JPH0674281B2 - Alkali-soluble cellulose and its dope - Google Patents

Description

TECHNICAL FIELD The present invention relates to a cellulose suitable for obtaining a useful cellulose molded article from a cellulose dope dissolved in a simple solvent, and a dope thereof.

[Conventional technology]

Conventionally, as a cellulose having a relatively high degree of polymerization (about 500) which can be dissolved in an aqueous solution of an alkali metal hydroxide at a concentration of 3% by weight or more, the cellulose II type cellulose disclosed in JP-A-60-42401 is known. It's just being done. This cellulose is obtained by once dissolving natural cellulose and regenerating it, and it is not costly to industrially obtain a molded article by redissolving such alkali-soluble cellulose in alkali. For such a purpose, a technique for solubilizing natural cellulose (having a cellulose I crystal type) in an alkali by a more economical treatment is desired.

[Problems to be solved by the invention]

An object of the present invention is to provide an alkali-soluble cellulose having a cellulose I crystal form as a raw material for obtaining useful molded articles such as fibers and membranes, and a cellulose dope suitable for obtaining a cellulose molded article. It is in.

[Means for solving problems]

In one aspect thereof, the present invention has a viscosity average degree of polymerization of 100 to 7
Cellulose I having a crystal form of Cellulose type I at 00 and having a C _{3 value} in the solid state ¹³ C nuclear magnetic resonance spectrum using the cross polarization / magic angle rotation method.
Degree of intramolecular hydrogen bonding of hydroxyl groups bonded to C and C ₆ positions
Provided is alkali-soluble cellulose characterized by having Hb of 50% or less.

However, Hb is defined by the following formula.

Here, Ic ₄ and Ic ₆ are the integrated intensities of all regions of the c ₄ and c ₆ carbon peaks, respectively, and Ic ₄ h and Ic ₆ h are the integrated intensities of a broad peak group appearing at high magnetic field in the region. is there.

The present invention provides, in another aspect, a cellulose dope suitable for molding, characterized in that the above-mentioned cellulose is substantially dissolved in an alkaline aqueous solution in an amount of 3% by weight or more.

The alkali-soluble cellulose of the present invention is a solid ¹³ C obtained by the cross polarization / magic angle rotation method.
- nuclear magnetic resonance (hereinafter, abbreviated as "NMR") is evaluated by the method, C _3, C ₆ position intramolecular hydrogen bonding involved in OH groups (Hb) are 5
It is less than 0%.

The intramolecular hydrogen bond referred to in the present invention will be described with reference to FIGS. 1 and 2. 1 and 2 are solid-state high-resolution ¹³ C NMR of cellulose of the present invention and comparative cellulose, respectively.
The spectrum is shown. In both figures, the symbols C ₁ and C ₆ on the peaks respectively indicate the identification of carbon peaks constituting the glucose ring of cellulose. Supra (K.Kamide) like: Polymer Journal (Polymer Journal) 16, 701 ( 1985)
Peak the peak identification of ¹³ C-NMR of the cellulose solids is being performed, the intramolecular hydrogen bonding of C ₃ position said it is reflected in the C ₄ carbon peak, which is shaded area was destroyed intramolecular hydrogen bonds Equivalent to (the peak integrated intensity in the shaded area is Ic
₄ h). This peak is a superposition of various peaks. Sharp peak of 89.9ppm full C ₃ -O ₅ '
It is a C ₄ carbon peak corresponding to an intramolecular hydrogen bond. C ₆
The intramolecular hydrogen bonding property of the position can be evaluated directly from the C ₆ carbon peak, and the shaded portion corresponds to the peak when the intramolecular hydrogen bond is broken (peak integrated intensity is Ic ₆ h).

The specific measurement method of cross polarization / magic angle ¹³ C-NMR is as follows. The nuclear magnetic resonance spectrum was measured using a JEOL JNM-FX200 spectrometer at 50.1 MHz using a CP / MAS method, with a contact time of 2 _ms , a pulse interval of about 5 _sec , and an integration count of 400 to 10
It was 00.

The cellulose of the present invention is Need to meet. The lower the Hb, the higher the solubility in alkali, and moreover the transparency and stability of the solution.
If the Hb exceeds 50%, the undissolved content reaches several% or more of the original cellulose even if the dissolution method is appropriately selected, so it cannot be said to be the best dope for molding.

The cellulose of the present invention basically contains a cellulose I-type crystal part and has a degree of polymerization of 100 to 700. It has one of the major characteristics that it has a cellulose I type crystal part, and it is shown that it can be obtained by a treatment that does not change the crystal structure of natural cellulose. When the degree of polymerization is less than 100, the processability when the cellulose of the present invention is dissolved in an alkali and molded, and the sufficient mechanical strength of the molded product are impaired. The upper limit is not limited, but if it exceeds 700, there is a sharp increase in viscosity when dissolved in an alkali and a decrease in solution stability.
700 or less is good.

