JPH07207197A - Resin composition for electrostatic coating - Google Patents

Abstract

PURPOSE:To provide a resin composition for electrostatic coating prepared by mixing a specific salicylic compound into powder of a thermoplastic resin, and suitable for the frictional charging process because of its large frictional charge capacity. CONSTITUTION:The composition is prepared by mixing powder of thermoplastic resin such as polyethylene, polypropylene, nylon, or vinyl chloride resin with an alkaline earth metal salt of (alkyl) salicyclic acid, preferably in an amount of 0.05 to 10wt.% base on the total weight of the composition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin powder composition for electrostatic coating containing a thermoplastic resin powder as a main component, and more specifically, coating with a triboelectric electrostatic powder coating machine. Particularly, it relates to a thermoplastic resin composition for powder coating.

[0002]

2. Description of the Related Art Powder coating materials have many advantages over solvent-based coating materials because they do not use a solvent, and the demand for them has expanded rapidly in recent years due to the progress of coating machines. Regarding the coating method of powder coating material mainly composed of thermoplastic resin such as polyethylene, polypropylene, nylon and vinyl chloride resin, the fluidized dipping coating method has been generally adopted in the past. The electrostatic coating method based on the corona discharge method has come to be widely used mainly for reasons such as easy management and powder change and low energy cost.

On the other hand, as the electrostatic coating method, in addition to the electrostatic coating method by the corona discharge method, there is an electrostatic coating method by the friction charging method (tribo charging method). This electrostatic coating method uses a high voltage. Since it does not, there is less risk of electric shock, the electric field strength is weaker, it is easier to enter the recess than the corona charging method, and it is hard to cause electrostatic repulsion, so a smoother coated surface can be obtained. Therefore, application to the thermoplastic resin is desired. However, the thermoplastic resin powder coating composition adopted in the fluid immersion coating method or the electrostatic coating method using the corona discharge method cannot be used in the electrostatic powder coating method using the friction charging method because the charge amount is too small. Is the current situation.

[0004]

Means for Solving the Problems As a result of intensive studies for solving the above problems, the present inventors have obtained a mixture of an alkaline earth metal salt of salicylic acid or alkylsalicylic acid with a vinyl chloride resin powder. The inventors have found that the resin composition is easily charged to a high charge amount by friction, and have completed the present invention.

That is, the present invention is a triboelectrification type electrostatic powder coating resin composition obtained by mixing an alkaline earth metal salt of salicylic acid or alkylsalicylic acid with a powder of a thermoplastic resin.

The alkylsalicylic acid in the present invention is preferably an alkylsalicylic acid having one or two alkyl groups having 5 or less carbon atoms, and more preferably
An alkylsalicylic acid having one or two alkyl groups having 4 or less carbon atoms such as a t-butyl group, and particularly preferably one having two t-butyl groups. Also, as alkaline earth metals, calcium, strontium,
Examples thereof include barium, beryllium and magnesium, and preferably strontium, barium and magnesium.

In the present invention, the salt of alkylsalicylic acid or salicylic acid and an alkaline earth metal is blended with the powder of the thermoplastic resin, and the preferred blending amount of the metal salt is based on the entire resin composition. , 0.05-10% by weight
Is. If it is less than 0.05% by weight, it is difficult to obtain a predetermined effect of improving the coating property, while if it exceeds 10% by weight, the smoothness and mechanical properties of the coating film tend to be deteriorated.

The metal salt in the present invention is required to be uniformly dispersed in the powder coating composition, and for that purpose, the particle diameter is preferably 0.1 to 20 μm. 0.1
If it is less than μm, the smoothness of the coating surface is likely to be deteriorated especially in a system with a large amount of addition, while if it exceeds 20 μm, the coating surface is liable to be bumped and the charge adjusting effect is not sufficiently exerted, resulting in friction. There is a possibility that the initial purpose of improving the coatability when the electrostatic powder coating machine of the charging type is used cannot be achieved. The metal salt is added to the resin powder according to the usual powder coating production process, either by the melt blending method added during the melt mixing of the resin or the dry blending method added during the pulverization of the resin which is the latter half of the production process. It can be carried out.

The thermoplastic resin in the resin composition for powder coating of the present invention includes polyethylene, polypropylene,
Nylon such as 11-nylon and 12-nylon, vinyl chloride resin and the like can be mentioned. Further, as the vinyl chloride resin, a vinyl chloride homopolymer obtained by a suspension polymerization method and a vinyl chloride copolymer composed of vinyl chloride and other vinyl monomers can be used. Specific examples of the copolymer Examples thereof include vinyl acetate-vinyl chloride copolymer, ethylene-vinyl chloride copolymer, vinylidene chloride-vinyl chloride copolymer and the like.

