Strontium carbonate dispersion and redispersible powder obtained therefrom
AssigneeSolvay Infra Bad Hoenningen GmbH
InventorsKarl Koehler, Ferdinand Hardinghaus
Life of this patent
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Abstract
The invention discloses dispersions of preferably modified strontium carbonate in organic liquids, for example in alcohols, ketones or particularly methylene chloride. The dispersions are usable for the preparation of polymers which have reduced birefringence or no birefringence and are therefore suitable for optical applications. The powder obtainable after the removal of the organic liquid can surprisingly be converted back to a dispersion with little energy.
Claims27
A dispersion comprising rod-shaped strontium carbonate particles comprising a crystallization inhibitor and having a length of not more than 1000 nm as determined by laser diffraction, dispersed in a composition comprising a dispersant and at least one organic liquid, wherein at least 90% of said rod-shaped strontium carbonate particles have a maximum length of not more than 1000 nm and wherein the dispersant and crystallization inhibitor are different from one another,
- the dispersant comprising at least one functional group selected from the group consisting of carboxylate, phosphate, phosphonate, bisphosphonate, sulphate and sulphonate functional groups, said dispersant further comprising one or more optionally substituted polyether groups,
- the crystallization inhibitor being selected from the group consisting of hydroxy-substituted carboxylic acid compounds, optionally in the form of the sodium or ammonium salt;
- phosphonic acid compounds having an alkyl or alkylene radical with a chain length of 1 to 10 carbon atoms optionally substituted by one or more hydroxyl groups, and optionally in the form of the sodium or ammonium salt;
- compounds which contain at least one nitrogen atom and at least one carboxylic acid or phosphonic acid radical, optionally substituted by one or more hydroxyl groups, and optionally in the form of the sodium or ammonium salt;
- polyamino acids;
- sulphur-substituted carboxylic acids having 1 to 20 carbon atoms (calculated without the carbon atoms of the COO group) and 1 or more COO groups, optionally in the form of the sodium or ammonium salt;
- polyacrylates, optionally in the form of the sodium or ammonium salt;
- polyethers;
- ether sulphonates optionally in the form of the sodium or ammonium salt;
- esters of phthalic acid and derivatives thereof;
- esters of polyglycerol;
- amines;
- esters of fatty acids;
- and mixtures thereof.
A redispersible powder comprising dispersant coated rod-shaped strontium carbonate particles comprising a crystallization inhibitor and having a length of not more than 1000 nm, whereby said dispersant coated rod-shaped strontium carbonate particles are obtained by a process comprising removing organic liquid from a dispersion comprising rod-shaped strontium carbonate particles comprising a crystallization inhibitor and having a length of not more than 1000 nm as determined by laser diffraction, dispersed in a composition comprising a dispersant and at least one organic liquid, wherein at least 90% of said rod-shaped strontium carbonate particles have a maximum length of not more than 1000 nm and wherein the dispersant and crystallization inhibitor are different from one another,
- the dispersant comprising at least one functional group selected from the group consisting of carboxylate, phosphate, phosphonate, bisphosphonate, sulphate and sulphonate functional groups, said dispersant further comprising one or more optionally substituted polyether groups, the crystallization inhibitor being selected from the group consisting of hydroxy-substituted carboxylic acid compounds, optionally in the form of the sodium or ammonium salt;
- phosphonic acid compounds having an alkyl or alkylene radical with a chain length of 1 to 10 carbon atoms optionally substituted by one or more hydroxyl groups, and optionally in the form of the sodium or ammonium salt;
- compounds which contain at least one nitrogen atom and at least one carboxylic acid or phosphonic acid radical, optionally substituted by one or more hydroxyl groups, and optionally in the form of the sodium or ammonium salt;
- polyamino acids;
- sulphur-substituted carboxylic acids having 1 to 20 carbon atoms (calculated without the carbon atoms of the COO group) and 1 or more COO groups, optionally in the form of the sodium or ammonium salt;
- polyacrylates, optionally in the form of the sodium or ammonium salt;
- polyethers;
- ether sulphonates optionally in the form of the sodium or ammonium salt;
- esters of phthalic acid and derivatives thereof;
- esters of polyglycerol;
- amines;
- esters of fatty acids;
- and mixtures thereof.
Dependencies are inferred from the claim text.