GB2315220A - Absorbent Article - Google Patents

Abstract

An air-laid, bound absorbent article in which the binding agent is introduced at the air-laying stage and a method for the manufacture of said article.

Description

Method of Making Absorbent Articles The present invention relates to a method of making absorbent articles such as sanitary napkins and pads, incontinence garments and disposable diapers. In particular, but not exclusively, it relates to a method of making absorbent articles comprising waterabsorbent material, in particular, the water-absorbent polymeric material known as superabsorbent material.

As used herein, the term "water" when used alone or in the phrases "waterabsorbing", "water-absorbent" and "water-swellable" is understood to mean not only water but also aqueous media such as, in particular, electrolyte solutions such as body fluids.

Absorbent articles such as sanitary napkins, pads, incontinence garments and disposable diapers have been known for many years and much effort has been made to improve the functional efficiency of such articles to make them more absorbent, more comfortable to wear and less obtrusive to the wearer.

In general, such products have a core which includes a water-absorbent layer. This water-absorbent layer may be formed from any suitable water-absorbent material including wood pulp, rayon, tissue or any of the water-absorbing polymer compositions known as superabsorbent polymers A number of absorbent compositions have been developed which exhibit the capacity to be water-absorbing. Known compositions may be in any suitable form including particles and fibers. U.S. Patent numbers 3,954,721 and 3,983,095, which are incorporated herein by reference, disclose preparations for derivatives of copolymers of maleic anhydride with at least one vinyl monomer in fibrous form. The fibrous copolymers are rendered hydrophillic and water-swellable by reaction with ammonia or an alkali metal hydroxide. U.S. Patent No. 3,810,468, which is incorporated herein by reference, discloses lightly cross-linked olefin-maleic anhydride copolymers prepared as substantially linear copolymers and then reacted with a diol or a diamine to introduce cross-linking. The resultant lightly cross-linked copolymers are treated with ammonia or an aqueous or alcohol solution of an alkali metal hydroxide. U.S.

Patent No. 3,980,663, which is incorporated herein by reference, describes waterswellable absorbent articles made from carboxylic polyelectrolytes via cross-linking with glycerine diglycidyl ether.

European Published Application No. 0 268 498 (incorporated herein by reference) describes a water-absorbent composition formed by causing a substantially linear polymer of water-soluble ethylenically unsaturated monomer blends comprising carboxylic and hydroxylic monomers to cross-link internally.

Further examples of water-absorbent compositions are those produced from a copolymer of an a,ss unsaturated monomer having at least one pendant unit selected from a carboxylic acid group and derivatives thereof and a copolymerisable monomer.

A proportion of the pendant units are present in the final copolymer as the free acid and a proportion as the salt of the acid. These copolymers are capable of being crosslinked, either internally or with a variety of cross-linking agents, to form the waterswellable composition. Examples of water-swellable compositions of this type can be found in U.S. Patent Nos 4,616,063, 4,705,773, 4,731,067, 4,743,244, 4,788,237, 4,813,945, 4,880,868 and 4,892,533 and European Patent Nos 0 272 074 and 0 264 208 and European Published Application No. 0 436 514 which are incorporated herein by reference.

Derivatives of carboxylic acid groups include carboxylic acid salt groups, carboxylic acid amide groups, carboxylic acid imide groups, carboxylic acid anhydride groups and carboxylic acid ester groups.

Other examples of water-absorbent compositions can be found in US 4,798,861, WO 93/17066, WO 93/255735, WO 93/24684, WO 93/12275, European Published Application Nos 0 401 044, 0 269 393, 0 326 382, 0 227 305, 0 101 253, 0 213 799, 0 232 121, 0 342 919, 0 233 014, 0 268 498 and 0 397 410, British Patent Application Nos 2 082 614, 2 022 505, 2 270 030, 2 269 602 and 2 126 591, U.S.

Patent Nos 4,418,163, 4,418,163, 3,989,586, 4,332,917, 4,338,417, 4,420,588 and 4,155,957 and French Patent Application No. 2 525 121 which are all incorporated herein by reference.

Water-absorbent material of the kinds referred to in the above-mentioned patents and applications may be in any suitable form including powder, granular and fibers; the fibers may be straight or may be curled and/or crimped. Details of such curly/crimped fibers may be found in US 4,822,453, 4,888,453 5,462,793 and 4,898,462 which are incorporated herein by reference. In one alternative material, the water-absorbent polymer may be coated onto the whole or a part of the surface of other materials such as non-water-absorbent fibers. Details of one type of fibers of this type may be found in WO 96/15307 which is incorporated herein by reference.

