Claims
- 1. A composition comprising a finely-divided ceramic solid whereof the primary particles have a mean diameter of below 25 microns and a dispersant which is an organic comound of the formula ##STR5## wherein A is a divalent aliphatic radical containing 17 carbon atoms;
- J is a hydrogen, a metal, ammonium, or substituted ammonium;
- T is an optionally substituted alkyl, cycloalkyl, polycycloalkyl, aryl or polyaryl group wherein the optional substituent is at least one group selected from hydroxy, halo and alkoxy groups; and
- n has a value from 1 up to 3.
- 2. The composition of claim 1 wherein the primary particles of the ceramic solid have a mean diameter of below 10 microns.
- 3. The composition of claim 1 which contains from 0.1% up to 20% by weight of the dispersant, based on the weight of the ceramic solid.
- 4. The composition of claim 1 wherein the ceramic solid is selected from alumina, silica, zirconia, silicon carbide, silicon nitride, boron nitride, sialons, metal titanates, Mullite and Cordierite.
- 5. The composition of claim 1 wherein the ceramic solid is silica, a metal oxide, or a mixture of metal oxides, including mixtures of one or more metal oxides with silica.
- 6. The composition of claim 1 wherein the divalent aliphatic radical A is ##STR6##
- 7. The composition of claim 1 which also contains an organic medium in which the ceramic solid is dispersed and in which the dispersant is at least partially soluble.
- 8. The composition of claim 7 which contains from 20% to 98% by weight of the ceramic solid.
- 9. The composition of claim 7 wherein the ceramic solid is dispersed in an organic medium which is at least plastic under processing conditions and is selected from polyethylene, polypropylene, polystyrene, polymethylmethacrylate, paraffin wax, polyethylene wax, and fatty alcohols.
- 10. The composition of claim 1 which additionally includes resins, binders, fluidizing agents, anti-sedimentation agents, plasticisers and other dispersing agents or surfactants.
- 11. The composition of claim 1, wherein the ceramic solid is selected from alumina, silica, zirconia, silicon carbide, silicon nitride, boron nitride, sialons, metal titanates, Mullite and Cordierite and the dispersant is one in which the divalent aliphatic radical A is ##STR7##
- 12. The composition of claim 1 wherein the ceramic solid is alumina and the dispersant is one in which the divalent aliphatic radical A is ##STR8##
- 13. A process for producing a composition containing a finely-divided ceramic so lid whereof the primary particles have a mean diameter of below 25 microns, which comprises adding a dispersant during the preparation of the ceramic solid or subjecting a mixture of the ceramic solid and a dispersant to a grinding operation, wherein the dispersant is an organic compound having the formula ##STR9## wherein A is a divalent aliphatic radical containing 17 carbon atoms;
- J is a hydrogen, a metal, ammonium, or substituted ammonium;
- T is an optionally substituted alkyl, cycloalkyl, polycycloalkyl, aryl or polyaryl group wherein the optional substituent is at least one group selected from hydroxy, halo and alkoxyl groups; and
- n has a value from 1 up to 3.
- 14. The composition of claim 1 wherein the ceramic solid is silica, a metal oxide, other than pigmentary titanium dioxide or iron oxide, or a mixture of metal oxides, including mixtures of one or more metal oxides with silica.
- 15. A composition comprising a finely-divided ceramic solid which is selected from alumina, silica, zirconia, silicon carbide, silicon nitride, boron nitride, sialons, metal titanates, Mullite and Cordierite, and whereof the primary particles have a mean diameter of below 25 microns together with a dispersant which is an organic compound of the formula ##STR10## wherein A is a divalent aliphatic radical containing 17 carbon atoms;
- J is a hydrogen, a metal, ammonium, or substituted ammonium;
- T is an optionally substituted alkyl, cycloalkyl, polycycloalkyl, aryl or polyaryl group wherein the optional substituent is at least one group selected from hydroxy, halo and alkoxy groups; and
- n has a value from 1 up to 3.
- 16. A composition comprising a finely-divided ceramic solid whereof the primary particles have a mean diameter of below 25 microns, a dispersant which is an organic compound of the formula ##STR11## and an organic medium in which the ceramic solid is dispersed and in which the dispersant is at least partially soluble, wherein the organic medium is at least plastic under processing conditions and is selected from polyethylene, polypropylene, polystyrene, polymethylmethacrylate, paraffin wax, polyethylene wax and fatty alcohols, and
- A is a divalent aliphatic radical containing 17 carbon atoms;
- J is a hydrogen, a metal, ammonium, or substituted ammonium;
- T is an optionally substituted alkyl, cycloalkyl, polycycloalkyl, aryl or polyaryl group wherein the optional substituent is at least one group sleeted from hydroxy, halo and alkoxy groups; and
- n has a value from 1 up to 3.
