JPH02145456A - Crystalline glass and production thereof - Google Patents

Abstract

PURPOSE:To readily obtain a crystalline glass having excellent thermal shock resistance, mechanical strength, heat resistance, water resistance, etc., by adding a specific needle crystalline depositing promoter to a soda lime based glass powder at a prescribed amount, preforming the mixture, heat-treating the resultant preform while controlling temperature and time and depositing a needle crystal. CONSTITUTION:A needle crystal depositing promoter (e.g., calcium carbonate or sodium nitrate) selected from carbonate, nitrate, hydroxide of alkaline earth metals or nitrate of alkali metals is prepared. One or more kind of needle crystalline depositing promoters are added at an amount of 1-10wt.% expressed in terms of oxide. Then the resultant mixed powder or mixed sludge is preformed and then heated at a proper temperature between softening point or pour point of soda lime based glass for 10-60min and a needle crystal (e.g., wollastonite) is deposited to provide the crystalline glass useful as a heat- resistant and high-strength building material, etc.

Description

Detailed Description of the Invention (Field of Industrial Application) 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) Soda-lime glass is widely used for building and other window materials, containers, etc. because it is easily vitrified and can be manufactured at low cost.

When manufacturing these materials, it is extremely important to avoid devitrification, that is, the precipitation of crystals, and to maintain transparency, and in this respect, the soda lime system is the best among the various component systems that are resistant to devitrification. It belongs to this category and has traditionally been awarded the award.

On the other hand, adding an alkaline earth metal carbonate such as calcium carbonate or magnesium carbonate to glass powder such as soda lime as a foaming agent and foaming by heating is known, for example, in JP-A-61-2
It is known as disclosed in No. 19742. However, in order to produce foam glass, it is not necessary to add a large amount of blowing agent (although it has been pointed out that adding a large amount may actually make the bubble diameter uneven or create cavities due to abnormal foaming. Not limited to the preceding example, there has been no attempt to employ the foaming agent as a needle-like crystal precipitation accelerator.

On the other hand, there have been attempts to add a nucleating agent to soda-lime glass and forcibly crystallize it through heat treatment to impart decorative properties or improve mechanical strength, and to use the glass in building materials and the like.

In Japanese Patent Publication No. 42-2271, a fluorine content or further titanium oxide or zirconium oxide was added to soda lime-based raw materials, in Japanese Patent Publication No. 45-3554, heavy metal sulfides were added to soda lime-based raw materials, and in Japanese Patent Publication No. 49-69730. Similarly, it is disclosed that iron sulfide or manganese sulfide is added, each is melted and vitrified, and then crystallized by heat treatment.

In these methods, silica crystals such as cristobalite and tridymite are preferentially precipitated in addition to needle-shaped crystals such as wollastonite. However, silica crystals are undesirable because they undergo abnormal volume changes due to transition in the low-temperature heating range, which can cause distortion or collapse of the product.

Further, uniform dispersion of the nucleating agent requires advanced technology from raw material preparation to melt preparation. Generally, the nucleating agent used is one with a high specific gravity and an extremely fine powder, so careful attention must be paid to its segregation, and appropriate techniques are required.

Furthermore, the method of forming glass and then heat-treating and crystallizing it again has disadvantages such as poor production efficiency and deformation during the heat treatment process.

There are also disclosed examples in which crystals are precipitated without a nucleating agent.

Japanese Patent Publication No. 36-16729 discloses an opalescent glass in which fine powder of soda-lime glass is integrated with phosphates such as sodium and potassium as a binder, and the glass is devitrified and opalescent in the devitrification temperature range.

However, addition of phosphate preferentially precipitates silica crystals as described above, and thus does not improve mechanical strength or thermal shock resistance.

The present invention solves the above problems and produces a crystalline glass with excellent mechanical strength and thermal shock resistance, that is, a dense crystalline glass or It is an object of the present invention to provide crystalline foam glasses and also to provide a suitable method for producing these crystalline glasses.

