JPH05320360A - Aqueous dispersion of fluororesin powder - Google Patents

Abstract

PURPOSE:To obtain the dispersion liquid having low viscosity and excellent water-repellency and dispersion stability, giving a coating film free from white spot and useful for lubrication agent, etc., by dispersing an effective amount of an oleophilic surfactant and fluororesin powder in water. CONSTITUTION:The dispersion liquid is produced by dispersing (A) powder of a fluororesin such as tetrafluoroethylene resin (having a diameter of preferably <=5mum) and (B) an active amount of an oleophilic surfactant having an HLB of <=10 (e.g. glycerol resin acid ester) in (C) water. The weight ratios of A/B/C are preferably 1/ (100-0.05)/(1-100).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous dispersion prepared by dispersing fluororesin powder in water. The aqueous dispersion of the fluororesin powder of the present invention can be used as a lubricant, an extreme pressure additive, a release agent and the like.

[0002]

2. Description of the Related Art Fluororesin is excellent in heat resistance, oil resistance, chemical resistance, weather resistance, electrical characteristics, mechanical strength, etc., and is therefore used in various applications such as powder, pellets, paste or dispersion liquid. It is used.

As the dispersion liquid of the fluororesin powder, the dispersion medium may be water, various organic solvents, etc., and a fluorine-based water-soluble surfactant has been sometimes used. In addition, a thickener such as a water-soluble polymer may be added to disperse it in a very viscous dispersion medium.

[0004]

The dispersion medium of the fluororesin powder dispersion is preferably water rather than organic solvent from the viewpoint of environmental pollution. However, since the fluororesin powder has poor compatibility with water, it was difficult to obtain a stable aqueous dispersion of these two components. In particular, it has been very difficult to obtain a finely stable aqueous dispersion of fluororesin powder in the state of primary particles.

That is, conventional commercially available dispersions of fluororesin powder have the following problems.

In use, it must be well mixed with stirring.

Since large aggregates of fluororesin powder are present, unevenness occurs when applied to the object to be coated.

The use of a water-soluble surfactant or thickening agent may cause white spots on the coating film of the article to be coated, or may not be able to obtain a predetermined water repellency.

An object of the present invention is to provide an aqueous dispersion of fluororesin powder which solves the above-mentioned problems of the prior art.

[0010]

According to the present invention, the above object is achieved by an aqueous dispersion of a fluororesin powder containing an effective amount of a lipophilic surfactant and the fluororesin powder dispersed in water. be able to.

The diameter of the fluororesin powder is preferably 5 μm
It is below.

The preferred lipophilic surfactant is HLB10.
It has at least the lipophilicity of the following lipophilic surfactants.

The fluororesin is preferably a tetrafluoroethylene resin, a tetrafluoroethylene-perfluorovinyl ether copolymer resin, a tetrafluoroethylene-hexafluoropropylene copolymer resin, a tetrafluoroethylene-ethylene copolymer resin. , Polyvinylidene fluoride resin, trifluorochloroethylene resin, vinylidene fluoride-hexafluoropropylene copolymer resin, and vinyl fluoride resin.

[0014]

A preferred embodiment of the fluororesin is generally represented by a chemical formula in which hydrogen of a hydrocarbon is replaced with fluorine (which may contain a halogen element such as chlorine, oxygen, etc.), and a resin which is solid at room temperature (generally Plastic resin). For example, it can be synthesized by polymerizing a monomer in which one or more hydrogen atoms of ethylene are replaced with fluorine atoms. Preferred fluororesins include tetrafluoroethylene resin, tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin, tetrafluoroethylene-hexafluoropropylene copolymer resin, tetrafluoroethylene-hexafluoropropylene-perfluoroalkoxy resin. Ethylene copolymer resin, tetrafluoroethylene-ethylene copolymer resin, trifluoroethylene chloride resin, trifluorochloroethylene-ethylene copolymer resin, vinylidene fluoride resin,
Examples thereof include vinyl fluoride resin.

The lipophilic surfactant is insoluble or sparingly soluble in water at room temperature, and is preferably a surfactant having a lipophilicity equal to or higher than that of a lipophilic surfactant having an HLB of 10 or less. That is, not only a nonionic surfactant but also an ionic surfactant may be used. For example, glycerin fatty acid ester, sorbitan fatty acid ester, pentaerythritol fatty acid ester, ethylene glycol fatty acid ester, polyglycerin, sucrose higher fatty acid ester, polyethylene glycol higher alcohol or higher fatty acid adduct (short polyethylene glycol chain) Etc.

