JP6241849B2 - Method for producing silylated cellulose, silylated cellulose fiber obtained by the production method, regenerated cellulose fiber, and fiber-reinforced plastic molded product containing them - Google Patents

Description

The present invention relates to a method for producing silylated cellulose capable of silylating cellulose at a lower temperature and lower pressure than before, a silylated cellulose fiber obtained by melt spinning the silylated cellulose obtained by the production method, The present invention relates to a regenerated cellulose fiber obtained by desilylation of a silylated cellulose fiber, and a fiber reinforced plastic molded body containing the silylated cellulose fiber or the regenerated cellulose fiber.

A composite material (fiber reinforced plastic: FRP), which is made of glass fiber and other fibers with increased strength, is widely used in industrial products because it is lightweight and has excellent strength and heat resistance. Examples of uses of fiber reinforced plastics include automotive parts such as bumpers and door steps, furniture such as chairs, bathtubs, and boat hulls.

Glass fiber is generally used as the fiber added to the plastic. However, since glass fiber has a large specific gravity, there is a drawback that the weight of the FRP molded body increases. Further, the FRP molded body to which glass fiber is added has a problem that molten glass adheres to the heating furnace and is not suitable for recycling.

On the other hand, as in Patent Document 1, a technique for reinforcing a tire with cellulose fibers has been proposed. In the invention of Patent Document 1, a silylating agent having an O—Si—O—Si skeleton described in (Chemical Formula 1) of Claim 1 or Si— described in (Chemical Formula 2) of Claim 1 is used. A silylating agent having an xO-Si skeleton is used to silylate cellulose to obtain a cellulose derivative. The synthesized cellulose derivative is melt-spun and formed into a fiber shape.

Examples 1 to 19 of Patent Document 1 describe various silylation conditions. The reaction temperature of silylation is in the range of 100 to 140 ° C., and the reaction time is in the range of 2 to 8 hours. is there.

On the other hand, Table 1 of Patent Document 2 describes a method for silylating a carbohydrate such as a sugar. Specifically, No. 4 in Table 1 is reacted with cellulose acid degradation product (sugar) in the presence of ammonia and hexamethyldisilazane at 100 ° C under pressure (in an autoclave) to silylate the sugar. It is described to do. The degree of sugar substitution in No. 4 is 2.9. In claim 1, it is described that the reaction is carried out at a temperature of about 0 to 200 ° C., but in Table 1, the reaction temperature is in the range of 80 to 100 ° C.

Special table 2001-521072 JP-A-6-340687

Patent Document 1 and Patent Document 2 described above disclose methods for silylating cellulose and sugar, but the reaction temperature of the silylation reaction was relatively high at 100 to 140 ° C or 80 to 100 ° C. In addition, as seen in Patent Document 2, the operation in the silylation reaction is complicated, such as the necessity of performing the silylation reaction under a pressurized condition, and equipment that can withstand the reaction under pressure to perform the reaction. There was a problem that would be necessary. In the case of Patent Document 2, since the reaction is performed on a small scale, an autoclave that can be procured at a relatively low cost is used as an apparatus. However, when this reaction is converted into a large scale and industrialized, problems of operation and equipment appear more remarkably.

In view of the above problems, an object of the present invention is to provide a method capable of producing a silylated cellulose by allowing a silylated reaction to proceed under milder reaction conditions. Moreover, the silylated cellulose fiber formed by melt-spinning the silylated cellulose manufactured by the said method is provided. And the regenerated cellulose fiber formed by desilylating the said silylated cellulose fiber is provided. Furthermore, it aims at providing the fiber reinforced plastic molding which mix | blended the said silylated cellulose fiber or the said regenerated cellulose fiber.

