阅读说明：本技术 乙酸纤维素组合物及成型体 (Cellulose acetate composition and molded article ) 是由 贺旭东 铃木雅彦 于 2019-07-18 设计创作，主要内容包括：本发明的课题在于提供具有优异的生物降解性及水解性、以及优异的热成型性的乙酸纤维素组合物。乙酸纤维素组合物,其含有乙酰基取代度为0.4以上且小于1.4的乙酸纤维素、及柠檬酸酯系增塑剂,相对于上述乙酸纤维素及上述柠檬酸酯系增塑剂的合计量100重量份而言,上述柠檬酸酯系增塑剂的含量为3重量份以上。(The invention provides a cellulose acetate composition having excellent biodegradability and hydrolyzability and excellent thermoformability. A cellulose acetate composition comprising a cellulose acetate having an acetyl substitution degree of 0.4 or more and less than 1.4 and a citrate plasticizer, wherein the content of the citrate plasticizer is 3 parts by weight or more based on 100 parts by weight of the total amount of the cellulose acetate and the citrate plasticizer.)

1. A cellulose acetate composition comprising:

cellulose acetate having a degree of substitution with acetyl groups of 0.4 or more and less than 1.4, and

a plasticizer of a citric acid ester series,

the content of the citrate plasticizer is 3 parts by weight or more based on 100 parts by weight of the total amount of the cellulose acetate and the citrate plasticizer.

2. The cellulose acetate composition according to claim 1 wherein the citrate-based plasticizer is at least one selected from the group consisting of triethyl citrate and acetyl triethyl citrate.

3. The cellulose acetate composition according to claim 1 or 2, wherein the cellulose acetate has an acetyl substitution degree of 0.4 or more and 1.1 or less.

4. The cellulose acetate composition according to any one of claims 1 to 3 wherein the cellulose acetate composition is used for thermoforming.

5. A molded article obtained by molding the cellulose acetate composition according to any one of claims 1 to 4.

6. The shaped body according to claim 5, wherein the shaped body is a film.

7. The shaped body according to claim 5, wherein the shaped body has a hollow cylindrical shape.

8. The molded body according to claim 5, wherein the molded body is a member for a roll cigarette of an electronic cigarette.

Technical Field

The present invention relates to a cellulose acetate composition and a molded article.

Background

In recent years, there has been an increasing demand for electronic cigarettes that do not use fire, as compared to conventional paper-wrapped cigarettes. The electronic cigarette is roughly classified into 2 types, including: a type of aerosol or gas generated by heating and sucking a solution in which nicotine is dissolved in an organic solvent; and a type in which tobacco leaves (here, the tobacco leaves include a processed material of the tobacco leaves or a simulated tobacco leaf such as a base material impregnated with a cigarette component) are heated (not burned) and then an aerosol containing scattered nicotine is sucked. However, in japan, nicotine itself is designated as a pharmaceutical product, and its sale is prohibited in principle, and the handling of nicotine is limited. In such a case, an electronic cigarette of aerosol or gas type, which is produced by heating and drawing a solution in which nicotine is dissolved in an organic solvent, cannot be sold. In countries other than japan, there are many countries that are prescribed as pharmaceuticals. The iQOS (registered trademark) by Philip Morris corporation is a type in which tobacco leaves are heated using a special cigarette roll and then an aerosol containing scattered nicotine is sucked.

As a paper roll cigarette used for an electronic cigarette, for example, patent document 1 discloses the following paper roll cigarette: the cigarette has a structure in which a mouthpiece (mouth piece), an aerosol cooling element, a support element, and an aerosol-forming substrate are arranged in this order from a side close to a mouthpiece, and describes a cigarette comprising a cellulose acetate tow filter as the mouthpiece, a polylactic acid sheet as the aerosol cooling element, a hollow cellulose/acetate tube body as the support element, and a cigarette as the aerosol-forming substrate.

In the electronic cigarette of the type in which tobacco leaves are heated, after smoking is completed, components other than the tobacco leaves of the dedicated roll cigarette remain. Therefore, an environmental problem may occur due to discarding of the remaining member. In order to cope with this environmental problem, as described above, biodegradable polylactic acid is used as a material for the cooling portion of the roll cigarette used in the electronic cigarette.

The degree of substitution with acetyl groups of cellulose acetate used in cellulose acetate tow filters and cellulose acetate tubes is generally preferably low from the viewpoint of excellent biodegradability, but a certain degree of substitution with acetyl groups is required from the viewpoint of ease of processing by thermoforming, little influence on odor absorption, and the like. In order to obtain more excellent thermoformability and physical properties, additives such as a plasticizer may be added to cellulose acetate (patent documents 2,3 and 4).

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2015-503335

Patent document 2: international publication No. 2016/203657

Patent document 3: japanese patent laid-open publication No. 2015-140432

Patent document 4: japanese laid-open patent application No. 2001 and 048840

Disclosure of Invention

Problems to be solved by the invention

Patent document 2 describes adding polyvinyl alcohol to cellulose acetate having a total degree of substitution of acetyl groups of 0.4 to 1.6. Patent document 3 describes that polyethylene glycol is used as a plasticizer added to cellulose acetate having an acetyl substitution degree of 0.5 to 1.0.

However, in particular, when polyvinyl alcohol or polyethylene glycol is added to each component of a conventional cigarette filter or an electronic cigarette (a component involved in smoking including a component used for a mouthpiece such as a cellulose acetate tow filter, a component serving as a cooling element of an aerosol, and a component serving as a supporting element such as a hollow cellulose/acetate tube), there is a concern about an influence on the taste of smoking.

Polyethylene glycol varies in state depending on the degree of polymerization, and has a liquid state when the degree of polymerization is low at room temperature, and a solid state when the degree of polymerization is high. Although liquid polyethylene glycol is preferable in that it is easily uniformly dispersed in cellulose acetate, it easily bleeds out from cellulose acetate, and solid polyethylene glycol may be difficult to uniformly disperse in cellulose acetate. Therefore, polyethylene glycol is not easy to be treated as a plasticizer for cellulose acetate.

Patent document 4 describes that the acetylation degree of a cellulose acetate resin composition containing a citrate compound and a cellulose acetate resin are 40.03 to 62.55%, that is, the substitution degree is 1.5 to 3.0, but such a cellulose acetate resin composition is poor in hydrolyzability.

Although the addition of a conventional plasticizer can improve the thermoformability of cellulose acetate, the biodegradability and thermoformability of the obtained cellulose acetate composition are not achieved at the same time. The invention provides a cellulose acetate composition having excellent biodegradability and hydrolyzability and excellent thermoformability.

Means for solving the problems

A first aspect of the present invention relates to a cellulose acetate composition containing a cellulose acetate having an acetyl substitution degree of 0.4 or more and less than 1.4 and a citrate-based plasticizer, wherein the content of the citrate-based plasticizer is 3 parts by weight or more relative to 100 parts by weight of the total amount of the cellulose acetate and the citrate-based plasticizer.

In the cellulose acetate composition, the citrate-based plasticizer may be at least one selected from the group consisting of triethyl citrate and acetyl triethyl citrate.

In the cellulose acetate composition, the degree of substitution of the acetyl group of the cellulose acetate may be 0.4 to 1.1.

Among the cellulose acetate compositions, the cellulose acetate composition can be used for thermoforming.

The second aspect of the present invention relates to a molded article obtained by molding the above cellulose acetate composition.

The molded article may be a film.

The molded article may have a hollow cylindrical shape.

