DE2200611A1 - Ceramic clay bodies and processes for making ceramic products from them - Google Patents

Description

DIPL.-ING. KLAUS BEHN

DIPL.-PHYS. ROBERT MONZHUBER A Z. UUU \

PATENT LAWYERS

8 MUNICH 22 Wl DENMAYERSTRASSE 6 TEL (0811) 22 25 30-29 51 92

7th January 1972

A 42271 Pl / ib

ENGLISH CLAYS LOVERING POCHIN & COMPANY LIMITED, John Keay House, St. Austell, Cornwall, England

Ceramic clay bodies and processes for making ceramic products therefrom

The invention relates to ceramic clay bodies and is particularly, but not exclusively, concerned with with clay masses that are suitable in the manufacture of ceramic sanitary ware or earthenware crockery.

Conventional ceramic bodies generally contain lumpy clay (ball clay), kaolin, and finely divided quartz a flux which can be, for example, Cornish stone (which is a suitable source of feldspar) or fatty stone syenite.

Ball clay is a sedimentary kaolinite clay that is

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Merck banking house. Finck & Co., Munich. No. 25464 I Bankhaus H. Aufhauser. Munich. No. 261300 postal check: Munich 20904

Telegram address: patent senior

commonly found in connection with a content of free quartz and organic or carbonaceous material, e.g. lignite. A spherical clay suitable for use in a ceramic composition should contain no more than a certain amount of free quartz or carbonaceous material. When the entire quartz content of the Kugeltons than about 60 weight high -.%, The ball clay tends to have a good strength, but since the entire quartz content includes a high proportion of impure quartz, which is generally associated with iron oxide and titanium, A ceramic mass containing this spherical clay tends to give a body of poor color when fired compared with a body obtained by firing a mass containing a less quartz clay with added pure silica. If the carbonaceous matter content of the spherical clay is higher than about 5% by weight , the amount introduced into the ceramic mass with the spherical clay limits the burning rate. Under these circumstances, the burning rate, which must be sufficiently small to oxidize the carbonaceous matter, becomes too low.

Significant inventories of ball clay are available which were previously deemed unsuitable for use in the manufacture

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ceramic masses were considered because of their content of quartz-containing or carbon-containing matter, and for this reason such spherical tones were not for sale. Nonetheless, it is often necessary to remove these tones from Mining poor quality to reveal layers of better clay. There are also large amounts of coarse residual kaolin available that arise during the separation of mined kaolin in order to get as much pin kaolin as possible recovering particles that have an equivalent spherical diameter of 2 microns or less, used as a paper coating pigment is used. The coarse kaolin residue has heretofore been of little or no commercial value .

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It has now been found that if a first spherical tone, which has a relatively high quartz content, a second spherical tone, which contains a relatively high amount of carbonaceous matter, unojein coarse residual kaolin are mixed, preferably in approximately equal proportions, the resulting mixture is a clay that has properties that make it suitable for use in ceramic bodies. In particular, is looking for a feature The invention provides a mass of clays suitable for use in the manufacture of ceramic Bodies containing two or all three of the mixture components indicated above, namely one first spherical clay, a second spherical clay and a coarse residual kaolin, of which no mixture component is over 50% by weight of the mass in which (a) the first spherical tone has a total quartz content of not more than 75 Weight- ^ has a combined content of iron oxide and titanium of not more than 3 * 5 weight-Ji, a carbonaceous one Matter of not more than 1 weight- ^, and composed of particles of which not less than 4o weight- # are less than 1 micron based on an equivalent sphere diameter; (b) the second spherical tone has a total quartz content of not more than 50% by weight, a combined iron oxide and titanium content

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of not more than 3.5% by weight, a carbonaceous matter of not more than 20% by weight, and consisting of particles of which not less than 40% by weight are less than 1 micron, based on an equivalent sphere diameter (c ) The coarse residue kaolin has a combined iron oxide and titanium content of no more than 1.5% by weight and consists of particles of which no more than J> 0 % by weight are larger than 53 microns, of which 30 to 95 Weight- ^ are greater than 10 microns, based on an equivalent sphere diameter, and of which at most 20 weight- ^ are less than 2 microns, based on an equivalent sphere diameter.