A silylated cellulose characterized by reacting pretreated cellulose, an acid catalyst, and a silylating agent represented by the following (Chemical Formula 1) or (Chemical Formula 2) at 0 to 55 ° C. and 0.08 to 0.11 MPa. The above problem is solved by the manufacturing method. In the formula of (Chemical Formula 1), R _{1 to} R ₆ are the same or different and are a lower alkyl group having 1 to 4 carbon atoms, a lower alkenyl group having 1 to 4 carbon atoms, or an aryl group, and R ₇ is , A hydrogen atom. (Formula 2) R ₈ ~R ₁₀ in the formula of the same or different, a lower alkyl group having 1 to 4 carbon atoms, a lower alkenyl group, or an aryl group having from 1 to 4 carbon atoms, R ₁₁ ~ R ₁₂ is the same or different and is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, or NR ₁₁ R ₁₂ is a heteroaryl group containing a nitrogen atom. In the formula, Si is silicon and N is nitrogen. The present inventors have studied a method for performing a silylation reaction under mild conditions, and found that a silylating agent having a Si-NH-Si skeleton, a Si-NH ₂ skeleton, or a Si-N skeleton and an acid catalyst exist. If it is below, it discovered that silylated cellulose could be manufactured on mild reaction conditions, such as room temperature and atmospheric pressure, and came to complete this invention. In the present invention, “silylation” means R ₁ R ₂ R ₃ —Si group or R ₁ R ₂ R ₃ —Si group in (Chemical Formula ₁ ), or R ₈ R ₉ R ₁₀ —Si group in (Chemical Formula 2). Indicates that a specific functional group is substituted with a group.

In the method for producing silylated cellulose, the pretreatment of cellulose is preferably performed by adding cellulose to an alkaline solution and stirring (sometimes referred to as mercerization). By adding and stirring the cellulose to the alkaline solution, the hydrogen bond between the hydroxyl groups of the cellulose can be broken to improve the silylation efficiency.

In the method for producing silylated cellulose, trifluoroacetic acid, methanesulfonic acid, p-toluenesulfonic acid, or trifluoromethanesulfonic acid is preferably used. By using together with the above silylating agent (Chemical Formula 1), silylation can be carried out under mild reaction conditions.

In the method for producing silylated cellulose, the time for reacting the pretreated cellulose, the acid catalyst, and the silylating agent of (Chemical Formula 1) is preferably 0.3 to 2 hours. In the present invention, the silylation reaction can be completed under milder reaction conditions than before and in a short time.

According to the method for producing silylated cellulose, silylated cellulose having a substitution degree of 1.8 to 3.0 can be obtained. The degree of substitution herein refers to the degree to which the hydroxyl group in glucose constituting cellulose is substituted. Since the number of glucose hydroxyl groups in cellulose is 3, the degree of substitution is 3.0. By making the degree of substitution within the above range, as will be described later, the heat resistance required for melt spinning the silylated cellulose or mixing the silylated cellulose fiber with the melted plastic and molding the cellulose Can be given to.

Silylated cellulose fibers can be obtained by melt spinning the silylated cellulose obtained by the method for producing silylated cellulose. The melt spinning is preferably performed by heating the silylated cellulose obtained by the above-described method for producing silylated cellulose with an extruder to 230 to 250 ° C. and then extruding it from a spinneret. The silylated cellulose obtained by the above production method can be easily formed into a thread shape within the above temperature range without impairing the quality.

As a raw material for the above-mentioned method for producing silylated cellulose, a raw material cellulose having a polymerization degree of 1000 or more is used for silylation reaction, and when the obtained silylated cellulose is melt-spun, the silylated cellulose fiber is drawn, Silylated cellulose fibers having a high tensile strength can be obtained. In stretching, it is preferable to stretch when the silylated cellulose fiber is in the temperature range of 200 to 250 ° C.

A regenerated cellulose fiber can be obtained by desilylating the silylated cellulose fiber. This regenerated cellulose fiber can be suitably used as a raw yarn for clothing fabrics and a decorative fabric such as curtains.

A fiber reinforced plastic molding can be obtained by blending the above silylated cellulose fiber or the above regenerated cellulose fiber into a plastic. Since silylated cellulose fiber or regenerated cellulose fiber has a specific gravity about half that of glass fiber, it is possible to obtain a plastic molded body that is lightweight and excellent in strength.

According to the method for producing silylated cellulose of the present invention, silylated cellulose can be produced at a lower temperature and lower pressure than in the past. The silylated cellulose obtained by this production method can be formed into silylated cellulose fibers, that is, yarns, by melt spinning. When this silylated cellulose fiber is desilylated, a regenerated cellulose fiber can be obtained. Silylated cellulose fiber can be suitably used for applications such as automotive parts. The regenerated cellulose fiber can be suitably used for applications such as clothing fabrics. If a silylated cellulose fiber or a regenerated cellulose fiber is cut into a predetermined length, added to a melted plastic, and molded, a lightweight and strong plastic molded body can be obtained.

It is a reaction formula when making cellulose into a mercer. It is a reaction formula when cellulose is silylated in the presence of hexamethyldisilazane and trifluoroacetic acid.

