JPS6055548B2 - Iron pipe coated with copolymer water dispersion - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an iron pipe whose inner and outer surfaces, or only the outer surface, are coated with a specific aqueous copolymer dispersion. Corrosion resistance, chemical resistance, and impact resistance can be achieved by coating the inner and outer surfaces or only the outer surface of iron pipes with an aqueous copolymer dispersion that forms a dry coating with excellent chemical resistance and adhesion to metals. The aim is to provide iron pipes with excellent properties.

Currently, iron pipes used as water pipes, industrial water pipes, gas pipes, etc. are made of bituminous and synthetic resins such as coal tar, asphalt, and tar epoxy to prevent external corrosion due to underground corrosion and internal corrosion due to fluids. Painted with bituminous paint containing.

However, these paints pose safety and hygiene problems such as fire hazards due to the solvents contained in the paints, coal tar, toxicity in the painting work environment due to the solvents, odors, and even air pollution. At the same time, it takes a long time to dry, which poses a problem in terms of the working process, and this causes lack of color, which can easily damage the coating film.

The present inventors conducted research to improve the drawbacks of conventional iron pipes as described above, and found that by coating iron pipes with an aqueous dispersion of a copolymer having a specific monomer composition, the above-mentioned problems could be improved. It was found that the shortcomings could be improved. That is, the present invention provides (4
) Conjugated diolefin having 4 to 6 carbon atoms, 1 carbon atom
Conjugated diolefin 5 having 4 to 6 carbon atoms and selected from the group consisting of acrylic acid alkyl esters derived from ~18 alkanols and methacrylic acid alkyl esters derived from alkanols having 4 to 18 carbon atoms.
5-5% by weight of one or more monomers, which must be at least 5% by weight;
(B) Ethylenically unsaturated aromatic monomer and carbon atom number 1
40 to 85% by weight of one or more monomers selected from methacrylic acid alkyl esters derived from alkanols of ~3 and (C) 1 to W weight% of one or more monomers of ethylenically unsaturated carboxylic acids. It can be summarized as a copolymer aqueous dispersion obtained by emulsion copolymerizing a monomer mixture composed of To provide an iron pipe with a strong coating film, good impact resistance, and excellent corrosion resistance.

The copolymer aqueous dispersion having the composition used in the present invention can be polymerized until the polymerization rate of the monomer reaches almost 100%,
Moreover, since it is a completely water-based vehicle that does not particularly require the addition of five organic solvents when formulating a paint, the above-mentioned safety and hygiene problems are naturally solved.

In the copolymer of the present invention, as the conjugated diolefin having 4 to 6 carbon atoms used as the first component, ζ is butadiene-1,3,2-methylbutadiene-1,3,2-chlorobutadiene-1,3 , 2,3-dimethylbutadiene-1
, 3, etc., but in consideration of copolymerizability with other monomers and economic efficiency, it is preferable to use butadiene-1,3.

Next, the number of carbon atoms used as the first component is 1 to 1.
Examples of acrylic acid alkyl esters derived from 8 alkanols and methacrylic acid alkyl esters derived from alkanols having 4 to 18 carbon atoms include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, and acrylic acid alkyl esters derived from alkanols having 4 to 18 carbon atoms. n-butyl acid,
Isobutyl acrylate, n-octyl acrylate, 1-2-ethylhexyl acrylate, decyl acrylate, octadecyl acrylate, n-butyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, methacrylic acid Examples include octadecyl.

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 is observed at all, and it is difficult to obtain a sufficient effect. In order to obtain this, it is preferable that the amount is 10% by weight or more.

Moreover, in order to form a coating film with good elasticity and impact resistance, the amount of conjugated diolefin having 4 to 6 carbon atoms is required to be 5% by weight or more, preferably 1% or more. On the other hand, if the amount of the first component monomer exceeds 5%, the coating film becomes too soft and the mechanical stability of the aqueous copolymer dispersion decreases, for example, when it is difficult to use in a pump during airless coating. This leads to deterioration in painting workability such as agglomeration and clogging in the spray gun.
Therefore, the first component is 5% by weight of a conjugated diolefin having 4 to 6 carbon atoms, preferably 1% or more of one or more monomers, preferably 5% to 5% by weight, preferably 10 to 5% by weight. % is used.

Examples of the second component, methacrylic acid alkyl ester derived from an ethylenically unsaturated aromatic monomer and an alkanol having 1 to 3 carbon atoms, include styrene, α-methylstyrene, vinyltoluene, chlorostyrene, 2, 4
-dibromustyrene, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, and the like.

These monomers are used for the purpose of imparting hardness to the paint film, but if the proportion is less than 4% by weight, the paint film becomes too soft, and conversely, if it exceeds 85% by weight, it becomes too hard. As a result, the film formation temperature becomes high, making it impossible to form a homogeneous coating.

