A new type of hybrid net bag suitable for litchi and longan

Abstract

The application relates to the technical field of agricultural packaging, and discloses a novel hybrid net bag suitable for lychee and longan, which comprises a light-transmitting polyethylene waterproof film and a lower modified polyamide net screen with covalently bonded crosslinked networks. The lateral edges of the light-transmitting polyethylene waterproof film are continuously hot-melt spliced with the lateral edges of the lower modified polyamide net screen with covalently bonded crosslinked networks, the film is cut according to a width of 40 cm and is folded along the longitudinal direction, and the side edges and the bottom edges are high-frequency heat-sealed and edge-pressed to be sealed. The light-transmitting polyethylene waterproof film blocks top rainwater, the lower modified polyamide net screen with covalently bonded crosslinked networks with a pore size of 6-9 microns blocks external pollen penetration and discharges water vapor in the bag, the hydrophobic and antibacterial structure on the fiber surface eliminates the water film air resistance effect caused by water adhesion, maintains the unobstructed wet and exhaust discharge channels, and destroys the high-humidity environment causing the flower soaking phenomenon.

Description

Technical Field

[0001] This invention relates to the field of agricultural packaging technology, specifically a novel hybrid mesh bag suitable for lychee and longan. Background Technology

[0002] In the cultivation of litchi and longan, flower spike bags are used to isolate them from external environmental factors. These bags prevent rainwater runoff and protect against pests and diseases. During the flowering period, the bags also intercept micron-sized pollen and alter the temperature and humidity of the microenvironment surrounding the flower spikes.

[0003] Existing technologies for preparing flower spike bags utilize single paper materials or plastic films pieced together. Some flower spike bags employ polyamide mesh as the wrapping material, with polyhexamethylene guanidine hydrochloride and siloxanes added to the aqueous solution used for preparing the treatment. The polyamide mesh is impregnated with the treatment solution and then dried and cured in an oven, resulting in the adhesion of antibacterial and hydrophobic components to the surface of the polyamide mesh fibers.

[0004] Flower spike bags made from a single material cannot simultaneously meet the requirements of blocking rainwater at the top and allowing ventilation and moisture removal at the bottom. Polyamide mesh with large physical pores cannot block the penetration of micron-sized pollen, while polyamide mesh with small physical pores easily accumulates moisture during the rainy season, forming a water film that blocks airflow. This water film obstructs the ventilation channels, leading to a high-humidity environment inside the bag and causing flower rot. During the preparation of the treatment solution, polyhexamethylene guanidine hydrochloride molecules undergo molecular aggregation and demulsification in the single-phase aqueous solution. During the drying and curing stage of the polyamide mesh, the treatment solution forms a physical liquid film at the mesh openings, and the dried and cured treatment solution clogs the physical pores of the polyamide mesh.

[0005] Therefore, this invention proposes a novel hybridization net bag suitable for litchi and longan to overcome the shortcomings of the prior art. Summary of the Invention

[0006] The technical problem solved by this invention is that bagging of lychee and longan cannot simultaneously achieve waterproofing at the top and breathability and moisture removal at the bottom, and the microenvironment inside the bag breeds pathogens, causing the fruit to rot.