The molded article may be a member for a roll cigarette of an electronic cigarette.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, a cellulose acetate composition having excellent biodegradability and hydrolyzability and excellent thermoformability can be provided.

Drawings

FIG. 1 is a graph showing the measurement results of the biodegradability (% by weight).

Detailed Description

[ cellulose acetate composition ]

The cellulose acetate composition of the present disclosure contains cellulose acetate having an acetyl degree of substitution of 0.4 or more and less than 1.4, and a citrate plasticizer, and the content of the citrate plasticizer is 3 parts by weight or more relative to 100 parts by weight of the total amount of the cellulose acetate and the citrate plasticizer.

[ cellulose acetate ]

(degree of substitution with acetyl group)

The cellulose acetate contained in the cellulose acetate composition of the present disclosure has an acetyl substitution degree of 0.4 or more and less than 1.4, and the acetyl substitution degree is preferably 0.4 or more and 1.1 or less, and more preferably 0.7 or more and 1.0 or less. When the degree of substitution with an acetyl group is within this range, the cellulose acetate composition of the present disclosure has biodegradability superior to cellulose, and is also excellent in hydrolyzability and thermoformability.

Here, the excellent thermoformability means specifically: for example, the molten state of the melt (melt) can be adjusted to a range suitable for thermoforming, that is, the viscosity at the time of melting can be made to be in a range suitable for thermoforming.

In the present disclosure, thermoforming means to give a predetermined shape by cooling while exerting plasticity deformable by heating, and examples of a method of thermoforming include heating compression molding, melt extrusion molding, injection molding, and the like.

On the other hand, when the degree of substitution with an acetyl group is less than 0.4, the resulting cellulose acetate composition is inferior in biodegradability, water decomposability, and thermoformability. When the degree of substitution with acetyl groups is 1.4 or more, the biodegradability tends to be poor.

The degree of substitution of acetyl groups by cellulose acetate can be determined by the following known titration method: the degree of substitution of cellulose acetate was determined by dissolving cellulose acetate in an appropriate solvent in accordance with the degree of substitution. The degree of substitution with an acetyl group can also be measured by converting a hydroxyl group of cellulose acetate into a completely derivatized Cellulose Acetate Propionate (CAP) according to the method of Otsuka (Tezuka, Carboydr. Res.273,83(1995)), dissolving the cellulose acetate in deuterated chloroform, and then measuring the resultant by NMR.

Further, the degree of substitution of acetyl groups is according to ASTM by utilizing the following formula pair: the acetylation degree obtained by the measurement method of acetylation degree in D-817-91 (test method of cellulose acetate or the like) was calculated in terms of the acetylation degree. This is the most common way to determine the degree of substitution of cellulose acetate.

DS＝162.14×AV×0.01/(60.052-42.037×AV×0.01)

And (2) DS: degree of substitution by acetyl group

AV: degree of acetylation (%)

First, 500mg of dried cellulose acetate (sample) was precisely weighed, dissolved in 50ml of a mixed solvent of ultrapure water and acetone (volume ratio: 4: 1), and then 50ml of a 0.2N-sodium hydroxide aqueous solution was added thereto to carry out saponification at 25 ℃ for 2 hours. Then, 50ml of 0.2N-hydrochloric acid was added, and the amount of acetic acid released was titrated with a 0.2N-aqueous sodium hydroxide solution (0.2N-sodium hydroxide equivalent solution) using phenolphthalein as an indicator. In addition, a blank test (test without using a sample) was performed by the same method. Then, AV (degree of acetylation) (%) was calculated according to the following formula.

AV (%) ═ a-B × F × 1.201/sample weight (g)

A: 0.2 titration amount (ml) of N-NaOH equivalent solution

B: titration amount (ml) of 0.2N-NaOH equivalent solution in blank test

F: factor of 0.2N-NaOH equivalent solution

In the present disclosure, the substitution degree of acetyl groups may be a total substitution degree of acetyl groups, that is, a sum of average substitution degrees of acetyl groups at the 2,3, and 6 positions of the glucose ring of cellulose acetate.

(composition distribution index (CDI))

The cellulose acetate composition of the present disclosure preferably contains cellulose acetate having a Composition Distribution Index (CDI) of 3.0 or less (e.g., 1.0 to 3.0). The Composition Distribution Index (CDI) is preferably smaller in the order of 2.8 or less, 2.0 or less, 1.8 or less, 1.6 or less, and further 1.3 or less. The lower limit is not particularly limited, and may be 1.0 or more.

The lower limit of the Composition Distribution Index (CDI) is 0 in calculation, but this is achieved by using a special synthesis technique such as acetylating only the 6-position of a glucose residue with 100% selectivity without acetylating the other positions, and such a synthesis technique is not known. In the case where all of the hydroxyl groups of the glucose residue were acetylated and deacetylated with the same probability, the CDI was 1.0, but in the actual reaction of cellulose, a considerable amount of measures were required to approach such an ideal state. The control of such composition distribution has not been paid much attention to the prior art.

The cellulose acetate composition of the present disclosure becomes more excellent in thermoformability by making the Composition Distribution Index (CDI) of cellulose acetate small and the composition distribution (intermolecular substitution degree distribution) uniform.

Here, the Composition Distribution Index (CDI) is defined by a ratio of an actual value of the half width of the composition Distribution to a theoretical value [ (the actual value of the half width of the composition Distribution)/(the theoretical value of the half width of the composition Distribution) ]. The half width of the composition distribution is also referred to as "half width of the intermolecular substitution degree distribution" or simply as "half width of the substitution degree distribution".

In order to evaluate the uniformity of the degree of substitution with acetyl groups of cellulose acetate, the size of the half-value width (also referred to as "half-peak width") of the maximum peak of the intermolecular substitution degree distribution curve of cellulose acetate was used as an index. The half-value width is a width of a graph when the substitution degree of acetyl group is taken as a horizontal axis (x axis) and the amount of the acetyl group present at the substitution degree is taken as a vertical axis (y axis), and when the height of the peak is half the height in the graph (chart), and is an index showing a standard of the fluctuation of the distribution. The half width of the composition distribution (half width of the degree of substitution distribution) can be determined by High Performance Liquid Chromatography (HPLC) analysis. A method of converting the horizontal axis (elution time) of the elution curve of cellulose ester in HPLC into the degree of substitution (0 to 3) is described in Japanese patent application laid-open No. 2003-201301 (paragraphs 0037 to 0040).

(theoretical value of half-value Width of composition distribution)

The half width of the composition distribution (half width of the degree of substitution distribution) can be calculated as a theoretical value in the probability theory. That is, the theoretical value of the half width of the composition distribution is obtained by the following formula (1).

[ mathematical formula 1]

m: total number of hydroxyl groups and acetyl groups in cellulose acetate 1 molecule

p: probability that hydroxyl group in cellulose acetate 1 molecule is substituted with acetyl group

q＝1-p

DPw: weight-average degree of polymerization (value obtained by GPC-light scattering method using cellulose acetate propionate obtained by propionylating all the remaining hydroxyl groups of cellulose acetate)

Further, the theoretical value of the half width of the composition distribution expressed by the degree of substitution and the degree of polymerization is as follows. The following formula (2) is defined as a theoretical value for determining the half width of the composition distribution.

