JP2007002123A - Fine chitosan particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To economically provide fine chitosan particles useful as a material for compounding with one or more polymers or the like. <P>SOLUTION: Fine chitosan particles are characterized by being produced from a living thing without passing through a dissolution process and having a deacetylation degree of ≥60%, 1 mass% solution viscosity of 1.5 to 1,000 mPa s, and a ≤100 μm diameter particle content of ≥90%. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to chitosan fine particles, and particularly to chitosan fine particles useful for complexing with a polymer compound other than chitosan.

  Chitosan is a polysaccharide that is known to exist in nature, but is industrially produced by deacetylating chitin separated from crustaceans such as shrimp and crab. This chitosan is practically used as a biodegradable polymer compound or a plant activity regulator.

  Chitosan has been put into practical use in various fields as a functional polymer compound having functions such as film-forming properties, antibacterial properties, water retention and aggregating ability. Application as a safe function-imparting agent that can be used is progressing. For example, it is widely used as a coating material for imparting antibacterial and deodorizing properties to various films, nonwoven fabrics, and textile products. Currently, chitosan is used for so-called supplements, and 80 mesh pass (particle size: about 200 μm) powder is in circulation.

  Chitosan, like chitin, is a particularly difficult-to-grind substance among high molecular compounds, and with currently available dry grinders, the limit is that it can be ground to about 80 mesh passes distributed for supplements. It was extremely difficult to obtain chitosan fine particles having a particle diameter of 100 μm or less, which is suitable for complexing with a polymer compound.

As a compounding method aiming at imparting a function of chitosan, there is a compounding of chitosan particles with other polymer compounds. This complexing method is excellent in versatility because there is no restriction that chitosan must be once in solution. For example, a chitosan-polyethylene composite can be easily obtained by mixing chitosan particles in a low melting point polyethylene melt. In addition, chitosan particle-containing particles, fibers, membranes and the like can be obtained from a solution obtained by mixing chitosan particles in a polymer compound solution according to a conventional method.
JP-A-9-221502 JP 63-20302 A JP-A-55-133401

  The above-mentioned compounding method using chitosan particles is basically free from restrictions on the partner to be compounded and has a great advantage in terms of wide versatility, but it is sufficient between the compounded chitosan particle and the partner polymer compound. In many cases, there is no chemical bond, and it is simply combined by physical and electrical forces. For this reason, dropping off of chitosan particles existing on the surface of the composite material becomes a problem.

  In addition, in the chitosan particle-containing coating material, when chitosan powder of about 80 mesh pass distributed for supplements is used, the coating film surface becomes too uneven, and thus the coating surface is particularly desired to have an uneven surface. It can be used only for extremely limited purposes.

In addition, considering the applications that can enter the human body orally, for example, food applications are the most important uses of end products in chitosan particles, it is consistent from chitin-containing biomaterials to chitosan microparticles. Thus, it is preferable to produce chitosan fine particles without dissolving chitin or chitosan. Also, this is often more economical.
Accordingly, an object of the present invention is to economically provide chitosan fine particles useful as a composite material with other polymer compounds.

The above object is achieved by the present invention having the following constitution.
1. 90 degree particles having a degree of deacetylation of 60% or more and a 1% by mass solution viscosity of 1.5 mPa · s or more and 1,000 mPa · s or less and a particle size of 100 μm or less produced from the raw material organism without passing through the dissolution process are 90%. % Chitosan microparticles characterized by being above.
2. 2. The chitosan fine particles according to 1 above, wherein the particles having a particle size of 50 μm or less are 90% or more.
3. 2. The chitosan fine particles according to 1, wherein particles having a particle size of 50 μm or less are 90% or more and particles having a particle size of 1 μm or less are 10% or less.

4). 4. The chitosan fine particles according to any one of 1 to 3 obtained by pulverizing with a jet mill or a ball mill.
5. 5. The chitosan fine particles according to 4 above, wherein the raw material pulverized by a ball mill or a jet mill is chitosan powder pulverized by at least one pulverizer other than the ball mill or jet mill.
6). 6. The chitosan fine particles according to 4 or 5 above, wherein the pulverized raw material is chitosan having a 1% by mass solution viscosity of 1,000 mPa · s or less.

