JPWO2015105030A1 - Method for producing cellulose - Google Patents

Abstract

A method for producing cellulose having a degree of polymerization of 350 or less, comprising at least the following steps using a chemical pulp as a raw material, wherein the alkali extraction step is performed at 0 to 65 ° C. (A) Process of treating chemical pulp with aqueous solution containing sulfuric acid, hydrogen peroxide and monopersulfuric acid (b) Alkali extraction process

Description

  The present invention relates to a method for producing cellulose having a polymerization degree of 350 or less.

  Cellulose is used in various applications such as foods, pharmaceuticals, and industrial applications.

  Addition of cellulose to foods provides a thickening and dispersing effect, thereby improving the texture. Further, the water absorbency and oil absorbency are effective for improving the texture of fried foods.

  In pharmaceuticals, it is used as an excipient for the purpose of molding, increasing the amount, and diluting in solid preparations such as tablets, powders (powder) and granules.

  In addition, it is widely used as a filter aid that is added to a slurry to improve filterability. Furthermore, cellulose may be added to improve the welding workability of the coated arc welding rod or to provide excellent mechanical properties. Cellulose is sometimes used as a base material for automobile friction materials as an alternative to asbestos.

  Patent Document 1 discloses a method for producing a cellulose product having a level-off polymerization degree by hydrolyzing refined wood pulp or the like with mineral acid, ferric chloride or the like. The whiteness of the obtained cellulose is disclosed. There is no description about.

  Pulp is a polymer having a polymerization degree exceeding 1500 (viscosity average molecular weight 200,000), whereas cellulose is preferred to have a polymerization degree of 350 (viscosity average molecular weight 57,000) or less, and 300 (viscosity average molecular weight 40,000). 8,000) or less is particularly preferred. When trying to synthesize cellulose by degrading this pulp with hydrochloric acid or sulfuric acid, using a concentrated or low-dilution solution to shorten the reaction time may cause coloration and decrease whiteness. Many.

  In order to avoid this coloring, a method using high-purity dissolving pulp or cotton litter as a raw material is known (Non-Patent Document 1).

  Patent Document 2 discloses a method for producing microcrystalline cellulose using unbleached kraft pulp or bleached kraft pulp as a raw material. This method utilizes hydrolysis with a peroxy acid rather than hydrolysis with only a mineral acid such as hydrochloric acid or sulfuric acid. This document describes that the whiteness of the produced cellulose is higher than that of the raw material, but the whiteness is not satisfactory.

  Patent Document 3 discloses a method of treating wood chips made of wood powder with an acidic aqueous solution, and describes that hydrogen peroxide may be used in combination. This method is for obtaining fine fibrous cellulose, and is not a method for obtaining cellulose having a polymerization degree of 350 or less, and also cannot obtain high whiteness cellulose.

U.S. Pat. No. 2,978,446 Special table 2003-504427 gazette JP 2012-36508 A

Pulp and Paper Technology Times, August 1985, 5 pages

  An object of the present invention is to provide a method for improving the whiteness of cellulose in a method for producing cellulose having a polymerization degree of 350 or less using chemical pulp as a starting material.

