JP2000336101A - Production of hydroxypropyl cellulose - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject cellulose capable of reducing the amount of propylene oxide while maintaining qualities, excellent not only in an economical aspect but also in an environmental aspect, useful as a medicine additive by using a cellulose having a high relative viscosity. SOLUTION: (B) Propylene oxide is added to (A) a cellulose of formula I (n is 100-2,000) having >=12 relative viscosity to give the objective cellulose of formula II [R is (CH2-CH(CH3)-O)m--H] (m is 0 or 1-5). Preferably 1 pt.wt. of the component A is reacted with <=2.5 pts.wt. of the component B. For example, the component A, an organic solvent such as toluene, etc., an aqueous solution of sodium hydroxide are fed to a reactor, mixed and the mixed solution is reacted with the component B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to hydroxypropylcellulose (HPC) which is particularly useful as an excipient.
A method for producing the same.

[0002]

2. Description of the Related Art In general, HPC is produced by adding propylene oxide to cellulose in the presence of sodium hydroxide or the like (JP-A-2-235901). If the added amount of propylene oxide is small, the HPC becomes a low molecular weight, and when washed, the HPC is dissolved in waste water and the yield is reduced.
Propylene oxide is added until it is around the weight part (hereinafter referred to as weight pulp ratio). When cellulose having a relative viscosity of about 11, which is commonly used, was used, 2.6 to 2.7 parts by weight of propylene oxide was required for 1 part by weight of cellulose. However, the excess propylene oxide is of the formula (II
Since the propylene glycol represented by the formula (I) is contained in wastewater, it is important to reduce the amount of propylene oxide not only from an economical point of view but also from an environmental point of view.

[0003]

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(Where l represents an integer of 1 to 4)

[0005]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above problems, and as a result, have found that the use of cellulose having a high relative viscosity can reduce the amount of propylene oxide while maintaining the product. We have found and completed the present invention.

That is, the present invention is a process for producing HPC represented by the formula (II), wherein propylene oxide is added to cellulose having a relative viscosity of 12 or more represented by the formula (I).

[0007]

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[0008]

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[Wherein n is from 100 to 2000, and R is
-(CH ₂ -CH (CH ₃ ) -O) _m -H (where m represents 0 or an integer of 1 to 5, provided that not all R in the formula (II) are m = 0 at the same time). ). ]

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The cellulose having a relative viscosity of 12 or more used in the present invention is not particularly limited. Particularly, 14 to 20 cellulose is preferable. To carry out the production method of the present invention, cellulose, an organic solvent and an aqueous solution of sodium hydroxide are added to a reaction vessel and mixed. Propylene oxide is added to this mixed solution and reacted. The propylene oxide to be added is usually added in two portions so that the addition becomes uniform. The proportion to be added is about 2 parts by weight of propylene oxide per 1 part by weight of cellulose for the first time,
The method of adding the remainder the second time is preferred. After completion of the reaction, the target compound can be obtained by removing the organic solvent and then performing washing with warm water or the like.

As the organic solvent used in the present invention, a solvent inert to the reaction such as toluene can be used, and the amount of the solvent used is 1 to 10 parts by weight based on 1 part by weight of cellulose. The concentration of the aqueous sodium hydroxide solution is not particularly limited, but is usually 2
The amount is preferably about 0%, and the amount is 0.1 to 1 part by weight in the case of a 20% aqueous solution with respect to 1 part by weight of cellulose. Although the amount of propylene oxide used does not affect the quality at most, it is preferably from 2.2 to 2.5 parts by weight based on 1 part by weight of cellulose from the viewpoint of economy and environment as described above.

[0012]

Next, the present invention will be described in more detail by way of examples. Example 1 (Experiment (C) in which the amount of propylene oxide added for the second time was reduced by 8% using cellulose (I) having a relative viscosity of 14.6)

In a reaction vessel, 220 g of cellulose (I), 2 g
85 g of 0% sodium hydroxide aqueous solution, 752 g of toluene
Was stirred at room temperature while replacing with nitrogen. While raising the temperature, 463 g of the first propylene oxide was added and the mixture was aged at 80 ° C., and after cooling, 72 g of the second propylene oxide was added and the mixture was further aged at 85 ° C. After removing toluene, the reaction solution was washed with warm water and dried under vacuum to obtain hydroxypropylcellulose (II) (weight pulp ratio: 2.14).

