Paper making and fiber liberation – Processes and products – Non-fiber additive
Reexamination Certificate
2001-05-04
2003-06-24
Fortuna, Jose A (Department: 1731)
Paper making and fiber liberation
Processes and products
Non-fiber additive
C162S177000, C162S174000, C162S158000
Reexamination Certificate
active
06582559
ABSTRACT:
This application claims priority under 35 U.S.C. §§119 and/or 365 to 00201630.1 filed in Europe on May 4, 2000; and 00201693.9 filed in Europe on May 11, 2000; the entire content of which is hereby incorporated by reference.
The present invention relates to the use of multifunctional aldehyde-containing polymers as temporary wet strength agents for paper and tissue applications, as well as non-wovens.
Wet strength is an important characteristic of paper and tissue products, and in non-woven products. Wet strength of such products can be increased by using wet strength additives. The most widely used wet strength additives for the paper industry are melamine-formaldehyde and urea-formaldehyde. There is a tendency, however, to move away from such oil-based chemicals, because they are not renewable and have a poor biodegradability. Carboxymethyl cellulose (CMC) is currently used in combination with PAE (polyamino-amide epichlorohydrin) as a wet strength agent (see Espy, TAPPI Journal, 78, 90 (1995)). However, CMC is also partly dependent on oil-based materials (monochloroacetic acid) and, moreover, is a rather expensive material.
Oxidized celluloses have the advantage of being accessible from renewable raw materials only and possibly of being less expensive than CMC, while they may have comparable properties to CMC. However, the oxidation of cellulose is hampered by the poor solubility of cellulose, making it insufficiently accessible to oxidizing agents.
Aldehyde functions have been recognized as being useful in binding cellulose fibers, to improve wet strength of the fibers. Thus, dialdehyde starch (TAPPI, 57, 81 (1974); and TAPPI 45, 750 (1962)) and dialdehyde guar and the like (WO 97/36054) have been proposed as paper wet strength additives. U.S. Pat. No. 3,087,852 and U.S. Pat. No. 4,001,032 disclose cationic dialdehyde starch, obtained by reacting dialdehyde starch with betaine hydrazide, to be used as a paper strengthening additive.
U.S. Pat. No. 5,935,383 discloses the use of anionic compounds, such as sulfato-ethylamino-halotriazines, for providing the cellulose surface with additional anionic sites suitable for retaining a high proportion of cationic wet strength additives such as PAE resin on the cellulose.
WO 99/23117 and WO 99/23240 describe the oxidation of cellulose and starch, respectively, with TEMPO and an oxidative enzyme (laccase) and oxygen at pH 4-9 resulting in products containing low levels of carbaldehyde and carboxyl groups.
U.S. Pat. No. 3,553,193 describes the oxidation of starch with bromite or hypobromite, which results in varying levels of carbonyl (ketonic) and carboxyl groups depending on the oxidation conditions, with a carbonyl/carboxyl ratio of between 2:1 and 8:1. The oxidation products are stated to be suitable as paper strength additives. The oxidation of starch with sodium hypochlorite is believed first to yield keto groups. In a later stage of oxidation aldehyde groups may be formed. The mechanism postulated by Whistler (J. Am. Chem. Soc., 79, 6460 (1957), see also PhD thesis of Floor, Delft University of Technology, 1989) however states that a diketo group is formed, which decomposes with OH— and is oxidized. One has to assume that hypobromite reacts in an analogous way. A recent publication of Deary and Davies in Carbohydr. Research 309, 17-29 (1998) reviews the bromine oxidation and confirms that keto groups are the primary products from bromine oxidation. From their experiments with &agr;-cyclodextrins they conclude also that the keto product is formed. They present no evidence for the formation of aldehydes. Also, Torneport et al (Starch 42, 413-417 (1990)) and Salomonsson et al (Carbohydrate Res. 217 (1991)) state that oxidation of starch with bromine species (Br
2
:CH=1/40 to 1/1) at: pH 7 results in keto groups and carboxylic acids, It is known that higher pH's lead to higher carboxylate contents.
