KR20210063651A - Dissolving pulp from jute bast fiber and preparation method thereof - Google Patents

Abstract

The present invention relates to a dissolving pulp and a method for manufacturing the same. More specifically, the present invention relates to a dissolving pulp derived from Corchorus capsularis bast fibers, and a method for manufacturing the same, wherein the present invention can provide the dissolving pulp derived from Corchorus capsularis bast fibers with high cellulose purity without a hemicellulose removal process, and thus the method for manufacturing the same.

Description

Dissolving pulp from jute bast fiber and its manufacturing method {Dissolving pulp from jute bast fiber and preparation method thereof}

The present invention relates to a dissolving pulp and a method for manufacturing the same, and more particularly, to a dissolving pulp derived from jute bast fiber and a manufacturing method thereof.

Stable supply is an important factor to achieve an ecosystem that can sustainably reproduce. In order to solve this problem, interest in agricultural-based fibers that can be grown in the textile-based industry is growing. Agricultural fibers are often used as reinforcing elements in thermoplastics, but demand is also growing in traditional textile industries such as the pulp and paper industry and rayon fibers.

Jute, along with kenaf, has a fast biomass growth rate and is an annual plant that grows well in India, Pakistan and Bangladesh. The country of origin is China, and Bengal, Pakistan, accounts for 90% of the world's production. The fibers that are spun after soaking the skin in water to separate it from the bundle are thin and soft, but are weak against friction, so they are pulped for high-quality processing, and then pulp for dissolution can be produced and then processed into rayon fibers.

Unlike wood, bast fiber has a low lignin content and a high cellulose content, making it possible to produce high-yield chemical pulp compared to wood, and lignin removal is also more advantageous than woody material. In order to manufacture rayon fiber, the dissolving pulp is dipped in 17.5% caustic soda solution, converted to alkali cellulose, left to adjust, and then reacted with carbon disulfide to dissolve in cellulose xanthate and aged in dilute caustic soda solution. After spinning, it is regenerated into cellulose. In rayon fiber, carbon disulfide (CS2) has been traditionally used as a process for dissolving cellulose and then regenerating it, but lung damage caused by carbon disulfide vapor has caused various industrial accidents. In order to solve this problem, processes using an eco-friendly solvent are being tried.

Copper ammonium rayon fiber is a rayon fiber made by dissolving cellulose with a mixed solution of copper sulfate, ammonia, and caustic soda and then injecting it into water. It is thin and has good gloss, but the production cost is relatively high. Lyocell is made by dissolving cellulose fiber using an amine oxide solvent and then regenerating it. Since more than 95% of the solvent is recovered and reused, it is a process that can solve various environmental pollution and industrial accidents caused by components harmful to the human body in the existing rayon fiber industry It has been adopted by industry and produced as several commodities. Since the purity of cellulose in the pulp must be high in order to be used as pulp for dissolution, there is a problem in that the chemical pulp must be processed after removing hemicellulose.

Registered Patent Publication No. 10-1282830 Registered Patent Publication No. 10-1391032 Registered Patent Publication No. 10-1952316

In order to solve the above problems, the present invention is to provide a pulp for dissolution derived from jute bast fiber having a low hemicellulose content and a high cellulose content.

In addition, in order to provide the pulp, it is intended to provide a method for producing a pulp for dissolution derived from jute bast, which is simpler than a conventional method for producing pulp.

In order to achieve the above object, the present invention provides a pulp for dissolution derived from jute bast fibers.

The present invention also provides a method for producing pulp for dissolution derived from jute bast fibers.

The cellulose purity of the pulp may be preferably 80% or more, more preferably 85% or more, more preferably 90% or more.

In addition, the length of the fibers included in the pulp is 1.4 to 1.8mm, preferably 1.45 to 1.7mm. The width of the fiber is 18 to 23 μm, preferably 19 to 22 μm.

The pulp for dissolution derived from jute bast fiber of the present invention is prepared by administering a chemical solution and cooking at a high temperature.

The chemical is preferably an alkali solution, and the alkali solution _{includes, but is not limited to, alkalis such as sodium hydroxide (NaOH), sodium oxide (Na 2} O), sodium sulfide, potassium hydroxide, and potassium carbonate.

The alkali solution is not limited, but may preferably have a concentration of 10 to 30% (v/v).

In addition, the alkali solution may include bast fiber: alkali solution in a weight ratio of 1: 5 to 7.

Anthraquinone may be additionally included in the alkaline solution. In this case, the anthraquinone may be included in an amount of 0.001 to 0.3 parts by weight, preferably 0.05 to 0.2 parts by weight, based on 100 parts by weight of the bast fiber.

The cooking temperature is 170 to 190°C, preferably 170 to 180°C, respectively. When the temperature is lower than the cooking temperature, components other than the cellulose are not decomposed and the purity of the cellulose may be lowered.

