JPS62501A - Production of cellulose acetate - Google Patents

Abstract

PURPOSE:To obtain cellulose acetate of an excellent hue even when a cellulose material of somewhat low quality must be used, by converting a cellulose material subjected to a specified swelling treatment into an acetate ester and saponifying the ester by aging. CONSTITUTION:1pt.wt. cellulose material such as low-grade viscose cellulose of a low alpha-cellulose content is poured into 5-45pts.wt. swelling agent such as dimethyl sulfoxide and swollen at room temperature - 100 deg.C for 1-150hr to an acetic acid content >=40wt%, separated from the liquid by centrifugation, washed with water and gently dried. This swollen cellulose material is converted into an acetate ester and saponified by aging.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing cellulose acetate, and more specifically to acetic acid retention! The present invention relates to a method for producing cellulose acetate, characterized by using a cellulose raw material that has been subjected to a swelling treatment of 40% or more.

(Prior art) Cellulose acetate is one of the cellulose organic acid esters, and its uses are wide-ranging, such as clothing fibers, cigarette filter chips, filtration, films, paints, and fillers for optical resolution. Among the cellulone derivatives, it is produced in the highest quantity (and is industrially important).

To produce cellulose acetate, first, cellulose raw materials such as wood pulp and cotton linters are pretreated with an appropriate amount of acetic acid, and then poured into a pre-cooled acetic acid mixture to convert into acetic acid ester. cellulose). In this case, 1. For example, an acetic acid mixture is used that uses acetic acid as a solvent, acetic anhydride as an esterifying agent, and sulfuric acid as a catalyst. It is normal to use a considerable excess of the stoichiometric amount. In order to hydrolyze excess acetic anhydride remaining in the system after the acetylation reaction and neutralize a portion of the esterification catalyst, carbonates, acetates, etc. of calcium, magnesium, iron, aluminum, or zinc are added. Add an aqueous neutralizing agent solution consisting of a hydroxide or oxide.

Next, the obtained primary cellulose acetate is heated at 50 to 90°C in a state where a small amount of acetylation reaction catalyst, such as sulfuric acid, remains.
Saponification and aging by keeping at a set value of acetylation degree,
The degree of polymerization is changed to secondary cellulose acetate. Once secondary cellulose acetate having the set degree of acetylation and degree of polymerization is obtained, the catalyst remaining in the system is completely neutralized using the above-mentioned neutralizing agent again. , Sometimes without neutralization, the saponification-ripening reaction completed solution is poured into water or dilute acetic acid (or water or dilute acetic acid is poured into the saponification-ripening reaction-finished solution) to separate the secondary cellulose acetate, and the secondary cellulose acetate is washed. Cheap.

Obtain the product by chemotaxis.

(Problems to be Solved by the Invention) Fibers, films, and
The color of plastics is generally slightly yellowish, and this phenomenon is particularly noticeable in the case of acetate made from wood pulp, which may have poor appearance even if it satisfies all other required properties. In this respect, the product value is significantly reduced.

Therefore, in order to industrially obtain fibers, films, and plastics, in order to reduce this yellowness and increase whiteness, they must be treated with white pigments, fluorescent brighteners, bleaching agents, and antioxidants, or during molding. Generally, secondary measures such as addition are taken. It goes without saying that such secondary measures are not essential solutions or solutions (and there are limits to their effectiveness).

In general, it has become difficult to obtain high-quality cellulose raw materials that are cost-effective due to global resource constraints and pollution problems at pulp manufacturing factories. There is a trend of conversion from high-grade wood pulp to low-grade wood pulp. However, when cellulose acetate is produced using low-grade wood pulp as a raw material, there is a significant increase in the yellowness of the product.

Significantly reduce product value.

What is the cause of the yellow color of cellulose acetate and processed products obtained from it? (There are many references and researchers have made various claims, but among the hemicellulose components in wood pulp, It is generally pointed out that the main cause is non-cellulose components, mainly Kinran (TaPPi), 57°77
(1974), Tappi, 46+
581 (1963)).

The present inventors focused on the pretreatment process of cellulose raw materials,
The result of intensive research to produce cellulose acetate with excellent hue.

Cellulose raw materials treated to increase the degree of swelling have improved acetylation reactivity, furthermore, the hemicellulose content in the raw materials, especially the quincelain content, has been reduced, and the hue of the resulting secondary cellulose acetate has been improved. I got this knowledge.

Based on this knowledge, further studies were conducted, and it was found that the above-mentioned hue improvement effect as well as other excellent effects could be obtained, and the present invention was arrived at.

