US20220034039A1

US20220034039A1 - Fast disintegrating paper products and methods of making

Info

Publication number: US20220034039A1
Application number: US17/312,251
Authority: US
Inventors: Lokendra Pal; Lucian Lucia; Ved P. Naithani
Original assignee: North Carolina State University
Current assignee: North Carolina State University
Priority date: 2018-12-18
Filing date: 2019-12-18
Publication date: 2022-02-03
Also published as: WO2020132120A1

Abstract

Described are compositions for use in paper products including a modified starch, paper products including a modified starch, and methods of making paper products, and the like. The compositions can include a pulp slurry and a modified starch and can include hardwood fibers, softwood fibers, non-wood fibers, or a combination thereof. Provided for are paper products, such as tissue paper, having a basis weight below 150 gsm. Also provided for are methods for making paper products that can include mixing a pulp slurry with an enzymatically modified starch derivative.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of and priority to U.S. Provisional Application Ser. No. 62/781,113, having the title “FAST DISINTEGRATING PAPER PRODUCTS AND METHODS OF MAKING”, filed on Dec. 18, 2019, the disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND

One-time use items such as toilet tissue papers are specifically designed to disintegrate (reduce to small fragments) quickly when they come in prolonged contact with agitated water such as in a toilet. However, the majority of hand towels or facial tissues do not disintegrate in water nearly as well due to the inclusion of wet strength additives such as polyamidoamine epichlorohydrin (PAE). The use of recycled fibers from unbleached (brown) old corrugated containers (OCC) and bleached (white) mixed office waste (MOW) further exacerbate the disintegration issue since traces of unwanted materials, such as glues used during the manufacturing of boxes or book binding, can interfere in fibers and water interaction. The development of easily recyclable and/or flushable towels and facial tissues are therefore of importance to consumers and businesses for a number of reasons including environmental consciousness, transience of the applications, significant financial burdens caused in maintenance and disposal due to potential sewage blockages and damages (if flushed accidently), and handling of waste to landfill.

SUMMARY

The present disclosure provides for compositions for use in paper products including a modified starch, paper products including a modified starch, and methods of making paper products, and the like.
An aspect of the present disclosure includes compositions including a pulp slurry and a modified starch. The modified starch can have a cyclic structure with water solubility greater than 10 mg/mL when immersed in water at about 25° C. The pulp slurry can include hardwood fibers, softwood fibers, non-wood fibers, or a combination thereof.
An aspect of the present disclosure includes paper products, such as tissue paper, having a basis weight below 150 gsm. The paper products can include a blend of hardwood fibers and softwood fibers. The total fiber content can be at least 80 wt % of the total weight of the paper product. The product can include a modified starch that can be from about 0.02 wt % to about 10 wt % of the total weight of the paper product.
An aspect of the present disclosure includes methods for making paper products that can include mixing a pulp slurry with an enzymatically modified starch derivative. The pulp slurry can contain a blend of hardwood fibers and softwood fibers.

BRIEF DESCRIPTION OF THE DRAWINGS

Further aspects of the present disclosure will be more readily appreciated upon review of the detailed description of its various embodiments, described below, when taken in conjunction with the accompanying drawings.

FIGS. 1A-B provide examples of typical pulp and handsheet preparation methods of the present disclosure, with and without pretreatment step. FIG. 10 shows the structure of cyclodextrin and its derivatives, where R═—H for β-Cyclodextrin, R═—CH₂CHOHCH₃for 2-Hydroxypropyl-β-cyclodextrin, R═—CH₃for Methylated β-cyclodextrin, or R═—(CH₂)₄SO₃—Na+ for Sulfobutylether β-cyclodextrin sodium salt

FIG. 2 is a graph of pulp freeness of plain OCC and refined OCC with and without pretreatment by autohydrolysis.

FIG. 3 provides the bulk properties of various OCC pulps dosed with various levels of GPAM or β-cyclodextrin.

FIG. 4 compares the dry tensile strength of OCC, and OCC with GPAM or CD additive.

FIG. 5 is an example of the immediate wet tensile strength (0 seconds) of various OCC sheet configurations described herein.

FIG. 6 graphs the wet tensile strength of various OCC sheet configurations over time.

FIGS. 7A-7C show disintegration of sheets including GPAM (3, 6, 9 lbs. per ton, respectively) in water for 5 minutes.

FIGS. 8A-8C show disintegration of paper sheets including cyclodextrin (3, 6, 9 lbs. per ton, respectively) in water for 5 minutes.

FIGS. 9A-9C show disintegration of pretreated OCC+cyclodextrin (9 lbs./ton) sheets in water for 30, 60 and 120 seconds, respectively.

FIG. 10 illustrates the dry tensile strength of various types of pretreated OCC pulp.

FIG. 11 illustrates the immediate wet tensile strength of various types of pretreated OCC pulp.

FIG. 12 illustrates the wet tensile strength (2400 seconds) of OCC and pretreated OCC pulp over time.

FIG. 13 compares the wet tensile strength of pretreated OCC pulp with additives.

FIG. 14 shows the disintegration of OCC, OCC+GPAM and POCC+CD sheets in 60 seconds.

FIG. 15 shows examples of disintegration testing of a dual stage treatment (pretreatment using autohydrolysis followed by β-cyclodextrin addition) at different times, according to embodiments of the present disclosure. Commercial toilet paper and towel paper are shown for comparative purposes.

FIGS. 16A-16H provide comparisons of the characteristics of various papers treated with compositions according to the present disclosure. FIG. 16I is a legend for FIGS. 16A-16H.

FIGS. 17A-17F show examples of disintegration testing of control towels and towels containing GPAM compared with β-cyclodextrin, GPAM, and soy lecithin according to embodiments of the present disclosure.