[0007] To address the problems encountered, the present invention provides the following technical solution: This invention provides a novel hybridization net bag suitable for litchi and longan, comprising: A translucent polyethylene waterproof film and a lower modified polyamide mesh with a cross-linked network covalently bonded to its surface; The transverse edges of the translucent polyethylene waterproof film and the lower modified polyamide mesh, which has a cross-linked network covalently bonded to the surface, are continuously heat-fused together using an ultrasonic welding machine. The translucent polyethylene waterproof film and the lower modified polyamide mesh, which has a cross-linked network covalently bonded to the surface, are cut to a width of 40cm and folded in half longitudinally. The translucent polyethylene waterproof film and the lower modified polyamide mesh, which has a cross-linked network covalently bonded to the surface, are then sealed with high-frequency heat sealing at the overlapping sides and bottom. The lower modified polyamide mesh, with a cross-linked network covalently bonded to its surface, is prepared by treating the polyamide mesh with a composite cross-linking working solution; the preparation steps of the lower modified polyamide mesh with a cross-linked network covalently bonded to its surface include: Add 60.0% to 70.0% of the total mass of the composite crosslinking working solution to the reactor at room temperature. Then, add 0.5% to 1.0% of the total mass of the composite crosslinking working solution and 0.2% to 0.5% of the total mass of the composite crosslinking working solution to the reactor in sequence. Stir at 150 rpm to 200 rpm for 15 to 20 minutes. Slowly add 0.5% to 1.0% of the total mass of the composite crosslinking working solution of polyhexamethylene guanidine hydrochloride aqueous solution to the reactor. After standing for 3 to 8 minutes, uniformly sprinkle 1.5% to 2.5% of the total mass of the composite crosslinking working solution of sodium lignosulfonate into the reactor. Increase the stirring speed of the reactor to 400 rpm to 500 rpm for high shear dispersion for 20 to 30 minutes to obtain a submicron-sized pre-complexed microcolloid dispersion. Reduce the stirring speed of the reactor to 150 rpm to 200 rpm, and slowly add 4.0% to 6.0% of the total mass of the composite crosslinking working solution of hydroxyl-terminated polydimethylsiloxane emulsion and 1.5% to 2.5% of the total mass of the composite crosslinking working solution to the submicron-scale pre-complexed microcolloid dispersion. After stirring for 15 min to 20 min, add deionized water to the reactor to make up the total mass of the composite crosslinking working solution to 100.0%. Maintain stirring at a stirring speed of 150 rpm to 200 rpm for 15 min to 25 min to obtain the composite crosslinking working solution. Polyamide mesh with a mesh size of 6 to 9 micrometers is continuously drawn through a composite crosslinking working liquid at a linear speed of 20 m / min to 30 m / min. The polyamide mesh impregnated with the composite crosslinking working liquid is squeezed using a twin-roll milling machine to control the water roll-out rate of the polyamide mesh to 65% to 70%. The physical liquid film bridges of the polyamide mesh are broken by blowing the mesh with a high-pressure air knife system. The polyamide mesh is then pre-dried in an oven at 80°C to 90°C for 1.5 to 2.0 minutes. Subsequently, the polyamide mesh is baked and cured in a high-temperature oven at 150°C to 160°C for 1.5 to 2.0 minutes. After cooling and winding, a lower modified polyamide mesh with a crosslinked network covalently bonded to its surface is obtained.

[0008] A translucent polyethylene waterproof membrane provides light transmittance and blocks rainwater from washing away from the top. A lower modified polyamide mesh with a cross-linked network covalently bonded to its surface provides airflow channels at the bottom and allows internal moisture to escape.

[0009] In the preparation of the composite crosslinking working solution, polyhexamethylene guanidine hydrochloride, carrying a cationic charge, exhibits molecular aggregation in a single-phase aqueous solution. Citric acid provides acidic conditions, fatty alcohol polyoxyethylene ether provides nonionic surfactant dispersion, and sodium lignosulfonate provides anionic groups. Polyhexamethylene guanidine hydrochloride and sodium lignosulfonate undergo an electrostatic attraction reaction, forming a submicron-scale pre-complexed microcolloid dispersion under high-shear dispersion conditions. The steric hindrance effect of the submicron-scale pre-complexed microcolloid dispersion blocks direct contact between cationic molecules, maintaining the stability of the dispersion.

[0010] Hydroxyl-terminated polydimethylsiloxane emulsions provide a low surface energy structure. γ-glycidoxypropyltrimethoxysilane acts as a crosslinking agent; the methoxy group of γ-glycidoxypropyltrimethoxysilane hydrolyzes in acidic deionized water to generate a silanol group, which then undergoes a polycondensation reaction with the terminal hydroxyl groups of the hydroxyl-terminated polydimethylsiloxane. The epoxy groups of γ-glycidoxypropyltrimethoxysilane undergo ring-opening addition reactions with the guanidine groups of polyhexamethylene guanidine hydrochloride and the amide bonds on the surface of the polyamide mesh.

[0011] During the high-temperature baking and curing stage, moisture evaporation promotes ring-opening addition and condensation reactions. Polyhexamethylene guanidine hydrochloride and hydroxyl-terminated polydimethylsiloxane form a covalently cross-linked network on the surface of the polyamide mesh through a cross-linking reaction with γ-glycidoxypropyltrimethoxysilane. This covalently cross-linked network fixes polyhexamethylene guanidine hydrochloride to the fiber surface of the polyamide mesh, giving the fiber surface hydrophobic and water-wetting-resistant properties.

[0012] The high-pressure air knife system blows through the mesh of the polyamide mesh to break the liquid film bridge, preventing the composite crosslinking working fluid from clogging the mesh after drying, and maintaining the unobstructed structure of the moisture and air exhaust channels of the lower modified polyamide mesh with a covalently bonded crosslinked network on the surface.

