Method for preparing paper pulp from industrial hemp noil fibers

Abstract

The invention discloses a method for preparing paper pulp from industrial hemp noil fibers. The method comprises the steps of hemp cutting, acid pickling, water washing, ultrasonic oscillation, biological enzyme treatment, water washing, chemical pulping, water washing and pulp grinding. The oscillation temperature of the ultrasonic oscillation is 45-55 DEG C, the oscillation time is 30-35 minutes, the oscillation frequency is 40-45 kHz, and the oscillation power is 200-250 W; in the biological enzyme treatment, pectinase and laccase in a mass ratio of 5: 1 are used as a compound enzyme, the addition amount of the compound enzyme is 12% (o.w.f), the pH value is 4.0-4.5, and the temperature is 50-55 DEG C; the liquid ratio is 1: (18-22), and the treatment time is 240-270 minutes. According to the method, industrial hemp noil fibers are recycled, and the industrial hemp noil raw materials are more suitable for pulping by adopting the pretreatment technology of ultrasonic oscillation and biological enzyme treatment; the pressure, the temperature and the chemical quantity of later chemical pulping treatment are reduced, and the emission of degradation products is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of pulping and papermaking, and in particular, relates to a method for preparing pulp from industrial hemp noil fibers. Background Art

[0002] Industrial hemp (Cannabis sativa) is the most common type of hemp, also known as hemp, fire hemp, Kuima, thread hemp, cold hemp, is an ancient bast fiber plant, with a low content of tetrahydrocannabinol (THC) (THC < 0.3%), and is a non-toxic hemp variety. It is planted as a raw fiber crop for natural textiles. The main components of industrial hemp fiber are cellulose, hemicellulose, lignin, pectin, water-soluble substances, etc. The fiber has the advantages of antibacterial, antistatic, and anti-ultraviolet, and can be used to produce high- and medium-grade textiles. As early as the Western Han Dynasty, hemp fiber was widely used as a textile raw material. The fabric has good air permeability and antibacterial properties. In the spinning process of hemp fiber, a large amount of hemp is produced after being combed by a large cutter, a small cutter, and a circular machine, which is thrown away as waste. Except that the fiber length of hemp is damaged compared with that of industrial hemp (7-40mm, average 22.5mm), the other properties of hemp are the same. The length of hemp fiber cell is 5-25mm, average 15mm, which is much longer than wood fiber (0.8-2.5mm). The average aspect ratio of hemp fiber is about 500. The lignin content of hemp fiber is also lower than that of wood fiber, which has become the premise of good papermaking fiber raw material. However, the industrial hemp hemp produced in the textile process contains a large amount of pectin and lignin. Pectin and lignin wrap the fiber in the form of fiber bundles and cannot be used directly for papermaking. It must be dispersed into single fibers and fully absorb water, swell and soften before it can be used as a high-quality fiber raw material for papermaking. The amorphous area in the dense fiber is wrapped inside the fiber, the secondary wall is thicker, and the wall cavity ratio is 0.4 on average, which is larger than the wall cavity ratio of other wood fibers. The wall thickness resistance is large, and it is difficult to absorb water, stretch and penetrate chemical liquids. It requires a long time of chemical treatment, which increases the risk of degradation of cellulose fiber, reduces the degree of polymerization of the fiber, and cannot be used to make high-strength paper in the later stage. Summary of the invention

[0003] The present invention aims to solve at least one of the technical problems in the above-mentioned related art to a certain extent. To this end, the present invention adopts a chemical mechanical pulping method after pre-treating the noil fiber. The pre-treatment method is to use ultrasonic-complex enzyme synergistic treatment to remove a large amount of pectin and lignin in advance, and after pre-treatment, the time, temperature and amount of chemicals for chemical treatment in the later pulping are also reduced.

[0004] The present invention adopts the following technical solution:

[0005] First,

[0006] The embodiment of the present invention provides a method for preparing pulp from industrial hemp noil fibers, comprising S1: cutting hemp; S2: pickling; S3: water washing; S4: ultrasonic vibration; S5: biological enzyme treatment; S6: water washing; S7: chemical pulping; S8: water washing, S9: pulping steps;

[0007] In the method, the hemp noil produced during the spinning of hemp fibers is used as raw material;

[0008] In step S4, the conditions of ultrasonic oscillation are: oscillation temperature is 45-55°C, oscillation time is 30-35min, oscillation frequency is 40-45kHz, and oscillation power is 200-250W;

[0009] In step S5, the bio-enzyme treatment is carried out using pectinase and laccase in a mass ratio of 5:1 as a composite enzyme, the amount of composite enzyme added is 12% (owf), the pH value is 4.0-4.5, the temperature is 50-55°C; the liquid ratio is 1:(18-22), and the treatment time is 240-270min.

