JPH0559149B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a lead chromate pigment with improved anti-scattering properties, light resistance, chemical resistance, especially heat resistance, and a method for producing the same. Lead chromate pigments are mainly composed of lead chromate, and include "primrose yellow" which has an orthorhombic green-yellow color, "medium yellow" which has a wide range of monoclinic yellow to orange color tones, and square. There is "Molybdate Orange" or "Molybdate Red" which has a crystalline orange to red tone, and is an excellent pigment with a clear green-yellow to red hue and a large hiding power, and is used for coloring paints, printing inks, and synthetic resins. It is widely used. The object of the present invention is to provide lead chromate pigments with improved pigment properties suitable for these uses. BACKGROUND OF THE INVENTION However, these lead chromate pigments have inherent drawbacks. That is, when lead chromate pigments come into contact with acids, alkalis, or sulfides in the atmosphere, or are exposed to heat or ultraviolet rays, their inherent color tone changes and discolors. The reason for this is that the former is thought to be caused by the dissolution and/or reaction of lead chromate, which is a so-called chemical resistance problem, whereas the latter is caused by the reduction phenomenon of hexavalent chromium. This is thought to be a problem of so-called heat resistance. In recent years, many modified lead chromate pigments that solve these drawbacks have been proposed and put into practice. For example, there are silica-coated lead chromate pigments that have improved pigment properties by forming a continuous silica film on the surface of lead chromate pigment particles (Japanese Patent Publication No. 46-9555, Japanese Patent Publication No. 46-34788). As a further improvement on this, there is a silica-zirconium double layer lead chromate pigment in which a thin layer of zirconium oxide is interposed between the silica film and the pigment particle surface (Japanese Patent Publication No. 14254/1982). Although these silica-coated lead chromate pigments have significantly improved the various resistances of pigments, they do not have resistance under friction when used, so further improvements to this have been made in Japanese Patent Publication No. 46-42713 and Japanese Patent Application Laid-Open No. 46-42713. 55−
Publication No. 78064, Japanese Patent Application Laid-Open No. 1982-78065, Japanese Patent Application Publication No. 1983
- Alkaline earth metal salts of rosin acids or higher aliphatic acids, organic phosphates, as typified by Publication No. 106962,
There are silica-coated lead chromate pigments surface-treated with a long-chain alkylamine salt, a long-chain quaternary ammonium salt, or a thermoplastic resin. [Problems to be solved by the invention] The modifications of silica-coated lead chromate using organic surface treatment agents that have been proposed so far each have their advantages and disadvantages.
Comprehensive evaluation of untreated silica-coated lead chromate pigments and various resistances shows that no significant improvement is expected, and the current situation is that they must be used by adjusting their characteristics. For example, silica-coated lead chromate treated with lead rosinate or higher fatty acid salts has some improvement in heat resistance, but other resistances tend to deteriorate, and it is not only dust-producing, but also difficult to store. There is a risk of ignition. The present invention was developed with the aim of more comprehensively improving silica-coated lead chromate pigments, and as a result of intensive research aimed at improving the affinity between the silica film and the pigment, it was discovered that the silica-coated lead chromate pigments were brought into close contact with an organosilicon compound. As a result, the present invention was completed based on the discovery that a very stable chromic acid powder pigment that overcomes the drawbacks of the prior art can be obtained. [Means and effects for solving the problems] The gist of the present invention is to provide a substantially continuous amorphous silica film on the surface of a lead chromate pigment, and to apply a silane coupling agent or a silane coupling agent on the film. This is a modified silica-coated lead chromate pigment, characterized in that an organosilicon compound selected from / and silicone oil is sequentially present. The lead chromate pigment in the present invention is a pigment whose main component is lead chromate (PbCrO ₄ ), and has a color index of No. 77600.
