CA1307524C - Dispersions of chitin and product therefrom - Google Patents
Dispersions of chitin and product therefromInfo
- Publication number
- CA1307524C CA1307524C CA000595862A CA595862A CA1307524C CA 1307524 C CA1307524 C CA 1307524C CA 000595862 A CA000595862 A CA 000595862A CA 595862 A CA595862 A CA 595862A CA 1307524 C CA1307524 C CA 1307524C
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- CA
- Canada
- Prior art keywords
- chitin
- sodium
- bleach
- group
- dispersion
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
- C08B37/00—Preparation of polysaccharides not provided for in groups C08B1/00 - C08B35/00; Derivatives thereof
- C08B37/0006—Homoglycans, i.e. polysaccharides having a main chain consisting of one single sugar, e.g. colominic acid
- C08B37/0024—Homoglycans, i.e. polysaccharides having a main chain consisting of one single sugar, e.g. colominic acid beta-D-Glucans; (beta-1,3)-D-Glucans, e.g. paramylon, coriolan, sclerotan, pachyman, callose, scleroglucan, schizophyllan, laminaran, lentinan or curdlan; (beta-1,6)-D-Glucans, e.g. pustulan; (beta-1,4)-D-Glucans; (beta-1,3)(beta-1,4)-D-Glucans, e.g. lichenan; Derivatives thereof
- C08B37/0027—2-Acetamido-2-deoxy-beta-glucans; Derivatives thereof
- C08B37/003—Chitin, i.e. 2-acetamido-2-deoxy-(beta-1,4)-D-glucan or N-acetyl-beta-1,4-D-glucosamine; Chitosan, i.e. deacetylated product of chitin or (beta-1,4)-D-glucosamine; Derivatives thereof
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
- A61L15/00—Chemical aspects of, or use of materials for, bandages, dressings or absorbent pads
- A61L15/16—Bandages, dressings or absorbent pads for physiological fluids such as urine or blood, e.g. sanitary towels, tampons
- A61L15/22—Bandages, dressings or absorbent pads for physiological fluids such as urine or blood, e.g. sanitary towels, tampons containing macromolecular materials
- A61L15/28—Polysaccharides or their derivatives
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
- A61P17/00—Drugs for dermatological disorders
Abstract
ABSTRACT OF THE DISCLOSURE
Ground chitin is rendered dispersible on mild shearing by pretreating the chitin with an aqueous bleach solution.
Ground chitin is rendered dispersible on mild shearing by pretreating the chitin with an aqueous bleach solution.
Description
YATRNl' L)~U-l /
DISPERSIONS OF CHITIN AND PRODUCT TE~EE~EFROM
The Government of the United States of America has rights in this invention pursuant to Grant No. NA8-3AA-D-00017 awarded by the U. S.
Department of Commerce.
BACKGROUND OF THE INVENTION
Field of the Invention .
The invention is in the field of chitin dispersions useful in the treatment of wounds as dispersions per se and as certain other products such as paper-like structures which result from the coalescence of chitin in said dispersions.
sackground and Descr tion of the Prior Art Chitin i8 a widely distributed polysaccharide occurring as the structural compound in the form of alpha chitin in the exoskeletons of such crustaceans as shri~p, krill, crabs, and lobsters and in the form of beta chitin in the internal pens of squid. Chitin occurs also in the exoskeletons of some insects and in the cell walls of some fungi. Indeed, chitin is second only to cellulose in tonnage o available natural polymers.
The repeating unit of the chitin polymer is 2-N-acetylglucosamine wherein a small fraction of the amino yroups are unacetylated.
Chitin and its derivativas, especially deacetylated chitin, so-called chitosan, and derivatives, are finding increasing use as wound healing adjuvants, metal ion scavengers, waste water treatment and food processing compound~, and cosmetic aids.
A major deterrent to the wider use of chitin per se is its intractability. Chitin is modestly soluble in a few uncommon solvents.
For example, Capozza in German Patent 2,505,305 reported solubility in hexafluoroisopropanol, hexafluoroacetone, and its sesquihydrate. Austin in U.S. Patent 4,062,921 employed dimethylacetamide or N-methylpyrroLidone `~ ' 5 ~ ~
~ontaining several percent of lithium chloride to dissolve chitin and Balassa et al applied the classical viscose/xanthate process to chitin, as reported in MIT Sea Grant Keport, MIT SG /8-7, p,296.
Dispersions of microcrystalline chitin have been prepared, albeit at the expense of significant hydrolytic degradation of the polymer chain, through pretreatment with hot strong acids, as reported, for example, by Dunn et al in U. S. Patents 3,847,897 and 4,034,121, Austin et al in U.
S. Patent 4,286,087 and Castle et al in U. S. Patent 4,532,321. Yalpani in "Chitin in Nature and Technology", Plenum Press, New York, N.Y. (19~6) teaches dispersions of chitin prepared by extensive high pressurs shearing, for example, 3 to 40 passes through a high energy mill at pressures of 4,000 to 15,000 psi ~281 to 1055 kg/cm2).
Sagar et al in British patents 2,182,560 and 2,188,135 teach the preparation of wound dressings, inter alia, by pouring a slurry of ~ashed fungal mycelia into ~olds or onto a continuous paper-making apparatus, and freeze-drying the resultant mat. The mycelia are bleached before employment in a wet bandage.
SUMMARY OF TXE INVENTION
In the process of dispersing chitin in aqueous medium by shearing, the improvement comprising pretreating said chitin with an oxidizing bleach selected rom one of the group~ of peroxygen bleaches and labile halogen bleaches the group o peroxygen bleaches consisting of hydrogen and alkali metal peroxide, alkaline earth and alkali metal perborato, percarbonate, peroxymonosulfate, persul~ate, bromate; and the group o~
labile halogen bLeaches consisting of alkali metal and alkaline ~arth hypohalite and dihalo-s-triazinetriones, whereby said chitin is rendered dispersible by mild shearing to fonm stable dispersions.
The dispersions form paper-like structures, hereinafter referred to as papers, when subjected to conventional paper making processes or on simple drying on a substrate, for example on a plate according to the process taught by Battista et al in U. S. Patent 2,978,446 for microcrystalline cellulose. As used in claims, the term 'coalescing' is taken to mean a process in which chitin in dispersion is separated from the aqueous medium by evaporation or by filtration or both and the chitin . .
.
1 3()752~
particles come together. The papers, as well as ~ubstrates treated with said dispersions, such as bandages or other wound dressings, are tho~ght to be useful in accelerating wound healing, as taught by ~alassa ln U. ~.
Patent 3,903,268. The labile halogen bleaches introduce halogen into the S chitin molecule, possibly conferring antiseptic properties on the chitin.