In order to solve the above-mentioned problems, the present inventors paid attention to the processing conditions of the alkali extraction step after treating the pulp with an aqueous solution containing sulfuric acid and hydrogen peroxide, and intensively studied the relationship between the alkali extraction temperature and the whiteness. As a result, the present invention has been completed.
That is, the present invention is as follows, for example.
[1] A method for producing cellulose having a degree of polymerization of 350 or less, comprising a chemical pulp as a raw material and having a degree of polymerization of 350 or less, comprising at least the following steps and performing an alkali extraction step at 0 to 65 ° C.
(A) Process of treating chemical pulp with aqueous solution containing sulfuric acid, hydrogen peroxide and monopersulfuric acid (b) Alkali extraction step [1-1] (a) Aqueous solution containing sulfuric acid, hydrogen peroxide and monopersulfuric acid A process of treating chemical pulp with
(B) A method for producing cellulose having a polymerization degree of 350 or less, including an alkali extraction step performed at 0 to 65 ° C.
[1-2] (a) a step of treating chemical pulp with an aqueous solution containing sulfuric acid, hydrogen peroxide and monopersulfuric acid;
(B) including an alkali extraction step performed at 0 to 65 ° C.
A method for producing cellulose having a polymerization degree of 350 or less and a whiteness of 95% or more.
[1-3] The method for producing cellulose according to [1-2], wherein the whiteness is 97% or more.
[2] The method for producing cellulose according to [1] to [1-3], wherein the (b) alkali extraction step is performed at 0 to 50 ° C.
[3] The cellulose according to any one of [1] to [2], comprising (c) a solid-liquid separation step and / or (d) a washing step between the step (a) and the step (b). Manufacturing method.
[4] The aqueous solution containing sulfuric acid, hydrogen peroxide and monopersulfuric acid is prepared by previously mixing sulfuric acid and hydrogen peroxide solution to prepare a monopersulfuric acid aqueous solution, and then diluting the monopersulfuric acid aqueous solution with water. The method for producing cellulose according to any one of [1] to [3], which is prepared by:
[5] The method for producing cellulose according to [4], wherein the sulfuric acid and the hydrogen peroxide solution are mixed at 20 to 100 ° C.
[6] The molar ratio of hydrogen peroxide to sulfuric acid in the aqueous solution containing sulfuric acid, hydrogen peroxide, and monopersulfuric acid is 1: 0.1 to 1: 5, and any one of [1] to [5] The manufacturing method of the cellulose of description.
[7] The method for producing cellulose according to [4], wherein the concentration of monopersulfuric acid in the aqueous monopersulfuric acid solution is 0.01 to 20% by weight.
[8] The method for producing cellulose according to any one of [1] to [7], wherein the (b) alkali extraction step is performed at a pH of 11 to 13.
[9] The method for producing cellulose according to any one of [1] to [8], wherein the alkaline agent used in the alkali extraction step (b) is an inorganic alkaline substance.

  When producing cellulose having a polymerization degree of 350 or less by the production method of the present invention, the whiteness of the cellulose is improved.

<Outline of manufacturing method>
In one embodiment of the present invention, cellulose can be produced as follows.
A chemical pulp as a raw material is treated with an aqueous solution containing sulfuric acid, hydrogen peroxide and monopersulfuric acid, and then an alkali extraction step is performed. Furthermore, the process including the washing | cleaning process after alkali extraction is performed.

<Chemical pulp>
Chemical pulp is produced from pulp chips. Examples of the raw material for pulp chips include coniferous trees represented by radiata pine and spruce, and broadleaf trees represented by eucalyptus and acacia. These coniferous and hardwood pulps can be used alone or in combination of two or more. When a plurality of types are used in combination, the combination is not limited at all.

Chemical pulp is produced by using the above-mentioned pulp chip as a raw material, sulfite cooking method or kraft cooking method, or a combination of these methods.
The chemical pulp produced by the above method may be either non-bleached pulp or bleached pulp, or a combination thereof.

In addition, chemical pulp includes papermaking pulp and highly purified dissolving pulp, both of which can be used, and these can be used in combination.
The chemical pulp may be used in a water-containing state after cooking or bleaching, and a dried plate or roll pulp may be used.

  The chemical pulp used in the present invention may be any of the above types of pulp, but bleached pulp is preferably used.

<Method for producing aqueous solution containing sulfuric acid, hydrogen peroxide and monopersulfuric acid>
An aqueous solution containing sulfuric acid, hydrogen peroxide, and monopersulfuric acid can be prepared by mixing an aqueous hydrogen peroxide solution, sulfuric acid, and water. The order of input is not particularly limited. For example, an aqueous hydrogen peroxide solution, sulfuric acid and water may be added to the reaction vessel and mixed, or a hydrogen peroxide aqueous solution and sulfuric acid may be mixed in advance to prepare a monopersulfuric acid aqueous solution, and then optionally added. It may be diluted with water. Hereinafter, an aqueous solution obtained by mixing an aqueous hydrogen peroxide solution and sulfuric acid when the aqueous hydrogen peroxide solution and sulfuric acid are mixed in advance and then optionally diluted with water is also referred to as “monopersulfuric acid aqueous solution (1)”. The aqueous solution after being diluted with is also referred to as “monopersulfuric acid aqueous solution (2)”.

