JPH0365525A - Crystal glass and production thereof - Google Patents

Abstract

PURPOSE:To obtain dense crystalline glass or crystalline foam glass excellent in mechanical strength or thermal shock resistance by heat-treating a precursor raw material composed of soda-lime-based glass powder, LiO2-containing glass as an acicular crystal deposition accelerator or further a foaming agent. CONSTITUTION:The aforementioned crystalline glass is a heat-treated formed body of soda-lime-based glass powder, needle-like crystal deposition accelerator or further a foaming agent as a precursor raw material and contains 20-60vol.% acicular crystals and LiO2-containing glass is used as a needle-like crystal deposition accelerator. The LiO2-containing glass is preferably glass containing >=10wt.% Li2O and the needle-like crystals to be deposited are wollastonite, devitrite, Na2CaSi3O8, lithium silicate, etc.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a crystalline glass in which acicular crystals are precipitated on a soda-lime glass, that is, a crystalline foam glass and a dense crystalline glass, and further relates to the crystalline glass. Concerning the manufacturing method.

[Prior art and its problems 1] The applicant previously disclosed in Japanese Patent Application No. 63-216143 that a needle-like crystal precipitation promoter consisting of soda-lime-based glass powder and an alkali metal hydroxide or carbonate, etc. proposed a crystalline glass made by molding and heat-treating a mixture of

The acicular crystal precipitation accelerator generates gas when decomposed and melted, and the melt reacts with the glass matrix to promote the precipitation of acicular crystals to form crystalline foam glass. However, in order to obtain a dense crystalline glass, it is necessary to densify the glass in a thermally softened state by means such as compression, which makes the process complicated and increases the manufacturing cost.

Further, the acicular crystal precipitation accelerator also acts as a foaming agent, but it is difficult to control both the amount of crystal precipitation and the force and specific gravity based on foaming.

For example, in order to precipitate a large amount of crystals in a short period of time, it is necessary to add a acicular crystal precipitation accelerator to soda-lime glass in an amount exceeding 5 wt%, but this increases the amount of foaming and although the bulk specific gravity is low, Forms open air bubbles and deteriorates water absorption resistance.
Or conversely, it is difficult to obtain a stable state, such as gas components easily escaping and a tendency toward densification occurring.

In addition, JP-A No. 63-144134 discloses that glass mixed raw material powders with high and low softening points are put into a mold, heated and fused, shaped into a press bottom shape, and further heat-treated to precipitate crystals. However, it is mentioned that low softening point glass is used as a mere binder during molding instead of known PVA etc., and for glass that does not contain 120 minutes as described, needles as in the present invention are used. It does not exhibit effective action as a crystal precipitation accelerator.

The present invention relates to an improvement on the invention previously filed by the applicant, and focuses on the fact that lithium compounds are extremely effective in promoting the precipitation of needle-like crystals.By employing Li20-containing glass as a lithium source, mechanical The purpose of the present invention is to provide dense crystalline glass or crystalline foam glass with excellent strength and thermal shock resistance.

[Means for Solving the Problems] The present invention provides a soda-lime based glass powder, a needle crystal precipitation accelerator,
Alternatively, a heat-treated molded article further using a blowing agent as a precursor raw material, a crystalline glass containing 20 vol% or more and 60 vol% or less of needle-like crystals, wherein the needle-like crystal precipitation promoter is Li20-containing glass, is preferable. The Li20-containing glass is a glass containing 10 wt% or more of Li20, and the acicular crystals are wollastonite, debitrite, N
a2 Ca5130a, lithium silicate, and the method for producing the crystalline glass, in which an acicular crystal precipitation accelerator is added to soda-lime glass powder.
A mixed powder or mixed sludge containing 1 to 10 wt% in terms of i20 is preformed, and then heated and maintained for 10 to 60 minutes at an appropriate temperature between the softening point and pour point of the soda lime glass to form acicular crystals. It consists of making it precipitate.

In the present invention, waste soda lime glass (referred to as glass cullet), which is often used for sheet glass, container glass, etc., is used as a starting material, and 150 meshes (10
0LIm). In order to react favorably with the acicular crystal precipitation accelerator described later, it is desirable that the specific surface area is large and that the particles are fine, and in particular, the particle size is preferably below the above-mentioned particle size.