Therefore, one or more monomers as the second component are used in an amount of 40 to 85% by weight.

Ethylenically unsaturated carboxylic acids as the third component include acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, and unsaturated dicarboxylic acid monoalkyl esters, such as monomethyl maleate, monoethyl fumarate, itaconic acid. Examples include mono-n-butyl. These monomers are necessary components to improve the mechanical stability and freezing stability of the aqueous copolymer dispersion, and also to improve the adhesion of the coating film to iron pipes, and the proportion of these monomers is 1% by weight. %
If it is less than 1%, it will not be effective, and if it exceeds 1%, the water resistance of the coating will decrease, and furthermore, when the pH of the copolymer aqueous dispersion after polymerization is adjusted with alkali, the viscosity will be significantly reduced. It becomes expensive and becomes unsuitable as a paint.

For this reason, one or more monomers of the third component may be
Use in the range of ~1 rut amount%.

In preparing the copolymer in the present invention, one or more types of other copolymerizable monomers can be used in addition to the above-mentioned monomers, as long as it is not necessary.

Examples of such monomers include acrylonitrile,
Unsaturated nitriles such as methacrylonitrile, vinyl acetate,
Vinyl esters such as vinyl propionate, vinylidene halides such as vinylidene chloride and vinylidene bromide, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate. hydroxyalkyl esters of ethylenically unsaturated carboxylic acids such as glycidyl acrylate, glycidyl methacrylate, and acrylamide, methacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, N- Examples include butoxymethylacrylamide, N-butoxymethylmethacrylamide, diacetone acrylamide, hydroxymethyldiacetone acrylamide, and the like. The copolymer aqueous dispersion used in the present invention is prepared by a conventional emulsion polymerization method, in which the above-mentioned monomer mixture is emulsified and dispersed in water using an emulsifier, and a free radical generating catalyst is used to disperse the monomer mixture in water. Emulsion polymerization may be carried out at 10CfC. As the emulsifier, anionic and nonionic surfactants are used, and each can be used alone or in combination.

Examples of anionic surfactants include potassium oleate,
Fatty acid salts such as sodium oleate, sulfate ester salts of higher aliphatic alcohols such as sodium lauryl sulfate, sulfate ester salts of fatty acid glycerides such as sodium sulfate ricinoleate triglyceride,
Alkyl allyl sulfonates such as sodium isopropylbenzenesulfonate, sodium isopropylnaphthalene sulfonate, alkyl diphenyl ether disulfonates such as sodium isopropyl diphenyl ether disulfonate, and higher alkyl sulfosuccinic acids such as sodium octylsulfosuccinate. Examples include salt.

Examples of nonionic surfactants include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether and polyoxyethylene oleyl ether, polyoxyethylene alkyl phenyl ethers such as polyoxyethylene nonylphenyl ether, and polyoxyethylene monomers. Examples include polyoxyethylene alkyl esters such as lauryl ester, and polyoxyethylene sorbitan alkyl esters such as polyoxyethylene sorbitan monostearate.

These emulsifiers are usually used in an amount of about 0.3 to 7 parts by weight per 100 parts by weight of the monomer mixture, but they are effective in controlling paint formulation, foaming during painting, water resistance, chemical resistance, and
Considering the influence on corrosion resistance, the range is 0.3 to 1. Preferably, it is a weighing section.

In order for the aqueous copolymer dispersion used in the present invention to form a uniform coating film on the surface of the iron pipe, it is preferable to use a chain transfer agent in emulsion polymerization. Examples of the chain transfer agent include n-dodecyl mercaptan, Third
For example, when using tertiary dodecyl mercaptan, monomer mixtures can be mentioned. Per 10 weighing parts, 0
．． It is preferable to use 2 to 1.5 parts by weight.

In the above example, the tertiary dodecyl mercaptan is 0. If the amount is less than 1 part, the molecular weight of the copolymer becomes too large, and as a result, it is difficult to form a homogeneous coating film, and the coating film tends to develop fine cracks, resulting in poor elasticity, corrosion resistance, and adhesion to iron pipes. Adversely affect.

On the other hand, if it is used in an amount exceeding 15 parts by weight, the copolymer particles become sticky and the mechanical stability of the coating material decreases, as well as the water resistance and chemical resistance of the coating film. Next, as the polymerization catalyst, a general water-soluble catalyst that forms free radicals can be used. For example, peroxide catalysts such as potassium persulfate, ammonium persulfate, hydrogen peroxide, and tertiary butyl hydroperoxide, and water-soluble inorganic reductions of these peroxides and ferrous salts, sodium bisulfite, etc. A redox catalyst in combination with a water-soluble organic reducing agent such as an alcohol or a polyamine can be used.