DESCRIPTION OF THE PR~FERRED EMBODIMENTS
The invention is readily carried out by the artisan using easily available materials. Commercial oxidizing bleaches are operable, i.e.those selected from the group consisting of hydrogen or alkali metal peroxides, alkaline earths and alkali metal perborates, percarbonates, perox~vnosulfates, persulfates, bromates, h~ohalites, and the dihalo-s-triazinetriones. Those preferred are hydrogen peroxide, sodium hypochlorite, sodium perborate, sodium percarbonate, sodiu~
peroxymonosulfate, potassium and sodium persulfate, sodiu~ bromate, and sodium dichloro-s-triazinetrion. Most preferred is hydrogen peroxide.
The bleaches of the invention are those which are operable at room temperature or slightly ab~ve, say from about 15 deg. C to about 50 deg.
C. When those bleaches containing labile halogen such as the hypohalites are employed, the end product may contain halogen. This comes about because chitin contains acetamido and amino groups which are readily halogenated. The m~lecular weight of the product may also be reduced, whereas the ~olecular weight of invention products treated with pero~ygen bleaches are essentially unchanged.
The pH of the reaction medium is not critical, although there are some preferred conditions, as the artisan will recogniz~. For ~xample aqueous hydrogen peroxide per se ls a sluggish bleach; raising the pH to about 11.5 increas~s the reaction rate so as to make it practical-for use at room temperature. Near the other end of the pH scale, aqueous sodium ~onoperoxysulfate has a pH of a~out 4.0 and is readily operahle at this pH
at room temperature.
The artisan will select a suitable concentration of bleach by experiment to accommodate to the purity of the chitin which varies with the source of the chitin and the method of isolation. Commercial chitin may contain impurities such as proteins, lipids, colorants and the like 1 30752~
., which consume at least some of the bleach. As a rule, concentr~tions of ~rom 1-5% by weight of bleach in water are employed, although more or less may be used as requlred.
The mechanism by which the chitin is so changed as to become readily dispersible is unknown. As demonstrated in examples, substantial reduction in molecular weight is not, in all cases, a precondition for ready dispersibility, as in the art.
The term 'mild shearing' as used in claims, means shearing conditions considerably milder than those taught by Yalpani supra.
Illustrative of the degree of shearing taught in this application is the shearing provided by a simple blender, similar to those often seen in household kitchens, comprising an open atmospheric pressure container having at the bottom a simple propeller-like device capable of turning at say 20,000 rpm. Such a device is referred to infra as a 20,000 rpm blender and the process as mild shearing. The art device employed by Yalpani supra, is a laboratory homogenizer Model l5M (Gaulin Corporation), which pumps the slurry repeatedly through a mill at high pressure, thus providing much more severe shearing.
The dispersions of the invention, upon drying, coalssce forming paper-like structures. The papers vary in appearance from that of coarse filter paper to parchment in the case of beta chitin. Additives may be employed to modify the properties of the papers. Such additives, normally added to the dispersions, comprise softeners and humectants such as those often added to cellulose papers. Examples of useful additives are glycerine, ethylene glycol, and N-acetylethanol2mine. Although the disper~ions ar~ remarkably stable,as set out in exampLes, stabilizers such as carboxymethyl cellulose and polyvinyl alcohol can b2 employed to further stabilize the dispersions for special purposes. Other materials, for example fibrous materials can be added for special effects. Such materials comprise, for example, cellulose pulps, ground cellulose, glass fibers, polyester fibrils and the like.
Although flat, i.e. planar, papers are descrihed in examples it is within the invention to prepared shaped papers, for example, papers formed to fit a body part such as a heel. Such a procedure is within the skill of the artisan who might pour a dispersion into a porous mold much as clay ...
,:' 1 30752~
~Lip is poured into porous plaster of Paris molds to prepare so-called 'green' hollow c~ramic articles.
EY~MPLES
The chitin e~ployed in the following examples came from several sources, as Follows:
Alpha chitin:
Dungeness crab (Cancer ma~istus) obtained commercially from Protan, Inc., Redmond, WA
Tanner/Snow Crab (Chionectes bairdi) obtained commercially from Bioshell Corp~, Albany, OR
Blue Crab (Callineact_s sapidus) obtained rom the Chesapeake Bay.
Work up was carried out in the usual manner (See Zikakis ed. Chitin, Chitosan and Related Enzymes, Academic Press, Inc. Orlando, Florida (1984) p.xviii).
Beta chitin.
Squid (Loligo species) obtained from the North Atlantic Ocean. Work up was as above, except that the decalcification procedure was omitted as unnecessary.
Chitin, regardless of source, was ground to the mesh stated in examples.
Hydrogen peroxide, 3% was of pharmaceutical grad0 and sodium hypochlorite was a commercial preparation such as is used in home laundries. Other chemicals were chemically pure materials purchasad in the laboratory chemicals trade.
Molecular weights were determlned by intrinsic viscosity uslng a N,N-dimethylacetamide / 5% lithium chloride sol~ent mixture and Mark-Houwink constants according to the method of Susan H. Sennett, Thesis, University of Delaware, June 198S.
Examples demonstrate the use of the preferred bleaches, i.e.
hydrogen peroxide, sodium perborate, sodium percarbonate, sodium borate, sodium peroxymonosulfate, sodium hypochlorite, and sodium dichloro-s-triaæinetrione.
1 3075~
Example 1 This example demonstrates a process of the invention wherein hydrogen peroxide is applled ln a prelLmlnary ~leacnlng step at autogenous p~ to oxidize adventitious impurities, followed by more severe treatment with hydrogen peroxide at pH 11.5 to render the chitin dispersible.
Alpha chitin from Dungeness crab, 15 g., 20 mesh , was stirred overnight at room temperatu~e with 300 ml of 3% hydrogen peroxide. The chitin was filtered and washed with four 250 ml portions of distilled water. The wet filter cake was suspended in 750 ml of 1% hydrogen peroxide and the pH of the mixture was adjusted to 11.5 by dropwise addition of 50% sodium hydroxide. The mixture was stirred overnight at room temperature, filtered, and the filter cake was washed with five 2000 ml portions of distilled water.
The filter cake, after pressing on the filter to remove excess water, lS was suspended in 400 ml of distilled water and blend~d for 15 minutes in a 20,000 rpm blender. The resulting creamy dispersion contained about 3.75 wt.% solids and showed no appreciable syneresis after seven months.
A portion of the dispersion, when spread on a stainles~ steel plate and allowed to dry under room conditions, yielded a paper having the appearance of coarse filter paper.
Example 2 This example illustrates the process of Example 1 applied to alpha chitin derived from Tanner crdb. The yield was about 90%. Fifteen minute blending, as in Example 1, of a mixture of 3 wt.~ treated chitin in wat~r Z5 yielded a colorles~ dispersion showing no syneresis after one year.
Example 3 This example illustrates a procedure avoiding the preliminary bleaching step of Examples 1 and 2.
