Paper making and fiber liberation – Processes and products – Non-uniform – irregular or configured web or sheet
Reexamination Certificate
1997-10-30
2001-11-13
Chin, Peter (Department: 1731)
Paper making and fiber liberation
Processes and products
Non-uniform, irregular or configured web or sheet
C162S112000, C162S113000, C162S115000
Reexamination Certificate
active
06315864
ABSTRACT:
FIELD OF THE INVENTION
The present invention is generally directed to liquid absorbent products, such as paper wiping products, baby diapers, personal care products, disposable garments, and the like. For instance, in one embodiment, the present invention is directed to paper wiping products that are not only strong, absorbent and soft, but also have the look and feel of cloth or linen.
BACKGROUND OF THE INVENTION
Absorbent products such as paper towels, industrial wipers, baby wipers, diapers, food service wipers, feminine products, and other similar products are designed to include several important properties. For example, the products should have good bulk, a soft feel and should be highly absorbent. The products should also have good strength even when wet and should resist tearing. Further, for most applications, the products should have good stretch characteristics, should be abrasion resistant and should not deteriorate in the environment in which they are used.
In the past, many attempts have been made to enhance and increase certain physical properties of paper wiping products and other similar articles. Unfortunately, however, when steps are usually taken to increase one property of a wiping product, other characteristics of the product may be adversely affected. For instance, in pulp fiber based wiping products, softness can be increased by decreasing or reducing interfiber bonding within the paper web. Inhibiting or reducing fiber bonding, however, adversely affects the strength of the product. In fact, perhaps the most difficult and complex problem to solve in designing a paper wiping product is the ability to increase softness without decreasing strength.
One particular process that has proven to be very successful in producing paper towels and other wiping products is disclosed in U.S. Pat. No. 3,879,257 to Gentile, et al., which is incorporated herein by reference in its entirety. In Gentile, et al., a process is disclosed for producing soft, absorbent, single ply fibrous webs having a laminate-like structure.
The fibrous webs disclosed in Gentile, et al. are formed from an aqueous slurry of principally lignocellulosic fibers under conditions which reduce interfiber bonding. A bonding material, such as a latex elastomeric composition, is applied to at least one surface of the web in a spaced-apart pattern. The bonding material provides strength to the web and abrasion resistance to the surface.
Once the bonding material is applied to at least one side of the web, the web can be brought into contact with a creping surface. Specifically, the web will adhere to the creping surface according to the pattern by which the bonding material was applied. The web is then creped from the creping surface with a doctor blade. Creping the web mechanically debonds and disrupts the fibers within the web, thereby increasing the softness, absorbency, and bulk of the web.
In one alternative embodiment disclosed in Gentile, et al., both sides of the paper web are creped after the bonding material has been applied.
The processes disclosed in Gentile, et al. have provided great advancements in the art of making disposable wiping products. It would be desirable, however, if the softness of the paper products disclosed in Gentile, et al. could be increased without substantially compromising the strength of the products. It would also be very desirable if more cloth-like wiping products could be produced. As paper wiping products have evolved, the softness, look and feel of the paper products have become increasingly more important.
Specifically, one of the primary purposes of disposable paper wiping products is to serve as a substitute for various cloth and textile fabrics. As such, it is very desirable to be able to design a high strength paper wiping product that has a softness, look and feel that closely assimilates cloth.
Thus, there currently remains a need for a paper wiping product that closely assimilates the look and feel of cloth. A need also exists for a cloth-like paper wiping product that has improved softness over conventional products while still remaining strong. A need further exists for a cloth-like paper wiping product that does not become as compressed when wet as conventional products and therefore also has the feel of a cloth product during use.
A need also currently exists for an improved method of producing a base web made from pulp fibers, staple fibers, and mixtures thereof for use not only in various wiping products, but also in other products that are required to absorb fluids. In this regard, a need exists for a base web having improved absorbency and improved fluid pickup capabilities. A need further exists for an improved process for orienting fibers in the Z direction within a base web in order to improve absorbency and other various characteristics.
SUMMARY OF THE INVENTION
The present invention recognizes and addresses the foregoing drawbacks and deficiencies of prior art constructions and methods.
Accordingly, it is an object of the present invention to provide an improved process for producing a base web made from pulp fibers, staple fibers, or mixtures thereof.
It is another object of the present invention to provide an improved liquid absorbent product.
Another object of the present invention is to provide an improved method for producing cloth-like paper wiping products.
It is another object of the present invention to provide disposable wiping products that have the appearance and feel of a cloth product.
Still another object of the present invention is to provide a cloth-like paper wiping product that is softer than many conventional products while still having comparable strength.
Another object of the present invention is to provide a method for producing a cloth-like base web by applying a bonding material to at least one side of a hydroneedled web and then creping at least one side of the web.
It is another object of the present invention to provide a cloth-like paper wiping product that is made by subjecting a base web to two different mechanical debonding steps.
Another object of the present invention is to provide a method for producing a base web by applying a bonding material to at least one side of a hydroneedled web and then creping at least one side of the web followed by at least one post-creping step, such as microcreping at least one side of the web or applying a solution to the web, in order to further enhance various properties of the web.
Still another object of the present invention is to provide a cloth-like base web that is soft, has improved absorbency, has good dry strength, has good wet strength, is tear-resistant, is abrasion-resistant, and retains its bulk when wet or dry.
These and other objects of the present invention are achieved by providing a method for forming a cloth-like base web that includes the steps of first hydroneedling a web containing pulp fibers, staple fibers, or mixtures thereof. Once the web is hydroneedled, a bonding material is then applied to at least one side of the web and at least one side of the web is then creped.
It has been discovered that hydroneedling the web prior to applying a bonding material increases the softness of the web and, of particular significance, gives the web the appearance and feel of a cloth product. Also of significance, it has been further unexpectedly discovered that the process of the present invention not only increases softness but also does not adversely affect the strength of the web in comparison to conventionally made base webs.
As used herein, hydroneedling a web refers to a process by which the web is subjected to a plurality of fluid jets. For instance, a process for hydroneedling pulp fiber webs is disclosed in U.S. Pat. No. 5,137,600 to Barnes, et al., which is incorporated herein by reference in its entirety. In Barnes, et al., a wet-laid non-woven web of pulp fibers is hydraulically needled on a wire mesh by a plurality of water jets.
In one preferred embodiment of the present invention, the bonding material, which can be a latex, is applied to both s
Anderson Ralph L.
Radwanski Fritz
Skoog Henry
Waldroup Donald E.
Chin Peter
Dority & Manning P.A.
Kimberly--Clark Worldwide, Inc.
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