JPH0819369B2 - Anticorrosion composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Object of the Invention "Industrial field of application" The composition of the present invention relates to a composition used for corrosion protection of metals, and is produced by using iron which is particularly susceptible to corrosion. It is particularly useful for corrosion protection of structures such as tanks, bridges, and roofs, and is effective in the field of civil engineering and construction, but can also be used in other fields when metal corrosion protection is required.

"Conventional Technology" For corrosion protection of metal buildings and structures such as iron tanks, bridges and roofs, rust preventive paints and cement-based coating materials have been widely used.

However, all of them have advantages and disadvantages as described below.

The anticorrosive paint is composed of a coating film forming material such as epoxy resin, chlorinated rubber, alkyd resin, vinyl resin, etc. and a zinc- or lead-based anticorrosion pigment. Although it has a rust preventive function based on the water blocking effect, it cannot be applied thickly with conventional coatings, so pinholes occur due to coating defects, floating of coatings due to poor surface treatment, peeling, and mechanical damage. Weaknesses in rust prevention are likely to occur due to scratches on the coating reaching the metal surface, and once rust occurs, it has the drawback that corrosion progresses rapidly from the rusted part. It has a drawback that it is difficult to perform sufficient maintenance because it is necessary to completely remove the film.

On the other hand, the cement-based coating material has a unique anti-corrosion function due to alkali, and possesses features not found in organic materials.

In other words, since it is possible to apply thick coating, it is unlikely that coating defects will occur, and even if defective parts occur, rust will not spread easily due to the self-closing action and repair is easy, Inadequate adhesion causes peeling, lacks elasticity, cannot follow the slight movement of metal and causes cracks, and lacks water-tightness and air-tightness, resulting in neutralization and salt damage. It also has the drawback of losing rust prevention power.

The present inventors to solve the above problems, as shown in JP-A-60-260662, the cement,
Cationic acrylic Elmajeon 30 to 10 in terms of resin
A composition containing 0% was proposed.

However, it has been found that this composition has a drawback in anticorrosion property at a young age. That is, when the amount of the resin component is increased as in these compositions, the hardening reaction of the cement is delayed, corrosive substances such as chloride ions easily infiltrate in the early stage of hardening, and the iron is passivated. Due to the small elution of water-solubilized calcium, when these compositions were used in a corrosive environment such as the coast, rusting was sometimes observed at an early stage.

"Problems to be Solved by the Invention" The present invention solves the drawbacks of the previously proposed anticorrosion composition, that is, the inferior anticorrosion property at the age of a young material and the conventional anticorrosion It was made through intensive studies in order to solve the problems that the composition had such as poor durability performance and lack of repair performance.

(B) Structure of the Invention "Means for Solving Problems" The present invention relates to an anticorrosive composition having excellent durability and good workability obtained by solving the above problems. There is a solution to the above problems with respect to cement, a cationic acrylic emulsion consisting of an acrylic resin having a glass transition temperature of 20 ℃ or less and nitrite can be achieved by a composition for anticorrosion. It was made with the heading.

Cement The cement in the present invention is not particularly limited, and may be a general one mainly composed of calcium oxide and silicon oxide such as Portland cement, alumina cement, hydraulic cement, mixed cement, etc., either alone or as a mixture. You can use it.

Acrylic emulsion A cationic acrylic emulsion made of an acrylic resin having a glass transition temperature of 20 ° C. or less in the present invention means one or more of acrylic acid ester and methacrylic acid ester, preferably 20 to 100% by weight, more preferably 35 to 100% by weight. %, A cationic emulsion obtained by polymerizing a monomer or a mixture of monomers by a conventional emulsion polymerization method, and usually having a solid content of 30 to 70% by weight.

Specific examples of the acrylic acid ester and methacrylic acid ester include acrylic acid and methacrylic acid methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, n-amyl, iso-. Amyl, n-hexyl, n-heptyl, oxoheptyl,
There are esters such as n-octyl, 2-ethylhexyl, n-nonyl, oxononyl, n-decyl and oxodecyl.

