accordingly, an object of the present invention is to provide pinhole resistance,
An object of the present invention is to provide a resin composition powder capable of forming a coating film having excellent metal adhesion and transparency by a powder coating method without deterioration due to oxidation or heat. Another object of the present invention is to provide a powder capable of obtaining a transparent product by a wide range of powder processing without deterioration. SUMMARY OF THE INVENTION The present invention relates to an ethylene / unsaturated carboxylic acid copolymer having an unsaturated carboxylic acid content of 5 to 30% by weight or an ionomer having an average particle size of 30%.
An ethylene / unsaturated carboxylic acid copolymer containing 70 to 98% by weight of a powder having a particle size of 0 μm or less, an antioxidant, and having an unsaturated carboxylic acid content of 5 to 30% by weight or an ionomer having an average particle size of 300 μm; The present invention relates to a powder processing composition obtained by dry blending the following powder with 30 to 2% by weight. The ethylene / unsaturated carboxylic acid copolymer used in the present invention has an unsaturated carboxylic acid content of 5 to 30.
%, Preferably 7 to 20% by weight. If the unsaturated carboxylic acid content is less than the above range, transparency,
If the metal adhesion is not sufficient and the content is too large, pulverization becomes difficult. Here, as the unsaturated carboxylic acid,
Examples thereof include acrylic acid, methacrylic acid, monomethyl maleate, and maleic anhydride. Among them, acrylic acid or methacrylic acid is particularly preferable. If necessary, another polar monomer such as an acrylate, a methacrylate, or a vinyl acetate may be copolymerized in the copolymer. Such a copolymer can be obtained by copolymerizing ethylene, an unsaturated carboxylic acid, and if necessary, another polar monomer under high temperature and high pressure. In the present invention, an ionomer in which a part of the carboxyl groups in the copolymer is neutralized with metal ions can be used instead of the copolymer. Representative examples of the metal ion in the ionomer include lithium, sodium, potassium, magnesium, calcium, zinc, and the like, and the degree of neutralization is 80 mol% or less, preferably 60 mol% or less. The copolymer or its ionomer has a melt flow rate at 190 ° C. and a load of 2160 g of from 1 to 500 g / 10 min, especially from 10 to 200 g.
It is preferable to use one with g / 10 minutes. That is,
When a material having a very low melt flow rate is used, there are disadvantages that the pulverization efficiency in producing powder is poor, the film forming property in powder coating is poor, and a uniform coating film is difficult to obtain. On the other hand, when a material having an excessively high melt flow rate is used, problems such as sagging and dripping tend to occur during powder coating, and the resulting coating film tends to be insufficient in strength and tend to be brittle. In the present invention, a powder of the above-mentioned ethylene / unsaturated carboxylic acid copolymer or its ionomer (hereinafter sometimes referred to as a main powder) and an ethylene / unsaturated carboxylic acid copolymer or its A dry blend of a powder of an ionomer blended with an antioxidant and, if necessary, other additives (hereinafter sometimes referred to as a blended powder). The compounded powder is blended with the above copolymer or its ionomer, an antioxidant, and other additives as necessary by using a melt mixing device such as an extruder, and the blended powder is obtained by means such as mechanical pulverization. It was obtained by grinding. As the antioxidant, various types such as phenol type, sulfur type and phosphorus type can be used.
In particular, use of a phenol type is preferred. Representative of other additives that may be blended as required are ultraviolet absorbers and light stabilizers. For these specific names, see 11
691 chemical products (January 1991, published by Chemical Daily)
873-917. The mixing ratio of the antioxidant in the compounded powder is preferably in the range of 0.1 to 5% by weight, particularly preferably 0.2 to 5% by weight. When other additives are added in addition to the antioxidant, the total amount of both additives is preferably 5% by weight or less. If the amount of the antioxidant is too small,
If the effect of preventing deterioration cannot be sufficiently exhibited, and if the content thereof is too large, poor appearance and poor transparency of a film obtained by powder coating are liable to occur. In addition, when powder coating is performed by the fluid immersion method, classification due to a density difference is likely to occur, which is not preferable. From the viewpoint of transparency, it is preferable to use the same ethylene / unsaturated carboxylic acid copolymer or its ionomer as the main powder and that of the blended powder in view of transparency. The average particle size of the main powder and compound powder is 300 μm or less, usually 5 μm.
It is in the range of 0 to 300 μm, preferably 100 to 200 μm. When a powder having an average particle diameter exceeding 300 μm is used, it is difficult to obtain a uniform coating film in powder coating. The mixing ratio of the main powder and the compounded powder is 70
The latter is used in an amount of 30 to 2 parts by weight, preferably 20 to 5 parts by weight, based on 100 to 98 parts by weight, preferably 80 to 95 parts by weight.
If the mixing ratio of the compounded powder is too small, uniform dispersion at the time of baking is difficult, resulting in poor heat resistance, which is not preferable. If the mixing ratio exceeds 30% by weight, transparency is deteriorated, which is not preferable. The mixing ratio of the main powder and the compounding powder is such that the antioxidant concentration in the composition is 0.01 to 1% by weight,
It is particularly preferable to select the amount to be 0.02 to 0.5% by weight. That is, if the concentration of the antioxidant is too low, the heat resistance becomes poor. On the other hand, if the concentration is too high, the appearance tends to be poor due to bleeding and the cost is high, which is not preferable. Dry blending of the main powder and the compounded powder can be easily performed by using a usual powder mixing apparatus, for example, a Henschel mixer, a rotary mixer or the like. EFFECT OF THE INVENTION The composition of the present invention in which a specific proportion of an antioxidant-containing compounded powder is blended with the main powder, has excellent transparency, metal adhesion, pinhole resistance, oxidation resistance or thermal deterioration. Because of its excellent properties, it can be used for various powder processing.