In addition to the above-mentioned polymerization additives, additives commonly used in emulsion polymerization can be used in the preparation of the copolymer aqueous dispersion as necessary. Antioxidants, ultraviolet absorbers, etc., which are intended to prevent deterioration of electrolyte copolymers such as salts and sulfates, can be mentioned.

The aqueous copolymer dispersion obtained by emulsion polymerization with the above composition until the polymerization rate reaches % or more is adjusted to pH 7 to 10 using a pH adjuster to improve mechanical stability and freezing stability. It is preferable to adjust.

Examples of pH adjusters include water-soluble nonvolatile and volatile inorganic bases such as sodium hydroxide, potassium hydroxide, and ammonia, diethylamine, triethylamine, n-propylamine, isopropylamine, n-butylamine, monoethanolamine, and diethanolamine. , triethanolamine, dimethylethanolamine, morpholine, and N-methylmorpholine, but ammonia or amines are preferred in consideration of the water resistance of the coating film. The aqueous copolymer dispersion that has undergone emulsion polymerization is stripped or concentrated to remove unreacted monomers and adjust the solid content to 40 to 50%.

The aqueous copolymer dispersion thus prepared may contain various additives in order to provide coating suitability for methods such as spray coating, brush coating, and roll coating. for example,
In the coating process, methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose, polyvinylpyrrolidone, ammonia casein, polyvinyl alcohol, alkali-soluble polyacrylic acid ester, polyacrylate, polyacrylamide, A water-soluble polymer such as polyethylene oxide is added.

In addition, if necessary, a water-soluble or water-dispersible thermosetting resin, for example, a precondensate of a polyfunctional amino compound such as methylolated or alkoxymethylated urea or melamine, and formaldehyde or a formaldehyde glyoxal mixture. It is also possible to add aminoformalin resin, epoxy resin, phenol resin, xylene resin, etc. represented by .

Furthermore, unless otherwise prohibited, rust preventive pigments such as zinc chromate and strontium chromate, coloring pigments such as carbon black and titanium dioxide, and extender pigments such as calcium carbonate, talc, clay, and aluminum hydroxide may be added. Also, tar emulsions, pitch emulsions and asphalt emulsions can be added.

In addition, in order to impart properties required in processes such as paint formulation, storage, and painting operations, we also use colloid stabilizers, dispersants, wetting agents, pigment antisettling agents, antifoaming agents, antifreeze agents, and preservatives. Additives that act as fungicides, film-forming aids, leveling agents, anti-sag agents, etc. can be appropriately blended as needed. In carrying out the present invention, the aqueous copolymer dispersion prepared by the above method is applied to the surface of the iron pipe by airless spraying, air spraying, rolling, brushing, etc. so that the dry film thickness is 80p or more. .

In coating the copolymer aqueous dispersion, the iron pipe is coated with 60%
It is preferable that the temperature is between 90°C and 90°C.

For example, when painting an iron pipe heated to 70℃,
The paint dries quickly due to the temperature of the iron pipe itself, forming a tough, elastic, and uniform coating with excellent adhesion to the surface of the iron pipe. This coating film has excellent water resistance, chemical resistance, and corrosion resistance. Next, the present invention will be explained in more detail with reference to Examples.

In addition, 1 part in the following examples indicates 1 part by weight. Example 1 10 parts of the monomer mixture listed in Table 1 below, 0.5 part of sodium lauryl sulfate, 1.0 part of tertiary dodecyl mercaptan
m1 0.05 part of ammonium ethylenediaminetetraacetate,
0.1 part of potassium persulfate and 150 m of ion-exchanged water were placed in a nitrogen-substituted autoclave with a stirrer, and 6CfC
Polymerization was carried out until the polymerization rate reached % or more, and then unreacted monomers were removed by stripping.

Next, adjust the pH to &0 with ammonia water, and the solid content is 40%.
An aqueous copolymer dispersion was prepared.

The obtained copolymer aqueous dispersion was degreased with Lutzker thinner to prepare Migagi mild steel plate JIS-B3l4 manufactured by Tamoto Test Panel Co., Ltd.
0.8×70×1507n, 17TL) using a 10 mil applicator, dried with hot air at 80C, left at room temperature for 5 days, and then subjected to a coating film physical property test.

The properties of the aqueous copolymer dispersion and the test results for the physical properties of the coating film are shown in Table 1, and the aqueous copolymer dispersion of the present invention shows extremely good results in both stability and physical properties of the coating film.

The evaluation symbols for coating film physical properties in the table below mean the following.

