JPS5867765A - Water-based coating composition and its preparation - Google Patents

Abstract

PURPOSE:To prepare a water-dispersed slurry paint having excellent storage stability and coating property, in a short time, independently of the type of stirrer, by using powdered emulsion, thereby enabling the dispersion of the fine resin powder in an aqueous medium even with high-speed mixing. CONSTITUTION:A water-based coating composition is prepared by dispersing (A) fine powder of a resin (preferably fine powder of epoxy resin, acrylic resin, etc. having particle size of <=100mu) in (B) water in the presence of (C) powdered emulsion (dry powder obtained by drying synthetic resin emulsion e.g. by spray- drying), by high-speed mixing. The weight ratio of the resin powder to the powdered emulsion is preferably 100:0.5-40:60, and the amount of water is preferably 900-40pts.wt. per 100pts.wt. of the mixture having the above composition.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a water-based coating composition and a method for producing the same. More specifically, the present invention relates to the provision of a water-based coating composition that has excellent storage stability and coating workability.

Conventional water-based paints and emulsion paints are limited to low molecular weight because the resin used is water-soluble or emulsified, resulting in poor coating performance, and changes in the coating environment can cause problems such as sagging and flaking. Workability was also poor. In order to improve this problem, for example, Japanese Patent Application Laid-Open No. 50-65581
As disclosed in the above issue, there is a technique for mixing and dispersing fine resin powder and hardening agent fine powder in water-soluble paint or emulsion paint. However, when mixing and dispersing powder in emulsion paint, it is necessary to prevent the emulsion from being destroyed. The mixing and dispersing operation must be performed at low speeds (for example, 1000 to 8000 rpm or less with a disper), and as a result, the degree of mixing and dispersion of the powder is not good, and the storage stability of the paint is at stake (for example, powder precipitation may occur). , the surface of the paint becomes rough), and the painting workability is also poor (for example, sagging occurs during painting, the paint adhering to the tip of the gun causes wrinkles that adhere to the object to be coated, and poor dispersion of resin particles). clogging of the gun tip).

As a result of intensive research to solve these problems, the present inventors have found that by using a powder emulsion, it is possible to satisfactorily mix and disperse fine resin powder and the like into an aqueous medium at high speed. The present invention has now been completed.

That is, the gist of the present invention is a water-based coating composition characterized in that fine resin powder is dispersed in water in the presence of a powder emulsion, and the coating composition characterized in that the dispersion is carried out by high-speed mixing. It lies in the manufacturing method of things.

According to the present invention, a slurry water-dispersed paint that does not have the problems of coating workability such as sagging and lumps during painting, and storage stability such as powder precipitation and surface roughness can be produced using a stirrer. It can be manufactured in a short time by high-speed mixing without being affected by the type.

The powder emulsion spikes used in the present invention are known per se, and are made by drying a synthetic resin emulsion by a method such as spray drying to form a dry powder, and can easily be made into an emulsion by adding water and stirring and mixing. It is something that can be restored. For resin emulsions with low glass transition and softening points, inorganic powders (e.g., silica, clay)'
(il- It is desirable to use a powder emulsion added to prevent caking. Commercially available products include, for example, "Movinyl Powder SA" and "Movinyl Powder DM200J" manufactured by Hoechst Synthesis. In terms of coating film performance, it is preferable to use a resin that is compatible with the resin fine powder described below in terms of composition.

The fine resin powder of the present invention refers to epoxy resin, Acrylic IJ/
Fine powders of thermosetting or thermoplastic resins commonly used in paints, such as L/resin, polyester resin, vinyl chloride resin, nylon resin, cellulose acetate butyrate resin, etc., can be used.

Additives such as curing agents, pigments, leveling agents, etc., which are generally used in paints, may be blended into this fine resin powder as necessary. Generally, fine resin powder is obtained by uniformly mixing a composition by a method such as melt-kneading and pulverizing it, but if necessary, fine resin powder and fine curing agent powder are manufactured separately. It may also be dry mixed. The particle size of the powder is preferably 100 microns or less.

In the present invention, the resin fine powder and the powder emulsion have a weight ratio of 100 to 40:
It is preferable to use a ratio of 60%. If the amount of the latter powder emulsion is too small, the mixing and dispersion of the powder, storage stability when made into a paint, and painting workability will be poor, which is undesirable.On the other hand, if it is too much, sagging will easily occur during painting, making it difficult to paint. Workability is poor, and coating film performance tends to decrease due to the large amount of low-molecular resin. In addition, a total of 100 parts (parts by weight,
It may be used in a ratio of 900 to 40 parts of water to water (the same applies hereinafter). The ratio may be appropriately selected based on the conditions generally adopted for ordinary paints, especially slurry water dispersion paints. In addition, a known neutralizing agent or other dispersing agent that is blended into a slurry water-dispersed coating material may be added as necessary.

To obtain the desired coating composition by mixing and dispersing the above resin fine powder and powder emulsion in water, use all means capable of high-speed mixing and dispersion operations (e.g., high-speed disperser, gate mixer) and carry out the following procedure. It's okay to be.

(a) Fine resin powder, powder emulsion, and water are mixed and dispersed simultaneously.

(b) First, a fine resin powder and a powder emulsion are dry mixed using a conventional mixer (eg, Henschel mixer, blender), and this mixture is mixed and dispersed in water.

(C) First, fine resin powder is mixed and dispersed in water, and a powder emulsion is mixed and dispersed in the dispersion liquid.

(d) First, the powdered etulsion is mixed and dispersed in water, and the entire fine resin powder is mixed and dispersed in the dispersion liquid.

In either case, the high-speed mixing and dispersion operation may be carried out at room temperature until a good dispersion state is obtained in the target coating composition.

