JPS58176252A - Polyethylene composition for powder coating - Google Patents

Abstract

PURPOSE:To provide the titled compsn. capable of forming a film having excellent ESCR resistance, smoothness and adhesion, by incorporating an ethylene/ vinyl acetate copolymer in a specified ethylene/alpha-olefin copolymer graft-modified with a carboxylic acid. CONSTITUTION:An ethylene/vinyl acetate copolymer having a vinyl acetate content of 5-45wt% is added to an ethylene/alpha-olefin copolymer graft-modified with 0.01-3wt% unsaturated carboxylic acid or anhydride such as acrylic acid or maleic anhydride and having a density of 0.94 or below and an MI of 5 or above in such a proportion as to give a vinyl acetate concn. of 0.3-2wt% after blending. The mixture is melt-kneaded with heating by using an extruder or heated rollers and then crushed to a particle size of 500mu or below to obtain a polyethylene compsn. for powder coating.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a powdered polyethylene resin composition for powder coating.

More specifically, the present invention relates to a powder coating method in which a resin powder is adhered to an object to be coated or at the same time heat is applied to finally form a coating film, such as an electrostatic powder coating method, a scattering method, a fluidized dipping method, and a thermal spraying method. The present invention relates to a powdered polyethylene resin composition that forms a coating film by the above-mentioned powder coating method, etc., and in particular, the present invention provides that the coating film obtained by the powder coating method has excellent B80R and surface smoothness, and has good adhesion to the object to be coated. The present invention relates to a polyethylene resin composition for powder coating with excellent properties.

Powder coating methods have recently become increasingly popular as an alternative to conventional liquid paints. This is because the powder coating method does not require any adjustment or mixing of the paint, and because it does not use solvents, there are almost no problems with air pollution, health hazards, or fire hazards. This is because it has various advantages such as not requiring much skill and being able to form a thick film without causing "sag". The synthetic resin powder used for this powder coating is as follows:
Various materials such as polyethylene, nylon, polyester, acrylic, and epoxy are known. Among these, polyethylene resin is an important powder coating resin because it is inexpensive, has excellent chemical resistance, and excellent weather resistance.

Low-density curvature polyethylene produced by high-pressure manufacturing method has traditionally been used as polyethylene resin, but E80R
Due to its inferior properties and poor adhesion, its range of applications as a durable anti-corrosive material is severely limited. In order to improve B8ORt, attempts have been made to lower the MI of high-pressure low-density polyethylene or blend it with ethylene-vinyl acetate copolymer, but in order to make B8OR as a coating film sufficient, MI for high pressure low density polyethylene
It is necessary to make the k extremely small or to blend it with a large amount of ethylene vinyl acetate copolymer. In the case of products with extremely low MI, it is nearly impossible to finish the adhered resin powder completely by heating a smooth coating (hereinafter referred to as the baking process) using normal powder coating methods, and the result is only a poor appearance. In other words, in the powder coating method, the powder is usually first applied to the coating material using methods such as static electricity or thermal welding. It is desirable for the powder composition to have as high an MI as possible, due to external heating, the properties of the powder itself, or the properties of the coated material. Note that MI in the present invention is MI defined in ASTM D 1238.
It refers to the value measured by the measurement method (load 216 ot).

Blending with Taden's ethylene-vinyl acetate copolymer also improves E80RFi, but it not only causes problems with poor appearance and pinholes, but also with baking.

Over time, thermal decomposition occurs, the oil resistance of the coating film decreases, and other properties as a coating film deteriorate significantly, and the properties of polyethylene are lost.

On the other hand, there are various methods for improving the adhesive properties of polyurethane, including graft modification with unsaturated carboxylic acids or their acid anhydrides.

However, in order to improve the adhesion of conventional high-pressure low-density polyethylene, when it is powder-coated with the above-mentioned graft-modified polyethylene, not only does the B5OR decrease significantly, but also the surface smoothness decreases. There was found.