Hereinafter, modes for carrying out the invention will be described.

In the method for producing silylated cellulose of the present invention, the cellulose is pretreated. In the pretreatment, the hydrogen bond of the crystallized cellulose is broken so that the silylating agent shown in the above (Chemical Formula 1) or (Chemical Formula 2) can easily access the hydroxyl group of glucose constituting the cellulose molecule. As the pretreatment, the mercerization described above can be suitably employed. In addition, a method of adding cellulose to an ammonia solution and pressurizing it with an autoclave or the like to explode the cellulose can be employed. In the latter case, since the pressure treatment is involved, the former can be suitably employed.

Examples of the alkaline solution used in mercerization include an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, an aqueous calcium hydroxide solution, and an aqueous barium hydroxide solution. It is preferable to use an aqueous sodium hydroxide solution that can be procured at low cost. Sodium hydroxide is preferably added to the solvent so that the sodium hydroxide solution is 15 to 60% by weight (hereinafter sometimes referred to as wt%) based on the total weight of the solution, More preferably, it is 40% by weight. If the amount of sodium hydroxide added is small, hydrogen bond breakage may be insufficient, and silylation may not be performed sufficiently. When there is much addition amount of sodium hydroxide, the molecular weight of a cellulose may fall. Mercerization dissociates protons from hydroxyl groups in glucose in cellulose molecules (see FIG. 1). The mercerization temperature is preferably in the range of 5 to 60 ° C.

After cellulose is mercerized, it is filtered or centrifuged to precipitate the cellulose (hereinafter referred to as centrifuge), and the alkaline solution is removed. And a solvent is substituted from an alkaline solution to a polar solvent by adding a polar solvent to a cellulose. Examples of the polar solvent include those that are not inconvenient to handle and do not interfere with the subsequent silylation reaction. For example, N-methylpyrrolidone (NMP), N, N-dimethylacetamide (DMAc), dimethylsulfoxide (DMSO), tetrahydrofuran, dimethylsulfone, tetramethylfuran and the like can be mentioned.

When replacing the solvent, filtration or centrifugation is performed as described above. If excessive suction is performed by suction filtration during filtration, or if excessive centrifugal force is applied during centrifugation, cellulose may aggregate and the silylation efficiency may be reduced. Therefore, in the case of centrifugation, the centrifugal force is preferably in the range of 2000 to 4000 × g.

A silylating agent and an acid catalyst are added to cellulose substituted with a polar solvent. If the silylating agent and the acid catalyst are added at once, the hydroxyl group of cellulose may not be appropriately silylated, so the acid catalyst is gradually added to the polar solvent containing the silylating agent and cellulose by an operation such as dropping. It is preferable to go. More preferably, the acid catalyst is diluted with a polar solvent and added dropwise.

Among the silylating agents of the above (Chemical Formula 1), compounds in which R _{1 to} R ₆ are lower alkyl groups include bis (trimethylsilyl) amine (common name: hexamethyldisilazane (HMDS)), bis (triethylsilyl) amine. Bis (tripropylsilyl) amine, bis (tributylsilyl) amine, and the like. Here, examples in which R _{1 to} R ₆ are the same in (Chemical Formula 1) are given, but R _{1 to} R ₆ may be different from each other in the range of 1 to 4 carbon atoms. For example, di-n-ethyltetramethyldisilazane such as 1,3-di-n-ethyltetramethyldisilazane, di-n-propyltetramethyldisilazane such as 1,3-di-n-propyltetramethyldisilazane, etc. And di-n-butyltetramethyldisilazane such as silazane and 1,3-di-n-butyltetramethyldisilazane.

Among the silylating agents of the above (Chemical Formula 1), compounds in which R _{1 to} R ₆ are lower alkenyl groups include divinyltetramethyldisilane such as 1,3-divinyl-1,1,3,3-tetramethyldisilazane. Diallyltetramethyldisilazane such as silazane, 1,3-diallyl-1,1,3,3-tetramethyldisilazane, 1,3-di (1-butenyl) -1,1,3,3-tetramethyldi And dibutenyltetramethyldisilazane such as silazane. Here, examples in which R _{1 to} R ₆ are different in (Chemical Formula 1) have been given, but R _{1 to} R ₆ may be the same in a range of 1 to 4 carbon atoms.

