JPH06115939A - Bismuth subcarbonate composition having improved thermal stability and its production - Google Patents

Abstract

PURPOSE:To improve thermal stability of bismuth subcarbonate. CONSTITUTION:A composition wherein amorphous silica is precipitated on the surface of fine particles of bismuth subcarbonate is produced and its production method is provided. This production is carried out by adding under heating a solution of a silicate to a water dispersion of bismuth subcarbonate made to have at least 90% or more particles having 10mum or smaller particle diameters to precipitate and apply 1-30wt.% amorphous silica calculated as SiO2 based on bismuth subcarbonate to the surface of the particles.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bismuth subcarbonate composition used as an X-ray fluoroscopic contrast agent for medical devices made of plastic such as vascular catheter and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, barium sulfate has been mainly used as an X-ray fluoroscopic contrast agent for medical devices made of resin such as vascular catheter. For example, it was necessary to use 40 to 60% of barium sulfate with respect to the resin used in order to obtain a contrasting effect on a blood vessel catheter made of vinyl chloride, polyolefin, or Teflon resin. Such a large amount of addition markedly deteriorates the properties of the resin, and thus has a drawback that it cannot be used as a cathel. Further, kneading such a large amount of barium sulfate into the resin makes the working process difficult and raises the cost.

[0003]

DISCLOSURE OF THE INVENTION The present inventors have conducted extensive studies on an X-ray contrast agent which does not have the above-mentioned problems, and have found that bismuth subcarbonate has an excellent effect as an X-ray contrast agent. Attention has been paid to the fact that it lacks thermal stability and is decomposed or colored by heat when it is kneaded with a resin, and as a result of further studies, the above problems could be solved.

[0004]

That is, as a means for improving the thermal stability of bismuth subcarbonate, the present invention is to deposit amorphous silica on the surface of bismuth subcarbonate particles. As a result of differential thermogravimetric analysis, it was confirmed that the product showed good thermal stability.

According to the results of the differential thermogravimetric analysis, untreated bismuth subcarbonate has a sharp endothermic peak at 395 ° C., which causes a considerable heat loss. The endothermic peak of the bismuth subcarbonate composition deposited at 2 wt% was 481 ° C, the endothermic peak of 8 wt% deposited was 538 ° C, and the endothermic peak of 18 wt% deposited was It was not observed up to 600 ° C, and the weight loss was also slight. From this point of view, the present invention defines the range of the amount of amorphous silica deposited with respect to the particles of bismuth subcarbonate as 1 to 30% by weight, as will be described later.

To produce the composition of the present invention, bismuth subcarbonate is dispersed in water and then overdispersed by a disperser or an emulsifier, at least 90% of which has a particle size of 10
The dispersion is made so as to form fine particles of μm or less. At this time, the bismuth concentration of the aqueous dispersion is suitably 40% by weight or less for reasons of dispersibility. Next, the liquid temperature is set to 60 ° C. or higher, preferably about 80 ° C., and the silicate solution is added while stirring. As the silicate, in addition to inorganic salts such as sodium silicate, organic silicates such as orthoethyl silicate may be used.

By the addition of the silicate solution, amorphous silica is deposited on the surface of bismuth subcarbonate particles, and the amount of deposition in this case is in the range of 1 to 30% by weight as SiO ₂ (based on bismuth subcarbonate). Is suitable, and a mineral acid such as sulfuric acid or nitric acid is added at the same time to keep the pH of the liquid at 9 to 11, or after the addition of the silicate solution, the total amount of the mineral acid is added to make the pH of the liquid 9 to 1
Set to 1. After stirring for 30 minutes or more and neutralizing with a mineral acid, silica is deposited on the surface of the particles and the coating is completed. Next, this is filtered, washed with water, dried, and the dried product is crushed with a hammer mill or the like to obtain a bismuth subcarbonate composition having significantly improved thermal stability.

The reason why the amount of the amorphous silica deposited is limited to the range of 1 to 30% by weight is that it is difficult to obtain the required thermal stability at 1% by weight or less, and the workability of kneading with the resin is low. If the amount exceeds 30% by weight, the characteristic of high specific gravity originally possessed by bismuth subcarbonate is impaired,
This is because the X-ray contrast effect is reduced.

[0009]

【Example】

Example 1 1.5 kg of bismuth secondary carbonate (reagent, manufactured by Kanto Chemical Co., Inc.) was dispersed in 10 liters of pure water, and then dispersed for 1 hour with a Dispamill (manufactured by Hosokawa Micron). While heating and stirring this dispersion at 80 ° C. or higher, No. 3 sodium silicate (SiO ₂
The content is 28.5% by weight, and the amount of deposited amorphous silica is 2% by weight (as SiO ₂ ) (107 g). At this time, dilute sulfuric acid was also added to maintain the pH of the solution at 9 to 11, and the solution was further stirred for 1 hour and then neutralized to pH 6 to 8 with sulfuric acid.

Next, this was filtered, washed with water, dried, and then ground with a hammer mill to obtain a bismuth subcarbonate composition. As a result of differential thermogravimetric analysis, the endothermic peak was 481 ° C. The particle size distribution is 97% when the particle size is 8.0 μm or less,
The average particle size was 0.95 μm and the whiteness was 91. When 50% by weight of this was added to a vinyl chloride resin and a kneading test was carried out, there was no problem in workability, and neither decomposition nor coloring was observed. Incidentally, the untreated product of bismuth subcarbonate (reagent, manufactured by Kanto Kagaku Co., Ltd.) had an endothermic peak of 395 ° C. and could not be used.

Example 2 1.5 kg of bismuth subcarbonate (reagent, manufactured by Kanto Kagaku Co., Ltd.) was dispersed in 10 liters of pure water, and then dispersed for 1 hour with a Dispamill (manufactured by Hosokawa Micron). While heating and stirring this dispersion at 80 ° C. or higher, No. 3 sodium silicate (SiO ₂
18.5 g (content of 28.5% by weight, amount of amorphous silica deposited is 18% by weight as SiO ₂ ). At this time, dilute sulfuric acid was also added to maintain the pH of the solution at 9 to 11, and the solution was further stirred for 1 hour and then neutralized to pH 6 to 8 with sulfuric acid.

Next, this was filtered, washed with water, dried, and then ground with a hammer mill to obtain a bismuth subcarbonate composition. As a result of differential thermogravimetric analysis, no endothermic peak was recognized up to 600 ° C. The particle size distribution is 9 when the particle size is 8.0 μm or less.
The average particle size was 3%, the average particle size was 1.61 μm, and the whiteness was 90. When 30% by weight of this was added to a vinyl chloride resin and a kneading test was carried out, there was no problem in workability, and neither decomposition nor coloring was observed.

[0013]

EFFECTS OF THE INVENTION According to the present invention, by selecting the amount of the amorphous silica deposited in the range of 1 to 30% by weight, a whiteness of 90% or more and an arbitrary thermal stability can be obtained, which is substantially harmless for medical use. Since a bismuth subcarbonate composition most suitable as an X-ray contrast agent for a device can be obtained, the medical effect is great.

Claims (2)

[Claims] 1. A bismuth subcarbonate composition with improved thermal stability, characterized in that amorphous silica is deposited on the surface of fine particles of bismuth subcarbonate. 2. A silicate solution is added to an aqueous dispersion of bismuth subcarbonate in such a manner that particles having a particle size of 10 μm or less occupy at least 90% or more are added to the bismuth subcarbonate as SiO _2. A method for producing a bismuth subcarbonate composition with improved thermal stability, characterized in that 1 to 30% by weight of amorphous silica is deposited and coated on the surface of the particles.