JP2017036171A - High intensity molding for manufacturing opaque silica glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molding capable of easily and stably manufacturing highly pure and opaque silica glass excellent in infrared radiation shading property.SOLUTION: With mixed powder 2 of non-crystalline silicon oxide powder and inorganic carbon powder having a particle diameter and a mixture ratio, in which the content of water to the total weight of non-crystalline silicon oxide powder and inorganic carbon powder is 3 to 12 weight %, and inorganic carbon powder, only water of a quantity introduced from the specific surface area is mixed and pressure-molded to manufacture highly pure and opaque non-transparent silica glass. The opaque non-transparent silica glass molding has an impurity quantity of each metal for each metal Na, Mg, Al, K, Ca, Cr, Fe, Cu and Zn of 10 ppm or less. In order to prepare the powder 2 to be used in the molding, when the agitating work for non-crystalline silicon oxide powder and the mixed powder 2 of the inorganic carbon powder is performed by means of a resin ball 3, water is added by the atomization of a spray 4 during the agitating work of the mixed powder.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a molded article having physical properties suitable for producing a high-purity opaque silica glass excellent in infrared light shielding properties and a method for producing the same.

  Opaque silica glass is used for applications that require heat barrier properties. The heat shielding property is related to the infrared light shielding property, and an opaque silica glass having a higher light shielding property is superior in heat shielding property.

  Conventionally, as a method for producing such opaque silica glass, a method in which a foaming agent such as silicon nitride is added to crystalline silica or amorphous silica and melted (for example, see Patent Documents 1 and 2) is known. ing. However, in the opaque silica glass produced by such a production method, the foaming agent is vaporized to form pores, so that the average diameter of the pores is large, and those having the strength to withstand practical use have a low number density of pores. There is a problem that the light shielding property of infrared light is lowered.

JP-A-4-65328 JP-A-5-254882

 The present invention relates to a molded body obtained by pressure-molding a mixed powder of an amorphous silicon oxide powder and an inorganic carbon powder for producing an opaque silica glass excellent in infrared light shielding properties, and mixing impurities is minimized. The object is to provide a molded body with significantly improved strength of the molded body.

  The present inventors can produce an opaque silica glass having good properties by mixing substantially non-crystalline silicon oxide powder, inorganic carbon powder and a predetermined amount of water, and then pressure-molding the mixture. The present inventors have found that a molded article can be obtained, and have completed the present invention.

  That is, the present invention is a molded object for opaque silica glass substantially composed of an amorphous silicon oxide powder, an inorganic carbon powder and water, and contains water relative to the total weight of the amorphous silicon oxide powder and the inorganic carbon powder. The amount is 3 to 12% by weight.

  Hereinafter, the present invention will be described in more detail.

  The molded body of the present invention is used for producing an opaque silica glass having good properties by firing using an electric furnace or the like. During the baking and heating, water contained in the molded body is removed by evaporation, and the inorganic carbon powder disappears by oxidative combustion. Thereafter, the bonding of the amorphous silicon oxide powder proceeds due to the sintering phenomenon and changes to an integrated glass. However, a space remains in the place where the inorganic carbon powder was present, and innumerable pores are generated in the glass. As a result, an opaque silica glass having a structure in which countless pores are dispersed in the glass is obtained.

  The molded body of the present invention consists essentially of amorphous silicon oxide powder, inorganic carbon powder and water, and does not contain an organic binder. The organic binder not only has a problem with the contained inorganic impurities, but also needs to be debindered before firing, so that one extra step is required.

  Further, the amount of each metal impurity of Na, Mg, Al, K, Ca, Cr, Fe, Cu, and Zn in the molded body is preferably 10 ppm or less, and more preferably 5 ppm or less. This is because when the opaque silica glass produced from the molded body is used for semiconductor production or the like, contamination of impurities must be prevented. Furthermore, when the amount of the above-mentioned metal impurities is increased, cristobalite is generated in the silica glass when the molded body is fired, which may cause cracks.

  The molded body of the present invention is characterized in that the water content is 3 to 12% by weight based on the total weight of the amorphous silicon oxide powder and the inorganic carbon powder. By adding water, the strength of the molded body is greatly improved as compared with the case where water is not added. This is presumably because the surfaces of the amorphous silicon oxide powder and the inorganic carbon powder are covered with water, so that the powders are easily bonded via water. If the amount of water added is less than 3% by weight, the amount of increase in the strength of the molded product becomes small, which is not preferable. Further, even when 12% by weight or more of water is added, there is almost no increase in the strength of the molded body, or on the contrary, there is a tendency that the strength of the molded body is decreased, and there is no advantage that only the fluidity of the powder is deteriorated. .

  Next, the manufacturing method of this invention is demonstrated.

  The production method of the present invention is characterized in that when the amorphous silicon oxide powder and the inorganic carbon powder are mixed and the obtained mixed powder is stirred, water is added by spraying.

The amorphous silicon oxide powder as the raw material powder preferably has an average particle size of 20 μm or less and a specific surface area of 1 m ² / g or more. When the average particle size is larger than 20 μm or the specific surface area is smaller than 1 m ² / g, sintering requires a high temperature and a long time, which is not preferable from the viewpoint of increasing the risk of cracking due to the occurrence of cristobalite. Amorphous silicon oxide powder produced by various production methods can be adjusted to the above particle size by pulverization and classification with a jet mill, ball mill, bead mill or the like.

