JPS59191770A - Curable water-base coating composition - Google Patents

Abstract

PURPOSE:To provide the titled compsn. with good coatability, capable of forming cured films excellent in resistance to water and corrosion, by incorporating isocyanate compds. and polymeric water dispersions yielded by emulsion polymn. in the presence of a particular water-base copolymer. CONSTITUTION:5wt% or higher crosslinkable functional group-contg. water- soluble ethylenic monomer (a), 20wt% or higher water-soluble ethylenic monomer without crosslinkable functional groups (b), 75wt% or lower water-insoluble ethylenic monomer (c), and 40wt% or lower org. thiol compd. (d) are copolymerized in a water medium. Then, 100pts.wt. monomer mixture comprising 5- 50wt% monomer (a) and 95-50wt% monomer (b and/or c) is subjected to emulsion copolymn. in the presence of 0.5-50pts.wt. said water-base copolymer to form a polymeric water dispersion. Said dispersion, isocyanate compds., and, if necessary, any other additives are mixed to yield curable water-base coating compsns.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel and useful curable aqueous coating composition, and more particularly, to a crosslinkable non-crosslinkable coating composition using a specific water-soluble curable copolymer as a polymerizable emulsifying dispersion material. An aqueous polymer dispersion obtained by emulsion polymerization of ethylenically unsaturated monomers containing saturated monomers, that is, an aqueous polymer dispersion that does not contain commonly used surfactants, and isocyanate compounds or their polymers. It is possible to provide a cured coating film with significantly improved physical properties, water resistance, corrosion resistance, chemical resistance, etc., as well as excellent coating workability. Furthermore, the present invention relates to a curable, water-dispersed coating composition that is effective in preventing air pollution because it does not contain organic solvents in its volatile components, and can be used both at room temperature and during forced drying.

Traditionally, as part of pollution countermeasures such as air pollution prevention,
Although water-based paints made from solvent-type thermosetting polymers are widely used, they are not originally satisfactory as high-performance paints and have several drawbacks.

In other words, with conventionally used water-dispersed paints, the gloss of the resulting paint film is poor, and the surfactant used as an emulsifier remains in the paint film, resulting in poor water resistance, corrosion resistance, and weather resistance. It cannot be said that the surface active agent is sufficient, and the coating workability is also poor due to the foaming caused by the surfactant.

In addition, when a formaldehyde-based resin is used in combination to form such a thermosetting coating film, there is a problem of toxicity of the formaldehyde released.

Furthermore, in recent years there has been an increasing demand for energy conservation, and not only low-temperature baking but also forced drying and, even more advanced, demand for the performance of cured coatings when drying at room temperature.

However, the present inventors aimed to provide a curable coating composition that can solve all of the above-mentioned problems and also meet social needs.
In order to overcome the drawbacks of conventional emulsion polymerization methods that use surfactants, we have also conducted intensive studies on the suitability of curing agents, and as a result, we have completed the present invention.

That is, the present invention comprises at least 5% by weight of a water-soluble ethylenically unsaturated monomer (a-1) containing a crosslinkable functional group, and at least 20% by weight of a water-soluble ethylenically unsaturated monomer (a-1) containing no such functional group. (a-2), 0 to 75% by weight of a water-insoluble ethylenically unsaturated monomer (a-3), and 0 to 40% by weight of an organic thiol compound (a -4) to these (a-1), (a-2), (a-3) and (a-4)
An aqueous copolymer obtained by copolymerizing the sum of monomers of each group in 100 layers in water is used as a polymerizable emulsion-dispersed material, and the polymerizable emulsion-dispersed material is subjected to emulsion polymerization as described below. The ethylenically unsaturated monomer (a -1) and 95 to 5% by weight of the ethylenically unsaturated monomer (a-3) and/or the ethylenically unsaturated monomer (a-2). The present invention provides a curable aqueous coating composition comprising a combined aqueous dispersion (A) and an isocyanate compound or a polymer thereof (B) as essential components.

As described above, the present invention is directed to an aqueous polymer dispersion obtained by emulsion copolymerization (A ) and an isocyanate compound or a polymer thereof (B) as a curing agent for the constituent polymers of the polymer dispersion (A) as essential components. .

