JPH03254866A - Surface treatment of metal - Google Patents

Abstract

PURPOSE:To form a protective film composed of a metal having good abrasion resistance and chemical resistance by treating the surface of a metal with a hexavalent chromium-containing finely divided metal dispersion at first before applying a specific aqueous coating composition thereto. CONSTITUTION:At first, the surface of a metal such as the under-floor metal of a car is treated with a hexavalent chromium-containing finely divided metal dispersion containing sodium bichromate, succinic acid and the like. Subsequently, an aqueous coating composition based on an aqueous emulsion polymer composed of a polymer of a monoethylenic unsaturated monomer having one vinyl or vinylidene group such as methyl acrylate or ethyl acrylate is applied to the treated metal to form a film. As mentioned above, when this film is formed to the surface of the metal after the discontinuous anticorrosive film consisting of the finely divided metal and the hexavalent chromium-reduced matter is formed thereto at first, the film and the anticorrosive film are bitten in and closely bonded to the surface of the metal by anchor effect. Therefore, the metal can be protected from a flown pebble or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a surface treatment method for protecting the surface of metal.

[Conventional technology]

For example, metal members and parts such as fuel tanks and side sills placed under the floor of a car may be damaged by pebbles, sand, etc. thrown up while the car is running (referred to as chipping), and are used to prevent rainwater and roads from freezing. Tar paint and tar-urethane paint to prevent corrosion due to contact with inorganic salts etc.

Coated with polyvinyl chloride sol, etc.

The above paint forms a thick film of about 500 to 1000 microns on the surface of the member, and its viscoelasticity buffers flying pebbles and the like to prevent scratches on the surface.
Prevent direct contact with inorganic salts, etc.

[Problem to be solved by the invention]

However, the above-mentioned conventional paints lack durability, and as mentioned above, it was only possible to satisfactorily protect the surface of the above-mentioned member with a thick coating film of about 500 to 1000 microns.

Furthermore, the above-mentioned conventional paints contain organic solvents and organic plasticizers, are toxic and flammable, and are difficult to handle.

[Means to solve the problem]

The present invention, as a means for solving the above-mentioned conventional problems,
After treating the surface of the metal with a finely divided metal dispersion containing hexavalent chromium, aqueous emulsion polymerization of one or more types of heptanoethylenically unsaturated monomers having one vinyl group or vinylidene group is carried out. The present invention provides a method for treating the surface of metal by applying an aqueous coating composition mainly composed of metal.

〔metal〕

The metals used in the present invention are mainly iron, carbon steel, nickel chromium steel, nickel chromium molybdenum steel, chromium steel, chrome molybdenum steel, aluminum chrome molybdenum steel, low manganese steel, manganese chrome steel, silicon manganese steel, and molybdenum steel.

Mainly iron or steel such as high manganese steel.

[Hexavalent chromium-containing fine metal dispersion] The hexavalent chromium-containing fine metal dispersion used in the present invention includes A (hexavalent chromium supplying substance) and, if desired, B (6
Dispersion of C (metals with a greater ionization tendency than the metal to be treated, or finely divided alloys thereof) in a solvent such as water or alcohol using D (surfactant). It was forced upon me.

A (hexavalent chromium supplying substance) is sodium dichromate,
Dichromates such as potassium dichromate and ammonium dichromate, sodium chromate, potassium chromate,
Contains virtually all water-soluble inorganic compounds of hexavalent chromium, such as chromate salts such as ammonium chromate and chromic anhydride.

B (hexavalent ROM reducing substance) is defined in Japanese Patent No. 6245.
Succinic acid as described in No. 86, carbon number 14
or mixtures thereof with one or more compounds selected from aspartic acid, acrylamide, succinimide, and 04-C14 aliphatic ketomonocarboxylic acids.

C (a metal with a greater ionization tendency than the metal to be treated, or a refined product of an alloy thereof) is, for example, when the metal to be treated is iron, it may include zinc, manganese, aluminum, magnesium, a mixture thereof, or an alloy thereof. To be elected.

