JPS6225708B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing surface-treated spherical barium sulfate, and more specifically, it has excellent resin affinity,
Therefore, the present invention relates to a method for producing surface-treated spherical barium sulfate having pigment properties equivalent to or better than titanium oxide except for hiding power. Barium sulfate is generally produced by an aqueous reaction in which an aqueous solution of a barium salt such as barium chloride, barium sulfide, or barium nitrate is reacted with an aqueous solution of sulfate or sulfuric acid, and such barium sulfate usually has primary particles of 0.3 to 2.0. It is a spherical particle of about μ,
After filtration and washing with water, the resulting wet cake is dried and pulverized to be used as a product for various purposes. Conventionally, barium sulfate is generally used in resin molded products such as sheets, films, containers, industrial parts, and decorative items.
Barium sulfate is used as an extender pigment in various fields such as the production of paints and inks, but it is originally used as an extender pigment that takes advantage of the chemical and physical stability of barium sulfate. For this reason, various restrictions have hitherto been imposed on its use. For example, as mentioned above, the primary particle size of barium sulfate is usually 0.3 to 2.0μ, but
During drying and pulverization, primary particles agglomerate,
When used as a product, barium sulfate will contain tens of percent of particles larger than 2μ, and barium sulfate with such a particle size distribution will reduce the gloss of the paint film, so it needs to have clear gloss. Not suitable for use in paints. In addition, since the barium sulfate particle surface is inert as mentioned above, it has poor affinity with some resins, and when used in paints containing such resins, barium sulfate aggregates and the paint viscosity decreases. It becomes expensive and the necessary paint performance cannot be obtained. On the other hand, in the paint industry, titanium oxide has traditionally been widely used as a pigment to give strength to paint films, but titanium oxide is expensive, so there has been a desire to develop pigments to replace it. There is. As a result of intensive research in order to solve the various problems mentioned above, the present inventors have determined that by depositing water and liquefied liquid on the inert surface of barium sulfate particles and modifying the surface, it is possible to improve the relationship between resin and barium sulfate particles. Barium sulfate with excellent affinity can be obtained, and the barium sulfate thus obtained has pigment properties equivalent to or better than titanium oxide, except for hiding power. In the field where titanium oxide was previously used, the inventors discovered that titanium oxide could be used as a substitute, leading to the present invention. Therefore, the present invention provides surface-treated barium sulfate that has excellent resin affinity and can form a coating film with good physical properties such as strength, hardness, and brightness when used in paints. The purpose is to provide a manufacturing method. The method for producing surface-treated barium sulfate according to the present invention comprises barium ion-containing particles having an average diameter of 0.1.
An aqueous alkali silicate solution is added to an aqueous slurry of ~0.5μ of barium sulfate to form barium silicate on the surface of the barium sulfate, and then mineral acid is added to the slurry to decompose the barium silicate into hydrated silica and sulfuric acid. It is characterized by being deposited on barium surfaces. The barium sulfate used in the present invention needs to have an average particle size in the range of 0.1 to 0.5 μ. If the average particle size is smaller than 0.1μ, even if the surface is treated according to the present invention, the cohesive force between the particles is usually strong, and for example, the dispersibility in paint is poor.
The coating film becomes inferior in gloss. On the other hand, if the particle size is larger than 0.5μ, the coating film gloss will not be sufficient when added to a paint. Barium sulfate having the average particle size as described above, for example, preferably has a concentration of 0.3 to 1.2 mol/
, a barium sulfide aqueous solution at a temperature of 30 to 70℃, and a concentration of
0.5 to 5 mol/sulfuric acid aqueous solution at a temperature of 20 to 70°C is continuously introduced into the reaction tank, so that the excess amount of barium ions in the reaction solution is 0.01 to 0.1 mol/.
