JP2538323B2 - Cellulose acetate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to xylose in the constituent components of the main peak when the outflow pattern is measured by a gel per liquid chromatography (GPC) method using cellulose acetate as an acetone solution. The present invention relates to a novel cellulose acetate characterized in that the total content of mannose is 2 mol% or more, and particularly in a cellulose acetate made from low-grade wood pulp having an α-cellulose content of 88-93%. It is to provide a cellulose acetate having excellent transparency, transparency and spinnability.

(Prior Art and Problems Thereof) Cellulose acetate is one of the organic acid esters of cellulose, and its applications are widely used in clothing fibers, cigarettes, filters, chips, plastics, films, paints, etc. It has the highest production volume and is of industrial importance.

Conventionally, cellulose acetate is manufactured using a raw material pulp with a relatively high α-cellulose content, but in general, the cellulose raw material is of a high quality that is cost-effective due to global resource constraints and pollution problems at pulp manufacturing plants. Is expected to be difficult to obtain. Under such circumstances, the development of cellulose acetate using low-grade wood pulp having a low α-cellulose content is desired, but in reality, cellulose acetate produced using low-grade wood pulp is transparent and transient. And it has many problems in terms of quality such as spinnability.

It is considered that this is because the content of hemicellulose (polysaccharide consisting of xylose, mannose, etc.), which is a component other than cellulose, in wood increases as the α-cellulose content of wood pulp decreases. There is. That is, when hemicellulose is present in the wood pulp, a gel-like substance that does not dissolve in acetone is generated when the pulp is acetylated. The mechanism of this formation is described in detail in the Journal of Wood Science, Volume 34, P346-353 (1988), but the presence of hemicellulose inhibits the acetylation reaction of cellulose and causes the insoluble of acetone in which hemicellulose acetate and cellulose acetate are molecularly associated. To produce a gel. Therefore, the use of low-grade wood pulp as a raw material causes a large amount of hemicellulose to be contained in the raw material, which leads to an increase in gels that cause deterioration of transparency and transparency. However, removal of hemicellulose from the raw material will inevitably raise the quality of the raw material, leading to an increase in cost and a decrease in yield due to the removal of hemicellulose. Therefore, when using low-grade wood pulp as a raw material for cellulose acetate,
It is desired to develop a cellulose acetate in which hemicellulose remains in the product cellulose acetate and does not form a gel.

In order to solve these problems, the present inventors have examined the relationship between the state of presence of hemicellulose contained in cellulose acetate and the gel-like substance, and leaving the hemicellulose in cellulose acetate, the gel-like substance. The present invention has been completed by finding that it is necessary to set the distribution state of hemicellulose in cellulose acetate within a specific range in order to obtain cellulose acetate having a low content, that is, a good transient property.

(Means for Solving the Problem) In the present invention, the distribution state of hemicellulose was discussed in relation to the GPS pattern. This point will be described first.

In recent years, gel permeation chromatography (Ge
l Permeation Chromatography, abbreviated as GPC below. )
The research using is done. (Journal of the Textile Society, 31st
Volume, P90-99 (1975), Kamiede et al .; Journal of the Wood Science Society, Volume 34 (19
88) P346-353, Ueda et al.) In the present invention, the measurement conditions by the GPC method and the preparative conditions for each peak appearing in the GPC pattern are defined as follows.

GPC measurement conditions Tosoh GPC system (pump: HLC-8030, detector: LS-
8000, GPC column; TSK _gel GMPW _XL acetone packing) Measuring solvent: acetone, sample concentration and injection volume are 0.2% and 100μ, respectively
l, the rate of solvent flowing through the column is 1 ml / min.

Preparative conditions Waters preparative system 500A, GPC column; diameter 69 mm
It was filled with a mixture of Wako FPG gel 3000S and FPG 2500S at a ratio of φ: 60 cm and 14: 9.

The sample concentration is 2%, the injection volume is 30 ml, and the solvent flow rate through the column is 100 ml / min. Peak A and peak B
Was fractionated as one fraction and the main peak was fractionated as the other fraction.

FIG. 1 shows a model of the pattern when GPC measurement is carried out by dissolving cellulose acetate in acetone.