Other kinds of water-absorbent materials may be used including naturally occurring water-absorbent material. One such water-absorbent material is the as starchy material such as that proposed by the US Department of Agriculture in 1969-1970.

Peat moss may also be used a water-absorbent material. In this connection, reference may be made to US 5,477,627 5,429,242 5,374,260 4,992,324 4,676,871 4,573,988 4,560,372 4,540,454 4,537,590 and 4,226,237 which are incorporated herein by reference. Alginates have also been proposed as suitable water-absorbent material.

An example of the use of such alginates are those suggested by Beghin/Kayserberg.

Whatever material is used for the absorbent layer, the core is generally backed by a fluid-impervious backing sheet to protect clothing and the surrounding area from soiling and to prevent leakage of the body fluid which would cause embarrassment to the user. Any suitable backing material may be used.

The article generally has a water-permeable non-woven type cover-sheet which defines the surface of the article which will, in use, be in contact with the user. The cover sheet is intended to insulate the wearer from contact with water that has been absorbed into the core, thus the cover sheet should allow water to pass through it into the core but remain dry and soft to the touch. Any suitable material may be used as thee cover-sheet. One example of a suitable cover-sheet is described in US 5257982 which is incorporated herein by reference.

The absorbent article may additionally include other material, such as a watermanagement layer, a distribution layer and the like.

A water-absorbent core for a feminine hygiene product is generally produced by allowing the water-absorbent material to be air-laid onto a conveyor, the resultant bat of water-material may be held in place on the conveyor by means of a vacuum. The fibers of the core are, if required, bonded. Bonding may be carried out using bicomponent fibers that are introduced into the core during the air laying procedure.

The bicomponent fibers may be polyethylene/polypropylene. After the fiber bat has been formed, it is heated such that the polyethylene melts to bind the bat whilst the polypropylene core of the bicomponent fibers remains intact. The topsheet and the back sheet are then applied.

We have now discovered that this method, which has previously been thought to be unusable in the production of diapers can indeed be used. Thus it is now possible to obtain a pre-bonded air laid core. This enables cores to be made separately from the process for producing the diaper. There are cost saving implications in producing the core as a separate component. One further benefit is that the cores as bound webs may readily be handled. For example of folding of the core is required before it is used in the diaper, the folding process may be readily carried out without the requirement for a support such as tissue paper which has been required heretofore.

We have also discovered that where the air laid process is used for producing absorbent articles such as diapers, sanitary towels, pant liners and the like, the core may be formed onto a layers of the final article which will in the final product be adjacent to the core. In a simple article, the layer may be the top sheet or the back sheet. However, where the article is to include an additional layer between the cover sheet and the core it is this layer onto which the core may be formed. Thus, the layer may be, for example, a distribution layer or a water-management layer.

Thus in one embodiment of the present invention a layer of the absorbent article is placed on a conveyor and the core material is air laid onto the layer. When binding of the core is effected, preferably via the bicomponent fibers described above the layer will be bound to the core. Surprisingly, the efficacy of the layer is not effected by use of this binding technique.

Whilst the present invention has been described with reference to sanitary napkins and pads, incontinence garments and disposable diapers it will be understood that the invention is equally applicable to other products which require high water-absorption capability such as pant liners, training pads, tampons, adult incontinence pads, bandages, patient underpads (for example pads of the type described in US 3,814,101 US 4,342,314 and EP 0 052 403 which are incorporated herein by reference), mortuary pads, casket liners, forensic examination pads, meat trays, soaker pads for food use, medical tray pads, fenestration drapes, other medical related articles, seed germination pads, capillary mats, baby bibs, desiccant strips for anti-rust use, bath mats, packaging, sorbents, clothing, breast pads, underarm pads, surgical and dental sponges, bandages, industrial wipes, domestic wipes, wipes, filters, cable wrap, food preservation articles, roofing materials, automotive trim, furniture, gasket, sealants, pond liners, bedding, clothing, cement, household pet litter, soil modifiers, wound covers and the like.

Claims (1)

1. Claim:

   1. An absorbent article such as a diaper comprising a core comprising a pre bonded air-laid layer comprising water-absorbent material.