In addition to the acrylic acid alkyl ester, as a monomer used in the production of an acrylic emulsion, there are vinyl monomers copolymerizable with acrylic acid ester and methacrylic acid ester, specifically acrylic acid or methacrylic acid, ethylene. , Vinyl acetate, vinyl chloride, vinylidene chloride, acrylonitrile, styrene, butadiene, acrylic amide, methylol acrylic amide, vinyl propionic acid ester, itaconic acid ester, maleic acid ester, crotonic acid ester, dimethylaminoethyl methacrylic acid ester, trimethylamino Ethyl methacrylic acid ester hydrochloride, etc. are used.

If the amount of acrylic acid ester and methacrylic acid ester in the monomer used in the production of the acrylic emulsion in the present invention is less than 20%, the weather resistance of the foodstuff containing the cationic acrylic emulsion thus obtained is deteriorated. It has drawbacks and is not preferable.

As a method of making the emulsion cationic, a method of producing the above-mentioned monomer by a generally known emulsion polymerization method in the presence of a cationic surfactant, or a known emulsion in the presence of nonionic and / or anionic surfactants There is a method in which a cationic surfactant is added to and mixed with an emulsion obtained by a polymerization method to make the emulsion cationic.

Cationic surfactants used to make the emulsion cationic include generally commercially available secondary and tertiary amine type surfactants and quaternary ammonium salt type surfactants. To improve the adhesion of
The use of quaternary ammonium salt type cationic surfactants is preferred.

Specific examples of the quaternary ammonium salt type surfactant include lauryl trimethyl ammonium chloride, stearyl trimethyl ammonium chloride, distearyl dimethyl ammonium chloride, alkylbenzyl dimethyl ammonium chloride and lauryl dimethyl benzyl ammonium chloride.

In the present invention, since the acrylic emulsion has a cationic property, the adhesion to the metal surface is dramatically improved, and a good dispersion of cement and aggregate can be obtained. An excellent cured product can be obtained, and it can be used as a raw material of an anticorrosive material having excellent durability.

The acrylic emulsion of the present invention has a glass transition temperature of 20.
It consists of an acrylic resin below ℃, but the glass transition temperature (hereinafter referred to as Tg point) is the temperature at which various properties of the amorphous polymer change suddenly. Below this temperature, the amorphous polymer The temperature is such that the movement of the molecular segments of the part is frozen.

To actually measure the Tg point of an acrylic resin, as an example, measure the thermal expansion at various temperatures, plot the specific volume for each temperature, and measure the temperature at the bending point in the obtained curve. A general method of asking can be adopted.

However, in practice, the Tg point of a homopolymer is already known, and the Tg point of a copolymer is as follows when the value of the Tg point of a homopolymer consisting of individual homomonomers is known. It can be calculated by the formula.

W ₁ : Weight fraction of component 1.

W ₂ : 〃 of ingredient 2.

Wn: Weight fraction of component n.

Tg ₁ : Tg (° K) of component 1 homopolymer Tg ₂ : 〃 ₂ 〃 (° K) Tgn: 〃n 〃 (° K) where W ₁ + W ₂ + …… + Wn = 1.

The major known Tg points of homopolymers (all Tg points in the arc) are polymethyl acrylate (8 ° C), polybutyl acrylate (-54 ° C), poly-2-ethylhexyl acrylate (-55 ° C). ), Polymethylmethacrylate (105 ℃) Polystyrene (100 ℃) Polyvinyl acetate (30
C.) Polymethacrylic acid (130.degree. C.) and the like.

Next, as an example of calculating the Tg point of the copolymer, the Tg point of the copolymer of 70 parts by weight of butyl acrylate (hereinafter abbreviated as “part” and 30 parts of styrene) is −23 ° C. when calculated from the above formula.

As described above, the method for obtaining the Tg point has been described. The Tg point of the polymer in the acrylic emulsion used in the anticorrosion composition of the present invention is the above formula and the Tg point (the one not described is Maruzen Co., Ltd.). Refer to the published Chemical Handbook, etc.).