[0013] This invention provides a novel hybridization net bag suitable for litchi and longan, which has the following beneficial effects: 1. This invention uses a translucent polyethylene waterproof film and a lower modified polyamide mesh with a cross-linked network covalently bonded to the surface, with a mesh size of 6 to 9 micrometers, to seal the opening. The translucent polyethylene waterproof film blocks rainwater from washing away the top, while the lower modified polyamide mesh with a cross-linked network covalently bonded to the surface has a smaller pore size than pollen grains, blocking pollen penetration. This maintains air circulation inside the flower spike bag and allows water vapor to escape, thus disrupting the high humidity environment that causes flower rot.

[0014] 2. This invention prepares a submicron-scale pre-complexed microcolloid dispersion by adding sodium lignosulfonate to an aqueous solution of polyhexamethylene guanidine hydrochloride for high-shear dispersion. The steric hindrance effect generated by the electrostatic attraction reaction between polyhexamethylene guanidine hydrochloride and sodium lignosulfonate blocks the contact of cationic molecules and prevents the molecular aggregation and demulsification of polyhexamethylene guanidine hydrochloride in the aqueous solution.

[0015] 3. This invention utilizes γ-glycidyl etheroxypropyltrimethoxysilane to form a covalent cross-linked network on the surface of polyamide mesh through condensation and ring-opening addition reactions. This covalent cross-linked network fixes hydroxyl-terminated polydimethylsiloxane and polyhexamethylene guanidine hydrochloride to the fiber surface, constructing a hydrophobic and antibacterial structure. Combined with a high-pressure air knife system to blow away the physical liquid film bridges in the mesh of the polyamide mesh, this invention eliminates the water film air resistance effect formed by moisture adhering to the mesh positions while maintaining the physical porosity of the polyamide mesh, thus keeping the dehumidification and exhaust channels unobstructed. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of a novel hybrid net bag suitable for lychee and longan provided by the present invention.

[0017] Figure 2 This is a particle size distribution curve of the composite crosslinking working fluid in the test example of the present invention.

[0018] Figure 3 The infrared spectrum of the lower modified polyamide mesh after rinsing is shown in the test example of this invention.

[0019] Figure 4 This is a graph showing the relationship between wet air permeability and pressure drop in the test examples of this invention.

[0020] Figure 5 This is a fungal growth curve diagram from a test example of the present invention.

[0021] Figure 6 This is a graph showing the change in fracture strength with UV aging time in the test examples of this invention. Detailed Implementation

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] See Figure 1 This invention provides a novel hybridization net bag suitable for litchi and longan. The recommended overall dimensions are 35cm in length and 40cm in width, meaning the width of the two flattened bottom panels is 40cm, and the diameter of the circle formed when the bag is unfolded is approximately 25cm, providing ample space and ease of operation for fruit growers. The upper part of the hybridization net bag is a translucent polyethylene waterproof film 1, and the lower part is a modified polyamide mesh 2. The connection between the translucent polyethylene waterproof film 1 and the modified polyamide mesh 2 is a transverse ultrasonic continuous heat-fused seam 3. To improve service life and ease of operation, the lower closure of the net bag abandons the traditional thin iron wire and uses a durable drawstring 6 for closure.

