JPS6228190B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an aqueous coating composition containing an aqueous resin and a fine resin powder as film-forming components. Paints containing organic solvents are being replaced by water-based paints because they have health and safety problems such as adverse effects on the human body, explosions and fires, and pollution problems such as air pollution. However, with general water-based paints, in order to dissolve and disperse in water, it is necessary to introduce a large amount of hydrophilic groups into the molecule and use a resin whose molecular weight is not very high. Membrane performance is not sufficient. In addition, water-based paints have poor coating workability because they are difficult to formulate to a high nonvolatile content concentration, and furthermore, pigment dispersibility is not good, so when a high-quality finished appearance is required, such as for automobiles, the gloss and brightness of the paint film must be maintained. It has problems such as insufficient image quality. On the other hand, a problem specific to powder coatings is that if the glass transition temperature is too low, blocking occurs, which limits their usability and makes it impossible to obtain coatings with sufficient performance. Although curing agents are used to improve the physical properties of the coating film and lower the baking temperature, curing agents that react during paint production (mixing and dispersing in the molten state) cannot be used, and therefore are generally used to form a film. The baking conditions at this time must be high temperatures. Paints in which powder paints are dispersed in water in the form of a slurry are also known, but these are mainly composed of powder paints. Slurry-type paints generally have difficulty increasing the concentration of non-volatile matter, making it difficult to apply thick films, and even after painting, the adhesion of the paint film is insufficient. It is difficult to obtain the appropriate viscosity and fluidity required for painting by spraying, there are problems with painting workability, and the coating film does not have gloss. There are also problems with storage stability such as sedimentation during paint storage. Slurry type paints generally do not exhibit sufficient coating film performance such as water resistance due to the use of dispersants. The biggest problem with current slurry-type paints is the above-mentioned painting workability, and for this reason, they have not yet been put into practical use. The present invention relates to the improvement of the above water-based dispersion type paint, which not only has good coating workability, but also has good water dispersion stability and storage stability of the composition, and the water resistance of the formed coating film. The present invention provides an aqueous coating composition with excellent properties. The gist of the present invention is to contain at least one base-neutralized aqueous resin having a water tolerance of 4 or more and a surface tension of 51 dyne/cm or less in a 1% solution, as a substantial film-forming component; and at least one type of insoluble resin fine powder, which does not have a functional group that can react with itself and with each other, and has a solid content weight ratio of 98:2 to 45:55. The water-based paint composition is characterized by: The aqueous resin used in the present invention has functional groups capable of forming a three-dimensional crosslinked structure such as carboxylic acid groups, sulfonic acid groups, phosphoric acid groups, hydroxyl groups, oxirane groups,
active methylol group, reactive carbon-carbon unsaturated group,
It has an isocyanate group or a blocked isocyanate group, a halogen group, etc., and a functional group for making it water-soluble (e.g., a carboxylic acid group, a sulfonic acid group,
Any type of resin may be used as long as it has a hydroxyl group), and the types of resins include, for example, alkyd type, polyester type, maleated oil type, maleated polyalkadiene type,
Examples include epoxy type and acrylic type. Introduction of functional groups into the resin may be carried out according to general methods, and may be carried out by selecting monomers and controlling the polymerization reaction. Specifically, in the case of alkyd-based and polyester-based resins, a carboxyl group may be introduced in the reaction step of a polybasic acid and a polyhydric alcohol to form an aqueous resin. In the case of maleated oils, carboxyl groups may be introduced by treating a drying oil (eg, linseed oil, castor oil, soybean oil, tung oil) with maleic anhydride to form an aqueous resin. For maleated polyalkadiene systems,
For example, polybutadiene (e.g. 1,2-polybutadiene, 1,4-polybutadiene, 1,2- and 1,
4-copolymerized polybutadiene), polyisoprene or polycyclopentadiene with an unsaturated carboxylic acid (e.g. maleic anhydride,
