12; United States Patent

US007541396B2

(12;

United States Patent

(io) Patent No.: US 7,541,396 B2 (45) Date of Patent: Jun. 2, 2009

Luo et al. (54)

(75)

(73)

(*)

METHOD FOR MAKING CARBOXYALKYL CELLULOSE Inventors: Mengkui Luo, Auburn, WA (US); Amar N. Neogi, Kenmore, WA (US); S Ananda Weerawarna, Seattle, WA (US); Andrew J Dodd, Seattle, WA (US)

5,470,964 A

11/1995 Qin

5,498,705 A

3/1996 Oin

5,532,221 A

7/1996 Huang et al.

5,550,189 A

10/1996 Komai et al.

5,562,740 A *

10/1996 Cooketal 9/1997 Allen etal.

Assignee: Weyerhaeuser NR Company, Federal Way, WA (US)

5,725,601 A *

3/1998 Tajiri et al

8/120

5,731,083 A *

3/1998 Bahiaetal

428/393

Notice:

5,734,025 A

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6/1998 Chen

5,792,856 A

8/1998 Allen etal.

Subject to any disclaimer, the term of this patent is extended or adjusted under 35 U.S.C. 154(b) by 426 days.

5,800,418 A

Appl.No.: 11/026,291

(22)

Filed:

Dec. 29, 2004

(65)

Prior Publication Data US 2006/0137838 Al

(52) (58)

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5,668,273 A

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8/1996 Qin et al.

5,561,114 A

Jun. 29, 2006

Int. CI. C08B 11/00 (2006.01) C08B 11/12 (2006.01) C08L1/26 (2006.01) U.S. CI 524/45; 524/42; 536/56; 536/84; 536/97; 536/98; 162/9; 162/157.6 Field of Classification Search 424/45, 424/42; 536/56,84,97,98; 162/9,157.6 See application file for complete search history.

(56)

U.S. PATENT DOCUMENTS 2,811,519 3,574,818 3,589,364 3,638,698 3,723,413 3,900,463 3,936,441 3,965,091 4,043,921 4,063,018 4,066,828 4,068,067 4,254,258 4,389,513 4,418,524 4,507,474 4,547,570 4,615,923 4,650,716 4,650,863 4,689,408 4,734,478 4,771,105 4,783,510 4,972,007 5,026,596 5,221,722 5,229,294 5,247,072 5,324,823 5.451.296

A A A A A A A A A A A A A * A A A A A A A A A A A A A A A * A A A *

10/1957 4/1971 6/1971 2/1972 3/1973 8/1975 2/1976 6/1976 8/1977 12/1977 1/1978 1/1978 3/1981 6/1983 12/1983 3/1985 10/1985 10/1986 3/1987 3/1987 8/1987 3/1988 9/1988 11/1988 11/1990 6/1991 6/1993 7/1993 9/1993 6/1994 9/1995

Touey Takehara et al. Dean et al. Woodman et al. Chatterjee et al. Yadaet al. Hoist et al. Hoist et al. Hessert et al. Ohnaka et al. Hoist et al. Hoist et al. Durso Miyazaki Ito et al. Raehse et al. Garner Marx Gelman Felcht et al. Gelman Tsubakimoto et al. Shirai et al. Saotome Herzog et al. Saotome Sehm Foster Ning et al. Asakawa et al. Pikulin et al

10/1998 Pappas et al.

5,998,511 A

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6,121,409 A

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HI 909 H

References Cited

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(Continued) FOREIGN PATENT DOCUMENTS CA

2072918 Al

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(Continued) 536/98

OTHER PUBLICATIONS Rydholm, Sven, "Pulping Processes" Interscience Publishers, 1965, pp.362, 1156.* (Continued) Primary Examiner—Eric Hug Assistant Examiner—Dennis Cordray (74) Attorney, Agent, or Firm—Christensen O'Connor Johnson Kindness; John M Crawford (57)

436/8

1 162/241

ABSTRACT

Methods for making the carboxyalkyl cellulose. 20 Claims, 4 Drawing Sheets

US 7,541,396 B2 Page 2

WO

U.S. PATENT DOCUMENTS 6,500,947 6,531,593 6,593,468 6,602,994 6,656,974 6,686,464 6,765,042 2002/0139496 2003/0027787 2004/0000012 2006/0142478

Bl 12/2002 West et al. Bl 3/2003 Luo et al. Bl 7/2003 Lange et al. Bl 8/2003 Cash et al. Bl 12/2003 Renn et al. Bl 2/2004 Harding et al. Bl 7/2004 Thornton et al. Al 10/2002 Hu et al. Al 2/2003 Couture et al. Al 1/2004 Scarpello et al. Al * 6/2006 Luo et al

