JPS63170231A - Production of plate crystal glass - Google Patents

Abstract

PURPOSE:To easily obtain the title long and large-sized plate crystal glass having strength, by press-molding the powdery mixture of glass materials in the softening zone of the low-softening point glass with the belts carrying the mixture in between and rolls, and then heat-treating and crystallizing the compact. CONSTITUTION:The powder of glass materials having different softening points is heated to a specified temp. while being held between a couple of conveying belts, hence only the low-softening point glass is softened, and the high-softening point glass is not softened. The half-softened glass material is passed between two rolls along with the belts, and press-molded. The obtained plate compact is heat-treated, and the glass material powder constituting the compact is softened, fused together, densified, and crystallized.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for manufacturing plate-shaped crystallized glass suitable for architectural, decorative, etc. purposes.

(Prior art) Conventional production of crystallized glass involves melting a glass raw material containing a nucleating agent, shaping it by roll forming or various other forming means, and then performing crystallization heat treatment to precipitate crystals. It was made of glass.

In addition, as a method of obtaining crystallized glass without containing a nucleating agent, glass corpuscles are accumulated in a mold and heat treated.
A method (accumulation method) of fusing and crystallizing each small body is disclosed in Japanese Patent Publication No. 55-29018.

Further, as disclosed by the present inventors in "Japanese Patent Application No. 60-284150," a green compact obtained by press-molding fine powder of a glass-like raw material (glass) is heat-treated to soften and fuse to make it integrally densified. There is a method (referred to as the press method) that attempts crystallization with the same composition.The press method described above mainly uses a glassy raw material with a composition that precipitates strong wollastonite crystals. □The range is wide. In other words, the composition range of glass that can be used as a raw material for hardening is wide.

(Problems to be Solved by the Invention) Among the conventional methods described above, the method in which a nucleating agent is included and the glass product is formed and then heat-treated to achieve crystallization is that the nucleating agent is more expensive than the raw material. The problem with this method is that during the period of softening and fusion of the glass bodies, if the growth rate of precipitated crystal nuclei is fast and the composition has already entered the period of crystal growth, crystallization may occur. The accompanying increase in viscosity makes it difficult to fuse and integrate the bodies. In other words, there are restrictions on the component composition of the glass bodies that can be used, and it is not suitable even if they contain a nucleating agent or a coloring agent that has a nucleating effect.

The following pressing method of the prior invention by the present inventors heat-treats a green compact of fine powder of glassy raw material, so the softening point can be lowered due to the close contact between the powders and the large contact area. Glass powders can be softened, fused together, and densified at temperatures that are even higher than that of conventional glass powders.

In other words, in the above-mentioned accumulation method, since the glass bodies are coarse grained and simply in an accumulated state, their softening and fusing is substantially carried out at a temperature considerably higher than the softening temperature, and therefore, depending on the composition, crystals may already have grown, as described above. In contrast, in the press method, fusion and densification are performed at a low temperature slightly above the softening temperature, and crystal growth occurs by further raising the temperature. This means that the nucleating agent or cutting 8
The same is true when it contains a coloring agent that has the effect of creating fusing,
Crystallization can occur after densification.

However, in the above pressing method, if the green compact is large or thin, it is easily damaged during transportation or sintering, and in order to maintain its shape, a binder (such as organic binder polyvinyl alcohol, etc.) is required. It is necessary to add inorganic binders (such as alumina cement), and not only do these binders have little to do with the properties of the finished product, but residual binders can lead to a decline in product properties. There is. In such cases, it is necessary to incorporate a binder removal step during sintering to actively remove the binder, but removing the binder is often difficult and poses problems in terms of productivity and cost.

Another problem is that the production of powder compacts using conventional molds is unsuitable for producing long plate-like compacts.

