JPS6225626B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides a novel boron-containing bone ash and its production for use in the production of bone china. The effect of using boron-containing materials as fluxes in producing bone chainers is to promote the formation of the microcrystalline phase that is characteristic of bone chainers, thus allowing bone chainers to be used for shorter times and/or at lower and wider firing temperatures than usual. It will be possible to make a range. Bone china is made by firing a mixture of clay, bone ash, and flux. Usually this clay is primarily kaolin or chiaina clay. The most commonly used flux is Cornish stone, but other natural feldspathic materials such as nepheline and syenite can also be used. Bone ash, such as that used in the manufacture of bone china, is first made by treating animal bones with hot or boiling water to remove gelatin, collagen and other organic matter. In this state, the bone is said to be degelatinized. This is then calcined to a temperature of about 1000°C to burn off the remaining organic matter. Calcined bone or bone ash is essentially (approximately 80%) with some calcium carbonate or small amounts of fluoride.
Calcium phosphate. The ceramic composition for making bone china is typically 50% bone ash, 25% china clay, and 25% coalwall stone. These are aqueous slurries or slips suitable for molding in plaster moulds; or by thoroughly mixing the granular components and usually wet milling to produce plastic clays that are cast or molded with low water content. It is made from ceramic base. After drying to evaporate the water, this molder in the "green" state is fired to a temperature close to 1250°C so as to yield an unglazed "China bisque" ware of low porosity and characteristic translucency. . The bisqueware is then coated with a glaze slip and refired to a temperature of approximately 1100°C to produce glazed porcelain. One of the main characteristics of vessels produced in this way is their white color and translucence, for which bone china (sometimes referred to as fine china or English bone china) is famous. Because of its strength, it also makes it possible to create articles with thinner walls than with other forms of pottery, which increases their light weight, translucency and resistance to thermal shock. The final microstructure of bone china resulted from reactions during firing, in which the originally formed crystalline material was dissolved and new crystals formed. After firing, bone china consists of approximately 70% crystalline and 30% glassy phases. The crystals are mainly β-tricalcium phosphate and anorthite (limefeldspar). Bone china's high crystal content explains its good mechanical strength. Bone china of substantially the type and composition described above has been in production for two hundred years and the changes in formulation and manufacturing have been revolutionary. This composition requires higher firing temperatures than those required for porcelain, so the firing cycles are relatively long and the cost of the kiln and fuel used is higher. Firing times are also longer compared to porcelain to allow the formation of a calcium phosphate-based phase that imparts unique strength and translucency. Certain boron-containing compositions are used as fluxes and methods are known for producing ceramic clay ware, referred to as "white porcelain", from clay, flint and flux. According to U.S. Pat. No. 3,532,522, borates other than alkali metal borates,
For example, calcium borate is used as a flux. According to US Pat. No. 3,704,146, a ground vitreous frit containing B ₂ O ₃ is used as a flux in the oxide analysis. The present invention provides a method of enhancing the formation of calcium phosphate microcrystalline phases through the inclusion of boron-containing materials.
This boron-containing material serves as a flux or part of a flux. This inclusion aids in vitrification and allows ceramics to be produced at low temperatures or in short periods of time, or both. An added advantage is that the temperature range for firing is expanded. This practice reduces fuel consumption, allows the use of simpler kilns, increases firing speeds, and helps avoid warping of the ceramics by allowing a wider temperature range as well as lower temperatures as required. Thus, in one aspect of the invention, the boron-containing flux is combined with boron ash; this may be an inherently water-insoluble borate or one of the fluxes mentioned above as a flux for white ceramics, or a water-soluble bone oxide. It may be any of the containing materials (but if water soluble this must be combined with the bone ash to become insoluble). The boron-containing material is melted or sintered, or calcined with calcined bone, or calcined with degelatinized bone to bind the boron-containing material to the bone ash, so that this simultaneously converts bone into bone ash and binds this boron-containing material thereto. The boron-containing material is boron phosphate, an inorganic borate other than an alkali metal borate (e.g., calcium borate), or U.S. Pat.
SiO 2 , B 2 O 3 , CaO and/or SiO ₂ , B ₂ O ₃ , CaO and/or
or a crushed vitreous frit containing MgO and Na ₂ O. Grinding these materials into slips (or plastic clays) with bone ash, kaolin, and optionally cornwallite, or blending them with bone or bone ash as required for water-soluble boron-containing materials. Either of these materials can be used in the method of the invention. The boron-containing material may alternatively be borated bone formed by the reaction of boric acid or one of its water-soluble salts with bone. For example, boric acid or its salts can be combined with the bone ash by being melted or sintered with the bone ash, and the resulting material is incorporated as a powder into the slip. An alternative method of formulation is to apply an aqueous solution of a _B2O3 -containing material (or an aqueous suspension of a water-insoluble boron-containing material) to the _bone , preferably after degelatinizing the bone and before calcining it to form bone ash. and then calcining the bone and adsorbent or absorbent. Suitable water-soluble boron oxide feedstocks include boric acid, sodium borate in a 1:4 _Na2O : _B2O ratio, and borax (sodium tetraborate).
