An untreated fluff pulp and a microwave-assisted pneumatic drying method thereof

Abstract

The application discloses untreated fluff pulp and a microwave-assisted airflow drying method thereof, and relates to the technical field of fluff pulp production. The method comprises the following steps: forming a shape by beating the untreated fluff pulp fibers after being dispersed in water, performing microwave irradiation pre-drying after dewatering through pressing, performing hot air airflow final drying, and finally performing raising treatment to obtain the untreated fluff pulp. Through the synergistic effect of microwave pre-drying and airflow final drying, the water in the fiber is rapidly vaporized by using the penetrating heating of the microwave to expand the fiber structure, and then the water is instantly taken away by the hot air, so that the fiber cutinization and densification are avoided. The untreated fluff pulp prepared through the process has a pulp board tightness of less than 0.5 g / cm 3 , a dry bulk density of not less than 22 cm 3 / g, and a water absorption time of less than 5 s, and the bulkiness and liquid absorption performance are significantly improved without adding any debonding agent, the drying time is short, the energy consumption is low, and the method has a good industrial application prospect.

Description

Technical Field

[0001] This invention belongs to the field of fluff pulp production technology, specifically relating to an untreated fluff pulp and its microwave-assisted airflow drying method. Background Technology

[0002] Untreated fluff pulp refers to virgin pulp sheets obtained directly after debonding, papermaking, pressing, and drying, without the addition of any unbonding agents, softeners, or surfactants during its production. Because the surface of untreated fluff pulp fibers retains natural hydroxyl groups, the fibers have strong hydrogen bonds, making them highly susceptible to fiber keratinization and surface hardening during traditional drying processes. This results in products with high density, poor bulk, and a significant decrease in liquid absorption rate and volume. However, untreated fluff pulp offers significant advantages such as good natural fiber integrity, high biocompatibility, and complete biodegradability, making it particularly suitable for medical care and maternal and infant hygiene products where additives are strictly limited.

[0003] Currently, the two main conventional drying methods for fluff pulp are cylinder drying and airflow drying. Cylinder drying uses a hot press roller to heat and pressurize the wet pulp board, achieving high production intensity. However, the high temperature and pressure severely crush and densify the fibers of untreated fluff pulp, irreversibly destroying the original natural crimp and porous structure of the fibers, making it difficult to meet the demands of high bulk and fast absorption products. While airflow drying can avoid the damage to fibers caused by mechanical pressure to some extent, for untreated fluff pulp, the high-speed hot air acting for a long time causes the surface moisture to evaporate rapidly, forming a dense, keratinized hard shell. This hard shell greatly increases the mass transfer resistance of internal moisture migration to the surface and hinders the diffusion of internal moisture outward, resulting in uneven drying inside and outside the fiber. At the same time, the high-temperature airflow can also cause thermal degradation of cellulose, further reducing the hydrophilicity and softness of the fiber. In addition, simple airflow drying usually requires extremely high air volume and temperature to achieve the target moisture content, resulting in high overall energy consumption, and there is a significant contradiction between drying efficiency and product quality.

[0004] To address the technical challenges of untreated fluff pulp during traditional drying processes, such as significant fiber damage, easy collapse of pore structure, and insufficient bulk and liquid absorption, existing technologies attempt to weaken the bonding force between fibers by adding debonding agents. However, the introduction of chemical additives poses risks to biosafety, increases production costs, and may affect the biodegradability and natural properties of the product. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide an untreated fluff pulp and its microwave-assisted airflow drying method, so as to solve the technical problems of easy keratinization and densification, insufficient fluffiness and liquid absorption performance, and high energy consumption of untreated fluff pulp during drying.

[0006] To achieve the above objectives, the present invention employs the following technical solution: In a first aspect, the present invention provides a microwave-assisted airflow drying method for untreated fluff pulp, comprising the following steps: S1, the untreated fluff pulp fibers are dispersed in water and then formed into a wet fluff pulp board; S2, the wet fluff pulp board obtained in S1 is pressed to obtain the pressed fluff pulp board. S3, microwave pre-dry the pressed fluff pulp board to obtain microwave pre-dried fluff pulp board. S4, the microwave pre-dried fluff pulp board is dried by hot air flow to obtain a dried fluff pulp board. S5, the dried fluff pulp board is subjected to a fluffing treatment to obtain the untreated fluff pulp.

