JP3799558B2 - Barium sulfate, process for producing the same and resin composition - Google Patents

Description

【００４５】
表１の結果から、本発明の実施例による硫酸バリウムはワニス中に一次粒子まで容易に分散し、樹脂単独（ブランク）の塗膜とほとんど変わらない光沢の優れた塗膜を得ることができることが認められた。
【００４６】
【表２】

【００４７】
表２から、実施例の硫酸バリウムを顔料とした塗膜は比較例１や市販品を顔料とした場合に比べ、顔料添加量を多くしても透明度の減少は極めて少なく、良好な透明塗膜が形成されることが判る。
【００４８】
【発明の効果】
以上のとおり、本発明によればキレート能を有する有機リン化合物で表面改質された超微細で均一な一次粒子径を備え、粒子相互が凝集した場合にも容易に脱アクロメレートし得る粒子性状の硫酸バリウムを提供することができる。この硫酸バリウムは、含Ｂａ²⁺水溶液と含ＳＯ₄ ^2- 水溶液をキレート能を有する有機リン化合物の存在下で瞬間反応させる本発明の製造方法により効率よく工業生産することが可能となる。また、本発明の硫酸バリウムは各種樹脂類に対する分散性が極めて優れているから、これを配合することにより高品質の樹脂組成物を提供することができる。特に体質顔料として配合した塗料の塗膜には、良好な光沢性と透明性が同時に付与し得る効果がもたらされる。
【図面の簡単な説明】
【図１】実施例１で得られた硫酸バリウム粉末の粒子構造を示した電子顕微鏡写真（拡大倍率：１０万倍）である。
【図２】比較例１で得られた硫酸バリウム粉末の粒子構造を示した電子顕微鏡写真（拡大倍率：１０万倍）である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to barium sulfate excellent in dispersibility for various resins, its production and application technology, and in particular, possesses excellent dispersibility through the reaction of an aqueous solution containing Ba ^{2+ and an} aqueous solution containing SO ₄ ^2−. The present invention relates to barium sulfate having ultrafine particles, a method for producing the same, and a resin composition containing the barium sulfate.
[0002]
[Prior art]
Barium sulfate is generally produced by an aqueous solution reaction in which an aqueous solution of sulfate or sulfuric acid is reacted with an aqueous solution of barium chloride, barium sulfide, barium nitrate, barium hydroxide, barium carbonate, etc., but barium sulfate produced by this method is used. Has a large primary particle size of usually 0.3 to 2.0 μm, and therefore, when blended with paints or inks as a transparent pigment or extender, for example, the problem of impairing transparency and surface gloss due to light scattering of barium sulfate particles There is. Such a problem can be eliminated by blending barium sulfate having a finer primary particle size.
[0003]
Conventionally, as a technique for producing fine barium sulfate, for example, at the stage of reacting a sodium sulfate aqueous solution and a barium sulfate aqueous solution, a specific metaphosphate is allowed to coexist in the sodium sulfate aqueous solution, and the molar ratio of sodium sulfate is changed to barium sulfate. In contrast, a method in which a stoichiometrically excessive amount is present (Japanese Patent Publication No. 50-33984), a barium sulfide aqueous solution and a sulfuric acid aqueous solution are controlled so that the barium sulfide concentration becomes excessive, and a continuous reaction vessel In a method of reacting in an extremely short time under effective stirring (JP-A-57-51119), a method of reacting an aqueous sulfuric acid solution with an aqueous barium sulfide solution to produce barium sulfate, In this method, barium sulfide is always present in excess, and water-soluble alkali silicate is present (Japanese Patent Laid-Open No. 58-120520). A method of spraying and drying a medium containing a precipitate formed by reacting an aqueous solution of barium salt separately and simultaneously with an accurate stoichiometric ratio, and the resulting precipitate is disclosed (JP-A-2-83211). Yes.
[0004]
However, barium sulfate obtained by such a conventional method has a fine primary particle diameter, but apparent secondary particles are aggregated large particles. In addition, since the inert surface modification of the barium sulfate particle surface cannot be performed, the affinity becomes worse depending on the type of resin. When barium sulfate is blended with a paint containing such a resin having poor affinity, the barium sulfate itself agglomerates to increase the viscosity of the paint, resulting in a situation where normal paint performance cannot be obtained.