A carboxyl group may be introduced by adding hymic anhydride, fumaric acid, itaconic acid) to form an aqueous resin. In the case of epoxy resins, in addition to various epoxy resins typified by the reaction between bisphenol A and epichlorohydrin, various other compounds having epoxy groups can be used. These may be water-soluble or water-dispersible by introducing an acidic group (eg, carboxylic acid group, sulfonic acid group) into part or all of the oxirane group. In the case of acrylics, α/β-unsaturated carboxylic acids (e.g. acrylic acid, methacrylic acid, cinnamic acid, crotonic acid, fumaric acid, citraconic acid, maleic anhydride) and acrylic esters (e.g. methyl ester, ethyl ester, propyl ester,
butyl ester, hexyl ester, lauryl ester) and/or methacrylic ester (e.g., methyl ester, ethyl ester, propyl ester, butyl ester, hexyl ester, lauryl ester), and if necessary, polymerize other polymerizable monomers. Any aqueous resin obtained by the above method may be used. These resins may be urethane-modified in a conventional manner as long as their water-based properties are not impaired. The above aqueous resins can be made aqueous by conventional methods by replacing their acidic groups with basic substances (e.g., monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monoisopropylamine, diisopropylamine, diethylenetriamine, Neutralized with triethylenetetramine, monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine, dimethylethanolamine, morpholine, methylmorpholine, piperazine, ammonia, sodium hydroxide, potassium hydroxide, lithium hydroxide) do it. In the present invention, at least one of the above-mentioned aqueous resins () may be used, but the aqueous resin must have a water tolerance of 4 or more and a surface tension of 1% by weight solution of 51 dyne/cm or less. use. By using such a water-based resin (), a target coating composition having good water dispersion stability and coating workability can be obtained. If the water tolerance deviates from the above range, the viscosity of the target coating composition tends to increase, and the water dispersion stability is impaired, resulting in poor coating work. When the surface tension deviates from the above range, the viscosity of the target coating composition tends to increase and the water dispersion stability tends to be impaired. In more detail, the above water-based resin () is from 0.3 to
5 m·mol/g, preferably 0.5 to 4 m·mol/g
Total amount of hydrophilic functional groups (e.g. carboxylic acid group, sulfonic acid group, phosphoric acid group, active methylol group) and 500~
Advantageously, it has a number average molecular weight of 20,000, preferably from 700 to 5,000. If the total amount of hydrophilic functional groups deviates from the above range, the viscosity of the coating composition tends to become too high and the water resistance of the coating film tends to decrease. When the molecular weight deviates from the above range, the dispersion stability of the resin fine powder () and pigment in the target coating composition tends to decrease, the water resistance and corrosion resistance of the coating film decrease, and the smoothness of the coating film tends to decrease. When the hydrophilic functional group is a carboxylic acid group, the amount is 0.2 to 4 m・
mol/g, preferably 0.3 to 3 m·mol/g, and if it is a hydroxyl group, the amount is 0.2 to 3 m·mol/g,
Preferably 0.3 to 2 m·mol/g is advantageous in each case. From the above points, the water-based resins () include the above-mentioned alkyd-based, polyester-based, acrylic-based,
Epoxy systems, maleated oil systems and maleated polyalkadiene systems are preferred. Furthermore, in the present invention, water-based resins that belong to the above-mentioned water-based resins () in terms of type, but do not meet requirements such as water tolerance, surface tension, molecular weight, etc. () may be used in combination with at least one resin having a functional group that can react with the functional group through condensation reaction, addition reaction, ring-opening reaction, etc. Specifically, preferable examples of combinations of functional groups include:
Examples include a hydroxyl group and an acidic group (especially a carboxylic acid group) and/or a blocked isocyanate group, an active methylol group and a hydroxyl group and/or a carboxylic acid group, an oxirane group and a carboxylic acid group, and reactive carbon-carbon unsaturated groups. Particularly preferred are active methylol groups and hydroxyl and/or carboxylic acid groups, and specific examples include combinations of melamine resins and alkyd resins, acrylic resins, or maleated resins. In addition, it is desirable to combine so that the quantitative ratio of functional groups which can react with each other at this time is 1:10 to 10:1, preferably 1:5 to 5:1. Further, the proportion of the other aqueous resin relative to the total aqueous resin is preferably 85% by weight or less, preferably 60% by weight or less. By using such other water-based resins in combination, the solvent resistance of the coating film can be improved. The fine resin powder (2), which is another essential component used in the present invention, is insoluble in water and does not have functional groups capable of reacting with itself or with the aqueous resin (2). Specifically, such fine resin powders include polyolefin, vinyl resin, cellulose resin, polyamide, polycarbonate, fluorine resin, acrylic resin, alkyd resin, polyester, and polyether. system,