[0007] A further improvement of this invention is that the water temperature in S1 is 60-75℃, the dewatering time is 3-5 min, the slurry concentration during dewatering is 0.8%-1.2%, and the basis weight of the wet flocked pulp board is 600-750 g / m³. 2 .

[0008] A further improvement of the present invention is that, in S2, a hydraulic press is used to press the pulp at a pressure of 3-5 MPa, and the dryness of the pulp board after pressing is controlled to reach 36%-43%.

[0009] A further improvement of the present invention is that the pressing in S2 is segmented pressing, with a total pressing time of 2-3 minutes, and the dry blanket and filter paper are replaced after each segment of pressing.

[0010] A further improvement of the present invention is that the microwave power of the microwave irradiation pre-drying in S3 is 300-700 W, and the drying time is 60-200 s.

[0011] A further improvement of the present invention is that the final drying temperature of the hot air flow in S4 is 90-105℃, the drying time is 1-3 min, and the moisture content of the dried fluff pulp board is 8%-10%.

[0012] A further improvement of the present invention is that, between S3 and S4, a buffer balancing step is included: the microwave-pre-dried fluff pulp plate is allowed to stand in the air for 10-30 seconds to equilibrate.

[0013] A further improvement of the present invention is that, in step S4, when the microwave pre-dried fluff pulp board is subjected to hot air final drying, metal meshes are clamped on the upper and lower sides of the fluff pulp board respectively.

[0014] Secondly, the present invention also provides an untreated fluff pulp, which is prepared by the above-described preparation method.

[0015] A further improvement of the present invention is that the density of the untreated fluff pulp is less than 0.5 g / cm. 3 The dry loft should be no less than 22 cm. 3 / g, water absorption not less than 9 g / g, water absorption time less than 5 s.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a microwave-assisted airflow drying method for untreated fluff pulp. The method first pre-dries the pressed wet pulp board using microwave irradiation. The penetrating heating of microwaves causes simultaneous vaporization of both internal and surface moisture within the fibers, overcoming the drawbacks of traditional hot air drying, which results in external dryness and internal dampness, and the formation of a hard crust on the surface. This achieves consistent dryness throughout the pulp board. Simultaneously, the vapor pressure generated by the rapid vaporization of internal moisture helps to expand the fiber structure, promoting natural fluffiness and expansion of the pulp board, laying the foundation for a porous structure for subsequent drying. Finally, a hot airflow is used for final drying, with high-speed hot air instantly contacting and removing moisture, avoiding damage to the fiber structure caused by mechanical extrusion. Through the synergistic effect of microwaves and airflow, this process effectively prevents fiber keratinization and surface densification without the addition of any debonding agents, achieving a final product dry bulk of 23.05-26.66 cm⁻¹. 3 / g, with a density as low as 0.39-0.46 g / cm³. 3 The water absorption time is shortened to 3.19-3.70 s, and the water absorption reaches 9.17-10.79 g / g, resulting in a significant improvement in product quality. Simultaneously, because microwave pre-drying rapidly increases the internal moisture temperature of the slurry plate and removes some moisture, the hot air temperature and air volume required for subsequent airflow drying are significantly reduced, leading to a substantial decrease in overall energy consumption. The entire drying process can be completed within minutes, greatly shortening drying time and improving production efficiency. Furthermore, microwave power and hot air temperature can be independently and precisely controlled, resulting in strong process stability and making it more suitable for large-scale industrial production, demonstrating promising industrialization prospects.