[0005]
[Problems to be solved by the invention]
Therefore, there is a strong development of barium sulfate that has a fine primary particle size, can be easily deagglomerated even when the particles agglomerate with each other, and exhibits excellent dispersibility in various resins. It is requested.
[0006]
The present inventors have found that the view of the fact, the results of extensive studies on barium sulfate fine texture having excellent dispersibility to various resins, reaction-containing Ba ²⁺ solution and containing SO ₄ ^2-solution In the process of forming the barium sulfate, the reaction is instantaneously performed in the presence of an organophosphorus compound having a chelating ability, and the fine particle surface is modified with the organophosphorus compound having the chelating ability. It was confirmed that the secondary agglomerates were easy to be deagglomerated and showed good dispersibility in various resin systems.
[0007]
The present invention was developed based on such knowledge, and its purpose is to provide ultrafine barium sulfate having excellent dispersibility for various resins, a method for producing the same, and a resin composition containing the barium sulfate. There is to offer.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the barium sulfate according to the present invention is a fine particle having an average primary particle diameter of 0.1 μm or less, and the particle surface thereof is aminoalkylenephosphonic acid, ethylenediaminetetraalkylenephosphonic acid, It is characterized by being treated with alkylmethane-1-hydroxy-1,1-diphosphonic acid or 2-hydroxyphosphonoacetic acid .
[0009]
Further, the method for producing barium sulfate according to the present invention is a method for producing barium sulfate by a reaction of an aqueous solution containing Ba ^{2+ and an} aqueous solution containing SO ₄ ^2-
A sulfuric acid solution containing aminoalkylenephosphonic acid, ethylenediaminetetraalkylenephosphonic acid, alkylmethane-1-hydroxy-1,1-diphosphonic acid, or 2-hydroxyphosphonoacetic acid and an aqueous Ba ²⁺ containing solution are simultaneously injected into the reactor. And
Average residence time (t) calculated by the following formula:
t = v / (A + B)
(In the formula, v represents the capacity (l) of the reactor , and A and B represent the injection rates (l / min) of the aqueous sulfuric acid solution and the aqueous Ba ²⁺ solution, respectively ) .
Passing through the reactor so that is within 10 seconds,
It is a feature of the construction to proceed by the above.
[0010]
Furthermore, the resin composition provided by the present invention is obtained by dispersing and blending the above barium sulfate in the range of 1 to 50 parts by weight per 100 parts by weight of the resin.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
The barium sulfate according to the present invention is an ultrafine particle having an average primary particle size of 0.1 μm or less, and has a relatively small particle shape as considered from the electron micrograph (magnification 100,000 times) in FIG. It is uniform and characterized by very few coarse particle portions exceeding 0.1 μm. In addition, it is an important constituent of the present invention that the surface of the fine particles is modified with an organophosphorus compound having chelating ability. Here, the primary particle size of barium sulfate was measured by an electron microscope observation method at a magnification of 100,000 times or more, and the particle surface was treated with an organophosphorus compound having a chelating ability. It means a state in which an organophosphorus compound forms a barium salt and is interposed between the surfaces of particles or between particles.
[0012]
The ultrafine barium sulfate particles surface-treated with an organophosphorus compound having a chelating ability according to the present invention can be easily deagglomerated in the use stage even if secondary agglomerates are formed in the dry powder. The fluidity and redispersibility are very good. Furthermore, surface treatment with an organophosphorus compound having chelating ability improves compatibility with various resins and dispersibility in various dispersion media. Therefore, excellent transparency and paint gloss when blended into paints, etc. Can be given.
[0013]
Alkylmethane-1-hydroxy-1,1-diphosphonic acid (salt) is the most effective organophosphorus compound having chelating ability used for surface modification treatment of barium sulfate particles, and its content is that of barium sulfate. Although it varies depending on the use, the type of the compound, etc., in many cases, 0.1 to 10 weight with respect to the theoretical reaction amount of the total phosphate source as a partial alternative phosphate source for the SO ₄ ^-containing compound as a raw material. %, Preferably in the range of 0.3 to 8% by weight.
