DE2851027A1 - THIN PORCELAIN AND PROCESS FOR ITS PRODUCTION - Google Patents

Description

51 706-BR

Applicant: United States Borax & Chemical Corporation, 3075 Wilshire Boulevard, Los Angeles _? California, USA

Thin porcelain and its method of manufacture

The invention relates to the production of thin porcelain (fine earthenware or bone china, hereinafter always referred to as "thin porcelain") made of clay, bone ash and a flux containing boron; The invention particularly relates to a method of making thin porcelain and a new one containing boron Bone ash, a method of making the same, and its use for making thin Porcelain. The effect of using a material containing boron as a flux in the manufacture of Thin porcelain consists in the formation of the microcrystalline phase necessary for thin porcelain is characteristic, is promoted, making it possible to make thin porcelain using a wider one Firing temperature range, to produce within a shorter time and / or at lower temperatures than usual. The invention particularly relates to a thin porcelain made by incorporating a Boron-containing compound in the starting mixture in water-insoluble form. The use of the boron-containing compound leads to a reduction and Broadening of the applicable firing temperature range.

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Thin porcelain is made by firing a Mixture of clay, bone ash and a flux. Usually the clay consists mostly of kaolin or china clay. The most common flux is granite from Cornwall (Cornish Stone), it can but also other naturally occurring feldspar materials such as nepheline and syenite can be used.

Bone ash, such as that used for the production of thin porcelain, is produced, by first treating all animal bones with hot or boiling water to make gelatin, collagen, and others remove organic materials from it. In this state the bones are in a de-gelatinized state before. They are then calcined to a temperature of about 1000 C to remove the remaining organic material to burnJ calcined bones or bone ash consist (consists) essentially (about 80%) of calcium phosphate with a little calcium carbonate and a little Fluoride.

Ceramic compounds for the manufacture of thin porcelain are typically 50% bone ash, 25% of kaolin (China Clay) and 25% Cornish stone _e They are prepared by wet milling the particulate by intimately mixing and usually Components for the production of an aqueous slurry or clay slurry suitable for casting in plaster molds,

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or, with a lower water content, a plastic one Clay that can be shaped into a ceramic body. After drying to evaporate the These shaped bodies then become water in the "green" state up to a temperature within the range Fired at 1250 C to divide unglazed "Bis ^ it porcelain" with a low porosity and a characteristic transparency. The bisque porcelain is then glazed with clay (Pottery paste) and re-fired to a temperature of around 1100 C to produce glazed porcelain. One of the essential characteristics of porcelain made in this way is its Transparency, coupled with its white color, for the thin porcelain (sometimes called fine china or English thin porcelain) is famous. Because of its strength, it is also possible to produce molded bodies with a thinner wall cross-section than with other forms of ceramic goods (pottery), whereby the weight is decreased, the transparency and the resistance to thermal shock are improved.

The microstructure of the fine porcelain finally obtained is a result of the reactivity during firing, whereby the originally formed crystalline materials have dissolved and new crystals have formed. After firing, fine porcelain consists of around 70% crystals and around 30 % of crystals

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vitreous phase. The crystals consist mainly of ß-triealcium phosphate and anorthite (a lime feldspar). The high crystal content of the thin porcelain is responsible for its good mechanical strength.

Thin porcelain of the type and composition described above is already used Manufactured for about 200 years and changes related warm evolutionary on its composition and manufacture. The composition requires a higher firing temperature than that required for earthenware and therefore the burning cycle is comparatively longer and the costs for both the furnace and the fuel used, are higher. The firing temperature is also lengthened compared to earthenware to allow the phases to form based on calcium phosphate, which give the characteristic 'strength and transparency.

Methods of making ceramic pottery, referred to as "earthenware", from clay, flint and a flux using certain boron-containing compositions as the flux are known. According to US Pat. No. 3,532,522, a borate other than an alkali borate is used as a flux, for example calcium borato. According to US Pat. No. 3,704,146, a ground glass-like frit which contains B ₂ O ₃ in its oxidialysis is used as a flux. .

