JPH05140332A - Production of cellulose molded product - Google Patents

Abstract

PURPOSE:To obtain the subject product in a pollution-free process, excellent in dyeability, etc., by coagulating, in a medium with highly dehydrating power, a dope prepared by dissolving cellulose in an aqueous alkaline solution and then by molding the coagulated product. CONSTITUTION:Firstly, a dope >=3wt.% in cellulose concentration is prepared by dissolving an alkali-soluble cellulose having >=100 polymerization degree in an aqueous alkali solution (pref. of sodium hydroxide or lithium hydroxide) at <=16 deg.C (pref. -10 to 10 deg.C). Then, this dope is coagulated in a medium with highly dehydrating power (e.g. sulfuric acid anhydride, polyphosphoric acid) and then molded, thus obtaining the objective cellulose molded product in a pollution-free process. This molded product has mechanical properties comparable to those of existing cellulose molded products and an excellent dyeability because of having such a solid structure that the intermolecular hydrogen bond has been extremely destroyed.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a cellulose molded article typified by a film, a fiber (including a hollow fiber and a non-woven fabric), a powder and the like, which is prepared from a dope comprising substantially alkali-soluble cellulose and an alkaline aqueous solution. It relates to a method of manufacturing.

[0002]

2. Description of the Related Art Generally, molded articles of cellulose (fibers, films, powders) are produced by dissolving a cellulose in a solvent by a certain method and introducing a solution into a medium which is a non-solvent. Currently, the dissolution method of cellulose industrially used for the above purpose is a so-called cellulose that was already discovered about 100 years ago (the latter half of the 1890s). There are only two methods: reacting carbon sulfide and then dissolving it in alkali (viscose method) or dissolving cellulose in copper ammonia solution (copper ammonium method). It is interesting in that it is a technology that was discovered before. Cellulose in the solution obtained by these methods, the cellulose is not dissolved as it is, in order to return to cellulose because it is dissolved as a certain cellulose derivative,
In addition to solidification, a process called regeneration is required. It has been conventionally known that control of this regeneration process is an important factor that determines the fiber physical properties of the fiber, and modification of the dope and coagulation conditions (coagulation bath composition, coagulation temperature, coagulation bath length, bath flow, nozzle) ), Etc., the coagulation / regeneration conditions that provide the optimum yarn physical properties from various angles have been investigated. For example, in the viscose rayon method, a method using a Mueller bath, polynosic method, H
The W modulus method, the strong rayon method, the Lilienfeld method using high-concentration sulfuric acid in the coagulation bath, and the like, and the copper ammonium method include the falling tension spinning method. In any of the above methods, it is not possible to avoid the generation of toxic gases and the emission of heavy metals in the process of preparing a solution and the process of manufacturing a molded product, and there is no problem from the viewpoint of work environment and global environment. I can't say. In addition to this, as a method of dissolving cellulose, cadmium (cadmium / ethylenediamine / alikari), nioxene (nickel / ethylenediamine / alkali),
Metal complexes such as EWNN (iron / tartaric acid / alikari) have been mainly studied, but in terms of safety and economy, they do not surpass the copper ammonium method and the viscose method. On the other hand, the viscose method using carbon disulfide is overwhelmingly adopted by many companies in the present regenerated cellulose fiber industry. However, from the above viewpoint, there is a concern that the viscose method may remain industrially viable in the West. Is getting up in A notable manifestation is the withdrawal of many companies from the viscose rayon business in the 1960s and 1970s (first wave), and with the rise of anti-environmental destruction movements that are currently being pushed on a global scale. It is becoming an urgent task for companies to create an environment / safety-oriented system (second wave). In the former case, as a reflection on the existing dissolution method, research into dissolving cellulose directly in an organic solvent and closing the fiber or film manufacturing process to obtain a new regenerated cellulose molded product has been conducted since the 1970s. , Mainly in the United States. As a result, many dissolution methods were found, but all of them use complicated multi-component solvents, and they are put to practical use (industrialization) due to the high cost of the solvent itself, toxicity, explosiveness, difficulty in solvent recovery, etc. The current situation is that there are no examples. Almost all of these newly discovered solubilization methods are in the form of certain derivatives of cellulose, and the derivatives are dissolved in an appropriate solvent. There is no big difference.