The present inventors have shown in FIG. 1 to clarify the site where hemicellulose (including hemicellulose acetate produced by acetic acid; hereinafter, this hemicellulose / hemicellulose acetate is simply referred to as hemicellulose) in cellulose acetate is shown. The peaks A and B and the main peak were collected by a preparative GPL apparatus, and the constituent sugar composition was investigated. As a result, in the case of cellulose acetate, which is inferior in transparency and transparency, hemicellulose is all present in the peaks A and B, but almost not in the main peak.

Here, the main peak is a peak due to cellulose acetate completely molecularly dispersed in an acetone solution. Peak A is a gel-like associated molecule, which causes deterioration of transparency and transparency. Further, although the peak B is not clear yet, it is considered to be an abnormal molecule involving a sulfate ester group and the like.

Therefore, if hemicellulose is found such that hemicellulose is mainly present in the main peaks other than peaks A and B, hemicellulose is incorporated in cellulose acetate, but hemicellulose does not cause gel formation and contains gel. There is a possibility that cellulose acetate with a small amount and good quality can be obtained.

Therefore, the present inventors have conducted a study on a method for producing cellulose acetate containing a large amount of hemicellulose in its main peak in the GPC pattern of cellulose acetate produced using a low-grade raw material pulp, and the present applicant first The cellulose acetate produced by the application method (Japanese Patent Publication No. 60-17442) has an α-cellulose content of 88 as the raw material pulp.
Despite its low quality of -93%, it has excellent transparency and transparency, and 2 in the main peak of its GPC pattern.
It was found to contain more than mol% hemicellulose.

This is because the acetylation reaction at the hemicellulose-existing site increased due to the softening of the low-grade pulp sheet, and a part of the hemicellulose chemically and physically bound to the cellulose by performing the oxidation / aging reaction at high temperature. Hydrolysis occurred, and the gel-like substance caused by hemicellulose was dispersed, and the hydrolyzed hemicellulose remained in small fragments and remained bound to cellulose acetate, which is an acetate of cellulose. It is considered that the main peak contains hemicellulose (containing xylose, mannose, etc. as the main constituent sugar) due to the above reasons. Further, in this case, if the destruction of hemicellulose is extremely advanced, the binding of cellulose is also destroyed, and the destroyed hemicellulose is washed away at the time of washing in the final step of oxidation.

Therefore, in order to control the destruction of hemicellulose, the high temperature reaction is carried out with the amount of acidic catalyst during acetylation as small as possible. The production of cellulose acetate containing hemicellulose in the main peak of the GPC pattern made it possible to determine the degree of hemicellulose destruction by three factors: softening of the low-grade pulp sheet, high-temperature oxidation with a small amount of acid catalyst, and high-temperature aging. Probably because I was able to control.

The following production method is an example of the production method of the cellulose acetate of the present invention.

Α-cellulose content as a cellulose raw material is 88 ~ 93
%, And the basis weight of the pulp sheet is 300 to 8
50g / m ² , density 0.40 ~ 0.50g / cm ³ , burst strength 50 ~ 350KP
The wood pulp sheet in each range of a is used. Such a pulp sheet can be obtained by controlling the dehydration rate of the pulp sheet and / or adding a softening agent before entering the dryer during the existing pulp manufacturing process.

When the pulp sheet having the predetermined basis weight, density and burst strength obtained in this way is treated with a dry crusher such as a hammer mill or an attrition mill, a small amount of scale-like particles with an equivalent diameter of about 3 to 5 mm Although it is a mixture of pulp pieces, it is a fluffy crushed pulp as a whole.

Activate the pre-treated crushed pulp,
Spray 0 to 100 parts of glacial acetic acid to 0 parts (parts by weight, the same applies hereinafter), and in a closed container with a stirrer at a temperature of 30 to 50 ° C at 0.5.
Stir the pulp for ~ 2 hours.

Then, a mixture containing 200 to 400 parts of acetic anhydride, 0 to 350 parts of glacial acetic acid, and 0.5 to 5 parts of an acidic catalyst is added,
Mix with stirring. The contents generate heat due to the reaction, but 20-60
Adjust so that the temperature rises at an almost constant rate over
No temperature above 50 ° C and below 85 ° C, then 3 ~
Hold for 20 minutes to acetylate the cellulose and obtain primary cellulose acetate.

