JPS581697B2 - surface treatment agent - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in surface treatment agents, and particularly to surface treatment agents that are effective as surface conditioners for painting welded parts of steel products.

Paint films on steel products such as ships and onshore steel structures are affected by residual alkaline substances in welding slag near welds.
Because defects such as blisters and rust occur, the following defect prevention measures are taken for the base material for painting of welded parts, but each method has the following drawbacks.

(a) The method of applying a phosphoric acid-based neutralizing agent had poor adhesion to the top coat because the salt produced after neutralization remained.

(b) The method of hiding alkaline substances with an epoxy-based coating agent was insufficient because water penetrated over a long period of time, causing blistering.

(C) The method of applying an acidic coating agent (already applied) is effective, but the long-term storage stability of the coating agent is poor and the effectiveness varies.

The present inventors aimed at the long-term storage stability of (e) above, eliminated the dispersion of the effect, that is, improved the adhesion of the coating agent to the welded part, and As a result of intensive studies aimed at improving rust prevention during outdoor exposure, the following findings were obtained.

That is, when preparing an ethylsilicate condensate, which is a spreading agent for a coating agent, the type of common solvent, amount of catalyst, silica concentration, and reaction temperature that participate in the condensation reaction are determined by the gelation (storage) of the ethylsilicate condensate. It was confirmed that this had a significant effect on stability).

Specifically, it is as follows. (1) Conventional products used ethyl alcohol (2 carbon atoms) as a solvent, but by using alcohols with 3 to 4 carbon atoms (isopropyl alcohol, n-butyl alcohol, isobutyl alcohol), storage is possible. Sex has been extended.

(2) By specifying the catalyst as phosphoric acid and reducing the amount added, the rust prevention ability was improved and the storage life was extended.

(3) Conventional product with silica concentration of 22 to 26% to 18 to 22%
silica precipitation during condensation reaction and storage, gelation that occurred in a short period of time, etc., were eliminated.

(4) The lack of condensation reaction due to the changes in (1) to (3) above can be solved by increasing the temperature during coating agent production and allowing the chemical reaction to proceed sufficiently during coating agent production. Storage stability has improved and adhesion to steel plates has also improved.

The present invention was developed based on the above findings, and consists of ethyl silicate, C3-4 alcohol, water, and phosphoric acid in proportions such that SiO2 in the total amount of the spreading agent is 18-22% by weight. Spreading agent 40~ obtained by condensation reaction of
45% by weight, total amount of pigment or dye and additives 55~
60% by weight of the surface treating agent.

The surface treatment agent of the present invention can be applied to ships, land plants, welded parts of steel structures, and welded parts of steel products.

The spreading agent in the present invention is prepared by mixing alcohol and phosphoric acid, gradually injecting ethyl silicate into the mixture, and even after the mixture becomes transparent, the mixture is slowly heated at a predetermined temperature, usually 40 to 60°C, for a predetermined period of time. The mixture is prepared by continuous stirring.

In this case, as mentioned in (3) above, the ethyl silicate is made of 45 to 40% SiO2 by weight, for example, so that the SiO2 content in the four components is 18 to 22% by weight.
Use 50% by weight.

In addition, water is used for hydrolysis to merize ethyl silicate, but since the presence of excess water causes silica precipitation, when using the above ethyl silicate, 5 to 6 weight It is preferable to use %.

Phosphoric acid is used as a catalyst, and some of this phosphoric acid remains even after the condensation reaction and exhibits an acidic reaction, which helps neutralize the alkali remaining in the welding area and forms a phosphoric acid film on the iron surface that spreads. Helps the adhesion of the agent.

Therefore, if the amount of phosphoric acid added is too small, the effect will be lost, and if it is too large, it will be wasteful, so when the above-mentioned ethyl silicate is used, it is preferably added in an amount of 0.03 to 0.06% by weight.

Furthermore, alcohol is used as a common solvent for ethyl silicate, water, and phosphoric acid, and in order to smoothly dissolve each component, reaction operation, and post-reaction treatment, when using the above ethyl silicate, the alcohol must be 39 to 55% by weight. It is preferable to use %.

Furthermore, the higher the number of C atoms in alcohol, the slower the reactivity.
Although it is desirable from the viewpoint of improving storage stability, the effectiveness as a common solvent is almost at its limit when the number of carbon atoms is 4, so in the present invention, the number of carbon atoms is 3 to 4.

40 to 45% by weight of the spreading agent obtained as described above,
Titanium white, baride, lithobon, precipitated barium sulfate,
Clay, extender pigments such as alumina white, coloring pigments such as carbon black, Bengara, copper phthalocyanine, Prussian blue, etc., dyes, and various other additives, such as paint film anti-sagging agents, improving adhesion with top coats. MIO (Micaceous Iron Oxide)
, mica-like iron oxide), zinc phosphate powder for improving rust prevention, etc., in a content of 55 to 60% by weight, and sufficiently kneaded using a glass bead paint shaker etc., the surface of the present invention can be obtained. A treatment agent is produced.

When the surface treatment agent of the present invention produced as described above is applied as a coating conditioner for welded parts, the ethyl silicate monomer is mixed with phosphoric acid as a catalyst in solvent alcohol during the preparation of the spreader. What reacts with water and hydrolyzes as shown in formula (1) below to become a colloidal ethyl silicate condensate is deposited on the surface of steel structures in the presence of an alkaline substance, which is one of the components of welding slag. It is thought that the fixation occurs due to the reaction mechanism shown in equation (2).