(Means for Solving the Problems) The present invention has been made for the purpose of solving the problems of the prior invention described above and producing plate-shaped crystallized glass, and its characteristic means are low and high softening points. A mixture of different glassy raw material powders is sandwiched between a pair of conveyor belts, and together with the conveyor belts, a mixture of different glassy raw material powders with a temperature higher than the softening point of the low softening point glassy raw material powder and lower than the softening point of the high softening point glassy raw material powder is held. After heating to the molding temperature to soften the low softening point glassy raw material powder, it is further passed between two rolls together with a clamping belt to be press-formed to obtain a plate-shaped molded body. By heat-treating, the glassy raw material powders constituting the compact are softened and fused to each other to become denser and to precipitate crystals.

(Function) A mixture of glassy raw material powders with different low softening points (hereinafter referred to as raw material powders) is heated to a molding temperature that is above the softening point of the low softening point raw material powder and below the softening point of the high softening point raw material powder. After softening the low-softening point raw material powder, the heated mixture is passed between two rolls and pressure-molded, so the softened raw material powder acts as a binder, and the unsoftened high-softness Point raw material powders and powders are integrated with each other. Therefore, the various problems mentioned above caused by the use of conventional non-component binders are solved.

In addition, since the softened powder is the powder itself that constitutes the compact,
Unlike a binder, which has a limited amount, it can be added in a large amount, and a molded product with high strength can be obtained even if the pressing force is relatively small.

In addition, since it is pressure molding of softened and unsoftened mixed powder,
Compared to when the gold powder is softened and molded, air trapped between the powder can escape easily, resulting in a healthy molded product. In other words, the softened powder deforms to expel air while filling the gaps between the particles, and the slits between the unsoftened particles act as air passages.

Furthermore, since the molding means is so-called roll molding, the heated mixed powder can be continuously supplied, a long plate-shaped molded product can be easily obtained, and the thickness can be easily changed.

In addition, since the raw material powder mixture (hereinafter referred to as mixed powder) is heated and roll-formed while being held between a pair of conveyor belts, the belts cover the mixed powder surface and prevent contact with the outside air. At the same time, the heat retained by the belt suppresses the heat dissipation of the mixed powder and prevents its temperature from decreasing, resulting in an excellent hot forming effect.

Note that the above-mentioned mixed powder is not limited to two types of mixed powder;
In this case, the molding temperature is higher than the softening point of the raw material powder with the lowest softening point and lower than the softening point of the raw material powder with the highest softening point, and the softened powder is one type. I would like to add that there are no limitations.

(Example) Next, an example of the present invention will be described based on FIGS. 1 and 2.

FIG. 1 is an explanatory diagram of an example of the vertical roll forming method according to the embodiment of the present invention, in which 3a and 3b are respectively stretched over feed rollers 4a+4b and one direction change rollers 5a, 5b, 5c, and 5d so as to be able to rotate freely. 6a+ sb, 6c+ 6d+ 7a+ 7b
+7c+7d are guide rollers for maintaining belt spacing and verticality.

Note that although the figure shows a case where the conveyance section is vertical, it is also possible to provide a conveyance section with an appropriate inclination angle.

The mixed powder 2 stored in the omper 1 is loaded between the pair of opposing belts 3a and 3b, is conveyed while being held therebetween, and is heated by passing between the heating devices 8a and Bb.

Heating can be done by appropriate means such as electric heating or gas combustion, and the heating temperature is a molding temperature that is higher than the softening point of the low softening point raw material powder and lower than the softening point of the high softening point raw material powder. In other words, the low softening point raw material powder is softened, and the high softening point raw material powder is left unsoftened. In this case, even if a part of the low-softening point raw material powder is not softened due to uneven heating, there is no problem as long as a press-molded product with the necessary strength can be obtained due to the caking effect of the softened powder. It is also possible to preheat the mixed powder 2 to be stored at a temperature below the softening point of the low softening point raw material powder, thereby increasing the molding speed. Also belt 3a
, 3b can also be preheated in the same way.

The heated mixed powder 2a passes between the rolls 9a and 9b while being sandwiched between the bells) 3a and 3b, and is press-formed to form a plate-shaped compact lO, and the bells) 3a and 3b are respectively The direction is changed by the direction change rollers 5a and 5c and the movement is made. Note that the rolls 9a and 9b can also be preheated.