decahydrate). Calcination of bones containing boric acid or similar materials
It is not necessarily sufficient to make _{the B2O3} completely water-insoluble, and at least one extra glass-forming oxide precursor such as sodium silicate,
It has been found that insolubilization can be improved by also using potassium carbonate, sodium sulfate and calcium hydroxide. Alternatively or additionally, boron phosphate can be used as the insoluble boron-containing flux. This can be added in the form of a prepared boron phosphate formed in situ by adding an equimolar mixture of boric acid and phosphoric acid to the bone before calcination. Immerse the bone fragments in an aqueous liquid containing _B2O3 and optionally another oxide source, dry and then add enough to react, or simply deposit a glassy layer on the surface of the bone _. Calcinate at forming temperature. After grinding for a casting slip or moldable clay, it is not essential that this glassy layer interacts fully with the calcium phosphate matrix at this stage, but is satisfactory in the case of clay and other ingredients. It is desirable that the borate glass formed be sufficiently insoluble in water. Alternatively, pre-calcined bone is also soaked in a borate-containing solution, dried and calcined again to insolubilize absorbed or adsorbed salts prior to grinding. Although it is well known that bone ash calcium phosphate has a large surface area and therefore high liquid absorption capacity, the porosity and internal surface area of degelatinized but uncalcined bone are not sufficient for the practice of the present invention. It has been found suitable for receiving boric acid or borate salts. The advantage of degelatinized bone is that only one calcination and grinding step is required to prepare a satisfactory ceramic body component, thus impacting cost and fuel savings. Only boric acid (or B ₂ O ₃ or metaboric acid)
When used as _{a B2O3} source and no other glass- _forming oxide precursors are used, the bone reacts during calcination to form the CaO- _P2O5 - _{B2O3 phase} . It appears that all possible ratios of composition within this ternary phase system have not been studied, but compositions that are decomposed by water
Calcium borates _of 2CaO- _P2O5 - _B2O3 are described in _the literature. Calcium borate compositions have been found to become disproportionate upon heating to high temperatures. For example, the composition 2CaO.P ₂ O ⁵ .B ₂ O ₃ undesirably melts at about 1050° C. to form β-2CaO.P ₂ O ₅ liquid B ₂ O ₃ . Related compositions within this ternary system behave similarly and the effect of calcium phosphate crystallization and syneresis of the B ₂ O ₃ -containing liquid phase also appears to occur in the composition where Na ₂ O is first introduced. It can be done. During traditional bone china firing, bone phosphate, kaolin and cornwall stone interact to form a glassy phase;
β-calcium phosphate and anorthite subsequently crystallize from this. Total melting does not occur; a further refractory phase remains and helps retain the shape and relative stiffness of the fired article. According to the present invention, the interaction of particulate components _{is B2O3} in calcined bone.
Facilitated by the presence of containing materials. This allows a corresponding and satisfactory degree of vitrification to take place at lower temperatures and shorter firing schedules, without shape deformation. The mechanism is not completely understood, but release of a B ₂ O ₃ rich phase and interaction and binding with siliceous components is likely. The microcrystalline phase that remains after cooling is likely similar to that contained in conventional bone china, but the size and shape of the crystallites and the proportions of each crystalline phase are different. Upon calcination to a suitable temperature, insolubilization of initially highly soluble B ₂ O ₃ materials, such as sodium borate, occurs by chemical reaction with the calcium and phosphate components of the bone. Thus, one feature of the invention is bone ash for the production of bone china containing calcined bone formulated by calcining a source of B ₂ O ₃ . Another feature of the invention is degelatinizing animal bones;
immersing the bone fragments in an aqueous solution or suspension of a B ₂ O _3- containing compound, whereby the B ₂ O ₃ or its precursors are absorbed or adsorbed into the bone; and the bone is calcined. This is a method for producing bone ash, which involves converting it into bone ash. Thus, the borate flux is introduced in particulate form into the bone before or during calcination, so that during the final stages of this calcination process the calcium phosphate and B ₂ O ₃ -containing materials begin to interact. The amount of _{B2O3 -} containing compound incorporated into the bone-clay mixture must be sufficient to provide about 0.5 to about 6%, preferably about 1 to ₄ %, by weight _B2O3 in the composition. No. When boron salt treated bone is used, the bone should have about 1 to about 12% _B2O3 , preferably about ₂ to 8%. The following examples illustrate the invention: EXAMPLE Preparation of borated bone The four bone samples of Table 1, reference symbols A, B, C and D, were prepared from degelatinized and calcined bone, Five samples in Table 1, reference symbols E, F, G,
H and J were prepared from degelatinized but uncalcined bone. Samples A and E were treated with an aqueous boric acid solution to introduce the amount of B ₂ O ₃ shown in the table; Sample B
and F as sodium borate (1:4Na ₂ O:
B ₂ O ₃ ) in the amount shown in the table.
Na ₂ O and B ₂ O ₃ were introduced; Samples C and G were treated with an aqueous solution of borax to introduce the amounts of Na ₂ O shown in the table.
Samples _{D and H were treated with an aqueous solution of borax and sodium silicate to introduce the amounts of B 2 O 3 , Na 2 O and SiO 2 shown in the table ;} J was heated with an aqueous solution of boric acid and phosphoric acid and the amounts shown in the table were introduced.

