Preparation method of anti-rebound paper-based thread and anti-rebound paper-based thread

Abstract

The invention discloses a preparation method of an anti-rebound paper-based thread and a product, and belongs to the technical field of plant fiber reinforced processing. According to the method, a high-density fiber skeleton is constructed through hydraulic forced densification, so that the density of a thread area reaches 1.1-1.3 g / cm; then dip-coating a modified silicate system containing 4% of nano silica sol and 5% of glycerol, and locking fiber deformation through a cross-linking reaction; and finally, precisely slitting in a semi-solidified state. The thread form retention rate of the prepared paper-based thread is larger than or equal to 95%, the surface hardness is improved by 3-4 times, opening and closing can be supported for 300 times or above, and the problems of springback, layering and abrasion of a traditional paper thread are solved. When being matched with paste packaging, the regenerated plant cellulose barrier layer is arranged on the inner wall of the tube body, and the section is coated with the water-based acrylic acid layer, so that the tube is environment-friendly, low in cost and suitable for precise packaging scenes.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of plant fiber reinforced processing, in particular to a preparation method of a paper-based thread with anti-rebound and a paper-based thread with anti-rebound prepared by the method. BACKGROUND

[0002] With the popularization of environmental protection concept, paper packaging is widely used due to its advantages of biodegradability and renewability, especially in the field of precision packaging, the demand for paper thread structure is increasing. However, the existing paper spiral structure preparation technology has many problems to be solved: Paper has strong shape memory and elastic modulus, and the traditional indentation thread will rebound rapidly after demolding, resulting in fuzzy tooth shape and insufficient tightening torque; the paper tube is usually wound by multiple layers of paper tape, and when subjected to rotational shear force, the interlayer bonding force is insufficient and easy to cause thread peeling and delamination; the hardness of pure paper fiber is low, and a large amount of paper powder will be generated after multiple rotations, resulting in a large fitting gap and finally causing the tooth slipping phenomenon. These problems seriously limit the application of paper thread in high-frequency rotation and opening and closing precision packaging scenarios. SUMMARY

[0003] The present application aims to overcome the technical defects of existing paper spiral structure, such as severe rebound, low tooth shape precision, easy delamination and powder dropping, and insufficient mechanical strength, caused by loose fibers and elastic memory, and provides a preparation method combining physical densification and chemical in-situ locking, as well as a high-strength paper-based thread with high dimensional stability, plastic-like physical properties and green environmental protection, which meets the needs of high-frequency rotation and opening and closing precision packaging.

[0004] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows: A preparation method of a paper-based thread with anti-rebound, comprising the following steps: a. Hydraulic forced densification: the paper tube formed by conventional winding is placed in a high-precision spiral hydraulic mold, and treated by 15-30 MPa of radial and axial coordinated high pressure for 10-30 minutes. This step can force the micro air between the paper fibers to be discharged, so that the fibers produce plastic deformation and embed each other, and finally the physical density of the thread area of the paper tube is increased from 0.6-0.8 g / cm³ to 1.1-1.3 g / cm³, forming a high-density fiber skeleton with a preliminary geometric shape.

[0005] b. Impregnation and hardening: A modified silicate system is prepared, using industrial sodium silicate as the main agent, and adding 3.5%~4.5% by mass of nano-silica sol and 4.5%~5.5% by mass of glycerol. The preferred ratio is 4% by mass of nano-silica sol and 5% by mass of glycerol. This ratio range is within the allowable error range of conventional industrial production processes. Within this range, the modified silicate system can achieve effective penetration of nanoparticles and cross-linking and locking of fibers, while ensuring a balance between thread hardness and toughness, thus achieving the anti-rebound and anti-delamination technical objectives of this invention. The densified paper tube is impregnated at 25-40℃ for 5-15 minutes, followed by curing at 60-80℃ for 20-40 minutes. Nanoscale silica particles can quickly penetrate into the micropores of the fiber after hydraulic pressure. The silicate forms hydrogen bonds with the hydroxyl groups in the paper fiber and undergoes in-situ polymerization, forming a hard inorganic network between the fibers. This network acts like a chemical scaffold to lock the fiber, preventing it from returning to its original shape and completely solving the springback problem. At the same time, glycerin acts as a toughening agent to prevent the threads from cracking during screwing.

