JPS6410544B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] This invention is a stable and non-polluting cellulose ester that is obtained by dissolving in water a water-soluble cellulose ester obtained by acting an esterifying agent on a dimethyl sulfoxide/formaldehyde mixed solvent solution of cellulose. This invention relates to a method for producing molding dope that does not require any additional processing. The molding dope obtained by the production method of the present invention allows fibers and films of high molecular weight cellulose derivatives to be produced pollution-free and at low cost. The resulting molded article has high water absorption properties, and the fibers are particularly useful in the clothing and medical fields. [Prior art and problems to be solved by the invention] Because cellulose has strong intermolecular and intramolecular hydrogen bonds, it has traditionally been difficult to use metal complexes such as copper ammonia, quaternary amines, strong acids, etc. It has been said that it is soluble only in the medium in which it is mixed. Even now, the copper ammonium method and the viscose method are widely used in the actual production of cellulose fibers and films. However, these industrial methods have drawbacks such as high water consumption, the need to recover heavy metals, and high energy consumption. In recent years, new organic solvents for cellulose have been searched to overcome these drawbacks.
An industrial method has also been proposed in which cellulose is dissolved in an organic solvent and the resulting dope is directly spun and shaped. For example, JP-A-53-70121 discloses a method in which cellulose is dissolved in a dimethyl sulfoxide/formaldehyde system and the resulting dope is extruded into a gas atmosphere containing ammonia. However, when directly molding this dope, it requires a large amount of energy to remove dimethyl sulfoxide, which is a high boiling point solvent, by vaporization, and a complicated process is required to recover the solvent, resulting in high costs. It has been found that this method has many fatal drawbacks, such as the accompanying effects on the human body and the problem of decomposition of the solvent itself. In order to solve the technical and economical difficulties associated with the molding of cellulose, the present inventors have developed a nonionic cellulose derivative that is closer to cellulose, that is, a nonionic cellulose derivative with a low degree of substitution, which is safe, non-polluting, and has a low degree of substitution. We have been actively investigating methods of dissolving it in a low-cost solvent such as water and molding it. Generally, chemically modifying cellulose in a heterogeneous system to obtain such a target product is difficult to set reaction conditions such as controlling the degree of substitution of the obtained product and suppressing a decrease in the degree of polymerization. It is not suitable for stabilizing the quality of substitution degree products. For example, when cellulose is heterogeneously oxidized with acetic anhydride using a sulfuric acid catalyst, it is inevitable that the degree of polymerization of the starting cellulose will decrease dramatically, and it is difficult to obtain a degree of substitution of 2.0 or less. Recently, Earl. B. Seymour, E. L.
Johnsson; Journal of Polymer. Science (RB Seymour, EL Johnson; Journal
of Polymer Science), Vol. 16 (1978), describes the process of dissolving cellulose in a dimethyl sulfoxide/formaldehyde system and then esterifying the cellulose with acetic anhydride using pyridine as a catalyst. It is taught that by selecting the following, an acetone-soluble derivative with extremely little decrease in the degree of polymerization can be obtained. On the other hand, the range of degree of substitution in which water solubility can be maintained in conventional cellulose derivatives, particularly nonionic cellulose ethers such as methylcellulose and ethylcellulose, has been determined by N. M. Bikarus, L.
Segal, Cellulose and Cellulose Derivatives (NMBikals, L.Segal,
Cellulose and Cellulose Derivatives) P193,
It is usually 0.7-0.8, and 0.5-0.6 for ethylcellulose with a very low degree of polymerization (DP) (DP<150), as described in Wiley Interscience, New York (1971). It is. It is said that if the degree of substitution is lower than these ranges, it will dissolve only in an alkaline aqueous solution. In order to achieve the above objective, the present inventors have discovered the advantages of a cellulose solution using a dimethyl sulfoxide/formaldehyde mixed solvent, namely, the depolymerization of cellulose is small and the reaction is uniform when chemically modifying cellulose. Taking advantage of the feature that the degree of substitution can be easily controlled, intensive studies were conducted on the reactivity of the cellulose solution with various reactants, the solubility of the obtained products, etc. As a result, they surprisingly discovered a nonionic cellulose ester that not only has a high molecular weight and is soluble in water over an extremely wide range of degrees of substitution, but also can be crosslinked and/or regenerated into cellulose through post-treatment. This led to the invention. [Means for Solving the Problems] The method for producing a molding dope according to the present invention involves allowing an esterification agent to act on a dimethyl sulfoxide/formaldehyde mixed solvent solution of cellulose, and dissolving the resulting water-soluble cellulose ester in water. It is characterized by This molding dope is stable and non-polluting. That is, cellulose is preferably dissolved in a dimethyl sulfoxide/formamide mixed solvent to obtain methylolated cellulose, and an esterifying agent such as acetic anhydride, methylene diacetate, or ethylene diacetate is added to the same system. It is a dope made by preparing a water-soluble cellulose ester with a degree of substitution of 0.3 to 0.8 and then dissolving this cellulose ester in water, and is extremely stable and non-polluting, and has excellent moldability. The main characteristics of the molding dope obtained through these series of processes are: 1) The degree of polymerization of the cellulose ester in the dope can be increased to a high degree of polymerization (DP
1000) and 2) the degree of substitution of cellulose ester in the dope.
