Provided is a method for producing hydroxypropyl methyl cellulose (HPMC) having high hydroxypropoxy content, low ash content, and low insoluble fiber content. More specifically, provided is a method for producing HPMC having a methoxy degree of substitution of from 1.4 to 2.2 and a hydroxypropoxy molar substitution of from 0.5 to 1.0, including steps of: bringing sheet-like or chip-like pulp into contact with an alkali metal hydroxide solution to obtain a reaction product mixture containing alkali cellulose, removing a liquid portion from the reaction product mixture to obtain the alkali cellulose, reacting the alkali cellulose with an etherifying agent to obtain a crude HPMC, disintegrating the crude HPMC into a disintegrated crude HPMC, dispersing the disintegrated crude HPMC in water to obtain a slurry, filtering the slurry to obtain a cake, and washing the cake.

The present invention relates to a method for producing modified cellulose fibers having cellulose I crystal structure, comprising: step A: introducing Substituent Group A to cellulose fibers via an ether bond in a solvent comprising water in the presence of a base, and step B: introducing Substituent Group B to cellulose fibers via an ether bond in a solvent comprising water in the presence of a base, wherein the method includes the steps A and B concurrently, or in the order of the step A and then the step B. The cellulose fibers of the present invention obtained by the method for production of the present invention have favorable dispersibility in a hydrophobic medium and a controlled increase in viscosity.

A method for producing a highly viscous water-soluble cellulose ether has a small undissolved fiber content and a high loose bulk density. More specifically, a production method includes steps of: bringing cellulose pulp into contact with an alkali metal hydroxide solution to obtain an alkali cellulose mixture; draining the alkali cellulose mixture to obtain an alkali cellulose; reacting the alkali cellulose with an etherifying agent to obtain a water-soluble cellulose ether mixture; washing and draining the water-soluble cellulose ether mixture to obtain a first moist cellulose ether; mixing the first moist cellulose ether with water to obtain a second moist cellulose ether; coarsely pulverizing the second moist cellulose ether with a coarse pulverizer to obtain a coarsely pulverized cellulose ether; cooling the coarsely pulverized cellulose ether; and then drying and pulverizing the coarsely pulverized cellulose ether.

A method for producing a highly viscous water-soluble cellulose ether has a small undissolved fiber content and a high loose bulk density. More specifically, a production method includes steps of: bringing cellulose pulp into contact with an alkali metal hydroxide solution to obtain an alkali cellulose mixture; draining the alkali cellulose mixture to obtain an alkali cellulose; reacting the alkali cellulose with an etherifying agent to obtain a water-soluble cellulose ether mixture; washing and draining the water-soluble cellulose ether mixture to obtain a first moist cellulose ether; mixing the first moist cellulose ether with water to obtain a second moist cellulose ether; coarsely pulverizing the second moist cellulose ether with a coarse pulverizer to obtain a coarsely pulverized cellulose ether; cooling the coarsely pulverized cellulose ether; and then drying and pulverizing the coarsely pulverized cellulose ether.

Modified cellulose fibers comprising cellulose fibers bound to one or more substituents, via an ether bonding, selected from substituents represented by the following general formula (1) and substituents represented by the following general formula (2) and one or more substituents selected from substituents represented by the following general formula (3) and substituents represented by the following general formula (4): CH.sub.2CH(OH)R.sub.1 (1); CH.sub.2CH(OH)CH.sub.2(OA).sub.nOR.sub.1 (2); CH.sub.2CH(OH)R.sub.2 (3); CH.sub.2CH(OH)CH.sub.2(OA).sub.nOR.sub.2 (4), wherein the modified cellulose fibers have cellulose I crystal structure.

Modified cellulose fibers comprising cellulose fibers bound to one or more substituents, via an ether bonding, selected from substituents represented by the following general formula (1) and substituents represented by the following general formula (2) and one or more substituents selected from substituents represented by the following general formula (3) and substituents represented by the following general formula (4): CH.sub.2CH(OH)R.sub.1 (1); CH.sub.2CH(OH)CH.sub.2(OA).sub.nOR.sub.1 (2); CH.sub.2CH(OH)R.sub.2 (3); CH.sub.2CH(OH)CH.sub.2(OA).sub.nOR.sub.2 (4), wherein the modified cellulose fibers have cellulose I crystal structure.

There are provided hydroxypropyl methyl cellulose (HPMC) having a high solubility in an organic solvent even when it has a degree of substitution (DS) of methoxy groups and a molar substitution (MS) of hydroxypropoxy group which are the same as those in the conventional art; and others. Specifically, there are provided HPMC having the MS of from 0.1 to 0.5; a ratio (referred to as MF at 3-position/MS) of 0.12 or more, as calculated by dividing a molar fraction (referred to as MF at 3-position) of anhydroglucose units in which only a hydroxy group at the 3-position carbon is substituted with a hydroxypropoxy group and none of hydroxy groups at the 2-position and 6-position carbons is substituted with a hydroxypropoxy group by the MS; and a viscosity at 20 C. of from 1.0 to 50 mPa.Math.s, as determined in a 2% by mass aqueous solution; and others.

There are provided hydroxypropyl methyl cellulose (HPMC) having high solubility even when keeping the molar substitution (MS) of hydroxypropoxy groups conventional; and others. More specifically, there are provided HPMC having a molar substitution (MS) of hydroxypropoxy groups of from 0.1 to 0.5, a ratio (referred to as MF at 3-position/MS) of 0.12 or more, as calculated by dividing a molar fraction (referred to as MF at 3-position) of anhydroglucose units in which only a hydroxy group at the 3-position carbon is substituted with a hydroxypropoxy group and none of hydroxy groups at the 2-position and 6-position carbons is substituted with a hydroxypropoxy group by the molar substitution (referred to as MS) of hydroxypropoxy groups, and a viscosity at 20 C. of more than 50 mPa.Math.s and not more than 150000 mPa.Math.s, as determined in a 2% by mass aqueous solution; and others.

A method for producing a highly viscous water-soluble cellulose ether has a small undissolved fiber content and a high loose bulk density. More specifically, a production method includes steps of: bringing cellulose pulp into contact with an alkali metal hydroxide solution to obtain an alkali cellulose mixture; draining the alkali cellulose mixture to obtain an alkali cellulose; reacting the alkali cellulose with an etherifying agent to obtain a water-soluble cellulose ether mixture; washing and draining the water-soluble cellulose ether mixture to obtain a first moist cellulose ether; mixing the first moist cellulose ether with water to obtain a second moist cellulose ether; coarsely pulverizing the second moist cellulose ether with a coarse pulverizer to obtain a coarsely pulverized cellulose ether; cooling the coarsely pulverized cellulose ether; and then drying and pulverizing the coarsely pulverized cellulose ether.

A method for producing a highly viscous water-soluble cellulose ether has a small undissolved fiber content and a high loose bulk density. More specifically, a production method includes steps of: bringing cellulose pulp into contact with an alkali metal hydroxide solution to obtain an alkali cellulose mixture; draining the alkali cellulose mixture to obtain an alkali cellulose; reacting the alkali cellulose with an etherifying agent to obtain a water-soluble cellulose ether mixture; washing and draining the water-soluble cellulose ether mixture to obtain a first moist cellulose ether; mixing the first moist cellulose ether with water to obtain a second moist cellulose ether; coarsely pulverizing the second moist cellulose ether with a coarse pulverizer to obtain a coarsely pulverized cellulose ether; cooling the coarsely pulverized cellulose ether; and then drying and pulverizing the coarsely pulverized cellulose ether.