JPH04337365A - Production of polyphenylene sulfide composition for powder coating use - Google Patents

Abstract

PURPOSE:To provide the title composition freed from problems concerning poor fluidity inherent in conventional such compositions, thus excellent in coatability, and capable of giving coating film of uniform thickness. CONSTITUTION:Polyphenylene sulfide resin powder is dryblended with color pigment and/or inorganic filler followed by heat treatment at a temperature T (the glass transition temperature of said resin <= T <= its melting point), thus obtaining the objective composition.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method for producing a polyphenylene sulfide composition for powder coating, and more specifically, a method for producing a polyphenylene sulfide composition for powder coating, which has excellent coating workability and can provide a coating film of uniform thickness. The present invention relates to a method for producing a polyphenylene sulfide composition.

0002

[Conventional technology]

Polyphenylene sulfide, whose basic unit is [Chemical 1], has excellent properties such as heat resistance, water resistance, chemical resistance, abrasion resistance, and electrical insulation. It is used in fields such as anti-corrosion, chemical-resistant coating, and electrical insulation coating.

[0003] Paints based on polyphenylene sulfide are usually produced by applying powdered paint or slurry paint to the surface of the object to be coated and then melting it to form a film. The coating is applied by preheating powdered paint and spraying or dipping it onto the surface of the object to be coated. This is because polyphenylene sulfide has the property of being insoluble in any organic solvent.

0004

[Problems to be Solved by the Invention] Polyphenylene sulfide compositions for powder coating are composed of polyphenylene sulfide powder containing additives such as coloring pigments, inorganic fillers, surface conditioners, and ultraviolet stabilizers. Ru. The polyphenylene sulfide composition for powder coating can also be produced by mixing the above raw materials, melt-kneading them using an extruder, etc., and then pulverizing them. It is better to omit this and produce the product by simply mixing each raw material in a mixer such as a Henschel mixer, which is the so-called dry blend method.
It is industrially useful because it has high manufacturing efficiency and low manufacturing cost.

However, the polyphenylene sulfide composition for powder coating produced by such a dry blending method has the following drawbacks during powder coating. In other words, powder coatings produced by the dry blending method described above do not necessarily have good powder fluidity, and for this reason, for example, in electrostatic spray painting, the powder discharge from the gun becomes unstable. As a result, there were problems in that continuous coating work was hindered and it was difficult to obtain a film with a uniform thickness.

In addition, in fluidized dip coating, the fluidized state of the powder in the powder fluidized tank is unstable, and in extreme cases, the powder may come into a bumping state and be scattered around the fluidized fluidized tank. As a result, it is difficult to maintain a stable flow state, which causes problems in continuous coating work and makes it difficult to obtain a film with a uniform thickness.

[0007] These poor coating workability and the resulting non-uniform coating thickness are a big problem, especially when coating is carried out continuously on an industrial scale, and the resulting coating simply has a poor appearance. In addition to this, it also causes unfavorable effects on the performance of the coating, which significantly limits the use of this coating.
A solution to this problem is strongly desired.

The cause of the decrease in coating workability is closely related to the particle size of the powder. That is, in general, if the particle size of a powder coating is too coarse or too fine, it will have an unfavorable effect on the workability of painting. If it is too coarse, electrostatic spraying tends to clog the gun during painting, and on the other hand, if it is too fine, especially around 20
When the content of fine powder of .mu.m or less is large, the fluidity of the powder decreases, causing adverse effects such as the above-mentioned problems in coating work and non-uniform coating thickness.

[0009] In order to prevent these problems, it is important to appropriately adjust the particle size of the powder, and in particular, it is important to keep the content of fine powder of 20 μm or less as low as possible. It is. For this reason, in the case of ordinary powder coatings, the particle size is adjusted by adjusting the pulverization conditions when pulverizing the melt-kneaded material into powder during production.

However, when a powder coating is made by simply dry blending a colored pigment and/or an inorganic filler with polyphenylene sulfide resin powder, the above-mentioned pulverization conditions cannot be met because there is no pulverization step during the manufacturing process. Particle size cannot be adjusted by adjustment. Moreover, the colored pigments and inorganic fillers used for paints are generally fine particles of 20 μm or less, so the polyphenylene sulfide powder coating obtained by dry blending these particles uses polyphenylene sulfide powder with a low fines content. Even in the case of powder, it is inevitable that the powder will have a high content of fines. For this reason, the fluidity of the powder coating is reduced, and the powder coating workability is not necessarily good. Needless to say, this tendency becomes more pronounced as the proportion of the colored pigment and inorganic filler increases.

The present invention solves the above-mentioned problems of polyphenylene sulfide compositions used for powder coating, and produces a polyphenylene sulfide composition for powder coating that has excellent coating workability and can obtain a film of uniform thickness. The purpose is to provide a method.

