Absorbent structure in an absorbent article

Details Absorbent structure in an absorbent article Absorbent structure in an absorbent article

2000-08-30

2003-12-02

Lo, Weilun (Department: 3761)

Surgery

Means and methods for collecting body fluids or waste material

Absorbent pad for external or internal application and...

C604S369000, C604S375000, C604S377000

Reexamination Certificate

active

06657101

ABSTRACT:

TECHNICAL FIELD
The present invention refers to an absorbent structure in an absorbent article such as a diaper, a pant diaper, an incontinence guard, a sanitary napkin etc. said absorbent structure comprises an open-cell foam structure, the pore walls of said foam structure comprising a liquid-storing material having the capacity to store more than 7% synthetic urine defined according to the CRC method.
BACKGROUND
Absorbent articles of the above mentioned kind are intended to absorb body liquids such as urine and blood. Such absorbent articles usually have a liquid pervious topsheet, which during use is facing the wearer's body. They further have a liquid impervious backsheet, e g a plastic film, a plastic coated nonwoven or a hydrophobic nonwoven, and an absorbent structure enclosed between the liquid pervious topsheet and the liquid impervious backsheet.
It is desired that absorbent articles of the above mentioned kind are thin an discrete to use. It is further important that absorbent articles of the above mentioned kind have a high liquid acquisition capacity as well as liquid distributing and liquid storing capacity. In order to fulfil these requirements it is common that the absorbent structure contains two or more layers having different properties.
In order to obtain a good liquid acquisition capacity it is important that the liquid acquisition layer has a high morentaneous liquid acquisition capacity. Open, bulky structures with large capillaries have a high momentaneous liquid acquisition capacity and examples of such material are cellulosic fluff pulp of thermomechanic or chemithermomechanic (CTMP) type, chemically stiffened cellulosic fibers, synthetic fiber structures of different kind and porous foam materials.
In order to obtain a good liquid storing capacity it is common that the absorbent structure comprises one or more layers which contain superabsorbent materials. Superabsorbent materials are crosslinked polymers with the capacity to absorb liquid many times their own weight. A commonly occurring superabsorbent material is crosslinked polyacrylate. The absorption mechanism of such superabsorbents is based on the fact that the polymer chain contains a plurality of anionic carboxy groups, which make it possible for the polymer to by means of osmotic forces absorb aqueous liquids. The superabsorbent material is often in the form of small particles, which are arranged and contained in a fibrous matrix. The fibrous matrix usually consists of cellulosic fluff pulp of thermomechanic, chemical or chemithermomechanic type, but a certain amount of synthetic fibers is also commonly occurring, One problem with absorbent structures containing superabsorbent material, is that it is difficult to distribute and maintain the superabsorbent material in the desired location in the absorbent structure, both during storage and during use of the article. Another problem with absorbent structures containing superabsorbent material, is so called gel blocking. This problem occurs by the fact that the liquid-containing superabsorbent particles swell and form a gel. The gel blocks the liquid transport and gives rise to an accumulation of liquid in certain portions of the absorbent structure while other portions of the structure becomes more or less non-utilized.
One problem occuring in absorbent structure containing several layers, is that the uniting capacity of the absorbent core during use can be insufficient. This can involve that the structure breaks or crumbles. A further problem with absorbent structures containing several different layers is that it can be difficult to achieve a good liquid transport between the different layers. The joining is also costly and material- and energy demanding.
Another known liquid-absorbing structure is polymeric foams with open cells. Polymeric foams with superabsorbent properties for use in absorbent articles are disclosed in for example EP 0,044,624 and in U.S. Pat. No. 4,394,930. One problem with polymeric foams having superabsorbent properties is however that they are relatively weak, i e such foam materials tend to break when mechanically loaded.
In EP 0,598,833 there is disclosed a foam material for use as an absorbent structure in for example diapers. The foam material has a specified pore volume, specific surface area and ability to recover its volume after compression. The foam consists of a so called “HIPE”-foam (high internal phase emulsion), which means that the foam is produced by polymerization of a water-in-oil emulsion.
In U.S. Pat. No. 3,598,742 there is disclosed an open-cell foam which for increasing the strength of the foam contains between 30 and 90 weight percent fibers, based on the dry weight of the foam. The structure is manufactured by mixing fibers, surfactant, water and a thickener with a dispersion containing a film-forming water insoluble substance. The water insoluble substance is for example polyvinyl acetate and copolymers thereof.
There is further in SE9801694-2 disclosed an absorbent structure comprising a carrier material in the form of an open-cell foam, at which the foam in its pore structure contains hydrophilic fibers. The function of the carrier material is to create a structure having high resilient recovery both in dry and wet condition.
DESCRIPTION OF THE INVENTION
The problem of providing an integrated absorbent structure for use in an absorbent article having a sufficient high liquid distributing as well as liquid acquisition capacity, has been substantially eliminated by the present invention.
An absorbent porous structure according to the invention comprises a polymeric open-cell foam structure, in which the pore walls of the foam structure comprises a liquid-storing material, at which the liquid-storing material in the pore walls of the foam structure has the ability to store more than 7% synthetic urine, defined according to the CRC method. The absorbent structure is mainly characterized by that the pores of the foam structure contains hydrophilic fibers, at which at least the main part of the hydrophilic fibers are firmly anchored in the pore walls of the foam structure, and that the fiber amount is at least 10% by weight of the total weight of the open-cell foam in dry condition.
The definition “liquid-storing material” according to the invention refers to a material which has the capacity to store more than 7% synthetic urine, defined according to the CRC method. The liquid-storing capacity is measured by letting the material absorb liquid freely until saturated at which weight
(saturation)
is obtained. After that the sample is centrifugated during 10 minutes at 1500 rpm, which approximately corresponds to a load of 300 g. The sample is weighed after centrifugation, at which weight
(centrifugation)
is obtained. By then calculating the quotient between weight
(centrifugation)
and weight
(saturation)
and multiply with 100 the storage capacity of the sample in percent is obtained.
The advantage of the absorbent structure according to the invention is that it has good liquid storage capacity and good liquid distribution. By the fact that the foam contains a relatively high amount of fibers the mechanical properties of the foam are further improved, which involves that the structure withstands higher mechanical stresses than a foam of a superabsorbent material without fibers or alternatively with a small amount of fibers. The ability of the foam to withstand both tensile and shearing stresses is improved. Further the foam is more easily compressed, i e it can be compressed to higher densities and yet expand when whetted. The latter improves the capacity of the foam to by capillary action absorb liquid after compression and since often thinness of absorbent articles are strived at, fiber addition may give certain advantages. Fiber addition further improves the liquid distributing capacity of the foam. Another advantage associated with an absorbent foam structure according to the invention, is that it is more flexible and pliable than a structure that is mainly based on fibers. By the fac

Affiliated with

Also associated with

Rating

Absorbent structure in an absorbent article does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Absorbent structure in an absorbent article, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Absorbent structure in an absorbent article will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3153466