[0024] Example 1: This embodiment provides a method for preparing a novel hybrid net bag suitable for litchi and longan, including the following steps: Add 65.0% of the total mass of the composite crosslinking working solution to the reactor at room temperature. Then, add 0.8% of the total mass of the composite crosslinking working solution of citric acid and 0.3% of the total mass of the composite crosslinking working solution of fatty alcohol polyoxyethylene ether to the reactor in sequence. Stir at 180 rpm for 15 min. Slowly add 0.8% of the total mass of the composite crosslinking working solution of polyhexamethylene guanidine hydrochloride aqueous solution to the reactor. After standing for 5 min, uniformly sprinkle 2.0% of the total mass of the composite crosslinking working solution of sodium lignosulfonate into the reactor. Increase the stirring speed of the reactor to 450 rpm for high shear dispersion for 25 min to obtain a submicron-scale pre-complexed microcolloid dispersion. Reduce the stirring speed of the reactor to 180 rpm, and slowly add 5.0% of the total mass of the composite crosslinking working solution of hydroxyl-terminated polydimethylsiloxane emulsion and 2.0% of the total mass of the composite crosslinking working solution of γ-glycidyl etheroxypropyltrimethoxysilane to the submicron-level pre-complexed microcolloid dispersion. After stirring for 15 min, add deionized water to the reactor to make up the total mass of the composite crosslinking working solution to 100.0%. Maintain stirring at 180 rpm for 20 min to obtain the composite crosslinking working solution. Polyamide mesh with an 8-micron aperture was continuously drawn through a composite crosslinking working liquid at a linear speed of 25 m / min. The polyamide mesh impregnated with the composite crosslinking working liquid was squeezed by a twin-roll milling machine to control the water roll-out rate of the polyamide mesh at 68%. The physical liquid film bridges of the polyamide mesh were broken by blowing the mesh with a high-pressure air knife system. The polyamide mesh was then pre-dried in an 85°C drying oven for 1.8 min. Subsequently, the polyamide mesh was baked and cured in a 155°C high-temperature drying oven for 1.8 min. After cooling and winding, the lower modified polyamide mesh 2 with a crosslinked network covalently bonded to the surface was obtained. The translucent polyethylene waterproof film 1 and the lower modified polyamide mesh 2 with a cross-linked network covalently bonded to the surface are laid flat and aligned. The transverse edges of the translucent polyethylene waterproof film 1 and the lower modified polyamide mesh 2 with a cross-linked network covalently bonded to the surface are continuously heat-fused together using an ultrasonic welding machine. The spliced ​​material is cut into sections with an overall width of 40cm and a length of 35cm and folded longitudinally. The overlapping side edges 4 are pressed and sealed using high-frequency heat sealing to form a tubular bag. A folded edge binding channel 5 is formed at the lower edge of the bag, i.e., the bottom of the modified polyamide mesh 2. A durable drawstring 6 is threaded inside the folded edge binding channel 5 as the lower closure, resulting in a new type of hybrid mesh bag suitable for lychee and longan.

[0025] Example 2: This embodiment provides a method for preparing a novel hybrid net bag suitable for litchi and longan, including the following steps: Add 70.0% of the total mass of the composite crosslinking working solution to the reactor at room temperature. Then, add 1.0% of the total mass of the composite crosslinking working solution of citric acid and 0.5% of the total mass of the composite crosslinking working solution of fatty alcohol polyoxyethylene ether to the reactor in sequence. Stir at 200 rpm for 20 min. Slowly add 1.0% of the total mass of the composite crosslinking working solution of polyhexamethylene guanidine hydrochloride aqueous solution to the reactor. After standing for 8 min, uniformly sprinkle 2.5% of the total mass of the composite crosslinking working solution of sodium lignosulfonate into the reactor. Increase the stirring speed of the reactor to 500 rpm and perform high shear dispersion for 30 min to obtain a submicron-scale pre-complexed microcolloid dispersion. Reduce the stirring speed of the reactor to 200 rpm, and slowly add 6.0% of the total mass of the composite crosslinking working solution of hydroxyl-terminated polydimethylsiloxane emulsion and 2.5% of the total mass of the composite crosslinking working solution of γ-glycidyl etheroxypropyltrimethoxysilane to the submicron-level pre-complexed microcolloid dispersion. After stirring for 20 min, add deionized water to the reactor to make up the total mass of the composite crosslinking working solution to 100.0%. Maintain stirring at 200 rpm for 25 min to obtain the composite crosslinking working solution. Polyamide mesh with a mesh size of 9 micrometers was continuously drawn through a composite crosslinking working liquid at a linear speed of 30 m / min. The polyamide mesh impregnated with the composite crosslinking working liquid was squeezed by a twin-roll milling machine to control the water roll-out rate of the polyamide mesh at 70%. The physical liquid film bridges of the polyamide mesh were broken by blowing the mesh with a high-pressure air knife system. The polyamide mesh was then transported to a drying oven at 90°C for pre-drying for 2.0 min. Subsequently, the polyamide mesh was transported to a high-temperature drying oven at 160°C for baking and curing for 2.0 min. After cooling and winding, the lower modified polyamide mesh 2 with a crosslinked network covalently bonded to the surface was obtained. The translucent polyethylene waterproof film 1 and the lower modified polyamide mesh 2 with a cross-linked network covalently bonded to the surface are laid flat and aligned. The transverse edges of the translucent polyethylene waterproof film 1 and the lower modified polyamide mesh 2 with a cross-linked network covalently bonded to the surface are continuously heat-fused together using an ultrasonic welding machine. The spliced ​​material is cut into sections with an overall width of 40cm and a length of 35cm and folded longitudinally. The overlapping side edges 4 are pressed and sealed using high-frequency heat sealing to form a tubular bag. A folded edge binding channel 5 is formed at the lower edge of the bag, i.e., the bottom of the modified polyamide mesh 2. A durable drawstring 6 is threaded inside the folded edge binding channel 5 as the lower closure, resulting in a new type of hybrid mesh bag suitable for lychee and longan.