According to a further embodiment of the invention a clay mass is created which is suitable for the manufacture of ceramic objects. This clay mass contains 25 to 50 weight ^ of each (l) a first lumpy Clay, (2) a second lumpy clay, and (3) coarse residue kaolin, with (a) the first lumpy clay making up a total proportion of quartz under 75 weight ^, one combined

Iron oxide and titanium content of not more than 3.5% by weight, and
contains a fine carbon fraction of a maximum of 1% by weight and consists of particles of which no less than 40% by weight are smaller than 1 micron, based on an equi-

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valent ball diameter; the second lumpy clay (b) has a total content of quartz of no more than 50 weight-jb, a combined iron oxide and titanium content of no more than 5.5 weight- ^, a carbonaceous material of no more than 20 weight- ^ and consists of particles of which not) is less than ¹ weight K ^ of less than 1 micron, based on an equivalent spherical diameter; the coarse residue kaolin has a combined iron oxide and titanium content of no more than 1.5% by weight and consists of particles no more than 50% by weight of which are greater than 55 microns, 50 to 90% by weight thereof greater than 10 microns based on an equivalent sphere diameter, and 5 to 10 weight percentages thereof are smaller than 2 microns based on an equivalent sphere diameter.

Masses according to the invention advantageously have a total or at least 50 weight Weight of two or all three of the mixture components, namely the first spherical tone, the second spherical tone and the coarse residue kaolin. The masses advantageously contain at least 25 percent by weight of two or all three mixture components, namely the first ball clay, the second ball clay and the coarse residue kaolin.

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In the composition of the masses according to the invention, the coarse residue kaolin is often present from particles of which no more than 30% by weight are larger than 53 microns, of which 30-90 by weight ^ are larger than Io microns based on an equivalent Sphere diameter, and -of which 3 to io weight- ^ are less than 2 microns based on an equivalent sphere diameter.

The masses according to the invention preferably contain a flux agent of an amount of 10 to 40% by weight, based on the total weight of the mass, and may also contain a medium-sized ceramic kaolin in a ratio of 0 to 40% by weight, based on the Total weight of the mass, and silica of an amount up to 30% by weight, based on the total weight of the mass.

The invention also relates to a method of manufacturing a ceramic body which includes forming a mass according to the invention comprising a flux contains, which is added to the mass with water in order to form a compressible mixture, furthermore the introduction the mixture in a mold, pressing the mixture in the

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Shape at a pressure in the range of about 0.5 to Io tons per square inch, to form a green article, and thereafter firing the green article at a temperature in the range of ⁰ C to Looo 14OO ° C.

When the raw residual kaolin has a particle size distribution which is within the required limits, but has such an iron oxide and titanium content that the combined iron oxide and titanium content is greater than the acceptable maximum, the coarse residue kaolin becomes exposed to a high-intensity (e.g. greater than 10 000 gauss) non-homogeneous magnetic field, e.g. B. in one Jones Magnetic Separator to make it suitable for use in accordance with the present invention.

Advantageously, the clay mass has 20 to 4o weight- # of each mixture component - the first ball clay, the second ball clay and the coarse residue kaolin - on.

The two or three clays can be mixed using any suitable mixer is for mixing plastic materials, e.g. B. a Z-blade

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Mixer, a mixing drum or a pan mill, a pin beater mill or an edge roller mill. A mixing drum or a pan mill is preferred is needed, and mixing the clays consumes around 20 horsepower hours of energy per ton of dry concrete (5.3 χ Io joule / kg) consumed. It is more desirable Expend at least about 40 horsepower hours of energy per ton of dry lime (1.06 10 joules / kg) when mixing the clays.

Preferably, the ball tone, or at least one of the first and second ball tones defined in the Mass are needed, a fracture modulus (of a bone

2 dry specimens) of at least 60 kg / cm.

If a ceramic kaolin of medium quality is used in a mass according to the invention, it will generally consist of particles no more than 0.5 weight ^ larger than 53 microns, and of which 25 to 50 percent by weight are less than 2 Microns based on an equivalent sphere diameter.

The invention is illustrated in the following examples.

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Example I.

A first lumpy clay, a second lumpy clay, and a raw residue kaolin with those in the following Properties given in Table I were measured in equal parts by weight of the dry clay in a mixing drum or a pan mill mixed with each other, with about 53 HP-hours of energy per ton in the mixture of clays of dry clay (1.4 10 joule / kg) were consumed. The properties of the resulting blend are also shown in Table I.

