JPH0551544A - Coating composition having improved applicability - Google Patents

Abstract

PURPOSE:To obtain a coating composition which has excellent application workability and a less tendency to drip even if applied to a standing surface and accordingly can be applied in an increased thickness at one time, by imparting thixotropy to the composition. CONSTITUTION:A coating composition having improved applicability, which comprises as an essential binder component a resin in the form of a water-in-oil emulsion prepared by mixing water with an organic solvent solution of the resin.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel and useful coating composition having improved coatability. More specifically, the present invention uses a specific resin called a water-in-oil emulsion as a binder, has thixotropy, is hard to drip at the time of coating, and can be thickly coated at one time. It relates to an improved, very practical coating composition.

[0002]

2. Description of the Related Art Up to now, various paints have been applied in order to protect various base materials and to make them beautiful.

In recent years, from the viewpoint of resource saving and environmental protection, there is a strong demand to reduce the content of organic solvents in paints, and in fact, research into water-based paints and high solidification (high solidification) has been actively conducted. Has been done.

First, in the case of using water, the physical properties and finished appearance of the resulting coating film are often inferior. On the other hand, in the case of high solidification, although the finished appearance is excellent, the molecular weight of the resin must be reduced in order to keep the coating viscosity low with a high solid content. Therefore, when coating on the standing surface, However, there is a drawback that it is easy to sag and the workability of painting is poor.

In order to improve such drawbacks and drawbacks, various thixotropic agents such as microgels and non-aqueous resin dispersions (NAD) have been studied, but in the former case, Is not found to be sufficiently satisfactory, and in the latter case, the solvent content often increases when trying to obtain a sufficient effect,
Either case is not preferable.

[0006]

As described above, as long as the conventional technique is followed, the content of the organic solvent can be reduced, and the coating workability is extremely improved and the coating workability is extremely high. Obtaining the composition was extremely difficult.

[0007] Therefore, the problem to be solved by the present invention is, in part, to simply and easily reduce the content of the organic solvent without deteriorating the finished appearance of the solvent-soluble paint and the physical properties of the coating film. It is to develop a method of improving the thixotropy and, at the same time, improving the workability of coating while preventing the increase.

[0008]

Therefore, the present inventors have
In view of the advantages and disadvantages of the prior art, and focusing on the problems to be solved by the invention as described above, as to the improvement of the coating workability of the solvent-soluble paint, as a result of repeated studies, a resin A coating composition comprising a resin in the form of a water-in-oil emulsion formed by mixing water with an organic solvent (hereinafter abbreviated as a resin solution) as an essential component of a binder has desired performance. The present invention has been completed and the present invention has been completed.

That is, the present invention intends to provide a coating composition having improved coatability, which comprises a resin obtained by mixing a resin solution with water to form a water-in-oil emulsion as an essential component of a binder. It is a thing.

Here, the resin applicable in the present invention,
That is, although the resin which is an essential component of the binder is not particularly limited, for example, an epoxy resin, a urethane resin, an acrylic / acrylic styrene resin, a polyolefin resin, a fluorine resin, a vinyl acetate resin, styrene. Examples thereof include a butadiene-based resin, a melamine-based resin, a polyester-based resin, an alkyd-based resin or a phenol-based resin, or a composite-based resin of these.

Of these, for example, polyol-
For resin systems such as (poly) isocyanate-based resins whose curing reaction is significantly affected by the influence of water, use a block (poly) isocyanate to reduce the influence of moisture, etc. Of course, it is better not to apply the invention.

Although there is no particular limitation on the molecular weight, viscosity and solid content of the resin, from the point of view of the invention,
It is desirable to apply to a so-called high solidification resin having a low molecular weight, a low viscosity and a high solid content as much as possible.

The amount of water to be mixed is determined by the particle size of the water-in-oil emulsion to be formed, the coating workability required for the coating composition, etc. It is desirable to use within the range of 2 to 35% by weight, more preferably 5 to 25% by weight, based on the total resin solid content.

