JPS58111861A - Coated lead chromate pigment and its preparation - Google Patents

Abstract

PURPOSE:To prepare lead chromate pigment which is protected against discoloration due to high temp. or chemicals and has improved dispersibility in organic medium, by covering the pigment with a thin film of cured resin consisting of amino compd. HCHO and sulfamic acid. CONSTITUTION:A soln. of precondensate with terminal sulfonic acid group is prepared by interaction of (1) amino compd., (2) formaldehyde used in about 3-6mol per mol of the amino group of (1), (3) sulfamic acid used in 0.05-0.3mol on the same basis and, when necessary, (4) alcohol (e.g. methanol). Lead chromate pigment (e.g. PbCrO4) is dispersed in water and the above soln. of the precondensate is added to it. The precondensate is made to deposit on the surface of the pigment by changing the pH or by adding a heavy metal ion. The deposited film is cured by changing the pH or by heating to produce the pigment covered with cured film of 0.005-0.5mu thickness. USE:Coloring of traffic paint, etc. and plastics.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a lead chromate pigment having improved heat resistance, chemical resistance, and dispersibility in an organic medium, and a method for producing the same.

Lead chromate pigments, such as yellow lead and chrome permillion, have great hiding power, excellent solvent resistance, and vivid hues, and are considered m-based pigments.

It is widely used as a coloring agent for printing inks, synthetic resins, etc., but it is also used as a coloring agent for road paints, synthetic resins, etc. There is a disadvantage that under the conditions of using 69 temperature and vertical temperature, the color discolors strongly, and when inorganic chemicals such as hydrogen sulfide and alkali are used, the color discolors strongly. As a method for solving these drawbacks, a method is known, as typified by, for example, Japanese Patent Publication No. 46-9555, in which the surface of lead chromate pigment particles is implanted with amorphous silica. Although the pigment prepared by this method has excellent heat resistance and chemical resistance, #
& When finely dispersing it in the body, if a dispersion ridge with a large shearing force is used, the coating layer of the group III will be destroyed and its excellent performance cannot be maintained until the end. Also,
Since its surface is inorganic, fine dispersion in an organic medium is more difficult.

As a method to overcome the above-mentioned drawbacks, it has been considered to implant lead chromate pigment particles with organic substances such as various synthetic resins. It was almost impossible to cover the particles with a uniform thin film, and even if it was possible, it would not be possible to obtain excellent heat resistance, chemical resistance, or easy dispersibility. .

As a result of intensive research in order to solve the above-mentioned drawbacks of the prior art, the present inventor has found that the above-mentioned drawbacks of the prior art can be solved by coating lead chromate pigment particles with a specific organic material. Based on this knowledge, the present invention was completed.

That is, one aspect of the present invention is a lead chromate pigment coated with a thin film of a cured resin comprising an amino compound, formaldehyde and sulfuric acid, and a method for producing the pigment.

To explain the present invention in detail, the lead chromate pigment used in the present invention refers to a pigment containing lead chromate (PbCr04) as a component. The indicated #I family.

The lead romate pigment may be in the form of a dry powder, but the most preferable form is a suspension in water or an aqueous paste immediately after production or after aging, which is sufficiently peptized and finely dispersed. It is.

The material to be used in the present invention is an amine compound.

Main raw materials are formaldehyde and sulfuric acid,
Other alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, and phthyl alcohol can also be used. The above amino compounds include melamine,
It is a polyvalent amino compound such as urea, which can react with formaldehyde to form a polymethylol compound. The substrate used in the present invention, which is made of such raw materials, is formed by reacting the necessary components in water, an organic solvent, or a mixture thereof to form an initial condensate. The method for producing this initial condensate is known per se, but in the present invention, the proportions of each component used are different. That is, based on the amino compound used, formaldehyde is used in a proportion of about 3 to 6 moles per mole of amine group of the amino compound, and sulfamic acid is used in a proportion of about 0.05 to 0.3 moles. is preferable. When used in such a ratio, an initial condensate of formaldehyde and an amino compound having a sulfonic acid group at the terminal is formed. At this time, if sulfuric acid is not used or if the amount is below the above range, precipitation or deposition on the surface of the pigment particles will be insufficient, making it impossible to form a thin resin film and causing hil'.
Otherwise, agglomeration of pigment particles occurs and a satisfactory product cannot be obtained.

If too much sulfuric acid is used, precipitation of initial condensates on the surface of the #family particles will be insufficient and the 1L history will be affected by its Wl &
curing is unsatisfactory and a tough protective film cannot be formed.