[ mathematical formula 2]

And (2) DS: degree of substitution by acetyl group

DPw: weight-average degree of polymerization (value obtained by GPC-light scattering method using cellulose acetate propionate obtained by propionylating all the remaining hydroxyl groups of cellulose acetate)

In addition, in the case where the formula (1) and the formula (2) are more strictly taken into consideration the distribution of polymerization degree, the "DPw" of the formula (1) and the formula (2) should be replaced with a distribution function of polymerization degree and the whole formula should be integrated from the polymerization degree of 0 to infinity. However, if DPw is used, the equations (1) and (2) approximately give theoretical values with sufficient accuracy. When DPn (number average degree of polymerization) is used, the effect of the distribution of the degree of polymerization cannot be ignored, and therefore DPw should be used.

(actual measurement value of half width of composition distribution)

In the present disclosure, the actual measurement value of the half width of the composition distribution is the half width of the composition distribution obtained by HPLC analysis of cellulose acetate propionate obtained by propionylating all the remaining hydroxyl groups (unsubstituted hydroxyl groups) of cellulose acetate (sample).

In general, a cellulose acetate having an acetyl substitution degree of 2 to 3 can be analyzed by High Performance Liquid Chromatography (HPLC) without pretreatment, and the half width of the composition distribution can be determined. For example, Japanese patent application laid-open No. 2011-158664 discloses a composition distribution analysis method for cellulose acetate having a degree of substitution of 2.27 to 2.56.

On the other hand, the actual measurement value of the half width of the composition distribution (the half width of the degree of substitution distribution) is obtained as follows: the cellulose acetate was obtained by performing a pretreatment of derivatization of a residual hydroxyl group in the molecule before HPLC analysis and then performing HPLC analysis. The purpose of this pretreatment is to convert cellulose acetate having a low degree of substitution into a derivative that is easily soluble in an organic solvent, thereby enabling HPLC analysis. That is, the residual hydroxyl groups in the molecule were completely propionylated, and the completely derivatized Cellulose Acetate Propionate (CAP) was analyzed by HPLC to determine the half width of the composition distribution (measured value). Here, the derivatization must be complete, and only acetyl and propionyl groups are present, with no hydroxyl groups remaining in the molecule. That is, the sum of the degree of substitution of acetyl (DSac) and the degree of substitution of propionyl (DSpr) was 3. This is because, in order to prepare a calibration curve for converting the horizontal axis (elution time) of the HPLC elution curve of CAP into the degree of substitution with acetyl groups (0 to 3), the following relational expression is used: DSac + DSpr ═ 3.

The complete derivatization of cellulose acetate can be carried out by reacting propionic anhydride with N, N-dimethylaminopyridine as a catalyst in a pyridine/N, N-dimethylacetamide mixed solvent. More specifically, the propionylation is carried out using 20 parts by weight of a solvent mixture [ pyridine/N, N-dimethylacetamide (1/1 (v/v) ] as a solvent, 6.0 to 7.5 equivalents of propionic anhydride as a propionylation agent with respect to hydroxyl groups of the cellulose acetate, and 6.5 to 8.0 mol% of N, N-dimethylaminopyridine as a catalyst with respect to hydroxyl groups of the cellulose acetate, at a temperature of 100 ℃ for a reaction time of 1.5 to 3.0 hours, with respect to the cellulose acetate (sample). Then, after the reaction, methanol was used as a precipitation solvent to precipitate it, thereby obtaining a completely derivatized cellulose acetate propionate. More specifically, for example, a completely derivatized Cellulose Acetate Propionate (CAP) can be obtained by precipitating the reaction mixture by adding 1 part by weight of the reaction mixture to 10 parts by weight of methanol at room temperature, washing the obtained precipitate with methanol 5 times, and vacuum-drying at 60 ℃ for 3 hours. The weight-average degree of polymerization (DPw) was also measured by preparing a completely derivatized Cellulose Acetate Propionate (CAP) from a cellulose acetate (sample) by this method.

In the HPLC analysis, a plurality of cellulose acetate propionate having different acetyl substitution degrees are used as standard samples, HPLC analysis is performed under predetermined measurement apparatuses and measurement conditions, and a calibration curve [ a curve showing a relationship between an elution time of the cellulose acetate propionate and an acetyl substitution degree (0 to 3), usually a cubic curve ] is prepared using analysis values of the standard samples, and a half-value width (actual measurement value) of a composition distribution of the cellulose acetate (sample) is determined from the calibration curve. The relationship between the dissolution time and the acetyl group substitution degree distribution of cellulose acetate propionate was determined by HPLC analysis. This is a relationship between the elution time of a substance obtained by converting all the remaining hydroxyl groups in the sample molecule into propionyloxy groups and the acetyl substitution degree distribution, and therefore, the acetyl substitution degree distribution of the cellulose acetate obtained in the present disclosure is not substantially changed.

The conditions for the HPLC analysis are as follows.

The device comprises the following steps: agilent 1100 series

Column: waters Nova-Pak phenyl4 μm (150 mm. times.3.9 mm. phi.) + protective column

Column temperature: 30 deg.C

And (3) detection: varian 380-LC

Injection amount: 5.0. mu.L (sample concentration: 0.1% (wt/vol))

Eluent: solution A: MeOH/H₂O-8/1 (v/v), liquid B: CHCl₃/MeOH＝8/1(v/v)

Gradient: A/B80/20 → 0/100(28 min); flow rate: 0.7mL/min

In the substitution degree distribution curve [ the substitution degree distribution curve of cellulose acetate propionate having the presence amount of cellulose acetate propionate as the vertical axis and the substitution degree of acetyl group as the horizontal axis ] (also referred to as "intermolecular substitution degree distribution curve") obtained from the calibration curve, the half-value width of the substitution degree distribution was obtained as follows with respect to the maximum peak (E) corresponding to the average substitution degree. A base line (A-B) in contact with the base (A) on the low substitution degree side and the base (B) on the high substitution degree side of the peak (E) is drawn, and a perpendicular line is drawn from the maximum peak (E) to the lateral axis with respect to the base line. An intersection (C) of the perpendicular line and the base line (A-B) is determined, and a midpoint (D) between the maximum peak (E) and the intersection (C) is determined. A straight line parallel to the base line (A-B) is drawn through the intermediate point (D), and two intersections (A ', B') with the intermolecular substitution degree distribution curve are obtained. The width between the two intersection points on the horizontal axis is defined as the half width of the maximum peak (i.e., the half width of the degree-of-substitution distribution).

Such a half-value width of the substitution degree distribution reflects that the retention time (retention time) differs depending on how much the hydroxyl group of the glucose ring on one of the constituent polymer chains of the cellulose acetate propionate in the molecular chain of the sample is acetylated. Therefore, it is desirable that the width of the retention time represents the width of the composition distribution (in units of degree of substitution). However, HPLC has tube sections (protection columns for protecting columns, etc.) that do not contribute to distribution. Therefore, depending on the configuration of the measurement device, the width of the holding time, which is not caused by the width of the composition distribution, is often included as an error. This error depends on the length and inner diameter of the column, the length from the column to the detector, and the processing, and varies depending on the apparatus configuration. Therefore, the half width of the substitution degree distribution of cellulose acetate propionate can be generally determined as a correction value Z based on a correction formula shown below. When such a correction formula is used, even if the measurement devices (and measurement conditions) are different, the substitution degree distribution half-value width (actual measurement value) can be obtained more accurately as the same (substantially the same) value.

