JPH0676230B2 - Manufacturing method of crystalline glass - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing crystalline glass in which needle-like crystals are deposited on soda-lime glass, that is, crystalline foam glass and dense crystalline glass.

(Prior Art and Problems Thereof) Soda-lime glass is commonly used for buildings, other window materials, containers, etc. because it is easily vitrified and can be manufactured easily at low cost.

When manufacturing these materials, it is extremely important to avoid devitrification, that is, to prevent precipitation of crystals, and to maintain transparency. In that respect, the soda-lime type is the best devitrifying class among various component systems. Belongs to and has been prized since ancient times.

On the other hand, it is possible to add an alkaline earth metal carbonate such as calcium carbonate or magnesium carbonate as a foaming agent to glass powder such as soda lime and heat-foam it.
It is known as disclosed in No. 2. However, it is not necessary to add a large amount of foaming agent to produce foam glass,
It has been pointed out that the addition of a large amount rather makes the bubble diameter non-uniform or causes cavities due to abnormal foaming. Further, not limited to the preceding example, there is no attempt to employ the foaming agent as an acicular crystal precipitation accelerator.

On the other hand, there is an attempt to add a nucleating agent to soda-lime glass and forcibly crystallize it by heat treatment to impart decorative properties or improve mechanical strength and use it for building materials and the like.

In Japanese Examined Patent Publication No. 42-2271, soda lime-based raw material contains fluorine or further titanium oxide or zirconium oxide,
JP-B-45-3554 discloses that heavy metal sulfide is added to a soda-lime-based raw material, and JP-A-49-69730 discloses that iron sulfide or manganese sulfide is added in the same manner, and molten glass is crystallized by heat treatment. Has been done.

In these methods, in addition to acicular crystals such as wollastonite, silica crystals such as cristobalite and tridymite are preferentially precipitated. However, silica crystals are not preferable because they have an abnormal volume change due to the transition in the low temperature heating region, which gives distortion or collapse to the product.

Further, the uniform dispersion of the nucleating agent requires a high level of technology from the raw material preparation to the melt preparation. In general, a nucleating agent having a high specific gravity and an ultrafine powder is used, so that the segregation of the nucleating agent should be carefully performed and a corresponding technique is required.

Furthermore, the method of once forming glass and re-crystallizing by heat treatment has a bad effect such as poor production efficiency or deformation in the heat treatment process.

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

Japanese Examined Patent Publication No. 36729/36 discloses opalescent glass obtained by devitrifying and opacifying in the devitrification temperature region by integrating phosphates such as sodium and potassium as a binder into fine powder of soda-lime glass. However, the addition of phosphate does not lead to improvement in mechanical strength and thermal shock resistance because silica crystals are preferentially precipitated similarly to the above.

The present invention eliminates the above problems, by depositing needle-shaped crystals in soda-lime glass in a specific amount range, crystalline glass excellent in mechanical strength and thermal shock resistance, that is, dense crystalline glass or It is an object of the present invention to provide crystalline foam glass, and further to provide a suitable method for producing these crystalline glasses.

In addition, in the Japanese Patent Application No. 63-216143 filed earlier by the present applicant, soda lime glass powder and a needle-shaped crystal precipitation accelerator alkali metal carbonate or hydroxide are used as precursor raw materials, and thermal shock resistance Although the inventors have proposed a crystalline glass having excellent properties and mechanical strength, the present inventor further examined this, and as a result, a crystalline glass having a new needle-shaped crystal precipitation promoter adopted to improve water resistance and heat resistance. That is, the present invention has been achieved.

(Means for Solving Problems) The present invention is a method for producing crystalline glass containing 20 to 50 wt% of needle-shaped crystals, wherein carbonate of soda-lime glass powder, carbonate of alkaline earth metal, nitrate, water Oxide or a mixed powder or sludge obtained by adding 10 wt% of acicular crystal precipitation accelerator consisting of at least one selected from nitrates of alkali metals in terms of oxide is preformed, and then the soda lime silica glass 10 at an appropriate temperature between the softening point and pour point of
It is heated and maintained for 60 minutes to 60 minutes to allow acicular crystals to be contained, and the acicular crystals are wollastonite, devitrite, diopside, SrSiO ₃ , Ba ₂ Si ₃ O ₈ , BaSi.
And at least one of O _{3 and} Na ₂ CaSi ₃ O ₈ and maintaining the heating, or after heating and consolidating.

In the present invention, waste of soda-lime glass (referred to as glass cullet), which is often used for plate glass, container glass, etc., is used as a starting material, and this is used as 150 mesh (100 μ
mφ) to be pulverized and prepared. In order to react well with the needle-shaped crystal precipitation accelerator described later, its specific surface area is large,
Therefore, it is desirable that the particles are fine particles, and it is particularly preferable that the particle size is not more than the above-mentioned particle size.