[0010] The inventors found in the experimental process that the ultrasonic action time, temperature, frequency, etc., as well as the selection, addition amount, and ratio of the complex enzyme all affect the effect of the pretreatment process on the fiber bundle, and thus affect the overall pulping effect. Specifically, the ultrasonic oscillation of the present invention controls the oscillation temperature to be 45-55°C, the oscillation time to be 30-35min, the oscillation frequency to be 40-45kHz, and the oscillation power to be 200-250W. The unique "cavitation effect" produced by ultrasonic waves in water at a certain temperature forms a strong impact and damage to the fallen hemp immersed in warm water, causing a large number of cracks in the outer colloid layer, and then under the further continuous action of the cavitation bubbles, small colloid groups are formed, which are crushed into extremely small colloid particles with the help of the huge pressure and tensile force generated when the ultrasonic cavitation bubbles expand and rupture, or even decomposed. The experiment found that when the water temperature is about 50°C, the "cavitation effect" produced is strong. This "cavitation effect" continues to act on the cracks, causing them to extend inward, creating more gaps leading to the secondary wall, and the S layer of the secondary wall inside the fiber slides to produce concentric layer dislocation, thereby reducing cohesion and making the fiber soft and porous; the composite enzyme composed of pectinase and laccase enters more pores generated by ultrasonic impact to reach the fiber surface and inside, respectively degrading the remaining pectin and part of the lignin, opening up more space for the penetration of later chemicals and reducing the resistance to liquid penetration. It is also easier for chemicals to enter later. It should be noted that the refined hemp used in textiles requires a certain amount of pectin to weave the fibers in the form of fiber bundles for weaving, and papermaking requires that all fiber bundles be further dispersed into single fibers before they can be used for papermaking. This requires that adhesives such as pectin and lignin in the fiber bundles be degraded to an amount sufficient to bring the fibers to the separation point. The inventors experimentally found that when the composite enzyme selected pectinase and laccase, and the mass ratio was 5:1, and the amount of composite enzyme added was 12% (owf), the effect was best.

[0011] In some embodiments, the enzyme activity of pectinase is 30000 u / g, and the enzyme activity of laccase is 10000 u / g.

[0012] In order to ensure that the complex enzyme is in full contact with the fiber, in some embodiments, step S5 is performed by constant temperature oscillation in a water bath at a rotation speed of 100 rpm.

[0013] In some embodiments, the hemp cutting step of step S1 includes: cutting the fallen hemp to 11-12 mm. The fallen hemp fibers act as a long fiber skeleton in the structure of the paper sheet, providing strength indicators such as the tensile strength, tear resistance, and folding resistance of the paper sheet. However, the fibers should not be too long. If the fibers are too long, fiber flocculation will occur during papermaking, resulting in failure of normal production. The hemp cutting step of the present invention cuts the fallen hemp to 11-12 mm, leaving enough margin for the peeling reaction that occurs during the later chemical treatment of the fibers and sufficient mechanical beating.

[0014] In some embodiments, the pickling step of step S2 includes: adding the cut hemp fiber to an impregnation liquid at a liquid ratio of 1: (18-22), wherein the impregnation liquid is 0.5g / L sulfuric acid, and pickling for 100-120min at a temperature of 45-50°C. In a specific embodiment, a water bath constant temperature oscillator is used to ensure the temperature and fully pickle (the speed is 100rpm) to remove ash and metal ions in the production process and to swell and soften the fiber.

[0015] In some embodiments, the washing steps of step S3, step S6 and step S8 include: washing the noil fibers with warm water at 40-45° C. until they are neutral, washing out dissolved, degraded and suspended substances, and further purifying the noil fibers.

[0016] In some embodiments, the chemical pulping step of step S7 uses NaOH and Na 2 S kraft pulping, relative to the absolute dry raw material mass, Na 2 O, the amount of alkali is 18%, the sulfidation degree is 12%, the liquid ratio is 1:4, the heating time is 30min, the insulation time is 90min, and the cooking temperature is 100℃.

[0017] Since noil is the combing waste of phloem hemp fiber in the textile process, and after the preliminary pretreatment, the fiber exists in bundles. The pectin and lignin in the fiber bundles can be pulped by the sulfate method. The noil pretreated with ultrasound and compound enzymes reduces the adhesion between the intercellular layers of the fiber bundles, increases the pore gaps of the secondary wall S layer, and reduces the cohesion of the secondary wall. The fiber is initially swollen and softened, but there is still a large amount of pectin and lignin that affect the dispersion of the fiber bundle into single fibers and further swelling and softening. Since the process of pretreatment to degrade pectin and lignin produces a large number of pore gaps, a better quality fiber pulp can be obtained through a softer chemical treatment pulping condition than the conventional one.

[0018] The purpose of chemical treatment is to remove a large amount of lignin to reach the fiber separation point. The delignification reaction is the breaking of various connecting bonds between the structural units of lignin macromolecules. In addition to OH, the main reactants in kraft pulping are Na 2 HS produced by S hydrolysis -Through chemical reactions, lyophilic groups are introduced into lignin macromolecules, causing the lignin macromolecules to degrade and become alkali lignin and sulfide lignin with smaller molecular weight, simpler structure, and easy to dissolve in alkali solution. In lignin macromolecules, the connections between structural units are mainly various ether bonds and carbon-carbon bonds. The sulfate method produces the following reactions: (1) alkalization and cleavage of phenolic a-aryl ether or a-alkyl ether bonds; (2) alkalization and sulfide cleavage of phenolic β-aryl ether bonds; (3) alkalization and sulfide cleavage of non-phenolic β-aryl ether bonds; (4) cleavage of CC bonds between aryl-alkyl and alkyl alkyl; (5) cleavage of methyl aryl ether bonds. Lignin dissolution causes fiber dispersion.