Z＝(X²-Y²)^1/2

In the formula, X is a half-value width (uncorrected value) of a substitution degree distribution obtained by a predetermined measurement device and measurement conditions. Y ═ a-b) x/3+ b (0. ltoreq. x.ltoreq.3). Here, a represents the apparent half-value width of the substitution degree distribution of cellulose acetate having a substitution degree of 3 (actually, since the substitution degree is 3, there is no substitution degree distribution) determined by the same measuring apparatus and measuring conditions as those of X, and b represents the apparent half-value width of the substitution degree distribution of cellulose propionate having a substitution degree of 3 determined by the same measuring apparatus and measuring conditions as those of X. x is the acetyl substitution degree (x is more than or equal to 0 and less than or equal to 3) of the test sample

The cellulose acetate (or cellulose propionate) having a degree of substitution of 3 is a cellulose ester in which all of the hydroxyl groups of the cellulose are esterified, and is actually (ideally) a cellulose ester having no half width of the degree of substitution distribution (that is, a half width of the degree of substitution distribution of 0).

The theoretical formula of the substitution degree distribution described above is a calculation value in probability theory assuming that all of the acetylation and deacetylation proceed independently and equally. I.e. a calculated value based on a binomial distribution. Such an ideal situation does not exist in reality. Unless a special measure is taken to bring the hydrolysis reaction of cellulose acetate close to an ideal random reaction and/or to classify the composition in terms of post-treatment after the reaction, the substitution degree distribution of cellulose ester is considerably broader than the substitution degree distribution determined by the binomial distribution in probability theory.

As one of the special measures for the reaction, for example, it is conceivable to maintain the system under the conditions of equilibrium between deacetylation and acetylation. However, this is not preferable because the cellulose is decomposed by the acid catalyst. As a special countermeasure for the other reaction, a reaction condition is adopted in which the deacetylation rate of the low substitution substance is lowered. However, such a specific method has not been known. That is, no particular countermeasure for controlling the substitution degree distribution of cellulose ester so as to follow a reaction of a binomial distribution as in the reaction probability theory is known. Further, in various cases such as unevenness in the acetylation step (step of acetylating cellulose) and generation of partial or temporary precipitates due to water added in stages in the ripening step (step of hydrolyzing cellulose acetate), the degree of substitution distribution is developed in a wider direction than the two-term distribution, and it is practically impossible to avoid all of them and achieve ideal conditions. This is analogous to the situation where an ideal gas is ultimately the ideal product, and the actual gas behaves more or less differently.

In the synthesis and post-treatment of conventional cellulose acetate having a low degree of substitution, such a substitution degree distribution is not concerned at all, and the substitution degree distribution is not measured, verified, and examined. For example, according to the literature (journal of the society of fiber, 42, p25(1986)), it is stated that the solubility of cellulose acetate having a low degree of substitution is determined by the distribution of the acetyl groups in the 2,3,6 positions of the glucose residues, and the composition distribution is not considered at all.

According to the present disclosure, as described later, the distribution of the degree of substitution of cellulose acetate can be controlled unexpectedly by a countermeasure of post-treatment conditions after the hydrolysis process of cellulose acetate. According to the literature (CiBment, l., and Rivibre, c., bull.soc.stem., (5)1,1075(1934), Sookne, a.m., Rutherford, h.a., Mark, h., and Harris, m.j.research natl.bur.standards,29,123(1942), a.j.rosenthal, b.b.white ind.eng.chem.,1952,44(11), pp 2693 @ 96.), among precipitation classifications of cellulose acetate having a degree of substitution of 2.3, molecular weight-dependent classification and trace classification accompanied by the degree of substitution (chemical composition) are caused, without a report that significant classification can be achieved by the degree of substitution (chemical composition) as in the present disclosure. Furthermore, it has not been verified that the cellulose acetate having a low degree of substitution as in the present disclosure can control the degree of substitution distribution (chemical composition) by dissolution sorting and precipitation sorting.

Another countermeasure found by the inventors of the present application to narrow the substitution degree distribution is a hydrolysis reaction (ripening reaction) of cellulose acetate at a high temperature of 90 ℃ or higher (or more than 90 ℃). Conventionally, although the polymerization degree of a product obtained by a high-temperature reaction has not been analyzed and examined in detail, it is considered that cellulose is preferentially decomposed in a high-temperature reaction at 90 ℃ or higher. The idea can be said to be a guess based only on viscosity-related investigations (stereotype). The inventors of the present application have found that when cellulose acetate is hydrolyzed to obtain cellulose acetate having a low substitution degree, if the cellulose acetate is reacted in a large amount of acetic acid at a high temperature of 90 ℃ or higher (or at a temperature exceeding 90 ℃), preferably in the presence of a strong acid such as sulfuric acid, a decrease in the degree of polymerization is not observed, while a decrease in viscosity is accompanied by a decrease in CDI. That is, it has been found that the viscosity reduction accompanying the high-temperature reaction occurs not by the reduction of the polymerization degree but by the reduction of the structural viscosity by narrowing the distribution of the substitution degree. When hydrolysis of cellulose acetate is performed under the above conditions, not only a forward reaction but also a reverse reaction occurs, and therefore the CDI of the product (cellulose acetate having a low degree of substitution) has an extremely small value, and when the cellulose acetate composition of the present disclosure is constituted, the molten state is stable (in other words, the viscosity at the time of melting can be made within a range suitable for thermoforming), and particularly excellent thermoformability can be achieved. In contrast, when hydrolysis of cellulose acetate is performed under conditions that do not easily cause a reverse reaction, the substitution degree distribution is broadened by various factors, and in the case of the cellulose acetate composition constituting the present disclosure, it is difficult to stabilize the molten state, and good thermoformability may not be obtained.

(weight-average degree of polymerization (DPw))

The weight-average degree of polymerization (DPw) is a value obtained by GPC-light scattering using cellulose acetate propionate obtained by propionylating all the remaining hydroxyl groups of cellulose acetate (sample).

The cellulose acetate of the present disclosure preferably has a weight average degree of polymerization (DPw) in the range of 100 to 1000. When the weight-average polymerization degree (DPw) is too low, the thermoformability tends to be poor. If the weight-average degree of polymerization (DPw) is too high, biodegradability tends to be poor. The weight-average degree of polymerization (DPw) is preferably 100 to 800, more preferably 200 to 700.

The weight-average degree of polymerization (DPw) can be determined as follows: the measurement value was determined by subjecting a cellulose acetate (sample) to size exclusion chromatography after preparing a completely derivatized Cellulose Acetate Propionate (CAP) by the same method as in the case of determining the half-value width of the above-mentioned composition distribution (GPC-light scattering method).

As described above, the degree of polymerization (molecular weight) of cellulose acetate is measured by GPC-light scattering (GPC-MALLS, GPC-LALLS, etc.). Since solubility of cellulose acetate in a solvent varies depending on the degree of substitution, when the degree of polymerization of a wide range of degrees of substitution is measured, it is sometimes necessary to perform measurement and comparison in different solvent systems, and one of effective methods for avoiding this problem is to perform GPC-light scattering measurement in the same organic solvent by derivatizing cellulose acetate, dissolving the same organic solvent in the same solvent, and then measuring the same. As the derivatization of cellulose acetate for this purpose, propionylation is effective, and specific reaction conditions and post-treatment are as described in the description of the actual measurement value of the half height width of the above-mentioned composition distribution.