The above A and B are dissolved in a solvent such as water or alcohol, and C is dispersed in this solution, and D (surfactant) is added to stabilize the dispersion of C. Examples of D include alkylene glycol alkyl ethers such as propylene glycol butyl ether, alkylene glycol oxyalkyl ethers such as 1-butoxyethoxy-2-propatool, and alkylphenol polyoxyalkyl ethers such as polyoxyethylene nonylphenyl ether. etc. are included.

A more detailed explanation of the fine metal dispersion containing hexavalent chromium can be found, for example, in Japanese Patent Publication No. 52-904 and Japanese Patent Publication No. 52-1902.
Disclosed in the issue etc.

[Treatment of metal with finely divided metal dispersion containing hexavalent chromium] To coat the metal to be treated with the dispersion, general coating methods such as dipping treatment, spray treatment, brushing treatment, etc. are applied. After application, it is desirable to shake off the remaining dispersion from the treated material and to make it adhere uniformly by placing the treated material in a vibrating sieve or the like with a mesh attached to the bottom of the frame and applying vibrations. Of course, the above post-processing is not essential to the present invention.

After coating the metal surface with the dispersion, the temperature is 200-400°C.
The heating at this time is desirably carried out by, for example, infrared rays, but of course hot air drying may also be carried out. Infrared drying allows the heat treatment to be carried out uniformly. The anticorrosion film thus formed on the surface of the metal to be treated is mainly composed of finely divided metal and a reduced product of hexavalent chromium. The film treated with the conventional antirust treatment is a continuous film, but the film treated with the dispersion is discontinuous.

[Aqueous emulsion polymer]

The aqueous emulsion polymer used in the present invention is an aqueous emulsion polymer comprising one or more polymers of mono-ethylenically unsaturated monomers having one vinyl group or vinylidene group.

Mono-containing the above one vinyl group or vinylidene group
Ethylenically unsaturated monomers (hereinafter simply referred to as monomers) include methyl acrylate, ethyl acrylate, n-
Butyl acrylate, 1so-butyl acrylate, 2
-Ethylhexyl acrylate, cyclohexyl acrylate, tetrahydrofurfuryl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 1so-butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, tetrahydrofurfuryl methacrylate, stearyl Alkyl acrylates and alkyl methacrylates such as methacrylate, lauryl methacrylate, methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, 1so-butyl vinyl ether,
Vinyl ethers such as n-butyl vinyl ether, styrenes such as styrene and α-methylstyrene, nitrile monomers such as acrylonitrile and methacrylonitrile, fatty acid vinyls such as vinyl acetate and vinyl propionate, vinyl chloride, vinylidene chloride, fluoride, etc. Halogen-containing monomers such as vinyl chloride and vinylidene fluoride, olefins such as ethylene and propylene, dienes such as isoprene, chloroprene and butadiene, acrylic acid, methacrylic acid, itaconic acid, maleic acid, atorbic acid, citraconic acid, α-β unsaturated carboxylic acids such as crotonic acid, β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate, β-hydroxypropyl acrylate, β-hydroxypropyl methacrylate, hydroxyl group-containing monomers such as allyl alcohol, acrylamide, methacrylamide , amides such as diacetone acrylamide, other water-soluble monomers such as vinylpyrrolidone, vinylpyridine, and vinylcarbazole, and epoxy monomers such as glycidyl acrylate, glycidyl methacrylate, and glycidyl allyl ether.

The above monomers are emulsified in water using a surfactant and emulsion polymerized using a polymerization initiator, ultraviolet rays, radiation, etc. Examples of the surfactant used in the emulsion polymerization include anionic surfactants such as higher alcohol sulfate (Na salt or amine salt), alkylaryl sulfonate (Na salt), alkylnaphthalene sulfonate, and alkyl phosphate. , dialkyl sulfosuccinate, rosin soap, nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkylphenol ether, polyoxyethylene alkyl ester, polyoxyethylene alkylamine, polyoxyethylene alkylamide, sorbitan alkyl ester , polyoxyethylene sorbitan alkyl ester, and examples of cationic surfactants include trimethylaminoethyl alkylamide halogenide, alkylpyridinium sulfate, and alkyltrimethylammonium halide. The above examples are not intended to limit the invention.