FIGS. 18A-18B show the effects of various chemistries on dry and immediate wet tensile strengths of towel paper sheets according to embodiments of the present disclosure.

The drawings illustrate only example embodiments and are therefore not to be considered limiting of the scope described herein, as other equally effective embodiments are within the scope and spirit of this disclosure. The elements and features shown in the drawings are not necessarily drawn to scale, emphasis instead being placed upon clearly illustrating the principles of the embodiments.

DETAILED DESCRIPTION

Before the present disclosure is described in greater detail, it is to be understood that this disclosure is not limited to particular embodiments described, and as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting, since the scope of the present disclosure will be limited only by the appended claims.
Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range, is encompassed within the disclosure. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges and are also encompassed within the disclosure, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the disclosure.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present disclosure, the preferred methods and materials are now described.
As will be apparent to those of skill in the art upon reading this disclosure, each of the individual embodiments described and illustrated herein has discrete components and features which may be readily separated from or combined with the features of any of the other several embodiments without departing from the scope or spirit of the present disclosure. Any recited method can be carried out in the order of events recited or in any other order that is logically possible.
Embodiments of the present disclosure will employ, unless otherwise indicated, techniques of chemistry, material science, and the like, which are within the skill of the art.
The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how to perform the methods and use the materials and compositions disclosed and claimed herein. Efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperature, etc.), but some errors and deviations should be accounted for. Unless indicated otherwise, parts are parts by weight, temperature is in ° C., and pressure is at or near atmospheric. Standard temperature and pressure are defined as 20° C. and 1 atmosphere.
Before the embodiments of the present disclosure are described in detail, it is to be understood that, unless otherwise indicated, the present disclosure is not limited to particular materials, reagents, reaction materials, manufacturing processes, or the like, as such can vary. It is also to be understood that the terminology used herein is for purposes of describing particular embodiments only and is not intended to be limiting. It is also possible in the present disclosure that steps can be executed in different sequence where this is logically possible.
It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

Definitions and Abbreviations

Dry strength, or dry tensile strength, as used herein is the maximum tensile force developed in a test specimen before rupture on a tensile test carried to rupture under prescribed conditions. Tensile strength (as used herein) is the force per unit width of test specimen. The test was carried out using an Instron tensile tester with a standard finch cup fixture and no water (i.e. dry condition). Dry tensile strength=(max. load at break/width of the sample)/2
Wet strength, or wet tensile strength, as used herein is the maximum tensile force developed in a test specimen before rupture on a tensile test carried to rupture under prescribed conditions. Tensile strength (as used here) is the force per unit width of test specimen. The test was carried out using an Instron tensile tester with a finch cup fixture filled with water. Wet tensile strength=(max. load at break/width of the sample)/2 Decay, as used herein is reduction in tensile strength of paper over time when in contact with water.
Disintegration as used herein refers to reduction of tissue paper into small fragments in water with agitation under prescribed conditions. The disintegration test (as used here) is the evaluation of relative size and time to reduce a 10×10 cm²tissue sheet into fragments when dropped in a steady vortex of water in a 500 mL beaker placed on the magnetic stir plate filled with 400 mL of water at 23±3° C.
Freeness of Pulp, as used herein, refers to the drainage rate at which water drains through a fiber mat. A stock/furnish displays high freeness when water drains through the mat rapidly. The freeness referred herein was measured using Canadian Standard Freeness (CSF) tester as per Tappi T227 Freeness of pulp (Canadian standard method)
Stickies, as used herein, refer to hydrophobic contaminants such as those from as hot melt adhesives, pressure sensitive adhesives (PSAs), latex, elastomers, waxes, etc., including but not limited to ethylene vinyl acetate (EVA) copolymers, styrene-butadiene rubber (SBR), and hydrocarbon waxes.
Basis weight, as used herein, is the density of a paper product per 500 sheets expressed in grams per square meter (g/m²or gsm).
Abbreviations: PAE, polyamidoamine epichlorohydrin; OCC, old corrugated containers; POCC, pretreated OCC; OCC-R, OCC refined; POCC-R, POCC refined; CA, conventional additive; NC, novel chemistry; GPAM, Glyoxalated polyacrylamides; CD, cyclodextrin; SLP, soy lecithin protein or soy lecithin; FQA, Fiber Quality Analyzer