FIG. 2 is an explanatory view of an example of a horizontal roll forming method according to another embodiment, in which 3a and 3b are feed loafs 4a+4b and direction changing rollers 5a, respectively, as in the case of the vertical roll forming method.

5b, 5c, and 5d so that they can rotate freely, and have a conveying section in which they face each other at a predetermined interval and move in the horizontal direction as a pair. It is set up so that it can be rotated.

As in the case of the vertical type, the mixed powder 2 stored in the homper 1 is loaded between a pair of opposing belts 3a and 3b, is conveyed in a pinched manner, and is heated by passing through the heating devices 8a and 8b. .

It goes without saying that the mixed powder 2 and belts 3a and 3b can be preheated.

The thus heated mixed powder 2a passes between the rolls 9a and 9b while being held between the bells 3a and 3b, and is press-formed into a plate-shaped compact 10, and the belts 3a and 3b It changes direction and runs around by direction changing rollers 5a and 5c. Note that the roll 9a is used for roll forming.

9b can also be preheated.

The outline of the vertical and horizontal roll forming methods has been described above, and will be described in more detail below. First Bell) 3a.

To explain 3b, the material should preferably be a heat-resistant material such as heat-resistant steel or stainless steel, and the thickness should be such that the pressure applied to the powder can be transmitted over a wide range during roll forming. It has no effect, and if it is too generous, it will hinder running, so the appropriate thickness is 0.3 to 5 fi.

In addition, in order to prevent the softened powder from baking and adhering to the belt, it is effective to apply a coating to the surface of the belt that holds the mixed powder. The coating can be carried out by providing a mold coating W, 11.11, or by hand coating.

Although not shown, side guides may be provided for each of the belts 3a and 3b to prevent spillage of the mixed powder to the outside of the conveyed belt and to prevent the molded product from protruding to the outside of the belt (roll) during roll forming. Needless to say.

Next, regarding the pressure molding conditions of the mixed powder, it is desirable to heat the mixed powder to 700°C or less in view of the strength of the rolls. Desirable, but softening point 400℃
The following raw material powders are unsuitable as raw materials for crystallized glass, and the preferable low softening point range is 500 to 700°C.

In addition, the pressurizing pressure is preferably 5 to 300 kgf/aJ; that is, if it is less than 5 kgf/d, the bending strength of 10 kgf/- required for shape retention up to and during heat treatment cannot be obtained, whereas if it is more than 300 kgf/cs1, This is because there are problems in terms of the strength of the roll and, ultimately, in terms of economy.

The plate-shaped molded body formed as described above has the required dimensions (Reference: The finished plate-shaped crystallized glass product usually has a thickness of 8 to 50 Wa, a width of 600 to 900 M, and a length as required. 600 to 2,400 m), or after being cooled to room temperature, it is charged into a heating furnace and heated to a crystallization temperature higher than the softening point of the high softening point raw material powder, so that the powders of the molded body are mutually separated. This aims at softening, fusing, densification and crystallization.

The softened and fused interface between the glassy raw material powders tends to generate crystal nuclei, and many crystals are precipitated by the crystallization treatment described above.

Next, the composition of the glassy raw material powder suitable for implementing the method of the present invention and the reasons for limiting the same components will be listed, and specific examples in which the glassy raw material powder is not used will be described.

A) High softening point glassy raw material powder This raw material powder primarily precipitates wollastonite crystals (CaO/SiO□) during the crystallization heat treatment of the compact, giving strength and hardness to the product, and contains a coloring agent. In some cases, the product is colored or patterned.

Sing: 30-60% (weight percentage, below)
If it is less than 30%, the crystallization rate will be high, and the powders will not be sufficiently fused together and densified during heat treatment of the press-molded product. On the other hand, 60%
Exceeding this decreases the amount of crystals, resulting in a lack of strength and hardness.

/VgOs: 5 to 20% If it is less than 5%, the crystallization rate is fast and the powders are not sufficiently fused and densified during heat treatment of the press-molded body. On the other hand, if it exceeds 20%, it becomes difficult to uniformly precipitate crystals.

CaO: 25-45% If it is less than 25%, the amount of crystals precipitated will be small, and if it exceeds 45%, the crystallization rate will be high, and the fusion and densification of the powders will be insufficient during heat treatment of the pressed body.