(molecular weight distribution Mw/Mn)

The cellulose acetate of the present disclosure has a molecular weight distribution (molecular weight distribution Mw/Mn obtained by dividing the weight average molecular weight Mw by the number average molecular weight Mn) of preferably 3.0 or less and 1.8 or more, more preferably 2.5 or less and 1.9 or more, and further preferably 2.4 or less and 2.0 or more. When the amount exceeds 3.0 or less than 1.8, the molding stability (for example, the dimensional stability, strength and other physical properties of the molded article, more specifically, the stability is not liable to cause unnecessary irregularities on the surface of the molded article, voids are not liable to occur in the interior of the molded article, the variation in the mechanical strength of the entire molded article is small, and the molded article is not liable to deform in a short time immediately after molding) is poor. By setting the molecular weight distribution of cellulose acetate to 3.0 or less and 1.8 or more, good thermoformability can be achieved.

The number average molecular weight (Mn), weight average molecular weight (Mw), and molecular weight distribution (Mw/Mn) of cellulose acetate can be determined by a known method using HPLC. In the present disclosure, the molecular weight distribution (Mw/Mn) of cellulose acetate is determined as follows: in order to make the measurement sample soluble in an organic solvent, the determination was carried out by preparing a completely derivatized Cellulose Acetate Propionate (CAP) from a cellulose acetate (sample) and then subjecting the resultant to size exclusion chromatography under the following conditions in the same manner as in the case of obtaining the above-mentioned actual measurement value of the half width of the composition distribution (GPC-light scattering method).

The device comprises the following steps: GPC "SYSTEM-21H" manufactured by Shodex "

Solvent: acetone (II)

Column: GMHxl (Tosoh) 2 identical guard columns

Flow rate: 0.8ml/min

Temperature: 29 deg.C

Sample concentration: 0.25% (wt/vol)

Injection amount: 100 μ l

And (3) detection: MALLS (Multi-angle light scatter detector) (manufactured by Wyatt, "DAWN-EOS")

MALLS calibration standard: PMMA (molecular weight 27600)

The molecular weight distribution can be calculated from the weight average molecular weight and the number average molecular weight obtained by the measurement results according to the following formula.

Molecular weight distribution Mw/Mn

Mw: weight average molecular weight, Mn: number average molecular weight

[ citric acid ester-based plasticizer ]

The citrate plasticizer contained in the cellulose acetate composition of the present disclosure is not particularly limited as long as it is an ester compound of citric acid.

The citrate plasticizer is added to the cellulose acetate of the present disclosure, and thus the glass transition temperature of the obtained cellulose acetate composition can be efficiently lowered, and therefore, the composition can be easily melted by heating, and excellent thermoformability can be imparted to the cellulose acetate.

The cellulose acetate composition of the present disclosure contains 3 parts by weight or more of a citrate plasticizer per 100 parts by weight of the total amount of the cellulose acetate and the citrate plasticizer. The upper limit is not particularly limited, but is preferably 5 parts by weight or more and 40 parts by weight or less, more preferably 10 parts by weight or more and 35 parts by weight or less, still more preferably 15 parts by weight or more and 30 parts by weight or less, and most preferably 20 parts by weight or more and 30 parts by weight or less. When the amount is less than 3 parts by weight, sufficient thermoformability may not be imparted to the cellulose acetate. When the amount exceeds 40 parts by weight, the possibility of the citric acid ester plasticizer bleeding out becomes high.

The citrate plasticizer is obtained by condensing citric acid with alcohol. Such an alcohol may be a 1-membered alcohol or a 2-or more-membered alcohol.

The citrate-based plasticizer may be at least one selected from the group consisting of triethyl citrate, acetyl triethyl citrate, tributyl citrate, acetyl tributyl citrate, and acetyl 2-ethylhexyl citrate. Among these, at least one selected from the group consisting of triethyl citrate and acetyl triethyl citrate is preferable.

At least one citrate-based plasticizer selected from the group consisting of triethyl citrate and acetyl triethyl citrate is also excellent in solubility in water, and therefore contributes to excellent hydrolyzability of the cellulose acetate composition of the present disclosure. As the other citrate-based plasticizer, a citrate-based plasticizer can be suitably used as the citrate-based plasticizer of the present disclosure as long as it is water-soluble.

Further, at least one citrate-based plasticizer selected from the group consisting of triethyl citrate and acetyl triethyl citrate is not easily exuded from the cellulose acetate composition, is liquid at room temperature, and is easily uniformly dispersed in cellulose acetate, and therefore, is easily handled as a plasticizer.

In addition, when the cellulose acetate composition of the present disclosure is heated, at least one citrate-based plasticizer selected from the group consisting of triethyl citrate and acetyl triethyl citrate is relatively easily retained in the composition, and the composition is excellent in stability of physical properties and also excellent in workability.

At least one citrate-based plasticizer selected from the group consisting of triethyl citrate and acetyl triethyl citrate is a component that is considered safe even when ingested by humans, and is easily biodegradable, and therefore has a small load on the environment. In addition, the cellulose acetate composition obtained by adding a citrate plasticizer to the cellulose acetate of the present disclosure has improved biodegradability as compared with the case of a cellulose acetate monomer.

As described above, at least one citrate-based plasticizer selected from the group consisting of triethyl citrate and acetyl triethyl citrate is safe even when ingested by humans, and can impart excellent thermoformability to cellulose acetate, and therefore can be used as a material for a drug delivery capsule used in a so-called drug delivery system. Further, by adding at least one citrate-based plasticizer selected from the group consisting of triethyl citrate and acetyl triethyl citrate to cellulose acetate, the smoke flavor of the cigarette is not impaired even when the obtained cellulose acetate composition is used as a member of a cigarette.

The cellulose acetate composition of the present disclosure has excellent thermoformability and is therefore suitable for thermoforming.

[ production of cellulose acetate composition ]

The cellulose acetate compositions of the present disclosure may be made by: a citric acid ester-based plasticizer is added to cellulose acetate having an acetyl substitution degree of 0.4 or more and less than 1.4.

The cellulose acetate can be produced, for example, by (a) a hydrolysis step (ripening step) of cellulose acetate having a high degree of substitution, and (B) a precipitation step, and if necessary, (C) a washing and neutralization step.

(A hydrolysis step (aging step))

In this step, cellulose acetate having a high degree of substitution (hereinafter, sometimes referred to as "raw material cellulose acetate") is hydrolyzed. The degree of substitution of the acetyl group in the cellulose acetate having a high degree of substitution as a raw material is, for example, 1.5 to 3, preferably 2 to 3.

The hydrolysis reaction can be carried out by reacting the starting material cellulose acetate with water in an organic solvent in the presence of a catalyst (ripening catalyst). Examples of the organic solvent include acetic acid, acetone, an alcohol (e.g., methanol), and a mixed solvent thereof. As the catalyst, a catalyst generally used as a deacetylation catalyst can be used. As the catalyst, sulfuric acid is particularly preferable.

The amount of the organic solvent (e.g., acetic acid) used is, for example, 0.5 to 50 parts by weight based on 1 part by weight of the raw material cellulose acetate.

The amount of the catalyst (e.g., sulfuric acid) used is, for example, 0.005 to 1 part by weight based on 1 part by weight of the raw material cellulose acetate.

The amount of water in the hydrolysis step is, for example, 0.5 to 20 parts by weight based on 1 part by weight of the raw material cellulose acetate. The amount of water is, for example, 0.1 to 5 parts by weight relative to 1 part by weight of the organic solvent (e.g., acetic acid).

The reaction temperature in the hydrolysis step is, for example, 40 to 130 ℃.