According to the present invention, chitosan fine particles useful as a composite material with other polymer compounds and the like can be economically provided.
That is, the present inventors have made various studies on the prevention of dropping off of the chitosan particles from the composite material and the smoothing of the coating film surface. Chitosan fine particles having a particle size of 100 μm or less and 90% or more are optimal for the purpose. In order to obtain chitosan having a particle size as described above without uniformly dissolving chitin or chitosan from chitin-containing biological raw materials to chitosan fine particles, a 1% by weight solution viscosity of chitosan before micronization is 1,000 mPa It has been found that it is preferably s or less, and it has been found that it is important that the degree of deacetylation of chitosan is 60% or more for maintaining the original function of chitosan.

Next, the present invention will be described in more detail with reference to preferred embodiments.
Currently, industrially produced chitin is made from shells such as crabs, shrimps and giant clams, or squid shells. The inventors of the present invention once chitin acid hydrolyzed with hydrochloric acid, sulfuric acid or the like to obtain chitin having a molecular weight lower than that of chitin present in these chitin-containing biomaterials. Method of oxidative decomposition with oxidizing agents such as hypochlorous acid; Method of acid hydrolysis with hydrochloric acid, sulfuric acid, etc .; Method of electron beam irradiation; Mechanical stress is applied by various grinding machines such as pin mill, hammer mill, ball mill, jet mill, etc. Among the chitins obtained by reducing the molecular weight by a single method or a combination of the above, and deacetylating them into chitosan, the 1% by mass solution viscosity is 1.5 mPa · s or more and 1,000 mPa · s. The following chitosan was found to be much more excellent in grindability than chitosan prior to molecular weight reduction, and the 1% by mass solution viscosity was 1.5 mPa · s to 500 It has been found that chitosan is less Pa · s is excellent like especially biodegradable and bioactive.

  This is achieved by applying a method similar to the above-described chitin molecular weight reduction method to the low molecular weight chitosan obtained from the chitin or the conventional relatively high molecular weight chitosan deacetylated from the chitin not subjected to the low molecular weight treatment. The same applies to chitosan having a molecular weight. Chitin and chitosan are both difficult-to-grind substances, so far it has been difficult to produce chitosan fine particles from chitin in the raw material to the target chitosan without going through the step of dissolving the chitin or chitosan.

  In particular, from chitin in the raw material to the target chitosan, chitosan fine particle dry powder in which particles having a particle size of 100 μm or less are 90% or more without passing through the step of dissolving the chitin or chitosan, among which particles having a particle size of 50 μm or less It was extremely difficult to produce chitosan fine particle dry powder of 50% or more.

  On the other hand, a powder obtained by reducing the molecular weight by the above method was used as a pulverized raw material, and a ball mill or jet mill was used to obtain a chitosan fine particle dry powder having a particle size of 50 μm or less of 90% or more. Furthermore, in the jet mill, an extremely fine chitosan dry powder having an average particle size of 3.6 μm, a particle size of 10 μm or less and 100%, and a particle size of 1 μm or less within 5% could be obtained. The 1% by mass solution viscosity of this chitosan was 3 mPa · s. Moreover, when the chitosan solution after measuring the viscosity was cast into a glass plate and dried, a film serving as one index of the polymer compound was obtained. The obtained chitosan fine particles were clearly superior to conventional chitosan particles in terms of deodorization rate and ability as a deodorizer.

  In impact type pulverizers such as hammer mills and pin mills other than jet mills and ball mills, it has not been possible to efficiently obtain fine particulate chitin dry powders having a particle size of 50 μm or less of 90% or more. If the chitosan powder contains 10% or more particles having a particle size of 100 μm or more, when a complex with another polymer compound is formed, the surface lacks smoothness and the commercial value is lowered. Further, it is not economical to grind the particles having a particle size of 1 μm to 5% or more.

