Method for manufacturing finely processed cellulose material

Abstract

This invention provides a method for easily producing fine cellulose material from plant biomass. [Solution] A method for producing cellulose material comprising: a hydrothermal treatment step of hydrothermally treating plant biomass selected from sisal, palm, and jute in an acidic aqueous solution; a pulverization step of pulverizing the plant biomass that has undergone the hydrothermal treatment step; and a classification step of classifying the plant biomass that has undergone the pulverization step.

Description

Technical Field

[0001] The present invention relates to a method for producing fine cellulose materials from plant biomass.

Background Art

[0002] Cellulose is the most abundant renewable substance and has been widely used from ancient times to the present. Cellulose, which is a fiber derived from plants, has a small environmental impact, is a sustainable resource, and has excellent properties such as a high elastic modulus, high strength, and a low linear expansion coefficient. Therefore, it is used in a wide range of applications, for example, materials such as paper, films, and sheets, and composite materials of resins (for example, reinforcing agents for resins).

[0003] Conventionally, there has been a method for producing cellulose materials from plant biomass, but the development of a more rapid and simple method has been demanded. As such a method for producing cellulose materials, for example, a method has been proposed that includes a step of cutting a tree while keeping the bark attached to obtain chips, and a step of chemically pulping the obtained chips (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present invention is to provide a method for easily producing fine cellulose materials from plant biomass.

Means for Solving the Problems

[0006] The inventors of the present invention have discovered that fine cellulose material can be easily obtained by hydrothermally treating plant biomass selected from sisal, palm, and jute in an acidic aqueous solution, followed by pulverization and further classification, thereby completing the present invention.

[0007] In other words, the present invention is as follows: [1] A hydrothermal treatment step in which plant biomass of plant origin selected from sisal, palm, and jute is hydrothermally treated in an acidic aqueous solution, The plant biomass that has undergone the aforementioned hydrothermal treatment process is subjected to a crushing process, A classification process is performed on the plant biomass that has undergone the aforementioned crushing process, A method for producing a finely milled cellulose material, characterized by having the following features. [2] The method for producing the finely milled cellulose material according to [1] above, characterized in that the processing temperature of the hydrothermal treatment step is 120 to 140°C. [3] The method for producing the finely milled cellulose material according to [1] above, characterized in that the processing time for the hydrothermal treatment step is 20 to 40 minutes.

[0008] [4] A method for producing the finely milled cellulose material described in [1] above, characterized in that the cellulose material produced contains 70% by mass or more of cellulose. [5] The method for producing a finely milled cellulose material according to [1] above, characterized in that the classification process in the classification process is a process using a sieve shaker equipped with a brush for preventing clogging. [6] A method for producing a finely milled cellulose material according to [1] above, characterized in that the size of the finely milled cellulose material produced is less than 125 μm. [7] A method for producing the finely milled cellulose material according to [1] above, characterized in that the plant biomass is plant fiber. [Effects of the Invention]

[0009] According to the present invention, fine cellulose material can be easily produced from plant biomass. [Brief explanation of the drawing]

[0010] [Figure 1] These are photographs of cellulose materials produced using sisal hemp; the right image shows pulverized cellulose material that has undergone hydrothermal treatment, and the left image shows pulverized cellulose material that has not undergone hydrothermal treatment. [Figure 2] These are photographs of cellulose materials manufactured using palm oil. The image on the right shows pulverized cellulose material that has undergone hydrothermal treatment, while the image on the left shows pulverized cellulose material that has not undergone hydrothermal treatment. [Figure 3] These are photographs of cellulose materials manufactured using jute; the right image shows pulverized cellulose material that has undergone hydrothermal treatment, while the left image shows pulverized cellulose material that has not undergone hydrothermal treatment. [Modes for carrying out the invention]

[0011] The present invention provides a method for producing cellulose material, comprising: a hydrothermal treatment step of hydrothermally treating plant biomass selected from sisal, palm, and jute in an acidic aqueous solution; a pulverization step of pulverizing the plant biomass after the hydrothermal treatment step; and a classification step of classifying the plant biomass after the pulverization step. The production method of the present invention may include other steps before and after the hydrothermal treatment, pulverization, and classification steps.

[0012] The manufacturing method of the present invention allows for the easy production of fine cellulose material. Furthermore, the finely milled cellulose material obtained by the manufacturing method of the present invention is suitable as a material to be blended into resin-based composite materials. For example, when blending long-fiber cellulose material that has not been sufficiently milled, the viscosity increases, and if a large amount is added, molding may become difficult. However, when blending the fine cellulose material of the present invention, the increase in viscosity can be suppressed, making it possible to add large amounts.

[0013] The plant biomass used in the production method of the present invention is biomass derived from sisal, palm, and jute. Although the plant biomass used in the present invention is not easily micronized, it can be easily micronized by using the method of the present invention. These plant biomasses may be used alone or in combination of multiple species. The plant biomass (the plant biomass to be subjected to hydrothermal treatment) used in the present invention may have any shape such as fibrous, plate-like, chip-like, granular, rod-like, etc.