  The charging method may be slow as in the case of dropping or may be performed quickly. Moreover, there is no restriction | limiting in particular in a mixing apparatus, You may mix using a stirrer for a tank-type container, and the external circulation system which connects an external circulation apparatus to a container may be sufficient. Moreover, you may mix using a line mixer.

  In a method in which a hydrogen peroxide aqueous solution and sulfuric acid are mixed in advance and then optionally diluted with water, when preparing the monopersulfuric acid aqueous solution (1) by dropping the hydrogen peroxide aqueous solution into sulfuric acid, the reaction is performed at 20 ° C to 100 ° C. Desirably, it is preferably 30 ° C to 90 ° C, more preferably 40 ° C to 80 ° C.

  A method for preparing an aqueous solution containing sulfuric acid, hydrogen peroxide and monopersulfuric acid may be a batch method or a continuous method. Generally, the continuous method can make the equipment smaller.

Sulfuric acid having a 95% weight concentration and a 98% weight concentration is widely available, but is not limited thereto.
In sulfuric acid, Fe may be contained due to metal elution from a plant during production or a tank during storage, but it is preferable to use an Fe concentration of 100 ppm or less, more preferably 50 ppm or less, and further 20 ppm or less. Is preferred. If the Fe concentration is within this range, decomposition of peroxides such as hydrogen peroxide and monopersulfuric acid can be suppressed.

As the hydrogen peroxide aqueous solution, those having 35% weight concentration, 45% weight concentration, 50% weight concentration, 60% weight concentration, and 70% weight concentration are widely available, but not limited thereto.
Although Fe may be contained in the hydrogen peroxide aqueous solution due to metal elution from a plant during production or a storage tank, it is preferable to use one having an Fe concentration of 20 ppm or less.

  The mixing ratio of the aqueous hydrogen peroxide solution and sulfuric acid is such that the molar ratio of hydrogen peroxide to sulfuric acid (100%) contained in the aqueous solution after mixing is preferably 1: 0.1 to 1: 5, more preferably 1. : The mixing ratio is preferably 1: 1 to 1: 4.

  When the aqueous hydrogen peroxide solution and sulfuric acid are mixed in advance and then optionally diluted with water, the concentration of monopersulfuric acid in the resulting aqueous monopersulfuric acid solution (1) is preferably 0.01 to 20% by weight. This monopersulfuric acid aqueous solution (1) can be used as it is added to the pulp slurry. Alternatively, the monopersulfuric acid aqueous solution (1) can be diluted to form a monopersulfuric acid aqueous solution (2) and then added to the pulp slurry.

  Instead of preparing a monopersulfuric acid aqueous solution (1) or a monopersulfuric acid aqueous solution (2) in advance and then adding it to the pulp slurry, a commercially available aqueous solution containing monopersulfuric acid may be used. Alternatively, an aqueous solution obtained by diluting sulfuric acid with water or an aqueous hydrogen peroxide solution can be directly added to the pulp slurry to produce monopersulfuric acid in the reaction vessel.

<Monopersulfuric acid treatment>
Monopersulfuric acid treatment is a process in which chemical pulp is treated with an aqueous solution containing sulfuric acid, hydrogen peroxide and monopersulfuric acid to decompose the chemical pulp to produce cellulose. By adjusting the reaction conditions between the chemical pulp and the aqueous solution containing sulfuric acid, hydrogen peroxide and monopersulfuric acid, the cellulose obtained can be adjusted to a predetermined degree of polymerization.

The pulp concentration in the reaction solution containing an aqueous solution containing sulfuric acid, hydrogen peroxide and monopersulfuric acid and chemical pulp is preferably from 0.1 to 20% by weight, more preferably from 1 to 15%. % By weight.
The concentration of monopersulfuric acid in the reaction solution is 0.01 to 15% by weight, preferably 0.1 to 10% by weight, and more preferably 2 to 5% by weight.

The temperature during monopersulfuric acid treatment is 20 ° C to 130 ° C, preferably 50 ° C to 120 ° C, more preferably 70 ° C to 110 ° C.
The reaction time is 5 to 240 minutes, preferably 15 to 180 minutes at the above temperature.
The pH of the reaction solution is preferably 1 or less. When the pH is 1 or less, the pulp degradation rate can be increased.

