JP2006213778A - Mixed acid ester of cellulose and its manufacturing process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a high purity mixed acid ester of cellulose (cellulose acetate propionate, etc) containing an extremely small amount of fine foreign materials like unreacted cellulose. <P>SOLUTION: The manufacturing process of the mixed acid ester of cellulose comprises a series of steps involving an acylation step in which cellulose is acylated with an acylating agent corresponding to the mixed acid ester of cellulose in the presence of a sulfuric acid catalyst and acylating conditions (e.g. the time from the highest temperature reached during the acylation to the end of it) are adjusted and an aging step in which the acylated product is aged in the presence of the sulfuric acid catalyst and aging conditions (e.g. a base is added intermittently at least in three separate dosages from the start of the aging reaction to the end of it) are adjusted. The process produces the mixed acid ester of cellulose which contains ≤0.12 wt.% of the components insoluble to a mixed solvent of methylene chloride/methanol (by weight)=9/1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a cellulose mixed acid ester useful for forming a film (for example, an optical film such as a protective film for a polarizing plate), a production method thereof, and a film composed of the cellulose mixed acid ester.

  Since cellulose ester is excellent in optical properties, it is used as various optical films. For example, a polarizing plate used in a liquid crystal display device used in a thin flat panel display represented by a liquid crystal television is generally a polarizing plate protective film (polarizing film protective film) and a polarizing film formed of a cellulose ester film. And obtained by pasting together.

  The optical properties of such cellulose esters are reduced with deformation due to moisture absorption, peeling, change in refractive index, and the like. For this reason, when a polarizing plate having such a polarizing plate protective film is used under high temperature and high humidity, the thin film is cracked, the polarizing plate protective film is peeled off from the polarizing film, or the polarizing plate is protected. Problems such as film coloration may occur. Therefore, in the polarizing plate, the properties of the protective film for the polarizing plate covering the polarizing film have a great influence on the properties, and of course, when exposed to high temperature and high humidity in the car like car navigation, Even in typical home use, moisture resistance (or heat and humidity resistance) is required. Such deterioration due to moisture absorption is observed over time in optical films using cellulose acetate that is generally used, and also in display devices including this optical film.

  Thus, the cellulose ester used as an optical film has been conventionally known, and the cellulose ester has good moisture resistance (moisture and heat resistance) such as no deterioration under high temperature and high humidity and excellent dimensional stability. ) Is required. It is known that the cellulose mixed acid ester such as cellulose acetate propionate is superior in the moisture resistance (moisture and heat resistance) of the cellulose ester as compared with the cellulose acetate. For example, JP 2003-221455 A (Patent Document 1) contains a cellulose ester having a ratio (Mw / Mn) of weight average molecular weight Mw to number average molecular weight Mn of 1.8 to 3.5, A cellulose ester film having 10 or less specific bright spot foreign substances is disclosed. In this document, as the cellulose ester, cellulose triacetate, cellulose diacetate, and cellulose acetate propionate are preferable, and the total substitution degree of acetyl group and substitution degree of propionyl group and / or butyryl group is 2.4 or more and 3 It is preferable that the total of the substitution degree of the acetyl group and the substitution degree of the propionyl group and / or butyryl group is 2.5 or more and 2.85 or less, and the substitution degree of the acetyl group is 1.4. It is described that it is preferably 2.0 or less and that the moisture content of the film can be reduced and the heat and moisture resistance can be improved by increasing the ratio of the degree of substitution of propionyl group or butyryl group.

  Japanese Patent Laid-Open No. 10-45804 (Patent Document 2) uses cellulose as a catalyst to esterify cellulose with acetic acid or acetic anhydride and an organic acid having 3 or more carbon atoms or an anhydride thereof. A method for producing a mixed acid ester of cellulose having a specific substitution degree ratio in which a hydroxyl group is substituted with an acetyl group and an acyl group having 3 or more carbon atoms, wherein the maximum temperature of the esterification reaction is 35 to 50 A method for producing a mixed acid ester of cellulose that is adjusted to ° C. is disclosed. In the method of this document, a cellulose mixed acid ester having a relatively high average degree of polymerization can be obtained.

  On the other hand, in recent years, liquid crystal display devices represented by high-definition broadcasting and the like have been put into practical use and developed for high image quality and high definition, and accordingly, optical films (for polarizing plates) used in liquid crystal display devices, etc. For protective films and the like, there is an increasing demand for reduction of foreign substances contained in the film.

  As foreign substances contained in the cellulose ester film, those caused by the additive used, those caused by dust mixed in the production process, and non-acetylated or low acetylated cellulose ester fibers contained in the cellulose ester And what to do. Among these, those caused by dust mixed in the manufacturing process become optical defects as so-called black foreign matters. In addition to the black foreign matter, there is also a bright spot foreign matter.

  For example, Patent Document 1 discloses that a bright spot foreign matter exists as described above. A bright spot foreign material is a cellulose ester film placed between two polarizers placed in an orthogonal state (crossed Nicols), illuminated from the outside of one polarizer, and observed with a microscope from the outside of the other polarizer. Then, light leaks at the foreign matter portion and appears as a bright spot. Furthermore, Japanese Patent Application Laid-Open No. 2003-213004 (Patent Document 3) discloses a bright spot foreign matter as a foreign matter, a white foreign matter by reflection of irradiation light, and a so-called grainy foreign matter observed as a light emission phenomenon in a crossed Nicol state. Optical defects that are distinct from the above are also pointed out.

  Among the above-mentioned foreign matters, black foreign matters and the like are relatively easy to take countermeasures by cleaning the manufacturing process. On the other hand, the removal of foreign matters with a small particle diameter (fine foreign matters) such as bright spot foreign matters and grainy foreign matters has become increasingly important in recent studies in applications such as optical films.

  As described above, in the cellulose ester, the problem of the fine foreign matter as described above has attracted much attention and its improvement has been demanded. In particular, cellulose acetate propionate (CAP) other than cellulose acetate, cellulose acetate butyrate (CAB). When a cellulose mixed acid ester such as) is produced, unreacted cellulose or cellulose ester having a low degree of substitution is likely to occur, and the problem of fine foreign matters such as bright spot foreign matters and grainy foreign matters is further increased. . In addition, it is generally known that cellulose mixed acid ester is liable to generate foreign substances such as unreacted cellulose and cellulose ester having a low degree of substitution. For example, “Fiber-based resin (written by Kazuo Uta and Jun Marusawa, published daily) (Published by Kogyo Shimbun) (Non-patent Document 1) describes that when a propionyl group is to be introduced into cellulose, “as a catalyst, sulfuric acid is usually used, but the catalyst is the same as in the production of acetate butyrate. The effect is weak and the reaction is slow, and the disintegration of cellulose is remarkable, so the pretreatment activation is sufficient to obtain a propionate with uniform solubility, few unreacted fibers, and high viscosity. It is necessary to reduce the amount of acidified mixed acid ". Then, after completion of ripening, the sulfuric acid remaining with magnesium acetate is completely neutralized, then filtered to remove unreacted fibers and foreign matters, and then precipitated, washed, stabilized, dehydrated, dried and pulverized to obtain a product. The precipitation and washing are also more difficult than in the case of acetylcellulose because the bath is hydrophobic like the acetate butyrate. "

  Thus, in cellulose acetate butyrate and cellulose acetate propionate, it is common technical knowledge that unreacted fibers remain, and attempts have been made to reduce this. For example, in order to improve the reactivity of a fatty acid having 3 or more carbon atoms and catalytic sulfuric acid in esterification, for example, “CJ Malm: Svendk Kem. Tidskr, 73, 10 (1961)” (Non-patent Document 2) ) In the pretreatment, the cellulose is activated with acetic acid and then treated with butyric acid containing a small amount of sulfuric acid to sorb the sulfuric acid on the cellulose and then esterify, and the ratio of the ester mixed acid to the cellulose is made as small as possible. Techniques for increasing acid anhydride and catalyst sulfuric acid concentrations are described. US Patent No. 2,097,954 (Patent Document 4) proposes a pretreatment step in which cellulose is activated with acetic acid and then treated with butyric acid containing a small amount of sulfuric acid in cellulose mixed fatty acid ester having a high degree of acetylation. ing. However, in these methods, when used for molded articles or paint binders, which are conventional applications, it is possible to reduce the amount of foreign matter sufficiently if the dope is filtered. Even among optical films, they could not be used as optical films used for liquid crystal display devices.

  In addition, in US Pat. No. 2,250,201 (Patent Document 5), in cellulose mixed fatty acid esters having a high degree of substitution of propionyl or butyryl group, these mixed fatty acid esters are hydrophobic, so that bound sulfuric acid is difficult to be removed. A technique is disclosed in which dilute acetic acid is mixed at the time of water addition and heated to release bound sulfuric acid.

  However, these methods still cannot reduce foreign matters such as unreacted cellulose.

  Furthermore, in a cellulose mixed fatty acid ester, it is difficult to accurately remove such fine foreign matters by a usual method such as filtration. That is, in general, when a cellulose ester film is produced by a solution casting method, since an undissolved substance is usually present in the dope, it is common to perform a filtration treatment. In such a filtration, since the cellulose ester solution has a high viscosity, a filter press or a disk-shaped metal filter having a large filtration area is used as a filter medium. Since such a filter medium raises a pressure by capture | acquisition of an undissolved substance, it is necessary to replace | exchange regularly. At the time of replacement, it is necessary to remove the cellulose ester solution in the filter once. In recent years, as described above, the required quality for cellulose ester films has become more stringent, and in particular, as a method for removing cellulose ester having a non-acetylated or low acetylated degree, a conventional cellulose ester dissolved in a solvent is dissolved. It is difficult to obtain a target quality simply by filtering the liquid, that is, the dope liquid, and it has become necessary to remove foreign substances having a smaller particle diameter.

  Therefore, various filtration methods have been reported in order to remove such minute foreign matters. For example, in Patent Document 1, a dope solution obtained by dissolving a cellulose ester in a solvent is subjected to a filtration process of two or more stages (for example, the first stage is a filtration process using a filter paper, and the second stage is a filtration process using a metal filter. A method of forming a film through a certain filtration step) is disclosed. Further, in Patent Document 3, in the method for filtering a cellulose ester solution using cellulose filter paper, the cellulose filter paper has a minimum particle diameter of 3 μm or less and 0.5 μm or more of the retained particle diameter, and has a thickness. A filtration method is disclosed that is 3.5 to 4.5 mm and has a drainage time of 150 to 350 seconds.

Furthermore, in Japanese Patent Application Laid-Open No. 11-254466 (Patent Document 6), the number of bright spots having a diameter exceeding 0.05 mm is 0 per 1 cm ² , and the diameter is 0.01 to 0.05 mm. A cellulose ester film in which the number of bright spots in the range is 500 or less per cm ² is disclosed. In this document, in order to remove insoluble matters, a filter medium having an absolute filtration accuracy in the range of 0.005 mm or less (particularly 0.001 to 0.005 mm) is preferable. Thus, filtration is performed with a filter medium having high filtration accuracy. In other words, it is described that minute insoluble matters such as cellulose that has not been esterified and impurities can be effectively removed.

  Furthermore, in Japanese Patent Application Laid-Open No. 2003-326112 (Patent Document 7), in a method for filtering a polymer solution in which a polymer is dissolved in a solvent, at least one insoluble substance among insoluble substances contained in the polymer solution is disclosed. JP-A-2004-13897 (Patent Document 8) discloses a polymer solution filtration method characterized by using a filter medium having pores having a pore size larger than the size of the product. In the dope filtration method for removing foreign matter in a dissolved dope by filtration, the dope for filtering the foreign matter in the dope by arranging two or more filter units having a sintered metal filter having the same pore diameter in series A filtration method is disclosed.

  However, with respect to unreacted fibers that are bright defects of bright spot foreign matters and grainy foreign matters due to unreacted fibers, the removal accuracy is not sufficient even with the methods of these documents. This is because if the opening of the filter is reduced in order to filter out minute foreign matter, the filtration efficiency may decrease, and a cellulose mixed acid ester having a high degree of polymerization cannot be obtained, and the filtration efficiency is allowed to decrease. Even if it did, the bright spot foreign material and grainy foreign material which pass a filter medium became a problem.

  Therefore, the importance of suppressing the production of foreign substances such as unreacted cellulose and low-substituted cellulose ester has been increasing from the stage of cellulose mixed acid ester as a raw material.

Furthermore, not only to reduce unreacted cellulose, but also to reduce the amount of alkaline earth metals and alkali metals in order to improve the peelability at the time of casting in the cellulose ester film manufacturing process, and therefore, It is also required to reduce the amount of sulfuric acid contained in the cellulose ester. In addition, in order to provide wet heat resistance stability, it is necessary to reduce the amount of sulfuric acid (particularly bound sulfuric acid) contained in the cellulose ester. Then, it is necessary to add an alkaline earth metal and an alkali metal corresponding to the amount of sulfuric acid, and the amount of the alkaline earth metal and the alkali metal cannot be simply reduced. Furthermore, considering the strength of the film, there is a minimum degree of polymerization, and there is a need for a technique for reducing the amount of sulfuric acid and reducing unreacted cellulose while ensuring the degree of polymerization.
JP 2003-221455 A (claims, paragraph numbers [0025] [0026]) Japanese Patent Laid-Open No. 10-45804 (Claims) JP 2003-213004 A (claim, paragraph number [0002]) US Patent No. 2,097,954 (Claims) US Pat. No. 2,250,201 (Claims) JP 11-254466 A (claims, paragraph number [0015]) JP 2003-326112 A (Claims) JP 2004-1113897 A (Claims) “Fiber-based resin” (Kazuo Uta, Jun Marusawa, published by Nikkan Kogyo Shimbun, p103) “C.J. Malm: Svendk Chem. Tidskr, 73, 10 (1961)”

  Accordingly, an object of the present invention is to provide a high-purity cellulose mixed acid ester (cellulose acetate propionate and the like) having a remarkably small content of fine foreign matters such as unreacted cellulose and a method for producing the same.

  Another object of the present invention is to provide a cellulose mixed acid ester having excellent heat resistance and a high degree of polymerization, and a method for producing the same, as well as a cellulose mixed acid ester, which can reduce the content of fine foreign matters to a remarkably high level. There is to do.