The coating composition of the present invention obtained as described above is a nullary water dispersion coating excellent in storage stability and coating workability.

Next, the present invention will be specifically explained with reference to Examples and Comparative Examples. Parts refer to parts by weight.

Examples 1 to 9 and Comparative Examples 1 to 2 500 g of ion-exchanged water and the first
A predetermined amount of the powder emulsion shown in the table was added or not, and the mixture was stirred for 5 minutes at 500 Q rpm using a disper. Next, put a predetermined amount of fine resin powder shown in Table 1 into this, stir it with a glass rod, and then mix it with a disper for 5 minutes.
A nullary water dispersion paint was obtained by stirring at 0.000 rpm for 10 minutes. In Comparative Example 2, a nonionic surfactant (Emulgen 810J manufactured by Kao Atlas) was used.
i2g was added.

The properties of these nullary water dispersion paints are shown in Table 1.

In addition, ■ Movinyl Powder DM2QO: Hex [synthetic powder emulsion (special copolymer resin)].

■Movinyl Powder SA: Powder emulsion (modified vinyl acetate resin) manufactured by Hekinuto Synthesis.

■Thermosetting epoxy resin powder: 100 parts of epoxy resin (Epicor 1004j manufactured by Shell Chemical), 6 parts of dicyandiamide, 1 part of 2-methylimidazole, 80 parts of titanium oxide (Titanium R-82DJ manufactured by Ishihara Sangyo) and leveling agent. A powder obtained by melt-kneading 1 part of "Modaflow" (manufactured by Monsanto) using a Punuko Kneader PR-46 (manufactured by Busu Co., Ltd.) and mechanically pulverizing the mixture to an average particle size of 25 microns.

■Thermosetting polyester resin powder: Polyester resin (
75 parts of Bayer's [RiVlan U-, 502J), 2 blocks of blocked isocyanate (Bayer's "Fleran UIJ")
5 parts, titanium oxide (manufactured by Ishihara Sangyo [Titanium R-820J
) and 1 part of a leveling agent (manufactured by BASF [Acronal 4FJ]) were melt-kneaded in a Busco kneader PR-46, and the powder was mechanically pulverized to an average particle size of 25 microns.

■ Thermosetting acrylic resin powder Niacrylic resin (acrylic resin with a weight average molecular weight of 10,000 obtained by solution polymerizing 25 parts of glycidyl methacrylate, 80 parts of styrene, 37 parts of methyl methacrylate and 8 parts of n-butyl acrylate) 100 parts, 1, IO-decanedicarboxylic acid 2
0 parts, titanium oxide (Ishihara Sangyo “Titanium R-82, pJ
) and 1 part of a leveling agent (Modaflow manufactured by Monsanto) were melt-kneaded in a Busco kneader PR-46,
Powder mechanically ground to an average particle size of 25 microns.

■Thermosetting polyester resin: 100 parts of polyester resin ("Fleran U-502J" manufactured by Bayer), 30 parts of titanium oxide ("Titanium R-820" manufactured by Ishihara Sangyo) and leveling agent ("Acronal 4Fj" manufactured by BASF)
1 part was melt-kneaded in a Pnuco Kneader PR-46 and mechanically ground to an average particle size of 25 microns, and the powder was mixed with block isocyanate (Bayer's "Fleran Cross Linking Agent UIJ") 1
00 parts of titanium oxide (same as above) and 1 part of leveling agent (same as above) were bath-melted and kneaded in a Pnuko kneader PR-46 and mechanically crushed to an average particle size of 25 microns, in a weight ratio of 75 for the former and 250 for the latter. Dry mixed powder.

■Paint solid content sedimentation amount: Paint diameter 8cI11, height 1O
Place in a c11I container, cover and store at 25°C. One week later, the height of the precipitate was measured (Xα/10aR)
The amount of precipitation is determined by xtoo (%).

■ Paint surface roughness: Store the paint under the same conditions as the measurement of paint solid content precipitation, and visually judge the state of the paint liquid level at that time.

◎; Smooth liquid surface, same as initial condition.

×: The liquid surface was partially dry and the powder was exposed.

■Painting workability (gun tip toe υ): 5 kg using feeder 61 (painting gun manufactured by Iwata Painting Machine, caliber 0.8 MM)
/ Discharge stability when discharging paint at a pressure of c-.

◎: Stable discharge regardless of waiting time.

・×: Significant clogging at the gun tip, resulting in unstable discharge.

[Phase] Painting workability (puff): When painting under the same conditions as painting workability (gun tip clogging), the presence or absence of smudges caused by paint adhering to the tip of the gun and adhesion to the object to be coated. .

◎: Good without any lumps.

×: A bump occurred and the product was defective.

Patent applicant: Nippon Paint Co., Ltd. Representative Patent Attorney Aoyama Aoyama and 1 other person

Claims (1)

[Claims] 1. A water-based coating composition characterized in that fine resin powder is dispersed in water in the presence of a powder emulsion. 2. Resin fine powder: Powder emulsion has a weight ratio of 1
The composition according to item 1 above, wherein the proportion of water is 900 to 40 parts by weight to 100 parts by weight of the formulation having a ratio of 00:0.5 to 40:60. 3. A method for producing a water-based coating composition, which comprises dispersing fine resin powder in water by high-speed mixing in the presence of a powder emulsion. 4. The manufacturing method of item 8 above, in which the powder emulsion, fine resin powder, and water king are all mixed and dispersed at the same time. 5. The manufacturing method of item 3 above, in which a mixture of a powder emulsion and a fine resin powder is mixed and dispersed in water. 6. The method of item 3 above, in which a powder emulsion is mixed and dispersed in a dispersion of fine resin powder and water. 7. The manufacturing method of item 3 above, in which fine resin powder is mixed and dispersed in a powder emulsion and water dispersion.