JPH10245260A - Low-temperature baking color cray - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a low-temperature baking color clay, usable for an interest ceramic art or production, etc., of an accessory, readily sinterable according to low-temperature baking in a nichrome wire electric furnace, etc., and providing new pastel color colorful colored ceramics. SOLUTION: This low-temperature baking color clay is prepared by adding 0-22wt.% SiO2 -based powder and 0.2-5wt.% pottery color pigment as aggregates to a basic component containing 45-75wt.% high-grade white kaolin or clay with <=1wt.% content of colored transition metallic oxides such as Fe2 O3 and 45-20wt.% calcium carbonate fine powder having <=2μm average particle diameter. The resultant low-temperature baking color clay is formed and baked to produce colored ceramics of various colors hardly having any water absorptivity by baking at a relatively low temperature of <=1,000 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention is intended for use as a hobby for pottery, teaching materials or daily necessities, to become pastel-colored non-water-absorbing colored ceramics by firing at a relatively low temperature of 1000 ° C. or less. It relates to a low temperature firing color clay that can be used.

[0002]

2. Description of the Related Art In general, high-temperature sintering at 1200 ° C. or more is required to obtain dense ceramics having no water absorption. Due to the need to be stable compounds that do not react, very limited ones have been used. For this reason, in order to densify at a low temperature of 1000 ° C. or less, a method of kneading and firing with a large amount of vitreous powder such as a low-melting frit has been performed in some parts. However, there is a serious drawback in that the degree of plasticity is poor, the plastic formability is poor, and the molded body is softened and deformed during firing and it is difficult to maintain the shape. In addition, such a vitreous calcined material dissolves a part of the pigment, and its surface is covered with a relatively thick glass layer, so that the coloring is indirect, the coloring effect is poor, and a large amount of expensive pigment is required. Not only
Pastel-colored dense ceramics that directly indicate the color of the pigment could not be produced at a low temperature of 1000 ° C. or lower.

[0003]

Therefore, the present invention is based on the most commonly used raw materials of industrially inexpensive ordinary ceramics, such as kaolin or clay, calcium carbonate and silica, which are most commonly used as ceramic raw materials. A low-temperature fired color clay that can be easily fired at a relatively low temperature of 1000 ° C. or less, that is, a simple nichrome wire electric furnace, and is a beautiful colored ceramic without water absorption in various pastel colors. It is something to offer.

[0004]

Therefore, in the present invention, F
Content of colored transition metal oxide such as e ₂ O ₃ is 1 wt%
The following high-grade white kaolin or clay is 45-75wt
%, An average particle size of 2 μm or less
0~45wt%, 0~22wt% powders of SiO ₂ quality and the ceramic colored pigment in a proportion of 0.2~5wt%,
It is characterized in that it is pasteurized colored ceramics of various colors without water absorption when fired at a relatively low temperature of 1000 ° C. or lower.

[0005]

The present inventors have found that kaolinite-type or halloysite-type fine kaolin or clay 75-55 wt%,
In the case of a composition in which fine particles of calcium carbonate having an average particle size of 1.5 μm are in a ratio of 25 to 45 wt%, solid solution formation between thermal decomposition products of kaolin and calcium carbonate proceeds during the firing process, and 800 to In a very narrow temperature range of 900 ° C., it was found that solid solution formation was almost completed before silicate crystal precipitation, and the product at this stage was an aggregate of amorphous fine particles containing an appropriate amount of CaO. Yes, it has been found that it has extremely high viscosity, maintains a molded shape, has remarkable low-temperature sinterability, and densifies at 875 ° C. to 950 ° C. Furthermore, it has been found that even if SiO ₂ -based powder such as silica is added to this basic component up to about 30 wt%, a sufficiently dense sintered body can be obtained at 1000 ° C. or less. Is what you do.

The low-temperature densification by the composition of the present invention is based on a mechanism different from porcelain, ie, vitrification, and many inorganic pigments are substantially stable at a low temperature of 1000 ° C. or less, and are almost exclusively crystalline. It is characterized by being a sintered ceramic. As a result, a state in which the inorganic pigment particles are dispersed in the dense polycrystal without any deterioration is achieved, and a unique pastel-colored coloring effect not available in conventional colored ceramics can be exhibited for the first time. is there.

