JPH03259937A - Powdered polyolefin resin composition - Google Patents

Abstract

PURPOSE:To obtain the title composition excellent in environmental stress cracking resistance and edge covering and useful for powder coating by mixing a polyolefin of a specified hardness with an elastomer and an adhesive linear low density polyolefin. CONSTITUTION:A powdered polyolefin resin composition comprising 60-90wt.% polyolefin of a Durometer D hardness of 60 or above, 3-15wt.% elastomer and 5-25wt.% adhesive linear low density polyethylene. Examples of the high hardness polyolefin to be used include high density polyethylene and polypropylene. Examples of the elastomer to be used include ethylene/propylene rubbers, ethylene/propylene/diene copolymers and ultralow density polyethylenes. The adhesive linear low density polyethylene most desirably used is one modified with maleic acid.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention has excellent environmental stress cracking resistance and edge coverage for use in powder coating methods such as fluidized dipping, electrostatic coating, and spraying. The present invention relates to an excellent powder polyolefin resin composition.

[Conventional technology and its problems]

Powdered resins are widely used as materials for powder coating methods such as fluidized dipping methods, electrostatic coating methods, and scattering methods.

The various powder coating methods described above have a number of advantages, such as not using dangerous solvents, high coating efficiency, and the ability to coat a thick film with a -degree coating. Among various powder resins, powder polyolefins have particularly excellent properties such as heat resistance, weather resistance, chemical resistance, and resistance to environmental stress cracking, and are suitable as materials for powder coating. In addition, grades with improved adhesion to metals have been developed, but because the hardness of the coating film surface of conventional products is low, their use is exclusively limited to indoor use. Surface hardness can be increased by using highly crystalline resins such as high-density polyethylene, but
Environmental stress cracking resistance and edge coverage (highly crystalline resins have a high shrinkage rate or residual stress after molding, so
The coating film on the edges or corners of the object to be coated becomes thinner, and in extreme cases, the coating film may break. The ability to maintain the coating thickness on ridges or corners close to the coating thickness on other flat or curved surfaces (called edge coverage) is greatly reduced and cannot be put to practical use. .

[Means to solve the problem]

The present invention provides a powder polyolefin resin composition that eliminates the drawbacks of the conventional powder polyolefins described above.

That is, the present invention uses 60 to 90% by weight of a polyolefin with a durometer D hardness of 60 or more (hereinafter referred to as high hardness polyolefin), 3 to 15% by weight of an elastomer, and 5 to 90% by weight of an elastomer.
This invention relates to a powdered polyolefin resin composition comprising 25% by weight of adhesive linear low density polyethylene.

High-hardness polyolefins include high-density polyethylene,
Examples include poly and propylene.

The powder polyolefin resin composition of the present invention contains 60 to 90% by weight of the above-mentioned high hardness polyolefin. If the content is less than 60% by weight, the hardness of the composition will not be sufficiently high, and if it exceeds 90% by weight, the environmental stress resistance of the coating film formed using the resulting composition will be reduced. Cracking property or edge covering property is not sufficiently improved.

As the elastomer, ethylene-propylene rubber,
Examples include ethylene-propylene-diene copolymer, styrene-ethylene-butylene-styrene copolymer, and ultra-low density polyethylene.

The elastomer is added in an amount of 3 to 15% by weight, particularly preferably 5 to 12% by weight. If the amount added is less than 3% by weight, the environmental stress cracking resistance and edge coverage will hardly be improved. If the amount added exceeds 15% by weight, the hardness of the resulting composition will be low, and the hardness of the coating film formed using this composition will also be low, making it impossible to use outdoors.

The adhesive linear low-density polyethylene includes so-called acid-modified polyethylene in which an unsaturated carboxylic acid and its derivatives are grafted onto linear low-density polyethylene, and a silane coupling agent is grafted onto linear low-density polyethylene. Examples include silane-modified polyethylene. Examples of unsaturated carboxylic acids include acrylic acid, maleic acid, fumaric acid, itaconic acid, and silatconic acid, but maleic acid is generally most often used. Derivatives of unsaturated carboxylic acids include anhydrides, esters, etc., but maleic anhydride and itaconic anhydride are common.

