WO2018217179A2

WO2018217179A2 - A ceramic composition

Info

Publication number: WO2018217179A2
Application number: PCT/TR2017/050492
Authority: WO
Inventors: Sefik Baran TARHAN
Original assignee: Kaleseramik Canakkale Kalebodur Seramik Sanayi Anonim Sirketi
Priority date: 2016-11-01
Filing date: 2017-10-11
Publication date: 2018-11-29
Also published as: WO2018217179A3

Abstract

The invention is related to a ceramic composition that is lighter, that is thinner, that has a high breaking strength and that has a low single support deformation rate and that has a water absorption value above 0.5% and that will be used in production of ceramic sanitary wares and tiles.

Description

DESCRIPTION A CERAMIC COMPOSITION

TECHNICAL FIELD OF THE INVENTION

The invention is related to a ceramic composition that is especially lighter than similar ceramic compositions having the same volume, that is thinner, that has a high breaking strength that has a low single support deformation rate, that has a water absorption value above 0.5% and that will be used in production of ceramic sanitary wares and tiles.

PRIOR ART

Ceramic is an inorganic compound that is formed by bonding and sintering of one or more metals with a non-metal element. After production stages, the ceramic becomes a material which is hard and non-deforming, which is not easily affected from any external factors except some special factors and that are used in many fields. Most frequent applications are sanitary wares and floor tiles.

Ceramic sanitary wares are the general name for the products such as sink, lavatory, toilet bowl, bidet, urinal, shower tray etc. that are manufactured from ceramic in color/white, glazed/unglazed forms which are usually used in living spaces like bathrooms, kitchens and toilets. Ceramic sanitary wares are hard and nonporous materials that are produced from ceramic which have a glassy phase at a high rate after being fired. Ceramic sanitary wares are expected to meet hygiene standards, to have a certain resistance against scratches and impacts, to have a lower water absorption rate when compared to alternatives and to meet user's expectations in terms of aesthetics.

In order to obtain the desired ceramic structure, high temperature firing is required. However, high temperature firing brings about a permanent deformation called pyroplastic deformation (high temperature deformation). High temperature firing causes more deformation on products that are larger than normal, flat and have thin walls and a chiseled form; the product cannot be shaped in the desired aesthetic form. Pyroplastic deformation is a problem that is not possible to correct, this problem increases the amount of reject and therefore causes serious financial losses.

In order to minimize pyroplastic deformation, the wall thickness of the ceramic sanitary wares is produced to be relatively thicker. Due to thicker walls of the ceramic sanitary wares, products which are more resistant to deformation and fractures are obtained. However, having thicker walls concurrently means a heavier product. The weight is an important factor for especially the people who work in transportation and installation phases of the ceramic products in terms of ergonomics and occupational health and safety.

At the same time, the products having thicker walls and being heavier requires use of more raw materials. Thus, cost per unit product increases.

Besides, since the products having thicker walls and being heavier causes various limitations in terms of design, it is a negative issue that obstructs unique designs. In the World Intellectual Property Organization (WIPO) document with the application numbered WO2014139993, a ceramic material is mentioned. In order to obtain amorphous phase in the ceramic compositions, the fluxing agents are melted with S1O2 at high temperatures and fritted by being poured into cold water. After being ground, the fritted composition is added into the slip and slip casting operation is started to produce porous ceramic. The formula of the said invention is given as (composition rates by weight) S1O2 1 8-35%, AI2O354-76%, Na₂O 0,5-2%, K2O 0,5-2%, T1O2 0-4%, U2O 0-7%, CaO 0-1 %, MgO 0-5%, Fe₂O₃ 0-2%, B2O3 0-6%, BaO 0-4%.