Priority Claims (1)
| Number |
Date |
Country |
Kind |
| 8607596 |
Mar 1986 |
GBX |
|
THE COMPOSITION
This application is a continuation-in-part of application Serial No.022,091 which was filed Mar. 5, 1987, now abandoned.
The present invention relates to a novel dispersible composition of a finely divided ceramic solid and a dispersant, and to a dispersion of the composition in an organic medium.
A number of dispersions of inorganic pigments, lakes and toners containing dispersing agents derived from hydroxycarboxylic acids are known from UK Patent No. 1342746. We have now found that dispersions of finely divided ceramic solids can also be made using dispersing agents derived from hydrocarboxylic acids. When using dispersions of ceramic solids in many ceramic processing operations it is frequently most advantageous to have a very high ceramic solids content dispersion combined with the lowest possible viscosity. Surprisingly we have now found that the relatively low molecular weight dispersing agents, which are least effective for dispersing many inorganic pigments, are the most effective for dispersing ceramic solids.
According to the present invention there is provided a composition comprising a finely-divided ceramic solid whereof the primary particles have a mean diameter of below 25 microns and a dispersant which is an organic compound of the formula ##STR1## wherein A is a divalent aliphatic radical containing 17 carbon atoms;
The composition may comprise an intimate mixture of the two components, for example a coating of the dispersant on the finely-divided primary particles of the solid. Preferably the primary particles of the ceramic solid have a mean diameter of below 10 microns. The composition may be dry, in which case the primary particles of the solid may be aggregated. Alternatively, the composition may be in the form of a dispersion of the solid in an organic medium, preferably one which is a liquid, or at least plastic, under ambient or processing conditions.
The composition preferably contains from 0.1% to 20%, and more preferably from 0.2% to 10%, by weight of the dispersant, based on the weight of the ceramic solid. In the dispersion form, the composition preferably contains from 20% to 98% by weight of the ceramic solid, the precise quantity depending on the nature of the solid and the relative densities of the ceramic solid and organic medium.
The composition may be prepared by mixing the component using any suitable mixing technique. Alternatively the dispersant may be added to the ceramic solid during the preparation of the latter, preferably during the later or finishing stages of Preparation, for example, if the ceramic solid is obtained as a dispersion or suspension in water during the later stages of its preparation, the dispersant may be added to the aqueous mixture as a solution or emulsion. The water may be removed from the resulting mixture to give a composition of the ceramic solid and the dispersant. The composition may also be prepared by subjecting a mixture of the ceramic solid and the dispersant, preferably in the organic medium, to a grinding operation sufficient to reduce the particle size of the ceramic solid to below 25 microns and especially below 10 microns. Where the organic medium is a volatile liquid this may be subsequently removed by evaporation, if the composition is required in a dry form. Where the organic medium is a solid or Plastic material at ambient temperatures, for example a resin, the mixing of the components and subsequent grinding operation may be carried out at an elevated temperature so that the organic medium and the composition is in a fluid or plastic, form.
The composition, whether dry or in the form of a dispersion, may contain other ingredients, such as resins (where these do not already constitute the organic medium), binders, fluidizing agents, anti-sedimentation agents, plasticisers, and other dispersing agents or surfactants.
The composition is particularly suitable for use in non-aqueous ceramic processes, especially tape-casting, doctor-blade processes, slip-casting, extrusion and injection moulding type processes.
The solid may be any ceramic material, especially a material which it is desired to stabilize in a finely divided state in an organic medium. A preferred solid is a ceramic material from any of the recognized classes of ceramic materials described, for example, in "Modern Ceramic Engineering" by D.W. Richerson, published by Marcel Dekker (New York and Basel) in 1982).
Examples of suitable ceramic materials are alumina, especially calcined alumina, silica, zirconia, including partially stabilized zirconias and tetragonal zirconia polycrystal, silicon carbide, silicon nitride, boron nitride, sialons, metal titanates, especially barium titanate, Mullite and Cordierite. The ceramic solid is preferably a metal oxide or silica or a mixture of metal oxides, including mixtures with silica.
Where the composition of the present invention is in the form of a dispersion, the organic medium should be one in which the dispersant is at least partially soluble at a temperature at which the organic medium is in a fluid, or at least plastic form.