  The monopersulfuric acid treatment can be carried out using a continuous apparatus using a reaction tube or a tower, or a batch reaction tank. A stirring blade may be used so that the reaction solution can be sufficiently circulated, and the reaction solution may be circulated through the extraction line.

In order to accelerate the penetration of the drug into the pulp, a surfactant can be used as a penetrant.
Examples of the surfactant include a cationic surfactant, an anionic surfactant, a twin surfactant, a nonionic surfactant, and the like, but are not particularly limited. Any of these may be used alone or in combination.

In order to accelerate the monopersulfuric acid treatment, an organic acid, phosphoric acid, ozone, or the like may be added and ultraviolet irradiation may be performed. Even when any one of the above is used alone, the processing can be promoted, but some may be used in combination.
Examples of the organic acid include formic acid, acetic acid, propionic acid, and oxalic acid.
Ozone can be manufactured more easily than oxygen using oxygen, air, or PSA (pressure swing adsorption).

  Furthermore, the reaction is also accelerated by irradiating ultraviolet rays in the reaction cell. Ultraviolet rays are classified into UVA, UVB, and UVC. As the ultraviolet irradiation device, either a low-pressure ultraviolet lamp mainly generating UVB or UVC or a high-pressure ultraviolet lamp mainly generating UVA can be used, but a low-pressure ultraviolet lamp is preferably used.

<Process after monopersulfate treatment>
The product obtained by monopersulfate treatment is further processed by a process comprising the following steps. The processing order of each process is not limited to the order described here.
(C) Solid-liquid separation step (d) Washing step after solid-liquid separation step (b) Alkali extraction step (e) Dehydration step after alkali extraction step (f) Washing step after alkali extraction step (g) Drying step The following steps may be included.
(H) Grinding process (i) Classification process

  (C) The solid-liquid separation step is a step of solid-liquid separation of cellulose from a reaction solution by a centrifuge, a filter press, a belt press, an Oliver filter, a Young filter, or the like.

  (D) The washing step after the solid-liquid separation step is a step of removing the drug by bringing the cellulose to which the drug has adhered into contact with water. For example, a stirring tank having an impeller type stirrer can be used.

  In addition, when using a centrifuge, an Oliver type filter, a Young filter, etc., the washing | cleaning process after (d) solid-liquid separation can also be performed simultaneously with (c) solid-liquid separation process.

  (B) The alkali extraction step is intended to elute and remove impurities that are not removed by washing with an alkaline agent. The alkaline extraction step is mainly aimed at neutralizing the acid component remaining in the cellulose and elution of lignin and other coloring impurities, but hemicellulose and resin components can also be eluted.

It is preferable to perform an alkali extraction process at 0-65 degreeC, More preferably, it is 10-60 degreeC. If the temperature of the alkali extraction step is within this range, cellulose having a sufficiently high whiteness can be obtained. The temperature of the alkali extraction step may be any temperature within the above range, for example, 0 ° C., 5 ° C., 10 ° C., 15 ° C., 20 ° C., 25 ° C., 30 ° C., 35 ° C., 40 ° C., 45 ° C., 50 Lower limit of 5 ° C, 55 ° C or 60 ° C to 5 ° C, 10 ° C, 15 ° C, 20 ° C, 25 ° C, 30 ° C, 35 ° C, 40 ° C, 45 ° C, 50 ° C, 55 ° C, 60 ° C or 65 ° C Temperature. Specifically, 0-50 degreeC, 0-40 degreeC, 0-30 degreeC, 0-25 degreeC, 20-65 degreeC, 30-65 degreeC, 40-65 degreeC, 50-65 degreeC etc. are mentioned. The lower limit temperature should just be the temperature which does not freeze, for example, 0 degreeC, 10 degreeC, and 20 degreeC are illustrated. When the temperature of the alkali extraction step is higher than 80 ° C., there may be a problem that the whiteness of the cellulose is lowered or colored.
The alkali extraction step is preferably performed at pH 10-13, and more preferably at pH 11-13.