Here, typical examples of the crosslinkable functional group-containing water-soluble ethylenically unsaturated monomer (a-1) include:
α,β- such as hydroxyethyl (meth)acrylate
Hydroxyl group-containing monomers such as hydroxyalkyl esters of unsaturated acids; α,β-amides of unsaturated acids such as (meth)acrylamide, or α such as N-methylolacrylamide or N-alkoxymethylacrylamide
, amide group-containing monomers such as various derivatives of amides of β-unsaturated acids; and glycidyl group-containing monomers such as glycidyl (meth)acrylate.

The ethylenically unsaturated monomer (a-1) is used in an amount of at least 5% by weight in the aqueous copolymer.
, preferably present in an amount of 10% by weight or more,
If it is less than 5% by weight, water resistance etc. will be poor due to a decrease in crosslinking properties, which is not preferable.

In addition, the water-soluble ethylenically unsaturated monomer (a-2) that does not have a crosslinkable functional group mentioned above refers to the various functional group-containing water-soluble ethylenically unsaturated monomers (a-2) listed in 1. It refers to all water-soluble ethylenically unsaturated monomers except 1), and among them, particularly representative ones include monomers having a sulfonic acid group such as vinyltoluenesulfonic acid or vinylsulfonic acid. monomers containing carboxyl groups, such as unsaturated basic acids such as (meth)acrylic acid or crotonic acid, or unsaturated dibasic acids such as maleic acid, fumaric acid or itaconic acid, and their salts; ; Monovinylpyridine such as vinylpyridine, 2-methyl-5-vinylpyridine;
2-dimethylaminoethyl (meth)acrylate, β(t
- Ester containing an amino group that can form a salt of (meth)acrylic acid such as butylamino)ethyl (meth)acrylate, 2-hydroxy-5-(meth)acryloxypropyl trimethylammonium salt; 2-dimethylamino Alkylamino group-containing vinyl ethers such as vinyl ether; alkylamino group-containing (meth)acrylamides such as N-(2-dimethylaminoethyl)acrylamide or methacrylamide; They can be used in combination, and the appropriate amount used is 20 to 95% by weight, preferably 40 to 95% by weight. If the resultant aqueous copolymer is used as a dispersant, particles may aggregate or the polymerization may not proceed smoothly. Dispersion stability decreases.

The carboxyl group-containing monomers listed here, such as unsaturated basic acids or unsaturated dibasic acids, are usually included in the above-mentioned functional group-containing monomers (a-1>). However, when pl+ is adjusted at the end of emulsion polymerization (pl+ is usually 7 or more, preferably 8 to 9
), since it forms a salt, in the present invention, for convenience, the water-soluble unsaturated monomer (a-2) that does not contain the functional group is used.
Included in 1! Please keep this in mind.

Furthermore, the water-insoluble ethylenically unsaturated monomer (
Typical examples of a-3) include unsaturated carboxylic acid esters such as (meth)acrylic acid alkyl esters or maleic acid dialkyl esters; α-olefins such as ethylene or propylene; and styrene or α-methylstyrene. Aromatic vinyls: Typical examples include vinyl esters such as vinyl acetate, vinyl propionate, and vinyl persate, as well as vinyl chloride, vinylidene chloride, and acrylonitrile; two or more of these can be used in combination; The appropriate amount to be used is 0 to 75% by weight, preferably 0 to 50% by weight. When used in excess of this range, emulsion polymerization performed using the resulting aqueous copolymer will not proceed smoothly.

Furthermore, representative organic thiol compounds (a-4,) represented by the above general formula CI) include alkyl mercaptans such as n-octyl mercaptan and n-dodecyl mercaptan; benzyl mercaptan or dodecylbenzyl mercaptan; These include aromatic mercaptans, thiocarboxylic acids, their salts or alkyl esters, and polythiols, and these are used in an amount of 0 to 40% by weight, preferably 0.2 to 30% by weight.

The use of these organic thiol compounds (a-4) has the effect of stabilizing the polymerization during obtaining the aqueous copolymer and facilitating the subsequent emulsion polymerization, but within the above range. If it is used in excess, the molecular weight of the constituent polymers of the resulting aqueous polymer dispersion will drop significantly, making it impossible to obtain the performance aimed at by the present invention.

Therefore, the monomers (a-1) of each group listed above, (
In any case, the total amount of a-2), (a-3) and (a-4) is always 100% by weight.

It is effective to react the various raw materials listed above with a radical-generating catalyst in water. Peroxides or persulfates; organic peroxides such as cumene hydroperoxide or t-butyl peroxide; or azo compounds such as azobisisobutyronitrile can be used as they are, and various compounds thereof can also be used. A redox polymerization method using a combination of various metal ions and various reducing agents known and commonly used may be applied.