Polymerization initiators used in the above emulsion polymerization include commonly used polymerization initiators such as lyllium persulfate, sodium persulfate, ammonium persulfate, lyllium perborate, sodium perborate, hydrogen peroxide, and water-soluble azo compounds. is used, and a reducing agent such as sodium sulfite, sodium hyposulfite, ascorbic acid, copper sulfate, etc. may also be used as a decomposition accelerator for the polymerization initiator.

In producing the aqueous emulsion polymer of the present invention, the monomer is usually in the range of about 30 to 65% by weight, the surfactant is usually in the range of 1 to 10% by weight,
The amount of the polymerization initiator is usually about 0.01 to 5% by weight.

Furthermore, in the present invention, the aqueous emulsion polymer includes polyvinyl alcohol, polyacrylates, carboxymethylcellulose, ethoxycellulose, starch, modified starch, gelatin,
It may contain a thickener or protective colloid such as casein, a wetting agent or viscosity improver such as ethylene glycol, propylene glycol, or glycerin, an ultraviolet absorber, an anti-aging agent, and the like.

It is desirable that vinylidene chloride and/or vinyl chloride be copolymerized into the aqueous emulsion polymer of the present invention. The vinylidene chloride and/or vinyl chloride is usually contained in the above polymer in an amount of about 5 to 90% by weight. Further, both vinylidene chloride and vinyl chloride are copolymerized in the above polymer, and the total amount of vinylidene chloride and/or vinyl chloride is 5 to 90% by weight, and the total amount of vinylidene chloride and vinyl chloride is 5 to 90% by weight, and the amount of vinylidene chloride and vinyl chloride is 5 to 90% by weight. The proportion of vinylidene is preferably 5 to 80 parts by weight.

Furthermore, the above vinylidene chloride (a) and vinyl chloride (b)
is preferably copolymerized with one or more alkyl acrylates and/or alkyl methacrylates (c) containing 1 to 12 carbon atoms in the alkyl group. In the above polymer, vinylidene chloride (a) is usually used.
and vinyl chloride (b) is in the range of 20:80 to 95:5, vinylidene chloride (,) is contained in the polymer in an amount of 75% by weight or less, and the alkyl acrylate and/or alkyl methacrylate (c) is the sum of vinylidene chloride (a) and vinyl chloride (b) of 10
When it is set as 0 parts by weight, it is contained in 2 to 45 parts by weight.

Furthermore, vinylidene chloride (a), vinyl chloride (b), alkyl acrylate and/or alkyl methacrylate (c) which are polymers of the aqueous emulsion polymer of the present invention
The copolymer preferably contains one or more α-β unsaturated carboxylic acids (d). in this case,
The α-β unsaturated carboxylic acid (d) is contained in the copolymer in a proportion of 30% by weight or less.

[Third component]

In the aqueous coating composition of the present invention, pigments such as calcium carbonate, titanium white, chrome yellow, and carbon black, rock wool, metal fibers, carbon fibers, potassium titanate short fibers, seaweed, etc. are added to the aqueous emulsion polymer as a third component. Inorganic fillers such as foam stone, glass fiber, wollastonite, fibrous basic magnesium sulfate, organic fillers such as polyester fiber, acrylic fiber, polyamide fiber, acetate fiber, urethane fiber, rust preventive agent, etc. are mixed. However, it is particularly desirable to add a rust-preventing pigment. Examples of the above rust-preventive pigments include potassium, sodium, calcium, magnesium, barium, strontium, zinc, lead, manganese, iron, and chromium in oxyacids such as glycolic acid, lactic acid, β-oxybutyric acid, malic acid, tartaric acid, and citric acid. , salts with metals such as molybdenum and tungsten, calcium silica, barium metaborate, and zinc phosphate. Two or more of these may be used in combination.

[Preparation]

The aqueous coating composition of the present invention is prepared by kneading the above composition using a conventional mixing machine such as a three-roll mill, a ball mill, or an atomizer-1 mill.

〔Painting〕

The aqueous coating composition of the present invention is usually applied to the metal surface treated with the above-mentioned dispersion by a general coating method such as dipping, spray coating, or brush coating. A thickness of about 250 to 500 microns is usually sufficient for the coating film.

