JP2000129165A - Rust preventive powder coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition preventing corrosion of a metal base material for a long period of time, giving a coating film having durability for a long period of time and having excellent rust preventive property by mixing a specific amount of a compound of hydrotalcites, etc., into the composition. SOLUTION: This rust preventive powder coating composition is composed of (A) 100 pts.wt. of a polyolefinic resin, (B) 0.01-10 pts.wt. of a hydrotalcite compound and (C) 0.01-10 pts.wt. of an aromatic acid salt. Preferably, the component A is (i) a resin having 5-80 g/10 min melt flow rate at 230 deg.C, concretely, a polypropylene resin such as modified polypropylene or non-modified polypropylene or (ii) a resin having 1-80 g/10 min melt flow rate at 190 deg.C, concretely a polyethylene resin such as modified polyethylene or non-modified polyethylene and the component C is at least one kind selected from a group of benzoates or phthalates.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a powder coating composition. More specifically, the present invention relates to a powder coating composition which gives a coating film having excellent rust prevention even in a hot water environment.

[0002]

2. Description of the Related Art Polyolefin polymers have been widely used in powder coatings because of their excellent workability and chemical resistance (Japanese Patent Application Laid-Open Nos. Sho 62-190265 and Hei 5-25229). JP-A-9-12928). However, when these powder coatings are used for water-based products, especially products used in hot water environments such as hot water supply pipes, iron-based paints are generated due to oxygen, moisture, etc. that have passed through the coating film during long-term use. There is a problem that the rust generated from the material causes swelling and the coating film is damaged, which is not sufficient in terms of long-term durability.

[0003]

DISCLOSURE OF THE INVENTION The present invention is applicable to a water-based product, particularly a product used in a hot water environment such as a hot water supply pipe. An object of the present invention is to provide a powder coating composition which is prevented over a long period of time and gives a coating film having long-term durability and which has excellent rust prevention.

[0004]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, by blending a polyolefin-based resin with a hydrotalcite compound and an aromatic acid salt, The present inventors have found that corrosion is prevented over a long period of time, and completed the present invention. That is, the present invention relates to (1) a rustproof powder obtained by blending 0.01 to 10 parts by weight of a hydrotalcite compound and 0.01 to 10 parts by weight of an aromatic salt with 100 parts by weight of a polyolefin resin. The coating composition, (2) the rust-preventive powder coating composition according to (1), wherein the polyolefin resin is a polypropylene resin or a polyethylene resin, (3) the polypropylene resin is a modified polypropylene, an unmodified polypropylene, Or a rust-preventive powder coating composition according to (2), which is a mixture of modified polypropylene and unmodified polypropylene, (4)
The rust-preventive powder coating composition according to (2) or (3), wherein the polypropylene-based resin is a resin having a melt flow rate of 5 to 80 g / 10 minutes at 230 ° C., (5) the polyethylene-based resin is modified polyethylene, (6) the rust-preventive powder coating composition according to (2), which is unmodified polyethylene or a mixture of modified polyethylene and unmodified polyethylene;
The rust-preventive powder coating composition according to (2) or (5), wherein the polyethylene resin is a resin having a melt flow rate at 190 ° C. of 1 to 80 g / 10 minutes, (7) the aromatic salt is benzoic acid The present invention relates to the rust-preventive powder coating composition according to (1) to (6), which is at least one selected from the group consisting of salts and phthalates.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The powder coating composition of the present invention is obtained by blending a hydrotalcite compound and an aromatic salt with a polyolefin resin. Examples of the polyolefin resin used in the present invention include a polypropylene resin and a polyethylene resin. Specific examples of the polypropylene resin include modified polypropylene, unmodified polypropylene, or a polypropylene resin composed of a mixture of modified polypropylene and unmodified polypropylene. Specific examples of the polyethylene resin include modified polyethylene, unmodified polyethylene,
Alternatively, a polyethylene resin composed of a mixture of a modified polyethylene and an unmodified polyethylene may be used.

The unmodified polypropylene includes 90 to 99% by weight of propylene and 2 to 2 carbon atoms other than propylene.
A random copolymer with 10 α-olefins of 10 to 1% by weight is preferred. Examples of the α-olefin include ethylene, 1-butene, 2-butene, 1-pentene, 2-pentene, 1-hexene, 1-heptene, 1-
Examples thereof include octene, 1-nonene, and 1-decene, and among them, ethylene, 1-butene, and 2-butene are preferable.
When the copolymerization ratio of the α-olefin is less than 1% by weight, the melting point of the coating composition is high, and the viscosity at the time of melting is large, so that a smooth coating film is hardly obtained.
The melting point of the coating composition decreases, and the heat resistance and surface hardness decrease.

