JP2598668B2 - Method for producing lignin fiber - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing fibers from lignin produced when cooking wood-based substances using a specific organic solvent as a cooking liquor.

2. Description of the Related Art There have been many attempts to convert lignin into fibers.Most of the attempts have been made by dry spinning from a mixed solution of synthetic polymers such as polyvinyl alcohol and polyethylene oxide, which have fiber forming ability, and kraft lignin. It is a method of obtaining lignin fiber by a wet method or a wet spinning method (US Pat. No. 3,461,082, JP-A-47-35323, etc.), and is not basically a method of converting lignin itself into a single fiber. On the other hand, recently, a method of producing carbon fibers from isolated lignin after treating wood with high-pressure saturated steam and high-temperature treatment with an organic solvent such as alcohol (Japanese Patent Laid-Open No. 62-110922)
However, lignin obtained by this method melts and flows by heating, but it is difficult to fibrillate by melt spinning in an untreated state, and following hydrocracking for fiberization, After heat treatment under a nitrogen stream,
For the first time it can be spun.

As described above, there has been no method for easily converting lignin into a fiber in a state of being isolated from wood or the like by an operation such as pulping.

Problems to be Solved by the Invention It is an object of the present invention to provide a method for producing lignin fiber that can be spun only by heating and melting lignin isolated from a wood-based material.

The present inventor has studied the fiberization of lignin, and as a result, has found that wood-based substances can be used in pulping by pulping by using an organic solvent composed of a mixture of phenols and glycols and water as a cooking liquor. The inventors have found that a fiber having good strength and heat resistance can be obtained by spinning the resulting lignin by heating and melting, and have accomplished the present invention.

 Hereinafter, the present invention will be described in detail.

Means for Solving the Problems Lignin used as a raw material in the present invention has recently been
Organic solvent digestion pulping process using a developed organic solvent (phenols or a mixture of phenols and glycols and water) as a cooking liquor (JP-A-58-6509).
No. 1). That is, by heating the wood-based material using the above organic solvent as a cooking liquor, the pulp and the three components of an aqueous layer in which hemicellulose is decomposed and dissolved as monosaccharides and an organic layer in which lignin is dissolved are dissolved. Lignin is obtained by concentrating the organic layer under reduced pressure. In the pulping process, no mention is made of the fibrous properties of the lignin obtained.

The wood-based material used in the present invention includes various lignocellulosic materials in addition to wood.

Phenols which are organic solvents used to obtain the lignin according to the present invention include phenol, cresol, xylenol, ethylphenol, propylphenol, guaiacol, 2-methoxy-4-methylphenol, 2-methoxyphenol.
Examples include alkyl-substituted phenols such as methoxy-4-ethylphenol and mixtures of these phenols.

Next, the composition and cooking conditions of the cooking liquor used to obtain lignin in the present invention, the cooking liquor,
The ratio between the phenols and water is not particularly limited, but the phenols: water is 5 volumes: 5 volumes to 10 volumes: 0 volumes, preferably 7 volumes: 3 volumes to 8 volumes: 2 volumes. The temperature is 150 to 200 ° C, preferably 160 to 190 ° C, particularly preferably 175 to 185 ° C, and the digestion time is one to several hours, preferably two to three hours.

The organic layer digested under the above conditions is concentrated under reduced pressure to obtain lignin. Here, in the Kraft method, which is the current mainstream process, lignin is dissolved in an alkaline solution, so enormous energy is required for concentration, but in the process of the present invention, it is dissolved in phenols,
Another advantage is that the energy used for concentration can be significantly reduced.

The lignin obtained in this manner is a lignin having a distinct melting point, although it differs depending on the tree species. These lignins are melted by heating, exhibiting a remarkable fiber-forming ability in this state, and can easily produce lignin fibers. The spinning method is preferably a melt spinning method, and the spinning temperature is slightly different depending on the melting point of the obtained lignin,
℃ is good. Such a fiber-forming ability is a property that is not readily found in lignin obtained by other pulping methods, for example, kraft lignin, while lignin directly extracted from wood with an organic solvent such as 1,4-dioxane is used. Also does not exist. From this fact, the lignin obtained by the present invention, that is, the fiber-forming ability is expressed only in the lignin obtained from an organic solvent digestion process using an organic solvent consisting of a mixture of phenols and water as a cooking liquor, the present invention. There is great significance of the invention.

Next, the curing / infusibility treatment of the lignin fiber thus obtained will be described. Although the lignin fiber obtained by the present invention has good spinnability, it is difficult to use it as it is because it is dangerous. In particular, in the production of carbon fiber, which is considered to be the most promising use of this lignin fiber, burning during high-temperature treatment of 800 ℃ ~ 3000 ℃,
Not melting is also an important property.

Originally, lignin contains a relatively large amount of oxygen in the molecule, so the infusibilization treatment time with oxygen etc. is shorter than that of polyacrylonitrile or pitch-based carbon fiber, and carbonization is rapid. It is characterized by high yield.