Means for Solving the Problems) That is, the present invention uses a cellulose raw material that has been subjected to a swelling treatment with an acetic acid retention of 40% or more in a method for producing secondary cellulose acetate in which a cellulose raw material is acetate-esterified and then aged and saponified. The present invention provides a method for producing cellulose acetate having an excellent hue.

The cellulose raw material in the present invention refers to dissolving pulp, and low-grade cellulose raw materials for viscose and cellulone ether with particularly low α-cellulose content can also be used for cellulose acetate.

In the present invention, the "acetic acid retention amount" is a morphological index representing the degree of swelling of cellulose raw materials, and is the amount of acetic acid contained in the sample after immersing the cellulose sample in acetic acid and removing the liquid by centrifugation under certain conditions. Says the value of amount (%). This is measured by the following method. Weigh out 1 g of a cellulose sample in terms of a dry sample and immerse it in acetic acid (in the case of a cellulose sample that has been subjected to swelling treatment, weigh out 1 g of a sample in terms of a dry sample, and gradually replace the swelling agent with acetic acid. , and finally complete replacement with acetic acid). Next, after centrifugation for 20 minutes at a centrifugal effect Z=1100, the weight of the acetic acid wet sample (Wg) is accurately weighed, and the sample is poured into 150-g distilled water and sealed. After standing for 15 minutes, use phenolphthalein as an indicator and add N/2Na.
Calculate the titration amount (Ad) by titration with OH and the retained acetic acid amount (cI6) using the following formula.

When carrying out the production method of the present invention, firstly, the acetic acid retention fi40%
The cellulose raw material is subjected to swelling treatment using a solvent that provides the above degree of swelling. As swelling agents, solvents such as ethanolamine, ethylenediamine, dimethylsulfoquine, formamide and the like are advantageously used. The amount of swelling agent used is 5 to 45 parts by weight per 1 part by weight of Cellulone raw material. Swelling is carried out either by standing still or under good stirring, and the optimum temperature and time for swelling are selected respectively. For example, the temperature is room temperature ~ 1
00c, the appropriate time is about 1 hour to 150 hours. After the swelling treatment, the swelling agent is removed from the cellulosic raw material by a suitable method. For example, when using a swelling agent that is compatible with water, remove as much of the solvent as possible by centrifugal dehydration or the like, then wash with water and gently dry, or replace the water with acetic acid. The cellulose raw material treated by this method is subjected to a known acetic acid esterification method,
Obtain secondary cellulose acetate.

(Effects of the Invention) The production method according to the present invention allows cellulose acetate with excellent color to be produced without revising the conventional acetylation process or saponification/ripening process, and for this reason, cellulose raw materials of slightly lower quality can also be used. can.

Furthermore, since the acetylation reactivity of the cellulose raw material is improved by improving the swelling state indicated by the amount of acetic acid retained, the time required for the acetylation process can also be shortened.

(Examples) Examples are shown below to specifically explain the present invention, but the present invention is not limited to the examples shown below. Furthermore, in the examples, parts refer to parts by weight, and % refers to % by weight.

The yellow color of cellulose acetate can be determined by adding a sample to a mixed solvent of methylene chloride and methanol (9/1 weight ratio) at 12%.
This solution was prepared according to ASTM-D-1925
(Yellowness Index x
It was measured by Hayi-colorimetric tf (Hunter Lab Model D25D2) according to Index). The measured value is obtained as a yellowness index, and the larger this value is, the more pronounced the yellowness is. The average degree of acetylation was measured and calculated according to the method of ASTM-D-871. The intrinsic viscosity of cellulose acetate is the viscosity of an acetone solution with a concentration of 0.2 g/d/25.
Calculated by measuring at 0.1°C.

After crushing Example I 4
It was 9.7%. After the swelling treatment, the pulp (acetic acid retention amount: 49.7%) was centrifugally dehydrated, washed with water, and then gently dried to a moisture content of 4%.

100 parts of glacial acetic acid was uniformly sprinkled on 100 parts of the above-treated pulp (moisture content: 4%), stirred and mixed at room temperature for 120 minutes, and then pre-cooled acetic anhydride 28
0 parts of acetic acid, 365 parts of acetic acid, and 15.0 parts of sulfuric acid, the mixture was stirred and acetylated at 45° C. or lower. Initially, the system had a heterogeneous fibrous shape, but as the reaction progressed, it changed from an opaque waxy shape to a pale yellow transparent starch syrup shape. The completion point of the acetylation reaction was defined as the point at which unacetized fiber pieces were no longer found in the starch syrup-like reaction mixture, and it took about 80 minutes after the start of the reaction.

After the acetylation reaction was completed, 43.6 parts of a 30% aqueous magnesium acetate solution was added to hydrolyze the excess acetic anhydride and neutralize a portion of the sulfuric acid, thereby stopping the acetylation reaction. At this time, the calculated amount of catalytic sulfuric acid remaining in the diabetic system was 6 parts.

