JPS606380B2 - Resin composition for water-based anticorrosion paint - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a resin composition for an aqueous anticorrosive coating used to protect metal surfaces, and in particular to prevent corrosion of steel plates.

Zinc-rich paints, which aim to be maintenance-free, have been widely used for their excellent corrosion prevention effects.

In recent years, there has been a demand for a change in materials for anticorrosive paints from the viewpoints of resource conservation, energy conservation, and pollution-free production, and inorganic zinc-rich paints are being actively studied.

Inorganic zinc-rich paints generally have better film conductivity, heat resistance, and corrosion resistance than organic zinc-rich paints, but
On the other hand, the surface treatment of the steel material needs to be strict, it is easily affected by weather and seasons, and it has poor acid resistance and alkali resistance. In addition, ethylsilicate-based self-curing alcohol-soluble zinc-rich paints, which are said to be particularly effective at high temperatures, contain large amounts of solvent, and problems in terms of resource conservation, safety, and hygiene remain unresolved. Therefore, organic zinc-rich paints that are water rut-resistant or water-shedding are desired, but so far there are none that are practically satisfactory.

The present inventors have developed a copolymer latex that can stably disperse zinc powder with excellent anticorrosion properties, has excellent adhesion and adhesion to various metal substrates, and exhibits complete anticorrosion performance. As a result of intensive development research, we have developed a water-soluble copolymer consisting of a salt of a polymer obtained by reacting one or more monomers of ethylenically unsaturated carboxylic acids and/or one type of ethylenically unsaturated carboxylic acid. A water-soluble copolymer made of a salt of a polymer obtained by reacting the above monomer with a sulfo group-containing product, and the average molecular weight of the polymer is 500 to 20,000.A water-soluble copolymer containing carboxyl groups. The present inventors have discovered that a copolymer latex containing zinc powder has excellent dispersibility of zinc powder and has a surprising effect on improving anticorrosion properties, and has thus completed the present invention.

That is, according to the present invention, (A) a conjugated diolefin having 4 to 6 carbon atoms, an acrylic acid alkyl ester derived from an alkanol having 1 to 18 carbon atoms, and 4 carbon atoms;
-1 or more monomers selected from the group consisting of acrylic acid alkyl esters derived from 18 alkanols 5
~60% by weight, (B) 30 to 85% by weight of one or more monomers selected from ethylenically unsaturated aromatic monomers and methacrylic acid alkyl esters derived from alkanols having 1 to 3 carbon atoms. and (C) when emulsion polymerizing a monomer polymer consisting of at least one monomer of ethylenically unsaturated carboxylic acid with a cloud content of 1 to 1, (D) ethylenically unsaturated carboxylic acid. A water-soluble copolymer (D,) and/or a salt of a polymer obtained by reacting one or more monomers.
or a water-borne copolymer (D2) consisting of a salt of a polymer obtained by reacting one or more monomers of ethylenically unsaturated carboxylic acid with a sulfo group-containing vinyl monomer; A carboxyl group-containing water-soluble copolymer having an average molecular weight of 500 to 20,000 was obtained by emulsion polymerization in the presence of 0.1 to 1 part by weight based on 100 parts by weight of the monomer mixture. Copolymer aqueous dispersion (1) and zinc powder (
b) The solid content weight ratio of (1)/(0) is 2'98 to 30
A resin composition useful as a water-based anticorrosive paint, which is obtained by mixing in a range of /70, is provided.

The composition of the present invention has extremely stable dispersibility of zinc powder having an anticorrosion function and anticorrosion pigments such as polyvalent metal oxides and hydroxides, has excellent adhesion and adhesion to metal substrates, and has elasticity. It forms a strong coating film rich in minerals, has good impact resistance, and significantly improves corrosion resistance and adhesion to top coat materials.

The copolymer aqueous dispersion (1) having the composition used in the present invention can be polymerized until the polymerization rate of the monomer reaches almost 100%, and in addition, the addition of an organic solvent is particularly important when formulating the coating material. As a completely water-based vehicle is not required, safety and hygiene concerns are naturally eliminated.