General Discussion

In response to the growing need for an efficient recyclable and flushable towel/tissue technology, described herein is a novel chemistry (NC) and process that allows for faster disintegration of towel and tissue products. This novel technology imparts dry and immediate wet tensile strength comparable to conventional additive (e.g. GPAM) used, but hydrolyzes rapidly in water leading to a fast disintegration of the towel into small fragments. The technology is simple to apply in the current tissue and towels manufacturing system. A further benefit of implementing this technology would be increased fiber quality and profitability of the paper recycling industry. This is very important since an increased use of recycled fibers in packaging, tissue, and towel products is being practiced to demonstrate good environmental stewardship practices and address energy concerns. However, major problems with recycle fibers are the loss of strength from changes in length, flexibility, swelling, bonding, and significant contamination. Further, the hydrophobic containments (stickies) incorporated with recycled fibers cause severe papermaking processing problems such as paper breaks and frequent washup cycles to reduce process contamination, thus negatively affecting the product quality and production costs. Furthermore, heavily impregnated and coated papers with wax or other hydrophobic materials are currently being diverted to landfill since current papermaking recycling systems can't handle this type of contamination.
In accordance with the purpose(s) of the present disclosure, as embodied and broadly described herein, embodiments of the present disclosure, in some aspects, relate to paper products and methods of making paper products.
In general, embodiments of the present disclosure provide for compositions for making paper products, such as compositions including a modified starch (e.g. cyclodextrin (CD)), and products including β-cyclodextrin. Paper products according to the present disclosure can have a basis weight that is below 150 gsm, or from about 15 to about 90 gsm. Products can include tissue paper used for facial tissue, kitchen towels, napkins, wipes, hand towels, and the like. Other products can include packaging products such as liners, kraft liners, white top liners, flexible packaging papers, copy papers, or paperboard.
The present disclosure includes methods for making paper products and paper products according to the methods and compositions described herein. Advantageously, the methods and compositions of the present disclosure provide for a higher quality of fiber furnish than that of existing conventional methods and compositions, resulting in paper products with desirable characteristics.
In various embodiments, the fibers can include OCC fibers, hardwood fibers (such as poplar, birch, and maples), softwood fibers (those originating from needle-bearing, coniferous trees, such as spruce, pine, and fir), non-wood fibers (e.g. bamboo, rice straw, straw, kenaf, hemp, abaca, flax, jute, sisal, synthetics, rag, cotton), and combinations thereof. For example, pulp or paper products according to the present disclosure may include about 0% to about 30% or about 10% to about 30% softwood fiber, about 50% to about 90% hardwood fiber, about 0% to about 90% non-wood fiber, or combinations thereof.
Some or all of the fibers included in the slurry can be fibers obtained from recycled OCC pulp or mixed office waste (MOW) pulp, so that resulting paper products contain recycled fiber content. The recycled fiber content can be from 0 to about 100% of the total fiber content, from about 0 to about 30% of the total fiber content, from about 30% to about 80% of the total fiber content, or from about 50% to about 80% of the total fiber content. The softwood content of the recycled OCC pulp can be about 10% to about 30%.
The OCC pulp can be subjected to a pretreatment process. The pretreatment process can be a chemical, mechanical, or combination process to remove hydrophobic contaminants such as glue, oil, latex, or waxes. The pretreatment process can improve furnish quality. In some embodiments, the pretreatment process can be autohydrolysis pulping process wherein the pulp is heated (such as steamed or pressure cooked) to a temperature in the range of about 90° C. to about 190° C., or about 160° C.
The pulp can be subjected to a washing process to separate the fibers from pulping liquor which may contains dissolved hydrophobic contaminants and wood extractives. The washing process can be carried out in rotary vacuum washers, rotary pressure washers, and atmospheric diffusion washers.
The pulp can be optionally subjected to a screening process to separate the fibers from coarser fibers, foreign matters such as plastics, metals, and dirt particles. The screening process can be carried out in a coarse, fine or combination of coarse and fine screens in vibrating, shaking, atmospheric or pressure screen mode.
The pulp can be optionally subjected to a bleaching process to increase aesthetic (brightness/whiteness) appearance and/or disinfect the pulp fibers using oxygen or chlorine dioxide bleaching process.
The pulp can be optionally subjected to a mechanical treatment such as refining process in a batch or continuous process to improve strength properties. The mechanical treatment of fibers can be carried out in beater equipped with rotating metal bars in a batch process or in a refiner equipped with rotating disks in a continuous process. The refiner can be a single disk or double disk refiners.
A modified starch can be added to the pulp. Starch can be obtained from various sources such as corn, potato, wheat, rice, and tapioca. In various embodiments, the modified starch can be an enzymatically modified starch by the action of cyclodextrin glucanotransferase, a transglycosidase that cleaves α-1,4 linkage in amylose (a fragment of starch) and form the cycle such as a cyclic oligosaccharide of 6, 7, or 8 glucose residues known as α-cyclodextrin, β-cyclodextrin, or γ-cyclodextrin, respectively. Cyclodextrins (FIG. 1C) have a relatively hydrophobic (less hydrophilic) internal cavity encased by hydrophilic groups. For example, β-cyclodextrin has an external hydrophilic shell that allows solubility in water and interaction with water saturated hydrophilic fibers while its hydrophobic cavity may be able to form complexes with hydrophobic contaminants such as stickies.
The complexes are stabilized by intermolecular forces such as van der Waals and hydrogen bond. In some embodiments, the formation of such complexes can be controlled by adjusting the pH and/or temperature of the fiber-water solution. In other embodiments, the modified starch can be derivatized through three available hydroxyl groups on each glucopyranose unit such as methyl-β-cyclodextrin, 2-hydroxyethyl-β-cyclodextrin, 2-hydroxypropyl-β-cyclodextrin, 2-hydroxyisobutyl-β-cyclodextrin, 2-hydroxypropyl-γ-cyclodextrin, to alter water solubility, crystallinity, and chemical complex formation properties with hydrophobic contaminants. Further, the fiber slurry may include detacking agents such as talc; surfactants such as anionic, non-ionic or cationic surfactants with different hydrophobicity/hydrophilicity; pH control aids such as acids or base solutions; retention aids such as cationic polyacrylamide, cationic starches; dyes and optical whitening agents; softening and debonding agents. Advantageously, the use of β-cyclodextrin as an alternative to GPAM provides good dry tensile strength and immediate wet tensile strength to paper products at a lower dosage rate, while simultaneously increasing the ability of the product to disintegrate upon immersion in water (such as flushing into a sewer system).
The addition of β-cyclodextrin can be made at any stage prior to formation of the fiber mat, such as before and/or after pretreatment, or before and/or after refining.
In an embodiment, freeness of a pulp formed using the methods and compositions described herein can be at least 100 CSF. In other embodiments, the freeness of the pulp can be greater than 175 CSF, or greater than 200 CSF.
In various embodiments, other additives can be included in the slurry. Such additives can include soy lecithin protein (SLP). The SLP to fiber ratio can be from about 0.05% to about 2.0%. Soy lecithin, a lipid, may also be used in the slurry for supporting fiber formation.
In various embodiments, a suitable wet strength agent can be included in the slurry along with the β-cyclodextrin to increase immediate wet strength. One example of a suitable wet strength agent is a glyoxalated strength agent or a cationic glyoxalated strength agent, for example, cationic glyoxalated polyacrylamide (G PAM). Other aldehyde-containing wet strength agents can be used. Non-limiting examples of commercially available temporary wet strength agents include Bubond® 818 (Buckman Laboratories International, Inc., Memphis, Tenn.), HercoBond®1194 (Solenis LLC, Wilmington, Del.), Fennobond 3000, Fennorez® 98 or Fennorez® 110 (Kemira Chemicals, Inc.). However, inclusion of GPAM or other wet strength agents can reduce the disintegration capabilities of a paper product when compared to a paper product using only β-cyclodextrin.
The present disclosure also includes methods for making paper products including mixing a pulp slurry with a modified starch derivative, wherein the pulp slurry comprises a blend of hardwood fibers and softwood fibers. The pulp slurry can include OCC pulp that has been pretreated using autohydrolysis pulping process. The modified starch derivative can be β-cyclodextrin. The method can further include forming the pulp into a fiber mat. The method can also optionally include a refining step before forming the mat. The mat can be creped, dried, or embossed to form a tissue paper product.
One aspect of the present disclosure includes composition comprising a pulp slurry and a modified starch, wherein the modified starch can have a cyclic structure and water solubility greater than 10 mg/mL when immersed at about 25° C., and wherein the pulp slurry can include hardwood fibers, softwood fibers, non-wood fibers, or a combination thereof. In various aspects, the modified starch can be β-cyclodextrin. The ratio of β-cyclodextrin to fiber can be from about 0.05% to about 5.0%. In various aspects, the composition can also include soy lecithin protein, wherein the soy lecithin to β-cyclodextrin ratio can be from about 1.0% to about 200%. Glyoxalated polyacrylamide (GPAM) can also be included, and the soy lecithin protein to β-cyclodextrin ratio can be from about 1.0% to about 200%. In various aspects, the pulp slurry can include about 0% to about 80% recycled fibers. The pulp slurry can be autohydrolyzed before mixing with the modified starch.
Another aspect of the present disclosure includes paper product that can have a basis weight below 150 gsm and can include a blend of hardwood fibers and softwood fibers. The total fiber content can be at least 80 wt % of a total weight of the paper product. The paper product can include a modified starch, wherein the modified starch can be from about 0.02 wt % to about 10 wt % of the total weight of the paper product. In various aspects, the modified starch can be β-cyclodextrin. In various aspects, the freeness of pulp is greater than 100 CSF. In some aspects, the total fiber content of the paper product can be about 50% to about 80% recycled fibers. The basis weight can be from about 20 to about 90 gsm. In some aspects, the total fiber content of the paper product can be about 10% to about 30% softwood fibers. In various aspects, the paper product can include at least one of soy lecithin protein and glyoxalated polyacrylamide.
Another aspect of the present disclosure includes methods for making a paper product, which can include mixing a pulp slurry with an enzymatically modified starch derivative. The pulp slurry can include a blend of hardwood fibers and softwood fibers. In various aspects, the fibers in the pulp slurry can include OCC pulp that has been pretreated using autohydrolysis pulping process. The pulp can then be formed into a fiber mat. The method can further include at least one of creping and drying.
Other systems, methods, features, and advantages of the present disclosure will be or become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description, be within the scope of the present disclosure, and be protected by the accompanying claims. In addition, all optional and preferred features and modifications of the described embodiments are usable in all aspects of the disclosure taught herein. Furthermore, the individual features of the dependent claims, as well as all optional and preferred features and modifications of the described embodiments are combinable and interchangeable with one another.