The reaction temperature and reaction time in this case may be selected as appropriate from the ranges commonly used in known and conventional radical polymerizations, and generally a range of 15 minutes to 15 hours at 20 to 90°C is appropriate.

Thus each group of monomers (a-1), (a-2), (a
The pn of the aqueous copolymers that are the reaction products of -3) and (a-4) is adjusted as appropriate. Usually, the pl+ of such aqueous copolymers is suitably in the range of 2 to 9.

Then, the aqueous copolymer obtained here is 5 to 50% by weight.
the ethylenically unsaturated monomer (a-1);
〇9- 0% by weight of the solid content based on 100 parts by weight of the mixture with the ethylenically unsaturated monomer (a-3) and/or the ethylenically unsaturated monomer (a-2) .5-50
These ethylenically unsaturated monomers (a-1), (a-2), (
It is used as a polymerizable emulsion dispersion for emulsion polymerization such as a-3), but if the amount used is less than 0.5 parts by weight, emulsion polymerization using the aqueous copolymer may become unstable. If the amount exceeds 50 parts by weight, the resulting aqueous polymer dispersion becomes viscous and eventually gels. Even if an aqueous Yoshiba polymer dispersion is obtained, its coating performance will be poor.

Here, the ethylenically unsaturated monomer (a-1) used to prepare the aqueous polymer dispersion has a concentration of 5 to 50
% by weight, preferably from 5 to 30% by weight, is suitable. If the amount used is less than 5% by weight, the original purpose of the present invention, which is to obtain a cured coating film with significantly improved physical properties, water resistance, corrosion resistance, chemical resistance, etc., cannot be achieved. Further, even if it is used in an amount exceeding 50% by weight, there is little improvement in coating film performance.

Furthermore, the ethylenically unsaturated monomer (a-1) copolymerizable with the ethylenically unsaturated monomer (a-1) used to prepare the polymer aqueous dispersion 10-liquid (A), which is a constituent component of the present invention. Unsaturated monomer (a-3) alone or these (a-1
) and (a-3) and the ethylenically unsaturated monomer (a
The amount of the mixture with -2) is within the range of 95 to 50% by weight, preferably 95 to 70% by weight of the total ethylenically unsaturated monomers to be subjected to emulsion polymerization.

The aqueous polymer dispersion (A) can be produced from these various ethylenically unsaturated monomers according to a conventional emulsion polymerization method.

However, as is clear from the above-mentioned structure, the composition of the present invention can be obtained without using surfactants of a commonly used type, and therefore various advantages as described below can be obtained. However, it goes without saying that this in itself does not preclude the use of a surfactant commonly used in emulsion polymerization in combination with the aqueous polymer.

However, it goes without saying that in this case, the disadvantages of conventional emulsion polymers are limited to a range in which they do not cause problems.

The aqueous polymer dispersion (A), which is a constituent component of the composition of the present invention thus obtained, has little foaming and is mechanically
It has excellent thermal stability and also good storage stability.

On the other hand, the isocyanate compound or the polymer (B) from the isocyanate compound, which is the other component of the composition of the present invention, may be any compound containing two or more isocyanate groups in the molecule. Although it is possible,
Among these, the most representative ones are tolylene diisocyanate (TDT; commercially available example is "Desmodur T" manufactured by Bayer AG in West Germany), hydrogenated TDI
, I-limethylolpropane (TMP)-TDT adduct (commercially available products include "Desmodur L, J"),
) Riphenylmethane triisocyanate (TTI;
Desmodur RJ), 4,4'-diphenylmethane diisocyanate (MDI; Desmodur 44J)
), hydrogenated MDI, H2'O-hexamethylene diisocyanate addition condensate ("Desmodur NJ"), xylene diisocyanate or 4,4'-dicyclohexylmethane diisocyanate.

It is also possible to use those prepared by a polyisocyanate-polyol mixing method, that is, those in which a polyol such as a hydrous acid group polyester or polyether is mixed with an excessive amount of a polyisocyanate such as Desmodur L listed above. However, it is also possible to use prepolymers prepared one-way, i.e. NGO-terminated prepolymers prepolymerized with a polyol and excess polyisocyanate as described above, or OH-terminated prepolymers prepolymerized with excess polyol. It is also possible to use a prepolymer to which an excess of polyisocyanate such as Desmodur L as listed above is added during use.