Table: For each sample, the bones were soaked in an aqueous solution, dried and then calcined at 1000°C. After calcination, samples A through D made from the calcined powder were lightly sintered and reground to pass through a 350 B.S. mesh. Samples E through J, in the form of bone pellets treated after calcination, were broken and ground to pass through a 350 B.S. mesh. EXAMPLES Ceramic Compositions Each of Samples A through J of the Examples was used as a component in ceramic materials, and two samples of calcined but unborated bone were similarly used as controls in ceramic materials. . The compositions of the 11 mixes are shown in Table 1.

【table】

Table: The dry powder was thoroughly mixed and compressed into 1/2 inch diameter x 1 inch long rods. These were placed in a kiln, heated to 1050°C at a rate of 100°C/hour, held at 1050°C for 6 hours, and gradually cooled to ambient temperature. In addition, a sample of the "standard bone china" mix (Control 2) was heated to 1250 DEG C., the normal firing temperature for bone china. Compressive strength measurements were performed on the samples to indicate the degree of vitrification. The results are shown in Table 1.

[Table] Examples Ceramic Compositions B As an alternative to the use of bone pre-blended with _{a 2O3 -} containing material, ceramic compositions can be prepared as a separate composition mixed with bone and other matrix ingredients.
It is possible _to introduce _B2O3 . In this example,
A substrate made by grinding together 50 parts of calcined bone, 10 parts of the borate flux "24S50" described in U.S. Pat. It was baked for 6 hours. This fired body has a compressive strength of 12,600 Psi, which is 26 times stronger than a control body (50 parts bone, 25 parts China clay, and 25 parts Cornwall stone) prepared and fired under the same conditions and at 1250°C. It was 1.2 times stronger than the control material fired at EXAMPLE This example shows that the use of a separate flux is not required when using the borated bone of the present invention. 100 parts of calcined bone were mixed with 20 parts of anhydrous borax and 10 parts of silica. The mixture was calcined at 1000° C. and ground to pass through a 350 B.S. mesh. A green mix was prepared from 65 parts of this borated bone and 35 parts of china clay, compacted and fired at 1050°C as in the examples. The firing base is
The strength was the same as that of the control material fired at 1250°C. EXAMPLE This example shows that bone china green bodies can be prepared with adequate strength and translucency using the flux of the present invention as the sole fluxing agent and firing to temperatures substantially below 1250°C. The bodies were prepared by kneading the composition of the table in water, removing excess water with a plaster of Paris vat, and extruding through an aerated pug mill. A 1/2" diameter x 6" length rod was made for translucency measurements. The modulus of rupture was determined by measuring the load applied at the midpoint required to fracture a sample supported on a 4 inch center. Translucency is measured by measuring the light transmitted through the sample and
It is expressed as a percentage of the amount of light of the same intensity transmitted through standard bone china fired at 1250°C. The results are shown in Table 1.