This can be controlled almost quantitatively by selecting the amount of reactant added. Here, the "degree of substitution" refers to the ratio of the number of substituents replacing hydrogen atoms of hydroxyl groups in the pyranose ring of the cellulose molecular chain to one pyranose ring. Cellulose, the raw material, exists naturally in the form of fibers. For example, in wood, fibers are stuck together with lignin, but by pulping, the lignin can be removed and the fibers can be liberated and purified for use. In addition, cotton has a low non-cellulose content in its natural state and is easy to purify, so it can be advantageously used as a raw material for cellulose. The degree of polymerization of the raw material can be adjusted depending on the purpose, and a degree of at least 100 is sufficient. Further, in order to improve the mechanical properties of the product, those having a degree of polymerization of 1000 or more can be used. Desirably, the dimethyl sulfoxide/formaldehyde molar ratio is from about 2/1 to about 4/1. Further, when cellulose is dissolved in a dimethyl sulfoxide/formamide mixed solvent, the cellulose concentration is preferably 5 to 10% by weight, although it depends on its degree of polymerization. The dissolution temperature is preferably 70 to 90°C in order to prevent decomposition of the solvent itself. The temperature in the reaction process after dissolution is suitably 20 to 70°C in order to prevent the degree of polymerization of the cellulose once dissolved from decreasing due to the reactant and solvent. When an acid anhydride such as acetic anhydride, methylene diacetate, or ethylene diacetate is used as a reactant, the amount of the reactant is 4 to 12 moles per glucose residue in cellulose for acetic anhydride; 1 for ethylene diacetate
moles to 14 moles. If the amount of the reactant is out of these ranges, the desired water-soluble product cannot be obtained, and in particular, if the amount of the reactant is large, it will not dissolve in water alone. These reactants react with cellulose to produce the desired target product even without a catalyst, but if a catalyst such as pyridine or sodium acetate is used, the reaction time to obtain the target product and the amount of reactant input can be reduced. I can do it. In addition, the degree of substitution of the polymer can also be determined by NMR spectrum analysis, infrared absorption spectrum analysis, etc. in the case of cellulose ester obtained using an acetylating agent, but by taking advantage of its water solubility, It can also be determined by dissolving cellulose ester in water, saponifying it with an alkali, and then neutralizing and titrating with an acid. The degree of substitution of the acetylated derivative in the present invention refers to that obtained by neutralization titration. The cellulose ester obtained in this way is
Products obtained from acetic anhydride, methylene diacetate, ethylene diacetate, etc. are soluble in water with a degree of substitution (DS) in the range of 0.3 to 0.8. DS is
When it exceeds 0.8, it becomes soluble in water/acetone and organic solvents. When DS is less than 0.3, it becomes soluble in inorganic acid aqueous solution. In the method of the present invention, the cellulose ester in the water-soluble range obtained in the process of preparing the molding dope has a chemical structure essentially different from that obtained by simply acetylating cellulose, and is a novel chemical. It has a structure. For example, derivatives obtained from acetic anhydride, methylene diacetate, and ethylene diacetate have acetoxymethylcellulose as a main component. The above-mentioned substitution degree range in which water solubility can be maintained is limited to cellulose esters having a degree of polymerization of about 500 or more, and even when the polymerization degree is smaller, the substitution degree range in which water solubility can be maintained is further expanded.
Here, the weight average molecular weight (or weight average degree of polymerization) of the water-soluble cellulose ester is the weight evaluated by the intrinsic viscosity number and light scattering established in dimethylacetamide for cellulose monoacetate with DS = 0.38. Relational formula for average molecular weight: [η]=
0.191×Mw ^0.60 (25℃) ([η] is the intrinsic viscosity and Mw is the weight average molecular weight. This is a more primary evaluation. In preparing the dope according to the present invention, the cellulose ester used Various methods can be used depending on the degree of polymerization and concentration of
If the concentration is below 15-20% by weight,
It can be easily prepared using an ordinary Coles-type dissolver or kneader. The melting temperature can be selected as appropriate. Also,
When both the degree of polymerization and the concentration are extremely high, it can be prepared by pre-kneading cellulose ester and water using a mixing roll used in the rubber industry, and then using an extruder or kneader.