(B) precipitation step)

In this step, after the completion of the hydrolysis reaction, the temperature of the reaction system is cooled to room temperature, and a precipitation solvent is added to precipitate cellulose acetate having a low substitution degree. As the precipitation solvent, an organic solvent miscible with water or an organic solvent having a high solubility in water can be used. For example, ketones such as acetone and methyl ethyl ketone; and alcohols such as methanol, ethanol, and isopropanol.

When a mixed solvent containing two or more solvents is used as the precipitation solvent, the same effect as that of precipitation separation described later can be obtained, and cellulose acetate having a narrow composition distribution (intermolecular substitution degree distribution), a small Composition Distribution Index (CDI), and a low substitution degree can be obtained.

Further, by further subjecting the cellulose acetate having a low degree of substitution obtained by precipitation to precipitation sorting (sorting precipitation) and/or dissolution sorting (sorting dissolution), it is possible to obtain a cellulose acetate having a narrow composition distribution (intermolecular substitution degree distribution) and a very small degree of substitution with a very small composition distribution index CDI.

The precipitation sorting may be performed, for example, as follows: the cellulose acetate (solid substance) having a low degree of substitution obtained by the precipitation is dissolved in water or a mixed solvent of water and a hydrophilic solvent (e.g., acetone) to prepare an aqueous solution having an appropriate concentration (e.g., 2 to 10% by weight, preferably 3 to 8% by weight), a poor solvent is added to the aqueous solution (or the aqueous solution is added to the poor solvent), the temperature is maintained at an appropriate temperature (e.g., 30 ℃ or lower, preferably 20 ℃ or lower), the cellulose acetate having a low degree of substitution is precipitated, and the precipitate is recovered.

(C) washing and neutralizing step)

The precipitate (solid substance) obtained in the precipitation step (B) is preferably washed with an organic solvent (poor solvent) such as an alcohol (e.g., methanol) or a ketone (e.g., acetone). It is also preferable to wash and neutralize with an organic solvent containing a basic substance (for example, an alcohol such as methanol, or a ketone such as acetone). Impurities such as a catalyst (e.g., sulfuric acid) used in the hydrolysis step can be efficiently removed by washing and neutralization.

Examples of the basic substance include alkali metal compounds (for example, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide), alkaline earth metal compounds (for example, alkaline earth metal carboxylates such as calcium acetate), and the like.

(addition of citrate plasticizer)

When a citrate-based plasticizer is added to the obtained cellulose acetate, the cellulose acetate and the citrate-based plasticizer are preferably mixed, and the mixing may be performed by a mixer such as a planetary mill, a henschel mixer, a vibration mill, or a ball mill. The henschel mixer is preferably used because homogeneous mixing dispersion can be performed in a short time. The degree of mixing is not particularly limited, and for example, in the case of a henschel mixer, it is preferably 10 minutes to 1 hour.

After mixing cellulose acetate with the citrate plasticizer, drying may be performed. As a drying method, for example, a method of drying by leaving at 50 to 105 ℃ for 1 to 48 hours is exemplified.

In addition, as a method of adding a citrate-based plasticizer to the obtained cellulose acetate, the following method may be used: cellulose acetate and a glyceride plasticizer are dissolved in a common good solvent, and after uniformly mixing, the solvent is volatilized. Examples of the common good solvent include water and a mixed solvent of dichloromethane and methanol (in a weight ratio of 9: 1).

When mixing cellulose acetate and a citrate plasticizer, a colorant, a heat stabilizer, an antioxidant, an ultraviolet absorber, and the like may be added depending on the use and specification of the molded article.

[ molded article ]

The molded article of the present disclosure is obtained by molding the cellulose acetate composition. The shape of the molded article is not particularly limited, and examples thereof include a one-dimensional molded article such as a fiber; two-dimensional molded articles such as films; and three-dimensional molded articles such as pellets, tubes, and hollow cylinders.

When a one-dimensional molded article such as a fiber is produced, the cellulose acetate composition of the present disclosure can be spun to obtain the fiber, and a spinning method thereof includes melt spinning (including a melt-blown spinning method).

For example, a fibrous cellulose acetate composite molded article can be obtained by heating and melting the above-mentioned cellulose acetate composition (pellets or the like) in a known melt extrusion spinning machine, spinning the composition from a spinneret, and drawing and winding the spun continuous long-fiber filament group with a high-speed and high-pressure air by an ejector, or by spreading and collecting the filament group on a support surface for collection to form a web. Further, the above-mentioned cellulose acetate composition melted by an extruder may be blown in a filament shape in a high-temperature and high-speed air flow from, for example, a die having several hundreds to several thousands of spinnerets per 1m width direction, and a resin obtained by stretching the fiber shape may be gathered on a conveyor belt, and entanglement and fusion of the fibers may be caused therebetween, thereby producing a nonwoven fabric (melt-blown spinning method). The spinning temperature in the melt spinning is, for example, 130 to 240 ℃, preferably 140 to 200 ℃, and more preferably 150 to 188 ℃. If the spinning temperature is too high, the molded article is significantly colored. If the spinning temperature is too low, the viscosity of the composition becomes low, and it becomes difficult to increase the spinning draft ratio, and productivity tends to decrease. The spinning draft ratio is, for example, about 200 to 600.

The fineness of the yarn obtained by the melt spinning method is, for example, 20 to 800 deniers (d), and preferably 40 to 800 deniers (d).

In particular, when the cellulose acetate tow filter is used as a cellulose acetate tow filter of a roll cigarette used in an electronic cigarette, the fineness may be 20 to 600 deniers (d). This is because, unlike conventional roll cigarettes, electronic cigarettes do not burn and therefore do not require removal of by-products generated by burning, and the cellulose acetate tow filter of a roll cigarette used in an electronic cigarette can have a filtering performance (performance) much lower than that of a filter used in a conventional roll cigarette. When the hollow cellulose acetate tube of the roll cigarette used in the electronic cigarette is manufactured from a tow, the manufacturing process including molding into a hollow shape takes time, and this also leads to an increase in manufacturing cost. In addition, there is also a method of increasing the denier of tow fibers (making the fibers thicker) in order to achieve low filterability of a filter, but there is a technical limit in the thickness in the production of thick denier tow fibers by conventional dry spinning. That is, if the thickness is too large, the solvent in the central portion does not evaporate, and the shape of the yarn is unstable. Since it is difficult to achieve a demand for a filter having a lower filterability for an electronic cigarette in the future, a thick tow or a three-dimensional molded body formed as described later can be used for melt spinning.

Next, when a two-dimensional molded article such as a film is produced, a melt film-forming method can be used. Examples of the melt film-forming method include extrusion molding and blow molding. Specifically, for extrusion molding, for example, the cellulose acetate composition of the present disclosure may be melt-kneaded by an extruder such as a single-screw extruder or a twin-screw extruder, extruded in a film form from a slit of a die, and cooled to produce a film or a sheet.

The thickness of the film obtained by the melt film-forming method is, for example, 1 to 1000. mu.m, preferably 5 to 500. mu.m, and more preferably 10 to 250. mu.m. In particular, when used as a cooling element for a roll cigarette used in an electronic cigarette, the film may have a thickness of 15 to 200 μm, 20 to 150 μm, 25 to 100 μm, or 35 to 70 μm. Since the amount of nicotine scattered by heating tobacco leaves is very small as compared with conventional paper-wrapped cigarettes, it is necessary to deliver (distribute) the nicotine to smokers (people who smoke electronic cigarettes) without loss as much as possible. In addition, in the type of heating tobacco leaves, nicotine is contained in droplets in aerosol, but the droplets are at a high temperature at the time of smoking, and therefore, cooling is required in advance. To satisfy these requirements, the thickness of the film may be in the above range.

