Method of making sanitary paper product from coarse fibers

Details Method of making sanitary paper product from coarse fibers Method of making sanitary paper product from coarse fibers

1998-09-30

2002-05-14

Nguyen, Dean T. (Department: 1731)

Paper making and fiber liberation

Processes of chemical liberation, recovery or purification...

Waste paper or textile waste

C162S060000

Reexamination Certificate

active

06387210

ABSTRACT:

BACKGROUND OF THE INVENTION
Typically in papermaking, a general correlation exists between fiber coarseness and softness or handfeel of the resulting paper product.
High quality fibers such as bleached northern softwood kraft fibers are fine, flexible and are used to produce soft, desirable tissue products. Conversely, mechanical pulping of softwoods produces high-yield, coarse, stiff fibers typically used to make newsprint.
Generally, newspapers contain mainly coarse, high yield fibers, typically stone groundwood (SGW), thermomechanical pulp (TMP), and/or chemithermomechanical pulp (CTMP) fibers. Such coarse newsprint fibers are usually highly refined to cause fractures and fibrillations which aid in imparting strength to the resulting newsprint. Such refining changes the freeness of the coarse fiber from “high” freeness fibers to “low” freeness fibers. If such refined, high-yield, coarse, mechanically pulped fibers were used in a tissue product the resulting sheet would not be soft, and therefore, most likely undesirable as a tissue product.
A thorough discussion of the relationship between tissue softness and fiber coarseness is contained in Canadian Patent No. 2,076,615. Attempts to produce soft tissue or towel type sanitary paper products from a majority of high yield, coarse fibers such as CTMP, TMP or SGW pulp have not been successful. Likewise, producing soft tissue and towel products by recycling old newspapers has not been very successful partially because the predominant fibers have low freeness, are coarse, and have a relatively high level of fines.
Other complicating factors in producing soft tissue and towel products from recycled newspapers are problems with papermachine operation due to poor drainage of low freeness fibers and problems with fines and other substances that accumulate in the papermachine water system (whitewater). These materials make it difficult to crepe the tissue sheet from the Yankee drying cylinder, and therefore necessitate operating the papermachine at conditions which do not promote maximum softness.
There is a long felt and unmet need for a soft paper product made from high-yield, coarse, fibers from sources such as recycled newspapers. There is also a need for an economical and practical process of treating high-yield, coarse fibers from recycled newspapers so they are suitable for making soft paper products. This need also extends to a process for treating newspapers
ewsprint fibers so they are suitable for making soft paper products as well as soft paper products containing such treated fibers.
DEFINITIONS
As used herein, the term “comprises” refers to a part or parts of a whole, but does not exclude other parts. That is, the term “comprises” is open language that requires the presence of the recited element or structure or its equivalent, but does not exclude the presence of other elements or structures. The term “comprises” has the same meaning and is interchangeable with the terms “includes” and “has”.
The term “machine direction” as used herein refers to the direction of travel of the forming surface onto which fibers are deposited during formation of a material.
The term “cross-machine direction” as used herein refers to the direction in the same plane which is perpendicular to the machine direction.
As used herein, the term “cellulose” refers to a natural carbohydrate high polymer (polysaccharide) having the chemical formula (C
5
H
10
O
5
)
n
and consisting of anhydroglucose units joined by an oxygen linkage to form long molecular chains that are essentially linear. Natural sources of cellulose include deciduous and coniferous trees, cotton, flax, esparto grass, milkweed, straw, jute, hemp, and bagasse.
As used herein, the term “pulp” refers to cellulose processed by such treatments as, for example, thermal, chemical and/or mechanical treatments.
As used herein, the term “coarseness” is the weight per unit length of fiber, expressed as milligrams per 100 meters. Typically, a fiber is considered coarse having a value greater than about 12 milligrams per 100 meters.
SUMMARY OF THE INVENTION
The present invention addresses the needs described above by providing a method of modifying coarse high-yield type pulp from sources such as recycled newspaper into pulps suitable for making soft tissue type products. In accordance with the present invention, coarse, low freeness high yield type pulp found in newsprint (i.e., newspapers) can be modified to produce soft tissue products by washing the pulp to reduce the proportion of fines in the pulp.
The method of making sanitary paper products from coarse fibers includes the steps of: (a) pulping coarse fibers in water with agitation to produce a pulp slurry, the pulp from the coarse fibers having an average fines content of greater than about 40%; (b) using an effective amount of pulp washing to reduce the fines content and increase the Canadian Standard Freeness; (c)introducing the pulp at a papermaking consistency into the headbox of a paper making machine; and (d)utilizing the pulp in a paper making process to produce sanitary paper products.
An effective amount of pulp washing may reduce the fines content to less than about 35% and increase the Canadian Standard Freeness by more than about 50. The pulp may be introduced into the paper making machine at a papermaking consistency ranging from about 1.0% to about 0.01%.
The present invention encompasses the method described above wherein the sanitary paper product made using the pulp is a tissue paper made at a basis weight between 7 and 35 pounds per ream. The sanitary paper product may also be a paper towel made at a basis weight between 12 and 40 pounds per ream. The sanitary paper product may also be a paper napkin made at a basis weight between 7 and 35 pounds per ream.
Generally, the pulp may be composed of cellulosic fibers at least 60% of which are coarse fibers having a Kajaani coarseness greater than 12 milligrams per 100 meters. For example, the pulp may be composed of recycled newspaper fibers at least 60% having a Kajaani coarseness greater than 17 milligrams per 100 meters.
The pulp from sources such as recycled newspapers may have an average fines content of greater than about 40% prior to treatment. For example, the pulp may have an average fines content of greater than about 46% prior to treatment. As another example, the pulp may have an average fines content of greater than about 48% prior to treatment.
The pulp from sources such as recycled newspapers may have a Canadian Standard Freeness of less than about 300 prior to treatment. For example, the pulp may have a Canadian Standard Freeness of less than about 270 prior to treatment. As another example, the pulp may have a Canadian Standard Freeness of less than about 200 prior to treatment.
According to the invention, the pulp from sources such as recycled newspapers is washed so that the fines content is reduced to less than about 35%. For example, the pulp is washed so that the fines content is reduced to less than about 30%. As another example, the pulp is washed so that the fines content is reduced to less than about 29%.
In an aspect of the invention, the pulp from sources such as recycled newspapers is washed so that the Canadian Standard Freeness is increased by more than about 50. For example, the pulp is washed so that the Canadian Standard Freeness is increased by more than about 70. As another example, the pulp is washed so that the Canadian Standard Freeness is increased by more than about 90.
The present invention also encompasses a method of modifying pulp from recycled newspapers to improve its tissue and towel making properties. The method of modifying pulp from recycled newspapers includes the steps of: (a) pulping newspapers in water with agitation to produce a pulp slurry, the pulp from the newspapers having an average fines content of greater than about 40%; (b) using an effective amount of pulp washing to reduce the fines content and increase the Canadian Standard Freeness; and (c) introducing the pulp at a papermaking consistency into the headbox

Affiliated with

Also associated with

Rating

Method of making sanitary paper product from coarse fibers does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Method of making sanitary paper product from coarse fibers, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of making sanitary paper product from coarse fibers will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2846416