Water-swelling polymers cross-linked with unsaturated amino alco

Details Water-swelling polymers cross-linked with unsaturated amino alco Water-swelling polymers cross-linked with unsaturated amino alco

1998-05-20

2000-07-11

Truong, Duc

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

525259, 5253288, 525 63, 525 64, 525 69, C08F 1608, C08F 1628

Patent

active

060874503

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to superabsorbent polymers for aqueous liquids, to a process for their production and to their use. The polymers based on carboxylate groups-containing monomers are obtained by using cross-linking agents based on unsaturated amino alcohols which, because of their structure, are active in both radical preliminary cross-linkage and thermal secondary cross-linkage. The cross-linked superabsorbent polymers have excellent properties.
Superabsorbent polymers are water-insoluble, cross-linked polymers which, under swelling and formation of hydrogels, are capable of absorbing large amounts of aqueous liquids and body fluids, such as urine or blood, and of retaining the absorbed liquid amount under a certain pressure. Owing to these characteristic absorption properties, the polymers are mainly used to incorporate them into sanitary articles, such as diapers and sanitary napkins, and in the cultivation of plants.
Commercially available superabsorbent polymers are mainly cross-linked polyacrylic acids or cross-linked starch/acrylic acid-graft co-polymers wherein the carboxyl groups are partially neutralized with sodium or potassium ions.
Superabsorbent polymers are mainly produced by polymerizing aqueous solutions of mixtures made of partially neutralized acrylic acid and cross-linker into a polymer gel which--after mechanical comminution--is dried and ground to a particular particle size. Alternatively, polymer powders may also be obtained by inverse suspension polymerization wherein the aqueous monomer phase is suspended with auxiliary agents in an oil phase, for example consisting of cyclohexane, and is subsequently polymerized.
The characteristic features of superabsorbers can be improved by secondary surface cross-linkage, in particular with respect to their liquid absorption under pressure; the known phenomenon of "gel blocking" where swollen polymer particles agglutinate and thus impair further liquid absorption and liquid distribution within the diaper is suppressed. During secondary cross-linkage the carboxyl groups of the polymer molecules are cross-linked at the surface of the superabsorber particles with cross-linking agents at elevated temperatures. Among others, multivalent metallic salts, glycidyl compounds, polyols, polyepoxides, polyamines, alkylene carbonates, and polyethylene glycols are used as cross-linking agents. The secondary cross-linking step may also be carried out repeatedly.
In the course of advancing superabsorbent polymers, the requirements made on these products have substantially changed in the last years. Initially, only the very high swelling capacity on contact with liquids had been the main factor in the development of superabsorbers; however, it was found later that, in addition to the liquid amount to be absorbed, the stability of the swollen gel is also of importance. The aim must be a balanced relation between retention and gel strength so that in practice liquid absorption may also take place against a pressure. This specific absorption property is referred to as absorption under pressure/load in EP 339 461. The method of determining the liquid absorption under load (AUL) is carried out with differing loads. With increasing requirements made on superabsorbers, it was found that the initial test load of 21 g/cm.sup.2 (0.3 psi) no longer measures the desired property standard necessary for incontinence products or diaper constructions with a low fluff content and large amounts of superabsorber. For this reason, application-proven pressure loads of 42 g/cm.sup.2 (0.6 psi) and 49 g/cm.sup.2 (0.7 psi) are also measured today.
In addition to a high level of retention and liquid absorption under load, superabsorbers must comprise small amounts of soluble constituents; these arise as a result of incomplete cross-linkage during polymerization reactions, and in use they are not completely retained in the polymer body. This finally reduces the superabsorber's capability of absorbing and distributing liquids in the diaper. For example, U.S. Re. 32,649 mentio

REFERENCES:
patent: 5314420 (1994-05-01), Smith et al.

Affiliated with

Also associated with

Rating

Water-swelling polymers cross-linked with unsaturated amino alco does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Water-swelling polymers cross-linked with unsaturated amino alco, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Water-swelling polymers cross-linked with unsaturated amino alco will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-543163