WO2020013312A1 - Acétate de cellulose et procédé de production d'un acétate de cellulose - Google Patents

Acétate de cellulose et procédé de production d'un acétate de cellulose Download PDF

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WO2020013312A1
WO2020013312A1 PCT/JP2019/027678 JP2019027678W WO2020013312A1 WO 2020013312 A1 WO2020013312 A1 WO 2020013312A1 JP 2019027678 W JP2019027678 W JP 2019027678W WO 2020013312 A1 WO2020013312 A1 WO 2020013312A1
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cellulose acetate
pulp
weight
cellulose
acetylation
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PCT/JP2019/027678
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Japanese (ja)
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美也 楢崎
博章 玉垣
数弘 山下
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株式会社ダイセル
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
    • C08B3/00—Preparation of cellulose esters of organic acids
    • C08B3/06—Cellulose acetate, e.g. mono-acetate, di-acetate or tri-acetate

Definitions

  • the present invention relates to cellulose acetate and a method for producing cellulose acetate.
  • Cellulose acetate is one of the organic acid esters of cellulose, which is a cellulose derivative, and is used for clothing fibers, filters or chips for tobacco, plastics, films, paints, pharmaceuticals, foodstuffs, cosmetics, and construction. It has a wide variety of uses, etc., and has a large production amount among cellulose derivatives, and is industrially important.
  • a typical industrial production method of cellulose acetate includes a so-called acetic acid method using acetic anhydride as an acetic acid agent, acetic acid as a diluent, and sulfuric acid as a catalyst.
  • the basic steps of the acetic acid method are: (1) a pretreatment step of disintegrating, disintegrating, or disintegrating and disintegrating a pulp raw material (dissolved pulp) having a relatively high ⁇ -cellulose content, and then spraying and mixing acetic acid; (2) an acetylation step of reacting the pretreated pulp with (1) a mixed acid comprising acetic anhydride, acetic acid and an acetylation catalyst (for example, sulfuric acid); and (3) a desired degree of acetylation by hydrolyzing cellulose acetate.
  • (4) a post-treatment step of separating, purifying, stabilizing, and drying the cellulose acetate having undergone the hydrolysis reaction from the reaction solution Patent Document 1, Non-Patent Document 1 ).
  • Cellulose acetate produced by the above method generally has a slight yellow tinge and has a poor appearance even when satisfying other required properties. Inviting. It is pointed out that this coloring is a main factor of yellowness generated from a hemicellulose component contained in pulp, which is a cellulose raw material, in particular, wood pulp (Non-Patent Documents 2 and 3).
  • Patent Document 1 a method of extracting an acetylated product of glucomannan into an organic solvent by adding an organic solvent can obtain cellulose acetate having excellent transparency (Patent Document 1) 2)
  • Patent Document 2 it is possible to obtain cellulose diacetate having excellent transparency by a method of once dissolving the aged cellulose diacetate in a solvent capable of dissolving the cellulose diacetate and recovering the same.
  • the cellulose acetate obtained by the conventional production method as described above did not sufficiently reduce the substances causing coloring.
  • hemicellulose component that is, an acetylated product of glucomannan
  • a coloring substance produced using a substance contained in cellulose as a starting material That is, it is a coloring substance starting from furfural contained in the raw material.
  • Furfural is a kind of aromatic aldehyde, and its chemical formula is (C 4 H 3 O) CHO, and 2-furancarboxaldehyde in IUPAC nomenclature.
  • celluloses contain a hemicellulose component, but when heated with dilute sulfuric acid, the hemicellulose component is hydrolyzed and converted mainly into sugars such as xylose. Under the same conditions, C5 saccharides, such as xylose, are further dehydrated, producing three water molecules and converted to furfural. Furfural is readily soluble in most organic solvents such as alcohols and ethers. However, furfural is polymerized in the process of acetylation of cellulose and becomes insoluble or hardly soluble in most organic solvents, including acetic acid, which is generally used as a solvent in the process of acetylation. The present inventors have found out that they remain in acetate to deteriorate the color, and have arrived at the present invention.
  • An object of the present invention is to provide a cellulose acetate having a sufficiently small amount of a substance causing coloring and having an excellent hue.
