Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J3/00—Processes of treating or compounding macromolecular substances
  • C08J3/12—Powdering or granulating
  • C08J3/14—Powdering or granulating by precipitation from solutions
• • A—HUMAN NECESSITIES
  • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
  • A01N—PRESERVATION OF BODIES OF HUMANS OR ANIMALS OR PLANTS OR PARTS THEREOF; BIOCIDES, e.g. AS DISINFECTANTS, AS PESTICIDES OR AS HERBICIDES; PEST REPELLANTS OR ATTRACTANTS; PLANT GROWTH REGULATORS
  • A01N43/00—Biocides, pest repellants or attractants, or plant growth regulators containing heterocyclic compounds
  • A01N43/02—Biocides, pest repellants or attractants, or plant growth regulators containing heterocyclic compounds having rings with one or more oxygen or sulfur atoms as the only ring hetero atoms
  • A01N43/04—Biocides, pest repellants or attractants, or plant growth regulators containing heterocyclic compounds having rings with one or more oxygen or sulfur atoms as the only ring hetero atoms with one hetero atom
  • A01N43/14—Biocides, pest repellants or attractants, or plant growth regulators containing heterocyclic compounds having rings with one or more oxygen or sulfur atoms as the only ring hetero atoms with one hetero atom six-membered rings
  • A01N43/16—Biocides, pest repellants or attractants, or plant growth regulators containing heterocyclic compounds having rings with one or more oxygen or sulfur atoms as the only ring hetero atoms with one hetero atom six-membered rings with oxygen as the ring hetero atom
• • 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
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L5/00—Compositions of polysaccharides or of their derivatives not provided for in groups C08L1/00 or C08L3/00
  • C08L5/08—Chitin; Chondroitin sulfate; Hyaluronic acid; Derivatives thereof
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2305/00—Characterised by the use of polysaccharides or of their derivatives not provided for in groups C08J2301/00 or C08J2303/00
  • C08J2305/08—Chitin; Chondroitin sulfate; Hyaluronic acid; Derivatives thereof

Definitions

• the present invention relates to a process for preparing particles of chitosan.
• Chitosan particles in this form which are prepared according to the process herein are "activated" in the sense that they are especially useful for providing plant care benefits.
• Chitosan is a modified carbohydrate polymer derived from the chitin component of the shells of crustaceans such as crabs, shrimp and cuttlefish. Chitosan is used for a wide variety of purposes including plant care, cosmetics additives, food and nutrition supplements and medical care uses.
• the procedure is a batch process which requires at least 12 - 24 hours for a production cycle.
• the single batches of the product are lacking homogeneity.
• the product has a distinct tendency toward degradation and its sorption capacity is rather poor resulting from the relatively low degree of development of the inner surface of the chitosan particles.
• Polish Patent No. 164,247 and Finnish Patent No. 83,426 both disclose a continuous method for producing microcrystallme chitosan.
• a solution of chitosan in aqueous acids and/or their salts is introduced to a reactor along with an aqueous solution of alkali metal hydroxides or salts.
• this alkaline suspension of the formed microcrystallme chitosan particles is continuously removed from the reactor.
• the alkaline solution may also be introduced directly to a recirculation system.
• This method has several drawbacks including a yield below 90%, and realization of chitosan agglomerates with an average particle size above 1 ⁇ m and water retention value below 5000%.
• the water retention value is an indication of the development of the inner surface.
• it is not possible to control the molecular, supermolecular and morphological structure of the chitosan particles produced.
• This continuous process also causes a substantial decrease of the average molecular weight of the generated microcrystallme chitosan as result of intensive degradation effects.
• the present invention provides a process for preparing particles of "microcrystallme” chitosan in the form of an aqueous suspension of such particles.
• the chitosan particles in the suspension are "activated” in the sense that the chitosan material in this form is especially useful for a number of purposes including in particular the provision of a variety of plant care benefits.
• an aqueous solution is formed, generally containing at least 0.001% and preferably from 0.01% to 10.0% by weight of chitosan which can be provided by any conventional chitosan source.
• This solution contains organic or inorganic acids and/or salts of such acids in an amount sufficient to maintain the solution at a pH which is low enough to completely solubilize the chitosan.
