A method for modifying fluff pulp

Abstract

This invention discloses a method for modifying fluff pulp, which can effectively increase the porosity between fibers, thereby improving its liquid conductivity. The preparation method includes the following steps: treating different types of softwood pulp boards with ultrasonic waves and 1,2,3,4-butanetetracarboxylic acid (BTCA) crosslinking. Ultrasonic pulverization effectively reduces the bonding force between fibers, while the polycarboxylic acid crosslinking method gives the fibers a large number of pores, improving fiber bulk and fixing fiber morphology. After this treatment, the fiber morphology shows significant curling, twisting, and indentation, thus affecting its liquid conductivity. The fluff pulp modification method of this invention uses commercial softwood pulp boards as raw materials. Through a simple and easy modification method, it effectively overcomes the shortcomings of domestically produced fluff pulp, such as slow absorption rate, long liquid absorption time, and low bulk, thus improving production efficiency.

Description

Technical Field

[0001] This invention relates to the fields of pulp and paper making and fine chemicals, and more specifically to a method for modifying fluff pulp. Background Technology

[0002] Flock pulp is a good liquid-absorbing wood pulp. When coated with superabsorbent polymer (SAP), it forms the absorbent padding layer of absorbent hygiene products, exhibiting superior liquid absorption capabilities while maintaining its structure after absorbing liquid. High absorption capacity, fast absorption speed, and high bulkiness are the main performance requirements for fluff pulp. Currently, commercial fluff pulp is available in pulp boards (flat or rolled). Downstream hygiene product manufacturers need to further process these boards through crushing and napping before use. Therefore, the fluff pulp boards must possess excellent napping properties to facilitate the molding of hygiene products in downstream processes. We rely on imports for over 90% of our fluff pulp. Domestically produced fluff pulp is mainly used in low- to mid-range consumer goods, primarily due to the scarcity of wood raw materials. Domestically produced fluff pulp has poor dry bulkiness and absorption performance, produces a lot of dust, and has poor padding stability. In view of the above, other additives are needed to impart the required properties. A common method is to add debonding agents to achieve the napping requirements of the fluff pulp board. However, the addition of debonding agents significantly reduces the absorption performance and bulkiness of bamboo fluff pulp. Ensuring the napping requirements while improving the water absorption and dry bulk of the fluff pulp will be a major challenge that the fluff pulp industry needs to overcome in the future. Summary of the Invention

[0003] In view of this, the present invention provides a technical means for modifying fluff pulp, which can effectively improve its liquid conductivity by changing the internal structure of the fiber, thereby promoting the development of domestic fluff pulp production enterprises.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A method for modifying fluff pulp includes the following processes:

[0006] Step 1: Dissolve the softwood pulp board into a suspension at room temperature;

[0007] Step 2: Use an ultrasonic pulverizer to ultrasonically treat the suspension described in Step 1;

[0008] Step 3: The suspension from Step 1 is extracted into a filter cake by vacuum filtration;

[0009] Step 4: Prepare the crosslinking agent solution;

[0010] Step 5: Add the cross-linking agent solution to the filter cake from Step 3, so that the filter cake is completely impregnated by the cross-linking agent;

[0011] Step 6: The cross-linking reaction in Step 5 proceeds at different temperatures for a period of time;

[0012] Step 7: Take out the sample, wash and dry it, and then break it into fluff pulp using a nail-type disperser.

[0013] In step 1, the types of coniferous wood pulp boards are black needlewood, larch, and Masson pine, but they can also be applied to broadleaf wood pulp boards, bamboo pulp, straw pulp, etc.

[0014] The ultrasonic treatment in step 2 was tested using a (JY92-II) ultrasonic pulverizer. The effect of ultrasonic treatment on wood fibers is similar to that of mechanical pulping. It can cause displacement and deformation of the fiber cell walls. While retaining the P layer and S1 layer, the fibers undergo strong internal fine fiberization. The higher the degree of fine fiberization, the stronger the water absorption capacity of the fibers.

[0015] The specific parameters for ultrasonic treatment in step 2 are set as follows: power is set to 200W, 400W, and 600W respectively; ultrasonic time is 2s; interval time is 2s; number of operations is 50; and cycle is 6.

[0016] The method for preparing the crosslinking agent solution in step 4 is as follows: add a mixed solution of 1,2,3,4-butanetetracarboxylic acid (BTCA) and sodium dihydrogen phosphate (NaH2PO4), stir until homogeneous, and then let stand for later use.

