JP3144957B2 - Cellulose fatty acid ester and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cellulose fatty acid ester and a method for producing the same. More specifically, transparency,
The present invention relates to a cellulose fatty acid ester having good filterability and spinnability, and a method for producing the cellulose fatty acid ester, which comprises producing such a cellulose fatty acid ester from low-grade pulp as a cellulose raw material.

[0002]

2. Description of the Related Art Cellulose fatty acid esters, especially cellulose acetate, are used in a wide variety of applications such as clothing fibers, cigarette filters, plastics, films, paints, and the like.
It occupies an industrially important position among cellulose derivatives.

[0003] Raw materials for producing cellulose fatty acid esters are mainly wood pulp, and among them, high-grade pulp having a high degree of purification is used. The reason for this is that, when a generally used manufacturing method is applied to low-grade wood pulp, a large amount of so-called insoluble residues that do not dissolve in the solvent are generated, and good spinnability, transparency as plastic, etc. This is because they are significantly impaired and filtration is required to ensure these qualities.

[0004] The basic production process of cellulose acetate, which is a typical cellulose fatty acid ester, is as follows: (1) Pulp raw material having a relatively high α-cellulose content is disintegrated and crushed.
A pretreatment step of spraying and mixing acetic acid; (2) an acetylation step of reacting the pretreated pulp of (1) with a mixed acid comprising acetic anhydride, acetic acid and an acetylation catalyst (for example, sulfuric acid); It comprises a ripening step in which cellulose acetate is hydrolyzed to a desired degree of acetylation, and (4) a post-treatment step in which cellulose acetate having undergone the ripening reaction is precipitated and separated from the reaction solvent, purified, stabilized, and dried.

[0005] In such a basic process of producing cellulose acetate, improved techniques from various viewpoints have been announced in order to obtain a high-quality cellulose ester using the low-grade pulp available at a low cost as described above. ing. In U.S. Pat. No. 3,676,764, the α-cellulose content is 92-93%.
After disintegrating the wood pulp in a dilute acetic acid aqueous solution to form a slurry, performing a so-called slurry pretreatment of repeating deliquoring and acetic acid substitution, and then performing an acetylation reaction by a conventional technique, and then a sulfuric acid catalyst in the reaction system. Is completely neutralized, and the reaction mixture is saponified and aged at 125 to 170 ° C. to obtain cellulose acetate having good transparency, filterability and spinnability. In the method of JP-A-56-59801, a high-grade pulp having a high α-cellulose content is dry-crushed by a usual method, and then a small amount of sulfuric acid is used as a catalyst to complete the acetylation reaction in a short time at a high temperature. After that, the sulfuric acid catalyst in the system is completely neutralized, and a saponification aging reaction is performed at 110 to 120 ° C. to obtain cellulose acetate having good transparency, filterability and spinnability. It states that this technology also enables the use of low grade pulp with low α-cellulose content. A feature common to the above techniques is that a saponification / ripening reaction is performed at a high temperature. This saponification and aging at high temperature promotes the destruction or change in the form of acetylated hemicellulose, which harms the properties of cellulose acetate, and renders them harmless.

Further, Japanese Patent Application Laid-Open Nos.
According to the publication No. −65401, the above-mentioned problem was noted, focusing on the fact that low-grade wood pulp sheets are generally dense and difficult to disintegrate, so that they have poor dispersibility in the reaction system and lead to the generation of insoluble residues. A statement that seeks to solve the point is disclosed. That is, JP-A-2-311501 discloses that a pulp sheet is softened by wet pulverization, and heat generated at the time of pulverization is removed as latent heat of evaporation, thereby eliminating thermal deterioration of pulp.
It is intended to obtain a cellulose material having high reactivity and to prevent the formation of a gel resulting from an unreacted substance or an insufficient reaction during the acetylation reaction. On the other hand, Japanese Patent Application Laid-Open No. 4-65401 discloses that, when dry crushing, by devising a crusher, the degradation of reactivity of the pulp during crushing is suppressed to a level that does not affect the acetylation reaction,
It is intended to prevent the formation of a gel resulting from an unreacted substance or an insufficient reaction during the acetylation reaction.

[0007]

However, the above-mentioned prior art has a limit in acetylating pulp having a particularly low α-cellulose content, for example, an α-cellulose content of 85 to 93%. The filterability could not be reduced.