In the German Patent and Trademark Office document with application numbered DE1 0145537, a ceramic composition that contains silicon dioxide, aluminum oxide and potassium oxide which is used in sanitary and other small items is mentioned. The invention discloses two separate compositions as having a water absorption rate below and above 0.5%. In these studies, the strength and impact test results are given, but test results for firing temperature deformation are not given. In order to produce thinner products, lack of this value is a disadvantage. The formula of said invention having absorption value lower than 0.5% is given as (composition rates by weight) S1O2 42- 59%, AI2O3 35 - 52%, Na₂0 0,5-2%, K2O 0,5-2%, ΪΊΟ2 0,5-4%, UO2≤ 2%, CaO < 4%, MgO≤ 4%, Fe203≤ 4%. The formula of the said invention having an absorption value higher than 0.5% is given as (composition rates by weight) S1O2 50 - 65%, AI2O3 30 - 50%, Na₂0 0,5 - 2%, K2O 0,5 - 2%, MgO or CaO 0.5 - 4%,Ti0₂ 0,5 - 2%, Li0₂< 2%, Zr0₂

In the document with the application Numbered EP0332457, multi-layered ceramic sublayers and a method for production thereof is mentioned. The formula of the composition in the invention is given as (composition rates by weight) AI2O3 45-60%, S1O2 24-33%, B2O3 2,4-3,3%, Na₂0 1 ,2-1 ,65%, K2O 0,8-1 ,1 %, CaO 3,2-4,4%, MgO 1 ,2- 1 ,65%, PbO 7,2-9,9%. In the Turkish Patent Office document with application Numbered TR 2014/15838, a slip composition prescription to be used in ceramic sanitary devices is mentioned and the materials used in the invention are 3-1 1 % feldspar, 6-16% quartz, 25-30% clay, 25-35% kaolin, 15-20% alumina and 2-8% wollastonite. In the invention that is directed towards lowering firing temperatures of the products and increasing the strength, the water absorption value is smaller than 4% and dry strength is 30-40 kg/cm2 and fired strength is 900-1 000 kg/cm².

Consequently, all of the above mentioned problems make it necessary to bring a novelty to the related field.

BRIEF DESCRIPTION OF THE INVENTION

The invention is related to a ceramic composition that enables production of products that are lighter, thinner, that have higher fracture strength and that have a low rate of deformation when compared to the ceramic compositions having the same volume.

In the invention, when compared to the known state of the art, the aluminum oxide ratio has been changed in order to increase formation of mullite crystals and the Na20 and K2O ratio and ratio of the used alkaline earth metal oxides have also been changed in the composition to decrease pyroplastic deformation. OBJECTS OF THE INVENTION The present invention is related to a ceramic composition that is lighter, that has higher strength and lower deformation rate when compared to ceramic compositions having the same volume to eliminate the above mentioned disadvantages and bring new advantages to the related technical field. The main object of the invention is to provide a ceramic composition structure that enables production of a lighter product when compared to a product having the same volume.

Another object of the invention is to provide a ceramic composition structure that enables production of a product having thinner walls when compared to a product with the same volume.

Yet another object of the invention is to provide a ceramic composition structure that enables production of a product with a lower deformation when compared to a product with the same volume even though it is lighter and it has thinner walls.

Yet another object of the invention is to provide a ceramic composition structure that enables production of a product having higher fracture strength. Another object of the invention is to provide a ceramic composition structure that enables use of fewer raw materials during production when compared to a product having the same volume.

Another object of the invention is to provide a ceramic composition structure that enables creation of more original designs by providing design freedom.

In order to achieve the above mentioned objects that will be apparent from the detailed description given below, the present invention is a ceramic composition. Accordingly, it comprises; · Al2O350-55%,aluminum (III) oxide or alumina

• S1O2 35-50%, silicon dioxide or silica • K2O 1 -10%, potassium oxide

• U2O 0-2%, lithium oxide

· B2O3 0-2%, boron trioxide

• MgO 0-5%,magnesium oxide

• CaO 0-5%, calcium oxide

• BaO 0-2%,barium oxide

• Fe203 0-3%, iron(lll)oxide

· T1O2 0-2%, titanium oxide

• Na20 0-0,1 %, sodium oxide at the ratios given above. Thus, it is enabled to produce a ceramic that has a water absorption value above 0.5 percent, that is resistant to deformation and that has a high strength value, and that is thinner and lighter.

DESCRIPTION OF THE TABLES

Table 1 shows the range of component ratios of the ceramic composition relative to the total weight.

