JPH0621184B2 - Cellulose type dope - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a cellulosic dope suitable for molding.

2. Description of the Related Art Generally, a molded product of regenerated cellulose is produced by dissolving cellulose in a solvent by a certain method and introducing the dope into a non-solvent or a regenerated solvent by using an extruder. . At present, the only methods of dissolving cellulose that are industrially used for the above purposes are the copper-ammonia method and the viscose method, which had been discovered in the late 1890s.

Of these, the copper-ammonia method is not necessarily the best method in terms of economy because it is necessary to recover copper ions and ammonia completely.

Other than these, although not industrially used, as a method for dissolving cellulose, metal complexes such as cadmium (cadmium / ethylenediamine / alkali), cooxene (cobalt / ethylenediamine / alkali), zincocene (zinc / ethylenediamine / alkali) ), Nioxene (nickel / ethylenediamine / alkali), EW
NN (iron / tartaric acid / alkali) is known. However, neither of them is a method that uses a large amount of toxic components such as heavy metals and amines and is economical, and does not rely on the copper ammonia method or the viscose method.

The viscose method is overwhelmingly adopted by many companies in the current regenerated cellulose industry, but the method used industrially is, without exception, per solid glucose residue and glucose constituting cellulose and Cellulose xanthate is produced by the reaction of 0.6 to 1 mol of carbon disulfide, and then this is dissolved in an alkaline aqueous solution to obtain viscose, which is used for molding. This method uses a large amount of carbon dioxide, which is a toxic gas, and its reaction efficiency is as low as 50-60%. Also, in the process of regenerating and molding, most of the carbon disulfide used is released in the form of hydrogen sulfide. The fact is that these gases are industrially recovered at a great expense. On the other hand, the emulsion sulfidation method (or wet sulfidation method) in which cellulose, carbon disulfide and an aqueous alkali solution are simultaneously reacted in a liquid phase is
Although research has been conducted for a long time (for example, Lilienteld DRP523271), it has not been industrialized yet. The cause is
Primarily, in this method, the reaction efficiency of carbon disulfide is low and a large amount of by-products are produced, so that even if a larger amount of carbon disulfide (1 to 1.5 mol per glucose residue) is required. Regardless, it was not possible to obtain a good dope suitable for molding. Of course, the emulsion method was studied for the purpose of streamlining by simplifying the process and shortening the time, and the waste of carbon disulfide was not a problem from the beginning. In that respect, it goes against the current social environment and technical ideas, and is unlikely to be industrialized in the future.

The above-mentioned problem of carbon disulfide recovery is extremely serious, and there are voices in Europe and the United States that the viscose method may be industrially viable. A notable manifestation is the removal of many companies from the viscose business (rayon business) in the 1960s and 1970s. As a reflection of these industrially existing dissolution methods, research into dissolving cellulose directly in an organic solvent and closing the fiber and membrane manufacturing process to obtain a new regenerated cellulose molded product has been carried out since the 1970s. , Mainly in the United States. As a result, many dissolution methods have been found, but all of them are complex multi-component solvents, and there are no practical examples due to the high cost of the solvent itself, toxicity, explosiveness, recovery difficulty, etc. is the current situation.
As can be seen from the history of such cellulose dissolution technology, it is extremely difficult to dissolve cellulose in a simple and inexpensive solvent.

