JPH01156377A - Ethylene polymer composition for powder coating - Google Patents

Abstract

PURPOSE:To provide the title compsn. which is free from bubble formation during powder coating and gives a coating film having excellent adhesive strength and heat resistance, by mixing an ethylene polymer modified with an unsatd. carboxylic acid, a polybutadiene rubber and an antioxidant in specified wt. proportions. CONSTITUTION:99.7-70wt.% ethylene polymer (e.g., low-density polyethylene) modified with an unsatd. carboxylic acid (e.g., maleic anhydride) or a deriv. thereof or an ethylene polymer compsn. obtd. by compounding the modified polymer with an unmodified ethylene polymer is mixed with 0.3-30wt.% polybutadiene rubber. 0.01-5pts.wt. antioxidant is added to 100pts.wt. resultant resin compsn. to prepare an ethylene polymer compsn. for powder coating. Suitable examples of the antioxidant are 2,2'-methylenebis(4-methyl-6-t- butylphenol) and trioctadecyl phosphite.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an ethylene polymer composition for powder coating, and more particularly to an ethylene polymer modified with an unsaturated carboxylic acid or a derivative thereof, or an unsaturated composition thereof. An ethylene polymer composition containing a modified ethylene polymer,
This invention relates to an ethylene polymer composition for powder coating, which contains a specific amount of polybutadiene rubber and an antioxidant.

[Prior art] Generally, polyethylene resin has high strength, chemical resistance, corrosion resistance, and is inexpensive, so injection molding,
It is used in a wide range of applications such as extrusion molding, blow molding, etc. to make films, containers, blow pins, etc.

However, since polyethylene resin does not have a polar group in its molecule, it has the drawback of extremely poor adhesion to other synthetic resins, metal wood, and other dissimilar materials. Therefore, attempts have been made to introduce functional groups by adding unsaturated carboxylic acids and the like to impart adhesive properties (for example, JP-A-50-4144).
.

Furthermore, compositions in which the adhesive properties are improved by modifying polyolefin polymers with solid rubber and unsaturated carboxylic acids (for example, JP-A-50-7847, JP-A-51-98784, JP-A-52-1999) Publication No. 8035, JP-A-52-80
334, JP-A-52-123443, JP-A-54-12408, etc.) or ethylene-α-
Compositions obtained by modifying olefin copolymer rubber with unsaturated carboxylic acids (JP-A-52-44689, JP-A-52-44689)
No. 49289, etc.) have been proposed, and attempts have also been made to protect metal surfaces by coating them with powder coating on metal surfaces.

[Problems to be Solved by the Invention] However, when the above-mentioned composition is used for paint-coated steel pipes, although the composition has satisfactory adhesion, for example, when connecting the coated steel pipes, In order to cut the flange surface smoothly, cutting is performed with a plane or the like. When looking at the cut surface of the coating layer, many fine bubbles are generated inside, which poses a practical problem. This tendency of bubbles becomes stronger as the wall thickness increases.

This is thought to be due to shrinkage strain that occurs when the heated and melted polyolefin polymer is cooled, and =3- is unavoidable when using a polyolefin polymer. Furthermore, since polymers for powder coating are exposed to high temperatures, they suffer from severe thermal deterioration, and improvements are needed.

The present invention has been made in order to eliminate the drawbacks of the prior art, and provides an ethylene polymer composition for powder coating that reduces shrinkage distortion, is less likely to generate bubbles during coating, and has less thermal deterioration. With the goal.

[Means for Solving the Problems] As a result of intensive studies, the present inventors have discovered an ethylene polymer composition that can achieve the above object, and have completed the present invention.

That is, the present invention provides (A) an ethylene polymer modified with an unsaturated carboxylic acid or a derivative thereof or an ethylene polymer composition 99.7-3 in which an unmodified ethylene polymer is blended therewith;
(C) 0.01 to 5.0 parts by weight of an antioxidant was blended to 100 parts by weight of a resin composition consisting of 0% by weight and (B) 0.3 to 30% by weight of polybutadiene rubber. The present invention provides an ethylene polymer composition for powder coating, which is characterized by the following.

