Opacity enhancement of tissue products with thermally expandable microspheres

Abstract

The present invention is generally directed to an opaque tissue product and a process for making the same. The tissue products of the present invention comprise thermally expandable microspheres which impart increased opacity to the tissues. The thermally expandable microspheres are added to a fiber furnish during the wet end of a manufacturing process for bath tissue, facial tissue, towels, or the like.

Description

[0001] The present invention is based on provisional patent application Serial No. 60 / 171,031 filed Dec. 16, 1999, and priority is hereby claimed therefrom.[0002] The present invention generally relates to a method of incorporating thermally expandable microspheres into tissue products so that the resulting products have increased opacity. More particularly, the present invention is directed to the incorporation of thermally expandable microspheres into the wet end of a tissue manufacturing process so as to impart increased opacity to tissue products such as bath tissue, facial tissue, and towels.[0003] As lower basis weight tissue products evolve, new technical challenges are created since many physical properties of tissue products depend on the number and compactness of fibers present in the structure after consolidation. The opacity or "see-through" of tissue products is becoming a limiting factor in fiber assemblies that utilize fewer fibers while maintaining the same or superi...

AI Technical Summary

Benefits of technology

0025] It is another object of the present invention to create opaque tissue products of lower basis weights than higher basis weight opaque tissue products currently available.

0026] Some of the above-mentioned objects and, perhaps, other objects are accomplished by incorporating thermally expandable microspheres into low basis weight tissue products (i.e., less than about 30 gsm). The thermally expandable microspheres may be added in the wet end of a tissue manufacturing process prior to forming the tissue web. In certain embodiments, the expandable microspheres may be added just in front of or at the headbox during the wet end of the paper making process.

Problems solved by technology

As lower basis weight tissue products evolve, new technical challenges are created since many physical properties of tissue products depend on the number and compactness of fibers present in the structure after consolidation.

The opacity or "see-through" of tissue products is becoming a limiting factor in fiber assemblies that utilize fewer fibers while maintaining the same or superior strength as traditional fiber assemblies.

But if the optical properties of different grades of paper can be well characterized using K-M mathematical model, changing those properties in a practical, cost-efficient way is more complicated.

For pulps that underwent a given pulping and bleaching process, it is not easy to change reflectance properties unless additives are used in the furnish, such as dyes to modify the absorption coefficient and fillers or pigments to increase light scattering.

Increasing the basis weight is also a possibility but this is against the current technological trend to lighter tissue products.

However, desired levels of opacity are not always met by such more traditional methods of opacity enhancement when lightweight tissue grades are involved.

Properties such as strength, softness, and low lint requirements become limiting factors in tissue grade applications.

Thermally expandable microspheres have been available for more than a decade; however, they have not been linked to opacity enhancement.

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