Table I.

first
lumpier
volume second
lumpier
volume rough mix
Return
standing
kaolin SiO (weight ^) 71.04 41.60 52.50 55 Fe ₂ O ^ (weight- ^) 0.85 I.08 0.97 0.95 TiO ₂ (weight ^) 1.71 0.62 O.O8 0.79 carbonaceous Matter (weight- ^) 0.2 12.0 4.0 Modulus of rupture (kg / cm) 65th 27.0 50.9

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first

lumpier

volume

second

lumpier

volume

coarse residue kaolin

mixture

Weight - ^ greater than 53 u
Weight percent greater than Io u

Weight - ^ less than 2 u

Weight - ^ less than 1 u

3.0

0.05

6.8

The mixture was then mixed with (a) fluorine-free Cornish stone, 100% by weight of particles smaller than 75 microns and 60 by weight - '^ of particles smaller than 10 microns exist, based on the diameter of a sphere, and have the following chemical composition:

Weight- ^ SiO ₂
Al ₂ O ₃
Fe ₂ O ₅ 79.5
12.0
O.O6

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- 11 = -

Weight- ^ TiO ₂ 0.01 MgO 0.09 CaO 0.2 K ₂ O 3.80 Na ₂ O 3.90 Loss at Heating + 0.45 fluorine 0.08

+ The content of organic matter is very small and is to be regarded as the sole part of the loss when heated.

(b) A ceramic kaolin of medium quality, which has such a particle size distribution that 0.1 By weight consisted of particles larger than 53 microns, 25% by weight of particles larger than 10 microns, based on an equivalent sphere diameter, and 38% by weight consisted of particles smaller than 2 microns to an equivalent ball diameter. The mixture thus obtained consisted of 50% by weight of the mixture of clays,

- 12 -

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J * -

55j8% by weight of the fluorinated Cornish stone, and 14.2% by weight of ceramic kaolin of medium quality. The mixture was made into a slurry with water and was deflocculated with sodium silicate to form a putty containing 71.8% by weight of pesticides. This was used to produce a sanitary article which had satisfactory pouring properties, green strength, burning properties and a satisfactory fired shape. For comparison, a typical conventional sanitary ware molding compound was prepared according to the following recipe: 22% by weight of lumpy clay, 51% by weight of silica, 15 % nepheline syenite, 0.125% by weight cobalt aluminate dye and 52% by weight of a medium quality ceramic kaolin. The lumpy clay, silica, nepheline syenite and medium quality ceramic kaolin had the following analyzes:

Weight- ^ pebble
Earth Nepheline
Syenite China-
volume lumpier
volume 99.5
0.05
0.02 56.5
24.1
0.11 47
58
0.7 SiO ₂
Al ₂ O ₃
Fe ₂ O ₃ 51
51
0.99

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Weight- ^ pebble Nepheline China- lumpier Earth Syenite volume volume o.oi 0.07 0.07 TiO ₂ 0.97 0.04 1.3 0.15 Cao 0.20 0.02 0.16 O.OÖ MgO 0.29 0.02 9.0 1.4 κ ₂ ο 2.1 O.o4 Ö.O. 0.08 Na ₂ O 0.24 Loss at 0.26 0.72 12.7 Heating 13.4

The organic matter content of lumpy clay is about 2 to 3% by weight, that of silica of nepheline syenid and ceramic kaolin

volume

medium quality is very small. The lumpy stock from particles, 68 of which were by weight smaller than 1 micron, based on the equivalent sphere diameter, and 78 percent by weight were less than 2 microns based on the equivalent sphere diameter. The silica consisted of particles, 100 of which by weight were ^ smaller were than 75 microns and 54 weight ^ greater than 10 Microns, based on the equivalent sphere diameter. The nepheline syenid consisted of particles, 100 of which

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⁴ IS

weight- ^ were less than 75 microns and 46 weight- ^ greater than lo microns, based on the equivalent sphere diameter. The ceramic kaolin of medium quality consisted of particles 0.1% by weight larger than 53 microns, 25% by weight larger than Microns and 38 weight ^ less than 2 microns.

The results obtained with the two casting compositions for sanitary articles are shown in the table below II indicated, in which the casting compound, which contains the clay mixture according to the invention, with "mass A" and the conventional casting compound is designated by "mass B".

Table II

Mass A Mass B 2
Casting rate (mm / min) 1.7 1.4 Dry strength (kg / cm) 37.9 26.5 Firing temperature ( ⁰ C) 1220 1230 Burn-in gloss ($ the re-
inflection of a light from
504 mu (nm) wavelength
% Water absorption 57 56 % Contraction less than
0.3 less than
0.3 11.1 10.3

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The mass A has the advantage of using ceramic kaolin, which is less expensive than that Mixture and also no silica is required, which is a dangerous silicon material.

