Paper products and methods for applying chemical additives to fibers in the ...

(54) PAPER PRODUCTS AND METHODS FOR APPLYING CHEMICAL ADDITIVES TO FIBERS IN THE MANUFACTURE OF PAPER

(75) Inventor: Graciela Jimenez, Appleton, WI (US)

Correspondence Address:
Timothy A. Cassidy, Esq.
Dority & Manning
Attorneys at Law, PA.
P.O. Box 1449
Greenville, SC 29602 (US)

(73) Assignee: Kimberly-Clark Worldwide, Inc.

(21) Appl. No.: 10/233,634

(22) Filed: Sep. 3, 2002

Related U.S. Application Data

(63) Continuation-in-part of application No. 09/589,450, filed on Jun. 7, 2000, now abandoned.

Publication Classification

(51) Int. CI.7 D21H 17/07; D21H 23/22;

D21H 27/30

(52) U.S. CI 162/158; 162/179; 162/164.1;

162/123; 162/124; 162/184;

162/185

(57) ABSTRACT

In the manufacture of tissue products from cellulose fibers, it is often desirable to enhance physical properties by the addition of chemical additives, including for example debonding agents. These additives serve to prevent or disrupt interfiber or intrafiber hydrogen bonding. Depending upon the nature of the chemical additive, debonding agents may also act as softening agents. During the papermaking process, chemical additives of this type can be added to fiber slurries in the wet end of a papermaking machine. Alternately, such additives may be sprayed upon tissue layers during manufacture, prior to assembly into multi-ply tissue structures. The chemical additives may include quaternary ammonium salts or organofunctional polysiloxanes. The chemical additives may include quaternary ammonium salts or organofunctional polysiloxanes or polysiloxanes. Some of the quaternary salts which may be used include salts comprised in part of imidazoline heterocyclic nitrogen ring structures.

PAPER PRODUCTS AND METHODS FOR APPLYING CHEMICAL ADDITIVES TO FIBERS IN THE MANUFACTURE OF PAPER

RELATED APPLICATIONS

[0001] The present application is a continuation-in-part application of U.S. Ser. No. 09/589,450 filed on Jun. 7,2000.

BACKGROUND OF THE INVENTION

[0002] In the manufacture of paper products from cellulose fibers, such as facial tissue, bath tissue, paper towels, dinner napkins and the like, it is often desirable to enhance product properties by the addition of chemical additives. Properties that may be enhanced using additives include: dry strength, wet strength, softness, absorbency, opacity, brightness and color.

[0003] Additives provided during papermaking, such as debonding agents, may provide a softening effect by reducing inter-fiber bonding within the tissue structure. However, using such additives often undesirably increases the amount of lint or sloughing of particles from the surface of the tissue during use by a consumer. Also, many additives or debonding agents undesirably reduce the strength of tissues.

[0004] Softness is a key attribute in tissue products. A feeling of softness imparts to human skin a clean and soothing effect. Improving the balance of tissue softness and strength is a continuous effort in tissue making. Tissue product designers attempt to maximize the strength and softness of tissues. It has been recognized as a general rule of tissue manufacture that the greater the strength of a given tissue, the lower the softness of that tissue. There is usually an inverse relationship between strength and softness. In general, prior efforts have been directed at achieving softness using chemicals directed at reducing the inter-fiber bonding within the tissue structure or coating the tissue surface with such chemicals. Mechanical means have been used in the art of tissue making to increase the softness of tissue paper. Many tissues are creped with a doctor blade to increase softness. Uncreped tissues sometimes are subjected to a rush transfer step to increase softness.

[0005] During the papermaking process, additives are commonly added to fiber slurries in the wet end of a papermaking machine. Wet end chemical addition may provide a relatively uniform distribution of chemical additives on the fiber surfaces of a tissue product. Additionally, wet end chemical addition sometimes facilitates the selection of a particular fraction to be treated with a specific chemical additive in order to enhance the performance of the paper, or to enhance the performance of a chemical additive. Wet end chemical addition enables multiple additives of various types to be added to a fiber slurry, either simultaneously or sequentially, prior to formation of the paper web. Topical spraying, printing or size press are other methods for chemical addition.

[0006] Compositions comprising about 80% imidazoline quaternary ammonium compound and about 10% polyethylene glycol have been used as debonders in tissue manufacture. Witco C-6027 produced by the Witco Chemical Company is one product that has been used in tissue manufacture to improve the softness of tissue. PCT International Publication WO 99/34057 discloses using Witco C-6092 as a softener/debonder in tissue manufacture.

[0007] Two component chemical softening compositions also have been used to soften tissue. In one process, chemical debonders which include mixtures of (1) quaternary ammonium compounds, and (2) polysiloxane, have been used in the manufacture of tissue. U.S. Pat. No. 5,573,637 shows the use of such a two-component quaternary/polysiloxane system in tissue manufacture. Binder materials also are described as being used in connection with such processes. A first step includes forming a papermaking aqueous furnish of fibers, including a mixture of at least one quaternary ammonium compound, with binder materials and a wetting agent. Then, in a second step, a solution comprising a polysiloxane compound is sprayed on the dry tissue web after creping. This two-step procedure, which uses quaternary compounds and a polysiloxane, has been reported to improve tissue characteristics.

[0008] What is needed in the industry is a chemical softening composition and technique of manufacture that will result in a softer, stronger tissue. A system that will provide to a final tissue product a desirable strength, with good tactile sensory softness characteristics in a process of manufacture that is relatively simple to apply at a reasonable cost would be highly desirable.

SUMMARY OF THE INVENTION

[0009] Tissues may be manufactured which exhibit softness and strength improvement using additives that can be applied into the wet end of a papermaking machine, or topically sprayed on the tissue web during manufacture. In one aspect of the invention, a tissue product is shown which comprises cellulosic fibers and an adsorbable chemical debonding additive. The additive includes, in some embodiments, a quaternary ammonium salt and a surfactant. The tissue product may employ an additive comprised of between about 10% and about 60% imidazoline quaternary ammonium salt. The tissue product also may be used in which the additive is comprised of or contains a lubricant.

[0010] In one alternative embodiment, the tissue product employs an additive comprising about 19-24% low to medium charge density imidazoline quaternary ammonium salts, about 15-20% high charge density dialkyl imidazoline quaternary ammonium salts, about 12-19% surface fiber lubricant, about 47-52% nonionic surfactants and wetting agents, and about 2% emulsion particle size control additives.

[0011] A multilayered product may be used, and the tissue may comprise a center layer consisting essentially of softwood fibers and two outer layers comprising about 50% or greater hardwood fibers. The product may be a layered tissue.

[0012] In one aspect of the invention, at least one outer layer of the tissue is capable of absorbing an additive which is applied to the tissue by spraying following assembly of the layers of the tissue. In one embodiment, the quaternary ammonium salt comprises in part a nitrogen ring compound. In other aspects of the invention, the quaternary ammonium salt comprises in part a dinitrogen ring compound. The quaternary ammonium salt may comprise a heterocyclic compound having more than one type of atom in a ring structure, which may or may not be aromatic.

[0013] A method of making a tissue product is also disclosed. The method may include: providing a fiber fur