Among the silylating agents of the above chemical formula (1), compounds in which R _{1 to} R ₆ are aryl groups include diphenyltetramethyldisilazane such as 1,3-diphenyl-1,1,3,3-tetramethyl-disilazane. , Ditolyltetramethyldisilazane, dixylyltetramethyldisilazane, and the like. Here, examples in which R _{1 to} R ₆ are different in (Chemical Formula 1) have been given, but R _{1 to} R ₆ may be the same in a range of 1 to 4 carbon atoms.

Among the silylating agents of the above (Chemical Formula 2), examples of the compound in which R _{8 to} R ₁₀ are lower alkyl groups include trimethylsilylamine, triethylsilylamine, tripropylsilylamine, tributylsilylamine and the like. Here, examples in which R _{8 to} R ₁₀ are the same in (Chemical Formula 2) are given, but R _{8 to} R ₁₀ may be different from each other in the range of 1 to 4 carbon atoms. Examples thereof include dimethylethylsilylamine, dimethylbutylsilylamine, dibutylethylsilylamine and the like.

Among the silylating agents of (Chemical Formula 2), examples of the compound in which R _{8 to} R ₁₀ are lower alkenyl groups include trivinylsilylamine, triallylsilylamine, tri (1-butenyl) silylamine and the like. Here, examples in which R _{8 to} R ₁₀ are the same in (Chemical Formula 2) are given, but R _{8 to} R ₁₀ may be different from each other in the range of 1 to 4 carbon atoms. Examples thereof include divinylmethylsilylamine, divinylbutylsilylamine, vinyldibutylsilylamine and the like.

Among the silylating agents of the above (Chemical Formula 2), compounds in which R _{8 to} R ₁₀ are aryl groups include dimethylphenylsilylamine, diethylphenylsilylamine, dibutylphenylsilylamine, methyldiphenylsilylamine, dimethyltolylsilylamine, Examples include dimethylxylylsilylamine. Here, an example in which R _{8 to} R ₁₀ are different in (Chemical Formula 2) has been given, but R _{8 to} R ₁₀ may be the same. An example is triphenylsilylamine.

Among the silylating agents of the above (Chemical Formula 2), R _{11 to} R ₁₂ are alkyl groups having 1 to 4 carbon atoms such as N, N-dimethylaminotrimethylsilane, N, N-diethylaminotrimethylsilane, N , N-dibutylaminotrimethylsilane, N-methyl-Nbutylaminotrimethylsilane, N, N-dimethylaminotriethylsilane and the like.

Among the silylating agents of the above (Chemical Formula 2), the compounds of the heteroaryl group in which —NR ₁₁ R ₁₂ contains nitrogen include trimethylsilylimidazole, triethylsilylimidazole, tripropylsilylimidazole, divinylmethylsilylimidazole, triphenyl Examples thereof include silylimidazole and diethylphenylsilylimidazole. N in “—NR ₁₁ R ₁₂ ” is a nitrogen atom in the heteroaryl group.

Examples of the acid catalyst include trifluoroacetic acid, methanesulfonic acid, p-toluenesulfonic acid, and trifluoromethanesulfonic acid. Any acid catalyst that dissociates protons other than those listed here can be used as long as it does not interfere with the silylation reaction.

Next, the reaction mechanism of silylation of cellulose will be described. The silylating agent of (Chemical Formula 1) has a Si—NH—Si skeleton, and it is presumed that the silylation reaction of cellulose proceeds as shown in the formula of FIG. That is, the protons supplied from the acid catalyst (trifluoroacetic acid in the case of FIG. 2) tend to be easily attached to nitrogen in the Si—NH—Si skeleton in the compound of (Chemical Formula 1) (hexamethyldisilazane in the case of FIG. Yes, when protons bind to nitrogen, nitrogen is positively charged. The hydroxyl group of cellulose acts as a nucleophile (δ ⁻ ) and attacks positively charged nitrogen to attack the R ₁ R ₂ R ₃ —Si group (trimethylsilyl group: TMS group in FIG. 2) and hydrogen of the hydroxyl group of cellulose. Replaces. As a result of the substitution reaction, R ₄ R ₅ R ₆ —Si—NH ₂ (trimethylsilylamine in FIG. 2) is by-produced. Proton is easily attached to nitrogen of R ₄ R ₅ R ₆ —Si—NH ₂ (trimethylsilylamine in FIG. 2) which is a by-product (Chemical Formula ₂ ), and the nitrogen is positively charged. As described above, the hydroxyl group of cellulose acts as a nucleophilic reagent (δ ⁻ ), and attacks positively charged nitrogen to form R ₄ R ₅ R ₆ —Si group (trimethylsilyl group in FIG. 2) and the hydroxyl group of cellulose. Replace with hydrogen. As a result of this substitution reaction, ammonia gas (NH ₃ ) is by-produced. As a result of the experiment, it has been confirmed that ammonia gas is by-produced after the reaction. From this, it is presumed that the reaction proceeds according to the above reaction mechanism. Here, an example in which the silylating agent of (Chemical Formula 1) is used has been described, but silylation occurs in the same reaction mechanism in the silylating agent of (Chemical Formula 2).

