JPH0260966A - Protective coating material for concrete reservoir - Google Patents

Abstract

PURPOSE:To make it possible to form a solventless coating material which can give a protective film excellent in chemical resistance and crack follow by mixing a base comprising a mixture of a specified compound having at least two active hydrogen groups with an inorganic powder with a curing agent comprising a polyisocyanate. CONSTITUTION:The title protective coating material contains a base comprising a mixture of a compound having at least two active hydrogen groups with an inorganic powder and a curing agent comprising a compound having at least two isocyanate groups and being applied after they are being mixed, wherein the compound having at least two active hydrogen atoms contains at least 30wt.% hydroxy-terminated liquid polybutadiene, and the inorganic powder is based on silica, aluminum silicate, magnesium silicate or a mixture thereof. As the curing agent, polymethylenpolyphenyl polyisocyanate is particularly desirable.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a protective coating for concrete storage tanks. In particular, the present invention can be applied to the surface of a concrete storage tank for storing acids, alkalis, or other chemicals to obtain a protective coating film with excellent chemical resistance and crack followability. This invention relates to a protective coating agent for concrete storage tanks that does not contain solvents.

[Conventional technology]

Conventionally, concrete surfaces have been painted or lined with various materials to prevent chemical deterioration of concrete storage tanks for storing chemicals and to prevent chemicals from leaking from cranks that occur in the concrete. For example, glass fiber reinforced unsaturated polyester resin (
A method of lining FRP (hereinafter referred to as FRP) using a trowel, roller, etc. is used. Another method is to apply an epoxy resin paint such as cool epoxy by spraying or using a roller.

[Problem to be solved by the invention]

Since FRP contains ester bonds in its molecular structure, the ester bonds are decomposed by the action of chemicals, particularly acids and alkalis, and the resin itself depolymerizes and deteriorates. For this reason, in the case of a storage tank coated with FRP, there is a problem in that the FRP gradually melts from the two surfaces and the protective layer disappears during use.

Furthermore, since the cured coating film of FRP and epoxy resin has little elongation, if a crank occurs in concrete, cracks will occur in the coating film at the location where the crank occurs. This is what is called poor crank followability. This poses a problem in that chemicals leak from the concrete crank. The larger the capacity of a concrete storage tank, the more likely it is that cracks will occur due to the hardening of the concrete.Recently, two types of additives have been studied to prevent the occurrence of cracks, but 1. is not possible at this stage.

Furthermore, there is no efficient construction method for FRP lining9.
Lining on concrete surfaces is often done by hand, which requires great skill and time. Furthermore, there are many variations in the coating film thickness, and coating defects are likely to occur in areas where the coating film is thin.

In the case of epoxy resin, both the base resin and curing agent have high viscosity, and a flammable solvent must be added before painting.If such flammable solvents are used in a sealed room such as a storage tank, there is a risk of explosion. It is inappropriate due to its gender.

The present inventors conducted extensive research with the aim of solving the above problems. In other words, the coating film is not subject to deterioration due to chemicals, the coating film does not crack even if cracks occur in concrete, and it can be applied efficiently to concrete surfaces without using flammable solvents. Through research on protective coating agents, we have completed the present invention.

[Means and effects for solving the problems] That is, the three present inventions.

In a protective coating agent for concrete storage tanks, which is applied by mixing a mixture of a compound having two or more active hydrogen groups and an inorganic powder as a main ingredient and a compound having two or more isocyane-11J as a hardening agent ( 11 The compound having two or more active hydrogen groups contains 30% by weight or more of hydroxyl group-terminated liquid polybutadiene.

(2) The inorganic powder is mainly composed of silica, aluminum silicate, or magnesium silicate alone, or a mixture thereof.

Provides protective coatings for concrete storage tanks.

The protective coating agent for concrete storage tanks of the present invention will be specifically described below.

In the specification, "compound having two or more active hydrogen groups"
is a compound containing two or more hydroxyl groups and/or amino groups in the molecule.

Such compounds with relatively high molecular weights include polyolefin polyols, polyether polyols, and polyester polyols.

As the polyolefin polyol, polybutadiene polyol (referred to as hydroxyl group-terminated liquid polybutadiene) and polyisoprene polyol obtained by polymerizing dienes such as butadiene and isoprene using hydrogen peroxide as an initiator can be used.

Specific examples of polyether polyols include polyoxypropylene polyol, polyoxyethylene polyoxypropylene polyol, and tetrahydrofuran, which are polymerized using propylene oxide or ethylene oxide as an initiator in the presence of an alkali catalyst. Polytetramethylene ether glycol obtained by ring-opening polymerization can be used.

As polyester polyols, polyethylene adipate, polybutylene adipate, polyhexylene adipate, polycaprolactone, and castor oil can be used, but polyester polyols are decomposed by chemicals such as acids and alkalis, causing deterioration of the coating film, so the amount used is limited. should be minimized as much as possible. In particular, polyester polyols with a high concentration of ester groups are susceptible to decomposition of ester bonds.