On the other hand, a few attempts have been made to manufacture a cellulose molded product by an environment-friendly process against these flows. JP-A-62-240328 and JP-A-62-240329 disclose a method for producing a molded article such as a film or a fiber from a dope obtained by dissolving cellulose in an alkaline aqueous solution. According to these, a solid structure of a molded product obtained by selecting a coagulant, in particular, one having a significantly changed intramolecular hydrogen bonding property is obtained. For example, in JP-A-62-240328, coagulation using an acid directly, or coagulation with water, a base, a neutral salt or the like once and then neutralization in an acid bath, causes destruction of intramolecular hydrogen bonds. Χam (C
In contrast to 3), a cellulose molded product having a content of 55% or less is obtained, whereas in JP-A-62-240329, χam (C3) is 55 to 8 by coagulating directly in an acidic bath containing a salt.
It is said that a 5% cellulose molded product can be obtained. Here, χam (C3) is solid-state high resolution NMR (CP / MAS
The degree of breakage of intramolecular hydrogen bonds, which can be evaluated by the method described in JP-A-62-116601.

The coagulant used in the method described in JP-A-62-240328 is an acid bath. Although the acid is directly used in the first bath, it is similar to the method of the present invention, but since the dehydration effect of the acid bath is low, only χam (C3) of the obtained molded product is 55% or less. In addition, JP-A-62-2403
Similarly, in the case of the method described in No. 229, the dehydration action of the acidic bath is not sufficient, so that an NMR solid structure (χam (C
3)) belongs to the same category as the molded product of the present invention, but as described later in Examples, there are differences in the higher-order structure (aggregation structure), and the various properties of the obtained cellulose molded product are different. In any case, it is suggested that the wet method governs the physical properties of the molded product from which the choice of coagulant is obtained. Further, the present inventors have examined the production method of a cellulose molded product by various methods from the dope consisting of this cellulose and alkali, the alkali and water, which was difficult and low spinability in the usual spinning method, as the coagulant. Even when used, it has succeeded in obtaining a cellulose molded article by forcibly flowing such a coagulation bath (JP-A-3-40806).

However, when the cellulose molded article is manufactured by these methods, since the dope basically consisting of cellulose and alkali is used, the molding process of the conventional method (the viscose method or the copper ammonium method) is used. There is no so-called regeneration process, which was an important factor in controlling various physical properties. Therefore, in these systems, which were characterized by the absence of a regeneration process (chemical reaction), the neutralization process was immediate coagulation or gelation, and the control of the agglomeration structure during coagulation, for example, the polymer was densely agglomerated during coagulation It is extremely difficult to control such as to cause deformation of the coagulated gel and the physical properties of the obtained cellulose molded product are not sufficiently satisfactory.

[0006]

As mentioned above, although the viscose method and the copper-ammonium method are historically classical manufacturing methods, the fact that they still play a fundamental role in the textile industry cannot be denied. Absent. However, given the current state of environmental problems on an international scale, it cannot be said that the industry has many problems. That is: It uses carbon disulfide and ammonia, which have an adverse effect on the human body, and they have explosive limits. : Contains heavy metal such as copper, and requires a large amount of energy and water for recovery / purification / disposal treatment because harmful waste gas is generated in the melting / coagulation / regeneration / scouring process. :
And more inevitably, it will have to be a labor-intensive business form. Etc.

On the other hand, in the case of organic solvent spinning of cellulose,
Although it has the advantage of not using heavy metals or volatile gases: Many of them involve chemical reactions during dissolution, so cellulose is dissolved in the form of a derivative in the dissolved state, and by-products are generated during regeneration (solvent itself). Metamorphosis) occurs, or it cannot be regenerated and eventually becomes a molded product as a cellulose derivative. : There is also a problem in terms of solvent recovery, such as high loss due to loss due to transformation due to reaction / regeneration of the solvent itself and high cost, and a large amount of energy required since there are many high boiling point solvents. : Of course, there are problems such as toxicity, decomposability and explosiveness of the solvent itself. From the point of view, it is hard to say that it is industrial.