  The time for the alkali extraction treatment may be, for example, about 30 minutes to 2 hours, 1 hour to 2 hours, and more specifically about 1 hour. According to the above method, a sufficient alkali extraction treatment can be performed in a time equivalent to or lower than that in the prior art even at a lower temperature, and cellulose having high whiteness can be obtained.

As the alkaline agent, an inorganic alkaline substance such as NaOH, KOH, ammonia or the like, or an organic alkaline substance such as trimethylammonium hydroxide can be used, but an inorganic alkaline substance is preferably used from the viewpoint of easy post-treatment.
The alkaline agent is preferably used at a concentration of 0.01% by weight to 10% by weight in the aqueous solution, more preferably 0.1% by weight to 1% by weight. The pulp concentration during the treatment is preferably 1 to 15% by weight.

  (E) In the dehydration step after the alkali extraction step, the cellulose containing the alkali extract is dehydrated by a centrifuge, a filter press, a belt press, an Oliver filter, a Young filter, or the like.

  (F) The washing | cleaning process after an alkali extraction process is a process refine | purified by making the cellulose which the alkali extract adhered adhere to water. For example, a stirring tank having an impeller type stirrer can be used. The cellulose after washing is dehydrated. The pH of the liquid adhering to cellulose after dehydration is preferably 5.5 to 7.5, and more preferably 6 to 7.2.

(G) As a drying method of the drying step, not only a method using a general dryer but also a method of substituting with a solvent can be used. Dryers include hot air dryers, steam tube dryers, full-year dryers, spray dryers, air dryers, drum dryers, continuous fluidized bed dryers, infrared dryers, high-frequency heat dryers, freeze dryers, Examples include rapid dryers. Examples of the method for substitution with a solvent include a method in which moisture is substituted with ethanol and then air-dried.
The drying temperature is preferably 30 to 220 ° C. Drying at 220 ° C. or lower is preferable because coloring due to thermal decomposition of cellulose can be suppressed.

(H) The pulverization step can be performed, for example, by using an impact mill and / or an airflow mill alone or in combination, and further by treating the same model multiple times.
The impact type mills are: Inomizer (made by Hosokawa Micron Corporation), Pulverizer (made by Hosokawa Micron Corporation), Fine Impact Mill (made by Hosokawa Micron Corporation), Super Micron Mill (made by Hosokawa Micron Corporation), Fine Mill (Japan Pneumatic Industrial Co., Ltd.) Company), Exceed Mill (manufactured by Sagano Sangyo Co., Ltd.), Ultraplex (manufactured by Sugano Sangyo Co., Ltd.), Contraplex (manufactured by Sugano Sangyo Co., Ltd.), Coroplex (manufactured by Sugano Sangyo Co., Ltd.), Sample Mill (Seishin Co., Ltd.) ), Bantam Mill (manufactured by Seishin Co., Ltd.), Tornado Mill (manufactured by Sansho Industry Co., Ltd.), Hammer Mill (manufactured by Sansho Industry Co., Ltd.), Nea Mill (manufactured by Dalton Co., Ltd.), Free Crusher (Nara Machinery Co., Ltd.) Made), New Smomizer (manufactured by Nara Machinery Co., Ltd.), turbo mill (manufactured by Freund Turbo Co., Ltd.), gather mill (manufactured by Nishimura Machinery Co., Ltd.), super powder mill (manufactured by Nishimura Machinery Co., Ltd.), blade mill (Nisshin Engineering) Co., Ltd.), Super Rotor (Nisshin Engineering Co., Ltd.), NPa Crusher (NPA System Co., Ltd.), Pulp Crusher (Zuikou Co., Ltd.), Wonder Blender (Osaka Chemical Co., Ltd.), Universal Mill ( Manufactured by Tokusu Kosakusho Co., Ltd.), cutter mill (manufactured by Tokyo Atomizer Manufacturing Co., Ltd.), turbo cutter (manufactured by Freund Turbo Corporation), knife mill (manufactured by Pulman), rotary cutter mill (manufactured by Nara Machinery Co., Ltd.), Pulp crusher (Zuiko Co., Ltd.) Like it is exemplified. As the airflow mill, NanoJet Mizer (Aisin Nanotechnology Co., Ltd.), MSC Mill (Nihon Coke Industries Co., Ltd.), Micron Jet (Hosokawa Micron Co., Ltd.), Counter Jet Mill (Hosokawa Micron Co., Ltd.), Cross Jet Mill (Manufactured by Kurimoto Steel Co., Ltd.), supersonic jet crusher (manufactured by Nippon Pneumatic Industry Co., Ltd.), super jet mill (manufactured by Nissin Engineering Co., Ltd.), selenium mirror (manufactured by Masuko Sangyo Co., Ltd.), new microcyclo Examples include mats (manufactured by Masuno Seisakusho Co., Ltd.) and kryptron (manufactured by Kawasaki Heavy Industries, Ltd.).