Further, when a three-dimensional molded article such as a hollow cylindrical article is produced, it can be produced by thermoforming. Specifically, for example, the granular cellulose acetate composition of the present disclosure can be formed into a desired three-dimensional molded body including a hollow cylindrical shape by heating compression molding, melt extrusion molding, and injection molding. As the equipment, for example, MEIHO CO., LTD injection molding machine Micro-1, and heating compression molding machine ML-48 for molding FRP test pieces manufactured by Tando, can be used. The heating temperature during molding may be set to 240 to 180 ℃, and the amount of the additive containing a citrate plasticizer may be appropriately adjusted.

The method for forming the cellulose acetate composition of the present disclosure into a pellet form is not particularly limited, and examples thereof include the following methods: first, cellulose acetate and a citrate-based plasticizer of the present disclosure are premixed in a dry or wet manner using a mixer such as a drum mixer, a henschel mixer, a ribbon mixer, or a kneader, and then melt-kneaded by an extruder such as a single-screw extruder or a twin-screw extruder, extruded in a strand form, and then cut to prepare pellets.

The specific method for forming a three-dimensional molded article by melt extrusion molding from the cellulose acetate composition of the present disclosure in the form of pellets is not particularly limited, and for example, injection molding, extrusion molding, vacuum molding, profile molding, foam molding, injection pressing, pressure molding, blow molding, gas injection molding, and the like can be used.

In addition to the method of preparing pellets by melt-kneading the cellulose acetate and the citrate plasticizer of the present disclosure with an extruder to obtain a molded article as described above, a molded article having a desired three-dimensional shape including a hollow cylindrical shape can be produced by heating and compression-molding the cellulose acetate having the citrate plasticizer adhered to the surface of the scale.

For the compression molding, a commercially available compression molding machine is used, and the processing is performed at a temperature of 150 to 240 ℃, preferably 230 ℃, and a pressure of 0.01MPa or more, preferably 0.5MPa for 30 seconds or more (preferably about 2 minutes). The scale of cellulose ester refers to a sheet-like cellulose ester obtained by acetylating cellulose, hydrolyzing the cellulose to adjust the average degree of substitution, and purifying and drying the cellulose ester.

The hollow cylindrical three-dimensional molded article may be used as it is as a hollow cellulose acetate tube of a roll cigarette used in an electronic cigarette, or may be a long member before cutting to obtain a hollow cellulose acetate tube of a roll cigarette used in an electronic cigarette by cutting the tube perpendicularly to the axial direction.

Examples

The present invention will be specifically described below with reference to examples, but the technical scope of the present invention is not limited to these examples.

The physical properties described in the examples and comparative examples described below were evaluated by the following methods.

< degree of acetyl substitution, weight average molecular weight (Mw), number average molecular weight (Mn), and composition distribution index CDI >

The degree of substitution with acetyl groups, the weight average molecular weight (Mw), the number average molecular weight (Mn), and the composition distribution index CDI were determined by the methods described above.

< evaluation of thermoformability >

The thermoformability was evaluated by the following method. In each of the examples and comparative examples, except for comparative example 3, pure water was dissolved in an amount of 5 parts by weight based on 1 part by weight of each sample, and a film having a thickness of about 120 μm was formed by a solution casting method (solution casting) using a glass substrate. In comparative example 3, a mixed solvent of acetone and water (weight ratio 9: 1) was used as the solvent in place of pure water, and the solvent was dissolved in a ratio of 5 parts by weight to 1 part by weight of the sample, and a film was produced by a solution casting method in the same manner as described above. Samples having a size of 0.3cm × 1cm were cut from each of the films prepared, and used as samples for evaluation.

Heating and pressurization were carried out under the following conditions using a small hot press HC300-01 (manufactured by AS ONE).

Heating to a set temperature: 150 ℃; 175 ℃; 200 ℃; 225 deg.C

Pressurizing pressure: 14.14Mpa

Heating and pressurizing time: 2min

After heating and pressurization, the melt state of the sample was confirmed, and thereby the thermoformability was evaluated according to the following criteria. When the sample melted, it was shown to be rendered plastic.

1: the test pieces were not melted at all and were not fused (in other words, the fused portion was 0%).

2: a part of the molten material was fused, and the overlapping portions of the test pieces were partially fused (in other words, the fused portion was about 30%).

3: more than half of the melt, and the overlapping portions of the test pieces were fused to more than half.

< evaluation of biodegradability >

Biodegradability was evaluated by a method of measuring biodegradability using activated sludge specified in JIS K6950. Activated sludge was obtained from the doragawa purification center in foggang county. The activated sludge was left to stand for about 1 hour, and about 300mL of the obtained supernatant (activated sludge concentration: about 360ppm) was used per 1 flask. The time when 30mg of the sample was stirred in the supernatant was defined as the start of the measurement, and the total of 31 measurements were performed every 24 hours until 720 hours later, that is, 30 days later. The details of the measurement are as follows. Biochemical Oxygen Demand (BOD) in each culture flask was measured using a coulometer OM3001 manufactured by large-chamber electric corporation. The percentage of Biochemical Oxygen Demand (BOD) relative to the theoretical Biochemical Oxygen Demand (BOD) upon complete decomposition based on the chemical composition of each sample was taken as the degree of biodegradation (wt%). Among them, the biodegradability was evaluated using measurement data up to 240 hours later.

< evaluation of hydrolysis >

The hydrolyzability was evaluated by the following method. From each film prepared for the evaluation of thermoformability, a sample having a size of 2cm × 2cm was cut out as a sample for evaluation of hydrolyzability.

A film sample was placed in a 100 ml-sized bottle containing 80ml of pure water, and the rotation was started at 14rpm using a rotary machine to confirm the change in shape and weight of the film sample with time. The shape was observed by naked eye. For the weight, the film sample was taken out from pure water, water droplets were wiped off, and after drying in a 105 ℃ dryer for 1 hour, the weight was measured by an analytical precision electronic balance, and the amount of weight change (%) from the weight of the film sample at the start of rotation was evaluated. The evaluation criteria shown in table 1 are as follows.

X: after 1 hour from the start of the rotation, neither breakage nor deformation was observed on the film sample, and the amount of change in weight of the film sample was reduced by less than 10%.

And (delta): 1 hour after the start of the self-rotation, the film sample had a weight change of less than 10% reduction but was broken or deformed; alternatively, the film sample was neither damaged nor deformed, but the amount of change in weight of the film sample was reduced by 10% or more.

O: the film sample was completely dissolved within 1 hour from the start of the spin.

< production example 1>

5.1 parts by weight of acetic acid and 2.0 parts by weight of water were added to 1 part by weight of a raw material cellulose acetate (trade name "L-50" manufactured by Daiiluo Co., Ltd., total degree of substitution of acetyl groups: 2.43, 6% viscosity: 110 mPas), and the mixture was stirred for 3 hours to dissolve the cellulose acetate. To this solution, 0.13 part by weight of sulfuric acid was added, and the resulting solution was maintained at 100 ℃ to conduct hydrolysis. To prevent the cellulose acetate from precipitating during hydrolysis, the addition of water to the system was carried out in 2 portions. That is, 0.67 parts by weight of water was added to the system over 5 minutes after 0.25 hours from the start of the reaction. After 0.5 hour, 1.33 parts by weight of water was added to the system over 10 minutes, and the reaction was further carried out for 1.25 hours. The total hydrolysis time was 2 hours. The time from the start of the reaction to the 1 st addition of water is referred to as the 1 st hydrolysis step (1 st ripening step), the time from the 1 st addition of water to the 2 nd addition of water is referred to as the 2 nd hydrolysis step (2 nd ripening step), and the time from the 2 nd addition of water to the end of the reaction is referred to as the 3 rd hydrolysis step (3 rd ripening step).