  The inorganic carbon powder that is a raw material powder preferably has an average particle size of 5 to 40 μm, and preferably 0.04 to 0.35 in volume ratio with the amorphous silicon oxide powder. If the added amount of the inorganic carbon powder is less than 0.04 in volume ratio, the amount of pores contained in the opaque silica glass is reduced, and the light shielding property of infrared light is lowered, which is not preferable. On the other hand, if the volume ratio exceeds 0.35, the density of the opaque silica glass becomes too low, which is not preferable. Examples of the inorganic carbon powder include graphite.

  The above-mentioned raw material powder is mixed, and 3 to 12% by weight of water based on the total weight of the amorphous silicon oxide powder and the inorganic carbon powder is added to the obtained mixed powder by spraying during the mixed powder stirring operation. .

  Hereinafter, a method of adding water to the mixed powder will be described with reference to FIG. The mixed powder 2 and the resin balls 3 are placed in the resin container 1, and water is added by spraying from the spray nozzle 4 while the container 1 is rotated and stirred so that the mixed powder 2 does not spill. In order to prevent the mixed powder from spilling from the container, the container is rotated and stirred while the container is tilted at an angle, or a lid with a hole of a minimum size is attached to the container and a spray nozzle is inserted through the hole. The method is preferred. There is no problem even if the container is a metal container coated with resin or the like, and the resin ball is particularly preferably a nylon ball with an iron core.

  Further, it is desirable that the spray nozzle can make droplets as small as possible. When the droplets are large, not only is it difficult to uniformly add water to the mixed powder, but the mixed powder agglomerates with water at the landing point of the droplets, causing lumps in the mixed powder, and finally the compact May become inhomogeneous.

  Thus, the mixed powder after water addition produced can obtain a molded object with high strength by press molding or CIP molding.

  The present invention relates to a molded body for producing an opaque silica glass excellent in infrared light shielding properties, and can significantly improve the molded body strength while minimizing contamination of impurities.

It is the figure which showed a mode that mixed powder was put into a container and water was added by spraying, rotating a container. It is the figure which showed the change of the crushing strength of the molded object with respect to the amount of water addition.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to such examples.

Example As an amorphous silicon oxide powder, a synthetic amorphous silica powder (manufactured by Nippon Kasei Co., Ltd., trade name “MKC silica PS200”) prepared by jet mill pulverization so as to have an average particle diameter of 6 μm is prepared. did. At this time, the specific surface area of the amorphous silicon oxide powder was 2.1 m ² / g. Next, spherical graphite powder having an average particle diameter of 18 μm (trade name “Nikabeads” manufactured by Nippon Carbon Co., Ltd.) is prepared as the inorganic carbon powder, and the volume ratio of the inorganic carbon powder to the amorphous silicon oxide powder is 0.1. Were mixed to prepare a mixed powder.

  Next, 2.0 kg of the mixed powder and 1.4 kg of iron ball-containing nylon balls were placed in a 10 L nylon pod, and pure water was sprayed into the pod using a spray while rotating and stirring the nylon pod. The amount of water added was adjusted to 3, 6, 8, and 12% based on the weight of the mixed powder.

  Next, 5-6 g of this powder was put into a uniaxial pressing die having an inner diameter of φ22 mm, and press molding was performed at a molding pressure of 20 MPa to produce three cylindrical molded bodies each having a height of around 10 mm. Next, the crush load measurement of the molded body was performed according to the following procedure.

  Attach a 500N load cell to the bending test machine AG-Xplus (manufactured by Shimadzu Corporation), place it on the bending test machine with the cylindrical side of the molding to be measured facing down, and push the cylindrical side from above with a φ35mm indenter (indenter lowering speed) 0.14 mm / s), and the load when the molded body breaks was measured. The results are shown in FIG.

  Next, after lightly removing the surface of the molded body produced by the above-described method with a SiC sandpaper, the molded body was analyzed by ICP-AES. As a result, Na, Mg, Al, K, Ca, Cr, Fe, Cu, The amount of each metal impurity of Zn was 1 ppm or less.

Comparative Example A molded body was produced in the same manner as in Example, except that the amount of water added was 0%, 1%, and 18% with respect to the mixed powder weight. Next, the crush load measurement of the molded body was performed in the same manner as in the example. The results are shown in FIG. When the amount of water added was 18%, signs of slurry began to appear, and it was extremely difficult to perform rotary stirring and filling into a press die.

  The present invention is a technique for producing a high-purity opaque silica glass excellent in infrared light shielding properties, and a molded body comprising a mixed powder of an amorphous silicon oxide powder and an inorganic carbon powder that has greatly improved strength. Thus, an opaque silica glass can be stably produced.

1. Resin container 2. Mixed powder Oil ball 4. spray nozzle

Claims (4)

A molded object for opaque silica glass substantially comprising an amorphous silicon oxide powder, an inorganic carbon powder and water, wherein the water content is 3 to 12 weights with respect to the total weight of the amorphous silicon oxide powder and the inorganic carbon powder. %, A molded article for opaque silica glass. 2. The molded article according to claim 1, wherein each metal impurity amount of Na, Mg, Al, K, Ca, Cr, Fe, Cu, and Zn is 10 ppm or less. When adding water to a mixed powder of an amorphous silicon oxide powder and an inorganic carbon powder in order to produce a powder for use in a molded body, water is added by spraying during the stirring operation of the mixed powder. The manufacturing method of the molded object of Claim 1 or 2. The method for producing a molded body according to claim 3, wherein the stirring operation is performed using a resin ball.

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