  Another object of the present invention is to provide a cellulose ester film capable of achieving both wet heat stability and optical properties at a high level.

  As a result of earnest studies to achieve the above-mentioned problems, the present inventors have made a cellulose mixed acid ester through a series of steps such as an acylation step, an aging (deacylation) step, and a precipitation treatment step (precipitation step). By adjusting the acylation conditions (for example, acylation time and acylation temperature), aging conditions (for example, multi-step neutralization, etc.), precipitation treatment conditions, etc., the cellulose mixed acid ester (cellulose acetate) at a remarkably high level. It was found that the content of non-soluble components (fine foreign matters) in propionate, etc.) can be reduced, and further, the amount of residual sulfuric acid can be reduced, and a cellulose mixed acid ester excellent in wet heat stability can be obtained. Was completed.

  That is, the cellulose mixed acid ester of the present invention (hereinafter sometimes simply referred to as mixed acid ester, cellulose ester, etc.) has an insoluble component content of 0 to a mixed solvent of methylene chloride / methanol (weight ratio) = 9/1. .12% by weight or less. The total average substitution degree of such a cellulose mixed acid ester may be about 2.6 to 2.99, and the content of the insoluble component may be 0.07% by weight or less.

The cellulose mixed acid ester may be a cellulose mixed acid ester having at least an acetyl group. For example, an aliphatic acyl group other than an acetyl group and an acetyl group (C _3-6 alkylcarbonyl group such as propionyl group and butyryl group) It may be a cellulose mixed acid ester having The above-mentioned cellulose mixed acid ester having an acetyl group includes (i) a total average substitution degree of 2.6 to 2.99, an average substitution degree of acetyl group of 1.5 or more, an acetyl group and an aliphatic C ₃₋ Cellulose acetate aliphatic C _3-6 acylate having a ratio (molar ratio) to ₆ acyl groups of the former / the latter = 95/5 to 60/40, (ii) the total average substitution degree is 2.6 to 2.99, acetyl Cellulose acetate aliphatic having an average group substitution degree of less than 1.5 and a ratio (molar ratio) of acetyl group to aliphatic C _3-6 acyl group of the former / the latter = 30/70 to 3/97 C _3-6 acylate and the like are included.

  In the present invention, a cellulose mixed acid ester having a relatively high degree of polymerization can be obtained even if the residual sulfuric acid amount is reduced. For example, in the cellulose mixed acid ester, the residual sulfuric acid amount (by weight) is 300 ppm or less, and the viscosity The average degree of polymerization may be about 200 to 400.

In the cellulose mixed acid ester of the present invention, the cellulose acetate aliphatic C _3-6 having a non-soluble component content of 0.07% by weight or less and satisfying the following (i) or (ii): Includes acylate.

(I) The total average degree of substitution is 2.6 to 2.97, the average degree of substitution of acetyl groups is 1.8 or more, and the ratio (molar ratio) of acetyl groups to aliphatic C _3-6 acyl groups is the former / the latter = 90 / 10-70 / 30, viscosity average degree of polymerization is 250-350, and residual sulfuric acid amount (weight basis) is 50-200 ppm.
(Ii) The total average substitution degree is 2.6 to 2.97, the average substitution degree of the acetyl group is 1 or less, and the ratio (molar ratio) between the acetyl group and the aliphatic C _3-6 acyl group is the former. / The latter = 20/80 to 5/95, the viscosity average degree of polymerization is 250 to 350, and the amount of residual sulfuric acid (weight basis) is 50 to 200 ppm.
The cellulose mixed acid ester of the present invention comprises an acylation step (i) in which cellulose is acylated with an acylating agent corresponding to the cellulose mixed acid ester in the presence of a sulfuric acid catalyst, and an aging step in which the cellulose is aged in the presence of a sulfuric acid catalyst ( and ii). In particular, in the present invention, the cellulose mixed acid ester is prepared while suppressing (or reducing) the production of residual sulfuric acid that can be an insoluble component without reducing the reactivity (ester reactivity, etc.) of the cellulose mixed acid ester. As a result, the content of the insoluble component is reduced to a remarkably high level as described above. For example, in the acylation step (i), when the time from the start of acylation to the stop of acylation is X, and the time from the time when the maximum temperature is reached in the acylation step to the stop of acylation is Y , [Y / X] × 100 may be acylated so as to be 40 to 85. In a typical method, in the acylation step (i), in the presence of 2 to 12 parts by weight of a sulfuric acid catalyst with respect to 100 parts by weight of cellulose and at a maximum temperature of 30 to 50 ° C., the value [Y / X] × 100 May be acylated so as to be 45 to 65. Such adjustment of the acylation time (and the amount of sulfuric acid used) is effective in suppressing the formation of residual sulfuric acid, and in particular, a cellulose mixed acid ester having an average degree of substitution of acetyl groups of 1.5 or more is produced. It is particularly useful for.

  In the aging step (ii), the base may be continuously added from the start of the reaction to the stop of the reaction, or the base may be added intermittently at least three times. Such a method is effective for reducing the residual sulfuric acid, and is particularly useful for producing a cellulose mixed acid ester having an average degree of substitution of acetyl groups of less than 1.5. Furthermore, the manufacturing method may include a step of adding an organic acid to the dope containing a cellulose mixed acid ester after the aging step (ii) is stopped, and separating the cellulose mixed acid ester by precipitation treatment. Such a precipitation treatment method is effective in reducing residual sulfuric acid, and in particular, by combining with the above-mentioned method of continuously adding a base or intermittently adding a base at least three times. Residual sulfuric acid can be efficiently reduced.

  The present invention also includes a cellulose ester film composed of the cellulose mixed acid ester. Such a cellulose ester film may be an optical compensation film for a liquid crystal display device or a protective film for a polarizing plate.

In the present specification, “bound sulfuric acid” means sulfuric acid bound to cellulose (a bound sulfuric acid component bound as a sulfate group such as a sulfate ester or a sulfonate group). “Total sulfuric acid” is a generic term for bound sulfuric acid, free sulfuric acid, etc., and may be referred to as “residual sulfuric acid”, “residual sulfuric acid component”, or simply “sulfuric acid”. In addition, “residual sulfuric acid” means (i) a reaction system that does not include sulfuric acid corresponding to sulfate (or precipitated sulfate) neutralized by addition of a base, and means free sulfuric acid and bound sulfuric acid. (Ii) When used for the cellulose ester as a product, the meaning includes sulfuric acid (H ₂ SO ₄ ) corresponding to bound sulfuric acid, free sulfuric acid, sulfate neutralized by addition of a base, and the like. Use. In addition, when the cellulose mixed acid ester is washed, the residual sulfuric acid contains almost no free sulfuric acid and sulfate, and often contains bound sulfuric acid. Further, in this specification, “initiation of acylation (or acylation reaction)” refers to cellulose (cellulose that may be activated) and an acylating agent (for example, acyl such as acetic anhydride or propionic anhydride). Means the point of contact with the carboxylic anhydride corresponding to the group), and “stopping acylation (or acylation reaction)” is a deactivation agent (such as water) to deactivate excess acylating agent. ) Is added.

  In the present specification, “ripening” or “ripening step” refers to acylating cellulose and then adding water, an aqueous solution (for example, an aqueous solution with water and organic carboxylic acids) and / or a base to the acylation reaction system. (Usually a base in the form of an aqueous solution) to decompose the acylating agent while allowing water to exist in the reaction system, and in the presence of a sulfuric acid catalyst (or residual sulfuric acid catalyst), deacylation and desulfation esterification Means to do. That is, in the “ripening reaction” in the ripening step, it seems that the deacylation reaction and the desulfurization ester reaction are proceeding competitively. Therefore, in this specification, “deacylation” and “desulfurization esterification” may be used in the same meaning as “aging”, and “deacylation and desulfation esterification” may be used. There is.

  Further, in this specification, “start of ripening reaction” or “start of reaction of ripening step” means adding water or a base (or an aqueous solution of a base) and ripening (deacylation and desulfation in the presence of water). Means to initiate esterification). The “ripening reaction” is often started after the acylation reaction is stopped or after the acylation reaction is stopped and the temperature is raised to a predetermined aging temperature, and “stopping the acylation reaction” and “starting the aging reaction”. May be used for consent. Further, “stopping the ripening reaction” or “stopping the reaction of the ripening step” means that the sulfuric acid remaining in the reaction system (residual sulfuric acid) is completely neutralized with an excessive amount of base. Further, “raw cellulose” means raw cellulose before acylation, and the amount of sulfuric acid catalyst added for acylation usually does not fluctuate until the base is added and is not lost.

  In the present invention, fine adjustment of unreacted cellulose and the like can be achieved by precisely adjusting acylation conditions (for example, acylation time and acylation temperature), aging conditions (for example, multi-step neutralization, etc.), precipitation treatment conditions, and the like. A highly pure cellulose mixed acid ester (such as cellulose acetate propionate) can be obtained with an extremely low content of foreign substances. Further, in the method of the present invention, the content of fine foreign matters can be reduced to a remarkably high level even in the case of a cellulose mixed acid ester having a low ester reactivity compared to cellulose triacetate and the like, and it is difficult to reduce the amount of residual sulfuric acid. A cellulose mixed acid ester having excellent properties and a high degree of polymerization can be obtained. Furthermore, in the film of the present invention, although it is a cellulose mixed acid ester, there is little residual sulfuric acid and fine foreign matters are reduced at a remarkably high level, so that the heat and humidity resistance (wet heat stability) and optical properties are improved. Can be achieved at a high level.

(Cellulose mixed acid ester)
In the cellulose mixed acid ester of the present invention, it is difficult to separate and remove from the cellulose mixed acid ester by filtration or the like, and the content of fine foreign matters (fine foreign matters) that can be optical defects is reduced to a significantly high level. Has been. In the present specification, such an insoluble component (fine foreign matter) is defined as a component (insoluble component) that does not dissolve in a mixed solvent of methylene chloride / methanol (weight ratio) = 9/1. To do. The non-soluble component is not particularly limited as long as it does not dissolve in the mixed solvent, but it is usually mainly derived from unreacted cellulose that has not reacted in the synthesis of cellulose mixed acid ester, low-substituted cellulose ester, and residual sulfuric acid. And other by-products derived from cellulose as a raw material, such as, for example, a bond-formed product in which cellulose mixed acid esters are bound via bound sulfuric acid and a metal component (such as calcium). Of these, the non-soluble component is mostly composed of unreacted cellulose and low-substituted cellulose ester. Among such undissolved components, foreign matters derived from residual sulfuric acid can be reduced by reducing the amount of sulfuric acid used as a catalyst, but it is easy to by-produce unreacted cellulose, low-substituted cellulose esters, and the like. Conversely, if the amount of sulfuric acid used as a catalyst is increased in order to reduce unreacted cellulose and the like, the residual sulfuric acid cannot be reduced, and foreign matters derived from the residual sulfuric acid are easily produced as a by-product. Further, if the esterification time is lengthened, the unreacted cellulose is reduced, but the polymerization degree of the cellulose mixed acid ester is lowered. Therefore, in the present invention, as described later, acylation conditions (for example, acylation time and acylation temperature), aging conditions (for example, multi-step neutralization, etc.), precipitation treatment conditions, etc. are precisely adjusted, and non- A cellulose mixed acid ester having a remarkably low content of soluble components is obtained.

  The content (content ratio) of the insoluble component of the cellulose mixed acid ester of the present invention may be 0.12% by weight or less (for example, about 0 to 0.11% by weight), for example, 0.10% by weight. % Or less (for example, about 0 to 0.09% by weight), preferably 0.07% by weight or less (for example, about 0.0001 to 0.06% by weight), more preferably 0.05% by weight or less (for example, 0.0005 to 0.04% by weight), in particular 0.03% by weight or less (for example, about 0.001 to 0.025% by weight) and 0.02% by weight or less [for example, 0 to 0.15%. It is also possible to set it to about 0.01% by weight (for example, about 0 to 0.05% by weight).

  In addition, content of the said insoluble component can be measured as follows, for example. A solution in which the cellulose mixed acid ester is dissolved at a ratio of 1% by weight in the mixed solvent (methylene chloride / methanol (weight ratio) = 9/1 mixed solvent) (however, insoluble components are not dissolved). Is filtered using a glass filter having a filter portion having a predetermined pore size (for example, a product name “G-4” equivalent product manufactured by Mutual Rikagaku Glass Mfg. Co., Ltd.), and deposits adhering to the filtration residue ( In order to wash the dope), the filter portion is washed with the mixed solvent, and then the glass filter containing the filtration residue is dried to a constant weight (constant weight). Then, the weight of the glass filter before and after filtration was measured, the weight of the glass filter after filtration (after filtration, washing and drying) was X (g), the weight of the glass filter before filtration was Y (g), and the solution used for filtration When the dry weight of the cellulose mixed acid ester is Z (g), the content of the insoluble component is calculated by the following formula.

  Content of non-soluble component = [(XY) / Z] × 100 (% by weight).

The cellulose mixed acid ester of the present invention is a cellulose ester having different acyl groups. Examples of the acyl group include an aliphatic acyl group [eg, a formyl group, an alkylcarbonyl group (eg, a C _2-20 alkylcarbonyl group such as an acetyl group, a propionyl group, a butyryl group, a pentanoyl group, a hexanoyl group, a heptanoyl group, Preferably a C _2-6 alkylcarbonyl group, more preferably a C _2-4 alkylcarbonyl group), a cycloalkylcarbonyl group (eg, a C _3-8 cycloalkylcarbonyl such as a cyclopentylcarbonyl group, a cyclohexylcarbonyl group, etc.)], An aromatic acyl group [an arylcarbonyl group (such as a C _6-10 arylcarbonyl group such as benzoyl group, phthaloyl group)] and the like.

The cellulose mixed acid ester is a cellulose ester having a combination of at least two different acyl groups (for example, 2 to 10, preferably 2 to 5, more preferably 2 to 3, particularly 2) among such acyl groups. I just need it. Typical combinations of different acyl groups include, for example, combinations of aliphatic acyl groups [for example, acetyl group and other aliphatic acyl groups (for example, propionyl group, butyryl group, hexanoyl group, cyclohexylcarbonyl group, etc. at least one) a combination of, a combination of an aliphatic acyl group and aromatic acyl group [e.g., C _2-6 alkylcarbonyl group (such as acetyl group) and an aromatic acyl group of an aliphatic C _3-7 acyl group (A combination with a benzoyl group and the like)] and the like.