[0007] The mixing ratio of kaolin and calcium carbonate is
It is necessary for the purpose of the present invention that the weight ratio be in the range of 55:45 to 75:25, and this compounding ratio mainly depends on the type and the ratio of the precipitated crystals when treated at a high temperature of 900 ° C. or higher. decide. At a temperature of about 900 ° C. or higher, crystals such as anorthite, gehlenite, and orastonite are precipitated, and these crystal particles help to develop a unique pastel color tone, and also prevent softening deformation of the molded product, and reduce the firing temperature range. Make it extremely wide. In general, the higher the amount of calcium carbonate, the better the low-temperature sinterability. However, if the weight ratio of kaolin to calcium carbonate is more than 55:45, gehlenite crystals are likely to precipitate before sintering and densification. In addition to poor bondability, water resistance also deteriorates, making it unsuitable for practical use. Also, with calcium carbonate having a weight ratio of less than 75:25, the amount of CaO solid-solutioned in the amorphous phase is insufficient, resulting in insufficient sinterability, and it is difficult to obtain a dense sintered body at about 900 ° C.

In general, it is desirable to make the raw material mixture finer in order to densify the sintered body at a low temperature.
It is extremely important that the calcium carbonate is extremely fine, and the particle size has been found to have the greatest effect.
According to the results of the experiment, when the average particle size of calcium carbonate in the composition is 1.5 μm, all sintering is sufficiently dense within the range of the above mixing ratio, but when the average particle size is 2.5 μm, Did not elaborate. Therefore, it is an important condition that the average particle size of calcium carbonate is 2 μm or less.

As the SiO ₂ powder to be added, silica stone (quartz) is the most suitable and most inexpensive. In the ordinary ceramic technique, feldspar and the like are melted and silica or alumina is added as an aggregate to the melt in an amount of about 30 wt%. However, in the low-temperature firing color clay of the present invention, the melt is fired during the firing process. When inorganic powders that do not generate and do not contain SiO ₂ , such as alumina, are mixed and used, sintering densification is hindered, and in order to keep water absorption almost zero, it cannot be added to about 5 wt% or more. According to the results of the experiment, it was found that even if only SiO ₂ -based powder such as silica stone was added up to about 25 wt%, sintering was not significantly inhibited, and sintering proceeded by partially reacting with CaO. Feldspar containing a large amount of SiO ₂ component also contains an alkali component, so it is used as a flux in ordinary porcelain. However, it does not melt at 1000 ° C., and its effect is somewhat lower than that of silica, but 15 wt%.
Up to this level, there is an effect of keeping the water absorption almost zero. CaO
Is a basic oxide, and an acidic oxide such as silica (SiO ₂ ) that partially reacts with CaO is most preferable.
It is considered that the higher the content of O _2, the more effective. The larger the amount of these SiO ₂ powders, the lower the firing shrinkage ratio, the higher the operability of the clay, the smaller the firing deformation, and the lower the cost of raw materials since silica is extremely inexpensive. There are advantages. However, 25wt
%, The sinterability is impaired even in the case of silica, and the low-temperature sinterability and non-water-absorbing properties which are the objects of the present invention are lost.

A boric acid glass powder containing a large amount of SiO ₂ is also effective, and even a small amount promotes crystallization of anorthite and the like to prevent deformation of a molded product, and is effective in shape stability, and lowers the densification temperature. Is preferred as an additive,
It is relatively expensive, and if the amount of addition is large, the production cost becomes high.
%.

[0011] The coloring inorganic compound used as a pigment for ceramics is often unstable at 1000 ° C or more and slightly fades.
Since the water absorption can be made zero at a relatively low temperature of 1000 ° C. or less, a simple nichrome electric furnace can be used as a firing furnace, and most ceramic pigments, almost all commercially available pigments for sketches and overpaints can be used. It is possible to realize unique colored ceramics that can be used and are extremely colorful and have a pastel color tone. Naturally, the more the amount of the pigment added, the deeper and more vividly colored ceramics can be obtained, but as the amount increases, the sintering is gradually inhibited and the water absorption begins to increase, and the coloring efficiency deteriorates, and the cost increases, which is naturally limited. . Actually, when the addition amount is about 5 wt%, the ceramic becomes extremely bright and strongly colored, and sufficiently vivid color development can be obtained even at 2 wt% or less. The lowest practical amount varies depending on the pigment, but is up to about 0.2 wt%.

The present invention provides a solution of kaolin pyrolyzate and CaO in an amorphous state in a non-crystalline state, a low-temperature sintering and densification thereof,
Because iO ₂ quality of the reaction by the addition of powder and firing shrinkage rate of the control and has as its basic principle, in a range that does not inhibit this, all that is used as a general technique of ceramic manufacture for additional purposes , An additive such as an organic binder for dry strength can be added and mixed in an appropriate amount.

Hereinafter, the production method of the present invention will be described in more detail with reference to laboratory examples, but the present invention is not limited thereto.