The isocyanate compound or polymer thereof (B
) is preferably blended in a range of 1 to 200% based on the solid weight of the aqueous polymer dispersion (A).

The composition of the present invention is obtained by using an aqueous copolymer without using a commonly used class of surfactants, and the aqueous copolymer itself is a polymer aqueous dispersion (A
), when the composition of the present invention is used as a coating agent, the crosslinkable functional groups contained in the aqueous copolymer also participate in the formation of a three-dimensional structure. , since it is digested as a film-forming component, it does not cause the above-mentioned drawbacks.

In this regard, secondly, the aqueous polymer dispersion (A) contains a crosslinkable functional group component derived from the aqueous copolymer as the dispersant and a crosslinkable monomer used in emulsion polymerization. The polymer aqueous dispersion (A) and the isocyanate compound or their polymer (B) are blended to form a film. In the form in which the composition of the present invention is used, the reaction is carried out without waste in all amounts of these two components (A) and (B), forming a dense three-dimensional network, and thus improving the mechanical properties of the coating film. and has sufficient hardness,
In addition to being strong, it also has water resistance, corrosion resistance, chemical resistance,
It is possible to obtain a glossy coating film with excellent solvent resistance.

Thirdly, in conventional water-soluble paints, the basic resin requires a large amount of carboxyl groups to make it water-soluble, and in order to neutralize this carboxyl group, a large amount of amines are used. It has to go through a neutralization process, and is dissolved in an aqueous solvent containing a large amount of water-soluble organic solvent in order to improve solubility, but the presence of such a large amount of carboxyl groups, which can be said to be excessive, can actually cause problems in the coating film. It is like forcing it to remain inside, and the result is alkali resistance,
This also leads to disadvantages such as poor water resistance, corrosion resistance, and weather resistance.On the other hand, the use of large amounts of organic solvents directly causes air pollution, and the amines used in the amine neutralization process have an amine odor that is harmful to the working environment. However, in the polymerizable aqueous dispersion used in the present invention, the amount of such carboxyl groups is small, and on the other hand, the composition of the present invention Since it does not contain any organic solvent, it is free from the aforementioned deterioration in coating film performance due to residual carboxyl groups, and can be applied to air pollution prevention measures.

Fourthly, it is possible to increase the non-volatile content during painting, which is limited by the current aqueous solution type paints, and therefore painting workability is also good.

Next, methods for applying the composition of the present invention include brush painting,
Various well-known coatings can be used, such as dip coating, spray coating, roller coating, or electrodeposition coating.

Furthermore, although the purpose of the composition of the present invention can be sufficiently achieved by simply drying it at room temperature after being coated by such a coating method, forced drying is preferable in order to further improve the performance.

In forming a paint using the composition of the present invention, a known and commonly used reaction accelerator such as boric acid, aluminum sulfate, alum, or chromium borate may be added in advance.

The composition of the present invention is particularly suitable as a paint for metals, but it can also be used for paper, textiles, concrete, cement, or similar materials, plastics, wood, and the like. It is also useful for other substrates that can be treated.

Next, the present invention will be specifically explained using reference examples, examples, and comparative examples, and all parts and percentages are based on weight unless otherwise specified.

Reference Examples 1 to 6 [Example of Preparation of Aqueous Polymer Dispersion (A)] Ethylenically unsaturated monomers and organic thiol compounds shown in Table 1 and water were charged into a stainless steel reaction vessel, and then subjected to filtration. Add 4 parts of potassium sulfate and bring to 80°
After reacting at C for 30 minutes to form an aqueous copolymer, each aqueous copolymer was used as a dispersant and 470 parts of n-butyl acrylate, 400 parts of styrene, 100 parts of β-hydroxyethyl acrylate and An ethylenically unsaturated monomer mixture consisting of 20 parts of acrylic acid was added dropwise over 180 minutes at the same temperature to polymerize, and then the pu was adjusted to 9 to form an aqueous polymer dispersion (A-1).
~(A-3) was obtained.

For comparison purposes, examples are shown in which the monomer composition constituting the aqueous copolymer described above deviates from the scope of the present invention (Reference Examples 4 and 5), and surfactants commonly used in the past. Example of emulsion polymerization using (Reference Example 6)
) and the control aqueous polymer dispersion (
A'-1) to (A'-3) were obtained.

As is clear from Table 1, if the composition ratio of the constituent monomer components of the aqueous copolymer used in emulsion polymerization deviates from the scope of the present invention, an aqueous polymer dispersion cannot be obtained. No (see Reference Examples 4 and 5).