0012

[Means and effects for solving the problems] In order to achieve the above-mentioned object, in the present invention, a colored pigment and/or an inorganic filler are dry-blended with a polyphenylene sulfide resin powder, and then a polyphenylene sulfide resin powder is dry blended with a colored pigment and/or an inorganic filler. Provided is a method for producing a polyphenylene sulfide composition for powder coating, which comprises performing heat treatment at a temperature above Tg and below melting point.

[0013] The polyphenylene sulfide powder used in the present invention is

It is a compound composed of repeating units of [Chemical formula 2], and can also include partially oxidized, branched or crosslinked compounds, and generally has a Tg of 85 to 95°C and a melting point of 28
The temperature is 0 to 290°C. The particle size is 150 μm, making it suitable for electrostatic spray coating, fluidized dip coating, thermal spraying, etc.
Hereinafter, it is preferable that the thickness is 100 μm or less.

The coloring pigment and/or inorganic filler used in the present invention are appropriately selected from among those commonly used in paints depending on the purpose and purpose. It is desirable that the material does not discolor due to heat. Such colored pigments and/or
Inorganic fillers include colored pigments such as titanium dioxide, Bengara, heat-resistant yellow lead, carbon black, and graphite; short glass fibers, glass beads, glass powder, glass flakes, calcium carbonate, barium sulfate, silica, and mica. Examples include inorganic fillers. In view of the effect on coating workability and uniformity of film thickness by the method for producing the composition of the present invention, the amount of the coloring pigment and/or inorganic filler is preferably 10 parts by weight or more, more preferably, based on 100 parts by weight of the polyphenylene sulfide resin. is 20 parts by weight or more.

The manufacturing method of the present invention is characterized by:
Coloring pigment and/or polyphenylene sulfide resin powder
Alternatively, the inorganic filler is dry-blended and then heat-treated at a temperature above the Tg and below the melting point of the polyphenylene sulfide resin. The present inventors have discovered that by performing the above heat treatment, the fluidity of the powder coating material is significantly improved, and therefore, the workability of coating and the uniformity of the film thickness are improved.

[0016] The flowability of a powder can be evaluated by measuring the value of the angle of repose. Generally, it is well known that powders with a lower angle of repose have better fluidity. The angle of repose of powders desirable for powder coating purposes is generally 45 degrees or less. Powder coatings obtained by simply dry-blending polyphenylene sulfide resin powder with colored pigments and/or inorganic fillers have a high angle of repose and therefore do not have sufficient flowability, resulting in poor coating operation. It cannot be said that the properties are necessarily good in terms of properties and uniformity of film thickness.

On the other hand, in the case of the polyphenylene sulfide powder coating obtained by heat treatment according to the method of the present invention, the angle of repose shows a low value, and therefore, the fluidity of the powder is good, and as a result, coating workability and Excellent film thickness uniformity. This is achieved by heat-treating the dry blended powder at a temperature higher than the Tg and lower than the melting point of the polyphenylene sulfide resin, during which the polyphenylene sulfide resin powder is thermally softened, and the resin powder particles interact with each other and the colored pigments interact with each other. As a result of thermal fusion with the particles of the inorganic filler and/or the particles of the inorganic filler, the particle size of the obtained powder is such that the fine powder content does not increase even though the fine particles of the coloring pigment and the inorganic filler are contained. , Therefore, this is thought to be due to the ability to maintain a low angle of repose.

The composition of the present invention is produced as follows. That is, first, the above-mentioned colored pigment and/or inorganic filler and polyphenylene sulfide resin powder are uniformly mixed using a stirring device such as a Henschel mixer. Next, the obtained mixture is heated at a temperature that is higher than the Tg and lower than the melting point of the polyphenylene sulfide resin.

The heating device can be arbitrarily selected from those that satisfy the above conditions, but heating devices equipped with a stirring device such as a Nauta mixer, for example, can provide more uniform heating. Using equipment is effective. The heating temperature needs to be higher than the Tg and lower than the melting point of the polyphenylene sulfide resin. If the heating temperature is below Tg, no thermal fusion occurs between the polyphenylene sulfide resin powder and the colored pigment and/or inorganic filler, making it impossible to achieve the effects of the present invention. Furthermore, if the heating temperature exceeds the melting point of the polyphenylene sulfide resin even slightly, the polyphenylene sulfide resin powder will be thermally melted and will no longer be powder-like, which is not preferable. More preferable heating temperature is 120℃~250℃
It is ℃. The same effect can be obtained by heating in air or inert gas. The heating time depends on the heating temperature, the amount of the composition, etc., but is usually 1 hour or more.

[0020] The polyphenylene sulfide composition produced by the production method of the present invention may contain additives such as surface conditioners and ultraviolet absorbers as necessary, as well as polyamide, polycarbonate, polysulfone, polyethersulfone, polyphenylene oxide, polyimide, polyamideimide,
Other polymers such as epoxy resins may also be mixed homogeneously.

The composition produced by the production method of the present invention can be applied to the surface of objects to be coated, such as metals, glass, and ceramics, by a conventional powder coating method. At this time, prior to powder coating, the surface of the object to be coated may be undercoated with an appropriate primer.