[0026] Example 3: This embodiment provides a method for preparing a novel hybrid net bag suitable for litchi and longan, including the following steps: Add 60.0% of the total mass of the composite crosslinking working solution to the reactor at room temperature. Then, add 0.5% of the total mass of the composite crosslinking working solution of citric acid and 0.2% of the total mass of the composite crosslinking working solution of fatty alcohol polyoxyethylene ether to the reactor in sequence. Stir at 150 rpm for 15 min. Slowly add 0.5% of the total mass of the composite crosslinking working solution of polyhexamethylene guanidine hydrochloride aqueous solution to the reactor. After standing for 3 min, uniformly sprinkle 1.5% of the total mass of the composite crosslinking working solution of sodium lignosulfonate into the reactor. Increase the stirring speed of the reactor to 400 rpm for high shear dispersion for 20 min to obtain a submicron-sized pre-complexed microcolloid dispersion. Reduce the stirring speed of the reactor to 150 rpm, and slowly add 4.0% of the total mass of the composite crosslinking working solution of hydroxyl-terminated polydimethylsiloxane emulsion and 1.5% of the total mass of the composite crosslinking working solution of γ-glycidyl etheroxypropyltrimethoxysilane to the submicron-level pre-complexed microcolloid dispersion. After stirring for 15 min, add deionized water to the reactor to make up the total mass of the composite crosslinking working solution to 100.0%. Maintain stirring at 150 rpm for 15 min to obtain the composite crosslinking working solution. Polyamide mesh with a mesh size of 6 micrometers was continuously drawn through a composite crosslinking working liquid at a linear speed of 20 m / min. The polyamide mesh impregnated with the composite crosslinking working liquid was squeezed by a twin-roll milling machine to control the water roll-out rate of the polyamide mesh at 65%. The physical liquid film bridges of the polyamide mesh were broken by blowing the mesh with a high-pressure air knife system. The polyamide mesh was then transported to an 80°C drying oven for pre-drying for 1.5 min. Subsequently, the polyamide mesh was transported to a 150°C high-temperature drying oven for baking and curing for 1.5 min. After cooling and winding, the lower modified polyamide mesh 2 with a crosslinked network covalently bonded to the surface was obtained. The translucent polyethylene waterproof film 1 and the lower modified polyamide mesh 2 with a cross-linked network covalently bonded to the surface are laid flat and aligned. The transverse edges of the translucent polyethylene waterproof film 1 and the lower modified polyamide mesh 2 with a cross-linked network covalently bonded to the surface are continuously heat-fused together using an ultrasonic welding machine. The spliced ​​material is cut into sections with an overall width of 40cm and a length of 35cm and folded longitudinally. The overlapping side edges 4 are pressed and sealed using high-frequency heat sealing to form a tubular bag. A folded edge binding channel 5 is formed at the lower edge of the bag, i.e., the bottom of the modified polyamide mesh 2. A durable drawstring 6 is threaded inside the folded edge binding channel 5 as the lower closure, resulting in a new type of hybrid mesh bag suitable for lychee and longan.

[0027] Comparative Example 1: Compared with Example 1, the difference is that sodium lignosulfonate was not added when preparing the composite crosslinking working solution. The mass ratio of the unadded sodium lignosulfonate was made up by deionized water, and all other aspects were the same.

[0028] Comparative Example 2: Compared with Example 1, the difference is that polyhexamethylene guanidine hydrochloride was not added when preparing the composite crosslinking working solution. The mass ratio of the unadded polyhexamethylene guanidine hydrochloride was made up by deionized water, and all other aspects were the same.

[0029] Comparative Example 3: Compared with Example 1, the difference is that γ-glycidoxypropyltrimethoxysilane was not added when preparing the composite crosslinking working solution. The mass ratio of the unadded γ-glycidoxypropyltrimethoxysilane was made up by deionized water, and all other aspects were the same.

[0030] Comparative Example 4: Compared with Example 1, the difference is that the polyamide mesh is not subjected to chemical modification treatment such as impregnation with composite crosslinking working solution and pre-drying and high-temperature baking. Instead, the original polyamide mesh with a pore size of 8 micrometers is directly heat-fused and spliced ​​with the light-transmitting polyethylene waterproof film 1 to make a mesh bag with a length of 35cm, a width of 40cm and a bottom drawstring 6. All other aspects are the same.