The pulp for dissolution prepared by the above method can produce pulp with high cellulose purity without going through a step of removing hemicellulose, unlike the conventional method for producing pulp for dissolution, thereby simplifying the process.

In addition, even in the bleaching stage, bleaching is performed well even with a small amount of bleach, so that the overall manufacturing process can be simplified.

The pulp for dissolution in the present invention is a refined chemical pulp, and is chemically specifically purified compared to paper pulp, and the purity is regulated. It is produced by cooking wood, and the cooking method includes a sulfurous acid method and an electrohydrolysis-kraft method, and may be selected according to the use, and is not particularly limited.

The use of the pulp for dissolution can be used as a raw material for cellulose derivatives such as chemical fiber, cellophane, plastic, synthetic glue, or as a raw material for cellulose chemical products such as artificial silk, staple fiber, and film, and there are different types of rayon pulp, acetate pulp, etc. have.

The present invention can provide a dissolving pulp derived from jute bast fiber having high cellulose purity without a hemicellulose removal process, and also can provide a manufacturing method thereof.

1 shows a conventional dissolving pulp manufacturing process.
Figure 2 shows the pulp manufacturing process for dissolution of the present invention.

Hereinafter, the present invention will be described in detail by way of Examples and Experimental Examples.

However, the following Examples and Experimental Examples are merely illustrative of the present invention, and the contents of the present invention are not limited to the following Examples and Experimental Examples.

<Examples 1 to 3>

Jute bast fiber from Bangladesh was provided by the Korea Textile Machinery Convergence Research Institute and used. After the jute bast fiber was sufficiently dried, the bast fiber was cut to 5 cm or less and used in the experiment.

Soda-anthraquinone cooking was performed for bast fiber (150.0 g dry basis) _{under the conditions of adding 20% active alkali (based on Na 2} O), liquid ratio (1:6, S:L), and anthraquinone (0.150 g) of chemical solution. . The cooking temperature was set to 172, 176, and 180℃, respectively, and the cooking was carried out at room temperature for 90 minutes to reach the target temperature and for 60 minutes after reaching the target temperature. After cooking, the remaining waste liquid was removed in the fibrillation and selection process, and the washed pulp was dehydrated in a centrifuge and stored in a refrigerator.

<Examples 4 to 9>

The jute bast fibers of Examples 1 to 3 were bleached. In order to explore the change in whiteness by bleaching conditions, the amount of chlorine dioxide input was varied at each stage. Total chlorine dioxide consumption was 1.0% (Examples 4 to 6) and 1.5% (Examples 7 to 9), two usage conditions was introduced a chlorine dioxide of 66.7% in the Do stage, and D stage ₁ the rest to the antecedent pulp based was put in Between chlorine dioxide bleaching, 1.0% of caustic soda based on whole dry pulp was added under basic washing conditions, followed by extraction and washing. Each reaction was carried out at 75° C. for 60 minutes.

<Experimental Example 1> Chemical composition analysis of jute bast fibers

Analysis of hydrophobic extract content (Tappi 204 cm-97), hydrophilic extract content analysis (Tappi 207 cm-99), acid-insoluble lignin content analysis (Tappi 222 om-88) for chemical composition analysis of jute bast fiber was carried out. In order to quantify the lignin present in the pulp, it was tested according to the kappa value analysis (Tappi 236 om-99), and the whiteness analysis handicraft paper production (Tappi 205 sp-95) and whiteness measurement (Tappi 525 om-92) methods were used. Changes in whiteness were observed before and after bleaching. In order to measure the moisture retention of the fibers, a moisture retention measurement (Water Rention Value, WRV, Tappi Useful Method UM 256) was performed. To analyze the fiber characteristics of jute bast fiber pulp, the length and width of the fiber were measured using a fiber analyzer (Kajaani Fiber Lab Fiber Analyzer, Metso, Finland). To analyze the carbohydrate composition of bast fiber, unbleached pulp, and bleached pulp, primary hydrolysis was performed with concentrated sulfuric acid, followed by dilution and secondary hydrolysis. ^{For 1} H-NMR analysis, heavy water (D ₂ O) was used instead of distilled water in acid hydrolysis. After the secondary hydrolysis, the ^{carbohydrate composition of the hydrolyzed product was measured through 1} H-NMR analysis (K TAPPI 48(2): 13-19, Kyuseong Lee et al. 2016).

The chemical composition analysis results of this jute bast fiber are presented in Table 1. Acetone extract content, lignin content, and polysaccharide content showed the chemical composition of typical jute bast fiber. As a result of analyzing jute hull part fibers, the extract content was lower than that of xylem, and the lignin content was 13.5%, which was lower than 23.9-25.% of xylem and less than jute caddis 14.7%.