Pigments represented by 77601, 77603, and 77605 [Color Index 2nd edition (1956)]. The above-mentioned pigment is a pigment whose main component is lead chromate, which is well known to those skilled in the art, and the history of its production does not matter in the present invention. In addition, in the production of lead chromate pigments, small amounts of metal oxides (defined as including hydrated oxides) are added to improve the efficiency of the stabilization operation of pigment crystal particles or to improve the bonding strength with the silica film. However, the lead chromate pigment in the present invention includes lead chromate pigments on which metal oxides have been deposited, regardless of the purpose. Examples of metal oxides include one or more metal oxides selected from zirconium, aluminum, titanium, cerium, magnesium, antimony, etc. The amount varies depending on the purpose of deposition, but in most cases, the total amount is The amount is 10% or less, preferably in the range of 0.5 to 5% by weight, calculated as anhydride. On the lead chromate pigment according to the present invention, a dense and discontinuous amorphous silica film is formed on the pigment,
Furthermore, an organosilicon compound is present on the coating. The presence of amorphous silica on the pigment can be confirmed by known analytical methods such as chemical analysis, X-ray analysis, and ESCA, and by observation with an electron microscope, it can be confirmed that fine particles form a dense and continuous film. This can be confirmed by depositing and coating the pigment particle surface. In the case of porous silica, it does not form a film, but instead forms an aggregate of free silica, and can be distinguished from a dense and continuous amorphous silica film. In the present invention, "substantially" means that the amount of such silica is small. In the present invention, an organosilicon compound is present in such a silica-coated lead chromate pigment. The organosilicon compound is a silane coupling agent and/or a silicone oil described below, and it may be one or more of these, and its presence may be caused by a dehydration reaction in the case of silane coupling due to the surface treatment described later. This refers to the case where it is present on the silica skin by chemical bonding or, in the case of silicone oil, physical adsorption. The presence of such organosilicon compounds can be easily confirmed by known analytical means such as chemical analysis, IR, and FT-IR. The amount of silica coating on the lead chromate pigment and the amount of organic silicon compound present vary depending on the use, the type of the compound, the manufacturing method, etc., but in most cases are within the ranges described below. Such lead chromate pigments are prepared by adding a silane coupling agent and/or an organosilicon compound selected from silicone oil to a silica-coated lead chromate pigment coated with a substantially continuous amorphous silica film, and then adding water or an organosilicon compound selected from silicone oil. It can be obtained by surface treatment by uniformly mixing and heating in the presence or absence of an organic solvent, or by heating after mixing. A dense, continuous, amorphous silica film may be formed on the lead chromate pigment by any known method. That is, it is carried out by adding or forming an active silica sol to a lead chromate pigment slurry to deposit fine silica particles on the surface of the pigment particles. When depositing silica, it is desirable to have pigment particles as uniformly and sufficiently dispersed as possible, so it is recommended to use sufficient vigorous stirring or shear dispersion using a homogenizer, Waring blender, or colloid mill. . It is also desirable to add a small amount of a dispersant such as sodium hexametaphosphate or sodium silicate. After preparing a uniform pigment slurry, the slurry is heated to a pH of 8 to 11, preferably 9 to 10,