It is produced by controlling the amount of the raw material aqueous solution fed into the reaction tank. The factor that has the greatest effect on the particle size of the barium sulfate produced is the excess amount of barium ions in the reaction tank. When the excess amount of barium ions in the reaction tank is less than 0.01 mol/mol, it is observed that particles close to a plate shape are produced and the particle size tends to become large. On the other hand, when the excess amount is greater than 0.1 mol/mol, it is not preferable in industrial implementation because it increases production costs. The excess amount of barium ions is usually supplied by barium sulfide as described above, but it is also possible to supply the excess amount by coexisting a water-soluble salt such as barium chloride or barium nitrate with barium sulfide. good. The concentration and temperature of the barium sulfide and sulfuric acid aqueous solutions used also affect the particle size of the barium sulfate produced; generally, the higher the concentration, the smaller the particle size, and the lower the concentration, the larger the particle size. Furthermore, the higher the reaction temperature, the larger the particle size. Therefore, the reaction temperature is appropriately selected depending on the concentration and temperature of the barium sulfide and sulfuric acid aqueous solution used, but usually 30
A range of ~70°C is preferred. Furthermore, the longer the residence time in the reaction tank, the larger the particle size of the barium sulfate produced, so it is usually preferably 10 minutes or less. However, depending on the concentration of barium sulfide or sulfuric acid aqueous solution, reaction temperature, etc., the residence time can be made longer. In the method of the present invention, it is convenient in terms of operation to treat the aqueous slurry in which barium sulfate is produced by the aqueous reaction between barium sulfide and an aqueous sulfuric acid solution with an alkali silicate as described above. Therefore,
In this case, the excess amount of barium ions in the water slurry containing barium sulfate is
It is 0.01 to 0.1 mol/. However, in the present invention, barium sulfate that has been powdered in advance is made into a water slurry, and water-soluble barium salts such as barium sulfide, barium chloride, barium nitrate, etc. are added thereto and dissolved, and sulfuric acid containing barium ions is prepared. It is also possible to prepare a slurry of barium in water and treat it with an alkali silicate. Also in this case, the amount of barium ions in the water slurry is preferably adjusted to a range of 0.01 to 0.1 mol/mole as described above. When the amount of barium ions is too small, the generation of barium silicate on the surface of barium sulfate due to the reaction between alkali silicate and barium ions will be insufficient, and the subsequent hydrolysis of barium silicate by mineral acid will be insufficient. No significant amount of hydrated silica is deposited on the barium sulfate surface. On the other hand, when the amount of barium ions is too large, it is uneconomical and a large amount of barium sulfate is newly generated, resulting in poor filterability of the barium sulfate obtained as a whole, and dispersion in the resin system. It is not desirable because it makes you feel inferior in sex. Further, the concentration of barium sulfate in the aqueous slurry of barium sulfate is preferably 0.2 to 1 mole, but is not limited to this. This concentration is determined by the concentration of the raw barium sulfide and sulfuric acid aqueous solution when using a slurry resulting from an aqueous reaction between barium sulfide and sulfuric acid, but even when the water slurry is prepared separately, if the concentration is too low, the treatment If the amount of liquid is too large, it will take time and effort to process, and if the amount is too large, the viscosity of the water slurry will become too high, resulting in poor processability, which is not preferable. In the method of the present invention, an alkali silicate is added to an aqueous slurry of barium sulfate as described above, and is reacted with excess barium ions in the aqueous slurry under alkaline conditions to generate barium silicate, which is deposited on the surface of barium sulfate. let In order to stably produce barium silicate, it is desirable that the pH is at least 9. As the alkali silicate, specifically, sodium silicate, potassium silicate, etc. are preferably used. The amount of alkali silicate added to the aqueous slurry of barium sulfate is determined relative to the barium sulfate in order to uniformly deposit barium silicate on the barium sulfate surface by reaction with the barium ions present in the slurry. The amount is 0.1 to 10% by weight, preferably 0.5 to 5% by weight in terms of SiO ₂ . If the amount of alkali silicate is too small, it will not be deposited uniformly on the surface of barium sulfate, and if it is too large, the hydrolyzed hydrated silica will cause the barium sulfate to aggregate.
When the barium sulfate thus obtained is used in a paint, it is not preferable because the resulting paint film will have poor dispersibility and gloss. Next, mineral acid is added to hydrolyze the barium silicate deposited on the barium sulfate surface, and the barium silicate is deposited as hydrous silica (SiC ₂ .nH ₂ O) on the barium sulfate surface. As the mineral acid, those that do not produce water-insoluble barium salts even if barium ions are still present in the slurry, such as hydrochloric acid and nitric acid, are preferable.
Sulfuric acid can also be used if necessary. Since this hydrolysis reaction occurs sufficiently at a pH of 7 or less, the pH of the water slurry is usually adjusted to a range of 2 to 7, but preferably the pH of the resulting barium sulfate pigment is
In order to make it 7±1, its PH is set to 6±1.
