Cross-linked pore containing microfibrillated cellulose prepared by freezing and solvent exchange

Claim 2

Absorbent product, comprising as an absorbent element therein fibrous cellulose pulp having been beaten and subjected to pore generation by means of freezing and solvent exchange and cross-linking with a cross-link­ing agent, there being intermolecular cross-links between macromolecular chains, said pulp comprising sheet-like particles of microfibrils, said sheet-like particles arranged as discontinuous walls surrounding void volumes, said absorbent element being capable of retaining good absorbency even after having been highly compressed.

Claim 3

The product of Claim 1, said product having been densified under pressure to a sample density of at least about 0.1 g/cm³, preferably to a sample density of at least about 0.4 g/cm³.

Claim 4

The product of Claim 1 or 2, wherein said pulp has a maximum Porous Plate Capacity of at least about 10 g/g, preferably of about 16 g/g, with a testing fluid of 1% of NaCl aqueous solution.

Claim 5

The product of any of the Claims 1 to 3, wherein said pulp has a Porous Plate Retention of at least about 5 g/g, preferably of about 8 g/g, with a testing fluid of 1% NaCl aqueous solution.

Claim 6

The product of any of the Claims 1 to 4, said absorbent element demonstrating a uniaxial Z direction swelling in the wet state.

Claim 7

A process for preparing a highly absorbent retentive cellulose pulp, said absorbent element being capable of retaining good absorbency even after having been highly compressed, said process comprising: a) forming an aqueous slurry of cellulose fibers; b) extensively beating said slurry to a degree such that at least the outermost of the secondary walls of said cellulose fibers are essentially completely disintegrated into microfibrillar form; c) freezing said slurry; d) submitting the resultant frozen cake to solvent exchange with a non-aqueous solvent; e) adding a cross-linking agent to the pulp; f) evaporating said non-aqueous solvent and heat curing said pulp, whereby said highly absorbent, retentive pulp results.

Claim 8

A process for preparing a highly absorbent retentive cellulose pulp, said absorbent element being capable of retaining good absorbency even after having been highly compressed, said process comprising: a) forming an aqueous slurry of cellulose fibers; b) extensively beating said slurry to a degree such that at least the outermost of the secondary walls of said cellulose fibers are essentially completely disintegrated into microfibrillar form; c) freezing said slurry; d) submitting the resultant frozen cake to solvent exchange with a non-aqueous solvent; e) adding a cross-linking agent to the pulp; f) evaporating said non-aqueous solvent and heat curing said pulp, whereby said highly absorbent, retentive pulp results.

Claim 9

The process of Claim 6, which comprises additionally compressing said absorbent element to produce a densified thin sheet having a sample density of at least about 0.1 g/cm³, preferably to a sample density of at least about 0.4 g/cm³.

Claim 10

The process of Claim 6 or 7, in which said cross-link­ing agent is selected from the group consisting of glutaraldehyde, formalin and a polyamine/amide epi­chlorohydrin adduct.

Claim 11

The process of Claim 6 or 7, in which said cross-link­ing agent is glutaraldehyde, catalyzed by zinc chloride.

Claim 12

The process of Claim 6 or 7, in which said non-aqueous solvent is selected from the group consisting of acetone, ethyl alcohol, butyl alcohol, butyl acetate, pyridine and benzene.

Claim 13

The process of Claim 10, in which said non-aqueous solvent is acetone.

Claim 14

Absorbent product, comprising, as an absorbent element therein, the cellulose pulp produced according to the process of any of the claims 6 to 11.

Claim 15

The product of any of the claims 1 to 5 and 12, wherein said product is a sanitary napkin.

Claim 16

The product of any of the claims 1 to 5 and 12, wherein said product is a catamenial tampon.

Claim 17

The product of any of the claims 1 to 5 and 12, wherein said product is a disposable diaper.

Claim 18

The product of any of the claims 1 to 5 and 12, wherein said product is a wound dressing.

Claim 19

The product of any of the claims 1 to 5 and 12, wherein the starting cellulose fibers are wood pulp.