In the copolymer of the present invention, the conjugated diolefin having 4 to 6 carbon atoms used as the first component (A) includes butadiene-1,3,2-methylbutadiene 1,3,2-chlorobutadiene- 1,3,2,3-dimethylbutadiene-
Among them, butadiene-1,3 is preferred, considering copolymerizability with other monomers and economical efficiency.
Next, an alkyl acrylate derived from an alkanonol having 1 to 18 carbon atoms and an alkyl methacrylate derived from an alkanol having 4 to 18 carbon atoms, which are also used as the first component (A), are used. The stell may be any one used in normal emulsion polymerization. These monomers are used alone or in combination of two or more to internally plasticize the copolymer, but if the proportion is less than 5% by weight, no effect will be observed;
Furthermore, in order to obtain a sufficient effect, it is desirable that the amount is 1% by weight or more.

On the other hand, if the proportion exceeds 60% by weight, the coating film becomes too soft and the mechanical stability of the copolymer dispersion decreases, resulting in, for example, agglomeration in the pump during airless coating.
This leads to deterioration of painting workability such as clogging in the spray gun. Therefore, the first component (A) has 4 carbon atoms.
- 6 conjugated diolefins, acrylic acid alkyl esters derived from C 1-18 alkanols, and methacrylic acid alkyl esters derived from alkanols having 4-18 carbon atoms. % by weight of the above monomers 5-6 preferably 10-6% by weight are used.

Examples of the methacrylic acid alkyl ester derived from an ethylenically unsaturated aromatic monomer and an alkanol having 1 to 3 carbon atoms as the second component (B) include styrene, Q
-Methylstyrene, vinyltoluene, chlorstyrene,
Examples include 2,4-dibromustyrene, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, and isopropyl methacrylate. These monomers are used for the purpose of imparting hardness to the coating film, but if the ratio is 3
If it is less than 85% by weight, the coating film will be too soft and
If it exceeds % by weight, it becomes too hard and the film forming temperature becomes high.
Unable to form a uniform coating.

Therefore, one or more monomers of the second component (B) are used in an amount of 30-85% by weight. Examples of the ethylenically unsaturated carboxylic acid as the third component (C) include acrylic acid, methacrylic acid, and methacrylic acid.

Tonic acid, maleic acid, fumaric acid, itaconic acid and unsaturated dicarboxylic acid monoalkyl esters, such as monomethyl maleate, monoethyl fumarate, mono-n-itaconic acid
Examples include butyl. These monomers are necessary components to increase the mechanical stability and freeze stability of the aqueous copolymer dispersion, and also to increase the adhesion of the coating film to metal substrates, and their proportions are If it is less than 1% by weight, it has no effect, and if it exceeds 1% by weight, the water resistance of the coating film decreases, and furthermore, when the pH of the aqueous copolymer dispersion after polymerization is adjusted with alkali, the viscosity becomes difficult. It becomes expensive and becomes unsuitable as a paint.

Therefore, one or more monomers for the third component (C) are used in an amount of 1 to 10% by weight.

Aqueous solution consisting of a salt of a polymer obtained by reacting one or more monomers of ethylenically unsaturated carboxylic acid when emulsion polymerizing the mixture of the monomers (A), (B) and (C) above. water-soluble copolymer (D,) and/or a water-soluble copolymer consisting of a salt of a polymer obtained by reacting one or more monomers of ethylenically unsaturated carboxylic acid with a sulfo group-containing vinyl monomer (D2), the average molecular weight of the polymer is 500 to 200
Emulsion polymerization by coexisting 0.1 to 10 parts by weight of a carboxyl group-containing water-soluble copolymer (D) of 0.00 to 10 parts by weight of a mixture of monomers (A), (B), and (C). However, examples of the ethylenically unsaturated carboxylic acids include acrylic acid, methacrylic acid, crotonic acid, maleic acid or its anhydride, fumaric acid, itaconic acid, and unsaturated dicarboxylic acid monoalkyl esters; Examples of vinyl monomers include allylsulfonic acid, methallylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, methacrylate ethylsulfonic acid,
Examples include polymerizable monomers having a sulfo group such as vinylsulfonic acid or their respective salts. Note that the sulfo groups of these monomers may be converted into sulfonate salts in advance. In addition, for the preparation of the carboxyl group-containing water-soluble copolymer,
Unless otherwise specified, one or more other copolymerizable monomers may be used in addition to the above monomers.