As the other starting material, an acicular crystal precipitation accelerator (hereinafter simply referred to as a precipitation accelerator) is used. What are acicular crystals? Wollastonite, devitrite, diopside, SrSiO ₃ , Ba ₂ Si _{3
O 8, BaSiO 3, Na 2} CaSi 3 O 8 or the like refers to a needle crystal of development.

These are appropriately selected as one or more kinds from alkaline earth metal carbonates, nitrates, hydroxides or alkali metal nitrates as a component for promoting the selective precipitation of needle crystals.

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

Precipitation accelerator in oxide conversion for the glass cullet powder
1 wt% to 10 wt% is added, and the mixture is wet- or dry-mixed and then press-molded into a desired shape or cast as sludge. If the addition amount is less than 1 wt%, the precipitation action of needle-like crystals is small, and if it exceeds 10 wt%, the crystal precipitation component region is changed, and crystals other than needle-like crystals are likely to precipitate.

In addition, in Japanese Patent Application No. 63-216143 filed by the applicant of the present invention, when an alkali metal carbonate or hydroxide is used as a precipitation accelerator, devitrite, Na ₂ CaS having a low melting point is used.
When a large amount of crystals containing a large amount of alkali metal such as i ₃ O ₈ or a large amount of wollastonite with a relatively high melting point is formed, while forming a low temperature melting glass matrix rich in alkali metals However, in any case, the heat resistance of the crystalline glass is poor and the water resistance is also deteriorated. When the alkaline earth metal compound in the present invention is used, needle-like crystals made of a high-melting alkaline earth metal silicate are easily deposited, and the glass matrix also contains a relatively large amount of alkaline earth metal and is heat and water resistant. It becomes an excellent crystalline glass.

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

Then the softening point of the raw glass ( ^10.65 poise in viscosity,
720 ℃ above normal glass, pour point (also 1
The temperature is raised to an appropriate temperature within the range of 0 ⁵ poise, 900 ° C.) or less and kept for 10 to 60 minutes. If it is less than the glass softening point, the reaction with the precipitation accelerator is insufficient, and if it exceeds the pour point, the tendency of crystal precipitation is weakened by approaching the liquidus temperature, that is, the vitrification temperature. Further, if less than 10 minutes, the precipitation of needle-shaped crystals is insufficient,
If it exceeds 60 minutes, depending on the precipitation accelerator, the crystal phase and the glass phase will react again to form a new glass phase, or the needle-shaped crystal precipitation will reach the end, and crystals such as cristobalite that adversely affect the heat resistance will be formed. Easy to deposit.

In the temperature range, the softened glass reacts with the decomposed and melted precipitation accelerator, and some of the decomposed gas components are trapped in the reaction viscous liquid and become foamy glass, while on the other hand, the grain boundaries and the reaction of the glass cullet powder. Crystal precipitation begins in the glass phase. A more preferable heat treatment temperature time range is 800 to 850 ° C, 30 to
60 minutes.

The precipitation accelerator is a melt component suitable for the precipitation of the needle-like crystals, which imparts a viscosity, and exists as a so-called heterogeneous substance that is difficult to melt and diffuse like a so-called nucleating agent and crystallizes based on it. Is different from the type that precipitates.

Among the alkaline earth metals, magnesium and calcium have a large effect of precipitating acicular crystals, and strontium,
Barium is slightly inferior to this. Even in the same alkaline earth metal system, the action of carbonate, nitrate and hydroxide is remarkable. However, strontium carbonate and barium carbonate, which have extremely high decomposition temperatures, are inferior in their action. It should be noted that sulfate, chloride and the like have almost no effect. Phosphate is also not preferred because silica crystals preferentially precipitate, which are likely to cause adverse effects on heat resistance and mechanical strength. The reason why the precipitation tendency differs depending on the alkaline earth metal or the type of compound even in the same alkaline earth metal system has not been elucidated, but one factor is the diffusion rate of alkaline earth metal ions and the dissociation temperature of the compound. It is presumed that it is doing.

In soda-lime glass, wollastonite, devitrite, Na ₂ CaSi ₃ O ₈ acicular crystals from the component region, as well as silica crystals such as cristobalite and tridymite, are precipitated, but in the system where a precipitation accelerator is added, silica crystals are formed. Precipitation is suppressed. Depending on the amount of precipitation accelerator added and heat treatment conditions, when a calcium compound is added, the needle crystals are further diopside in the case of a magnesium compound, and SrSiO _{3 in} the case of a strontium compound is a barium compound. In this case, Ba ₂ Si ₃ O ₈ and BaSiO ₃ are likely to precipitate.