Preferred cellulose mixed acid esters include cellulose mixed acid esters having at least an acetyl group [that is, cellulose acetate acylates having at least an acetyl group and another acyl group (acyl group other than acetyl group)], for example, an acetyl group and other Cellulose acetate aliphatic acylates having aliphatic acyl groups (for example, cellulose acetate aliphatic C _3-10 acylates such as cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate propionate butyrate, cellulose acetate hexanoate) , Preferably cellulose acetate aliphatic C _3-6 acylate) and the like, and cellulose acetate propionate and cellulose acetate butyrate are particularly preferable.

  In the cellulose mixed acid ester of the present invention, the total average substitution degree (total average substitution degree of acyl groups substituted at the 2, 3 and 6 positions of glucose units constituting cellulose) can be selected within a range that can provide sufficient moisture resistance. 3 or less (for example, about 2.5 to 3), for example, 2.55 to 2.99 (for example, 2.6 to 2.99), preferably 2.60 to 2.98 ( For example, it may be 2.6 to 2.97), more preferably 2.65 to 2.97, particularly about 2.7 to 2.96 (for example, 2.80 to 2.95).

  In the cellulose mixed acid ester of the present invention, the proportion of different acyl groups can be appropriately selected depending on the application. For example, in a cellulose mixed acid ester (cellulose acetate acylate) having at least an acetyl group, the average substitution degree of the acetyl group is, for example, 0.01 to 2.9 (for example, 0.05 to 2.8), preferably 0. .1 to 2.7, more preferably 0.2 to 2.5, particularly about 0.3 to 2.4. In particular, in cellulose acetate acylate, when (i) the degree of substitution of the acetyl group is relatively large, the average degree of substitution of the acetyl group is from 1.5 or more (for example, about 1.6 to 2.95). For example, 1.7 or more (for example, about 1.75 to 2.9), preferably 1.8 or more (for example, about 1.9 to 2.7), more preferably 2.0 or more (for example, about 2.1 to 2.6), especially 2.2 or more (for example, about 2.3 to 2.5). (Ii) When the degree of substitution of the acetyl group is relatively small, acetyl The average degree of substitution of the group can be selected from the range of less than 1.5 (for example, about 0.01 to 1.45), for example, 1.4 or less (for example, about 0.02 to 1.3), preferably 1 or less (for example, about 0.05 to 0.8), more preferably 0.6 or less (E.g., about 0.1 to 0.4) may in particular 0.3 or less (e.g., about 0.15 to 0.25).

  It should be noted that the smaller the degree of substitution of the acetyl group, that is, the higher the degree of substitution of other acyl groups such as propionyl group and butyryl group, the more difficult it is to reduce the amount of insoluble components and residual sulfuric acid. is there. In the present invention, even if such a cellulose mixed acid ester having a relatively low degree of substitution with an acetyl group is adjusted, the acylation conditions, aging conditions, precipitation treatment conditions, etc. are adjusted at a high level as described later. The content of the soluble component can be reduced.

In the cellulose acetate acylate, the ratio (molar ratio) between the acetyl group and other acyl groups (for example, aliphatic C _3-6 acyl group) is, for example, the former / the latter = 99/1 to 1/99. , Preferably 95/5 to 5/95, more preferably about 90/10 to 7/93. In particular, in cellulose acetate acylate, when (i) the degree of substitution of acetyl groups is relatively large, the ratio (molar ratio) of acetyl groups to other acyl groups is the former / the latter = 99/1 to 50/50. , Preferably 95/5 to 60/40, more preferably about 90/10 to 70/30. (Ii) When the degree of substitution of the acetyl group is relatively small, the acetyl group and other acyl groups The ratio (molar ratio) to the former / the latter = 50/50 to 1/99 (for example, 55/45 to 2/98), preferably 40/60 to 3/97 (for example, 30/70 to 3 / 97), more preferably about 20/80 to 5/95 (for example, 25/75 to 10/90).

  In cellulose acetate acylate, the average substitution degree of other acyl groups (or the total average substitution degree of other acyl groups) is, for example, 0.05 to 2.95 (for example, 0.1 to 2.9). ), Preferably 0.2 to 2.8, more preferably 0.3 to 2.7, and particularly about 0.4 to 2.6. In particular, in cellulose acetate acylate, when (i) the degree of substitution of acetyl groups is relatively small (that is, the degree of substitution of other acyl groups is relatively large), the average degree of substitution of other acyl groups is 1 .2 or more (for example, about 1.25 to 2.95), 1.5 or more (for example, about 1.6 to 2.93), preferably 1.8 or more (for example, 2.0) To about 2.9), more preferably 2.3 or more (for example, about 2.4 to 2.85), particularly 2.6 or more (for example, about 2.65 to 2.8), (Ii) When the degree of substitution of the acetyl group is relatively large, the average degree of substitution of other acyl groups can be selected from a range of less than 1.5 (for example, about 0.05 to 1.45), and 1.4 Or less (for example, about 0.2 to 1.3), preferably 1.2 or less (for example, 0.4 to 1.1), more preferably 1.0 or less (for example, about 0.45 to 0.9), particularly 0.8 or less (for example, about 0.5 to 0.75). Good.

The degree of substitution (degree of acylation) can be measured by a conventional method. For example, the degree of acetylation (degree of acetylation) is a unit according to 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 weight and 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 mixed acid ester (cellulose acetate acylate and the like) of the present invention can be selected from the range of 100 or more (for example, 120 to 800), for example, 150 to 500, preferably 200 to 400, more preferably. It may be about 250 to 350 (for example, 270 to 330), particularly about 290 to 320. In particular, when the degree of acetyl substitution is relatively large, the viscosity average degree of polymerization of the cellulose mixed acid ester is, for example, a viscosity average degree of polymerization of 180 to 500, preferably 200 to 400, more preferably about 250 to 350. Also good. In the present invention, as will be described later, a cellulose mixed acid ester having a relatively high degree of polymerization and a low content of insoluble components can be obtained even if it is a cellulose mixed acid ester that is less esterified than cellulose acetate.

The viscosity average degree of polymerization can be measured by Uda et al.'S limiting viscosity method (Kazuo Uda, Hideo Saito, Journal of Textile Science, Vol. 18, No. 1, pages 105-120, 1962). In addition, a solvent can be selected according to the substitution degree etc. of cellulose mixed acid ester. For example, a cellulose mixed acid ester is dissolved in a mixed solution of methylene chloride / methanol = 9/1 (weight ratio) to prepare a solution having a predetermined concentration c (2.00 g / L), and this solution is injected into an Ostwald viscometer. Then, the time t (second) for the solution to pass between the lines of the viscometer at 25 ° C. is measured. On the other hand, with respect to the mixed solvent alone, the passage time t ₀ (seconds) is measured in the same manner as described above, and the viscosity average polymerization degree can be calculated according to the following formula.

η _rel = t / t ₀
[Η] = (lnη _rel ) / c
DS = [η] / (6 × 10 - 4)
(Where t is the solution passage time (second), t ₀ is the solvent passage time (second), c is the cellulose mixed acid ester concentration (g / L), η _rel is the relative viscosity, and [η] is the limit. Viscosity and DS indicate average degree of polymerization).

  When the cellulose mixed acid ester is synthesized using sulfuric acid as a catalyst, the cellulose mixed acid ester usually contains a remaining sulfuric acid component as described in “acetic acid fiber” (published by Wadano Motomaru Maruzen Co., Ltd.). Such residual sulfuric acid components include free, adsorbed, bound in the form of an ester (bound sulfuric acid), solid inorganic sulfate, and the like. Among these sulfuric acid components, in the case of a cellulose mixed fatty acid ester washed by a conventional method (industrial washing or the like), the adsorbed or liberated one is usually a very small amount. The solid inorganic sulfate may remain because it is greatly affected by precipitation conditions and the like. In the cellulose mixed acid ester subjected to the washing treatment, most of the remaining sulfuric acid is bound sulfuric acid. Such bound sulfuric acid is difficult to remove by ordinary filtration, washing, etc., and as described above, by binding ionic bonds with metal components, by-products of cellulose mixed acid esters are by-produced and not dissolved. It is preferable that the amount be as small as possible because it can be a sexual component (fine foreign matter) and lowers the wet heat stability. However, even if the amount of sulfuric acid used as a catalyst is simply reduced, as described above, unreacted cellulose, low-substituted cellulose ester and the like are likely to be formed, and thus the amount of insoluble components cannot be reduced.

  The residual sulfuric acid amount (weight basis) of the cellulose mixed acid ester of the present invention is selected from the range of 1000 ppm or less (for example, about 0 to 700 ppm) in order to maintain wet heat stability and efficiently suppress the content of insoluble components. For example, it may be 500 ppm or less (for example, about 10 to 400 ppm), preferably 300 ppm or less (for example, about 20 to 350 ppm), and more preferably 250 ppm or less (for example, about 50 to 200 ppm).

  In particular, in the present invention, when the substitution degree of the acetyl group is relatively large, the residual sulfuric acid amount (particularly, the binding sulfuric acid amount) of the cellulose mixed acid ester is, for example, 200 ppm or less (for example, about 0 to 180 ppm), preferably 150 ppm. It can be reduced to the following (for example, about 10 to 130 ppm), more preferably 120 ppm or less (for example, about 20 to 110 ppm), and particularly about 50 to 100 ppm. In the present invention, even when the degree of substitution of the acetyl group is reduced (when the degree of substitution of other acyl groups such as propionyl group is increased), the residual sulfuric acid amount of the cellulose mixed acid ester is, for example, 300 ppm or less. (For example, about 0 to 280 ppm), preferably 250 ppm or less (for example, about 20 to 220 ppm), more preferably 200 ppm or less (for example, about 30 to 200 ppm), particularly 50 to 200 ppm (for example, about 80 to 180 ppm) You can also

  As described above, the amount of residual sulfuric acid often varies depending on the presence or absence of washing, and may usually be the amount of residual sulfuric acid in a cellulose mixed acid ester purified by washing (and drying). Cleaning (cleaning treatment) is performed, for example, under industrial conditions [for example, heating (for example, heating at about 70 to 90 ° C.) and sufficient time (15 minutes to 36 hours (for example, 2 to 4 hours)). )))], Etc., and may be carried out to the extent that the washed solution does not contain (substantially contain) the sulfuric acid component.

The residual sulfuric acid amount is preferably measured by a so-called combustion trap method that is not easily affected by solid inorganic sulfate. That is, in this combustion trap method, the residual sulfuric acid amount (or total sulfuric acid amount) is obtained by baking the dried cellulose mixed acid ester in an electric furnace at about 1300 ° C. and trapping the sublimated sulfurous acid gas in a hydrogen peroxide solution having a predetermined concentration. Then, this can be measured by titrating with a predetermined concentration of base (for example, sodium hydroxide aqueous solution). The obtained measured value is an amount in terms of SO ₄ ²⁻ , and is obtained in ppm as the sulfuric acid content in 1 g of the cellulose mixed acid ester in an absolutely dry state. The residual sulfuric acid amount cannot be measured using the method described in ASTM D871.

  In order to improve heat resistance stability, cellulose mixed acid esters usually contain metal components such as alkali metals (potassium, sodium, etc.) and alkaline earth metals (calcium, magnesium, strontium, barium, etc.). . These metal components have a high affinity for the metal support, greatly impairing the peelability of the cast dry film from the metal support, and also impairing the optical properties of the film. Although this detailed mechanism is not clear, in the acylation of cellulose, residual sulfuric acid or bound sulfuric acid component (sulfuric acid ester group or sulfonic acid group) is generated by catalytic sulfuric acid, and cellulose mixed acid ester is derived from cellulose and has a carboxyl group. Have. Since sulfuric acid ester groups and sulfonic acid groups are acidic groups, if they remain, the hydrolysis of cellulose ester itself is promoted. Therefore, in order to impart stability (particularly heat stability), when a heat stabilizer for alkali metals or alkaline earth metals, especially a calcium component (calcium salt, etc.) is added, the carboxyl group together with the sulfonic acid group becomes a metal. Form salts (such as calcium salts). However, these metal salts (calcium salts and the like) increase the adhesion to the metal support and reduce the peelability. In addition, the metal component may act on the bound sulfuric acid as described above to produce a non-soluble component as a by-product. Therefore, it is useful to reduce the content of metal components (calcium components and the like) within a range that does not impair the stability.

  In the cellulose mixed acid ester of the present invention, the content (weight basis) of the calcium component is relatively small and can be selected from the range of about 5 to 130 ppm, for example, 10 to 110 ppm (for example, 15 to 100 ppm), preferably 20 to It may be about 90 ppm (for example, 25 to 80 ppm), more preferably about 25 to 70 ppm (for example, 30 to 60 ppm), particularly about 30 to 55 ppm (for example, 35 to 50 ppm). In the cellulose mixed acid ester of the present invention, the content (weight basis) of the magnesium component is, for example, 5 to 1000 ppm (for example, 10 to 900 ppm), preferably 10 to 800 ppm (for example, 20 to 500 ppm), and more preferably. It may be about 20 to 300 ppm (for example, 25 to 250 ppm), particularly about 20 to 200 ppm (for example, 25 to 150 ppm), and usually about 25 to 80 ppm.

Furthermore, the chemical equivalent ratio (Ca / SO ₄ ratio) of calcium to the chemical equivalent (chemical equivalent in terms of sulfuric acid) of residual sulfuric acid (or total sulfuric acid, particularly bound sulfuric acid component) is, for example, 0.05 to 5.0, Preferably it is 0.1 to 3, more preferably 0.15 to 2 (for example, 0.18 to 1.5), especially about 0.2 to 1 (for example, 0.2 to 0.8). Good.