The reaction temperature of the silylation reaction is preferably 0 to 55 ° C, more preferably 5 to 40 ° C, and most preferably room temperature. The reaction temperature may be controlled by heating or cooling so as to be within the range, but it is preferable to carry out the reaction without heating or cooling at room temperature because the operation and equipment are the simplest. The reaction pressure of the silylation reaction is preferably 0.08 to 0.11 MPa, more preferably 0.09 to 0.105 MPa, and most preferably atmospheric pressure. Although the reaction pressure may be controlled so as to be within the range by pressurization or depressurization, it is most preferable to perform the reaction without applying pressure or depressurization under atmospheric pressure because the operation and equipment are simple.

According to the method for producing silylated cellulose, silylated cellulose having high heat resistance can be produced in a short reaction time of about 0.3 to 2 hours. There is a correlation between the substitution degree of the hydroxyl group of glucose constituting the cellulose and the heat resistance, and the higher the substitution degree, the higher the heat resistance. In the production method of the present invention, silylated cellulose having a substitution degree of 1.8 to 3.0 can be obtained. Thereby, excellent heat resistance with a glass phase transition temperature of 200 ° C. or higher can be realized. The degree of substitution is more preferably 2.0 to 3.0.

The silylated cellulose obtained by the above-mentioned method for producing silylated cellulose can be easily formed into a thread by heating and softening by any method (melt spinning). Since the glass phase transition point is 200 ° C. or higher, silylated cellulose fibers can be obtained by heating to 230 to 250 ° C. and extruding from a spinneret using a known extruder. By stretching the silylated cellulose fiber, the silylated cellulose can be oriented to increase the tensile strength. The stretching is preferably performed at a temperature equal to or higher than the glass phase transition temperature. More preferably, it is the range of 200-250 degreeC. If stretching is performed immediately after extrusion from the spinneret, stretching can be performed with high work efficiency. After the silylated cellulose fiber is cooled, it may be heated again to perform secondary stretching. The draw ratio is preferably 10 to 80 times. If the silylated cellulose fiber is immersed in an acidic solution and desilylated, regenerated cellulose fiber can be obtained.

By melting a base material such as polypropylene or polyethylene and adding the silylated cellulose fiber or regenerated cellulose fiber to the base material and molding it into a predetermined shape, a lightweight and strong fiber-reinforced plastic molded body is obtained. Can do. A molding method such as injection molding can be employed.

Hereinafter, examples of the present invention will be described in more detail.

[Example 1]
1 g of raw material cellulose (Nippon Paper Chemicals, W-400G) having a polymerization degree of 300 was put into 20 mL of a 24 wt% sodium hydroxide aqueous solution and maintained at 40 ° C. for 1 hour for mercerization. 80 mL of methanol was added to the suspension of cellulose and sodium hydroxide aqueous solution after mercerization, and this was filtered. The filtration residue was added to 30 mL of N-methylpyrrolidone (NMP), and the supernatant was removed by centrifugation at 3080 × g. NMP (10 ml) was added to the cellulose precipitated by centrifugation, and the solvent was replaced. To this was added 8 ml of hexamethyldisilazane (HMDS) represented by the following formula (2 mol per hydroxyl group of cellulose) at room temperature (24 ° C) and atmospheric pressure. Under stirring (about 0.1 MPa), a slurry was formed.

0.135 mL of trifluoroacetic acid (TFA) (0.1 mol of catalyst per mol of cellulose hydroxyl group, 0.1 / 1 × 100 = 10%) and NMP 10 ml mixed with the above slurry-like cellulose while stirring over 2 minutes It was dripped in. After completion of the dropwise addition of TFA, the slurry became transparent. As time passed, the reaction product precipitated and ammonia gas was by-produced. 100 ml of methanol was added to the suspension 30 minutes after the completion of the TFA addition, followed by filtration. The filter residue was vacuum dried at 50 ° C. for 16 hours.