[Effect]

When a metal surface is treated with a fine metal dispersion containing hexavalent chromium, a discontinuous antirust film is formed on the metal surface, which is mainly composed of the fine metal and a reduced product of hexavalent chromium. When the aqueous coating composition of the present invention is applied to the metal surface on which the discontinuous rust preventive film has been formed to form a coating film, a discontinuous rust preventive film is formed on the metal surface as described above, making it rough. Because of this, the coating film digs into the anti-corrosion film due to the anchor effect, resulting in good adhesion of the coating film.For example, when the metal surface is a member or part placed under the floor of a car, protects the metal surface from pebbles, sand, etc. blown away while driving, and protects the metal surface from scratches.

The aqueous emulsion polymer described above closely coats the surface of the object to be coated to protect the surface from contact with water, inorganic salts, etc. The aqueous emulsion polymer (A) contains vinylidene chloride and/or vinylidene chloride. Or if a copolymer made of vinyl chloride is used.

Improves adhesion, water permeability, moisture resistance, etc. of paint film.

However, from the viewpoint of weather resistance, it is desirable that the copolymer contains 90% by weight or less of vinylidene chloride and/or vinyl chloride. It is desirable to copolymerize an alkyl acrylate and/or alkyl methacrylate (c) containing 1 to 12 carbon atoms in the group, but for the water permeability and moisture resistance of the coating film, the above alkyl acrylate and/or When the total of vinylidene chloride (a) and vinyl chloride (b) is 100 parts by weight, the alkyl methacrylate (c) is preferably contained in an amount of 45 parts by weight or less. Furthermore, in order to further improve the adhesion to the metal surface, it is desirable to copolymerize an α-β unsaturated carboxylic acid (d), but if the amount of the α-β unsaturated carboxylic acid exceeds 30% by weight, the coating film has poor water resistance.

〔Example〕

Example 1 (Aqueous emulsion polymer 1) Into a reactor equipped with a stirrer, thermometer, and condenser were added 600 parts by weight of water, 2 parts by weight of ammonium polyacrylate, 5 parts by weight of polyoxyethylene alkylphenol ether, and 3 parts by weight of higher alcohol sulfate. After heating to 75°C and mixing and dissolving, 5 parts by weight of ammonium persulfate was added, and a monomer mixture having the following composition was continuously added dropwise over 3 hours.

Styrene 200 parts by weight 2-ethylhexyl acrylate 175/Fβ-hydroxyethyl methacrylate 10# methacrylic acid
5 After dropping the above monomer mixture, add 3 more
The mixture was heated to 75° C. for an hour and stirred, and then cooled to room temperature to obtain an aqueous emulsion polymer 1 having a viscosity of 1500 cps and an Ifi content of 40% by weight.

Example 2 (Aqueous Emulsion Polymer 2) 600 parts by weight of water, 7 parts by weight of rosin soap, and 3 parts by weight of alkyl phosphate were charged into a reactor similar to that in Example 1, and after mixing and dissolving by heating to 60°C, After adding 3 parts by weight of sodium perborate and 2 parts by weight of sodium hyposulfite, a monomer mixture having the following composition was continuously added dropwise over 3 hours.

Vinylidene chloride 400 parts by weight n-butyl acrylate 90 After dropping the above monomer mixture, it was further heated to 60°C for 2 hours and 80°C for 1 hour, stirred, and then cooled to room temperature to form an aqueous solution with a viscosity of 700 cps and a solid content of 50% by weight. Emulsion polymer 2 is obtained.

Example 3 (Aqueous emulsion polymer 3) A monomer mixture having the following composition was used in the same manner as in Example 2 to obtain a viscosity of 750 c.
An aqueous emulsion polymer 3 having a pse solid content of 55% by weight is obtained.

Vinylidene chloride 400 parts by weight Vinyl chloride 200 Ethyl acrylate
90 Example 4 (Aqueous emulsion polymer 4) Polymerization was carried out in the same manner as in Example 2 using a monomer mixture having the following composition, and then the pH was adjusted to 8 with ammonia and the viscosity was 4000c.
ps, an aqueous emulsion polymer 4 having a solid content of 60% by weight is obtained.

Vinylidene chloride 320 parts by weight Vinyl chloride 150 2-ethylhexyl acrylate 100 /'acrylic acid 20 Example 5 (Aqueous coating composition 1) Using the aqueous emulsion polymer 1 obtained in Example 1, the following composition shell homomixer was prepared. Aqueous coating composition 1 is obtained.

