JPH07265787A - Static coating method for resin molding - Google Patents

Abstract

PURPOSE:To provide a static coating method of superior coating properties, superior adhesiveness and superior productivity which generates no physical and coloring problems for a resin molding. CONSTITUTION:A coating material having charge on a molding is sprayed and made to adhere, after a complex composed of 2-6C alkylene oxide derivative having number-average molecular weight of 150-30,000 and containing 4-30C alkyl, alkenyl aryl or alkyl aryl at least on one end of a molecular terminal and soluble electrytic salt is kneaded into a molding raw material, and a molding surface prepared by forming a kneaded matter is corona discharge treated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for electrostatically coating resin moldings.

[0002]

2. Description of the Related Art As a conventional electrostatic coating method for a resin molded body, a conductive coating material containing a conductive metal powder is applied to the surface of the resin molded body as described in, for example, JP-A-50-66538. Etc. to form a conductive primer layer to impart conductivity, and then electrostatically paint, or knead an inorganic conductive material such as carbon black, carbon fiber, conductive mica into the raw material of the resin molded body. After that, it can be molded and then electrostatically coated.

However, as described in JP-A-50-66538, a conductive primer is formed on the surface of a resin molding.
When forming a layer, the adhesion between the surface of the resin molded body and the conductive primer applied to the surface is poor, and in order to improve this, it is necessary to form many kinds of conductive primer layers in multiple layers. As a result, there is a problem not only in terms of conductivity and productivity, but also in loss and cost during coating due to the use of many kinds of conductive primers.

Further, when an inorganic conductive material such as carbon black, carbon fiber or conductive mica is kneaded to perform electrostatic coating, a large amount of these materials must be kneaded into the raw material of the resin molding. However, there is a problem that the resin molded body is apt to be deteriorated in substance and that the coloring of the resin molded body affects the hue of the electrostatically coated surface.

Further, recently, according to Japanese Patent Application Laid-Open No. 3-101875, a complex of polyoxyalkylene polyol and a soluble electrolyte salt was kneaded into a resin molded material, and the kneaded product was molded to obtain a molded product surface. After plasma treatment,
Although a method of electrostatic coating has been disclosed, this method has a problem in that the plasma treatment is a batch method, so that the productivity is inferior and the molded product must be treated under reduced pressure.

[0006]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned drawbacks of the conventional method, does not cause a problem in the physical properties and coloration of the resin molded product, is excellent in the coating property and the adhesive property, and has a high productivity. To provide an excellent electrostatic coating method.

[0007]

In the present invention, a specific alkylene oxide derivative is kneaded into a raw material for a resin molded body, and after molding, the surface of the molded body is subjected to corona discharge treatment to make the surface of the molded body suitable for electrostatic coating characteristics. The inventors have found that it can be modified into one, and have solved the above problems.

That is, the present invention (a) has a number average molecular weight of 150 to 30,000 and an alkyl group having 4 to 30 carbon atoms, an alkenyl group, an aryl group or an alkylaryl group having 2 to 2 carbon atoms at least at one end of the molecule. The complex of the alkylene oxide derivative of 6 and an electrolyte salt soluble in these is kneaded into the (b) resin molded material, the kneaded product is molded, and the obtained molded product surface is subjected to corona discharge treatment,
An electrostatic coating method for a resin molded body, which comprises spraying and attaching a charged coating material to the molded body.

Examples of the complex used in the present invention include those formed from an alkylene oxide derivative having 2 to 6 carbon atoms and an electrolyte salt soluble therein, as described above.

The alkylene oxide derivative is produced by homopolymerization of an alkylene oxide having 2 to 6 carbon atoms with a compound having an active hydrogen group having 4 to 30 carbon atoms in the presence of a catalyst, or copolymerization of two or more thereof. Examples thereof include compounds obtained by treating the substance with a generally known purification method such as an ion exchange method, a neutralization filtration method, or an adsorption method.