Compounds containing two or more active hydrogen groups with a relatively small molecular weight and containing two or more hydroxyl groups in nine molecules include ethylene glycol, propylene glycol, 1,4-butanediol, and 1,3-butanediol. 6-hexanediol, neopentyl glycol, octanediol, bisphenol A.

Trimethylolpropane, glycerin, pentaerythritol, triethanolamine, bis(2-hydroxypropylaniline), and these fullylene oxide adducts have compounds that have two or more hydroxyl groups, and two or more amino groups exist in one molecule. Examples of compounds include diaminodiphenylmethane, methylenebis(orthochloroaniline) (hereinafter referred to as MOCA), phenylenediamine, tolylenediamine, ethylenediamine and piperazine. Furthermore, compounds having a hydroxyl group and an amino group in one molecule include monoethanolamine, jetanolamine, aminoethylethanolamine, and compounds in which alkylene oxide is added to a part of the amino group of the above-mentioned compounds having two or more amino groups. There is.

Among the compounds having two or more active hydrogen groups, polyolefin polyols are most preferred, especially.

Hydroxyl group-terminated liquid polybutadiene, preferably 1°4-
Hydroxyl-terminated liquid polybutadiene with a bond of 50% or more and a viscosity of 5 to 100 poise has a relatively low viscosity and is easy to apply, and the resulting coating film is.

It has good followability and other properties, and has excellent chemical resistance. Therefore, in order to achieve the object of the present invention, it is necessary to adjust the composition so that 30% by weight or more of the compound having two or more active hydrogen groups is hydroxyl group-terminated liquid polybutadiene.

Inorganic powders used as the main ingredient include silica, aluminum silicate, and magnesium silicate alone or in mixtures thereof, and specific examples include clay-kaolin clay, talc, and mica. The inorganic powder should be one that does not cause any chemical reaction with the chemicals, and should not cause swelling or other changes due to the chemicals. Since inorganic powder contains a small amount of water or is basic, adding it to the curing agent may cause deterioration of the curing agent, so it should be added to the main ingredient. Adding inorganic powder improves the chemical resistance of the coating film.

In addition, it can lower the permeability of chemicals, water, etc., and has the effect of making it difficult for chemicals to penetrate the paint film and reach the concrete surface. In addition, the addition of inorganic powder has the effect of improving the paintability of the coating material during construction.
Inorganic powder should be mixed into the paint and applied. The inorganic powder is usually 10 to 250 parts by weight, preferably 20 to 250 parts by weight per 100 parts by weight of the compound having two or more active hydrogen-containing groups.
150 parts by weight is used, and the average particle size of the powder is usually 0.
．． It can be from 1 to 50 microns, preferably from 0.5 to 10 microns.

The curing agent used in the present invention is a compound having two or more isocyanate groups in its molecule. Examples include 2.
4-1 lylene diisocyanate.

2.6-tolylene diisocyanate and mixtures thereof (hereinafter collectively referred to as TDI), diphenylmethane diisocyanate (hereinafter referred to as MDI), liquid MDI, polymethylene polyphenyl polyisocyanate (hereinafter referred to as crude MDI), hexamethylene diisocyanate 1 xylylene diisocyanate, There is an isocyanate-terminated prepolymer obtained by reacting isophorone diisocyanate, etc., and a compound having two or more of these isocyanate groups with a compound having two or more of the above-mentioned active hydrogen groups in a state of an excess of isocyanate groups. When selecting a hardening agent,
■The curing reaction proceeds from low to high temperatures, and its reactivity is optimal for construction.

■It should have a low vapor pressure so that it does not volatilize during installation, and ■It should be selected so that the cured coating film is difficult to decompose due to chemicals. Liquid MD I is most suitable for these conditions.

There is a crude MDI. In particular, 5 crude MDr is liquid even at low temperatures, the curing reaction proceeds even at low temperatures, the vapor pressure is low, and the resulting coating film has excellent chemical resistance.
Preferably, DI is used.

The protective coating agent for concrete storage tanks of the present invention is coated with
The cured paint film must have an elongation at break of 30% or more in the JIS 7113 tensile test. If the elongation at break is less than 30%, cracks will occur in the paint film when cracks occur in the concrete. , causing chemicals to leak from the storage tank.

If desired, the protective coating composition of the present invention may contain a catalyst, a colorant, a foaming inhibitor, an antioxidant, an anti-aging agent, and other additives and auxiliaries. .

It is preferable to apply the protective coating agent of the present invention using a two-component internal mixing type airless coating machine in terms of workability and coating performance.
It is not particularly limited. This application method is a method (airless spray method) in which the base agent and curing agent are sent to a two-component internal mixing type airless atomizer using a high-pressure metering pump, and the pressure is applied to atomize the paint (airless spray method). The airless spray method causes less paint to scatter during spraying, and almost no air bubbles are trapped in the paint film. Therefore, the maintenance of concrete storage tanks
This is the best M coating method. When painting by airless spraying, the base agent and curing agent should be mixed uniformly inside the coating machine using a static mixer or power mixer to avoid entraining air bubbles. There is an external mixing method in which the base resin and curing agent are sprayed separately and cured.
In this case, the coating film with sufficient performance cannot be obtained due to poor mixing of the base agent and the curing agent.