Next, 12.2 parts of a 30% aqueous magnesium acetate solution was added while the diluted solution was concentrated to about 600% in 30 minutes. The amount of residual sulfuric acid at this time was calculated to be 3.5 parts. Thereafter, water was added so that the bath concentration in the system was approximately 85%, and the temperature was further raised to stabilize it at 70'C. Thereafter, the aging reaction was continued for 2 hours at 70°C. 18.4 parts of a 30% aqueous magnesium acetate solution was added to the reaction-completed solution to completely neutralize the sulfuric acid and stop the reaction. A large amount of 10% acetic acid aqueous solution was added to the reaction-completed solution while vigorously stirring it to precipitate and separate secondary cellulose acetate. After the precipitated secondary cellulose acetate was collected by filtration, it was washed with water until it contained virtually no acetic acid. Thereafter, it was dehydrated and dried to obtain a secondary cellulose acetate product.

(The resulting cellulose acetate has an average degree of acetylation of 5.
4.7%, intrinsic viscosity 1.89, and yellowness coefficient 2.9.

Example 2 After crushing wood pulp with an α-cellulose content of approximately 96% (dissolving pulp, Rheocord XP manufactured by Leonia), 100 parts of the same pulp (water content 4%) was mixed with dimethyl sulfoxide 4.4
00 parts, and was stirred at 100° C. for 1 hour to perform a swelling treatment, and the acetic acid retention amount was 50.8%. The pulp after swelling treatment (acetic acid retention: 50.8%) was centrifuged to remove liquid, washed with water, and then gently dried to a moisture content of 4%.

100 parts of glacial acetic acid was evenly sprinkled on 100 parts of the above-treated pulp (water content 4%), and after stirring and mixing at room temperature for 120 minutes, the acetylation reaction was carried out in the same manner as in Example-1. A ripening reaction was then carried out to obtain secondary cellulose acetate. The completion point of the acetylation reaction was approximately 80 minutes after the start of the reaction. The cellulose acetate obtained in this manner had an average degree of acetylation of 54.8%, an intrinsic viscosity of 1.96, and a yellowness coefficient of 3.2.

Comparative Example 1 After crushing wood pulp with an α-cellulose content of approximately 96% (dissolving valve, Rheocord XP manufactured by Leonia), 100 parts of the same pulp (water content 4%) (acetic acid retention amount 30.2%) , 100 parts of glacial acetic acid was uniformly sprinkled thereon, and the mixture was stirred and mixed at room temperature for 120 minutes for pretreatment. The acetylation reaction and aging reaction were performed in the same manner as in Example-1 to obtain secondary cellulose acetate. The completion point of the acetylation reaction was about 90 minutes after the start of the reaction, which took a longer time than in Examples 1 and 2.

The cellulose acetate thus obtained had an average degree of acetylation of 54.8% and an intrinsic viscosity of 169. The yellowness coefficient was 6.4, the intrinsic viscosity was lower than that of Examples 1 and 2, and the yellowness was remarkable.

After crushing the pulp (dissolving valve, MAC-II manufactured by Wehaeuser), 100 parts of the same pulp (water content: 4%) was poured into 2,750 parts of dimethyl sulfoxide and allowed to stand at room temperature for 6 days for swelling treatment. The amount of acetic acid retained was 52.6%. After the swelling treatment, the bulb (acetic acid retention amount: 52.6%) was centrifuged to remove liquid, and then washed with water.

It was gently dried to a moisture content of 4%.

100 parts of glacial acetic acid was uniformly sprinkled on 100 parts of the above-treated bulb (water content 4%), and after stirring and mixing at room temperature for 120 minutes, acetylation reaction was carried out in the same manner as in Example-1. A ripening reaction was then carried out to obtain secondary cellulose acetate. The completion point of the acetylation reaction was approximately 78 minutes after the start of the reaction. The cellulose acetate thus obtained had an average degree of acetylation of 55.4%, an intrinsic viscosity of 1.80, and a yellowness index of 4.0.
The yellowness was improved by 47 types compared to Comparative Example-2.

Comparative Example 2 After crushing a wood bulb (dissolving bulb, MAc-n manufactured by Wehauser) with an α-cellulone content of approximately 94%, 100 parts of the same bulb (water content 4%) (acetic acid retention amount 38.1%) was crushed. Against.