[0022]

EXAMPLES Table 1 shows the compositions of the polyphenylene sulfide compositions used in Examples and Comparative Examples.

[0023]

[Table 1]

Example 1 The polyphenylene sulfide composition shown in (A) in Table 1 was dry blended by stirring the raw materials in a Henschel mixer at a rotation speed of 1800 rpm for about 20 seconds. Next, this powder was heat-treated in a heating furnace at 200° C. in an air atmosphere for 5 hours to produce a polyphenylene sulfide composition for powder coating.

Example 2 A polyphenylene sulfide composition for powder coating was produced in the same manner as in Example 1, except that the heat treatment conditions were 240° C. for 1 hour.

Example 3 A polyphenylene sulfide composition for powder coating was produced in the same manner as in Example 1, except that the heat treatment conditions were 150° C. for 10 hours.

Example 4 A polyphenylene sulfide composition for powder coating was produced in the same manner as in Example 1, except that the polyphenylene sulfide composition shown in (B) of Table 1 was used.

Example 5 Powder coating was carried out in the same manner as in Example 1, except that the polyphenylene sulfide composition shown in (C) in Table 1 was used and the heat treatment conditions were 240° C. for 1 hour. A polyphenylene sulfide composition for use was produced.

Example 6 A polyphenylene sulfide composition for powder coating was produced in the same manner as in Example 4, except that the heat treatment conditions were a 200° C. heating furnace in a nitrogen atmosphere for 5 hours. .

Comparative Example 1 A polyphenylene sulfide composition for powder coating was prepared by simply dry blending the polyphenylene sulfide composition shown in (A) in Table 1 at a rotational speed of 1800 rpm for about 20 seconds in a Henschel mixer. Manufactured.

Comparative Example 2 A polyphenylene sulfide composition for powder coating was produced in the same manner as in Comparative Example 1, except that the polyphenylene sulfide composition shown in (B) of Table 1 was used.

Comparative Example 3 A polyphenylene sulfide composition for powder coating was produced in the same manner as in Comparative Example 1, except that the polyphenylene sulfide composition shown in (C) of Table 1 was used.

Comparative Example 4 A polyphenylene sulfide composition for powder coating was produced in the same manner as in Example 1, except that the heat treatment conditions were 60° C. for 10 hours.

Comparative Example 5 Powder coating was carried out in the same manner as in Example 1, except that the polyphenylene sulfide composition shown in (B) of Table 1 was used and the heat treatment conditions were 300° C. for 5 minutes. A polyphenylene sulfide composition for use was produced.

Measurement of Angle of Repose The angle of repose of the powder compositions of Examples 1 to 6 and Comparative Examples 1 to 5 was measured using a powder tester (manufactured by Hosokawa Micron Co., Ltd.). Evaluation of coating workability and film thickness uniformity in electrostatic spray painting; Each composition was tested on a thin stainless steel plate (SUS304,
．． 5t x 300 x 300mm) with a cured film thickness of 60~7
Electrostatic spray painting was performed so that the thickness was 0 μm, and the painting workability at this time was evaluated. Next, the coated plate was heated at a temperature of 340°C for 1
After heating and curing for 0 minutes, the uniformity of the film thickness was visually observed.

Evaluation of coating workability and film thickness uniformity in fluidized dip coating: Each composition was placed in a powder fluidized tank and compressed air was fed into it through a perforated plate to bring it into a fluidized state. The presence or absence of changes in the flow state was observed. Next, after grit blasting, a hot rolled steel plate (5 tons x 70 x 150 mm) preheated to 350°C was immersed in a fluidized bath for 3 seconds so that the film thickness was about 200 μm, taken out, and heated at 340°C for 10 minutes. The film was cured by heating for a minute, and the uniformity of the resulting film was visually observed.

The coating workability and uniformity of film thickness of each composition were evaluated according to the criteria shown in Table 2, and the results are shown in Table 3 together with the measurement results of the angle of repose.

[0038]

[Table 2]

[0039]

[Table 3]

[0040]

Effects of the Invention As is clear from the above explanation, the composition produced by the production method of the present invention has excellent coating workability when used for powder coating, and the coating has a smooth surface and a uniform thickness. can be formed into a film. The base material is polyphenylene sulfide, and the film has excellent heat resistance, water resistance, chemical resistance, abrasion resistance, and electrical insulation properties, so it can be deposited on areas where such properties are required. Useful. In particular, heat-resistant and chemical-resistant pre-coated plates, insulation coatings for electrical and electronic parts, automobile parts, chemical plants, hot water pipes, hot spring piping, ship and seawater plant piping, oil field pipes, etc.
It is effective when applied to chemical-resistant and anti-corrosion coatings.

Claims (1)

[Claims] [Claim 1] A method for powder coating, characterized in that a colored pigment and/or an inorganic filler are dry-blended with a polyphenylene sulfide resin powder, and then heat treated at a temperature above the Tg and below the melting point of the polyphenylene sulfide resin. A method for producing a polyphenylene sulfide composition.