The ethylene polymer used in component (A) of the present invention includes low density polyethylene, medium/high density polyethylene, ethylene-propylene copolymer, ethylene-butene-1 copolymer, ethylene-4-methylpentene-1 Ethylene and carbon number 03 such as copolymer, ethylene-hexene-1 copolymer
-Copolymers with α-olefins of CI2, preferably 03 to C8, ethylene and vinyl acetate, (meth)acrylic acid, alkyl esters of methyl (meth)acrylate, ethyl, propyl, etc., glycidyl (meth)acrylate copolymers with etc., preferably having a density of 0.880 to 0.
．． It is a copolymer of polyethylene or ethylene and an α-olefin of 03 to C8 in the range of 940 g/cnl. These ethylene polymers can be used alone or in combination.

The ethylene polymer in the present invention is modified with an unsaturated carboxylic acid or a derivative thereof in the presence of an organic peroxide.

In the present invention, it is also possible to further add an unmodified ethylene polymer to the modified ethylene polymer.

The unsaturated carboxylic acids or their derivatives used here include monobasic acids, dibasic acids such as acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, citraconic acid, and their like. Examples include anhydrides, of which maleic acid or maleic anhydride is particularly preferred. Further, examples of derivatives of unsaturated carboxylic acids include metal salts, amides, imides, esters, etc. of the above-mentioned unsaturated carboxylic acids. These can be used alone or in combination of two or more.

Further, the organic peroxides used in the present invention include benzoyl peroxide, lauryl peroxide, dicumyl peroxide, tert-butyl peroxybenzoate, 2,5-dimethyl-2,5-di(t-butyl peroxide), ) Hexin-3 etc. are exemplified, and these are:
It is appropriately selected depending on the type of ethylene polymer, polybutadiene rubber, unsaturated carboxylic acid or derivative, etc.

The unsaturated carboxylic acid or its derivative is preferably contained in the above-mentioned ethylene polymer or the ethylene polymer composition in which an unmodified ethylene polymer is blended therewith.
It is contained in an amount of 5.0% by weight, more preferably 0.1 to 3.0% by weight. If the content is less than 0.05% by weight, the adhesive strength will be low, and if it exceeds 5.0% by weight, gelation or coloring of the resin will occur during the melt reaction.

The polybutadiene rubber that is component (B) of the present invention has a butadiene content of 80% by weight or more, and has a Mooney viscosity M L + +4 (100°C) 30 to 50.
．． Preferably, the number average molecular weight (Mn) is in the range of -5 x 104 to 1 x 106, and the weight average molecular weight (Mw) is in the range of 10 x 104 to 5 x 106.

Methods for blending this polybutadiene rubber include (1) a method in which polybutadiene rubber is blended when an ethylene polymer is modified with an unsaturated carboxylic acid or a derivative thereof in the presence of an organic peroxide; ) A method in which an ethylene polymer is modified in advance with an unsaturated carboxylic acid or its derivative in the presence of an organic peroxide to produce a modified ethylene polymer, and then a polybutadiene rubber is blended. Examples include a method of blending an appropriate amount of polybutadiene rubber during and after modification.

The blending ratio of the modified ethylene polymer as the component (A) or the ethylene polymer composition blended with the unmodified ethylene polymer and the polybutadiene rubber as the component (B) is 99% of the component (A). .7 to 70% by weight, and component (B) 0.3 to 30% by weight. If the amount of polybutadiene rubber (B) is less than 0.3% by weight, the generation of bubbles cannot be suppressed, and if it exceeds 80% by weight, the coating layer will be free of bubbles, but the adhesive strength and tensile strength will decrease. .

Further, as the antioxidant which is the component (C) of the present invention, at least one type or a combination of two or more types selected from phenolic antioxidants, phosphorus type antioxidants, and sulfur type antioxidants can be used. In particular, it is preferable to combine a phenol-based antioxidant and a phosphorus-based antioxidant because the effect is dramatically improved.