MgO: 0.2-8% Addition of 8% or less does not affect crystallization and product strength (lowers the softening point. In other words, MgO is added to adjust the softening point of high softening point glassy raw materials. However, 0.
The above effect is not observed at 2% or less.

Colorant: 0.5-15% As a coloring agent, depending on the desired color tone, Fe or Mn can be used.

Cr, Co, Cu+ Ni, Ti, V, Nd
, each oxide is used alone or in combination, but 0
．． At 5% or less, almost no coloring effect is observed;
If it exceeds 5%, it will cause adverse effects such as a decrease in product strength.

The high softening point glassy raw material powder can be a colorless raw material powder that does not contain the above-mentioned colorant, or it can be a colored raw material powder that contains a colorant.

In the case of colorless raw material powder, the above SiO□ up to MgO,
In the case of colored raw material powder, the coloring agent is also an essential ingredient,
In both cases, the total of Sing and AfzO++CaO should account for 85% or more. This is to keep the glass material of the raw material powder appropriate, and the raw material powder having such a composition hardly softens at 600°C.

In addition, when a high softening point glassy raw material powder is used as a colored raw material powder, its particle size is 200 mesh or less, and a low softening point glassy raw material powder is also 200 mesh or less, and when crystallized glass is produced from a mixture of the two, colored If a plain crystallized glass is obtained, the colored raw material powder is made into coarse particles, and the low softening point glassy raw material powder is made into 200 mesh or less, a colored mottled product can be obtained.

B) Low softening point glassy raw material powder As mentioned above, this raw material powder softens at low temperatures and acts as a binder, unifying the mixture with the high softening point glassy powder during pressure molding and forming. During heat treatment of the product, it is densified and some crystals are precipitated, which also contributes to improving the strength and hardness of the product.

SiO□: 55-75% If it is less than 55%, crystallization will be rapid, which will hinder the densification of the product. Moreover, if the content is 75% or more, the viscosity of the glass increases, causing problems in terms of densification.

NtOx: 15% or less If it exceeds 15%, the viscosity of the glass increases and the densification of the product becomes insufficient.

CaO: 5-15% If it is less than 5%, crystallization will hardly occur, resulting in insufficient strength and hardness. On the other hand, if it exceeds 15%, the viscosity of the glass increases and the densification of the product becomes insufficient.

Na2O+K2O: 10-20% Has the effect of controlling crystallization, and if it is less than 10%, crystallization will be rapid and the product will not be sufficiently densified. On the other hand, if it exceeds 20%, crystallization is slow and results in insufficient strength and hardness.

The above are essential components, and they are contained so that the sum of the above essential components accounts for 90% or more. This is to keep the glass material of the raw material powder appropriate.

Since this low softening point glassy raw material powder is used as a binder as described above, softening and fusion can be substantially performed at the softening point or at a low temperature slightly above the softening point. , 200 mesh or less fine powder is desirable. Of course, there is no problem even if some coarse particles are mixed. The low softening point glassy raw material powder with the above composition is heated to 500 to 600°C.
indicates a sufficiently softened state.

Note that the molded body made of the mixture of the raw material powders A and B described above can be subjected to crystallization heat treatment in the range of 800 to 1000°C.

Next, a specific example using a glassy raw material powder having the above composition range will be shown.

First, the composition of the raw material powder is listed in the table below. However, A is a high softening point glassy raw material powder (colored), and B is a low softening point glassy raw material powder.

Each of the glassy raw material powders A and B is obtained by melting the blended raw materials containing the above-mentioned respective components, and then pulverizing this to form glass bodies, which are further crushed in a ball mill to obtain raw material powders. And so.

The particle size and other manufacturing conditions are as follows.