[0019] During the chemical treatment process, while delignifying, cellulose and hemicellulose will inevitably degrade under the action of strong alkali. The main reactions of cellulose and hemicellulose in alkali solution are: peeling reaction, termination reaction, alkaline hydrolysis, saponification of acetyl groups in acetylated hemicellulose, demethoxylation of polyarabinan-4-O-methyl glucuronic acid-xylose and poly 4-O-methyl glucuronic acid xylose, and final deglucuronic acid reaction, which degrades into soluble low molecular weight products. The longer the time, the more degradation. Conventional traditional chemical treatment (the existing kraft process in the pulping industry is mainly used for the preparation of softwood pulp. The conventional process requires high temperature and high pressure of 160-170°C and 6-8 bar, a total alkali content of more than 25%, a sulfidation degree of more than 20%, a liquid ratio of 1:4, a heating time of 60 minutes, a heat preservation time of 240 minutes, a long chemical treatment time, great damage to cellulose, a low pulping yield, a large amount of degraded organic matter in the waste liquid, and a high treatment cost) about 20% (to the raw material) of carbohydrates are lost. The present invention increases the pore gaps between the fiber bundle and the surface and layers of the fiber cells through the early combined pretreatment of ultrasound and composite enzymes, reduces the penetration resistance of the chemical treatment liquid in the later stage, accelerates the chemical reaction, facilitates the alkalization and sulfidation fracture of lignin, shortens the reaction time of chemical delignification and pectin, reduces the degree of cellulose peeling reaction, and improves the yield of pulp with the same quality index. Pretreatment can reduce the total alkali content and sulfidation degree of chemical treatment (total alkali content 18%, sulfidation degree 12%), shorten the treatment time and temperature (heating time about 30 minutes, insulation time 90 minutes, cooking temperature 100°C), make the loss rate within 6%, and reduce the organic degradation of waste liquid, reducing environmental pollution. The pulping process saves energy and reduces consumption, reduces pollution and increases efficiency. The products of this pulping method retain the length and polymerization degree of the fiber, providing sufficient buffer for sufficient mechanical pulping in the later stage. The tear resistance, folding resistance, bursting resistance and tensile strength of the product are greatly improved.

[0020] In some embodiments, in the refining step of step S9, the refining concentration is 10%, the PFI mill revolution number is 30000r, and the beating degree is 25-28°SR. The function of refining is to mechanically treat the fiber suspension in water, subject the fibers to shear force, change the fiber morphology, and make the pulp acquire certain characteristics (such as mechanical strength and physical properties) to ensure that the paper-made products meet the expected quality requirements. The refining concentration of 10% can reduce mechanical damage when the thick and long fibers with smooth and hard surfaces and lack of bonding properties are rubbed against each other, and the fibers can be evenly distributed on the net during papermaking, and the paper is dense and flat, with a tight and uniform texture and greater strength. After the PFI grinding knife and the bottom knife are rubbed and rubbed at a speed of 30,000 r, the smooth fibers undergo the following changes: ① The cell wall is displaced and deformed; ② The outer cells of the primary wall and the secondary wall are broken; ③ The fibers further absorb water and swell; ④ The fallen hemp fibers are fibrillated; ⑤ The fallen hemp fibers are cut, at which point the fiber beating degree can reach 25-28°SR. The fibrillation makes the fiber surface fluffy, the two ends broomed, the internal concentric layers misaligned, the cohesion reduced, and the fibers become soft and plastic.

[0021] Second,

[0022] The present invention also provides application of the pulp prepared by the method in paper making.

[0023] Thirdly,

[0024] The present invention also provides paper made by papermaking using the pulp prepared by the method.

[0025] In some embodiments, the paper is paper sack paper.

[0026] In the embodiment of the present invention, the paper made by papermaking with pulp prepared by the above method has a folding endurance of ≥495 times under 9.8N prestressing conditions and a bursting index of 3.0-3.1KPa·m 2 ·g -1 , tensile index is 43-45N·m·g -1 .

[0027] The present invention has the following advantages and beneficial effects:

[0028] (1) The embodiment of the present invention recycles industrial hemp fallen fibers and uses them as long fiber raw materials in the papermaking process; and adopts the "ultrasonic vibration + bio-enzyme treatment" pretreatment technology to make the industrial hemp fallen raw materials more suitable for pulping; reduces the pressure, temperature, and amount of chemicals in the later chemical pulping process, thereby reducing equipment hazards and corrosion; reduces the emission of degradation products and reduces environmental pollution.

[0029] (2) The method of the present invention retains the length and polymerization degree of the fibers, providing sufficient buffer for subsequent mechanical refining. The tear resistance, folding resistance, bursting resistance and tensile strength of the product paper are greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a SEM image of fallen flax fiber before pretreatment in step (2) of Example 1 of the present invention;

[0031] Figure 2 This is a SEM image of the fallen flax fiber after pretreatment in step (4) of Example 1 of the present invention;

[0032] Figure 3 This is a SEM image of the fallen flax fiber after pretreatment + chemical treatment in step (5) of Example 1 of the present invention;

[0033] Figure 4 This is a SEM image of the noil fibers after pretreatment + chemical treatment + refining in step (6) of Example 1 of the present invention. DETAILED DESCRIPTION

[0034] Embodiments of the present invention are described in detail below. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0035] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0036] Where values ​​are described herein as a range, it should be understood that such disclosure includes disclosure of all possible sub-ranges within that range, as well as specific values ​​falling within that range, regardless of whether a specific value or a specific sub-range is explicitly stated.

[0037] The following are specific embodiments and comparative examples of the present invention. It should be further explained that the following comparative examples are not prior art and are only provided for comparison with the embodiments and are not intended to limit the present invention.

[0038] The instruments and reagents involved in the embodiments and comparative examples of the present invention are as follows:

[0039] Reagents:

[0040] Sulfuric acid (analytical grade, Liaoning Quanrui Reagent Co., Ltd.)

[0041] Pectinase (30000u / g, Jiangsu Ruiyang Biotechnology Co., Ltd.)