[0014]
Barium sulphate described above, when generating the barium sulfate by the reaction of free Ba ²⁺ solution and containing SO ₄ ^2-solution, produced by the method for momentarily reaction while simultaneously intervening organic phosphorus compound having chelating ability .
[0015]
As a Ba2 ^{+ -containing} compound serving as a barium source, for example, barium salts such as barium chloride, barium sulfide, barium nitrate, barium carbonate, barium hydroxide are appropriately used. On the other hand, examples of the SO ₄ ^2- compound include sulfuric acid and sulfates such as sodium sulfate. However, it is particularly preferable to use barium hydroxide as the Ba ²⁺ compound and sulfuric acid as the SO ₄ ²⁻ compound for the purposes of the present invention. This is because the desired ultrafine barium sulfate can be easily recovered because the by-product is water.
[0016]
The organophosphorus compound having chelating ability used in the present invention is a component that functions in place of a part of the above SO ₄ ^-containing compound as a phosphate source for the reaction. For example, aminoalkylenephosphonic acid, ethylenediaminetetraalkylenephosphone Typical examples include acid, alkylmethane-1-hydroxy-1,1-diphosphonic acid, and 2-hydroxyphosphonoacetic acid.
[0017]
Among these, as aminoalkylenephosphonic acid, for example, nitrilotrismethylenephosphonic acid, nitrilotrisethylenephosphonic acid, nitrilotrispropylenephosphonic acid, nitrilodiethylmethylenephosphonic acid, nitrilopropylbismethylenephosphonic acid, etc., as ethylenediaminetetraalkylenephosphonic acid, For example, ethylenediaminetetramethylenephosphonic acid, ethylenediaminetetraethylenephosphonic acid, ethylenediaminetetrapropylenephosphonic acid and the like, and as alkylmethane-1-hydroxy-1,1-diphosphonic acid, for example, methane-1-hydroxy-1,1- Examples include diphosphonic acid, ethane-1-hydroxy-1,1-diphosphonic acid, and propane-1-hydroxy-1,1-diphosphonic acid. These compounds may be partially or fully neutralized with an alkali metal salt such as sodium salt or potassium salt, or may be one or more.
[0018]
The production of barium sulfate is carried out by reacting the above three raw material components. The organophosphorus compound having chelating ability is 0.1 to 10% by weight, preferably 0.1% by weight to the theoretical reaction amount of the total phosphate source. It is set in the range of 0.3 to 8% by weight. When the content is less than 0.1% by weight, the production of barium organophosphate is insufficient, and the formation on the surface of the barium sulfate particles becomes insufficient, so that it is difficult to prevent the growth of barium sulfate particles. When the content exceeds 10% by weight, the effect is small for the added amount, and the practicality is poor from the economical aspect.
[0019]
In order to react in the presence of an organophosphorus compound having a chelating ability, usually, a means of bringing a mixed solution in which the compound is previously dissolved in a sulfuric acid (salt) aqueous solution into contact with a Ba ²⁺ solution is employed. As a method, a method in which an aqueous sulfate solution and an aqueous Ba ²⁺ solution are contacted in an aqueous solution of an organophosphorus compound having chelating ability may be employed.
[0020]
At this time, it is an important condition for the present invention that the above reaction is performed instantaneously. This instantaneous reaction means that barium sulfate precipitates are continuously produced within a short time as possible without back mixing in the reaction system. The reaction without back-mixing is always performed only by direct contact mixing of both liquids in the reaction system in which both raw material liquids are mixed and reacted, and during the reaction, reactions such as common ions and precipitated particles in the reaction system occur. It is not affected by the product. Such a reaction is achieved by quickly introducing both reaction solutions into a small volume reaction system and quickly discharging the reaction product out of the system.
