JPS6054352B2 - Aqueous coating composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel aqueous coating composition, and more particularly to a novel aqueous coating composition that exhibits excellent performance in coating film corrosion resistance, water resistance, hardness, and the like.

Conventionally, maleated natural drying oils, epoxy ester resins, maleated polybutadiene, and the like have been used as vehicles for water-based paints.

These are usually used after being neutralized with a base such as ammonia, amine, or caustic potash to make them water-soluble or water-dispersed.
In the case of electrodeposition coating, these resins are deposited on the object connected to the anode. However, there are some basic problems with this anodic electrodeposition coating method.
This cannot be said to be a method that fully satisfies recent demands for severe corrosion resistance.

In other words, in the case of anodic deposition electrodeposition coating, since the metal to be coated is an anode, it is ionized during electrodeposition coating, and the metal base and chemical conversion coating are eluted, and some of the metal ions remaining in the deposited coating film are removed from the coating. It tends to color the film and impair the corrosion resistance and alkali resistance of the paint film. On the other hand, in the case of cathodic deposition electrodeposition coating, there is no elution of metal or chemical conversion film, so there is no coloration, and a coating film that is excellent in terms of corrosion resistance, alkali resistance, etc. is used. Various studies have been conducted on the resins used in this cathodic electrodeposition coating.
No. 6), a modified acrylic resin made by radical copolymerization of an unsaturated compound having a basic amino group (Japanese Patent Publication No. 48-3714
No. 7), iminoamine-containing resins produced by the reaction of acid anhydride groups with diamines (Japanese Patent Application Laid-Open No. 119727/1983), and the like have been proposed.

However, coating films using these cathodically deposited resins generally have high curing temperatures, poor throwing power due to low conductivity of bath paints, poor stability of diluted paints, and significantly high raw material costs. However, it has several drawbacks and has not been widely put into practical use.

In addition, in the case of anodic deposition type electrodeposition paints, melamine resins and phenolic resins are often used in combination to improve the performance of the coating film, but in the case of cathodic deposition type paints, melamine resins and phenolic resins are often used in combination with the resin. Even if you add melamine resin, phenol resin, etc., which have basic amino groups and have the property of accelerating curing on the acidic side, the curing reaction may not be carried out sufficiently, so it is difficult to have sufficient curing properties. required. The object of the present invention is to provide a coating film that has the various functions that a cathodic deposition type electrodeposition coating should have, and that has excellent mechanical strength such as impact resistance and hardness, and chemical properties such as water resistance and corrosion resistance. The object of the present invention is to provide a coating composition that can impart the following properties.

These objects of the present invention are to partially add an organic compound containing a mercapto group to the double bonds of liquid polybutadiene, and to ionize the resulting mercaptan-modified polybutadiene at least partially with sulfonium. or by using a water-dispersible resin as a vehicle component of a water-dilutable coating composition.

The liquid polybutadiene used in the present invention is 50
Any compound having a number average molecular weight of 0 to 50,001, preferably 700 to 4,000, an iodine value of 100 to 5,001, preferably 150 to 480, and a 1.4 bond of 40% or more, preferably 50% or more, may be used. The terminal may be non-functional or may have a hydroxyl or carboxyl group.

However, if the molecular weight is less than 50, the drying properties and mechanical properties of the resulting coating film will be significantly reduced;
When it is larger than 0, gelation tends to occur during the addition reaction of the mercaptan compound, and water solubility decreases, making it impossible to obtain a smooth coating film.

If the iodine value is too low, air curing properties will be poor, and if it is too high, the weather resistance and mechanical properties of the coating will be impaired. On the other hand, in the case of polybutadiene having less than 40% of 1.4 bonds, gels tend to form when a mercaptan compound is added, and the corrosion resistance of the resulting coating film is extremely poor. Addition reactions between liquid polybutadiene and mercaptan compounds are carried out by, for example, Chemical Reactions ● of ● Polymers (Chemi
calReactiOnsOfPOlyTners) page 133 [Interscience Publishers (I
tersciencePubIishers), High Polymer Series (HighPOlymerSer
ies) Volume 196, published],
It may be carried out under conditions commonly used for rubbery polymeric materials, typically using an inert solvent such as benzene, toluene, or xylene, and a peroxide or azobisisobutyronitrile. 50-200℃ in the presence of catalyst
It will be carried out in

It can also be carried out in the presence of an acid catalyst, but there are problems such as the cyclization consumes more double bonds than necessary, making it unsuitable for curing the paint, and making the purification of the product complicated. be. Examples of mercaptan compounds used in the present invention include a) alkyl mercaptans such as methyl mercaptan, propyl mercaptan, butyl mercaptan, octyl mercaptan, and dodecyl mercaptan; b) 2-mercaptoethanol and 3-mercaptans.
Mercaptans having a hydroxyl group or phenolic hydroxyl group such as 2-propanediol, cysteine, mercaptophenol, and mercaptonaphthol; c) Mercaptans having a primary or secondary amino group such as 2-aminoethylmercaptan and mercaptoaniline; , d) Mercaptans containing a ruboxy group, such as thioglycolic acid, mercaptosuccinic acid, β-mercaptopropionic acid, and mercaptobenzoic acid, among which mercaptans containing a carbon number of 1
2J:). The one below will be awarded.