[0014]

Example 1 New Zealand kaolin was used as a raw material kaolin. This is a relatively high-purity kaolin containing halloysite as a main component, its chemical composition is% by weight,
iO ₂ : 49.78, Al ₂ O ₃ : 35.72, Fe ₂
O ₃ : 0.26, TiO ₂ : 0.12, CaO: tr,
MgO :, tr, K ₂ O: tr, Na ₂ O: 0.06,
Loss on ignition: 14.05, somewhat higher in SiO ₂ than the ideal kaolinite composition. Limestone that has been finely pulverized in advance so that the average particle size of the kaolin is 1.5 μm (chemical composition is approximately 100 wt% CaCO ₃ )
And a silica (quartz) powder having an average particle size of about 10 μm (chemical composition is approximately 100 wt% SiO ₂ ), and is blended at a blend ratio corresponding to each point of triangular coordinates of kaolin, calcium carbonate, and quartz in FIG. Then, 2 wt% of commercially available pale green ceramic pigments were added to each of these, and each was subjected to wet ball mill pulverization mixing for 24 hours, dewatered and kneaded, and dried to obtain various powdery plastic clay compounds. . Using these clay compounds, pellets each having a diameter of about 16 mm were formed at a molding pressure of 1 ton / cm ² by dry pressing.
It was fired in air at 1000 ° C. for 1 hour using a nichrome wire electric furnace.

In the obtained sintered body, a sample having an apparent porosity of almost zero is indicated by a mark, and a sample having an apparent porosity of 1% or more is indicated by a mark in FIG. The shaded portion in FIG. 1 is the composition region of the present invention, and the apparent porosity, that is, the region in which the densification progresses to almost zero water absorption (the value of the water absorption is about half of the apparent porosity). Value). Within the scope of the present invention, all the samples were sintered and densified until the water absorption rate was almost zero, and all of them developed a very beautiful pastel-colored light green color.

Further, in FIG. 1, 5 wt% of commercially available blue and yellow pigments were added to the kneaded clay having the composition of point A and point B, respectively, and the mixture was sufficiently mixed. And calcined at 1000 ° C. for 1 hour in the air. A
A dense sintered body with almost zero apparent porosity at both points B and B. When 5 wt% is added, the pastel color tone is extremely deep and vivid, and the ceramic is a vividly colored ceramic that is hardly distinguishable from the pigment itself. Was.

[0017]

In the past, plastic clays used for hobby ceramics and the like generally require a firing temperature of 1200 ° C. or higher.
At a temperature of 000 ° C or less, those which were hardly densified at all and could only obtain water-absorbing earthenware were replaced by inexpensive materials such as kaolin or clay, calcium carbonate and silica, which are most commonly used as ceramic materials. Ingredients are used as the main components, and an appropriate amount of ceramic pigment is blended with the raw materials. The plasticity is extremely excellent, and the molded shape can be easily formed at an extremely low temperature of 1000 ° C or less, that is, the temperature of a simple nichrome wire electric furnace. Colored ceramics that have been sintered and densified to almost zero while retaining the water absorption rate can be obtained, and the unique pastel-colored colorful coloring due to low-temperature firing is extremely suitable for pottery and educational materials, and accessories such as accessories It enables a completely new product for use and is extremely useful for crafts.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the composition range of the present invention and the apparent porosity after firing at 1000 ° C. for 1 hour.

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[Procedure amendment]

[Submission date] September 9, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction contents]

[0004]

According to the present invention, high-quality white kaolin or clay is 55 to 75 wt% and calcium carbonate fine powder having an average particle size of 2 μm or less is 45 to 25 wt%.
The basic component contained at a ratio of wt% contains SiO as an aggregate.
0-40 wt% of ₂ quality powder, 0-20w of glass powder
t%, and 0.2 to 5 wt% of the ceramic color pigment.
It is characterized in that it is a paste-colored ceramic having almost no water absorption of various colors in a relatively low-temperature baking at 1000 ° C. or less when added .

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction contents]

A boric acid-based glass powder containing a large amount of SiO ₂ is also effective, and even a small amount promotes crystallization of anorthite and the like to prevent deformation of a molded product, and has an effect on shape stability.
Also, soda-lime glass and frit for low temperature are 10-20
Densification temperature up to wt% without significant deformation
If these are used together, the above-mentioned silica stone
The addition amount of SiO ₂ powder is about 40 wt%.
Can be increased up to. Increase of these additions
Is accompanied by a slight color change, but the basic content of the present invention is
It does not change
It can be used to adjust plasticity, firing shrinkage, etc.
You.

Claims (1)

[Claims] 1. A high-quality white kaolin or clay having a content of a colored transition metal oxide such as Fe ₂ O ₃ of 1 wt% or less is 45 to 75 wt%, and a fine calcium carbonate powder having an average particle diameter of 2 μm or less is 20 to 20 wt%. 45 wt%, SiO ₂ powder
-22% by weight and a ceramic coloring pigment in a ratio of 0.2-5% by weight, and can be pastel-colored, non-water-absorbing colored ceramics by firing at a relatively low temperature of 1000 ° C. or less. Low temperature firing color clay.