JPS61252243A - Cellulose dope - Google Patents

Abstract

PURPOSE:To provide the titled dope having excellent stability and suitable for use in molding, adding CS2 to an aq. alkaline soln. contg. cellulose. CONSTITUTION:The temp. of an aq. soln. contg. an alkali (e.g. NaOH) at a concn. of 2-2.5mol/l is adjusted to -12-25 deg.C, and a least 3wt% cellulose having a dgree of polymn. of 700 or below is immersed therein and left to stand for 5min.18hr. The mixture is stirred at 10 deg.C or below to dissolve cellu lose, thus obtaining an aq. alkaline soln. contg. cellulose, 0.01-1.6mol (per glucose residue of cellulose) of CS2 is added to said aq. soln. and the soln. is left to stand at -12-40 deg.C for the least 7 days.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to cellulosic dopes suitable for molding.

BACKGROUND OF THE INVENTION In general, regenerated cellulose molded articles are made of cellulose,
It is produced by dissolving it in a solvent using a certain method and then introducing the dope into a non-solvent or regenerated solvent using an extruder. At present, the only methods for dissolving cellulose that are industrially used for the above purpose are the cuprammonium method and the viscose method, both of which were discovered in the late 1890s.

Among these, the copper ammonia method requires complete recovery of copper ions and ammonia, and is not necessarily the best method from an economic point of view.

In addition to these, although not used industrially, metal complexes such as cadxene (cadmium/ethylenediamine/alkaline 9), cooxene (cobalt/ethylenediamine/alkaline,
Di/cosene (zinc/ethylenediamine/alkali), nioxene (zinc/ethylenediamine/alkali), E
WNN (iron/tartaric acid/alkali) is known. However, none of these methods surpasses the cupric ammonia method or the viscose method in terms of ease of use, as they involve the use of large amounts of toxic components such as heavy metals and amines.

The viscose method has been adopted by the overwhelming majority of companies in the current regenerated cellulose industry, but without exception, the industrially used method uses solid alkali cellulose and the glucose residues that make up cellulose. First, cellulose xanthate is produced by a reaction with 0.6 to 1 mol of carbon disulfide, and then this is dissolved in an alkaline water bath to obtain viscose, which is then used for molding. This method uses a large amount of carbon disulfide, which is a poisonous gas, and the reaction efficiency is as low as 50-60%. Furthermore, during the regeneration and molding process, most of the carbon disulfide used is released in the form of hydrogen sulfide. The reality is that these gases are industrially recovered at great expense. On the other hand, there is an emulsion sulfurization method (or wet sulfurization method) in which cellulose, carbon disulfide, and alkaline water are reacted simultaneously in the liquid phase.
has been around for a long time (e.g. Li1ienteld D, R
, P523271 research has been progressing, but it has not been commercialized. The main reason for this is that in this method, the reaction efficiency of carbon disulfide is low and a large amount of by-products are produced, so that more carbon disulfide (per glucose residue, 1 to 1.5 mol) is produced. 1-Despite the need, a good dope suitable for molding could not be obtained. The emulsion method was originally researched for the purpose of simplifying the process and streamlining it by shortening the time, and waste of carbon disulfide was not a problem from the beginning. In this respect, it is completely contrary to the current social environment and technological philosophy, and it is unthinkable that it will be industrialized in the future.

The problem of carbon disulfide recovery mentioned above is extremely serious and
In Europe and America, there are concerns about the industrial viability of the viscose method. The remarkable manifestation of seven is! 960s-197
Many companies withdrew from the viscose business (rayon business) during the 2000s. As a reflection on these industrially existing dissolution methods, cellulose is directly dissolved in an organic solvent, and fibers and B! In 1977, research aimed at creating new regenerated cellulose molded products by closing the manufacturing process.
It has been practiced mainly in Canada and the United States since the 2000s. As a result, many dissolution methods were discovered, but all of them involve complex multi-component solvents, and none have been put to practical use due to the high cost, toxicity, explosiveness, and difficulty of recovery of the solvent itself. is the current situation. As can be seen from the history of cellulose dissolution technology, it is extremely difficult to dissolve cellulose in a simple and inexpensive solvent.