  Chitin is a polysaccharide widely distributed in nature, such as crustacean shells such as crabs and shrimps, microbial cell walls, mushrooms, and any chitin in chitin-containing organisms can be the subject of the present invention. Actually, shells such as crabs, shrimps, mantis, or squid shells are used as raw materials for reasons such as ease of harvesting, and these are also used in the present invention. In addition, any of chitin isolated by a conventionally known method using EDTA, a method using a proteolytic enzyme, a Hackman method, or an improved method thereof can be used. The isolation purity of chitin is not necessarily 100%, and it may be a protein or an inorganic substance that coexists with chitin in a chitin-containing organism depending on the purpose. In some cases, chitin is not isolated from these chitin-containing organisms, but can be processed as it is to obtain chitin-containing fine particles.

  In the present invention, chitin is deacetylated to chitosan. In this case, the degree of deacetylation is preferably 60% or more. Needless to say, when chitosan is used as a deodorant, the amount of amino groups in chitosan is better, and deacetylated products having a degree of deacetylation of 60% or less are not easily dissolved in dilute aqueous acetic acid. , No longer represent the characteristics of chitosan.

  In the present invention, when chitosan obtained by deacetylating chitin is not reduced in molecular weight or insufficient in molecular weight reduction, it is difficult to pulverize the obtained chitosan into fine particles.

  Usually, deacetylation occurs when chitin is immersed in an aqueous sodium hydroxide solution. In order to efficiently produce chitosan having a degree of deacetylation of 60% or more, chitin is immersed in an aqueous solution of sodium hydroxide of about 40% by mass or more and stirred at room temperature or more.

  As a specific example, a 42% by mass aqueous sodium hydroxide solution is prepared using ion-exchanged water having an electric conductivity of 1 μS or less and reagent-grade sodium hydroxide. 500 g of this 42 mass% sodium hydroxide aqueous solution is put into a 500 ml four-neck separable glass flask, and a four-necked stirring rod with a glass bowl-shaped blade, a thermometer, a nitrogen introduction tube (the tip of the introduction tube is the solution in the flask) And set the condenser so that it is immersed in the liquid at least 1/3 or more from the surface, and heat to 100 ° C. with stirring at 100 to 150 revolutions / minute under a nitrogen stream at a flow rate of about 2 L / min. Hold at 100-105 ° C for -20 minutes and then cool to 20 ° C. While nitrogen was constantly flowing, 20 g of chitin was added and the mixture was stirred for 1 hour at 100 to 150 rpm at 20 ° C. in a nitrogen stream at a flow rate of about 2 L / min, and then heated to 60 ° C. over about 1 hour. And stirred at a temperature of 60 to 65 ° C. for 16 hours. Thereafter, the content (chitosan) and the aqueous sodium hydroxide solution are promptly filtered, and the filtered chitosan is added to 1 L of ion-exchanged water at 10 to 15 ° C. and stirred for 10 minutes, and then the chitosan is filtered off. This operation is repeated 15 times. Thereafter, it can be dried in a vacuum dryer at 50 ° C. under reduced pressure for 16 hours to obtain dry chitosan having a water content of 10% or less.

  When measuring the solution viscosity of chitosan, the chitosan is dried at 105 ° C. for 24 hours in order to correct the amount of evaporation of chitosan used, the loss on drying (A mass%) is obtained, and the evaporation residue “(100−A )% ". Since the solution viscosity has a measurable viscosity range, the concentration of the measurement solution is two types in order to cope with one viscometer. The measurement of the low molecular weight chitosan was carried out using a chitosan evaporation residue “(100-A)%” concentration of 1 mass% and an acetic acid concentration of 1 mass%. In the case of relatively high molecular weight chitosan, the chitosan evaporation residue “(100-A )% ”Concentration 0.5% by mass and acetic acid concentration 0.5% by mass.

