Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – Waste paper or textile waste
Reexamination Certificate
2001-06-08
2002-08-13
Alvo, Steve (Department: 1731)
Paper making and fiber liberation
Processes of chemical liberation, recovery or purification...
Waste paper or textile waste
C162S006000, C162S072000, C162S077000, C162S078000, C162S161000
Reexamination Certificate
active
06432262
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the use of aldehyde donors, such as 1,3-bis(hydroxymethyl)-5,5-dimethylhydantoin, to stabilize peroxides in aqueous solutions and in particular circulating water slurries in papermaking applications.
BACKGROUND OF THE INVENTION
The bleaching of wood fibers frequently involves the use of peroxides, such as hydrogen peroxide. Hydrogen peroxide, however, is readily decomposed by catalase, an enzyme often found in recycled water (i.e. water from processing recycled paper). Most aerobic bacteria synthesize peroxide-degrading enzymes (e.g. catalase and peroxidase) as a defense against free-radical-producing peroxides that are formed during cell respiration. In a mill white water environment, temperatures and the availability of nutrients encourage bacterial growth. The presence of hydrogen peroxide stimulates bacteria to generate catalase to destroy it, sometimes enough to hamper or disable a hydrogen peroxide treatment stage. As a result, peroxide stability is limited and bleaching effectiveness is reduced. The conditions of recycled paper processing, deinking and bleaching are especially conducive to enzyme peroxide degradation.
Some of the methods employed to stabilize hydrogen peroxide include biocide treatments (e.g. peracetic acid treatment), use of high hydrogen peroxide dosages and steep bleaching.
U.S. Pat. No. 5,728,263 describes the use of dialdehydes and acetals thereof, such as glutaraldehyde, to inhibit the decomposition of peroxide in the treatment of recycled and other fiber pulps. Hydrogen peroxide stability is enhanced by the addition of glutaraldehyde. Glutaraldehyde, however, has a poor safety profile and high concentrations of it are required to inhibit peroxide decomposition.
U.S. Pat. No. 5,885,412 describes the use of certain hydroxyl amines and alkyl derivatives, including hydroxylammonium sulfate, ascorbic acid and formic acid, that suppress or inhibit hydrogen peroxide degradation by enzymes, such as peroxidases and catalases, during bleaching of cellulose fibers and do not affect microorganisms.
Great Britian Patent Publication No. 2,269,191 describes the use of an organic peracid that has a disinfectant effect on catalase producing microorganisms at neutral or acidic pH.
U.S. Pat. No. 4,908,456 teaches the use of methylolated hydantoin, especially 1,3-dimethylol-5,5-dimethylhydantoin (DMDMH) as an antimicrobial agent.
U.S. Pat. No. 5,405,862 teaches the preparation of low free formaldehyde DMDMH compositions which are used in biocidal effective amounts in any medium in which microbial growth is to be retarded.
There is a need for a method of stabilizing hydrogen peroxide in the presence of catalase and other peroxide degenerating enzymes that is not hazardous.
SUMMARY OF THE INVENTION
The present invention is a method of stabilizing hydrogen peroxide in an aqueous solution, such as a circulating water slurry, comprising a peroxide, such as hydrogen peroxide. The aqueous solution may include organic matter. The method comprises adding an aldehyde donor, such as a methylolhydantoin, to the solution (or slurry). The inventors have discovered that aldehyde donors significantly reduce the decomposition of hydrogen peroxide by catalase and other peroxide decomposing enzymes, which are often present in recycled paper. As a result, less hydrogen peroxide needs to be added to a solution to effectively bleach organic matter in the solution. Furthermore, aldehyde donors are safe to handle and cost effective.
Another embodiment is a method of bleaching recycled papers in a circulating water slurry comprising organic matter. The method comprises adding hydrogen peroxide and an aldehyde donor to the slurry.
Yet another embodiment is a method of inhibiting catalase and/or other peroxide decomposing enzymes in an aqueous solution, such as a circulating water slurry, comprising adding an aldehyde donor to the aqueous solution.
Yet another embodiment is a method of stabilizing a peroxide in an aqueous solution comprising maintaining a peroxide stabilizing effective amount of at least one aldehyde donor in the aqueous solution.