[0008]

Means for Solving the Problems The present inventors separated and recovered a large amount of insoluble residue remaining in an acetylation reaction solution obtained by acetylating a low-grade pulp having a low α-cellulose content. As a result of intensive studies, it was revealed that the insoluble residue was an aggregate composed of cellulose triacetate and glucomannan triacetate. Furthermore, it has been clarified that the insoluble residue retains the form of wood pulp fiber while swelling considerably in the acetylation reaction solution.

The present inventors have studied the solubility of acetylated glucomannan in low-grade pulp having a low α-cellulose content in various solvents based on this finding. The reaction can be carried out in a system in which a part of acetic acid as an agent is replaced with an organic solvent, or the reaction can be continued by adding it as a third component in the course of the reaction, or by adding the third component after the completion of the reaction. The insoluble residue can be reduced while keeping in the reaction solution without removing the acetate, and the α-cellulose content is extremely low-grade pulp as compared with the pulp conventionally used as a raw material.
It has been found that cellulose acetate excellent in filterability, transparency, spinning characteristics and the like can be produced. Furthermore, the present inventors have found that this method can be applied to the production of other cellulose fatty acid esters, and have completed the present invention.

That is, the present invention relates to a method for producing a cellulose fatty acid ester using a pulp having a low α-cellulose content as a raw material and a corresponding fatty acid as a diluent, the method comprising: Is added in any of the production steps.

[0011] The present invention also relates to the present invention, wherein the sum of the molar contents of mannose and xylose in the constituent sugar analysis is 7% or more of the sum of the molar contents of glucose, mannose and xylose, and the amount of filtration under predetermined conditions described below. It is intended to provide a cellulose fatty acid triester or a cellulose fatty acid diester, wherein a filtration amount P ₂ (g) for 40 minutes from 20 minutes to 60 minutes after the start of filtration in the measurement satisfies the following conditions. (A) Cellulose fatty acid triester P ₂ > −0.14η + 86 (B) Cellulose fatty acid diester P ₂ > −0.16η + 40 where η is the viscosity of a 6% solution (centipoise;
Note). The viscosity is measured by a method described later. ].

The cellulose fatty acid ester of the present invention contains a large amount of xylose and mannose in constituent sugar analysis and has excellent filterability and the like.

[I] The method for analyzing constituent sugars and the measurement conditions according to the present invention are defined by the following methods. (1) Analysis method Alditol acetate method (Borchadt, LG; Pipe
r, CV: Perform according to Tappi, 53, 257-260 (1970)). (2) Measurement conditions Gas chromatograph: Shimadzu GC-7A gas chromatograph Column: 10% Silar 10 C column (2 m) Injection temperature: 250 ° C Column temperature: 230 ° C Carrier gas: helium (40 ml / min) Results were measured three times Is evaluated by the average value. In the cellulose fatty acid ester of the present invention, the sum of the molar contents of mannose and xylose accounts for 7% or more of the sum of the molar contents of glucose, mannose and xylose.

[II] The measurement of the amount of filtration and the viscosity of a 6% solution is defined by the following method. (i) Filtration amount A cellulose acetate solution dissolved in a predetermined solvent at a predetermined concentration is passed through a predetermined filter cloth (diameter 15 mm, filtration area 1.77 cm ² ) at a predetermined temperature, and the amount of filtration to be filtered under a constant pressure is measured. At this time, the filtration amount up to 20 minutes after the start of filtration is calculated from P ₁ (g) and 20 minutes.
The amount of filtration for 40 minutes up to 60 minutes is defined as P ₂ (g). Measurement conditions are different between cellulose fatty acid triester and cellulose fatty acid diester due to their different solubility in solvents. The measurement conditions for each are as shown in Table 1.

[0015]

[Table 1]

(Ii) Viscosity of 6% solution: 6% by weight of cellulose fatty acid triester and cellulose fatty acid diester in the same solvent as in the filtration amount measurement.
Dissolve completely to a concentration. For this solution,
Using a Ostwald viscometer, the number of falling seconds (t ₁ ) is measured at 25 ± 0.1 ° C. Absolute viscosity at 25 ° C. η ₂ (c
P), the density D ₂ (g / ml) is also measured falling number of seconds (t ₂₎ in the same manner using the same viscometer with respect to the standard solution is known, the viscosity of the sample by the following equation eta ₁ (cP ) Is calculated. η ₁ = η ₂ / (D ₂ × t ₂ ) × D ₁ × t ₁ Here, η ₂ / (D ₂ × t ₂ ) is a conversion coefficient unique to the viscometer used. Also, D ₁ is the density of the sample solution, 1.235 g / ml for cellulose fatty acid triester, calculated as 0.823 g / ml for cellulose fatty acid diester. P ₂ calculated by the above method increases as fewer samples clogged by impurities particles, but the filterability index, which is influenced by the viscosity at the same time, the larger the sample the low viscosity. Relationship viscosity and filtration rate P ₂ is above (A),
The cellulose fatty acid ester of the present invention in the range of (B) contains a large amount of xylose and mannose in the constituent sugar analysis, has excellent filterability, and, needless to say, has an appropriate viscosity as a product. Means

Next, as an example of the production method of the present invention, a case where cellulose acetate is produced will be described.