As the other starting material a Li2O-containing glass, preferably L
A needle crystal precipitation accelerator made of glass containing 10% or more of i2O is used. The needle-like crystals are wollastonite,
Refers to crystals such as debitrite, Na2CaSi30a, and lithium silicate.

Note that Li20-containing glass is produced by mixing and melting the lithium compound raw material with other silica raw materials or further raw materials such as alumina, lime, and alkali, or by mixing and melting the lithium compound raw material with soda lime-based, aluminosilicate-based, borosilicate-based, etc. It is made by mixing with powder and melting it, and it melts at an extremely low temperature.

That is, the Li20-containing glass is melted by heat treatment and reacts with the heat-softened soda-lime glass powder to rapidly precipitate needle-shaped crystals, the particle size of which is the same as or smaller than that of the soda-lime glass powder. shall be.

A needle crystal precipitation accelerator is added to the soda-lime glass powder in an amount of 1 wt% to 10 int% (calculated as Li20), subjected to wet or dry IIL, and then pressed into a desired shape or cast as a sludge. .

If the amount added is less than 1iit%, the precipitation effect of needle-shaped crystals is small, and if it exceeds 10wt%, the region of crystallization components changes, and in particular, the glass matrix becomes excessively alkali, deteriorating heat resistance and chemical durability. More preferably 1w
The range is t% to 5%.

In addition, preforming is necessary to maintain the shape and to bring the cullet powder into close contact with the acicular crystal precipitation promoter.

Next, the softening point of the raw soda lime glass (in terms of viscosity,
107.61i voids, 720 in normal flat glass
°C) or above, pour point (also 105 bois, 900 °C)
The temperature is raised to an appropriate temperature within the following range and maintained for 10 to 60 minutes. If the temperature is below the glass softening point, the reaction with the acicular crystal precipitation accelerator is insufficient, and if it exceeds the pour point, the temperature approaches the liquidus temperature, that is, the vitrification temperature, and the crystal precipitation tendency weakens. In addition, if the time is less than 10 minutes, precipitation of needle-like crystals is insufficient, and 60 minutes
If the time exceeds 1 minute, the crystal phase and the glass phase may react again to form a new glass phase, depending on the acicular crystal precipitation accelerator, or the precipitation of acicular crystals may come to an end, which may adversely affect the heat resistance of cristobalite etc. The crystals given tend to precipitate.

In this temperature range, the softened raw soda-lime glass reacts with the molten needle-like crystal precipitation accelerator, and crystals begin to precipitate at the grain boundaries of the soda-lime glass powder and in the reacted glass phase.

The acicular crystal precipitation accelerator, that is, Li2O-containing glass, releases a large amount of gas components and lowers the bulk specific gravity, as when alkali metal salts and hydroxides are decomposed and melted, as proposed by the present applicant in the above-mentioned Hikari application. In addition, the lithium content, which is rich in reaction activity, quickly reacts with the thermally softened ring soda-lime glass powder, promoting the precipitation of needle-shaped crystals. It forms a dense and robust crystalline glass.

Soda-lime glass contains wollastonite, debitrite, Na2CaSi3-08
In addition to isoacicular crystals, cristobalite, tridymite, etc. are precipitated, and when a large amount of Li20 min is added, lithium silicate is precipitated.

In the present invention, the acicular crystals are contained in glass at a concentration of 20 to 60
Mechanical strength and heat resistance are significantly improved by containing vol%. *If the content is less than 20 vol%, these effects are small. If it is attempted to precipitate in excess of 60 vol%, cristobalite and the like will naturally occur due to the compositional range, which is not preferable because it will impair mechanical strength and heat resistance.

The crystalline glass produced in this way is dense, but when a known blowing agent such as calcium carbonate is added in advance, the bulk specific gravity is controlled depending on the amount added and heat treatment conditions. Forms quality foam glass.

Furthermore, a laminate of dense crystalline glass and crystalline foam glass or ordinary foam glass can be easily manufactured, and in this case, each raw material may be formed into a laminate and heat-treated at the same time.

[Examples (1 to 6)] SiO□71% by weight as sheet glass current powder.

