There is provided is a hydroxyalkyl alkyl cellulose exhibiting good flowability and high compressibility. More specifically, provided are a hydroxyalkyl alkyl cellulose having a volume-based average particle diameter, determined by dry laser diffractometry, of 50 to 100 m, and having, on a basis of a dynamic image analysis to divide all particles into fine particles, spherical particles and fibrous particles, a volume fraction of the fibrous particles consisting of long and short fibrous particles relative to all of the particles of 45 to 70%, and a volume fraction of the fine particles relative to all of the particles of less than 2.0%; a solid preparation including the hydroxyalkyl alkyl cellulose; and others.

There is provided is a hydroxyalkyl alkyl cellulose exhibiting good flowability and high compressibility. More specifically, provided are a hydroxyalkyl alkyl cellulose having a volume-based average particle diameter, determined by dry laser diffractometry, of 50 to 100 m, and having, on a basis of a dynamic image analysis to divide all particles into fine particles, spherical particles and fibrous particles, a volume fraction of the fibrous particles consisting of long and short fibrous particles relative to all of the particles of 45 to 70%, and a volume fraction of the fine particles relative to all of the particles of less than 2.0%; a solid preparation including the hydroxyalkyl alkyl cellulose; and others.

Provided are low-substituted hydroxypropyl cellulose (L-HPC) having a hydroxypropoxy content of from 5 to 16% by weight, and having, on a basis of a dynamic image analysis to divide all particles into fine, spherical, and fibrous particles consisting of long and short fibrous particles, a volume fraction of the long fibrous particles of from 15 to 50% and a volume fraction of the short fibrous particles of from 23 to 60%; and a solid preparation containing the L-HPC. Also provided is a method for producing the L-HPC including the steps: bringing sheet-like or chip-like pulp having a length-weighted average fiber length of from 2.40 to 3.50 mm into contact with an alkali metal hydroxide solution, reacting the resulting alkali cellulose with propylene oxide, and dispersing the resulting reaction product in water containing an acid to partially dissolve it therein, followed by neutralization with an acid to precipitate crude L-HPC.

Provided are low-substituted hydroxypropyl cellulose (L-HPC) having a hydroxypropoxy content of from 5 to 16% by weight, and having, on a basis of a dynamic image analysis to divide all particles into fine, spherical, and fibrous particles consisting of long and short fibrous particles, a volume fraction of the long fibrous particles of from 15 to 50% and a volume fraction of the short fibrous particles of from 23 to 60%; and a solid preparation containing the L-HPC. Also provided is a method for producing the L-HPC including the steps: bringing sheet-like or chip-like pulp having a length-weighted average fiber length of from 2.40 to 3.50 mm into contact with an alkali metal hydroxide solution, reacting the resulting alkali cellulose with propylene oxide, and dispersing the resulting reaction product in water containing an acid to partially dissolve it therein, followed by neutralization with an acid to precipitate crude L-HPC.

According to an example aspect of the present invention, there is provided a method of continuously dissolving cellulose carbamate in an alkaline aqueous phase to form a solution, comprising the steps of providing cellulose carbamate, mixing the cellulose carbamate with an aqueous alkaline solution to form a mixture, conducting the mixture through the mixing zone of a continuously operated mixing kneader at a temperature of 10 degrees Celsius or less to produce a solution of said cellulose carbamate in an alkaline aqueous phase, and recovering the cellulose carbamate containing aqueous phase.

According to an example aspect of the present invention, there is provided a method of continuously dissolving cellulose carbamate in an alkaline aqueous phase to form a solution, comprising the steps of providing cellulose carbamate, mixing the cellulose carbamate with an aqueous alkaline solution to form a mixture, conducting the mixture through the mixing zone of a continuously operated mixing kneader at a temperature of 10 degrees Celsius or less to produce a solution of said cellulose carbamate in an alkaline aqueous phase, and recovering the cellulose carbamate containing aqueous phase.

Disclosed are cellulose-based 5 flexible aerogels and xerogels containing bacterial cellulose nanorods, ribbons, fibers, and the like, wherein the gels have tunable optical, heat transfer, and stiffness properties. Further disclosed are highly transparent and flexible cellulose nanofiber-polysiloxane composite aerogels featuring enhanced mechanical robustness, tunable optical anisotropy, and low thermal conductivity.

Using an organic compound having a bottle brush structure, a material having softness and resilience and having excellent low-friction performance (SRT material) can be provided. Preferably, the SRT material contains a reinforcing filler, and may contain a lubricating liquid to be gelled.

There is provided a cellulose derivative that has a high amount of a chelate adsorption group introduced, has high hydrophilicity, and is capable of efficiently recovering boron.

The cellulose derivative of the present disclosure has a repeating unit represented by the following formula (1-1). In the following formula (I-1), R.sup.a is the same as or different from each other, and is a hydroxyl group or a group represented by the following formula (a). In the following formula (a), R.sup.1 represents a hydrogen atom or a methyl group. R.sup.2 represents a hydrogen atom or a hydrocarbon group optionally having a hydroxyl group. R.sup.3 represents a hydrogen atom or a hydrocarbon group. Note that at least one of all R.sup.3 contained in the cellulose derivative is the group represented by the following formula (a).

##STR00001##

A cellulosic material contains a cellulose derivative, and the cellulose derivative contains an ionic moiety as a chemical structure common to an ionic liquid. It is preferred that the ionic moiety has an imidazolium salt structure. It is also preferred that the ionic moiety is introduced into a repeating unit of a polymer chain having a repeating structure introduced into a cellulose backbone structure of the cellulose derivative.