[0031] Comparative Example 5: Compared with Example 1, the difference lies in the preparation steps of the composite crosslinking working solution. In this comparative example, the deionized water, citric acid, fatty alcohol polyoxyethylene ether, polyhexamethylene guanidine hydrochloride, sodium lignosulfonate, hydroxyl-terminated polydimethylsiloxane emulsion, and γ-glycidyl etheroxypropyltrimethoxysilane involved in the formulation were mixed at one time and stirred at 180 rpm for 60 min in a conventional manner. No stepwise pre-complexation and high-shear dispersion operations were performed. All other steps were the same.

[0032] Test Example 1: Take 100 mL of each of the composite crosslinking working solutions prepared in Examples 1, 2, 3 and Comparative Example 5, and inject them into centrifuge tubes with a capacity of 150 mL.

[0033] Centrifuge tubes containing the composite crosslinking working solution were symmetrically placed into the rotor of a room temperature high-speed centrifuge. The centrifugation speed was set to 4000 rpm and the continuous centrifugation time was 30 min.

[0034] After centrifugation, remove the centrifuge tube and pour out the supernatant. Collect the solid precipitate at the bottom of the centrifuge tube and place it in a vacuum drying oven. Set the temperature to 80°C and dry until constant weight. Use an analytical balance to weigh the mass of the dried solid precipitate.

[0035] The theoretical total solid content is calculated based on the theoretical mass ratio of each component in 100 mL of composite crosslinking working solution, and the precipitation rate is calculated as the ratio of the mass of dry solid phase precipitate to the theoretical total solid content.

[0036] Take 2 mL of each of the composite crosslinking working solutions from Example 1 and Comparative Example 5 before centrifugation, dilute them 100 times with deionized water at 25°C, and inject them into a cuvette. Use a dynamic light scattering nanoparticle size analyzer to test the particle size and light intensity distribution percentage of the particles in the sample, and plot the particle size distribution curve.

[0037] Table 1. Test data on centrifugal sedimentation rate of composite crosslinking working fluid

[0038] Figure 2 The horizontal axis represents particle size in nm; the vertical axis represents light intensity distribution in %. Figure 2 The solid red line represents Example 1, and the dashed blue line represents Comparative Example 5.

[0039] The test results are as follows: Based on the data in Table 1 and Figure 2 As can be seen from the content, the precipitation rate of the composite crosslinking working solutions prepared in Examples 1, 2, and 3 was all less than 1.3% under centrifugation at 4000 rpm. Combined with... Figure 2Analysis of the particle size distribution curves in Example 1 showed that the peak light intensity distribution was concentrated in the 200 nm to 400 nm range, indicating a uniform submicron-level dispersion of the components. The composite crosslinking working solution prepared in Comparative Example 5 achieved a centrifugal sedimentation rate of 86.42%. Figure 2 The main peak of the particle size distribution in Comparative Example 5 shifted to the range of 5000 nm to 10000 nm, resulting in the formation of large particle agglomerates.

[0040] Changing the feeding sequence and shear speed alters the colloidal compatibility between components. The composite crosslinking working solution contains cationic polyhexamethylene guanidine hydrochloride and anionic sodium lignosulfonate. In Comparative Example 5, all components were added to water at once and stirred at a low speed of 180 rpm. The anionic and cationic groups underwent electrostatic adsorption, resulting in crosslinking and the formation of insoluble macromolecular polyelectrolyte flocs within a short time. Examples 1 to 3 prepared liquid media through a stepwise feeding method. First, nonionic fatty alcohol polyoxyethylene ether was introduced to coat the charged groups, creating steric hindrance and restricting the free coiling and collision of molecular chain segments. Subsequently, combined with high-speed shearing, the molecular clusters in the liquid phase were forcibly dispersed, preventing large-area complexation and demulsification between anions and cations, and maintaining the suspension stability of the microcolloids.

[0041] Test Example 2: The modified polyamide mesh 2 prepared in Example 1, the modified polyamide mesh 2 prepared in Comparative Example 3, and the original polyamide mesh in Comparative Example 4 were cut to obtain test samples with a size of 20cm×20cm.

[0042] At a temperature of 25℃, the initial water contact angle of the sample surface was tested using a contact angle measuring instrument with the seat drop method. Each sample was measured 5 times at different positions and the average value was recorded.

[0043] The sample block was fixed in a stainless steel porous fixture and placed under the spray head of a simulated rainstorm scouring test machine. The constant water pressure was adjusted to 0.25 MPa and the water flow rate was set to 12 L / min. The sample block surface was continuously scoured for 72 hours.