The coated pigment of the present invention can be prepared by finely dispersing the pigment in an aqueous paste or suspension in water, or by finely dispersing the powdered pigment in water and adjusting the concentration to an appropriate concentration (for example, a concentration of about 2 to 20% by weight).
The aqueous solution of the above-mentioned initial condensate, the organic III agent solution, or the mixed solvent solution is prepared as i1! These solutions are mixed using an appropriate method, and the above-mentioned initial condensate is precipitated or deposited on the surface of the pigment particles by changing the pH or adding heavy metal ions. This is obtained by curing the coating formed by the method. The thickness of the coating on the surface of the material particles can be changed appropriately by changing the raw material ratio of the initial mixture, the ratio of the mixture to the pigment, the method of mixing the two, changes in pH, etc. The thickness of such a cured film is about 0.00000000000000000000000000000000000000000000000000000 0.5 microns, and the weight ratio of the pigment to the coating is about 1-100 parts by weight per 100 parts by weight of the pigment. At thicknesses and weights above this range, it is preferable to
The coloring strength etc. tends to decrease slightly, and if the thickness and weight are less than the above range, sufficient heat resistance, chemical resistance and easy dispersibility cannot be obtained. In coated pigments, the particles are not adhered to each other, and the particle surface is about o, oo
It is coated with a continuous hardened resin film with a thickness of ~0.5 microns, and even when used as a coloring component in road paints, various plastics, or paints, it will not change color under high temperature conditions. Its heat resistance is at least as good as that of conventional silica coatings. Furthermore, its dispersibility in organic media such as paints and plastics is much better than that of conventional pigments), especially in the case of conventional silica-coated pigments under high shear forces. In contrast, the pigment of the present invention satisfactorily solves such drawbacks, whereas the coating of the pigment is destroyed and its performance is lost.

Next, the present invention will be specifically explained with reference to Examples. Note 1
In the first part of the text, Fi- is based on weight.

Example 1 40 parts of melamine, 100 parts of 35% formalin.

Mix and stir 20 parts of methanol and 24 parts of water, and heat to 80°C.
When the temperature was raised to , it dissolved to be colorless and transparent. Next KC bath solution at 45C
2.4 parts of sulfuric acid was added and reacted with 1
The reaction solution was dropped into -tkt-water and the reaction was carried out until the initial condensate was precipitated, and then 20% of sodium hydroxide was added to 5.5% of the solution.
1 part and 20 parts of methanol were added to terminate the reaction.

30 parts of this resin solution is dissolved in 100 parts of water and used as a dropping liquid.

On the other hand, add water to a 6-aqueous paste containing 100 parts of G-colored yellow lead to make a sufficiently peptized dispersion, adjust its pH to 8.5 to 9, and slowly stir this dispersion. At the same time, 130 parts of the above resin bath IQ was added to this solution for 1 hour.

Next, adjust the pH to 5 with acetic acid! ll11!11shi, 90
Stirring was continued for 3 hours at °C to cure the formed film.

Thereafter, it was filtered, washed with water, and dried to obtain 00 parts of the composite lead chromate pigment of the present invention. Analysis of this preparation showed that the weight of coating material was approximately 10 parts per 100 parts by weight of pigment. Further, the state of the particles was observed using an electron microscope, and as shown in FIG. 1, the thickness of the coating was approximately 0.02 microns, and it was found to be a uniform continuous coating.

Example 2 50 parts of an 80% aqueous solution of methylated methylolmelamine resin was diluted and dissolved with 40 parts of a 50% methanol aqueous solution, 2 parts of sulfuric acid was added to the solution, and the mixture was reacted at 45 to 50°C for 20 minutes.

20-4.6 parts of aqueous caustic soda solution was added to neutralize. After cooling, 10 parts of methanol was added to terminate the reaction to obtain a solution of the initial condensate. This solution had a solids content of about 40% and remained clear and dissolved when diluted with water. Thirty parts of the above resin solution was diluted with 100 g of water to prepare a liquid for dropping.

On the other hand, an aqueous paste containing 100 il of chrome vermilion was dissolved and dispersed in 2000 parts of water.

The pH was adjusted to 8.5 to 9, and the above resin solution for dropping was added dropwise to this solution while stirring slowly. After the dropping was completed, the pH of the solution was adjusted to 5, and stirring was continued for 4 hours at 90"cK. conduct,
Filtered, washed with water, dried at 90°C, coated pigment of the present invention 110
I got the department. When this pigment was analyzed, the electrical charge of the material to be tested was approximately 1Os per part of pigment 100] [100% of pigment was placed], and when 11 parts were observed with electron am-, the thickness of the material to be tested was approximately 0.
．． 02 microns, and the aFi coverage was a uniform continuous coating.

Example 3 15 parts of the resin solution obtained in Example 1 and 5 parts of the resin obtained in Example 2
The WIls portion was diluted with 100 s of water to prepare a solution for dropping.