[0017] This invention also provides an untreated fluff pulp, prepared using the aforementioned microwave-assisted airflow drying method, which effectively preserves the natural porous structure of the fibers without the need for any unbonding agents. Compared to fluff pulp prepared by traditional cylinder drying or pure airflow drying, this product has a pulp board density of less than 0.5 g / cm³. 3 The dry loft should be no less than 22 cm. 3 With a water absorption capacity of not less than 9 g / g and a water absorption time of less than 5 s, the dry fluffiness and liquid absorption performance are significantly improved. At the same time, it retains the inherent advantages of untreated fluff pulp being natural, safe, and biodegradable. It can fully meet the application requirements of high-end absorbent hygiene products and medical care products for high fluffiness, fast absorption, and high safety, and has broad market application prospects. Detailed Implementation

[0018] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0019] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0020] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0021] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0022] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0023] This invention provides a microwave-assisted airflow drying method for untreated fluff pulp and the untreated fluff pulp obtained by this method. Untreated fluff pulp refers to pulp without the addition of any unbonding agents, softeners, or surfactants. Its fiber surface retains natural hydroxyl groups, and the inter-fiber hydrogen bonds are strong, resulting in significant advantages such as good fiber integrity, high biocompatibility, and complete biodegradability. It is commonly used in basic dressings, industrial cushioning packaging, medical care pads, and pet absorbent pads. However, in traditional drying processes, untreated fluff pulp is prone to fiber keratinization and surface hardening, leading to high density, poor bulk, and difficulty in meeting the requirements of high-end absorbent products in terms of absorption rate and volume. Existing technologies attempt to weaken the inter-fiber bonding by adding unbonding agents, but the introduction of chemical additives poses biocompatibility risks, increases production costs, and may affect the product's biodegradability. To address these technical challenges, this invention proposes a synergistic drying scheme using microwave-assisted airflow drying, achieving precise control of the moisture content and drying effect of the fluff pulp board without the addition of any chemical unbonding agents.

[0024] The microwave-assisted airflow drying method for untreated fluff pulp provided by the present invention includes the following steps: S1. Untreated fluff pulp fibers are dispersed in water and then formed into a wet fluff pulp board. Specifically, the fluff pulp fibers are dispersed using hot water at 60-75℃ for 3-5 minutes, with a pulp concentration of 0.8%-1.2% during dispersion. Hot water dispersion effectively disperses the fibers while preventing bacterial growth. After dispersion, the pulp is transferred to a paper sheeter for forming, controlling the basis weight of the wet fluff pulp board to be 600-750 g / m³. 2 .

[0025] S2, the wet fluff pulp obtained in S1 is pressed to obtain pressed fluff pulp. Specifically, a hydraulic press is used to press the pulp at a pressure of 3-5 MPa (preferably 4 MPa). The pressing method is segmented pressing, with a total pressing time of 2-3 minutes. After each segment of pressing, the dry felt and filter paper are replaced to fully remove free water from the wet fluff pulp. Through pressing, the dryness of the pressed fluff pulp is controlled to reach 36%-43%.

[0026] S3. The pressed fluff pulp board is pre-dried by microwave irradiation to obtain a microwave pre-dried fluff pulp board. Specifically, the pressed fluff pulp board is placed in a microwave drying oven and pre-dried by microwave irradiation at a microwave power of 300-700 W for 60-200 s. In this stage, the penetrating heating characteristics of microwaves are utilized to heat both the internal and surface moisture of the fluff pulp board simultaneously. Heat is generated from within the fibers, causing the moisture to vaporize rapidly. This process has two important functions: First, microwaves can selectively heat the moisture inside the fibers, allowing the internal moisture to diffuse to the surface in a timely manner during the subsequent drying process, preventing the surface moisture from evaporating too quickly and forming a dense, keratinized hard shell, thus effectively preventing fiber keratinization and surface densification. Second, the rapid vaporization of the moisture inside the fibers generates outward vapor pressure, which helps to expand the fiber structure, causing the fluff pulp board to naturally fluff up and expand, laying the foundation for the formation of a stable porous structure in the subsequent final airflow drying stage.

[0027] Preferably, between S3 and S4, a buffer balancing step is also included: the microwave pre-dried fluff pulp board is left to stand in the air for 10-30 seconds to balance, so that the moisture and temperature distribution inside and on the surface of the fluff pulp board is more uniform, further ensuring the uniformity of subsequent drying.

