Textiles: fiber preparation – Assembling – Web forming
Patent
1997-06-04
1999-04-13
Biefeld, Diana L.
Textiles: fiber preparation
Assembling
Web forming
19296, 19304, D01G 2500
Patent
active
058931970
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND
The present invention concerns a method for the manufacture of an absorbing structure in an absorbent product, such as a sanitary napkin, panty liner, incontinence protector, diaper or similar article, which is manufactured by means of air-permeable shaping elements, combined with the use of electric potential differences.
TECHNICAL BACKGROUND
Many different designs of such absorbent products are known. The absorption body in such products is conventionally produced by dry defibrating cellulose pulp in the form of rolls, bales or sheets, and converting it in fluffed-up form into a pulp web, sometimes with the inclusion of so-called super absorbents, that is, polymers with the capacity to absorb several times their own weight of water or body fluids.
Pulp cores are often compressed, partly to increase their wicking ability, and partly to reduce the bulk of the pulp core to achieve a product which is as compact as possible.
The absorption body can also include other components which can, for example, increase its wicking ability as well as increase its resistance to deformation during use. An example of such components is cellulose fibres which are stiffened by chemical or other means. Other examples of such components are different types of connecting fibres.
A problem which occurs during the manufacture of these products is that current methods for forming webs of individual absorption structures are complicated. They are also limiting in speed, and limit the ability to manufacture more complicated absorption structures having multiple layers and with admixture of different types of for example super absorbents, connecting fibres or such like.
In connection with this technical field, it is usual to use suction to fill moulds on a so-called web former with absorbent material by supplying the mould with a mixture of air and absorbent material, whereby the air flows through the air-permeable surfaces and leaves behind its load of absorbent material. As the layers of deposited material are in themselves air-permeable, successive layers of material can be laid down until the moulds are filled. WO-A-90 05511 and EP 155 752 show two arrangements which use such a method and which include such moulds. These arrangement further show rotating brush means for the removal of surplus absorbent material which lies above the top level of the mould.
U.S. Pat. No. 4,675,144 shows an alternative arrangement for manufacturing an absorption body, whereby a web of fibres is built up on an endless air-permeable belt, called a wire cloth, in a manner similar to that described above. Absorption bodies are then cut out from the built-up fibre web.
Further, EP 0,010,756 shows a process for manufacturing a non-woven material, whereby the fibres are given an electrical charge when they pass between two rollers between which an electrostatic field is present. The fibres are subsequently collected on a moving collector surface.
TECHNICAL PROBLEM
One problem with manufacturing the above-mentioned products by means of such arrangements or similar arrangments is the difficulty of controlling the distribution in the absorption body of the fibres or other absorption materials, such as polyacrylate, CMC, etc. This difficulty can lead to undesirable density and thickness variations in the absorption body. Furthermore, there is no control over the orientation that each fibre takes up in the absorption body which leads to disadvantages such as uncontrolled directions of flow, poor tensile strength in varying directions as well as reduced absorption capacity.
BRIEF DESCRIPTION OF THE INVENTION
The problem of controlling the material distribution and orientation is solved in the present invention by giving such materials, before they arrive at the web former, a powerful electrical charge by means of an electrostatic field which is generated as the material arrives, for example by means of rotating wheels, a grid or similar means. Grounding the web former moulds, either partially or wholly, produces potential differences which
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Biefeld Diana L.
SCA Molnlycke AB
Worrell Jr. Larry D.
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