Examples of such monomers include conjugated diolefins, ethylenically unsaturated aromatic monomers, alkyl acrylates, alkyl methacrylates, and the like. As long as the average molecular weight of the carboxyl group-containing water-soluble copolymer is in the range of 500 to 20,000, no significant difference in performance will be observed no matter what method is used to synthesize it.

The salts of these polymers are preferably alkali metal salts such as sodium salts and potassium salts, or ammonium salts, but some salts of alkali metals may also be used, and an unneutralized portion may be left. . The proportion of the water-soluble copolymer (D) consisting of the salts of these copolymers is the monomer (A), (
If the amount is less than 0.1 part by weight based on 10 parts by weight of the mixture of B) and (C), there will be no effect on the dispersibility of zinc powder and antirust pigments such as polyvalent metal oxides and hydroxides; If the weight part of the monomer (A) is exceeded, the water resistance of the coating film will decrease and
The copolymerizability of the mixture of , (B) and (C) is also significantly inhibited, the polymerization rate decreases, and an emulsified dispersion in a stable particle state cannot be obtained.

In order to improve the adhesion to the metal substrate and the corrosion resistance of the coating film, the carboxyl group-containing water-soluble copolymer (D) is preferably used in monomers (A), (B) and (C). ) is 0.3 to 7 parts by weight per 100 parts by weight of the mixture. The aqueous copolymer dispersion (1) used in the present invention is prepared by a conventional emulsion polymerization method. For example, a mixture of the above monomers (A), (B and (C)) is emulsified and dispersed in water using an emulsifier, and a free radical generating catalyst is used in the presence of a water-dropping copolymer (D). Emulsion polymerization may be carried out at a temperature of 10,000 ml.For the preparation of the copolymer aqueous dispersion (1), additives commonly used in emulsion polymerization can be used as necessary, such as chain transfer agents, polymerization stabilization, buffering effects, etc. Electrolytes such as phosphates and sulfates for the purpose of oxidation, UV absorbers, etc. for the purpose of preventing deterioration of the copolymer can be used.With the above composition, the polymerization rate is 98% or more. A copolymer dispersion (1
) to increase mechanical stability and freeze stability.
It is preferable to adjust the pH to 7 to 10 using a regulator. The copolymer aqueous dispersion after emulsion polymerization is stripped and concentrated to remove unreacted monomers and adjust the solid content to 40 to 50%. In the composition of the present invention, in order to reduce the amount of zinc dust (b) and not to reduce the anticorrosive performance, powders of metals having a valence of two or more, such as aluminum powder or magnesium powder, may be used in combination. do not have. Further, unless otherwise prohibited, polyvalent metal oxides and hydroxides may be used in combination with the zinc metal powder.

Such polyvalent metal oxides and hydroxides include copper, silver, beryllium, magnesium, calcium, strontium, barium, zinc, cadmium, aluminum, zirconium, tin, lead, antimony, bismuth, chromium, molybdenum, Examples include oxides and hydroxides of metals having a valence of two or more from Group 1 to Blood Group of the Periodic Table, such as manganese, iron, cobalt, and nickel. The mixing ratio of the copolymer aqueous dispersion (1) and the zinc metal powder (0) used in the present invention is in the range of 2'98 to 30/70 in solid content weight ratio (1)/(b). be. If the solid content weight ratio of the aqueous copolymer dispersion is less than 2% by weight, the pigment fixing ability of the coating film will be poor, the adhesion to the metal substrate will be reduced, and the anticorrosion performance will not be sufficiently exhibited, and the weight of 3. If it exceeds %, the pigment dispersion stability and adhesion to metal substrates are excellent, but the anticorrosion function deteriorates and sufficient anticorrosion properties are not exhibited. The resin composition of the present invention can be obtained by uniformly mixing the aqueous copolymer dispersion (1), zinc dust (0), and other additives using a conventional mixing means.