[0028] S4. The microwave-pre-dried fluff pulp board is then subjected to hot air final drying to obtain a dried fluff pulp board. Specifically, the microwave-pre-dried (and buffered) fluff pulp board is placed in a hot air drying oven and subjected to hot air final drying at a temperature of 90-105℃ for 1-3 minutes. During the final air drying process, high-speed hot air carries away moisture diffused from the surface and interior of the fluff pulp board, allowing the fluff pulp board to reach the final target moisture content. Since most of the moisture has been removed from the fluff pulp board in the microwave pre-drying stage (S3), and the internal moisture temperature has been effectively increased, the required hot air temperature and drying time in this stage are significantly reduced compared to traditional pure air drying, effectively avoiding damage to the fibers from prolonged high temperatures. After final air drying, the moisture content of the fluff pulp board is controlled at 8%-10%. Preferably, during hot air drying in the air drying oven, a metal mesh is clamped on both the upper and lower sides of the fluff pulp board to ensure uniform drying and prevent the fluff pulp board from bending and deforming under the action of hot air.

[0029] S5, the dried fluff pulp board is subjected to a fluffing treatment to obtain the untreated fluff pulp finished product, which can be used for subsequent processing of absorbent products.

[0030] This invention also provides an untreated fluff pulp, prepared using the above-described method. The untreated fluff pulp dried using the method of this invention retains a well-preserved natural fiber structure and exhibits excellent product performance: pulp board density is less than 0.5 g / cm³. 3The dry loft should be no less than 22 cm. 3 / g, water absorption not less than 9 g / g, water absorption time less than 5 s.

[0031] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0032] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" represents weight percentage, "parts" represents parts by weight, and "ratio" represents weight proportion.

[0033] Example 1 This embodiment provides a microwave-assisted airflow drying method for untreated fluff pulp, including the following steps: S1, Wet pulp dissolution and papermaking: Softwood pulp is dissolved in hot water at 75℃ for 3 minutes to achieve a dissolution concentration of 1.0%, and then formed at the same temperature to obtain wet fluff pulp board.

[0034] S2, Pressing and Dehydration: The wet fluff pulp board obtained in S1 is pressed using a hydraulic press at a pressure of 4MPa. The pressing time is 1+1+1min. After each pressing, the dry felt and filter paper are replaced to control the dryness of the fluff pulp board to 41%.

[0035] S3, Microwave Pre-drying: Transfer the fluff pulp board after pressing in S2 to a microwave drying oven and pre-dry it under microwave irradiation at a microwave power of 700W for 90s. Then, let the microwave pre-dried fluff pulp board stand in the air for 20s to achieve equilibrium.

[0036] S4, Final airflow drying: The buffered and balanced fluff pulp board is placed in a 100℃ hot airflow drying oven for final drying. The drying time is 2 minutes, and the moisture content of the fluff pulp board after drying is controlled to be 9%±1%.

[0037] S5, Post-treatment and performance testing: The dried fluff pulp board of S4 is subjected to a napping treatment to obtain untreated fluff pulp; the thickness, basis weight, bursting strength of the obtained fluff pulp board, as well as the liquid absorption time, liquid absorption volume, and dry bulk of the fluff pulp after napping are measured.

[0038] After the above-described process, the performance indicators of the untreated fluff pulp obtained in this embodiment are as follows: fluff pulp board basis weight is 660 g / m³. 2 It has a thickness of 1.57mm and a density of 0.42g / cm. 3 The bursting strength is 1112 kPa. A 3.05 g sample was used to test its liquid absorption performance. The absorption time was 3.19 s, the wet weight of the fully absorbed fluff pulp was 35.97 g, the water absorption was 10.79 g / g, the absorption rate was 1.04 s / g, the pile height was 3.70 cm, and the dry loft was 23.82 cm. 3 / g.

[0039] Example 2 This embodiment provides a microwave-assisted airflow drying method for untreated fluff pulp, including the following steps: S1, Wet pulp dissolution and papermaking: Softwood pulp is dissolved in 70℃ hot water for 4 minutes to achieve a dissolution concentration of 1.0%, and then formed at the same temperature to obtain wet fluff pulp board.

[0040] S2, Pressing and Dehydration: The wet fluff pulp board obtained in S1 is pressed using a hydraulic press at a pressure of 4MPa. The pressing time is 1+1+1min. After each pressing, the dry felt and filter paper are replaced to control the dryness of the fluff pulp board to 43%.

[0041] S3, airflow drying: Place the fluff pulp board after pressing in S2 into a hot airflow drying oven at 105℃ for drying for 2 minutes.