  More specifically, about 150 g of ion-exchanged water having an electric conductivity of 1 μS or less is taken into a 200 ml glass beaker and set to 20 ° C. Into this, 2.0 g (1% by weight solution) or 1.0 g (0.5% by weight solution) of dry chitosan obtained as described above is added, and the resin has a length of about 50 mm and a thickness of about 8 mm. Stir with a coated rotor at 20-22 ° C. for about 1 minute at low speed. Next, 2.0 g of reagent grade acetic acid (1% by mass solution) or 1.0 g (0.5% by mass solution) is added, and ion-exchanged water having an electric conductivity of 1 μS or less is further added. After adjusting so that it may become 200.0g, it stirs at 20-22 degreeC. After the top of the beaker is covered with wraps or the like, the rotation speed is adjusted so that the center of the liquid surface is recessed by about 1 to 2 mm as the solution viscosity increases, and stirring is continued at a temperature of 20 to 22 ° C. for 3 hours. Then, stirring is stopped and the mixture is allowed to stand at a temperature of 20 to 22 ° C. for 10 hours. Then, after adjusting the number of rotations so that the center of the liquid surface is recessed by about 1 to 2 mm at a temperature of 20 to 22 ° C. and stirring for 1 hour, a rotational viscometer (Toki Sangyo Co., Ltd. TV-10M Viscosity is measured with a mold). When the solution viscosity is 2 to 20 mP · s, the rotor number 19 is the rotor. When the solution viscosity is 20 to 200 mP · s, the rotor number 20 is the rotor. When the viscosity is 100 to 1,000 mP · s, the rotor with the rotor number 21 is used. When the solution viscosity is 400 to 4,000 mP · s, the rotor with the rotor number 22 is used.

The degree of deacetylation of chitosan is measured by the following colloid titration method.
1. 1. Chitosan evaporation residue 1) Accurately measure 1.5 g of sample in a constant weighing bottle and record the mass A (g).
2) With the lid of the weighing bottle removed, place in a 105 ° C. blower dryer and heat for 1.5 hours.
3) After covering the weighing bottle in the blower dryer, take it out in a silica gel desiccator and let it cool.
4) Measure the mass and calculate the evaporation residue according to the following calculation formula [1].
Evaporation residue of chitosan (%) = {mass (g) after heating and cooling (sample) mass (g) −constant weight of weighing bottle tare (g)} ÷ sample mass A (g) × 100... [1]

2. Preparation of chitosan / acetic acid aqueous solution 1) Accurately measure 1.00 g in terms of evaporation residue of 1) above in a 200 ml glass beaker.
2) Add 198.0 g of water and stir and disperse with a magnetic stirrer.
3) Measure 1 ml of acetic acid with a measuring pipette and drop it into the dispersion.
4) Cover the beaker with polywrap (registered trademark), stop stirring at 20-25 ° C for about 4 hours, and after sufficient stirring, leave it in the room at 20-25 ° C overnight (about 16 hours). .
5) After standing still, it is sufficiently stirred again at 20-25 ° C. for about 2 hours.

3. Colloid titration 1) Into a 200 ml glass beaker, accurately measure 20.00 g of the aqueous solution dissolved in 1) above, add 180.0 g of water, cover with polywrap, and stir with a magnetic stirrer for 1 hour.
2) After stirring, accurately measure 10.00 g of the solution in a 200 ml conical beaker, add 50 ml of water and 2-3 drops of 0.1% toluidine blue aqueous solution and mix.
3) Colloidal titration with colloid titration reagent N / 400 aqueous polyvinyl potassium sulfate. The end point is the point at which the color of the aqueous solution changes from blue to reddish purple.

4). Calculation method of degree of deacetylation The degree of deacetylation of chitosan is calculated according to the following formula [2].
Deacetylation degree (%) = (free amino group) ÷ {(free amino group) + (bonded amino group)} × 100 (2)
= (X / 161) ÷ {(X / 161) + (Y / 203)} × 100
Where X = free amino group mass in chitosan = 1/400 × 1/1000 × F × 161 × (V−B), Y = bonded amino group mass in chitosan = 0.5 × 1 / 100-X
161: Equivalent molecular weight of glucosamine residue 203: Equivalent molecular weight of N-acetylglucosamine residue F: Factor of N / 400 aqueous potassium potassium sulfate solution V: Titration value in sample of aqueous N / 400 aqueous potassium potassium sulfate solution (ml)
B: Titration value in the blank test of N / 400 potassium polyvinyl sulfate aqueous solution (ml)

"reagent"
(1) Acetic acid: reagent special grade (2) N / 400 potassium polyvinyl sulfate aqueous solution: Wako Pure Chemicals Lot. YPG8290 F = 1.01 Purchased on November 16, 2004 (A new type of N / 400 aqueous potassium potassium sulfate solution was released in 2004. Here, it is assumed that an improved new type is used.)
(3) Toluidine blue indicator solution: Wako Pure Chemicals Lot. YLK9939