  It should be noted that the metal content of calcium and the like is determined by atomic absorption spectrometry for the sample obtained after the cellulose mixed acid ester washed (and dried) is completely burned and then pretreated by dissolving ash in hydrochloric acid. It can be measured. The measured value is expressed in ppm as the metal content in 1 g of completely dry cellulose ester. In addition, it can also be measured by analyzing the absolutely dry cellulose mixed acid ester by microdigest wet decomposition apparatus (sulfuric acid decomposition), pretreatment with alkali melting and then using ICP-AES (dielectric coupling plasma emission spectroscopic analysis apparatus). .

The chemical equivalent ratio of calcium to the total sulfuric acid [Ca / SO ₄ ratio] is calculated from the calcium content and the sulfuric acid amount as the molar ratio of the Ca / SO ₄ ratio. That is, by dividing the sulfuric acid amount by 96, the sulfuric acid content in 1 g of cellulose ester can be expressed in mol units, and by dividing the calcium content by 40.1, calcium content in 1 g of cellulose ester can be expressed. The amount can be expressed in mol.

(Method for producing cellulose mixed acid ester)
The cellulose mixed acid ester is usually an acylation step (i) of acylating cellulose with an acylating agent corresponding to the cellulose mixed acid ester in the presence of a sulfuric acid catalyst, and a step of partially neutralizing the sulfuric acid catalyst as necessary. And a aging step (ii) [or deacylation step (ii)] in which aging (or hydrolysis, deacylation) is performed in the presence of a sulfuric acid catalyst (or residual sulfuric acid). it can. That is, for cellulose mixed acid esters, if necessary, the cellulose is activated (or pretreated), then acylated with an acylating agent in the presence of a sulfuric acid catalyst, and then the acylating agent is decomposed to stop esterification. In addition, it can be produced by partially neutralizing if necessary and aging (or hydrolysis, deacylation). More specifically, the cellulose mixed acid ester usually uses an activation treatment step in which cellulose is activated (activation step) with an organic carboxylic acid (acetic acid, propionic acid, butyric acid, etc.) corresponding to an acyl group, using a sulfuric acid catalyst. A triacyl ester (cellulose triacylate) is prepared by an acylating agent (acetic anhydride, propionic anhydride, butyric anhydride, etc., especially acetic anhydride) (acylation step), and an excess amount of acylating agent (especially acetic anhydride). The aging step (deacylation step or saponification / ripening step) that adjusts the acylation degree by aging (or hydrolysis, deacylation) is decomposed (or deactivated). Can be manufactured. In general, a cellulose mixed acid ester (or a purified cellulose mixed acid ester) is obtained through a precipitation treatment step (and a washing treatment step) in which a dope containing a cellulose mixed acid ester obtained through such an aging step is precipitated. As for a general method for producing a cellulose ester, “Wood Chemistry” (above) (Umeda et al., Kyoritsu Publishing Co., Ltd., 1968, pages 180 to 190) can be referred to.

  The cellulose mixed acid ester of the present invention is also aged in the presence of a sulfuric acid catalyst, in the presence of a sulfuric acid catalyst, in the presence of a sulfuric acid catalyst, and an acylation step in which cellulose is acylated with an acylating agent corresponding to the cellulose mixed acid ester. It can be manufactured through a series of steps including an aging step. In particular, in the present invention, the activation treatment step, acylation step, ripening (deacylation) step, precipitation treatment as described above are carried out in order to significantly reduce the content of insoluble components and improve the wet heat stability. In a series of processes through the process (precipitation process) etc., by precisely controlling or adjusting the acylation conditions in the acylation process, the aging conditions in the ripening process, the precipitation method, etc., and further combining these conditions, The cellulose mixed acid ester can be prepared. Specifically, in the method of the present invention, the above-mentioned conditions are adjusted precisely to suppress (or reduce) the formation of residual sulfuric acid, and the cellulose mixed acid ester is synthesized (prepared), thereby significantly reducing insoluble components. A cellulose mixed acid ester having a low content, high wet heat stability, and a relatively high degree of polymerization is efficiently produced.

  As the cellulose (pulp), wood pulp (conifer pulp, hardwood pulp) or cotton linter can be used. These celluloses may be used alone or in combination of two or more.

(Activation process)
The activation step is not always necessary, but is usually performed in order to efficiently carry out acylation (acetylation, propionylation, butylation, etc., particularly C _3-6 acylation such as propionylation). .

  The activation step can be performed, for example, by treating cellulose with an acid component. Examples of the acid component include organic acids (such as organic carboxylic acids corresponding to acyl groups of mixed acid esters such as acetic acid, propionic acid, and butyric acid, depending on the type and ratio of different acyl groups of the target cellulose mixed acid ester. ) And inorganic acids (particularly sulfuric acid). The acid component may be a hydrous component containing water. The acid component may be used alone or in combination of two or more.

  When the cellulose acetate acylate is produced, it may be activated with an acid component containing at least acetic acid [acetic acid alone, an acid corresponding to acetic acid and other acyl groups (such as propionic acid)].

  Although sulfuric acid can efficiently activate the acylation reaction, it may remain in the final product as bound sulfuric acid. Therefore, in the present invention, activation treatment with an organic acid is performed without using sulfuric acid. Also good.

  The amount of the acid component used (in the case of the water-containing component, the amount of the acid component not containing water) is 5 to 500 parts by weight, preferably 10 to 450 parts by weight, more preferably 20 to 400 parts by weight, based on 100 parts by weight of cellulose. It may be about a part. When at least acetic acid is used as the acid component, the amount of acetic acid used is 5 to 400 parts by weight, preferably 10 to 350 parts by weight, and more preferably about 20 to 330 parts by weight with respect to 100 parts by weight of cellulose. May be.

  When acetic acid and other organic acids are used, the ratio (weight ratio) between acetic acid and other organic acids (carboxylic acids corresponding to other acyl groups such as propionic acid and butyric acid) is the former / the latter = 99. / 1 to 10/90, preferably about 80/20 to 20/80. In particular, when a cellulose mixed acid ester having a high degree of acetyl substitution is obtained, the ratio (weight ratio) between acetic acid and other organic acids (carboxylic acids corresponding to other acyl groups such as propionic acid and butyric acid) is the former / the latter = It may be 99/1 to 50/50, preferably 95/5 to 60/40 (for example, 90/10 to 65/35), and more preferably about 85/15 to 70/30.

  The activation treatment is not limited as long as the cellulose and the acid component can be contacted (or mixed). For example, the method of spraying cellulose on the acid component, the method of immersing cellulose in the acid component, and the cellulose and acid using a mixer. Examples thereof include a method of mixing the components, a method of combining these, and the like. In a typical activation treatment, cellulose and an acid component may be mixed using a mixer such as a kneader. The activation treatment may be performed at room temperature, under cooling or under heating, and the heating temperature may be 35 to 80 ° C, preferably 40 to 70 ° C, and more preferably about 50 to 60 ° C. The activation treatment time (particularly the activation treatment time under heating) may be about 5 minutes to 3 hours, preferably about 10 minutes to 2 hours, and more preferably about 30 minutes to 1 hour.

(Acylation step (i))
In the acylation step, cellulose (or the activated cellulose) and an acylating agent are contacted (or mixed) for acylation.

  In the acylation step (i), sulfuric acid is usually used as a catalyst in many cases. In the acylation step (i), the amount of the sulfuric acid catalyst (hereinafter sometimes simply referred to as sulfuric acid) used as the acylation catalyst is usually 20 parts by weight or less of the sulfuric acid catalyst with respect to 100 parts by weight of cellulose (raw material cellulose). (For example, about 0.5 to 15 parts by weight), preferably 15 parts by weight or less (for example, about 0.8 to 12 parts by weight), more preferably 12 parts by weight or less (for example, 2 to 12 parts by weight), particularly You may carry out in presence of 10 weight part or less (for example, about 2-8 weight part). When sulfuric acid is used in the pretreatment (activation treatment), the sulfuric acid used in this pretreatment can also be used as an acylation catalyst. That is, when sulfuric acid is used in the pretreatment, the total amount of sulfuric acid added in the pretreatment step and the acylation step is the total amount of sulfuric acid as the acylation catalyst.

  In particular, when obtaining a cellulose mixed acid ester having a relatively high acetyl average substitution degree (for example, an average substitution degree of acetyl group of 1.5 or more), the amount of sulfuric acid catalyst used as an acylation catalyst in the acylation step (i) Can be selected from the range of about 0.5 to 15 parts by weight with respect to 100 parts by weight of cellulose (raw cellulose), usually 1 to 10 parts by weight (for example, 5 to 12 parts by weight), preferably 1 It may be 5 to 8 parts by weight, more preferably 2 to 5 parts by weight, particularly about 2.5 to 4.5 parts by weight.

The acylating agent may be an organic acid such as acetic acid (an organic acid corresponding to an acyl group) or an organic acid halide such as acetic acid chloride (an organic acid halide corresponding to an acyl group). Corresponding carboxylic anhydrides (C _2-6 alkanecarboxylic anhydrides such as acetic anhydride, propionic anhydride, butyric anhydride) are often used. These acylating agents (such as acid anhydrides) may be used alone or in combination of two or more. Depending on the degree of substitution of the desired cellulose mixed acid ester, etc., when an acid component corresponding to an acyl group (for example, acetic acid) is used in the activation treatment, this acid component is used as an acylating agent. You may use as it is. For example, when cellulose acetate acylate is obtained, acetic acid is used in the activation treatment step, and in the acylation step, an acylating agent (for example, propionic anhydride) corresponding to another acyl group is used without using acetic acid. May be used. Usually, an acyl group having 3 or more carbon atoms is less likely to bind to cellulose than an acetyl group. Therefore, in the acylation step, at least an acylating agent (propionic anhydride, butyric anhydride, etc.) corresponding to an acyl group having 3 or more carbon atoms is often used.

  The amount used (total amount) of the acylating agent (acetic anhydride, propionic anhydride, etc.) in the acylation step (esterification step such as acetylation step) is for example 100 parts by weight of cellulose (raw cellulose). For example, it may be about 150 to 700 parts by weight, preferably about 250 to 600 parts by weight, and more preferably about 300 to 500 parts by weight (for example, 350 to 450 parts by weight). Further, when producing the cellulose acetate acylate, the ratio of acylating agent corresponding to the acetyl group (especially acetic anhydride) and acylating agent corresponding to other acyl group (propionic anhydride, butyric anhydride, etc.) is The former / the latter (weight ratio) = 90/10 to 0/100, preferably 80/20 to 0/100, and more preferably about 70/30 to 0/100. In particular, when cellulose acetate acylate having a high degree of acetylation is obtained, the ratio between the acylating agent corresponding to the acetyl group and the acylating agent corresponding to the other acyl group is the former / the latter (weight ratio) = 90/10. -30/70, preferably 85 / 15-40 / 60, more preferably 70 / 30-50 / 50 (for example, 65 / 35-55 / 45).

The acylation step is usually often performed in a solvent (or diluent). Such a solvent (or diluent) may be a liquid acylating agent among the acylating agents, and may be an organic carboxylic acid (C _2-6 alkanecarboxylic acid such as acetic acid, propionic acid, butyric acid). Etc., in particular, an organic carboxylic acid corresponding to an acyl group) may be used as a solvent.

  In addition, since the acylation reaction is an exothermic reaction, components (acylating agent, sulfuric acid and, if necessary, a diluent) that are brought into contact with cellulose may be cooled in advance. The cooling temperature (precooling temperature) may be, for example, about −50 ° C. to 10 ° C., preferably −40 ° C. to 0 ° C., and more preferably about −30 ° C. to −10 ° C.

  As described above, acylation (acylation reaction) can be performed by contacting (or mixing) cellulose (or the activated cellulose) and an acylating agent (and sulfuric acid). The acylation reaction is usually an exothermic reaction, and the temperature in the reaction system rises to reach the maximum temperature and then falls. Specifically, the temperature in the reaction system increases with the start of the acylation reaction (or the start of contact between cellulose and the acylating agent (and sulfuric acid)), and reaches the maximum temperature. Usually, in the vicinity of this maximum temperature, most of the cellulose (for example, about 60 to 90%) is often acylated. After reaching this maximum temperature, acylation further proceeds, but the temperature in the system gradually decreases due to heat dissipation by the solvent and finally cellulose triacylate is produced. If the temperature in the reaction system rises too much, the acylation cannot be carried out uniformly, and if the temperature in the system becomes too low after reaching the maximum temperature, the acylation is difficult to proceed.

  Therefore, the acylation reaction can be usually performed while adjusting the reaction temperature. For example, the reaction temperature is -15 ° C to 60 ° C, preferably -10 ° C to 45 ° C, more preferably -5 ° C to 35 ° C (for example,- 5 ° C. to 30 ° C.), particularly in the temperature range of about −5 ° C. to 25 ° C. (for example, −5 ° C. to 20 ° C.). In particular, the reaction temperature from the time when the maximum temperature is reached until the acylation is stopped may be adjusted while heating as necessary, for example, 15 to 60 ° C., preferably 15 to 50 ° C., more preferably You may hold | maintain at about 20-45 degreeC.

  The maximum temperature (maximum temperature in the acylation step) is, for example, 15 to 60 ° C, preferably 15 to 55 ° C (for example, 20 to 45 ° C), and more preferably about 50 ° C or less (25 to 50 ° C). It may be. In particular, when a cellulose mixed acid ester having a relatively high acetyl average substitution degree (for example, an average acetyl group substitution degree of 1.5 or more) is obtained, the maximum temperature is 25 to 50 ° C, preferably 30 to 50 ° C, more preferably. May be about 35 to 45 ° C. In particular, when obtaining a cellulose mixed acid ester having a relatively small acetyl average substitution degree (for example, an average substitution degree of acetyl group of less than 1.5), the maximum temperature is 15 to 45 ° C, preferably 15 to 35 ° C. More preferably, it may be 30 ° C. or lower (for example, about 20 to 30 ° C.).

  The time from the start of acylation to the termination of acylation (total acylation time) may be, for example, 1 to 12 hours, preferably 1.5 to 10 hours, and more preferably about 2 to 8 hours. In particular, when a cellulose mixed acid ester having a high degree of acetyl substitution is obtained, the total ester time may be about 1 to 4 hours, preferably about 1.5 to 3 hours (for example, 2 to 3 hours).