Comparing the composition of the polysaccharide composition, the cellulose content is 64.6%, which is higher than most of the jute. In the analysis of monosaccharides and hydrolysis products after acid hydrolysis, the content of acetic acid originating from acetyl groups bound to the polymer of hemicellulose was 5.0%, which is considered to be higher than that of conifers or hardwoods hemicellulose. It was reported that the content of xylan was lower in both hemp bast fibers and cob fibers than in hardwoods.

The composition of jute bast fibers. unit: % ingredient jute bast fiber jute jute fiber Branch fiber cellulose 64.6 39.3 63.1 63.1 lignin 13.5 25.1 12.7 12.7 hemicellulose xylene 11.2 15.8 13.5 14.1 acetyl group 5.0 met 1.1 Arabinogalactan 4.3 Etc 12.4 11.0 11.0 extract 0.3 0.8 0.2 0.3

<Experimental Example 2> Changes in yield and composition of jute bast fibers according to pulping conditions

As a result of the chemical composition analysis in Table 1, it can be estimated that the bast fiber has a high cellulose content and low xylan and lignin content, so that when making pulp under basic conditions, the yield is higher and the kappa value is lower than that of hardwoods. The results of soda anthraquinone pulping at different temperatures are presented in Table 2. The yield was 62.1% for cooking at 170°C, and the yield decreased as the cooking temperature increased (56.7% for cooking at 178°C). The soda-anthraquinone pulp cooked at 20% active alkali concentration had a yield of 56.7-62.1% and a kappa value of 7.8-13.8%, which was higher than that of hardwoods and had a lower kappa value. When the neck of jute was kraft pulped, the yield was 41.1% and the kappa value was 25.1, but in the bast fiber krafting process, the yield was 51.6% and the kappa value was 16.4. This is because the lignin components constituting jute bast fibers can be easily decomposed under basic conditions, and cellulose and xylan components, which have high resistance to hydrolysis under basic conditions, are the main components of jute bast fibers. As a result of structural analysis of jute bast fibers, the S/G ratio is 2.1, and the ratio of S-type lignin derived from sinapyl alcohol is high, and 72% of the lignin binding forms are β-0-4, which can be easily decomposed under basic conditions. . In the case of jute cork, the ratio of conifery alcohol-based and synapyl alcohol-based decomposition products was 13.0%: 25.2% in the xylem in the alkali nitrobenzene oxide analysis, but 10.8%: 36.0% for bast fibers. The proportion of the type lignin was higher.

The pulp made from the jute bast fiber according to the present invention was made in various yields and kappa values according to the pulping process and conditions. In acetic acid pulping, it was cooked to a kappa value of 42-56 and a yield of 76-90%, and in ethanol pulping, it was cooked to a kappa value of 66-69 and a yield of 60-79%. In the case of soda pulping, the yield is 68-75% in the kappa value range of 50-78, and the pulp made under these conditions has high residual lignin, so it is estimated that the cost of the bleaching process is very high compared to this process. The jute bast fiber pulp produced by the kraft process showed a similar trend as in this study, with a yield of 58.5-62.2% in the range of kappa value of 9.4-15.3.

As a result of calculating the decomposition rates of cellulose and xylan compared to the raw material, the decomposition degree of cellulose was 15.5% at 170°C, 16.6% at 174°C, and 19.8% at 178°C. decomposition occurred. The degree of decomposition of xylan was 33.0% at 170°C, 46.4% at 174°C, and 56.3% at 178°C. Similarly, the decomposition became more severe as the cooking temperature increased. As shown in Table 3, as the temperature increased, the degree of decomposition of xylan was more severe than that of cellulose. Therefore, high-temperature cooking is more advantageous to make pulp raw materials for dissolution with high cellulose purity, and it is suitable as a pulp raw material for dissolution with a cellulose purity of 91.4% under cooking conditions of 178°C.

Pulp properties of the present invention Temperature (℃) Yield (%) kappa value Brightness (whiteness) (% ISO) 170 62.1 13.8 37.9 174 59.9 11.6 40.6 178 56.7 7.8 43.5

Chemical composition of the pulp of the present invention Temperature (℃) Yield (%) Cellulose (%) Xylan (%) Cellulose purity (%) 170 62.1 54.6 7.5 87.9 174 59.9 53.9 6.0 90.0 178 56.7 51.8 4.9 91.4

<Experimental Example 3> Chlorine dioxide bleaching properties of the pulp of the present invention

Chlorine dioxide bleaching of pulp of the present invention Pulp Temperature (℃) Step D0 Step D1 ClO ₂ Concentration% whiteness ClO ₂ Concentration % whiteness 170 0.67 53.4 0.33 67.7 1.00 58.6 0.50 76.6 174 0.67 56.5 0.33 73.5 1.00 64.4 0.50 81.8 178 0.67 68.8 0.33 83.1 1.00 76.4 0.50 84.9

Chlorine dioxide bleaching properties of the pulps of Examples 4 to 9 were compared. In the case of 3-step bleaching using 1.0% chlorine dioxide, the whiteness of the pulp made at 170°C reached 67.7% ISO and the pulp at 174°C reached 73.5% ISO whiteness, but the pulp cooked at 178°C reached 83.1% ISO whiteness. . The bleaching of the pulp cooked at high temperature was easier.