Water 22 parts by weight Ethylene glycol monobutyl ester 3 n Antifoaming agent (silicon type) 0.2 #Methoxycellulose
1.8 Antirust pigment 3 Calcium bicarbonate 20 Aqueous emulsion polymer 1 50 Example 6 (Aqueous coating composition 2) Using the aqueous emulsion polymer 2 obtained in Example 2, the following composition was prepared in a homomixer. Mix to obtain aqueous coating composition 2.

Water 26.5 parts by weight Propylene glycol 3.5 Sorbitan alkyl ester 0.3 Antifoaming agent (silicon type) 0
．． 2 #Ethoxycellulose 1.5 Rust preventive pigment 3 Calcium bicarbonate 15 Aqueous emulsion polymer 2 50 #Example 7 (Aqueous coating composition 3) Using the aqueous emulsion polymer 3 obtained in Example 3, the following The composition was mixed in a homomixer to obtain aqueous coating composition 3.
get.

Water 22 parts by weight Ethylene glycol monobutyl ether 3.5 Dialkyl sulfosuccinate 0.2 Antifoaming agent (silicon type)
0.3 #Anti-rust pigment 4 Calcium bicarbonate 20 Aqueous emulsion polymer 4 50 Example 8 (Aqueous coating composition 4) Using the aqueous emulsion polymer 4 obtained in Example 4, the following composition was added to a homomixer. and mix to obtain aqueous coating composition 4.

Water 22 parts by weight Ethylene glycol monobutyl ether 3,5n dialkyl sulfosuccinate 0.3 Antifoaming agent (silicon type) 0.2 0 Tsukuwool 10 Rust preventive pigment 4 Calcium carbonate 15 Water-based engineered marsillon polymer 4 45 Umbrella: Rockwool has an average diameter of 5 microns and an average length of 200 microns.

[Practical test]

Aqueous coating compositions 1 to 1 prepared in Examples 5 to 8 above
91. Preparation of test piece (1) A dispersion liquid having the following composition was used.

CrOs 40g/
Q finely divided zinc (average particle size 2.9μ) 200g/Q lignosulfonate 0.5g/Ω solvent
A carbon steel plate of 150 x 70 x 0.8 m of water is immersed in the above dispersion, and after draining, heat treatment is performed at 300°C. In this way, a rust preventive film is formed on the surface of the carbon steel plate.

Aqueous coating compositions 1 to 4 were applied to the carbon steel plate on which the rust preventive film was formed in this way, respectively, and dried at 80°C for 30 minutes to prepare test pieces 1 to 4 with a coating film thickness of 300 microns. did.

The test pieces 1 to 4 were left at room temperature for 7 days, and then tested.

2. Preparation of test piece (2) A dispersion liquid having the following composition is used.

Zinc dichromate 60 g/Q finely divided zinc (average particle size 3μ) 170g/ρ finely divided aluminum 30 g/Q (average particle size 15μ) polyethylene oxide 0.7g/Q solvent
Water: Isopropanol F: 3 mixed solution 150x70X
A nickel-chromium steel plate of 0.8 mm is immersed in the above dispersion, drained, and then heat-treated at 300°C. In this way, a rust-preventing film is formed on the surface of the nickel-chromium steel plate.

Aqueous coating compositions 1 to 4 were respectively applied to the nickel chromium steel plates on which the anticorrosion film was formed in this way, and the same coating as for test pieces 1 to 4 was performed to prepare test pieces 5 to 8. The test piece 5
-8 were left at room temperature for 7 days in the same manner as test pieces 1-4, and then tested.

3. Test method (1) Nut drop test Using an M-4 brass nut with a drop of 2 m, the above test pieces 1 to 8 were held at an angle of 60° from the horizontal plane, 3 kg at a time, and dropped onto the surface of the test piece. Measure the maximum weight that can be dropped without exposing the surface of the material.

(2) Gravelometer test Using a JA-400 flying stone tester manufactured by Suga Test Instruments Co., Ltd., 500 g of No. 6 crushed stone was sprayed onto the surfaces of the test pieces 1 to 8 at an air pressure of 5 kg/cat. The above spraying is performed three times.