It was found that multifunctional polymers, especially biopolymers, having both aldehyde functions and carboxylic acid and/or other anionic functions, the ratio between aldehyde functions and anionic functions (hereafter referred to as A/C ratio) being at least 0.75:1, preferably at least 2:1, up to about 15:1, preferably up to 10:1, are very useful as wet strength additives. These polymers are excellent substitutes for known wet strength agents such as carboxymethyl cellulose (CMC) and dialdehyde starch because of their better ecological acceptability (degradability) and their improved water-solubility and thus better accessibility to further reagents, and an improved functionality.
The polymers to be used can be of a synthetic type, such as a copolymer of acrylic acid and acrolein, a copolymer of maleic acid and maleic (mono)aldehyde, appropriately modified polyvinyl alcohol or appropriately (aldehyde-)substituted polyacrylic acid or the like, having the desired level of aldehyde groups and the desired A/C ratio.
It is preferred, however, that the polymer is a biopolymer. Suitable biopolymers include (modified) peptides and proteins, proteoglycans and in particular polysaccharide-types of polymer. Examples of polysaccharides include &agr;-1,4-glucans (the “starch family”, including amylose, amylopectin, dextrins and cyclodextrins), &agr;-1,6-glucans (dextran) and mixed &agr;-glucans such as pullulan, &bgr;-1,4-glucans (cellulose), &bgr;-1,3-glucans such as scleroglucan and curdlan, xyloglucans, glucomannans and galactomannans (guar and locust bean gum), other gums including heterogeneous gums like xanthan, ghatti, carrageenans, alginates, pectin, (arabino)xylans (hemicellulose), &bgr;-2,1- and &bgr;-2,6-fructans (inulin and levan), etc. The biopolymers may also be synthetically modified.
The simultaneous presence of aldehyde and anionic, such as carboxyl (—CO
2
H), sulfo (—SO
3
H) and phosphono (—PO
3
H
2
) groups, can be achieved by various methods. These methods comprise:
(1) introduction of anionic groups by addition, followed by introduction of aldehyde functions, e.g. by oxidation; here, the anionic groups such as carboxyl groups or other acid groups may be introduced e.g. by carboxyalkylation, sulfatation, sulfoalkylation, phosphatation, or the like, or they may be present in polymers which already have added acid groups by biosynthesis such as sulfate groups in carrageenans; the aldehyde functions can be introduced e.g. by oxidation of 1,2-dihydroxyethylene groups (such as those at the 2,3-position of 1,4-linked or 1,6-linked glucans) using periodate-type oxidizing agents, or by partial oxidation of hydroxymethyl groups (such as those at the 6-position of 1,4-linked or 1,3-linked glucans) using nitric oxide (NOx) types of oxidizing agents;
(2) introduction of carboxyl groups by oxidation of hydroxymethyl groups followed by introduction of aldehyde functions by oxidation as under (1); here, the carboxyl (anionic) groups are introduced by oxidation of the hydroxymethyl groups, such as those at the 6-position of 1,4-linked or 1,3-linked glucans, using NOx-type of oxidizing agents, or they may be present in polymers already containing 6-carboxyl groups by biosynthesis, if necessary after hydrolysis of ester groups, such as pectins, xanthans and alginates; the aldehyde groups can again be introduced e.g. by oxidation of 1,2-dihydroxyethylene groups, or by partial oxidation of further hydroxymethyl groups;
(3) controlled oxidation of hydroxymethyl groups (such as those at the 6-position of 1,4-linked or 1,3-linked glucans) so as to partly convert them to aldehyde functions and to convert only a (minor) part of the aldehyde functions so obtained to carboxyl functions;
(4) introduction of aldehyde groups, e.g. by oxidation of 1,2-dihydroxyethylene groups (such as those at the 2,3-position of 1,4-linked or 1,6-linked glucans) using periodate-type oxidizing agents, followed by partial further oxidation thereof to carboxyl groups using different oxidizing agents such chlorite or bromine;
(5) introduction of (protected) aldehyde groups (e.g. furan acetals) by etherification, e.g. as described in U.S. Pat. No. 4,731,162 and U.S.
Besemer Arie
Sandberg Sussan
Thornton Jeffrey Wilson
Van Brussel-Verraest Dorine Lisa
Burns Doane Swecker & Mathis L.L.P.
Fortuna José A
SCA Hygiene Products Zeist B.V.
LandOfFree
Aldehyde-containing polymers as wet strength additives does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Aldehyde-containing polymers as wet strength additives, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Aldehyde-containing polymers as wet strength additives will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3140390