Preferably, the silica sol, in other words "activated silica", is deposited at 80-90°C. The method of depositing "activated silica" is defined in Japanese Patent Publication No. 46-9555, and this method is also followed in the present invention, but in many cases, the reaction is gradually carried out by simultaneously adding an aqueous solution of sodium silicate and sulfuric acid. Preferably, the resulting activated silica is deposited on the surface of the lead chromate pigment particles. After the silica coating treatment for lead chromate pigments, a known flocculant is added to perform solid-liquid separation in order to increase the recovery efficiency of solid-liquid separation.In this case, when aluminum sulfate or aluminum alum is used as the flocculant, Due to hydrolysis, hydrated alumina is further deposited on the silica, so the silica film formed in the present invention contains hydrated oxides such as alumina mixed in from the inorganic flocculant. The amount of silica based on such silica deposition varies depending on the intended use of the pigment, but is generally from 5 to 30%, preferably from 10 to 25%, as SiO ₂ based on the total weight of the finished pigment. The reason for this is that if it is less than 5%, the effect of the silica coating will be insufficient, and if it exceeds 30%, the pigment concentration will decrease. In the present invention, the surface of the silica-coated lead chromate pigment is treated by adding an organosilicon compound to the pigment. This surface treatment varies depending on the type of organosilicon compound used, but is usually prepared by adding an organosilicon compound to an aqueous slurry, overcake, or dry powder of silica-coated lead chromate pigment, along with an organic solvent or emulsifier if necessary. This can be carried out by thoroughly mixing, dehydrating or removing the solvent, and heating at 100 to 150°C. Note that the separation and drying steps can be omitted during the mixing treatment, or when the organic solvent can be removed by natural drying after mixing. The mixing means in the above surface treatment may be uniformly carried out using a desired mixer such as a normal stirrer, homogenizer, colloid mill, homomixer, screw mixer, V-rigid mixer, or Henschel mixer. In such surface treatment, the organosilicon compound that can be used in the present invention improves the affinity between the silica film and the lead chromate pigment, or if the addition and use of the compound can be expected to improve the pigment properties,
Examples include, but are not limited to, the following compounds. Typical silane coupling agents include methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, vinyltrichlorosilane, γ-chloropropyltrimethoxysilane, γ
-chloropropylmethyldimethoxysilane, γ-
(2-aminoethyl)aminopropyltrimethoxysilane, γ-(2-aminoethyl)aminopropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, N-β-(N-
vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, vinyltriacetoxysilane, hexamethyldimethoxysilane, Silazane, vinyltris(methoxyethoxy)silane, vinyltrimethoxysilane, vinyltriethoxysilane, γ
-mercaptopropylmethyldimethoxysilane,
γ-anilinopropyltrimethoxysilane, etc.
Examples of silicone oils include dimethylpolysiloxane, methylphenylpolysiloxane, and methylhydrogenpolysiloxane. or,
Epoxy modified products, alkyl modified products, amino modified products, carboxyl modified products of silicone oil,
Examples include alcohol-modified products, fluorine-modified products, alkylaralkyl polyether-modified products, epoxy polyether-modified products, polyether-modified products, and modified or unmodified silicone resins. Note that two or more of the above compounds can be used in combination as necessary. Further, the amount of the above compound used is suitably in the range of 1 to 40%, preferably 1 to 30%, based on the total weight of the finished pigment. The reason for this is that if it is less than 1%, the modification effect of the silica-coated lead chromate pigment is insufficient, and if it exceeds 40%, no modification effect can be expected for the amount used. [Example] Hereinafter, the present invention will be described in more detail with reference to Examples, where all parts represent parts by weight. Example 1 2500 parts of lead chromate pigment (CI-No.77600) and water
JIS No. 3 sodium silicate (SiO ₂ = 29% by weight, molar ratio SiO ₂ /Na ₂ O =
3.2) After adding 142 parts, stir and disperse uniformly at room temperature. If desired, this pigment dispersion slurry is subjected to a dispersion treatment using a shearing machine such as a homogenizer (Harrell Homogenizer No. L manufactured by Kokusan Seiko Co., Ltd.). Next, maintain the temperature of this slurry at 95℃ and add sodium hydroxide aqueous solution as necessary to adjust the pH.
=9.0~10.0. _Next , 10,000 parts of a 5.5% by weight sodium silicate aqueous solution (liquid A) and 12,000 parts of a 2.25% by weight sulfuric acid aqueous solution (liquid B) were simultaneously added to the stirred slurry for about 3 hours. Added. A
The slurry temperature remains at 95 degrees while adding liquid and B liquid.
Maintain the temperature at ℃ and control the pH to 9.0 to 10.0.