Table 2 shows the ratios of the components of an exemplary ceramic composition relative to the total weight. DETAILED DESCRIPTION OF THE INVENTION

In this detailed description, a ceramic composition of the invention is described through non-limiting examples to provide a better understanding of the matter. The invention is related to a ceramic composition that is used in production of ceramic sanitary wares and tiles etc. that has a low deformation rate, that has high strength, and has thinner walls when compared to ceramic products having the same volume, and that has a water absorption rate above 0.5%. In Table 1 , the component ratio ranges of the ceramic composition of the invention are given relative to the total weight.

As seen on the formula given above, AI2O3 ratio is between 50-55%. According to the Hooke's Law, as the Young's Modulus increases the tensile stress required to stretch the material also increases.

In the Hooke Elasticity Law, σ= E x ε formula is given. In this formula, σ is tensile stress, E is Young's modulus and ε is strain. Young's modulus for AI2O3 is 360 GPa. Since the Young's modulus of AI2O3 is higher than other components, as AI2O3 ratio increases the tensile stress and strength of which the composition resists increase as well.

Mullite is the only stable phase that forms when the temperature is increased from room temperature to very high temperatures under normal atmospheric pressure in the AI2O3 - S1O2 system and its melting point is 1810°C and its softening point is 1650°C. It forms in all ceramic products that contain alumina and silica. It has physical properties such as high melting point, high chemical resistance, low thermal expansion coefficient, low dielectric constant, high bending resistance, high creeping resistance and good thermal shock resistance when the temperature is lowered from high temperatures to room temperature. The formation of mullite crystals increases the strength of the composition. In the ceramic composition of the invention, as the aluminum oxide (AI2O3) ratio increases, the amount of formed mullite crystals ( 3AI2O3.2S1O2 ) increase as well. As mullite crystals increase, a stronger ceramic composition is obtained.

Pyroplastic deformation is the bending of the ceramic body during firing due to gravity effect. Pyroplastic deformation of the ceramic materials is a result of viscous flow during sintering. Sintering is the heat treatment that enables bonding of particles to each other at high temperatures. Under dynamic load, even though the rheological behavior of the ceramics during sintering is interpreted by the viscoelastic model; pyroplastic deformation is caused by viscous flow (since there is a huge amount of liquid phase during firing or since the viscosity of the liquid phase is low) that the material is subjected in a certain time period and also it is associated with the stress the material is subjected during sintering. In the composition of the invention, in order to minimize pyroplastic deformation, the ratio of K2O is increased and permanent deformations at high temperatures that are called pyroplastic deformations are decreased. In the composition of the invention, feldspar minerals are used as fluxing agents to perform the melting operation. Said feldspar minerals are albite and orthoclase. The ratio of albite NaAISi30s (Na2OAI_©3^»6Si02) and orthoclase KAIS13O8 (K₂OAl203*6Si02) used in the composition are studied. When ratio of albite is decreased and ratio of orthoclase is increased, the ratio of Na20 in the composition is decreased and the ratio of K2O in the composition is increased. As K2O is increased, permanent deformations at high temperatures which are called pyroplastic deformations are decreased.

In order to decrease the pyroplastic deformation, in the composition of the invention, anorthite, diopside etc. crystals are formed by keeping the amount of alkaline earth metal oxides (CaO, MgO etc.) between a certain and narrow range. The created crystals prevented the viscosity of the amorphous phase from decreasing at high temperatures. In addition, the crystals formed by keeping the CaO ratio in a certain range have increased the strength of the composition.

The stable form of the silicon dioxide at room temperature is beta quartz. By heating the beta quartz to 573°C, alpha quartz is formed at this temperature. This reaction is reversible and at the same time the quartz exhibits a growth in volume. By keeping the heating process at a slow rate, the alpha quartz transforms to alpha tridymite at 873°C and to alpha cristobalite at 1470°C. These transformation series end at 1713°C by melting. After firing, the residual crystal quartz left in the composition causes micro cracks. Said cracks increase tendency to fracture. By decreasing the ratio of S1O2 in the composition, the cracks based on quartz phase transformation are decreased and thus loss of strength is decreased to a minimum. The results obtained in the tests performed on the composition of the invention are as follows;

Strength: 690-850 kg/crm²(according to 3-point bending test)

Single support deformation value: 8-14 mm

Water absorption value: 2-3,5 %

Fired shirinkage value: 9-10,5 %

According to the test results, the ratio of components used in the composition has made the strength, shrinkage and deformation values approach to the ideal level.