Dungeness crab alpha chitin, 10 g., 40 mesh, was suspended in 200 ml.
of 3% hydrogen peroxide and the pH of the mixture was adjusted to 11.5 by dropwise addition of 20% sodium hydroxide. The mixture was stirred overnight at 17 deg. C. and the fluffy white product was separated by filtration from a pale yellow filtrate. The filter cake, after washing 1 30~5~ ~
with water, was added to fresh water to yield a 1% mixture whlch was blended as in Example 1. ~rhe resultlng dispersion showed 2-3 wt.
syneresis a~ter three ~onths stanalng.
The molecular weight of two preparations was found to be 6.37 x 10~
and 6.79 x 10~. The starting material had a molecular weight, as measured by the same method, of 6.44 x 10~.
Example 4 This example illustrates the preparation of an invention dispersion using hydrogen peroxide and beta chitin from squid pens, the preparation of a paper from the dispersion, and the use of an additive for softening the paper.
Beta chitin from squid pens, 7.5 g., 20 mesh, was added to 150 ml. of 3% hydrogen peroxide previously adjusted to pH 11.5 by dropwise addition of 50 wt.% sodium hydroxide, and the mixture was stirred overnight.
lS Although the product appeared gelatinous, it was reaaily filtered.
It was washed with water until the filtrate was neutral. The ~ashed product (2.5 wt.%) was blended in 300 ml. of fresh water, as in Example l, to yield a dispersion which wa~ stabl2 for at least four months.
On drying a portion of the dispersion on a flat plate, a parchment-like paper formed which was reminiscent of the original squid pens. ln a second experiment, an amount of bis-(2-hydroxyethyl ether) equal to about 8 wt.% of the chitin, was added to a portion of the dispersion. On drying, a softer paper was produced .
The molecular woight of the starting beta chitin was 3.2 x l0*; a~ter processing, the molecular weight was found to b~ essentially unchang~d i.e. 1.41 x 10~.
Example 5 This example illustr~tes the use of sodium perborate tetrahydrate as a bleach in the invention process applied to alpha chitin.
Alpha chitin from Dunyeness crab, l0 g., 40 mesh, h'aS suspended in 200 ml. of water containing 10 g. of sodium perborate tetrahydrate. The initial pH was ll. The mixture was stirred overnight at 35 deq. C.
The product, a~ter separation by filtration, was washed ~lith fresh water until the filtrate was neutral. The product was blended in 250 ml of water as in Example 1. The dispersion containing about 4 wt.% solids, was stable for at least four months at room temperature.
Example 6 This example illustrates the use of sodium percarbonate as a bleach in the treatment of alpha chitin according to the invention.
Alpha chitin from Dungeness crab~ 10 g., 20 mesh, was suspended in 300 ml. of water containing 10 g. of sodium percarbonate ~perhydrate~.
The mixture was stirred overnight at 35 deg. C. The product was filtered and rinsed four times on the funnel with 300 ml. portions of water. The filter cake resembled table salt . The product was dispersed as in Example 1 in 350 ml. of water to yield a thick creamy and stable dispersion. Drying of the dispersion on a plate yielded a paper.
Example 7 This example illustrates the use of sodium perborate tetrahydrate AS
a bleach in the treatment of alpha chitin according to the invention.
Alpha chitin from Blue crab, }0 g., 40 mesh, was added to a solution of 10 g. sodium perborate tetrahydrate in 300 ml. water and the mixture was stirred overnight at 34 deg. C. The product was filtered and repeatedly wash~d on the funnel. The wet filter cak~ was dispers~d in 320 ml. wat~r as in Example 1 to produce a creamy dispersion containing about 3 wt.~ solids. The dispersion, slightly off white, yielded a coarse pap0r on drying on a plate.
.
Example 8 This example illustrates the use of potassium peroxymonosulfate as a bleach in the treatment of alpha chitin according to the invention.
A mixture of 10 g. of 40 mesh alpha chitin from Dungeness cr~b, 10 g. of potassium peroxymonosulfate and 200 ml. of water were stirred overnight at 36 deg. C. The initial pH of the mixture was 4. The product was filtered and washed four times on the funnel with 200 ml. portions of water. The filter cake was blended as in Example 1. The creamy white ', - :, , ' :
1 30752~
, dispersion containing 3.3 wt.~ solids was stabLe for at least four months.
The dispers1on on drying on a plate yieLded a paper.
E~ample 9 This example illustrates the use of sodiu~ hypochlorite as ~ bleach in the treatment of alpha chitin according to the invention. ~t is shown that active chlorine is apparently introduced into the chitin molecule and the molecule is so modified that the product is no longer soluble in dimethylacetamide/lithium chloride.
Alpha chitin from Dungeness crab, 20 g., 20 mesh, was added -to a room temperature mixture of 100 ml. of water and 100 ml. 5% sodiu~
hypochlorite household bleach. Reaction occurred at once with foaming, gas evolution and bleaching of the chitin. The product was filtered and washed once with 1.4 1. of water and thereafter resuspended three times in 900 ml. of fresh water with intermediate centrifuging.
The washed product was blended in 150 ml. of water as in Example 1.
The thick creamy dispersion had the odor of free chlorine. The dispersion was stable for at least seven months. On drying on a plate, a white paper was formed. The presence of free chlorine was established through the liberation of iodine from potassium iodide.
Example 10 This example demonstrates the use of sodium dichloro-s-triazinetrione as bleach in the treatment of alpha chitin from Dungeness crab.
Alpha chitin from Dungeness crab, 10 g., 20 mesh, was suspended in 300 ml. of water containing 10 grams of sodium dichloro-s-triazinetrione.
The mixture was stirred overnight at 36 deg. C. The product was filtered and washed with four 300 ml. portions of water. The wet filter cake was blended in 300 ml. of water as in Example 1. The creamy white dispersion had a chlorine odor and formed a paper on drying on a glass plate. The molecular weight was determined to be 1.77 x 105.
~-` 1 307524 Example 11 This example demonstrates the preparation o~ chitin papers by allowing disperslons o~ the lnve~tlon to dry on a porous su~scrate ln a m~nner simulating commercial pap~r making wherein dispersoids are taken up S on s~reens and thereafter dried.
Although it is not critical to do so, dispersions are preferably diluted to about 0.5 wt.% solids before depositing the dispersed chitin on the porous substrate, preferably by applying suction to the bottom side.
The porous substrate may be a fine screen, for example, or unglazed 10 porcelain. Preferably the wet mats are removed fro~ the substrate before drying them, for example, by allowing them to dry under room conditions. Other means may, of course, be employed. Various solid additives, preferably fibrous materials, can be added to modify the properties of the papers.
Papers need not be planar. It is within the invention to fabricate papers of other shapes by, for example, employing porous molds of suitable shapes. For example, papers can be prepared to fit body parts such as an ankle.
Table 1 shows the effects of several additives on the paper product.
Dispersion, Fibrous Ratio (wt.) Product Ex. No. Additive Chitin/Ad- appearance ditive .