On the other hand, when the degree of polymerization (hereinafter abbreviated as DP) of cellulose becomes extremely small (e.g. DP: 10), it is naturally susceptible to alkalis.
It is known that it also dissolves in hot dimethyl sulfoxide. The DP of No. 7 is less than 20, so it cannot be used as a cellulose molded product because it does not have sufficient mechanical properties. The reason why cellulose with extremely low DP is soluble in alkalis and the like is because the characteristic polymer properties of cellulose, for example, the molecular form defined by hydrogen bonds, etc., are lost. or,
It is also a well-known fact that an aqueous solution of caustic soda having a concentration of around 10% by weight has a strong swelling effect on cellulose having a high degree of polymerization. Journal Op Pract, Tam 9.
N.F., vol. 158, p. 233 (1941) (
Journal of Prakt, Chem, ,
N, F., 158° 233 (1941)) shows the solubility of natural cellulose, mercerized cellulose, and reprecipitated (possibly regenerated) cellulose in lO f/ls aqueous caustic soda solution. There is no description of dissolution conditions or polymer concentration, but according to it, natural,
Mercerized cellulose is said to be soluble up to a degree of polymerization (DP) of 400, and reprecipitated cellulose is soluble up to a DP of 1200. However, these descriptions contain considerable arbitrariness, and it is expected that they also included strongly swollen gels even though they were called soluble. As a result of further tests by the present inventors, the solubility of cellulose in 10 wt. of caustic soda at -5° to 5°C is influenced by the polymer concentration and degree of polymerization. If so, centrifuge (20,000 rpm, 46 minutes),
When the gel was removed, even at a polymer concentration of 0.5%, not all of the gel was dissolved. Therefore, Journal Op Pract Chem, N.N.S., Vol. 158, No. 2
33 pages (1941) (Journal of Pr.
akt, Chem,, N, F,, 158°233 (
1941) in the description of ``1941)'' means that it has a low concentration and contains gel, and cannot be used industrially. Facts used in fractional dissolution (
For example, 1. “Purification and chemical reactions of polymeric substances”, P128~
132. It is also known from the Society of Polymer Science and Technology (edited by the Society of Polymer Science, 1958, Kyoritsu Publishing). This is an operation in which cellulose is divided into alkali-soluble and insoluble parts depending on its molecular weight and molecular chain assembly state, and the former soluble part includes gel. These facts indicate that cellulose with a high degree of polymerization, which you want to dissolve, at a high concentration and in an alkali of a single composition, is
In the history of the cellulose industry, such a cellulose/alkaline solution has never been used as a molding dope.

Taking these conventional techniques into consideration, the present inventors filed a patent application in
No. 8-149148 discloses an alkali dope in which cellulose with a relatively high degree of polymerization, which has been pretreated to control its structure, is dissolved at a high concentration. However, this dope also has the disadvantage of gelling due to extremely long storage or the action of heat. Problems to be Solved by the Invention The present inventors have discovered that viscose (Arcel sulfurization method and emulsion sulfurization method) The present invention was arrived at as a result of extensive research into a method for comprehensively solving the drawbacks of two independent prior art techniques for cellulose alkali dope.

The object of the present invention is to provide an extremely stable cellulosic dope suitable for molding.

Means for Solving the Problems The present invention provides an alkaline aqueous solution containing cellulose.
A cellulose-based dope suitable for molding is formed by adding carbon disulfide at a temperature of 0.01 mol or more per glucose residue constituting cellulose at a temperature of 0.0 to 40°C.

The cellulose used in the present invention is wood pulp, cotton, acid hydrolysates thereof, those treated with chlorine or hydrogen peroxide, and extruder (Extnmder) under high temperature and high pressure.
) treated, blasted, dissolved in a solvent and regenerated by various methods, crushed in a ball mill, treated with ultrasonic waves, etc. Generally, D
P is less than 700, but even if the DPO is more than 700,
The solution may be one in which only the alkali-soluble portion is separated by centrifugation or the like. Especially with a certain degree of polymerization (for example, around 500) and a high concentration (more than 5% by weight)
When it is desired to dissolve cellulose, cellulose whose intramolecular hydrogen bonds have been weakened by the above-described treatment can be used. (Japanese Patent Application No. 58-149148). The alkalis to be dissolved are caustic soda, lithium hydroxide, and caustic potash, and the final concentration is adjusted to 2 to 2.5 mot/L. The cellulose alkaline solution is prepared as follows. That is, a 2-2.5 mot/L alkaline aqueous solution is pre-adjusted to -12°C to 25°C, cellulose is immersed, and after being left for 5 minutes to 18 hours, or at the same time as immersion, it is mixed at 10°C or less. Stirring, dissolving method, or 3.5~
5 moj/l alkaline aqueous solution and cellulose
Mix at ~25°C, stir, dilute with alkali at 10°C or less, mix and dissolve, and finally adjust the alkaline strength to 2~2.5.
This is done by adjusting to mot/l.