After performing the silica coating treatment in this manner, in order to efficiently recover the treated product, 2000 parts of an 8.3% by weight aqueous aluminum sulfate solution is added, and the pH is adjusted to 6.4 with an aqueous sodium hydroxide solution. The mixture was then washed with water, filtered and dried in a conventional manner, and pulverized to obtain about 3,200 parts of a silica-coated lead chromate pigment. Next, the obtained silica-coated lead chromate pigment
2,500 parts of γ-methacryloxypropyltrimethoxysilane and 50 parts of methylhydrogenpolysiloxane (alcohol-modified product) dissolved in xylene. 10 at FM10B]
Mixed for a minute. The temperature inside the mixer at this time is
It was 90 degrees Celsius. After mixing, the solvent was completely removed by air drying to obtain a modified silica-coated lead chromate pigment. In the resulting modified silica-coated lead chromate pigment composition, the lead chromate pigment was identified by X-ray diffraction, and chemical analysis and transmission electron microscopy (100,000x magnification) revealed that it was dense and had no continuity. It was observed that a shaped silica film was coated on the surface of the lead chromate pigment particles. Furthermore, the presence of the organosilicon compound was confirmed by chemical analysis, IR, and FT-IR. below,
For the pigments of each example, the coverage of amorphous silica and the presence of organosilicon compounds were confirmed by the same analysis procedure as in Example 1. I was able to confirm. Example 2 250 parts of an organosilicon compound [polyether-modified silicone oil: SH3746 manufactured by Toray Silicone Co., Ltd.] was slowly added to an aqueous slurry containing 2500 parts of a pigment coated with silica in the same manner as in Example 1. Stir and mix thoroughly to ensure close contact.
Next, a modified silica-coated lead chromate pigment was obtained through filtering, drying (130°C), and pulverization steps. Example 3 Sodium dichromate (Na ₂ Cr ₂ O ₇・2H ₂ O)
A sodium chromate aqueous solution of 1,268 parts and 361 parts of sodium hydroxide dissolved in water to make a total volume of 20,000 parts was mixed with a 14.84% by weight lead nitrate aqueous solution of 20,000 parts at a temperature of 50°C.
Gradually add and react for about 30 minutes while stirring. Furthermore, after continuing stirring for 30 minutes, _ZrO2
Gradually add 37.6 parts of a dilute aqueous solution of zirconium sulfate, followed by an aqueous sodium carbonate solution.
Adjust to PH=6.4. Furthermore, wash with water using the usual method.
The mixture was filtered, dried and ground to obtain a zirconium oxide-coated lead chromate pigment. Subsequently, 2,500 parts of this zirconium oxide-coated lead chromate pigment was coated with silica in the same manner as in Example 1 to obtain a silica-coated lead chromate pigment containing zirconium oxide. Next, 2500 parts of this pigment, 200 parts of γ-(2-aminoethyl)aminopropylmethyldimethoxysilane, and 50 parts of a silicone resin liquid with a nonvolatile content of 5% by weight [SR2410: manufactured by Toray Silicone Co., Ltd.] were mixed together. A modified silica-coated lead chromate pigment was obtained by performing a close contact treatment in a shell mixer for 10 minutes and then air drying. Examples 4 to 8 Example 3 except that the intervening oxide and the organosilicon compound diluted with a solvent were used as shown in Table 1 below.
Each modified silica-coated lead chromate pigment was obtained in exactly the same manner as above.

[Table] Example 9 Primrose color lead chromate pigment (CI-No.