4 none - parchment 6 none - coarse filter paper 1 glass fiber 7/3 smooth pulp slick paper 1 same 1/3 slick creaseable paper ` 1 30752~ ~
1 wood filter 7/3 rough paper pulp ~lexible paper l Hardwood 2/1 flexible dissolving paper pulp 9 same 2/1 bright white flexible paper Example 12 - This example demonstrates one use of the dispersions of the invention in the preparation of wound dressings. Dispersions prepared under Examples 1, 2, 4, 8, and 9 were spread on 4 in. (10.2 cm.) square ~ prewetted commercial wound dressing pads by means of a glass rod. The dressing containing the dispersion of B ample 8 was found after drying to have taken up 0.32 g. of chitin. Naturally, one may add more or less chitin. The wet or dry dressing can be enclosed in a protective envelope and sterilized, e.g. by autoclaving, as is conventional in the art.
To summarize, it is within the skill of the art to employ the invention dispersions in several ways, for example:
1. The dispersion per se can be applied directly to the wound and thereafter the wound can be wrapped in conventional dressings or;
DISPERSIONS OF CHITIN AND PRODUCT TE~EE~EFROM
The Government of the United States of America has rights in this invention pursuant to Grant No. NA8-3AA-D-00017 awarded by the U. S.
Department of Commerce.
BACKGROUND OF THE INVENTION
Field of the Invention .
The invention is in the field of chitin dispersions useful in the treatment of wounds as dispersions per se and as certain other products such as paper-like structures which result from the coalescence of chitin in said dispersions.
sackground and Descr tion of the Prior Art Chitin i8 a widely distributed polysaccharide occurring as the structural compound in the form of alpha chitin in the exoskeletons of such crustaceans as shri~p, krill, crabs, and lobsters and in the form of beta chitin in the internal pens of squid. Chitin occurs also in the exoskeletons of some insects and in the cell walls of some fungi. Indeed, chitin is second only to cellulose in tonnage o available natural polymers.
The repeating unit of the chitin polymer is 2-N-acetylglucosamine wherein a small fraction of the amino yroups are unacetylated.
Chitin and its derivativas, especially deacetylated chitin, so-called chitosan, and derivatives, are finding increasing use as wound healing adjuvants, metal ion scavengers, waste water treatment and food processing compound~, and cosmetic aids.
A major deterrent to the wider use of chitin per se is its intractability. Chitin is modestly soluble in a few uncommon solvents.
For example, Capozza in German Patent 2,505,305 reported solubility in hexafluoroisopropanol, hexafluoroacetone, and its sesquihydrate. Austin in U.S. Patent 4,062,921 employed dimethylacetamide or N-methylpyrroLidone `~ ' 5 ~ ~
~ontaining several percent of lithium chloride to dissolve chitin and Balassa et al applied the classical viscose/xanthate process to chitin, as reported in MIT Sea Grant Keport, MIT SG /8-7, p,296.
Dispersions of microcrystalline chitin have been prepared, albeit at the expense of significant hydrolytic degradation of the polymer chain, through pretreatment with hot strong acids, as reported, for example, by Dunn et al in U. S. Patents 3,847,897 and 4,034,121, Austin et al in U.
S. Patent 4,286,087 and Castle et al in U. S. Patent 4,532,321. Yalpani in "Chitin in Nature and Technology", Plenum Press, New York, N.Y. (19~6) teaches dispersions of chitin prepared by extensive high pressurs shearing, for example, 3 to 40 passes through a high energy mill at pressures of 4,000 to 15,000 psi ~281 to 1055 kg/cm2).
Sagar et al in British patents 2,182,560 and 2,188,135 teach the preparation of wound dressings, inter alia, by pouring a slurry of ~ashed fungal mycelia into ~olds or onto a continuous paper-making apparatus, and freeze-drying the resultant mat. The mycelia are bleached before employment in a wet bandage.
SUMMARY OF TXE INVENTION
In the process of dispersing chitin in aqueous medium by shearing, the improvement comprising pretreating said chitin with an oxidizing bleach selected rom one of the group~ of peroxygen bleaches and labile halogen bleaches the group o peroxygen bleaches consisting of hydrogen and alkali metal peroxide, alkaline earth and alkali metal perborato, percarbonate, peroxymonosulfate, persul~ate, bromate; and the group o~
labile halogen bLeaches consisting of alkali metal and alkaline ~arth hypohalite and dihalo-s-triazinetriones, whereby said chitin is rendered dispersible by mild shearing to fonm stable dispersions.
The dispersions form paper-like structures, hereinafter referred to as papers, when subjected to conventional paper making processes or on simple drying on a substrate, for example on a plate according to the process taught by Battista et al in U. S. Patent 2,978,446 for microcrystalline cellulose. As used in claims, the term 'coalescing' is taken to mean a process in which chitin in dispersion is separated from the aqueous medium by evaporation or by filtration or both and the chitin . .
.
1 3()752~
particles come together. The papers, as well as ~ubstrates treated with said dispersions, such as bandages or other wound dressings, are tho~ght to be useful in accelerating wound healing, as taught by ~alassa ln U. ~.
Patent 3,903,268. The labile halogen bleaches introduce halogen into the S chitin molecule, possibly conferring antiseptic properties on the chitin.
DESCRIPTION OF THE PR~FERRED EMBODIMENTS
The invention is readily carried out by the artisan using easily available materials. Commercial oxidizing bleaches are operable, i.e.those selected from the group consisting of hydrogen or alkali metal peroxides, alkaline earths and alkali metal perborates, percarbonates, perox~vnosulfates, persulfates, bromates, h~ohalites, and the dihalo-s-triazinetriones. Those preferred are hydrogen peroxide, sodium hypochlorite, sodium perborate, sodium percarbonate, sodiu~
peroxymonosulfate, potassium and sodium persulfate, sodiu~ bromate, and sodium dichloro-s-triazinetrion. Most preferred is hydrogen peroxide.
The bleaches of the invention are those which are operable at room temperature or slightly ab~ve, say from about 15 deg. C to about 50 deg.
C. When those bleaches containing labile halogen such as the hypohalites are employed, the end product may contain halogen. This comes about because chitin contains acetamido and amino groups which are readily halogenated. The m~lecular weight of the product may also be reduced, whereas the ~olecular weight of invention products treated with pero~ygen bleaches are essentially unchanged.
The pH of the reaction medium is not critical, although there are some preferred conditions, as the artisan will recogniz~. For ~xample aqueous hydrogen peroxide per se ls a sluggish bleach; raising the pH to about 11.5 increas~s the reaction rate so as to make it practical-for use at room temperature. Near the other end of the pH scale, aqueous sodium ~onoperoxysulfate has a pH of a~out 4.0 and is readily operahle at this pH
at room temperature.