The water-soluble dope prepared in this way is stable for a long period of time. As mentioned above, it is expected that the mechanical properties, particularly the strength, Young's modulus, etc. of a molded article formed from a dope containing a high concentration of cellulose ester with a high degree of polymerization will be significantly improved. Furthermore, the dope obtained by the present invention is excellent in economical efficiency since water is used as a solvent, and there is no emission of toxic gas or scattering of heavy metals during molding from the dope, and the dope is non-polluting.
Furthermore, since water is used as a solvent, it is also possible to add a water-soluble crosslinking agent and other additives to the dope to facilitate post-processing of the molded product. For example, by taking advantage of the characteristics of the method of synthesizing cellulose ester, which is a component of the present invention, in the synthetic product purification stage, 10%
A cellulose ester containing ~20% by weight of paraformaldehyde is isolated, used to prepare a water-soluble dope, and dry-spun to produce a water-insoluble or highly swellable yarn. The above-mentioned additives also include metal salts, highly polar organic solvents, other cellulose chemical modifiers, etc., and each is selected and used depending on the purpose. If a metal salt that is foamable at high temperatures is used, foams for sponges and the like can be formed. When molding cellulose ester dope,
Unlike the case of using a high boiling point organic solvent, water can be removed with low energy, and cost increases due to loss of recovery of the solvent can also be prevented. Water is harmless to humans, and the working environment is also very good. Furthermore, by spinning the dope obtained according to the present invention,
The fibers obtained by such post-crosslinking treatment have high water absorption properties and are particularly useful for clothing and medical purposes. [Example] Next, the present invention will be explained with reference to an example. The following examples are intended to illustrate specific examples of the invention, and should not be construed as imposing any limitations on the invention. Example 1 100 g of purified cellulose linter prepared by immersing in 2N sulfuric acid to have an average degree of polymerization of 2900 was vacuum dried, added to 5 flasks containing 2 primary dimethyl sulfoxide and 100 g of paraformaldehyde, and heated at 90°C. Dissolved with stirring for 10 hours. Heating was carried out in a silicon bath. After confirming that the cellulose was completely dissolved, the mixture was cooled to 40°C, 150 g of acetic anhydride and 46 g of pyridine were added, and acetation was carried out with stirring for 3 hours. The resulting solution was poured into a 20 volume container containing 10 volumes of methanol while stirring vigorously, and precipitated at room temperature. The precipitate was filtered using a polyester filter cloth to remove about 70% of the methanol solution. Dissolve the filtrate in water,
Thereafter, the precipitation operation with methanol was repeated three times, and the resulting precipitate was dried in vacuum for 24 hours.
The obtained compound was ground into a fine powder, and 5 g of the compound was dissolved in water with stirring at room temperature. As a result, it was found to be water-soluble up to a concentration of 40% by weight at room temperature, and to be water-soluble up to about 60% by weight when heated at 60°C. As a result of quantifying the degree of acetyl substitution of the compound by neutralization titration, the degree of substitution was 0.60, and as a result of molecular weight measurement using a light scattering photometer, the degree of polymerization was 2.110.
It was hot. The C ¹³ -NMR spectrum of this product obtained in heavy water is shown in Figure 1, A. It is clearly different from ordinary cellulose acetate, and is mainly identified as acetoxymethylcellulose. Example 2 In the same manner as described in Example 1, 100 g of medicated absorbent cotton was dissolved in a mixed solvent of dimethyl sulfoxide/paraformaldehyde, a certain amount (72 g) of pyridine was added, and the amount of acetic anhydride was adjusted as shown in the table. By making various changes, eight types of compounds with different degrees of acetylation were obtained. The degree of substitution of each compound was evaluated by neutralization titration, and 10 g of each compound was poured into 100 ml of water at room temperature with stirring to investigate the solubility.
It was soluble in water with a degree of substitution ranging from 0.3 to 0.8.

[Table] ○Dissolution, △Gelation, ×Insoluble.
Example 3 The composite having a polymerization degree of 2.110 obtained in Example 1 was dissolved in water at a concentration of 15% by weight to obtain a dope. The dope was wound at a winding speed of 100 m/min, a processing temperature of 400°C,
Discharge rate 2.22g/min, number of mouth holes 12, mouth hole diameter d=
Dry spinning was carried out under the condition of 0.5 m/m. The obtained yarn had a single yarn denier of 16.7 d, a tensile strength of 2.5 g/d, a tensile elongation of 7%, and an official moisture content of 15.5% as measured by the method according to JISL1037, and was swollen in water. Comparative Example 1 Purified cellulose linter prepared by the method described in Example 1 was triacetated using glacial acetic acid, acetic anhydride, and sulfuric acid, and then treated with concentrated hydrochloric acid as a catalyst.