[0042] Laccase (10000u / g, Jiangsu Ruiyang Biotechnology Co., Ltd.)

[0043] Cellulase (10u / mg, Hefei Qiansheng Biotechnology Co., Ltd.)

[0044] Hemicellulase (200u / mg, Hefei Qiansheng Biotechnology Co., Ltd.)

[0045] Sodium hydroxide (analytical grade, Jiamusi Huaguang Fine Chemical Factory)

[0046] Sodium sulfide (Sinopharm Chemical Reagent Co., Ltd.)

[0047] instrument:

[0048] PHS-3C Precision Desktop pH Meter (Hangzhou Qiwei Instrument Co., Ltd.)

[0049] Water bath constant temperature oscillator (HSY-C Changzhou Jintan Jingda Instrument Manufacturing Co., Ltd.)

[0050] BK-600D CNC ultrasonic cleaner (Jinan Buck Ultrasonic Technology Co., Ltd.)

[0051] YL1622-4080120 Multifunctional Ultrasonic Cleaning Machine (Yunyi Ultrasonic Co., Ltd.)

[0052] Digester (TD1-15, Xianyang Tongda Light Industry Equipment Co., Ltd.)

[0053] Fiber standard disintegrator (GBJ-A, Changchun Yueming Small Testing Machine Co., Ltd.)

[0054] Vertical refiner (PFI refiner, Xianyang Tongda Light Industry Equipment Co., Ltd.)

[0055] Shaw-type beating meter (Shandong Zhongyi Testing Instrument Co., Ltd.)

[0056] Fast Kasai Paper Sheet Former (S001A)

[0057] Detection:

[0058] Shaw-type beating tester (GB / T3332-1982)

[0059] Quantitative determination (GB / T451.2-2002)

[0060] Tear strength test (GB / T455-2002)

[0061] Burst strength test (GB / T454-2020)

[0062] Folding endurance test (GB / T457-2008)

[0063] Tensile strength determination (GB / T22898-2008)

[0064] Embodiment 1:

[0065] (1) Cut the hemp into 12mm lengths. This ensures that the long fibers are not lost too much and leaves enough room for loss in the later cooking and pulping.

[0066] (2) The fiber was added with an impregnation liquid at a liquid ratio of 1:20, and the impregnation liquid was 0.5g / L sulfuric acid. The fiber was pickled at a temperature of 50°C for 120 minutes. A water bath constant temperature oscillator was used to maintain the temperature and fully pickled to remove ash and metal ions in the production process and to soften the fiber. The fiber was washed with 40°C warm water until it was neutral, and dissolved, degraded and suspended substances were washed out. The SEM image of the fiber is shown in Figure 2. Figure 1 shown.

[0067] (3) The cleaned fallen flax fibers are vibrated in a CNC ultrasonic cleaner at a temperature of 50°C, a vibration frequency of 40kHz, and a vibration power of 200W for 30 minutes, and then washed with 40°C warm water to wash out the crushed pectin particles and dissolved substances.

[0068] (4) The composite enzyme solution was added to the noil fiber at a liquid ratio of 1:20, the composite enzyme dosage was 12% (owf), the mass ratio of pectinase to laccase was 5:1, the pH value was 4.0, the temperature was 50°C, the water bath constant temperature oscillation frequency was 100 rpm, the treatment time was 240 min, and the pectin and lignin adhesives degraded from the noil fiber were completely washed out with 40°C warm water. The SEM image of the noil fiber is shown in Figure 2. Figure 2 shown.

[0069] (5) Chemical preparation of hemp pulp is done by using the sulfate pulping process (NaOH and Na 2 S), relative to the absolute dry raw material mass, expressed as Na 2 The pre-treated noil was chemically treated under the following conditions: 18% alkali, 12% sulfidation, 1:4 liquid ratio, 30min heating time, 90min heat preservation time, and 100℃ cooking temperature. After treatment, the pulp was fully washed with 40℃ warm water until the suspension was neutral. The noil fiber was fully dispersed with a fiber disintegrator; the SEM image of the noil fiber is shown in the figure. Figure 3 shown.

[0070] (6) The fully dispersed noil fibers were refined using a vertical refiner (PFI refiner) at a pulping concentration of 10% and a rotation speed of 30,000 r / min. The beating degree was measured using a Shaw beating degree meter (the beating degree in Example 1 was 25° SR). The remaining pulp was reserved. Figure 4 shown.

[0071] (7) The slurry was dispersed in a fiber standard disintegrator for 5 minutes and was sheeted using a fast Kaesai paper former (S001A) without adding any chemical additives. The papermaking weight was 200 g / m 2 Paper sheets, testing physical indicators.

[0072] pass Figure 1-Figure 4 It can be seen that before pretreatment, the fallen flax fibers are smooth and stiff; after pretreatment, gaps appear on the surface and the fibers are swollen; with continued chemical treatment, the fallen flax fibers become further soft and plastic, the primary walls of the fibers are degraded to a certain extent, the fibers can be flattened, and become more swollen and porous; with continued pulping, most of the primary walls of the fibers are mechanically broken, the surface becomes filamentous and fluffy, and the two ends are broomed, making them softer and more plastic.

[0073] Example 2

[0074] (1) Cut the hemp into 12 mm lengths.

[0075] (2) The fiber was added with an impregnation solution at a liquid ratio of 1:20, wherein the impregnation solution was 0.5 g / L sulfuric acid, and the fiber was pickled at 50°C for 120 min. A water bath constant temperature oscillator was used to maintain the temperature and fully pickled. After pickling, the fiber was washed with 40°C warm water until it was neutral.