Example 2 (Experiment (C) using cellulose (I) having a relative viscosity of 18.5 and reducing the amount of propylene oxide added second time by 8%)

In a reaction vessel, 220 g of cellulose (I), 2 g
85 g of 0% sodium hydroxide aqueous solution, 752 g of toluene
Was stirred at room temperature while replacing with nitrogen. While raising the temperature, 463 g of the first propylene oxide was added and the mixture was aged at 80 ° C., and after cooling, 72 g of the second propylene oxide was added and the mixture was further aged at 85 ° C. After removing toluene, the reaction solution was washed with warm water and dried under vacuum to obtain hydroxypropylcellulose (II) (pulp weight ratio: 2.09).

Comparative Example 1 (Experiment (B) in which the amount of propylene oxide added for the second time was reduced by 4% using cellulose (I) having a relative viscosity of 6.9)

In a reaction vessel, 220 g of cellulose (I), 2 g
85 g of 0% sodium hydroxide aqueous solution, 752 g of toluene
Was stirred at room temperature while replacing with nitrogen. While raising the temperature, 463 g of the first propylene oxide was added and the mixture was aged at 80 ° C., and after cooling, 96 g of the second propylene oxide was added and the mixture was further aged at 85 ° C. After removing toluene, the reaction solution was washed with warm water and dried under vacuum to obtain hydroxypropylcellulose (II) (weight pulp ratio: 1.95).

Comparative Example 2 (Standard experiment (A) using cellulose (I) having a relative viscosity of 11.3)

In a reaction vessel, 220 g of cellulose (I), 2
85 g of 0% sodium hydroxide aqueous solution, 752 g of toluene
Was stirred at room temperature while replacing with nitrogen. While raising the temperature, 463 g of propylene oxide for the first time was added and aged at 80 ° C., and after cooling, 120 g of propylene oxide for the second time was added and further aged at 85 ° C. After removing toluene, the reaction solution was washed with warm water and dried under vacuum to obtain hydroxypropyl cellulose (II) (weight pulp ratio: 2.11).

Comparative Example 3 (Experiment (B) using cellulose (I) having a relative viscosity of 11.3 and reducing the amount of propylene oxide to be added for the second time by 4%)

In a reaction vessel, 220 g of cellulose (I), 2 g
85 g of 0% sodium hydroxide aqueous solution, 752 g of toluene
Was stirred at room temperature while replacing with nitrogen. While raising the temperature, 463 g of the first propylene oxide was added and the mixture was aged at 80 ° C., and after cooling, 96 g of the second propylene oxide was added and the mixture was further aged at 85 ° C. After removing toluene, the reaction solution was washed with warm water and dried under vacuum to obtain hydroxypropylcellulose (II) (pulp weight ratio: 2.06).

The results are shown in Table 1 below, including a comparison of the weight pulp ratio depending on the amount of propylene oxide.

[0023]

[Table 1]

[0024]

According to the present invention, by using cellulose having a high relative viscosity, the amount of propylene oxide can be reduced without lowering the weight pulp ratio. In addition, by reducing the amount of propylene oxide, it is possible to suppress polypropylene glycols which are by-products, to reduce the ratio contained in the wastewater when washed, and to greatly improve the environment.

Claims (2)

[Claims] 1. A method for producing hydroxypropyl cellulose represented by the formula (II), wherein propylene oxide is added to cellulose having a relative viscosity of 12 or more represented by the formula (I). Embedded image Embedded image Wherein n is from 100 to 2000 and R is-(CH ₂ -CH
(CH ₃ ) -O) _m -H (where m represents 0 or an integer of 1 to 5, provided that not all Rs in the formula (II) are simultaneously m = 0). ] 2. The process according to claim 1, wherein the reaction is carried out with 2.5 parts by weight of propylene oxide per 1 part by weight of cellulose.