Other methods include hand coating and air spraying, but these methods have the following drawbacks and are not preferred.

In the hand-applying method, the base agent and hardener are mixed in a suitable container such as a bundt and applied with a trowel. Since it takes a long time from mixing to application, it is necessary to extend the pot life, so hardening is difficult. It takes a long time.

Furthermore, the construction requires skill, and the coating film tends to be uneven. However, for repair painting of small areas or areas that cannot be painted with airless spray, it is better to apply by hand.

The air spray method is a method in which the base agent and curing agent are sent using a low-pressure metering pump, and the paint is atomized using air pressure.Since the paint is atomized using a large amount of air during spraying, there is no chance of the paint scattering. The paint film has a large amount of air, and the coating workability is poor, and the resulting paint film also entrains a large amount of air, resulting in a decrease in the performance of the paint film.

Chemicals stored in the concrete storage tank of the present invention include alkalis such as sodium hydroxide, potassium hydroxide and calcium hydroxide; inorganic acids such as sulfuric acid, hydrochloric acid and nitric acid; salts such as sodium carbonate, sodium sulfate and common salt; water.

There is sewage, seawater and industrial wastewater.

Specific examples include chemical tanks and distribution reservoirs at water treatment plants, chemical tanks and sewage treatment plants at sewage treatment plants, waste liquid treatment tanks at factories, and even concrete structures built near coastlines.

〔Example〕

Hereinafter, the present invention will be specifically explained with reference to Examples and Comparative Examples. In addition, "parts" in Examples and Comparative Examples are parts by weight.

Examples and Comparative Examples The base resin and curing agent shown in Table 1 were mixed and coated on release paper to a thickness of 3 mm. The resulting coating film was cured at room temperature for 7 days and then subjected to testing.

Polybutadiene R-15HT: Hydroxyl group-terminated liquid polybutadiene, manufactured by Idemitsu Arco ■, hydroxyl value 11B + wgKO
H/g.

Polybutadiene R-45NT: Hydroxyl group-terminated liquid polybutadiene, manufactured by Idemitsu Arco OS, hydroxyl value 46.5 mgK
Otl/g Castor oil modified polyol; manufactured by Ito Oil Co., Ltd., hydroxyl value 167 mg KO) I/g.

Polyhardener 〇-200: Polypropylene glycol, manufactured by Daiichi Kogyo Seiyaku ■, hydroxyl value 56 mg KOH/g Polyhardener PA-4007 Aromatic amine polyol, manufactured by Daiichi Kogyo Seiyaku ■, water fj1 base value 430 mg KOIl/g
.

Inorganic powder: All have an average particle size of 1-10 microns.

Hardness: According to JIS K 6301.

Tensile strength: According to J[S 7113.

Elongation at break: According to JIS X 7113.

Crack followability: According to the method of salt damage countermeasure guidelines for road bridges (Japan Road Association).

Adhesion strength: 2. Based on the method of salt damage countermeasure guidelines for highway bridges (Japan Road Association).

Chemical resistance: According to JIS K 7114.

As is clear from the examples, the protective coating agent for concrete storage tanks of the present invention has good coating properties, and the crack followability of the resulting coating film is 0.4I, which is the standard of the guideline for salt damage prevention for road bridges.
It has superior chemical resistance.

Comparative Example 1 contains castor oil as a main component, and when immersed in acid or alkali, the ester bonds decompose, resulting in a decrease in film thickness and softening of the coating film. Even if castor oil or castor oil-modified polyol is used as in Examples 2 and 3,
When the main component is polybutene polyol, it has excellent chemical resistance.

When polypropylene glycol is used as the main component as in Comparative Example 2, the coating film easily absorbs chemicals, water, etc. and softens. Furthermore, since barium sulfate is used as the inorganic powder in Comparative Example 2, the inorganic powder reacts with chemicals, particularly sodium hydroxide, decomposes into barium hydroxide and sodium sulfate, and is eluted from the coating film.

In Comparative Example 3, since no inorganic powder was used, chemicals easily permeated and the coating film tended to soften somewhat.

In Comparative Example 4, the strength of the coated film was high, but it had poor crank followability due to lack of elongation.

As described above, the coating agent according to the present invention is extremely excellent as a 2g agent for concrete storage tanks.

〔Effect of the invention〕

The protective coating film obtained by the bag side for protecting the concrete storage tank of the present invention is not only resistant to chemicals, especially against acids, alkalis, and salts, but also because the coating film is made of a material that has elongation. It has better crank followability than conventional FRP and Epoquine resin, and there is no leakage of i-products.

Claims (1)

[Scope of Claims] A concrete storage tank constructed by mixing a mixture of a compound having two or more active hydrogen groups and an inorganic powder as a main ingredient and a compound having two or more isocyanate groups as a hardening agent. In the protective coating agent, (1) the compound having two or more active hydrogen groups contains 30% by weight or more of hydroxyl-terminated liquid polybutadiene, and (2) the inorganic powder is silica, aluminum silicate, or silicate. A protective coating agent for concrete storage tanks, characterized in that the main component is magnesium oxide or a mixture thereof.