  • a first aspect of the present invention relates to cellulose acetate having a content of a compound represented by the following general formula (a) of 0 ppb or more and 100 ppb or less and a total degree of acetyl substitution of 2.3 or more and 2.6 or less.
  • the second step of the present invention is a step (1) of pretreating the pulp by contacting it with acetic acid, and a step (2) of reacting the cellulose contained in the pulp with acetic anhydride to acetylate after the pretreatment.
  • diacetamide may be added to the acetic anhydride in the acetylation step (2).
  • diacetamide may be added in an amount of 50 ppm or more and 200 ppm or less based on the weight of the acetic anhydride.
  • diacetamide may be added to the acetic acid in the pretreatment step (1).
  • diacetamide may be added in an amount of 350 ppm to 1500 ppm based on the weight of the acetic acid.
  • the degree of vacuum in the acetylation reaction system at the start of the acetylation reaction may be 9.3 kPa or less.
  • the maximum temperature in the reaction system may be 100 ° C or more and 200 ° C or less.
  • Cellulose acetate In the cellulose acetate of the present disclosure, the content of the compound represented by the following general formula (a) is 0 ppb or more and 100 ppb or less, and the total degree of acetyl substitution is 2.3 or more and 2.6 or less.
  • the content of the compound represented by the general formula (a) is 0 ppb or more and 100 ppb or less
  • the content is preferably 0 ppb or more and 80 ppb or less, more preferably 0 ppb or more and 50 ppb or less, 0 ppb or more and 30 ppb or less are more preferable.
  • the compound represented by the above general formula (a) is a polymer of furfural generated in the process of producing cellulose acetate, and is a substance that directly causes coloring of cellulose acetate, in particular, a factor that increases the hue value of the absorbance method. Is a substance. Therefore, the content is preferably smaller, and most preferably 0 ppb.
  • the content of the compound represented by the general formula (a) in the cellulose acetate of the present disclosure can be quantified by high performance liquid chromatography (HPLC).
  • HPLC high performance liquid chromatography
  • the measurement conditions by HPLC are, for example, as follows.
  • Analyzer Corona CAD (manufactured by Thermo)
  • Gradient: A solution / B solution 10/90 (25 min) ⁇
  • a solution / B solution 50/50 (0.1 min) ⁇
  • a solution / B solution 10/90 (29.9 min)
  • Total degree of acetyl substitution Where the total degree of acetyl substitution of the cellulose acetate of the present disclosure is 2.3 or more and 2.6 or less, it may be 2.4 or more and 2.6 or less, and may be 2.4 or more and 2.5 or less. In order to lower the total acetyl substitution degree, it is necessary to carry out hydrolysis to proceed with deacetylation, but with the progress of deacetylation, the compound represented by the general formula (a) is also generated. Easier to do. However, the cellulose acetate of the present disclosure has a sufficiently low content of the compound represented by the general formula (a), despite the low degree of total acetyl substitution of 2.3 or more and 2.6 or less, and is excellent. Has a hue.
  • the total acetyl substitution degree is the sum of the average acetyl substitution degrees at positions 2, 3, and 6 of the glucose ring of cellulose acetate.
  • the total degree of acetyl substitution of cellulose acetate can be measured by a known titration method in which cellulose acetate is dissolved in an appropriate solvent according to the degree of substitution, and the degree of substitution of cellulose acetate is determined. According to the method of Tezuka (Tezuka, Carbonydr. Res. 273, 83 (1995)), the total acetyl substitution degree was determined by converting the hydroxyl group of cellulose acetate into a fully derivatized cellulose acetate propionate (CAP) and then dissolving in deuterated chloroform. , NMR ( 13 C-NMR or 1 H-NMR).
  • the total degree of acetyl substitution is determined by converting the degree of acetylation determined according to the method for measuring the degree of acetylation in ASTM: D-817-91 (test method for cellulose acetate or the like) by the following equation. This is the most common method of determining the total degree of acetyl substitution of cellulose acetate.
  • DS 162.14 ⁇ AV ⁇ 0.01 / (60.252-42.037 ⁇ AV ⁇ 0.01)
  • DS Total substitution degree of acetyl AV: Degree of acetylation (%)
  • AV (degree of acetylation) (%) is calculated according to the following equation.
  • AV (%) (AB) ⁇ F ⁇ 1.201 / sample weight (g)
  • the compound represented by the general formula (a) can be sufficiently reduced, so that cellulose acetate having an excellent absorbance hue can be obtained.