[Example 2]
Cellulose with a polymerization degree of 1500 (Nippon Paper Chemicals, W-100GK) was used as the raw material cellulose, and NMP40ml was added to the cellulose precipitated by centrifugation to replace the solvent, and HMDS 8ml (2mol per hydroxyl group of cellulose) In addition, the mixture was stirred at room temperature (24 ° C.) to form a slurry, and 0.135 mL of trifluoroacetic acid (TFA) (0.1 mol of catalyst per mol of cellulose hydroxyl group, 0.1 / 1 × 100 = 10%) and 10 ml of NMP were mixed. The reaction was carried out in the same manner as in Example 1, except that the total amount of the product was dropped over the slurry-like cellulose while stirring over 2 minutes. As in Example 1, the slurry became transparent after completion of the dropwise addition of TFA, and as the time further passed, the reaction product precipitated and ammonia gas was by-produced.

[Example 3]
The concentration of sodium hydroxide solution used in mercerization was 18 wt%, N, N-dimethylacetamide (DMAc) was used instead of NMP, reaction temperature (HMDS was added to cellulose substituted with DMAc) The reaction was carried out in the same manner as in Example 2 except that the heating temperature was changed to 30 ° C. and the reaction time was changed to 1 hour. As in Example 2, the slurry became transparent after the completion of the dropwise addition of TFA, and as time passed, the reaction product precipitated and ammonia gas was by-produced.

[Example 4]
The concentration of sodium hydroxide solution used in mercerization was 25 wt%, the reaction time of mercerization was changed to 2 hours, the acid catalyst used was changed to methanesulfonic acid, and the reaction temperature (NMP The reaction was carried out in the same manner as in Example 2 except that the heating temperature after addition of HMDS to solvent-substituted cellulose was changed to 22 ° C. As in Example 2, the slurry became transparent after the completion of the dropwise addition of TFA, and as the time further passed, the reaction product precipitated and ammonia gas was by-produced.

[Example 5]
The reaction was carried out in the same manner as in Example 1 except that the concentration of the sodium hydroxide solution used in mercerization was 25 wt% and that the acid catalyst used was changed to p-toluenesulfonic acid. As in Example 1, the slurry became transparent after the completion of the dropwise addition of TFA, and as the time further passed, the reactants precipitated and ammonia gas was by-produced.

[Example 6]
The concentration of sodium hydroxide solution used in mercerization is 25wt%, the acid catalyst used is changed to trifluoromethanesulfonic acid, the reaction temperature (heating temperature after adding HMDS to NMP solvent-substituted cellulose) ) Was carried out in the same manner as in Example 2 except that the point was changed to 22 ° C. As in Example 2, the slurry became transparent after the completion of the dropwise addition of TFA, and as the time further passed, the reaction product precipitated and ammonia gas was by-produced.

[Comparative Example 1]
The concentration of sodium hydroxide solution used in mercerization was 25 wt%, the reaction temperature (heating temperature after adding HMDS to cellulose substituted with NMP) was changed to 22 ° C, and the reaction time was 1 hour. The same procedure as in Example 2 was conducted except for the point changed to 1, the use of 1,1,3,3-tetramethyldisilazane (TMDS) represented by the following formula (Chemical Formula 4) as the silylating agent. The reaction was performed. There was no change in the slurry after dropping TFA, and no ammonia gas was produced as a by-product.

[Comparative Example 2]
The reaction was carried out in the same manner as in Example 2 except that the reaction temperature (heating temperature after addition of HMDS to cellulose substituted with NMP) was changed to 60 ° C. and the reaction time was changed to 1 hour. It was. Immediately after dropping TFA, a rapid reaction occurred and a translucent lump was formed. Although ammonia gas was produced as a by-product, the resulting mass did not reach the desired degree of substitution.

[Degree of substitution]
The reactants obtained by vacuum drying in each Example and Comparative Example are analyzed by proton nuclear magnetic resonance by the following method to identify the compound and determine the substitution degree (DS) of the hydroxyl group in the glucose unit constituting cellulose. It was. The glucose unit has 3 hydroxyl groups per unit, and the maximum degree of substitution is 3.0 (DS ≦ 3.0). As a result of measurement, Examples 1 to 6 were found to be trimethylsilylated celluloses having the respective substitution degrees described in Table 1. Since the reactants obtained in Comparative Examples 1 and 2 could not be dissolved in a solvent such as chloroform or tetrahydrofuran (THF), measurement by proton nuclear magnetic resonance (1H-NMR) can be performed. There wasn't.