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The present invention now relates to a method for improving the formation of the microcrystalline Calcium phosphate phases by incorporating a Boron containing substance. The boron-containing substance can serve as a flux or as part of the flux. This addition supports the glazing and enables the production of porcelain at a lower temperature or within a shorter period of time or both. Another advantage is that the temperature range when burning expands xcLrd. This will reduce fuel consumption reduced, simpler furnaces can be used, the burning speed is increased and a deformation of the material due to the wider temperature ranges is avoided and lower temperatures are required.

According to one aspect of the invention, the boron-containing flux is combined with the bone ash; can it is either one of the water-insoluble borates or flux, as they continue above as a flux for earthenware, or it can be a water-soluble, boron oxide act containing material (but if it is water-soluble it must be bound to the bone ash to make it insoluble). The boron containing material can be bound to the bone ash by being melted or sintered or with calcined bone is calcined, or by the fact that it is calcined with the entgelatinier th bones, so that in the Cnlci-

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at the same time, the bones are converted into bone ash and bonding the boron-containing material thereto.

The boron-containing substance may be boron phosphate, an inorganic borate other than an alkali metal borate (e.g. a calcium borate) or a ground glass frit, the oxide analysis of which is SiO, B "0", Contains CaO and / or MgO as well as Na “0, as in the US patent 3,704,146 or British Patent 1,254,717. These materials can be used in the According to the invention methods can be used, either by mixing them into the clay sludge (or into the plastic clay) together with bone ash, kaolin and optionally Cornish stone or by combining the same with bone or bone ash as required for the water-soluble boron-containing materials.

The boron-containing material may alternatively consist of borate treated bones that are obtained by reacting the bones with boric acid or one of its water-soluble salts. For example, boric acid or a salt thereof can be combined with the bone ash by melting or sintering them together with the ash and the material obtained thereby as a powdery material incorporated into the clay mud. Another combination method is that you get an aqueous solution of the B "0_ containing material (or an aqueous suspension of a water-insoluble> boron-containing material) adsorbed to the bone, preferably after the bone is de-gelatinized and before it is used for manufacture

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ir

have been calcined from bone ash, and then calcined the bones and the adsorbate or absorbate. Preferred water-soluble, boron oxide-producing materials are boric acid, sodium borate with a ratio of Na ~ O; B "0 of 1: 4 and borax (sodium tetraborate decahydrate) _Q

Calcining bones containing boric acid or similar material is not always sufficient, to make the B «CL completely insoluble in water, and it was therefore found that the insolubilization can be improved by also including the precursor of at least one other glass-forming oxide, e.g. Sodium silicate, potassium carbonate, aluminum sulfate and calcium hydroxide are used. Alternatively or additionally can Boron phosphate can be used as an insoluble, boron-containing flux. It can be manufactured in the form of Boron phosphate, which is formed in situ by adding an equimolar mixture of boric acid and phosphoric acid to it added to the bones prior to calcination.

The fragments of bones, which in an aqueous liquid, which is the B «0_ source and possibly the additional Containing oxide, are soaked, dried, and then calcined at a temperature sufficient for the reaction with or for the simple formation of a layer of glass on the surfaces of the bones. It is not It is essential that the glass layer fully reacts with the calcium phosphate substrate at this stage however, it is advisable that the borate glass formed in water.

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is sufficiently insoluble that by adding clay and other ingredients after "milling, castable clay slurries or malleable clays can be satisfactorily prepared or adsorbed salts prior to grinding It is known that bone ash calcium sulfate has a large specific surface area and therefore has a high liquid absorbency, but it has been found that the porosity and internal surface area of the de-gelatinized but uncalcined bones The advantage of using de-gelatinized bones is that only one calcination and milling process is required to produce a satisfactory ceramic body component ch is, whereby cost and fuel savings can be achieved _o