  • the absorbance hue of cellulose acetate at a wavelength of 430 nm can be determined by the following method.
  • Absorbance method hue (cm -1 ) absorbance (AB) / cell thickness (cm) / cellulose acetate concentration (% by weight) ⁇ 100
  • the cellulose acetate of the present disclosure has a 6% viscosity of preferably 60 mPa ⁇ s or more, more preferably 80 mPa ⁇ s or more, further preferably 90 mPa ⁇ s or more, and most preferably 100 mPa ⁇ s or more. Further, it may be 160 mPa ⁇ s or less, 130 mPa ⁇ s or less, or 110 mPa ⁇ s or less.
  • the 6% viscosity is less than 60 mPa ⁇ s, the molecular weight of cellulose acetate is too small, and when formed into a molded product, its mechanical strength (particularly brittleness) tends to be inferior. Further, when the 6% viscosity exceeds 160 mPa ⁇ s, when a mixed solution containing cellulose acetate is sent to a precipitation tank through a line in a process of producing cellulose acetate, the cellulose acetate is easily clogged in the line, and the production efficiency of cellulose acetate is increased. Will decrease.
  • a solution in other words, a dope
  • a solvent such as methylene chloride or acetone
  • the 6% viscosity is a viscosity obtained by using an Ostwald viscometer to measure a 6 wt / vol% solution obtained by dissolving 3.00 g of a dry sample in 39.90 g of a 95% acetone aqueous solution.
  • the filtration rating KW cellulose acetate of the present disclosure preferably 400 ml -1 or less, 200 ml -1, more preferably less, 100 ml -1 more preferably less, 95 ml -1 or less is most preferred.
  • the filtration degree can be measured by the following method.
  • a predetermined filter cloth width (diameter 15 mm, filtration area 1.77 cm 2 ) was prepared by dissolving a cellulose acetate solution in a 95% acetone aqueous solution to a concentration of 20% by weight at 30 ° C. under a constant pressure (2 kgf / cm 2 ). And filter.
  • P 1 (ml) the filtration amount up to 20 minutes after the start of filtration
  • P 2 (ml) the filtration degree from 20 minutes to 60 minutes
  • the filtration degree KW (ml ⁇ 1 ) was calculated by the following equation. calculate.
  • KW [(2-P 2 / P 1 ) / (P 1 + P 2 )] ⁇ 10 4
  • the filtration degree KW is an index of filterability since it indicates the amount of insoluble components in the cellulose acetate solution. According to the above formula, the smaller the KW value, the smaller the amount of insoluble components in the solution and the better the filterability of cellulose acetate.
  • composition ratio of sugar chain components As the composition ratio of the sugar chain component of the cellulose acetate of the present disclosure, the total of the three components of the mannose unit (Man), the xylose unit (Xyl), and the glucose unit (Glc) is 100, and the mannose unit (Man) and the xylose unit
  • the total content (mol%) of (Xyl) is preferably 5.0 or less, more preferably 4.0 or less. Further, from the viewpoint of the environmental load in the production of pulp as a raw material and the production cost, the total content (mol%) of mannose units (Man) and xylose units (Xyl) may be 1.0 or more.
  • composition ratio of the sugar chain component can be measured by chromatography.
  • Cellulose acetate of the present disclosure can be produced by the method for producing cellulose acetate described below.
  • the method for producing cellulose acetate according to the present disclosure includes a step (1) of pretreating pulp by contacting with acetic acid, and a step of acetylating the cellulose contained in the pulp by reacting with acetic anhydride after the pretreatment. (2) a step of hydrolyzing the cellulose acetate obtained by the acetylation (3), and a step (4) of precipitating the cellulose acetate having a degree of acetyl substitution adjusted by the hydrolysis, The diacetamide is added by the step (3). Diacetamide may be added in any of the steps up to the hydrolysis step (3).
  • Pulp can be used as a cellulose source as a raw material of the cellulose acetate of the present disclosure.
  • Pulp includes, for example, wood pulp and linter pulp. In particular, wood pulp can be used.
  • Wood pulp includes softwood pulp and hardwood pulp.
  • Softwood pulp includes, for example, softwood pulp obtained from spruce, pine, boxwood and the like.
