JPH06299102A - Vinyl chloride-based powder coating for electrostatic coating - Google Patents

Abstract

PURPOSE:To obtain a vinyl chloride-based powder coating for electrostatic coating, not producing any pinhole even if a body to be coated, having relatively complicate shape, e.g. an exterior fence is subjected to electrostatic coating and excellent in infiltration. CONSTITUTION:This powder coating for electrostatic coating consisting essentially of a vinyl chloride-based resin, a plasticizer and a stabilizer is characterized by including 5-50pts.wt. pyromellitic acid alkyl ester based on 100pts.wt. vinyl choride-based resin therein.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vinyl chloride powder coating material for electrostatic coating suitable for electrostatically coating an object to be coated having a relatively complicated shape such as an outdoor fence.

[0002]

2. Description of the Related Art Conventionally, a fluidized-bed coating method has been mainly used for coating an outdoor fence, but in recent years, this coating has been shifting to an electrostatic coating method. The reason for this is that the electrostatic coating method is easier than the fluidized immersion coating method in terms of film thickness control and powder change, small lot production is possible, and energy and cost are low, which is technical and economical. This is due to an advantage.

However, while electrostatic coating has the above-mentioned advantages, it has a drawback that powder is unlikely to enter fine parts of the object to be coated. For this reason, for example, when coating a grid-shaped outdoor fence or the like, it is not possible to completely apply the paint to the intersections of the base materials, and it is easy to cause the generation of minute pinholes to which the paint does not adhere. When performing fence coating by electrostatic coating, usually, in order to improve efficiency, several fences are coated at a time to coat them at the same time.However, the above-mentioned lack of intrudability increases as the number of fences processed increases. This gives an inconvenience of increasing the degree of occurrence of pinholes.

[0004]

For the above-mentioned reasons, it has been difficult to electrostatically coat an outdoor fence with two or more sheets stacked on top of each other. The present inventors have conducted extensive studies to solve such problems, and as a result, when a specific amount of pyromellitic acid alkyl ester is added to a vinyl chloride resin alone or together with other plasticizers, it is involved in electrostatic coating. It was confirmed that the property was remarkably improved, and that the degree of pinhole generation in small parts could be effectively suppressed.

The present invention was developed on the basis of the above-mentioned findings, and an object thereof is to provide a vinyl chloride powder coating material for electrostatic coating which is excellent in penetration.

[0006]

The vinyl chloride powder coating composition for electrostatic coating according to the present invention, which has been made to achieve the above object, comprises a vinyl chloride resin, a plasticizer and a stabilizer as main components. The powder coating for electrocoating is characterized in that it contains 5 to 50 parts by weight of alkyl pyromellitic ester per 100 parts by weight of vinyl chloride resin.

The vinyl chloride resin constituting the present invention includes a vinyl chloride homopolymer obtained by polymerizing a vinyl chloride monomer by a suspension polymerization method and a vinyl chloride containing vinyl chloride and another vinyl monomer. A system copolymer etc. are used suitably. As a commercially available vinyl chloride resin, for example, a product name “Aron PVC-TS7” manufactured by Toagosei Chemical Industry Co., Ltd.
00 "or" Aron PVC-TS800 "can be used. As the vinyl chloride copolymer,
Examples thereof include random copolymers such as vinyl acetate-vinyl chloride copolymer, ethylene-vinyl chloride copolymer and vinylidene chloride-vinyl chloride copolymer. In addition to the above polymers, vinyl chloride graft copolymers such as ethylene-vinyl acetate-vinyl chloride graft copolymer and polyurethane-vinyl chloride graft copolymer may be used.

When the above vinyl chloride homopolymer or vinyl chloride random copolymer is used, the degree of polymerization thereof is preferably in the range of 700 to 1100. If the degree of polymerization is less than 700, the thermal stability tends to decrease, while 1
If it exceeds 100, the meltability tends to decrease. Also,
The particle size of the powder is preferably in the range of 60 to 100 μ.

The vinyl chloride powder coating composition for electrostatic coating according to the present invention must contain an alkyl ester of pyromellitic acid as an essential requirement. The pyromellitic acid alkyl ester to be contained is a compound represented by the following general formula.

[0010]

[Chemical 1]

In the chemical formula 1, R ₁ , R ₂ , R ₃ and R ₄ are each a saturated aliphatic hydrocarbon group having 1 to 13 carbon atoms, such as methyl group, ethyl group, propyl group, butyl group, pentyl group and hexyl group. Group, heptyl group, octyl group, nonyl group,
A decyl group, an undecyl group, a dodecyl group, a tridecyl group and the like are shown. Each of these may be linear or branched, and may be a single product or a mixed product of two or more kinds. Further, R ₁ , R ₂ , R ₃ and R ₄ may be the same or different. The most effective structure for suppressing pinholes in electrostatic coating is R ₁ , R ₂ , R ₃ ,
All of R ₄ are 2-ethylhexyl groups.