[0007] The modified polypropylene is composed of 90 to 99% by weight of propylene and 2 to 1 carbon atoms other than propylene.
A resin in which either a random copolymer or a block copolymer with 0 to 10% by weight of an α-olefin is graft-modified with an unsaturated carboxylic acid or an anhydride thereof is preferably used. Examples of the unsaturated carboxylic acid or anhydride thereof include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, and itaconic anhydride, and among them, maleic anhydride is preferable.

In the present invention, the unmodified polypropylene or the modified polypropylene may be used alone, but a polypropylene resin comprising a mixture of the unmodified polypropylene and the modified polypropylene is preferably used.

The polypropylene resin of the present invention includes:
A resin having a melt flow rate (MFR) of 5 to 80 g / 10 minutes at 230 ° C., which is an index of the fluidity of the resin at the time of melting, is preferably used. When the MFR is less than 5 g / 10 minutes, the meltability is insufficient, and the smoothness of the coating film surface may be deteriorated. When the MFR exceeds 80 g / 10 minutes, the surface smoothness is improved, but In addition to the difficulty, the desired coating film may not be obtained because the melting point is lowered.

The unmodified polyethylene used in the present invention includes, for example, ethylene homopolymers such as low-density polyethylene and high-density polyethylene;
Linear low-density polyethylene, which is a copolymer with an olefin, may be mentioned. As the modified polyethylene used in the present invention, a resin obtained by graft-modifying the above unmodified polyethylene with an unsaturated carboxylic acid or an anhydride thereof is preferably used. Examples of the unsaturated carboxylic acid or anhydride thereof include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, and itaconic anhydride.

In the present invention, the above-mentioned unmodified polyethylene or the above-mentioned modified polyethylene may be used alone, but a polyethylene resin comprising a mixture of the above-mentioned unmodified polyethylene and the above-mentioned modified polyethylene is preferably used. The polyethylene resin of the present invention preferably has an MFR at 190 ° C. of 1 to 80 g / 10 minutes. If the MFR is less than 1 g / 10 minutes, the meltability is insufficient, so that the smoothness of the coating film surface is deteriorated, and the MFR is less than 8 g / 10 min.
If it exceeds 0 g / 10 minutes, the physical properties are extremely reduced, and it cannot be used as a coating film.

The hydrotalcite compound used in the present invention is represented by the following general formula (1): [M 2 ⁺ _{1 -X} M ³⁺ _X (OH) ₂ ] ^{X +} [A ⁿ⁻ _{X / n} · mH ₂ O] ^X− (1) (where M ²⁺ is Mg ²⁺ , Mn ²⁺ , Fe ²⁺ , Co ²⁺ , N
i ²⁺ , Cu ²⁺ , or Zn ²⁺ , and M ³⁺ represents Al ³⁺ , F 2
e ^3+, Cr ^3+, represents Co ^3+, or I ^3+, A ^n- is OH
^{-, F -, Cl -,} Br -, NO 3 -, CO 3 2-, SO 4 2-, F
^{_{e (CN) 6 3-, CH}} 3 COO -, represents the oxalate ion or salicylate ion, n represents addresses these 1-3
Represents an integer. m represents a positive integer, and X represents 0 <X ≦
0.33), for example, Mg ₆ Al ₂ (OH) ₁₆ CO ₃ .4H ₂ O, Mg
_{4 · 3} Al ₂ (OH), such as _{12 · 6 CO 3 · mH 2} O can be cited. The compounding amount of the hydrotalcite compound is usually 0.01 to 10 parts by weight, preferably 0.1 to 8 parts by weight based on 100 parts by weight of the polyolefin resin. The compounding amount of the hydrotalcite compound is 0.1.
When the amount is less than 01 parts by weight, sufficient rust prevention effect is not exhibited, and
If the amount exceeds 0 parts by weight, the rust-preventing effect is sufficient, but the workability and the surface smoothness of the coating film in powder coating are impaired, and it becomes difficult to form a good coating film.