Then, the present lignin fiber was examined for its infusibility treatment, and it was found that it could be easily cured and infused by heating. The curing and infusibilization method may be heating in air, and the curing and infusibilization temperature is 150 to 300 ° C.
Preferably, it is 170-260 ° C. The rate of temperature rise from room temperature may be 1 to 10 ° C / min or less. The lignin fiber after the heat treatment has a high strength, and its value as a fiber is sufficient. Further, the lignin fiber does not undergo any thermal melting or thermal deformation even when heated to 800 ° C. or more in an inert gas, and has satisfactory properties as a carbon fiber precursor.

Hereinafter, the present invention and its effects will be specifically described with reference to examples.

Example 1 For 1 kg of wood chip, the mixture of tricresole and water was 5 and the ratio of tricresole to water was 8 volumes to 2 volumes as cooking liquor.
Cooked for hours. The obtained organic layer was concentrated under reduced pressure by an evaporator to prepare lignin. This lignin was melted at 190 ° C., and the yarn was pulled out. The obtained filamentous material was a glossy brown fiber and had a diameter of 50 to 100 μ, but became thinner with an increase in the winding speed, and 10 to 20 at a speed of 100 m / min.
The μ was the majority.

The wound lignin fiber is transferred into a furnace, heated to 200 ° C. at a rate of 3 ° C./min from room temperature, and maintained for 1 hour, after which the infusibility / insolubilization is completed. The atmosphere in the furnace is air. The strength of the obtained lignin fiber is as follows. Tensile strength is 3.1kg / mm ² , elongation 1.2%, elastic modulus 268
kg / mm ² . Next, the lignin fiber was heated to 1000 ° C. in a nitrogen atmosphere, but did not melt. In addition, it was insoluble in organic solvents such as tetrahydrofuran.

Example 2 For 1 kg of wood chip, the mixture of tricresole and water was 7 and the ratio of tricresole to water was 7 volumes to 3 volumes as cooking liquor.
Cooked for hours. The organic layer was concentrated under reduced pressure with an evaporator,
Lignin was prepared. The lignin was melt spun at 195 ° C. and wound up to a diameter of 40 μ.

The lignin fiber thus obtained was transferred into a furnace in an air atmosphere, heated from room temperature to 220 ° C. at a rate of 1 ° C./min, and completed infusibility and insolubilization in 1 hour. The strength of this lignin fiber is 3.6kg / mm ² , elongation 3.2%, elastic modulus 159kg / m
m ² ,

Example 3 For 1 kg of wood chip, the mixture of tricresole and water was 6, and the ratio of tricresole to water was 7 volumes to 3 volumes as cooking liquor.
Cooked for hours. The organic layer was concentrated under reduced pressure with an evaporator,
Lignin was prepared. This lignin was melt spun at 200 ° C. and wound up to a diameter of 50 μm.

Subsequently, the fiber is heated in a furnace in an air atmosphere from room temperature for 22 minutes.
The temperature was raised to 0 ° C. and heat-treated for 4 hours. The tensile strength of this fiber was 6.0 kg / mm ² , elongation 2.8%, and elastic modulus 305 kg / mm ² .

Next, a result of spinning in the same manner using lignin obtained by a conventional method as a raw material is shown as a comparative example.

Comparative Example 1 Lignin was prepared from beech wood by the kraft cooking method. When this lignin was heated to 190 ° C., it melted slightly but no spinnability.

Comparative Example 2 Lignin was prepared from beech wood using an organic solvent extraction method using 1,4-dioxane. The lignin was heated to 190 ° C., but hardly melted and no spinnability.

Effect of the Invention As described above, wood and lignocellulosic substances can be easily converted into lignin fiber by a melt spinning method from lignin obtained from an organic solvent digestion process in which an organic solvent composed of a mixture of phenols and water is used as a cooking liquor. It has become clear that can be manufactured. Further, the lignin fiber is cured and made infusible by heating, so that a lignin fiber having sufficient strength and heat resistance can be produced.

This result shows that lignin fibers can be easily produced from inexpensive lignin, a by-product of pulp production, and subsequently carbonized and graphitized to produce activated carbon or carbon fibers, which are high value-added products. Bring effect.
Furthermore, the lignin referred to in the present invention has been repeatedly and effectively used so far, but there is still no solid one, and it is merely burned as energy. There is also an effect that a high value-added product can be obtained from lignin that has been regarded as such waste.

Claims (2)

(57) [Claims] The present invention is characterized in that lignin obtained in a cooking process in which a wood-based substance is heated using an organic solvent composed of a mixture of phenols and water as a cooking liquor is collected, heated and melted and spun. A method for producing lignin fiber. 2. A method for producing a lignin fiber, characterized by curing and infusifying the lignin fiber obtained in claim (1) by heating.