[Proton nuclear magnetic resonance]
20 mg of the reaction product of each example and each comparative example was dissolved in 1500 mg of chloroform-d. Thereafter, 20 μL of tetrachloroethane (TCE) was added to the solution as an internal standard substance and stirred well. The trimethylsilyl group was quantified by proton nuclear magnetic resonance, and the degree of substitution (DS) was determined by the following equations 1 to 3. In the formula, Y is the weight (g) of the reaction product of each example or each comparative example, TCE is the TCE weight (g), XTCE is the purity of TCE, P0ppm is the peak area value of the trimethylsilyl group. Yes, P6ppm is the TCE peak area value. 378 is the molecular weight of TMSC when DS = 3, 27 is the number of hydrogen atoms of the trimethylsilyl group when DS = 3, 167.84 is the molecular weight of TCE, and 2 is the number of hydrogen atoms of TCE .

[Melt spinning]
Using the single screw extruder (Toyo Seiki Seisakusho Co., Ltd., Labo Plast Mill 50MR), the reaction product obtained in each Example and each Comparative Example was melt-spun. The die has a circular spinneret with a diameter of 0.6 mm. The temperature of the kneading part of the extruder is 230 ° C. and less than 20 MPa, and the temperature of the extrusion port is 240 ° C. After extruding from the spinneret at a pressure of 20 MPa or less, the product was cooled by blowing air and wound on a bobbin while being drawn. The winding speed is 20 m / min. The wound fiber was subjected to a stretching spinning heating plate (Imoto Seisakusho Co., Ltd., IMC-1A24 type) and further subjected to secondary stretching at 220 ° C. The total draw ratio of the primary stretch and the secondary stretch is 53 times.

When the reactants obtained by the methods of Examples 1 to 4 were melt-spun and drawn by the above method, the white yarn was discharged without interruption, and a silylated cellulose fiber having a diameter of 0.07 mm was obtained. It was made (indicated by ◎ in Table 1). When the reactants obtained by the methods of Examples 5 and 6 were melt-spun by the above method, 0.07 mm diameter silylated cellulose fibers could be obtained (indicated by o in Table 1). On the other hand, when the reactants obtained by the methods of Comparative Examples 1 and 2 were spun by the above method, a yellow-brown cake made of papasa was just discharged from the spinneret and could not be formed into a yarn ( (Indicated by x in Table 1).

(Measurement of tensile strength)
The tensile strength of the monofilament stretched as described above was measured at a tensile rate of 100 μm / sec using a cooling and heating stretch observation stage (Japan Hightech Co., Ltd .; 10073B). The measurement was conducted by melt spinning the trimethylsilylated cellulose synthesized by the method of Example 1 and then stretching it. As a representative example, the tensile strength was 659.8 MPa and the fiber diameter was 18.79 μm. Next, this fiber was immersed in a mixed solution of 2-propanol-water-35% hydrochloric acid solution heated to 75 ° C. (mixing ratio was 12: 8: 1 by volume in the order described) for 2 minutes. Then, the regenerated cellulose fiber was obtained by wash | cleaning with methanol and drying. With respect to this regenerated cellulose fiber, the tensile strength was measured by the same measurement method as described above, and it was 602.8 MPa.

Example 2 When the tensile strength of melt-spun trimethylsilylated cellulose synthesized by the method and then stretched was measured by the same method as described above, the tensile strength was 735.5 MPa and the fiber diameter was 13.62 μm. there were. Subsequently, when the molecular weight of the silylated cellulose constituting this fiber was examined by gel permeation chromatography according to the following method, the molecular weight was 501870 (degree of polymerization: about 1490).