FOREIC}N PATENT DOCUMENTS EP EP WO WO WO

0 566 118 0 796 070 WO 95/11925 WO 96/15137 WO 99/20318

B2 Bl Al Al A2

10/1993 9/1997 5/1995 5/1996 4/1999

wo wo

WO 00/27886 Al WO 00/39390 WO 00/47628 A2

5/2000 7/2000 8/2000

OTHER PUBLICATIONS

525/54 1

Barbucci R et al., Swelling behavior of carboxymethylcellulose hydrogels in relation to cross-inking, pH and charge density, Macromol 33: 7475-7480 (2000). Heinze et al., "Studies on the synethsus and characterization fo carboxymethylcellulose," Die Ang Makro Chem 266: 37-45 (1999). Kalman et al., "Effect of the reaction condition on the degree of substitution on carboxymethyl cellulose," Colloid Polym Sci 266: 716-720(1999). Klemm et al., "Etherization of Cellulose, Comprehensive Cellulose Cehmistry, vol. 2: Functionalization of Cellulose" and Appendix, p. 353, Wiley-VCH (2001). Zhang et al, "Solvent effect on carboxymethylation of cellulose," / ApplPoly Sci 49: 741-746 (1993). * cited by examiner

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US 7,541,396 B2 1 METHOD FOR MAKING CARBOXYALKYL CELLULOSE FIELD OF THE INVENTION The present invention relates to methods for making the carboxyalkyl cellulose. BACKGROUND OF THE INVENTION Personal care absorbent products, such as infant diapers, , ,. . ^-^j JJ--j+^-n adult incontinent pads, and lemimne care products, typically . it contain an absorbent core that includes superabsorbent polymer particles distnbuted within a fibrous matrix. Superabsorbents are water-swellable, generally water-insoluble absorbent materials having a high absorbent capacity for body fluids. Superabsorbent polymers (SAPs) in common use are mostly derived from acrylic acid, which is itself derived from oil, a non-renewable raw material. Acrylic acid polymers and SAPs are generally recognized as not being biodegradable. Despite their wide use, some segments of the absorbent products market are concerned about the use of non-renewable oil derived materials and their non-biodegradable nature. Acrylic acid based polymers also comprise a meaningiul portion of the cost structure of diapers and incontinent pads. Users of SAP are interested in lower cost SAPs. The high cost derives in part from the cost structure for the manufacture of acrylic acid which, in turn, depends upon the fluctuating price of oil. Also, when diapers are discarded after use they normally contain considerably less than their maximum or theoretical content of body fluids. In other words, in terms of their fluid holding capacity, they are "over-designed". This "over-design" constitutes an inefficiency in the use of SAP. The inefficiency results in part from the fact that SAPs are designed to have high gel strength (as demonstrated by high absorbency under load or AUL). The high gel strength (upon swelling) of currently used SAP particles helps them to retain a lot of void space between particles, which is helpful for rapid fluid uptake. However, this high "void volume" simultaneously results in there being a lot of interstitial (between particle) liquid in the product in the saturated state. When there is a lot of interstitial liquid the "rewet" value or "wet feeling" of an absorbent product is compromised.

2 cellulose and that is cost effective. In this way, the superabsorbent composition canbe used in absorbent product designs that are efficient such that they can be used closer to their theoretical capacity without feeling wet to the wearer. The 5 present invention seeks to fulfill this need and provides further related advantages. SUMMARY OF THE INVENTION 10

The invention provides methods for making carboxyalkyl cellulose. In one embodiment, the method comprises treating

a ul havi P P ^ a kaPPa value of from about 1 to about 65 with a carboxyalkylating agent to provide a carboxyalkyl celluJ , , , ,. ° ^ r ^ , .,,,.. lose. In one embodiment, the method comprises alkalizing a 15 pulp having a kappa value of from about l ^ about 65 ^ provide ^ alkalized pulp. ^d etherifying the alkalized pulp with a carboxyalkylating agent to provide a carboxyalkyl cellulose. In another embodiment, the method comprises crosslinking a pulp having a kappa value of from about 1 to 20 about 65 to provide a crosslinked pulp; alkalizing the crosslinked pulp to provide an alkalized pulp; and etherifying the alkalized pulp with a carboxyalkylating agent to provide a c^oxya^y1 cellulose,

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same become better understood by reference to the 30 following detailed description, when taken in conjunction with the accompanying drawings, wherein: FIG. 1 is a cross sectional view of an absorbent construct incorporating a superabsorbent composition of the invention and having an acquisition layer; 35 FIG. 2 is a cross sectional view of an absorbent construct incorporating a superabsorbent composition of the invention and having acquisition and distribution layers; FIGS. 3A-C are cross sectional views of absorbent articles incorporating a composite including a superabsorbent corn40 position of the invention and the absorbent constructs illustr ated in FIGS. 1 and 2, respectively; and FIG 4 is a schematic illustration of a device for measuring Absorbency Under Load (AUL) values,