  The reaction system after reaching the maximum temperature is preferably acylated uniformly to the inside of the cellulose, and in order to reduce bound sulfuric acid, it is preferable to increase the time until the acylation is stopped after reaching the maximum temperature. It is known. However, if the time until the acylation is stopped is too long, the degree of polymerization decreases, which may lead to a decrease in recovery rate in precipitation washing, a decrease in film strength, and a decrease in film productivity.

  Therefore, in the present invention, by uniformly adjusting the acylation temperature and the time (and the maximum temperature) from when the maximum temperature is reached to when the acylation is stopped, uniform acylation and cellulose combined with sulfuric acid are obtained. Acylation may be carried out while achieving both suppression of the formation of mixed acid esters. For example, when the total ester time is X (hours) and the time from when the maximum temperature is reached until the acylation stops (sometimes referred to as late acylation time) is Y (hours), the value [Y / X] × 100 (%) [ie, the ratio of the late acylation time to the total acylation time (%)] can be selected from the range of 30 to 95 (for example, 35 to 90). For example, the acylation may be performed so as to be 40 to 80), preferably 45 to 70 (for example, 45 to 65), and more preferably about 50 to 60. Such adjustment of the late acylation time is effective in reducing unreacted cellulose and suppressing the formation of residual sulfuric acid (particularly bound sulfuric acid) and adjusting the degree of polymerization to an appropriate one. It is useful for reducing the residual sulfuric acid of a cellulose mixed acid ester having a high degree of acetylation (for example, a cellulose mixed acid ester having an average substitution degree of acetyl group of 1.5 or more). When obtaining a cellulose mixed acid ester having a small degree of acetylation (for example, a cellulose mixed acid ester having an average substitution degree of acetyl group of less than 1.5), the value [Y / X] × 100 (%) is, for example, 40 to 95, preferably 50 to 90, and more preferably about 60 to 90.

  A cellulose ester (cellulose triacylate such as cellulose triacetate) can be produced by the acylation reaction as described above. Then, after reaching a predetermined acylation degree (usually total substitution degree 3), the acylation reaction is stopped, and the sulfuric acid component (or residual sulfuric acid component) is used as an aging catalyst (or a deacylation catalyst) for aging. (Deacylation or hydrolysis).

  As described above, the acylation reaction is stopped by adding water or a mixed solvent of water and an organic carboxylic acid (particularly, an organic carboxylic acid corresponding to an acylating agent) to the reaction system, In many cases, the addition of a solution (particularly an aqueous solution) deactivates an acylating agent (particularly, an excessive acylating agent such as acetic anhydride). In other words, the acylation reaction is stopped by using a deactivator (water, a mixed solvent of water and an organic carboxylic acid, an aqueous base solution, etc.) that can deactivate the excess acyl agent in the reaction system (acylation reaction system). It can carry out by adding to. When an aqueous base solution (especially an aqueous base solution) is used to stop the acylation reaction (deactivation of the acylating agent), an aqueous solvent (water) is added to the reaction system while decomposing (deactivating) the acylating agent. In addition, the content of the aqueous solvent (especially water) in the ripening step can be adjusted by the presence of water such as alcohol, in particular water), and the sulfuric acid catalyst can be partially neutralized (and further multistage neutralized). Such partial neutralization (and further, multi-stage neutralization) is effective in reducing bound sulfuric acid (particularly bound sulfuric acid generated in the aging step) because aging can be achieved while reducing the sulfuric acid catalyst. In particular, since acyl groups having 3 or more carbon atoms such as propionyl group and butyryl group are difficult to reduce residual sulfuric acid, such partial neutralization (particularly multistage neutralization) has a relatively high degree of acetyl substitution. In a small cellulose mixed acid ester (for example, a cellulose mixed acid ester having an average substitution degree of acetyl group of less than 1.5), it is effective in suppressing the formation of bound sulfuric acid. Therefore, in order to stop the acylation reaction (or after the acylation step), an aqueous base solution (particularly an aqueous base solution) is added to partially neutralize the sulfuric acid component (and stop the acylation reaction), which will be described later. The aging step (ii) may be used.

  Examples of the base include alkali metal compounds, alkaline earth metal compounds, Group 13 metal compounds of the periodic table, transition metal compounds, and ammonia. Examples of alkali metal compounds include hydroxides (sodium hydroxide, potassium hydroxide, etc.), carbonates (sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, etc.), organic acid salts (sodium acetate, potassium acetate, etc.) Etc.) and the like. Examples of alkaline earth metal compounds include hydroxides (magnesium hydroxide, calcium hydroxide, strontium hydroxide, barium hydroxide, etc.), carbonates (magnesium carbonate, calcium carbonate, calcium bicarbonate, etc.), organic acid salts, and the like. (Acetates such as magnesium acetate and calcium acetate). Examples of the periodic table Group 13 metal compound include hydroxides such as aluminum hydroxide, organic acid salts (such as acetates), and the like. Examples of the transition metal compound include transition metal hydroxides such as iron, copper, and zinc, and organic acid salts (acetates, etc.). These bases can be used alone or in combination of two or more. Of these bases, in partial neutralization, usually, at least one base selected from alkali metal compounds and alkaline earth metal compounds is often used. In particular, a base selected from a sodium compound, a potassium compound, a magnesium compound and a calcium compound (preferably at least a magnesium compound and / or a calcium compound) is often used.

The base may be used in the form of a granular material, but is usually used in the form of a liquid (for example, an aqueous solvent solution, particularly an aqueous solution). In an aqueous solution of a base (particularly an aqueous solution), as an aqueous solvent (an aqueous solvent constituting an aqueous solution of a base), as described above, C _1-4 alkanol such as water, alcohols (methanol, ethanol, propanol, isopropanol, etc.) Etc.). These aqueous solvents may be used alone or in combination of two or more. A preferred aqueous solvent is water (water alone). In the aqueous solution of the base, the concentration of the base can be appropriately adjusted according to the contents of sulfuric acid and the aqueous solvent in the aging step described later.

  The amount of the base used for partial neutralization can be adjusted according to the amount of sulfuric acid (residual sulfuric acid amount) in the aging reaction described later, and for example, with respect to 1 equivalent of sulfuric acid catalyst (prepared sulfuric acid catalyst) in the reaction system, It may be about 0.1 to 0.9 equivalent, preferably 0.2 to 0.8 equivalent, more preferably about 0.3 to 0.7 equivalent (for example, 0.3 to 0.6 equivalent).

  In addition, the addition of the deactivator may be performed all at once, may be performed continuously, or may be performed in a plurality of times. When adding continuously or divided into a plurality of times, the addition time (time required for addition) of the quenching agent is, for example, 1 minute to 2 hours, preferably 5 to 60 minutes, more preferably about 10 to 30 minutes. There may be.

(Aging process (ii))
The reaction system in which the acylation reaction is stopped (and partially neutralized) is subjected to the aging step (ii). In the aging step, cellulose acylate deacylation reaction and desulfurization ester reaction are performed.

  The aging step may be performed by newly adding another acid catalyst, but can usually be performed in the presence of the sulfuric acid catalyst used in the acylation step. The aging step is 20 parts by weight or less (for example, about 0.5 to 15 parts by weight), preferably 15 parts by weight or less (for example, 0.8 to 12 parts by weight) with respect to 100 parts by weight of cellulose (raw cellulose). Part), more preferably 10 parts by weight or less (for example, about 2 to 8 parts by weight).

  In particular, in the case of partial neutralization, the aging step is carried out in an amount of 5 parts by weight or less (for example, about 0.5 to 5 parts by weight) of sulfuric acid catalyst, preferably 4 parts by weight or less (100 parts by weight of cellulose (raw cellulose)) ( For example, about 0.8 to 3.5 parts by weight), more preferably 3 parts by weight or less (for example, about 1 to 2.2 parts by weight), particularly 2 parts by weight or less (for example, 1.2 to 1.8 parts by weight). Part).

  In the aging step (ii), water, an organic acid (for example, an organic acid corresponding to an acyl group such as acetic acid and propionic acid, particularly acetic acid), and an aqueous solvent such as a mixed solvent thereof are newly added for aging. You may go. The addition amount (use amount) of the aqueous solvent is, for example, about 50 to 800 parts by weight, preferably about 100 to 600 parts by weight, and more preferably about 300 to 500 parts by weight with respect to 100 parts by weight of cellulose (raw material cellulose). May be.

  In addition, when the acylation reaction is stopped (or when the aging step is started), as described above, even if the base (aqueous solution of the base) is added and partially neutralized, the remaining sulfuric acid component (particularly the bound sulfate group concentration) is reduced. It may not be reduced sufficiently. In particular, cellulose acetate acylate having a relatively low degree of acetyl substitution often cannot effectively reduce the amount of residual sulfuric acid even if it is partially neutralized by simply adding a base and ripened as it is.

  Therefore, in the present invention, in the ripening step, multi-stage neutralization (multi-stage neutralization), that is, a predetermined amount of base is continuously added to the reaction system, or intermittently (or stepwise) divided into multiple times. By adding to, the aging reaction (deacylation and desulfation ester reaction) may be carried out while neutralizing (partially neutralizing) continuously or multiple times. In the present invention, the amount of sulfuric acid in the reaction system is reduced by continuous or intermittent addition (or addition method), and sulfuric acid (sulfuric acid ester groups) introduced in the form of cellulose ester bonds is efficiently desorbed to form bound sulfuric acid. Can be reduced. That is, the deacylation reaction and the desulfurization reaction seem to be competitive reactions as described above. In such a reaction system, by continuously or intermittently adding a base, the elimination efficiency of residual sulfuric acid components (such as bound sulfuric acid) can be selectively increased, and the generated metal sulfate can be removed as a sulfuric acid component. . In particular, when an alkali metal compound or an alkaline earth metal compound is added, an insoluble sulfate metal salt (especially an alkaline earth metal sulfate such as magnesium sulfate) is generated in the reaction system, and the sulfuric acid component can be removed from the reaction system along with precipitation. .

  In addition, a base can be substantially continuously added by dripping or adding a base to a reaction system in a predetermined form (a liquid such as an aqueous solution, a form such as a powder) at a short interval. When the base is added in a plurality of times, the base is added at least 3 times (for example, 3 to 100 times), preferably 4 times or more (4 to 100 times), more preferably 5 times or more (5 to 5 times). 100 times). In order to ripen industrially advantageously, it is often at least 3 times, for example, 3 to 50 times (for example, 3 to 20 times), preferably about 4 to 25 times (4 to 20 times), It may be about 3 to 10 times. If the initial sulfuric acid catalyst (the sulfuric acid catalyst after the acylation reaction is stopped or at the start of ripening) is partially neutralized with a base and ripened (deacylated) twice or less, the amount of residual sulfuric acid (particularly the amount of bound sulfuric acid) ) Cannot be greatly reduced, and therefore it is difficult to reduce the content of insoluble components. In addition, the addition of the base can be performed from the start of the reaction to the stop of the reaction in the aging step. That is, the addition of a base for stopping the acylation reaction (or starting the aging reaction) and stopping the aging process is not included in the addition of the base in the aging process.

  The amount of the base for partial neutralization (addition of the base in the aging step) is 0.1 to 0.00 per partial neutralization (or neutralization operation) per partial equivalent of the sulfuric acid catalyst in the reaction system. It can be selected from a range of about 9 equivalents, preferably 0.2 to 0.8 equivalents, more preferably about 0.3 to 0.7 equivalents (for example, 0.3 to 0.6 equivalents). Furthermore, such partial neutralization can be repeated in the aging step.

  The addition mode of the base is not particularly limited, and an equal amount of base may be added continuously or intermittently to the reaction system, and the addition amount of the base is increased in the early stage of the ripening step (or ripening reaction). The amount of base added may be reduced continuously or intermittently (stepwise) as it reaches the end, the amount of base added is reduced early in the ripening process, and the amount of base added continuously or stepwise as it reaches later May be increased. In many cases, the amount of base added in the initial stage is larger than that in the latter stage of the ripening step. When the base is added in several steps, in a preferred embodiment, 10 to 90 equivalent% (preferably with respect to the initial sulfuric acid catalyst amount (residual sulfuric acid amount) in the first time (first addition of the base in the aging step). Is often neutralized by adding a base of about 25 to 90 equivalent%, more preferably 30 to 70 equivalent%, particularly 40 to 60 equivalent%) to carry out an aging reaction (first aging reaction). A base may be partially neutralized by adding about -80 equivalent% (for example, 45 to 55 equivalent%) of base, and an aging reaction (first aging reaction) may be performed. By adding such a base (or neutralization treatment), the initial amount of sulfuric acid can be reduced to about 10 to 75% by weight (preferably 30 to 70% by weight, more preferably 40 to 60% by weight). The maturing reaction can be carried out while desorbing.

  In the ripening step, a ripening reaction may be carried out by adding a base continuously or intermittently, but it is preferable to carry out the reaction while controlling the amount of residual sulfuric acid within a predetermined range. For example, the aging reaction can be carried out while controlling the amount of residual sulfuric acid [S] in the reaction system to the amount represented by the following formula (1).

[S] = 2 / [a (k × t + 4 / [S] ₀ )] (1)
(Wherein [S] is the amount of sulfuric acid (parts by weight) relative to 100 parts by weight of the raw material cellulose, [S] ₀ is the amount of sulfuric acid (parts by weight) relative to 100 parts by weight of the raw material cellulose before neutralization (before the addition of the base), and coefficient a 0.5 to 2, coefficient k is 0.01 to 0.1, t is the elapsed time (minutes) from the start of base addition in continuous addition, and elapsed time (minutes) from the addition of base in stepwise addition Is shown.)
More specifically, the base is added continuously or intermittently (stepwise) to control the amount of sulfuric acid [S] in the reaction system to the range represented by the following formula (2), and the aging reaction is performed. Can do.