The resin composition of the present invention can be applied directly to a metal substrate, such as a steel material, without an undercoat or anticoating treatment, and dried to improve corrosion resistance, adhesion, heat resistance, and low-temperature properties. And a protective film with excellent impact resistance can be formed.

Next, the present invention will be explained in more detail with reference to Examples.

Note that "parts" in each example indicate "parts by weight." Example 1 32 parts of butadiene, 65 parts of styrene, 3 parts of acrylic acid,
Carboxyl group-containing water-soluble copolymer 0 to 1 of the first notation
2 parts (variable), 0.0 parts sodium alkylbenzenesulfonate.
6 parts, 0.1 part of ammonium ethylenediaminetetraacetate,
Tarsia IJ - 0.1 part of dodecyl mercaptan, 0.1 part of potassium persulfate. Moribe and 145 parts of ion-exchanged water were placed in a nitrogen-substituted autoclave equipped with a Fumoto Azusa machine, and polymerization was carried out at 6,000 for 1 hour.Then, the pH was adjusted to 9 with caustic potash to obtain a copolymer water dispersion with a solid content of 40%. I got the liquid.

Next, 93 parts of zinc powder was added to 7 parts (dry weight parts) of the above copolymer moisture teaching solution, mixed well to prepare a water-dispersible paint, and a polished steel plate (manufactured by Nippon Test Panel Co., Ltd., JISB3) was added.
141, 0.8 x 70 x 150 sails) using a 3 mil applicator, dried with hot air at 8000 for 1 minute, and then subjected to a corrosion resistance test using salt spray.

Table 1 shows the properties of the aqueous copolymer dispersion, the dispersibility of zinc dust, and the results of salt spray resistance.

From Table 1, it can be seen that the aqueous copolymer dispersions of the examples of the present invention have extremely good zinc powder dispersibility and salt spray resistance. Table 1* Types of water-soluble copolymers containing canoleboxyl groups
Sodium salt of a polymer obtained by reacting acrylic acid and maleic acid.

) Sodium salt of the polymer obtained by reacting acryl-zoic acid with methallylsulfonic acid Sodium salt of the polymer obtained by reacting acryl-zoic acid※※Judgment◎ ヲE Always good ○ Good △ Bad × Very Bad Example 2 Monomeric polymer mixture 10 listed in Table 2 1.0 parts of sodium salt of a polymer obtained by reacting acrylic acid and maleic acid with an average molecular weight of 3000 , 0.6 part of sodium alkylbenzenesulfonate, 0.1 part of ammonium ethylenediaminetetraacetate, 0.1 part of tertiary-dodecylmercaptan, 0.1 part of potassium persulfate. 145 parts of gunpowder and ion-exchanged water were charged into a nitrogen-substituted autoclave equipped with a dehydrator, and polymerization was carried out at 60 qo.Then, the pH was adjusted to 91* with caustic potash, and a copolymer with a solid content of 40% was charged. An aqueous polymer dispersion was obtained.

Next, zinc powder was added in the same manner as in Example 1, the coating film was adjusted,
Salt spray resistance, salt water resistance, water resistance, adhesion to metal plates, and impact resistance were tested.

Table 2 shows the properties of the aqueous copolymer dispersion, the dispersibility of the zinc powder, and the test results for the coating film performance.