A pretreatment was performed by uniformly spraying 100 parts of glacial acetic acid and stirring and mixing at room temperature for 120 minutes. The acetylation reaction and ripening reaction were carried out in the same manner as in Example 1 to obtain secondary cellulose acetate. The completion point of the acetylation reaction was approximately 93 minutes after the start of the reaction. The cellulose acetate thus obtained had an average acetylation of 11 s of 5.3% and an intrinsic viscosity of 1.88.
．． The yellowness coefficient was 766, and the yellowness was more pronounced than in Example-3.

Example 4 After crushing wood pulp with an α-cellulose content of about 94% (Dissolving Valve, Alinutaple manufactured by Western Valve),
When 100 parts of the same pulp (water content 4%) was put into 2.750 parts of dimethyl sulfoquine and allowed to stand at room temperature for 6 days for swelling treatment, the amount of acetic acid retained was 50.9%. After the swelling treatment, the bulb (acetic acid retention amount: 50.9%) was centrifuged to remove liquid, washed with water, and then gently dried to a moisture content of 4%.

100 parts of glacial acetic acid was evenly sprinkled on 100 parts of the above-treated pulp (water content 4%), and after stirring and mixing at room temperature for 120 minutes, the acetylation reaction was carried out in the same manner as in Example-1. A ripening reaction was then carried out to obtain secondary cellulose acetate. The completion point of the acetylation reaction was approximately 80 minutes after the start of the reaction. The thus obtained cellulose acetate had an average degree of acetylation of 55.7%, an intrinsic viscosity of 1.81, and a yellowness index of 3.2, and the yellowness was improved by 51% compared to Comparative Example-3.

Comparative Example 3 After crushing wood pulp (dissolving pulp, Alinutable manufactured by Western Valve) with an α-cellulose content of approximately 94%,
100 parts of the same pulp (moisture content 4%) (acetic acid retention j132,
6%) was uniformly sprinkled with 100 parts of glacial acetic acid, and the mixture was stirred and mixed at room temperature for 120 minutes for pretreatment. The acetylation reaction and aging reaction were performed in the same manner as in Example-1 to obtain secondary cellulose acetate. The completion point of the acetylation reaction was approximately 95 minutes after the start of the reaction. The cellulose acetate thus obtained had an average degree of acetylation of 55.2% and an intrinsic viscosity of 1.
81. The yellowness coefficient was 6.5, and the yellowness was more pronounced than in Example-4.

Example 5 After crushing wood pulp with an α-cellulose content of approximately 91% (dissolving valve, L-5 manufactured by Jujo Paper Industries), 100 parts of the same pulp (
When 2.750 parts of dimethyl sulfoquine (water content: 4%) was put into 2.750 parts of dimethyl sulfoquine and allowed to stand at room temperature for 6 days for swelling treatment, the amount of acetic acid retained was 52.3%.

After the swelling treatment, the bulb (acetic acid retention amount: 52.3%) was centrifuged to remove liquid, washed with water, and then gently dried to a moisture content of 4%.

100 parts of glacial acetic acid was evenly sprinkled on 100 parts of the above-treated pulp (water content 4%), and after stirring and mixing at room temperature for 120 minutes, the acetylation reaction was carried out in the same manner as in Example-1. A ripening reaction was then carried out to obtain secondary cellulose acetate. The completion point of the acetylation reaction was approximately 91 minutes after the start of the reaction. The cellulose acetate thus obtained had an average degree of acetylation of 55.1%, an intrinsic viscosity of 1.60, and a yellowness index of 6.7, and the yellowness was improved by 43% compared to Comparative Example-4.

Comparative Example 4 After crushing wood pulp (dissolving pulp, L-5 manufactured by Jujo Paper) with an α-cellulose content of approximately 91%, 100 parts of the same pulp (
water content 4%) (acetic acid retention amount 37.4%), 100
of glacial acetic acid was uniformly sprinkled thereon, and the mixture was stirred and mixed at room temperature for 120 minutes for pretreatment. The acetylation reaction and ripening reaction are
Secondary cellulose acetate was obtained in the same manner as in Example-1. The completion point of the acetylation reaction was approximately 97 minutes after the start of the reaction. The cellulose acetate thus obtained had an average degree of acetylation of 55.3% and an intrinsic viscosity of 1.59. yellowness coefficient 11
．． 7, and the yellowness was more remarkable than in Example-5.

Claims (1)

[Scope of Claims] 1) A method for producing secondary cellulose acetate in which a cellulose raw material is acetate-esterified and then aged and saponified, characterized in that a cellulose raw material subjected to a swelling treatment with an acetic acid retention of 40% or more is used. manufacturing method. 2) The method for producing cellulose acetate according to claim 1, characterized in that an organic solvent is used for the swelling treatment to achieve an acetic acid retention of 40% or more. 3) The method for producing cellulose acetate according to claim 2, wherein the organic solvent is dimethyl sulfoxide.