[0021]
In order to carry out the reaction continuously without such back mixing, a small-volume mixing device that exhibits a powerful stirring effect is used as a reactor. As such means, for example, a method in which a sulfuric acid aqueous solution containing an organophosphorus compound having a chelating ability and a barium hydroxide aqueous solution, which are blended at a constant ratio using a centrifugal pump as a reaction vessel, is continuously reacted, or a static mixer as a reaction vessel. Although there is a method of performing an instantaneous continuous reaction, it is particularly preferable to adopt the latter method.
[0022]
Since the static mixer has a structure in which a necessary number of elements twisted 180 degrees in the left and right directions are alternately arranged in a pipe, the fluid passing through the static mixer flows through the elements. It is mixed and reacted uniformly and instantaneously under the three mixing actions of splitting the flow, reversing the flow, and turning the flow. Therefore, the raw Ba 2 ⁺ aqueous solution and the SO ₄ ² -containing aqueous solution containing the organophosphorus compound having the chelating ability are instantaneously mixed and discharged without any back mixing in the reaction system. Consistently finer and more stable barium sulfate particles continuously than those prepared with the backmixing action such as the common ion effect in the conventional batch type or pump type agitation reactors. Obtainable.
[0023]
The molar ratio between the Ba ²⁺ compound and the SO ₄ ^2- compound containing the organophosphorus compound having a chelating ability may be either an excess of barium salt or sulfate, but preferably the exact stoichiometry It is to make it react in a target ratio. However, the pH during the reaction is usually 5 to 8, preferably 7 in a neutral region. This is because the generated barium sulfate particles can be recovered without the need for frequent operations such as washing with water.
[0024]
The reaction temperature depends on the solubility of the raw material Ba ²⁺ compound in water, but generally the average particle size tends to increase when measured at high temperature. Therefore, it is desirable to carry out the reaction at 70 ° C. or lower.
[0025]
The reaction proceeds by simultaneously injecting into the reactor a sulfuric acid solution (solution A) containing an organophosphorus compound having chelating ability and a Ba ^{2+ -containing} aqueous solution (solution B) and passing through the reactor. The reaction is carried out under conditions such that the average residence time (t) of the raw material system passing through the reactor is within 10 seconds, preferably 1 second or less. The average residence time t (second) of the raw material system in the reaction system is a relational expression of t = v / A + B, where v is the capacity of the reactor (l), A and B are an aqueous sulfuric acid solution and Ba ²⁺ containing Ba ^2+, respectively. It represents the injection rate (l / min) of the aqueous solution].
[0026]
In order to obtain an average residence time of 10 seconds or less, there is no particular limitation on the maximum flow rate of the raw material aqueous solution supplied to the static mixer or the like, and it depends on the length of the static mixer, the number of elements, the inner diameter, etc. It is preferable to carry out the reaction by supplying the raw material aqueous solution at min or more, preferably 1.5 l / min or more. In addition, the raw material concentration is not particularly limited, but in many cases, the raw material concentration is adjusted so that the slurry concentration of the barium sulfate to be generated is 5% by weight or more, preferably 10 to 30% by weight.
[0027]
After producing fine barium sulfate by the above reaction, each process of filtration separation, drying and pulverization is sequentially performed by a conventional method to obtain a product, but in the present invention, the fine droplets of slurry and drying are simultaneously performed. Preferably spray drying is applied. The reason why spray drying is suitable is that if the drying takes a long time, the primary particles are likely to cause hard secondary agglomeration, making redispersion difficult, and because the particles are fine, the filtration operation cannot be performed easily. Is to eliminate these difficulties.
[0028]
The barium sulfate obtained in the above process has a uniform and ultrafine particle property in which the primary average particle size is usually in the range of 0.01 to 0.2 μm and the average primary particle size is 0.1 μm or less. . Such uniform and the ultrafine barium sulfate particles are formed includes a formation reaction of barium sulfate by the reaction of free Ba ²⁺ compound containing SO ₄ ^{2-compound-containing} Ba ²⁺ compound and chelating Since the barium salt formation reaction of the organophosphorus compound by reaction with the organophosphorus compound proceeds in the same reaction system, the barium salt of the organophosphorus compound has a function to suppress the growth of barium sulfate particles, and at the same time a static mixer, etc. This is presumed to contribute to the formation of uniform and ultrafine barium sulfate in combination with the action of the instantaneous reaction due to.