If boric acid (or B ₂ O "or metaboric acid) is used alone as the B" 0 source and no other glass-forming oxide precursors are introduced, the bones react during calcination to form CaO-P ₂ O -B ₂ O_ phases _{or the like} Compositions in all possible proportions within this ternary phase system have not yet been investigated, the literature only states that a calcium boron phosphate may be used with the composition

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2CaO * Po ^ c * ^ 9 ^ 0 ^c ^ ^{in: c} ^ water is decomposed. It has now been found that calcium borophosphate compositions disproportionate when heated to a high temperature. For example, the composition 2CaO · P ^ O ₁ - • B "0" melts incongruently at about 1050 C to form β-2CaO · Po ° 5 ^and liquid B ₃ O. Related compositions within this ternary system behave similarly and it will assumed that the effect of a calcium phosphate phase crystallization and syneresis occur a B "0-containing liquid phase in compositions, has been introduced in the beginning of Na ^ O _1. During the firing of conventional thin porcelain, the bone phosphate, the kaolin and the Cornish stone react with one another to form glass phases, from which ß-calcium phosphate and anorthite then crystallize. Complete melting does not occur and the more difficult-to-melt phases persist, helping to maintain the shape and maintain the relative rigidity of the molded article during firing. According to the invention, the interaction between the particulate components is accelerated by the presence of a _{substance containing B 2} O_ in the calcined bones occurs. The mechanism is not yet fully understood, but it is believed that an

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B O rich phases are released and that these with react with the siliceous components and combine with them. The microcrystalline phases that appear after the Cooling persists, likely resembling those found in conventional thin china are, the size and shape of their crystallites and the proportions of the respective crystalline phases are different from it.

When calcining to a suitable temperature, insolubilization of the initially readily soluble Bo ^ " Substance, such as B. sodium borate, by chemical reaction with the calcium and phosphate content of the bones.

According to a further aspect, the present invention relates to a bone ash for the production of thin porcelain, which contains or consists of calcined bones into which a B ^ O ^ source has been incorporated by calcination. According to a further aspect, the present invention relates to a method for the production of these bone ash, which consists in that one animal bones degelatinised, the fragments of the bone "soaking-containing compound, whereby B" ₉ 0 in an aqueous solution or suspension of a B O 'or a precursor thereof of the. .Bone is absorbed or adsorbed to the bone, and the bone is calcined to convert it to bone ash. In this way, a borate flux in finely divided form can be introduced into the bones before or during the calcination, so that

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calcium phosphate during the final stages of this calcination and the B "O-containing material to each other begin to react.

The amount of B "0" -containing compound incorporated into the bone-clay mixture should be sufficient to produce a composition with about 0.5 to about 6% by weight of B "0", preferably about 1 to about 4% by weight. B "0 ^{to he} S ^e hen ₀ If bones treated with borate are used, the bone should have a content of B" 0 from about 1 to about 12 weight "-% preferably from about 2 to about 8 wt .-%.

The invention is illustrated in more detail by the following examples, without, however, being restricted thereto.

example 1 Manufacture of borate treated bones

Four bone samples, A, B, C and D in Table I below, were prepared from bone that had been de-gelatinized and had been calcined, and 5 samples, Samples E, F., G, II and J in the following! Table I, were made from bones that had been de-gelatinized but not calcined. Samples A and E x -nirden with an aqueous Boric acid solution treated to that in the following Table I the specified B "0" quantity, samples B and F

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were treated with an aluminum borate solution (Nn ₉ O: B ^ O = 1: 4) in order to introduce the amounts of Na ₂ O and B_0 given in the following table, samples C and G were treated with a borate solution to give the in to introduce the amounts of Ka ₉ O and B ₂ O given in Table I, samples D and H were treated with an aqueous solution of borax and sodium silicate in order to obtain the amounts of B “0, Ua _? 0 and SiO, and the sample J was heated with an aqueous solution of boric acid and phosphoric acid to introduce the amounts of II "B0" and II PO shown in Table I.

Table I.