The amount of the mercaptan compound used in the reaction may be sufficient to solubilize or disperse the mercaptan-modified polybutadiene in water when the mercaptan-modified polybutadiene is sulfonium ionized. The sulfur content inside is 1.5~
The amount is 25% by weight, preferably 2 to 2% by weight.

During this reaction, a solvent may be added to reduce the viscosity of the reaction mixture and facilitate the reaction, but in that case, after the reaction is complete, unreacted mercaptan compounds and solvent are distilled off by vacuum or extraction. is preferable. Mercaptan-modified polybutadiene is made water-soluble or water-dispersible by ionizing the sulfur atoms contained in the molecule in the form of sulfide bonds with sulfonium according to a conventional method.

Examples of methods for ionizing sulfonium include formic acid,
A method of treating in the presence of an organic or inorganic acid such as acetic acid, propionic acid, butyric acid, lactic acid, hydroxyacetic acid, hydrochloric acid, phosphoric acid and an epoxy compound such as ethylene oxide, propylene oxide, epichlorohydrin, allyl glycidyl ether, etc. There is a method of treating sulfide with an alkyl halide such as methyl chloride, ethyl chloride, benzyl chloride, etc., which are known as sulfonium ionizing agents. The amount of these treatment agents used may be at least the amount necessary to solubilize or disperse the resin in water, and preferably not more than the equivalent amount of the sulfide group. At this time, it is appropriate that the pH of the system containing the produced aqueous resin be 2 to 9, preferably 3 to 7. The mercaptan-modified polymer thus made water-soluble or water-dispersible is usually prepared as an aqueous solution or dispersion of 5 to 6% by volume, but an aqueous coating composition is prepared.
When this composition is used as a water-based paint, it is appropriate to mix a common pigment such as titanium white, strontium chromate, carbon black, etc. in an amount of 40 parts by weight or less per 10 parts by weight of the resin. In addition, anti-aging agents, fillers, etc. may be added if desired.

Of course, it can also be used in combination with other water-soluble resins. In addition, when using the water-based paint obtained in this way for brush painting or spray painting, which is cured at room temperature or by baking, it is appropriate to mix metal soaps such as cobalt, lead, and manganese as a dryer. When used for electrodeposition coating, melamine resin,
Thermosetting water-soluble resins such as phenol resins and epoxy resins can also be mixed. The present invention will be explained in more detail below with reference to Examples.

Note that all parts and percentages in Examples and Reference Examples are based on weight. Reference Example Sample A Liquid polybutadiene (number average molecular weight: 1100125 Viscosity at °C 800 centipoise, cis-1A bond content by infrared absorption spectrum 53%, trans-1.Sakura bond content 9%, and 1.2-type bond content (%) 2 (1) parts, 2-aminoethyl mercaptan 6 Prostitute, xylene 3 prostitute,
14 parts of a mixture of 3 parts of citrus butyl peroxide
After heating to 0° C. and reacting under reflux for 4 hours, the solvent was removed under reduced pressure to obtain 258 parts of a reaction product.

The viscosity of this product is 34,000 centipoise/25°C;
The sulfur content was 9.1% by weight. Sample B The reaction was carried out in exactly the same manner as in Sample A, except that 6 parts of 2-methylcaptoethanol was used in place of (1) part of 2-aminoethylmercaptan, and the sulfur content was 8. A reaction product having a weight of % and a viscosity of 27,500 centipoise/25°C was obtained.

Sample C 6 parts of n-butyl mercaptan instead of (1) part of 2-aminoethyl mercaptan? The reaction was carried out in the same manner as for sample A except that sulfur content was 7. Thickness %, viscosity 2
A reaction product of 100 centipoise/25°C was obtained.

Sample D The reaction was carried out in exactly the same manner as in Sample A except that thioglycolic acid 1 part was used instead of 2-aminoethyl mercaptan (1 part), and the sulfur content was 9. Heel weight%, viscosity 3100
A reaction product of 0 centipoise/25°C was obtained.

Sample E Instead of the polybutadiene used in the production of Sample A, commercially available liquid 1.4 polybutadiene (trade name) was used.
Polyoil 110, manufactured by Hyuls, number average molecular weight 160
0, Sis-1.4 = 74%, Trans-1.4 = 25%
The reaction was carried out in the same manner as in Sample A except that sulfur content 8. A reaction product was obtained with a weight of 13,000 centipoise/25° C. and a viscosity of 13,000 centipoise/25°C.

Sample F Commercially available liquid 1,2-polybutadiene (manufactured by Nippon Soda Co., Ltd.,
Number average molecular weight 1000. The reaction was carried out in the same manner as in Test F4A except that 90% vinyl) was used, and the sulfur content was 9.
．． A semi-solid reaction product was obtained.

