Silica shaped bodies and process for preparing same

Details Silica shaped bodies and process for preparing same Silica shaped bodies and process for preparing same

1987-04-28

1989-08-01

Dixon, Jr., William R.

Compositions: ceramic

Ceramic compositions

Carbide or oxycarbide containing

501 96, 501 94, 501154, 501133, 501123, 4283126, C04B 3515

Patent

active

048533513

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

This invention relates to novel silica shaped bodies having improved heat insulating properties and a process for preparing the same.


DESCRIPTION OF RELATED ART

Silica heat insulating materials are required to have various properties such as lightweight properties, excellent heat insulating properties, high fire resistance, sufficiently high strength to withstand handling and shaking, etc. In recent years, there is a great demand for materials of improved heat insulating properties.
Processes are known for improving heat insulating properties by incorporating an opacifier into silica heat insulating materials. For example, British Patent No. 1205572 discloses a heat insulating material comprising microporous silica aerogel particles and an opacifier both supported by a fibrous material. British Patent No. 1350661 describes the foregoing heat insulating material enclosed with a bag of fiber-glass cloth or the like. Although outstanding in heat insulating properties, these heat insulating materials have the drawbacks of being extremely low in strength and finding a limited use.


SUMMARY OF THE INVENTION

It is an object of this invention to provide a novel silica shaped body which has outstanding heat insulating properties over a wide temperature range of low to high temperatures and is lightweight and also a process for preparing the shaped body.
It is another object of the invention to provide a novel silica shaped body which has outstanding heat insulating properties over a wide temperature range and is lightweight while retaining fully satisfactory strength for use and also a process for preparing the shaped body.
Other features of the present invention will become more apparent from the following description.
This invention provides a silica shaped body comprising a multiplicity of interconnected secondary particles of amorphous silica, voids interspersed between the secondary particles, and at least one inorganic inactive substance selected from among carbonaceous substance, carbide, nitride and metallic oxide and physically united with the secondary particles.
Our research has revealed that when a shaped body of secondary particles of amorphous silica already developed by the applicant and disclosed in U.S. Pat. No. 4230765 comprises a large number of interconnected secondary particles of amorphous silica and at least one inorganic inactive substance selected from among carbonaceous substance, carbide, nitride and metallic oxide and physically united with the secondary particles, the shaped body has the following characteristics;
(1) despite the presence of the above-specified inactive substance, the shaped body retains fully satisfactory strength for use and is lightweight,
(2) the shaped body has improved heat insulating properties over a wide temperature range of low to high temperatures, afforded by the presence of the inactive substance and
(3) the shaped body has remarkably improved heat insulating properties at high temperatures of at least 200.degree. C.


BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a photomicrograph of a prior art, rutile-free crystal slurry;
FIG. 2 is a photomicrograph of a crystal slurry according to the present invention;
FIG. 3 is a photomicrograph of a prior art rutile-free slurry of secondary particles of amorphous silica; and
FIG. 4 is a photomicrograph of secondary particles of amorphous silica containing rutile according to the present invention.


DESCRIPTION OF PREFERRED EMBODIMENTS

The silica shaped body of this invention can be produced, for example, by adding the above-specified inactive substance to the starting slurry to be subjected to a hydrothermal synthesis reaction in the process disclosed in U.S. Pat. No.4230765 for preparing a shaped body of secondary particles of amorphous silica.
The process of the above U.S. patent comprises subjecting a starting slurry containing a siliceous material, calcareous material and water to a hydrothermal synthesis reaction with heating and stirring under an elevated pressure to prepare an aque

REFERENCES:
patent: 4162924 (1979-07-01), Kubo et al.
patent: 4230765 (1980-10-01), Takahashi et al.
patent: 4298386 (1981-11-01), Kubo et al.
patent: 4455246 (1984-06-01), Schmidt et al.
patent: 4476234 (1984-10-01), Jones et al.
patent: 4647499 (1987-03-01), Takahashi et al.
patent: 4656146 (1987-04-01), Schlett et al.

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