(I) The classification step is an operation for selecting cellulose according to the particle diameter by a dry classification, wet classification or sieving classification method. The obtained cellulose can be classified and used if necessary.
If a spray dryer is used, drying, refinement, and classification can be performed simultaneously.

<Manufactured cellulose>
(1) Whiteness The measuring method of the whiteness of the cellulose produced by the method of the present invention is as follows.
Using a color difference meter, the surface color of the sample on the powder and paste sample stage was measured to determine Hunter whiteness. Hunter whiteness (W) is obtained by the following equation.
W = 100 − [(100−L) ² + a ² + b ² ] ^1/2
L: Lightness index a: Color coordinate indicating blue-yellow dimension b: Color coordinate indicating green-red dimension According to a preferred embodiment of the present invention, cellulose having a whiteness of 95% or more, preferably 97% or more can be obtained. it can.

(2) Average polymerization degree The average polymerization degree of the cellulose produced by the method of the present invention is preferably 350 or less, particularly preferably 300 or less. The average degree of polymerization is, for example, 100 to 350, 150 to 350, 200 to 350, 100 to 300, 150 to 300, 200 to 300, 100 to 250, or 200 to 300. The average degree of polymerization is determined by a viscosity measurement method using copper ethylenediamine described in the 16th revised Japanese Pharmacopoeia Manual, crystalline cellulose confirmation test (3).

(3) Molecular weight The molecular weight of the cellulose produced by the method of the present invention is a numerical value obtained by multiplying the average degree of polymerization by 162, preferably 25,000 to 70,000, more preferably 16,000 to 57,000. preferable.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples. In each example, the monopersulfate concentration, whiteness, average degree of polymerization (DP), and pH are values measured by the following methods.

(1) Test conditions <Method for quantifying monopersulfuric acid>
The total peroxide concentration in the monopersulfate aqueous solution was quantified with a titration reagent 0.1N sodium thiosulfate and an indicator starch. Next, the hydrogen peroxide concentration in the monopersulfate aqueous solution was quantified with a titration reagent 0.025N cerium sulfate and an indicator ferroin. The monopersulfuric acid concentration was obtained by subtracting the hydrogen peroxide concentration from the total peroxide concentration.

<Whiteness>
Using a color difference meter (Nippon Denshoku Co., Ltd. SE-2000), the surface color of the sample was measured using the powder and paste sample stage, and the Hunter whiteness was determined. Hunter whiteness (W) is obtained by the following equation.
W = 100 − [(100−L) ² + a ² + b ² ] ^1/2
L: Lightness index a: Color coordinate indicating blue-yellow dimension b: Color coordinate indicating green-red dimension

<Average polymerization degree>
Average polymerization degree was calculated | required by the viscosity measuring method using the copper ethylenediamine of the 16th revision Japanese Pharmacopoeia commentary and the crystalline cellulose confirmation test (3) description.

<Viscosity average molecular weight>
The average degree of polymerization was multiplied by 162 and then rounded off to the nearest hundred.

<PH>
The pH of the reaction solution was measured using a pH (D-51, manufactured by Horiba, Ltd.) meter.

<Analysis of raw material pulp>
Bleached hardwood pulp was used as raw material. Whiteness = 95.1, average degree of polymerization = 1556, viscosity average molecular weight = 254000.