[0042] S4, Microwave Pre-drying: The fluff pulp board after airflow drying is transferred to a microwave drying oven and pre-dried by microwave irradiation for 100s under microwave power of 560W, and the moisture content of the fluff pulp board after drying is controlled to be 9%±1%.

[0043] S5, Post-treatment and performance testing: The dried fluff pulp board of S4 is subjected to a napping treatment to obtain untreated fluff pulp; the thickness, basis weight, bursting strength of the obtained fluff pulp board, as well as the liquid absorption time, liquid absorption volume, and dry bulk of the fluff pulp after napping are measured.

[0044] After the above-described process, the performance indicators of the untreated fluff pulp obtained in this embodiment are as follows: fluff pulp board basis weight is 650 g / m³. 2 It has a thickness of 1.51 mm and a density of 0.43 g / cm. 3 The bursting strength is 1182 kPa. A 3.05 g sample was used to test its liquid absorption performance. The absorption time was 3.51 s, the wet weight of the fully absorbed fluff pulp was 35.67 g, the water absorption rate was 10.70 g / g, the absorption rate was 1.15 s / g, the pile height was 3.46 cm, and the dry loft was 22.30 cm.3 / g.

[0045] Example 3 This embodiment provides a microwave-assisted airflow drying method for untreated fluff pulp, including the following steps: S1, Wet pulp dissolution and papermaking: Softwood pulp was dissolved in hot water at 65℃ for 4 minutes to a dissolution concentration of 1.2%, and then formed at the same temperature to obtain wet fluff pulp board.

[0046] S2, Pressing and Dehydration: The wet fluff pulp board obtained in S1 is pressed using a hydraulic press at a pressure of 4MPa. The pressing time is 1+1min. After each pressing, the dry felt and filter paper are replaced to control the dryness of the fluff pulp board to 39%.

[0047] S3, Microwave Pre-drying: Transfer the fluff pulp board after pressing in S2 to a microwave drying oven and pre-dry it for 120 seconds under microwave irradiation at a microwave power of 400W. Then, let the microwave pre-dried fluff pulp board stand in the air for equilibration buffer for 15 seconds.

[0048] S4, Final airflow drying: The buffered and balanced fluff pulp board is placed in a hot airflow drying oven at 105℃ for final drying. The drying time is 2 minutes, and the moisture content of the fluff pulp board after drying is controlled to be 9%±1%.

[0049] S5, Post-treatment and performance testing: The dried fluff pulp board of S4 is subjected to a napping treatment to obtain untreated fluff pulp; the thickness, basis weight, bursting strength of the obtained fluff pulp board, as well as the liquid absorption time, liquid absorption volume, and dry bulk of the fluff pulp after napping are measured.

[0050] After the above-described process, the performance indicators of the untreated fluff pulp obtained in this embodiment are as follows: fluff pulp board basis weight is 700 g / m³. 2 It has a thickness of 1.69 mm and a density of 0.41 g / cm³. 3 The bursting strength is 1251 kPa. A 3.05 g sample was used to test its liquid absorption performance. The absorption time was 3.68 s, the wet weight of the fully absorbed fluff pulp was 35.96 g, the water absorption was 10.79 g / g, the absorption rate was 1.21 s / g, the pile height was 3.88 cm, and the dry loft was 24.98 cm. 3 / g.

[0051] Example 4 This embodiment provides a microwave-assisted airflow drying method for untreated fluff pulp, including the following steps: S1, Wet pulp decomposition and papermaking: Softwood pulp is decomposed in hot water at 60℃ for 5 minutes to a decomposition concentration of 0.8%, and then formed at the same temperature to obtain wet fluff pulp board.

[0052] S2, Pressing and Dehydration: The wet fluff pulp board obtained in S1 is pressed using a hydraulic press at a pressure of 4MPa. The pressing time is 1+1min. After each pressing, the dry felt and filter paper are replaced to control the dryness of the fluff pulp board to 36%.

[0053] S3, Microwave Pre-drying: Transfer the fluff pulp board after pressing in S2 to a microwave drying oven and pre-dry it under microwave irradiation for 200s at a microwave power of 360W. Then, let the microwave pre-dried fluff pulp board stand in the air for 30s to achieve equilibrium.

