JP3340480B2 - Polypropylene resin powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polypropylene resin powder suitable for powder coating of metal products. More specifically, when a polypropylene resin powder is used as a metal product coating, it has excellent adhesion to metal, high surface hardness, and excellent heat resistance, chemical resistance, ESCR resistance, and hot water resistance. Have.

[0002]

2. Description of the Related Art Conventionally, metal products (for example, bicycle baskets, drainage shelves, refrigerator nets, etc.) are resistant to corrosion and chemicals.
In order to impart functions such as stain resistance and decorativeness, a method of applying a polyethylene powder to the surface by a fluid immersion method, an electrostatic coating method, a rolling coating method, or the like has been widely adopted.
However, polyethylene has a problem in durability because of low adhesion to metal.

As a means for solving this problem, a method utilizing polyethylene modified with maleic anhydride or the like is disclosed in
8-2358, JP-A-58-142945 and JP-A-59-30841.
By increasing the adhesion to metal and improving the durability in this way, polyethylene powder is used in the field of products requiring durability, such as fences, and the field of application is expanding. However, polyethylene coatings are easily scratched,
It has drawbacks such as low usable temperature, and improvement is desired. Compositions using polypropylene having better heat resistance than polyethylene are disclosed in JP-A-62-190265 and JP-A-01-297174. However, in all cases, the durability of the coated polypropylene film is insufficient, and a more improved product is desired.

[0004]

DISCLOSURE OF THE INVENTION The present invention has a corrosion resistance, a chemical resistance, a stain resistance and a decorative property equal to or higher than that of a polyethylene coating film, and has a high surface hardness and a high heat resistance. An object of the present invention is to provide a polypropylene resin powder capable of forming an excellent coating film on a metal product.

[0005]

Means for Solving the Problems The present inventors have made intensive studies to overcome the above-mentioned problems, and as a result, have accomplished the present invention. That is, in the present invention, (A) the MFR is 5 to 5.
A content of polypropylene of 90 to 40% by weight and (B) a vinyl aromatic hydrocarbon of more than 60% by weight and 90% by weight or less, and at least one vinyl aromatic hydrocarbon polymer block X and at least 1 Olefin compound polymer block Y, and the degree of unsaturation of block Y is not more than 20%. The present invention relates to a polypropylene-based resin powder comprising a mixture of 10 to 60% by weight of a modified block copolymer modified by binding by weight.

(A) As the polypropylene polymer,
Homopolymers obtained by homopolymerizing propylene, random copolymers or block copolymers obtained by copolymerizing propylene and ethylene, multi-component copolymers obtained by copolymerizing propylene, ethylene and one or more other α-olefins, and two kinds thereof The thing which combined the above is mentioned.
The MFR of the polypropylene-based polymer needs to be 5 to 200, preferably 20 to 175, and more preferably 25 to 130. When the MFR is lower than 5, the fluidity at the time of melting is poor, so that the surface of the coated product is not smooth. On the other hand, if the MFR is higher than 200, the physical properties such as the tensile strength and the impact resistance of the coating film are extremely deteriorated, so that they cannot withstand long-term use. In the copolymer of propylene and ethylene, ethylene in the copolymer is 0.1 to 2
A range of 5% by weight, preferably 0.3 to 10% by weight is preferred.

[0007] From the viewpoint of impact resistance and low-temperature resistance, the use of block copolymer is recommended. Examples of the α-olefin used in the multi-component copolymer include 1-butene and 1-butene.
Hexene and 1-octene are exemplified, but 1-butene is preferred from the viewpoint of raw material price. The content of ethylene and α-olefin in the multi-component copolymer is preferably in the range of 0.1 to 20% by weight, preferably 0.3 to 10% by weight, and the ratio of ethylene to α-olefin is not particularly limited.

(B) The modified block copolymer is a block copolymer comprising a vinyl aromatic hydrocarbon polymer block X and at least one olefin compound polymer block Y whose degree of unsaturation does not exceed 20%. This is hereinafter referred to as a “base block copolymer”) to which a carboxylic acid group or a derivative thereof is bonded. The vinyl aromatic hydrocarbon polymer block is obtained by polymerizing at least one of styrene, α-methylstyrene, vinyltoluene and the like, and styrene is preferred. Here, the olefin compound polymer block Y is a monoolefin such as ethylene, propylene, 1-butene and isobutylene, or a conjugated diolefin such as butadiene, isoprene and 1,3-pentadiene, 1,4 hexadiene, norbornene and norbornene. One or more olefin compounds selected from non-conjugated diolefins such as derivatives are polymerized or copolymerized, and the unsaturation of the block is 20%.
It is as follows. Specific examples of the “base block copolymer” include a hydrogenated product of a block copolymer of a vinyl aromatic hydrocarbon and a conjugated diolefin, and a block copolymer of a vinyl aromatic hydrocarbon and a monoolefin. Can be Preferably, the non-conjugate degree of the conjugated diolefin portion of the block copolymer composed of the vinyl aromatic hydrocarbon polymer block and the polymer block mainly composed of conjugated diolefin is selected so as not to exceed 20%. It is a hydrogenated product.