It was hydrolyzed with glacial acetic acid water at 40°C for 12 days.
The obtained cellulose acetate shows water solubility,
The degree of substitution measured by neutralization titration was 0.61. In addition, the degree of polymerization was determined by light scattering photometry.
It was 300. The C ¹³ -NMR spectrum of this compound is shown in Figure 1B. This composite was dissolved in water at a ratio of 15% by weight, and spun under the same dry spinning conditions as described above. As a result, the resulting spun yarn had a tensile strength of 1.3 g/d and an elongation of 30%. As is clear from the comparison between the above results and the results of Example 3, molded articles with excellent mechanical properties can be obtained from the high polymerization degree composite according to the present invention. Example 4 Compound 1.5 obtained by the method described in Example 1
g was dissolved in 150 ml of water. The intrinsic viscosity [η] of the obtained solution was measured every 10 days for 3 months immediately after synthesis. Immediately after measurement [η] = 430cm ³ /g (25℃)
After being stored in a water bath at 25°C for 3 months, [η] = 410 cm ³ /g (25°C), the solution was clear and no gelation was observed, indicating extremely good stability. . Example 5 Dimethyl sulfoxide obtained in Example 1/
Add 176 to 806 g of acetic anhydride without a catalyst to the paraformaldehyde dope while stirring at room temperature.
Various reaction solutions with different degrees of acetation were prepared by reacting for a certain period of time. Each of the obtained reaction solutions was poured into a container 20 containing 10 methanol with strong stirring, and precipitated at room temperature. After thorough washing with methanol and drying, about 95 g of synthesized product was obtained from each reaction solution. 10g of each of the obtained compounds was added at room temperature.
Pour it into 100ml of water while stirring and check the solubility.
The degree of substitution of each compound was measured by neutralization titration. As a result, it showed water solubility in a substitution degree range of 0.3 to 0.8. The NMR analysis results of the resulting compound were the same as those obtained in Example 1. Example 6 Add 0.2 g of catalyst to the dimethyl sulfoxide/paraformaldehyde dope in Example 1.
of sodium acetate and stirred thoroughly, heated to 80℃ using an oil bath to dissolve methylene diacetate from 50 to 50℃.
1960 ml of the solution was added and the reaction was carried out for 10 hours while stirring to produce counter solutions with different degrees of reactivity. Each of the obtained reaction solutions was precipitated in methanol to obtain compounds with different degrees of substitution. When 10 g of each compound was poured into 100 ml of water, the degree of substitution determined by neutralization titration showed water solubility in the range of 0.30-10.8. The NMR analysis results of the resulting compound were the same as those obtained in Example 1. Example 7 Cellulose obtained in Example 1/dimethyl sulfoxide/paraformaldehyde/acetic anhydride/
After crudely precipitating the pyridine-based dope in methanol, it was filtered, and the precipitate was dried in vacuum for 24 hours. The formalin content of this product was determined by an acetylacetone/steam distillation color method and was found to be 3% based on the weight of the fiber. This composite was dry spun in the same manner as described in Example 3, with a tensile strength of 3.0 g/d, a tensile elongation of 4%, and an official moisture content of 10.4.
% yarn was obtained. Furthermore, although the yarn was left in aqueous solution at 25°C for 10 days, no swelling or deterioration of the yarn was observed.
As a result of weaving using this thread, an extremely stiff fabric was obtained.

[Brief explanation of drawings]

A represents a C ¹³ -NMR spectrum of the dope according to the present invention, and B represents a C ¹³ -NMR spectrum of an aqueous solution of water-soluble cellulose acetate obtained by hydrolyzing conventional cellulose diacetate.

Claims (1)

[Scope of Claims] 1. A method for producing a molding dope, which comprises treating a solution of cellulose in a dimethyl sulfoxide/formaldehyde mixed solvent with an esterifying agent and dissolving the resulting water-soluble cellulose ester in water. 2. Claim 1: A water-soluble cellulose ester having a degree of substitution (DS) of 0.3DS0.8 is obtained by the action of an esterifying agent selected from acetic anhydride, methylene diacetate, and ethylene diacetate. Method for producing the described molding dope. 3. A method for producing a molding dope according to claim 1, in which acetoxymethylcellulose is obtained as a water-soluble cellulose ester.