EXAMPLES

Now having described the embodiments of the disclosure, in general, the examples describe some additional embodiments. While embodiments of the present disclosure are described in connection with the example and the corresponding text and figures, there is no intent to limit embodiments of the disclosure to these descriptions. On the contrary, the intent is to cover all alternatives, modifications, and equivalents included within the spirit and scope of embodiments of the present disclosure.

Example 1

INTRODUCTION

The disintegration of paper towel and tissue is essential to circumvent occlusions in residential and commercial disposal systems and to avoid downstream environmental offloading. To mitigate the risk of a sewer clogging, it is necessary to find a paper towel that can disintegrate and move quickly through a sewer system. Flushable consumer products play a role in sanitary sewer overflow as large solids that move and disintegrate slowly in sewer pipes. Annual averages of 50,000 sanitary sewer overflows (SSOs) and 400,000 backups in basements occur as a result of pipe blockages in the United States of America (USA).^1,2Subsequently, sanitary sewer overflow leads to financial problems and significant public health concerns with outbreaks of diseases such as cholera, giardiasis, cryptosporidiosis, and hepatitis.³The tissue paper may include functional additives to enhance physical, mechanical, or absorption characteristics such as density, smoothness, softness, porosity, wettability, mechanical strength, moisture, and water absorption. Furthermore, tissue or towels may include special additives such as temporary wet strength agents or softener/debonders to help it retain its structural integrity and surface feel during usage when in contact with moisture, water, and other fluids.
It was found that β-cyclodextrin (CD), a cyclic oligosaccharide, can bind to hydrophobic containments such as stickies while being soluble in water due to hydrophilic groups. The present disclosure demonstrates an unusual interaction of fiber and CD that leads to high-bulk systems and a significant reduction in disintegration time. The key to faster disintegration and other tissue properties depends on: (1) homogeneous blending of chemical reagents (CD) in a furnish containing a specific surface area; (2) hydrophilic/hydrophobic balance amongst fibers, fines, and lignin content to create an optimum system for interfacial bonding and economics.
There are several factors that may affect how quickly a specific paper towel disintegrates. Some of these factors include fiber thickness, bulk, porosity, initial dry and wet strength, hydrophobic contaminants (stickies level) of the paper towel, as well as swirling action (flow rate) and temperature of water in a toilet. In the studies described herein, wet strength using a conventional additive (GPAM) and a novel chemistry (cyclodextrin) additive were compared for paper towel manufacturing. Consumers prefer specific brown paper towel qualities and will not necessarily buy a paper towel that disintegrates more quickly if it does not have adequate strength and absorption qualities. The towel paper should demonstrate high dry and wet tensile strength during the time used for hand wiping and disintegrate when flushed to avoid clogging. Paper towels are not designed to break down in water like toilet paper. The goal of this study was to determine the ideal qualities that a brown paper towel should have to disintegrate when it comes in to contact with water at some extent and to formulate a towel with such qualities. The compositions described herein include a cyclic oligosaccharide of 6, 7, or 8 glucose residues known as α-cyclodextrin, β-cyclodextrin, or γ-cyclodextrin, respectively, which can trap hydrophobic contaminants and covalently bind with cellulose upon dehydration. The result is a generation of both dry and wet tensile strength and fast disintegration when in contact with water.