• the aqueous solution of the first step is partially neutralized by adding a neutralizing agent while subjecting the solution to shear agitation. The neutralizing agent addition and the agitation are sufficient to convert the solution into a continuous gel phase having a pH of from 5.0 to 6.9
• the partially neutralized gel formed in the previous step is maintained under shear agitation for at least 10 seconds after the gel phase has been formed in order to homogenize the gel phase.
• This agitated homogenized gel is then further neutralized under continuing agitation by addition of more neutralizing agent sufficient to raise the pH within the homogenized gel phase to above 6.9, preferably above 7.3. Agitation is preferably continued for at least another 10 seconds after this elevated pH is reached. This then forms a gel-like suspension of discrete particles of activated microcrystalline chitosan having desirable properties.
• the aqueous solution formed in the initial step can be filtered prior to neutralization to remove insoluble matter such as may have been introduced with the chitosan source.
• the chitosan particles of the eventually formed gel-like suspension may be washed, e.g., with water, to remove such materials such water soluble salts.
• the chitosan particles produced by the process of this invention are characterized by having an average particle size of from 2 to 20 ⁇ m.
• Preferably also such particles further have a water solubility of at least 90% at pH 6 after 24 hours.
• an aqueous solution of chitosan is formed.
• This can be accomplished by combining chitosan with an aqueous solution containing organic or inorganic acids or their salts.
• Such acids can include, for example, acetic acid, lactic acid, salicylic acid, hydrochloric acid, and the like.
• Sufficient acid or salt thereof must be utilized to maintain this solution at a pH wherein the chitosan is essentially completely dissolved, i.e., solubilized. Agitation sufficient to facilitate chitosan dissolution may be utilized.
• chitosan Any conventional source of chitosan may be utilized to form the chitosan solution.
• Such chitosan sources may be those derived from shellfish or may be fungally derived.
• Commercially available chitosan sources are marketed, for example, under the tradenames "Chitosan” by Nanson, Inc. of Redmond, Washington , USA and “Chitoclear” by Primex Ingredients SA of Avaldsnes, Norway.
• the chitosan is utilized to an extent which is sufficient to form a concentration of chitosan in the aqueous solution of at least 0.001% by weight. More preferably, the solution will contain from 0.01% to 10.0% by weight, most preferably from 0.01% to 1.5% by weight.
• such a solution may optionally be filtered before further processing in order to remove therefrom any insoluble material which might remain therein.
• insoluble material for example, may have been introduced into the solution from the chitosan source.
• the chitosan solution formed in the first essential process step is partially neutralized. This is accomplished by adding a neutralizing agent to the solution while maintaining the solution under shear agitation.
• Neutralization agents which can be used in this step include hydroxides such as sodium, potassium and ammonium hydroxides and their salts.
• these neutralization agents are combined with the first step chitosan solution in the form of aqueous solutions having a neutralizing agent concentration of from 0.01% to 20% by weight.
• Partial neutralization in this second essential process step is effected while the combined chitosan/neutralizing agent solution is maintained under shear agitation.
• Both the addition of the neutralizing agent and the shear agitation should be sufficiently carried out in order to convert the solution into a continuous gel phase having a pH within the range of from 5.0 to 6.9.
• shear agitation to the extent of from 10 to 1000 sec "1 (rpm) can be used.
• the gel phase is next subjected to continued shear agitation in order to homogenize this gel phase.
• continued shear agitation is carried out for a period of at least 10 seconds and preferably for a period of from 1 to 60 minutes.
• shear agitation utilized at this point is applied to the extent of from 100 to 5000 sec "1 .
• the homogenized gel phase from the previous step is further neutralized while still being subjected to shear agitation.
• neutralizing agent is added to the extent needed to raise the pH within the gel to above 6.9, and preferably to within the range of 7.1 to 7.5, e.g., above 7.3. This generally occurs under shear agitation of from 10 to lOOOsec "1 .
• high shear agitation 100 to 5000 sec "1 ) can be used to homogenize the suspension.
• the same type and form of neutralizing agents as specified above for the partial neutralization step can be utilized in this further neutralization step.
• the neutralizing agent used in this further neutralization step does not have to be identical to the neutralizing agent used in the partial neutralization step.
• This further neutralization step produces a gel-like suspension of discrete particles of chitosan.
• this suspension of particles at this point can be washed, e.g., with water, to remove therefrom any residual soluble salt impurities.
• the chitosan particles in the suspension may also be concentrated, recovered and/or dried in conventional manner.
• the process of this invention may be carried out in either a batch-wise or continuous format.