[0017] In step 4, the mass ratio of BTCA to NaH2PO4 is 1:1;

[0018] In step 4, the effective component of the crosslinking agent is BTCA, and its mass fraction in the mixture is 1%, 2%, and 5%.

[0019] In step 6, the reaction temperature is set to 80℃, 100℃, 120℃, 140℃, and 160℃ respectively.

[0020] The cross-linking reaction described in step 4 begins with the reaction of the catalyst NaH2PO4 with BTCA to form an anhydride, which further forms a phosphate-BTCA compound. Due to the low electron cloud density of the carbonyl group, this compound exhibits higher reactivity and can better react with cellulose to form ester bonds. The hydroxyl groups on the cellulose molecules provide reaction cross-linking sites, and a large number of BTCA molecules are sufficient to form a 3D network of cellulose, resulting in an intrafiber cross-linked structure.

[0021] As can be seen from the above technical solution, compared with the prior art, the present invention discloses a novel method for modifying fluff pulp, which has the following beneficial effects:

[0022] This invention uses different types of commercial softwood pulp sheets as raw materials and employs a simple method combining ultrasonic treatment and cross-linking. The process is short and easy to operate, which can significantly improve the twisting and crimping of fluff pulp fibers, thereby controlling their liquid conductivity. Attached Figure Description

[0023] Figure 1 Microscopic images of black needle villi pulp after different processing methods.

[0024] Figure 2 The infrared spectra of black needle wool pulp after different processing methods are shown. Detailed Implementation

[0025] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] Example 1

[0027] (1) Pulp preparation: Select 5g of different types of softwood pulp boards, dissolve them evenly at room temperature, measure their moisture content with a rapid moisture meter, and then transfer them to a 500ml beaker for later use.

[0028] (2) Washing and drying: The slurry sample is filtered into a filter cake using a vacuum filtration device for later use;

[0029] (3) Preparation of crosslinking agent: Add 3.86g sodium dihydrogen phosphate (NaH2PO4) and the same mass of 1,2,3,4-butanetetracarboxylic acid (BTCA) to prepare 100ml aqueous solution;

[0030] (4) Apply the crosslinking agent solution drop by drop onto the filter cake through a dropper to ensure that the entire filter cake is completely soaked;

[0031] (5) Place the filter cake in an 80℃ oven and react for 1 hour;

[0032] (6) Wash away unreacted substances with deionized water, then dry and use a nail-type disperser to dry dissociate the fluff pulp.

[0033] Example 2

[0034] (1) Pulp preparation: Select 5g of different types of softwood pulp boards, dissolve them evenly at room temperature, measure their moisture content with a rapid moisture meter, and then transfer them to a 500ml beaker for later use.

[0035] (2) Ultrasonic treatment: Parameter settings: ultrasonic power 400W, ultrasonic time 2s, interval time 2s, number of cycles 50, cycle 6. Amplitude bar (ultrasonic probe) immersion depth: 1-2cm, liquid level adjusted to above 30mm, probe should be centered and not touching the wall;

[0036] (3) Washing and drying: dry separation of fluff pulp using a nail-type disperser.

[0037] Example 3

[0038] (1) Pulp preparation: Select 5g of different types of softwood pulp boards, dissolve them evenly at room temperature, measure their moisture content with a rapid moisture meter, and then transfer them to a 500ml beaker for later use.

[0039] (2) Ultrasonic treatment: Parameter settings: ultrasonic power 600W, ultrasonic time 2s, interval time 2s, number of cycles 50, cycle 6. Amplitude bar (ultrasonic probe) immersion depth: 1-2cm, liquid level adjusted to above 30mm, probe should be centered and not touching the wall;

[0040] (3) Washing and drying: The slurry sample is filtered into a filter cake using a vacuum filtration device for later use;

[0041] (4) Preparation of crosslinking agent: Add 3.86g sodium dihydrogen phosphate (NaH2PO4) and the same mass of 1,2,3,4-butanetetracarboxylic acid (BTCA) to prepare 100ml aqueous solution;

[0042] (5) Apply the crosslinking agent solution drop by drop onto the filter cake through a dropper to ensure that the entire filter cake is completely soaked;

[0043] (6) Place the filter cake in a 120℃ oven and react for 1 hour;

[0044] (7) Wash away unreacted substances with deionized water, then dry and use a nail-type disperser to dry dissociate the fluff pulp.