Materials

Recycled fibers from old corrugated containers (OCC) were used. β-cyclodextrin (Cavamax W7, Wacker Chemicals) was procured from Sigma Aldrich and SLP (Performix® E) was procured from Archer Daniels Midland. GPAM was procured from Kemira Chemicals, Inc.

Methods

Old corrugated containers (OCC) recycled pulp before and after pretreatment was used for tissue handsheets. The pretreatment of OCC, referred as autohydrolysis pulping process was done at 160° C. for 20-30 minutes in a finger reactor. The methods described herein used autohydrolysis pulping process for pretreating OCC pulp to selectively dissolve and remove unwanted materials such as glue, stickies in OCC that interfere with fiber-water interactions.
Canadian standard freeness (CSF), consistency, and pH was measured on the pulp and then refined in either a Valley beater or PFI mill (a measured amount of pulp of specified stock concentration is beaten between the roll bars and bedplate of a laboratory beater). Freeness of pulp was measured according to the Tappi T227 method. Valley beater refining was done according to Tappi T200 Test Method. Samples were withdrawn at regular intervals during refining treatment to determine their beating degree and to be made into laboratory handsheets for evaluation (to nearly 175 CSF and adjusted the pH to 7).
PFI refining was done as per Tappi T248. PFI refining of pretreated OCC pulp was done at 3000 revolutions.
The addition of chemicals was in the 4% consistency thick stocks, mixed for 5 minutes in the laboratory blender, and then diluted to 0.3% consistency of the pulp. The handsheets were made in a British handsheet mold and dried in a drum drier at 220° F. The process of pulp and handsheets preparation is shown in FIGS. 1A and 1B.
Fiber dimensions were analyzed using a Fiber Quality Analyzer (FQA). Approx. 0.5 g of pulps in 150 mL distilled water was disintegrated. After complete disintegration (i.e., separation of fiber bundles), the sample was further diluted using distilled water to a consistency of 0.0075±0.0025%.
The tissue sheet disintegration testing was performed using following protocol: 1) Place the magnetic stir bar in the 500 ml beaker and add the water to the beaker until it reaches the 400 ml mark, (2) Measure the temperature of the water before starting the test. The water must be 23±3° C. (3) Place the 500 ml beaker on the magnetic stir plate and start the agitation. Adjust the power of the magnetic stir plate to form the vortex. The base of the vortex should be around the 150 ml mark. (4) Prepare 10×10 cm squares of tissue sheets, (5) Add the sample to the center of the vortex without folding and start the stop watch. Note the time and visually verify if the disintegration is complete.
Physical testing of the tissue sheets included basis weight, caliper, bulk, dry tensile, and wet tensile strength properties.

Results

Pulp Properties

The fiber properties of OCC, OCC-R, POCC, and POCC-R are shown in Table 1.1. POCC refers to OCC pretreated by autohydrolysis pulping process, while OCC-R and POCC-R are fibers subjected to refining. Length weighted average fiber length is calculated as the sum of individual fiber lengths squared divided by the sum of the individual fiber lengths. The fines are an object that are less than 0.20 mm in length and report fines as a total percentage of fiber based on an arithmetic basis or length weighted basis. The percentage of fines on an arithmetic basis is the number of fines divided by the total number of fibers (fines included) multiplied by 100. The percentage of fines on a length weighted basis is the sum of the fines length divided by the total length of fibers and fines in the sample. As expected, mechanical refining tends to decrease fiber length and increase fines content due to fiber cutting and fibrillation action during mechanical treatment (refining). As shown in FIG. 2, the pretreatment of OCC unexpectedly increases freeness (˜30%) bringing in the range of virgin fibers. This is mainly due to the removal of unwanted materials such as glue and stickies added during the manufacturing of corrugated boxes. The freeness of pulp is designed to give a measure of the rate at which a dilute suspension of pulp (3 g of pulp in 1 L of water) may be drained. The freeness, or drainage rate, has been shown to be related to the surface conditions and swelling of the fibers.