Yet another embodiment is a method of inhibiting catalase and/or other peroxide decomposing enzymes in an aqueous solution, such as a circulating water slurry, comprising maintaining a peroxide decomposing enzyme inhibiting effective amount of at least one aldehyde donor in the aqueous solution.
DETAILED DESCRIPTION OF THE INVENTION
In any identified embodiments, the term “about” means within 50%, preferably within 25%, and more preferably within 10% of a given value or range. Alternatively, the term “about” means within an acceptable standard error of the mean, when considered by one of ordinary skill in the art.
The present invention provides a method of stabilizing a peroxide, such as hydrogen peroxide, in an aqueous solution comprising the peroxide. The method comprises adding to or maintaining an aldehyde donor in the aqueous solution. Generally, the peroxide is added to the solution in the form of a bleaching solution.
The aqueous solution can be (i) a circulating water slurry comprising organic matter or (ii) a slurry dilution water. Generally, a slurry dilution water contains little (<0.2% by weight), if any, organic matter. Slurry dilution waters are frequently added to dilute or form solutions containing organic matter, especially pulp. Furthermore, slurry dilution water is frequently recovered from circulating water slurries containing organic matter by methods known in the art.
The term “aldehyde donor” as used herein is defined as any material which is not an aldehyde but upon aqueous dilution liberates a compound which gives positive reactions with aldehyde identifying reagents, i.e. a compound which can identify aldehyde groups. Generally, the liberated compound has the formula
where R is any functional group. In other words, the term “aldehyde donor” includes any compound which is not an aldehyde but when hydrolyzed forms an aldehyde or a compound which gives positive reactions with aldehyde identifying reagents. Examples of aldehyde identifying reagents include, but are not limited to, Benedicts solution, Tollens reagent, and acetyl acetone.
Suitable aldehyde donors include, but are not limited to, imidazolidinyl urea, Quaternium-15, diazolidinyl urea, bromonitropropanediol, methenamine, 5-bromo-5-nitro-1,3-dioxane, sodium hydroxymethylglycinate, 3,5-dimethyl-1,3,5,2H-tetrahydrothiadiazine-2-thione, hexahydro-1,3,5-tris(2-hydroxyethyl)triazine, hexahydo-1,3,5-triethyl-s-triazine, polymethoxy bicyclic oxazolidine, tetrakis (hydroxymethyl) phosphonium sulfate, methylolhydantoins, and any combination of any of the foregoing.
Preferred aldehyde donors include, but are not limited to, methylolhydantoins, such as monomethyloldimethylhydantoins (MMDMHs), dimethyloldimethylhydantoins (DMDMHs), and any combination of any of the foregoing. Examples of methylolhydantoins include, but are not limited to, 1-hydroxymethyl-5,5-dimethylhydantoin (a MMDMH), 3-hydroxymethyl-5,5-dimethylhydantoin (a MMDMH), and 1,3-bis(hydroxymethyl)-5,5-dimethylhydantoin (DMDMH) mixtures (which are available as aqueous solutions under the tradenames Dantogard® and Glydant® from Lonza Inc. of Fair Lawn, N.J.). Other preferred aldehyde donors include, but are not limited to, low free formaldehyde compositions of dimethyloldimethylhydantoin, such as those described in U.S. Pat. No. 5,405,862, which is hereby incorporated by reference. Preferably, the aldehyde donor has a free formaldehyde concentration of less than 0.2% based on 100% total weight of aldehyde donor. Low free formaldehyde compositions reduce workplace exposure risk to formaldehyde. Generally, the weight ratio of methylolhydantoins to peroxide ranges from about 10:1 to about 1:1000.
According to a preferred embodiment, the aldehyde donor is a mixture of 1-hydroxymethyl-5,5-dimethylhydantoin, 3-hydroxymethyl-5,5-dimethylhydantoin, and 1,3-bis(hydroxymethyl)-5,5-dimethylhydantoin. Preferably, the mixture has a free formaldehyde concentration of les
Borokhov Olga
Lutz Patrick Jay
Ney Bill
Sinden Richard
Sweeny Philip Gerdon
Alvo Steve
Darby & Darby
Lonza Inc.
LandOfFree
Method of bleaching recycled papers with hydrogen peroxide... 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 bleaching recycled papers with hydrogen peroxide..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of bleaching recycled papers with hydrogen peroxide... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2948969