77603) 2500 parts were used in the same manner as in Example 1 to obtain a silica-coated primrose color lead chromate pigment. Next, 100 parts of this pulverized prepared pigment was added to 500 parts of a 5% by weight diluted solution of dimethylpolysiloxane emulsion (SM8701, manufactured by Toray Silicone Co., Ltd.), and the mixture was stirred and mixed at a temperature of 45° C. for 30 minutes. Next, the slurry was separated and dried at 110°C for 3 hours to obtain a modified silica-coated lead chromate pigment. Example 10 Molybdate orange (chrome vermilion,
A silica-coated molybdate orange pigment was obtained by the same silica treatment procedure as in Example 1 using CI-No. 77605). Then, this ground and prepared pigment
2500 parts, 150 parts of γ-mercaptopropyltrimethoxysilane and 150 parts of alcohol-modified silicone oil were intimately mixed with a small amount of organic solvent for 10 minutes in a Henschel mixer. After mixing, a modified silica coated molybdate orange pigment was obtained. Comparative Examples 1 to 9 The treatments with organosilicon compounds in Examples 1 and 3 to 10 were carried out in the same manner as in the previous example except that the treatments with organosilicon compounds in Examples 1 and 3 to 10 were not performed. Each uncoated silica-coated lead chromate pigment was prepared. Comparative Example 10 Based on the method of Example 1 of Japanese Patent Publication No. 46-42713, a rosin-treated silica-coated lead chromate pigment was obtained as follows. Lead chromate pigment (CI-No.
77600) and 1000 parts of water are stirred at room temperature until homogeneous. Next, add 16.7 parts of JIS No. 3 sodium silicate solution to this while stirring. Pass this slurry through a homogenizer to disperse the pigment, then heat the slurry to a temperature of 90 to 95.
℃ and adjust the pH to 9.0-9.5 by adding sodium hydroxide if necessary. Next, add 96 parts of JIS No. 3 sodium silicate solution to water.
a solution diluted with water to a volume equivalent to 500 parts;
670 parts of water containing 14.4 parts of sulfuric acid (96%) are simultaneously added into the above prepared slurry at a constant rate of about 3 parts per minute. After the addition is complete, continue stirring for an additional 15 minutes to adjust the pH of the sodium hydroxide aqueous solution to 8.0-9.0. Meanwhile, water containing 4.5 parts of sodium hydroxide 300
A transparent rosin solution containing 33.3 parts of hydrogenated rosin (Harima Kasei Kogyo Co., Ltd., Harimaku After stirring for about 15 minutes, an aqueous solution of 100 parts of water and 15.9 parts of calcium chloride is added over 15 minutes to precipitate the rosinate salt. This product was washed with water, filtered, dried, and ground in a conventional manner to obtain a calcium rosin treated silica-coated lead chromate pigment. Performance tests of the Example products and Comparative Example products obtained as described above were evaluated in the following manner, and the results are shown in Table-2. 1 Heat resistance (1-1) Test and preparation of test piece 500 parts of high-density polyethylene resin [Mitsui Petrochemical Industries, Ltd., Hi-Zex 2100J] and sample
Color chips for testing are prepared from a mixture of 2.5 parts and 165° C. using an extruder (30 m/mφ extruder manufactured by Thermo Plastik Industries Co., Ltd.). Next, the color chips are molded using a screw-type injection molding machine [manufactured by Yamashiro Seiki Seisakusho Co., Ltd.].
SAV-30-A type] at a temperature of 200℃
Injection mold with a 24 second cycle time to create standard test panels. Below 280℃ and
Test panels are prepared in the same manner as standard panels, except that they are allowed to stay at each temperature of 320°C for 5 minutes. (1-2) Evaluation method The test pieces of molded panels obtained at molding temperatures of 200°C, 280°C, and 320°C were evaluated visually and with a color difference meter, with the molded panel at a temperature of 200°C as a standard product. A change in hue is determined by comparison.
In addition, the result is "10" if there is no change in color.
It is expressed in a scoring system with a complete discoloration being given a score of "1". 2 Light resistance (2-1) Preparation of test piece 2.0 parts of the sample and 1.0 part of castor oil were placed in a Hoover type muller (manufactured by Tester Sangyo Co., Ltd.) at a load of 67.5 kg.