45

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In personal care absorbent products, U.S. southern pine In one aspect: the invention provides a carboxyalkyl cellufluffpulpiscommonlyusedinconjunctionwiththeSARThis lose The carboxyalkyl cellulose of the invention is made fluff is recognized worldwide as the preferred fiber for absor- 50 from pUip having a high lignin content, high kappa value, bent products. The preference is based on the fluff pulp's high hemicellulose content, and high degree of polymerizaadvantageous high fiber length (about 2.8 mm) and its relative tion compared to conventional pulps used to make carboxyeaseofprocessingfromawetlaidpulpsheettoanairlaidweb. alkyl cellulose. Pulps useful in making carboxyalkyl celluFluff pulp is also made from renewable and biodegradable lose of the invention include pulps made from pulping cellulose pulp fibers. Compared to SAP, these fibers are inex- 55 processes that do not include a pre-hydrolysis step. Useful pensive on a per mass basis, but tend to be more expensive on pulps include pulps prepared by processes having cooking a per unit of liquid held basis. These fluff pulp fibers mostly times shorter and cooking temperatures lower that convenabsorb within the interstices between fibers. For this reason, a tional pulping processes. Other usefiil pulps include pulps fibrous matrix readily releases acquired liquid on application prepared by processes that do not include extensive bleaching of pressure. The tendency to release acquired liquid can result stages, The ul in significant skin wetness during use of an absorbent product P P from which the carboxyalkyl cellulose is made has a ka that includes a core formed exclusively from cellulosic fibers. PPa •l*e off•m, ^ 1 }0 ahof 6? • £ f6 e.mbodiJ * 1 * J* 1 1 -jr-jt. r -A ment, the pulp Irom which the carboxyalkyl cellulose is made c, Such products also tend to leak acquired liquid because liquid , ,,_,-_,, ^^ , /.„ T 1 1„. . , . ,. 1^1 , , has a kappa value ol Irom about 2 to about 40. In one embodiis not effectively retained in such a fibrous absorbent core. 65 ^^ ^ pulp from which ^ carboxyalkyl cellulose is made A need therefore exists for a superabsorbent composition that is made from a biodegradable renewable resource like

has a kappa value of about 35. Kappa value was determined by standard method TAPPI T-236.