Then, an unsaturated carboxylic acid group or a derivative thereof is bonded to the "base block copolymer" by an addition reaction to obtain a modified block copolymer. In the "base block copolymer", the weight ratio between the vinyl aromatic hydrocarbon polymer block X and the olefin compound polymer block Y is 60/40 to 90/10, preferably 65/35.
８５85/15. Further, each of the polymer blocks may contain two or more polymer blocks, and each block may have the same structure or may have a different structure. The number average molecular weight is 20,000 to 500.
000, preferably 40,000 to 400,000, and a molecular weight distribution of 1.05 to 10 is recommended. The double bond based on the conjugated diene contained in the olefin compound polymer block Y has a degree of unsaturation of 2 in the block.
It is necessary not to exceed 0%. If the degree of unsaturation contained in the block Y exceeds 20%, the weather resistance and heat resistance of the powder are adversely affected, which is not preferable.

Compounds used in the addition reaction of unsaturated carboxylic acid groups or derivatives thereof include, for example, maleic acid, fumaric acid, itaconic acid, maleic halide, dicarboxylic acid anhydride, ester, amide And imides such as acrylic acid and methacrylic acid, and their monocarboxylic acid esters and amides. Of these, maleic anhydride is preferred.

The amount of the molecular unit containing a carboxylic acid group or a derivative thereof contained in the modified block copolymer, that is, the addition amount of the unsaturated carboxylic acid group or the derivative thereof is defined as “base”.
0.05 to 2 per 100 parts by weight of "sblock copolymer"
0 parts by weight, preferably 0.1 to 15 parts by weight, more preferably 0.15 to 10 parts by weight. If it is less than 0.05, the adhesion performance is not exhibited at all, while if it exceeds 20 parts by weight, the adhesion performance is not improved as compared with the amount less than 20 parts by weight, and the heat resistance is lowered.

90 to 40% by weight of the component (A) and 60 to 10% by weight of the component (B) are melt-kneaded by a single-screw extruder, a twin-screw extruder or the like to form a uniform composition. When the amount of the component (A) is less than 40% by weight, heat resistance and high surface hardness cannot be sufficiently achieved. On the other hand, if it is more than 90% by weight, the adhesion and the elongation of the coating film are insufficiently improved, resulting in poor durability. Preferably, a range of 85 to 50% by weight of the component (A) and 50 to 15% by weight of the component (B) is used. It is advantageous to add the pigment or the master batch of the pigment during the melt-kneading and simultaneously perform the coloring to simplify the production process. Furthermore, antioxidants, weathering agents, lubricants, crystal nucleating agents, antibacterial agents, antifungal agents, antistatic agents,
It is possible to improve the performance of the polypropylene resin powder by a method of simultaneously adding a filler, a peroxide and the like.

It is important for the polypropylene resin powder suitable for powder coating that the powder has good fluidity. For this purpose, the average particle size of the powder is 10 to 500 μm.
m 2 and a bulk density in the range of 0.2 to 0.6 g / cm ³ are used. The preferred particle size of the powder depends on the coating method,
80～300Myu m in a fluidized immersion method, 50～200Myu m in electrostatic coating, in the roll coating method is recommended 80~400μ m. To obtain good powder flowability, the bulk density is preferably 0.25 to 0.58 g /
cm ³ , more preferably 0.3 to 0.55 g / cm ³ is recommended.

As a method for obtaining such a polypropylene resin powder, it is produced by various mechanical grinding methods at a temperature of 0 ° C. or less, preferably -10 ° C. or less. Furthermore, it is also possible to improve the powder fluidity by stirring at a high speed at a temperature lower than the melting point of the powder after pulverization. In addition, a method of mixing and coloring carbon black, metal powder, and the like using a high-speed mixer or the like after pulverization, and a method of mixing inorganic materials such as finely divided silica and talc to improve powder performance are also adopted. It is possible.

[0015]

EXAMPLES The present invention will be further described below with reference to examples, but the present invention is not limited to these examples. The physical properties in the examples were measured by the following methods. 1) MFR: JIS K-6758 230 ° C, load: 2.16 kg 2) Average particle size: The powder was sieved with a shaking sieve, and the particle size of 50% by weight was determined as the average particle size from an integral curve with respect to the particle size. 3) Tensile elongation: A flat plate of 2 mm was prepared by press molding of powder, and measured by a tensile test method (JIS K-6760). 4) Surface hardness: Shore-D hardness was measured according to JIS K6760. 5) Adhesion strength: A metal test piece is coated by the fluid immersion method, and 11 parallel cuts (interval: 1 mm) reaching the base of the test piece with a thin blade with a thin blade and parallel cuts at right angles thereto Eleven pieces (interval: 1 mm) were inserted to make a grid (100 pieces), a cello tape was stuck thereon, and then peeled off, and the adhesion strength was indicated by the number of peeled coating films. In other words, 0/100 indicates that the adhesiveness is very high without any peeling, and 100/100 indicates that the adhesive has been completely peeled off and that there is no adhesiveness.