In the method for producing cellulose acetate of the present invention, the wood pulp used as the cellulose raw material is a low-grade pulp having an α-cellulose content of 85 to 93% by weight. Usually such pulp is available in sheet form, where the basis weight of the sheet is 300-850 g / m ² and the density is 0.40-0.50 g / c
The m ³ and the burst strength are preferably those of 50 to 350 KPa, but are not limited thereto.

It is not always necessary to carry out a pretreatment prior to the reaction, but it is generally carried out. For example, pulp is processed by a crusher to make fluffy crushed pulp. This crushed pulp is pre-treated and activated by, for example, spraying and mixing 20 to 100 parts by weight of acetic acid with respect to 100 parts by weight of the crushed pulp, and in a closed vessel equipped with a stirrer, at a temperature of 20 to 50 ° C. For example, a method of stirring the pulp for 0.5 to 2 hours is used (pretreatment step).

Then, acetic anhydride 200 to 40 as an acetylating agent
0 parts by weight, 300 to 500 parts by weight of acetic acid, and 0.5 to 5 parts by weight of an acidic catalyst are added and mixed with stirring. The acetylation catalyst is not particularly limited as long as it promotes acetic acid esterification, such as sulfuric acid or perchloric acid, but is preferably sulfuric acid. There is no particular limitation on the order of addition, but if the catalyst comes into contact with the pulp, it will be decomposed, so it is preferable to use it in advance by mixing with acetic acid or acetic anhydride. The contents generate heat due to the reaction,
By adjusting the temperature to be raised at a substantially constant rate over 60 minutes, finally at a temperature of 50 ° C. or more and 85 ° C. or less, and subsequently maintaining the temperature for 3 to 20 minutes to acetylate the cellulose, Cellulose triacetate (primary cellulose acetate) is obtained (acetylation step).

Next, when cellulose diacetate (secondary cellulose acetate) is obtained, a hydrolysis reaction (saponification / ripening) of cellulose triacetate is performed. The acetylation catalyst in the acetylation reaction mixture is neutralized, and then steam is introduced into the system under a pressure of 1 to 10 kg / cm ^{2 to} raise the temperature in the system to 125 ° C to 170 ° C.
C., and the temperature is preferably maintained for 3 minutes or more and 6 hours or less in this temperature range, whereby acetyl groups of cellulose triacetate can be hydrolyzed to obtain cellulose diacetate having a desired degree of acetylation (ripening step). After the aging step, the reaction mixture is put into a dilute aqueous acetic acid solution, collected as a precipitate, washed, purified, and dried (post-treatment step).

The organic solvent may be added to any of the above-mentioned pretreatment step, acetylation step, ripening step and post-treatment step, or may be added in a plurality of steps. The amount of the organic solvent added is 10% by weight or more of a diluent such as acetic acid, preferably 10 to 90%.
% By weight.

The above is a typical method for producing cellulose acetate by the acetic acid method, and various variations are possible.

As described above, one of the features of the production method of the present invention resides in that a fatty acid corresponding to a target cellulose fatty acid ester is used as a diluent in the reaction.

Another feature of the present invention is that an organic solvent is added as a third component at any stage corresponding to a series of processes from activation of pretreatment in the acetic acid method to recovery and recovery by precipitation. It is in. The specific method of adding the organic solvent is not particularly defined. In the case of the acetic acid method, the addition of the organic solvent may be performed in the pretreatment activation step. However, the addition of the organic solvent causes swelling inhibition of the pulp fiber and delays in the acetylation reaction. It may be difficult to efficiently dissolve the cellulose acetate having a substitution degree into the reaction system. Therefore, preferably in the acetylation step, and more preferably at the stage where the acetylation reaction of the wood pulp has considerably progressed, the reaction is continued by adding an organic solvent as the third component to obtain a cellulose fatty acid triester. In this case, an insoluble material composed of a highly substituted cellulose fatty acid ester and a glucomannan fatty acid ester can be effectively dissociated and dissolved. Further, the organic solvent can be added in the aging step or the post-treatment step.