A powder ---20~50 mesh powder: 30~40%
Powder of 200 mesh or less: 60-70% B powder ---
・Powder of -200 mesh or less: Mixing ratio of 98% or more---
-----A: B -1: 1 Pressure molding------
-・Horizontal roll molded compact dimensions...--111--Thickness 25m, width 900ws Mixed powder heating temperature--5
70℃ Roll and belt preheating temperature---400~50
0℃ roll forming pressure --------・15 Pupil f/c
d Coating mold for floor plate - graphite coating mold: thickness 0.2 (bending strength of plate-shaped molded product at room temperature) --- 15.2 kgf/aJ For the above plate-shaped molded product, 900°C x 4 hours As a result of the crystallization heat treatment, a crystallized glass in which wollastonite crystals were mainly precipitated was obtained. Next, the surface of the glass was polished and cut into a predetermined size to obtain a desired building member.

(Effects of the Invention) The present invention is as described above, and it is possible to mold a press-molded body without using a binder (softening of a low softening point powder among the mixed powder of glassy raw material powder constituting the molded body). In the area, the mixed powder is compressed by rolls together with a belt that pinches and conveys the mixed powder, which solves various problems caused by the conventional use of binders. , it was possible to easily produce a long plate-shaped molded body with sufficient strength.Then, by heat-treating the molded body for crystallization, it achieved the luster of glass, the strength and hardness of ceramics. It is possible to easily produce plate-shaped crystallized glass having both the same properties and coloring and mottled patterns, and the industrial value of the present invention is enormous.

[Brief explanation of the drawing]

FIG. 1 is an explanatory sectional view of one example of the vertical roll forming method according to the embodiment of the present invention, and FIG. 2 is an explanatory sectional view of one example of the horizontal roll forming method according to the embodiment of the present invention.
It is an explanatory sectional view of an example. 1--Hopper, 2--Mixed powder (mixture of glassy raw material powders with different softening points from low to high), 2a--Heated mixed powder, 3a, 3b-Transport belt, 4a, 4t
r-Feed roller, 5a, 5b, 5c, 5d---
One direction change roller, 6a+6b, 6c, 6d, 7
a, 7b, 7c, 7d=-guide roller, 8as
8b - heating device, 9a, 9b - roll, 1 (1-=
Plate-shaped molded body, 11.--Paint coating device. Patent Applicant Kubota Iron Works Co., Ltd. Figure 1 Figure 2 Text

Claims (3)

[Claims] (1) A mixture of glassy raw material powders with different softening points (low and high softening points) is sandwiched between a pair of conveyor belts, and together with the belts, a mixture of glassy raw material powders with a softening point higher than the softening point of the low softening point glassy raw material powder and a high softening point After softening the low softening point glassy raw material powder by heating it to a molding temperature below the softening point of . A method for producing plate-shaped crystallized glass, characterized in that the glass-like raw material powders constituting the molded body are softened and fused to each other and densified by heat-treating the molded body, while crystals are precipitated. (2) The weight percentage of high softening point glassy raw material powder is Si
O_2: 30-60%, Al_2O_3: 5-20%,
A glassy raw material powder containing CaO: 25 to 45% and MgO: 0.2 to 8% as essential components, and containing SiO_2, Al_2O_3, and CaO in a total of 85% or more, and is low softening point glassy. The weight percentage of the raw material powder is SiO_2
: 55-75%, Al_2O_3: 15% or less, CaO
: 5-15%, Na_2O+K_2O: 10-20% as essential components, and SiO_2, Al_2O_3, Ca
2. The method for producing plate-shaped crystallized glass according to claim 1, wherein the glass-like raw material powder contains O and Na_2O+K_2O in a total amount of 90% or more. (3) The weight percentage of high softening point glassy raw material powder is Si
O_2: 30-60%, Al_2O_3: 5-20%,
CaO: 25-45%, MgO: 0.2-8% Colorant:
It is a glassy raw material powder containing SiO_2, Al_2O_3 and CaO in a total of 85% or more, with a weight percentage of low softening point glassy raw material powder and SiO_2 as an essential component.
: 55-75%, Al_2O_3: 15% or less, CaO
: 5-15%, Na_2O+K_2O: 10-20% as essential components, and SiO_2, Al_2O_3, Ca
The method for producing plate-shaped crystallized glass according to claim 1, wherein the glass-like raw material powder contains O and Na_2O+K_2O in a total amount of 90% or more.