[0076] (3) The cleaned fallen flax fibers were vibrated in a CNC ultrasonic cleaner at a temperature of 55°C, a vibration frequency of 45kHz, and a vibration power of 200W for 35 minutes, and then washed with 40°C warm water until neutral.

[0077] (4) The fiber was added with a complex enzyme solution at a liquid ratio of 1:18, with a complex enzyme dosage of 12% (owf), a mass ratio of pectinase to laccase of 5:1, at a pH of 4.5, a temperature of 50°C, a water bath constant temperature oscillation frequency of 100 rpm, a treatment time of 240 min, and then washed with 40°C warm water until neutral.

[0078] (5) Using the kraft pulping process (NaOH and Na 2 S) to prepare hemp pulp, relative to the absolute dry raw material mass, Na 2 O, 18% alkali, 12% sulfidation, 1:4 liquid ratio, 30min heating time, 90min heat preservation time, 100℃ cooking temperature, the pre-treated noil is chemically treated. After treatment, it is fully washed with 40℃ warm water to neutrality, and the noil fiber is fully dispersed with a fiber disintegrator for standby use.

[0079] (6) The fully dispersed fallen flax fibers are refined using a vertical refiner (PFI refiner) at a pulping concentration of 10% and a rotation speed of 30,000 r / min. The beating degree is measured using a Shaw-type beating degree meter (the beating degree of Example 2 is 26° SR), and the remaining pulp is reserved.

[0080] (7) The slurry was dispersed in a fiber standard disintegrator for 5 minutes and was sheeted using a fast Kaesai paper former (S001A) without adding any chemical additives. The papermaking weight was 200 g / m 2 Paper sheets, testing physical indicators.

[0081] Example 3

[0082] (1) Cut the hemp into 12 mm lengths.

[0083] (2) The fiber was added with an impregnation solution at a liquid ratio of 1:20, wherein the impregnation solution was 0.5 g / L sulfuric acid, and the fiber was pickled at 50°C for 120 min. A water bath constant temperature oscillator was used to maintain the temperature and fully pickled. After pickling, the fiber was washed with 40°C warm water until it was neutral.

[0084] (3) The cleaned fallen flax fibers were vibrated in a CNC ultrasonic cleaner at a temperature of 45°C, a vibration frequency of 40kHz, and a vibration power of 250W for 35 minutes, and then washed with 40°C warm water until neutral.

[0085] (4) The fiber was added with a complex enzyme solution at a liquid ratio of 1:22, the dosage of the complex enzyme was 12% (owf), the mass ratio of pectinase to laccase was 5:1, the pH value was 4.5, the temperature was 55°C, the water bath constant temperature oscillation frequency was 100 rpm, the treatment time was 270 min, and it was clarified with 40°C warm water to neutral.

[0086] (5) Using the kraft pulping process (NaOH and Na 2 S) to prepare hemp pulp, relative to the absolute dry raw material mass, Na 2 O, 18% alkali, 12% sulfide, 1:4 liquid ratio, 30min heating time, 90min heat preservation time, 100℃ steaming temperature, the pre-treated noil is chemically treated. After treatment, it is fully washed with 40℃ warm water to neutrality, and the noil fiber is fully dispersed with a fiber disintegrator for standby use.

[0087] (6) The fully dispersed fallen flax fibers are refined using a vertical refiner (PFI refiner) at a pulping concentration of 10% and a rotation speed of 30,000 r / min. The beating degree is measured using a Shaw-type beating degree meter (the beating degree in Example 3 is 28° SR), and the remaining pulp is reserved for later use.

[0088] (7) The slurry was dispersed in a fiber standard disintegrator for 5 minutes and was sheeted using a fast Kaesai paper former (S001A) without adding any chemical additives. The papermaking weight was 200 g / m 2 Paper sheets, testing physical indicators.

[0089] Comparative Example 1-1

[0090] The difference from Example 1 is that the noil fibers obtained in step (2) are directly sheeted using a fast Kaesai paper former (S001A) without adding any chemical additives, and the papermaking weight is 200 g / m 2 Paper sheets, testing physical indicators.

[0091] Comparative Example 1-2

[0092] The difference from Example 1 is that the noil fibers obtained in step (4) are directly sheeted using a fast Kaesai paper sheet former (S001A) without adding any chemical additives, and the papermaking weight is 200 g / m 2 Paper sheets, testing physical indicators.

[0093] Comparative Examples 1-3

[0094] The difference from Example 1 is that the noil fibers obtained in step (5) are directly sheeted using a fast Kaesai paper former (S001A) without adding any chemical additives, and the papermaking weight is 200 g / m 2 Paper sheets, testing physical indicators.

[0095] The strength indexes of the paper sheets prepared by different hemp noil fiber processing processes of Example 1, Example 2, Example 3 and Comparative Examples 1-1, 1-2, 1-3 are shown in Table 1. By comparing Example 1 and Comparative Examples 1-1, 1-2, 1-3 in Table 1, it can be seen that before pretreatment, the indicators of the hemp noil fiber are low, and the paper sheets cannot form enough hydrogen bonds, only physical interweaving. Since the fibers are smooth and stiff, the contact between the fibers is point contact, and the strength index is low; after pretreatment, the fibers are moistened and swelled, become softer, and have a certain deformation ability, and the contact between the fibers of the paper sheets is The fiber has more points and its strength index is improved; with the chemical treatment, the fallen flax fiber is further soft and plastic, can be flattened, and is more swollen and porous. Due to the degradation of the primary wall of the fiber, a part of the hydrogen bonds are exposed, the bonding area and hydrogen bonds of the paper sheet are significantly increased, and the strength index is greatly improved; with the pulping, most of the primary wall of the fiber is mechanically broken, the surface is fibrillated and raised, and the two ends are fibrillated, which makes it softer and plastic, and the inside and outside are fibrillated at the same time, that is, the inside is soft and the outside is fibrillated, exposing a large number of hydroxyl groups, the contact area of ​​the paper sheet is sharply increased, a large number of hydrogen bonds are formed, and various strength indexes are sharply improved.