[0054] S4, Final airflow drying: The buffered and balanced fluff pulp board is placed in a 95℃ hot airflow drying oven for final drying. The drying time is 3 minutes, and the moisture content of the fluff pulp board after drying is controlled to be 9%±1%.

[0055] S5, Post-treatment and performance testing: The dried fluff pulp board of S4 is subjected to a napping treatment to obtain untreated fluff pulp; the thickness, basis weight, bursting strength of the obtained fluff pulp board, as well as the liquid absorption time, liquid absorption volume, and dry bulk of the fluff pulp after napping are measured.

[0056] After the above-described process, the performance indicators of the untreated fluff pulp obtained in this embodiment are as follows: fluff pulp board basis weight is 600 g / m³. 2 It has a thickness of 1.55mm and a density of 0.39g / cm. 3 The bursting strength is 1230 kPa. A 3.05 g sample was used to test its liquid absorption performance. The absorption time was 3.70 s, the wet weight of the fully absorbed fluff pulp was 35.84 g, the water absorption rate was 10.75 g / g, the absorption rate was 1.21 s / g, the pile height was 3.65 cm, and the dry loft was 23.50 cm. 3 / g.

[0057] Example 5 This embodiment provides a microwave-assisted airflow drying method for untreated fluff pulp, including the following steps: S1, Wet pulp dissolution and papermaking: Softwood pulp is dissolved in hot water at 75℃ for 3 minutes to achieve a dissolution concentration of 1.0%, and then formed at the same temperature to obtain wet fluff pulp board.

[0058] S2, Pressing and Dehydration: The wet fluff pulp board obtained in S1 is pressed using a hydraulic press at a pressure of 3MPa. The pressing time is 1+1+1min. After each pressing, the dry felt and filter paper are replaced to control the dryness of the fluff pulp board to 40%.

[0059] S3, First airflow drying: Place the fluff pulp board after pressing in S2 into a hot airflow drying oven at 100℃ for the first airflow drying, and the drying time is 1 minute.

[0060] S4, Microwave Pre-drying: Transfer the fluff pulp board after the first airflow drying treatment to a microwave drying oven and pre-dry it with microwave irradiation for 60s under a microwave power of 700W. Then, let the microwave pre-dried fluff pulp board stand in the air for equilibration buffer for 15s.

[0061] S5, Second airflow drying: The buffered and balanced fluff pulp board is placed again in a 100℃ hot airflow drying oven for a second airflow drying. The drying time is 1 minute, and the moisture content of the fluff pulp board after drying is controlled to be 9%±1%.

[0062] S6, Post-treatment and performance testing: The dried S5 fluff pulp board is subjected to a napping treatment to obtain untreated fluff pulp; the thickness, basis weight, bursting strength of the obtained fluff pulp board, as well as the liquid absorption time, liquid absorption volume, and dry bulk of the fluff pulp after napping are measured.

[0063] After the above-described process, the performance indicators of the untreated fluff pulp obtained in this embodiment are as follows: fluff pulp board thickness is 1.51 mm, and density is 0.44 g / cm³. 3 The bursting strength is 1212 kPa. A 3.05 g sample was used to test its liquid absorption performance. The absorption time was 3.34 s, the wet weight of the fully absorbed fluff pulp was 35.60 g, the water absorption was 9.17 g / g, the absorption rate was 1.10 s / g, the pile height was 3.68 cm, and the dry loft was 23.70 cm. 3 / g.

[0064] Example 6 This embodiment provides a microwave-assisted airflow drying method for untreated fluff pulp, including the following steps: S1, Wet pulp dissolution and papermaking: Bamboo pulp is dissolved in 75℃ hot water for 3 minutes to achieve a dissolution concentration of 1.0%, and then formed at the same temperature to obtain wet fluff pulp board.

[0065] S2, Pressing and Dehydration: The wet fluff pulp board obtained in S1 is pressed using a hydraulic press at a pressure of 4MPa. The pressing time is 1+1+1min. After each pressing, the dry felt and filter paper are replaced to control the dryness of the fluff pulp board to 43%.