Examples of the active hydrogen group-containing compound having 4 to 30 carbon atoms include alcohols having 4 to 30 carbon atoms such as butyl alcohol, pentyl alcohol, hexyl alcohol, octyl alcohol, dodecyl alcohol, hexadecyl alcohol and octadecyl alcohol, C4 to C30 alkenyl alcohols such as nonenyl alcohol, decenyl alcohol and octadecenyl alcohol, etc., C4 to C30 such as octylphenol, nonylphenol, dinonylphenol and dodecylphenol.
Of C4 to C30 alkylamines such as phenols, octylamine, dodecylamine and octadecylamine, benzyl alcohol, phenethyl alcohol and the like, but preferably 8 to 20 carbon atoms, particularly preferably 12 to 18 carbon atoms. And an active hydrogen group-containing compound having an alkyl group, an alkenyl group, an aryl group, or an alkylaryl group.

When the carbon number is less than 4, the compatibility between the complex and the raw material for the resin molded product is poor, and the complex easily bleeds out from the resin molded product, which may adversely affect the coating film after electrostatic coating. high. When the carbon number is more than 30, the compatibility between the complex and the raw material for the resin molded product is improved, the complex is less likely to exist on the surface of the resin molded product, and the effect of corona treatment is reduced, so that the coating efficiency is difficult to improve. .

Examples of the alkylene oxide having 2 to 6 carbon atoms include ethylene oxide, propylene oxide and 1,2-
Butylene oxide, 1,2-hexene oxide, cyclohexene oxide and the like can be mentioned.

The alkylene oxide derivative has a number average molecular weight of 150 to 30,000, preferably 150 to 10,000, and particularly preferably 150 to 5,000. When the number average molecular weight exceeds 30,000, the compatibility between the complex and the raw material for the resin molded body is improved,
It becomes difficult for the complex to exist on the surface of the resin molded body, and the effect of corona treatment becomes small, so that it is difficult to improve the coating efficiency.

The soluble electrolyte salt which is another component forming the complex includes lithium chloride, lithium bromide,
Sodium bromide, lithium iodide, sodium iodide,
Examples thereof include inorganic ion salts such as potassium iodide, lithium nitrate, lithium perchlorate, sodium perchlorate, lithium thiocyanate, sodium thiocyanate, potassium thiocyanate, and lithium borofluoride.

The amount of the electrolyte salt added in the complex formation is 0.1 to 10% by weight based on the alkylene oxide derivative.
It is preferably 0.5 to 8% by weight, particularly preferably 1 to 5% by weight. If the addition amount exceeds 10% by weight, it is preferable for improving the conductivity, but physical properties are deteriorated and surface bleeding occurs in terms of compatibility with the resin, so there is no great advantage, and if less than 0.1% by weight. , The effect of conductivity is not recognized.

The complex is prepared by dissolving the soluble electrolyte salt in water, methanol, methyl ethyl ethyl ketone, tetrahydrofuran, acetone, methylene chloride or the like alone or in a mixed solvent in advance, and further dissolving the alkylene oxide derivative in this solution. Then, a method is preferred in which, after forming a uniform solution, the solvent is removed to obtain a complex.

The amount of the complex added is 0.01 to 10% by weight, preferably 0.0
It is 5 to 5% by weight, particularly preferably 0.1 to 3% by weight. If the amount added exceeds 10% by weight, it is preferable for improving conductivity, but physical properties are deteriorated and surface bleeding occurs in terms of compatibility with the resin, which may adversely affect the coating film after electrostatic coating. High and no big advantage. Also 0.01
If the amount is less than wt%, the electroconductivity tends to deteriorate, and the coating efficiency is difficult to improve.

When the complex is kneaded into the raw material of the resin molded body, as long as the effect of the present invention is not essentially changed,
Other types of antistatic agents, processing stabilizers and the like can also be used in combination.

The resin molding material used in the present invention includes polyolefin resins such as polyethylene, polypropylene and rubber-containing polypropylene (containing ethylene-propylene copolymer rubber), ABS resins, acrylic resins, polyamide resins, polyvinyl chloride resins. , A resin having a high surface resistance value such as a polycarbonate resin, a polyacetal resin, and a phenol resin.

As a method of kneading the above complex into a raw material for a resin molded body, a commonly used method such as a twin-screw extruder type or a hot roll type is used, and a molding method is injection molding,
Any method such as calendering, compression molding and SMC method can be used.