After the hydrolysis was performed, the temperature of the system was cooled to room temperature (about 25 ℃), and 15 parts by weight of a precipitation solvent (methanol) was added to the reaction mixture to form a precipitate.

The precipitate was recovered as a wet cake having a solid content of 15% by weight, 8 parts by weight of methanol was added, and deliquoring was performed until the solid content was 15% by weight, whereby washing was performed. This operation was repeated 3 times. The washed precipitate was further washed 2 times with 8 parts by weight of methanol containing 0.004% by weight of potassium acetate, neutralized and dried to obtain cellulose acetate having a degree of substitution with acetyl groups of 0.87. With respect to the obtained cellulose acetate, the degree of substitution with acetyl group, weight average molecular weight (Mw), number average molecular weight (Mn), and Composition Distribution Index (CDI) were measured. The results are shown in Table 1.

< example 1>

95 parts by weight of cellulose acetate having an acetyl substitution degree of 0.87 obtained in production example 1 and 5 parts by weight of triethyl citrate as a citrate plasticizer were dissolved in 500 parts by weight of pure water as a solvent and uniformly mixed. Then, the solvent was evaporated by changing the conditions in the order of 3min at room temperature, 30min in a 45 ℃ dryer and 30min in a 150 ℃ dryer to obtain a cellulose acetate composition.

The obtained cellulose acetate composition was evaluated for thermoformability, biodegradability and hydrolyzability by the methods described above. The results are shown in Table 1.

< examples 2 to 4>

A cellulose acetate composition was obtained in the same manner as in example 1 except that the cellulose acetate having an acetyl group substitution degree of 0.87 obtained in production example 1 and triethyl citrate were changed to the amounts shown in table 1, respectively.

The obtained cellulose acetate composition was evaluated for thermoformability, biodegradability and hydrolyzability by the methods described above. The results are shown in table 1, table 2 and fig. 1.

< comparative example 1>

A cellulose acetate composition was obtained in the same manner as in example 1 except that the cellulose acetate having an acetyl group substitution degree of 0.87 obtained in production example 1 and triethyl citrate were changed to the amounts shown in table 1.

The obtained cellulose acetate composition was evaluated for thermoformability, biodegradability and hydrolyzability by the methods described above. The results are shown in Table 1.

< comparative example 2>

100 parts by weight of the cellulose acetate having an acetyl substitution degree of 0.87 obtained in production example 1 was dissolved in 100 parts by weight of pure water as a solvent, and uniformly mixed. The solvent was evaporated by changing the conditions in the order of 3min at room temperature, 30min in a 45 ℃ dryer and 30min in a 150 ℃ dryer.

The obtained product was evaluated for thermoformability, biodegradability and hydrolyzability by the methods described above. The results are shown in table 1, table 2 and fig. 1.

< production example 2>

5.1 parts by weight of acetic acid and 2.0 parts by weight of water were added to 1 part by weight of a raw material cellulose acetate (trade name "L-50" manufactured by Daiiluo Co., Ltd., total degree of substitution of acetyl groups: 2.43, 6% viscosity: 110 mPas), and the mixture was stirred for 3 hours to dissolve the cellulose acetate. To this solution, 0.13 part by weight of sulfuric acid was added, and the resulting solution was maintained at 95 ℃ to conduct hydrolysis. To prevent the cellulose acetate from precipitating during hydrolysis, the addition of water to the system was carried out in 2 portions. That is, 0.67 parts by weight of water was added to the system over 5 minutes after 0.3 hour of the initiation of the reaction. After 0.7 hour, 1.33 parts by weight of water was added to the system over 10 minutes, and the reaction was further carried out for 1.5 hours. The total hydrolysis time was 2.5 hours. The time from the start of the reaction to the 1 st addition of water is referred to as the 1 st hydrolysis step (1 st ripening step), the time from the 1 st addition of water to the 2 nd addition of water is referred to as the 2 nd hydrolysis step (2 nd ripening step), and the time from the 2 nd addition of water to the end of the reaction is referred to as the 3 rd hydrolysis step (3 rd ripening step).

After the hydrolysis was performed, the temperature of the system was cooled to room temperature (about 25 ℃), and 15 parts by weight of a precipitation solvent (methanol) was added to the reaction mixture to form a precipitate.

The precipitate was recovered as a wet cake having a solid content of 15% by weight, 8 parts by weight of methanol was added, and deliquoring was performed until the solid content was 15% by weight, whereby washing was performed. This operation was repeated 3 times. The washed precipitate was further washed 2 times with 8 parts by weight of methanol containing 0.004% by weight of potassium acetate, neutralized and dried to obtain cellulose acetate having a degree of substitution with acetyl groups of 1.7. With respect to the obtained cellulose acetate, the degree of substitution with acetyl group, weight average molecular weight (Mw), number average molecular weight (Mn), and Composition Distribution Index (CDI) were measured. The results are shown in Table 1.

< comparative example 3>

100 parts by weight of the cellulose acetate having an acetyl substitution degree of 1.7 obtained in production example 2 was dissolved in 500 parts by weight of a mixed solvent of dichloromethane/methanol (weight ratio 9: 1), and uniformly mixed. The solvent was evaporated by changing the conditions in the order of 3min at room temperature, 30min in a 45 ℃ dryer and 30min in a 150 ℃ dryer.

The obtained product was evaluated for thermoformability, biodegradability and hydrolyzability by the methods described above. The results are shown in table 1, table 2 and fig. 1.

< reference example 1>

100 parts by weight of cellulose acetate having an acetyl substitution degree of 2.1 was dissolved in 500 parts by weight of a mixed solvent of dichloromethane/methanol (weight ratio 9: 1), and uniformly mixed. The solvent was evaporated by changing the conditions in the order of 3min at room temperature, 30min in a 45 ℃ dryer and 30min in a 150 ℃ dryer.

The resultant was evaluated for biodegradability by the above-described method. The results are shown in FIG. 1.

< reference example 2>

Biodegradability was evaluated in the same manner as in reference example 1, except that cellulose acetate having an acetyl substitution degree of 2.9 was used instead of cellulose acetate having an acetyl substitution degree of 2.1. The results are shown in FIG. 1.

[ Table 1]

[ Table 2]

As shown in table 1, in comparative examples 1 and 2, cellulose acetate having an acetyl substitution degree of 0.4 or more and less than 1.4 was used, and therefore, the biodegradability was excellent, but the content of triethyl citrate was small or the cellulose acetate did not contain triethyl citrate, and therefore, the cellulose acetate was not melted at all even by heating and pressing, and the thermoforming was not performed.

In comparative example 3, since cellulose acetate having an acetyl substitution degree of 1.4 or more was used and no citrate-based plasticizer was contained, the cellulose acetate was not melted at all even by heating and pressing, and thus, thermoforming was not possible. In addition, the hydrolyzability is also poor.

On the other hand, it is understood that the cellulose acetate compositions of examples 1 to 4 have not only excellent biodegradability but also excellent thermoformability and hydrolysis ability, since the cellulose acetate having an acetyl group substitution degree of 0.4 or more and less than 1.4 is used and a proper amount of triethyl citrate is contained.