The temperature of this barium silicate hydrolysis reaction is not particularly limited, but is usually 40°C or higher, preferably 60°C or higher.
~90℃. The surface-treated barium sulfate obtained in the above manner has excellent resin affinity, so when it is used as a pigment in the production of paints, inks, resin molded products, etc., it improves physical properties such as strength, hardness, and gloss. According to the present invention, an excellent resin product is provided.
Such surface-treated barium sulfate can be further treated with a silane coupling agent, or by depositing hydrated oxides of metals such as aluminum, titanium, zirconium, and bad lead, to further increase the affinity of barium sulfate to resins. . That is, another method for producing surface-treated barium sulfate according to the present invention is to add an alkaline silicate aqueous solution to an aqueous slurry of barium sulfate containing barium ions and having an average particle size of 0.1 to 0.5 μm to coat the surface of the barium sulfate with barium silicate. is produced, then a mineral acid is added to the slurry, the barium silicate is decomposed into hydrous silica and deposited on the barium sulfate surface, and the barium sulfate thus obtained is treated with a silane coupling agent. . When treating barium sulfate on which hydrated silica has been deposited with a silane coupling agent, the silane coupling agent may be added to and mixed with an aqueous slurry of barium sulfate, or the barium sulfate on which hydrated silica has been deposited may be filtered, washed with water, After drying, it may be mixed with a silane coupling agent, but from the viewpoint of workability, after depositing hydrated silica on barium sulfate in an aqueous slurry as described above, adding a silane coupling agent to this aqueous slurry. It is preferable to add. In any case, the amount of silane coupling agent added is 0.01 to 2% by weight relative to barium sulfate.
Preferably it is 0.05 to 1% by weight. Various types _of silane coupling agents are already known, and they usually have the following general formula: , a mercapto group, an organic group containing a halogen, etc., and R represents an alkyl group.) Preferred specific examples include vinyltrimethoxysilane, γ-anilinopropyltrimethoxysilane, methyltrimethoxysilane, etc. Examples include silane, γ-methacryloxypropyltrimethoxysilane, and γ-glycidoxytrimethoxysilane. Even if barium sulfate is treated as it is with a silane coupling agent, the surface of the barium sulfate particles is inactive, so the silane coupling agent will not be deposited on the barium sulfate. However, according to the present invention, hydrated silica is pre-deposited. Since the silane coupling agent reacts with the hydroxyl group of the hydrous silica and is bonded to the barium sulfate particle surface, the barium sulfate thus obtained has an excellent affinity for the resin. It comes to have. Furthermore, another method for producing surface-treated barium sulfate according to the present invention is to add an alkaline silicate aqueous solution to an aqueous slurry of barium sulfate containing barium ions and having an average particle diameter of 0.1 to 0.5 μm to coat the surface of the barium sulfate with silicic acid. After producing barium and then adding mineral acid to the slurry to decompose the barium silicate into hydrous silica and depositing it on the barium sulfate surface, and adding an aqueous solution of a water-soluble metal compound to the thus obtained slurry of barium sulfate. , it is also characterized in that a hydrous oxide of the metal is deposited on the surface of barium sulfate by neutralizing with an alkali or acid depending on the metal compound. In this method, it is preferred to deposit hydrated silica on barium sulfate in an aqueous slurry of barium sulfate, as described above, and then subsequently treat this slurry, but once the silica-deposited barium sulfate is filtered. After washing with water, drying, and pulverizing, the slurry can be processed again. The amount of silica-deposited barium sulfate in the water slurry is not particularly limited, but is usually 0.2 to 1 mol/,
Preferably it is in the range of 0.4 to 0.8 mol/. In addition, in order to uniformly deposit the hydrated oxide on the barium sulfate, the amount of the water-soluble metal compound added to this water slurry is 0.2 to 10% by weight in terms of the metal oxide relative to the barium sulfate. % is preferred, particularly 0.5 to 5% by weight. The alkali or acid for decomposing the above-mentioned water-soluble metal compound is not particularly limited, but usually sodium hydroxide, potassium hydroxide, ammonia, etc. are used as the alkali, and hydrochloric acid, nitric acid, etc. are used as the acid. The amount is sufficient for the water-soluble metal compound to form a hydrous oxide, and is usually added so that the pH of the water slurry is 7±1. Further, the temperature of this hydrolysis reaction is not particularly limited, but is usually 40°C or higher, preferably 60 to 90°C. In the present invention, the water-soluble metal compound is not particularly limited as long as it can form a hydrous oxide with an alkali or acid after being added as an aqueous solution to the silica-deposited barium sulfate slurry, and includes the above-mentioned aluminum, titanium, zirconium, It will be clear that in addition to zinc, various metal compounds can be used. For example, to form hydrated alumina,