In addition, the present applicant has previously filed patent application No. 63-21614.
In No. 3, we proposed a crystalline glass with excellent thermal shock resistance and mechanical strength that uses soda-lime glass powder and carbonate or hydroxide of alkali metals, which are accelerators for the precipitation of needle crystals, as precursor raw materials. As a result of further investigation, the present inventors have discovered a crystalline glass with improved water resistance and heat resistance that employs a new acicular crystal precipitation promoter, thereby achieving the present invention.

(Means for Solving the Problems) The present invention is a heat-treated molded article using soda-lime-based glass powder and a needle-like crystal precipitation accelerator as precursor raw materials.
- In the crystalline glass containing t% or more and 50wt% or less, the acicular crystal precipitation promoter is one type selected from carbonates, nitrates, hydroxides of alkaline earth metals, or nitrates of alkali metals. Specifically, the needle-like crystals include wollastonite, debitrite, diopside, 5rSi03, BazSi30g, Ba5ic.
, or Na, CaSi, 0. Regarding products consisting of one or more of
The mixed powder or mixed sludge added with vt% 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 precipitate needle-like crystals. and further comprises compacting during or after maintaining the heating.

In the present invention, soda lime glass waste (referred to as glass cullet), which is often used for sheet glass, container glass, etc., is used as a starting material, and 150 meshes (1
00 μmφ) or less. In order to react favorably with the acicular crystal precipitation accelerator described later, it is desirable that the specific surface area is large and therefore the particles are fine, and in particular, the particle size is preferably equal to or less than the above-mentioned particle size.

A needle crystal precipitation promoter (hereinafter simply referred to as a precipitation promoter) is used as the other starting material. Acicular crystals include wollastonite, debitrite, diopside, SrSiO, etc.
BazSi, , Os, BaSiO3, Na.

Refers to crystals that develop into needle shapes such as Ca5i30s.

As a component that promotes the selective precipitation of these needle-shaped crystals, one or more types of alkaline earth metal carbonates, nitrates, hydroxides, and alkali metal nitrates are appropriately selected.

These are melted by heat treatment and rapidly precipitate needle-like crystals by reaction with the glass powder, and like the glass cullet powder, those having a diameter of 150 meshes (100 μmφ) or less are used.

A precipitation accelerator is added to the glass cullet powder in an amount of 1 wt % to 10 wt % in terms of oxide, mixed wet or dry, and then press-molded into a desired shape or cast as a sludge. When the amount added is less than 1 wt%, the action of precipitating needle-like crystals is small, and when it exceeds 1 lht%, the region of crystal precipitated components changes, and crystals other than needle-like crystals tend to precipitate.

In addition, Japanese Patent Application Laid-Open No. 63-21614, which the present applicant previously applied for,
In No. 3, when an alkali metal carbonate or hydroxide is used as a precipitation accelerator, low melting point debitrite, Na, CaSi, 0. A large amount of crystals containing a large amount of alkali metals may be precipitated or a glass matrix may be formed, but in either case, the heat resistance of the crystalline glass is poor and the water resistance is also deteriorated. When the alkaline earth metal compound of the present invention is used, needle-like crystals made of alkaline earth metal silicate with a high melting point are easily precipitated, and the glass matrix also contains a relatively large amount of alkaline earth metal, resulting in heat resistance and water resistance. It becomes a crystalline glass with excellent properties.

In the present invention, a more preferable addition range of the precipitation accelerator is 5 wt% to 10 wt%. In addition, preforming is necessary to maintain the shape and to bring the cullet powder into close contact with the precipitation accelerator.