2 / [a (0.1 × t + 4 / [S] ₀ )] ≦ [S] ≦ 2 / [a (0.01 × t + 4 / [S] ₀ )] (2)
(Wherein [S], [S] ₀ , a and t are the same as above)
In the above formulas (1) and (2), the amount of sulfuric acid [S] ₀ relative to 100 parts by weight of the raw material cellulose before neutralization (before addition of the base) is the base addition conditions (addition amount, addition method) and the residual sulfuric acid component Although it can be obtained by extrapolation based on the relationship with the amount, it is difficult to actually measure the amount of sulfuric acid in the reaction system before neutralization. Therefore, from a practical viewpoint, in the method of adding the base continuously or stepwise, the amount of sulfuric acid in the reaction system within 3 minutes from the addition (or completion of addition) of each base (based on 100 parts by weight of raw cellulose) The aging reaction may be carried out by controlling the amount of sulfuric acid) [S] within the range represented by the following formula (3). That is, the aging reaction may be performed while replacing the above formula (2) with the following formula (3) and controlling the amount of sulfuric acid in the reaction system.

2 / (0.1 × t + 4 / [S] ₀ ) ≦ [S] ≦ 2 / [0.6 (0.01 × t + 4 / [S] ₀ )] (3)
(Wherein [S] is the amount of sulfuric acid (parts by weight) relative to 100 parts by weight of the raw material cellulose, and [S] ₀ is the amount of sulfuric acid in the reaction system (parts by weight) relative to 100 parts by weight of the raw material cellulose before the addition of the base (before the addition of the base) ), T indicates the elapsed time (minutes) from the start of base addition in continuous addition, and the elapsed time (minutes) from base addition in stepwise addition)
In formula (3), [S] ₀ is often measured as the amount of sulfuric acid (parts by weight) after 3 to 5 minutes (particularly after 3 minutes) from the addition (or completion of addition) of each base. The amount of sulfuric acid (parts by weight) in the reaction system means the amount of residual sulfuric acid in the reaction system (particularly, the amount of residual sulfuric acid component including bound sulfuric acid).

The above formulas (1) to (3) are relational expressions obtained experimentally by determining a rate constant based on the reaction kinetics indicating the relationship between the degree of substitution of sulfate groups and the rate of desulfation. Elapsed time t from the addition of the base (elapsed time (minutes) from the start of the addition of the base in continuous addition, and elapsed time (minutes) from the end of the addition of the base in each addition operation in the stepwise or intermittent addition, for example, In formula (3), 3-5 minutes after the completion of base addition of the base), the amount of sulfuric acid in the reaction system relative to the amount of sulfuric acid (residual sulfuric acid amount) [S] _{0 in} the reaction system before the addition of the base (Residual sulfuric acid amount) [S] is reduced at a predetermined rate. That is, the formulas (1) to (3) indicate that the amount of sulfuric acid before addition of the base (the amount of sulfuric acid added or the amount of residual sulfuric acid) [S] _{0 is the} initial neutralization by adding the base (for example, time t = 0). The amount of sulfuric acid (the amount of residual sulfuric acid) [S] is reduced to a predetermined ratio (for example, 40 to 60% by weight, particularly 45 to 55% by weight) (or a predetermined amount of sulfuric acid remains) for acylation. means. Before the first addition of the base, the amount of sulfuric acid (residual sulfuric acid amount) [S] in the reaction system before the addition of the base corresponds to the amount of sulfuric acid used (or charged amount) used in the reaction.

  In the ripening reaction, if necessary, other acid catalysts (proton acid, Lewis acid) may be used, but usually the remaining sulfuric acid is often used as a catalyst for the ripening reaction. The aging reaction may be performed in an inert gas atmosphere or in an air atmosphere.

  The degree of acylation (acetylation degree, propionylation degree, etc.) is adjusted by such continuous or multi-stage ripening reaction (deacylation reaction, desulfation ester reaction), the amount of bound sulfuric acid is small, and the predetermined acylation degree Cellulose mixed acid ester (cellulose acetate propionate etc.) can be produced efficiently. In particular, when ripening by such continuous or multi-stage ripening reaction, even if it is a mixed acid ester having a relatively low degree of acetyl group substitution (for example, a mixed acid ester having an average degree of acetyl group substitution of less than 1.5), the efficiency is improved. It can be prepared while reducing the residual sulfuric acid well, and the generation of insoluble components can be suppressed at a high level. Furthermore, the amount of residual sulfuric acid (particularly the amount of bound sulfuric acid) in the produced cellulose ester can be greatly reduced and the amount of residual sulfuric acid can be controlled without reducing the amount of catalytic sulfuric acid in the acylation step.

  The reaction (aging reaction) in the aging step (ii) may be performed at, for example, 20 to 120 ° C, preferably 30 to 100 ° C, more preferably about 40 to 90 ° C. The reaction temperature can be selected from the range of, for example, 5 minutes or more (for example, 10 minutes to 5 hours), and preferably 15 minutes to 3 hours (for example, 20 minutes). Minutes to 3 hours), more preferably about 25 minutes to 2 hours (for example, 25 to 60 minutes). The aging reaction may be performed in an inert gas atmosphere or in an air atmosphere.

  The ripening can be stopped (or terminated) by completely neutralizing the sulfuric acid catalyst (or residual sulfuric acid) (or neutralizing the sulfuric acid catalyst to such an extent that it does not substantially act as a catalyst). In a series of reactions, the total amount of base used (including the amount of base used for partial neutralization) can be selected from a range of about 0.9 to 2 equivalents per 1 equivalent of sulfuric acid (amount of sulfuric acid charged). Usually, it may be about 0.9 to 1.5 equivalents (for example, 1 to 1.5 equivalents), preferably about 1 to 1.3 equivalents (for example, 1 to 1.2 equivalents).

  After termination of the ripening, a dope containing a cellulose mixed acid ester is obtained, and this dope is usually precipitated or precipitated to separate the cellulose mixed acid ester as a product. In particular, prior to precipitation, a dope obtained by adding or mixing an organic acid (for example, an organic acid corresponding to an acyl group such as acetic acid, in particular acetic acid) to the dope (so-called organic acid kneaded dope) is precipitated. By doing so, the amount of residual sulfuric acid can be reduced efficiently. The organic acid may be added in the form of an organic acid solution (for example, an organic acid aqueous solution). In this method, the concentration of the organic acid solution (organic acid aqueous solution) is gradually reduced, the organic acid concentration is reduced by a method of gradually kneading (adding) a poor solvent (such as water) for the cellulose mixed acid ester. You may make it precipitate, reducing. The method of precipitating the dope to which the organic acid is added is particularly effective in further reducing the amount of residual sulfuric acid by combining with the continuous or multistage aging reaction. For example, a mixed acid ester having a relatively low degree of substitution of acetyl groups (for example, a mixed acid ester having an average degree of substitution of acetyl groups of less than 1.5) is obtained by performing the continuous or multistage aging reaction and the dope to which the organic acid is added. You may manufacture combining the method of carrying out precipitation processing.

  In the kneading (addition of an organic acid or an organic acid solution), the use amount (or addition amount) of the organic acid is, for example, 50 to 400 parts by weight, preferably 100 to 100 parts by weight in terms of the organic acid. May be about 80 to 300 parts by weight, more preferably about 100 to 200 parts by weight. The mixing of the organic acid may be performed under stirring, and the stirring speed may be about 50 to 3000 rpm (preferably 100 to 1000 rpm). The mixing time (or stirring time) may be 1 to 30 minutes, preferably about 2 to 20 minutes.

  The precipitation treatment can be usually performed by adding a poor solvent for cellulose mixed acid ester such as water or an organic acid solution (for example, acetic acid aqueous solution) to the dope (a dope in which an organic acid may be mixed). . In the precipitation treatment, the addition amount (use amount) of the poor solvent can be appropriately selected. For example, 100 to 1000 parts by weight, preferably 200 to 800 parts by weight, and more preferably 300 to 600 parts by weight with respect to 100 parts by weight of the dope. It may be about a part. The precipitation treatment may be performed with stirring, and the stirring speed may be the same as described above.

  The cellulose mixed acid ester obtained through the series of steps as described above is usually washed (cleaning treatment) in order to remove impurities and the like. The cleaning process may be usually performed using water or the like, and the cleaning conditions may be the same. In a typical method, the cellulose mixed acid ester may be washed with water, and further washed with warmed water (for example, hot water at 70 to 99 ° C.).

  In addition, after the ripening step (ii), in order to enhance the heat stability of the cellulose ester, a neutralizer composed of the base as necessary [preferably an alkali metal compound and / or an alkaline earth metal compound, particularly at least calcium. Compound (such as calcium hydroxide)] may be added. The neutralizing agent may be added after the aging step, for example, after the precipitation treatment (particularly after precipitation and washing). You may add a neutralizing agent with the form of aqueous solution (for example, calcium hydroxide aqueous solution).

[Cellulose mixed acid ester film and production method thereof]
The cellulose mixed acid ester of the present invention forms various molded products (one-dimensional molded products such as fibers, two-dimensional molded products such as films, sheets, and coating films (or thin films), and three-dimensional molded products). Useful for. The sheet (or film) may be a single sheet or a laminated sheet in which a plurality of sheets are laminated.

  In particular, the cellulose mixed acid ester of the present invention has a remarkably small content of fine foreign substances, is excellent in optical properties, and is excellent in moisture resistance (particularly moist heat resistance), and therefore forms a film (particularly an optical film). Useful for.

  Such a film composed of the cellulose mixed acid ester of the present invention (cellulose mixed acid ester film, sometimes simply referred to as a film) is formed by a melt film forming method (extrusion molding method or the like) depending on the degree of substitution or the type of acyl group. ) Or solution casting method (casting method). In the present invention, a film having excellent flatness may be usually produced by a solution casting method.

  In the solution casting method, the cellulose mixed acid ester film is obtained by casting a dope (or an organic solvent solution) containing a cellulose mixed acid ester and an organic solvent onto a peelable support, and peeling the formed film from the peelable support. It can be manufactured by drying.

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

The organic solvent for preparing the dope may be a halogen-based organic solvent (particularly a chlorine-based organic solvent) or a non-halogen-based organic solvent (particularly a non-chlorine-based organic solvent). The cellulose mixed acid ester of the present invention is often soluble in at least a halogen-based organic solvent (particularly a chlorine-based organic solvent). The organic solvents may be used alone or in combination of two or more. For example, a chlorinated organic solvent and a non-chlorinated organic solvent may be combined. Examples of the halogen organic solvent (particularly chlorine organic solvent) include halogenated hydrocarbons (particularly chlorinated hydrocarbons) such as dichloromethane and chloroform. Examples of non-halogen organic solvents (particularly non-chlorine organic solvents) include esters (acetates such as methyl acetate, ethyl acetate, amyl acetate, and butyl acetate) and ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone). Dialkyl ketones such as cyclohexanone), ethers (chain ethers such as diethyl ether, cyclic ethers such as dioxane and tetrahydrofuran), alcohols (for example, C such as methanol, ethanol, isopropanol, and n-butanol). _1-4 alkanols).

  For the dope, various additives such as plasticizer [phosphate ester plasticizer, carboxylic ester plasticizer (phthalate ester, adipic acid ester, sebacic acid ester, citrate ester, etc.), triacetin etc.], Stabilizers (antioxidants, ultraviolet absorbers, deterioration inhibitors, etc.), lubricants (particulate lubricants), flame retardants, mold release agents and the like may be added. Further, a retardation increasing agent (such as a retardation increasing agent described in JP-A-2001-139621), a release agent (such as a releasing agent described in JP-A-2002-30909), or the like may be added to the dope. .

  The dope can be prepared by using a conventional method such as a high temperature dissolution method or a cooling dissolution method. The cellulose ester concentration in the dope may be about 10 to 35% by weight, preferably about 20 to 30% by weight (for example, 15 to 25% by weight). Moreover, in order to obtain a high quality film (such as a film for a liquid crystal display device), the dope may be further filtered.

  A film can be produced by casting a dope on a support using a casting die or the like and drying. Usually, a dope is cast on a support, preliminarily dried, and then a predried film containing an organic solvent is dried to produce a film.

  The thickness of the film can be selected according to the application, and may be, for example, about 5 to 200 μm, preferably about 10 to 150 μm, and more preferably about 20 to 100 μm.

  In the melt film-forming method, for example, the cellulose mixed acid ester (and other components such as a plasticizer as necessary) is melt-mixed with an extruder or the like, extruded from a die (T-die, ring die, etc.), and cooled. You may manufacture a film by doing. The melt mixing temperature can be selected from a range of, for example, about 120 to 250 ° C.

  The film may be stretched. By the stretching treatment, the film can be efficiently oriented. The film can be oriented by conventional methods (drawing, stretching, etc.), for example, uniaxial or biaxial, and may be oriented using the draw ratio of the take-up roll, gripping the end of the film with a chuck You may extend and orient. As the stretching method, heat stretching can be preferably used. For example, in the melt film forming method, the film-like melt extruded from the die of the extruder is taken and cooled by a cooling means such as a cooling roll while being stretched in the uniaxial direction. Examples thereof include a method, a method of cooling a film-like melt extruded from a die, and stretching at a predetermined temperature (a temperature equal to or higher than the glass transition temperature and lower than the melting point). In the solution casting method, the preliminary drying film containing a solvent may be oriented by stretching. From the viewpoint of film productivity, a melt film formation method, particularly a melt extrusion method is preferred. Further, the film only needs to be oriented in at least one direction (longitudinal or take-up direction MD or width direction TD), and may be oriented in a tolerance or orthogonal direction, but is stretched biaxially. Most preferred.

  The degree of orientation (stretch ratio) of the film is 1.2 to 8 times, preferably 1.2 to 4 times, more preferably 1.2 to 3 times, particularly about 1.4 to 2 times in at least one direction. There may be. In the biaxially stretched film, the MD direction is about 1.1 to 8 times (for example, 1.1 to 5 times, preferably 1.1 to 2 times, more preferably 1.2 to 1.5 times), It may be about 1.0 to 4 times (for example, 1.0 to 3 times, preferably 1.0 to 2 times, more preferably 1.1 to 1.5 times) in the TD direction.