On the other hand, it is known that when the degree of polymerization (hereinafter, abbreviated as DP) of cellulose becomes extremely small (for example, DP10), it dissolves not only in alkali but also in hot dimethyl sulfoxide.
Its DP is 20 or less, and it cannot be used as a cellulosic molded article because it does not have sufficient mechanical properties. The reason why cellulose having an extremely low DP is dissolved in alkali or the like is that the polymer characteristic of cellulose, for example, the molecular form defined by hydrogen bond is lost. Again 1
It is also well known that an aqueous caustic soda solution having a concentration of about 0% by weight has a strong swelling action on cellulose having a high degree of polymerization. Journal of Pract, Chem. , N. F. , 158, p. 233 (1941) [Jounal of Prak
t, Chem., NF, 158 , 233 (1941)], shows the solubility of natural cellulose, mercerized cellulose, and reprecipitated (probably regenerated) cellulose in a 10 wt% caustic soda aqueous solution. Although there is no description about dissolution conditions, polymer concentration, etc., it is said that natural and mercerized cellulose are soluble up to a degree of polymerization (DP) = 400, and reprecipitated cellulose up to DP = 1200. However,
It is anticipated that these statements included considerable arbitrariness and also included gels that were soluble and strongly swollen at all times. As a result of additional tests by the present inventors, 10 at -5 ° to 5 ° C.
Solubility of cellulose in wt% caustic soda is affected by polymer concentration and degree of polymerization, eg DP = 360
In the case of (acid hydrolyzed cotton linter), centrifugation (20,000 rpm, 46 minutes) and gel removal operation did not completely dissolve the polymer even at a polymer concentration of 0.5%. Therefore, Journal of Pract Chem. , N. F. , 158, p. 233 (1941) [Jounal of Prakt, Che
m., NF, 158 , 233 (1941)] means "soluble", which means that it is a low concentration and contains gel.
It is not industrially available. These points are due to the fact that alkali was used for the fractional dissolution of cellulose in each lateral order (for example, “Purification and chemical reaction of polymer substances”, P128-132, edited by The Polymer Society of Japan, 1958, Kyoritsu Shuppan). Also known from. This is an operation of dividing into an alkali-soluble portion and an insoluble portion, depending on the molecular weight of cellulose and the state of aggregation of molecular chains. The former soluble portion includes gel. These facts indicate that it is technically very difficult to dissolve cellulose having a high degree of polymerization to be dissolved at a high concentration in almost a single composition of alkali. In fact, in the history of the cellulose industry, such a cellulose / alkaline solution has never been used as a molding dope.

In consideration of these conventional techniques, the present inventors have made
No. 149148 shows alkali dope prepared by dissolving pre-treated structure-controlled pre-treated cellulose in relatively high concentration at high concentration. However, it has a drawback that the dope is gelled by the action of heat for a very long time or the action of heat.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The inventors of the present invention have earnestly conducted research on a method for comprehensively solving the drawbacks of two independent prior arts, viscose (Arsell sulfurization method and emulgillon sulfurization method) and cellulose alkali dope. As a result, the present invention has been achieved.
The present invention aims to provide an extremely stable cellulosic dope suitable for molding.

Means for Solving the Problems The present invention relates to an alkaline aqueous solution containing cellulose.
A cellulosic dope suitable for molding, characterized in that carbon disulfide is added at 0.01 mol or more per glucose residue constituting cellulose at a temperature of not lower than 40 ° C and not higher than 40 ° C.

The cellulose used in the present invention is wood pulp, cotton, acid hydrolysates thereof, those treated with chlorine or hydrogen peroxide, those treated with an extruder under high temperature and high pressure, those subjected to blasting treatment. , Those dissolved in a solvent and regenerated by various methods, those crushed by a ball mill, those sonicated and the like are used. Generally the DP is 700
Although it is as follows, it may have a DP higher than that or a solution in which only the alkali-soluble portion is separated by centrifugation or the like. In particular, when it is desired to dissolve cellulose in a high concentration (5% by weight or more) with a certain degree of polymerization (for example, 500th position), use of cellulose having weak intramolecular hydrogen bonds by the above treatment. You can (Japanese Patent Application No. 58-149148). Dissolved alkalis are caustic soda, lithium hydroxide and caustic, which are finally adjusted to a concentration of 2 to 2.5 mol /.
The alkaline solution of cellulose is prepared as follows.
That is, predict an aqueous solution of 2 to 2.5 mol /,
Adjust the temperature to 12 ℃ to 25 ℃, soak the cellulose, 5 minutes to 18
Mixing and stirring at 10 ℃ or less
Dissolution method, or mixing 3.5-5 mol / alkali aqueous solution and cellulose at -12 ° C-25 ° C, stirring and diluting with diluted alkali at 10 ° C or less, mixing and dissolving, and finally setting alkaline strength to 2 By adjusting to 2.5 mol /. The concentration of cellulose is not limited, but in consideration of molding, it is preferably dissolved in 3% by weight or more.
Such a solution generally gels easily at 40 ° C. or higher. Therefore, carbon disulfide is added to the above solution in an amount of 40
The mixture is mixed under conditions of not higher than ℃, preferably -12 ℃ ~ 10 ℃, and mixed and stirred for about 20 minutes or more. The amount of carbon disulfide added is per glucose residue constituting the dissolved cellulose,
If it is 0.01 or more, compared with the original cellulose dope, the effect of improving the dissolved state and prolonging the period for stable storage can be obtained. Become a dope. Although there is no upper limit to the addition of carbon disulfide, the addition of 0.6 mol or more is similar to the viscose method currently used industrially in terms of economy and environmental problems, and the industrial merits are reduced.