A B C D E FGHJ (parts)

Calcined bones

de-gelatinized
bone

^H 3 ^B0 3

9.8

2.2

86.4

9.4 4.2

78.9

8.6

9.6

2.9

88
9.8

2.2

87.6
8.6

3.8

80.1 8.6

8.8 2.5

100

5.8 9.2

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For each sample, the bones were immersed in the aqueous solution immersed, dried and then calcined at 1000C. After calcining, Samples A through D, from a calcined powder, lightly sintered and then ground again, until they have a sieve with a mesh size of 0.045 mm (350 B.S. mesh.) passed. After calcining, Samples E through J were in the form of small lumps the treated bones were presented, crushed and ground until they passed a sieve with a clear mesh size of 0.045 mm (350 13.S. mesh.) passed.

Example 2 Ceramic compounds

Each of Samples A to J of Example 1 was used as a component in a ceramic mixture and two samples Bones made from calcined but not treated with borate were used in a corresponding manner as reference material (Control) Used in Ceramic Mixture The compositions of the 11 mixes are as follows Table II indicated *

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Table 11

Bones (parts) B. (55.6) Cornish
Stone
(Parts) kaolin
(Parts) Control
le 1 Calcined
Bone (50) C. (56.8) 25th 25th Control
le 2 "(50) D. (57.9) 25th 25th A. E. (62.6) 19.4 25th B. F. (52.6) 18.2 25th C. G (56.8) 17.1. 25th D. treated with borate
delte bones A. H (57.1) 12.4 25th E. Il J (62.4) 22.4 25th F. Il (55.0) 18.2 25th G 11 17.9 25th II ti 12.6 25th J Il 20th 25th Il M. Il

The dry powders were mixed thoroughly and pressed into 2.54 cm (one inch) long rods 1.27 cm (1/2 inch) in diameter. They were introduced into a furnace and the temperature was raised at a rate of 100 ° C / hour to 1050 ^Q C for 6 hours maintained at 1050 C and slowly cooled to ambient temperature. In addition, samples of the "standard fine porcelain mixture" (control 2) were heated to 1250 ° C., the normal firing temperature for thin porcelain.

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TrS- -

Compressive strength measurements were carried out with the samples, to determine the degree of glazing. The received Results are given in Table III below.

Table III

Burned
temperature
( ⁰ O Print free
kg / cm ' activity in
(psi) x times longer than
. control 2 Con
trol
le 1 1050 33.7 (480) Con
trol
le 2 1250 752.2 (10700) A. 1050 942.1 (13400) . 1.3 B. ti 907.3 (12900) 1.2 C. Il 1106.2 (15800) 1.5 D. Il 844 (12000) 1.1 E. ti 773 (11000) 1.0 F. It 872.1 (12400) 1.2 G Il 1040.2 (14800) 1.4 H It 640 (9100) 0.9 J Il 773 (11000) 1.0

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Example 3 Ker amik ammens e t tion

Instead of using bones into which a substance containing B "0" has been previously incorporated, it is also possible to introduce BoOo · * - ^{η in the} form of a separate composition in admixture with the bones and other body components into the ceramic mixture. In this example, a molded article was made by grinding together 50 parts of calcined bone, 10 parts of borate flux "24 S50" as described in US Pat. No. 3,707,146, 20 parts of kaolin and 20 parts of Cornish stone for 6 hours was fired at 1050 C. The fired molding exhibited a pressure

2
strength of 886.2 kg / cm (12600 psi), which was 26 times that of the control molding (made from 50 parts of bone, 25 parts of kaolin, 25 parts of Cornish stone) which had been produced and fired under identical conditions and the compressive strength of which was 1.2 times that of the control molded body fired at 1250 ° C., on v / ies.

Example 4

This example shows that the use of a separate flux is not essential when the inventive, borate treated bones can be used. 100 parts of calcined bone were mixed with 20 parts of anhydrous Borax and 10 parts silica mixed. This mixture

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was calcined at 1000 C and ground until it passed a sieve with a mesh size of 0.045 mm (350 mesh B.S.) happened.

A mixture was prepared from 65 parts of these borate-treated bones and 35 parts of kaolin pressed as in Example 2 and fired at 1050 G. The fired molded articles had the same strength like a control molded body fired at 1250 ° C.