On the other hand, in the prior art relating to a method for producing a molded article such as a film or a fiber from a dope prepared by dissolving cellulose in an alkaline aqueous solution, the control of the agglomeration structure at the time of coagulation (dense coagulation at the time of coagulation or coagulation gel Is extremely difficult to obtain, and various physical properties of the obtained cellulose molded product have not been sufficiently satisfied. In view of such a point, the present inventors systematically studied the coagulability of a dope obtained by dissolving cellulose in an alkaline aqueous solution from the viewpoint of producing a cellulose molded product by an environment-friendly process. As a result, it was surprisingly found that the use of a medium having a highly dehydrating action as a coagulant enables easy control of the agglomeration structure and solid structure during coagulation. That is, in the case of the system of the present invention which basically uses a dope consisting only of cellulose and alkali, it was an important factor for controlling various physical properties in the molding process of the conventional method (viscose method or copper ammonium method). Despite the absence of a regeneration process, the use of a medium with a high degree of dehydration as a coagulant can promote desolvation without causing immediate coagulation or gelation during the neutralization process. It succeeded and arrived at this invention.

The present invention provides a process for producing a novel cellulose molded product, which is free from the risk of generation of exhaust gas or explosion during the spinning process, and which is free from environmental pollution due to waste liquid, waste gas and the like. It is an object. That is, an object of the present invention is to construct a method for producing a next-generation cellulose molded product that is sufficiently satisfactory from the industrial and environmental viewpoints.

[0010]

Means for Solving the Problem The present invention provides a highly dehydrated dope for producing a cellulose molded article by a wet method from a dope obtained by dissolving substantially alkali-soluble cellulose in an alkaline aqueous solution. In a medium having
It is a method for producing a cellulose molded product which is characterized by being coagulated and molded.

Cellulose which can be used in the method of the present invention is so-called alkali-soluble cellulose which can be dissolved in an alkaline aqueous solution at a low temperature, for example, JP-A-60-4240.
The cellulose disclosed in No. 1 and JP-A No. 62-116601 is preferably used. Further, an alkali-soluble cellulose derivative having a degree of substitution of 0.2 or less can be used. As for the kind of the substituent, if the degree of substitution is 0.2 or less, it can be used regardless of whether it is an ether group or an ester group.
When the degree of substitution is 0.2 or more, the properties of the substituent are reflected in the properties of the obtained cellulose molded product, which is not preferable in physical properties (for example, mechanical properties). Specifically, alkyl cellulose such as methyl, ethyl and propyl, hydroxyalkyl cellulose such as hydroxyethyl and hydroxypropyl, carboxyethyl cellulose, carbamoylethyl cellulose, cyanoethyl cellulose, oxycellulose, cellulose nitrate and the like are used.

The degree of polymerization of cellulose is preferably at least 100 in consideration of the physical properties of the obtained molded product and operability during molding. On the other hand, the cellulose concentration is a problem to be determined depending on the degree of polymerization of cellulose and the solvent composition, but it is preferably contained in an amount of 3% by weight or more from the economical viewpoint and the physical properties of the obtained molded product. Sodium hydroxide, lithium hydroxide and the like are preferably used as the alkaline aqueous solution which is the solvent. In this case, the concentration of the alkali hydroxide is 5 to 15%, and the preferable concentration varies depending on the kind, but in the case of sodium hydroxide, 7 to 10% by weight is preferably used. The dissolution is performed at 16 ° C. or lower, preferably −10 ° C. or higher and 10 ° C. or lower. In addition, if necessary, a third component, for example, titanium oxide for making a dull tone, a surfactant for adjusting the spinnability,
A crosslinking agent for imparting a function or an alkali-soluble polymer may be added.