Phenolic antioxidants include hindered phenol compounds, specifically 2,2'-methylenebis(4-methyl-et-butylphenol), 4,4
'-Butylidenebis (3-methyl-6-butylphenol), 4,4'-thiobis (3-methyl-et
-butylphenol), tetrakis[methylene 3- (
4'-Hydroxy-3',5'-di-t-butylphenyl)propionate comethane, n-octadecyl 3-(
4'-hydroxy-3', 5'-di-t-butylphenyl)propionate, 2,4-bisoctylthio-[
1-(4'-hydroxy-3',5'-di-t-butylanilino)-1,3,5-triazine, L, 3.5
-) Lis(4'-hydroxy-3',5'-di-t-
butylbenzyl)-1,3,5-) riazine-2,4,
6(LH,3H,5H)-trione, 1.3.5-tris-(3'-hydroxy-2', 6'-dimethyl-4'
-1-butylbenzyl) -1,3,5-triazine-2,4,6(IH,3H,5H)-)ion, L, 3
．． Examples include 5-trimethyl-2,4,64lis(4'-hydroxy-3',5'-di-t-butylbenzyl)benzene.

Examples of phosphorus-based antioxidants include compounds such as phosphite, phosphite, and phosphophenanthrene. ) phosphite, tris(
2,4-di-t-butylphenyl) phosphite, 9
．． 10-dihydro-9-oxa-10-phosphonophenanthrene-10-oxide, tetrakis(2,4-
di-t-butylphenyl)-4,4'-biphenylene diphosphonite, and the like.

Examples of sulfur-based antioxidants include thiols and sulfites, specifically 3,3'-thiodipropionic acid, didodecyl 3,3'-thiopropionate, dioctadecyl 3,3'-thio Propionate, pentaerythryltetrakis (3-dodecylthiopropionate)
, pentaerythrityltetrakis (3-octadecylthiopropionate), and the like.

The amount of the antioxidant, which is component (C), is preferably 0.01 to 5.0 parts by weight, based on 100 parts by weight of the resin composition, which is the total amount of components (A) and (B). 0.05～
It is 1.0 part by weight.

If the amount of component (C) is less than 0.1 part by weight, the resin will deteriorate, resulting in coloration, gelation, etc., which is not preferable.

Further, if the amount exceeds 5.0 parts by weight, no further improvement in the blending effect can be expected and there is a risk that processability and mechanical properties may be impaired, which is not preferable.

The melt reaction or melt mixing temperature is determined by taking into consideration the deterioration of the ethylene polymer and polybutadiene rubber used, and the decomposition temperature of the organic peroxide, but generally 1.
It is in the range of 50 to 300°C.

Powder coating as referred to in the present invention refers to heating and melting plastic powder on the surface of an object to form a continuous film, and a fluidized dipping method, a thermal spraying method, an electrostatic coating method, etc. are used. The ethylene polymer composition of the present invention forms a bubble-free coating layer when it is powdered and coated on a metal surface. This powdering can be done by a conventional method, but specific examples include mechanical pulverization at room temperature or freezing, precipitation from a solvent, etc. Either of these methods can be used in conjunction with the powder coating method. can. The particle size of the powder is 30 to 200 meshes, preferably 40 to 150 meshes, more preferably 50 to 100 meshes, in order to obtain a uniform, bubble-free and strongly adhesive coating layer.

Furthermore, the equipment used for the melt reaction or melt mixing may be a general kneading machine such as a Banbury mixer, kneader, mixing roll, -shaft, twin-screw extruder, etc., and these can be used alone or in combination for easier operation. I can do it. Further, the melt reaction may be carried out in the presence of a solvent.

[Example] Hereinafter, the present invention will be described in detail based on Examples and the like.