A method of mixing water with a resin solution to form a stable water-in-oil (reverse phase or WO type) emulsion is not particularly limited, but among them, However, to mention only representative methods, (1) the resin itself has a reactive functional group such as a hydroxyl group, an amino group, a (poly) ethylene oxide group or a carboxyl group, and is highly hydrophilic. Use one.

(2) As the solvent, those having high hydrophilicity such as lower alcohols, cellosolves, carbitols, ketones or esters are used. (3) The resin is, for example, a carboxyl group (amino group)
And the like, and has an acid value (amine value), some or all of them are neutralized with amines (acids) or the like to increase the hydrophilicity of the resin.

(4) A surfactant is added to the resin solution. (5) Water-soluble and / or water-dispersible resin and water-insoluble resin are used in combination. (6) The methods of (1) to (5) above may be used in combination.

Of these, the method (5) is particularly preferable because it has high versatility regardless of the type of resin. In this case, it is necessary to pay attention to the compatibility between the water-soluble and / or water-dispersible resin and the water-insoluble resin.

The use ratio of these water-soluble and / or water-dispersible resin and water-insoluble resin is in the range of 1:99 to 40:60 in terms of the weight ratio of the solid content of the former resin to the latter resin. preferable.

The method of adding the water-soluble and / or water-dispersible resin to the water-insoluble resin is as follows. Water-solubilized (water-dispersed) water may be added in advance,
You may add the thing before adding water.

It is particularly preferable to use the emulsion polymer obtained by emulsion polymerization as a part of the water-soluble and / or water-dispersible resin because the water-in-oil emulsion obtained tends to have high thixotropy.

The method of mixing the resin solution and water is such that the smaller the particle size of the water-in-oil emulsion formed, the easier the coating workability of the obtained coating composition and the better the stability. Therefore, the amount of water used is small, and a coating composition having a high solid content and good dryability is easily obtained, which is preferable.

For this reason, it is preferable that the mixing is sufficiently performed. The mixing / stirring device is not particularly limited, but a high shearing device is preferable, and for example, a high speed disperser, a homogenizer, or a (homomic) line mill can be used.

In the case of a pigment addition system, water may be added together with the resin at the time of dispersing the pigment, and mixed, and a water-in-oil emulsion resin prepared separately when diluting the ordinary pigment paste with the resin may be used. May be used.

Further, water may be added before coating and mixed and stirred before use. Next, regarding the pigment, the hiding property of the resulting coating film, the hardness, the improvement of the rust preventive property and the substrate adhesion property,
Also, for coloring, it is used at an appropriate time as needed, but in consideration of various physical properties of the obtained coating film, the amount used is 100 parts by weight of the solid content of the resin (binder). It is preferably 200% by weight or less, more preferably 150% by weight or less.

The pigment used is not particularly limited,
Well-known and commonly used ones are used. Specifically, various metal oxides such as titanium oxide and zinc oxide; various extender pigments such as talc, mica, calcium carbonate, clay and barium sulfate; metaboric acid. Various rust-preventive pigments such as barium, aluminum hydrogen phosphate, calcium molybdate, and strontium chromate; various iron oxides such as red iron oxide; and various organic or inorganic coloring pigments such as carbon and phthalocyanine blue. ,
These may be used alone or in combination of two or more,
Of course.

In forming a coating material, a pigment anti-settling agent, a thickener, an antifoaming agent, a leveling agent, a wetting agent, a cross-linking agent, a drier, a thixotropic agent, a water repellent, a pigment dispersant, an ultraviolet absorber,
Various known and conventional additives such as antioxidants and flame retardants can be used.

The drying conditions are not particularly limited, and normal temperature drying, heat drying or baking can be applied.

[0028]

EXAMPLES Next, the present invention will be described more specifically with reference to Reference Examples, Examples and Comparative Examples, but all are based on weight unless otherwise specified.