Next, saponification and aging are carried out. The temperature in the system is 125 ° C or higher and 170 ° C or higher by neutralizing the acidic catalyst in the primary cellulose acetate reaction mixture and introducing steam into the system under pressure.
It is preferable to maintain the temperature in the following range for 3 minutes or more and 6 hours or less, whereby the primary cellulose acetate can be hydrolyzed to obtain secondary cellulose acetate having a desired degree of acetylation. The average degree of acetylation is 53 to 57%.

The secondary cellulose acetate reaction mixture is put into a dilute aqueous solution of acetic acid, recovered as a precipitate, washed, purified and dried.

The cellulose acetate of the present invention can be obtained by this method, but the present invention is not limited to this method.

(Effects of the Invention) The cellulose acetate according to the present invention uses low-grade pulp having a low α-cellulose content and is excellent in durability.
Next is cellulose acetate.

Since the novel cellulose acetate of the present invention is excellent in transparency, transparency and spinnability, it is suitable for applications such as acetate fiber for tobacco filter tow, acetate fiber for clothing and hollow fiber.

(Examples) Hereinafter, the production method of such cellulose acetate and physical properties such as transitivity will be specifically described by way of examples, but prior to the examples, methods for measuring various physical properties of cellulose acetate used in the present invention are described below. Show.

Constituent sugar analysis method: The type of constituent sugar of cellulose acetate and its content were measured by the alditol acetate method (Tappi, 53 , 25
7-260 (1970). ).

The constituent sugar composition components described in this patent are calculated from the peaks based on glucose residues and the peaks based on xylose and mannose on the gas chromatograph, and the molar content of each is calculated, and the total of these three components is set to 100. The content of constituent sugars was expressed in mol%. For the sake of simplicity, the total of mol% based on xylose and mannose residues may be referred to as a hemicellulose content in part in this patent.

Oxidation degree: ASTM D-871 (1970) Viscosity: Cellulose acetate dissolved in 96% acetone aqueous solution to 20% concentration, at 25 ± 0.1 ℃, steel ball (diameter 6.32mm, weight 1.043)
g) Time required for dropping 10 cm in a tube with an inner diameter of 25.9 mm filled with cellulose acetate solution (seconds) Excessive: Pass the cellulose acetate solution dissolved in 20% concentration in 96% acetone aqueous solution at 50 ° C through a specified cloth. , Excess amount under constant pressure is measured, and the excess Kw is calculated by the following formula.

P ₁ : Overload for 20 minutes from overstart (ml) P ₂ : Overload for 40 minutes from 20 to 60 minutes (ml) The basis weight of the raw pulp sheet is JIS P-8124-1976, the density is JIS
P-8118-1976 and burst strength were measured according to JIS P-8112-1976.

Examples will be shown below for specifically explaining the present invention, but the present invention is not limited to the examples shown below.

In the examples, “parts” means “parts by weight” and “%” means “% by weight”.

Example 1 Sulfite dissolving pulp (α-cellulose content 92.4
%) Was disintegrated in water and a wet pulp sheet was prepared using a square (20 cm × 25 cm) handmade paper machine. The water content of this product was 85%. This was dried in a hot air dryer at 50 ° C to obtain a dry sheet. The basis weight of the sheet was 680 g / m ² , the density was 0.47 g / cm ³ , and the burst strength was 254 KPa.

The pulp sheet thus obtained was crushed using an attrition mill. This pulp was put into a pretreatment machine, and 100 parts of glacial acetic acid was uniformly sprayed to 100 parts of 5% water pulp and mixed at 40 ° C. for 30 minutes to activate the pretreatment. 250 parts of acetic anhydride, 375 parts of acetic acid, 1.0 part of sulfuric acid cooled to 12 ° C in advance
Part of the mixed liquid was prepared in a kneading type acetylation machine, and the above-mentioned pretreated activated pulp was charged and mixed with stirring. The contents generate heat due to the reaction between water and acetic anhydride accompanying the raw material pulp and the reaction between cellulose and acetic anhydride, but from around the initial 16 ° C,
It was adjusted by external cooling so as to reach 77 ° C over 60 minutes, and further maintained at 77 ° C for 12 minutes to carry out an oxidation reaction.