[0029]
The barium sulfate obtained in the present invention can be used as a filler, an extender pigment, a dispersion aid, an anti-settling agent, or a rust preventive pigment blended in various resins. In particular, those having a primary particle size of 0.19 μm or less are useful as pigments having excellent transparency because they do not reflect the wavelength of visible light.
[0030]
Examples of resins used as a matrix when a resin molded product such as a sheet, a film, or a container is obtained by blending ultrafine barium sulfate according to the present invention with various resins as a filler include, for example, polyvinyl chloride resin, polyethylene resin, Polypropylene resin, polyamide resin, polycarbonate resin, polyester resin, polystyrene resin, ABS resin, AS resin, thermoplastic resin such as thermoplastic acrylic resin, epoxy resin, unsaturated polyester resin, diallyl phthalate resin, phenol resin, urea resin, etc. A thermosetting resin is mentioned. In addition, as a resin for forming a coating film used as a body pigment, a phenol resin, an alkyd resin, a melanin resin, a guanazine resin, a vinyl resin, an epoxy resin, a polyamine resin, an acrylic resin, a polybutadiene resin, a polyester resin , Urethane resin, silicon resin, fluorine-containing resin, and the like. In particular, when used as an extender for paints, a coating film with good gloss and texture can be obtained.
[0031]
The amount of addition of barium sulfate according to the present invention to the above resins depends on the resin or its use. For example, in the case of obtaining various resin molded products such as sheets, films, containers, etc., the range of conventional filler blending amounts It is usually 1 to 50% by weight based on 100 parts by weight of the resin. Further, when used as an extender for forming a coating film, it is usually 1 to 50% by weight based on the paint vehicle. When the resin is blended, by performing a strong shear dispersion treatment, the secondary agglomerated barium sulfate particles are easily deagglomerated, and a resin composition excellent in dispersibility can be obtained.
[0032]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these examples.
[0033]
Example 1
A solution A was prepared by dissolving 206.6 g of barium hydroxide [Ba (OH) ₂ .8H ₂ O] in 893.4 g of water. Further, 62.3 g of 97 wt% sulfuric acid and 3.3 g of 60 wt% aqueous solution of methane-1-hydroxy-1,1-diphosphonic acid (3 wt% based on the theoretical reaction amount of the total phosphoric acid source) were added to water. It melt | dissolved in 977.0g and prepared B liquid. These A liquid and B liquid are heated to 50 ° C., and then a static mixer (manufactured by Noritake Company Limited; 4 / 1-N40-170-0) A liquid and B at a flow rate of 1.5 l / min using a pump. The liquids were simultaneously supplied and reacted instantaneously in the reaction system to obtain an aqueous slurry of barium sulfate. Subsequently, it was separated by filtration, dried at 120 ° C. for 2 hours, and pulverized to obtain a white powder of barium sulfate. The obtained white powder of barium sulfate was magnified 100,000 times with an electron microscope and the average primary particle size was measured. As a result, it was 0.01 μm. FIG. 1 is an electron micrograph (magnification of 100,000 times) showing the particle structure of ultrafine barium sulfate obtained in this example, and it can be seen that it exhibits extremely uniform and fine particle properties.
[0034]
Next, 17.5 parts by weight of baking type alkyd resin [Dainippon Ink Chemical Co., Ltd., “Betcozol J-524” non-volatile content 60%] and melamine resin [Dainippon Ink Chemical Co., Ltd., “ 15 parts by weight of the above-mentioned barium sulfate powder was added to a mixed varnish consisting of 8.9 parts by weight and 4.9 parts by weight of xylene, and 60 minutes and 120 minutes by a paint conditioner. After dispersion for 180 minutes, each varnish was applied onto a glass plate using a 6 mil applicator, dried at room temperature, and baked at 140 ° C. for 20 minutes. Thus, about 20 degree / 20 degree specular reflectance was measured with the gloss meter about the coating film of resin obtained as a coating film and a blank as a blank, and the glossiness of the coating film was evaluated. The results are shown in Table 1. For comparison, commercial barium sulfate was also evaluated in the same manner, and the results are listed in Table 1.