(2) Examples and Comparative Examples <Synthesis Example 1: Production of monopersulfuric acid aqueous solution>
To 14.0 g of 35 wt% aqueous hydrogen peroxide, 44.6 g of 95 wt% sulfuric acid was added dropwise with stirring so that the temperature did not exceed 70 ° C. After completion of the addition, the mixture was ice-cooled to obtain a monopersulfuric acid aqueous solution.
This aqueous solution had a pH of −0.20 and a monopersulfuric acid concentration of 17.0% by weight.

<Example 1>
Bleached hardwood pulp (whiteness 95.1, polymerization degree 1566) 15 g (absolute dry weight) was chopped into a length of 40 mm and a width of 5 mm, and the 17.0 wt% monopersulfate aqueous solution (pH = -0.20) 30 g and the ion-exchanged water having a weight such that the pulp concentration in the reaction solution was 10% by weight were immersed in a solution sufficiently mixed and reacted at 105 ° C. for 2 hours.
After the reaction, suction filtration was performed, and after washing with ion exchange water three times, suction filtration was performed again. 1% by weight aqueous sodium hydroxide solution (1000 mL) was added to the filtered residue to adjust the pH to 12.9, followed by heating at 60 ° C. (alkali extraction treatment temperature) for 1 hour.
Thereafter, suction filtration was performed, and water washing with ion exchange water was performed three times, and then suction filtration was performed again. The filtered residue was dried with a box-type dryer and pulverized with an impact-type small pulverizer (manufactured by Sansho Industry, Tornado Mill).
The analysis results of the obtained cellulose are shown in Table 1.

<Example 2>
The same treatment as in Example 1 was performed except that the alkali extraction treatment temperature was 50 ° C. The analysis results are shown in Table 1.

<Example 3>
The same treatment as in Example 1 was performed except that the alkali extraction treatment temperature was 25 ° C. The analysis results are shown in Table 1.

<Comparative Example 1>
The same treatment as in Example 1 was performed except that the alkali extraction treatment temperature was 100 ° C. The analysis results are shown in Table 1.

<Comparative example 2>
The same treatment as in Example 1 was performed except that the alkali extraction treatment temperature was 80 ° C. The analysis results are shown in Table 1.

As described above, according to the production method of the present invention, cellulose having high whiteness can be obtained.
By the production method of the present invention, cellulose for food, pharmaceutical use, industrial use, etc. can be suitably produced.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

Claims (10)

A method for producing cellulose having a degree of polymerization of 350 or less, comprising at least the following steps using a chemical pulp as a raw material, wherein the alkali extraction step is performed at 0 to 65 ° C.
(A) Process of treating chemical pulp with aqueous solution containing sulfuric acid, hydrogen peroxide and monopersulfuric acid (b) Alkali extraction process   The said (b) alkali extraction process is a manufacturing method of the cellulose of Claim 1 performed at 0-50 degreeC.   The method for producing cellulose according to claim 1 or 2, further comprising (c) a solid-liquid separation step and / or (d) a washing step between the step (a) and the step (b).   The aqueous solution containing sulfuric acid, hydrogen peroxide and monopersulfuric acid is prepared by previously mixing sulfuric acid and hydrogen peroxide solution to prepare a monopersulfuric acid aqueous solution, and then diluting the monopersulfuric acid aqueous solution with water. The method for producing cellulose according to any one of claims 1 to 3.   The method for producing cellulose according to claim 4, wherein the mixing of the sulfuric acid and the hydrogen peroxide solution is performed at 20 to 100 ° C.   The cellulose according to any one of claims 1 to 5, wherein a molar ratio of hydrogen peroxide to sulfuric acid in the aqueous solution containing sulfuric acid, hydrogen peroxide and monopersulfuric acid is 1: 0.1 to 1: 5. Manufacturing method.   The manufacturing method of the cellulose of Claim 4 whose density | concentration of the monopersulfuric acid in the said monopersulfuric acid aqueous solution is 0.01-20 weight%.   The said (b) alkali extraction process is a manufacturing method of the cellulose of any one of Claims 1-7 performed by pH 11-13.   The method for producing cellulose according to any one of claims 1 to 8, wherein the alkali agent used in the (b) alkali extraction step is an inorganic alkaline substance.   The method for producing cellulose according to claim 1, wherein the cellulose has a whiteness of 95% or more.