As seen in Table 2, all of the aqueous copolymer dispersions of the examples of the present invention show extremely good results. Table 2 Table 2 (Continued) ◎ Very K Good ○ Good Good △ Bad ) to 7 parts by dry weight of Zinc Powder 93 B, and further added 0.5 part of antifoaming agent Nopco NXZ (manufactured by San Nopco Co., Ltd.), and thoroughly stirred using a disperser to prepare a paint. .

The obtained paint was applied to a sandblasted steel plate heated to a surface temperature of 65q0 so that the dry film thickness was approximately 40 mm, and then left at room temperature for 1 day. A tarepoxy paint (JISK 5664 Type 3) was applied as a top coat on the surface under the same conditions so that the dry film thickness was about 50Q, and then left for 5 days. Both were subjected to a film performance test.

At the same time, as a comparative example, a solvent-based inorganic zinc-rich paint and an organic zinc-rich paint were applied to a dry film thickness of approximately 40 mm, and after being left at room temperature for 4 days, a top coat was applied to the above-mentioned paint. Tarepoxy paint (JISK56
6643 type) was coated to a dry film thickness of about 50 mm, and then left for 5 days and subjected to a coating performance test.

The test results are shown in Tables 3 and 4.

Table 3 Note 1) Judgment depends on the state of rust on the scratched part (the same applies below).

(◎Very K good;○Good;△Poor;×Very K poor) Note 2) The test piece used for the bond test was scratched with a knife to reach the base K (the same applies below). Table 4 (Test results on sandblasted steel plate coated with zinc-rich primer paint and tareboxy paint as top coat) Examples
4 Solid content weight ratio (1) of the copolymer aqueous dispersion prepared in Example 2 (Example 1 of the second notation) (1) and zinc powder (0)
(m is 1/992-98 5/9fu 7/93 10/
90, 15/85 25'75 30/70 and 40'
The paint * was prepared so that it might be 60.

The resulting paint was applied to a sandblasting board to a dry film thickness of 30 degrees Fahrenheit, dried for 10 minutes in a hot air dryer at 65°C, and subjected to a paint film/performance test.

The test results are shown in Table 5. Table 5 Example 5 93 parts of zinc powder was added to 7 parts by dry weight of the copolymer aqueous dispersion prepared in Example 2 (Examples 22 and 26 of the second notation), and further antifoam agent Nopco NXZO was added. ．． A paint was prepared by adding 5 parts and stirring thoroughly using a disperser.

The obtained paint was placed on a sandblasting board (1.6 x 70 x 1
50 Yanagi) to a dry film thickness of 40 F, dried at room temperature for one week, and subjected to a coating film performance test.

The test results are shown in Table 6.

Table 6

Claims (1)

[Claims] 1 (A) From the group consisting of conjugated diolefins having 4 to 6 carbon atoms, alkyl acrylates derived from alkanols having 1 to 18 carbon atoms, and alkyl methacrylates derived from alkanols having 4 to 18 carbon atoms. 5 to 60% by weight of one or more selected monomers, (
B) Ethylenically unsaturated aromatic monomer and carbon atom number 1-
30 to 85% by weight of one or more monomers selected from methacrylic acid alkyl esters derived from alkanols of No. 3, and (C) 1 to 10% by weight of one or more monomers of ethylenically unsaturated carboxylic acids. When emulsion polymerizing a monomer mixture consisting of % of (D) ethylenically unsaturated carboxylic acid,
A water-soluble copolymer (D_1) consisting of a salt of a polymer obtained by polymerizing more than one type of monomer and/or one or more monomers of ethylenically unsaturated carboxylic acid and a sulfo group-containing vinyl monomer A water-soluble copolymer (D_2) consisting of a salt of a polymer obtained by polymerizing a carboxyl group-containing water-soluble copolymer (D_2) having an average molecular weight of 500 to 20,000 with a monomer of Copolymer aqueous dispersion (I) and zinc powder ( II) with a solid content weight ratio of (I)/(II) of 2/
A resin composition for an aqueous anticorrosive paint obtained by mixing in a range of (98) to (30)/(70).