The corona discharge treatment of the resin molded body utilizes a phenomenon that occurs when a high voltage is applied between two conductors at normal pressure by a high frequency power source. The so-called generated corona is treated as an object (molded body). It is a method of contacting the surface of.

Corona discharge treatment conditions may be such that corona discharge occurs, for example, an applied voltage of 10 to 50K.
V, processing time is 100 seconds or less. Note that, in effect,
It suffices that the surface resistance of the non-treated resin molded product is reduced by corona discharge treatment (less than 10 ¹⁴ Ω), and any device may be used as long as it satisfies such a condition.

Next, as the electrostatic coating method, a method using electric centrifugal air, an airless atomizing type coating machine or the like can be used, and the applied voltage is about -30 KV to -120 KV. Further, as the coating material at this time, any ordinary coating material such as urethane type, acrylic type, alkyd type and melamine type can be used.

[0025]

In the resin molded product obtained by the method of the present invention, the cation and anion of the soluble electrolyte salt in the complex kneaded into the resin can move through the ether-bonded oxygen in the alkylene oxide derivative. Therefore, ionic conductivity is generated in the resin, as a result, the surface resistance value is lowered, and further exhibits a synergistic effect with the surface modification effect by the corona discharge treatment after molding,
It enables electrostatic coating with excellent coating properties that has never been seen before.

[0026]

【Example】

Production Example 1. Using 186 g of dodecyl alcohol as a starting material, potassium hydroxide as a catalyst, and successively introducing 90 g of ethylene oxide by a conventional method, desalting and refining were carried out.
260 g of an alkylene oxide derivative having a number average molecular weight of 270 (calculated from a hydroxyl value) was obtained. A solution prepared by dissolving 3 g of lithium perchlorate in 20 g of methanol was added to 100 g of this alkylene oxide derivative and stirred to obtain a uniform solution, and then methanol in the solution was topped under reduced pressure to obtain a complex.

Production Example 2. Starting from 186 g of dodecyl alcohol and using potassium hydroxide as a catalyst, 520 g of ethylene oxide was successively introduced by a conventional method, followed by desalting and refining to obtain a number average molecular weight of 700 (calculated from a hydroxyl value).
690 g of the alkylene oxide derivative of A solution prepared by dissolving 3 g of lithium perchlorate in 20 g of methanol was added to 100 g of this alkylene oxide derivative and stirred to obtain a uniform solution, and then methanol in the solution was topped under reduced pressure to obtain a complex.

Production Example 3. Using 186 g of dodecyl alcohol as a starting material and potassium hydroxide as a catalyst, 500 g of ethylene oxide and 65 g of propylene oxide were prepared by a conventional method.
After successively introducing 0 g, desalting and purification were carried out to obtain 1180 g of an alkylene oxide derivative having a number average molecular weight of 1200 (calculated from a hydroxyl value). To 100 g of this alkylene oxide derivative, 3 g of lithium perchlorate was added to 2 parts of methanol.
After adding a solution dissolved in 0 g and stirring to make a uniform solution, methanol in the solution was topped under reduced pressure to obtain a complex.

Production Example 4. Starting from 186 g of dodecyl alcohol and using potassium hydroxide as a catalyst, 1,400 g of 1,2-butylene oxide and 700 g of ethylene oxide were successively introduced by a conventional method, followed by desalting and refining to obtain a number average molecular weight of 2000 (hydroxyl value. 1940 g of alkylene oxide derivative (calculated from the above) was obtained. 3 g of sodium thiocyanate in 100 g of this alkylene oxide derivative
Was added to 20 g of methanol, and the mixture was stirred to form a uniform solution. Then, methanol in the solution was topped under reduced pressure to obtain a complex.

Production Example 5. Using 65 g of n-butyl alcohol as a starting material and potassium hydroxide as a catalyst, 60 g of 1,2-butylene oxide and 60 g of ethylene oxide were mixed by a conventional method, and after the successive introduction, desalting and purification were carried out. 160 g of an alkylene oxide derivative having an average molecular weight of 170 (calculated from the hydroxyl value) was obtained. A solution prepared by dissolving 5 g of lithium perchlorate in 20 g of methanol was added to 100 g of this alkylene oxide derivative and stirred to form a uniform solution, and then methanol in the solution was topped under reduced pressure to obtain a complex.