[0006] c. Precision Slitting: Once the modified silicate system has reached a semi-cured state after the hardening reaction, the paper tube is precision slitting, with the slitting accuracy controlled within ±0.05mm. At this point, the paper tube has plastic-like machinability, with clean cuts without burrs, ensuring the length accuracy of the threaded section and the perpendicularity of the end face, facilitating a precise fit with the cap.

[0007] The present invention also provides a springback paper-based thread prepared by the above method, with a thread profile retention rate of ≥95%, a surface hardness of 3-4 times that of pure paper fiber, a shear strength that can support more than 300 opening and closing operations, a thread area density that is stable at 1.1-1.3 g / cm³, and a silicate cross-linked network containing nano-silica sol and glycerol formed between the paper fibers.

[0008] To adapt to special packaging scenarios such as ointments, a regenerated plant cellulose barrier layer can be set on the inner wall of the paper-based threaded tube. The barrier layer is laminated with the tube body through a water-based adhesive to prevent ointment penetration. A water-based acrylic layer is set on the cut surface of the paper-based thread to prevent grease from seeping into the cut surface and causing damage to the paper tube.

[0009] Compared with the prior art, the present invention has the following beneficial effects: 1. Zero springback: High-density fiber skeleton is constructed through hydraulic forced densification, combined with the cross-linking and locking effect of modified silicate system, so that the thread profile retention rate is increased to more than 95%, and there is no springback after 30 days, and the tightening torque is stable. 2. High hardness and wear resistance: The surface hardness of the thread is increased by 3-4 times, with excellent shear strength. It can withstand more than 300 opening and closing tests. It is not easy to generate paper dust during use, and the mating gap is stable, avoiding stripping. 3. Anti-delamination: Chemical cross-linking enhances the bonding force between paper fibers and between layers, effectively solving the problem of thread peeling and delamination caused by rotational shear force; 4. Environmentally friendly and low-cost: Modified silicate systems are less expensive than high-performance synthetic resins, and the materials are green and environmentally friendly, meeting the requirements of sustainable development; 5. High precision: Precision cutting in the semi-solid state ensures the accuracy of the thread length and the perpendicularity of the end face, meeting the requirements for precision fit. Attached Figure Description

[0010] Fig. 1 This is a flowchart of the preparation method of the present invention; Fig. 2 A schematic diagram of the structure of the anti-springback paper-based thread; Fig. 3 for Fig. 2 AA sectional view. Detailed Implementation

[0011] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. The embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0012] Example 1: Preparation of a general-purpose anti-rebound paper-based thread like Figs. 1 to 3 As shown, taking the preparation of a general-purpose anti-springback paper-based thread as an example, the preparation steps are as follows: 1. Raw material preparation: 80 g / m² bleached sulfate wood pulp paper was selected as the base material and wound into paper tubes using a winding machine. The tension was controlled at 5-8 N during winding, with 6 layers. The final paper tube had an outer diameter of 18 mm, an inner diameter of 14 mm, and a length of 100 mm. The initial density was measured to be 0.7 g / cm³. 3 The spiral hydraulic mold is made of Cr12MoV material, with a triangular thread profile, a thread angle of 60 degrees, a pitch of 2mm, and a mold dimensional accuracy of IT7 grade. The modified silicate system raw materials include industrial sodium silicate with a modulus of 3.2 and a solid content of 30%, nano-silica sol with a particle size of 20-50nm and a solid content of 25%, and glycerol with a purity of 99.5%.

[0013] 2. Hydraulic Forced Densification: The wound paper tube is uniformly placed into the cavity of a high-precision spiral hydraulic mold. A Y32-100 four-column hydraulic press is started, and the radial pressure is gradually increased from 0 MPa to 20 MPa, while the axial pressure is simultaneously increased to 15 MPa at a rate of 2 MPa / min. After the pressure stabilizes, it is maintained for 20 minutes, during which the mold cavity temperature is monitored using the mold's built-in temperature sensor to ensure it remains between 25-30℃. After processing, the pressure is slowly released at a rate of 1 MPa / min, and the paper tube is removed. The density of the threaded area is tested using the water displacement method, and the result is 1.2 g / cm³. 3 The fibers are tightly embedded to form a regular high-density fiber skeleton, the threads are initially formed and there is no obvious springback, the density of the thread stress area is higher than that of the non-stress area of ​​the tube body, forming a gradient density structure.