The unsaturated carboxylic acid and its derivatives are usually grafted to linear low density polyethylene in an amount of about 0.01 to 3% by weight. A predetermined amount of grafting may be carried out during modification, or a resin grafted at a high concentration may be diluted with the same or different unmodified resin to obtain a predetermined grafting amount of the resin. If the amount of grafting is too small, the desired improvement in adhesive strength will not be achieved, and if it is too large, not only will there be no further improvement in adhesive strength, but also there is a risk of gel formation, which is undesirable.

As the silane coupling agent, vinyltrialkoxysilane is preferable, and examples thereof include vinyltris(β-methoxyethoxy)silane, vinyltriethoxysilane, vinyltrimethoxysilane, T-methacryloxypropyltrimethoxysilane, and the like.

The silane coupling agent is usually grafted to the linear low density polyethylene in an amount of about 0.15 to 0.3% by weight. If the amount of grafting is too small, the desired adhesive strength will not be achieved, and even if the grafting amount is too large, the adhesive strength will not be improved any further.

Grafting of unsaturated carboxylic acids and their derivatives or silane coupling agents onto linear low density polyethylene is generally carried out by melt extrusion in the presence of organic peroxides, which can be carried out using an ordinary single-screw extruder. Combination with Banbury mixer and other mixers is also possible.

As the penetrating oxide, t-butyl hydroperoxide, t-butyl peroxybenzoate, 2゜5-dimethyl-2,5-di(t-butylperoxy)hexane,
α,α-bis(t-butylperoxy-m-isopropyl)benzene, di-isopropylbenzene hydroperoxide, di-t-butyl peroxide, 2.5-
Examples include dimethyl-2,5-di(t-butylperoxy)hexane-3,1,1,3,3-tetramethylbutyl hydroperoxide.

The amount of organic peroxide added is 10% of linear low density polyethylene.
The range of 0.05 to 0.2 parts by weight is preferable relative to 0 parts by weight. If the amount of organic peroxide is less than 0.05 parts by weight, sufficient adhesive strength cannot be obtained. If the amount exceeds 0.2 parts by weight, excess peroxide not consumed in modification may cause crosslinking or decomposition reactions of linear low-density polyethylene, cause burning or lumps, or cause decomposition products. This is not desirable because the odor becomes strong.

The adhesive linear low density polyethylene is 5 to 25% by weight.
, particularly preferably in an amount of 10 to 20% by weight. If the amount added is less than 5% by weight, the adhesion will be poor;
If it exceeds 0% by weight, the hardness of the resulting composition will be low, and the hardness of the coating film formed using this composition will also be low, making it impossible to use outdoors.

As linear low density polyethylene, butene is added to ethylene.
1. Copolymerization of α-olefins such as hexene-1,4-methyl-pentene-1 and octene-1 by known methods such as solution method, slurry method, and gas phase method under conditions of relatively low temperature and low pressure. Any conventional copolymer can be used without any restriction.

The powder polyolefin resin composition of the present invention contains a high-hardness polyolefin, an elastomer, and an adhesive linear low-density polyethylene, as well as additives such as an antioxidant, a lubricant, an ultraviolet absorber, a pigment, and a filler, if necessary. The mixture is melt-kneaded using conventional equipment such as a single-screw or multi-screw extruder or a Banbury Goxa-1 heating roll, pelletized using a twin-screw extruder, etc., and then ground using the pellets at room temperature or under freezing conditions. It can be manufactured by a method such as grinding and powdering.

The powder polyolefin resin composition of the present invention can be applied to metals, ceramics, and other materials by various powder coating methods such as fluidized dipping, electrostatic coating, electrostatic current dipping, and rotational molding. The object to be painted may be coated with an epoxy-based, urethane-based, or other primer, or may be subjected to treatments such as chemical conversion treatment, sandblasting, shot blasting, and the like. The thickness of the coating film varies depending on the application, but is approximately 200μ to several thicknesses, usually 300μ to 5μ.
It is within the range of a.