That is, it is useful as a material for powder coating such as a fluid immersion method or a thermal spraying method, and particularly as a coating material for corrosion prevention or decoration of metal products. It can also be used as a material for rotational molding or slush molding. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Production of powder (1) Production of main powder Methacrylic acid content 10% by weight, melt flow rate 3
5 g / 10 min ethylene / methacrylic acid copolymer (E.
MAA) was frozen with liquid nitrogen, finely pulverized with an impact pulverizer, and then classified to obtain a 60-mesh pass powder. (Average particle size: about 200 μm) (2) Production of blended powder 100 parts by weight of the above-mentioned E / MAA copolymer before pulverization, 1 part by weight of Irganox 1076 (manufactured by Ciba Geigy) as an antioxidant, and weather resistance Sanol LS770 as stabilizer
2 parts by weight (manufactured by Sankyo Co., Ltd.) were melt-mixed using a twin-screw extruder to obtain a pellet-like blend. Next, a powder of 60 mesh pass was obtained according to the method of (1). (3) Preparation of Powder by Conventional Method 100 parts by weight of E / MAA copolymer, 0.1 part by weight of Irganox 1076 (manufactured by Ciba Geigy) as an antioxidant, and weather stability As an agent, 0.2 part by weight of SANOL LS770 (manufactured by Sankyo Co., Ltd.) was melt-mixed using a single screw extruder to obtain a pellet-like blend. Then, according to the method of (1), a powder of 60 mesh pass was obtained. (Average particle size: about 200 μm) Preparation of Molded Product for Evaluation (1) Preparation of Press Sheet A predetermined amount of the powder blend was heated to 160 ° C. using a hot press.
After preheating for 5 minutes, further 160 ° C for 5 minutes, 100 kg / cm
After pressurizing to ² and cooling, a hot pressed sheet having a thickness of 1 mm was prepared. (2) Preparation of Powder Coated Product on Metal A glossy metal square plate having a thickness of 2 mm is heated in an oven at a preheating temperature of 260 to 300 ° C. for 10 minutes. Then, the powder was uniformly coated on the square plate, baked in an oven at an oven temperature of 200 ° C. for 5 minutes, and then cooled at room temperature. The thickness was about 0.5 mm. 3. Physical property evaluation method (1) Transparency The transparency of the press sheet and the powder-coated product were compared visually with the conventional product. (2) Pinhole resistance The presence or absence of bubbles or the like on the powder-coated powder-coated product was visually determined. (3) Adhesive Strength A 0.5 mm-thick sheet of the powder-coated product was subjected to a peeling test under the condition of 180 ° peeling to measure the adhesive strength, and an adhesive strength of 2 kg / 20 mm width or more was judged to be acceptable. (4) Heat Resistance The above powder-coated product was heated in an oven at 200 ° C. for further 30 minutes, and the presence or absence of discoloration was visually determined. (5) Weather Resistance The above powder-coated product was irradiated with a sunshine weatherometer at 63 ° C. for 500 hours, and the appearance change was visually judged. [Examples 1 and 2, Comparative Example 1] E · MAA main powder and blended powder were mixed in 90/10, 80/20 and 50/5.
A press sheet and a powder-coated product were prepared using the powder composition mixed at a weight ratio of 0, and various physical properties such as transparency and adhesiveness were measured. Table 1 shows the results. [Comparative Examples 2 to 3] Further, E.MAA powder prepared by a conventional melt blending method and E used as a main powder of Examples 1 and 2 without adding an antioxidant or a weathering agent were used.
-The comparison with the press sheet and the coated product by MAA powder was also performed. Table 1 shows the results. In the results of Table 1, the composition of Comparative Example 1 in which the amount of the compounded powder was larger than that of the main powder was inferior in the transparency of the product, and the additive was added by a conventional melt blending method. Similarly, when powder was used (Comparative Example 2), good transparency was not obtained, and both the press sheet and the coated product became cloudy. Further, when a powder containing neither an antioxidant nor a weathering agent is used (Comparative Example 3), heat resistance and weather resistance are poor. On the other hand, a product having good transparency can be obtained from the powder composition according to the composition of the present invention, and also excellent in weather resistance and heat resistance,
It has good quality as a powder coating such as a surface coating material. [Table 1] E • MAA: Ethylene / methacrylic acid copolymer (MAA 10% by weight, MFR 35dg / min)

Claims (1)

(57) [Claim 1] Powder 70 having an average particle size of 300 μm or less of an ethylene / unsaturated carboxylic acid copolymer having an unsaturated carboxylic acid content of 5 to 30% by weight or an ionomer thereof. ~ 98
30% by weight of an ethylene / unsaturated carboxylic acid copolymer or an ionomer having an average particle size of 300 μm or less containing an antioxidant and having an unsaturated carboxylic acid content of 5 to 30% by weight. % For dry powder processing.