[0096] Table 1 Strength index of paper sheets prepared from hemp noil fibers with different processing technologies

[0097]

[0098] Comparative Example 2-1

[0099] Different from Example 1, Comparative Example 2-1 uses pectinase and hemicellulase in a ratio of 5:1, the pH of the complex enzyme system is 4.5, the water bath shaking temperature is 55° C., and the amount of complex enzyme added is 12% (owf).

[0100] Comparative Example 2-2

[0101] Different from Example 1, Comparative Example 2-2 uses pectinase, cellulase and hemicellulase in a ratio of 3:2:1, the pH of the complex enzyme system is 4.5, and the amount of complex enzyme added is 12% (owf).

[0102] Comparative Examples 2-3

[0103] Different from Example 1, Comparative Example 2-3 uses pectinase, laccase and hemicellulase in a ratio of 4:1:1, a pH of 4.5, a water bath shaking temperature of 55° C., and a compound enzyme addition amount of 12% (owf).

[0104] The strength indicators of paper sheets prepared by different hemp noil fiber processing processes in Example 1 and Comparative Examples 2-1, 2-2, and 2-3 are shown in Table 2; It can be seen from Table 2 that the enzyme combination has a great influence on the strength of the paper sheet, and the strength of the paper sheet is reflected in the strength of the fiber itself and the strength of the bonding between cellulose fibers. The synergistic effect of pectinase and laccase is better. The analysis reason may be: the combination of pectinase and laccase has a significant effect on the coating layer formed by the residual pectin and lignin of the noil produced by the hemp fiber in the spinning yarn, which can disperse the fiber into single fibers, and then continue to penetrate into the secondary wall of the fiber through the interlayer gap, further exerting its effect, while ensuring the efficiency of enzymatic hydrolysis, reducing fiber damage and maintaining fiber strength to the greatest extent.

[0105] Table 2 Strength indexes of paper sheets prepared from hemp noil fibers in different embodiments and comparative examples

[0106]

[0107]

[0108] Comparative Example 3-1

[0109] Different from Example 1, the ratio of pectinase to laccase in the composite enzyme solution of Comparative Example 3-1 is 4:1.

[0110] Comparative Example 3-2

[0111] Different from Example 1, the ratio of pectinase to laccase in the composite enzyme solution of Comparative Example 3-2 is 6:1.

[0112] Comparative Example 3-3

[0113] Different from Example 1, the ratio of pectinase to laccase in the composite enzyme solution of Comparative Example 3-3 is 1:1.

[0114] Comparative Examples 3-4

[0115] Different from Example 1, the ratio of pectinase to laccase in the complex enzyme solution of Comparative Example 3-4 is 1:2.

[0116] Comparative Examples 3-5

[0117] The difference from Example 1 is that the dosage of the complex enzyme solution in Comparative Example 1 is 10% (owf).

[0118] Comparative Examples 3-6

[0119] The difference from Example 1 is that the dosage of the complex enzyme solution in Comparative Example 1 is 14% (owf).

[0120] The strength indexes of the paper sheets prepared by different hemp fiber treatment processes of Example 1 and Comparative Examples 3-1, 3-2, 3-3, and 3-4 are shown in Table 3; It can be seen from Table 3 that when the amount of the composite enzyme remains unchanged, adjusting the ratio of the two enzymes (4:1, 6:1, 1:1, and 1:2) will reduce the overall pretreatment effect, because the pectin and lignin adhesives in the intercellular layer of the fiber bundle are spatially interwoven. The experiment found that for the hemp fiber produced by spinning yarn, the ratio of pectinase and laccase is 5:1, and the effect is the best. The reason for the analysis may be that at this ratio, pectin and lignin can maintain almost the same removal speed, thereby achieving the best removal effect. When the total amount of the composite enzyme remains unchanged, when the ratio of pectinase and laccase is 1:1, 1:2, or 4:1, the pectin degradation effect is weakened, the pectin cannot be fully degraded, and the residual glue coated on the surface and inside of the fiber bundle increases, which hinders the penetration of the chemical treatment solution in the later stage and the removal of the primary wall and the secondary wall during pulping. 2 The fibrillation of the fiber layer eventually leads to a decrease in exposed free hydroxyl groups and a decrease in various bonding strengths. When the ratio of pectinase to laccase is 6:1, the lignin in the fiber bundle cannot be fully degraded. The reduction in the amount of laccase slows down the removal of lignin. Pectin and lignin are in a state of mutual interweaving and mutual growth, and the presence of lignin weakens the continued degradation and removal of pectin.

[0121] The strength indexes of the paper sheets prepared by different hemp noil fiber processing processes in Example 1 and Comparative Examples 3-5 and 3-6 are shown in Table 3; It can be seen from Table 3 that the amount of compound enzyme added is small (10% in Comparative Examples 3-5), which cannot fully degrade pectin and lignin, increases residual glue, reduces the pretreatment effect, and ultimately leads to a decrease in the physical indexes of the paper sheets. The amount of compound enzyme added should not be too large. When the amount of compound enzyme added is 14% (Comparative Examples 3-6), the physical indexes of the paper sheets are not significantly improved, which is basically equivalent to Example 1. Considering factors such as cost, the amount of compound enzyme added is 12%, which is the best.