Example 5

This example shows that moldings made of thin porcelain have sufficient strength and transparency can be prepared using the flux of the present invention as the only one. Flux and firing at temperatures well below 125O ° C.

Moldings were produced by impregnating the composition given in Table IV below with water, Remove the excess water on a plaster trowel and extrude through a vented mixing drum, Rods 15.24 cm (6 inches) long and 1.27 cm in diameter were used to determine transparency (1/2 inch) made. The modulus of rupture was determined by determining the load applied to the center, which was required to break a sample supported at 10.16 cm (4 inch) centers. The transparency was determined by measuring the throughput

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Sample transmitted light and it was expressed as a percentage of the amount of light of the same intensity, which was let through by conventional thin porcelain fired at 1250 ° C. The results obtained are given in Table V below.

Table IV

Together- Calci- Kao- Bento- Borat ⁺ / BoratV Borphosphat

mated lin nit 24 S50 A S50

settlement

Wr. bone

1 63 31 1 5 5 3 2 63 32 1 4th 3 2 3 63 31 1 4th 64 32 1 5 64 32 1 6th 65 32 1

/ as disclosed in U.S. Patent 3,704,146.

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Table V

Together
settlement
No. Burned
temperature
( ⁰ C) Modulus of rupture in ^
kg / crn2 (lbs / inch) By ~
sightseeing
(%) 844-1050 (12,000-15,000) 1 1180 977.3 (13,900) 103 2 1215 1090 (15,500) .118 3 1180 794.1 (11,300) 109 4th 1215 1064.1 (15,200). 113 5 1180 1333.3 (18,900) 47 6th 1250 1200 (17,000) 102 control 1250

Although the invention has been explained in more detail above with reference to preferred embodiments, it is however, it goes without saying for the person skilled in the art that it is by no means restricted to this, but that this is in can be changed and modified in many ways without thereby falling outside the scope of the present Invention is abandoned.

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Claims (2)

51 706-BR Applicant: United States Borax & Chemical Corporation, 3075 WiIshire Boulevard, Los Angeles, California, USA claims 1. A method of making thin porcelain by firing a mixture containing bony fish and clay, characterized in that a boron-containing compound is added to the mixture prior to firing, which is in a water-insoluble form, adds. 2. The method according to claim 1, characterized in that that the boron-containing compound is a borate flux used. 3. The method according to claim 1 or 2, characterized in that the boron-containing compound with bone combined. 4. The method according to any one of claims 1 to 3, characterized in that granite rock in the mixture from Cornwall (Cornish Stone) is included. 5. The method according to any one of claims 1 to 4, characterized in that the boron-containing compound 909822 / 08Ö0 ORIGI NAL INSP ECTED combined with bone by treating the bones with a source of boron oxide and then calcining them. 6. The method according to claim 5, characterized in that the boron oxide source is aqueous boric acid or aqueous Sodium borate is used. 7. Thin porcelain, characterized in that it is produced by the method according to any one of claims 1 to 6 has been" 8. Bone ash for the production of thin porcelain, characterized in that it consists of calcined Bones into which a B "O" source is incorporated by calcining has been. 9. A process for the production of bone ash, characterized in that animal bones are de-gelatinized which Fragments of bones in an aqueous solution or suspension of B "0 or a compound that, when heated is converted into B "O", soaking, whereby B "0" or its precursor is absorbed by the bones or adsorbed on the bones, and the bones are calcined, to transfer them to bone ash. 10. A process for the production of bone ash, characterized in that animal bones are de-gelatinized and calcined, the bone ash in an aqueous solution of B "0 or a compound which, when heated, in B ₉ O is converted, soaks, whereby B ₉ U or its precursor is absorbed by the bone ash or adsorbed on the bone ash, and the bone ash is calcined. 11. The method according to claim 9 or 10, characterized ^ that aqueous boric acid is used as the boron oxide source
or aqueous sodium borate is used. 2 2/0800