When the amount of chlorine dioxide used was increased to 1.5%, the whiteness reached 76.6%, 81.8%, and 84.9% ISO after three-step bleaching of the pulp, respectively. High temperature cooking (178°C) and 1.5% chlorine dioxide bleaching are required to produce industrially satisfactory bleached pulp. Because jute bast fibers react easily to bleaching, they can be bleached with a small amount of chlorine dioxide. The bast fiber pulp made by the kraft pulping process reached 84.6-85.4% ISO whiteness with 1.5% chlorine dioxide bleaching, whereas the pulp made from jute bundle reached 80.8-85.6% ISO whiteness with 3.0% chlorine dioxide bleaching.

<Experimental Example 4> Physical properties of the pulp of the present invention

4-1. Water Retention Value

As shown in the chemical composition analysis results in Table 1, the high content of acetyl groups in the polysaccharide of jute bast fiber showed low water retention compared to other materials. Since the acetyl group and the hydrophobic lignin were removed during the pulping process, water retention increased as the pulping progressed. As shown in Table 5, this trend was more pronounced when cooking at high temperature and after bleaching.

After separating thermo-mechanical pulp by particle size and measuring the water retention while bleaching, the WRV value of small particles was higher than that of large particles, and the moisture retention of hypochlorous acid-hydrogen peroxide bleaching or hypochlorous acid-ozone bleaching pulp was higher than that of unbleached pulp was better.

The WRV of undried bleached pulp is 171%, that of dry pulp is 150%, and the WRV value is 132-149% depending on the drying temperature, and the higher the drying temperature, the lower the water retention.

Water retention power of the pulp of the present invention Temperature(℃) WRV (%) unbleached bleaching 170 116 165 174 154 176 178 167 197

It was confirmed that the pulp with poor fiber water retention was restored to water retention during the bleaching process.

<Experimental Example 5> Analysis of the fiber properties of the pulp of the present invention

Table 6 shows the results of analyzing the width and length of the fibers according to the present invention. As a result of the experiment, the fiber length was in the range of 1.49-1.68 mm, and the fiber width decreased as the cooking temperature increased.

On the other hand, the fibers made from acetic acid pulping according to the existing process were 2.5 mm in length and 20.0 μm in width, which was longer than the fibers included in the pulp of the present invention, but the width of the fibers was similar to the fibers of the present invention.

Fiber form of pulp according to the invention 170℃ 174℃ 178℃ Fiber length (mm) 1.68 1.49 1.64 Fiber width (μm) 21.1 20.5 19.6 Refinement (%) 2.55 4.42 1.08

Fiber form - Nicem

Combining the results of the above experimental examples, the present invention was able to prepare a dissolving pulp that can be used as a raw material for rayon fibers having a high cellulose content. The purity of cellulose was about 88% in cooking at 170°C, reaching 90.0% in cooking and bleaching at 174°C, and the purity of cellulose reached 91.4% at 178°C, confirming that it can be used as a raw material for dissolving pulp. The pulp according to the present invention was also easily bleached with chlorine dioxide, so that it was possible to reach the ISO standard of 80% whiteness using a small amount of chlorine dioxide.

Claims (10)

Dissolving pulp derived from jute bast fibers. The pulp for dissolution derived from jute bast fiber according to claim 1, wherein the pulp has a cellulose purity of 85% or more. The pulp for dissolution derived from jute bast fiber according to claim 1, wherein the pulp has a cooking temperature of 170 to 190°C. A method for producing a pulp for dissolution derived from jute bast fibers by administering a chemical solution to the jute bast fibers and cooking them. 5. The method according to claim 4, wherein the chemical solution is an alkaline solution. 5. The method of claim 4, wherein the alkali solution is selected from sodium hydroxide, sodium sulfide, potassium hydroxide, and potassium carbonate. [Claim 5] The method of claim 4, wherein the chemical solution contains jute bast fiber: alkali solution in a weight ratio of 1: 5 to 7. The method according to claim 7, wherein the alkali solution has a concentration of 10 to 30% (v/v). 5. The method of claim 4, wherein the chemical may further contain anthraquinone, and the anthraquinone is included in an amount of 0.001 to 0.3 parts by weight based on 100 parts by weight of the bast fiber. Way. 5. The method of claim 4, wherein the cooking temperature is 170 to 190°C.

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