[0045] Experimental characterization:

[0046] (1) The surface morphology of the fluff pulp treated with different methods was characterized by scanning electron microscopy (Hitachi S-3400NII) (the top figure shows 20 μm, and the bottom figure shows 200 μm), such as Figure 1 As shown, at a scale of 200 μm, the fiber morphology is relatively fine after the cross-linking reaction, and the twisted structure has not changed significantly; while at 20 μm, the fiber surface becomes rough and has a concave state after the cross-linking reaction; it is worth noting that under the synergistic effect of the cross-linking reaction and ultrasound, the fiber surface undergoes a large twisting and curling phenomenon.

[0047] (2) The changes in functional groups of the modified fiber were characterized by Fourier transform infrared spectroscopy (FT-IR), 3331cm -1 The peak at 1720 cm⁻¹ represents the stretching vibration of the -OH group in cellulose molecules. After the cross-linking reaction, the intensity of this peak significantly decreased, indicating that the use of the cross-linking agent weakens the intermolecular hydrogen bonding, overcomes the rigidity of cellulose molecules, thereby increasing the porosity between fibers and promoting liquid conductivity. Simultaneously, after a simple ultrasonic treatment combined with the cross-linking agent, the fibers produced new characteristic peaks, including one at 1720 cm⁻¹. -1 The absorption peak at this point is the C=O stretching vibration of the ester bond, which also proves that the carboxyl group in the crosslinking agent molecule forms an ester bond with the hydroxyl group on cellulose.

[0048] Furthermore, it should be noted that the technical solution of this invention has a short process, and the control of fluff pulp fiber morphology can be completed through "ultrasound + cross-linking". Currently, fluff pulp sold on the market generally has poor water conductivity. Due to insufficient control of fluff pulp fiber morphology and a lack of systematic research on fluff pulp modification processes, the quality of domestic fluff pulp is far inferior to that of imported fluff pulp. This invention controls the twisting and curling of fluff pulp fibers through a simple and easy method, thereby improving its water conductivity. This process can provide new technical guidance for the fluff pulp industry and downstream hygiene product industry.

[0049] The various embodiments in this specification are described in parallel, with each embodiment focusing on the differences from the other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0050] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for modifying fluff pulp, characterized in that, Includes the following steps: The softwood pulp board was uniformly dispersed into a suspension at room temperature; the suspension was then ultrasonically treated using an ultrasonic pulverizer. The suspension was filtered to obtain a filter cake. Crosslinking agent solutions of different concentrations were prepared and added dropwise to the filter cake to carry out crosslinking reactions at different temperatures. The crosslinking reaction first involves the catalyst sodium dihydrogen phosphate (NaH2PO4) reacting with 1,2,3,4-butanetetracarboxylic acid (BTCA) to form an anhydride, which further forms a phosphate-BTCA compound. Due to the low electron cloud density of the carbonyl group, this compound has higher reactivity and can better react with cellulose to form ester bonds. The hydroxyl groups on the cellulose molecules provide reaction crosslinking sites. A large number of BTCA molecules are sufficient to form a 3D network of cellulose, producing an intrafiber crosslinked structure, which can significantly improve the tumbling, twisting, and crimping of fluff pulp fibers, thereby controlling their liquid conductivity. The sample was taken out, washed and dried, and then broken into fluff pulp by a nail-type disperser.

2. The method for modifying fluff pulp according to claim 1, characterized in that, The raw material for the coniferous wood pulp board is black needle pine, larch, and Masson pine.

3. The method for modifying fluff pulp according to claim 1, characterized in that, Ultrasonic treatment was tested using a JY92-II ultrasonic pulverizer. The effect of ultrasonic treatment on wood fibers is similar to that of mechanical pulping, which can cause the fiber cell walls to turn over, twist, and curl, thereby increasing the porosity between fibers. In addition, the fiber undergoes strong internal fibrillation while retaining the P layer and S1 layer. The higher the degree of fibrillation, the stronger the fiber's water absorption capacity.

4. The method for modifying fluff pulp according to claim 3, characterized in that, The specific parameters for ultrasonic treatment are set as follows: power is set to 200W, 400W or 600W, ultrasonic time is 2s, interval time is 2s, number of operations is 50, and cycle is 6.

5. The method for modifying fluff pulp according to claim 1, characterized in that, Crosslinking agent solution preparation method: Add BTCA and NaH2PO4 mixed solution, stir evenly and let stand for later use.

6. The method for modifying fluff pulp according to claim 5, characterized in that, The effective component of the crosslinking agent is BTCA, which has a mass fraction of 1%, 2%, or 5% in the mixture; the mass ratio of BTCA to NaH2PO4 is 1:

1.

7. The method for modifying fluff pulp according to claim 1, characterized in that, The reaction temperature for the crosslinking reaction can be set to 80℃, 100℃, 120℃, 140℃ or 160℃.

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