  • Examples of the hardwood pulp include hardwood pulp obtained from eucalyptus, acacia, and the like.
  • the pulp may be used alone or in combination of two or more. For example, softwood pulp and hardwood pulp may be used in combination.
  • the ⁇ -cellulose content of the raw pulp is preferably 85% by weight or more, more preferably 90% by weight or more.
  • the ⁇ -cellulose content is preferably 98% by weight or less, 96% by weight or less, particularly preferably 95% by weight or less.
  • the ⁇ -cellulose content is particularly preferably from 90% by weight to 95% by weight.
  • Pulp having a ⁇ -cellulose content of more than 98% by weight has a naturally low furfural content derived from cellulose and a low furfural content in the pulp in the acetylation step. Although the color of cellulose acetate obtained from pulp having an ⁇ -cellulose content exceeding 98% by weight as a raw material is good, it is expected that it will be difficult to obtain such a raw material having a high ⁇ -cellulose content in the future. .
  • Pulps having an ⁇ -cellulose content of more than 98% by weight are usually called dissolving pulp and prepared by a special purification method. Such a preparation method has a large environmental burden. In the future, it is expected that reduction of the environmental load will be required more, and there is concern about future resource supply.
  • ⁇ -cellulose content can be determined as follows.
  • the pulp of known weight is continuously extracted at 25 ° C. with 17.5% and 9.45% aqueous sodium hydroxide solution, and the soluble portion of the extract is oxidized with potassium dichromate to obtain the pulp.
  • the weight of ⁇ , ⁇ -cellulose is determined from the volume of potassium dichromate thus obtained.
  • the value obtained by subtracting the ⁇ , ⁇ -cellulose weight from the initial pulp weight is defined as the weight of the insoluble portion of the pulp, that is, the weight of ⁇ -cellulose (TAPPI (T203).
  • TAPPI T203
  • the ratio of the weight of the insoluble portion of the pulp to the weight of the initial pulp is the ⁇ -cellulose content (% by weight).
  • the saccharide constituent ratio of the obtained cellulose acetate changes depending on the difference in the ⁇ -cellulose content of the raw pulp.
  • the pulp as a raw material has a low ⁇ -cellulose content
  • the content of xylan and mannan naturally increases as the sugar composition ratio of cellulose acetate.
  • Pulp can be used in the form of a sheet.
  • a sheet having a basis weight of 300 g / m 2 or more and 850 g / m 2 or less, a density of 0.40 g / cm 3 or more and 0.60 g / cm 3 or less, and a burst strength of 50 kPa or more and 1000 kPa or less is preferable.
  • the present invention is not limited to these.
  • the method for producing cellulose acetate according to the present disclosure may include a step of pulverizing pulp in advance. Thereby, the reaction proceeds efficiently and uniformly in the subsequent steps, and the handling becomes easy.
  • the crushing step is particularly effective when the pulp is supplied in sheet form.
  • the wet disintegration method is a method in which water or steam is added to pulp (particularly, sheet pulp) to disintegrate.
  • the wet crushing method include, for example, a method of performing activation by steam and strong shear stirring in a reactor, or a method of disintegrating in a dilute acetic acid aqueous solution to obtain a slurry, and then repeatedly removing the liquor and replacing with acetic acid.
  • the method include a method of performing processing.
  • the dry crushing method is a method of crushing pulp (particularly, sheet-like pulp) in a dry state.
  • Examples of the dry crushing method include, for example, a method of finely crushing a pulp coarsely crushed by a disc refiner having pyramid teeth, a fine crushing by a disc refiner having linear teeth, and a cylindrical outer box having a liner attached to an inner wall thereof.
  • a turbo mill having a plurality of disks rotating at high speed around the center line of the outer box and a number of wings radially attached to the center line between the disks, hitting with the wings, Crushes the crushed material supplied into the outer box by three types of impact action, consisting of collision with the air, and high-frequency pressure vibration generated by the action of the high-speed rotating disk, wing, and liner. And the like.
  • any of these pulverizing methods can be appropriately used.
  • unreacted cellulose can be reduced by a two-step pulverizing method using a disc refiner and a turbo mill in this order. It is preferable because the filtration degree of the obtained cellulose acetate can be improved (in other words, the value of the filtration degree can be lowered).