[0014] 3. Impregnation and hardening: Prepare the modified silicate system according to the following proportions: Place 100 kg of industrial sodium silicate into a stainless steel mixing vessel, turn on the stirrer and set the speed to 300 rpm, slowly add 4 kg of nano-silica sol (the optimal value within the range of 3.5%~4.5% preferred in this invention), stir for 15 minutes until uniformly mixed, then add 5 kg of glycerol (the optimal value within the range of 4.5%~5.5% preferred in this invention), and continue stirring for 20 minutes to obtain a uniform and transparent modified silicate system. The viscosity of the system was measured to be 25 mPa at 25°C. s. Place the densified paper tube into an immersion coating equipment, set the coating temperature to 30℃, and the coating time to 10 minutes, ensuring that the paper tube is completely submerged in the system. During this period, lift the paper tube up and down once every 2 minutes to promote full penetration of the system. After coating, remove the paper tube and drain off the excess system on the surface for 2 minutes. Then place it in a 101-3 electric thermostatic forced-air oven, set the temperature to 70℃, and cure for 30 minutes. During the curing process, maintain the oven air velocity at 1.5m / s to ensure uniform curing.

[0015] 4. Precision Slitting: After the oven cools naturally to below 40℃, remove the paper tube. At this point, the modified silicate system is in a semi-solid state, and the hardness is measured to be D40-45 using a Shore hardness tester. Fix the paper tube on the chuck of a CJK6136 CNC lathe, select a YT15 type carbide cutting tool, set the spindle speed to 800 r / min and the feed rate to 0.1 mm / r, and perform precision slitting on the paper tube to a length of 50 mm. The precision is controlled by the lathe's built-in grating ruler, and the final slitting accuracy reaches ±0.03 mm. After slitting, observe the cut surface for no burrs or fiber shedding, and the end face perpendicularity error does not exceed 0.02 mm.

[0016] 5. Performance Testing: The thread profile was observed using a 50x magnifying optical microscope, with a thread profile integrity of 98% and a thread profile retention rate of 96%. The surface hardness of the thread was tested using a Type D Shore hardness tester, yielding a result of 65D, which is 3.6 times the hardness of pure paper fiber (18D). Shear strength was tested using a WDW-10 universal testing machine at a testing speed of 5 mm / min, yielding a shear strength of 8.5 MPa. A dedicated testing fixture was used to simulate actual use scenarios, performing opening and closing operations at a frequency of 10 times per minute. After 300 cycles, the thread fit clearance was tested, and the change compared to the initial state did not exceed 0.01 mm. There was no delamination or powdering, and the tightening torque remained stable between 0.8 and 1.0 N·m. The product was placed in an environment with a temperature of 25℃ and humidity of 60%. After 30 days, the thread showed no springback, and the dimensional change rate did not exceed 0.1%.

[0017] Example 2: Preparation of anti-rebound paper-based threads for paste packaging 1. Basic Preparation: Bleached sulfate wood pulp paper with a basis weight of 90 g / m² was selected as the substrate and wound into a paper tube. The winding tension was controlled at 6-9 N, with 8 layers. The paper tube had an outer diameter of 22 mm, an inner diameter of 18 mm, a length of 80 mm, and an initial density of 0.65 g / cm³. 3 The parameters of the spiral hydraulic mold are consistent with those in Example 1. The Y32-100 four-column hydraulic press was started, with the radial pressure set to 25 MPa, the axial pressure to 18 MPa, and the pressure increase rate to 2.5 MPa. After the pressure stabilized, it was maintained for 15 minutes. During the densification process, the mold cavity temperature was controlled between 28-32℃. After depressurization, the paper tube was removed, and the density of the threaded area was measured to be 1.25 g / cm³. 3 The same modified silicate system as in Example 1 was prepared, and the dipping temperature was set to 35°C for 8 minutes, with the paper tube lifted once every 1.5 minutes during the dipping process. After draining for 2 minutes, the paper tube was placed in an electrically heated constant-temperature forced-air drying oven at 75°C for 25 minutes of curing. Once the oven cooled to below 40°C, the paper tube was removed, and its Shore hardness was measured to be D42-46. It was then slit using a CJK6136 CNC lathe with a slit length of 45mm and a slit accuracy of ±0.04mm; the cut quality met the requirements.