The artisan will select a suitable concentration of bleach by experiment to accommodate to the purity of the chitin which varies with the source of the chitin and the method of isolation. Commercial chitin may contain impurities such as proteins, lipids, colorants and the like 1 30752~
., which consume at least some of the bleach. As a rule, concentr~tions of ~rom 1-5% by weight of bleach in water are employed, although more or less may be used as requlred.
The mechanism by which the chitin is so changed as to become readily dispersible is unknown. As demonstrated in examples, substantial reduction in molecular weight is not, in all cases, a precondition for ready dispersibility, as in the art.
The term 'mild shearing' as used in claims, means shearing conditions considerably milder than those taught by Yalpani supra.
Illustrative of the degree of shearing taught in this application is the shearing provided by a simple blender, similar to those often seen in household kitchens, comprising an open atmospheric pressure container having at the bottom a simple propeller-like device capable of turning at say 20,000 rpm. Such a device is referred to infra as a 20,000 rpm blender and the process as mild shearing. The art device employed by Yalpani supra, is a laboratory homogenizer Model l5M (Gaulin Corporation), which pumps the slurry repeatedly through a mill at high pressure, thus providing much more severe shearing.
The dispersions of the invention, upon drying, coalssce forming paper-like structures. The papers vary in appearance from that of coarse filter paper to parchment in the case of beta chitin. Additives may be employed to modify the properties of the papers. Such additives, normally added to the dispersions, comprise softeners and humectants such as those often added to cellulose papers. Examples of useful additives are glycerine, ethylene glycol, and N-acetylethanol2mine. Although the disper~ions ar~ remarkably stable,as set out in exampLes, stabilizers such as carboxymethyl cellulose and polyvinyl alcohol can b2 employed to further stabilize the dispersions for special purposes. Other materials, for example fibrous materials can be added for special effects. Such materials comprise, for example, cellulose pulps, ground cellulose, glass fibers, polyester fibrils and the like.
Although flat, i.e. planar, papers are descrihed in examples it is within the invention to prepared shaped papers, for example, papers formed to fit a body part such as a heel. Such a procedure is within the skill of the artisan who might pour a dispersion into a porous mold much as clay ...
,:' 1 30752~
~Lip is poured into porous plaster of Paris molds to prepare so-called 'green' hollow c~ramic articles.
EY~MPLES
The chitin e~ployed in the following examples came from several sources, as Follows:
Alpha chitin:
Dungeness crab (Cancer ma~istus) obtained commercially from Protan, Inc., Redmond, WA
Tanner/Snow Crab (Chionectes bairdi) obtained commercially from Bioshell Corp~, Albany, OR
Blue Crab (Callineact_s sapidus) obtained rom the Chesapeake Bay.
Work up was carried out in the usual manner (See Zikakis ed. Chitin, Chitosan and Related Enzymes, Academic Press, Inc. Orlando, Florida (1984) p.xviii).
Beta chitin.
Squid (Loligo species) obtained from the North Atlantic Ocean. Work up was as above, except that the decalcification procedure was omitted as unnecessary.
Chitin, regardless of source, was ground to the mesh stated in examples.
Hydrogen peroxide, 3% was of pharmaceutical grad0 and sodium hypochlorite was a commercial preparation such as is used in home laundries. Other chemicals were chemically pure materials purchasad in the laboratory chemicals trade.
Molecular weights were determlned by intrinsic viscosity uslng a N,N-dimethylacetamide / 5% lithium chloride sol~ent mixture and Mark-Houwink constants according to the method of Susan H. Sennett, Thesis, University of Delaware, June 198S.
Examples demonstrate the use of the preferred bleaches, i.e.
hydrogen peroxide, sodium perborate, sodium percarbonate, sodium borate, sodium peroxymonosulfate, sodium hypochlorite, and sodium dichloro-s-triaæinetrione.
1 3075~
Example 1 This example demonstrates a process of the invention wherein hydrogen peroxide is applled ln a prelLmlnary ~leacnlng step at autogenous p~ to oxidize adventitious impurities, followed by more severe treatment with hydrogen peroxide at pH 11.5 to render the chitin dispersible.
Alpha chitin from Dungeness crab, 15 g., 20 mesh , was stirred overnight at room temperatu~e with 300 ml of 3% hydrogen peroxide. The chitin was filtered and washed with four 250 ml portions of distilled water. The wet filter cake was suspended in 750 ml of 1% hydrogen peroxide and the pH of the mixture was adjusted to 11.5 by dropwise addition of 50% sodium hydroxide. The mixture was stirred overnight at room temperature, filtered, and the filter cake was washed with five 2000 ml portions of distilled water.
The filter cake, after pressing on the filter to remove excess water, lS was suspended in 400 ml of distilled water and blend~d for 15 minutes in a 20,000 rpm blender. The resulting creamy dispersion contained about 3.75 wt.% solids and showed no appreciable syneresis after seven months.
A portion of the dispersion, when spread on a stainles~ steel plate and allowed to dry under room conditions, yielded a paper having the appearance of coarse filter paper.
Example 2 This example illustrates the process of Example 1 applied to alpha chitin derived from Tanner crdb. The yield was about 90%. Fifteen minute blending, as in Example 1, of a mixture of 3 wt.~ treated chitin in wat~r Z5 yielded a colorles~ dispersion showing no syneresis after one year.
Example 3 This example illustrates a procedure avoiding the preliminary bleaching step of Examples 1 and 2.
Dungeness crab alpha chitin, 10 g., 40 mesh, was suspended in 200 ml.
of 3% hydrogen peroxide and the pH of the mixture was adjusted to 11.5 by dropwise addition of 20% sodium hydroxide. The mixture was stirred overnight at 17 deg. C. and the fluffy white product was separated by filtration from a pale yellow filtrate. The filter cake, after washing 1 30~5~ ~
with water, was added to fresh water to yield a 1% mixture whlch was blended as in Example 1. ~rhe resultlng dispersion showed 2-3 wt.
syneresis a~ter three ~onths stanalng.
The molecular weight of two preparations was found to be 6.37 x 10~
and 6.79 x 10~. The starting material had a molecular weight, as measured by the same method, of 6.44 x 10~.
Example 4 This example illustrates the preparation of an invention dispersion using hydrogen peroxide and beta chitin from squid pens, the preparation of a paper from the dispersion, and the use of an additive for softening the paper.
Beta chitin from squid pens, 7.5 g., 20 mesh, was added to 150 ml. of 3% hydrogen peroxide previously adjusted to pH 11.5 by dropwise addition of 50 wt.% sodium hydroxide, and the mixture was stirred overnight.
lS Although the product appeared gelatinous, it was reaaily filtered.
It was washed with water until the filtrate was neutral. The ~ashed product (2.5 wt.%) was blended in 300 ml. of fresh water, as in Example l, to yield a dispersion which wa~ stabl2 for at least four months.