That is, hitherto, no polyethylene composition for powder coating has been found that has excellent coating film smoothness and B5OR and excellent adhesion to the object to be coated.

The present inventors have conducted intensive studies to find a polyethylene resin composition for powder coating that has excellent coating film smoothness and ESOR as well as excellent adhesion to objects to be coated, and as a result, has arrived at the present invention. .

That is, the present invention provides an ethylene-α olefin copolymer modified with a density of 0.940 or less and an MI of 5 or more, which is wholly or partially graft-modified with 0.01 to 3% by weight of an unsaturated carboxylic acid or its acid anhydride. A polyethylene composition for powder coating, which is obtained by blending ethylene vinyl acetate copolymer with 100 parts by weight of a resin composition, and powdering a resin composition in which the concentration of vinyl acetate after blending is 0.2 to 5 parts by weight of the whole. It is related to.

The present invention will be explained in more detail below.

In the present invention, the ethylene-α-olefin copolymer is a copolymer with α-olefin containing 50 mol% or more of ethylene, and examples of the a-olefin include propylene, butene, pentene, 4-methylpentene- 1
, hexene, octene, etc.

The MI of such a copolymer is 5 t/10 minutes or more, and if the MI is lower than this, it is difficult to form a uniform coating film, and the more preferable MI range is FiIO to 100 f/10 minutes.

Further, the density of such a copolymer is preferably 0.940 t/cps" or less, more preferably tiO,935 to 0.91
0t/cW? within the range of When the MI is 5 r and the density is 0.940 f151 or more, the wasan of the resulting coating film is extremely low and it cannot be used as an anticorrosion coating.

Such a copolymer can be produced by a method such as solution polymerization, gas phase polymerization, or slurry polymerization using a transition metal catalyst. On the other hand, the ethylene-a olefin originally has poor adhesive properties, and in order to improve this in the present invention, all or part of the copolymer is graft-modified with an unsaturated carboxylic acid or its acid anhydride. Examples of unsaturated carboxylic acids or their acid anhydrides include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, maleic anhydride,
Itaconic anhydride and the like may be used, but these may be used alone or in a mixture of two or more. The amount of unsaturated carboxylic acid or its acid anhydride used is 0.1 to 3% by weight, more preferably 0.03 to 23 to 2% by weight, based on the ethylene-α olefin copolymer. When the amount of modification is less than the above range, there is almost no effect of improving adhesion, and when it is more than the above range, the heat resistance decreases, making it undesirable as a powder coating composition.

Note that various methods can be used to prepare the ethylene-α-olefin copolymer graft-modified with an unsaturated carboxylic acid or its acid anhydride. One method is to simultaneously melt and mix an LDM ethylene-α olefin copolymer, an unsaturated carboxylic acid or its acid anhydride, a radical generator, and other additives as necessary, to perform graft modification. As a means, the ethylene-α olefin copolymer is dissolved or suspended in a suitable solvent, and an unsaturated carboxylic acid or its acid anhydride, a radical generator, and other additives as necessary are simultaneously melt-mixed. There is a method of at least graft modification. Furthermore, a modified ethylene-α-olefin copolymer which has been graft-modified in advance can be used as a master patch and melt-blended with an unmodified ethylene-α-olefin copolymer.

It has been found that the modified ethylene-a-olefin copolymer with improved adhesion exhibits strong adhesion to coated objects when a coated tube is formed by a powder coating method. However, M.I.
The modified ethylene-α olefin copolymer having 5 or more is
A drawback was found that the gsOR of the coating film decreased. On the other hand, by blending the ethylene-vinyl acetate copolymer, which is another important composition of the present invention, with the modified ethylene-α-olefin copolymer, we have successfully improved the gsOR and discovered scales. It was found that there was almost no reduction in surface smoothness due to ethylene vinyl acetate blends such as polyethylene, and almost no pinholes, which may be caused by this.

The ethylene vinyl acetate copolymer used in the present invention is
Any commercially available material may be used as long as it contains 5 to 45% of vinyl acetate.