[0018] 2. Regenerated Plant Cellulose Barrier Layer Composite: A 0.08mm thick RC-01 type regenerated plant cellulose film is selected as the barrier layer, and a polyvinyl alcohol-based adhesive with a solid content of 15% and a viscosity of 30 mPa·s is used as the water-based adhesive. The slit paper tubes are fixed on the support shaft of the laminating equipment, and the water-based adhesive is evenly coated onto the inner wall of the paper tubes using a coating roller, with a coating amount of 8g / cm². 3The regenerated plant cellulose film was then bonded to the inner wall of the paper tube using a pressure roller. The bonding pressure was set at 0.3 MPa, the bonding temperature at 50°C, and the bonding speed at 0.5 m / min. After bonding, the paper tube was placed in a constant temperature and humidity chamber at 60°C and 40% for 2 hours to allow the adhesive to fully cure. Finally, the peel strength between the barrier layer and the inner wall of the paper tube was tested to be no less than 1.2 N / 15 mm.

[0019] 3. Water-based acrylic coating on the cut surface: A water-based acrylic emulsion with a solid content of 30% and a hardness of 3H is selected and coated on the cut surface of the paper base thread using a roller coating method. The coating equipment parameters are adjusted to control the coating thickness at 15-20μm. After coating, the paper tube is placed in an oven at 65℃ and dried for 15 minutes. After drying, the cut surface is smooth, without drips or bubbles.

[0020] 4. Compatibility and Performance Testing: The prepared product was used for lipstick packaging. The lipstick formula consisted of 30% beeswax, 25% petrolatum, 15% lanolin, 20% liquid paraffin, and 10% pigment. The lipstick was poured into a paper-based threaded inner tube, and the sliding assembly and cap were assembled. The tube was then placed in an accelerated aging chamber at 40℃ and 75% humidity for 7 days before testing. The lipstick showed no leakage or deterioration; the inner wall of the paper tube was free of moisture and deformation; there were no traces of grease seepage on the cut surface, and the paper tube was undamaged; the sliding assembly opened and closed smoothly without jamming, and the sliding assembly and lipstick were firmly bonded without separation. Performance testing revealed a 97% thread profile retention rate, a surface hardness of 68D, and a shear strength of 9.2 MPa. After 200 opening and closing cycles, all performance characteristics showed no significant degradation, meeting the requirements for lipstick packaging.

[0021] Example 3: Preparation of anti-rebound paper-based threads under different process parameters 1. Adjustment of hydraulic forced densification parameters: Using paper tubes and molds of the same specifications as in Example 1, start the Y32-100 four-column hydraulic press, set the radial pressure to 15MPa and the axial pressure to 12MPa, with a pressurization rate of 1.5MPa / min. After the pressure stabilizes, maintain it for 30 minutes, and control the mold cavity temperature at 25-30℃. After depressurization, the density of the threaded area is measured to be 1.1g / cm³. 3 The fibers form a high-density skeleton with no obvious resilience.

[0022] 2. Adjustment of dip coating penetration curing parameters: Prepare the same modified silicate system as in Example 1, set the dip coating temperature to 25°C, the dip coating time to 15 minutes, drain for 3 minutes after dip coating, place in an electric heating constant temperature forced air drying oven, set the temperature to 60°C, and cure for 40 minutes.

[0023] 3. Precision Slitting and Performance Testing: After the oven cools to below 40℃, the paper tubes are removed and tested for Shore hardness (D38-42). CNC lathes are used for slitting, with a slitting accuracy of ±0.05mm. Performance testing results show a 95% thread profile retention rate, a surface hardness of 62D, and a shear strength of 8.0MPa. After 300 opening and closing tests, there was no delamination or powder shedding. The thread clearance variation did not exceed 0.015mm, and there was no springback after 30 days, meeting the requirements for general-purpose precision packaging.

[0024] Comparative experiment 1. Experimental setup: Paper tubes of the same specifications as in Example 1 were selected, and only hydraulic forced densification treatment was performed. The process parameters were the same as in Example 1: radial pressure 20MPa, axial pressure 15MPa, treatment time 20 minutes, without dip coating penetration hardening and precision slitting processes. The operating environment temperature was 25℃ and humidity was 60%, consistent with the experimental group.