The organic solvent which is the third component used in this reaction may be any as long as it does not inhibit the desired esterification reaction, but preferably has an excellent solubility in glucomannan acetylated product. Specifically, a compound that is aprotic and contains one or two dipolar groups such as a halogen-carbon bond, a carbonyl group, a nitro group, a sulfur-oxygen bond, and an ether bond, A liquid having a melting point of 50 ° C. or lower and being mixed with a fatty acid as a diluent at an arbitrary ratio is exemplified. Preferred as the organic solvent used in the present invention, dichloromethane,
Halogenated hydrocarbon solvents such as chloroform, carbon tetrachloride, 1,1,2,2-tetrachloroethane, trichloroethylene, dichloroacetic acid, nitromethane, nitroethane,
A nitro compound-based solvent such as 1-nitropropane can be exemplified.

If the addition of water in the steps of neutralization, aging, precipitation or the like is inconvenient in terms of process such as phase separation of the organic solvent, the melting point of the organic solvent may be lower than that of the diluent. For example, the organic solvent may be partially or entirely removed by heating the reaction solution or reducing the pressure of the reaction system at an appropriate stage. When an organic solvent is added after the reaction, it may be removed by washing, heating, or reducing the pressure.

Examples of the cellulose fatty acid ester produced by the production method of the present invention include cellulose propionate, cellulose butyrate, cellulose acetate-propionate or cellulose acetate-butyrate in addition to the cellulose acetate described above. When these are produced, one or more of the corresponding fatty acids may be used in a desired ratio instead of the acetic acid used in the above-mentioned method for producing cellulose acetate.

[0029]

The cellulose fatty acid ester of the present invention comprises
Despite being manufactured from low-grade pulp with low α-cellulose content, unprecedented excellent transparency, filterability,
It has high spinnability and enables advanced utilization of low-grade pulp, which was impossible in the past. In addition, the production method of the present invention is economically advantageous because it can be carried out without significantly revising the conventional cellulose fatty acid ester production process.

[0030]

The present invention will now be described in more detail with reference to the following Examples, which by no means limit the scope of the present invention. Unless otherwise specified, parts in Examples are parts by weight, and% means% by weight.

Examples 1 to 10 and Comparative Example 1 Dissolving pulp by sulfite method (α-cellulose content: 87.5
%) Was disintegrated in water with a household mixer, replaced with acetone, and dried. This pulp is put into a pretreatment machine and 5% moisture pulp
Sprinkle 100 parts of acetic acid evenly on 100 parts,
Mix for minutes and activate pretreatment. On the other hand, a mixed solution of 250 parts of acetic anhydride, 375 parts of acetic acid, and 1.0 part of sulfuric acid, which had been cooled to 12 ° C. in advance, was prepared in a kneading and kneading acetylator, and the above-mentioned pretreated activated pulp was charged and mixed. The contents generate heat due to the reaction between water and acetic anhydride and the reaction between cellulose and acetic anhydride accompanying the raw material pulp.From the initial temperature of around 16 ° C, the contents are externally cooled to reach 77 ° C over 60 minutes. And then 125 parts of an organic solvent (see Table 2) were added. In addition, 77
C. for 12 minutes to carry out an acetylation reaction. Next, the insoluble portion was recovered by centrifugation (7000 rpm, 30 minutes), and the amount of the insoluble residue in the obtained cellulose triacetate was quantified. Both the obtained cellulose triacetate and the insoluble residue thereof had an acetylation degree of about 61%. Table 2 shows the amount of insoluble residue in each acetylation reaction. In Comparative Example 1, no organic solvent was added. As can be seen from the amount of the insoluble residue, the addition of the organic solvent improved the filterability and resulted in a cellulose triacetate product having good transparency.

[0032]

[Table 2]

Examples 1, 2, 5, 6 and Comparative Example 1
The sum of the molar contents of mannose and xylose and the amount of filtration (P ₂ ) in the constituent sugar analysis of the cellulose triacetate obtained in the above,
The 6% solution viscosity (η) is as shown in Table 2, and the cellulose triacetate of Examples 1, 2, 5 and 6 has P ₂ > −0.14η +
The product satisfied 86 conditions.