However, R: C2H5 However, Fe: Substrate of the steel structure M1+: Alkali metal M2+: Alkaline earth metal And, the catalyst phosphoric acid in the above formula (1) remains even after the reaction is completed and becomes acidic ( It exhibits a pH of 2 to 3) and causes a neutralization reaction with the alkaline substance in the welding slag, producing salt and water as shown in equation (3) below.

MO+HA→MA+H2O (3) However, M
: Alkali metal or alkali metal In this way, the alkaline substance in the weld is neutralized and hidden, and it adheres to the steel, and the steel surface is further protected by the top coat applied on top of it.

Specific examples of the surface treatment agent of the present invention are given below.

Example 1 Four types of spreading agents were prepared by mixing them in the following proportions.

All percentages shown in the following specific examples represent weight %.

(Spreading agent 1) Ethyl silicate (contains 50% and 40% SiO2)
(20% as SiO2 in the total amount of spreading agent)
) Normal butyl alcohol 45% Water 5% Phosphoric acid (H
3PO4) 0.06% or more of the composition was subjected to a condensation reaction at 50° C. for 5 hours.

(Spreading agent 2) Ethyl silicate (contains 45% and 40% SiO2)
(18% as SiO2 in the total amount of spreading agent)
) Isobutyl alcohol 49.5% water
A composition containing 5.5% phosphoric acid (as H3PO4) 0.06% or more was subjected to a condensation reaction at 45°C for 5 hours.

(Spreading agent 3) Ethyl silicate (contains 55% and 40% SiO2)
(22% as SiO2 in the total amount of spreading agent)
%) Isopropyl alcohol 39% Water 6% Phosphoric acid (as H3PO4) 0.03% or more of the composition was subjected to a condensation reaction at 60°C for 5 hours.

(Spreading agent 4) Ethyl silicate (contains 50% and 40% SiO2) (2% as SiO2 in the total amount of spreading agent)
0%) Isopropyl alcohol 44.5% water
55% phosphoric acid (as H3PO4) 0.05% or more composition at 40°C
The condensation reaction was carried out for a period of time.

After preparing the above four types of spreading agents, they were allowed to stand at room temperature for one day and night, and then the performance of the spreading agents was observed, and the results are shown in Table 1.

From the results in Table 1, spreading agent 2 (the one with the least amount of SiO2)
It can be seen that this product has the best storage stability, which is more than 10 times that of the conventional product.

In addition, the solvent can be changed from conventional ethyl alcohol to carbon number 3 to 4.
It has also become clear that the performance improves as the SiO2 concentration and the amount of catalytic phosphoric acid are lowered than before.

Example 2 Using Spreading Agents 1 and 2 from Example 1, pigments and various additives were blended in the proportions shown below, and thoroughly kneaded in a glass bead paint shaker to produce six types of surface treatment agents.

(Surface treatment agent 1) Spreading agent 2 40% titanium white (powder) [Extender pigment] 56% carbon black (powder) [Coloring pigment] 2% Erosil (trade name of Tegusa AG, West Germany) [Coating 2% film anti-sagging agent] ] (Surface treatment agent 2) Spreading agent 3 45% titanium white (powder) 51% carbon black (powder) 2% talc powder [paint film sagging prevention agent] 2% (Surface treatment agent 3) Spreading agent 2 40% Titanium white (powder) 53% carbon black (powder) 2% MIO*
5%* This is to improve adhesion with top coat paint, and forms minute roughness on the surface coated with surface treatment agent.

Also, MIO is a leafing type particles, which improves water resistance. It is also intended above.

(Surface treatment agent 4) Spreading agent 3 40% titanium white (powder) 45% Bengara (powder) [coloring pigment] 5% MIO
10% (Surface treatment agent 5) Spreading agent 2 45% Titanium white (powder) 48% Carbon black (powder) 2% Zinc phosphate (powder) * 5% *To improve rust prevention, it is used to improve the rust resistance of steel plates. Forms a chemical conversion film on the base surface.

(Surface treatment agent 6) - Spreading agent 3 40% titanium white (powder) 48% carbon black (powder) 2% zinc phosphate (powder)
10% Example A mild steel plate measuring 50 mm wide x 200 mm long x 10 mm thick was sandblasted, and the two test plates were butted vertically and a low hydrogen welding rod (Kobe Steel LB-52) was used. Layered welding was performed.

Five hours after welding, the slag in the welded area was simply removed using a disc sander tool, and the surface treatment agent described in Example 2 was applied with a brush to a dry film thickness of 20 to 30 microns.

After being exposed outdoors for 5 hours, a steel ship oil-based paint, a chlorinated rubber-based paint, and an epoxy-based paint were spray-coated on separate test plates.

After drying indoors for 7 days, it was immersed in a test solution of 3% saline solution at 40°C, and the state of defect occurrence in the coating film was observed and evaluated.

Note that this condition is the most severe for the welded area coating.

In addition, a similar comparative test was conducted for two conventional methods for relative evaluation.

The above results are shown in Table 2.

The paint film near the bead was markedly blistered.

It is presumed that the defects in the coating film of Comparative Example 2 were caused by water penetrating through the coating film of the top coat, dissolving the alkaline substance in the welded area, becoming highly alkaline (pH 11 or higher), and destroying the coating film.

Claims (1)

[Claims] 1 Spreading agent 40 obtained by condensation reaction of ethyl silicate, C3-4 alcohol, water and phosphoric acid in a proportion such that SiO2 is 18 to 22% by weight in the total amount of the spreading agent
~45% by weight plus a total amount of pigments or dyes and additives 5
A surface treatment agent comprising 5 to 60% by weight.