On drying a portion of the dispersion on a flat plate, a parchment-like paper formed which was reminiscent of the original squid pens. ln a second experiment, an amount of bis-(2-hydroxyethyl ether) equal to about 8 wt.% of the chitin, was added to a portion of the dispersion. On drying, a softer paper was produced .
The molecular woight of the starting beta chitin was 3.2 x l0*; a~ter processing, the molecular weight was found to b~ essentially unchang~d i.e. 1.41 x 10~.
Example 5 This example illustr~tes the use of sodium perborate tetrahydrate as a bleach in the invention process applied to alpha chitin.
Alpha chitin from Dunyeness crab, l0 g., 40 mesh, h'aS suspended in 200 ml. of water containing 10 g. of sodium perborate tetrahydrate. The initial pH was ll. The mixture was stirred overnight at 35 deq. C.
The product, a~ter separation by filtration, was washed ~lith fresh water until the filtrate was neutral. The product was blended in 250 ml of water as in Example 1. The dispersion containing about 4 wt.% solids, was stable for at least four months at room temperature.
Example 6 This example illustrates the use of sodium percarbonate as a bleach in the treatment of alpha chitin according to the invention.
Alpha chitin from Dungeness crab~ 10 g., 20 mesh, was suspended in 300 ml. of water containing 10 g. of sodium percarbonate ~perhydrate~.
The mixture was stirred overnight at 35 deg. C. The product was filtered and rinsed four times on the funnel with 300 ml. portions of water. The filter cake resembled table salt . The product was dispersed as in Example 1 in 350 ml. of water to yield a thick creamy and stable dispersion. Drying of the dispersion on a plate yielded a paper.
Example 7 This example illustrates the use of sodium perborate tetrahydrate AS
a bleach in the treatment of alpha chitin according to the invention.
Alpha chitin from Blue crab, }0 g., 40 mesh, was added to a solution of 10 g. sodium perborate tetrahydrate in 300 ml. water and the mixture was stirred overnight at 34 deg. C. The product was filtered and repeatedly wash~d on the funnel. The wet filter cak~ was dispers~d in 320 ml. wat~r as in Example 1 to produce a creamy dispersion containing about 3 wt.~ solids. The dispersion, slightly off white, yielded a coarse pap0r on drying on a plate.
.
Example 8 This example illustrates the use of potassium peroxymonosulfate as a bleach in the treatment of alpha chitin according to the invention.
A mixture of 10 g. of 40 mesh alpha chitin from Dungeness cr~b, 10 g. of potassium peroxymonosulfate and 200 ml. of water were stirred overnight at 36 deg. C. The initial pH of the mixture was 4. The product was filtered and washed four times on the funnel with 200 ml. portions of water. The filter cake was blended as in Example 1. The creamy white ', - :, , ' :
1 30752~
, dispersion containing 3.3 wt.~ solids was stabLe for at least four months.
The dispers1on on drying on a plate yieLded a paper.
E~ample 9 This example illustrates the use of sodiu~ hypochlorite as ~ bleach in the treatment of alpha chitin according to the invention. ~t is shown that active chlorine is apparently introduced into the chitin molecule and the molecule is so modified that the product is no longer soluble in dimethylacetamide/lithium chloride.
Alpha chitin from Dungeness crab, 20 g., 20 mesh, was added -to a room temperature mixture of 100 ml. of water and 100 ml. 5% sodiu~
hypochlorite household bleach. Reaction occurred at once with foaming, gas evolution and bleaching of the chitin. The product was filtered and washed once with 1.4 1. of water and thereafter resuspended three times in 900 ml. of fresh water with intermediate centrifuging.
The washed product was blended in 150 ml. of water as in Example 1.
The thick creamy dispersion had the odor of free chlorine. The dispersion was stable for at least seven months. On drying on a plate, a white paper was formed. The presence of free chlorine was established through the liberation of iodine from potassium iodide.
Example 10 This example demonstrates the use of sodium dichloro-s-triazinetrione as bleach in the treatment of alpha chitin from Dungeness crab.
Alpha chitin from Dungeness crab, 10 g., 20 mesh, was suspended in 300 ml. of water containing 10 grams of sodium dichloro-s-triazinetrione.
The mixture was stirred overnight at 36 deg. C. The product was filtered and washed with four 300 ml. portions of water. The wet filter cake was blended in 300 ml. of water as in Example 1. The creamy white dispersion had a chlorine odor and formed a paper on drying on a glass plate. The molecular weight was determined to be 1.77 x 105.
~-` 1 307524 Example 11 This example demonstrates the preparation o~ chitin papers by allowing disperslons o~ the lnve~tlon to dry on a porous su~scrate ln a m~nner simulating commercial pap~r making wherein dispersoids are taken up S on s~reens and thereafter dried.
Although it is not critical to do so, dispersions are preferably diluted to about 0.5 wt.% solids before depositing the dispersed chitin on the porous substrate, preferably by applying suction to the bottom side.
The porous substrate may be a fine screen, for example, or unglazed 10 porcelain. Preferably the wet mats are removed fro~ the substrate before drying them, for example, by allowing them to dry under room conditions. Other means may, of course, be employed. Various solid additives, preferably fibrous materials, can be added to modify the properties of the papers.
Papers need not be planar. It is within the invention to fabricate papers of other shapes by, for example, employing porous molds of suitable shapes. For example, papers can be prepared to fit body parts such as an ankle.
Table 1 shows the effects of several additives on the paper product.
Dispersion, Fibrous Ratio (wt.) Product Ex. No. Additive Chitin/Ad- appearance ditive .
4 none - parchment 6 none - coarse filter paper 1 glass fiber 7/3 smooth pulp slick paper 1 same 1/3 slick creaseable paper ` 1 30752~ ~
1 wood filter 7/3 rough paper pulp ~lexible paper l Hardwood 2/1 flexible dissolving paper pulp 9 same 2/1 bright white flexible paper Example 12 - This example demonstrates one use of the dispersions of the invention in the preparation of wound dressings. Dispersions prepared under Examples 1, 2, 4, 8, and 9 were spread on 4 in. (10.2 cm.) square ~ prewetted commercial wound dressing pads by means of a glass rod. The dressing containing the dispersion of B ample 8 was found after drying to have taken up 0.32 g. of chitin. Naturally, one may add more or less chitin. The wet or dry dressing can be enclosed in a protective envelope and sterilized, e.g. by autoclaving, as is conventional in the art.
To summarize, it is within the skill of the art to employ the invention dispersions in several ways, for example:
1. The dispersion per se can be applied directly to the wound and thereafter the wound can be wrapped in conventional dressings or;
2. The dispersion can be applied to the dressing before applying the dressing to the wound, either moist or after drying or;
3. A paper of the invention, optionally containing ono or more pharmaceutically acceptable additives, can be applied directly to the wound before applying a conventional dressing or the paper can be applied as a part of a dressing package. The paper and packet can be employed either 7~et or dry.
Example 13 This example demonstra~es the ~mployment of se ?eral humectants.