Reference Example 1 (Preparation Example of Water-Insoluble Alkyd Resin) In a reactor equipped with a heating device, a stirrer, a reflux device, a water separator, a thermometer and a dropping device, 150 parts of castor oil and trimethylolpropane were added. 234 parts, 125 parts of neopentyl glycol, 100 parts of 1,6-hexanediol
Parts, 275 parts of isophthalic acid and 242 of adipic acid
A portion was charged, and the temperature was raised to 220 ° C. over 8 hours with stirring in a nitrogen stream.

Next, the acid value is kept at 10 at the same temperature.
And a resin having a hydroxyl value of 150 was obtained. After cooling down,
Dilute solids to 70% with cellosolve acetate and add 25
Gardner viscosity at ℃ (hereinafter abbreviated as viscosity)
To obtain a resin solution of VW. Hereinafter, this is abbreviated as S-1.

Reference Example 2 (Preparation Example of Water-Insoluble Acrylic Resin) 200 parts of xylene and 120 parts of n-butanol were charged in a reactor equipped with a heating device, a stirrer, a reflux device, a thermometer and a dropping device. The temperature was raised to 125 ° C.

While maintaining the same temperature, 200 parts of styrene,
A monomer mixture consisting of 480 parts of n-butyl methacrylate, 220 parts of n-butyl acrylate, 80 parts of β-hydroxyethyl methacrylate and 20 parts of acrylic acid, 100 parts of xylene, tert-butylperoxy (2 -Ethyl hexanoate) 100 parts, te
A catalyst (polymerization initiator) mixture consisting of 5 parts of rt-butylperoxybenzoate and 5 parts of azobisisobutyronitrile was added dropwise over 5 hours.

Furthermore, the temperature was maintained for 10 hours to obtain a resin solution having a solid content of 70% and a viscosity of XY. Hereinafter, this is abbreviated as S-2. Examples 1 to 4 and Comparative Examples 1 to 3 Various coating compositions, that is, paints were prepared with the following formulations. The compositions (blending ratios) of the respective paints are summarized in Table 1.

[0034]

Note 1) The amount of water described in the table includes the amount of water contained in the above-mentioned aqueous resin. Note 2) S-1 and S-2 are used respectively for the preparation of so-called millbase (pigment paste), while S-3 and W-1, W-2,
W-3 and W-4 are as follows, respectively.

S-3 ... "Super Beckamine L-
109-65 "[Butyl etherified melamine resin manufactured by Dainippon Ink and Chemicals, Inc .; solid content = 65%] W-1 ..." Watersol S-685-IM "
(Water-soluble methyl etherified melamine resin manufactured by the same company; solid content = 80%) W-2 ... "Watersol S-751" (water-soluble acrylic resin manufactured by the same company; solid content = 50%) W -3 ... "Watersol CD-520" (water-dispersible alkyd resin manufactured by Doujinsha Co., Ltd .; solid content = 40%) W-4 ... ... "Boncoat EC-740" (acrylic emulsion polymer manufactured by Dojo Co., Ltd.) ; Solid content = 40%)

<< Coating Formulation (relative to 100 parts of binder solid content) >> S-1 or S-2 (solid content = 70%) Total amount "Taipec R-820" [100 parts titanium oxide manufactured by Ishihara Sangyo Co., Ltd.] ───────────────────────────────── (Disperse the above with a sand mill to obtain a paste with a PWC of 50%. did.)

However, S-3 and W-1, W-2 and W-3 are all added to the above paste and stirred, then water is added and dispersed by a high speed disperser. In addition, the system in which W-4 is mixed is one in which the entire amount of water is added to this W-4 and then dispersed with a high-speed disper.