The aromatic salt used in the present invention includes:
Benzoates or phthalates are preferably used. Examples of the benzoates include benzoic acid, o
-Tert-butylbenzoic acid, m-tert-butylbenzoic acid, p-tert-butylbenzoic acid, salicylic acid,
m-hydroxybenzoic acid, potassium salt, sodium salt, lithium salt, calcium salt of p-hydroxybenzoic acid,
Magnesium salts, aluminum salts and the like can be mentioned. Among them, benzoic acid, o-tert-butylbenzoic acid, m-tert-butylbenzoic acid, p-tert-butylbenzoic acid, salicylic acid, m-hydroxybenzoic acid,
Potassium and sodium salts of p-hydroxybenzoic acid are preferably used, especially benzoic acid and p-tert-
Butyl benzoic acid and potassium and sodium salts of salicylic acid are more preferably used. Examples of the phthalates include potassium, sodium, lithium, calcium, magnesium, and aluminum salts of phthalic acid, isophthalic acid, and terephthalic acid. Among them, potassium salts and sodium salts of phthalic acid, isophthalic acid and terephthalic acid are preferably used, and potassium salts and sodium salts of phthalic acid are more preferably used.

The amount of the aromatic salt is usually 0.01 to 10 parts by weight, preferably 0.1 to 8 parts by weight, based on 100 parts by weight of the polyolefin resin. When the amount of the aromatic salt is less than 0.01 part by weight, the rust-preventing effect is not sufficiently exhibited. In addition, the surface smoothness of the coating film is impaired, and it becomes difficult to form a good coating film.

The powder coating composition of the present invention is prepared by kneading the polyolefin resin with the hydrotalcite compound and the aromatic salt using various kneading machines such as an extruder, a heating roll, a Banbury mixer, and a kneader. After heating and melting and kneading, the mixture is formed into, for example, pellets. The obtained pellets are further pulverized by a mechanical pulverization method, a freeze pulverization method using liquid nitrogen, or the like, and classified by a sieve or the like to obtain a powder coating composition having a target particle size. The powder coating composition thus obtained further includes a colorant, a heat stabilizer,
Additives such as antioxidants, ultraviolet absorbers, lubricants, pigments and the like can be appropriately compounded.

The powder coating composition of the present invention is applied to a substrate by a known powder coating method, for example, a fluid immersion method, an electrostatic coating method, a thermal spraying method, a spraying method and the like. The substrate is not particularly limited, and for example, metals, mainly iron, iron alloys, zinc, or plated products thereof are preferably used.

[0017]

EXAMPLES The present invention will be described in more detail with reference to the following Examples and Comparative Examples, but the present invention is not limited to these Examples.

Example 1 95% by weight of unmodified polypropylene, polypropylene
80 parts by weight of a random copolymer of ethylene and 5% by weight of polyethylene (manufactured by Sumitomo Chemical Co., Ltd .: Noblen Z131), modified polypropylene graft-modified with maleic anhydride (adhesive polypropylene manufactured by Mitsui Petrochemical Industries, Ltd.)
20 parts by weight, hydrotalcite (Kyowa Chemical Industry Co., Ltd.)
_{Ltd.: DHT-4A, Mg 4 ·} 3 Al 2 (OH) 12 · 6 CO 3 ·
3 parts by weight of mH ₂ O) and 0.5 parts by weight of sodium benzoate were premixed with a Henschel mixer, and then melt-kneaded at 190 ° C. using an extruder to obtain pellets. The MFR of the obtained resin at 230 ° C. was 30 g / 10 minutes. The obtained pellets were freeze-pulverized using liquid nitrogen and classified into a 60-mesh pass to obtain a powder coating composition of the present invention.

The obtained powder coating composition was placed in a fluidized immersion tank, and air was fed from the bottom of the porous tank to maintain a stable fluidized state. A 70 mm × 150 mm × 2 mm steel plate test piece pre-heated in an oven at 340 ° C. for 6 minutes was immersed therein for 8 seconds. After the test piece was taken out, it was post-heated in a 200 ° C. oven for 2 minutes and allowed to cool at room temperature to obtain a coated product. The obtained coated product is immersed in hot water of 80 ° C.
A durability test was performed. Table 1 shows the evaluation results.