[Gel permeation chromatography]
The reaction product obtained in Example 2 was dissolved in chloroform to a concentration of 1 wt%. Using gel permeation chromatography (JASCO Corporation, RI-2031 Plus), measurement was performed at a flow rate of 1 mL / min using chloroform as a mobile phase in a column heated to 40 ° C. As shown in the following equations 4 and 5, the molecular weight per glucose molecule in trimethylsilylated cellulose is calculated from the degree of substitution measured in advance by 1H-NMR, and the molecular weight obtained by gel permeation chromatography is trimethylsilylated. The degree of polymerization (DP) was determined by the molecular weight per glucose molecule in cellulose. In the formula, 159 is the difference between glucose and hydroxyl protons, 73 is the molecular weight of the trimethylsilyl group, 3 is the molecular weight of the hydroxyl group proton of glucose, and MW _TMSC is the glucose per molecule in trimethylated cellulose. The molecular weight, DS is the degree of substitution determined from 1H-NMR, and MW _GPC is the molecular weight of trimethylsilylated cellulose obtained by GPC.

[Manufacture of fiber-reinforced plastic moldings]
The glass phase transition point of the glass phase transition of the trimethylsilylated cellulose fiber (Example 2) having a tensile strength of 735.5 MPa and a fiber diameter of 13.62 μm was measured with a differential scanning calorimeter (DSC) (Seiko Instruments; EXSTAR DSC6200). The transfer temperature was 203 ° C. Using alumina as a reference, the sample was cooled at −20 ° C. for 30 minutes, and then heated to 270 ° C. at a rate of temperature increase of 10 ° C./min. Since the thermal decomposition of TMSC occurred from 270 ° C, the temperature was set to 270 ° C. The pellets of this trimethylsilylated cellulose fiber and polypropylene (Prime Polymer Co., Ltd., J-700GP) are put into a hopper of an injection molding machine, and conveyed inside the cylinder heated by a heating jacket while applying pressure with a screw. It extruded into the metal mold | die from the extrusion port of the front-end | tip. The temperature of the extrusion port was set to 185 ° C. The mold was removed from the mold to produce an automobile door step. Since this door step was reinforced with trimethylsilylated cellulose fibers, it had sufficient strength. The weight was lighter than that reinforced with glass fiber.

Claims (12)

A method for producing silylated cellulose, comprising reacting pretreated cellulose, an acid catalyst, and a silylating agent represented by the following (Chemical Formula 1 ) at 0 to 55 ° C and 0.08 to 0.11 MPa.
[In the formula of (Chemical Formula 1), R _{1 to} R ₆ are the same or different and are lower alkyl groups having 1 to 4 carbon atoms,
R7 is a hydrogen atom. ] The method for producing silylated cellulose according to claim 1, wherein the pretreatment of cellulose is to add cellulose to an alkaline solution and stir. The method for producing silylated cellulose according to claim 1 or 2, wherein the acid catalyst is trifluoroacetic acid, methanesulfonic acid, p-toluenesulfonic acid, or trifluoromethanesulfonic acid. The method for producing silylated cellulose according to any one of claims 1 to 3, wherein the time for reacting the silylating agent and cellulose is 0.3 to 2 hours. The method for producing silylated cellulose according to any one of claims 1 to 4, wherein the degree of substitution of the silylated cellulose to be produced is 1.8 to 3.0. The method for producing silylated cellulose according to any one of claims 1 to 5, wherein a glass phase transition temperature of the silylated cellulose to be produced is 200 ° C or higher. Method for producing a silylated cellulose fibers to produce a silyl cellulose fibers by melt-spinning the resulting silylated cellulose by the production method described in any one of claims 1 to 6. The method for producing silylated cellulose fibers according to claim 7, wherein the melt spinning is one in which silylated cellulose is heated to 230 to 250 ° C with an extruder and extruded from a spinneret to form into a yarn shape. A silylation reaction was carried out using a raw material cellulose having a polymerization degree of 1000 or more as a raw material of the method for producing silylated cellulose according to any one of claims 1 to 6, and the resulting silylated cellulose was obtained by melt spinning. The method for producing a silylated cellulose fiber according to claim 7 or 8, wherein the silylated cellulose fiber is stretched. The method for producing a silylated cellulose fiber according to claim 9, wherein the silylated cellulose fiber obtained by melt spinning is stretched at a temperature of 200 to 250 ° C. A method for producing a regenerated cellulose fiber, comprising desilylating the silylated cellulose fiber obtained by the method according to claim 7 to produce a regenerated cellulose fiber . Fiber-reinforced plastic for manufacturing a fiber-reinforced plastic molded by blending a regenerated cellulose fiber obtained by the method described in silylated cellulose fibers or claim 11 obtained by the method described in any one of claims 7 to 10 A method for producing a molded body .