Method of making porous, absorbent macrostructures of bonded absorbent particles surface crosslinked with cationic amino-epichlorohydrin adducts
OwnerEbrahim Rezai, Frank H. Lahrman +1inventors
InventorsEbrahim Rezai, Frank H. Lahrman, Toshiaki Iwasaki
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Abstract
Porous, absorbent macrostructures that, upon contacting liquids such as water or body exudates (e.g., urine), swell and imbibe such liquids, and are useful in absorbent articles such as diapers, adult incontinence pads, and sanitary napkins are disclosed. These porous macrostructures comprise bonded absorbent particles that are surface crosslinked with cationic, preferably polymeric, amino-epichlorohydrin adducts.
Claims31
A method for making a porous, absorbent macrostructure comprising an interparticle bonded aggregate having pores interconnected by intercommunicating channels so that the macrostructure is liquid permeable, the method comprising the steps of:
- (a) providing a multiplicity of precursor particles of substantially water-insoluble, absorbent, hydrogel-forming, polymer material having anionic functional groups;
- (b) treating the precursor particles with a cationic amino-epichlorohydrin adduct, the cationic adduct being in an amount sufficient to be capable of reacting with the polymer material at the surface of the precursor particles so as to cause effective surface crosslinking;
- (c) physically associating the treated precursor particles to form an aggregate having pores interconnected by intercommunicating channels;
- and
- (d) reacting the cationic adduct with the polymer material of the precursor particles so as to cause effective surface crosslinking and to provide a porous, absorbent, interparticle bonded aggregate macrostructure.
A method for making a porous, absorbent sheet comprising an interparticle bonded aggregate having pores interconnected by intercommunicating channels so that the sheet is liquid permeable, the method comprising the steps of:
- (a) providing a multiplicity of precursor particles having a mass average particle size less than about 300 microns and comprising a substantially water-insoluble, absorbent, hydrogel-forming, polymer material selected from the group consisting of hydrolyzed starch-acrylonitrile graft copolymers;
- partially neutralized starch-acrylonitrile graft copolymers;
- starch-acrylic acid graft copolymers, partially neutralized starch-acrylic acid graft copolymers;
- saponified vinyl acetate-acrylic ester copolymers;
- hydrolyzed acrylonitrile copolymers;
- hydrolyzed acrylamide copolymers;
- slightly network crosslinked products of any of the foregoing copolymers;
- partially neutralized polyacrylic acid;
- slightly network crosslinked products of partially neutralized polyacrylic acid;
- and mixtures thereof;
- (b) applying to the precursor particles an aqueous treatment solution having a pH of from about 4 to about 9 and comprising:
- (i) a cationic polymeric amino-epichlorohydrin resin in an amount of from about 0.1 to about 5 parts by weight, per 100 parts by weight of the precursor particles;
- and optionally
- (ii) a plasticizer in an amount of from about 5 to about 60 parts by weight, per 100 parts by weight of said precursor particles;
- (c) physically associating the treated precursor particles to form an aggregate having pores interconnected by intercommunicating channels;
- (d) forming the aggregate into a sheet;
- and
- (e) reacting the cationic polymeric resin with the polymer material of the precursor particles so as to cause effective surface crosslinking and to provide a porous, absorbent interparticle bonded aggregate sheet having a thickness between about 0.5 mm and about 10 mm, a density of from about 0.8 to about 1.1 g/cc, and a circumscribed dry volume of at least about 500 mm.
Dependencies are inferred from the claim text.