Next, the temperature is raised to an appropriate temperature within the range of the softening point of the raw glass (viscosity: 107.65 voids, 720°C for regular plate glass) and below the pour point (also 10' voids, 900°C) for 10 to 60 minutes. Hold. Note that below the glass softening point, the reaction with the precipitation accelerator is insufficient, and above the pour point, the temperature approaches the liquidus temperature, that is, the vitrification temperature, and the tendency for crystal precipitation to weaken. Also, if the time is less than 10 minutes, the precipitation of needle-like crystals will be insufficient, and if the time exceeds 60 minutes, depending on the precipitation accelerator, the crystal phase and the glass phase may react again to form a new glass phase, or the needle-like crystals may not be sufficiently precipitated. Precipitation reaches its end, and crystals such as cristobalite, which have an adverse effect on heat resistance, tend to precipitate.

In this temperature range, the softened glass reacts with the decomposed and melted precipitation accelerator, and some of the decomposed gas components are captured in the reaction viscous liquid to form a foam glass, while the grain boundaries of the glass cullet powder and the reaction Crystals begin to precipitate into the glass phase. In addition, a more preferable range of heat treatment temperature and time is 800 to 850°C.
, 30 to 60 minutes.

Precipitation accelerators provide melt components and viscosity suitable for the precipitation of the needle-like crystals, and like so-called nucleating agents, they exist as foreign substances that are difficult to melt and diffuse, and are used to form crystals based on them. It is different from the type that precipitates.

Of the alkaline earth metals, magnesium and calcium have the greatest effect on precipitating needle-like crystals, while strotium,
Valium is slightly inferior to this. Furthermore, even in the same alkaline earth metal system, the effects of carbonates, nitrates, and hydroxides are significant. However, strontium carbonate and barium carbonate, which have extremely high decomposition temperatures, are inferior in their effectiveness. Note that sulfates, chlorides, etc. have almost no effect. Further, phosphates are not preferred because silica crystals, which tend to cause adverse effects on heat resistance and mechanical strength, preferentially precipitate.

It is not clear why the precipitation tendency differs depending on the alkaline earth metal or depending on the type of compound even in the same alkaline earth metal system, but it may be due to factors such as the diffusion rate of the alkaline earth metal ion and the dissociation temperature of the compound. It is presumed that they are doing so.

In soda-lime glass, silica crystals such as wollastonite, debitrite, and NazCaSi3oll needle crystals, as well as cristobalite and tridymite, precipitate due to its component range, but in systems in which a precipitation accelerator is added, the precipitation of silica crystals is suppressed. Ru. Although it depends on the amount of precipitation accelerator added and the heat treatment conditions, when a calcium compound is added, the above-mentioned acicular crystals are added, when a magnesium compound is added, diopside is added, and when a strontium compound is added, Sr is added.
If SiO+ is a barium compound, Ba2Si30B
, Ba5ins are likely to precipitate.

In the present invention, 20 to 50 acicular crystals are added to the glass.
Mechanical strength and heat resistance are significantly improved by including wt%. If the amount is less than 20wt%, their effects are small. If it is attempted to precipitate more than 50iyt%, silica crystals will also be generated, which is natural due to the compositional range, and this will impair mechanical strength and thermal shock resistance, which is not preferable. More preferably, it is in the range of 23 to 45 wt%.

The crystalline glass produced in this manner forms crystalline foam glass in which countless bubbles remain, and by passing through an annealing process, the product becomes a product with even bubbles.

On the other hand, if compression means, such as passing between a pair of rolls and squeezing between the rolls, are used during heat treatment or in a thermally softened state after heat treatment, bubbles can be appropriately released and crystals with controlled bulk specific gravity can be obtained. The result is fine foam glass, or dense crystalline glass with most of the bubbles escaping. A product is obtained by further slow cooling.

(Example) 5iOz71% by weight as plate glass cullet powder, A
1z031.6%, Ca011%, MgO2,1%, N
Particle size 20 with a composition of 13% a2O, 0.8% K2O
A sample adjusted to less than 0 mesohydr was prepared. Commercially available carbonates, nitrates, hydroxides, and sodium nitrate of magnesium, calcium, strontium, and barium were prepared as precipitation accelerators.