An alkaline solution of cellulose (hereinafter simply referred to as a dope) obtained by such a method is anhydrous sulfuric acid, sulfuric acid, halogenated sulfuric acid, thiosulfuric acid, sulfurous acid, hydrochloric acid, hydrobromic acid, hydrofluoric acid, nitric acid, A highly dehydrating medium composed of at least one selected from phosphoric acid, pyrophosphoric acid, metaphosphoric acid, polyphosphoric acid, hypophosphorous acid, trifluoroacetic acid, thiocyanate, metal halides and the like is used as a coagulant. It is molded by using it. Here, having a highly dehydrating action means having a high action of drawing out water in the dope into the medium. For example, in the case of sulfuric acid, sulfuric acid having a concentration having an osmotic pressure π of 390 atm or more is used. Therefore, when using these media,
It is used in a relatively high concentration aqueous solution, that is, in a concentration range having a dehydrating action on water or an alkaline aqueous solution. Since the concentration range varies depending on the medium used, it cannot be uniquely specified.
-80 wt% (π: 395 to 1620 atm), in the case of hydrochloric acid 40 to 42.5 wt% (π: 1355 to 1619)
atm), in the case of nitric acid, 60 to 80% by weight (π: 133
0-6070 atm), in the case of polyphosphoric acid 60-90
A range of weight% is preferably used. However, here, the osmotic pressure π of hydrochloric acid and nitric acid shows a value calculated as a regular solution (Raoul's law holds) even in a high concentration region. Although such an acid exhibits a high osmotic pressure π even at a concentration above the above, it is not practical in view of decomposition action, dissolution action, metamorphosis action and handling property (high smoke emission, high viscosity) to cellulose. Further, naturally, when these media are mixed and used, the concentration of one component may be lower than the above concentration. Similarly, the coagulant of the present invention can provide the action and effect described below even when another coagulant is used in the primary coagulation bath and then used in the secondary coagulation bath. On the other hand, the temperature of the coagulating bath at the time of molding is not particularly limited, but a lower temperature at which gelation of the dope does not occur is preferable. Particularly preferably, it is -8 ° C to 10 ° C. When the temperature is -8 ° C or lower, the solvent in the dope is frozen, which is not preferable, and when the temperature is 10 ° C or higher, the main chain of the cellulose molecule is cleaved (depolymerized) due to the hydrolysis action of the medium, or gelation of the dope itself occurs. It is not preferable because it occurs.

According to the method of the present invention, there is no particular restriction on the molding method, and it is sufficient to carry out the usual film forming method and spinning method. For example, in the film forming method, a stock solution for film formation is cast on a supporting plate such as a glass plate using an applicator or a knife coater, and then immersed / coagulated (any temperature, time) in the medium having the dehydrating action. After that, it may be washed with water / dried.

Of course, a slit nozzle may be used to discharge directly in the coagulation bath. In fiberization, the spinning solution is discharged into the coagulation bath using a wet nozzle having ordinary pores, a nozzle for hollow fibers, or a jet nozzle, and then stretched if necessary and washed / dried and wound. Just take it. In the case of powdering, the stock solution for molding may be dropped into a coagulation bath under high-speed stirring to form a powder.

[0016]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited thereto.

[0017]

Examples 1 to 3 and Comparative Examples 1 to 3 100 parts of softwood pulp (Alaska pulp) having a degree of polymerization of 1300 was immersed in 1000 parts of water for 3 hours and then dehydrated with a dehydrator to obtain 190 parts of hydrous cellulose. Obtained. This hydrous cellulose was steamed at 235 ° C. for 25 seconds using an explosive treatment device (manufactured by Nippon Kagaku Kikai) to obtain cellulose soluble in an alkaline aqueous solution having a degree of polymerization of 340. 100 g of this cellulose was dissolved in 1900 g of an 8% by weight aqueous sodium hydroxide solution at 5 ° C. using a homogenizer to obtain a uniform solution. 300 such solution
After filtering using 2 mesh metal nets and 2 polyamide nonwoven fabrics, the mixture was left to stand to be degassed to obtain a spinning dope.
Using a spinning machine with a gear pump,
From a nozzle having 100 holes of 0.08 mmΦ, a sulfuric acid bath having the concentration shown in Table 1 was discharged at a discharge rate of 30.16 ml / min. The coagulation bath was coagulated at a temperature of −5 ° C. under the condition of a dipping length of 25 cm, dried on a hot roll at 120 ° C. through a washing step, and wound on a paper tube at 60 m / min.
Table 1 shows Examples 1 to 3 and Comparative Examples 1 to 3. TS, T
E, KS, and Xc are tensile strength, tensile elongation, knot strength, and X-ray crystallinity, respectively. When 20% or 40% sulfuric acid is used, the spinnability is good but TS and T
Since it has low physical properties such as E and KS, it is not practical as a fiber. Further, when 90% sulfuric acid was used, the cellulose in the dope was dissolved or decomposed, and spinning was impossible. on the other hand,
In the case of the method of the present invention and Examples 1 to 3, TS, TE, KS, X
Both c and c are similar to existing regenerated cellulose fibers and can be sufficiently used as fibers for clothing.

