Subject of the Invention The invention relates to a new slip composition/receipt to be used in the production of ceramic sanitary ware.

State of the Art

The production of ceramic sanitary ware consist of grinding, mixing, forming by molding, drying, glazing and firing processes. Ceramic sanitary ware are produced by using two different slip receipts as vitrified and FFC (Fine Fire Clay) as a standard.

Vitrified slip receipts have low water absorption values but have high firing deformation values in parallel thereto. Their fired strengths are around 550-600 kgf/cm ² . Firing deformations are reduced using calcined kaoline in the slip receipts called Fine Fired Clay (FFC) and thereby, the production of ceramic sanitary ware with a size above 1 m is provided, in parallel to this; water absorption values are in between 7.5-9.5 %. Their fired strengths are only 350-400 kgf/cm2 due to the porous structures thereof. Of the ceramic sanitary ware, strip thicknesses rise up to 17 mm due to forming, strength and firing deformations in the big sinks in conventional receipts. In order to provide the production of products with thinner strips in aesthetic sense, new receipt/composition studies are needed to solve the dry strength after forming likely to occur due to the thin structure of the product, pyroplastic deformation during firing and strength problems subsequent to firing.

Although ceramic sanitary ware can currently be produced with the use of many alternative materials, these materials cannot meet the expectations of the ceramic products in terms of the hygiene, high surface hardness of the glaze and scratch resistance in parallel thereto. Although more aesthetic, bigger, sharper models with low diameters are produced with the use of alternative materials, it is of great importance for many designers and users, who desire to utilize the advantages of ceramics, to provide the production of these models of ceramics. In addition to all of these visual and physical expectations, the production of ceramic sanitary ware is a difficult and costly process due to the weights of the products, complex shapes thereof, and the excess of energy and labor requirement in the production. The higher raw material and energy costs of the products the lower the labor efficiency becomes as the weights of sink and a water closet are 14.0 kg and 19.0 kg on average, respectively. Besides, difficulties are experienced during transportation. As everything is gradually minimized in modern life, the use of light and ergonomic products deems it necessary to conduct innovative studies in heavy products. Gradual reduction of the product thicknesses of the ceramic coating materials and the tendency towards the thin ceramic tile production become a driving force with respect to the production of thinner and lighter ceramic sanitary ware products. In the present state of the art, raw material and energy consumption during production is too much due to the product sizes and weights, and the emissions are also quite high in relation to the energy used.

A new receipt composition is developed in the study conducted within the scope of the invention, no modification is made as a production method in the process.

Studies with respect to reducing the firing temperatures of the products have been conducted in the present state of the art and a new composition with respect to reducing raw material, energy and transportation costs and also increasing the productivity is developed within the scope of the invention. Objects of the Invention

The object of the invention is to develop a composition through which the production of ceramic sanitary ware, which are thinner than the products in the present state of the art but have a high strength value, lower firing deformation value, and can be designed more freely with the lower energy and raw material need, can be realized. References

1: Mullite crystals 2: Anorthite crystals

HSR (High strength receipt): The composition developed within the scope of the invention Vitrified: The composition of the vitrified structure

FFC (Fine fired clay): The composition of the FFC structure

Description of the Figures

Figure 1: The structure which is prepared with the composition developed within the scope of the invention and examined with scanning electron microscope.

Figure 2: The figure where the water absorption, strength and deformation values of the structures obtained with the vitrified receipt, FFC receipt and the new composition developed within the scope of the invention are compared.

Description of the Tables: Table 1. Content comparison of the FFC composition/receipt (FFC), vitrified composition/receipt and the composition/receipt (HSR) developed within the scope of the invention

Table 2. Phases detected in HSR, vitrified and FFC receipt compositions subsequent to firing Table 3. Dry strength, average fired strength, apparent relative density and water absorption values of the HSR, vitrified and FFC receipts/compositions

Detailed Description of the Invention

The invention relates to a new slip composition/receipt to be used in the production of ceramic sanitary ware.

As a production method, no modification is made in the process within the scope of the invention. Ceramic sanitary ware products are the products which are fired at a high temperature (1200°C), have a water absorption value below 0.5 %, and the strength values of which vary between 550-600 kgf/cm ² . Sintering of these products is provided by the liquid phase (> 30 %) in the structure. Due to the liquid phase sintering, these products are referred to as vitrified products. In FFC structures, the liquid phase ratio is very low due to the low firing deformation expectation. Therefore, water absorption values and strength values vary between 7.5-9.5 % and 350-400 kgf/cm ² , respectively. In this study, calcined kaoline, which is used for reducing the firing deformation in FFC slip receipts, are not used. Moreover, a new composition/receipt, the water absorption value of which is close to the vitrified structure but the fired strength value of which is far above the vitrified structures, namely rises up to 900-1000 kgf/cm ² , is developed. While in the present state of the art the firing deformation is reduced with the addition of calcined kaoline into the structure in FFC structures, firing deformation is reduced with the formation of anorthite crystals in liquid phase in the new receipt/composition developed within the scope of the invention. To reduce the water absorption values, the reduction of vitreous phase viscosity is utilized by increasing the alkaline earth additions. To increase the strength, on the other hand, studies are conducted in light of the theories described below.