Example 1 Linear low density polyethylene (melt flow rate (MFR) -2 g/10 min, density = 0) as an ethylene polymer
．． 922g/cd, Product name: 1 stone Nirex AF33
40, manufactured by Nippon Petrochemical Company), and this was mixed with 0.25 parts by weight of maleic anhydride and 2.5-dimethyl-2,5-
di(tert-butylperoxy)hexyne-80,
(A) was passed through an extruder (50 mmφL/D=24) heated to 180-230°C by 03 parts by weight.
When obtaining 95 parts by weight of modified linear low density polyethylene (hereinafter referred to as modified LLDPE), (B) polybutadiene rubber (Mooney viscosity ML++4 (100°C) 35,
Cis-1,4 bond content 94%, product name: JSRBR0
02L, manufactured by Nihon Gosei Rubber Co., Ltd.) (hereinafter referred to as BR-1), and after modification, 2.5 parts by weight of the same BR-1 as above and (C) pentaerythryl-tetrakis [ 3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] (Product name: Irg
0.2 parts by weight of Nox 1010 (manufactured by Ciba Geigy) (referred to as Antioxidant-1) was added thereto, and then pulverized to obtain an ethylene polymer composition with an average particle size of 70 mesh.

Example 2 BR-1 was added to 95 parts by weight of modified LLDPE obtained in the same manner as in Example 1 except that no polybutadiene rubber was added.
An ethylene polymer composition having an average particle size of 70 mesh was obtained in the same manner as in Example 1 except that 5.0 parts by weight was added.

Example 3 BR-15.0 parts by weight was blended with 95 parts of modified LLDPE during modification, and after modification, polybutadiene rubber was not added, but otherwise the same procedure as in Example 1 was carried out to obtain an average particle size of 7.
An ethylene polymer composition having 0 mesh was obtained.

Example 4 Polybutadiene rubber (hereinafter referred to as BR, -2) containing 18% of cis-1,4 bond was used, and in the same manner as in Example 1, an ethylene-based rubber with an average particle size of 68 mesh was used. A combined composition was obtained.

Example 5 An ethylene polymer composition was obtained in the same manner as in Example 1 except that the particle size of the pulverized composition was 50 mesh.

Example 6 An ethylene polymer composition was obtained in the same manner as in Example 1 except that the particle size of the pulverized composition was 95 mesh.

Example 7 BR-1 to 80 parts by weight of modified LLDPE
10 parts by weight is added at the time of modification, and after this modification, the above BR
An ethylene polymer composition having an average particle size of 65 mesh was obtained in exactly the same manner as in Example 1, except that -115 parts by weight was further added.

Example 8 5 parts by weight of BR-IQ was added to 99 parts by weight of modified LLDPE during modification, and after this modification, the above BR-10,
An ethylene polymer composition having an average particle size of 75 mesh was obtained in exactly the same manner as in Example 1, except that 5 parts by weight was further added.

Example 9 The polymer composition of Example 1 was further added with a phosphorous antioxidant, tetrakis(2,4-di-t-butyl)-4,4'-biphenylenephosphonite (trade name: PEPQ).

(manufactured by Ciba Geigy) (hereinafter referred to as antioxidant-2) 0.
2 parts by weight were blended to obtain an ethylene polymer composition with an average particle size of 70 mesh.

Comparative Example 1 An ethylene polymer composition having an average particle size of 70 mesh was obtained in the same manner as in Example 1, except that no polybutadiene rubber was added.

Comparative Example 2 BR-1 was mixed with ethylene-propylene copolymer (EP)
An ethylene polymer composition having an average particle size of 71 mesh was obtained in exactly the same manner as in Example 1 except that R) was used.

Comparative Example 3 An ethylene-based polymer with an average particle size of 72 mesh was prepared in the same manner as in Example 1, except that BR-1 was changed to polyisobutylene (trade name: Vistanex #, 140, manufactured by Esso Kagaku ■) (PIB). A combined composition was obtained.

Comparative Example 4 Modified LLDPE 99. For B-Okibe, BR
-10.2 parts by weight was added at the time of modification, and after the modification, no polybutadiene rubber was added, otherwise the same procedure as in Example 1 was repeated to obtain an ethylene polymer composite acid having an average particle size of 70 mesh.

Comparative Example 5 BR-110 parts by weight was added to 85 parts by weight of modified LLDPE during modification, and after this modification, the above BR-125
An ethylene polymer composition having an average particle size of 40 mesh was obtained in exactly the same manner as in Example 1, except that an additional part by weight was added.

