JPH0233721B2 - KETSUSHOSERUROOSUNOSEIZOHOHO - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel method for producing crystalline cellulose. More specifically, the present invention relates to a method for producing crystalline cellulose having new functions in a high yield by selecting the form of the starting material and acid hydrolysis conditions. Mineral acids such as hydrochloric acid and sulfuric acid are applied to cellulose raw materials such as cotton linters, wood pulp, and recycled fibers to cause a heterogeneous acid hydrolysis reaction, and the resulting acid-insoluble residue is collected and leveled off. The method of purifying crystalline cellulose itself is known. For example, according to U.S. Pat. No. 3,954,727,
At least about 92% alpha cellulose content and 5
~6.5% beta cellulose content, 5%
Cellulose, which has a solubility in NaOH aqueous solution of about 2 to 4% and a viscosity of 110 to 180 mP, is processed by chemical decomposition and mechanical decomposition at the same time.
There is a disclosure of a method for obtaining crystalline cellulose by hydrolysis with dilute acids, especially 1% sulfuric acid, at ~160°C for 20-45 minutes. In addition, U.S. Patent No. 3,141,875 discloses that viscose rayon fibers, cotton linter pulp, refined wood pulp, etc. are used and acid hydrolyzed with 2.5 N hydrochloric acid for about 15 minutes to produce particles of 1 micron or less. There is a disclosure of a method for obtaining crystalline cellulose containing at least 1% by weight of particles. In addition, "excipient": JP-A-53-127553 discloses a method for obtaining crystalline cellulose with special properties by shredding dissolving pulp or kraft pulp and treating it at high temperature with an aqueous solution of hydrochloric acid of various concentrations; A method of shredding dissolving pulp and hydrolyzing it in a 1% sulfuric acid solution at 115°C for 35 minutes under pressure, and a method of shredding rayon waste and hydrolyzing it in a 1% sulfuric acid solution at 105°C for 120 minutes. There is a disclosure. By the way, as is partly clear from the text of the specification, the method for producing crystalline cellulose described above uses cotton linters, raw materials for crystalline cellulose,
Regarding recycled fibers and wood pulp, it is necessary to
It has been used in the form of sheets or rolls, which have been dried and then loosened or cut into pieces as appropriate for acid hydrolysis. In other words, the microcrystalline cellulose raw material is provided in a dry state, which is then rewetted in an acid hydrolysis step. In such conventional methods, cellulose comes into contact with acid before it is sufficiently swollen, so a reaction occurs gradually from the surface of cellulose, producing oligomers or water-soluble glucan with a low degree of polymerization. There was a problem that the amount of acid-insoluble residue recovered, ie, the yield of crystalline cellulose, was low. Furthermore, when crystalline cellulose containing these impurities is used, for example, as an excipient for pharmaceuticals, it does not meet the water soluble content test standards of the Japanese Pharmacopoeia "Crystalline Cellulose", which specifies the properties of crystalline cellulose. If the product fails to pass the test, the whiteness of the product itself decreases, or if it is mixed with an unstable drug such as vitamin C and used as an elixir, it may easily turn brown over time and reduce its commercial value. . To prevent this, it is possible to repeatedly purify the acid-insoluble residue obtained by acid hydrolysis, that is, crystalline cellulose, but as is well known, crystalline cellulose tends to form a stable colloidal dispersion in water. Filtration, washing, decantation, etc. using water are extremely difficult and undesirable as they increase utility costs. Furthermore, in Japanese Patent Publication No. 55-8334, in order to improve the permeability of mineral acids into the cellulose raw material, the cellulose raw material is pressurized in advance with a roller,
There are also disclosures of a method of making the pressure roller brittle, but this method makes it difficult to maintain the pressure roller.
Equipment costs are also high. The present invention does not have the problems of the conventional crystalline cellulose production method as described above, and the produced crystalline cellulose has a high yield and whiteness, and is resistant to unstable drugs such as vitamin C. The present invention also provides a novel method for producing crystalline cellulose that does not cause browning. That is, the present invention is a method for producing crystalline cellulose in which wet pulp (hereinafter referred to as WPS) obtained through a pulping process is subjected to heterogeneous acid hydrolysis by applying a mineral acid to the wet pulp (hereinafter referred to as WPS). According to the method for producing crystalline cellulose of the present invention,
There is no need to loosen, shred, or pressure embrittle the raw material of cellulose using rollers, which was conventionally done, and there is no need to refine the crystalline cellulose produced. It is possible to produce crystalline cellulose that has high yield and whiteness, and does not cause browning over time when formed into a solid preparation with unstable drugs such as vitamin C, isoniazid, etilefrine hydrochloride, and imipramine hydrochloride. The wet pulp obtained through the pulping process in the present invention usually refers to the wood preparation process → cooking/framing process → selection/dehydration process → bleaching process → molding (paper,
It is not a dry pulp that is manufactured through the process (sheet, chip) process → drying process, but WSP that has gone through the bleaching process in the pulp manufacturing method described above. For the acid hydrolysis in the present invention, the conditions conventionally used for the production of crystalline cellulose can be used as they are, but the following ranges are particularly preferred. That is, the types of mineral acids that can be used are nitric acid, hydrochloric acid, and sulfuric acid.
Hydrochloric acid and sulfuric acid are preferred, and sulfuric acid is particularly preferred. Nitric acid often causes coloring phenomena in the resulting products, and hydrochloric acid requires corrosion resistance in the process equipment and is difficult to maintain the equipment, as is well known. In addition, the concentration of mineral acids is approximately
The range is preferably 0.1N to 2.5N, preferably 0.13N to 2.0N. If it is less than 0.1N, it is not preferable because it takes a very long time to level off or requires particularly high temperature conditions, probably because the mineral acid does not penetrate well into the cellulose fibers. Also, there is no advantage to be gained by using mineral acids at concentrations greater than 2.5N. Note that the mineral acid concentration in the present invention also takes into account the amount of water derived from WPS. The temperature conditions when hydrolyzing WPS with the above-mentioned mineral acid concentration are determined by the three factors: the concentration of the mineral acid used as described above and the treatment time described later. You can't take it out and decide. However, if the temperature is below about 90°C, it will take an extremely long time to process it if carried out industrially, and if it is above 160°C, the acid will be extremely corrosive to the reaction equipment and energy consumption will be large, which is not desirable. so 90℃~160℃,
Preferably, it is carried out at a temperature between the boiling point and 140°C under normal pressure. Further, the treatment time is achieved by maintaining the temperature for about 10 minutes to 180 minutes after reaching a predetermined temperature condition.
Naturally, when treating WPS at around the boiling point under normal pressure using a low concentration acid aqueous solution, a long reaction time of approximately 100 to 180 minutes is required, and when high temperature treatment is performed with a high concentration acid, The reaction is completed in an extremely short time. Pulp solid content vs. acid aqueous solution amount during acid hydrolysis,
That is, the bath ratio is preferably in the range of 3 to 50 times, preferably 5 to 30 times, and more preferably 8 to 20 times. If the bath ratio is less than 3 times, sufficient stirring during acid hydrolysis cannot be achieved,
If the bath ratio is 50 or more, time is required for filtration after the reaction, and no advantage is obtained. Acid hydrolysis can be carried out either batchwise or continuously. Direct acid hydrolysis of WPS using the above conditions,
This is carried out by purifying and drying the resulting acid-insoluble residue. The present invention will be explained in detail below with reference to Examples. Example 1 WPS obtained through a sulfite pulp (SP) process using coniferous wood as a raw material was processed at a pulp solid content concentration of 10
% and add 20 to 30 volumes of autoclave.
I prepared Kg. Finally, the sulfuric acid concentration is 1N and the bath ratio is
An aqueous sulfuric acid solution was added to give a concentration of 13, and the mixture was hydrolyzed at 120°C for 30 minutes. After completion of the reaction, the resulting acid-insoluble residue was washed and neutralized, air-dried, coarsely pulverized, and passed through a Nara free pulverizer model M-2 to obtain crystalline cellulose A. The yield of acid-insoluble residue based on α-cellulose contained in WPS was 96%. A sheet-like paper product of sulfite pulp (SP) made from softwood (hereinafter simply referred to as pulp sheet) is shredded and placed in an autoclave with a dry weight of 2 kg, and the final sulfuric acid concentration is 1N and the bath ratio is 13. An aqueous sulfuric acid solution was added so that the resultant mixture was hydrolyzed at 120°C for 30 minutes. Crystalline cellulose (B) was then obtained according to the above operating conditions. The yield of undissolved residue based on α-cellulose contained in the pulp sheet is:
It was 93%. Example 2 The physical properties of the crystalline celluloses (A) and (B) obtained in Example 1 were compared. The results are shown in Table-1.