TABLE 1.1

Fiber properties of various OCC pulps

Tests	OCC	OCC-R	POCC	POCC-R

Pretreatment (P)	No	No	Yes	Yes
Refining (R)	No	Yes	No	Yes
Freeness, CSF (mL)	460	170	597	208
Fiber Length Lw (mm)	1.54	1.51	1.40	1.15
Fines (%)	42.6	47.2	41.8	44.2
Fines (%) (Lw)	8.88	10.32	8.42	10.75
Curl Index (Lw)	0.07	0.06	0.16	0.08
Mean width (μm)	22.50	22.95	21.80	22.30
Kink Index (1/mm)	1.19	1.08	2.25	1.44

Physical Properties:

Normally an increase in bulk is accompanied by a decrease in strength. It is exceptional to obtain an increase in both bulk and strength. Tissue sheets made from OCC pulps with a novel chemical additive (beta cyclodextrin) showed higher bulk when compared to conventional additives such as GPAM (glyoxelated polyacrylamide) traditionally used to enhance the wet strength of tissue paper, especially at the medium dosage rate. Further, the dry tensile strength also increased at low dosage rates when compared to the control as well as the conventional additive (CA).

TABLE 1.2

Tissue Sheets Physical Properties

Test

OCC

OCC +

OCC + CD +

Only

OCC + GPAM

OCC + CD

CD + SLP

SLP + GPAM

Addition Level (lbs./ton)

	0	3	6	9	3	6	9	3 + 3	3 + 3 + 3

Basis Weight (g/m²)	40.8	40.0	39.2	39.4	40.1	37.9	39.2	42.4	41.4
Bulk (cm³/g)	4.425	4.468	4.329	4.393	4.540	4.736	4.391	4.045	4.265
Dry Tensile	3166	3075	3355	3489	3595	3405	3031	3726	4428
Strength, gf/in
Dry Tensile Index	77.5	76.9	85.5	88.7	89.7	89.8	77.3	87.9	106.9
(Dry Tensile
Strength/Basis Weight)

Dry Tensile Strength:

As shown in Table 1.2 and FIG. 4, dry tensile first increases and then plateaus with an increase in dosage of conventional additive (GPAM). CD provides the highest dry strength at a low dosage rate (3 lbs./ton). Dry strength decreases with increase in dosage of CD. When compared to the conventional additive system, the CD system according to the present disclosure can achieve an equivalent dry tensile strength at low to medium addition levels.

Wet Tensile Strength:

Wet tensile strength of OCC sheets increases with the GPAM dosages from 3, 6 and 9 lbs./ton, but decrease with the CD dosages from 3, 6 and 9 lbs./ton irrespective of the bulk. As illustrated in FIG. 5 and Table 1.3, the CD system according to the present disclosure can achieve an immediate wet tensile strength at medium to high level addition levels that is equivalent to conventional additives.

TABLE 1.3

Immediate wet strength (0 seconds)

Sample ID/	0	3	6	9
Dosage Levels	(lb/ton)	lbs./ton	lbs./ton	lbs./ton

OCC	134.6
OCC + GPAM		215.0	192.8	184.3
OCC + CD		123.1	167.9	174.9
OCC + CD (3) +			231.1
SLP (3)
OCC + CD (3) +				310.1
SLP (3) + GPAM (3)

TABLE 1.4

Wet tensile strength at different time (from 0 to 2400 seconds)

Time (sec.)	0	15	30	60	120	600	2400

OCC	134.6	133.0	97.1	94.8	92.5	91.7	91.5
OCC + GPAM	215.0	181.3	173.6	158.4	150.3	145.1	144.1
(3 lbs./ton)
OCC + GPAM	184.3	163.2	158.0	148.1	146.1	134.5	120.8
(9 lbs./ton)
OCC + CD	123.1	97.5	97.4	96.9	96.6	84.4	82.5
(3 lbs./ton)
OCC + CD	174.9	165.0	98.1	101.0	97.5	85.5	81.8
(9 lbs./ton)

As shown in Table 1.4 and FIG. 6, the CD system according to the present disclosure can achieve an equivalent immediate wet tensile similar to GPAM.

Disintegration Evaluations:

FIGS. 7A-8C show the disintegration of paper towel sheets after immersion in water for 5 minutes. FIGS. 7A-C show OCC pulp sheets treated with GPAM at 3, 6, and 9 lbs./ton, respectively. FIGS. 8A-C show OCC pulp sheets treated with β-cyclodextrin at 3, 6, and 9 lbs./ton, respectively. The β-CD sheets showed better disintegration at lower dosages under prescribed conditions.

Dual Treatment of OCC Pulp:

In the dual treatment of OCC, pulp was pretreated in the first stage using autohydrolysis pulping process to dissolve and wash hydrophobic contaminants such as stickies or other materials that interfere with decay of the towels followed by β-cyclodextrin addition in the second stage. The pretreatment process conditions and chemical dosage was selected to enhance the dry tensile strength, immediate wet tensile strength and to enable faster disintegration of towel paper.
The pulp fibers obtained after pretreatment of the OCC were refined to some extent and then treated with GPAM and CD additives and tested for disintegration. OCC pulp was pretreated before incorporating the CD system to significantly enhance disintegration (i.e. flushability) while maintaining dry and immediate wet tensile strength properties. Pretreatment enhances post-treatment efficacy and overall improves furnish quality (i.e. reduced hydrophobic and foreign contaminants).
The pretreated OCC pulp was refined with PFI mill for 2000 revolutions before adding CD and GPAM additives. The pretreated OCC pulp shows increased dry tensile strength as well as increased immediate wet tensile strength with the treatment of CD 9 lbs./ton as shown in FIGS. 10 and 11. The dry tensile strength of OCC pulp decreased with pretreatment (POCC); however post-treatment with CD and/or CD-GPAM improved dry tensile strength to desired levels. The CD system of the present disclosure can achieve an equivalent dry tensile strength with and without conventional additives as shown in FIG. 10. The dual stage treatment (i.e. pretreatment using autohydrolysis followed by β-cyclodextrin addition) can achieve an equivalent or higher immediate wet tensile strength similar to commercial additives (FIG. 11).
The dual stage treatment can achieve an equivalent or faster wet tensile decay over time as OCC only, as shown in FIG. 12. The fastest decay was obtained with pretreated OCC (POCC) and POCC with CD additive (FIG. 13).