Further, it is preferable that tFi is blended with the modified ethylene-α olefin copolymer, and that the concentration of vinyl acetate after blending is 0.2 to 541 #% of the total.

More preferable range: (~2% by weight) If the concentration of vinyl acetate after blending is 0.2% by weight or less, no improvement effect can be found in the coating film E80R, and 5% by weight.
If the temperature exceeds that level, the surface smoothness may deteriorate significantly, and the heat resistance may deteriorate.
This is not preferable as it shows a significant decrease in oil resistance etc.

In addition to the above composition, the powder coating composition of the present invention may include colorants, heat stabilizers, ultraviolet absorbers, antistatic agents, lubricants, thickeners, coating aids, flame retardants, fillers, and others. It may contain additives.

To produce the powder coating composition of the present invention, for example, a modified ethylene-α-olefin copolymer, an ethylene-vinyl acetate copolymer, and other additives are mixed in an extruder, heating roll, Banbury mixer, etc. It is obtained by heating, melting and kneading using a machine. Furthermore, as a pulverizer for pulverizing the composition for powder coating, pulverizers specifically designed for resins are commercially available domestically and overseas, and although any pulverizer can be used, the particle size of the powder is is 500μ or less, more preferably 300μ or less, and the average particle size is 250μ to 100μ
A range of μ is preferred.

The powder polyethylene composition of the present invention is applicable to all powder coating methods. For example, metal porcelain, ceramics, and other materials can be coated by powder coating methods such as flow-dipping methods, electrostatic coating methods, thermal spraying methods, and electrostatic current immersion methods. Furthermore, the coated product obtained using the powder polyethylene composition '4IJ of the present invention has a smooth coating surface and no pinholes (
Because it has excellent gsOR and excellent layer density, it is suitable for fields that require corrosion resistance, durability, chemical resistance, and appearance, such as fences, industrial products, kitchen parts, etc. 4!1!
It can be used in a wide range of applications, including mulberry materials and various baskets.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example I MI 1sr/lo min, density 0, 930 r/cm
”]: 85 parts by weight of r-thiL/7-butene coelectrolyte, 0.5 weight ratio graft modification of maleic anhydride, density 0.930 f/31, MI 5 f/10 min ethylene-butene copolymer Combined 10 parts by weight and vinyl acetate content 14
5 parts by weight of WL Ryukyu's ethylene vinyl acetate copolymer was melt-kneaded using an extruder, and M114f710 minutes was prepared by graft-modifying 0.05 weight 1% maleic anhydride and having a vinyl acetate concentration of 0.7 weight %. A pellet-like resin composition having a density of 0.930 f/cW1" was obtained. The pellet-like resin composition was crushed in a Bollman pp-8 (manufactured by Pohlman Co., Ltd.) crusher.
It was ground using a 0 mesh sieve. The obtained powder was placed in a fluidized immersion tank to form a fluidized bed. Then, in the fluidized bed, 8POO-8B specified in JI803141 was added.
Degrease a mild steel plate (150m x 70cm x 3.21) and
After heating in an electric furnace at 0° C., the sample was immersed for 2 seconds and then allowed to cool to room temperature to obtain a coated flat test piece.

The B5OR, adhesiveness, surface smoothness, and presence or absence of pinholes of the test piece were evaluated by the following methods. The evaluation results are shown in Table 1.

+1) B S OR Rotate the center of the painted flat test piece at 180° with R = 5■
The sample was bent and immersed in a 5% Antalox C0630 aqueous solution at 50°C, and the time until cracks appeared was measured.

The time kFso value until cracks appeared in 5 out of 10 test pieces was used as the criterion.

(2) Adhesiveness A 90° peel test (chuck speed 10/min) was performed by making a 10-width incision in the coating film of the coated flat test piece using JI8/6301 and determining the adhesiveness.

(3) Surface smoothness: The surface smoothness of the pinhole-coated plate-like test piece was visually determined and indicated as excellent, good, fair, or poor.