6) Impact strength: DuPont impact test method (JI
SK-5400 Measure the coating strength of the metal test piece at an impact strength of 0.5 kg-m), apply 物 for those with no cracks in the coating, ○ for those with small cracks, and △ for those with large cracks. The thing from which the film was peeled was represented by x. 7) Toughness resistance test: Two cuts were made on the coating film of the metal test piece with a thin blade so as to reach the base of the test piece, and the test piece was placed in a wet tester (JIS Z-0228).
After leaving for 00 hours, observe the state of rust from the cut,
If the rust does not expand, ○ indicates that the rust is slightly expanding.
The thing which rust is expanding was represented by x.

[0017]

Examples 1 to 7 (1) Production of modified block copolymer Butadiene and styrene were block-copolymerized in n-hexane solvent with tetrahydrofuran as a vinyl content regulator using n-butyllithium as a polymerization catalyst. This was subjected to a hydrogen pressure of 7 kg / cm ² and a temperature of 50 kg in cyclohexane using cobalt naphthenate and triethylaluminum as catalysts.
After hydrogenating at 90 ° C. for 5 hours to hydrogenate about 90% of the double bond of the butadiene block, the catalyst residue was removed by washing with aqueous hydrochloric acid-methanol. For 100 parts by weight of the hydrogenated block copolymer, 3 parts by weight of maleic anhydride and 0.1 part by weight of Perhexa 25B (manufactured by NOF Corporation)
Was uniformly mixed and then supplied to a screw extruder to perform a malein reaction to obtain a modified block copolymer shown in Table 1. (2) Manufacture of polypropylene-based resin powder Polypropylene and the modified block copolymer shown in Table 2 and pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxy) were used for these resin components. Phenyl) propionate] 1000 ppm and tetrakis (2,4-di-t-butylphenyl) -4,4'-biphenylenephosphonite 2000 ppm
Using a 0 mm φ twin screw extruder, the mixture was kneaded at 220 ° C to form pellets. The pellets were cooled below -20 ° C. with liquid nitrogen and pulverized by mechanical pulverization, the average particle size of 200 by taking out those passing through the sieve having a mesh opening 250 [mu] m
to obtain a polypropylene powder mu m. This powder was formed into a 2 mm flat plate by press molding, and the tensile elongation was measured. The surface hardness was also measured. The results are shown in Table 2. (3) was coated the powder by fluidized-bed coating the rolled steel sheet painted 0.6mm thickness of the polypropylene resin powder to form a coating film of 380μ m. Table 2 shows the measurement results of physical properties of the coating film.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

Comparative Example 3 B of Example 1 was used as a modified block copolymer.
Propylene powder was produced under the same conditions as in Example 1 except that the vinyl content of the butadiene portion in Example 1 was 35%. Its tensile elongation is 34% and its surface hardness is Shore-D.
71. In addition, the performance of the coating film is 65/10 adhesion strength.
0, impact strength △, and touch resistance test x.

[0021]

Comparative Example 4 B of Example 1 was used as a modified block copolymer.
Propylene powder was produced under the same conditions as in Example 1 except that the product to which maleic anhydride was not added was used.
Its tensile elongation is 240% and its surface hardness is Shore-D71.
Met. The performance of the coating film was as follows: adhesion strength 0/100, impact strength ○, and touch resistance test X.

[0022]

EFFECT OF THE INVENTION The coating of a metal product with the polypropylene resin powder of the present invention has excellent properties such as a surface that is less likely to be damaged and a higher usable temperature than a polyethylene coating,
In addition, the durability is greatly improved compared to a coating film coated using a conventional polypropylene resin powder.

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Claims (1)

(57) [Claims] 1. A (A) polypropylene polymer having an MFR of 5 to 200, 90 to 40% by weight and (B) a vinyl aromatic hydrocarbon content of more than 60% by weight and 90% by weight or less, It has at least one vinyl aromatic hydrocarbon polymer block X and at least one olefin compound polymer block Y, and the degree of unsaturation of the block Y is 2
A mixture comprising a modified block copolymer in which a carboxylic acid group or a derivative thereof is bonded to a block copolymer, which is not more than 0%, which is an olefin-based compound polymer block, in an amount of 0.05 to 20% by weight, and 10 to 60% by weight. Tona is, powder
The average particle size of the body is 10 to 500 μm, and the bulk density is 0.2 to
A polypropylene-based resin powder for powder coating, which is 0.6 g / cm ³ .