Example II

A first lumpy clay, a second lumpy clay, and a coarse residue kaolin with that in the following Properties given in Table III are in the same weight ratio of dry clay in one Mixing drum mixed, with about 51 hp-hours of energy per ton of dry clay when mixing the clays (1, J5 x 10 joules / kg) were consumed. The coarse residue kaolin In the form of an aqueous suspension it initially had a magnetic field of an intensity of I8OOO Gauss run through in a Jones magnetic separation to to reduce the iron content of the clay. The properties of the mixture are also given in Table III.

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Table III

first
lumpier
volume second
lumpier
volume coarser
Return
standing
China-
volume mixture SiOp (weight percent) 71.04 41.60 50.1 53.4 Fe ₂ O ^ (weight- ^) 0.85 1.08 O.69 O.9I TiO ₂ (weight ^) 1.71 0.62 0.09 0.83 carbonaceous Material (weight- ^) 0.2 12.0 4.0 Modulus of rupture (kg / cm) 65.0 27.0 52.I Weight - ^ greater than 53 u
, Weight- ^ greater than lo u
Weight- ^ smaller 3.0 4.6 11 than 2 u 90 Weight- ^ smaller as 1 u
/ 3 45 78

- 17 -

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The mixture was mixed with No.64. To give BS cobalt dye, and medium with the same freed of fluorine Cornish stone and ceramic kaolin quality, as it has been used in Beisjiel I is a mixture consisting of 36 wt -.% Of the mixture of clay, 4 wt -.% of silica, 36 wt -.% of the liberated fluorine Cornish stone, 0.125 wt .- ^ of No. 64 BS cobalt dye and 24 wt -.% Ceramic kaolin medium variety. The mixture was made with water to form a slurry and deflocculated with sodium silicate, to form a casting composition containing 70.2 wt% solids _r.

The properties of the potting compound are given in Table IV.

Table IV

2
Casting rate (mm / min) 1.5 Dry strength (kg / cm) 32.3 Firing temperature ( ⁰ C) 1240 Baked gloss in % of the right flexed light in 5θ4 mu (mn)
/ 60 ; j water absorption less than 0.3 > o contraction (linear) 02/11

? 0 H H 3 0/1 (H 1

Example III

. 50 wt -fo the same re as described in Example II, 27 wt -.% Of the same kaolin medium variety, 16 wt -.% Of the same, freed from fluorine Cornish stone, 28 wt -.% Of silica, and 1 ^ 025 wt .- ^ of No. 64 BS cobalt dye were mixed together in a mixing drum to form a clay or earthenware composition, using about 11 horsepower hours of energy per t (1,000 kg) based on dry solids during mixing (2, 9 times 10 joules / kg). The modulus of rupture of the mass after drying on "O humidity at 110 ° C was 29.4 kg / cm, and the modulus of rupture of extruded rods of about 6 mm diameter made from the mass and fired at 1180 ° C , was 474 kg / cm, the water absorption was 11 $ and the baked gloss was in the range of 80% reflection of 504 nm -% of medium of ceramic kaolin variety, 53 wt .-% silica, 16 wt -.% of fluorine liberated Comish stone and 0.125 wt .- # of cobalt dye was ceramic, kaolin and the basic silica were the same. like her at the

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IO

conventional casting compound for sanitary objects in Example I were used and the fluorinated Cornish stone was the same as that used in Example I. was needed. The lumpy clay consisted of particles 94% by weight of which were smaller than 2 microns by weight on the equivalent sphere diameter, and 87 wt .- ^ were less than 1 micron based on the equivalent sphere diameter. The analysis of the lumpy clay was as follows:

Weight % 47 SiO ₂ 56 Al ₂ O ^ 1.2 Fe ₂ O ^ 0.7 TiO ₂ 0.5
2.4 MgO
CaO
K ₂ O 0.4 Na ₂ O 12.2 Loss at
Heat

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- 20 -

The organic matter content of the lumpy clay was $ 1.1 wt. The ingredients were mixed together in a mixer drum using approximately 9.9 horsepower hours of energy per 1000 kg of dry solids (2.6 by 10 joules / kg) during mixing. The modulus of rupture of the mass after drying on "O-Moisture" at 110 C was> 8.6 kg / cm, and the modulus of rupture of rods with a diameter of about 6 mm, which were extruded from the mass and fired at 118O C, was 4.66 kg / cm ^: The water absorption was 9.5 $ and the baked gloss was 79 $ reflection from 504 nm light.