On the other hand, an aqueous paste containing 100 parts of molybdate orange was peptized and dispersed in 20009 water, and the p
While adjusting H to 8.5 to 9 and stirring this dispersion,
The above-mentioned dropping liquid was added dropwise to this dispersion. Dripping completed @
The pH was adjusted to 5, and 20 parts of 511 barium chloride water bath solution was added. Next, the mixture was stirred at 90C for 3 hours, filtered, washed with water, and dried to obtain 110s of pigment A of the present invention. Analysis of this pigment revealed that the weight of the target material was approximately 10 parts per 100 parts of the pigment, and the weight of the target material was approximately 10 parts per 100 parts of the pigment. The average thickness was approximately 0.02 microns.

Example 4 100% 50% methanol/water III solution containing 721,720 parts of methylol and 20 parts of methylated methylolmelamine
and 2 parts of sulfuric acid.

After reacting at 45-50C for 10 minutes, 4.6 parts of 20-caustic soda aqueous solution was added to terminate the reaction. This reaction solution had a solid content of about 40% and remained a clear solution even when diluted with water. 15 parts of this resin solution was diluted with 100 parts of water to prepare a dropping liquid.

On the other hand, add 2 parts of an aqueous paste containing 100 parts of 10G yellow lead.
Peptized and dispersed in 1,000 parts of water, and the pH of the dispersion was adjusted to 8.
．． 579, and while stirring this dispersion liquid, the above-mentioned dropping liquid was added dropwise to this dispersion liquid.After the completion of six drops, the p of the liquid was
After adjusting n to 5 and stirring at 90°C for 3 hours, filtration,
aqueous.

After drying, 110 parts of the coated pigment of the invention were obtained.

When this pigment was analyzed, the weight of the coating material was 100%.
It is about 10 parts by weight, and the thickness of the film is about 0.
, 02 miku σ.

Performance Test Example 1 (Heat Resistance Test) Using the coated pigment of the present invention obtained in the above example, an untreated pigment, and a commercially available 7 Lika mapped lead chromate pigment, polyethylene was colored to a pseudo degree of 5-. A test piece was obtained, and a heat resistance test was conducted using this test piece.
The results shown in Table 1 below were obtained.

Judgment method: □ There is no change in color.

Stitched, color has completely disappeared It was determined by the naked eye as O.

Comparative test force 2 (dispersibility test) 50 parts each of the nine coated pigments of the present invention obtained in the above examples, untreated pigments and commercially available silica-coated lead chromate pigments,
25 parts of linseed oil-modified alkyd varnish (solid content 60s) and 25 parts of solvent were placed in a mayonnaise-type glass pin containing %80m glass beads, and a dispersibility test was conducted using Red Devil's paint conditioner. (JI
Based on SK5400 Paint General Test Method Section 4.5 Tube A Method)
. The results were as shown in Table 2 below.

Table 2 Comparative Test Example 3 (Chemical Resistance and Light Resistance Test) Using the coated pigment of the present invention obtained in the above example, an untreated pigment, and a commercially available silica-coated lead chromate pigment, the following chemical resistance was measured. A durability test and a weather resistance test were conducted, and the results shown in Table 3 below were obtained.

. Alkali resistance・・・・・・・・・311N Otori O
100 mK of H$1 solution 5 f of porcelain pigment was immersed and treated for 1 hour with occasional stirring, then washed with water, filtered, and dried. The treated pigment and the pigment that has not been immersed are made into a paint using lacquer, applied in two coats with an applicator, and the degree of change is judged.

. Resistance to sulfide... River... Make a lacquer into a paint, apply it to a glass plate with an applicator, immerse the coated plate in saturated sulfide water at room temperature for 30 minutes, and compare it with the coated plate before dipping. Determine the degree of change.

0 Weather resistance: Convert it into a lacquer and apply it to an aluminum plate with an applicator. This coated plate was irradiated for 100 hours with a Weather-O-meter vh.

Compare the painted plate before irradiation and determine the degree of change.

””-”Nee! − The judging method is to give a score of 10 if there is no change in one color.

A completely discolored sample was rated as 0.

451

Claims (1)

[Scope of Claims] (υ A lead chromate pigment seeded with a thin film of a cured resin consisting of an amino compound, formaldehyde and 5. sulfuric acid. (2) An amino compound, formaldehyde and 5. sulfuric acid.
1. A method for producing a lead chromate pigment, which comprises precipitating an initial condensate consisting of an amino acid in an aqueous medium to precipitate individual particles of a lead chromate pigment, and then curing the pigment. (2) The lead chromate pigment according to claim 417, wherein a portion of the methylol groups of the initial condensate of an amino compound, formaldehyde, and sulfuric acid are lower alkylated. (4) The manufacturing method according to claim (2), wherein a part of the methylol groups of the initial compound is lower alkylated.