JP3403785B2 - Powder processing composition - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition for powder processing capable of forming a coating film having excellent transparency, metal adhesion and pinhole resistance. More specifically, the present invention relates to a powder processing composition useful as a surface coating material for improving decorative properties and corrosion resistance of metal products. [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, it is necessary to use an extruder to knead the antioxidant into the pellets in order to prevent the discoloration of the coating film accompanying thermal deterioration during powder coating. [0003] When such a formulation is adopted for an ethylene / unsaturated carboxylic acid copolymer, the reason is not clear yet, but the coated surface using the resin kneaded by an extruder becomes cloudy when viewed from obliquely above. And found not to be completely transparent. [0004] This phenomenon is also observed when ordinary pellets are re-extruded and kneaded with an extruder. Therefore, it has been found that the painted surface becomes cloudy regardless of the presence or absence of the additive, even when the additive is added to the resin in advance or when the additive is not added. [0005] Accordingly, the present inventors have
Using an extruder or the like, even using pellets kneaded with additives, obtain a powder for powder coating of an ethylene / unsaturated carboxylic acid copolymer or an ionomer thereof such that a transparent coating film can be obtained. The study was conducted in order to do so. As a result, the inventors have found that a composition obtained by the following formulation can achieve the object, and reached the present invention. Accordingly, an object of the present invention is to provide a resin composition powder capable of forming a coating film having excellent transparency, metal adhesion and pinhole resistance by a powder coating method. It is a further object of the present invention to provide a transparent resin composition powder which does not become cloudy even when the resin is melt-kneaded with an extruder or the like for pelletization for kneading the additive. [0008] SUMMARY OF THE INVENTION The present invention is an unsaturated carboxylic acid content of 5 to 15 wt% of the ethylene-unsaturated carboxylic acid copolymer or phthalic acid ester plasticizer to the ionomer 0. A composition for powder processing having an average particle size of 300 μm or less, which is obtained by kneading and compounding 3 to 5.0% in an extruder . The ethylene / unsaturated carboxylic acid copolymer used in the present invention has an unsaturated carboxylic acid content of 5 to 15%.
%, Preferably 8 to 13% 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% 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, particularly 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 phthalate plasticizer is added as a liquid additive to the copolymer or its ionomer. Di-phthalate plasticizers
2-ethylhexyl phthalate (DOP), diisononyl phthalate (DINP), di-n-octyl phthalate, di-n-decyl phthalate, ditridecyl phthalate, dibutyl phthalate (DBP) or a mixture thereof, and di-2-ethylhexyl phthalate (DOP), DINP, DBP and the like are generally easily available and have excellent transparency improving effects. The blending ratio of the phthalate plasticizer in the blended powder is 0.3 to 5.0.
It is preferable that the content be in the range of 0.5% to 3.0% by weight. If the amount of the phthalate ester-based plasticizer is too small, the effect of improving the transparency after melt mixing of the powder-off product is small, and if the amount is too large, the plasticizer bleeds on the painted surface. Or lowering of the adhesive strength between the painted surface and the metal surface. In the present invention, in addition to the phthalic ester-based plasticizer, an antioxidant and other additives can be added to the above-mentioned ethylene / unsaturated carboxylic acid copolymer. By adding an antioxidant to an ethylene / unsaturated carboxylic acid copolymer containing a phthalic acid ester-based plasticizer or an ionomer thereof, industrially, oxidation and heat during baking of a powder coating product are reduced. It is also possible to prevent deterioration based on the above. Since the phenomenon of cloudiness on the painted surface caused by kneading such an antioxidant using an extruder can be prevented by blending a phthalate plasticizer or the like, the present invention provides an antioxidant. It is particularly useful for a powder processing composition containing 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 (Jan. 1991, published by The Chemical Daily), pages 878 to 917. The liquid phthalate plasticizer can be kneaded by injecting it into a barrel of a single screw extruder with a pump or the like, or by feeding it to a twin screw extruder together with an ethylene / unsaturated carboxylic acid copolymer. . On the other hand, a powdery additive such as an antioxidant can be kneaded by being added together with the above copolymer using a single screw extruder or a twin screw extruder. The pellets containing the phthalate plasticizer are usually cooled and frozen with liquid nitrogen or the like, then finely pulverized by a pulverizer and then classified. The average particle size of the plasticizer-added ethylene / unsaturated carboxylic acid copolymer powder thus obtained is 300μ.
m, usually 50-300 μm, preferably 100-2
It is in the range of 00 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. According to the present invention, a specific ratio of a phthalate ester plasticizer or the like is mixed with an ethylene / unsaturated carboxylic acid copolymer in an extruder.
The composition of the present invention kneaded and compounded has excellent transparency, metal adhesion, smoothness, and pinhole resistance.