[0035]
Further, 0 to 30 parts by weight of the barium sulfate powder and the commercially available barium sulfate powder produced in 100 parts by weight of the mixed varnish having the above composition were added to prepare a transparent paint, and the transparent paint was applied to a 6 mil applicator on a glass plate. Were applied in parallel, dried at room temperature, and baked at a temperature of 140 ° C. for 20 minutes to form a coating film having a film thickness of 68 μm. About this coating film, the transmittance | permeability of the perpendicular ray was measured by the Hunter system L value, and the transparency of the coating film was evaluated. The results are shown in Table 2 in comparison with the amount of barium sulfate (pigment) added.
[0036]
Comparative Example 1
Liquid B was prepared by dissolving 64.2 g of 97 wt% sulfuric acid in 975.8 g of water. Others were made to react with liquid A and liquid B by a static mixer under the same conditions as in Example 1, then separated by filtration, dried and pulverized at 120 ° C. for 2 hours to obtain a white powder of barium sulfate. With respect to the obtained white powder of barium sulfate, the average primary particle diameter was measured in the same manner as in Example 1. As a result, it was 0.05 μm. FIG. 2 is an electron micrograph (magnification of 100,000 times) showing the particle structure of barium sulfate obtained in this comparative example. The particle size is extremely large and non-uniform compared to FIG. Is recognized.
[0037]
About the obtained barium sulfate powder, the glossiness and transparency of the paint film were evaluated in the same manner as in Example 1, and the results are listed in Tables 1 and 2.
[0038]
Example 2
206.6 g of barium hydroxide [Ba (OH) ₂ .8H ₂ O] was dissolved in 893.4 g of water to prepare solution A. 64.13 g of 97 wt% sulfuric acid and 0.107 g of 60 wt% aqueous solution of ethane-1-hydroxy-1,1-diphosphonic acid (0.1 wt% based on the theoretical reaction amount of the total phosphoric acid source) Solution B was dissolved in 977.0 g of water. After liquid A and liquid B were heated to 50 ° C., they were simultaneously supplied to a static mixer (manufactured by Noritake Company Limited; 4 / 1-N40-170-0) at a flow rate of 1.5 l / min using a pump. The reaction was carried out instantaneously to obtain an aqueous slurry of barium sulfate. Subsequently, the obtained aqueous slurry was supplied to a 2500 rpm atomizer at a flow rate of 2.5 l / min, sprayed into an air stream at 200 ° C. and spray-dried to obtain a white powder of barium sulfate. The average primary particle diameter of the obtained white powder of barium sulfate was determined by an electron micrograph of 100,000 times and found to be 0.01 μm.
[0039]
About the obtained barium sulfate powder, the glossiness and transparency of the paint film were evaluated in the same manner as in Example 1, and the results are listed in Tables 1 and 2.
[0040]
Example 3
Liquid B of Example 2 was mixed with 63.56 g of 97 wt% sulfuric acid and 1.07 g of a 60 wt% aqueous solution of nitrilotrismethylenephosphonic acid (1 wt% based on the theoretical reaction amount of the total phosphoric acid source). A white powder of barium sulfate was produced under the same conditions as in Example 2 except that the composition was dissolved in 977.0 g. The average primary particle size of the obtained white powder of barium sulfate was 0.01 μm.
[0041]
About the obtained barium sulfate powder, the glossiness and transparency of the paint film were evaluated in the same manner as in Example 1, and the results are listed in Tables 1 and 2.
[0042]
Example 4
Solution B of Example 2 was dissolved in 975.8 g of water with 57.7 g of 97 wt% sulfuric acid and 6.42 g of 2-hydroxyphosphonoacetic acid (10 wt% based on the theoretical reaction amount of the total phosphoric acid source). Instead of the composition, white powder of barium sulfate was produced under the same conditions as in Example 2. The average primary particle size of the obtained white powder of barium sulfate was 0.01 μm.
[0043]
About the obtained barium sulfate powder, the glossiness and transparency of the paint film were evaluated in the same manner as in Example 1, and the results are listed in Tables 1 and 2.