  • the acetic acid is contacted, for example, preferably by adding 10 to 500 parts by weight to 100 parts by weight of cellulose contained in the pulp. Can be done. At this time, acetic acid having a concentration of 99% by weight or more can be used.
  • a method of bringing pulp into contact with acetic acid for example, a method of adding acetic acid or acetic acid containing 1 to 10% by weight of sulfuric acid (sulfur-containing acetic acid) in a single step; A method of adding acetic acid or sulfur-containing acetic acid in two or more steps, such as a method of adding sulfur-containing acetic acid, a method of adding acetic acid after a certain period of time from the addition of sulfur-containing acetic acid, and the like. As a specific means of the addition, there is a method of spraying and stirring.
  • the activation of the cellulose contained in the pulp by the pretreatment is performed by adding acetic acid and / or sulfur-containing acetic acid to the pulp, and then allowing the pulp to stand at a temperature of 17 ° C to 40 ° C for 0.2 hours to 48 hours. Or sealing and stirring under conditions of 17 ° C. or more and 40 ° C. or less for 0.1 hour or more and 24 hours or less.
  • diacetamide may be added to the acetic acid, and the amount of diacetamide added may be 350 ppm or more and 1500 ppm or less based on the acetic acid. .
  • the pretreatment step (1) by adding diacetamide to the acetic acid, it is not necessary to add diacetamide to acetic anhydride.
  • the acetylation was specifically activated, for example, by a pretreatment to a mixture of acetic acid, acetic anhydride and sulfuric acid. It can be started by adding the cellulose contained in the pulp, or by adding a mixture of acetic acid and acetic anhydride and sulfuric acid to the cellulose contained in the pulp activated by the pretreatment.
  • acetic acid having a concentration of 99% by weight or more can be used. It is preferable to use sulfuric acid having a concentration of 98% by weight or more.
  • the ratio of acetic acid and acetic anhydride is not less than 300 parts by weight and not more than 600 parts by weight of acetic acid.
  • the acetic anhydride is preferably 200 parts by weight or more and 400 parts by weight or less, more preferably 240 parts by weight or more and 280 parts by weight or less with respect to 350 parts by weight or more and 530 parts by weight of acetic acid.
  • the amount of sulfuric acid is preferably from 5 to 15 parts by weight, more preferably from 7 to 13 parts by weight, even more preferably from 8 to 11 parts by weight.
  • step (2) of reacting cellulose contained in the pulp with acetic anhydride to acetylate it is preferable to add diacetamide to acetic anhydride.
  • the amount of diacetamide added is preferably from 10 ppm to 500 ppm, more preferably from 50 ppm to 200 ppm, based on the weight of acetic anhydride. When the content is in this range, cellulose acetate having particularly excellent hue can be obtained.
  • diacetamide As a method of adding diacetamide, it is preferable that cellulose contained in the pulp be added to acetic anhydride before reacting with the acetic anhydride. In other words, it is preferable to prepare diacetamide in advance as an acetic anhydride solution. This is because by uniformly bringing the pulp into contact with the pulp, it is possible to uniformly exert a coloring suppression effect.
  • the acetylation step (2) may be performed under reduced pressure or normal pressure as described below, and will be described separately for each case.
  • the degree of vacuum in the acetylation reaction system be 70 Torr (9.3 kPa) or less at least at the start of the acetylation reaction.
  • the lower limit is not particularly limited, it is, for example, 60 Torr (8.0 kPa) or more.
  • This method has an advantage that cooling of a mixed solution of acetic acid and acetic anhydride for suppressing a rise in temperature due to the acetylation reaction becomes unnecessary.
  • the degree of vacuum in the acetylation reaction system is 70 Torr (9.3 kPa) or less from at least the start of the acetylation reaction until the cellulose acetate is converted from a non-uniform state to a uniform state. This is for suppressing a temperature rise accompanying the acetylation reaction.
  • a mixture containing sulfuric acid and acetic acid is added to start the acetylation reaction, and the vapor of the mixture of acetic acid and acetic anhydride that evaporates is condensed by a condenser and distilled out of the reaction system.
  • the reaction product is gradually concentrated, and when a predetermined amount (a distillate amount corresponding to a target reaction rate) is distilled or when the liquid to be distilled almost disappears, the inside of the reaction system is brought to normal pressure, The pressure is maintained for 1 minute or more and 30 minutes or less from the time when the pressure or the temperature in the reaction system stops rising.