Al1031.6%, Ca011%, Mg02.1%,
A particle having a composition of 13% Na2O and 200.8% and a particle size of 200 mesh or less was prepared. Lithium hydroxide was added and mixed to the same current powder as the needle crystal precipitation accelerator, and 5 to 20 wt of Li was added.
% (those containing 1,iz O>20 wt% are difficult to vitrify), and the particle size of this glass was adjusted in the same manner as the current powder. Commercially available calcium carbonate powder was prepared as a blowing agent.

Adding and mixing an acicular crystal precipitation accelerator to the current powder, or further adding and mixing a foaming agent to the current powder,
It was pressed under a pressure condition of 50 kg/cd to obtain a preform. This was heated to a predetermined temperature in an electric furnace, maintained for a predetermined time, and then gradually cooled to obtain various crystalline glasses.

The following measurements were performed on these samples.

Determination of specific gravity aIq: by a known measuring means using a fixed specific gravity bottle.

Identification of crystals; mainly by X-ray diffraction and reading observation.
MA analysis was also used.

Measurement of the amount of crystals in the solid phase: The area ratio of the crystal phase was measured under reading on an arbitrary cut surface of the sample, and the volume ratio was determined.

Heat resistance test: A sample of 50 mm x 20 mm thick was set in an electric furnace and heated to 900°C, held at that temperature for 60 minutes, allowed to cool, and the sample was taken out. The samples were classified into 3 ranks: good if the crystals did not deteriorate, fair if the crystals showed a tendency to decrease but did not lose their shape, and poor if the crystals had progressed to vitrification and softening and lost their shape.

Thermal shock test (quenching test); 50 heavy east exit) <23 asl'
After setting the sample X in an electric furnace and holding it at 500°C, take it out and immediately put it in water at 10'C to cool it rapidly.The one with no cracks visually inspected is good, and the one with small cracks is judged as good. Items were classified into three ranks: acceptable, and items that developed large cracks or collapsed.

Water absorption rate: soak the sample in room temperature water for 36 hours, then take it out, calculate the water absorption rate from the weight change before and after, less than 1wt% is excellent, 1wt% or more 2 or more 2 L is good, 2-1% or more 4
It was classified into 4 ranks: acceptable if it was less than wt%, and unacceptable if it was 4ht% or more.

Furthermore, the compressive strength of some of the samples was measured.

For reference, please refer to the patent application filed earlier by the applicant in 1983.
According to the invention of No.-216143, a comparative test was also conducted on a crystalline glass sample obtained by adding lithium carbonate as a needle crystal precipitation accelerator to soda lime glass powder and subjecting it to bottom shape and heat treatment in the same manner (Comparative Reference Example 3). ).

Sample preparation conditions and test results are shown in Table 1.

In Comparative Reference Example 1, the amount of Li20 in the Li20-containing glass is small, and therefore the effect of rapid precipitation of needle crystals is small. Comparative Reference Example 2 has an excessive amount of Li added to the original glass for 20 minutes, resulting in improved heat resistance and water absorption resistance, while Comparative Reference Example 3 uses lithium carbonate as a needle crystal precipitation promoter, resulting in improved water absorption resistance. There are some difficulties. On the other hand, it was clear that all of the examples were excellent.

[Effects of the Invention] The crystalline glass of the present invention has excellent thermal shock resistance and mechanical strength, and is useful as a heat-resistant, high-strength building material.It is also extremely easy to manufacture, and has a high bulk density and high thermal shock resistance. The ability to freely manufacture crystalline foam glass with controlled conditions will have many effects.

Claims (1)

[Claims] 1) Heat treatment molding using soda-lime-based glass powder and a needle crystal precipitation accelerator, or a blowing agent as a precursor raw material, comprising:
A crystalline glass comprising 20 vol% or more and 60 vol% or less of acicular crystals, wherein the acicular crystal precipitation promoter is Li_2O-containing glass. 2) Li_
Claim 1, wherein the 2O-containing glass is a glass containing 10 wt% or more of Li_2O, and the acicular crystals are made of one or more of wollastonite, debitrite, Na_2CaSi_3O_8, or lithium silicate.
The crystalline glass described. 3) A mixed powder or mixed sludge in which 1 to 10 wt% of Li_2O-containing glass is added in terms of Li_2O to soda-lime glass powder is preformed, and then it is heated at an appropriate temperature between the softening point and pour point of the soda-lime glass for 10 1. A method for producing crystalline glass, characterized in that heating is maintained for 60 minutes to 60 minutes to precipitate needle-like crystals.