  Although the cellulose mixed acid ester of the present invention is a mixed acid ester, the content of foreign matter (fine foreign matter) such as unreacted cellulose, cellulose ester having a low substitution degree, foreign matter derived from bound sulfuric acid is remarkably low, and high purity. Therefore, it is possible to achieve both high heat and moisture resistance and optical characteristics at a high level. In addition, the cellulose mixed acid ester of the present invention can have a relatively high degree of polymerization, and is advantageous from the viewpoint of film strength, productivity, and the like. Therefore, the cellulose mixed acid ester of the present invention can be used for various optical films, for example, color filters, base films for photographic photosensitive materials, films for display devices (for example, optical compensation films such as optical compensation films for liquid crystal display devices), polarized light, etc. It can be used as a protective film for a plate, a base film for an antireflection film, and the like. In particular, the cellulose mixed acid ester of the present invention can be suitably used for polarizing plates, optical compensation sheets (particularly optical compensation sheets for liquid crystal display devices) and the like. The said polarizing plate can be comprised with the film of this invention formed in the polarizing film and the at least one surface (especially both surfaces) of this polarizing film, for example. The optical compensation sheet can be composed of, for example, the film of the present invention, an alignment film formed on at least one surface of the film, and an optical anisotropic layer formed on the alignment film.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. In the following examples and comparative examples, each characteristic was measured as follows. In the following examples and comparative examples, “parts” means “parts by weight” unless otherwise specified.

<Non-soluble component>
A solution in which cellulose mixed acid ester (cellulose acetate propionate) is dissolved in a mixed solvent of 1% by weight in methylene chloride / methanol (weight ratio) = 9/1 (however, insoluble components are not dissolved) ) Is filtered using a glass filter (trade name “G-4”, manufactured by Mutual Rikagaku Glass Co., Ltd.) having a filter portion having a pore diameter of 5 to 10 μm, and deposits (dope) adhering to the filtration residue After washing the filter part with the mixed solvent, the glass filter containing the filtration residue is dried to a constant weight (constant weight). Then, the weight of the glass filter before and after filtration was measured, the weight of the glass filter after filtration (after filtration, washing and drying) was X (g), the weight of the glass filter before filtration was Y (g), and the solution used for filtration When the dry weight of the cellulose mixed acid ester is Z (g), the content of the insoluble component is calculated by the following formula.

  Content of non-soluble component = [(XY) / Z] × 100 (% by weight).

<Measurement of substitution degree>
A sample was butylated with butyric acid in a pyridine solvent, then a ¹³ C-NMR spectrum was measured with a chloroform solvent, and the intensity of three signals of acetylcarbonyl carbon appearing in the vicinity of 169.1 to 170.2 ppm was integrated to obtain acetylcarbonyl. The carbon signal integrated intensity ΣAc was calculated, and the propionylcarbonyl carbon signal integrated intensity (Pr was calculated by integrating the intensity of the 3 signals of propionylcarbonyl carbon appearing in the vicinity of 172.7 to 173.6 ppm. It was as follows.

Measurement solvent: CDCl ₃ (about 3 ml used)
Measurement temperature: 40 ℃
Sample amount: 160-180mg (φ10mm)
Observation nucleus: ¹³ C ( ¹ H complete decoupling)
Number of data points: 32768
Pulse angle and time: 45 °, 9μsec
Data acquisition time: 0.9667 sec
Wait time: 2.0333 sec
Integration number: 18,000 times The degree of substitution (DS) was determined by the following equation. In the following formula, ΣAc represents the acetylcarbonyl carbon signal integrated intensity, and ΣPr represents the propionylcarbonyl carbon signal integrated intensity.

Degree of substitution (DS) = 3 × ΣAc / (ΣAc + ΣPr)
<Measurement of degree of polymerization>
Cellulose mixed acid ester is dissolved in a mixed solution of methylene chloride / methanol = 9/1 (weight ratio) to prepare a solution having a predetermined concentration c (2.00 g / L), and this solution is injected into an Ostwald viscometer, The time t (seconds) for the solution to pass between the viscometer markings at 25 ° C. is measured. On the other hand, for the mixed solvent alone, the passage time (second) t ₀ was measured in the same manner as described above, and the viscosity average degree of polymerization was calculated according to the following formula.

η _rel = t / t ₀ [η] = (ln η _rel ) / cDP = [η] / (6 × 10 ⁻⁴ )
(Where t is the solution passage time (second), t ₀ is the solvent passage time (second), c is the cellulose mixed acid ester concentration (g / L), η _rel is the relative viscosity, and [η] is the limit. Viscosity and DP indicate average degree of polymerization).

<Calcium (Ca) component content>
After the dried cellulose mixed acid ester was completely burned, it was measured by atomic absorption after pretreatment by dissolving ash in hydrochloric acid. The measured value is obtained in ppm as the calcium content in 1 g of the cellulose mixed acid ester in an absolutely dry state.

<Magnesium (Mg) component content>
After the dried cellulose mixed acid ester was completely burned, it was measured by atomic absorption after pretreatment by dissolving ash in hydrochloric acid. The measured value is obtained in units of ppm as the magnesium content in 1 g of the cellulose mixed acid ester in an absolutely dry state.

<Residual sulfuric acid amount>
A solution obtained by adding a methyl red / methylene blue mixed indicator to 1% by weight of hydrogen peroxide and neutralizing with a 0.01 mol / liter NaOH solution from reddish purple to a slight reddishness is used as an absorbing solution. On the other hand, the tubular furnace in which the oxygen inlet and the absorption bottle are set is heated to 1250 to 1350 ° C. 80 ml of the absorbent is put into a heated absorption bottle, and 1.0 g of dried cellulose mixed acid ester is collected in a combustion boat and set near the inlet of the tubular furnace. While supplying oxygen at a flow rate of 2 to 2.5 liters / minute, the combustion boat is gradually pushed into a tubular furnace with a quartz rod and carbonized. After the sample is carbonized, it is pushed into the center of the tubular furnace and completely incinerated. After the supply of oxygen is stopped and the absorption liquid is transferred to a beaker, the absorption bottle is washed with distilled water, and the washing liquid is combined with the absorption liquid. Concentrate the absorbent with the washings on an electric heater until it reaches about 70-80 ml. A methyl red / methylene blue mixed indicator is added to the concentrated absorbent and titrated with a 0.01 mol / liter NaOH solution, and the end point is the point when the color becomes slightly yellow with a slight orange color (Aml). Based on this titration amount (Aml) and the titration amount (Bml) of the blank test similarly conducted, the residual sulfuric acid is calculated by the following formula.

Residual sulfuric acid amount = {[(A−B) × F × 0.048] / W} × [100 / (100-M)]
[Wherein, W represents the sample weight (g), M represents the sample moisture (%), and F represents a factor of the NaOH titrant of 0.01 mol / liter (mol / l)].

(Example 1)
As a pretreatment (activation treatment) acid, 309.6 parts of acetic acid and 72.4 parts of propionic acid are uniformly distributed per 100 parts of dry weight of cellulose containing about 7% by weight of water, and 30 parts at 54 ° C. Mixed for minutes. And the pre-processed cellulose (mixture) was cooled to 10 degreeC. No catalytic sulfuric acid was used in this pretreatment.

  Next, this mixture was charged into an esterification reactor, and 158.6 parts of acetic anhydride, 222.0 parts of propionic anhydride, 3.8 parts of sulfuric acid and 2.2 parts of propionic acid had been pre-cooled to -20 ° C. Then, esterification was performed. The maximum temperature in esterification was adjusted to 40 ° C. The heating rate was 0.5 ° C./min. The time to reach the maximum temperature (arrival time) was 65 minutes, and the time from the time when the maximum temperature was reached until the end of esterification (late acylation time) was 75 minutes. The total acylation time was 140 minutes and the ratio of late acylation time to total acylation time was 53%. The acylation reaction is stopped by adding a mixed solution of 105.5 parts of acetic acid and 35.2 parts of water over 20 minutes as a reaction stopper to the reaction system to deactivate excess hydrolysis (hydrolysis). ).

  Next, after the addition of the mixed solution, the temperature of the reaction solution was kept at 80 ° C., and 316.5 parts of acetic acid and 105.5 parts of water were added and aged for 50 minutes. Then, 40.6 parts of a 15% by weight aqueous magnesium acetate solution was added to neutralize the sulfuric acid in the system, and the ripening was completed (stopped). Deionized water was added to the dope after termination of ripening to precipitate the mixed fatty acid ester.

  Next, the solid-liquid was separated after standing for 30 minutes in the state of slurry after precipitation. The precipitated cellulose ester is washed with deionized water for 2 hours (washed before running water), then washed with hot water at 96 to 97 ° C. for 60 minutes, and further washed with deionized water for 120 minutes, followed by stabilization treatment. A dilute solution of calcium hydroxide was added as (heat resistant treatment). Then, after leaving for 30 minutes, centrifugal liquid removal was performed to obtain cellulose acetate propionate (CAP). Table 1 shows the characteristics of the cellulose acetate propionate obtained.

(Example 2)
As a pretreatment (activation) acid, 316.5 parts of acetic acid and 72.4 parts of propionic acid are uniformly distributed per 100 parts of dry weight of cellulose containing about 7% by weight of water, and 30 parts at 54 ° C. Mixed for minutes. And the pre-processed cellulose (mixture) was cooled to 10 degreeC. No catalytic sulfuric acid was used in this pretreatment.

  Next, this mixture was charged into an esterification reactor, and 152.7 parts of acetic anhydride, 222.0 parts of propionic anhydride, 3.8 parts of sulfuric acid and 2.2 parts of propionic acid which had been pre-cooled to -20 ° C were mixed. Then, esterification was performed. The maximum temperature in esterification was adjusted to 40 ° C. The heating rate was 0.5 ° C./min. The time to reach the maximum temperature was 65 minutes, and the time from the point of reaching the maximum temperature to the end of esterification (late acylation time) was 75 minutes. The total acylation time was 140 minutes and the ratio of late acylation time to total acylation time was 53%. The acylation reaction is stopped by adding a mixed solution of 105.5 parts of acetic acid and 35.2 parts of water over 20 minutes as a reaction stopper to the reaction system to deactivate excess hydrolysis (hydrolysis). ).

  Next, after the addition of the mixed solution, the temperature of the reaction solution was kept at 80 ° C., and 316.5 parts of acetic acid and 105.5 parts of water were added and aged for 30 minutes. Then, 40.6 parts of a 15% by weight aqueous magnesium acetate solution was added to neutralize the sulfuric acid in the system, and the ripening was completed (stopped). Deionized water was added to the dope after termination of ripening to precipitate the mixed fatty acid ester.

  Next, the solid-liquid was separated after standing for 30 minutes in the state of slurry after precipitation. The precipitated cellulose ester is washed with deionized water for 2 hours (washed before running water), then washed with hot water at 96 to 97 ° C. for 60 minutes, and further washed with deionized water for 120 minutes, followed by stabilization treatment. A dilute solution of calcium hydroxide was added as (heat resistant treatment). Thereafter, after leaving for 30 minutes, centrifugal drainage was performed to obtain cellulose acetate propionate. Table 1 shows the characteristics of the cellulose acetate propionate obtained.

(Example 3)
As a pretreatment (activation treatment) acid, 54 parts of acetic acid was uniformly distributed per 100 parts of dry weight of cellulose containing about 7% by weight of water and mixed at 20 ° C. for 60 minutes. And the pre-processed cellulose (mixture) was cooled to 10 degreeC. No catalytic sulfuric acid was used in this pretreatment.

  Next, this mixture was charged into an esterification reactor, and a mixture of 152.7 parts of acetic anhydride, 222.0 parts of propionic anhydride, and 4.0 parts of sulfuric acid, which had been pre-cooled to -20 ° C, was added to the esterification reactor. Made. The maximum temperature in esterification was adjusted to 40 ° C. The heating rate was 0.5 ° C./min. The time to reach the maximum temperature was 65 minutes, and the time from the point at which the maximum temperature was reached to the end of esterification (late acylation time) was 100 minutes. The total acylation time was 165 minutes and the ratio of late acylation time to total acylation time was 61%. The acylation reaction was stopped by adding a mixed solution of 105.5 parts of acetic acid and 35.3 parts of water over 20 minutes as a reaction stopper to the reaction system to deactivate excess hydrolysis (hydrolysis). ).

  Next, after the addition of the mixed solution, the temperature of the reaction solution was kept at 80 ° C., and 316.5 parts of acetic acid and 105.5 parts of water were added and aged for 30 minutes. And 45.7 parts of magnesium acetate 15 weight% aqueous solution was added, the sulfuric acid in a system was neutralized, and ripening was complete | finished (stop). Deionized water was added to the dope after termination of ripening to precipitate the mixed fatty acid ester.

  Next, the solid-liquid was separated after standing for 30 minutes in the state of slurry after precipitation. The precipitated cellulose ester is washed with deionized water for 2 hours (washed before running water), then washed with hot water at 96 to 97 ° C. for 60 minutes, and further washed with deionized water for 120 minutes, followed by stabilization treatment. A dilute solution of calcium hydroxide was added as (heat resistant treatment). Thereafter, after leaving for 30 minutes, centrifugal drainage was performed to obtain cellulose acetate propionate. Table 1 shows the characteristics of the cellulose acetate propionate obtained.

(Comparative Example 1)
30 parts of acetic acid and 67.9 parts of propionic acid are uniformly distributed as pretreatment (activation treatment) acid per 100 parts of dry weight of cellulose containing about 7% by weight of water, and 30 parts at 54 ° C. Mixed for minutes. And the pre-processed cellulose (mixture) was cooled to 10 degreeC. No catalytic sulfuric acid was used in this pretreatment.

  Next, this mixture was charged into an esterification reactor, and 106.4 parts of acetic anhydride, 247.2 parts of propionic anhydride, 3.5 parts of sulfuric acid and 2.1 parts of propionic acid had been pre-cooled to -20 ° C. Then, esterification was performed. The maximum temperature in esterification was adjusted to 40 ° C. The heating rate was 1.5 ° C./min. The time to reach the maximum temperature was 20 minutes, and the time from the point of reaching the maximum temperature to the end of esterification (late acylation time) was 130 minutes. Total acylation time was 150 minutes and the ratio of late acylation time to total acylation time was 87%. The acylation reaction was stopped by adding a mixed solution of 98.7 parts of acetic acid and 32.9 parts of water as a reaction stopper to the reaction system over 20 minutes to deactivate excess anhydride (hydrolysis). ).