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Claims (12)

2200511 PATENT CLAIMS f1.y A mass of clays suitable for the manufacture of ceramic products, characterized in that it contains two or all three substances of a first lumpy clay, a second lumpy clay and a coarse residual kaolin, neither of which is present in any quantity which exceeds 50 wt * 5 wt .- ^ b, a carbonaceous material of not not more than 1.0 wt .- ^ and of particles of less than 40 wt -% is smaller than one micron, relative to the equivalent spherical diameter;. (b) that the second lump-shaped clay has a total content of crystal of not more than 50 wt -.%, has a combined Iron oxide and titanium content of not more than 3.5 wt -.%, a content of Kohlenctoff-matter of not more than 20 wt .- ^, and of particles no less than 209830/1 04 1 . 4O wt -% is smaller than one micron, relative to the equivalent spherical diameter; and (c) the coarse residue kaolin a combined Iron oxide and titanium content of not more than 1.5 wt -.% has and consists of particles of which are not more greater than JO ^ to 95 wt .- than ten microns, based on the equivalent sphere diameter, and not more than 20% by weight are smaller than two microns, based on the equivalent sphere diameter. 2. A mass according to claim 1, characterized in that it has a total of at least 50 ^ of two or all contains three substances, the first lumpy clay, the second lumpy clay and the coarse residue kaolin. 5 mass according to claim 1 or 2, characterized in that that they are at least 25% of each of two or all three the first lumpy clay, the second lumpy clay and the coarse residue kaolin. 4. Mass according to claim 1, 2 or 3, characterized in that that the coarse residual kaolin consists of particles of which no more than JO wt .- # are larger than fifty-three microns of which 30 to 90 wt .- ^ larger - 23 20983 0/1041 are than 10 microns, based on the equivalent spherical diameter, of which 3 to tO wt -.% are smaller than 2 microns, based on the equivalent Kugeldurehmesser. 5. mass of clays suitable for use in the manufacture of ceramic products, characterized in that 25 to 50 wt -. Having% of each of at least two blend components, namely (1) a first lumpy tone ( 2) a second lumpy clay, (3) a coarse residual kaolin, and in that (a) the first lumpy clay has a total quartz content of not more than 75% by weight, a combined iron oxide and titanium content of not more than 3, not 5 wt .- #, a content of carbon matter of more than 1 wt - having% and consists of particles of which not less than 40 wt -% are smaller than one micron, relative to the equivalent spherical diameter.;. (b) that the second lump-shaped clay has a total silica content of not more than 50 wt -fo, a combined Iron oxide and titanium content of not more than 3.5 wt -..%, a content of carbon matter of not more than 20 wt .- ^, and is composed of particles of which not less than 4θ wt -.% are smaller than one micron, relative to the equivalent Kugeldurchmes- - 24 209830/1 041 ser, and that (c) the coarse Rüek "standskaolin a combined Iron oxide and titanium content of not more than 1.5 wt .- ^ has and consists of particles of which not more than JO percent - are than 53% larger microns. of which 30 to 90 wt -.% greater than 10 microns, based on the equivalent spherical diameter, of which 3 to wt -.% are smaller than 2 microns, in relation to the equivalent spherical diameter. 6. Composition according to any one of the preceding claims, characterized in that the mass of 25 to 50 wt -% of each component includes, the first sound clumpy, clumpy of the second tone and the coarse Rückstandskaolins.. 7 · mass according to one of the preceding claims, characterized characterized that the first lumpy clay and / or the second lumpy clay has a fracture modulus (a bone dry no specimen) of at least 60 kg / cm. 8. A composition according to any of the preceding claims, characterized in that it further comprises a fluxing agent in an amount of 10 to 40 wt -% comprising, based on the total weight of the composition.. 9. Mass according to claim 8, characterized in that - 25 209830/104 1 the flux is a fluorinated Cornish stone. 10. Composition according to one of the preceding claims, characterized in that it further comprises a ceramic Medium quality kaolin, in an amount from 0 to 40 wt .- ^ based on the total weight of the Dimensions. 11. A method for manufacturing ceramic products, characterized by the steps of: (a) forming a composition according to claim 8, (b) mixing the composition with water to form a compessible mixture, (c) introducing the mixture in a mold, (d) pressing the mass in the mold at a pressure in the range of 0.3 up to 10 t per square inch to form a green product, and (e) thereafter firing the green product at a temperature in the range of 1000 ° C to 14OO ° C. 12. Ceramic body which is produced from a mass or by a method according to any one of the preceding claims is. 209830/1 04 1