[0034]

[Table 3]

Examples 11 to 20 and Comparative Example 2 Sulfite dissolving pulp (α-cellulose content: 87.5%)
Was disassembled using an attrition mill. The fluff-crushed pulp was dried to a moisture content of 5%. The pulp was put into a pretreatment machine, and 100 parts of 5% moisture pulp was added to 100 parts.
A part of acetic acid was uniformly dispersed and mixed at 40 ° C. for 30 minutes to activate the pretreatment. On the other hand, acetic anhydride 250 previously cooled to 12 ° C
Of acetic acid, 375 parts of acetic acid, and 1.0 part of sulfuric acid were prepared in a kneading type acetylator, and the above-mentioned pretreated activated pulp was charged and mixed. The contents generate heat due to the reaction between water and acetic anhydride and the reaction between cellulose and acetic anhydride accompanying the raw material pulp.From the initial temperature of around 16 ° C, the contents are externally cooled to reach 77 ° C over 60 minutes. Then, 125 parts of an organic solvent (see Table 4) was added, and the mixture was further kept at 77 ° C. for 12 minutes to perform an acetylation reaction. In Comparative Example 2, no organic solvent was added. Next, after removing the organic solvent from the reaction solution by reaction heat, 10 parts of a 20% aqueous magnesium acetate solution was added and mixed to completely neutralize the sulfuric acid in the system and to make the magnesium acetate excessive. The completely neutralized reaction mixture was transferred to an autoclave, and steam with a gauge pressure of 5 kg / cm ² was blown in with stirring while stirring to reach 150 ° C. over about 60 minutes. After holding at 150 ° C for 50 minutes, the reaction was slowly flushed to the atmosphere to bring the reaction mixture to 100 ° C. The reaction mixture was added with a dilute acetic acid aqueous solution under vigorous stirring, separated as flaky cellulose acetate, thoroughly washed with water, and dried.

The flaked cellulose diacetate obtained has an acetylation degree of about 55%, and the viscosity and the amount of filtration are as shown in Table 4.
The product was excellent in filterability and spinnability. Example 1
The sum of the molar contents of mannose and xylose in the constituent sugar analysis of cellulose diacetate obtained in 1, 12, 15, 16 and Comparative Example 2 was 7.5, 7.2, 7.0, 7.1 and 7.3, respectively, while the filtration amount was As shown in Table 4, Example 11,
Cellulose diacetates 12, 15, and 16 were products satisfying P ₂ > −0.16η + 40.

[0037]

[Table 4]

The degree of acetylation of cellulose acetate was measured by AS
Performed in accordance with TM D-871 (1970).

Claims (7)

(57) [Claims] 1. The sum of the molar contents of mannose and xylose in the analysis of the constituent sugars is 7% or more of the sum of the molar contents of glucose, mannose and xylose, and the start of filtration in the measurement of the amount of filtration under predetermined conditions. A cellulose fatty acid triester characterized in that a filtration amount P ₂ (g) for 40 minutes from 60 minutes to 60 minutes satisfies the following condition (A). (A) P ₂ > −0.14η + 86 [where η is the viscosity (centipoise) of a 6% solution. ] 2. The sum of the molar contents of mannose and xylose in the analysis of constituent sugars is 7% or more of the sum of the molar contents of glucose, mannose and xylose, and filtration is started under a predetermined condition. A cellulose fatty acid diester characterized in that the filtration amount P ₂ (g) for 40 minutes from 60 minutes to 60 minutes satisfies the following condition (B). (B) P ₂ > −0.16η + 40 [where η is the viscosity (centipoise) of a 6% solution. ] 3. A method for producing a cellulose fatty acid ester using a pulp having a low α-cellulose content as a raw material and a corresponding fatty acid as a diluent, comprising producing an organic solvent of 10% by weight or more based on the diluent. A method for producing a cellulose fatty acid ester, which is added in any of the steps. 4. The method for producing a cellulose fatty acid ester according to claim 3, wherein a halogen-based solvent is used as the organic solvent in an amount of 10% by weight or more and 90% by weight or less based on the diluent. 5. The method for producing a cellulose fatty acid ester according to claim 3, wherein a nitro compound solvent is used as the organic solvent in an amount of from 10% by weight to 90% by weight based on the diluent. 6. The cellulose fatty acid ester to be produced is cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate-propionate or cellulose acetate-butyrate, according to any one of claims 3 to 5. A method for producing the cellulose fatty acid ester according to the above. 7. The method for producing a cellulose fatty acid ester according to claim 3, wherein the produced cellulose fatty acid ester is cellulose acetate.