[Table] As mentioned above, the crystalline cellulose obtained from pulp sheets has a high water-soluble content of 3.5 mg/5 g according to the Japan Bureau's crystalline cellulose analysis method, and the upper limit standard is 4.
Although the value was close to mg/5g and required sufficient control during the purification process, crystalline cellulose starting from WPS showed a very low value and was proved to be easy to purify. In addition, crystalline cellulose (B) has low whiteness,
Moreover, it is clear that when combined with vitamin C, its stability is sub-affected. Example 3 After acid hydrolyzing the WPS used in Example 1 under the conditions shown in Table 2, the resulting acid-insoluble residue was washed and filtered with 30 times the amount of water, neutralized, and then dissolved in a 50% alcohol solution. The crystalline cellulose particles were re-dispersed at a concentration of 10% in the liquid, stirred thoroughly, and the crystalline cellulose particles were ground and dispersed, centrifuged to remove the liquid, dried in a hot air dryer at 60°C, crushed, and sieved to obtain the crystalline cellulose sample. C to G were obtained, and the physical properties of the samples were evaluated. The results are shown in Table-3.

【table】

[Table] Sample C, which had a low hydrochloric acid concentration, had a low whiteness and a slightly high water soluble content as a result of long-term high temperature treatment. Sample F, which had a low treatment temperature of 80° C. and a short treatment time, had a high water-soluble content and poor vitamin C stability, probably due to insufficient acid hydrolysis. Sample G, which had too high an acid concentration, had a low yield and a decrease in whiteness. Comparative Example Using the pulp sheet used in Example 1 as a starting material, it was hydrolyzed under the conditions D and E in Table 2 of Example 3, and then subjected to the same treatment to produce samples D-R,
ER was obtained and the physical properties of both were evaluated. The results are shown in Table 4.

【table】

Claims (1)

[Scope of Claims] 1. A method for producing crystalline cellulose, which comprises applying a mineral acid to wet pulp obtained through a pulping step to perform heterogeneous acid hydrolysis. 2 Heterogeneous acid hydrolysis with mineral acid concentration of 0.1 normal to 2.5
Regulations, processing temperature 90°C to 160°C, processing time 10 minutes to 180°C
2. The method for producing crystalline cellulose according to claim 1, wherein the method is carried out at a bath ratio of 3 to 50. 3. The method for producing crystalline cellulose according to claim 2, characterized in that hydrochloric acid or sulfuric acid is used as the mineral acid.