The current powder and the needle-like crystal precipitation accelerator are dry mixed in a predetermined ratio, or wet mixed by adding 7 wt % of water, and the product obtained by dry mixing is pressed under a pressure condition of 20 kg/aft, and wet mixed. The sludge obtained by mixing was cast and dried to obtain a preformed product. This was heated to a predetermined temperature in an electric furnace at a rate of 400° C./hour, held for a predetermined time, and then gradually cooled to obtain various foamed samples. Furthermore, some of the samples were taken out of the furnace after heat treatment, sandwiched between steel plates preheated to the relevant temperature, and manually compressed by rolling a roller from above to remove air bubbles to obtain dense samples.

The following measurements were performed on these samples.

Specific gravity measurement: by known measuring means using a specific gravity bottle.

Identification of crystals; mainly by X-ray diffraction and observation under a microscope, EP
MA analysis was also used.

Measurement of the amount of crystals (weight percentage volume ratio) in the solid phase; known Oh
According to the quantitative method proposed by Robert Trickler, if the background intensity of glass at 2θ-20 to 25° in X-ray diffraction is Ig, that of a 100χ crystal is Ic-, and that of the sample is Is, then The amount (wtχ) is given by = Ig-4s/Ig-1c. A calibration curve was created and quantified according to this method. In addition, a quantitative method based on observation under a mirror was used as an auxiliary method.

Thermal shock test (quenching test): A sample of 50 mm opening x 20 mm thickness was placed in an electric furnace and held at 500°C, then taken out and immediately placed in water at 10°C to be rapidly cooled. , items with small cracks are acceptable, items with large cracks or collapse are unacceptable.
Classified into ranks.

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

In addition, phosphates, boric acid, lead compounds, sulfates, and chlorides were added to soda-lime glass powder, and press-molded products were prepared, heat-treated in the same way, and measured and compared.

Sample preparation conditions and measurement results are shown in Table 1 (Example) and Table 2.
Shown in the table (comparative example).

As is clear from the table, the products of the present invention have excellent thermal shock resistance and mechanical strength. In Comparative Example 1.2 to which phosphate was added, silica precipitated as the main crystal. It is presumed that in Comparative Examples 3.4 to which boric acid and lead compounds were added, no crystals were precipitated, but rather the vitrification region was expanded. Comparative example 5
The sulfates and chlorides of 7 to 7 remain without being decomposed and do not exhibit crystal precipitation effects. All of these comparative examples are inferior in heat resistance and mechanical strength.

(Effects of the Invention) The heat-treated and formed crystalline glass made from cheap and easily available soda-lime-based glass waste and a specific acicular crystal precipitation accelerator as precursor raw materials in the present invention has excellent thermal shock resistance, mechanical strength, heat resistance, It has excellent water resistance and is useful as a heat-resistant, high-strength building material.
Moreover, the production thereof is extremely easy, and it has the effect that crystalline foam glass and dense crystalline glass can be produced freely.

Claims (1)

[Scope of Claims] 1. A heat-treated molded article using soda-lime glass powder and a needle-like crystal precipitation accelerator as precursor raw materials, wherein the needle-like crystals are 20vo
In the crystalline glass containing 1% or more and 50vol% or less, the acicular crystal precipitation promoter is one selected from carbonates, nitrates, hydroxides of alkaline earth metals, or nitrates of alkali metals. A crystalline glass characterized by the above. 2. Acicular crystals are wollastonite, debitrite, diopside, SrSiO_3, Ba_2Si_3O_6
, BaSiO_3, or Na_2CaSi_3O_8. 3. Preform a mixed powder or mixed sludge in which 1 to 10 wt% of an acicular crystal precipitation accelerator is added in terms of oxide to soda lime glass powder, and then form a mixture between the softening point and pour point of the soda lime glass. A method for producing crystalline glass, characterized in that heating is maintained at an appropriate temperature for 10 to 60 minutes to precipitate needle-like crystals. 4. The method for producing crystalline glass according to claim 3, wherein the crystalline glass is compacted while maintaining heating or after maintaining heating.