The content of the alkyl pyromellitic ester needs to be in the range of 5 to 50 parts by weight per 100 parts by weight of the vinyl chloride resin. If the content of the alkyl pyromellitic acid ester is less than 5 parts by weight, the effect of improving the penetrability is not exhibited, and if it exceeds 50 parts by weight, the compatibility between the alkyl pyromellitic acid ester and the vinyl chloride resin deteriorates. Alkyl pyromellitic acid ester will bleed out from the coating film.

In the present invention, it is also possible to use a plasticizer other than the above-mentioned pyromellitic acid alkyl ester used as an essential component, and examples of such a plasticizer include di-n-butyl phthalate and phthalic acid-n-phthalate. Octyl, di-2-ethylhexyl phthalate, diisooctyl phthalate, octyldecyl phthalate, diisodecyl phthalate,
In addition to butylbenzyl phthalate and di-2-ethylhexyl isophthalate, phthalate plasticizers such as phthalate esters of higher alcohols having about 11 to 13 carbon atoms,
Trimellitic acid-based plasticizers such as n-octyl-n-decyl trimellitate, tri-2-ethylhexyl trimellitate, triisodecyl trimellitate, and tri-n-octyl trimellitate, di-2-ethylhexyl adipate, Di-n-decyl adipate, di-2-ethylhexyl adipate, dibutyl sebacate, di-2 sebacate
-Fatty acid ester-based plasticizer such as ethylhexyl, tributyl phosphate, tri-2-ethylhexyl phosphate, 2-ethylhexyl diphenyl phosphate, tricresyl phosphate-based phosphate ester plasticizer, epoxidized soybean oil, epoxidized linseed Oils, epoxy-based plasticizers such as epoxidized tall oil fatty acid-2-ethylhexyl, and the like,
These are used alone or in combination of two or more. Preferred is tri-2-ethylhexyl trimellitate.

The preferred amount of the plasticizer compounded in the powder coating composition of the present invention, that is, the preferred total amount of the pyromellitic acid alkyl ester and the above compounds, varies depending on the type of vinyl chloride resin used in combination, but is usually a vinyl chloride resin. The amount is in the range of 30 to 60 parts by weight with respect to 100 parts by weight, and more than half of the total amount of the plasticizer is preferably alkyl pyromellitic ester.

Examples of the stabilizer include β-diketone compounds such as dehydrobenzoylacetic acid, stearoylbenzoylmethane, dibenzoylmethane and dehydroacetic acid, or their sodium salts or potassium salts, perchlorates such as sodium perchlorate and barium perchlorate. Acid salts, metal stearates such as zinc stearate, calcium stearate, zinc oleate, calcium oleate, zinc laurate and calcium laurate, organotin compounds such as dibutyltin mercapto, dibutyltin laurate and dibutyltin malate, organic phosphites and Hydrotalcite and the like can be mentioned. The stabilizer is added in an amount of 0.5 to 10 parts by weight based on 100 parts by weight of the vinyl chloride resin.

In addition to these main components, it is preferable to add 1 to 8 parts by weight of a fine vinyl chloride resin having an average particle size of 0.5 to 3 μm for the purpose of improving the fluidity of the powder.
This type of fine-grained vinyl chloride resin can be synthesized by emulsion polymerization of vinyl chloride resin. For example, the product name "Luron Paste 772" manufactured by Tosoh Corporation is used.
Alternatively, a commercially available product such as “Geon 121” manufactured by Nippon Zeon Co., Ltd. may be used.

In addition to the above components, a lubricant, an antioxidant,
A flame retardant, an ultraviolet absorber, an inorganic filler, a pigment and the like can be added within a range that does not impair the penetration property in electrostatic coating. As the pigment, an ordinary coloring pigment and, if necessary, so-called extender pigment such as calcium carbonate, barium sulfate, zinc white, silica, and silica sand powder can be used, and the range is 30 parts by weight or less per 100 parts by weight of the vinyl chloride resin. Is preferably added. If the amount of the pigment added exceeds 30 parts by weight, the mechanical strength of the coating film may decrease. Further, since the ultraviolet absorber can improve the light stability, it is preferably added to the coating material for the outdoor fence.

In the vinyl chloride powder coating composition for electrostatic coating of the present invention, the above components are put into a high speed mixer equipped with a heating jacket such as a Henschel mixer, and 100 to 1 parts are added.
It can be prepared by a general process of mixing at a temperature of about 50 ° C. for 10 to 60 minutes and then sieving.

[0019]

The vinyl chloride-based powder coating composition for electrostatic coating according to the present invention is a powder coating composition comprising a vinyl chloride-based resin, a plasticizer and a stabilizer, and is 5 to 50 parts by weight per 100 parts by weight of the vinyl chloride-based resin. It is characterized by a component system containing a part of pyromellitic acid alkyl ester. The pyromellitic acid alkyl ester functions to increase the plasticity during electrostatic coating and to effectively improve the penetrability of the coating, either alone or together with other plasticizers used in combination. Through such action, even when three or more outdoor fences having a fine grid shape are hung and electrostatically coated,
It is possible to form a normal coating film that does not generate pinholes at intersections and the like.

[0020]

EXAMPLES Examples of the present invention will be specifically described below in comparison with comparative examples.