Examples of suitable fluid organic media are aliphatic and aromatic hydrocarbons and halogenated hydrocarbons such as hexane, cyclohexane, heptane, toluene, xylene, chlorobenzene, chloroform, trichloroethylene and 1,1,1-trichloroethane; ketones such as iso-butyl ketone, cyclohexanone and isophorone; esters such as butyl acetate and propyl acetate; ethers such as tetrahydrofuran and 2-butoxyethylacetate; and higher alcohols, that is alcohols containing at least four carbon atoms, such as n-butanol and hexanol. Such media may also be used in admixture with polar organic media such as lower alcohols, that is alcohols containing up to three carbon atoms, for example methanol, ethanol and iso-propanol, glycols, for example ethylene glycol and propylene glycol, and glycol ethers, for example 2-ethoxyethanol, providing the dispersant is still soluble in the mixture. Compositions of this type if fluid, are particularly suitable for use in tape-casting, doctor-blade and slip-casting type processes.
Examples of suitable organic media that are either fluid or at least plastic under ambient or processing conditions are polyethylene, polystyrene, polypropylene and polymethylmethacrylate, particularly the low molecular weight forms of these polymers, paraffin and polyethylene waxes and fatty alcohols, that is alcohols containing at least ten carbon atoms, such as hexadecanol and octadecanol. Compositions of this type, if plastic under processing conditions, are particularly suitable for use in injection moulding and extrusion type processes.
The dispersant is an organic compound of the general formula: ##STR2## wherein A, J, T and n are all as
Optional substituents in the group T include hydroxy, halo and alkoxy groups. If the optional substituent is a hydroxy group, the dispersant may have been derived by simply polymerizing a hydroxycarboxylic acid and optionally neutralizing with an appropriate basic material. In other cases, the terminating group may be derived by including a chain terminating compound with the structure ##STR3## in the polymerization process in which the group T does not contain a hydroxy group as a substituent.
Preferred examples of the divalent aliphatic radical A are ##STR4##
If J is a metal, preferred metals are lithium, sodium, potassium and the alkaline earth metals. If J is a substituted ammonium group, preferred groups are those derived from alkyl amines such as octadecylamine, diethylamine and triethylamine, alkanolamines such as triethanolamine, arylamines such as aniline and toluidine and di- and polyamines such as ethylene diamine, diethylene triamine and triethylene tetramine.
The dispersant may be prepared, for example, by heating a suitable hydroxycarboxylic acid, for example 12-hydroxystearic acid or ricinolaic acid, optionally in the presence of a suitable chain terminating agent such as a non-hydroxylic substituted carboxylic acid, preferably an alkanoic or alkenoic acid containing at least 10 carbon atoms, for example stearic, oleic, linoleic or linolenic acid, and optionally in the presence of a suitable esterification catalyst such as tetrabutyl titanate, zirconium naphthenate, zinc acetate or toluene sulphonic acid, at a temperature of from 150 to 250.degree. C. The water formed in the esterification reaction is removed from the reaction medium, and this can be conveniently done by passing a stream of nitrogen over the reaction mixture, or by carrying out the reaction in the presence of a solvent such as toluene or xylene, and distilling off the water as it is formed.
If the dispersant is a metal salt, it can be conveniently made by heating the product from the above esterification reaction with an oxide, hydroxide or carbonate of the metal at a convenient temperature, for example between 150.degree. and 250.degree. C. If the dispersant is an ammonium salt, it can be conveniently made by heating the product from the above esterification reaction with the appropriate amine at a convenient temperature, for example just above the melting point of the esterification reaction product. Such salts may also be made in situ during the grinding operation.
US Referenced Citations (5)
| Number |
Name |
Date |
Kind |
|
3778287 |
Stansfield et al. |
Dec 1973 |
|
|
3996059 |
Stansfield et al. |
Dec 1976 |
|
|
4366280 |
Yukawa |
Dec 1982 |
|
|
4398955 |
Stansfield et al. |
Aug 1983 |
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4797440 |
Schofield et al. |
Jan 1989 |
|
Foreign Referenced Citations (2)
| Number |
Date |
Country |
| 2204531 |
Aug 1973 |
DEX |
| 1342746 |
Jan 1974 |
GBX |
Non-Patent Literature Citations (2)
| Entry |
| Derwent Abstract 83-830506, 1983, "Ceramic Porous Body Production". |
| Derwent Abstract 85-214380, 1985, "Resin for Pigment Dispersion". |
Continuation in Parts (1)
|
Number |
Date |
Country |
| Parent |
22091 |
Mar 1987 |
|
Patent Grant
4954177