Three different theories are developed on the strength of the ceramic structures. According to mullite hypothesis, strength of the structure is described as interlocking of the small mullite cores such as felt. Especially, high mullite amount means that high ratio of mullite crystals are interlocked, which in turn means high bending strength. Bending strength also depends on the factors such as firing temperature affecting the mullite amount and size.

According to the strength hypothesis with dispersed phase, dispersing particles such as quartz and mullite limit the size of cracks formed and increase the strength in vitreous phase of porcelain structure.

According to the matrix reinforcement hypothesis, compressive stresses are formed as a result of the distribution of different thermal expansion coefficients in the vitreous phase. This effect is known as "pre-stressing effect".

Strength of the vitrified structure is described by the sum of these theories. However, residual quartz have positive and negative effects on the strength.

In hypotheses of strength enhancement with dispersing phase and mullite, it is claimed that residual quartz in the fired structure is harmful to the strength due to the α-β conversion during cooling in the structure. It is argued that the reduction of quartz amount or the use of fine grain-size quartz (pulverized quartz) are required to increase the strength. In the composition developed within the scope of the invention, the grain size of quartz is taken as less than 5 microns, quartz amount is reduced and Al ₂ 0 ₃ is added and thus hair cracks which are likely to occur from the residual quartz are minimized.

Plastic clay is used for increasing the strength in the composition developed within the scope of the invention. In the composition developed within the scope of the invention kaoline ratio is promoted for increasing mullite formation and feldspar ratio is adjusted for reducing the pyroplastic deformation. Al ₂ 0 ₃ is added into the composition to increase the strength.

The composition developed within the scope of the invention comprises feldspar at a ratio of 3-11 % by weight, quartz at a ratio of 6-16 % by weight, clay at a ratio of 25-30 % by weight, kaoline at a ratio of 25-35 % by weight, alumina at a ratio of 15-20 % by weight and wollastonite at a ratio of 2-8 % by weight. Content of the composition is illustrated in the table.

Table 4. Content comparison of the FFC composition/receipt (FFC), vitrified position/receipt (Vitrified) and the composition/receipt (HSR) developed within the scope of the invention

Table 5. Phases detected in HSR, vitrified and FFC receipt compositions subsequent to firing

Table 6. Dry strength, average fired strength, apparent relative density and water absorption values of the HSR, vitrified and FFC receipts/compositions

Sample HSR Vitrified FFC

Dry strength 30-40 20-30 20-30

(kg/cm2)

Average Fired 900- 600-700 350- Strength (kg/cm2) 1000 450

Apparent Relative 2-3 2-3 2-3

Density (g/cm3)

Water absorption <4 <0.5 7.5-9.5

(%)

Flexure graph of the vitrified structures and the structure formed with the composition developed within the scope of the invention is illustrated below. Within the scope of the inv n ion, studies are conducted in between 1190-1195°C and 12-14 hours of firing periods.

Time-dependent sintering curve of the vitrified structure is given in the attachment. When the graph is examined, a behavior in {+) direction is observed up to about 1022°C and a deformation in (-) direction is started to be seen in the structure after this temperature. The structure assumes its initial state around 1100°C. The temperature at which the deformation occurs most rapidly is determined from the first derivative curve of the deformation. In the sample examined with the regime given, deformation reaches maximum speed at two points (~1137°C and ~1236°C). In the sample, of the two temperature ranges at which the deformation accelerates, the first range is between 1137°C -1162°C, then the second range which is thought to arise from vitreous phase with the increase of the temperature is between 1162°C-1236°C. According to literature, the peak temperature at which it first accelerates is related to the melting of the feldspar. Then, when high temperatures are reached, the vitreous structure interacts with the other components of the structure and starts to dissolve. In this case, the medium becomes more viscous. In the regime applied to the sample, deformation is observed at a rate of 5.85 %.

Time-dependent sintering curve of "HSR" structure obtained with the new composition developed within the scope of the invention is given in the attachment. When the graph is examined, a behavior in (+) direction is observed up to about 1057°C and a deformation in (-) direction is observed in the structure after this temperature. The structure assumes its initial state around 1135°C. The temperature at which the deformation occurs most rapidly is determined from the first derivative curve of the deformation. In the sample examined with the regime given, deformation reaches maximum speed at two points (~1134°C and ~1246°C). In the sample, of the two temperature ranges at which the deformation accelerates, the first range is between 1134°C -1172°C, then the second range which is thought to arise from vitreous phase with the increase of the temperature is between 1172°C -1246°C. According to literature, the peak temperature at which it first accelerates is related to the melting of the feldspar. Then, when high temperatures are reached, the vitreous structure interacts with other components of the structure and starts to dissolve. In this case, the medium becomes more viscous. In the regime applied to the sample, deformation is observed at a rate of 1.33 %.

Thanks to the composition developed within the scope of the invention, products, which are thinner but have higher strength values, are obtained.