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. EXAMPLE An ethylene / methacrylic acid copolymer (E · MA)
A) was blended with various additives, and the pellets obtained by melt-mixing with an extruder were pulverized, powder-processed and formed, and the physical properties of the molded product were evaluated. The method for preparing the molded article for evaluation and the method for evaluating physical properties are as follows. 1. Preparation of Molded Product for Evaluation (1) Preparation of Press Sheet A predetermined amount of the powder blend was prepared using a hot press machine.
After preheating at ℃ for 5 minutes, further 160 ℃ for 5 minutes, 100kg
/ Cm ² , and after 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) Preparation of sample for adhesion test 1 mm thick press sheet prepared in (1) and 0.4 mm
Thick iron square plate (length 100 mm x width 25 mm x thickness 0.
4 mm) in a 1 mm thick space at 160 ° C. for 4 minutes. In addition, the thickness of the resin layer after the heat bonding was 0.6 mm. 2. Physical property evaluation method (1) Transparency The transparency of the pressed sheet and the powder-coated product was visually determined. (2) Smoothness (pinhole resistance) The presence or absence of bubbles and the like on the powder-coated product was visually determined. (3) Adhesive strength The sheet for the adhesive test was subjected to a peeling test under the condition of peeling at 130 ° C. to determine the adhesive strength, and the adhesive strength was 8 kg / 25 mm.
A width or more was considered acceptable. (4) Heat resistance The powder-coated product was heated in an oven at 200 ° C. for 30 minutes, and the discoloration was visually determined. Example 1 100 parts by weight of an ethylene / methacrylic acid copolymer (E.MAA) having a methacrylic acid content of 10% by weight and a melt flow rate of 35 g / 10 minutes, and di-2 as a phthalate ester plasticizer -1.5 parts by weight of ethylhexyl phthalate (DOP, manufactured by Kao) was melt-kneaded using a twin-screw extruder to obtain a pellet-like blend. Next, the compounded pellet was frozen with liquid nitrogen, finely pulverized with an impact pulverizer and then classified to obtain a powder processing composition having a 60 mesh pass (average particle size of about 200 μm).
m). A press sheet and a powder-coated product were prepared using this powder composition, and various physical properties such as transparency and adhesiveness were measured. Table 1 shows the results. Example 2 Instead of DOP, diisononyl phthalate (DIN) was used as a phthalate ester plasticizer.
(P, manufactured by Kao Corporation) Except for using 1.5 parts by weight, melt kneading and pulverization were carried out in the same manner as in Example 1 to obtain a powder of 60 mesh pass (average particle size: about 200 μm). Various physical properties of a molded article prepared using this powder composition were measured. Table 1 shows the results. [Example 3] Irganox 1076 (manufactured by Ciba-Geigy) was used as an antioxidant in the formulation of Example 1.
Melt kneading and pulverization were performed in the same manner as in Example 1 except that 0.1 part by weight was added, to obtain a powder having a 60 mesh pass (average particle size: about 200 μm). Various physical properties of a molded article prepared using this powder composition were measured. Table 1 shows the results. [Comparative Example 1] The same E.
The pellets obtained from the MAA copolymer alone using a single screw extruder were pulverized to obtain a powder having a 60 mesh pass (average particle size: about 200 μm). Various physical properties of a molded article prepared using this powder composition were measured. Table 1 shows the results. [Comparative Example 2] Melt kneading and pulverization were performed in the same manner as in Example 1 except that the compounding amount of DOP was changed to 0.2 part by weight with respect to 100 parts by weight of E · MAA, and powder of 60 mesh pass was used. A body was obtained (average particle size: about 200 μm). Various physical properties of a molded article prepared using this powder composition were measured. Table 1 shows the results. [Comparative Example 3] Irganox 1076 (manufactured by Ciba-Geigy) was added to the formulation of Comparative Example 1 as an antioxidant.
Melt kneading and pulverization were performed in the same manner as in Comparative Example 1 except that 0.1 part by weight was added, to obtain a powder having a 60 mesh pass (average particle size: about 200 μm). Various physical properties of a molded article prepared using this powder composition were measured. Table 1 shows the results. As is apparent from the results in Table 1, E · MA
In the compositions of Comparative Examples 1 and 3 in which only the A copolymer or only the E · MAA copolymer and the antioxidant were kneaded, the transparency of the product was poor. Not improved. On the other hand, a product having good transparency was obtained from the E.MAA copolymer powder processing composition of the present invention containing a specific amount of a phthalate ester plasticizer. [Table 1] * Adhesion state (circle): Interface peeling (Material): Substrate destruction ** Heat resistance 〇: Excellent △: Slightly poor ×: Poor

Claims (1)

(57) [Claims 1 unsaturated carboxylic acid content of 5 to 15 wt% of the ethylene-unsaturated carboxylic acid copolymer or phthalic acid ester plasticizer to the ionomer 0. 3 to 5.0%
Is kneaded and compounded in an extruder, and has a mean particle size of 300 μm or less.