[0066] S3, Microwave Pre-drying: Transfer the fluff pulp board after pressing in S2 to a microwave drying oven and pre-dry it under microwave irradiation at a microwave power of 560W for 90s. Then, let the microwave pre-dried fluff pulp board stand in the air for 20s to achieve equilibrium.

[0067] S4, Final airflow drying: The buffered and balanced fluff pulp board is placed in a hot airflow drying oven at 105℃ for final drying. The drying time is 2 minutes, and the moisture content of the fluff pulp board after drying is controlled to be 9%±1%.

[0068] S5, Post-treatment and performance testing: The dried fluff pulp board of S4 is subjected to a napping treatment to obtain untreated fluff pulp; the thickness, basis weight, bursting strength of the obtained fluff pulp board, as well as the liquid absorption time, liquid absorption volume, and dry bulk of the fluff pulp after napping are measured.

[0069] After the above-described process, the performance indicators of the untreated fluff pulp obtained in this embodiment are as follows: fluff pulp board basis weight is 660 g / m³. 2 It has a thickness of 1.45mm and a density of 0.45g / cm. 3 The bursting strength is 1196 kPa. A 3.05 g sample was used to test its liquid absorption performance. The absorption time was 3.66 s, the wet weight of the fully absorbed fluff pulp was 35.34 g, the water absorption was 10.59 g / g, the absorption rate was 1.20 s / g, the pile height was 3.60 cm, and the dry loft was 23.18 cm. 3 / g.

[0070] Example 7 This embodiment provides a microwave-assisted airflow drying method for untreated fluff pulp, including the following steps: S1, Wet pulp dissolution and papermaking: Bamboo pulp is dissolved in 70℃ hot water for 4 minutes to achieve a dissolution concentration of 0.8%, and then formed at the same temperature to obtain wet fluff pulp board.

[0071] S2, Pressing and Dehydration: The wet fluff pulp board obtained in S1 is pressed using a hydraulic press at a pressure of 4MPa. The pressing time is 1+1+1min. After each pressing, the dry felt and filter paper are replaced to control the dryness of the fluff pulp board to 40%.

[0072] S3, Microwave Pre-drying: Transfer the fluff pulp board after pressing in S2 to a microwave drying oven and pre-dry it under microwave irradiation at a microwave power of 700W for 60s. Then, let the microwave pre-dried fluff pulp board stand in the air for equilibration buffer for 10s.

[0073] S4, Final airflow drying: The buffered and balanced fluff pulp board is placed in a 100℃ hot airflow drying oven for final drying. The drying time is 2 minutes, and the moisture content of the fluff pulp board after drying is controlled to be 9%±1%.

[0074] S5, Post-treatment and performance testing: The dried fluff pulp board of S4 is subjected to a napping treatment to obtain untreated fluff pulp; the thickness, basis weight, bursting strength of the obtained fluff pulp board, as well as the liquid absorption time, liquid absorption volume, and dry bulk of the fluff pulp after napping are measured.

[0075] After the above-described process, the performance indicators of the untreated fluff pulp obtained in this embodiment are as follows: fluff pulp board basis weight is 600 g / m³. 2 It has a thickness of 1.43 mm and a density of 0.46 g / cm. 3 The bursting strength is 1276 kPa. A 3.05 g sample was used to test its liquid absorption performance. The absorption time was 3.45 s, the wet weight of the fully absorbed fluff pulp was 35.26 g, the water absorption rate was 10.56 g / g, the absorption rate was 1.13 s / g, the pile height was 3.58 cm, and the dry loft was 23.05 cm. 3 / g.

[0076] Example 8 This embodiment provides a microwave-assisted airflow drying method for untreated fluff pulp, including the following steps: S1, Wet pulp dissolution and papermaking: Bamboo pulp is dissolved in 65℃ hot water for 5 minutes to achieve a dissolution concentration of 1.2%, and then formed at the same temperature to obtain wet fluff pulp board.

[0077] S2, Pressing and Dehydration: The wet fluff pulp board obtained in S1 is pressed using a hydraulic press at a pressure of 4MPa. The pressing time is 1+1min. After each pressing, the dry felt and filter paper are replaced to control the dryness of the fluff pulp board to 36%.