【table】

[Table] Example Analytical values based on oxides are Na ₂ O 10%, CaO 10%,
25% B ₂ O ₃ , 5% A ₂ O ₃ and 5% SiO ₂ were prepared by the method described in British Patent Specification No. 1254717,
It was ground to a powder sufficient to pass 350 mesh through a British standard sieve. 725g of degelatinized bone (approximately 500g is solid)
225 g of absorbed water) is slurried in 60 ml of water in the form of pellets with an average size of about 1 cm.
Mixed with 64.5g of finely ground frit. 3 of the mixture
Calcined at 1000℃ for an hour. The resulting material was dry ground and wet milled to obtain easily fluxed bone with a fine powder containing 3.59% B ₂ O ₃ . Using this fluxed bone, slips of bone chainers having the following composition were prepared. 69 g of fluxed bone 31 g of china clay 50 ml of water The mixture, after being deflocculated with a polyacrylate peptizer, resulted in a free-flowing slip with a low viscosity suitable for slurry casting. Examples (i) As described in British Patent Specification No. 1254717
Na ₂ O 10.3%, CaO 11.7%, B ₂ O ₃ 44.7% and
A frit containing 33.3% SiO ₂ was prepared and milled. 725 g of degelatinized bone (including initially absorbed water) was mixed with 37.5 g of frit slurried in 50 ml of water. The mixture was calcined and ground as in _the example to obtain easily fluxed bone containing 3.95% _B2O3 . (ii) Easily fluxed bone was treated with Na ₂ O10.3
%, MgO 11.7%, B ₂ O ₃ 44.7% and SiO ₂ 33.3%. Bone borated with both CaO-containing and MgO-containing frits was made into slips with chain relays and water. This slip was also suitable for slurry casting. EXAMPLES The compositions comprising borated bone, clay and water described in the Examples and in can be dehydrated to a paste-like consistency. The resulting plastic clay, which has a lower water content than the slip, can be molded into plates, saucers and other dish-like shapes using known techniques. Various modifications and variations of the present invention may be made and, as long as such modifications are consistent with the spirit of the invention, they are intended to be included within the scope of the claims.

Claims (1)

[Claims] 1. Bone ash for producing bone china, which is obtained by adding a boron compound to calcined bone ash by calcination or sintering of a water-soluble or water-insoluble boron-containing substance. 2 The source of boron oxide is analyzed on an oxide basis.
Bone ash according to claim 1, which is a ground glass frit containing B ₂ O ₃ . 3 Fritt analyzed B ₂ O ₃ based on oxides,
Bone ash according to claim 2, comprising SiO ₂ , Na ₂ O and at least one of CaO and MgO. 4. Bone ash according to claim 2, wherein the frit further comprises Al ₂ O ₃ . 5. Degelatinizing the animal bones, by immersing the bone fragments in an aqueous solution or suspension of B ₂ O ₃ or a compound that is converted to B ₂ O ₃ by heating.
A method for producing bone ash, which comprises absorbing or adsorbing B ₂ O ₃ or its precursor into bone, and converting the bone into bone ash by calcining the bone. 6. The method according to claim 5, wherein aqueous boric acid or aqueous sodium borate is used as the source of boron oxide. 7. The method of claim 5, wherein the quality material is ground glass frit containing B ₂ O ₃ on an oxide basis analysis. 8 Fritz analyzed B ₂ O ₃ based on oxides,
8. The method of claim 7, comprising _SiO2 , _Na2O and at least one of CaO and MgO. 9. The method of claim 8, wherein the oxide-based analysis of the frit also includes Al ₂ O ₃ . 10 Degelatinizing or calcining animal bones, soaking the bone ash in an aqueous solution of B ₂ O ₃ or a compound that is converted to B _{2 O 3 on heating, thereby converting B 2 O 3 or its} precursors. A method for producing bone ash, which comprises absorbing or adsorbing it into bone ash and calcining the bone ash.