Comparative Example 6 Modified LLDPE [i5 parts by weight was mixed with BR-125 parts by weight at the time of modification, and after the modification, 10 parts by weight of the above polybutadiene rubber was further added. An ethylene polymer composition having an average particle size of 70 mesh was obtained.

Comparative Example 7 An ethylene polymer composition having an average particle size of 70 mesh was obtained in exactly the same manner as in Example 1, except that no antioxidant was added.

Experimental Example 1 A blasted steel plate prepared by heating the ethylene polymer compositions obtained in Examples 1 to 9 and Comparative Examples 1 to 7 to 280°C by a fluidized dipping method was immersed for 30 seconds to obtain a 2 mm thick coating layer. . This 2 mm thick coating layer was cut with a plane to a thickness of 1 mm.
．． It was set to 5 mm. Visually determine the number of bubbles per ci on the surface, and then cut a 10 mm wide slit to make 18
The adhesive strength was measured in a 0° peel test (based on JIS K6251), and the tensile strength and elongation of the composition (JIS K6251) were measured.
IS K [based on 17BO-1966] was determined.

These results are shown in Table 1.

Experimental Example 2 The ethylene polymer compositions obtained in Example 1.9 and Comparative Example 1.7 were subjected to fluidized dipping at a temperature of 320° C., which was stricter than that in Experimental Example 1.

The results are shown in Table 2.

As is clear from the results in Table 2 and above, Examples 1 to 9 generate almost no bubbles and are excellent in various properties such as adhesive strength, tensile strength, and elongation. On the other hand, Comparative Examples 1 to 7 generate many bubbles and are inferior in various properties such as adhesive strength.

[Effects of the Invention] As explained above, since the ethylene polymer composition for powder coating of the present invention contains polybutadiene rubber, it is possible to form a coating layer on a metal surface by a method such as powder coating. Sometimes, bubbles are not generated inside the coating layer and the adhesive strength is strong. Furthermore, due to the combination of antioxidants, there is little thermal deterioration even at high temperatures, and coloring is less likely to occur. In particular, the performance is further improved by using a phenolic antioxidant and a phosphorus antioxidant together. In addition, the ethylene polymer composition for powder coating of the present invention has adhesive properties to an extremely wide range of materials such as metals such as aluminum foils or plates and iron plates, plywood such as veneer, lumber, glass, and ceramics. Provides a bubble-free coating layer.

Therefore, the ethylene polymer composition for powder coating of the present invention can be used in a wide range of industrial materials, construction materials, civil engineering materials, and packaging materials. It can be effectively used for coating steel pipes, etc.

Claims (1)

[Claims] 1. (A) An ethylene polymer modified with an unsaturated carboxylic acid or a derivative thereof, or an ethylene polymer composition in which an unmodified ethylene polymer is blended with the ethylene polymer 99.7
-30% by weight, (B) polybutadiene rubber 0.3-30% by weight, (C) antioxidant 0
．． 01 to 5.0 parts by weight of an ethylene polymer composition for powder coating. 2. The ethylene polymer composition for powder coating according to claim 1, wherein the antioxidant is at least one selected from phenolic antioxidants, phosphorus antioxidants, and sulfur antioxidants. thing. 3. The ethylene polymer composition for powder coating according to claim 1 or 2, wherein the antioxidant is a combination of a phenolic antioxidant and a phosphorus antioxidant. 4. The ethylene polymer is an ethylene homopolymer or a copolymer of ethylene and an α-olefin of C_3 to C_8, and has a density of 0.86 to 0.940 g/cm.
The ethylene polymer composition for powder coating according to claim 1, 2 or 3 falling within the scope of ^3. 5. Claims 1 to 4, wherein the content of the unsaturated carboxylic acid or its derivative is in the range of 0.05 to 5.0% by weight of the ethylene polymer or ethylene polymer composition. The ethylene polymer composition for powder coating according to any one of the above. 6. Claims 1 to 6, wherein the unsaturated carboxylic acid or its derivative is maleic acid or maleic anhydride.
The ethylene polymer composition for powder coating according to any one of Item 5.