Sodium aluminate is preferably used as the water-soluble aluminum compound. Further, in order to deposit hydrous titanium oxide, for example, titanyl sulfate can be suitably used. According to the present invention, this reaction can also be carried out at a higher temperature and under pressure, and in this case, a hydrated metal oxide such as hydrated alumina can be more stably deposited on the surface of barium sulfate. When using an aqueous slurry of barium sulfate that has not been treated with silica, barium sulfate has almost no affinity for these metal oxides, so the hydrated oxides do not precipitate on the barium sulfate and can stand alone. Barium sulfate does not undergo any surface treatment as it precipitates. However, according to the method of the present invention, the hydrated metal oxide is uniformly and strongly deposited on the barium sulfate surface, which is thought to be because the hydrated silica deposited on the barium sulfate surface forms a bond with the hydrated metal oxide. , barium sulfate with extremely good resin affinity is obtained. Furthermore, barium sulfate treated in this manner has excellent subsequent workability such as filterability. As mentioned above, barium sulfate on which silica is deposited, barium sulfate on which barium sulfate is further treated with a silane coupling agent, or barium sulfate on which a hydrous metal oxide such as hydrous alumina is deposited can be filtered by the usual method. , washed with water, dried, and then crushed to be used as a product. However, for applications such as water-soluble resin paints, inks, and coated papers,
The wet cake after filtration and washing with water can be used as it is. As described above, the surface-treated barium sulfate obtained by the present invention has extremely good affinity for resins, so when used in paints, etc., it forms a coating film with excellent mechanical strength and gloss, and , has pigment properties equivalent to or better than titanium oxide, which was used to obtain coating film strength, etc., and thus,
It can replace conventional titanium oxide. The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples in any way. In the following, parts and % indicate parts by weight and % by weight, respectively. Example 1 (a) Production of surface-treated barium sulfate A barium sulfide aqueous solution with a concentration of 0.74 mol/hour and a temperature of 48°C and a sulfuric acid aqueous solution with a concentration of 1.28 mol/hour and a temperature of 25°C were mixed into a sulfuric acid aqueous solution of 900/hour and a barium sulfide aqueous solution of 1,600 mol/hour. The barium sulfide aqueous solution was continuously supplied at a flow rate of ~1800/hour to a reaction tank with a capacity of 250 and equipped with a stirrer, and the temperature was adjusted while adjusting the flow rate of the barium sulfide aqueous solution so that the excess barium ion in the reaction solution was 0.03 mol/hour. 52
℃ and an average residence time of 6 minutes. The average particle size of the barium sulfate thus obtained was approximately
It was 0.2μ. This water slurry of barium sulfate was divided into four equal parts, and the first water slurry was filtered and washed with water using a filter press, dried, and then pulverized using a fluid energy mill. The barium sulfate thus obtained is referred to as comparative barium sulfate. The second slurry is made by heating it to 70℃ and making a 30%
After adjusting the pH to 10 by adding caustic soda aqueous solution,
An aqueous sodium silicate solution of 100 g/in terms of SiO ₂ was added to barium sulfate in an amount of 1.0% in terms of SiO ₂ . After stirring for 10 minutes, adjust the pH with approximately 10% hydrochloric acid aqueous solution.
6.0 and aged for 30 minutes to deposit hydrated silica on barium sulfate, followed by filtering, washing with water, drying, and pulverization in the same manner as the comparative barium sulfate, to obtain barium sulfate 1, a product of the present invention. . The third water slurry was treated in the same manner as in the production of the above-mentioned product of the present invention, including aging, and then a 30% caustic soda aqueous solution was added to adjust the pH to 7.