(150 pounds) and knead twice at 100 revolutions to form a uniform paste. this paste
2.5 parts and melamine alkyd resin [NOF
Mix well with 6.0 parts of Nitsusan Melami No. 1 and 2 type clear manufactured by Co., Ltd. to form a paint. Next, apply it evenly to the aluminum foil with a 6 mil applicator and leave it for 60 minutes.
Create a test piece by baking for 60 minutes in a hot air constant temperature dryer set at 130℃. (2-2) Test and evaluation method The test piece was tested using a fade meter [Suga Test Instruments Co., Ltd.]
FA-2 model, light source: carbon arc lamp] for 500 hours. For this exposed test piece, a visual and color difference meter [manufactured by Nippon Denshoku Kogyo Co., Ltd., model ND-504DE]
Changes in hue are determined using a scoring system in which no change in color is given a score of "10", and cases where the color has completely changed are given a score of "1". 3 Dust scattering rate 100 parts of the sample powder was placed in a 300 ml beaker, a Gakken dust measuring device was set at a height of 15 mm above the beaker, and a magnetic stirrer was used using a bar-shaped stirrer with a length of 40 mm and a diameter of 7 mm. The sample is stirred in the apparatus at a speed of 60 revolutions per minute. The dust measuring device suctions at an air flow rate of 30 per minute for 5 minutes to cause the dust generated by stirring the sample to adhere to the inside of the measuring device. The weight of the attached dust was measured, and the rate was expressed as a percentage as the dust generation rate. 4. Acid resistance (4-1) Preparation of test piece Prepare a test piece using the same procedure as for preparing the test piece used for the light resistance test, except for replacing the aluminum foil with a glass plate. (4-2) Test and evaluation method Immerse each test piece in concentrated salt (12N) at 20℃ for 15 minutes. The changes in hue of the test pieces subjected to the immersion test are determined visually and with a color difference meter, and are expressed in a scoring system, with no change in color being rated "10" and those completely discolored being rated "1".

〔Effect of the invention〕

The modified silica-coated lead chromate pigment of the present invention is surface-treated with an organosilicon compound, but has better resistance to friction than conventional silica-coated lead chromate pigments or their rosin-treated products. It is excellent and improves pigment resistance overall. Furthermore, although this is an unexpected and interesting effect, the effect of preventing the product powder from scattering is also significantly improved, which can be said to be of great practicality. This superior effect is probably due to the fact that a tighter silica film is imparted to the pigment particles by the reaction between the silica film and the organosilicon compound, or that a more stable film is formed on the silica film by the formation of an organosilicon polymer. It is understood that this is due to the formation of

Claims (1)

[Claims] 1. A substantially continuous amorphous silica film on the surface of a lead chromate pigment, and an organosilicon compound selected from a silane coupling agent and/or a silicone oil sequentially present on the film. A modified silica-coated lead chromate pigment characterized by: 2 Lead chromate pigments are CI-77600, CI-77601,
The modified silica-coated lead chromate pigment according to claim 1, which is one or more selected from CI-77603 or CI-77605 lead chromate pigments. 3. The lead chromate pigment according to claim 1 or 2, in which one or more hydrated oxides selected from magnesium, cerium, aluminum, titanium, zirconium, or antimony is deposited. Modified silica coated lead chromate pigment. 4 Based on the total weight of lead chromate pigment, metal hydrated oxide is 0 to 5% (anhydrous equivalent), amorphous silica is
5-30% as _SiO2 and 1% as organosilicon compound
A modified silica-coated lead chromate pigment according to claim 1 comprising a proportion of .about.40%. 5 A silane coupling agent or/and an organosilicon compound selected from silicone oil is added to a silica-coated lead chromate pigment coated with a substantially continuous amorphous silica film, and the presence or absence of water or an organic solvent is added. 1. A method for producing a modified silica-coated lead chromate pigment, which comprises uniformly mixing the pigment in the presence of silica and heating it, or surface-treating it by heating after mixing. 6. The method for producing a modified silica-coated lead chromate pigment according to claim 5, wherein the mixing is carried out using a Henschel mixer.