An amount of the below indicated conventional humectallts equal to 10%
of the solids was mixed with selected dispersions ~f E~ les. ~e s mi~res were spread on flat stainless steel plates and allowed to dry, thereby forming papers according to the invelllion. The results are shown in Table 2 ol10wing.
Table 2 Expt. No. Dispersion Humectant Product ~xample No. Description , 1 7 none hard paper 2 7 N-acetylethanol- soft paper amine 3 7 bis-~2-hydroxy- intenmediate ethyl3ether between 1 ~nd 2 4 7 glycerine ~oft paper 4 none fl~xible translucent paper 6 4 N-H~etylethanol- ~ofter than 5 amine 7 4 bis-~2-hydro~y- flexible, ~oft ethyl)ether paper 8 4 glycerine Rlightly harder than 7 9 8 none hard pap~r, low tear Ltr*ngth 8 N-acetylethanol- softe~ than 9, amine ~tronger 11 8 bis-(2 hydroxy-softness between ethyl~ether 9 and 10 ~r ~
..~
1 30752~ ~
12 8 glycerine hard paper, much thicker Example 14, Comparative This example demonstrates that unbleached chitin cannot, outside the invention, be dispersed to form stable emulsions on mild shearing.
The experiment of ~xample 6 was repeated with the change that sodium percarbonate bleach was not employed. When chitin of the same batch was suspended in water and blended as in Example 1, the product resembled a puree containing visible particles. It began almost immediately to flocculate.
Example 13 This example demonstra~es the ~mployment of se ?eral humectants.
An amount of the below indicated conventional humectallts equal to 10%
of the solids was mixed with selected dispersions ~f E~ les. ~e s mi~res were spread on flat stainless steel plates and allowed to dry, thereby forming papers according to the invelllion. The results are shown in Table 2 ol10wing.
Table 2 Expt. No. Dispersion Humectant Product ~xample No. Description , 1 7 none hard paper 2 7 N-acetylethanol- soft paper amine 3 7 bis-~2-hydroxy- intenmediate ethyl3ether between 1 ~nd 2 4 7 glycerine ~oft paper 4 none fl~xible translucent paper 6 4 N-H~etylethanol- ~ofter than 5 amine 7 4 bis-~2-hydro~y- flexible, ~oft ethyl)ether paper 8 4 glycerine Rlightly harder than 7 9 8 none hard pap~r, low tear Ltr*ngth 8 N-acetylethanol- softe~ than 9, amine ~tronger 11 8 bis-(2 hydroxy-softness between ethyl~ether 9 and 10 ~r ~
..~
1 30752~ ~
12 8 glycerine hard paper, much thicker Example 14, Comparative This example demonstrates that unbleached chitin cannot, outside the invention, be dispersed to form stable emulsions on mild shearing.
The experiment of ~xample 6 was repeated with the change that sodium percarbonate bleach was not employed. When chitin of the same batch was suspended in water and blended as in Example 1, the product resembled a puree containing visible particles. It began almost immediately to flocculate.
Claims (21)
1. In the process of dispersing chitin in aqueous medium by shearing, the improvement comprising pretreating said chitin with an aqueous oxidizing bleach, whereby said chitin is rendered dispersible by mild shearing thereby forming a stable emulsion.
2. The process of claim 1 wherein said bleach is selected from the group consisting of hydrogen, alkaline earth and alkali metal peroxide, alkaline earth and alkali metal perborate, percarbonate peroxymonosulfate, persulfate, bromate, hypohalite, and the dihalo-s-triazinetriones.
3. The process of claim 1 wherein said bleach is selected from the group consisting of hydrogen peroxide, sodium hypochlorite, sodium perborate, sodium percarbonate, sodium peroxymonosulfate, potassium and sodium persulfate, sodium bromate, and sodium, dichloro-s-triazinetrione.
4. The process of claim 1 wherein said bleach is hydrogen peroxide.
5. The dispersion resulting from mild shearing in aqueous medium of chitin pretreated with an aqueous oxidizing bleach.
6. The dispersion of claim 5 wherein said oxidizing bleach is selected from the group consisting of hydrogen, alkaline earth and alkali metal peroxide, alkaline earth and alkali metal perborate, percarbonate, peroxymonosulfate, persulfate, bromate, hypohalite, and the dihalo-s-triazinetriones.
7. The dispersion of claim 5 wherein said oxidizing bleach is selected from the group consisting of hydrogen peroxide, sodium hypochlorite, sodium perborate, sodium percarbonate, sodium peroxymonosulfate, potassium and sodium persulfate, sodium bromate, and sodium dichloro-s-triazinetrione.
8. The dispersion of claim 5 wherein said bleach is hydrogen peroxide.
9. The paper resulting from coalescing an aqueous dispersion of chitin formed by the process comprising pretreating said chitin with an aqueous oxidizing bleach preliminary to shearing said chitin in water.
10. The paper of claim 9 wherein said chitin is pretreated with a bleach selected from the group consisting of hydrogen, alkaline earth and alkali metal peroxide, alkaline earth and alkali metal perborate, percarbonate, peroxymonosulfate, persulfate, bromate, hypohalite, and the dihalo-s-triazinetriones.
11. The paper of claim 9 wherein said chitin is pretreated with a bleach selected from the group consisting of hydrogen peroxide, sodium hypochlorite, sodium perborate, sodium percarbonate, sodium peroxymonosulfate, potassium and sodium persulfate, sodium bromate, and sodium dichloro-s-triazinetrione.
12. Chitin dispersible on mild shearing in a 20,000 rpm blender, resulting from treatment of chitin with an oxidizing bleach.
13. The chitin of claim 12 wherein said bleach is selected from the group consisting of hydrogen, alkaline earth and alkali metal peroxide, alkaline earth and alkali metal perborate, percarbonate, peroxymonosulfate, persulfate, bromate, hypohalite, and the dihalo-s-triazinetriones.
14. The chitln of claim 12 wherein said bleach is selected from the group consisting of hydrogen peroxide, sodium hypochlorite, sodium perborate, sodium percarbonate, sodium peroxymonosulfate, potassium and sodium persulfate.
15. The chitin of claim 12 wherein said bleach is hydrogen peroxide.
16. The dispersion of claim 5 containing a fibrous additive.
17. The dispersion of claim 16 wherein said additive is selected from the group consisting of glass fiber pulp and wood paper pulp.
18. The dispersion of claim 5 containing additionally a humectant.
19. The dispersion of claim 18 wherein said humectant is selected from the group consisting of N-acetylethanolamine, bis-(2-hydroxyethyl)ether and glycerine.