Examples 1 to 3 Vinyl chloride resin having a degree of polymerization of 700 and an average particle size of 30 to 90 μm (“TS-700M” manufactured by Toagosei Chemical Industry Co., Ltd.)
For 100 parts by weight, tetra-2-ethylhexyl pyromellitate [Asahi Denka Kogyo KK, "UL-8
0 ”] and tri-2-ethylhexyl trimellitate [“ TOTM ”manufactured by Mitsubishi Gas Chemical Co., Inc.] in the compounding amounts shown in Table 1, and dibutyltin mercapto [Nitto Kasei Co., Ltd.] as a stabilizer. "TVS # 1315"] and 0.5 part by weight of carbon black as a pigment were put into a Henschel mixer equipped with a heating jacket and heated and mixed at a temperature of 100 to 150 ° C for about 20 minutes. After cooling to a temperature of 70 ° C. or lower, 5 parts by weight of emulsion-polymerized fine particles of vinyl chloride [“Geon 121” manufactured by Nippon Zeon Co., Ltd.] were added to impart powder fluidity, and the mixture was stirred for 5 minutes. The obtained mixture was classified with a 60-mesh sieve to produce a vinyl chloride resin powder coating material.

With respect to each of the above vinyl chloride type powder coating materials, the penetration property during electrostatic coating was evaluated as follows. Figure 1
Three grid fences (40 cm in length and 30 cm in width) shown in (3) were stacked in parallel and suspended, and electrostatic coating was applied from both sides using each vinyl chloride powder coating material. The electrostatic coating equipment is "GX from Onoda Cement Co., Ltd.
Use 3600 ", voltage 80KV, discharge pressure MAIN 3kgf /
cm ^2, SUB1kgf / cm ^2, and set the pattern 0kgf / cm ^2,
The conditions of a gun-fence distance of 20 cm and a fence interval of 10 cm were applied.

The penetrability of the coating film was evaluated by visually observing the number of pinholes generated at the intersection of the mesh fences 2 located in the center and judging by the following criteria. ×: 20 or more pinholes were generated △: 5 to 20 pinholes were generated ◯: 1 to 5 pinholes were generated ◎: No pinholes were generated The evaluation results were used for the vinyl chloride powder coating material. The results are shown in Table 1 in comparison with the component composition.

Comparative Example 1 40 parts by weight of tri-2-ethylhexyl trimellitate (“TOTM” manufactured by Mitsubishi Gas Chemical Co., Inc.) was used as a plasticizer for 100 parts by weight of the same vinyl chloride resin as in the example. The same amounts of dibutyltin mercapto (stabilizer) and carbon black (pigment) were blended as in the example, and the vinyl chloride powder coating material was manufactured under the same conditions as in the subsequent examples. Using the obtained vinyl chloride-based powder coating material, the penetration property during electrostatic coating was evaluated in the same manner as in Examples, and the results are also shown in Table 1.

Comparative Example 2 The plasticizer of Comparative Example 1 was replaced with 40 parts by weight of diisodecyl phthalate (“DIDP” manufactured by Asahi Denka Kogyo KK) which is a phthalate of a higher alcohol having 8 to 10 carbon atoms. Manufactured vinyl chloride powder coating materials under the same conditions. Using the obtained vinyl chloride powder coating,
Table 1 also shows the results of evaluation of the penetration property during electrostatic coating as in the examples.

[0026]

[Table 1]

From the results shown in Table 1, when the vinyl chloride powder coating for electrostatic coating satisfying the composition of the present invention is used, the penetration property during electrostatic coating is remarkably improved, and three grid-like outdoor fences are hung. It is possible to effectively suppress the occurrence of pinholes even when the coating is performed in this state. On the other hand, the paints of Comparative Examples 1 and 2 which do not contain the pyromellitic acid alkyl ester, which is an essential component of the present invention, are inferior in penetration property as compared with the Examples, and can suppress the occurrence of pinholes in the central fence. could not.

[0028]

As described above, according to the present invention, a high performance chloride for electrostatic coating that exhibits excellent penetration during electrostatic coating and can normally form a coating film without pinholes. A vinyl-based powder coating is provided. Therefore, it is possible to remarkably improve the productivity particularly when electrostatic coating is performed in a state where three or more outdoor fences are suspended.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a state of a fence used for electrostatic coating of an example.

[Explanation of symbols]

 1 mesh fence 2 mesh fence 3 mesh fence

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuhiko Ando 1-1 Funami-cho, Minato-ku, Aichi Prefecture Nagoya City Toagosei Chemical Industry Co., Ltd. Nagoya Research Institute (72) Inventor Yoshito Fujiki Nagoya City, Aichi Prefecture 1 Touna Synthetic Chemical Industry Co., Ltd. Nagoya Research Institute, No. 1 Funami-cho, Minato-ku

Claims (1)

[Claims] 1. A powder coating for electrostatic coating, which comprises a vinyl chloride resin, a plasticizer and a stabilizer as main components, and contains 5 to 50 parts by weight of an alkyl pyromellitic ester per 100 parts by weight of the vinyl chloride resin. A vinyl chloride powder coating material for electrostatic coating.