Sample G Commercially available liquid polybutadiene (B-200 manufactured by Nisseki Chemical Co., Ltd.) was used instead of the polybutadiene used in the production of Sample A.
The reaction was carried out in the same manner as in Sample A except that 01 (number average molecular weight 200, 65% vinyl, 35% 1.4 bond) was used, and the reaction product had a sulfur content of 8.9% by weight and a viscosity of 65000 centipoise/25°C. thing! I got it.

Sample H Nitchennaphthenate diethylaluminum chloride Liquid polypentadiene obtained by polymerizing 1.3-pentadiene in a benzene solvent using water as a catalyst (number average molecular weight 32001 iodine value 347, cis (1.4+1.2
)=75.9%, transformer (1.4+1.2)=24.
The reaction was carried out in exactly the same manner as in sample A except that polybutadiene (1%) was used instead of polybutadiene, and the sulfur content was 7. Limeage %,
A reaction product having a viscosity of 19,500 centipoise/25°C was obtained.

Sample 1 When the reaction was carried out in the same manner as in Sample A except that raw linseed oil was used in place of the polybutadiene used in the production of Sample A, only an additive with a sulfur content of 20.5% by weight was obtained.

Example 1 (1) Preparation of water-soluble varnish 20 parts* of butyl cellosolve was added to 1 (1) part of each sample obtained in the reference example, and lactic acid and cellosolve corresponding to 0.9 equivalents of the sulfur content were added. After adding an equivalent amount of butyl glycidyl ether and 3 parts of distilled water and stirring at 60°C for 2 hours, distilled water was further added to prepare a water-soluble varnish with a solid content concentration of 40% and a pH of 3 to 7.

)) Preparation of pigment dispersion 100 parts of the water-soluble varnish prepared in (1), 2 parts of titanium oxide
5 parts of lead oleate, 1 part of lead oleate, and 0.3 parts of carbon black were mixed and stirred for 1 hour using a pigment disperser to obtain a paste-like dispersion.

() Preparation of aqueous solution 126 parts of the dispersion prepared in (2) and 1 part of the water-soluble varnish obtained in (1) were mixed, and distilled water was added to make the solid content 10.
%, pH 3 to 7 was prepared.

1) Electrodeposition conditions: Using the aqueous solution prepared in (3) as the electrodeposition liquid, using the iron phosphate-treated dull steel plate as the cathode, the bath temperature was 25°C, and the distance between the electrodes was 7 crr.
Under i (i) conditions, electricity was applied for 2 minutes under a voltage of 5.0 to 120V, and after the electricity was finished, the test piece coated with cathode electrodeposition was taken out, washed with water, air-dried, and then powdered at a specified temperature for 3 minutes. Burnt.

The performance of the obtained baked film was measured, and the results shown in Table 1 were obtained. It can be seen that it has excellent corrosion resistance, impact resistance, and coating appearance. On the other hand, polybutadiene with a vinyl content of 90% becomes almost gel-like at the stage of the addition reaction with the mercaptan compound, and it is extremely difficult to make it water-soluble, so that a smooth film cannot be obtained (composition F). In addition, polybutadiene with a vinyl content of 65% provides a smooth film, but lacks luster due to poor fluidity and is also poor in corrosion resistance. On the other hand, when polypentadiene is used as a starting material, the coating film is generally brittle and has poor corrosion resistance and water resistance (composition H).
Furthermore, it is not possible to obtain sufficient coatings from natural drying oils (composition 1). Comparative Example 1 Except for using 2 parts of 2-aminoethyl mercaptan and 5 parts of tertiary butyl peroxide,
Mercaptan addition reaction was carried out according to the preparation conditions of Sample A in Reference Example to obtain a product with a sulfur content of 26%.

Using this, cathodic electrodeposition coating was performed according to Example 1, and when baked at 190°C for 30 minutes, the coating film hardness was ω, and the salt spray resistance test showed spot rust on the entire surface after 15 hours. Comparative Example 2 In the preparation of Sample A in the Reference Example, the number average molecular weight was 60.
When all the procedures were carried out in the same manner as in the case of Sample A except that liquid polybutadiene No. 00 was used, the reaction product with the mercaptan compound partially gelled, and even if it was water-solubilized and electrodeposited, a smooth coating could not be obtained. No film was obtained.

Claims (1)

[Scope of Claims] 1. A polybutadiene having a sulfide bond obtained by reacting a mercaptan compound with a liquid polybutadiene having a number average molecular weight of 500 to 5,000 and having at least 40% of 1.4-bonds, and having a sulfur content of 1. An aqueous coating composition comprising a water-soluble or water-dispersible resin obtained by at least partially sulfonium ionizing 5 to 25% by weight of mercaptan-modified polybutadiene. 2. The composition according to claim 1, wherein the polybutadiene contains 50% or more of 1,4-bonds. 3. The composition according to claim 1, wherein the mercaptan compound is a mercapto group-containing compound having 12 or less carbon atoms.