The preferred degree of polymerization of vinyl chloride resin is 60.
It is 0-1100. The degree of polymerization of vinyl chloride resin is 6
If it is less than 00, the mechanical strength and weather resistance of the coating film tend to be insufficient, while if it exceeds 1100, the meltability may become insufficient.

The average particle size of the above-mentioned thermoplastic resin powder is
The range of 10 to 200 μm is preferable. Average particle size is 10μ
When it is less than m, the powder properties are remarkably deteriorated, and secondary aggregation and blocking are likely to occur. As a result, the amount of resin discharged from the coater becomes unstable, continuous coatability cannot be maintained, film thickness tends to vary, and the coater must be cleaned more frequently, resulting in reduced workability. There's a problem. On the other hand, if the average particle size exceeds 200 μm, the coating efficiency may be reduced and it may be difficult to obtain a smooth coated surface.

The powder coating resin composition of the present invention, which contains the powder of the above-mentioned thermoplastic resin and the alkaline earth metal salt of salicylic acid or alkylsalicylic acid as essential components, may optionally further contain a pigment, a plasticizer and a filler. Agents, additives and the like can be added. When a vinyl chloride resin is used as the thermoplastic resin, the vinyl chloride resin 100
It is preferable to use about 30 to 50 parts by weight of a plasticizer per part by weight.

[0013]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples. The number of parts shown below represents parts by weight. <Examples 1 to 3> Polymerization degree 700 and average particle size 30 to 90 μm
m vinyl chloride resin [manufactured by Toagosei Co., Ltd., trade name TS-700M] 100 parts, tri-2-ethylhexyl trimellitate 40 parts, dibutyltin mercapto 7 parts, epoxidized linseed oil 3 parts Then, 5.0 parts of titanium oxide as a pigment was charged into a Henschel mixer with a heating jacket, and heated and mixed at a temperature of 100 to 150 ° C. for about 20 minutes. Then, after cooling to 70 ° C. or lower, emulsion-polymerized fine particles of vinyl chloride [manufactured by Nippon Zeon Co., Ltd., trade name Ge
on121] was added, and the mixture was stirred for 5 minutes. Finally, the barium salt of di-t-butylsalicylic acid was added in the amounts shown below, and the mixture was further stirred for 1 minute.

Example 1: Barium di-t-butylsalicylate 0.2 parts Example 2: 〃 0.4 parts Example 3: 〃 0.6 parts The mixture obtained by the above operation is sieved with a 60 mesh sieve. Classification was carried out to produce a vinyl chloride resin powder coating resin composition.

The resin composition for powder coating of the above example was used to evaluate the triboelectrification characteristics during electrostatic coating. The triboelectrification characteristics were evaluated by using a tribo electrostatic type electrostatic coating machine (trade name: The friction) manufactured by Matsuo Sangyo Co., Ltd.
It depended on the charge amount (μA) when the coating material was continuously discharged for 2 minutes at 0 g / min. By this method, continuous coating on an actual line is possible when the charge amount is 2 μA or more. The evaluation results are as follows. Example 1: Tribo charge amount (μA) 6.5 Example 2: 〃 7.0 Example 3: 〃 7.5

<Embodiments 4 to 5> The g-t in Embodiment 2
Vinyl chloride in the same manner as in Example 2 except that the barium butylsalicylate salt was changed to magnesium di-t-butylsalicylate (Example 4) or strontium di-t-butylsalicylate (Example 5). A resin composition for powder coating of a base resin was produced. The evaluation results of the triboelectric charging characteristics of the above coating resin composition were as follows. Example 4: Tribo charge amount (μA) 5.5 Example 5: 〃 6.0

Comparative Example 1 A vinyl chloride resin powder coating resin composition was produced in the same manner as in Example 1, except that barium di-t-butylsalicylate was not used. The evaluation result of triboelectric charging characteristics of the coating resin composition was 0.8 μA in triboelectric charge amount, which did not reach the minimum charge amount of 2 μA necessary for coating.

[0018]

EFFECTS OF THE INVENTION According to the present invention, a resin composition for powder coating, which contains a thermoplastic resin powder as a main component and is easily charged by friction, can be easily obtained, and the composition has no problems. Applicable to triboelectric electrostatic coating.

Claims (1)

[Claims] 1. A mixture of an alkaline earth metal salt of salicylic acid or alkylsalicylic acid with a powder of a thermoplastic resin.
A resin composition for triboelectric electrostatic powder coating.