The particle size of the chitosan fine particles is measured by the following method.
The particle size distribution is measured using a laser diffraction / scattering particle size distribution measuring apparatus [LA-300 manufactured by Horiba, Ltd. (laser light wavelength: 650 nm)], and 30 to 50 mg of chitosan fine particles are mixed with 100 ml of reagent-grade grade methanol. After mixing and dispersing in an ultrasonic bath (output 300 W, frequency 40 kHz) for 1 minute, the sample was set in a batch cell and the sample concentration was adjusted so that the transmittance was in the range of 70 to 95%. As measurement conditions, the number of data acquisition was 10 times, the number of repetitions was 30, the refractive index was 1.50-0.00i, and the particle size distribution was calculated based on volume.

  In a preferred embodiment of the present invention, chitin is first reduced in molecular weight with a protonic acid such as hydrochloric acid or sulfuric acid. It is advantageous to reduce the molecular weight at the same time in the decalcification step with hydrochloric acid during the isolation of chitin. For example, 1 part by mass of crab shell is dispersed in 30 parts by mass of water, 1 part by mass or more of hydrochloric acid is added thereto, and the mixture is stirred at 20 ° C. or higher, preferably 30 ° C. or higher for 5 hours or longer. As a result, chitin having a low molecular weight of 0.5% by mass when the chitin obtained is chitosan-converted to a viscosity of 700 mPa · s or less can be obtained.

  Oxidative decomposition of chitin with oxidizing agents such as hydrogen peroxide and hypochlorous acid; Acid hydrolyzing with hydrochloric acid, sulfuric acid, etc .; Electron beam irradiation method; Various pulverizations such as pin mill, hammer mill, ball mill, jet mill, etc. The molecular weight is reduced by a method of applying mechanical stress with a machine. Any of the above methods can be used basically, but each has advantages and disadvantages, and since the final target product is chitosan fine particles, it may be used alone, but the above methods may be combined according to the purpose to reduce the molecular weight. It is preferable to implement. However, pulverization to particles having the final target particle size at the chitin stage is not preferable because filtration during subsequent deacetylation becomes difficult and loss increases. Considering the deacetylation in this way, it is preferable to keep the pulverization to about 90% through a sieve having an opening of about 1 mm. This chitin is deacetylated into chitosan, and this chitosan is necessary. Accordingly, the molecular weight may be lowered by applying the same method as in the case of chitin.

  For the reduction of the molecular weight of chitin or chitosan, for example, the electron beam irradiation method is the simplest to operate, and the combination of this with a pulverizer is effective, but the restriction that electron beam irradiated products cannot be used for food applications. There is. On the other hand, since chemical decomposition of chitin or chitosan is usually a reaction in water, in order to reduce the molecular weight by this method, it is necessary to dry the obtained decomposition product before pulverization. From this point of view, the molecular weight reduction after the deacetylation is particularly effective by a method using a pulverizer, particularly a chitosan fine particle dry powder in which particles having a particle size of 100 μm or less are 90% or more, of which the particle size is 50 μm or less. In order to obtain a chitosan fine particle dry powder having particles of 50% or more, a jet mill or a ball mill is effective, but the chitin-containing raw material organism not reduced in molecular weight is used as it is or 0.5% by mass when chitosan is used. When chitin or chitosan having a solution viscosity of 700 mPa · s or more and not having a low molecular weight is used, the desired particle size cannot be obtained by a pulverizer alone. Therefore, before grinding with a jet mill or a ball mill, the ability to lower the molecular weight of impact- or shear-stressed chitin or chitosan, such as hammer mills other than jet mills, pin mills, ball mills, vibration mills, planetary motion mills, etc. It is desirable to reduce the molecular weight with a pulverizer.

  The molecular weight reduction and pulverization conditions may be appropriately selected according to the desired particle size, molecular weight, degree of deacetylation, and combination of the desired chitosan fine particle dry powder. The obtained chitosan fine particle dry powder may contain moisture, and does not need to be re-dried in particular. However, the water content after pulverization is 10% by mass or more and the moisture needs to be less than that. In some cases, it may be dried after pulverization.