Examples include polydiene systems, and at least one of these may be used. Such fine resin powder () may have a particle size that can be dispersed when it is made into a paint.
It is sufficient if it is 500μ or less. This fine resin powder ()
may be produced according to a conventional method, for example, one or more resins may be mixed and dispersed using a heated melt mixer, and then ground to a predetermined particle size using a grinder. At this time, appropriate amounts of pigments and additives may also be added. In the coating composition of the present invention, the water-based resin () and the fine resin powder () are combined in a solid content such that the former
45-98% by weight, preferably 50-90% by weight and the latter 55
It may be blended in a proportion of ~2% by weight, preferably 50-10% by weight. If the amount of the former is too small, the dispersion stability of the latter will deteriorate and the smoothness of the coating film will be impaired. On the other hand, if the amount of the former is excessive, the water resistance of the paint film will be poor, the viscosity of the paint will be high, the solid content of the paint will not decrease, and the painting workability will be poor (pinholes and sagging are likely to occur). Become). The present invention relates to an aqueous coating composition using water (preferably deionized water) as a medium, but if necessary a small amount of an organic solvent (e.g. ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono Butyl glycol, methanol, ethanol, isopropyl alcohol, n-butyl alcohol, sec-
butyl alcohol, t-butyl alcohol, dimethylformamide) may also be used. In the present invention, in addition to the above-mentioned essential components, various pigments and additives (eg, modifiers, dispersants, surface conditioners) can be used as necessary. These may be blended into the aqueous resin (), the resin fine powder (), or both. Conventional techniques may be employed for producing the coating composition of the present invention. For example, when blending pigments, prepare a pigment paste in advance using a portion of the water-based resin (), and then mix the remaining amount of the water-based resin (), resin fine powder (), and other agents. , just mix and disperse. According to the coating composition of the present invention obtained in this way, the drawbacks of water-based coatings and powder coatings can be improved, and in particular, it has excellent coating workability, water dispersion stability, and water resistance that cannot be obtained with slurry-type coatings. is obtained. Next, the present invention will be specifically explained with reference to Examples and Comparative Examples. In addition, parts mean parts by weight. Example 1 Preparation of paint paste (1): Water-based resin (1) ⁽¹⁾ 300 parts Resin fine powder (1) ⁽²⁾ 14 parts Rutile type titanium oxide pigment (TiO ₂ ) 100 parts Deionized water 40 parts Above composition The materials were placed in a stainless steel container and mixed and dispersed for 30 minutes at room temperature using a paint conditioner to obtain a white paint paste (1). In addition, (1): Alkyd resin, water tolerance 10 or more, surface tension 42 dyne/cm, acid value 55, hydroxyl value 40, neutralization rate with dimethylethanolamine 80%, solid content 40
Weight%, molecular weight 1360. Water tolerance: 5g of the above water-based resin varnish
Weigh it into a 100ml beaker, mix and dilute it with deionized water, and find the water dilution ratio when you can no longer read the No. 1 type when looking through the beaker. Surface tension: The above aqueous resin varnish is diluted with deionized water to prepare a solution with a solid content of 1% by weight and used as a measurement sample. Measurement was done using CB manufactured by Kyowa Kagakusha.
-It was carried out using a VP type surface tension meter. (2): Nylon resin "Nylon 12" manufactured by Unitika Co., Ltd. Preparation of paint composition (1): 1. In a stainless steel container, 400 parts of paint paste (1) and hexamethoxymethylolmelamine resin (hereinafter referred to as
A white coating composition (1) was obtained by mixing and dispersing 17 parts of HMMM (abbreviated as HMMM) for 15 minutes at room temperature using a lab mixer. When this product was allowed to stand at room temperature for 2 months, no sedimentation occurred and it exhibited good dispersion stability. Examples 2 to 5 and Comparative Example 1 Paint pastes and paint compositions were obtained using the same means and methods as in Example 1, except that the raw materials shown in Table 1 below were used. The details of the aqueous resin and fine resin powder used are shown in Tables 2 and 3, respectively.