  • the highest temperature in the acetylation reaction system is preferably 55 ° C or more and 75 ° C or less, and 60 ° C or more and 70 ° C or less. Is more preferable.
  • the pulp is poured into an uncooled acetylation mixture (a mixed solution containing acetic acid, acetic anhydride, and sulfuric acid), and the mixture is stirred.
  • the reaction can be realized by generating heat of reaction of acetic acid and raising the temperature.
  • a mixture containing 200 to 400 parts by weight of acetic anhydride and 5 parts by weight or less of an acidic catalyst (eg, sulfuric acid) is added to 100 parts by weight of cellulose pulp, and the mixture is added for 20 minutes to 40 minutes. It can reach the final temperature of 55 ° C. or more and 75 ° C. or less in less than minutes.
  • the time required for the acetylation reaction under reduced pressure conditions is preferably from 40 minutes to 60 minutes.
  • the time required for acetylation refers to the time from when cellulose pulp starts reacting with acetic anhydride (particularly, when cellulose pulp starts acetylating reaction by contacting with acetic anhydride, a solvent and a catalyst). It means the time until the neutralizer is charged.
  • ⁇ Normal pressure condition> A method for producing cellulose acetate under normal pressure conditions will be described. In the case of acetylation under normal pressure conditions, it is necessary to lower the temperature of acetic anhydride and acetic acid to be added in order to control the reaction temperature.
  • the maximum temperature in the acetylation reaction system is preferably in the middle temperature range. Specifically, the temperature is preferably from 38 ° C. to 52 ° C., and more preferably from 42 ° C. to 50 ° C. This is because cellulose acetate having more excellent hue can be obtained.
  • acetylation is performed so that the highest temperature in the acetylation reaction system is in the middle temperature range, it is preferable to include a step of precooling acetic anhydride.
  • acetic acid and a catalyst are brought into contact with cellulose in addition to acetic anhydride, it is more preferable to pre-cool them all.
  • the mixture may be precooled.
  • the pre-cooling temperature is preferably from -25 ° C to -10 ° C, more preferably from -22 ° C to -20 ° C.
  • the highest temperature in the reaction system in the acetylation step (2) can be set to a medium temperature range (about 38 ° C. or more and about 52 ° C. or less), and cellulose acetate having more excellent hue can be obtained. This is because
  • an acetylated mixed solution containing acetic acid as a solvent, acetic anhydride as an acetylating agent, and sulfuric acid as a catalyst is previously cooled to ⁇ 25 ° C. or more and ⁇ 10 ° C. or less, and cellulose (pulp) is poured into the acetylated mixed solution.
  • the amount of acetic anhydride is used in a substantial excess over the amount of cellulose reacting therewith and the amount of water present in the system.
  • the temperature of the cooled acetylated mixed solution is raised by the reaction heat of acetic anhydride, but the maximum temperature can be set to 38 ° C. or more and 52 ° C. or less.
  • the reaction may be carried out without adding any heat to the inside and outside of the reaction system under stirring conditions, or the reaction system may be cooled to a medium temperature by cooling with a refrigerant under stirring conditions.
  • a reactor used in the acetylation step (2) a known reactor (acetylation reactor) usually used when producing cellulose acetate can be used, but a miscible reactor is preferable.
  • the time required for the acetylation reaction under normal pressure conditions is desirably 60 minutes to 90 minutes.
  • the time required for acetylation is defined as the time from when cellulose pulp starts to react with acetic anhydride (particularly, when cellulose pulp starts acetylation by contacting with acetic anhydride, a solvent and a catalyst). It means the time until the introduction of the wadding agent.
  • the temperature should be raised as long as possible to suppress the depolymerization acetylation reaction and promote the acetylation reaction to reduce unreacted substances.
  • the degree of acetyl substitution is adjusted by using a neutralizing agent consisting of water (including water vapor); dilute acetic acid; or a carbonate, acetate, hydroxide or oxide such as calcium, magnesium, iron, aluminum or zinc;
  • the acetylation reaction can be performed by adding the acetylation reaction. Water reacts with acetic anhydride present in the reaction mixture containing cellulose acetate to form a carboxylic acid, and after adjusting the degree of acetyl substitution, the water content of the reaction mixture containing cellulose acetate is at least 5 mol% based on the carboxylic acid. It can be added so as to be 70 mol% or less.