As described above, according to the method of the present invention, it is possible to obtain a fiber having the same physical properties as the existing one by an extremely simple dope composed of cellulose, alkali and water by a process without environmental pollution.

[0019]

Examples 4 to 8 and Comparative Examples 4 to 6 100 g of alkali-soluble cellulose prepared according to the method of Example 1 was used as 5.6.
A homogenized solution was obtained by dissolving it in 1900 g of a wt% lithium hydroxide aqueous solution at -5 ° C using a homogenizer. This solution was filtered using three 300-mesh metal nets and then left to stand to defoam to obtain a stock solution for film formation. This stock solution for film formation was cast on a glass plate using an applicator with a casting thickness of 1 mm, immersed in a coagulation bath shown in Table 2 for 5 minutes, and then thoroughly washed with cold water at 5 ° C. A part of the raw film (wet film) after washing with water was frozen with liquid nitrogen and dried with a freeze dryer. The cross-sectional structure of this dried film was observed with an electron microscope to evaluate the coarseness and coarseness of the aggregated state.
The remaining film was sandwiched between filter papers and vacuum dried, and then used for measuring the strength and elongation. The results are summarized in Table 2. The agglomeration structure (cross section) was judged visually based on the density of the agglomerated state observed by an electron microscope based on the presence / absence of a void and its size. O indicates a dense structure having a void hole diameter of 50 nm or less, and X indicates a coarse structure having a void hole diameter of 200 nm or more. In addition, the strength and elongation were measured using a tensile tester “Tensilon” manufactured by Toyo Baldwin.

In Table 2, Examples 4 to 8 and Comparative Examples 4 to 6
Indicates. Example 8 and Comparative Examples 4 and 5 show the effect of coagulation bath temperature. As is apparent from the table, it is shown that the coagulation structure and strength of the obtained film do not increase even if the solidification temperature is low or high. In the case of Comparative Example 4, the coagulation temperature was lower than the freezing temperature of the dope, so gelation and freezing of the dope occurred,
In the case of Comparative Example 5, it is presumed that the film was inferior due to gelation of the dope and decomposition of cellulose itself. Further, in Comparative Example 6, as in the film obtained by the method of the present invention, the degree of destruction of intramolecular hydrogen bonds is large (χa
m (C3) = 73%), but the agglomerated structure and strength are inferior to those of the method of the present invention.

This coagulation bath composition is almost equivalent to the Mueller bath composition used in the current viscose rayon method. On the other hand, as seen in Examples 4 to 8, according to the method of the present invention, a cellulose film having strength equal to that of commercially available cellophane (viscose method) emits toxic gases such as carbon disulfide and hydrogen sulfide. Can be made from a process without.

[0022]