Next, the present invention will be described more specifically with reference to examples and comparative examples. “Part” or “%” other than the degree of deacetylation and particle size is based on mass.
Example 1
1 part of the coarse crab shell that has passed through a sieve with a mesh opening of 4 mm is dispersed in 30 parts of water, and 1 part or more of hydrochloric acid is added thereto, and the mixture is stirred at 20 ° C. or more, preferably 30 ° C. or more and 5 hours or more. . Thereafter, the decalcified crab shell is filtered off, redispersed in 30 parts of water, and then filtered off. After repeating this operation 10 times, redispersed in 30 parts of water, added 3 parts of sodium hydroxide, heated and stirred to 70 ° C. for 3 hours, filtered off chitin, and redispersed in 30 parts of water. And then filter. This operation was repeated 10 times and then dried with hot air at 50 ° C. for 20 hours to obtain raw material chitin. When this chitin was used as chitosan and a solution viscosity of 0.5% was measured, it was 500 mPa · s.

  100 parts of this chitin was dispersed in 2,000 parts of water, 2.5 parts of sodium carbonate was added, 0.15 part of sodium bromite was added, and the mixture was stirred at room temperature for 6 hours. The chitin is filtered off, redispersed in 30 parts of water and then filtered off. This operation was repeated 5 times and then dried with hot air at 50 ° C. for 20 hours to obtain chitin. This chitin was deacetylated to chitosan and a solution viscosity of 1.0% was measured and found to be 480 mPa · s. This chitosan was pulverized with a hammer mill and passed through a sieve having an opening of 400 μm. When 1.0% solution viscosity of this chitosan was measured, it was 120 mPa · s.

  Further, this chitosan was pulverized with a ball mill for 48 hours to obtain chitosan fine particles (A-1). When the particle size distribution of the chitosan fine particles was measured, the center of the particle size distribution was 10 μm, and the fine particles of 100 μm or less were 90% or more. When 1.0% solution viscosity of this chitosan was measured, it was 8 mPa · s.

  Furthermore, this chitosan was pulverized with a jet mill to obtain chitosan fine particles (B-1). The center of the particle size distribution of the chitosan fine particles was 4.5 μm, and the fine particles of 10 μm or less were 100%. It was 4 mPa * s when the solution viscosity of 1.0% of this chitosan was measured.

  Further, this chitosan was pulverized with a jet mill to obtain chitosan fine particles (B′-1). The center of the particle size distribution of the chitosan fine particles was 3.2 μm, 10 μm or less was 100%, and 1 to 10 μm was 99%. It was 2 mPa * s when the solution viscosity of 1.0% of this chitosan was measured. The degree of deacetylation of this product was 87%.

Example 2
The raw material chitin of Example 1 was deacetylated to obtain chitosan having a deacetylation degree of 66%. This was coarsely crushed with a pin mill and then crushed with a planetary motion mill to obtain chitosan particles passing through a sieve having an opening of 200 μm. This was divided into two and one was pulverized with a ball mill to obtain chitosan fine particles (A-2). The center of the particle size distribution of the chitosan fine particles was 32 μm, and particles with 100 μm or less being 90% or more were obtained. When 1.0% solution viscosity of this chitosan was measured, it was 340 mPa · s.

  The other chitosan was pulverized with a jet mill to obtain chitosan fine particles (B-2). The center of the particle size distribution of the chitosan fine particles was 5.8 μm, 10 μm or less was 75%, and 100 μm or less was 90% or more. When 1.0% solution viscosity of this chitosan was measured, it was 9 mPa · s. The degree of deacetylation of this product was 66%.

Comparative Example 1
One part of the coarsely crushed crab shell that has been passed through a sieve having a mesh size of 4 mm is dispersed in 30 parts of ice water, and further cooled with ice from the outside. To this, 0.8 part of hydrochloric acid was added dropwise little by little with stirring so that the internal temperature would not exceed 3 ° C. After completion of dropping, the mixture is stirred for 5 hours or more at an internal temperature of 3 ° C or lower. Thereafter, the decalcified crab shell is filtered off, redispersed in 30 parts of water, and then filtered off. After repeating this operation 10 times, re-dispersed in 30 parts of water under a nitrogen stream, added 3 parts of sodium hydroxide, heated and stirred to 40 ° C. for 3 hours, filtered off chitin, and in 30 parts of water. After redispersion, filter off.