  • the hydrolysis reaction does not proceed, and the depolymerization proceeds, resulting in a low-viscosity cellulose acetate. If the amount exceeds 70 mol%, the cellulose acetate after the acetylation reaction (cellulose acetate before the hydrolysis) precipitates. Since the reaction exits the hydrolysis reaction system, the hydrolysis reaction of the precipitated cellulose acetate does not proceed.
  • Dilute acetic acid refers to an aqueous acetic acid solution having an acetic acid concentration of 1% by weight or more and 50% by weight or less.
  • concentration of magnesium acetate in the aqueous solution is preferably 5% by weight or more and 30% by weight or less.
  • the sulfate ion concentration in the reaction mixture containing cellulose acetate is high, the sulfate ester cannot be removed efficiently, so that an aqueous solution of an alkaline earth metal salt of acetic acid such as magnesium acetate or a mixed solution of acetic acid-water is added. It is preferable to reduce the sulfate ion concentration by forming an insoluble sulfate. It is preferable to adjust the sulfate ion of the reaction mixture containing cellulose acetate to 1 part by weight or more and 6 parts by weight or less based on 100 parts by weight (in terms of cellulose) of cellulose acetate.
  • the hydrolysis step (3) there is a method of performing hydrolysis at a high temperature using steam (high-temperature aging).
  • the hydrolysis step (3) can be performed at any temperature in the reaction system at normal temperature (medium temperature) or high temperature.
  • the hydrolysis performed at room temperature is referred to as room temperature aging, and refers to a case where the highest temperature in the reaction system is 55 ° C or higher and lower than 100 ° C, and preferably 55 ° C or higher and lower than 90 ° C.
  • Hydrolysis performed at a high temperature is referred to as high-temperature aging, and refers to a range where the highest temperature in the reaction system is 100 ° C. or more and 200 ° C. or less.
  • high temperature aging the temperature in the system is raised using steam.
  • the hydrolysis of cellulose acetate is preferably performed at normal temperature (medium temperature) from the viewpoint of hue. That is, the hydrolysis reaction proceeds sufficiently, and the depolymerization of the hemicellulose component caused by the low-grade pulp hardly occurs as compared with the high temperature, so that cellulose acetate having more excellent hue can be obtained.
  • a mixture containing the cellulose acetate and a precipitant such as water or dilute acetic acid are mixed to produce cellulose acetate (precipitate). Can be separated to obtain a precipitate. Further, as the precipitant, dilute acetic acid is preferable.
  • the precipitate may be washed with water to remove free metal components and sulfuric acid components.
  • an alkali metal compound and / or an alkaline earth metal compound, particularly a calcium compound such as calcium hydroxide, as a stabilizer to the water during washing with water.
  • the cellulose acetate may be dried.
  • the method for drying is not particularly limited, and a known method can be used.
  • drying can be performed under conditions such as air blowing or reduced pressure.
  • Examples of the drying method include hot air drying.
  • Patent Document 2 a method of adding an organic solvent in a process of producing cellulose acetate (Patent Document 2), a method of once dissolving cellulose diacetate in a solvent having good solubility, and recovering the same (Patent Document 2) 3), but these have an effect only when a low-grade pulp having a low ⁇ -cellulose content is used, and cannot be used when a pulp having a high ⁇ -cellulose content is used.
  • the method for producing cellulose acetate of the present disclosure instead of extracting or removing a substance that causes coloring (for example, furfural) from a raw material, it is possible to inhibit a polymerization reaction that generates a substance that causes the coloring. it can. In this way, unlike the conventional technology, the substance causing coloring (for example, furfural) is not reduced from the raw material, but the substance causing coloring (for example, furfural) remains in the product. By preventing the above, cellulose acetate having a good hue can be obtained without particularly reducing a substance causing coloring (for example, furfural) from the raw material.
  • a substance that causes coloring for example, furfural
  • ⁇ -cellulose content> The pulp of known weight is continuously extracted at 25 ° C. with 17.5% and 9.45% aqueous sodium hydroxide solution, and the soluble portion of the extract is oxidized with potassium dichromate to obtain the pulp.
  • the weight of ⁇ , ⁇ -cellulose was determined from the volume of potassium dichromate thus obtained.