The degree of polymerization mentioned here is a viscosity average molecular weight measured by the following method.

Reagent grade ethylenediamine 900g, distilled water 2414g,
The mixture was gradually added while keeping it at 0 ° C, and 318 g of special grade cadmium oxide was gradually mixed while stirring and keeping the mixture at 0 ° C for 2 to 3 hours, and allowed to stand at -15 ° C overnight. To this supernatant (950 ml), ethylenediamine (60 ml) and distilled water (155 ml) caustic soda (14 g) are added to give a cadoxene stock solution.

As the degree of polymerization, the viscosity average degree of polymerization determined from the viscosity in the cadoxene solution was used. The method will be described in detail. While keeping the weighed cellulose at 6 ° C. or lower, it is dissolved in a cadoxene stock solution, diluted with distilled water in the same volume as the cadoxene stock solution, and the concentration is designated as c (g / dl). Water fall seconds Approximately 80 to 120 seconds (20
℃) was measured with an Ubbelohde viscometer at 25 ℃, the falling time of the cellulose / cadoxene solution was t, and the falling time of the 2-fold diluted cadoxene solution was t _0, and [η] = 1im
Intrinsic viscosity defined by {(t / t ₀ -1) / c} is calculated from the viscosity equation of Brown, Wikstrm (Euro.Polym.J., 1 , 1 (1966) description) [Η] = 3.85 ・ 10
^The viscosity average molecular weight Mv obtained by substituting for ² · Mv ^0.76 was divided by 162 to obtain the viscosity average degree of polymerization. When determining the intrinsic viscosity, the solution of the following quadratic equation may be obtained from the value of the number of seconds of dropping at a single concentration using an empirical rule regarding the concentration dependence of the viscosity.

ck [η] ² + [η] -v = 0 However, v = (t / t ₀ -1) / c k = 0.08361v + 0.2061 The cellulose of the present invention can be produced, for example, by the following method. Natural cellulose as a raw material, for example, wood pulp, cotton linter, hemp, etc. containing 10 to 300% of water,
Charge this into a heat insulation type pressure resistant container, and from the outside 10 to 50 kg / cm ²
Of water vapor is introduced and left under that pressure for a few seconds to a few minutes, the valve of the pressure vessel is opened and the pressure is rapidly returned to normal pressure.
A small hole nozzle attached to the valve is rapidly passed.

In this manufacturing process, a small amount of acid, salt, alkali, hydrogen peroxide or the like may be added to water to perform the above operation. The pressure in the pressure vessel may be adjusted by using nitrogen gas together. It can also be obtained by impregnating a raw material pulp with a hydrogen medium, treating it with an extruder having a screw arrangement for preventing excessive backflow of water, and discharging it together with water vapor from the head part. The barrel temperature can be adjusted by an external heating method, and it is recommended to keep it at about 50-240 ℃.

The cellulose dope of the present invention is obtained by dissolving the cellulose obtained by the above method in an alkaline aqueous solution at a low temperature. In this case, the alkali concentration of the alkaline aqueous solution is 5 to 15% by weight, and in the case of caustic soda, 8 to 12% by weight is preferably used. Other than the above, lithium hydroxide, potassium hydroxide, cesium hydroxide and the like are used as the alkali. The cellulose concentration is a problem to be determined depending on the degree of polymerization of cellulose, but it contains 3% by weight or more from the economical point of view. The melting temperature is 16 ° C. or lower, preferably lower temperature.

The cellulose dope thus obtained is used for forming fibers, membranes, etc., and in some cases, it can be applied as a coating solution for other materials, or as a dipping solution to give properties not found in other materials as dipping solutions.

〔The invention's effect〕

The cellulose of the present invention is an alkali-soluble cellulose having a cellulose I crystal type, and a cellulose dope suitable for various applications as described above can be industrially obtained advantageously.

〔Example〕

Hereinafter, the present invention will be specifically described with reference to Examples.
The present invention is not limited to these.