  Next, after the addition of the mixed solution, the temperature of the reaction solution was kept at 60 ° C., and 296.3 parts of acetic acid and 98.66 parts of water were added and aged for 60 minutes. And 37.9 parts of magnesium acetate 15 weight% aqueous solution was added, the sulfuric acid in a system was neutralized, and ripening was complete | finished (stop). Deionized water was added to the dope after termination of ripening to precipitate the mixed fatty acid ester.

  Next, the solid-liquid was separated after standing for 30 minutes in the state of slurry after precipitation. The precipitated cellulose ester is washed with deionized water for 2 hours (washed before running water), then washed with hot water at 96 to 97 ° C. for 60 minutes, and further washed with deionized water for 120 minutes, followed by stabilization treatment. A dilute solution of calcium hydroxide was added as (heat resistant treatment). Thereafter, after leaving for 30 minutes, centrifugal drainage was performed to obtain cellulose acetate propionate. Table 1 shows the characteristics of the cellulose acetate propionate obtained.

(Comparative Example 2)
30 parts of acetic acid and 67.9 parts of propionic acid are uniformly distributed as pretreatment (activation treatment) acid per 100 parts of dry weight of cellulose containing about 7% by weight of water, and 30 parts at 54 ° C. Mixed for minutes. And the pre-processed cellulose (mixture) was cooled to 10 degreeC. No catalytic sulfuric acid was used in this pretreatment.

  Next, this mixture was charged into an esterification reactor, and 106.4 parts of acetic anhydride, 247.2 parts of propionic anhydride, 3.5 parts of sulfuric acid and 2.1 parts of propionic acid had been pre-cooled to -20 ° C. Then, esterification was performed. The maximum temperature in esterification was adjusted to 40 ° C. The heating rate was 0.3 ° C./min. The time to reach the maximum temperature was 100 minutes, and the time from the point at which the maximum temperature was reached to the end of esterification (late acylation time) was 50 minutes. Total acylation time was 150 minutes and the ratio of late acylation time to total acylation time was 33%. The acylation reaction was stopped by adding a mixed solution of 98.7 parts of acetic acid and 32.9 parts of water as a reaction stopper to the reaction system over 20 minutes to deactivate excess anhydride (hydrolysis). ).

  Next, after the addition of the mixed solution, the temperature of the reaction solution was kept at 60 ° C., and 296.3 parts of acetic acid and 98.66 parts of water were added and aged for 60 minutes. And 37.9 parts of magnesium acetate 15 weight% aqueous solution was added, the sulfuric acid in a system was neutralized, and ripening was complete | finished (stop). Deionized water was added to the dope after termination of ripening to precipitate the mixed fatty acid ester.

  Next, the solid-liquid was separated after standing for 30 minutes in the state of slurry after precipitation. The precipitated cellulose ester is washed with deionized water for 2 hours (washed before running water), then washed with hot water at 96 to 97 ° C. for 60 minutes, and further washed with deionized water for 120 minutes, followed by stabilization treatment. A dilute solution of calcium hydroxide was added as (heat resistant treatment). Thereafter, after leaving for 30 minutes, centrifugal drainage was performed to obtain cellulose acetate propionate. Table 1 shows the characteristics of the cellulose acetate propionate obtained.

(Example 4)
As a pretreatment acid, 28.5 parts of acetic acid was uniformly distributed as a pretreatment acid per 100 parts of dry weight of cellulose containing about 7% by weight of water and mixed at 20 ° C. for 60 minutes. And the pre-processed cellulose (mixture) was cooled to 10 degreeC. No catalytic sulfuric acid was used in this pretreatment.

  Next, this mixture was charged into an esterification reactor, and 444.1 parts of propionic anhydride that had been pre-cooled to -20 ° C, 93.6 parts of propionic acid as a diluting acid, and 4.3 parts of sulfuric acid were mixed. In addition, esterification was performed. The maximum temperature in esterification was adjusted to 25 ° C. The heating rate was 0.3 ° C./min. The time to reach the maximum temperature was 50 minutes, and the time from the point at which the maximum temperature was reached to the end of esterification (late acylation time) was 280 minutes. Total acylation time was 330 minutes and the ratio of late acylation time to total acylation time was 85%. The acylation reaction was stopped by adding a mixed solution of 75.5 parts of acetic acid and 38.9 parts of water as a reaction terminator over 20 minutes to deactivate the excess anhydride (hydrolysis). ).

  Next, after the addition of the mixed solution, the temperature of the reaction solution was kept at 60 ° C., and 226.4 parts of acetic acid and 116.6 parts of water were added and aged for 60 minutes. Then, 53.9 parts of a 15% by weight aqueous solution of magnesium acetate was added at a constant rate over 30 minutes to continuously neutralize the sulfuric acid in the system and complete (stop) aging.

  After termination of the ripening reaction, 300 parts of acetic acid was added and stirred for 5 minutes until uniform. Then, the dope (acetic acid kneaded dope) to which acetic acid was added was placed in a 10% by weight aqueous acetic acid solution as a precipitating agent and precipitated by vigorous stirring.

  Next, the solid-liquid was separated after standing for 30 minutes in the state of slurry after precipitation. The precipitated cellulose ester is washed with deionized water for 2 hours (washed before running water), then washed with hot water at 96 to 97 ° C. for 60 minutes, and further washed with deionized water for 120 minutes, followed by stabilization treatment. A dilute solution of calcium hydroxide was added as (heat resistant treatment). Thereafter, after leaving for 30 minutes, centrifugal drainage was performed to obtain cellulose acetate propionate. Table 2 shows the characteristics of the cellulose acetate propionate obtained.

(Example 5)
As a pretreatment acid, 107.6 parts of acetic acid and 1.0 part by weight of sulfuric acid were uniformly distributed per 100 parts of dry weight of cellulose containing about 7% by weight of water and mixed at 20 ° C. for 45 minutes. And the pre-processed cellulose (mixture) was cooled to 10 degreeC.

  Next, this mixture was charged into an esterification reactor, and 954.6 parts of butyric anhydride that had been pre-cooled to -20 ° C, 267.4 parts of acetic acid as a diluting acid, 449.8 parts of butyric acid, and 10.9 parts of sulfuric acid were mixed. Then, esterification was performed. The maximum temperature in esterification was adjusted to 20 ° C. The heating rate was 0.3 ° C./min. The time to reach the maximum temperature was 60 minutes, and the time from the point at which the maximum temperature was reached to the end of esterification (late acylation time) was 340 minutes. Total acylation time was 400 minutes and the ratio of late acylation time to total acylation time was 85%. The acylation reaction was stopped by adding a mixed solution of 115.1 parts of acetic acid and 119.3 parts of water as a reaction stopper to the reaction system over 15 minutes to deactivate excess anhydride (hydrolysis). ).

  Next, after the addition of the mixed solution, a mixed solution containing 394.1 parts of acetic acid, 48.8 parts of water and 9.8 parts of magnesium acetate is added, and the temperature of the reaction solution is kept at 60 ° C. and stirred for 10 minutes, Further, a mixed solution containing 70.1 parts of acetic acid, 8.7 parts of water and 1.8 parts of magnesium acetate was added, and the temperature of the reaction solution was kept at 60 ° C. and stirred for 20 minutes. Further, 70.1 parts of acetic acid, After adding a mixed solution containing 8.7 parts and 1.8 parts of magnesium acetate and maintaining the temperature of the reaction liquid at 60 ° C. for 20 minutes, 26.8 parts of acetic acid, 20.4 parts of water and magnesium acetate were further added. A liquid mixture containing 6.4 parts was added to neutralize the mixture to complete (stop) ripening.

  After termination of the ripening reaction, a total of 290 parts of acetic acid and 360 parts of water was added to 1000 parts of the dope, and the water concentration in the dope was gradually increased to cause precipitation.

  Next, the solid-liquid was separated after standing for 30 minutes in the state of slurry after precipitation. The precipitated cellulose ester is washed with deionized water for 2 hours (washed before running water), then washed with hot water at 96 to 97 ° C. for 60 minutes, and further washed with deionized water for 120 minutes, followed by stabilization treatment. A dilute solution of calcium hydroxide was added as (heat resistant treatment). Then, after leaving for 30 minutes, centrifugal drainage was performed to obtain cellulose acetate butyrate. Table 2 shows the characteristics of the cellulose acetate butyrate obtained.

(Comparative Example 3)
As a pretreatment acid, 28.5 parts of acetic acid was uniformly distributed per 100 parts of the dry weight of cellulose containing about 7% by weight of water and mixed at 54 ° C. for 30 minutes. And the pre-processed cellulose (mixture) was cooled to 10 degreeC. No catalytic sulfuric acid was used in this pretreatment.

  Next, this mixture was charged into an esterification reactor, and 444.1 parts of propionic anhydride that had been pre-cooled to -20 ° C, 93.6 parts of propionic acid as a diluting acid, and 4.3 parts of sulfuric acid were mixed. In addition, esterification was performed. The maximum temperature in esterification was adjusted to 25 ° C. The heating rate was 0.3 ° C./min. The time to reach the maximum temperature was 50 minutes, and the time from the point at which the maximum temperature was reached to the end of esterification (late acylation time) was 280 minutes. Total acylation time was 330 minutes and the ratio of late acylation time to total acylation time was 85%. The acylation reaction was stopped by adding a mixed solution of 75.5 parts of acetic acid and 38.9 parts of water as a reaction terminator over 20 minutes to deactivate the excess anhydride (hydrolysis). ).

  Next, after the addition of the mixed solution, the temperature of the reaction solution was kept at 60 ° C., and 226.4 parts of acetic acid and 116.6 parts of water were added and aged for 60 minutes. Then, 53.9 parts of a 15% by weight aqueous solution of magnesium acetate was added over 6 minutes to neutralize, and ripening was completed (stopped). Deionized water was added to the dope after termination of ripening to precipitate the mixed fatty acid ester.

  Next, the solid-liquid was separated after standing for 30 minutes in the state of slurry after precipitation. The precipitated cellulose ester is washed with deionized water for 2 hours (washed before running water), then washed with hot water at 96 to 97 ° C. for 60 minutes, and further washed with deionized water for 120 minutes, followed by stabilization treatment. A dilute solution of calcium hydroxide was added as (heat resistant treatment). Thereafter, after leaving for 30 minutes, centrifugal drainage was performed to obtain cellulose acetate propionate. Table 2 shows the characteristics of the cellulose acetate propionate obtained.

Claims (15)

  Cellulose mixed acid ester in which the content of an insoluble component in a mixed solvent of methylene chloride / methanol (weight ratio) = 9/1 is 0.12% by weight or less.   The cellulose mixed acid ester according to claim 1, wherein the total average substitution degree is 2.6 to 2.99, and the content of the insoluble component is 0.07% by weight or less.   The cellulose mixed acid ester according to claim 1, which has at least an acetyl group and an aliphatic acyl group other than an acetyl group. (I) The total average degree of substitution is 2.6 to 2.99, the average degree of substitution of the acetyl group is 1.5 or more, and the ratio (molar ratio) of acetyl group to aliphatic C _3-6 acyl group is the former / the latter = 95 / 5-60 / 40 cellulose acetate aliphatic C _3-6 acylate, or (ii) the total average degree of substitution is 2.6-2.99, the average degree of substitution of acetyl groups is less than 1.5, 2. The cellulose according to claim 1, wherein the ratio (molar ratio) of acetyl group to aliphatic C _3-6 acyl group is cellulose acetate aliphatic C _3-6 acylate of the former / the latter = 30/70 to 3/97. Mixed acid ester.   The cellulose mixed acid ester according to claim 1, wherein the amount of residual sulfuric acid (weight basis) is 300 ppm or less, and the viscosity average polymerization degree is 200 to 400. The cellulose mixed acid ester according to claim 1, which is a cellulose acetate aliphatic C _3-6 acylate having a non-soluble component content of 0.07% by weight or less and satisfying the following (i) or (ii).
(I) The total average degree of substitution is 2.6 to 2.97, the average degree of substitution of acetyl groups is 1.8 or more, and the ratio (molar ratio) of acetyl groups to aliphatic C _3-6 acyl groups is the former / the latter = 90 / 10-70 / 30, viscosity average degree of polymerization is 250-350, and residual sulfuric acid amount (weight basis) is 50-200 ppm.
(Ii) The total average substitution degree is 2.6 to 2.97, the average substitution degree of the acetyl group is 1 or less, and the ratio (molar ratio) between the acetyl group and the aliphatic C _3-6 acyl group is the former. / The latter = 20/80 to 5/95, the viscosity average degree of polymerization is 250 to 350, and the amount of residual sulfuric acid (weight basis) is 50 to 200 ppm.   An acylation step (i) in which cellulose is acylated with an acylating agent corresponding to a cellulose mixed acid ester in the presence of a sulfuric acid catalyst, and an aging step (ii) in which the cellulose is aged in the presence of a sulfuric acid catalyst. The manufacturing method of cellulose mixed acid ester of description.   In the acylation step (i), when the time from the start of acylation to the stop of acylation is X, and the time from the time when the maximum temperature in the acylation step is reached to the end of acylation is Y, the value [ The production method according to claim 7, wherein acylation is performed so that Y / X] × 100 is 40 to 85.   In the acylation step (i), the value [Y / X] × 100 is 45 to 65 at a maximum temperature of 30 to 50 ° C. in the presence of 2 to 12 parts by weight of a sulfuric acid catalyst with respect to 100 parts by weight of cellulose. The production method according to claim 8, wherein the acylation is carried out.   The manufacturing method of Claim 8 or 9 which manufactures the cellulose mixed acid ester whose average substitution degree of an acetyl group is 1.5 or more.   The production method according to claim 7, wherein in the ripening step (ii), the base is continuously added from the start of the ripening reaction to the termination of the ripening reaction, or the base is added intermittently at least three times.   The production method according to claim 11, further comprising the step of adding an organic acid to the dope containing cellulose mixed acid ester after the aging step (ii) is stopped, and separating the cellulose mixed acid ester by precipitation treatment.   The manufacturing method of Claim 11 or 12 which manufactures the cellulose mixed acid ester whose average substitution degree of an acetyl group is less than 1.5.   A cellulose ester film comprising the cellulose mixed acid ester according to claim 1.   The film according to claim 14, which is an optical compensation film for a liquid crystal display device or a protective film for a polarizing plate.