[0014] (Sisal) Sisal is a plant of the genus Yucca in the family Asparagaceae. As the part used in the present invention, leaves are preferred, and fibers collected from the leaves are preferred.

[0015] (Palm) Palm is a monocotyledonous plant of the genus Cocos in the family Arecaceae. As the part used in the present invention, fruits are preferred, and fibers collected from the fruits are preferred.

[0016] (Jute) Jute is a plant of the genus Corchorus in the family Malvaceae, including Corchorus capsularis and Corchorus olitorius. As the part used in the present invention, stems are preferred, and fibers collected from the stems are preferred.

[0017] The micronized cellulose material obtained by the production method of the present invention is a cellulose material from which lignin, hemicellulose, etc. have been removed from plant biomass, and preferably contains 70% by mass or more of cellulose, more preferably 80% by mass or more of cellulose, and even more preferably 85% by mass or more of cellulose.

[0018] Hereinafter, each step will be described. [Hydrothermal treatment step] The hydrothermal treatment step is a step of subjecting plant biomass to hydrothermal treatment in an acidic aqueous solution. In this step, for example, a container in which the plant biomass is immersed in the acidic aqueous solution is placed in a high-pressure reactor such as an autoclave or a pressure cooker, and heated to carry out a reaction in the presence of high-temperature and high-pressure steam. By the hydrothermal treatment of this step, delignification and / or hemicellulose removal can be achieved.

[0019] The hydrothermal treatment temperature is, for example, above 100 to 200 °C, and from the viewpoint of performing the treatment efficiently, 110 to 180 °C is preferable, 120 to 160 °C is more preferable, and 120 to 140 °C is even more preferable. The pressure is the saturated steam pressure. Also, the treatment time depends on the temperature and pressure, but for example, it is about 1 to 360 minutes, preferably about 1 to 60 minutes, more preferably 10 to 50 minutes, and even more preferably about 20 to 40 minutes. The present invention can achieve sufficient delignification and hemicellulose removal of plant biomass in a short time.

[0020] Examples of the acidic aqueous solution include aqueous solutions of nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, etc., and two or more different acidic aqueous solutions may be mixed and used. Among these, a nitric acid aqueous solution is preferable because it is relatively easy to handle and can more effectively exhibit the effects of the present invention.

[0021] The acid concentration of the acidic aqueous solution is, for example, 0.05 to 5.0 M, and from the viewpoint of more effectively decomposing the components of plant biomass, 0.1 to 3.0 M is preferable, and 0.2 to 2.0 M is more preferable.

[0022] The addition amount of the acidic aqueous solution to the plant biomass is, for example, preferably 1 to 40 ml, more preferably 10 to 30 ml, and even more preferably 15 to 25 ml per 1 g of the plant biomass.

[0023] The pH of the acidic aqueous solution is, for example, 4.0 or less, preferably 3.0 or less, more preferably 2.0 or less, and even more preferably 0.3 to 2.0.

[0024] [Grinding treatment step] The pulverization process is a process of pulverizing plant biomass that has undergone the hydrothermal treatment process. The method of pulverizing the plant biomass is not particularly limited, and known pulverizers can be used. The size of the plant biomass after pulverization is preferably less than 1 mm, more preferably less than 800 μm, even more preferably less than 500 μm, particularly preferably less than 250 μm, and most preferably less than 125 μm. The lower limit is not particularly limited, but for example, it is 10 μm or more and 20 μm or more. The size of the plant biomass refers to a size in which 40% or more, preferably 50% or more, more preferably 60% or more, and even more preferably 70% or more pass through a sieve of a predetermined size. For example, plant biomass with a size of less than 1 mm refers to plant biomass that passes through a 1 mm sieve at a rate of 50% or more. In the method of the present invention, since the hydrothermal treatment is performed before pulverization, it is possible to pulverize more finely compared to methods that do not perform hydrothermal treatment.

[0025] [Classification process] The classification process involves classifying the plant biomass that has undergone the crushing process. The classification method in this process is not particularly limited and can include, for example, sieve classification, air classification, cyclone classification, centrifugal classification, suspension classification (liquid classification), electrostatic classification, etc. In the present invention, sieve classification is preferred.

[0026] Specifically, a preferred method for classification by sieving is to use a sieve shaker equipped with a clogging prevention device. Although the cellulose material pulverized after the hydrothermal treatment of the present invention can be made finer, it tends to aggregate and clog, making it difficult to classify it to its actual size. However, by using a sieve shaker equipped with a clogging prevention device, the aggregated cellulose material can be dispersed, making it possible to classify it appropriately. Furthermore, by making this sieve shaker a multi-stage type, it is possible to obtain cellulose material in multiple desired size ranges. When using a multi-stage type, it is preferable to install the clogging prevention device at least on the top stage, but it may also be installed on each stage.

[0027] The tools used to prevent clogging are not particularly limited as long as they can break down the agglomeration of the crushed plant biomass and disperse it to prevent clogging. Examples include brush-like members (brush cleaners) that are placed on a sieve to disperse and push out the crushed plant biomass that gets stuck in the sieve mesh, and lumpy bodies such as spheres and regular polygons. For brush-like members, the brush portion is preferably made of nylon, and for lumpy bodies, for example, metal coated with nylon is preferred. It is preferable to use both brush-like members and lumpy bodies in combination, and it is preferable to use multiple of each. [Examples]

[0028] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0029] <Manufacturing of finely processed cellulose materials> We manufactured a finely milled cellulose material using plant biomass.