[0025] 2. Performance Testing: 12 hours after demolding, the density of the threaded area in the control group was measured to be 1.18 g / cm³. 3 The thread profile retention rate was 70%; after 24 hours, the thread rebounded by 30%, the thread profile became blurred, the thread felt loose, and the tightening torque dropped to below 0.3 N·m; after 48 hours, the thread rebound rate reached 35%, and some areas showed fiber lifting; after 50 opening and closing operations, the thread showed obvious delamination, produced a large amount of paper dust, and the mating clearance increased to more than 0.1 mm, making it unusable.

[0026] 3. Results Analysis: Comparative experiments show that hydraulic forced densification alone cannot achieve long-term locking of thread deformation, resulting in products with severe springback, delamination, and poor wear resistance. This invention, however, utilizes a combination of hydraulic forced densification, dip-coating penetration hardening, and precision slitting, employing a modified silicate system with a specific ratio to achieve permanent locking of fiber deformation. Furthermore, through gradient density structures, barrier layer composites, and sectional coating designs, it effectively addresses the technical pain points of traditional paper threads, significantly improving the overall performance of paper-based threads.

[0027] The mixing ratio range of 3.5%~4.5% nano-silica sol and 4.5%~5.5% glycerol defined in this invention is an equivalent range of industrial process error determined based on the optimal value of 4% / 5%. All mixing ratio schemes within this range can achieve technical effects that are basically consistent with the optimal value. However, simply using hydraulic forced densification to impregnate a modified silicate system without any mixing ratio cannot solve the core technical pain points of traditional paper thread coating.

[0028] Those skilled in the art can adjust the process conditions within the parameter range defined in the claims based on the above embodiments to achieve the technical effects of the present invention. The equipment and raw material specifications selected in the embodiments are merely illustrative examples; using other equipment with equivalent functions and compliant raw materials will not affect the implementation of the present invention.

Claims

1. A method for preparing anti-rebound paper-based threads, characterized in that, Includes the following steps: a. Hydraulic forced densification: The wound paper tube is placed into a spiral hydraulic mold and densified by coordinating radial and axial high pressure, so that the density of the paper tube thread area reaches 1.1-1.3 g / cm³. b. Impregnation and hardening: The densified paper tube is impregnated with a modified silicate system, which includes industrial sodium silicate, nano silica sol and glycerol, wherein the mass fraction of nano silica sol is 3.5%~4.5% and the mass fraction of glycerol is 4.5%~5.5%. The system penetrates into the micropores of the paper fiber through nano-penetration, and at the same time, the silicate reacts with the hydroxyl groups in the paper fiber to form an inorganic network that locks the fiber compression deformation. c. Precision slitting: After the modified silicate system has hardened to the preset strength, the paper tube is precisely slitted to obtain anti-springback paper-based threads.

2. The preparation method according to claim 1, characterized in that, In step a, the pressure range of the synergistic high pressure is 15-30 MPa, and the densification treatment time is 10-30 minutes.

3. The preparation method according to claim 1, characterized in that, In step b, the dip coating temperature is 25-40℃, the dip coating time is 5-15 minutes, and after dip coating, it is cured at 60-80℃ for 20-40 minutes.

4. The preparation method according to claim 1, characterized in that, In step c, the preset strength is semi-cured, and the cutting accuracy is controlled within ±0.05mm.

5. The preparation method according to claim 1, characterized in that, In the modified silicate system, the mass fraction of nano-silica sol is 4%, and the mass fraction of glycerol is 5%.

6. A type of anti-rebound paper-based thread, characterized in that, The paper-based thread is prepared by any of the preparation methods described in claims 1-5. The thread profile retention rate is ≥95%, the surface hardness is 3-4 times that of pure paper fiber, the shear strength can support more than 300 opening and closing operations, the thread area density is 1.1-1.3 g / cm³, and a silicate cross-linked network containing nano-silica sol and glycerol is formed between the paper fibers.

7. The anti-rebound paper-based thread according to claim 6, characterized in that, The inner wall of the paper-based threaded tube is provided with a regenerated plant cellulose barrier layer, which is laminated with the tube body by an aqueous adhesive.

8. The anti-rebound paper-based thread according to claim 6, characterized in that, The cut surface of the paper-based thread has a water-based acrylic layer.

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