20. A wound dressing treated with a chitin dispersion o claim 5, 6, 7, or 8.
21. In the process of dispersing chitin in aqueous medium by shearing, the improvement comprising pretreating said chitin with an aqueous oxidizing bleach selected from one of a first group and a second group wherein said first group consists of peroxygen bleaches and said second group consists of labile halogen bleaches.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/214,977 US4931551A (en) | 1988-07-05 | 1988-07-05 | Dispersions of chitin and product therefrom |
| US07/214,977 | 1988-07-05 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1307524C true CA1307524C (en) | 1992-09-15 |
Family
ID=22801143
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000595862A Expired - Fee Related CA1307524C (en) | 1988-07-05 | 1989-04-06 | Dispersions of chitin and product therefrom |
Country Status (6)
| Country | Link |
|---|---|
| US (1) | US4931551A (en) |
| JP (1) | JPH02124903A (en) |
| CA (1) | CA1307524C (en) |
| DE (1) | DE3922119A1 (en) |
| FR (1) | FR2634767B1 (en) |
| GB (1) | GB2220417A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107354800A (en) * | 2017-06-30 | 2017-11-17 | 华南理工大学 | A kind of method that the tissue substitute material with ECM structures is prepared based on paper process |
Families Citing this family (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5300494A (en) * | 1986-06-06 | 1994-04-05 | Union Carbide Chemicals & Plastics Technology Corporation | Delivery systems for quaternary and related compounds |
| US5308663A (en) * | 1989-06-20 | 1994-05-03 | Kanai Juyo Kogyo Company Limited | Biodegradable nonwoven fabric and its molding vessel |
| JP2579610B2 (en) * | 1990-09-28 | 1997-02-05 | 鳥取大学長 | In vivo filler |
| US5204452A (en) * | 1990-11-14 | 1993-04-20 | E. I. Du Pont De Nemours And Company | N-halochitosans, their preparation and uses |
| JPH074244B2 (en) * | 1991-06-25 | 1995-01-25 | 日本水産株式会社 | Microorganism-immobilized carrier and method for producing the same |
| JP3254013B2 (en) * | 1991-09-10 | 2002-02-04 | ジョンソン・アンド・ジョンソン・メディカル・インコーポレイテッド | Dressing material and its manufacturing method |
| CA2180826A1 (en) | 1994-01-13 | 1995-07-20 | Richard J. Ii Stoner | Organic disease control system |
| US6610229B1 (en) * | 2000-08-14 | 2003-08-26 | General Motors Corporation | Fiber preform process employing a porcelain enamel coated screen tool |
| EP1433380A1 (en) * | 2002-12-24 | 2004-06-30 | Inve Technologies N.V. | Process for decapsulating crustacean or rotifer eggs |
| CA2568665C (en) * | 2004-06-01 | 2009-10-06 | Pulp And Paper Research Institute Of Canada | Papermaking additive |
| US10214596B2 (en) | 2013-11-18 | 2019-02-26 | National Research Council Of Canada | Chitin nanocrystals and process for preparation thereof |
| CN115403682A (en) * | 2022-10-13 | 2022-11-29 | 浙江工业职业技术学院 | Preparation method of chitin |
Family Cites Families (21)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA515424A (en) * | 1955-08-09 | American Viscose Corporation | Oxidized regenerated cellulose compositions | |
| CA731639A (en) * | 1966-04-05 | Yasuda Yoshifumi | Method of manufacturing oxycellulose materials | |
| BE564287A (en) * | 1957-01-28 | |||
| US3903268A (en) * | 1968-02-12 | 1975-09-02 | Lescarden Ltd | Chitin and chitin derivatives for promoting wound healing |
| US3914413A (en) * | 1971-02-10 | 1975-10-21 | Leslie L Balassa | Process for facilitating wound healing with N-acetylated partially depolymerized chitin materials |
| US4056432A (en) * | 1971-07-06 | 1977-11-01 | Calgon Corporation | Process for making paper products of improved dry strength |
| US3847897A (en) * | 1971-09-07 | 1974-11-12 | Ralston Purina Co | Microcrystalline chitin |
| US4034121A (en) * | 1971-09-07 | 1977-07-05 | Ralston Purina Company | Foods with microcrystalline chitin |
| US3911098A (en) * | 1974-02-11 | 1975-10-07 | American Cyanamid Co | Medicament carrier |
| US4062921A (en) * | 1976-02-19 | 1977-12-13 | University Of Delaware | Solvents for and purification of chitin |
| US4286087A (en) * | 1979-09-21 | 1981-08-25 | University Of Delaware | Chitin powder and process for making it |
| JPS5716999A (en) * | 1980-06-17 | 1982-01-28 | Kogyo Gijutsuin | Production of regenerated chitin fiber paper |
| US4405324A (en) * | 1981-08-24 | 1983-09-20 | Morca, Inc. | Absorbent cellulosic structures |
| US4532321A (en) * | 1982-06-14 | 1985-07-30 | University Of Delaware | Microcrystalline chitin and method of manufacture |
| JPS5986640A (en) * | 1982-11-09 | 1984-05-18 | Daicel Chem Ind Ltd | Chitin suspension and production thereof |
| CA1248450A (en) * | 1984-04-05 | 1989-01-10 | Kazuo Kigasawa | Soft patch |
| DE3583263D1 (en) * | 1984-08-03 | 1991-07-25 | Unitika Ltd | SHAPED CHITINE ITEMS. |
| JPS61174227A (en) * | 1985-01-29 | 1986-08-05 | Kimitsu Kagaku Kenkyusho:Kk | Decoloration and deodorization of chitosan |
| JPS61240963A (en) * | 1985-04-18 | 1986-10-27 | ユニチカ株式会社 | Wound covering protective material |
| GB8527686D0 (en) * | 1985-11-09 | 1985-12-11 | Shirley Inst | Wound dressing |
| GB8607131D0 (en) * | 1986-03-21 | 1986-04-30 | Shirley Inst | Production of textile &c |
-
1988
- 1988-07-05 US US07/214,977 patent/US4931551A/en not_active Expired - Lifetime
-
1989
- 1989-04-06 CA CA000595862A patent/CA1307524C/en not_active Expired - Fee Related
- 1989-05-18 GB GB8911427A patent/GB2220417A/en not_active Withdrawn
- 1989-06-27 JP JP1162828A patent/JPH02124903A/en active Pending
- 1989-07-05 FR FR898909061A patent/FR2634767B1/en not_active Expired - Fee Related
- 1989-07-05 DE DE3922119A patent/DE3922119A1/en not_active Withdrawn
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107354800A (en) * | 2017-06-30 | 2017-11-17 | 华南理工大学 | A kind of method that the tissue substitute material with ECM structures is prepared based on paper process |
Also Published As
| Publication number | Publication date |
|---|---|
| DE3922119A1 (en) | 1990-03-08 |
| FR2634767B1 (en) | 1991-07-19 |
| JPH02124903A (en) | 1990-05-14 |
| GB8911427D0 (en) | 1989-07-05 |
| US4931551A (en) | 1990-06-05 |
| FR2634767A1 (en) | 1990-02-02 |
| GB2220417A (en) | 1990-01-10 |
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