Examples 9 to 11, Comparative Examples 7 to 8 Acid hydrolysis of high α cellulose pulp (manufactured by Leonia Co., α cellulose content 95.4%) using 50N aqueous sulfuric acid at 50 ° C. for 60 minutes. Then, a cellulose having a viscosity average degree of polymerization of 340 was obtained.
Using this cellulose as a starting material,
The alkali-soluble low-substituted cellulose derivative of 3 was prepared to produce a cellulose molded product. (1) Preparation of methyl cellulose (MC): 48.6 g of the cellulose prepared by the above method was dissolved in 923.4 g of a 9 wt% caustic soda aqueous solution at 5 ° C., and 7.56 g of dimethyl sulfate (0.2 mol of cellulose) and After 30.2 g of dimethyl sulfate (0.8 mol of cellulose) was added / mixed, the mixture was heated to 50 ° C. and reacted for 60 minutes. These dopes were reprecipitated in ethanol, repeatedly washed several times with ethanol / 2% by weight acetic acid (1/1, vol / vol), and then thoroughly washed with water. Subsequently, the mixture was replaced with acetone and vacuum dried. The obtained derivative was dissolved in an 8.65 wt% sodium hydroxide aqueous solution and the substitution degree was evaluated by NMR measurement. As a result, the substitution degree was 0.08 and 0.41. (2) Preparation of hydroxypropyl cellulose (HPC): 48.6 g of the cellulose prepared by the above method
After immersion in 600 g of a 7.5 wt% caustic soda aqueous solution at 30 ° C. for 30 minutes, pressing was performed to obtain 135 g of alkali cellulose. This alkali cellulose was placed in a closed container equipped with a degassing port, degassed with a vacuum pump, and then 2.6 g of propylene oxide (vs. 0.12 mol of cellulose)
1) was injected and reacted at 40 ° C. for 2 hours. After reprecipitating this mixture in ethanol and repeating washing several times with ethanol / 2% by weight acetic acid (1/1, vol / vol),
Washed well with water. Subsequently, the mixture was replaced with acetone and vacuum dried.
Similarly, 17.0 g of propylene oxide which is a reaction agent
It was also prepared by injecting (0.8 mol of cellulose). The obtained derivative was dissolved in an 8.65 wt% sodium hydroxide aqueous solution and the substitution degree was evaluated by NMR measurement. As a result, the substitution degree was 0.06 and 0.38. (3) Preparation of carbamoylethyl carboxyethyl cellulose (CEC): Cellulose 4 prepared by the above method
8.6 g was dissolved in 93.4% 9 wt% caustic soda aqueous solution at 92 ° C at 5 ° C, 4.32 g of acrylamide (0.2 mol of cellulose) was added / mixed, and then heated to 50 ° C and reacted for 60 minutes. .. This dope was reprecipitated in ethanol several times and ethanol / 2% by weight acetic acid (1/1, vo
After repeating the washing with 1 / vol), it was thoroughly washed with water. Subsequently, the mixture was replaced with acetone and vacuum dried. The obtained derivative was dissolved in a 8.65 wt% sodium hydroxide aqueous solution to obtain NM.
As a result of evaluating the substitution degree by R measurement, the substitution degree was 0.13.

42 g of each cellulose derivative was added at 5 ° C.
A homogenizer was dissolved in 558 g of a 9.5 wt% aqueous sodium hydroxide solution using a homogenizer. The solution was filtered using 1 sheet of 400-mesh metal net and 2 sheets of polyamide nonwoven fabric, and then allowed to stand naturally for defoaming to obtain a spinning dope. Using a extruder equipped with a gear pump, this spinning dope was discharged from a nozzle having 22 holes of 0.08 mmΦ into a 65 wt% sulfuric acid bath with an amount of 2.2 ml /
It was discharged at min. The coagulation bath temperature is -7 ° C and the immersion length is 3
After coagulating under the condition of 0 cm, wash through the washing process to 120 ℃
It was dried on a hot roll of, and wound on a paper tube at 20 m / min.

Table 3 collectively shows the physical properties of the obtained fibers. According to the method of the present invention, not only pure cellulose but also a low-substituted cellulose derivative exhibiting alkali solubility can be used to obtain a yarn having physical properties comparable to those of existing regenerated cellulose fibers, but it is usually known as alkali-soluble. When the cellulose derivatives having the above substitution degree range (Comparative Examples 7 and 8) are used, the tensile strength (TSw) when wet is weak, and the washability is poor, which is not practical.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

[Table 3]

[0028]

INDUSTRIAL APPLICABILITY The present invention produces a cellulose molded article having good physical properties from a dope consisting essentially of cellulose, alkali and water. In terms of process, there is no danger of generation of waste gas or explosion during the molding process. It has the advantage of being able to provide a process that does not cause environmental pollution due to waste liquid or waste gas. Further, in terms of physical properties, the same level as existing fibers and films, which was impossible in the prior art to obtain a cellulose molded product having good physical properties from a dope consisting of substantially cellulose, alkaline and water, was used. It is possible to form a structure in which intramolecular hydrogen bonds are severely broken while having mechanical properties. Due to such structural characteristics, in the case of fiber, it is possible to obtain a fiber having excellent resin processability and dyeability. Further, in the case of a film, a film having high flexibility can be obtained.

Claims (1)

[Claims] 1. When producing a cellulose molded article by a wet method from a dope prepared by dissolving substantially alkali-soluble cellulose in an alkaline aqueous solution, the dope is coagulated and molded in a medium having a highly dehydrating action. A method for producing a cellulose molded product, which is characterized by being made at the most.