To this slurry, γ-methacryloxypropyltrimethoxysilane was added in an amount of 0.5% based on barium sulfate, and the slurry was further aged for 30 minutes. Thereafter, the product was filtered, washed with water, dried, and pulverized in the same manner as above to obtain barium sulfate 2, a product of the present invention. The fourth water slurry was made by adding 2.0% sodium aluminate in terms of A1 ₂ O ₃ to barium sulfate to a pH 6.0 water slurry in which hydrated silica was deposited in the same manner as the barium sulfate product of the present invention. After the addition, the pH was adjusted to 7.0 with about 10% aqueous hydrochloric acid to deposit hydrated alumina on the barium sulfate. Thereafter, the product was filtered, washed with water, dried, and pulverized to obtain barium sulfate 3, a product of the present invention. (b) Preparation of paint and evaluation of physical properties of paint film Polyester resin (M- manufactured by Dainippon Chemical Co., Ltd.)
6003)/Melamine resin (manufactured by Dainippon Chemical Co., Ltd. J-
Solvetsuso #150/n-butanol/butyl cellosolve (weight ratio 70/20/10) was added to a resin mixture of 820) (solid content ratio 85/15) to prepare a resin solution with a resin solid content of 50% by weight. Regarding 100 parts of this solution, as shown in the table, the average particle diameter of barium sulfate 1, 2, 3 of the present invention, barium sulfate of the comparison product, or silica-alumina treated
A paint was prepared by adding and mixing 0.3 μm of commercially available titanium oxide with carbon black. This paint was adjusted to a spray viscosity and a dry film thickness of 30μ was applied to a zinc phosphate-treated mild steel plate with dimensions of 70 x 150 x 0.6 mm.

[Table] The polyester paint film was formed by spray painting and baking at 160°C for 30 minutes. Mechanical strength of this coating JIS Z 2247 (A method)
Erichsen test and JIS K 5400-6.13
(Method B). Also,
Pencil strength was measured using the method according to JIS K 5400-6.14.
Furthermore, changes in gloss were examined at 20°-20° specular gloss. The results are also shown in the table. In the table, paints 1, 2, and 3 are paints containing surface-treated barium sulfate as a pigment obtained by the method of the present invention, paint 4 is a comparison paint containing barium sulfate that has not been surface-treated, and paint 5 is a paint containing barium sulfate as a pigment.
is a commercially available paint containing titanium oxide. All of the paints containing barium sulfate according to the present invention have gloss, strength, and hardness that are almost equal to or higher than those of paints containing titanium oxide, whereas the comparative paints containing barium sulfate have the above-mentioned physical properties. It is clear that they are inferior in both respects.

Claims (1)

[Claims] 1. Spherical barium sulfate having an average particle diameter of 0.1 to 0.5 μm is produced by an aqueous reaction in which an aqueous barium sulfide solution and an aqueous sulfuric acid solution are reacted in the presence of an excess amount of barium ions, and the barium ions An aqueous alkali silicate solution is added to an aqueous slurry of spherical barium sulfate containing spherical barium sulfate to generate barium silicate on the surface of the spherical barium sulfate, and then mineral acid is added to the slurry to decompose the barium silicate into hydrated silica. A method for producing surface-treated spherical barium sulfate, which comprises depositing it on the surface of spherical barium sulfate. 2 Spherical barium sulfate having an average particle size of 0.1 to 0.5 μm is produced by an aqueous reaction in which a barium sulfide aqueous solution and a sulfuric acid aqueous solution are reacted in the presence of an excess amount of barium ions, and spherical barium sulfate containing this barium ion is produced. Add an aqueous alkali silicate solution to the water slurry to generate barium silicate on the surface of the spherical barium sulfate, then add mineral acid to the slurry to decompose the barium silicate into hydrous silica, which is deposited on the surface of the spherical barium sulfate. A method for producing surface-treated spherical barium sulfate, which comprises treating the thus obtained spherical barium sulfate with a silane coupling agent. 3 Spherical barium sulfate with an average particle size of 0.1 to 0.5 μm is produced by an aqueous reaction in which an aqueous barium sulfide solution and an aqueous sulfuric acid solution are reacted in the presence of an excess amount of barium ions, and spherical barium sulfate containing this barium ion is produced. Add an aqueous alkali silicate solution to the water slurry to generate barium silicate on the surface of the spherical barium sulfate, then add mineral acid to the slurry to decompose the barium silicate into hydrous silica, which is deposited on the surface of the spherical barium sulfate. After adding an aqueous solution of a water-soluble metal compound to the thus obtained spherical barium sulfate thriller, neutralization is performed with an alkali or acid depending on the metal compound to form a hydrated oxide of the metal on the surface of the spherical barium sulfate. A method for producing surface-treated spherical barium sulfate, the method comprising depositing surface-treated spherical barium sulfate.