US 7,541,396 B2 In one embodiment, the pulp from which the carboxyalkyl The carboxyalkyl cellulose of the invention has an Absorcellulose is made is a kraft pulp. bency Under Load (AUL) value of at least about 5 g/g. In one embodiment, the carboxyalkyl cellulose has an Absorbency In one embodiment, the carboxyalkyl cellulose is a carUnder Load value of from about 5 g/g to about 20 g/g. Absorboxymethyl cellulose. In one embodiment, the carboxyalkyl cellulose is a carboxyethyl cellulose. 5 bency Under Load value was determined by the method described in Example 5. The carboxyalkyl cellulose of the invention is made from a In one embodiment, the carboxyalkyl cellulose is a waterpulp having a lignin content of from about 0.15 to about 10 soluble carboxyalkyl cellulose, comprising a pulp treated percent by weight based on the weight of the cellulose. Lignin with an amount of carboxyalkylating agent sufficient to procontent was determined by the methods described in 10 vide a carboxyalkylated pulp having a degree of carboxy Examples 6 and 7. substitution from about 0.4 to about 1.4. The carboxyalkyl cellulose of the invention is made from a In one embodiment, the carboxyalkyl cellulose is a pulp having a hemicellulose content of from about 0.1 to crosslinked, water-soluble carboxyalkyl cellulose. The about 17 percent by weight based on the weight of the cellucrosslinked, water-soluble carboxyalkyl cellulose comprises lose. Hemicellulose content was determined by the methods 15 is a pulp treated with an amount of carboxyalkylating agent described in Examples 6 and 7. sufficient to provide a carboxyalkylated pulp having a degree The carboxyalkyl cellulose of the invention is derived from of carboxy substitution from about 0.4 to about 1.4, and unbleached or lightly bleached pulps. Unbleached and lightly treated with an amount of a crosslinking agent sufficient to bleached pulps include celluloses, hemicelluloses, and maintain the carboxylalkyl cellulose soluble in water. In one lignins. Therefore, products of the invention derived from embodiment, the invention provides a water-soluble carboxyunbleached or lightly bleached pulps may include carboxyalkyl cellulose, comprising a crosslinked pulp treated with an alkyl hemicelluloses and carboxyalkyl lignins, in addition to amount of carboxyalkylating agent sufficient to provide a carboxyalkyl celluloses. carboxyalkylated pulp having a degree of carboxy substitution from about 0.4 to about 1.4. In another embodiment, the The carboxyalkyl cellulose of the invention is made from a invention provides a water-soluble carboxyalkyl cellulose, pulp having a degree of polymerization of from about 1200 to comprising a carboxyalkylated pulp having a degree of carabout 3600. Degree of polymerization was determined by boxy substitution from about 0.4 to about 1.4 treated with an standard method ASTM D1795. amount of a crosslinking agent sufficient to maintain the The carboxyalkyl cellulose of the invention has a degree of carboxyalkylated pulp soluble in water. carboxyl substitution of from about 0.4 to about 1.4. Degree In the above embodiments, the pulp from which the carof carboxy substitution was determined by titration. 30 boxyalkyl cellulose is made has a kappa value of from about A1 percent by weight aqueous solution of the carboxyalkyl 1 to about 65. cellulose of the invention has a viscosity greater than about A general method for making a representative carboxym100 cP. In one embodiment, a 1 percent by weight aqueous ethyl cellulose of the invention is described in Example 1. solution of the carboxyalkyl cellulose of the invention has a Representative procedures for making carboxymethyl celluviscosity greater than about 600 cP. In one embodiment, a 1 lose of the invention are described in Examples 2 and 3. percent by weight aqueous solution of the carboxyalkyl celThe properties of carboxymethyl celluloses of the invenlulose of the invention has a viscosity greater than about 1000 tion, pulp from which the carboxymethyl celluloses are made, cP In one embodiment, a 1 percent by weight aqueous soluand commercially available carboxymethyl celluloses are tion of the carboxyalkyl cellulose of the invention has a viscompared in Tables 1 and 2 below. cosity greater than about 2000 cP In one embodiment, a 1 In Table 1, the kappa value, sugar composition, degree of percent by weight aqueous solution of the carboxyalkyl eel- 40 carboxy substitution (DS), viscosity for 1 percent by weight lulose of the invention has a viscosity greater than about 4000 aqueous solutions, and color of carboxymethyl celluloses for cP Viscosity was determined by standard method ASTM the carboxymethyl celluloses of the invention (Entries D2196-99. Al -Ol), carboxymethyl cellulose prepared by the method of The carboxyalkyl cellulose of the invention has a Free 45 the invention from a fully bleached southern pine pulp Swell Capacity of at least about 20 g/g. In one embodiment, (NB416) and fully bleached spruce pulp (PA), and commerthe carboxyalkyl cellulose has a Free Swell Capacity of from cially available carboxymethyl celluloses are compared. about 20 g/g to about 80 g/g. Free Swell Capacity was deterEntry CMC (250,000) and CMC (700,000) refer to carmined by the method described in Example 4. boxymethyl celluloses commercially available from Aldrich The carboxyalkyl cellulose of the invention has a CentriChemical Co. (Milwaukee, Wis.) having molecular weights fuge Capacity of at least about 10 g/g. In one embodiment, the 50 of 250,000 and 700,000, respectively. Entry CMC 9H4F carboxyalkyl cellulose has a Centrifuge Capacity of from refers to a carboxymethyl cellulose commercially available about 10 g/g to about 50 g/g. Centrifuge Capacity was deterunder the designation AQUALON from Hercules Corp., mined by the method described in Example 4. Hopewell, Va. TABLE 1 Carboxymethyl cellulose properties.

CMC properties Pulp

CMC

Al Ala

H I

Kappa

HPLC sugar/solid method , wt % Xylan

Mannan lignin

CMC solution viscosity, 100 rpm concentration

0.01% CMC

Wt%

Wt%

Wt%

DS

Wt%

cP

0.66 0.16

0.87 0.05

0.32 0.60

0.92 1.09

0.82 0.82

140 296

Color

US 7,541,396 B2 TABLE 1-continued Carboxymethyl cellulose properties.

CMC properties Pulp Al Bl CI Dl El Fl Gl HI 11 Jl Kl LI Ml Nl Ol NB416 PA

CMC solution viscosity, 100 rpm

HPLC sugar/solid method, wt % Xylan

CMC

Kappa

75 77 78 79 80 81 82 83 84 95 96 97 98 93 94 J control

2.4 4.7 5.0 18.4 20.6 20.9 19.9 17.9 17.4 16.9 13.6 16.3 23.4 1.48 3.53

Wt %

0.08 0.34 0.19 1.34 1.31 1.32 1.22 1.27 1.39 0.60 0.46 0.41 1.07 0.95 1.13 3.38 1.12 CMC (250000 CMC (700000 CMC 9H4F

Mannan lignin

0.01%

concentration

CMC

Wt %

Wt %

DS

Wt%

cP

Color

0.08 0.06 0.28 0.541 0.493 0.505 0.441 0.528 0.526 0.38 0.01 0.01 0.22