[0044] After the rinsing time was completed, the sample was taken out and placed in a forced-air drying oven and dried at 80℃ for 1.5 hours. The water contact angle of the sample surface after rinsing was measured using a contact angle measuring instrument.

[0045] Two grams each of sample blocks from Example 1 and Comparative Example 3, after being rinsed and dried, were placed on the crystal surface of an attenuated total reflectance accessory and analyzed using a Fourier transform infrared spectrometer with a scanning range of 4000 cm⁻¹. -1 Up to 500cm -1 Resolution is 4cm -1 Absorption signals were collected under specific conditions, data were acquired, and infrared spectra were plotted.

[0046] Table 2. Water wash fastness test data of hydrophobic crosslinked network

[0047] Figure 3 The horizontal axis represents the wave number, in cm. -1 The vertical axis represents light transmittance, in percent. Figure 3 The solid red line represents Example 1, and the dashed blue line represents Comparative Example 3.

[0048] The test results are as follows: Based on the data in Table 2 and Figure 3 The results show that the surface of the original polyamide mesh in Comparative Example 4 lacks hydrophobic groups, and the initial water contact angle is 62.4°. After 72 hours of continuous rinsing, the water contact angle of the mesh in Comparative Example 3 decreased by 35.8°, and the surface became hydrophilic.

[0049] In Example 1, the lower modified polyamide mesh 2 showed a contact angle decrease of 3.7° after rinsing, maintaining a hydrophobic state of 132.5°. Combined with... Figure 3 Analysis shows that the curve in Comparative Example 3 is at 1100cm. -1 Up to 1000cm -1 The light transmittance of the interval is close to 100%, and it lacks the stretching vibration characteristics of silicon-containing cross-linked groups.

[0050] The curve in Example 1 is at 1085 cm. -1 Up to 1020cm -1 Absorption peaks caused by Si-O-Si and Si-OC bonds appeared in the range. In Example 1, γ-glycidoxypropyltrimethoxysilane was added. Under baking conditions of 155°C, the epoxy groups of the silane molecule underwent a ring-opening addition reaction with the active groups on the surface of sodium lignosulfonate and polyamide fibers. The silanol groups generated by the hydrolysis of methoxy groups underwent a dehydration condensation reaction with the hydroxyl-terminated polydimethylsiloxane emulsion. The chemical bonding process constructed a covalent network film on the surface of the polyamide fibers.

[0051] Comparative Example 3 did not contain γ-glycidoxypropyltrimethoxysilane. The siloxane molecules in the formulation could not be chemically anchored to the fiber surface, and their adhesion was disrupted and washed away by mechanical water flow. The preparation method in Example 1 triggered a covalent bonding reaction, ensuring the surface water resistance of the mesh bag under long-term rainfall conditions.

[0052] Test Example 3: The modified polyamide mesh 2 prepared in Examples 1, 2, and 3, as well as the original polyamide mesh of Comparative Example 4, were cut to obtain test samples with a size of 20cm × 20cm.

[0053] A fabric air permeability tester was used, with the test pressure drop parameter set to 100 Pa and the test area set to 20 cm². 2 .

[0054] The dry test sample is held flat on the test table, and the test instrument is started to measure the initial dry air permeability of the sample. Each sample is tested 5 times in different areas and the average value is recorded.

[0055] Using an atomizing spraying device, spray 20 mL of deionized water evenly at a distance of 15 cm from the surface of the sample block, and let it stand for 60 seconds to simulate the adhesion state of rainfall.

[0056] The sample with surface moisture was fixed back in the test bench, and the measurement was started under the same 100Pa pressure drop condition to obtain the wet air permeability.

[0057] The percentage of breathability retention is calculated by dividing the wet breathability by the initial dry breathability.

[0058] Table 3. Test data of wet air permeability and waterproof membrane air resistance.

[0059] Figure 4 The horizontal axis represents the test pressure drop in Pa; the vertical axis represents the wet air permeability in mm / s. Figure 4 The solid line represents Example 1, and the dashed line represents Comparative Example 4.

[0060] The test results are as follows: Based on the data in Table 3 and Figure 4 According to the data, the air permeability of the original polyamide mesh in Comparative Example 4 was 530.2 mm / s in the dry state, and the air permeability decreased to 3.5 mm / s after spraying deionized water on the surface, with an air permeability retention rate of 0.6%.