Production Example 6. Octadecyl alcohol 270
g was used as a starting material, potassium hydroxide was used as a catalyst, and 3000 g of ethylene oxide, 1000 g of propylene oxide and 500 g of 1,2-hexene oxide were successively introduced by a conventional method, followed by desalting and refining to give a number average molecular weight of 45.
4450 g of an alkylene oxide derivative of 00 (calculated from the hydroxyl value) was obtained. This alkylene oxide derivative 10
A solution obtained by dissolving 7 g of lithium perchlorate in 20 g of methanol was added to 0 g, and the mixture was stirred to make a uniform solution. Then, methanol in the solution was topped under reduced pressure to obtain a complex.

Production Example 7. Octadecyl alcohol 27g
Starting material is used as a starting material, potassium hydroxide is used as a catalyst, and 1,2-hexene oxide 100 g, 1,2-butylene oxide 200 g and ethylene oxide 650 g are sequentially introduced by a conventional method, followed by desalting and purification to obtain a number average molecular weight. 90
925 g of an alkylene oxide derivative of 00 (calculated from the hydroxyl value) was obtained. This alkylene oxide derivative 100
A solution obtained by dissolving 3 g of lithium perchlorate in 20 g of methanol was added to g and stirred to obtain a uniform solution, and then methanol in the solution was topped under reduced pressure to obtain a complex.

Production Example 8. Using 220 g of nonylphenol as a starting material and 640 g of propylene oxide successively introduced by a conventional method using potassium hydroxide as a catalyst, desalting and refining were performed to obtain 630 g of an alkylene oxide derivative having a number average molecular weight of 600 (calculated from a hydroxyl value). Obtained. To 100 g of this alkylene oxide derivative, a solution prepared by dissolving 3 g of halofucca lithium in 20 g of methanol was added,
After stirring to form a uniform solution, methanol in the solution was topped under reduced pressure to obtain a complex.

Production Example 9. Using 34 g of dinonylphenol as a starting material and potassium hydroxide as a catalyst, 100 g of propylene oxide, 200 g of 1,2-butylene oxide and 2500 g of ethylene oxide were sequentially introduced by a conventional method, followed by desalting and refining to give a number average molecular weight of 25,000.
Alkylene oxide derivative 24 (calculated from hydroxyl value)
50 g was obtained. 100 g of this alkylene oxide derivative
A solution prepared by dissolving 9 g of lithium perchlorate in 20 g of methanol was added and stirred to obtain a uniform solution, and then methanol in the solution was topped under reduced pressure to obtain a complex.

Production Example 10. Benzyl alcohol 108g
Is used as a starting material, potassium hydroxide is used as a catalyst, and 100 g of cyclohexene oxide and 1600 g of ethylene oxide are sequentially introduced by a conventional method, and then desalting and purification are performed.
1540 g of an alkylene oxide derivative having a number average molecular weight of 1600 (calculated from a hydroxyl value) was obtained. A solution prepared by dissolving 1 g of lithium perchlorate in 20 g of methanol was added to 100 g of the alkylene oxide derivative and stirred to obtain a uniform solution, and then methanol in the solution was topped under reduced pressure to obtain a complex.

Production Example 11. After using 185 g of dodecylamine as a starting material and potassium hydroxide as a catalyst, 1,2-butylene oxide (400 g) and ethylene oxide (2400 g) were sequentially introduced by a conventional method, and then desalted and purified to obtain a number average molecular weight of 2700 (from the hydroxyl value. 2650 g of calculated alkylene oxide derivative was obtained. A solution prepared by dissolving 0.5 g of lithium perchlorate in 20 g of methanol was added to 100 g of the alkylene oxide derivative and stirred to obtain a uniform solution, and then methanol in the solution was topped under reduced pressure to obtain a complex.

