JP4073524B2 - Cellulose mixed ester solution and preparation method thereof - Google Patents

Description

【００６０】
表１で明らかなように、ゲル化特性を有するセルロース混合エステル溶液の剥離性は優れている。またアセチル基とプロピオニル基の置換基比率、綿濃度、溶媒組成を適度に調節することにより、ゲル化特性を最適化することができる。
【００６１】
【発明の効果】
以上のように本発明によれば、セルロースアセテートプロピオネートにおけるアセチル基の置換度とプロピオニル基の置換度が下記式（ I ）、（ II ）及び（ III ）の範囲内としたセルロースアセテートプロピオネートを用いることにより、優れた物性を有するセルロースエステルフィルムをソルベントキャスト法で製造できることが判明した。本発明の溶解方法により、様々な種類の有機溶媒を用いてセルロースエステル溶液を調製できるという効果を有する。本発明では、セルローストリアセテートフィルムと同程度又はそれ以上の物性を有するセルロースエステル成形物を様々な種類の有機溶媒を用いてソルベントキャスト法で製造することができる。
（ I ） 2.45＜ＤＳａｃｅ≦2.95
（ II ） 0.05≦ＤＳｐｒｏ＜0.55
（ III ）2.70＜ＤＳａｃｅ＋ＤＳｐｒｏ≦3.00
【図面の簡単な説明】
【図１】動的粘弾性の温度依存性からゲル化温度を求める方法を示す図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cellulose mixed ester solution and a method for preparing the same. The present invention relates to a cellulose mixed ester solution having gelling properties particularly at low temperatures and a method for preparing the same.
[0002]
[Prior art]
Cellulose acetate films are used in various photographic materials and optical materials because of their toughness and flame retardancy. The cellulose acetate film is a support for typical photographic light-sensitive materials, and is also used in liquid crystal display devices whose market is expanding in recent years due to its optical isotropy. As a specific application in a liquid crystal display device, a protective film for a polarizing plate and a color filter are typical. By the way, the cellulose acetate film is generally produced by a solvent cast method or a melt cast method. In the solvent cast method, a solution (dope) in which cellulose acetate is dissolved in a solvent is cast on a support, and the solvent is evaporated to form a film. In the melt casting method, cellulose acetate melted by heating is cast on a support and cooled to form a film. The solvent cast method can produce a film having higher planarity than the melt cast method. For this reason, the solvent cast method is generally employed for practical use.
[0003]
By the way, the solvent cast method is described in many documents. In recent years, in the solvent casting method, it is a problem to improve the productivity in the film forming process by shortening the time required from casting the dope on the support to peeling the molded film on the support. It has become. For example, Japanese Patent Publication No. 5-17844 proposes shortening the time from casting to stripping by casting a high-concentration dope on a cooling drum. It has not been improved. By the way, the solvent used in the solvent casting method is not only for dissolving cellulose acetate but also for various conditions. For example, in order to produce a film having excellent flatness and a uniform thickness economically and efficiently, it is necessary to prepare a solution (dope) having an appropriate viscosity and polymer concentration and excellent in storage stability. In order to prepare such a dope, the selection of the type of solvent is extremely important. Further, the solvent is required to be easily evaporated and to have a small residual amount in the film.
[0004]
Conventionally, various organic solvents have been proposed as a solvent for cellulose acetate, but a solvent that satisfies all the above requirements has been substantially limited to methylene chloride. In other words, solvents other than methylene chloride are hardly practically used. However, in recent years, the use of halogenated hydrocarbons such as methylene chloride has been significantly restricted from the viewpoint of protecting the global environment. Moreover, since methylene chloride has a low boiling point (41 ° C.), it is easily volatilized in the production process. This is also a problem in the work environment. On the other hand, general-purpose organic solvents such as acetone (boiling point: 56 ° C) and methyl acetate (boiling point: 57 ° C) have an appropriate boiling point and do not have a large drying load. There are few problems compared to organic solvents. However, acetone and methyl acetate have low solubility in cellulose acetate. Especially, cellulose triacetate with a substitution degree of 2.80 (acetylation degree: 60.1%) or more swells in acetone or methyl acetate at room temperature and hardly dissolves. .
[0005]
By the way, CJMalm et al. Paper (Ind.Eng.Chem., 43, 688, 1951) shows that cellulose propionate and cellulose butyrate have a wider range of solvent choices than cellulose acetate. Is described. That is, cellulose propionate and cellulose butyrate also dissolve in ketones and esters that cannot dissolve cellulose acetate. However, films produced from cellulose propionate or cellulose butyrate are inferior in mechanical strength and durability to cellulose acetate films. On the other hand, mixed fatty acid esters of cellulose such as cellulose acetate propionate or cellulose acetate butyrate are commercially available. For example, the Eastman Chemical catalog (1994) describes a large number of mixed fatty acid esters of cellulose. Many of them are soluble in common organic solvents such as acetone and methyl acetate. However, films produced from these mixed fatty acid esters of cellulose also have insufficient mechanical strength and durability. Actually, these commercial products are not sold as films but as raw materials for paints.
[0006]
Japanese National Publication No. Hei 6-501040 proposes using a melt cast method in place of the solvent cast method having the above-mentioned problems. However, the melt casting method has a problem in that the melting point of cellulose acetate is higher than the decomposition temperature. That is, cellulose triacetate having a high substitution degree of acetyl group is decomposed before being melted when heated. In order to solve this problem, in the invention described in the publication, the substitution degree of the acetyl group in the cellulose acetate is adjusted to 1.9 to 2.6. The publication also discloses cellulose acetate propionate, which defines the substitution degree of the propionyl group as 0 to 0.9. Specifically, Example B of the same publication describes cellulose acetate propionate having a substitution degree of acetyl group of 1.90 and a substitution degree of propionyl group of 0.71. In addition, Example C of the publication describes cellulose acetate propionate having an acetyl group substitution degree of 2.10 and a propionyl group substitution degree of 0.50. However, as described above, the solvent cast method can produce a film having higher planarity than the melt cast method. In other words, the film produced by the melt cast method has a problem in flatness. Usually, the planarity of the film can be improved by biaxial stretching, but when the film is stretched, the molecules are oriented and the optical anisotropy of the film is increased. Except for special applications, films used for photographic materials and optical materials are required to have optical isotropy. Therefore, in the production of the current cellulose ester film, the solvent cast method is widely adopted rather than the melt cast method.
[0007]
Further, JP-A-8-231761 uses a mixed fatty acid ester of cellulose having a total substitution degree of 2.6 to 3.0, an acetyl substitution degree of 2.0 to 2.7, and another acyl substitution degree of 0.3 to 0.8 as a means for solving the above problems. Propose that. However, cellulose mixed fatty acid esters chemically modified with other acyl groups have good acyl group motility, so the mechanical properties of the produced film, especially the elastic modulus, are low, and the toughness of the cellulose triacetate film is lost and high. It was still insufficient for use as a protective film or a photographic photosensitive material support requiring mechanical strength. In addition, it was considered that the acetyl substitution degree in the mixed fatty acid ester of cellulose was further increased and the substitution degree of other acyl groups was lowered to bring the physical properties closer to cellulose triacetate. Like cellulose triacetate, it can no longer be dissolved in a general-purpose organic solvent at room temperature, and it becomes impossible to produce a cellulose ester film by the solvent cast method.
[0008]
[Problems to be solved by the invention]
The present inventor further researched a method for producing a cellulose ester film by a solvent cast method. By the way, it is already known that the problem of the small number of organic solvents capable of dissolving cellulose acetate, particularly cellulose triacetate, can be solved by using other fatty acid esters of cellulose or mixed fatty acid esters of cellulose instead of cellulose acetate. (Described in the above-mentioned paper by CJMalm et al., Catalog of Eastman Chemical Co., or JP-A-8-231761). However, the cellulose ester film produced by the solvent cast method using these cellulose esters has remarkably inferior physical properties than the cellulose triacetate film.
[0009]
Then, the objective of this invention is providing the adjustment method of the cellulose mixed ester solution using various kinds of organic solvents which can obtain the cellulose-ester film which has the outstanding physical property.
[0010]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventors have selected cellulose acetate propionate as the cellulose mixed ester, and the total substitution degree of acetyl group and propionyl group of cellulose acetate propionate is 2.70. To 3.00, preferably 2.75 to 3.00, and further by increasing the degree of substitution of acetyl groups to 2.45 or more, preferably 2.70 or more, the gel is formed at an appropriate temperature in the film forming process even though it is a mixed ester. It has been found that the film forming characteristics can be improved. In addition, it has been found that the gelation characteristics of cellulose mixed ester solution can be optimized by appropriately adjusting the ratio of acetyl and propionyl groups in cellulose acetate propionate, the cotton concentration, and the solvent composition of non-halogen organic solvents. The present invention has been completed.
[0011]
That is, the present invention is a cellulose in which the hydroxyl group of cellulose is substituted with an acetyl group and a propionyl group, and the substitution degree of the acetyl group (DSace) and the substitution degree of the propionyl group (DSpro) satisfy the following formulas (I) to (III). By dissolving acetate propionate in an organic solvent, a cellulose mixed ester solution that gels in the process of cooling to 40 ° C. or lower and −40 ° C. is provided.
(I) 2.45 <DSace ≦ 2.95
(II) 0.05 ≦ DSpro <0.55
(III) 2.70 <DSace + DSpro ≦ 3.00
Further, cellulose acetate propionate satisfying the above formulas (I) to (III) is dispersed in an organic solvent and cooled to −110 ° C. to 20 ° C., and the cooled mixture is heated to 0 ° C. to 120 ° C. Thus, a method for preparing a cellulose mixed ester solution comprising a step of dissolving cellulose acetate propionate in a solvent is provided.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The cellulose mixed ester solution of the present invention is a solution obtained by substituting the hydroxyl group of cellulose with an acetyl group and a propionyl group and dissolving in an organic solvent, and gels in the process of cooling to 40 ° C. or lower and −40 ° C. It is. The gelation temperature of the cellulose mixed ester solution is to lower the cotton concentration by lowering the total substitution degree to cellulose, to the lower temperature side by lowering the degree of polymerization, to the lower temperature side by lowering the degree of acetyl substitution, and to lower the cotton concentration. To shift to the low temperature side. When the solvent for dissolving cellulose acetate propionate is a mixed solvent, the gelation temperature is shifted to the low temperature side by lowering the poor solvent ratio. By changing the above parameters, the gelation temperature can be optimized according to the process.
[0013]
The average substitution degree of the cellulose acetate propionate used in the present invention is particularly preferably 2.75 to 3.00. When the substitution degree of the acetyl group is 2.45 or less, the gelation temperature of the solution becomes too low, and when it is higher than 2.95, the gelation temperature of the solution becomes high. On the other hand, when the substitution degree of propionyl group is 0.05 or less, the gelation temperature of the solution becomes high, and when it exceeds 0.55, the gelation temperature of the solution becomes low. In any case, gelation does not occur in the process of cooling to 40 ° C. or lower and −40 ° C. Furthermore, if the average degree of substitution of the total of acetyl groups and propionyl groups is 2.70 or less, the gelation temperature will be low and gelation will not occur by -40 ° C.
[0014]
Although the gel of the cellulose mixed ester solution of the present invention is not clear about the mechanism of the gel formation, it is presumed that the cellulose crystal microcrystals are formed as crosslinking points of the three-dimensional network, and contain a solvent. Even in the state, it exhibits properties as a solid. In the film casting method or the like, the film can be peeled off from the drum after casting and drying. Therefore, in this state, for example, when a film is produced, the film is formed while the three-dimensional network structure of the cellulose ester is maintained. For example, the orientation of the cellulose ester molecular chain is suppressed, and the anisotropy of the film physical properties is eliminated. It is considered that mechanical characteristics and optical characteristics can be obtained.
[0015]
The mixed fatty acid ester of cellulose of the present invention can be synthesized using an acid anhydride or acid chloride as an acylating agent. When the acylating agent is an acid anhydride, an organic acid (for example, acetic acid) or methylene chloride is used as a reaction solvent. As the catalyst, an acidic catalyst such as sulfuric acid is used. When the acylating agent is an acid chloride, a basic compound is used as a catalyst. In the industrially most common synthesis method, cellulose is mixed with an organic acid component containing an organic acid (acetic acid, propionic acid) corresponding to acetyl group and propionyl group or an acid anhydride thereof (acetic anhydride, propionic anhydride). The cellulose ester is synthesized by esterification.
[0016]
The amount of the acetylating agent and propionylating agent used is adjusted so that the ester to be synthesized falls within the range of the substitution degree described above. The amount of the reaction solvent used is preferably 100 to 1000 parts by weight, more preferably 200 to 600 parts by weight with respect to 100 parts by weight of cellulose. The amount of the acidic catalyst used is preferably 0.1 to 20 parts by weight and more preferably 0.4 to 10 parts by weight with respect to 100 parts by weight of cellulose.
[0017]
The reaction temperature is preferably 10 ° C to 120 ° C, more preferably 20 ° C to 80 ° C. In addition, after completion | finish of acylation reaction, you may adjust a substitution degree by hydrolyzing (saponification) as needed.
[0018]
After completion of the reaction, the reaction mixture (cellulose ester dope) is separated using conventional means such as precipitation, washed and dried to obtain a mixed fatty acid ester of cellulose (cellulose acetate propionate).
[0019]
In the present invention, an organic solvent is used for preparing the cellulose mixed ester solution. This organic solvent is preferably substantially free of halogenated hydrocarbons such as methylene chloride. Here, “substantially free” means that the proportion of halogenated hydrocarbon in the organic solvent is less than 5% by weight, preferably less than 2% by weight.
[0020]
Preferred organic solvents are selected from ethers having 3 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, and esters having 3 to 12 carbon atoms.
[0021]
The ether, ketone and ester may have a cyclic structure. A compound having two or more functional groups of ether, ketone and ester (that is, —O—, —CO— and —COO—) can also be used as the organic solvent. The organic solvent may have another functional group such as an alcoholic hydroxyl group. In the case of an organic solvent having two or more types of functional groups, the number of carbon atoms may be within the specified range of the compound having any functional group.
[0022]
Examples of the ether having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole and phenetole.
[0023]
Examples of ketones having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclohexanone and methylcyclohexanone.
[0024]
Examples of the esters having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate and pentyl acetate.
[0025]
Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol, and 2-butoxyethanol.
[0026]
In addition to ethers, ketones and esters, other organic solvents may be used in combination. Examples of organic solvents that can be used in combination include nitromethane and alcohols having 1 to 6 carbon atoms (for example, methanol, ethanol, propanol, isopropanol, 1-butanol, t-butanol, 2-methyl-2-butanol, cyclohexanol). Is included.
[0027]
When ether, ketone and ester are used in combination with another organic solvent, the ratio of ether, ketone and ester in the mixed solvent is preferably 10 to 99.5% by weight, more preferably 20 to 99% by weight. 40 to 98.5% by weight is more preferable, and 60 to 98% by weight is most preferable.
[0028]
Further, in the present invention, a mixed solvent of a lower fatty acid ester and a lower alcohol is particularly preferable because a solution in which cellulose acetate propionate is dissolved gelates at a low temperature. In addition, the fact that the lower fatty acid ester is methyl acetate and the lower alcohol is ethanol enables gelation and peeling when forming a film from a solution. The molded film is more preferable because it has high mechanical properties and optical properties.
[0029]
In the present invention, the mixed solvent of methyl acetate and ethanol preferably contains 10 to 40% by weight of ethanol. When the ethanol content is out of the range of 10 to 40% by weight, it is difficult to optimize the gelation temperature.
[0030]
In the present invention, cellulose acetate propionate is dissolved in an organic solvent by a cooling dissolution method to form a solution (dope).
[0031]
In the dope formation, cellulose acetate propionate is first gradually added to an organic solvent with stirring at room temperature. At this stage, cellulose acetate propionate swells in the organic solvent but is not dissolved. The amount of cellulose acetate propionate is adjusted to be 10-40% by weight in the mixture. More preferably, it is 10 to 30% by weight. Arbitrary additives described later may be added to the organic solvent.
[0032]
Next, the mixture is cooled to 20 ° C. or lower and within a range of −110 ° C. During the cooling process, the solvent penetrates into the undissolved white turbid component to form bubbles and the mixture becomes colorless and transparent.
[0033]
Furthermore, when this is heated to 0 ° C. to 120 ° C., cellulose acetate propionate is dissolved in the organic solvent. The temperature rise may be left alone at room temperature or may be heated in a warm bath. In this way, a dope that is in a uniform solution state is obtained. If the dissolution is insufficient, the cooling and heating operations may be repeated. Whether or not the dissolution is insufficient can be determined by simply observing the appearance of the dope by visual observation.
[0034]
In the cooling and melting method, it is desirable to use a sealed container in order to avoid moisture mixing due to condensation during cooling. In the cooling and heating operation, if the pressure is applied during cooling and the pressure is reduced during heating, the dissolution time can be shortened. In order to perform pressurization and decompression, it is desirable to use a pressure-resistant container.
[0035]
The stability of the obtained dope is an important condition in the molding process. During transfer of the dope, undissolved substances are generated in the pipes, and solidification must occur during the stop period for maintenance of the manufacturing apparatus. The stability over time of the dope is related to the storage temperature and the dope concentration in addition to the properties of the cellulose acetate propionate described above.
[0036]
Moreover, you may add additives, such as a plasticizer, a deterioration inhibitor, and an ultraviolet-ray inhibitor, to the cellulose mixed ester solution of this invention according to the use. In order to improve the mechanical properties or increase the drying speed, it is common to add a plasticizer to the cellulose ester film. Examples of the plasticizer include phosphoric acid esters and carboxylic acid esters. For example, phosphoric acid esters include triphenyl phosphate (TPP) and tricresyl phosphate (TCP). Representative examples of the carboxylic acid ester include phthalic acid ester and citric acid ester. Examples of the phthalic acid ester include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP) and diester. Ethylhexyl phthalate (DEHP) is included, and citrate esters include acetyl triethyl citrate (OACTE) and acetyl tributyl citrate (OACTB). Examples of other carboxylic acid esters include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and various trimellitic acid esters. In the present invention, two or more plasticizers may be used in combination. Further, for example, in order to improve the heat and humidity resistance of the film to be produced, it is preferable to use a phthalate ester plasticizer such as DMP, DEP, DOP, DEHP. Of these, DEP is particularly preferably used.
[0037]
For example, when obtaining a film | membrane from the cellulose mixed ester solution of this invention, it can manufacture by the well-known solvent cast method. Regarding the solvent casting method, U.S. Pat. No. 49-5614, JP-A-60-176834, JP-A-60-203430 and JP-A-62-115035. A general solvent cast method is performed by casting the prepared cellulose ester solution (dope) on a mirror-finished support such as a drum or a band, drying, and then peeling off the film. Further, as a particularly preferred solvent casting method, disclosed in Japanese Patent Publication No. 5-17844, the dope is cast on a support having a surface temperature of 10 ° C. or less, and is exposed to wind for 2 seconds or more. There is a method in which the residual solvent is evaporated by drying with high-temperature air whose temperature is successively changed from 100 ° C to 160 ° C. According to this method, since the time from casting to stripping can be shortened, it is possible to downsize the casting equipment or increase the film forming speed to improve productivity. Therefore, this method is suitable for producing a membrane from the cellulose mixed ester solution of the present invention.
[0038]
Further, cellulose ester fibers may be produced from the cellulose mixed ester solution of the present invention. The cellulose ester fiber can be produced by spinning from a conventional method, for example, a cellulose mixed ester solution (dope) and removing the solvent. The removal of the solvent can be carried out under the same drying conditions as in the above film production. The fineness of the cellulose ester fiber is preferably 1 to 16 denier, more preferably 1 to 10 denier, and most preferably 2 to 8 denier. There is no restriction | limiting in particular about the cross-sectional shape of a cellulose-ester fiber. Examples of the cross-sectional shape include a circular shape, an oval shape, an irregular shape (for example, a Y shape, an X shape, an I shape, an R shape) and a hollow shape.
[0039]
【Example】
Hereinafter, the present invention will be described with reference to examples and comparative examples, but the present invention is not limited to these examples.
[0040]
The dynamic viscoelasticity of the solutions of Examples and Comparative Examples was measured as follows, and the gelation characteristics were evaluated.
Dynamic viscoelasticity
It measured using the automatic dynamic viscoelasticity measuring apparatus (Solid meter MR-500: manufactured by Rheology). A double cylinder was used as the sample attachment. After pouring the solution into the outer cylinder and inserting the inner cylinder, the outer cylinder is vibrated and cooled (cooling rate: about 1 ° C./min). The temperature dependence of the dynamic viscoelasticity of the sample solution (temperature dispersion: about − Up to 40 ° C.). The outer cylinder diameter was 2.306 cm, the inner cylinder diameter was 1.998 cm, the vibration angle was 0.5 degrees, and the vibration frequency was 0.1 Hz.
In the temperature dependence curve of the dynamic viscosity (η ′) obtained as described above, the temperature at which η ′ suddenly increases with gelation is obtained by extrapolation as shown in FIG. .
[0041]
The substitution degree of cellulose ester was measured as follows. 1.9 g of the dried cellulose ester was precisely weighed, 70 ml of acetone and 30 ml of dimethyl sulfoxide were added and dissolved, and then 50 ml of acetone was further added. While stirring, 30 ml of 1N sodium hydroxide aqueous solution was added and saponified for 2 hours. After adding 100 ml of hot water and washing the side of the flask, it was titrated with 1N-sulfuric acid using phenolphthalein as an indicator. Separately, a blank test was performed in the same manner as the sample. The supernatant of the solution after titration was diluted 100 times, and the composition of the organic acid was measured by an ordinary method using an ion chromatograph. From the measurement result and the acid composition analysis result by ion chromatography, the substitution degree was calculated by the following formula.
TA = (B−A) × F / (1000 × W)
DSace = (162.14 × TA) /
(1-42.14 x TA + (1-56.06 x TA) x (AL / AC))
DSpro = DSace × (AL / AC)
However, A is the sample titer (ml), B is the blank test titer (ml), F is the titer of 1N-sulfuric acid, W is the sample weight (g), TA is the total organic acid amount (mol / g), AL / AC represents the molar ratio of acetic acid (AC) and propionic acid (AL) measured by ion chromatography, DSace represents the substitution degree of the acetyl group, and DSpro represents the substitution degree of the propionyl group.
[0042]
Furthermore, the number average molecular weight of the cellulose ester was measured using a high performance liquid chromatography system (GPC-LALLS) in which a detector for detecting refractive index and light scattering was connected to a gel filtration column. The measurement conditions are as follows.
Solvent: methylene chloride
Column: GMHXL (manufactured by Tosoh Corporation)
Sample concentration: 0.1W / V%
Flow rate: 1.0ml / min
Sample injection volume: 300 μl
Standard sample: Polymethyl methacrylate (Mw = 218600)
Temperature: 24 ° C.
[0043]
[Example 1]
At room temperature (25 ° C.), 15 parts by weight of cellulose acetate propionate (hereinafter abbreviated as CAP-A) having an acetyl substitution degree of 2.72, a propionyl substitution degree of 0.23, a number average polymerization degree of 436, and a number average molecular weight of 126000 is 85 wt. A slurry having a CAP-A concentration of 15% by weight was prepared. A white undissolved material was observed in this slurry. The slurry was cooled for 1 hour in a methanol bath adjusted to 0 ° C. with dry ice. No white undissolved material was observed in the removed slurry, and many bubbles were generated due to the penetration of the solvent. After standing at room temperature for 10 minutes, the mixture was kept in a hot water bath set at 40 ° C. for 10 minutes. The taken-out mixture flowed sufficiently, no residual residue was observed, and CAP-A was dissolved in acetone. The CAP-A solution thus prepared was allowed to stand at room temperature for 1 week, but was stable with no change in fluidity and appearance.
[0044]
[Comparative Example 1]
At room temperature (25 ° C.), 15 parts by weight of CAP-A was mixed with 85 parts by weight of acetone to prepare a slurry having a concentration of 15% by weight of CAP-A. A white undissolved material was observed in this slurry. This slurry was allowed to stand at room temperature for 1 week, but the appearance of the mixture was not changed, and CAP-A was not sufficiently dissolved.
[0045]
[Example 2]
At room temperature (25 ° C.), 15 parts by weight of CAP-A was mixed with 85 parts by weight of tetrahydrofuran to prepare a slurry having a concentration of 15% by weight of CAP-A. In this slurry, white or cocoon-like undissolved substances were observed. The slurry was cooled in a methanol bath adjusted to -25 ° C with dry ice for 1 hour. The taken-out slurry did not show white or left-handed undissolved matter, and many bubbles were generated due to the permeation of the solvent. After standing at room temperature for 10 minutes, the mixture was kept in a hot water bath set at 40 ° C. for 10 minutes. The taken-out mixture flowed sufficiently, and no undissolved residue was observed. CAP-A was dissolved in tetrahydrofuran. The CAP-A solution thus prepared was allowed to stand at room temperature for 1 week, but was stable with no change in fluidity and appearance.
[0046]
[Comparative Example 2]
At room temperature (25 ° C.), 15 parts by weight of CAP-A was mixed with 85 parts by weight of tetrahydrofuran to prepare a slurry having a concentration of 15% by weight of CAP-A. In this slurry, white or cocoon-like undissolved substances were observed. This slurry was allowed to stand at room temperature for 1 week, but the appearance of the mixture was not changed, and CAP-A was not sufficiently dissolved.
[0047]
[Example 3]
At room temperature (25 ° C.), 20 parts by weight of CAP-A was mixed with 64 parts by weight of methyl acetate and 16 parts by weight of ethanol to prepare a slurry having a CAP-A concentration of 20% by weight. In this slurry, white or cocoon-like undissolved substances were observed. The slurry was cooled in a methanol bath adjusted to -15 ° C with dry ice for 1 hour. The taken-out slurry did not show white or left-handed undissolved matter, and many bubbles were generated due to the permeation of the solvent. After standing at room temperature for 10 minutes, the mixture was kept in a hot water bath set at 40 ° C. for 10 minutes. The taken-out mixture flowed sufficiently and no undissolved residue was observed. CAP-A was dissolved in a mixed solvent of methyl acetate and ethanol. The CAP-A solution thus prepared was allowed to stand at room temperature for 1 week, but was stable with no change in fluidity and appearance.
[0048]
[Comparative Example 3]
At room temperature (25 ° C.), 20 parts by weight of CAP-A was mixed with 64 parts by weight of methyl acetate and 16 parts by weight of ethanol to prepare a slurry having a CAP-A concentration of 20% by weight. In this slurry, white or cocoon-like undissolved substances were observed. The slurry was allowed to stand at room temperature for 1 week, but the appearance of the mixture was not changed and CAP-A was not sufficiently dissolved.
[0049]
Furthermore, the gelation characteristics of the cellulose mixed ester were evaluated by dynamic viscoelasticity as in the following Examples and Comparative Examples.
[0050]
[Example 4]
100 parts by weight of CAP-A was mixed with 400 parts by weight of a mixed solvent consisting of 80% by weight of methyl acetate and 20% by weight of ethanol to prepare a slurry having a cellulose acetate propionate concentration of 20% by weight. And cooled with dry ice / methanol overnight (about −70 ° C.), and then returned to room temperature to prepare a solution. The gelation characteristics of this solution were evaluated by the above dynamic viscoelasticity experiment.
[0051]
[Example 5]
100 parts by weight of CAP-A was mixed with 300 parts by weight of a mixed solvent consisting of 80% by weight of methyl acetate and 20% by weight of ethanol to prepare a slurry having a cellulose acetate propionate concentration of 25% by weight. And cooled with dry ice / methanol overnight (about −70 ° C.), and then returned to room temperature to prepare a solution. The gelation characteristics of this solution were evaluated by the above dynamic viscoelasticity experiment.
[0052]
[Example 6]
100 parts by weight of CAP-A was mixed with 233 parts by weight of a mixed solvent consisting of 80% by weight of methyl acetate and 20% by weight of ethanol to prepare a slurry having a cellulose acetate propionate concentration of 30% by weight. And cooled with dry ice / methanol overnight (about −70 ° C.), and then returned to room temperature to prepare a solution. The gelation characteristics of this solution were evaluated by the above dynamic viscoelasticity experiment.
[0053]
[Example 7]
100 parts by weight of CAP-A was mixed with 300 parts by weight of a mixed solvent consisting of 85% by weight of methyl acetate and 15% by weight of ethanol to prepare a slurry having a cellulose acetate propionate concentration of 25% by weight. And cooled with dry ice / methanol overnight (about −70 ° C.), and then returned to room temperature to prepare a solution. The gelation characteristics of this solution were evaluated by the above dynamic viscoelasticity experiment.
[0054]
[Example 8]
100 parts by weight of CAP-A was mixed with 300 parts by weight of a mixed solvent consisting of 75% by weight of methyl acetate and 25% by weight of ethanol to prepare a slurry having a cellulose acetate propionate concentration of 25% by weight. And cooled with dry ice / methanol overnight (about −70 ° C.), and then returned to room temperature to prepare a solution. The gelation characteristics of this solution were evaluated by the above dynamic viscoelasticity experiment.
[0055]
[Comparative Example 4]
100 parts by weight of cellulose acetate propionate (hereinafter abbreviated as CAP-B) having an acetyl substitution degree of 2.21, propionyl substitution degree of 0.58, a number average polymerization degree of 737 and a number average molecular weight of 212,000, methyl acetate 70% by weight and ethanol 30% by weight A slurry with a cellulose acetate propionate concentration of 30% by weight was prepared by mixing with 233 parts by weight of a mixed solvent consisting of 30% by weight, and allowed to stand at room temperature for a whole day and then cooled with dry ice / methanol for a day and night (about -70 ° C). Then, it returned to normal temperature and prepared the solution. The gelation characteristics of this solution were evaluated by the above dynamic viscoelasticity experiment.
[0056]
[Comparative Example 5]
After mixing 100 parts by weight of CAP-A with 300 parts by weight of acetone to prepare a slurry having a cellulose acetate propionate concentration of 25% by weight, the slurry was allowed to stand overnight at room temperature and cooled with dry ice / methanol overnight (approximately -70 ° C), and the solution was returned to room temperature to prepare a solution. The gelation characteristics of this solution were evaluated by the above dynamic viscoelasticity experiment.
[0057]
[Comparative Example 6]
100 parts by weight of commercially available cellulose mixed ester (registered trade name Celidoa, manufactured by Bayer, acetyl substitution degree 0.32, propionyl substitution degree 2.32, number average polymerization degree 718, number average molecular weight 219000: hereinafter abbreviated as CAP-C), methyl acetate After mixing with 233 parts by weight of a mixed solvent consisting of 70% by weight and 30% by weight of ethanol to prepare a slurry having a cellulose acetate propionate concentration of 30% by weight, the slurry was left overnight at room temperature and then dried with dry ice / methanol overnight. After cooling (about −70 ° C.), the solution was returned to room temperature to prepare a solution. The gelation characteristics of this solution were evaluated by the above dynamic viscoelasticity experiment.
[0058]
Table 1 summarizes the evaluation results of the gelation characteristics of Examples 4 to 8 and Comparative Examples 4 to 6. When the sample is taken out of the double cylinder at the end of the dynamic viscoelasticity measurement experiment (low temperature: about -25 ° C), the gel peelability is evaluated as “good” for those that can be removed while maintaining the shape. For those that collapsed, the gelation peelability was evaluated as “bad”.
[0059]
[Table 1]

[0060]
As is apparent from Table 1, the peelability of the cellulose mixed ester solution having gelling properties is excellent. Further, the gelation characteristics can be optimized by appropriately adjusting the substituent ratio of the acetyl group and the propionyl group, the cotton concentration, and the solvent composition.
[0061]
【The invention's effect】
As described above, according to the present invention, cellulose acetate propionate in which the substitution degree of acetyl group and substitution degree of propionyl group in cellulose acetate propionate is within the range of the following formulas (I), (II) and (III). It has been found that a cellulose ester film having excellent physical properties can be produced by a solvent cast method by using an nate. The dissolution method of the present invention has an effect that a cellulose ester solution can be prepared using various kinds of organic solvents. In the present invention, a cellulose ester molded product having physical properties equivalent to or higher than those of a cellulose triacetate film can be produced by a solvent cast method using various types of organic solvents.
(I) 2.45 <DSace ≦ 2.95
(II) 0.05 ≦ DSpro <0.55
(III) 2.70 <DSace + DSpro ≦ 3.00
[Brief description of the drawings]
FIG. 1 is a diagram showing a method for obtaining a gelation temperature from the temperature dependence of dynamic viscoelasticity.

Claims (6)

Cellulose acetate propio, in which the hydroxyl group of cellulose is substituted with an acetyl group and a propionyl group, and the substitution degree of the acetyl group (DSace) and the substitution degree of the propionyl group (DSpro) satisfy the following formulas (I ′) to (III ′) A solution obtained by dissolving an nate in an organic solvent,
A cellulose mixed ester solution, wherein the organic solvent is a mixed solvent of methyl acetate and ethanol, and gels in the course of cooling to 40 ° C. or lower and −40 ° C.
(I ') 2.70 <DSace ≦ 2.95
(II ') 0.05 ≦ DSpro ≦ 0.30
(III ') 2.75 ≦ DSace + DSpro ≦ 3.00 The cellulose mixed ester solution according to claim 1 , wherein the mixed solvent of methyl acetate and ethanol contains 10 to 40% by weight of ethanol. The cellulose mixed ester solution according to claim 1 or 2 , wherein the cellulose acetate propionate is contained in the organic solvent in an amount of 10 to 40% by weight. Cellulose acetate propionate satisfying the following formulas (I ′) to (III ′) is dispersed in an organic solvent substantially free of halogenated hydrocarbon, and cooled to −110 ° C. to 20 ° C. A method for preparing a cellulose mixed ester solution comprising a step of heating a mixture to 0 ° C. to 120 ° C. and dissolving cellulose acetate propionate in a solvent ,
A method for preparing a cellulose mixed ester solution, wherein the organic solvent is a mixed solvent of methyl acetate and ethanol .
(I ') 2.70 <DSace ≦ 2.95
(II ') 0.05 ≦ DSpro ≦ 0.30
(III ') 2.75 ≦ DSace + DSpro ≦ 3.00 The method for preparing a cellulose mixed ester solution according to claim 4 , wherein the mixed solvent of methyl acetate and ethanol contains 10 to 40% by weight of ethanol. 6. The method for preparing a cellulose mixed ester solution according to claim 4, wherein the cellulose acetate propionate is contained in the organic solvent in an amount of 10 to 40% by weight.

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