[0122] Table 3 Strength indexes of paper sheets prepared from hemp noil fibers in different embodiments and comparative examples

[0123]

[0124] Comparative Example 4-1

[0125] Different from Example 1, the ultrasonic treatment frequency of Comparative Example 4-1 is 24 kHz.

[0126] Comparative Example 4-2

[0127] Different from Example 1, the ultrasonic treatment frequency of Comparative Example 4-2 is 60 kHz.

[0128] Comparative Example 4-3

[0129] Different from Example 1, in Comparative Example 4-3, the ultrasonic oscillation was performed for 10 minutes.

[0130] Comparative Example 4-4

[0131] Different from Example 1, in Comparative Example 4-4, ultrasonic oscillation was performed for 60 minutes.

[0132] Comparative Examples 4-5

[0133] Different from Example 1, the temperature of ultrasonic oscillation in Comparative Examples 4-5 is 40°C.

[0134] Comparative Examples 4-6

[0135] Different from Example 1, the temperature of ultrasonic oscillation in Comparative Examples 4-6 is 60°C.

[0136] The strength indicators of paper sheets prepared by different hemp noil fiber processing processes in Example 1 and Comparative Examples 4-1, 4-2, 4-3, 4-4, 4-5 and 4-6 are shown in Table 4. It can be seen from Table 4 that the ultrasonic treatment frequency, treatment temperature and oscillation time have a great influence on the fiber properties, and thus affect the performance of the product paper.

[0137] By comparing Example 1 with Comparative Examples 4-1 and 4-2, it can be seen that the ultrasonic treatment frequency has an effect on the fiber properties. The low ultrasonic frequency (24kHz) has a weak "cavitation effect" on the fiber, poor impact and destructive ability, fewer colloid cracks, and slow colloid decomposition. The softness and porosity of the fiber inside and outside are weakened. However, when the ultrasonic frequency is increased to a certain level (60kHz), the damage to the fiber will be greater. The ultrasonic treatment frequency of 40kHz can achieve the best effect.

[0138] By comparing Example 1 with Comparative Examples 4-3 and 4-4, it can be seen that the ultrasonic oscillation time affects the fiber properties. If the time is too short (10 min), the sufficient impact effect cannot be achieved. If the time is too long (60 min), the fiber gains more energy, the cohesion decreases and the softening effect improves, but the fiber will also be damaged. The length-related indicators such as folding endurance and tearing endurance decrease significantly, and the bursting endurance and tensile strength begin to decrease.

[0139] By comparing Example 1 with Comparative Examples 4-5 and 4-6, it can be seen that the ultrasonic treatment temperature has an effect on the fiber properties. The ultrasonic wave produces a unique "cavitation effect" in water at a certain temperature to impact and destroy the colloid on the outer layer of the nova ash, forming a small colloid mass, and then the huge pressure and tensile force generated when the ultrasonic cavitation bubble expands and ruptures are crushed into extremely small colloid particles for removal. The water entering the nova ash fiber bundle and the fiber cell layer will also produce a "cavitation effect", causing cracks to appear inside the fiber, and continue to extend. This gap crack provides a channel for the later composite enzyme and chemical liquid to improve penetration. The effect of the "cavitation effect" is related to temperature. When the temperature is low, the nova ash fiber is not fully swollen, the water content inside the fiber is low, the crack gap produced by the "cavitation effect" is small, and the composite enzyme and the liquid contact channel area is small; when the temperature is high, the viscosity of the water is reduced, and the cavitation bubbles produced are larger than the size level of the pectin and lignin adhesives attached to the fiber, the impact force decreases, and the effect is weakened.

[0140] Table 4 Strength indexes of paper sheets prepared from hemp noil fibers in different embodiments and comparative examples

[0141]

[0142] Comparative Example 5-1

[0143] Different from Example 1, Comparative Example 5-1 does not have a pretreatment process (ultrasound + compound enzyme)

[0144] Comparative Example 5-2

[0145] Step (1) and step (2) are the same as those in Example 1; steps (3) and (4) are omitted;

[0146] After step (2), step (5) is directly carried out to chemically prepare hemp pulp, but the total alkali content is increased to 22%, the sulfidation degree is increased to 15%, the liquid ratio is still 1:4, the heating time is increased to 45 minutes, the heat preservation time is extended to 120 minutes, the cooking temperature is increased to 121° C., and the cooking absolute pressure is 2.049 MPa;

[0147] The refining speed in step (6) is directly increased to 40,000 rpm.

[0148] The strength indexes of the paper sheets prepared by different hemp noil fiber processing processes in Example 1 and Comparative Examples 5-1 and 5-2 are shown in Table 5. It can be seen from Table 5 that the various indexes of the paper sheets in Comparative Example 5-1 without pre-treatment pulping are very low.

[0149] From comparative example 5-2, it can be seen that in the absence of a pretreatment process, if the same physical indicators as those in Example 1 are to be achieved, the amount of chemical treatment and the time of chemical treatment need to be increased, and the temperature and pressure of chemical treatment need to be increased, resulting in an increase in the degraded organic pollutants and a decrease in the yield of crude pulp. In the later refining stage, the number of revolutions of refining is increased, resulting in an increase in energy consumption. The comparison of various consumption changes is shown in Table 6.

