Process for the preparation of superabsorbent polymers from polyacrylonitriles
AssigneeBayer Aktiengesellschaft
InventorsGisbert Michels, Thomas Gross
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Abstract
A process for the preparation of superabsorbent polymers by alkaline hydrolysis of polyacrylonitrile emulsions is disclosed. In an embodiment of the invention the process comprise preparing a PAN emulsion, subjecting the emulsion to alkaline hydrolysis, neutralizing the hydrolysate followed by drying, granulation and modifying the surface of the granular polymer by crosslinking. The process is characterized in that the isolation of the superabsorbent polymer entails neither alcohols nor organic solvents.
Claims19
A process for the preparation of a superabsorbent polymer (SAP) comprising:
- (a) subjecting a polyacrylonitrile (PAN) emulsion to alkaline hydrolysis to obtain a hydrolysate;
- (b) adding the hydrolysate to a water/acid mixture to produce a water-containing, gel-like superabsorbent polymer (SAP);
- (c) isolating the superabsorbent polymer (SAP), neither alcohols nor organic solvents being used in the isolating step;
- (d) drying the superabsorbent polymer (SAP) of step (c);
- (e) grinding the dry superabsorbent polymer (SAP);
- and
- (f) crosslinking the surface of the ground superabsorbent polymer (SAP) by means of,
- (i) spraying at least one surface modifying agent together with an acid solution onto the surface of the ground superabsorbent polymer (SAP),
- (ii) mixing the surface sprayed superabsorbent polymer (SAP), and
- (iii) heating the surface sprayed superabsorbent polymer (SAP) of step (ii) to a temperature of 100° to 200°.
A process for preparing a superabsorbent polymer (SAP) comprising:
- (a) subjecting a polyacrylonitrile (PAN) emulsion to alkaline hydrolysis in a self-cleaning reactor suitable for high-viscosity media to produce a hydrolysate;
- (b) neutralizing the hydrolysate with an acid and/or in an acid/water mixture to produce a water-containing, gel-like superabsorbent polymer (SAP);
- (c) drying the superabsorbent polymer (SAP);
- (d) granulating the superabsorbent polymer (SAP) to a desired particle size;
- and
- (e) modifying the surface of the granulated superabsorbent polymer (SAP) by means of,
- (i) spraying at least one surface modifying agent together with an acid solution onto the surface of the granulated superabsorbent polymer (SAP),
- (ii) mixing the surface sprayed superabsorbent polymer (SAP), and
- (iii) heating the surface sprayed superabsorbent polymer (SAP) of step (ii) to a temperature of 100° C. to 200° C.
Dependencies are inferred from the claim text.