• the sol form of the chitosan salt is transformed into gel.
• nucleation points appear for the agglomerates of chitosan.
• An agglomerate structure emerges and a physical-chemical modification of the initial gel form proceeds.
• the final agglomerate structure of the chitosan particles forms.
• the stabilization of the agglomerates of the physical/chemical modified chitosan particles proceeds in the final step of the process.
• a controlled structure of the product is formed with respect to the molecular, supermolecular and morphological characteristics of the resulting material.
• the chitosan particles produced by this invention are characterized herein as "microcrystalline” even though their degree of crystallinity is very low, and, in fact is much lower than the degree of crystallinity of commercial chitosan products which have a significant crystalline content. Perhaps more accurately, the particles herein can be characterized as "activated” given their utility in a number of contexts as described hereinafter.
• the chitosan material of the particles which are produced has a modified specific molecular structure having specific molecular weight and degree of polydispersity. It also has a supermolecular structure having certain morphological characteristics which provide relatively high porosity and relatively high ability to retain water in a capillary system.
• the modified chitosan can be prepared according to this invention with a yield of over 90%, usually 95-99.5%.
• the material is highly homogenous and well reproducible. It has average molecular weight which is close to that of the initial chitosan with lowered molecular polydispersity.
• the material also has a Water Retention Value (WRV) which is generally much higher than that for the starting chitosan. WRV will, in fact generally exceed 1000% and can even exceed 5000%, a value not attainable via previously known methods.
• WRV Water Retention Value
• the process of the instant invention permits realization of activated chitosan with a modified structure, in the form of a gel-like suspension, paste or powder.
• the gel-like form is stable with attainable agglomerate sizes below l ⁇ m.
• the average particle size of the chitosan particles in suspension will range from 2 to 20 ⁇ m.
• these particles will have a water solubility of at least 90%, preferably 95%, at pH 6 after 24 hours.
• the modified chitosan prepared according to the present invention can be applied in agriculture, medicine, pharmacy, veterinary medicine, chemical industry, health and beauty care products and environment protection.
• the activated chitosan produced by this invention is particularly useful in the area of plant care.
• a aqueous solution of sodium hydroxide With continual agitation at 60 rpm, a 0.25% aqueous solution of sodium hydroxide is introduced continuously through a metering pump to achieve pH 5.0 to 6.9 at which pH the chitosan salt is transformed from sol to gel with partial forming of the "microcrystalline" form.
• the product obtained is purified as in Example I.
• the chitosan produced is in the form of a white gel-like suspension with the following properties for the two trials as shown in Table 2:
• a set of equipment consisting of a reactor equipped with agitator, metering pumps and a recirculation assembly with pump and an outlet for the intermediate product connected to a second reactor is used in this Example.
• 1000 parts by wt of an aqueous solution containing 1.5% aqueous lactic acid and 1% chitosan with properties as in Example IV are introduced.
• a 1.5 % solution of chitosan in lactic acid is continuously introduced with the rate of 1200 wt parts per hour.
• a 0.75% NaOH solution is also introduced at a rate of 585 wt parts per hour which allows the pH to be kept at 6.7-6.9.
• the gel which is produced is directed to the second reactor.
• the mixture in the second reactor is homogenized at 4000 ⁇ m.
• the average retention time in the reactor is 30 minutes.
• the product obtained from the second reactor is purified as in Example I.
• the resulting chitosan in the form of a white gel-like suspension is obtained with an output of

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• Organic Chemistry (AREA)
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• Molecular Biology (AREA)
• Biochemistry (AREA)
• Agronomy & Crop Science (AREA)
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• Wood Science & Technology (AREA)
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• Polysaccharides And Polysaccharide Derivatives (AREA)
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• 2000
  • 2000-05-12 PL PL34013200A patent/PL340132A1/xx not_active Application Discontinuation
• 2001
  • 2001-05-10 WO PCT/US2001/015182 patent/WO2001087988A1/en not_active Application Discontinuation
  • 2001-05-10 CA CA002407584A patent/CA2407584A1/en not_active Abandoned
  • 2001-05-10 EP EP01937295A patent/EP1280829A1/de not_active Withdrawn
  • 2001-05-10 AU AU2001263046A patent/AU2001263046A1/en not_active Abandoned
  • 2001-05-10 JP JP2001585205A patent/JP2004501235A/ja not_active Withdrawn

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