  • the value obtained by subtracting the ⁇ , ⁇ -cellulose weight from the initial pulp weight was defined as the weight of the insoluble portion of the pulp, that is, the weight of ⁇ -cellulose (TAPPI T203).
  • the ratio of the weight of the insoluble portion of the pulp to the weight of the initial pulp is the ⁇ -cellulose content (% by weight).
  • Total acetyl substitution degree was measured by a method using 1 H-NMR according to the method of Tezuka described above.
  • ⁇ Filtration degree> Filtration was measured by the following method.
  • a predetermined filter cloth width (diameter 15 mm, filtration area 1.77 cm 2 ) was prepared by dissolving a cellulose acetate solution in a 95% acetone aqueous solution to a concentration of 20% by weight at 30 ° C. under a constant pressure (2 kgf / cm 2 ). And filtered.
  • P 1 (ml) the filtration amount up to 20 minutes after the start of filtration
  • P 2 (ml) the filtration degree KW (ml ⁇ 1 ) was calculated by the following equation. Calculated.
  • KW [(2-P 2 / P 1 ) / (P 1 + P 2 )] ⁇ 10 4
  • Man mannose unit
  • Xyl xylose unit
  • Glc glucose unit
  • Example 1 Wood pulp, Rayaceta-HJ (water content: about 3.0%, ⁇ -cellulose content: 98% by weight) as a cellulose raw material was pulverized into a fluff by a pulverizer. 100 parts by weight of fluffy cellulose pulp was placed in a pretreatment machine, and 38 parts by weight of glacial acetic acid was sprayed thereon, and activated by pretreatment (25 ° C., 60 minutes). Also, diacetamide was added to and dissolved in acetic anhydride so as to be 200 ppm to prepare an acetic anhydride solution. The cellulose pulp impregnated with acetic acid by the pretreatment was put into an acetylation reactor while stirring, and charged into the acetylation reactor.
  • Example 1 Cellulose acetate was obtained in the same manner as in Example 1 except that diacetamide was not added to acetic anhydride. Table 1 shows the results of evaluating the physical properties of the obtained cellulose acetate and each raw material.

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Abstract

La présente invention concerne un acétate de cellulose qui contient une quantité suffisamment petite d'une substance provoquant la coloration, et présentant donc une excellente teinte. L'invention porte sur un acétate de cellulose qui contient un composé représenté par la formule générale (a) en une quantité de 0 ppb à 100 ppb (limites comprises), tout en présentant un degré total de substitution acétyle de 2,3 à 2,6 (limites comprises).
PCT/JP2019/027678 2018-07-12 2019-07-12 Acétate de cellulose et procédé de production d'un acétate de cellulose WO2020013312A1 (fr)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS58176201A (ja) * 1982-04-12 1983-10-15 Daicel Chem Ind Ltd セルロ−ス・カルボン酸エステルの新規な製造方法
WO2017061474A1 (fr) * 2015-10-08 2017-04-13 株式会社ダイセル Acétate de cellulose et procédé et dispositif de production d'acétate de cellulose
WO2018066477A1 (fr) * 2016-10-03 2018-04-12 株式会社ダイセル Acétate de cellulose et procédé de production d'acétate de cellulose
WO2018139319A1 (fr) * 2017-01-25 2018-08-02 株式会社ダイセル Procédé de fabrication de flocons d'acétate de cellulose
WO2018139317A1 (fr) * 2017-01-25 2018-08-02 株式会社ダイセル Acétate de cellulose, et corps moulé

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS58176201A (ja) * 1982-04-12 1983-10-15 Daicel Chem Ind Ltd セルロ−ス・カルボン酸エステルの新規な製造方法
WO2017061474A1 (fr) * 2015-10-08 2017-04-13 株式会社ダイセル Acétate de cellulose et procédé et dispositif de production d'acétate de cellulose
WO2018066477A1 (fr) * 2016-10-03 2018-04-12 株式会社ダイセル Acétate de cellulose et procédé de production d'acétate de cellulose
WO2018139319A1 (fr) * 2017-01-25 2018-08-02 株式会社ダイセル Procédé de fabrication de flocons d'acétate de cellulose
WO2018139317A1 (fr) * 2017-01-25 2018-08-02 株式会社ダイセル Acétate de cellulose, et corps moulé

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