EXAMPLE 1

The ratio of the components of the exemplary composition relative to total weight is as given in Table 2.

B₂0₃ 0,1

Na₂0 0,01

K₂0 2,09

Table 2 The raw materials used for preparing the ceramic composition are first dissolved in water by using fast mixers. The obtained dense fluid slip mixture is passed through a sieve. The residue of the sieve must be maximum 3% for 63 microns. The prepared slip is aged for 3 days after being passed through a 120-micron sieve. After the slip is aged, casting operation is performed by pouring into plaster or resin mold. After casting, the products are held at a certain temperature, thus they dry better. Final finishings are made on the dried products and the final products are glazed and fired between 1200 °C-1300 °C.

One of the tests performed on the composition is the strength test. Strength measurement is conducted according to a 3-point bending test. The prepared slip is poured into a plaster mold having the dimensions of 1 2x2x1 ,5 cm. One day later the molds are opened and under normal conditions they are dried at 1 10 °C for 1 day in a drying oven. The dried products are fired in a process kiln and its strength is tested by the 3-point bending test. The 3-point bending test determines the maximum bending load which can be resisted, where said load is applied by a component such as a piston or like to a material positioned between 2 supports. The strength is determined as 840 kg/cm² as the result of the test.

Another test performed on the composition is the water absorption test. The water absorption test is performed according to TS EN 997:2012. In said test, 3 parts of the composition of which one side is glazed and the other side is not, and that has a surface area of 30 cm² is kept in a drying oven for 180 minutes at 100 °C and cooled in a desiccator. Then, the measurements are performed in a measurement device with 0.05 gr precision. Following this, the composition is left in boiling water for 120 minutes and left in the same water for 20 hours after boiling ends. Lastly, the measurements are again performed in a measurement device with 0.05 gr precision. The water absorption percentage is found by dividing the difference between the last and the first measurements by one hundred. Accordingly, when said composition is subjected to the water absorption test, 2.4% value is obtained.

Another test performed on the composition is the deformation test. In said test, the slip formed from said composition is poured into a bar shaped plaster molds and is left to wait for 3 hours. After 3 hours, the plaster molds are opened and the deformation samples are dried in a drying oven for a day at 100 °C. The dried material is compressed between two supports such that a certain part of it protrudes from these supports. The material is fired at 1220 °C for 16 hours. After this time, the change in deformation on the material is measured. The sample compositions exhibited 1 1 mm change when subjected to the deformation test. In standard vitrified products, this value goes up to 35 mm.

Another test performed on the composition is firing shrinkage test. Said test determines the linear shrinkage rate of the material after firing with respect to the pre-fired condition. It is determined that the sample composition has shrunk 9.2% when compared to the first length after being subjected to the said water shrinkage test.

The protection scope of the invention is defined in the appended claims and in no way, it can be limited by what is described in this detailed description for illustration. Also, it is apparent that a person skilled in the art can present similar embodiments in the light of what is described above without departing from the main theme of the invention.

Claims

1 . The invention is a ceramic composition that is lighter, that is thinner, that has a high breaking strength and that has a single support deformation rate between 8- 14 mm and has a water absorption value above 0.5%, and which will be used in the production of ceramic sanitary wares and tiles, characterized in that comprises,

• AI2O350-55%,

• Na₂0 0-0,1 %,

• K₂O 1 -1 0%,

• U2O 0-2%,

• CaO 0,5-5%,

• MgO 0,5-5%,

• Fe₂0₃0,5-3%,

• B2O3 0-2%,

• BaO 0-2%

by weight.

2. A ceramic composition according to Claim 1 , characterized in that comprises 1 -10% K2O by weight to prevent pyroplastic deformation.

3. A ceramic composition according to Claim 1 , characterized in that comprises 0,5-5% CaO and 0,5-5% MgO by weight to occur formation of crystals such as anorthite and diopside.

4. A ceramic composition according to Claim 1 , characterized in that comprises crystals such as anorthite and diopside to prevent viscosity of the amorphous phase from decreasing during high temperatures.