Next, 10 parts of a 20% magnesium acetate aqueous solution was added and mixed to completely neutralize sulfuric acid in the system and to make magnesium acetate excessive. The completely neutralized reaction mixture was transferred to an autoclave, and steam having a gauge thickness of 5 kg / cm ² was blown into the autoclave with stirring to reach 150 ° C. over about 60 minutes. At 150 ° C
After holding for 50 minutes, the reaction was brought to 100 ° C. by slowly flushing the reaction under air. The reaction mixture was added with a dilute acetic acid aqueous solution under vigorous stirring to separate it as flaky cellulose acetate, washed thoroughly with water, and dried.

The degree of oxidation of the obtained flaky cellulose acetate was 55.4.
%, The viscosity was 19 seconds.

When the GPC pattern of this cellulose acetate was examined, it showed three peaks as in FIG. Next, this cellulose acetate was separated and fractionated into a peak A + peak B and a main peak by the GPC method using a column packed with Wako FPG gel. The following table shows the results of examining the constituent sugars of each fraction.

From the table, this cellulose acetate contains 2 mol% of xylose and mannose in the main peak. Also,
The excess of this cellulose acetate is 167,
It was a product with excellent spinnability.

(Example 2) Sulfite dissolving pulp (α-cellulose content 91.5
%) In water and then a wet pulp sheet was prepared using a square handmade paper machine.

This product had a water content of 80% and was dried in a hot air dryer to obtain a dry sheet. The basis weight of the sheet was 740 g / m ² , and the breaking strength was 265 KPa. The pulp sheet thus obtained was subjected to an oxidation reaction by the same procedure as in Example 1,
Flakes like cellulose acetate were obtained. The obtained cellulose acetate had a degree of acetylation of 55.4% and a viscosity of 22 seconds.

When the GPC pattern of this cellulose acetate was examined, it showed three peaks as shown in FIG.

Next, this cellulose acetate was separated and fractionated into a peak A + peak B and a main peak by the GPC method using a column packed with Wako FPG gel. The following table shows the results of examining the constituent sugars of each fraction.

From the table, this cellulose acetate contains 3 mol% of xylose and mannose in the main peak. Also,
The excess of this cellulose acetate is 180,
It was a product with excellent spinnability.

Comparative Example 1 Sulfite dissolving pulp sheet (α-cellulose content
91.5%, sheet basis weight 750g / m ² , density 0.78g / cm ³ , burst strength
420 KPa) was crushed using an attrition mill. This pulp was put into a pretreatment machine, and 100 parts of glacial acetic acid was uniformly sprayed to 100 parts of 5% water pulp and mixed at 40 ° C. for 30 minutes to activate the pretreatment. Pre-cooled to 12 ℃ acetic anhydride 25
The pretreated activated pulp was added to a mixed solution of 0 part, 375 parts of acetic acid and 7 parts of sulfuric acid, and mixed by stirring. The reaction temperature was kept at 50 ° C or lower by external cooling, and the reaction was carried out for 1 hour.

Then, after partially neutralizing the sulfuric acid with magnesium acetate, water was added and the mixture was hydrolyzed at 50 ° C. until the acetylation degree reached 55%. The reaction product was separated into flakes-like cellulose acetate by adding dilute acetic acid aqueous solution, thoroughly washed with water, taken out and dried.

When the GPC pattern of this cellulose acetate was examined, it showed three peaks as shown in FIG.

Next, this cellulose acetate was separated and fractionated into a peak A + peak B and a main peak by the GPC method using a column packed with Wako FPG gel. The following table shows the results of examining the constituent sugars of each fraction.

From the table, this cellulose acetate contains less than 1% of xylose and mannose in the main peak.
Also, the excess of this cellulose acetate is 730,
Poor transitivity and spinnability.

[Brief description of drawings]

Figure 1 is a GPC curve. The vertical axis Δn represents the difference in refractive index and represents the amount of polymer in the solution. The horizontal axis represents the outflow time of the sample from the column. The peak A, peak B, and main peak are shown in this order from the earliest outflow time.

Claims (1)

(57) [Claims] 1. When only the main peak portion of a GPC pattern measured with a cellulose acetate / acetone solvent system is fractionated, the content of xylose and mannose in the constituent sugar composition components is 2 mol% or more. Cellulose acetate characterized by.