[0078] S3, Microwave Pre-drying: Transfer the fluff pulp board after pressing in S2 to a microwave drying oven and pre-dry it for 120 seconds under microwave irradiation at a microwave power of 400W. Then, let the microwave pre-dried fluff pulp board stand in the air for 30 seconds to achieve equilibrium.

[0079] S4, Final airflow drying: The buffered and balanced fluff pulp board is placed in a 95℃ hot airflow drying oven for final drying. The drying time is 3 minutes, and the moisture content of the fluff pulp board after drying is controlled to be 9%±1%.

[0080] S5, Post-treatment and performance testing: The dried fluff pulp board of S4 is subjected to a napping treatment to obtain untreated fluff pulp; the thickness, basis weight, bursting strength of the obtained fluff pulp board, as well as the liquid absorption time, liquid absorption volume, and dry bulk of the fluff pulp after napping are measured.

[0081] After the above-described process, the performance indicators of the untreated fluff pulp obtained in this embodiment are as follows: fluff pulp board basis weight is 660 g / m³. 2 It has a thickness of 1.47 mm and a density of 0.41 g / cm³. 3The bursting strength is 1164 kPa. A 3.05 g sample was used to test its liquid absorption performance. The absorption time was 3.50 s. After full absorption, the wet weight of the fluff pulp was 35.33 g, the water absorption was 10.58 g / g, the absorption rate was 1.15 s / g, the pile height was 3.58 cm, and the dry loft was 23.05 cm. 3 / g.

[0082] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A microwave-assisted airflow drying method for untreated fluff pulp, characterized in that, Includes the following steps: S1, the untreated fluff pulp fibers are dispersed in water and then formed into a wet fluff pulp board; S2, the wet fluff pulp board obtained in S1 is pressed to obtain the pressed fluff pulp board. S3, the pressed fluff pulp board is pre-dried by microwave irradiation to obtain microwave pre-dried fluff pulp board; S4, the microwave pre-dried fluff pulp board is dried by hot air flow to obtain a dried fluff pulp board. S5, the dried fluff pulp board is subjected to a fluffing treatment to obtain the untreated fluff pulp.

2. The microwave-assisted airflow drying method for untreated fluff pulp according to claim 1, characterized in that, The water temperature in S1 is 60-75℃, the descaling time is 3-5 min, the slurry concentration during descaling is 0.8%-1.2%, and the basis weight of the wet flocked pulp board is 600-750 g / m³. 2 .

3. The microwave-assisted airflow drying method for untreated fluff pulp according to claim 1, characterized in that, In S2, a hydraulic press is used to press the pulp at a pressure of 3-5 MPa, and the dryness of the pulp board after pressing is controlled to reach 36%-43%.

4. The microwave-assisted airflow drying method for untreated fluff pulp according to claim 1, characterized in that, The pressing described in S2 is a segmented pressing, with a total pressing time of 2-3 minutes. After each segment of pressing is completed, the dry blanket and filter paper are replaced.

5. The microwave-assisted airflow drying method for untreated fluff pulp according to claim 1, characterized in that, The microwave power for microwave irradiation pre-drying described in S3 is 300-700 W, and the drying time is 60-200 s.

6. The microwave-assisted airflow drying method for untreated fluff pulp according to claim 1, characterized in that, The final drying temperature of the hot airflow in S4 is 90-105℃, the drying time is 1-3 min, and the moisture content of the dried fluff pulp board is 8%-10%.

7. The microwave-assisted airflow drying method for untreated fluff pulp according to claim 1, characterized in that, Between S3 and S4, there is also a buffer equilibration step: the microwave pre-dried fluff pulp plate is left to stand in the air for 10-30 seconds to equilibrate.

8. The microwave-assisted airflow drying method for untreated fluff pulp according to claim 1, characterized in that, In S4, when the microwave pre-dried fluff pulp board is subjected to hot air final drying, metal meshes are clamped on the upper and lower sides of the fluff pulp board.

9. An untreated fluff pulp, characterized in that, It is prepared by the preparation method described in any one of claims 1-8.

10. The untreated fluff pulp according to claim 9, characterized in that, The untreated fluff pulp has a board density of less than 0.5 g / cm. 3 The dry loft should be no less than 22 cm. 3 / g, water absorption not less than 9 g / g, water absorption time less than 5 s.