Disintegration Testing Results:

The disintegration time reduced from 5 minutes to under 1 minutes with POCC-CD compared to OCC only and OCC-GPAM as shown in FIGS. 14A-C, which is similar or better than a commercial toilet tissue paper.
Further aspects of the present disclosure will be more readily appreciated upon review of the detailed description of its various embodiments, described below when taken in conjunction with accompanying drawings in FIGS. 16A-1. FIG. 16A shows a control sample (control 1) and embodiments of tissue paper that contains OCC fibers only, while FIG. 16B is another control sample (control 2) and embodiments of tissue paper that contains OCC fibers and addition of GPAM (conventional additive) to the slurry. The control 1 tissue paper (e.g. OCC alone) has a low dry tensile strength, low immediate wet tensile strength, a fast decay and doesn't fully disintegrate into small fiber fragments even after immersion at 5 minutes (possibly due to significant hydrophobic containments), while the addition of GPAM resulted in improved dry and wet tensile strength, slower decay over time that reduced disintegration. By comparison, FIG. 16C shows tissue paper with the addition of CD (test 1). This resulted in good dry and immediate wet tensile strength, but a faster decay than the conventional GPAM and better disintegration. The combination of CD with autohydrolyzed tissue paper (FIG. 16D, test 2) improved the disintegration over test 1 while imparting good dry and wet tensile strength. Test 3 combined tissue paper with CD and SLP (FIG. 16E), test 4 included autohydrolyzed tissue paper with the CD and SLP (FIG. 16F), test 5 included CD, SLP, and GPAM with tissue paper (FIG. 16G), and test 6 included CD, SLP, and GPAM with autohydrolyzed tissue paper. The addition of SLP and GPAM provide benefit of increased dry and immediate wet tensile strength but may reduce disintegration. The extended autohydrolysis as well as higher level of CD can be used to eliminate the negative effect of SLP and GPAM on disintegration. FIG. 16I provides a legend to interpret FIGS. 16A-H.

TABLE 1.5

Dry, immediate wet tensile (0 sec.) and wet strength at 2400 seconds

	Dosage	Dry Tensile	Immediate Wet
	Level	Strength	Tensile Strength	Wet strength
Sample	(lbs./ton)	(gf/in.)	at 0 sec. (gf/in.)	at 2400 sec. (gf/in.)

OCC	0	3166	134.6	91.5
OCC + GPAM − L	3	3075	215.0	144.1
OCC + GPAM − H	9	3355	184.3	120.8
POCC	0	2660	123.3	81.8
POCC + CD	9	3181	237.5	87.4
POCC + CD + GPAM	9 + 1	3121	189.0	114.5

TABLE 1.6

Wet tensile strength at different time (from
0 to 2400 seconds) with pretreatment

Time (sec.)	0	15	30	60	120	600	2400

POCC	123.3	121.8	119.4	114.4	112.6	106.7	81.8
POCC + CD	237.5	235.7	217.5	198.1	163.0	133.8	87.4
(9 lbs./ton)
POCC + CD	189.0	182.3	171.5	152.5	148.4	144.6	114.5
(9 lbs./ton) +
GPAM (1 lb/ton)

*data normalized to 40 gsm basis weight of the handsheet

Example 2

In this example, towels with modified methods of making and compositions from those in Example 1 were developed and tested. OCC pulp was obtained from ST Tissue LLC, Franklin, Va. The OCC pulp had the following properties: Freeness: 297 mL, pH: 6.0. The OCC pulp was refined using a PFI mill to a target of 180 mL freeness.
The refined pulp was treated with β-cyclodextrin, soy lecithin, GPAM, or combinations thereof (see Table 2.1 for descriptions of each sample). Towel handsheets were prepared with a modified process (low couch pressure) with a target basis weight of approximately 40 g/m²and dried using a drum dryer with two passes at 220° F. The towel handsheets were conditioned at 23° C. and 50% relative humidity before testing.

TABLE 2.1

Samples tested in Example 2 experiments

Sample ID	Additives

Control	None (Pulp AS IS)
SLP6 + CD3	Soy Lecithin (Performix ® E from ADM)
	at 6 lbs./ton + β-cyclodextrin
	(Cavamax W7 from Wacker) at 3 lbs./ton
GPAM6	Glyoxalated polyacrylamide (Fennorez 110)
	at 6 lbs/ton
GPAM1 + SLP6 + CD3	Fennorez	110 at 1 lbs./ton + Soy Lecithin
	(Performix ® E from ADM) at 6 lbs./ton +
	β-cyclodextrin (Cavamax W7 from Wacker)
	at 3 lbs./ton

Dry tensile strength, wet tensile strength, and disintegration were tested against control samples of pulp only and pulp with GPAM.
FIGS. 17A-17I show examples of disintegration testing of control towels and towels containing GPAM, compared to towels containing the additives listed in Table 2.1. Disintegration as used herein refers to reduction of tissue paper into small fragments in water with agitation under prescribed conditions. The disintegration test (as used here, and described in Example 1) is the evaluation of relative size and time to reduce a 10×10 cm²tissue sheet into fragments when dropped in a steady vortex of water in a 500 mL beaker placed on the magnetic stir plate filled with 400 mL of water at 23±3° C.
The tissue sheet disintegration testing was performed using the protocol described in Example 1. As shown in FIGS. 17A-B, control sheets do not disintegrate fully even after more than five minutes. Similarly, towels including GPAM at 6 lbs./ton remain intact after 3 minutes (FIGS. 17C-17E) and shredded into large pieces after 5 minutes (FIG. 17F). In contrast, towels containing soy lecithin and β-cyclodextrin (FIGS. 17G-17H) start to disintegrate in 1 minute and fully disintegrate in approximately 2 minutes. Those containing soy lecithin, β-cyclodextrin, and GPAM also begin to disintegrate in 1 minute (FIG. 17I).