In the present invention, the emulsion used has a Tg point of 20.
An emulsion containing an acrylic resin having a temperature of not higher than 10 ° C, preferably not higher than 10 ° C.

By setting the Tg point of the acrylic emulsion to 20 ° C. or less, the coating layer of the composition of the present invention on the metal surface follows the movement and structural movement of the metal due to expansion and contraction of the metal, and thus does not cause cracking or peeling. Yes, it is an action that cannot be expected if the temperature exceeds 20 ° C.

The acrylic resin having a Tg point of 20 ° C. or lower is obtained by polymerizing the acrylic acid ester and the methacrylic acid ester as described above, but in the present invention, it has 3 to 10 carbon atoms, more preferably 4 to 9 carbon atoms. What is obtained by superposing | polymerizing the alkyl acrylate ester which has the said alkyl group is preferable.

It is preferable to use the alkyl acrylate ester having an alkyl group having 3 to 10 carbon atoms because the following property can be further enhanced and water resistance and alkali resistance can be further imparted to the composition of the present invention.

Further, it is preferable to use a part of acrylic acid and methacrylic acid ester by changing them to (meth) acrylic acid ester of methyl and / or ethyl alcohol to obtain a better effect. The reason is that the lower acrylic acid ester is hydrolyzed by cement alkali and forms a crosslinked structure with Ca ²⁺ ions, so that the strength of the composition of the present invention, particularly the effect of improving the tensile strength and bending strength at a young age is obtained. be able to.

The amount of the lower (meth) acrylic acid ester used is preferably 0.5 to 10% by weight, more preferably 1 to 5% by weight, based on the monomers used for producing the acrylic emulsion. When the amount of the lower (meth) acrylic acid ester used exceeds 10%, the water resistance of the cured product of the composition of the present invention decreases, and when it is less than 0.5%, the above physical properties can be improved by forming a crosslinked structure. Can not.

Nitrite The nitrite in the present invention is a monovalent or divalent metal salt of nitrous acid, and specifically, lithium, sodium,
Examples thereof include potassium, calcium, and strontium, and these can be used alone or in combination.

Mixing ratio The mixing ratio of cationic acrylic emulsion and cement is preferably not less than 5 parts by weight and not more than 50 parts by weight of acrylic emulsion in terms of resin content based on 100 parts by weight of cement. If it is too small, the adhesion to the metal surface and airtightness There is a risk that the water solubility will decrease and the rust prevention effect will be insufficient.

If the amount of emulsion exceeds 50 parts by weight, the cement hardening reaction will be delayed and the anticorrosion performance at a young age will decrease, and the strength of the hardened product will also decrease, resulting in mechanical damage. It becomes easy to receive.

The blending ratio of nitrite and cement is preferably 0.1 parts by weight or more and 10 parts by weight or less with respect to 100 parts by weight of cement,
If the amount is too small, the anticorrosion effect becomes insufficient, and if the amount of nitrite exceeds 10 parts by weight, the hardening reaction of the cement may be adversely affected and the strength may be reduced.

Additives In the composition of the present invention, fine aggregate such as silica sand and river sand can be used in combination, and its preferable range is 500 with respect to cement.
It is not more than 400 parts by weight, more preferably not more than 400 parts by weight.

In order to prevent cracks and peeling due to drying shrinkage when the coating thickness exceeds 1 mm, it is particularly preferable to use sand in an amount of 500 parts by weight or less.

If the amount of sand used exceeds 500 parts by weight with respect to the cement, the strength, watertightness and airtightness of the hardened product will decrease.

Further, when the composition of the present invention is produced using an emulsion and cement, and when the water provided from the emulsion cannot be mixed alone, an appropriate amount of water can be mixed and used for adjusting the softness. The amount of water mixed with cement is preferably 100 parts by weight or less, more preferably 60 parts by weight or less, as the total amount of water brought from the emulsion and newly added water.

If the amount of water exceeds 100 parts by weight, the denseness of the cured product of the composition of the present invention will decrease, and the watertightness and airtightness will decrease.