1 Water resistance, salt water resistance, acid resistance, alkali resistance b1 0: No change from before the test 0: Slight whitening phenomenon is observed in the paint film 8: The paint film is opaque and white Δ: The paint film is white Blisters and rust are observed on the entire surface Evaluation of salt water spray resistance ◎: No change from before the test 0: Slightly blisters are observed 8: Blisters are observed ∆ : Prestars and rust have occurred on the entire surface. ×: Prestars and rust have occurred on the entire surface. Example 2 The copolymer aqueous dispersion prepared in Example 1 (the example listed in Table 1) 1 to 14) solid content 100W), 1 mark of talc and antifoaming agent (Nopco NXZ; San Nopco product) 0.5
ion exchange water was added to prepare a mixture having a solid content of 6% by weight.

Next, the above mixture was ground in a sand grind mill for 30 minutes to examine the stability of the grinding, and the obtained paint 20
0y was placed in a 200cc glass sample pin, sealed tightly, and left at 50C for one month to examine the storage stability of the paint.

As a result, all of the invention examples (Examples 7 to 14) were extremely stable. Table 2 shows the results.

Example 3 50 parts of talc and 10 parts of talc were added to 100 parts of the solid content of the aqueous copolymer dispersion prepared in Example 1 (Example 9 listed in Table 1).
5, 15, and 20 were added, and antifoaming agent Nopco NXZO. 5 parts to bring the total solids content of the mixture to 40
A paint was prepared by adding ion-exchanged water to the mixture and grinding it with a sand grind mill.

A polished mild steel plate (manufactured by Japan Test Panel Co., Ltd., JIS-B3l4l; 0.8
x70 x 150 TrL, Im) using a 10 mil applicator, dried in hot air at 80'C, left at room temperature for 5 days, and then subjected to a physical property test of the coating film.

The results are shown in Table 3, and all showed good performance.

Based on the solid content of 10 parts of Example 9), 150 parts of talc and the antifoam agent Nopco NXZO. Mix 5 parts, add ion-exchanged water, grind 3 parts with a sand grind mill, solid content 6%, viscosity 3@7 (#40 food cup)
A paint was prepared.

The obtained paint was airlessly applied to the inner and outer surfaces of a 10 iφ cast iron pipe whose surface temperature had been preheated to 75°C so that the dry film thickness was 90μ, and then left at room temperature for 5 days to perform other paint film performance tests. Served.

At the same time, as a comparative example, a tar paint containing a solvent-based epoxy resin was applied to a cast iron pipe under the same conditions to a dry film thickness of 90p, and subjected to the same paint film performance test.

As a result, both showed good performance, but the inventive example was better than the comparative example in terms of the incidence of scratches after coating, and the inventive example was slightly inferior in salt spray resistance. was.

The test results are shown in Table 4.

Solid content of the paint of the present invention example prepared in Example 4: 100 tI
In contrast to 1), two types of paints were prepared by adding tar emulsion and asphalt emulsion, each with a solid content of 10 W).

These paints were also very stable in a one month 50C storage stability test.

The above two types of paints were applied to cast iron pipes in the same manner as in Example 4.

The coated product exhibits good adhesion and chemical resistance, and the paint flows particularly well into the recesses on the surface of the cast iron pipe.
Further, the results of the salt water spray resistance test (100 hrs) showed no abnormality at all.

Example 6 and Comparative Examples Monomer mixture listed in Table 5 100 ml 1 Sodium lauryl sulfate 0.5 ml tertiary dodecyl mercaptan 1. 0.05 ml of ammonium ethylenediaminetetraacetate, 0.1 part of potassium persulfate, and 15 ml of ion-exchanged water were placed in a nitrogen-substituted autoclave equipped with a stirrer, and polymerization was carried out at 6σC until the polymerization rate was 1% or more, and then by stripping. Unreacted monomers were removed.

Next, the pH was adjusted to 8.0 with ani/monia water, and the solid content was 4.
A 0% copolymer aqueous dispersion was prepared.

A polished mild steel plate (JIS-B3l manufactured by Nippon Tent Panel Co., Ltd.
4O; 0.8 x 70 x 150 rn, h0 was coated using a 10 mil applicator, one powder was dried with hot air at 95°C, and after being left at room temperature for 5 days, it was subjected to a coating film physical property test.

Claims (1)

[Scope of Claims] 1 (A) Conjugated diolefin having 4 to 6 carbon atoms (I
), acrylic acid alkyl esters (II) derived from alkanols having 1 to 18 carbon atoms, and acrylic acid alkyl esters (II) having 4 to 18 carbon atoms
5 to 50% by weight of at least one monomer selected from methacrylic acid alkyl esters (III) derived from alkanols of 18 and necessarily containing 5% by weight or more of (I). (B) Ethylenically unsaturated aromatic Group monomer and number of carbon atoms: 1
At least one monomer selected from methacrylic acid alkyl esters derived from ~3 alkanols 40~
An iron pipe whose inner and outer surfaces or only the outer surface are coated with an aqueous dispersion of a copolymer comprising 85% by weight and (C) 1 to 10% by weight of at least one monomer of ethylenically unsaturated carboxylic acid.