JPH0735401B2 - Method for producing type I cellulosic acetate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to improvement of properties of cellulose triacetate in adsorbents, fibers, and other applications. More specifically, it relates to a method for obtaining type I cellulose triacetate (hereinafter abbreviated as CTAI) from cellulose triacetate.

[Conventional technology and problems]

Cellulose triacetate (hereinafter abbreviated as CTA) is known to have crystal polymorphism as in the case of cellulose. One of them, called CTAI, is usually obtained by heterogeneous acetylation of natural cellulose (acetylation method that does not go through the dissolved state in the reaction process), which is a thermodynamically unstable polymorph. Is considered. That is, as a rule, what is obtained from the solution of CTA by precipitation or dryness is type II cellulose triacetate (hereinafter
Abbreviated as CTA II), it is a polymorph that is considered to be a stable system. Therefore, with one exception, CTAI cannot be prepared from solution systems, which means that it is difficult to prepare CTAI that is fundamentally different from the morphology of natural cellulose as a raw material. To do. CTAI is, for example, an adsorption property [T. Shibata, I. Okamoto, K. Ishii, J. Liq. Chroma
tography, 9, 313 (1986)] and the like, are known to show different characteristics from CTA II. Therefore, if the technology to make free-form CTAI by casting from solution or other manufacturing methods is established, the range of application of CTA will be further expanded. To date, as a method to obtain CTAI from CTA solution,
Although a method of coagulating a concentrated solution using trifluoroacetic acid as a solvent with water or methanol has been reported, there are restrictions such as the need to use a strongly acidic solvent.

[Means for solving problems]

As a result of intensive studies, the present inventors have found that CTAI is produced by preparing a solution of CTA in a phenolic liquid as a solvent and drying or coagulating the solution.

That is, the present invention relates to a method for producing CTAI, which comprises drying or solidifying a solution of CTA in a phenolic liquid as a solvent.

CTAI in the present invention is defined by powder method X-ray diffraction spectrum. For reference, CTAI and CT with relatively high crystallinity
The X-ray diffraction spectrum of A II is shown in FIGS. 1 and 2.
The difference between the two is clear, and the CTA II has a diffraction angle 2θ of 8
The CTAI is characterized by three peaks around °, 10 ° and 13 ° and a set of peaks around 17 ° -19 °, while CTAI is 7-
Since they are characterized by peaks at 8 ° and 16 to 17 °, it is easy to distinguish them. In some cases, CTAI and CTA II peaks may appear together, but in this case, for convenience, the diffraction intensities of the 7-8 ° characteristic of CTAI and the 10-11 ° characteristic of CTA II, respectively. And the former is stronger, it belongs to the category of CTAI referred to in the present invention.

The cellulose triacetate (CTA) referred to in the present invention means that 90% or more of the hydroxyl groups of the corresponding cellulose having a weight average polymerization degree of 10 or more are acetylated.

Phenolic liquids include phenol, cresol (o, m, p form), 2,3-dimethylphenol, chlorophenol (o, m, p form), bromophenol (o, m form), iodophenol (o form). , m body), fluorophenol (o, m, p body)
Etc., a liquid having a melting point of 60 ° C. or lower.

In carrying out the present invention, it is not always necessary to use only a phenolic liquid as a solvent, and another solvent having a lower boiling point than this may be mixed.

To prepare CTAI from a CTA phenolic liquid solution in the present invention, the solution is dried to solidify or coagulate by distilling off the solvent, which is a phenolic liquid or another solvent, under an appropriate reduced pressure. Good. In this case, it is difficult to completely distill off the phenolic liquid, but normally, when the content is 20% or less, the characteristic X-ray diffraction peak of CTAI appears, and the intended product can be obtained.

On the other hand, it is also possible to precipitate using a non-solvent for CTA, but this method is particularly high in CTA content obtained by distilling off the above-mentioned solvent, from those already showing the CTAI diffraction pattern. Effective in removing phenolic liquids. In this case, a non-solvent having a low swelling property with respect to CTA (such as hexane) or a mixed liquid mainly containing this (such as hexane-2-propanol mixed liquid) is used.

The shape of CTAI produced using the method of the present invention may be any one such as particles, fibers, and films depending on the purpose of use, and a composition with a carrier or another substance that is not compatible with CTA. You can also

[Action]

It is not clear why the phenolic liquid produces CTAI in the method of the present invention, but it is likely that strong solvation interactions alter the conformation of the molecule, or high compatibility results in a highly concentrated solution state. Since it takes a special state such as liquid crystal, it is thought that it usually results in a different crystal lattice from the solution.

〔The invention's effect〕

With the method of the present invention, CTAI of various shapes can be easily performed.
It is possible to produce the above, and it is useful for effective utilization of cellulose.

〔Example〕

Hereinafter, the present invention will be specifically described with reference to Examples, but it goes without saying that the present invention is not limited to these Examples.

Note that Geigerflex manufactured by Rigaku Denki Co., Ltd. was used for the measurement of the X-ray diffraction spectrum in this example, and the slit widths were DS 1/2 ° and RS, respectively.
0.15 and SS 1/2 ° were used.

Example 1 Relatively low molecular weight (polystyrene-equivalent molecular weight determined by GPC using chloroform as a mobile phase is 9960 on a weight average,
(The number average was 6500) 2 g of cellulose triacetate and 660 mg of phenol were dissolved in 10 ml of dichloromethane, and then dichloromethane was evaporated to dryness under reduced pressure. 8 under reduced pressure (0.1 mmHg)
It heated at 0 degreeC and some phenols were distilled off. The cellulose triacetate produced by this treatment contained 19% residual phenol as determined by NMR spectroscopy. The X-ray diffraction spectrum is shown in FIG. 3, and the diffraction pattern characteristic of CTAI is clearly observed.

Example 2 Cellulose triacetate obtained in Example 1 was mixed with hexane and 2-
When washed with a mixed solution of propanol 9: 1, phenol was removed to a trace amount, but the X-ray diffraction spectrum of the obtained cellulose triacetate was almost the same as that in Example 1.

Example 3 The polystyrene reduced molecular weight determined by GPC (chloroform solvent) was 166,000 on a weight average, and the number average molecular weight was 58,000.
3 g of cellulose triacetate, 2 g of phenol, dichloromethane
After dissolving in 30 ml and applying the same treatment as in Example 1 and Example 2, the X-ray diffraction spectrum was measured. The spectrum obtained was characteristic of CTAI.

[Brief description of drawings]

1 and 2 show the X-ray diffraction spectra of CTAI and CTA II, respectively, and FIG. 3 shows the CTAI obtained in Example 1.
It is a figure which shows the X-ray diffraction spectrum of.

Claims (1)

[Claims] 1. A process for producing type I cellulose triacetate, which comprises drying or coagulating a solution of cellulose triacetate in a phenolic liquid as a solvent.