Further, conventionally known cement admixtures can be used in addition to the composition of the present invention.

Specific examples include water retention agents such as methyl cellulose and polyethylene oxide, quick-setting agents such as calcium chloride and sodium aluminate, organic and inorganic fiber materials, defoaming agents, sodium lignin sulnateate, oxycarboxylic acid, sodium polycarboxylate. Etc. and the like.

Method of Use As a method of using the composition of the present invention, that is, a method of coating, all conventionally known coating methods can be used. Specifically, it can be applied by brush coating, roller coating, gold iron coating, air spray or the like.

[Operation] As described above, the composition for anticorrosion has a cement and a Tg point of 20.
By using a cationic acrylic emulsion composed of an acrylic resin having a temperature of ℃ or less and nitrite, a film having excellent adhesion to a metal surface and excellent watertightness and airtightness can be obtained.
In addition, since it becomes a flexible film, it can follow the movement and structural movement due to the expansion and contraction of the metal, and since it exhibits the above-mentioned performance in a short period of time, it becomes a highly durable anti-corrosion food material. You can offer what you get.

"Examples" Next, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to the Examples.

All parts and percentages in the examples are actual parts and percentages by weight.

 The test methods used in the examples are as follows.

Adhesion performance with iron plate A black leather plate of 7 × 12 × 0.6 cm was coated with the composition of the present invention in a thickness of 2 mm by means of a metal iron, and was applied for 3 days, 7 days and 21 days at 20 ° C. and 60 ° C., respectively.
Cured under% RH environment. A notch reaching the surface of the iron plate with a size of 4 × 4 cm was made in this test body, a tensile test jig (4 × 4 cm) was attached with an epoxy adhesive, and the adhesive strength was measured with a Kenken-type adhesive strength tester. .

Rust prevention test 2,000 Hr by salt spray test after sealing the back and side with a dense wax after making a test piece by the same method as the item adhesion test
The rust preventive effect was examined by the degree of rusting afterwards.

Example 1 48 parts of 2-ethylhexyl acrylate, 2 parts of methyl acrylate, 50 parts of styrene, 2 parts of polyoxyethylene nonylphenol ether, 1 part of stearyltrimethylammonium chloride, 0.4 part of 2.2-azobis (2-amidinopropane) hydrochloride 70 ° C using a composition consisting of 100 parts of water
Emulsion polymerization was carried out at the above temperature to produce a cationic acrylic emulsion having a solid content concentration of 48%. Tg of the obtained copolymer
The point was 4 ° C.

Cement in 30 parts of this cationic acrylic emulsion
100 parts, No. 7 silica sand 100 parts, calcium nitrite 1 part, tap water
20 parts were kneaded to obtain the composition of the present invention.

A test piece was prepared using the above composition, various properties were measured, and the test results are summarized in Table 2. The adhesion to the iron plate and the rust preventive performance at each age showed good performance.

Examples 2-3 The acrylic emulsion shown in Table 1 was used, and the test body was prepared by the formulation shown in Table 2.

The results of various characteristic evaluation tests performed on these are shown in Table 2, and all show good performance.

Comparative Examples 1 to 4 As a comparative example, the acrylic emulsion shown in Table 1 was used to prepare a test body in the same manner as in Example 1. The results of various characteristic tests are also shown in Table 2, and all are significantly inferior to those obtained by the composition of the present invention.

(C) Effect of the invention As described in the characteristics of the composition of the present invention based on the data of the above-mentioned examples, the composition of the present invention has excellent adhesion to the iron plate, which is a typical metal, and rust resistance in various ages. Are better. Due to this characteristic, it can be used effectively for anticorrosion coating of reinforced concrete and metallic structures exposed to particularly corrosive environments such as marine structures as well as construction and civil engineering structures using metal, and maintenance and management costs You can get a significant reduction of.

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Claims (1)

[Claims] 1. An anticorrosion composition comprising cement, a cationic acrylic emulsion made of an acrylic resin having a glass transition temperature of 20 ° C. or lower, and nitrite.