Example 1 and Comparative Example 1 Each of the emulsions obtained in Reference Examples 1 and 6 (
For each 100 copies of A-1) and (A'-3), 5
2 parts of 0% dimethylethanolamine, 2 parts of "Texanol" (coating agent manufactured by Eastman Kodak Company, USA)
Department and [Disverse Color 817-901 J
(Black colorant manufactured by Dainippon Ink & Chemicals @) was added and stirred well.

Next, 25 parts of a 65% ethyl acetate solution of "Desmodur 44" (Mrl, manufactured by Bayer AG, West Germany) was added and mixed well.

Thereafter, the thus prepared black paint for automobile parts and chassis blanks was applied by spray to a soft steel plate that had been sothoplasted so that the dry NPX was 20 μm, and then left to dry at room temperature for 3 days. Ta.

Table 2 shows where the membrane performance tests were conducted on the two sample plates obtained here.

Table 2 Example 2 and Comparative Example 2 Each of the emulsions obtained in Reference Examples 2 and 6 (
For each 100 copies of A-2) and (A'-3), 5
2 parts of 0% dimethylethanolamine, 3JPall of "Texanol", rNs-200J (Nitto Funka ■
50 parts of Calcium Carbonate manufactured by
8 parts of Color 511-901, J were added and stirred well.

Next, 35 parts of a 65% ethyl acetate solution of Desmore 1-L 444 was added to this and mixed well.

However, the black primer paint thus obtained,
It was applied to a toluene-degreased JIS G-3141-D mild steel plate using an airless sprayer to a dry film thickness of 10,071 m, then force-dried at 80°C for 20 minutes, and then left to dry at room temperature overnight. I forced it.

The two sample plates obtained here were tested for coating film performance, and the results shown in Table 3 were obtained.

201 Example 3 and Comparative Example 3 Each of the emulsions obtained in Reference Examples 3 and 6 (
For each 100 copies of A-3> and (A'-3), 5
Add 2 parts of 0% dimethylethanolamine and 3 parts of "Texanol", add 75 parts of Bengara and 25 parts of zinc white.
of Desmodur 44 and stir well.
25 parts of a 65% ethyl acetate solution was added and mixed well.

Next, the thus obtained undercoat paint was applied in an amount of 1 on a JIS G-3141-8 mild steel plate that had been degreased with toluene.
Two base coat plates were prepared by brushing at 50 g/n and leaving to dry overnight.

On the other hand, 1 of the emulsion (A-1) obtained in Reference Example 1
To 00 parts, add 2 parts of 50% dimethylethanolamine and 3 parts of "Texanol", and further add 35 parts of [Tie Bake If-930J (rutile type titanium oxide manufactured by Ishiya Sangyo ■)] and stir well. Then, 25 parts of a 65% ethyl acetate solution of "Desmodur 44" was added and mixed well.

Next, the thus obtained top coat paint was brushed onto each of the above-mentioned undercoat coated plates at a coating weight of 130 g/rrr, and allowed to stand at room temperature for 3 days to dry.

A coating film performance test was conducted on the two sample plates obtained here, and the results shown in Table 4 were obtained.

21- Table 4 -22- 435-

Claims (1)

[Scope of Claims] (A> A polymer aqueous dispersion obtained by emulsion polymerization without using a surfactant, and (B) an isocyanate compound or a polymer thereof as essential components, and the aqueous polymer dispersion (A) contains at least 5% by weight of a water-soluble ethylenically unsaturated monomer (a-1) containing a crosslinkable functional group, and at least 20% by weight of a water-soluble monomer containing no such functional group. Ethylenically unsaturated monomer (a-2), 0 to 75% by weight of water-insoluble ethylenically unsaturated monomer (a-3), and 0 to 40% by weight of general formula % formula % (1) The organic thiol compound (a-4) shown above (
a-1), (a-2), (a-3> and (a-
4) An aqueous copolymer obtained by copolymerizing 100% by weight of each group of monomers in water is the total ethylenically unsaturated monomer as described below, which is subjected to emulsion polymerization. 1
0.5 to 50 parts by weight based on the solid content to 0.00 parts by weight.
9% by weight of the ethylenically unsaturated monomer (a-1);
5 to 5% by weight of the ethylenically unsaturated monomer (a-3)
and/or the ethylenically unsaturated monomer (a-2)
1. A curable aqueous coating composition obtained by emulsion copolymerizing.