【table】

【table】

[Table] All of the coating compositions obtained in Examples 2 to 5 exhibited good dispersion stability without forming a hard cake even after being left at room temperature for two months, but Comparative Example 1
The coating composition obtained in step 1 showed a sedimentation phenomenon after one week of standing, and did not return to its original state even after stirring. Example 6 The coating composition obtained in Example 1 was applied onto a matte steel plate to a dry film thickness of 30 μm, and after setting for 30 minutes, it was heated and dried at 160°C for 30 minutes to obtain a three-dimensional coating film. Ta. This product has a smooth surface and a gloss of 85 (60° gloss value), and there was no abnormality in the coating after 240 hours of immersion in 40°C warm water, and no abnormality after 1 hour of immersion in paint thinner. Ta. When the coating workability of this coating composition was evaluated, the pin film thickness limit was 45μ and the sagging film thickness limit was 47μ. Example 7 A baked dried coating film was obtained using the same means and method as in Example 8, except that the coating compositions obtained in Examples 2 to 5 and Comparative Example 1 were used. Table 4 shows the coating workability and film performance of each coating composition. In addition, the painting workability in the table is

【table】

[Table] Additional relationships Original patent No. 1350686 (Special Publication No. 13508-1983)
The invention of ``. as a substantial film-forming component.
at least one aqueous resin having a water tolerance of 4 or more and a surface tension of 51 dyne/cm or less in a 1% by weight solution; It contains at least one kind of water-insoluble resin fine powder, has a functional group that can react with the above, and has a solid content weight ratio of:
An aqueous paint composition characterized in that the ratio is 98:2 to 45:55. ”, which mainly contains an aqueous resin as a substantial film-forming component and a fine resin powder in a solid weight ratio of 98:2 to 45:55, but the present invention also has the above-mentioned main part as its main part, and achieves the same purpose as the invention of the original patent in that it aims to provide a water-based paint composition.
This invention falls under Article 31, Item 1 of the Patent Act. The difference between the original patent invention and the present invention is that in the relationship between the aqueous resin and the resin fine powder, the former has a functional group that can react with each other, and the latter has a functional group that can react with itself and with each other. The point is that it does not have any functional groups that can be used. Here, the term "reactive functional group" means not only a functional group that reacts but also a functional group that may react from the viewpoint of a chemical reaction.

Claims (1)

[Claims] 1. As a substantial film-forming component, (a) water tolerance is 4 or more, surface tension of 1% by weight solution is 51 dyne/cm or less, and number average molecular weight is 500.
(b) at least one type of aqueous resin in which at least one of water tolerance, surface tension, and number average molecular weight does not satisfy the conditions in (a) above; and water. and at least one kind of fine resin powder insoluble in the above, which does not have a functional group capable of reacting with itself and with (i.e. (a) and (b)), and has a solid content weight ratio of: 98:2~
45:55, and the ratio of (b) to 85% by weight or less.