In the present invention, the needle crystals are contained in the glass in an amount of 20 to 50% by weight.
By including it, mechanical strength and heat resistance are remarkably improved. If it is less than 20 wt%, those effects are small. When attempting to deposit more than 50% by weight, silica crystals are naturally generated in the component region, which impairs 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 a crystalline foam glass in which numerous bubbles remain, and becomes a product in which the bubbles are made uniform by the slow cooling process.

On the other hand, when heat treatment or in a heat softened state after heat treatment, if a means for compressing, for example, a means of passing between a pair of rolls and pinching between the rolls is taken, a bubble is appropriately escaped and a crystal having a controlled bulk density is controlled. It becomes a high quality glass or a dense crystalline glass with almost no bubbles. The product is obtained by further slow cooling.

(Example) As plate glass cullet powder, SiO ₂ 71% by weight%, Al ₂ O ₃ 1.6
%, CaO 11%, MgO 2.1%, Na ₂ O 13%, K ₂ O 0.8% and a particle size adjusted to 200 mesh or less were prepared. Commercially available magnesium, calcium, strontium, barium carbonate, nitrate, hydroxide, and sodium nitrate were prepared as precipitation accelerators.

The cullet powder and the needle-shaped crystal precipitation accelerator are dry mixed at a predetermined ratio, or 7 wt% of water is added and mixed for wet mixing, and the product obtained by dry mixing is pressed under a pressure condition of 20 kg / cm ^2. The sludge obtained by wet mixing was cast-molded and then dried to obtain a preform. Various foamed samples were obtained by raising the temperature to a predetermined temperature in an electric furnace at a rate of 400 ° C./hour, maintaining the temperature for a predetermined time, and then slowly cooling it. Further, some of the samples were taken out of the furnace after heat treatment, sandwiched between steel plates which had been preheated to the temperature in advance, and were manually rolled by a roller from above to be compressed to remove bubbles, thereby obtaining a dense sample.

The following measurements were performed on these samples.

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

Crystal identification; EPMA mainly by X-ray diffraction and observation under a mirror
Combined analysis.

Measurement of the amount of crystals (weight percentage volume ratio) in the solid phase; known Ohlb
According to the quantitative method proposed by erg-Strickler, if the background intensity of glass at 2θ = 20 to 25 ° in x-ray diffraction is Ig, that of 100% crystal is Ic, and that of the sample is Is, the crystal is Material (wt%) = Ig-Is / Ig-Ic. A calibration curve was prepared according to this method and quantified. In addition, a quantitative method based on observation under a mirror was adopted as an auxiliary.

Thermal shock test (quenching test); set a 50mm x 20mm thick sample in an electric furnace, hold at 500 ° C, take it out, immediately put it in water at 10 ° C, quench it, and check that there are no cracks visually. Good, those with small cracks were classified as good, and those with large cracks or collapsed were classified into three ranks.

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

In addition, phosphate, boric acid, lead compound, sulfate, and chloride were added to and mixed with soda-lime glass powder, and press-molded was prepared, heat-treated in the same manner, measured, and comparatively examined.

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

As is clear from the table, the present invention has excellent thermal shock resistance and mechanical strength. In those containing the phosphates of Comparative Examples 1 and 2, silica is precipitated as a main crystal. It is presumed that the crystals of Comparative Examples 3 and 4 to which boric acid and a lead compound were added did not precipitate crystals, but rather expanded the vitrification region. Comparative Example 5
The sulfates and chlorides of Nos. 7 to 7 remain without being decomposed and do not show a crystal precipitation effect. All of these comparative examples are inferior in heat resistance and mechanical strength.

(Effect of the invention) According to the present invention, crystalline glass such as crystalline foam glass and dense crystalline glass can be produced very easily, and the obtained crystalline glass has thermal shock resistance, mechanical strength and heat resistance, It has excellent water resistance, is useful as a heat-resistant and high-strength building material, is extremely easy to manufacture, and has an effect that crystalline foam glass or dense crystalline glass can be manufactured freely.

Claims (3)

[Claims] 1. A method for producing crystalline glass containing 20 to 50 wt% of needle-shaped crystals, wherein an alkaline earth metal carbonate, nitrate, hydroxide or alkali metal nitrate is added to soda lime glass powder. A mixed powder or mixed sludge containing 10% by weight of an acicular crystal precipitation accelerating agent selected from the group consisting of at least one selected from the above is preformed, and then the softening point or pour point of the soda lime silica glass is between At appropriate temperature
A method for producing crystalline glass, characterized in that heating is maintained for 10 to 60 minutes so that acicular crystals are precipitated and contained. 2. The acicular crystals are wollastonite, devitrite, diopside, SrSiO ₃ , Ba ₂ Si ₃ O ₈ , BaSiO ₃ or
_2. One or more kinds of Na ₂ CaSi ₃ O ₈ are included.
A method for producing the crystalline glass described above. 3. The method for producing crystalline glass according to claim 1 or 2, wherein the glass is made to be consolidated while being heated or after being heated.