[0030] [Plant biomass] As plant biomass, we prepared fibers extracted from sisal, palm, and jute. Each fiber was approximately 5 cm long. All plant biomass was dried in an oven for 48 hours to reduce its initial moisture content and then stored at room temperature in sealed plastic bags.

[0031] [Hydrothermal treatment with acidic solution] 12.5 g of weighed plant biomass was added to a 500 mL Erlenmeyer flask and mixed with 250 mL of 0.5 M nitric acid solution. The mouth of the Erlenmeyer flask was then sealed with aluminum foil, and the biomass mixture was treated in an autoclave (AS ONE Science Autoclave NCC-1701) under high-pressure steam at 132 °C for 30 minutes. After that, the treated plant biomass was filtered, rinsed with distilled water, and washed multiple times until the pH reached 6-7. After washing, it was dried overnight in an oven at 80 °C to obtain nitric acid autoclave-treated biomass.

[0032] [Crushing process] Nitric acid autoclave-treated plant biomass was pulverized using a pulverizer (DC-HOUSE 15KG / H 110V electric pulverizer) to obtain pulverized cellulose material. For comparison, plant biomass that had not undergone the above-mentioned hydrothermal treatment with acid was pulverized under the same conditions to obtain comparative pulverized cellulose material. Photographs of these pulverized cellulose materials are shown in Figures 1 to 3. In Figures 1 to 3, the right side shows the pulverized cellulose material that has undergone hydrothermal treatment, and the left side shows the pulverized cellulose material that has not undergone hydrothermal treatment.

[0033] [Classification process] Next, 5 g of pulverized cellulose material was classified using a sieve shaker. For comparison, a comparative pulverized cellulose material was also classified under the same conditions.

[0034] The following equipment was used. • Multi-stage sieve shaker (Teraoka Corporation, SNF-7) Inner diameter: 200mm Height: 45mm Mesh opening: 1mm, 500μm, 250μm, 125μm • Vibration dial scale: 100 • Vibration time: 10 minutes • Anti-clogging brush (brush cleaner): Shape: Reuleaux triangle Height: 65mm Width: 65mm Quantity: 6 pieces Nylon-coated steel ball Quantity: 10 pieces Weight: 1.08g / piece Diameter: 6.35mm

[0035] Classification was performed using the following method. A tray was placed in a sieve shaker, and four stainless steel sieves were stacked on top of each other in order of increasing mesh size. 5g of the sample, six brush cleaners, and ten nylon-coated steel balls were placed on top of the top stainless steel sieve with a 1mm mesh size. After vibrating for 10 minutes, the weight of the powder remaining on each sieve and in the tray was measured. Furthermore, if a brush cleaner or nylon-coated steel balls were not used, the aggregated cellulose material would not dissolve, causing the sieve to clog and preventing proper classification.

[0036] Table 1 shows the results of classifying the pulverized cellulose material, and Table 2 shows the results of classifying the comparative pulverized cellulose material.

[0037] [Table 1]

[0038] [Table 2]

[0039] As shown in Tables 1 and 2, it was confirmed that the manufacturing method of the present invention can produce cellulose material with a fiber size of less than 250 μm at a high rate of approximately 74% for sisal hemp, approximately 48% for palm fiber, and approximately 83% for jute fiber. Furthermore, it was confirmed that cellulose material with a fiber size of less than 125 μm can be produced at a high rate of approximately 51% for sisal hemp, approximately 22% for palm fiber, and approximately 61% for jute fiber. [Industrial applicability]

[0040] This invention is industrially useful because it enables the production of fine cellulose material from plant biomass.

Claims

1. A hydrothermal treatment process in which plant biomass selected from sisal, palm, and jute is hydrothermally treated in an acidic aqueous solution, The plant biomass that has undergone the aforementioned hydrothermal treatment process is subjected to a crushing process, A classification process is performed on the plant biomass that has undergone the aforementioned crushing process, A method for producing a finely milled cellulose material, characterized by having the following features.

2. A method for producing a finely milled cellulose material according to claim 1, characterized in that the processing temperature of the hydrothermal treatment step is 120 to 140°C.

3. The method for producing a finely milled cellulose material according to claim 1, characterized in that the processing time for the hydrothermal treatment step is 20 to 40 minutes.

4. A method for producing a finely milled cellulose material according to claim 1, characterized in that the cellulose material produced contains 70% by mass or more of cellulose.

5. The method for producing a finely milled cellulose material according to claim 1, characterized in that the classification process in the classification process is a process using a sieve shaker equipped with a brush for preventing clogging.

6. A method for producing a finely milled cellulose material according to claim 1, characterized in that the size of the finely milled cellulose material produced is less than 125 μm.

7. The method for producing a finely milled cellulose material according to claim 1, characterized in that the plant biomass is plant fiber.

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