The compositions T-1, T-2, T-3 and T- using the alkyd resin S-1 respectively.
No. 5 added 0.7 parts of 6% cobalt naphthenate and 1 part of 24% lead naphthenate to the above composition, while the melamine resin S-3 and Compositions T-1, T-2, T-4 using W-1
All of T-5, T-6, and T-7 were prepared by adding 3 parts of "Beckamine P-198" (a curing catalyst manufactured by Dainippon Ink and Chemicals, Inc.) to the above-mentioned composition. .

Further, the respective coating materials thus obtained were applied to various base materials as described below, and application tests were conducted. The results are collectively shown in Tables 2 to 4.

<Test base material> A: Untreated mild steel sheet (using a product of Nippon Test Panel Co., Ltd.) B: On a flexible board having a thickness of 3 mm, "Acridic A-181" [Dainippon Ink and Chemicals ( stock)
Acrylic sealer manufactured by Mitsui Chemical Co., Ltd.] diluted with xylene so that the solid content is 20%, applied at an amount of 150 g / m ^2, and dried.

<< Application Test >> Various formulations were applied to each substrate so that the dry film thickness was 30 μm (μm), and the following baking or normal temperature drying was performed, respectively. .

That is, first, the baking was performed at 23 ° C. for 1 hour in a constant temperature and constant humidity condition of 65% RH, and then left (setting) for 20 hours in a dryer at 140 ° C.
It was allowed to stand for 3 minutes and then left at room temperature for 3 days.

On the other hand, the normal temperature drying is carried out by leaving it to stand at room temperature for 21 days. After that, it was subjected to various tests as described below. The results are collectively shown in Tables 2, 3, and 4.

Among the tests described below, in the tests (1) to (4), the surfaces other than the coated surface were sealed with an acrylic urethane sealing agent.

<< Testing method for coating workability >> Anti-dripping property: Each substrate has a dry film thickness of 30 μm.
It is painted so that it will be m, stands vertically, and at room temperature for 1 hour,
Allow to dry after standing and visually determine the state of dripping. Finished appearance: visually judge the state of the coating film after baking or drying at room temperature using each of the above-mentioned base materials. << Testing method of coating film physical properties >> Gloss: 60 degree gloss is measured with a gloss meter. Adhesion to base material: Peeling test by cutting 100 squares in a 1 cm square on a coated surface with a cutter knife and pasting cellophane tape.

(100 ......... Completely adhered, 0 ......... Completely peeled off) Water resistance; At room temperature, the substrate is completely submerged in tap water,
Visually judge the condition after 4 weeks. Acid resistance: The substrate is completely immersed in 1% dilute sulfuric acid, and the state after 3 days is visually determined. Alkali resistance; saturated calcium hydroxide, 2
Completely submerge the base material in an aqueous solution of 15% sodium hydroxide,
Visually judge the condition after 2 weeks. Anticorrosion: Visually judge the state after 100 hours of testing with a salt spray tester. Accelerated weather resistance; with sunshine weather meter,
Measure the gloss retention (GR, 60 degrees) after 1,000 hours of testing.

[0048]

[Table 1]

[0049]

[0050]

[0051]

The coating composition of the present invention thus obtained has thixotropy, is difficult to drip even when applied to a standing surface, and can be applied thickly at a time. The sex is improved.

Also, probably because of the high latent heat of evaporation of water, the finished appearance during heating and drying is good. Moreover, the present invention is
It can be said that this is a highly useful invention in that a coating composition with improved coating workability can be simply provided without increasing the organic solvent content.

Claims (3)

[Claims] 1. A coating composition with improved coatability, comprising a resin, which is formed by mixing a resin solution with water to form a water-in-oil emulsion, as a binder. 2. The coating composition according to claim 1, wherein the binder is mixed with water in an amount of 2 to 35% by weight based on the solid content of the resin. 3. The binder is water-soluble and / or
Alternatively, the water-dispersible resin and the water-insoluble resin may be used in a weight ratio of the solid content of the former resin to the latter resin of 1:99 to 40:60.
The coating composition according to claim 1 or 2, wherein the coating composition is contained in a range such that the weight% is contained.