Production Example 12. Octadecyl alcohol 27
Using 0 g as a starting material and potassium hydroxide as a catalyst,
After successively introducing 1,2-butylene oxide (500 g) and ethylene oxide (800 g) by a conventional method, desalting and purification were carried out to obtain 1350 g of an alkylene oxide derivative having a number average molecular weight of 1400 (calculated from a hydroxyl value). 3 g of lithium perchlorate in 100 g of this alkylene oxide derivative
Was added to 20 g of methanol, and the mixture was stirred to form a uniform solution. Then, methanol in the solution was topped under reduced pressure to obtain a complex.

Examples 1-18. A predetermined amount of each complex was added to 1 kg of the raw material for the resin molded body, and the mixture was mixed with a twin-screw extruder.
The mixture was kneaded at 0 ° C for 10 minutes to obtain pellets. The pellets were molded using an injection molding machine (manufactured by Niigata Iron Works Co., Ltd., Hyper Shot) to obtain a molded body of 230 mm × 230 mm × 3 mm. The surface of this molded body was subjected to corona discharge treatment (high frequency power supply; manufactured by Kasuga Electric Co., Ltd., high frequency power supply HFS-203) at an applied voltage of 30 KV for 20 seconds to prepare a test piece, and immediately, the surface resistance of the test piece, And the tensile strength was measured.

The surface resistance was measured with a super insulation resistance meter 4329A type manufactured by YHP (Yokogawa Hewlett-Packard) at an applied voltage of 500 V and 30 seconds after the voltage was applied (humidity 65%, temperature. 20 ° C). Tensile strength is
It was measured according to JIS K 7113.

Next, the test piece obtained above was grounded, static voltage -40 KV, reciprocal stroke 400 m.
m, spraying distance 300 mm, conveyor speed 2.2 m /
Minute coating machine (manufactured by Landsberg Gema Ltd. μμBEL30
φ), urethane-based paint (Nippon Bee Chemical Co., Ltd. R-
315) was electrostatically coated and dried at 120 ° C. for 30 minutes, and then the film thickness and coating efficiency were measured.

Comparative Example 1. The same procedure as in Example 2 was carried out except that the complex was not added.

Comparative Example 2. Completely the same as in Example 2.
However, no corona discharge treatment was performed.

Comparative Example 3. In Comparative Example 1, “Polypropylene resin; manufactured by Union Polymer Co. "ME230" is a "polypropylene resin; Idemitsu Petrochemical Co., Ltd. Idemitsu Polypro J-
Instead of 465H ”, the same operation as in Comparative Example 1 was performed.

Comparative Example 4. Completely the same as in Example 2.
However, no corona discharge treatment was performed.

Comparative Example 5. The same procedure as in Example 17 was performed except that the complex was not added.

Comparative Example 6. Completely the same as in Example 17. However, no corona discharge treatment was performed.

Comparative Example 7. The same procedure as in Example 18 was performed except that the complex was not added.

Comparative Example 8. Completely the same as in Example 18. However, no corona discharge treatment was performed.

Next, the results of Examples 1-18 and Comparative Examples 1-8 are shown in Tables 1 and 2, respectively. As is clear from this table, excellent effects such as resin physical properties and coating efficiency of the coated product of the present invention were confirmed.

[0050]

[Table 1]

[0051]

[Table 2]

[0052]

According to the present invention, a resin having a high surface resistance value can be electrostatically coated with excellent coating efficiency, surface appearance, productivity, etc. without substantially impairing the physical properties of the resin. is there.

Claims (3)

[Claims] 1. A number-average molecular weight of 150-3000.
A complex of an alkylene oxide derivative having 2 to 6 carbon atoms, which is 0 and has an alkyl group, alkenyl group, aryl group or alkylaryl group having 4 to 30 carbon atoms on at least one end of the molecule, and an electrolyte salt soluble in these ( (B) Resin molding characterized by kneading into a raw material of a resin molded product, molding the kneaded product, subjecting the surface of the resulting molded product to corona discharge treatment, and then spraying and attaching a charged paint to the molded product. How to electrostatically coat your body. 2. The amount of soluble electrolyte salt added is 2 carbon atoms.
0.1 to 10 with respect to the alkylene oxide derivative of
The method for electrostatic coating of a resin molded article according to claim 1, wherein the method is the weight percent. 3. The electrostatic coating method for a resin molded body according to claim 1, wherein the amount of the complex added is 0.01 to 10% by weight based on the raw material of the resin molded body.