Example 1 100 g of Alaska pulp (DP = 1150) was immersed in a large amount of water,
After crushing with a homomixer, it was dehydrated by centrifugation to obtain 20 g of water-containing Alaska pulp. This was put in an external heat insulation type pressure resistant container of 2.0 and heated separately with an electric boiler 30 kg / c
Water vapor of m ² was introduced, and the pressure inside the container was kept at 30 kg / cm ² for 30 seconds. Then, the container valve was rapidly opened, and the treated cellulose was passed through a thin tube having a diameter of 15 mm and received in a receiver container. The treated cellulose was washed with water and then air-dried. The degree of polymerization of this cellulose was 550. Furthermore,
Hb was evaluated by solid-state ¹³ C-NMR by the above-mentioned method and found to be 37%.
Met. (See FIG. 1). 20g of this cellulose was put into 380g of 9.1wt NaOH aqueous solution which had been previously cooled to 4 ° C, stirred and dispersed with a home mixer for 20 seconds, and left at 4 ° C for 6 hours.
It was stirred again for 10 seconds. Observation of the thus obtained dope with a polarizing microscope showed that they were all well dissolved in the dark field. Further, the above cellulose solution was diluted with 9.1% by weight NaOH adjusted to 4 ° C. to make the cellulose content 1% by weight, and then centrifuged at 7200 rpm under cooling to separate the gel content, which was regenerated to obtain raw cellulose. When evaluated as an undissolved part, the dissolved part (Sa ₂ ) was 99.8% or more. This solution (containing 5% by weight of cellulose)
It was stable at 4 ° C for several days.

On the other hand, as a comparative example, the above raw material pulp was dispersed in 2N HCl,
So-called level-off cellulose (DP200) was obtained according to the method of Battista et al. (USP 2,978,446). The ¹³ C-NMR spectrum of this cellulose is shown in FIG. Obviously, as compared with the cellulose of the present invention (Fig. 1), the fraction in the shaded area is low,
Hb was 70%. When Sa ₂ of this cellulose was evaluated according to the above-mentioned method, it was found that Sa ₂ was 8 even though it had a polymerization degree of half or less of that of the cellulose of the present invention.
The content of 5% or less was unsuitable as a raw material for producing a dope for molding.

Example 2 Alaskan pulp dried under vacuum at 70 ° C. for 24 hours (DP = 1150)
100 g was left in a thermo-hygrostat at 20 ° C. and 65% RH for 3 days to obtain Alaska pulp having a water content (dry weight of cellulose) of 14%. This was put in a pressure vessel of external heating type 1.0, and 45 kg / cm ² of water vapor separately heated by an electric boiler was introduced, and the vessel internal pressure was kept for 15 seconds in a state of 45 kg / cm ² . Then, the open valve of the container was rapidly opened, the pulp having a diameter of 21.6 mm was passed through, and the cellulose was received in the receiver container. The treated cellulose was washed with water and then air-dried. The degree of polymerization of this cellulose was 394. 20 g of this cellulose was poured into 380 g of a 10 wt% NaOH aqueous solution that had been squeezed and cooled to 0 ° C., stirred for 30 seconds with a home mixer, allowed to stand at 4 ° C. for 15 hours, and again dissolved by stirring for 20 seconds. The obtained dope was uniform and highly transparent, and showed spinnability suitable for forming fibers and films.

Further, based on the above-mentioned method and Example 1, Hb and Sa ₂
The results were 23% and 99.6%, respectively.

[Brief description of drawings]

FIG. 1 shows a solid high-resolution ¹³ C-NMR spectrum of the cellulose of the present invention, and FIG. 2 shows a similar NMR spectrum of comparative cellulose. The symbols C _{1 to} C ₆ on the peaks respectively indicate the carbon positions constituting the glucose ring of cellulose.

Claims (2)

[Claims] 1. Cellulose I having a viscosity average degree of polymerization of 100 to 700.
Cellulose having a crystalline part of the mold, which is a solid using the cross-polarization / magic angle rotation method ¹³
Cellulose soluble in alkali, characterized in that in the C nuclear magnetic resonance spectrum, the degree Hb of intramolecular hydrogen bonding of hydroxyl groups bonded to the C ₃ and C ₆ positions is 50% or less. However, Hb is defined by the following formula. Where Ic ₄ and IC ₆ are the integrated intensities of the c ₄ and c ₆ carbon peaks, respectively, and Ic ₄ h and Ic ₆ h are the integrated intensities of the broad peaks appearing on the high magnetic field side in the regions. is there. 2. In the solid state ¹³ C nuclear magnetic resonance spectrum using the cross polarization / magic angle rotation method, the degree of intramolecular hydrogen bonding of the hydroxyl groups bonded to the C ₃ and C ₆ positions is 50% or less. There is a viscosity average degree of polymerization of 100
A cellulose dope suitable for molding, which is obtained by dissolving cellulose having a crystal type of cellulose I type at about 700 in substantially 3 wt% or more in an alkaline aqueous solution. However, Hb is defined by the following formula. Where Ic ₄ and Ic ₆ are the integrated intensities of the c ₄ and c ₆ carbon peaks, respectively, and Ic ₄ h and Ic ₆ h are the integrated intensities of the broad peaks appearing on the high magnetic field side in the regions. is there.