The method for evaluating the coating film is as follows. (1) Appearance The coating film surface was visually observed before the durability test and after the durability test. The evaluation is as follows. ：: Smooth surface ×: Poor in smoothness (2) Generation of rust The coating film was peeled off with a cutter knife, and the occurrence of rust on the metal surface and the coating film in contact with the metal was visually observed. The evaluation is as follows. ：: No rust was generated after 6 months. ：: No rust was generated after 3 months. ×: Rust was generated after 1 month. In general, if rust does not occur for 3 months, it can be determined that there is no practical problem.

Examples 2 to 11 and Comparative Examples 1 to 3 Same as Example 1 except that the mixing ratio of unmodified polypropylene and modified polypropylene, hydrotalcite and aromatic acid salts were changed as shown in Table 1. Thus, a powder coating composition was obtained. A coated article was evaluated in the same manner as in Example 1 using the obtained powder coating composition. The results are shown in Table 1.

Example 12 Linear low-density polyethylene which is an unmodified polyethylene (Ultzex 25100 manufactured by Mitsui Petrochemical Industries, Ltd.)
80 parts by weight of a modified polyethylene graft-modified with maleic anhydride (manufactured by Mitsui Petrochemical Industries, Ltd .: Admer NE)
100) 20 parts by weight of hydrotalcite (Kyowa Chemical Industry Co., _{Ltd.: DHT-4A, Mg 4 ·} 3 Al 2 (OH) 12 · 6
CO ₃ · mH ₂ O) 3 parts by weight, sodium benzoate 0.5
The parts by weight were premixed with a Henschel mixer and then melt-kneaded at 150 ° C. using an extruder to obtain pellets.
The MFR of the obtained resin at 190 ° C. was 10 g / 1.
It was 0 minutes. The obtained pellets were mechanically pulverized and classified into 40 mesh passes to obtain a powder coating composition of the present invention.

The obtained powder coating composition was placed in a fluidized immersion tank, and air was fed from the bottom of the porous tank to maintain a stable fluidized state. A 70 mm × 150 mm × 2 mm steel plate specimen pre-heated in a 360 ° C. oven for 4 minutes was immersed therein for 6 seconds. After removing the test piece, it was heated in an oven at 180 ° C. for 2 minutes and allowed to cool at room temperature to obtain a coated product. The obtained coated product is immersed in hot water of 80 ° C.
A durability test was performed. Table 2 shows the evaluation results.

Examples 13 to 17 and Comparative Examples 4 to 6 The mixing ratio of unmodified polyethylene and modified polyethylene,
A powder coating composition was obtained in the same manner as in Example 12, except that the hydrotalcite and the aromatic salt were changed as shown in Table 2. Example 1 using the obtained powder coating composition
The coated article was evaluated in the same manner as in 2. The results are shown in Table 2.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

The powder coating composition of the present invention is excellent in rust prevention by blending a hydrotalcite compound and an aromatic acid salt with a polyolefin resin, and can be used for a long time even in a hot water environment. A coating film having the above durability can be formed.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09D 123/26 C09D 123/26 (72) Inventor Tatsuro Okano 1384 Kamikano, Yachiyo-shi, Chiba Pref. F-term (reference) in the 2nd Research Laboratories of Chemical Industry Co., Ltd. 4J038 CB001 CB021 CB081 HA296 JA50 JA52 MA02 MA14 NA03

Claims (7)

[Claims] 1. A rustproof powder coating composition comprising 100 parts by weight of a polyolefin resin and 0.01 to 10 parts by weight of a hydrotalcite compound and 0.01 to 10 parts by weight of an aromatic salt. . 2. The rust preventive powder coating composition according to claim 1, wherein the polyolefin resin is a polypropylene resin or a polyethylene resin. 3. The rustproof powder coating composition according to claim 2, wherein the polypropylene resin is modified polypropylene, unmodified polypropylene, or a mixture of modified polypropylene and unmodified polypropylene. 4. The rustproof powder coating composition according to claim 2, wherein the polypropylene resin is a resin having a melt flow rate at 230 ° C. of 5 to 80 g / 10 minutes. 5. The rust preventive powder coating composition according to claim 2, wherein the polyethylene resin is modified polyethylene, unmodified polyethylene, or a mixture of modified polyethylene and unmodified polyethylene. 6. The rustproof powder coating composition according to claim 2, wherein the polyethylene resin is a resin having a melt flow rate at 190 ° C. of 1 to 80 g / 10 minutes. 7. The rustproofing powder according to claim 1, wherein the aromatic salt is at least one member selected from the group consisting of benzoates and phthalates. Body paint composition.