(3) Salt water spray test (S S T) Using a 5T-11L-180 salt water spray tester manufactured by Suga Test Instruments Co., Ltd., 5W/V was measured in a test tank adjusted to 35°C and humidity 95 to 98% RH. % saline solution is sprayed onto the sample surface.

The sample is (2) Test piece 1 after gravelometer test.
- 8, and test pieces 1 to 8 whose coating films were cut according to JISK-5400, and evaluation is performed according to JISK-5400.

4. Test results The test results are shown in Table 1.

(Left below) Table 1 Test piece Nut SST SST drop test (after gravelometer test) (cut) 1
24 2 22 18
3 13 24
2 24 15
5 25 27 0
16 15 5
27 12 4 2
8 15 2 1 ratio 1 skewer, 8 10 3 ratio 2 ning 210 11 3 umbrella,
Ratio 1: This is a comparative example in which an untreated carbon steel plate was used in aqueous coating composition 1.

*2 Ratio 2: This is a comparative example in which an untreated nickel-chromium steel plate was used in aqueous coating composition 1.

〔Effect of the invention〕

Looking at Table 1, it can be seen that the test pieces prepared by the treatment method of the present invention have extremely good abrasion resistance and chemical resistance compared to the comparative example using untreated steel plates. It is extremely excellent when used as a Furthermore, since the coating composition of the present invention is water-based, it is free from toxicity and fire hazards, and can be handled extremely safely and easily. Further, since the metal surface is subjected to a surface treatment with a finely divided metal dispersion containing hexavalent chromium, the rust prevention property and the adhesion of the paint are also improved.

Claims (1)

[Claims] 1. After the surface of the metal is treated with a fine metal dispersion containing hexavalent chromium, one or more monoethylenically unsaturated monomers having one vinyl group or vinylidene group are treated. Metal surface treatment method 2, characterized by applying an aqueous coating composition mainly composed of an aqueous emulsion polymer consisting of a polymer, wherein the aqueous emulsion polymer contains vinylidene chloride and/or vinyl chloride. Metal surface treatment method 3 according to claim 1, wherein the aqueous emulsion polymer is copolymerized with 5 to 90% by weight of vinylidene chloride and/or vinyl chloride. A metal surface treatment method 4 according to claim 1, wherein the aqueous emulsion polymer contains a total of 5 to 90% by weight of vinylidene chloride and vinyl chloride.
A metal surface treatment method 5 according to claim 1, wherein the proportion of copolymerized vinylidene chloride is 5 to 80 parts by weight when the total of vinylidene chloride and vinyl chloride is 100 parts by weight. The aqueous emulsion polymer contains vinylidene chloride (a), vinyl chloride (b) and alkyl groups containing 1 to
Method 6 for surface treatment of metal according to claim 1, which is a copolymer with one or more alkyl acrylates and/or alkyl methacrylates (c) containing 12 carbon atoms, the aqueous emulsion polymerization The polymer of product (A) contains vinylidene chloride (a), vinyl chloride (b), and 1 in the alkyl group.
A claim which is a copolymer of one or more alkyl acrylates and/or alkyl methacrylates (c) containing ~12 carbon atoms and one or more α-β unsaturated carboxylic acids (d) In the metal surface treatment method 7 according to item 1, the aqueous emulsion polymer has vinylidene chloride (a), vinyl chloride (b) and an alkyl group containing 1 to
It is a copolymer with one or more alkyl acrylates and/or alkyl methacrylates (c) containing 12 carbon atoms, and the polymerization ratio of vinylidene chloride (a) and vinyl chloride (b) is 20:80. From 95:5
and vinylidene chloride (a) is contained in the polymer in an amount of 75% by weight or less, and the alkyl acrylate and/or alkyl methacrylate (c) is a combination of vinylidene chloride (a) and vinyl chloride (b). When the total amount is 100 parts by weight, the metal surface treatment method 8 according to claim 5 contains 2 to 45 parts by weight, and the aqueous emulsion polymer contains α-β unsaturated 30% by weight of one or more carboxylic acids (d)
The metal surface treatment method according to claim 6, which is copolymerized in the following proportions: