JP2006137802A - Cellulose ester solution and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a cellulose ester solution which excels in filtration property and whose gelling property and releasability from a support (releasable support) can be controlled efficiently. <P>SOLUTION: In the method of manufacturing a cellulose ester solution via a first cooling dissolution process (the so-called cooling dissolution method), which comprises a first cooling process of cooling a mixture comprising a cellulose ester and a cooling solvent composed of a good solvent for this cellulose ester (such as methyl acetate) and a first heating process of heating the mixture after this first cooling process, the cellulose ester solution is manufactured further via a poor solvent addition process wherein a poor solvent for the cellulose ester (such as an alcohol) is added after the above first cooling process is completed and a second cooling process wherein the mixture, obtained via the above first cooling dissolution process and the above poor solvent addition process, is cooled. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a cellulose ester (particularly, cellulose acetate) solution containing a poor solvent (for example, C _1-4 alkanols such as ethanol and butanol), a method for producing the same, and a film obtained from the cellulose ester solution.

  Since cellulose esters such as cellulose acetate are excellent in optical isotropy, they are used as a support for photographic photosensitive materials, a polarizing plate protective film for liquid crystal display devices, a retardation film, a color filter, and the like. In general, a cellulose ester film is produced by a solution casting method (solvent cast method) or a melt casting method (melt cast method), but since a good film with high flatness is obtained, practically, Manufactured by a solution casting method.

  In such a solution casting method, a solution (or dope) in which cellulose ester is dissolved in a solvent is cast on a support, and the solvent is evaporated to form a film. Until now, in such cellulose ester solution (especially cellulose triacetate solution), it is difficult to dissolve cellulose ester with a normal organic solvent, and methylene chloride (methylene chloride) has been used as a solvent in terms of excellent solubility. There were many cases. However, halogen-based solvents such as methylene chloride (especially chlorine-based solvents) have a large impact on the human body and the environment and tend to be limited in their use. Therefore, cellulose ester solutions (cellulose acetate) can be used without using methylene chloride. It is desirable to prepare a solution), but cellulose esters have low solubility in conventional non-halogen solvents (such as acetone) and are difficult to dissolve in non-halogen solvents by ordinary methods. For this reason, attempts have been made to obtain a cellulose ester solution. As such a method, a cellulose ester is obtained by cooling a mixed system containing a general-purpose organic solvent such as methyl acetate and acetone and cellulose ester (particularly cellulose triacetate). A method of dissolving (so-called cooling dissolution method) is known.

  On the other hand, such a cellulose ester solution contains a poor solvent for the cellulose ester (for example, alcohols such as ethanol and butanol) in order to control (or improve) the gelation rate and the peelability from the support. Is preferred. That is, when the cellulose ester solution contains a poor solvent, the time from casting the dope on the support to peeling off the molded film on the support can be shortened, and the productivity of the film forming process can be reduced. Can be improved.

  From the above viewpoint, various attempts have been made to prepare a cellulose ester solution containing a poor solvent without using a halogen-based solvent (particularly a chlorine-based solvent) such as methylene chloride. For example, in JP-A-10-45917 (Patent Document 1), cellulose acetate having an average degree of acetylation of 58.0 to 62.5% and a solvent containing 50% by weight or more of methyl acetate are mixed, Cellulose comprising a step of swelling cellulose acetate with a solvent; a step of cooling the swelling mixture to −100 to −10 ° C., and a step of heating the cooled swelling mixture to 0 to 120 ° C. to dissolve the cellulose acetate in the solvent A method for producing an acetate solution is disclosed, wherein cellulose acetate particles are used in the swelling step, and 90% by weight or more of the particles have a particle diameter of 0.1 to 4 mm. . In Examples 2 to 8 of this document, cellulose acetate having a specific particle size and a mixed solvent of methyl acetate and a poor solvent (methanol, ethanol, butanol, cyclohexane, etc.) are mixed and swollen, and at −50 ° C. After cooling, it is described that a transparent and uniform solution was obtained by heating to 50 ° C.

  Japanese Patent Laid-Open No. 10-45950 (Patent Document 2) discloses a mixture of cellulose acetate having an average degree of acetylation of 58.0 to 62.5% and an organic solvent, and the organic solvents are different from each other. It is a mixed solvent of three kinds of solvents, the first solvent is selected from ketones having 4 to 12 carbon atoms and esters having 3 to 12 carbon atoms, and the second solvent is 1 to 5 carbon atoms. A step of cooling to -100 to -10 ° C a mixture selected from linear monohydric alcohols, wherein the third solvent is an alcohol having a boiling point of 30 to 170 ° C and a hydrocarbon having a boiling point of 30 to 170 ° C; In addition, a method for preparing a cellulose acetate solution comprising a step of heating the cooled mixture to 0 to 100 ° C. to dissolve the cellulose acetate solution in an organic solvent is disclosed.

  However, in the methods described in these documents, a good solvent such as methyl acetate and acetone and a poor solvent such as alcohols and hydrocarbons are mixed in advance and dissolved by cooling, so that the filterability of the cellulose acetate solution decreases. To do. When the filterability of the cellulose acetate solution is lowered, there arises a problem that the filter medium needs to be frequently replaced due to the state of filtration pressure, clogging of undissolved substances, and the work efficiency is lowered. Further, in these methods, when cooling with a system containing a poor solvent, the solubility (cooling solubility) is lowered, and a method such as setting the cooling temperature low is required, so that a large amount of energy is consumed.

  JP-A-10-324774 (Patent Document 3) discloses cellulose acetate having an average degree of acetylation of 58.0 to 62.5%, an ester having 3 to 12 carbon atoms, and 3 to 3 carbon atoms. A step of cooling a mixture of 12 ketones and an organic solvent selected from ethers having 3 to 12 carbon atoms to −100 to −10 ° C., and heating the cooled mixture to 0 to 150 ° C. in an organic solvent A method for preparing a cellulose acetate solution comprising a step of dissolving cellulose acetate in an alcohol having a boiling point of 30 to 170 ° C. after the step of cooling the mixture is completed and before, during or after the heating step Alternatively, a method for preparing a cellulose acetate solution in which a hydrocarbon having a boiling point of 30 to 170 ° C. is added to the mixture is disclosed.

  In the method described in this document, since the poor solvent is added after cooling and dissolving, cooling and melting are possible even at a relatively high temperature. However, even with such a method, the filterability of the cellulose acetate solution still decreases.

  In general, a cellulose ester solution (particularly a cellulose acetate solution) obtained by a cooling dissolution method has low stability (dissolution stability), and undissolved matter is generated in the piping during the transfer of the solution, or is left as it is (production device) Coagulation may occur during the suspension period for maintenance management). Therefore, an attempt has been made to obtain a highly stable cellulose ester solution using a special cellulose ester.

  For example, in Japanese Patent Application Laid-Open No. 11-5851 (Patent Document 4), the total degree of acetyl substitution at the 2nd, 3rd and 6th positions is 2.67 or more, and the degree of acetyl substitution at the 2nd and 3rd positions. A specific cellulose acetate having a total of 1.97 or less is disclosed. When such cellulose acetate is used, a stable solution (dope) can be obtained by a cooling dissolution method, and a cellulose acetate film having a low retardation value can be obtained. It is described that it is obtained. Specifically, the total degree of acetyl substitution at the 2nd and 3rd positions is 1.95, the degree of acetyl substitution at the 6th position is 0.92, and the total degree of acetyl substitution at the 2nd, 3rd and 6th positions is 2.86. 17 parts by weight of cellulose acetate, 80.28 parts by weight of a mixed solvent of methyl acetate / methanol / n-butanol (mixing ratio = 80/15/5% by weight) and 2.72 parts by weight of triphenyl phosphate (plasticizer) It is described that the swollen mixture was cooled to −30 ° C. and then warmed to room temperature, and the operation of cooling and warming was repeated once more to obtain a solution.

  Japanese Patent Application Laid-Open No. 2002-212338 (Patent Document 5) discloses that the total acyl substitution degree at the 2-position and the 3-position is 1.70 or more and 1.90 or less, and the acyl substitution degree at the 6-position is 0.8. Cellulose acylate having a viscosity of 88 or more is disclosed, and when such cellulose acylate is used, a cellulose acylate solution having excellent stability over time and low viscosity in a practical dope concentration region can be obtained by a cooling dissolution method or the like. It is described that it can be obtained.

  Further, JP-A-2002-338601 (Patent Document 6) shows that the acetyl substitution degree (2DS, 3DS, 6DS) at positions 2, 3, and 6 is (I) 2DS + 3DS <6DS × 4-1.70. , (II) 2DS + 3DS <−6DS × 4 + 5.70, and (III) cellulose acetate satisfying 2DS + 3DS> 1.80 are disclosed. When such cellulose acetate is used, it is easy to adjust solubility and viscosity. It is described that a simple cellulose acetate solution can be obtained.

However, with the specific cellulose ester described in these documents, even if the stability of the solution cooled and dissolved in a good solvent (or solubility in cooling and dissolution) can be relatively improved, if the poor solvent is contained, the solution still remains. The improvement of solubility and stability is insufficient, and the filterability cannot be improved sufficiently.
Japanese Patent Laid-Open No. 10-45917 (Claims, Examples) JP-A-10-45950 (Claims, Examples) JP-A-10-324774 (Claims) JP-A-11-5851 (Claims, Examples) JP 2002-212338 A (Claims, Examples) JP 2002-338601 A (claims, paragraph number [0012])

  Accordingly, an object of the present invention is to provide a method for producing a cellulose ester solution (particularly, a cellulose acetate solution) having excellent filterability even when a poor solvent is contained.

  Another object of the present invention is a method for producing a cellulose ester solution that is excellent in filterability, and that can efficiently control gelation and releasability from a support (peelable support), and cellulose ester obtained by this method. To provide a solution.

  Still another object of the present invention is to produce a film (for example, an optical film) having excellent film forming properties and stability (dissolution stability) and good film characteristics without using a halogen-based solvent such as methylene chloride. It is providing the manufacturing method of the cellulose-ester solution which can be formed, the cellulose-ester solution obtained by this method, and the film obtained from this cellulose-ester solution.

  As described above, in the method of Patent Document 3 (Japanese Patent Laid-Open No. 10-324774), by adding a poor solvent to the solution after cooling and dissolution, the poor solvent is removed even under relatively mild conditions. The solvent composition can be included. However, in the solution obtained by the method of this literature, cellulose acetate is dissolved by visual observation, and it seems that a stable solution is obtained, but a minute undissolved substance remains, and the filtration coefficient is reduced by filtration. It turned out that practical filtration was impossible.

  Therefore, as a result of intensive studies to achieve the above problems, the present inventors have cooled a mixture composed of a cellulose ester (particularly cellulose acetate) and a solvent containing a good solvent for the cellulose ester, and then added it. In the method of dissolving the cellulose ester by heating (so-called cooling dissolution method), after cooling the mixture at a relatively high good solvent concentration, adding a poor solvent for the cellulose ester and cooling again, Even if it contains a poor solvent, the solubility of cellulose ester can be improved, it has excellent filterability, and it has excellent film-forming properties that can efficiently control the gelation property after casting and the peelability from the support. The present inventors have found that a cellulose ester solution can be obtained and completed the present invention.

  That is, the method for producing a cellulose ester solution of the present invention includes a first cooling step for cooling a mixture containing a cellulose ester and a cooling solvent composed of a good solvent for the cellulose ester, and after the first cooling step. A method for producing a cellulose ester solution through a first cooling and dissolving step comprising a first heating step for heating a mixture of the cellulose ester, after the first cooling step is completed. A poor solvent addition step of adding a poor solvent, and a second cooling step of cooling the mixture obtained through the first cooling dissolution step and the poor solvent addition step.

  The cellulose ester may be cellulose acetate (for example, cellulose triacetate). The cellulose ester has a total of the average substitution degree at the 2-position and the 3-position of the glucose unit of 1.75 or more and the average substitution degree of the 6-position of the glucose unit of 0.80 or more (in particular, Cellulose acetate). Even such a highly substituted cellulose ester (particularly a cellulose ester having a high 6-position substitution degree) can be efficiently dissolved.

  In the first cooling step, in order to increase the solubility of the cellulose ester, the cellulose ester can usually be cooled with a high concentration good solvent. Therefore, in the first cooling step, for example, a cooling solvent composed of cellulose ester and at least one good solvent selected from esters, ketones and ethers, and the good solvent concentration is 92% by weight or more. And the mixture containing may be cooled. More specifically, in the first cooling step, the sum of the average degree of substitution at the 2nd and 3rd positions of the glucose unit is 1.80 or more, and the average degree of substitution at the 6th position of the glucose unit is 0.88. A mixture containing the above cellulose acetate and a cooling solvent composed of at least methyl acetate and having a good solvent concentration of 94% by weight or more may be cooled.

In the poor solvent addition step, the poor solvent may be added between the start of the first heating step and the start of the second cooling step. In the poor solvent addition step, the poor solvent to be added may be at least one selected from alcohols (for example, alkanols such as C _1-4 alkanol) and hydrocarbons. In the poor solvent addition step, the addition amount of the poor solvent may be, for example, about 3 to 50 parts by weight with respect to 100 parts by weight of the good solvent constituting the cooling solvent.

  As a typical method for producing the cellulose ester solution of the present invention, the following methods (i) to (iii) may be mentioned.

  (I) A first cooling step of cooling a mixture containing cellulose ester and a cooling solvent composed of a good solvent for the cellulose ester at −10 ° C. or lower, and a mixture after the first cooling step is 0 A method for producing a cellulose ester solution through a first cooling / dissolving step comprising a first heating step for heating to a temperature higher than or equal to ° C., wherein the cellulose ester solution is prepared after the first cooling step is completed. A poor solvent addition step of adding a poor solvent, a second cooling step of cooling the mixture obtained through the first cooling dissolution step and the poor solvent addition step at −10 ° C. or less, and this second cooling The manufacturing method of the cellulose-ester solution including the 2nd heating process which heats the mixture after a process to 0 degreeC or more.

  (Ii) a cellulose ester (in particular, cellulose acetate) having a total of the average substitution degree at the 2-position and the 3-position of the glucose unit of 1.85 or more and an average substitution degree of the 6-position of the glucose unit of 0.89 or more; A first cooling step of cooling a mixture comprising a good solvent for the cellulose ester (especially cellulose acetate) at −120 ° C. to −30 ° C., and after the first cooling step A method for producing a cellulose ester (particularly, cellulose acetate) solution through a first cooling / dissolving step comprising a first heating step of heating the mixture to 0 ° C. or higher, wherein the first heating step From the start of the process to the start of the second cooling step, obtained through the poor solvent addition step of adding alkanols, the first cooling dissolution step and the poor solvent addition step A second esterification step of cooling the mixture at −120 ° C. to −30 ° C., and a second heating step of heating the mixture after the second cooling step to 0 ° C. or higher. In particular, a method for producing a cellulose acetate solution.

(Iii) a cellulose ester (in particular, cellulose acetate) having a total of the average substitution degree at the 2-position and the 3-position of the glucose unit of 1.85 or more and an average substitution degree of the 6-position of the glucose unit of 0.89 or more; A first cooling step of cooling a mixture containing at least a good solvent composed of methyl acetate at a concentration of 94% by weight or more at −100 ° C. to −40 ° C., and the first cooling step A method for producing a cellulose ester (particularly, cellulose acetate) solution through a first cooling / dissolving step comprising a first heating step of heating a later mixture to 0 ° C. or higher, comprising: It is obtained through the poor solvent addition step of adding C _1-4 alkanols, the first cooling dissolution step, and the poor solvent addition step between the start of the heating step and the start of the second cooling step. Mixed A cellulose ester comprising a second cooling step for cooling the product at −100 ° C. to −40 ° C., and a second heating step for heating the mixture after the second cooling step to 0 ° C. or more (particularly , Cellulose acetate) solution production method.

  The present invention also includes a cellulose ester solution obtained by the production method. The cellulose ester solution of the present invention has high filterability despite containing a poor solvent. For example, the poor solvent concentration with respect to the entire solvent constituting the solution is 10% by weight or more (for example, about 10 to 30% by weight). The degree of filtration Kw when measured under conditions of a temperature of 25 ° C. and a filtration pressure of 294 kPa may be 70 or less (for example, about 30 to 70).

  Moreover, the cellulose ester film obtained from the said cellulose-ester solution is also contained in this invention. Such a cellulose ester film may be an optical film, for example, an optical compensation film for a liquid crystal display device or a protective film for a polarizing plate.

  In the present specification, the “good solvent” means that the cellulose ester can be dissolved through a cooling step regardless of whether or not the cellulose ester is dissolved at normal temperature or room temperature (normally not dissolved). Meaning a solvent, usually hydrocarbons and alcohols. In the present specification, the “cooling step” means a step of holding (or cooling) a mixture containing cellulose ester (and solvent) in a predetermined temperature range (cooling temperature range), and “heating step” The term “step” refers to a step of maintaining the mixture containing the cellulose ester after the cooling step in a predetermined temperature range.

  In the present invention, in a cooling dissolution method in which a cellulose ester is dissolved by cooling and heating a mixture composed of a cellulose ester and a solvent containing a good solvent (such as methyl acetate), the mixture after cooling is a poor solvent. After the addition, a cellulose ester solution (particularly a cellulose acetate solution) having excellent filterability can be obtained even if a poor solvent is contained by cooling again. In the cellulose ester solution obtained by such a method, since it is excellent in filterability and contains a poor solvent, it is possible to efficiently control gelation properties and releasability from a support (peelable support). Furthermore, in the cellulose ester solution of the present invention, by using a poor solvent such as alcohols, excellent film forming properties and stability (dissolution stability) can be obtained without using a halogen-based solvent such as methylene chloride. A film having good film characteristics (for example, an optical film) can be formed.

[Method for producing cellulose ester solution]
The production method of the present invention includes a first cooling step of cooling a mixture (sometimes referred to as a mixture (A)) containing a cellulose ester and a cooling solvent composed of a good solvent for the cellulose ester, and the first A method for producing a cellulose ester solution through a first cooling dissolution step comprising a first heating step for heating the mixture after the cooling step, wherein the first cooling step is completed. A poor solvent addition step of adding a poor solvent for the cellulose ester, a mixture obtained through the first cooling dissolution step and the poor solvent addition step (to distinguish from the mixture (A), referred to as a mixture (B)) And a second cooling step for cooling.

(First cooling step)
In the first cooling step, a mixture containing a cellulose ester and a cooling solvent (or a first cooling solvent) composed of a good solvent for the cellulose ester is cooled.

Examples of the cellulose ester include various cellulose esters having an acyl group (for example, an aliphatic acyl group). Representative cellulose esters include cellulose esters having a C _1-10 alkylcarbonyl group, such as cellulose alkylcarbonyl esters (cellulose C _2-6 alkylcarbonyl esters such as cellulose acetate, cellulose propionate, cellulose butyrate, Examples thereof include cellulose acetyl C _3-6 alkylcarbonyl esters (aliphatic mixed acid esters) such as cellulose acetate propionate and cellulose acetate butyrate. Preferred cellulose esters are cellulose C _2-4 alkylcarbonyl esters (particularly cellulose acetate) and cellulose acetyl C _3-4 alkylcarbonyl esters (particularly cellulose acetate propionate, cellulose acetate butyrate). In the field of optical films, cellulose acetate (cellulose diacetate, cellulose triacetate) having excellent characteristics is often used. These cellulose esters can be used alone or in combination of two or more.

  In the cellulose ester, the average substitution degree of the ester group (acyl group) (the total average substitution degree of ester groups substituted at the 2, 3 and 6 positions of the glucose units constituting the cellulose) is 0.5 to 3 (for example, 1 to 2.99), for example, 1.5 to 3 (eg 2 to 2.95), preferably 2.5 to 3 (eg 2.6 to 2.98), more preferably 2 About 0.7-3 (for example, 2.75-2.97) may be sufficient. In the present invention, the average degree of substitution is 2.6 or more (for example, 2.65 to 3), preferably 2.7 or more (for example, 2.73 to 2.98), more preferably 2.73 or more (for example, 2. Even if it is a cellulose ester (especially cellulose acetate) having a relatively high degree of substitution of about 2.75 to 2.95), especially 2.76 or more (for example, about 2.77 to 2.93) Can be dissolved well.

In the mixed acid ester, the average substitution degree of the acetyl group is, for example, about 1 to 2.9 (preferably 1.5 to 2.8, more preferably 1.7 to 2.7), and C _3-6 acyl. The average substitution degree of the group may be, for example, about 0.1 to 1 (preferably 0.2 to 0.8, more preferably 0.3 to 0.8).

  In addition, the average acetylation degree of a cellulose acetate is selected from the range of about 43.7-62.5% (average substitution degree of an acetyl group 1.7-3) according to a use or a characteristic among cellulose esters, for example. In general, it may be about 57.5 to 62.5% (average substitution degree of acetyl group is 2 to 3), preferably about 58 to 62.5% (for example, 58.8 to 61.3%). . In particular, dimensional stability, moisture resistance, heat resistance and the like are high, and an average degree of acetylation of 58 to 62.5%, preferably 58.5 to 62 for use as a film (film for photographic material or optical material). %, More preferably 59 to 62% (for example, 60 to 61%) of cellulose acetate (cellulose triacetate) is advantageously used.

  In addition, when the cellulose ester (especially cellulose acetate) which has a comparatively high substitution degree (especially high 6-position substitution degree) is used, the solubility of the cellulose ester in cooling melt | dissolution can be improved further. In such a highly substituted cellulose ester, the total of the average degree of substitution at the 2nd and 3rd positions of the glucose unit (the total of the average degree of substitution of the ester group or acyl group substituted at the 2nd and 3rd positions) is 1. It can be selected from a range of 6 or more (for example, about 1.67 to 2), for example, 1.70 or more (for example, about 1.72 to 1.97), preferably 1.75 or more (for example, 1.77 to 1.96 or more), more preferably 1.80 or more (for example, about 1.82 to 1.95), particularly 1.85 or more (for example, about 1.86 to 1.93).

  Further, in the cellulose ester having a high degree of substitution, the average degree of substitution at the 6-position of the glucose unit can be selected from a range of 0.70 or more (for example, about 0.75 to 1), for example, 0.80 or more (for example, 0.88 to 0.99), usually 0.87 or more (for example, about 0.87 to 0.99), preferably 0.88 or more (for example, about 0.88 to 0.98), Preferably, it may be 0.89 or more (for example, about 0.90 to 0.97).

  Such a highly substituted cellulose ester (particularly, cellulose acetate) is produced by a method described in JP-A-11-5851, JP-A-2002-212338, JP-A-2002-338601, or the like. be able to.

  The intermolecular and intramolecular substitution degree distribution of the cellulose ester (highly substituted cellulose ester, particularly cellulose acetate) may be a relatively small value from the viewpoint of solubility. That is, the degree of substitution of the cellulose ester is “average degree of substitution”, and the cellulose ester usually has a cellulose ester structure in which the total degree of substitution is higher than the above range (for example, cellulose ester having a total degree of substitution extremely close to 3) ), And such cellulose esters usually reduce solubility. Therefore, by lowering the substitution degree distribution and reducing the portion of the cellulose ester having a significantly high substitution degree as described above, this influence can be alleviated and the solubility in cooling dissolution can be improved.

Therefore, the cellulose ester (particularly cellulose acetate) usually has an absorption maximum of an infrared absorption spectrum at a wave number of 3450 to 3550 cm ⁻¹ (preferably 3455 to 3540 cm ⁻¹ , more preferably 3460 to 3530 cm ⁻¹ ). cage, the half-width of the absorption maximum, 135 cm ^-1 or less (e.g., 10～135Cm about ^-1), preferably about 130 cm ^-1 or less (e.g., about 30～130Cm ^-1), more preferably 125 cm ^-1 or less It may be about (for example, about 50 to 125 cm ⁻¹ ).

  The “half-value width” is the width at half the peak height of the chart when the wave number (corresponding to the degree of substitution) is on the horizontal axis (x axis) and the abundance at this wave number is on the vertical axis (y axis). It is an index representing the standard of variation in distribution. JP-A-2002-338601 can be referred to for details of such a half-value width and a measuring method.

  The cellulose acetate is often an acetyl group in all of the acyl groups, but may be a cellulose acetate containing a very small amount of an acyl group other than the acetyl group (for example, propionyl group, butyryl group, etc.). For this reason, in the said cellulose acetate, the ratio of the acetyl group with respect to the whole acyl group is 98 mol% or more (for example, about 98.5-100 mol%), for example, Preferably it is 99 mol% or more (for example, 99.3). 99.95 mol%), more preferably 99.5 mol% or more (for example, about 99.8 to 99.9 mol%).

The average degree of substitution (degree of acylation) can be measured by a conventional method. For example, the degree of acetylation (degree of acetylation) is in accordance with the degree of acetylation in ASTM: D-817-91 (test method for cellulose acetate etc.). It can be calculated by measuring the number of moles of acyl groups per unit weight and further measuring the ratio of each acyl group liberated by saponification by liquid chromatography. The acylation degree can also be analyzed by ¹ H-NMR and ¹³ C-NMR.

  The viscosity average polymerization degree of the cellulose ester (particularly, cellulose acetate) can be selected from the range of about 100 to 1000 (for example, 150 to 800), for example, 200 to 500 (for example, 230 to 450), preferably 250 to It may be about 400, more preferably about 270 to 380 (for example, 280 to 350).

  Cellulose esters can be used in various forms such as powder, granules, fibers, and crushed materials.

  In the mixture (A), the good solvent constituting the cooling solvent can be appropriately selected according to the type of cellulose ester (for example, the type of acyl group, the degree of substitution, the degree of acetylation, etc.) and can dissolve the cellulose ester. If it is, it will not specifically limit, For example, ester, ketones, ethers, nitroalkane (nitromethane, nitroethane, nitropropane, etc.), halogen-type solvents (for example, chlorine-type solvents, such as a methylene chloride), etc. are mentioned. These good solvents may be linear or have a branched chain structure or a cyclic structure. Note that halogen solvents such as methylene chloride (particularly chlorine solvents) are usually not used as good solvents from an environmental point of view. That is, the good solvent (and cooling solvent) usually does not contain a halogen-based solvent.

Typical esters include, for example, formate esters (eg, formic acid C _1-10 alkyl esters such as ethyl formate, propyl formate, pentyl formate), acetate esters [methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, acetic acid Acetic acid C _1-10 alkyl ester (preferably C _1-6 alkyl ester, more preferably C _1-4 alkyl ester of acetic acid) such as butyl, pentyl acetate, amyl acetate, 2-methoxyethyl acetate, 2-ethoxyethyl acetate Acetic acid C _1-4 alkoxy C _1-4 alkyl ester, etc.], Propionic acid ester (eg, propionic acid C _1-10 alkyl ester, such as ethyl propionate), etc. Esters (eg, C _2-6 alkanecarboxylic acid-C _1-10 alkyl esters, preferably C _2-4 alkanecarboxylic acid-C _1-6 alkyl ester)] and the like.

Representative ketones include dialkyl ketones (eg, diC _1-6 alkyl ketones such as acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, preferably diC _1-4 alkyl ketones), cycloalkanones (eg, C _5-10 cycloalkanone such as cyclohexanone and methylcyclohexanone, preferably C _5-8 cycloalkanone).

Representative ethers include, for example, dialkyl ethers (for example, diC _1-4 alkyl ethers such as diisopropyl ether), alkylphenyl ethers (such as anisole), alkanediol mono- or dialkyl ethers [for example, cellosolves (methyl cellosolve). , Ethyl cellosolve, butyl cellosolve, etc.), dialkoxyalkanes such as dimethoxymethane and diethoxyethane], cyclic ethers (tetrahydrofuran, 1,4-dioxane, 1,3-dioxolane, etc.) and the like.

The good solvents may be used alone or in combination of two or more. Of these good solvents, acetate esters (for example, C _1-10 alkyl esters such as methyl acetate) are preferred from the viewpoint of solubility and practical use. In particular, the good solvent is preferably composed of at least methyl acetate, and methyl acetate and another good solvent may be combined. In the good solvent, the ratio of methyl acetate to the other good solvent is the former / the latter (weight ratio) = 100/0 to 50/50, preferably 99/1 to 60/40 (for example, 97/3 to 70 / 30), more preferably about 95/5 to 80/20.

  The 1st cooling solvent should just be comprised with the said good solvent at least, and if it is a range which does not impair solubility, it may contain the poor solvent with respect to a cellulose ester. The poor solvent is not particularly limited, and examples thereof include hydrocarbons and alcohols. The poor solvent may be linear or may have a branched chain or a cyclic structure.

  Typical hydrocarbons include aliphatic hydrocarbons (for example, alkanes such as hexane, heptane, and octane), alicyclic hydrocarbons (such as cyclohexane), and aromatic hydrocarbons (benzene, toluene, xylene). Etc.).

Typical alcohols include, for example, aliphatic alcohols [for example, alkanols (methanol, ethanol, propanol, isopropanol, 1-butanol, 2-butanol, 3-butanol, 1-pentanol, 2-pentanol, 3 -C _1-8 alkanols such as pentanol, preferably C _1-6 alkanols, more preferably C _1-4 alkanols)], alicyclic alcohols [for example, cycloalkanols (cyclohexanol etc.)] and the like. It is done.

The poor solvent may be used alone or in combination of two or more. Of these poor solvents, alcohols [particularly alkanols such as C _1-4 alkanol (eg ethanol, butanol etc.)] are preferred.

  In the cooling step, in order to dissolve the cellulose ester efficiently, it is preferable to cool the cellulose ester in the presence of a relatively high concentration of a good solvent. Therefore, the good solvent concentration in the first cooling solvent can be selected from the range of 80% by weight or more (for example, about 80 to 100% by weight), and is usually 90% by weight or more (for example, 91 to 99.9% by weight). Degree), preferably 92% by weight or more (for example, about 93 to 99.5% by weight), more preferably 94% by weight or more (for example, about 94.5 to 99% by weight), particularly 95% or more (for example, 96 About 98% by weight).

  The said mixture (A) may contain additives, such as a plasticizer, as needed.

  In addition, in the said mixture (A), the density | concentration of a cellulose ester can be selected from the range of about 1-50 weight%, for example, 3-30 weight%, Preferably it is 5-25 weight%, More preferably, it is 8-20 weight% % May be sufficient. Moreover, in the said mixture, the ratio of a cooling solvent can be selected from the range of 1-100 weight part with respect to 1 weight part of cellulose esters, for example, 3-30 weight part, Preferably it is 3-20 weight part, More preferably May be about 4 to 10 parts by weight.

  The said mixture used for cooling (1st cooling) is obtained by mixing a cellulose ester and a 1st cooling solvent (and additives, such as a plasticizer as needed). Such mixing usually gives a mixture in which the cellulose ester is swollen. Mixing may be performed under cooling (for example, about −10 to 10 ° C.) or under heating (for example, about 30 to 55 ° C.), and may be performed at normal temperature or room temperature. Mixing may be performed by stirring or by a conventional method using a mixer or the like. In mixing, the order of addition of each component (mixing order) is not particularly limited. For example, when a good solvent and a small amount of a poor solvent are used as the first cooling solvent, the cellulose ester and the poor solvent are mixed. A good solvent may be mixed.

(First cooling step)
The mixture prepared as described above is subjected to a first cooling step. In the cooling step, the dissolution of the cellulose ester in the heating step described later is promoted by holding the mixture at a predetermined cooling temperature (cooling temperature range). The cooled mixture (A) is usually solidified in many cases.

  In the first cooling step, the cooling temperature can be selected from the range of −10 ° C. or lower (for example, about −20 to −150 ° C.), for example, −30 to −120 ° C., preferably −40 to −100 ° C., More preferably, it may be about −50 to −90 ° C.

  In the cooling step, the cooling time (the time maintained at the cooling temperature (or temperature range)) is, for example, 3 hours or more (for example, about 5 hours to 10 days), preferably 6 hours or more (for example, 8 to 48 hours), more preferably 10 hours or more (for example, about 12 to 36 hours), particularly 15 hours or more (for example, about 16 to 24 hours).

  Cooling may be performed in a closed system in order to prevent moisture from being mixed during cooling. The cooling may be performed under normal pressure, or may be performed under reduced pressure in order to shorten the cooling time.

  The cooling rate (rate until reaching the predetermined cooling temperature) is preferably as fast as possible, for example, 1 ° C./min or more (for example, 2 ° C./min to 10000 ° C./sec), preferably 3 It may be about ° C / min or higher (for example, 4 ° C / min to 1000 ° C / sec).

(First heating step)
The mixture that has undergone the first cooling step is subjected to a first heating step. In the heating step, the mixture is held at a predetermined temperature (temperature range) to dissolve the cellulose ester.

  In the heating step, the heating can be selected from the range of 0 ° C. or higher (for example, about 0 to 150 ° C.), for example, 5 ° C. or higher (for example, about 5 to 100 ° C.), preferably 10 to 80 ° C. Preferably, it can be performed at a temperature of about 15 to 50 ° C. (for example, 20 to 40 ° C.), and may be performed at room temperature or room temperature (for example, about 10 to 30 ° C., preferably about 15 to 25 ° C.). The heating is usually performed at room temperature or room temperature from the viewpoint of simplicity.

  In the warming step, the warming time (the time maintained at the temperature (or temperature range)) is not particularly limited as long as the cellulose ester can be dissolved, and is, for example, 10 minutes or longer (for example, about 30 minutes to 24 hours). ), Preferably 1 hour or more (for example, about 2 to 12 hours), more preferably 2 hours or more (for example, about 3 to 6 hours).

  The heating rate (rate until reaching the predetermined temperature) is, for example, 1 ° C./min or more (for example, 2 ° C./min to 10000 ° C./sec), preferably 3 ° C./min or more (for example, 4 ° C./minute to 1000 ° C./second). Further, the heating may be performed under normal pressure, or may be performed under pressure in order to shorten the heating time. Further, the heating may be performed by leaving the mixture (or the system including the mixture) at room temperature or room temperature, and the temperature of the system including the mixture is relatively set by adding a poor solvent described later. You may carry out by making it raise.

(Poor solvent addition process)
In the poor solvent addition step, the poor solvent is added (and mixed) to the mixture (mixture (A)) that has undergone the first cooling step. That is, the poor solvent may be added after at least the first cooling step has solidified the cellulose ester (or the cellulose ester has passed through an extremely high viscosity state). For example, the first cooling step is completed. It can be carried out in an appropriate stage from after (that is, after the cooling at the predetermined cooling temperature is completed) to the start of the second cooling step described later. Specifically, during the period from the end of the first cooling step to the start of the first heating step, during the first heating step, and from the end of the first heating step to the second cooling step. In the process leading up to the start of the process, a poor solvent is added.

  In a preferred embodiment, the poor solvent is added between the start of the first heating step and the start of the second cooling step (particularly, after the end of the heating step until the start of the second cooling step). To do.

As a poor solvent, the poor solvent (for example, alcohol etc.) illustrated by the term of the said 1st cooling process can be used. Preferable poor solvents to be added in the poor solvent addition step include alcohols [particularly alkanols such as C _1-4 alkanol (for example, ethanol, butanol, etc.)]. The poor solvent may be used alone or in combination of two or more. For example, when combining poor solvents, a poor solvent (such as methanol or ethanol) having a relatively high evaporation rate and a poor solvent (such as butanol or cyclohexanol) having a relatively low evaporation rate may be combined.

  In the poor solvent addition step, the number of times of addition of the poor solvent may be one or may be divided into a plurality of times (for example, 2 to 5 times, preferably about 2 to 3 times). Further, the poor solvent may be added stepwise (or intermittently) or continuously. In addition, the mixing after the addition of the poor solvent may be performed by stirring, or may be performed by a conventional method using a mixer or the like.

  In the poor solvent addition step, the addition amount (or total addition amount) of the poor solvent can be appropriately selected according to the poor solvent concentration in the finally obtained cellulose ester solution. For example, the good solvent (the first cooling) The good solvent constituting the solvent) can be selected from a range of 2 to 100 parts by weight, for example, 3 to 50 parts by weight, preferably 4 to 40 parts by weight, and more preferably about 5 to 30 parts by weight. It may be.

  Note that the poor solvent may be at normal temperature, and may be heated as necessary, for example, when the system after the first cooling step is efficiently heated.

  In addition, in a poor solvent addition process, you may add additives, such as a plasticizer (for example, the plasticizer mentioned later), as needed with a poor solvent.

(Second cooling step)
The mixture (mixture (B)) obtained through the first cooling dissolution step (that is, the first cooling step, the first heating step) and the poor solvent addition step is the second cooling step. It is cooled again. Usually, when a poor solvent is added to a solvent system containing a cellulose ester, the solubility of the cellulose ester is lowered, and the filterability of the resulting cellulose ester solution is lowered. And the cellulose-ester solution with such low filterability reduces the characteristic of a film | membrane. In the present invention, in addition to the first cooling step (particularly, the first cooling step in a system having a high good solvent concentration), addition of the poor solvent in the poor solvent addition step, and recooling after the addition (second cooling step) 2), the solubility of the cellulose ester can be improved or maintained even when a poor solvent is contained, and excellent filterability can be imparted to the cellulose ester solution. Therefore, the cellulose ester solution of the present invention can impart film forming characteristics such as high peelability from the support and gelation speed without impairing filterability, and these characteristics can be controlled.

  In the second cooling step, the cooling conditions such as the cooling temperature and the cooling time are the same as the cooling conditions described in the section of the first cooling step. For example, the cooling temperature is −10 ° C. or lower (for example, −30 To −120 ° C., preferably −40 to −100 ° C., more preferably about −50 to −90 ° C.), and the cooling time is 3 hours or longer [for example, about 5 hours to 10 days, preferably 6 hours or longer (for example, 8 to 48 hours), more preferably 10 hours or more (for example, about 12 to 36 hours), particularly 15 hours or more (for example, about 16 to 24 hours)].

  And usually, after the second heating step of heating (reheating) the mixture after the second cooling step (mixture (B), cellulose ester mixture), cellulose as a final dissolved product is obtained. An ester solution is obtained. In the second heating step, the same heating conditions as those in the first heating step [temperature (for example, heating of 0 ° C. or higher), heating time (for example, heating time of 10 minutes or more), etc. )].

  The manufacturing method only needs to include at least the first cooling dissolution step, the poor solvent addition step, and the second cooling step (and the second heating step), and is necessary after these steps. If present, the poor solvent addition step and the cooling step (for example, the second poor solvent addition step and the third cooling step) may be repeated.

[Cellulose ester solution]
The cellulose ester solution of the present invention is obtained as described above, and has high filterability despite containing a poor solvent.

  In the cellulose ester solution of the present invention, the concentration of the poor solvent with respect to the entire solvent constituting the solution (the total amount of the good solvent and the poor solvent) is, for example, 5% by weight or more (for example, 6 to 50% by weight), preferably 8% by weight. The above is (for example, 9 to 40% by weight), more preferably 10% by weight or more (for example, 10 to 30% by weight), and particularly 12% by weight or more (for example, about 12 to 20% by weight).

  In the cellulose ester solution of the present invention, the concentration of the cellulose ester may be, for example, 1 to 30% by weight, preferably 3 to 25% by weight, and more preferably about 5 to 20% by weight.

  The cellulose ester solution includes various additives such as plasticizers, stabilizers (antioxidants, ultraviolet absorbers, deterioration inhibitors, thermal stabilizers, etc.), lubricants (particulate lubricants), antistatic agents, and coloring. Agents, nucleating agents (crystal nucleating agents), flame retardants, mold release agents and the like may be included. In addition, the cellulose ester solution includes, as additives, a retardation increasing agent (such as a retardation increasing agent described in JP-A-2001-139621) and a release agent (such as a releasing agent described in JP-A-2002-309209). Etc. may be included.

The plasticizer is not particularly limited, and examples thereof include phosphate esters [tri-C _1-12 alkyl esters such as triethyl phosphate and tributyl phosphate, and tri-C _1-6 alkoxy phosphates such as tributoxyethyl phosphate. C _1-12 alkyl ester, phosphoric acid C _1-12 alkyl diaryl ester such as 2-ethylhexyl diphenyl phosphate, phosphoric acid C _1-3 alkyl-aryl diaryl ester such as triphenyl phosphate (TPP), cresyl diphenyl phosphate , Tricresyl phosphate (TCP), triaryl phosphates such as biphenyldiphenyl phosphate, condensed phosphates, etc.], aromatic carboxylates [dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP), phthalic acid Di C _1-12 alkyl esters such as 2-ethylhexyl (DEHP) phthalate C _1-6 alkoxy C _1-12 alkyl esters such as phthalic acid dimethoxyethyl phthalate such as butyl benzyl phthalate C _{1- 12} alkylaryl-C _1-3 alkyl ester, C _1-6 alkyl phthalyl C _2-4 alkylene glycolate such as ethyl phthalyl ethylene glycolate, trimellitic acid tri C _1-12 alkyl ester such as trimethyl trimellitic acid , Pyromellitic acid tetra-C _1-12 alkyl esters such as pyromellitic acid tetraoctyl], fatty acid esters [adipic acid esters such as dibutyl adipate and dioctyl adipate, azelaic acid esters such as dibutyl azelate, dibutyl sebacate, etc. Of sebacic acid ester, butyl oleate, Methylacetyl synolate], lower fatty acid esters of polyhydric alcohols (glycerin, trimethylolpropane, pentaerythritol, sorbitol, etc.) [triacetin (TA), diglycerin tetraacetate, etc.], glycol esters (dipropylene glycol dibenzoate, etc.) , Citric acid esters [acetyltributyl citrate (OACTB) and the like], amides [N-butylbenzenesulfonamide (BM-4) and the like], ester oligomers (caprolactone oligomers and the like), and the like.

  Examples of the condensed phosphate ester include resorcinol phosphates such as resorcinol bis (diphenyl phosphate), resorcinol bis (dicresyl phosphate); hydroquinone phosphates such as hydroquinone bis (diphenyl phosphate); biphenol bis (diphenyl phosphate), etc. Biphenol phosphates; bisphenol-A phosphates such as bisphenol-A bis (diphenyl phosphate); bisphenol-S phosphates such as bisphenol-S bis (diphenyl phosphate).

  The plasticizers may be used alone or in combination of two or more.

  In the cellulose ester solution, the ratio of additives (plasticizer, etc.) can be selected from the range of about 0.5 to 50 parts by weight, for example, 1 to 40 parts by weight, preferably 100 parts by weight of the cellulose ester. May be about 3 to 30 parts by weight, more preferably about 5 to 20 parts by weight.

  In addition, an additive may be added with respect to the cellulose-ester solution obtained through the said 2nd heating process, and may be added in the said various process. For example, as described above, the plasticizer may be added to the mixture before being subjected to the first cooling step, or may be added in the poor solvent addition step.

As described above, the cellulose ester solution of the present invention has high filterability despite containing a poor solvent. The degree of filtration (Kw) of the cellulose ester solution is, for example, 75 or less (for example, 20 to 75) when measured under conditions of a temperature of 25 ° C. and a filtration pressure (pressure) of 294 kPa (3 kg / cm ² ), preferably It is about 70 or less (for example, 30 to 70), more preferably about 65 or less (for example, 40 to 65). The degree of filtration is usually determined based on the filtration amount after filtration (constant pressure filtration) and passing through a predetermined filter medium [usually, a gold woven fabric (a plain fabric using cotton yarn of about 23.5 to 12 tex in length and width)]. Can do.

“Filtration degree (Kw)” is an index representing the high filterability of the solution, and is represented by Kw = k × 10000 (that is, 10,000 times k) when the filtration constant is k. . Then, filtration constant k, the filtration rate P ₁ at time t ₁ when the elapsed from the time t ₂ (≠ t ₁₎ filtration rate P ₂ Metropolitan during course, can be determined by the following formula (1).

k = {2- (P ₂ / P ₁ )} / 2 (P ₁ + P ₂ ) (1)
(Cellulose ester film and method for producing the same)
The cellulose ester solution of the present invention can be suitably used for various materials (films, fibers, etc.). In particular, since the cellulose ester solution has excellent filterability, it is useful for obtaining a film (for example, a high quality film such as a film for a liquid crystal display device) that requires a filtration treatment prior to film formation (film forming). It is.

  As described above, in order to remove impurities, the cellulose ester film is formed by a conventional method such as a solution casting method (casting method) after filtering the cellulose ester solution as necessary. Obtainable. The filtration treatment can usually be performed by a conventional method using a filter medium such as a wire mesh or flannel.

  In the solution casting method, the cellulose ester solution (or a filtrate thereof) is cast on a peelable support (and further dried if necessary), and the formed film is peeled off from the peelable support and dried. Thus, a cellulose ester film can be produced. In such a method, since the cellulose ester solution containing a poor solvent is used, the gelation property (gelation rate) after casting and the peelability from the peelable support can be improved and efficiently controlled. The film property can be improved.

  The peelable support may be usually a metal support (such as stainless steel), or may be in the form of a drum or belt (endless belt). The surface of the support is usually mirror-finished and often smooth.

  In many cases, after the cellulose ester solution is cast, the cellulose ester solution is usually dried with hot air or the like (primary drying), the film is peeled off from the substrate, and further dried with hot air or the like (secondary drying). The drying conditions can be appropriately selected according to the solvent composition, film thickness, and the like. The primary drying temperature (for example, hot air temperature) may be, for example, about 70 to 200 ° C. (preferably about 80 to 150 ° C.), and the drying time may be about 10 seconds to 10 minutes. In the present invention, since a relatively large amount of poor solvent is contained, gelation can be efficiently performed. The secondary drying temperature (for example, hot air temperature) may be, for example, 80 to 250 ° C. (preferably about 100 to 170 ° C.) and a drying time of about 1 minute to 2 hours.

  The thickness of a cellulose-ester film can be selected according to a use, for example, 3-500 micrometers (for example, 5-200 micrometers), Preferably it is 10-150 micrometers, More preferably, about 20-100 micrometers may be sufficient.

  The cellulose ester solution (dope) of the present invention is excellent in filterability despite containing a poor solvent. Moreover, the cellulose ester solution can achieve both high filterability and control of gelation and peelability from the support without using a halogen-based solvent such as methylene chloride, and has high film-forming properties. Therefore, the cellulose ester solution of the present invention can be suitably used as various molded articles, for example, fibers, various films (such as packaging films and optical films) or sheets.

  In particular, the cellulose ester solution of the present invention (especially cellulose acylate derivatives such as cellulose acetate) has high stability (dissolution stability) and high handleability during film formation, and film characteristics (surface smoothness, optical characteristics, etc.) ) Can be formed into a variety of high-quality films [for example, color filters, photographic light-sensitive material base films, liquid crystal display films, polarizing plate protective films (for example, at least one surface of a polarizing film) In particular, it can be suitably used as a protective film on both sides, an optical film such as an optical compensation film for liquid crystal display devices (such as a retardation film).

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. The filtration degree Kw was measured as follows.

(Measurement of filtration degree)
The cellulose triacetate solutions (samples) obtained in Example 1 and Comparative Examples 1 to 4 were each subjected to rotary shaking at 8 rpm (8 rpm) for 2 hours using a rotary shaker, and then set to 25 ° C. For 40 minutes, and the temperature was adjusted to 25 ° C.

On the other hand, on the lower lid of the filter equipped with a pressurizing machine, a specified filter medium [gold lacquer (cotton lawn, Nisshinbo fabric length 60 count 130, width 60 count 120, 250 driven)], specified washer (15φ), Then, after attaching the rubber packing in order, the measuring cylinder was arranged so as to be in close contact with the lower lid of the filter, and the temperature of the pressurizer and the filter was adjusted to 25 ° C. with a hot water jacket. Then, after the filter medium is moistened with acetone, the temperature-adjusted cellulose triacetate solution is quickly poured into a filter (filter medium) using a funnel, and the upper lid of the filter is firmly attached, at a temperature of 25 ° C. and a pressure of 3 kg. / Cm ² (294 kPa) conditions, the outflow amount (filtration amount) of the cellulose triacetate solution was measured after 20 minutes and after 60 minutes, and these measured values were applied to the above equation (1) for filtration. I asked for a degree. The filtration degree was obtained as an average value by repeating these series of operations 6 times (that is, measuring 6 times in total).

(Synthesis Example 1)
After pulverizing wood pulp having an α-cellulose content of about 97% by weight, 100 parts by weight of glacial acetic acid was uniformly sprayed on 100 parts by weight of the pulp, followed by stirring and mixing at room temperature for 90 minutes. The pulp was put into a pre-cooled mixed solution of 245 parts by weight of acetic anhydride, 365 parts by weight of acetic acid and 10 parts by weight of sulfuric acid, and the mixture was stirred and mixed to proceed the acetylation reaction at 45 ° C. or lower. The reaction system was non-uniform in the initial stage, but changed from an opaque bottle shape to a pale yellow transparent water tank shape as the reaction progressed. When no non-acetylated fiber pieces were found in the syrup-like reaction mixture, the reaction was terminated. It took about 220 minutes from the start of the reaction to the end of the reaction. At the end of the acetylation reaction, 28.7 parts by weight of an aqueous magnesium acetate solution (30% by weight) is added to hydrolyze excess acetic anhydride and neutralize some of the sulfuric acid, thereby stopping the acetylation reaction. did. The residual catalyst sulfuric acid in the reactor at the end of the reaction was calculated to be 4 parts by weight.

Next, 8.4 parts by weight of magnesium acetate aqueous solution (30% by weight) was added while raising the temperature of the reaction solution to about 60 ° C. over 30 minutes. Thereafter, water was added so that the bath concentration in the system was about 85% by weight, and the temperature was further raised to stabilize at 70 ° C. The aging reaction was continued at 70 ° C. for 30 minutes. At the end of the reaction, about 12.4 parts by weight of magnesium acetate aqueous solution (30% by weight) was added to completely neutralize the sulfuric acid, and the reaction was stopped. The reaction-terminated solution was charged with a large amount of 10% by weight aqueous acetic acid with vigorous stirring to precipitate and separate cellulose acetate. The precipitated cellulose acetate was collected by filtration and washed with water until it was substantially free of acetic acid. Thereafter, dehydration and drying were performed to obtain powdered cellulose triacetate. The viscosity average polymerization degree of the obtained cellulose triacetate was 300. According to the method of Tezuka et al. Described above, the obtained cellulose acetate was subjected to propionylation treatment, and then the degree of acetyl substitution at the 2-position, 3-position and 6-position was determined by measurement by ¹³ C-NMR. As a result, the total degree of acetyl substitution at the 2nd and 3rd positions was 1.91, the degree of acetyl substitution at the 6th position was 0.89, and the total degree of acetyl substitution at the 2nd, 3rd and 6th positions was 2.80. there were.

Example 1
At room temperature, 50 g (dry weight) of cellulose triacetate obtained in Synthesis Example 1, 7.66 g of ethanol, 3.34 g of triphenyl phosphate and 23.10 g of methyl acetate were mixed and stirred for 1 minute, and then allowed to stand for 15 minutes. Further, 233.97 g of methyl acetate was added and stirred for 1 minute to prepare a mixture containing cellulose acetate. The obtained mixture was stored in an ultra-low temperature refrigerator at −70 ° C. for about 16 hours and cooled (first cooling), and the cooled mixture was left at room temperature for about 4 hours. The temperature after standing was room temperature (25 ° C.).

  To the mixture after standing for 4 hours (cellulose triacetate solution), 2.66 g of biphenyldiphenyl phosphate, 11.55 g of butanol and 12.55 g of ethanol were added and stirred for 1 minute. This mixture was stored in an ultra-low temperature refrigerator at −70 ° C. for about 16 hours and cooled, and the cooled mixture was allowed to stand at room temperature for about 4 hours to obtain a uniform cellulose triacetate solution (cellulose triacetate concentration of 16% by weight). As described above, the temperature after standing was room temperature (25 ° C.).

(Comparative Example 1)
At room temperature, 20.21 g of ethanol, 23.10 g of methyl acetate and 11.55 g of butanol were mixed to obtain a mixed solvent. This mixed solvent, 50 g of cellulose triacetate obtained in Synthesis Example 1, 3.34 g of triphenyl phosphate, and 2.66 g of biphenyl diphenyl phosphate were mixed and stirred for 1 minute, and then allowed to stand for 15 minutes. Further, 233.97 g of methyl acetate was added and stirred for 1 minute to prepare a mixture containing cellulose acetate. The obtained mixture was stored in an ultra-low temperature refrigerator at −70 ° C. for about 16 hours and cooled, and the cooled mixture was allowed to stand at room temperature for about 4 hours to obtain a cellulose triacetate solution (cellulose triacetate concentration of 16% by weight). The temperature after standing was room temperature (25 ° C.).

(Comparative Example 2)
In Comparative Example 1, a cellulose triacetate solution (cellulose triacetate concentration of 16% by weight) was obtained in the same manner as in Comparative Example 1 except that the cooling time was changed to about 16 hours and changed to about 5 days.

(Comparative Example 3)
At room temperature, 20.21 g of ethanol, 23.10 g of methyl acetate and 11.55 g of butanol were mixed to obtain a mixed solvent. This mixed solvent, 50 g of cellulose triacetate obtained in Synthesis Example 1, 3.34 g of triphenyl phosphate, and 2.66 g of biphenyl diphenyl phosphate were mixed and stirred for 1 minute, and then allowed to stand for 15 minutes. Further, 233.97 g of methyl acetate was added and stirred for 1 minute to prepare a mixture containing cellulose triacetate. The obtained mixture was stored in an ultra-low temperature refrigerator at −70 ° C. for about 16 hours and cooled, and the cooled mixture was left at room temperature for about 4 hours to obtain a cellulose triacetate solution. The temperature after standing was room temperature (25 ° C.).

  The obtained cellulose triacetate solution was stored in an ultra-low temperature refrigerator at −70 ° C. for about 16 hours and re-cooled, and the cooled mixture was allowed to stand at room temperature for about 4 hours to obtain a cellulose triacetate solution (cellulose triacetate concentration of 16% by weight). Got. As described above, the temperature after standing was room temperature (25 ° C.).

(Comparative Example 4)
At room temperature, 50 g of cellulose triacetate obtained in Synthesis Example 1, 7.66 g of ethanol, 3.34 g of triphenyl phosphate, and 23.10 g of methyl acetate were mixed and stirred for 1 minute, and then allowed to stand for 15 minutes. Further, 233.97 g of methyl acetate was added and stirred for 1 minute to prepare a mixture containing cellulose acetate. The obtained mixture was stored in an ultra-low temperature refrigerator at −70 ° C. for about 16 hours and cooled, and the cooled mixture was left at room temperature for about 4 hours. The temperature after standing was room temperature (25 ° C.).

  To the mixture after standing for 4 hours (cellulose triacetate solution), 2.66 g of biphenyldiphenyl phosphate, 11.55 g of butanol and 12.55 g of ethanol were added, stirred for 1 minute, and the cellulose triacetate solution (concentration of cellulose triacetate of 16% by weight). )

  Table 1 shows the configurations of the cellulose triacetate mixture and the cellulose acetate solution obtained in Example 1 and Comparative Examples 1 to 4, and the degree of filtration. In Table 1, “whole solvent” means the whole cellulose triacetate mixture (or solution) [that is, cellulose triacetate, good solvent (methyl acetate), poor solvent (ethanol, butanol) and plasticizer (triphenyl phosphate, biphenyl). Concentration of solvent relative to the total amount of diphenyl phosphate], “total good solvent (methyl acetate)”, “total poor solvent”, “ethanol”, and “butanol” refer to the total solvent (ie, good The concentration (% by weight) relative to the total amount of solvent and antisolvent.

Claims (12)

  In a first cooling step for cooling a mixture containing a cellulose ester and a cooling solvent composed of a good solvent for the cellulose ester, and a first heating step for heating the mixture after the first cooling step A method for producing a cellulose ester solution through a configured first cooling and dissolving step, wherein a poor solvent adding step of adding a poor solvent for the cellulose ester after the first cooling step is completed, and the first The manufacturing method of the cellulose-ester solution including the 2nd cooling process which cools the mixture obtained through the cooling dissolution process of 1 and the said poor solvent addition process.   The production method according to claim 1, wherein the cellulose ester is cellulose acetate.   The cellulose ester is a cellulose acetate having a total of the average substitution degree at the 2-position and the 3-position of the glucose unit of 1.75 or more and the average substitution degree of the 6-position of the glucose unit of 0.80 or more. Manufacturing method.   In the first cooling step, a mixture comprising a cellulose ester and a cooling solvent composed of at least one good solvent selected from esters, ketones and ethers and having a good solvent concentration of 92% by weight or more. The manufacturing method of Claim 1 which cools.   In the first cooling step, a cellulose acetate in which the total of the average substitution degree at the 2-position and the 3-position of the glucose unit is 1.80 or more and the average substitution degree at the 6-position of the glucose unit is 0.88 or more, and at least The manufacturing method of Claim 1 which cools the mixture containing the cooling solvent which is comprised with methyl acetate and whose good-solvent density | concentration is 94 weight% or more.   The manufacturing method according to claim 1, wherein, in the poor solvent addition step, the poor solvent is added between the start of the first heating step and the start of the second cooling step.   In the poor solvent addition step, the poor solvent to be added is at least one selected from alcohols and hydrocarbons, and the addition amount of the poor solvent is 3 with respect to 100 parts by weight of the good solvent constituting the cooling solvent. The production method according to claim 1, which is ˜50 parts by weight. The total of the average substitution degree at the 2nd and 3rd positions of the glucose unit is 1.85 or more, and the cellulose acetate having an average substitution degree at the 6th position of the glucose unit of 0.89 or more and at least methyl acetate. A first cooling step in which a mixture containing a cooling solvent containing a solvent at a concentration of 94% by weight or more is cooled at −100 ° C. to −40 ° C., and the mixture after the first cooling step is added to 0 ° C. or more. A method for producing a cellulose acetate solution through a first cooling and dissolving step composed of a first heating step for warming, from the start of the first heating step to the start of the second cooling step In the meantime, the poor solvent addition step of adding C _1-4 alkanols, and the mixture obtained through the first cooling dissolution step and the poor solvent addition step are cooled at −100 ° C. to −40 ° C. 2 cooling process and this second The manufacturing method of Claim 2 including the 2nd heating process which heats the mixture after a cooling process of 0 to 0 degreeC or more.   A cellulose ester solution obtained by the production method according to claim 1.   The cellulose ester solution according to claim 9, wherein the concentration of the poor solvent with respect to the total solvent constituting the solution is 10% by weight or more, and the degree of filtration Kw is 70 or less when measured under conditions of a temperature of 25 ° C and a filtration pressure of 294 kPa.   A cellulose ester film obtained from the cellulose ester solution according to claim 10.   The cellulose ester film according to claim 10, which is an optical compensation film for a liquid crystal display device or a protective film for a polarizing plate.