The present invention will be explained in more detail below with reference to Examples.

In addition, in the following examples, the coating method, environmental stress cracking resistance,
The method for measuring edge coverage and the like and the resin used are as follows.

Using the powder produced by the method shown in the Example of the Eso method,
After heating a steel plate of 0m, width 50mm, and thickness 1.6mm to 250''C, it was immersed in a fluidized immersion tank for 10 seconds, and after being taken out,
The surface was finished by leaving it for 2 minutes in a constant temperature bath set at 00'C. The coating thickness was 500μ.

Durometer D hardness according to JIS K7215 逅1u 壜力14υ4性 Comply with JIS K6760.

Conditions: Igepal Co-630102 aqueous solution,
5 o "C1" C maiden l traverse = ratio visual acuity l'' Hold both ends of the illusion-painted m board in the long plane direction in a vise, bend and deform it until the bending angle of the center becomes 90°, and then Visually observe the presence or absence of cracks in the paint film.

For Ao 1, a 2 mm square cut was made on the entire surface of the U& grade coating film using a cutter, and the state of peeling was observed.

(1) High hardness polyolefin High density polyethylene (abbreviated as HDPE in the table) Ml
(g/10 min)/p (g/cffl)=2g10
．． 960 Polypropylene (abbreviated as PP in the table) MI/
ρ = 610.91o (ethylene-prohylene block copolymer) (2) Elastomer (abbreviated as 5EBS in the table) Styrene-ethylene-butylene-styrene copolymer old / 0 = 810.90 (However, MI (7) Measurements were made at a temperature of 200" C1 load 315 kg) (3) Adhesive linear low density polyethylene (AGL in the table)
Abbreviated as L> MI/p = 1010.919 (mtiL/7-butene-1 copolymer) Amount of maleic anhydride grafted: 1% by weight Examples 1 to 2 and Comparative Example 1 Composition and proportions shown in Table 1 A powder polyolefin resin composition was produced by the following method.

In addition to the composition in Table 1, 1000 ppm of antioxidant was added to each of the compositions shown in Table 1.
, 2000 ppm of ultraviolet absorber were added, and mixed for 2 minutes at room temperature using a super mixer (manufactured by Kawata).

This mixture was supplied to a twin-screw extruder with a set temperature of 240°C, melt-kneaded, and pelletized. These pellets were mechanically pulverized at room temperature using a CR pulverizer (manufactured by Turbo Kogyo ■), and classified using a 50-mesh sieve to adjust the particle size.

The above-described coating was carried out using this powder, and the surface hardness, environmental stress cracking resistance, and edge coverage were measured according to the above-described method, and a bending test and a base grain test were carried out.

The results are shown in Table 1.

As is clear from Table 1, the coating film coated using the powdered polyolefin resin composition of the present invention has high surface hardness and excellent environmental stress cracking resistance. In addition, the wall thickness of the ridge line etc. is maintained at about 70 to 80% of the thickness of the flat part.
It is an excellent coating film, with no peeling of the coating film on the bent part in the bending test, and no peeling of the coating film in the base grain test.

On the other hand, the coating film using the composition of the comparative example had sufficiently high surface hardness, but the environmental stress cracking resistance was very poor.
In addition, the coating film was extremely thin at the ridge lines, etc., and almost the entire coating peeled off and flaked off in the bending test and base grain test.

〔Effect of the invention〕

The coating film coated using the powdered polyolefin resin composition of the present invention has high surface hardness and has excellent environmental stress cracking resistance, edge coverage, and adhesion. It can be used outdoors, which is difficult to do with powder.

Claims (1)

[Claims] 60-90% by weight polyolefin with durometer D hardness of 60 or more, 3-15% by weight elastomer, 5-2
A powder polyolefin resin composition comprising 5% by weight of adhesive linear low density polyethylene.