In the case where the cellulose dope of the present invention has been added for 5 hours or more after the addition of carbon disulfide, most of the added carbon disulfide reacts with cellulose to form cellulose xanthate. Conventionally, the substitution degree of cellulose xanthate in viscose by the technology is 0.3 to 0.6 mol (hereinafter, DS = 0.
(Expressed as 3 to 0.6), the zanthate in the dope of the present invention has DS = 0.08 when 0.1 mol of carbon disulfide is added.
It is 2 and the melting state is similar to that of viscose, although it is extremely low. The reason for this is that the cellulose is dissolved in an alkali in advance, the intramolecular and intermolecular hydrogen bonds are broken, and carbon disulfide and cellulose react in a uniform phase, so that the introduction of the xanthate group becomes extremely uniform. This is probably because it is done.

The dope thus obtained can be easily solidified by adding it to water, a salt solution, a dilute acid, an organic solvent or the like to obtain a molded product such as a film or a fiber. In particular, by coagulating with water or dilute acid, or by washing after molding, the cellulose xanthate in the dope is easily regenerated into cellulose, and a molded product of pure cellulose is obtained.

Example As a present example, a method for obtaining a cellulosic dope which is well dissolved and hardly gelated by adding carbon disulfide to a cellulose alkaline solution will be described below.

While mixing 150 g of each type of cellulose with 2850 g of a 9.1 wt% caustic soda aqueous solution, while maintaining the mixed solution at 4 ° C,
Let stand for 1 hour, then stir for 1 hour in a Henschel type dissolver while keeping it at 4 ° C, add a predetermined amount of carbon disulfide, stir for 30 minutes while keeping at 4 ° C, and keep at 4 ° C for 4 hours. After that, leave at room temperature. Table 1 shows the solubilities of the dope determined with the naked eye after 0 day, 3 days, 10 days, and 20 days, starting from the time when the dope reached room temperature. However, pulp (Alaska pulp) and cotton linter are used as raw materials,
The acid hydrolyzate is immersed in 5N sulfuric acid at 60 ° C for 3 hours,
The product is washed with water and dried, and the regenerated product is a product obtained by dissolving cellulose in a copper ammonia solution and regenerating it with dilute sulfuric acid to form fibers.

The results of solubility determination are indicated by the following symbols.

G: gel, X: almost undissolved (slurry and opaque), Δ: semi-transparent, fibrous undissolved substance, ◯: transparent viscous liquid, and dope after 3 days flowed on glass plate The state of the film after being rolled, dipped in an aqueous solution of 14 g / dl sulfuric acid and 28 g / dl sodium sulfate to be solidified, washed with water and dried is shown in Table 1 by the following symbols. X: No film is formed, Δ: Cloudy and brittle, ◯: Transparent and slightly strong,
A: Transparent, remarkably high strength and elongation.

As a comparative example, the above-mentioned alkali dope without addition of carbon disulfide and various amounts of carbon disulfide were used in the usual viscose method (“Purification of Polymer and Chemical Reaction” P137,
The dope was prepared according to the Society of Polymer Science, edited by Kyoritsu Shuppan, and used as comparative examples.

EFFECTS OF THE INVENTION The cellulosic dope of the present invention is less prone to gelation due to long-term storage or heat, and a molded article obtained from the dope exhibits excellent mechanical properties.

Claims (2)

[Claims] 1. An alkaline aqueous solution containing cellulose-
Cellulosic dope suitable for molding, characterized in that carbon disulfide is added in an amount of 0.01 mol or more per glucose residue constituting cellulose at 12 ° C. or higher and 40 ° C. or lower. 2. The dope of cellulose according to claim (1), wherein the alkali is lithium hydroxide or sodium hydroxide.