[0150] Table 5 Fiber strength index of paper sheets prepared from hemp noil in different embodiments and comparative examples

[0151]

[0152] Table 6 Comparison of various consumption values ​​between Example 1 and Comparative Example 5-2

[0153] Example 1 Comparative Example 5-2 Total alkali content (%) 18 22 Degree of vulcanization (%) 12 15 Cooking time (min) 120 165 Cooking temperature (℃) 100 121 Cooking pressure (MPa) 1.013 2.049 Rough pulp yield (%) 94 75 Cooking liquor COD (mg / L) 15000 62500 Refining speed (r) 30000 40000 Refining energy consumption / ton pulp (KWh / T) 11000 15000

[0154] Comparative Example 6

[0155] Different from Example 1, step (3) and step (4) of Comparative Example 6 are replaced by the following steps:

[0156] The cleaned fallen hemp fibers are added with a composite enzyme solution at a liquid ratio of 1:20, with a composite enzyme dosage of 12% (owf), a mass ratio of pectinase to laccase of 5:1, and the fibers are oscillated at a pH value of 4.0, a temperature of 50°C, an oscillation frequency of 40kHz, an oscillation power of 200W in a CNC ultrasonic cleaner for 240 minutes, and then washed with 40°C warm water.

[0157] The strength indexes of the paper sheets prepared by different hemp noil fiber processing processes in Example 1 and Comparative Example 6 are shown in Table 7; It can be seen from Table 7 that the strength index of the paper sheets of Example 1 is significantly higher than that of Comparative Example 6. The reason may be that the biological enzyme treatment and the ultrasonic treatment are carried out simultaneously. Under the frequency and power of the ultrasonic wave of the present invention, after a certain period of impact of ultrasonic cavitation bubble expansion and rupture, the protein activity of pectinase and laccase is gradually inactivated, and the degradation effect on pectin and lignin is gradually weakened, which does not reach the pretreatment scheme of first performing ultrasonic oscillation and then performing composite enzyme treatment in Example 1.

[0158] Table 7 Strength index of paper sheets prepared from hemp noil fibers in Example 1 and Comparative Example 6

[0159]

[0160] In summary, the method of Example 1 of the present invention shows that the pretreatment has a certain destructive effect on the pectin and lignin in the fiber bundle, and also reduces the cohesion of the internal structure of the fiber to a certain extent. The method of preparing hemp noil fiber by pretreatment in Example 1 of the present invention can greatly improve the bursting index, tear index, tensile index, folding endurance and other properties of the papermaking sheet.

[0161] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for preparing pulp from industrial hemp noil fibers, characterized in that: The process includes S1: cutting hemp; S2: pickling; S3: washing; S4: ultrasonic vibration; S5: enzyme treatment; S6: washing; S7: chemical pulping; S8: washing, S9: pulping; In the method, the hemp noil produced during the spinning of hemp fibers is used as raw material; In step S4, the conditions of ultrasonic oscillation are: oscillation temperature is 45-55°C, oscillation time is 30-35min, oscillation frequency is 40-45kHz, and oscillation power is 200-250W; In step S5, the bio-enzyme treatment is carried out using pectinase and laccase in a mass ratio of 5:1 as a composite enzyme, the amount of composite enzyme added is 12% (owf), the pH value is 4.0-4.5, the temperature is 50-55°C; the liquid ratio is 1:(18-22), and the treatment time is 240-270min.

2. The method for preparing pulp from industrial hemp noil fibers according to claim 1, characterized in that: The enzyme activity of the pectinase is 30000u / g, and the enzyme activity of the laccase is 10000u / g; Furthermore, in step S5, constant temperature oscillation in a water bath is performed at a rotation speed of 100 rpm.

3. The method for preparing pulp from industrial hemp noil fibers according to claim 1, characterized in that: The hemp cutting step of step S1 includes: cutting the fallen hemp into pieces of 11-12 mm.

4. The method for preparing pulp from industrial hemp noil fibers according to claim 1, characterized in that: The pickling step of step S2 includes: adding the fallen flax fibers after the flax cutting process into an impregnation liquid according to a liquid ratio of 1: (18-22), wherein the impregnation liquid is 0.5g / L sulfuric acid, and pickling for 100-120min at a temperature of 45-50°C.

5. The method for preparing pulp from industrial hemp noil fibers according to claim 1, characterized in that: The chemical pulping step of step S7 adopts NaOH and Na2S sulfate method for pulping. Relative to the absolute dry raw material mass, the alkali amount is 18% in terms of Na2O, the sulfidation degree is 12%, the liquid ratio is 1:4, the heating time is 30 minutes, the insulation time is 90 minutes, and the cooking temperature is 100°C.

6. The method for preparing pulp from industrial hemp noil fibers according to claim 1, characterized in that: In the refining step of step S9, the refining concentration is 10%, the PFI mill rotation number is 30000r, and the beating degree is 25-28°SR.

7. The method for preparing pulp from industrial hemp noil fibers according to claim 1, characterized in that: The washing steps of step S3, step S6 and step S8 include: washing the fallen flax fibers with warm water at 40-45° C. until they are neutral.

8. Use of the pulp prepared by the method according to any one of claims 1 to 7 in paper making.

9. The paper made by pulp papermaking obtained by the method according to any one of claims 1 to 7, characterized in that: The paper is paper bag paper.

10. The paper according to claim 9, characterized in that The paper, under the condition of 9.8N prestress, has a folding endurance of ≥495 times and a bursting index of 3.0-3.1KPa·m 2 ·g -1 ;Tensile index is 43-45N·m·g -1 .

Images