Although the cellulose concentration is not limited, in consideration of molding, it is preferable that the cellulose concentration is dissolved in an amount equal to or more than 3. Such solutions generally gel easily at temperatures above 40°C. Therefore, carbon disulfide is present in the above solution at a temperature below 40°C.
Preferably, the temperature is between -12°C and 10°C, and the temperature is about 20°C.
Mix and stir for at least 1 minute.

If the amount of carbon disulfide added is 0.01 or more per glucose residue constituting dissolved cellulose, the dissolution state will be improved and the period of stable storage will be longer than that of the original cellulose dope. If it is more than 0.08 mol, the dope will be stable for more than 10 days at room temperature.There is no upper limit to the addition of carbon disulfide, but adding more than 0.6 mol is not economical or environmentally friendly. In terms of surface area, it will be on par with the viscose method currently being used industrially, and the industrial benefits will be small.

In the cellulose dope of the present invention, when 5 hours or more have passed after the addition of carbon disulfide, most of the added carbon disulfide reacts with cellulose to form cellulose xanthate. Conventionally, the degree of substitution of cellulose xanthate in viscose by technology is O,a~0.6 mol per glucose residue constituting cellulose (hereinafter DS=
0.3 to 0.6), but the xanthate in the dope of the present invention has a DS of
= 0.082, and although it is extremely low, the state of dissolution is comparable to that of viscose. The reason for this is that when cellulose is dissolved in alkali in advance, intramolecular and intermolecular hydrogen bonds are broken, and carbon disulfide and cellulose react in a homogeneous phase, so the introduction of xanthate groups is extremely uniform. This is thought to be due to the fact that

The dope thus obtained can be easily coagulated by adding it to water, a salt solution, a dilute acid, an organic solvent, etc. to obtain molded products such as films and fibers. In particular, if the dope is coagulated with water or dilute acid, or washed after molding, the cellulose xanthate in the dope can be easily regenerated into cellulose and a pure cellulose molded product can be obtained.

EXAMPLE As this example, a method for obtaining a cellulose dope that dissolves well and is difficult to gel by adding carbon disulfide to a cellulose alkaline solution will be described below.

Mix 150F of each type with 285Of 9.1% by weight caustic soda aqueous solution, leave the mixture for 1 hour while keeping it at 4℃, and then place it in a Henschel mold while keeping it at 4℃. After stirring for 1 hour in a dissolver, add a predetermined amount of carbon disulfide, stir for 30 minutes while keeping it at 4℃, and after keeping it at 4℃ for 4 hours, leave it at room temperature. Table 1 shows the solubility of the dope determined with the naked eye after 0 days, 3 days, 10 days, and 20 days. However, the raw materials used are pulp (Alaska pulp) and cotton linters, and the acid hydrolyzate is one that has been immersed in 5N sulfuric acid at 60'C for 3 hours, washed with water, and dried. It is made into fibers by regenerating it with dilute sulfuric acid from a solution dissolved in copper ammonia solution.

The solubility determination results are indicated by the following symbols.

G Nigel, Upper K
Flow [L, 14 r/dll, sulfuric acid, 28 r/da
.

After being immersed in an aqueous solution of sodium sulfate to solidify, the film was washed with water and dried, and the state of the film was indicated by the following symbols. X: Does not form a film, Δ: Cloudy and brittle, O
: Transparent and somewhat strong; ◎: Transparent, with extremely high strength and elongation.

As a comparative example, the above alkali dope without adding carbon disulfide and with various amounts of carbon disulfide were tested using the usual viscose method ("Purification and Chemical Reaction of R Polymeric Substances" P13).
7, edited by the Society of Polymer Science and Technology, Kyoritsu Shuppan), the dope was adjusted and each was used as a comparative example.

Table 1 Effects of the Invention The cellulose dope of the present invention is difficult to gel during long-term storage or by heat, and molded articles obtained from the dope exhibit excellent mechanical properties.

Claims (2)

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