The ionic lipophilic surfactant has a long alkyl chain and plural alkyl chains are present in the same molecule, such as lecithin,
Dialkyldimethylammonium salt, dialkylphosphoric acid ester, dialkylsulfosuccinic acid and the like can be used.

The preferred weight ratio of fluororesin powder: lipophilic surfactant: water in the aqueous dispersion of fluororesin powder of the present invention is 1: 100 to 0.05: 1 to 100.

The aqueous dispersion of the fluororesin powder of the present invention may contain various surfactants in addition to the lipophilic surfactant. The water-soluble surfactant and the water-soluble polymer can be contained within the range not causing the above problems.

The preferable diameter of the fluororesin powder for good dispersion is 5 μm or less. Particularly when the diameter is 1 μm or less, the dispersibility and stability of the powder are excellent.

The aqueous dispersion of the present invention can be produced, for example, as follows.

The fluororesin powder and the lipophilic surfactant are mixed to form a mixture. It is preferable to make a uniform mixture without unevenness. Uniformity can be further improved by heating and mixing as necessary. The mixing ratio of fluororesin powder / lipophilic surfactant is preferably 1/100 to 1 / 0.0 by weight.
Set to 5. This mixture is dispersed in water.

A hydrophilic surfactant or a water-soluble polymer can be added to the mixture as long as the above problems are not caused.

In order to disperse the mixture in water, water is added to the mixture and, for example, using a homomixer, 800
It can be carried out by treating at 0 rpm for 5 minutes.

[0024]

Example 1 Tetrafluoroethylene resin (hereinafter referred to as PTFE) powder which is a fluororesin powder (Polyflon TFE manufactured by Daikin Industries, Ltd .: average particle diameter 1 μm) 1
1 part by weight of the lipophilic surfactant sorbitan monostearate (HLB4.7) is added to 0 part by weight and mixed well. Purified water (89 parts by weight) was added to this mixture, and the mixture was treated at 8000 rpm for 5 minutes using a tabletop homomixer to obtain a dispersion liquid in which PTFE powder was dispersed in water.

(Evaluation) The dispersion of Example 1 was evaluated for stability and water repellency, and the average particle size of the dispersed phase was measured. The evaluation method was as follows.

Stability test: The dispersion was allowed to stand in a constant temperature bath at 40 ° C. for separation, and the state of sedimentation was visually evaluated and ranked as follows. ⊙: No change for 2 weeks or more ○: Slight sedimentation observed in 1 week Δ: Appearance of apparent change observed in 1 week X: Appearance of apparent change observed in 1 day

Water repellency: The dispersion was thinly applied on a glass plate and left to dry for 1 day. Using this glass plate, the contact angle with distilled water was measured and used as a measure of water repellency. The degree of water repellency was ranked according to the size of the contact angle as follows. ◎ ... 85 ° or more, ○ ... 70 ° to 85 °, Δ ... 50 °
~ 70 °, × ... 50 ° or less

Average particle size: A dilute solution of the dispersion was prepared, and the average particle size of the dispersed phase was measured by a light scattering method using Model N4 manufactured by Coulter.

(Results) The dispersion of Example 1 had stability ⊚, water repellency ⊚, and an average particle diameter of 300 nm.

[0030]

The aqueous dispersion of the fluororesin powder of the present invention is
Since the lipophilic surfactant is contained in an effective amount, the fluororesin powder can be stably and uniformly dispersed in water for a long period of time. Therefore, it can be used without stirring and mixing at the time of use, and the coating film is free from unevenness.

The aqueous dispersion of the fluororesin powder of the present invention does not require a water-soluble surfactant or thickener, so that it can be made to have a low viscosity. Produce the effect of.

No white spots appear on the coating film, and the bent portion does not become white even when the coated object is bent.

The coating film has excellent water repellency.

Claims (4)

[Claims] 1. An aqueous dispersion of a fluororesin powder, which comprises an effective amount of a lipophilic surfactant and is dispersed in water. 2. The aqueous dispersion of fluororesin powder according to claim 1, wherein the fluororesin powder has a diameter of 5 μm or less. 3. The aqueous dispersion of fluororesin powder according to claim 1, wherein the lipophilic surfactant has at least the lipophilicity of a lipophilic surfactant having an HLB of 10 or less. 4. The fluororesin is tetrafluoroethylene resin, tetrafluoroethylene-perfluorovinyl ether copolymer resin, tetrafluoroethylene-hexafluoropropylene copolymer resin, tetrafluoroethylene-ethylene copolymer resin. One or more of polyvinylidene fluoride resin, trifluorochloroethylene resin, vinylidene fluoride-hexafluoropropylene copolymer resin, and vinyl fluoride resin. Aqueous dispersion of fluororesin powder.