TABLE 2.2

Bulk, Dry Tensile, and Immediate Wet Tensile Tests

	Control			GPAM1 +
Sample ID/Tests	(No Chemistry)	SLP6 + CD3	GPAM6	SLP6 + CD3

Basis Weight, g/m²	Avg.	40.2	44.5	42.8	39
	SD	0.51	0.03	0.27	0.22
Caliper, mil	Avg.	6.20	6.87	7.12	6.5
	SD	0.24	0.11	0.88	0.88
Bulk, cm³/g	Avg.	3.91	3.92	4.23	4.23
Dry Tensile Strength,	Avg.	3619.7	4259.7	3854.1	4378.9
gf/in.	SD	478.3	227.0	301.3	366.4
Immediate wet Tensile	Avg.	149.9	162.9	239.2	220.0
Strength, gf/in.	SD	6.0	15.3	39.9	13.5

As shown in Table 2.2 and FIGS. 18A-18B, each of the addition of β-cyclodextrin and SLP together, GPAM in isolation, and a combination of all three increased both the dry tensile and wet tensile strength over that of OCC pulp alone. Shown are mean (Avg.) values and the standard deviations (SD) for each measurement.
Overall, the inclusion of β-cyclodextrin and SLP as described herein demonstrates a significantly faster disintegration over known compositions. Sheets containing β-cyclodextrin and SLP disintegrate within 1 min. while sheets with no added chemistry or only GPAM disintegrate in over 5 min. There is a slight reduction seen in the immediate wet tensile strength compared to GPAM only at 6 lbs./ton, which can be adjusted by increasing the GPAM dosage slightly. By including a low dosage of GPAM (1 lb/ton) with combined β-cyclodextrin and SLP chemistries, immediate wet tensile strength improved without significantly affecting the disintegration rate. Further, higher dry tensile strength is shown with β-cyclodextrin and SLP chemistries, with or without GPAM addition.
It should be noted that ratios, concentrations, amounts, and other numerical data may be expressed herein in a range format. It is to be understood that such a range format is used for convenience and brevity, and thus, should be interpreted in a flexible manner to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. To illustrate, a concentration range of “about 0.1% to about 5%” should be interpreted to include not only the explicitly recited concentration of about 0.1 wt % to about 5 wt %, but also include individual concentrations (e.g., 1%, 2%, 3%, and 4%) and the sub-ranges (e.g., 0.5%, 1.1%, 2.2%, 3.3%, and 4.4%) within the indicated range. In an embodiment, “about 0” can refer to 0, 0.001, 0.01, or 0.1. In an embodiment, the term “about” can include traditional rounding according to significant figures of the numerical value. In addition, the phrase “about ‘x’ to ‘y’” includes “about ‘x’ to about ‘y’”.
It should be emphasized that the above-described embodiments of the present disclosure are merely possible examples of implementations and are set forth only for a clear understanding of the principles of the disclosure. Many variations and modifications may be made to the above-described embodiments of the disclosure without departing substantially from the spirit and principles of the disclosure. All such modifications and variations are intended to be included herein within the scope of this disclosure.

Claims

1. A composition comprising a pulp slurry and a modified starch, wherein the modified starch has a cyclic structure and water solubility greater than 10 mg/mL when immersed at about 25° C., and wherein the pulp slurry comprises hardwood fibers, softwood fibers, non-wood fibers, or a combination thereof.

2. The composition according to claim 1, wherein the modified starch is β-cyclodextrin.

3. The composition according to claim 2, wherein a ratio of β-cyclodextrin to fiber is from about 0.05% to about 5.0%.

4. The composition according to claim 3, further comprising soy lecithin protein, wherein the soy lecithin protein to β-cyclodextrin ratio is from about 1.0% to about 200%.

5. The composition according to claim 4, further comprising glyoxalated polyacrylamide, wherein the soy lecithin protein to β-cyclodextrin ratio is from about 1.0% to about 200%.

6. The composition according to claim 2, wherein the pulp slurry is comprised of from about 0% to about 80% recycled fibers.

7. The composition according to claim 1, wherein the pulp slurry is autohydrolyzed before mixing with the modified starch.

8. A paper product having a basis weight below 150 gsm, comprising:

a blend of hardwood fibers and softwood fibers, wherein a total fiber content is at least 80 wt % of a total weight of the paper product; and

a modified starch, wherein the modified starch is from about 0.02 wt % to about 10 wt % of the total weight of the paper product.

9. The paper product according to claim 8, wherein the modified starch is β-cyclodextrin.

10. The paper product according to claim 8, wherein freeness of pulp is greater than 100 mL.

11. The paper product according to claim 8, wherein the total fiber content comprises from about 50% to about 80% recycled fibers.

12. The paper product according to claim 8, wherein the basis weight is from about 20 to about 90 gsm.

13. The paper product according to claim 8, wherein the total fiber content is comprised of from about 10% to about 30% softwood fibers.

14. The paper product according to claim 8, further comprising at least one of soy lecithin protein and glyoxalated polyacrylamide.

15. A method for making a paper product, comprising:

mixing a pulp slurry with an enzymatically modified starch derivative, wherein the pulp slurry comprises a blend of hardwood fibers and softwood fibers.

16. The method according to claim 15, wherein the fibers in the pulp slurry comprise OCC pulp that has been pretreated using autohydrolysis pulping process.

17. The method according to claim 15, further comprising forming pulp from the pulp slurry into a fiber mat.

18. The method according to claim 17, further comprising at least one of creping and drying.