[0044]
[Table 1]

[0045]
From the results in Table 1, barium sulfate according to the examples of the present invention can easily disperse to primary particles in the varnish, and can obtain a coating film with excellent gloss that is almost the same as the coating film of resin alone (blank). Admitted.
[0046]
[Table 2]

[0047]
From Table 2, the coating film using barium sulfate as a pigment in the example has a very small decrease in transparency even when the amount of pigment added is increased compared to Comparative Example 1 and the case where a commercial product is used as a pigment. It can be seen that is formed.
[0048]
【The invention's effect】
As described above, according to the present invention, a particle property that has an ultrafine and uniform primary particle size that is surface-modified with an organophosphorus compound having a chelating ability and can be easily deachromated even when the particles aggregate with each other. Barium sulfate can be provided. This barium sulfate can be efficiently industrially produced by the production method of the present invention in which a Ba-containing aqueous solution containing Ba ²⁺ and a SO ₄ ^-containing aqueous solution are reacted instantaneously in the presence of an organophosphorus compound having a chelating ability. Moreover, since the barium sulfate of this invention is very excellent in the dispersibility with respect to various resins, a high quality resin composition can be provided by mix | blending this. In particular, the coating film of the paint blended as an extender pigment has an effect that good gloss and transparency can be simultaneously imparted.
[Brief description of the drawings]
1 is an electron micrograph (magnification: 100,000 times) showing the particle structure of the barium sulfate powder obtained in Example 1. FIG.
2 is an electron micrograph (magnification: 100,000 times) showing the particle structure of the barium sulfate powder obtained in Comparative Example 1. FIG.

Claims (7)

The primary particles are fine particles having an average particle diameter of 0.1 μm or less, and the surface of the particles is aminoalkylenephosphonic acid, ethylenediaminetetraalkylenephosphonic acid, alkylmethane-1-hydroxy-1,1-diphosphonic acid, or A barium sulfate characterized by being treated with 2-hydroxyphosphonoacetic acid. Ba containing ²⁺ Aqueous solution and SO _Four ^2- In the method of producing barium sulfate by the reaction of an aqueous solution, the reaction is
In a reactor, a sulfuric acid solution containing aminoalkylenephosphonic acid, ethylenediaminetetraalkylenephosphonic acid, alkylmethane-1-hydroxy-1,1-diphosphonic acid, or 2-hydroxyphosphonoacetic acid and Ba-containing Ba ²⁺ Inject the aqueous solution at the same time,
Average residence time (t) calculated by the following formula:
t = v / (A + B)
(Where v is the capacity of the reactor (l) , A and B are sulfuric acid aqueous solution and Ba-containing Ba, respectively. ²⁺ Injection rate of aqueous solution (l / min) Represents. )
Passing through the reactor so that is within 10 seconds,
A process for producing barium sulfate, characterized in that the process proceeds with Ba containing ²⁺ Aqueous solution and SO _Four ^2- 3. The method for producing barium sulfate according to claim 2, wherein the reaction of the aqueous solution is performed using a static mixer as a reaction vessel. Ba containing ²⁺ Aqueous solution and SO _Four ^2- 3. The method for producing barium sulfate according to claim 2, wherein the reaction of the aqueous solution is performed using a centrifugal pump as a reaction vessel. Aminoalkylenephosphonic acid, ethylenediaminetetraalkylenephosphonic acid, alkylmethane-1-hydroxy-1,1-diphosphonic acid, or 2-hydroxyphosphonoacetic acid is added in an amount of 0.1 to 10 with respect to the theoretical reaction amount of the total phosphoric acid source. The method for producing barium sulfate according to any one of claims 2 to 4, which is set in a range of% by weight. The method for producing barium sulfate according to any one of claims 2 to 5 , wherein the Ba ²⁺ containing aqueous solution is a barium hydroxide aqueous solution, and the SO ₄ ^2- aqueous solution is a sulfuric acid aqueous solution. A resin composition comprising the barium sulfate according to claim 1 dispersed and blended in an amount of 1 to 50 parts by weight per 100 parts by weight of the resin.

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