  The above operation was repeated 10 times and then dried at 40 ° C. under reduced pressure for 20 hours to obtain chitin. The chitin was deacetylated to obtain chitosan having a degree of deacetylation of 72%, and a solution viscosity of 0.5% was measured and found to be 2500 mPa · s. This was frozen and ground to obtain chitosan particles passing through a sieve having an opening of 300 μm. When a 1.0% solution viscosity of this chitosan was measured, it was 1,340 mPa · s. This was crushed with a jet mill, but overloaded and the machine stopped. Microscopic observation of the slightly pulverized material showed that particles with a particle size of 50 μm were also observed, but there were many fibrous particles with a particle size of 200 to 300 μm, and chitosan fine particles with the desired particle size were not obtained.

Example 3
100 parts of the frozen pulverized product of Comparative Example 1 was dispersed in 2,000 parts of water, 10 parts of hydrogen peroxide was added, and the mixture was oxidatively decomposed at 60 ° C. for 5 hours with stirring. Chitosan is filtered off, redispersed in 30 parts of water and then filtered off. This operation was repeated twice and then dried at 40 ° C. under reduced pressure for 20 hours to obtain chitosan. When 1.0% solution viscosity of this chitosan was measured, it was 54 mPa · s.

  This was divided into two, and one was pulverized with a ball mill to obtain chitosan fine particles (A-3). The center of the particle size distribution of the chitosan fine particles was 25 μm, and 100 μm or less was 90% or more. It was 16 mPa * s when the solution viscosity of 1.0% of this chitosan was measured.

The other chitosan was deacetylated again to a degree of deacetylation of 99% and then pulverized by a jet mill to obtain chitosan fine particles (B-3). The center of the particle size distribution of the chitosan fine particles was 4.8 μm, 10 μm or less was 75%, and 100 μm or less was 90% or more. When 1.0% solution viscosity of this chitosan was measured, it was 5 mPa · s.

Table 1 below summarizes the particle size, viscosity, and degree of deacetylation of the chitosan after pulverization in the above Examples and Comparative Examples.

Example of use Using the chitosan particles of B'-1, chitosan particles of A-2, and chitosan particles of Comparative Example 1, 1% by mass of each was added to polyethylene pellets having a melting point of 140 ° C., powder blended, and then injected. An injection plate having an internal temperature of 160 ° C. and a residence time of 30 seconds was prepared as an 80 mm × 50 mm, 1 mm thick injection plate. The injection plate prepared from the B'-1 chitosan particles was visually surface-homogeneous and smooth when touched with a finger, and no detachment due to friction was observed. The injection plate made from the A-2 chitosan particles was visually surface-homogeneous and felt slightly uneven when touched with a finger, but it was almost insignificant, smooth as a whole, and no drop by friction was observed. . In contrast, chitosan particles were clearly observed on the injection plate produced using the chitosan particles of Comparative Example 1, and the presence of the particles was also confirmed by palpation. When the part was rubbed strongly, the particles dropped out.

  According to the present invention as described above, chitosan fine particles useful as a composite material with other polymer compounds and the like can be economically provided.

Claims (6)

  90 degree particles having a degree of deacetylation of 60% or more and a 1% by mass solution viscosity of 1.5 mPa · s or more and 1,000 mPa · s or less and a particle size of 100 μm or less produced from the raw material organism without passing through the dissolution process are 90%. % Chitosan microparticles characterized by being above.   The chitosan fine particles according to claim 1, wherein particles having a particle size of 50 μm or less are 90% or more.   The chitosan fine particles according to claim 1, wherein particles having a particle size of 50 µm or less are 90% or more and particles having a particle size of 1 µm or less are 10% or less.   The chitosan fine particle according to any one of claims 1 to 3, obtained by pulverizing with a jet mill or a ball mill.   The chitosan fine particles according to claim 4, wherein the raw material pulverized by a ball mill or a jet mill is chitosan powder pulverized by at least one pulverizer other than the ball mill or jet mill.   The chitosan fine particles according to claim 4 or 5, wherein the pulverized raw material is chitosan having a 1% by mass solution viscosity of 1,000 mPa · s or less.