Furthermore, the pinholes were also visually observed and their number (
The number of pinholes present on both sides of one flat plate was used as the criterion.

Example 2 MI7 graft-modified with 0.3% by weight of maleic anhydride, 98 coulometric parts of a modified ethylene-butene copolymer with a density of 0.925, and ethylene-vinyl acetate copolymer 2 with a vinyl acetate content of 14% by weight. The coulometric portion was melt-mixed and pelletized using an extruder, then powdered, and evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 3 MI20 obtained by graft-modifying 0.03% by weight of maleic anhydride, 90 parts by weight of a modified ethylene-butene copolymer having a density of 0.920, and ethylene-vinyl acetate copolymer 10 having a vinyl acetate content of 25% by weight. Parts by weight were melt-mixed and pelletized using an extruder, then powdered, and evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 4 MI15 obtained by graft-modifying 1.0% by weight of maleic anhydride, 95 parts by weight of a modified ethylene-butene copolymer having a density of 0.935, and ethylene-vinyl acetate coelectrolyte 531 having a vinyl acetate content of 35% by weight. The dragon part was melt-kneaded and pelletized using an extruder, then powdered, and evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 5 MI20 obtained by graft modification of 0.05% by weight of maleic anhydride, part by weight of modified ethylene-octene-1 copolymer 953 having a density of 0.925, and 5% by weight of ethylene vinyl acetate containing 10% by weight of vinyl acetate. A portion was melt-mixed and pelletized using an extruder, and then powdered, and evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 6 95 parts by weight of ethylene-butene copolymer with graft modification of 0.05% by weight of acrylic acid, MI 15f/10min, density 0.93097 country 3 and vinyl acetate 14
Example 1 After 5 parts by weight of ethylene vinyl acetate containing 5% by weight was melt mixed and pelletized using an extruder and then powdered.
It was evaluated in the same manner. The results are shown in Table 1.

Example I The coating performance was evaluated in the same manner as in Example 1 except that an ethylene-butene copolymer having MI3 and a density of 0.930 was used. The results are shown in Table 1.

Comparative Example 2 M115 obtained by graft-modifying 0.05 weight 11 maleic anhydride, 90 parts by weight of modified high-density polyethylene with a density of 0.955, and 10 parts by weight of ethylene-vinyl acetate copolymer containing 10% by weight of vinyl acetate. was melt-mixed and pelletized using an extruder, then powdered, and evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 3 Ethylene-vinyl acetate copolymer containing 9011 [parts] of a high-pressure process low-density polyethylene modified product having a density of 0-915 and an MI of 15, obtained by graft-modifying 0.1% by weight of maleic anhydride and 10% by weight of vinyl acetate. 10 parts by weight were melt-mixed and pelletized using an extruder, then powdered, and evaluated in the same manner as in Example 1.

The results are shown in Table IK.

Comparative Example 4 A modified ethylene-butene copolymer having a density of 0.930 and an MI of 15 obtained by graft-modifying 0.05% by weight of maleic anhydride was powdered and evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 5 Density 1i0.930. MI 15 ethylene-butene copolymer 95 parts by weight and vinyl acetate functional content 10@ii%
One part of the 5-layer ethylene-vinyl acetate copolymer was melt-kneaded and pelletized using an extruder, then pulverized, and evaluated in the same manner as in Example 1. The results are shown in Table 1.

Margin below

Claims (1)

[Claims] Density f, which is wholly or partially graft-modified with 0.01 to 3% by weight of unsaturated carboxylic acid or its acid anhydride.
Ethylene-vinyl acetate copolymer is blended with 100 parts by weight of a modified ethylene-α-olefin copolymer having an MI of 0.940 or less and an MI of 5 or more, so that the concentration of vinyl acetate after blending is 0.2 to 5% of the total concentration. Polyethylene composition for powder coating made by powdering a heavy Yoko 111 composition