[0061] The modified polyamide mesh 2 of Examples 1 to 3, after being sprayed with deionized water, exhibited a wet air permeability ranging from 402.4 mm / s to 531.8 mm / s, and an air permeability retention rate between 93.9% and 95.6%. (Combined with...) Figure 4 Analysis of the curve trend within the test pressure drop range of 50Pa to 200Pa shows that the wet air permeability of Example 1 increases non-linearly with the increase of pressure drop and remains in a relatively high range, while the wet air permeability of Comparative Example 4 is in a low range below 50mm / s throughout the entire test pressure drop range.

[0062] Comparative Example 4 used unmodified polyamide mesh with a pore size of 8 micrometers, lacking low surface energy structural features. When liquid water comes into contact with this size mesh, surface tension causes it to be pulled together at the gaps between adjacent yarns, forming a continuous liquid film that blocks the flow path of gas molecules, causing gas resistance.

[0063] In Example 1, the mesh surface was bonded with a siloxane network formed by cross-linking and curing a hydroxyl-terminated polydimethylsiloxane emulsion and γ-glycidyl etheroxypropyltrimethoxysilane. This low surface energy cross-linked network reduced the free energy of the fiber interface, hindering the wetting and spreading of water in the mesh area. Water molecules contracted into individual droplets at the mesh openings, maintaining the open state of the mesh and preserving normal gas exchange channels between the inside and outside. This treatment prevented fruit suffocation damage caused by poor air circulation inside the mesh bag during rainy weather.

[0064] Test Example 4: The lower modified polyamide mesh 2 prepared in Examples 1, 2, and 3 after being treated with continuous water flow for 72 hours in Test Example 2, as well as the lower modified polyamide mesh 2 prepared in Comparative Examples 2 and 3 and the original polyamide mesh of Comparative Example 4, were collected.

[0065] Place each group of mesh in a sterile operating table and use sterile scissors to cut it into pieces with an area of ​​about 0.5 square centimeters. Accurately weigh 1.5 grams of the pieces as the test sample.

[0066] The prepared concentration was 1.0 × 10⁻⁶. 5 A CFU / mL suspension of Peronophythora litchii spores was used as the inoculum.

[0067] The test samples were placed in sterile Erlenmeyer flasks containing 50 mL of inoculum solution, while a blank control group was set up with inoculum solution containing no mesh sample.

[0068] Transfer all Erlenmeyer flasks into a constant temperature shaking incubator, set the incubation temperature to 28℃ and the shaking speed to 150 rpm, and incubate continuously for 24 hours.

[0069] After the incubation period, 1 mL of culture medium was taken from each Erlenmeyer flask and serially diluted. The culture was then transferred to potato dextrose agar (PDA) plates using the pour method and incubated upside down in a 28°C incubator for 48 hours. Macroscopic colony counts were performed and the long-term antibacterial rate after elution was calculated.

[0070] Culture media were extracted from the Erlenmeyer flasks of Example 1 and Comparative Example 3, respectively. 2 mL samples were taken every 2 hours during the 0 to 24-hour culture period and placed in a quartz cuvette of a UV-Vis spectrophotometer. The absorbance value (OD600) was measured under the condition that the wavelength was set to 600 nm, and a fungal growth curve was plotted.

[0071] Table 4. Test data on long-lasting antifungal performance

[0072] Note: "-" in Table 4 indicates that the result was not measured.

[0073] Figure 5 The horizontal axis represents the incubation time in hours (h); the vertical axis represents absorbance in OD600. Figure 5 The solid line represents Example 1, and the dashed line represents Comparative Example 3.

[0074] The test results are as follows: Based on the data in Table 4 and Figure 5 According to the data, the original polyamide mesh of Comparative Example 4 was not treated with antibacterial agents, and the long-term antibacterial rate after washing was 0.0%.

[0075] In Comparative Example 2, polyhexamethylene guanidine hydrochloride was removed during the preparation process, resulting in a lack of active groups on the surface of the mesh fibers that could kill bacteria. After elution, the long-term antibacterial rate was only 3.8%. In Comparative Example 3, γ-glycidoxypropyltrimethoxysilane was missing, and the functional components failed to form a stable, solidified bonded layer. After 72 hours of water rinsing, most of the antibacterial components detached and were lost into the aqueous phase, leading to a decrease in the long-term antibacterial rate to 33.6%.

[0076] The modified polyamide mesh 2 of Examples 1 to 3 exhibited a long-lasting antibacterial rate ranging from 96.1% to 99.3% after washing. (Combined with...) Figure 5 Curve analysis within the system showed that, during the 0-24 hour culture period, the OD600 absorbance of the culture medium in Comparative Example 3 increased stepwise over time, indicating that the fungal cells in the system underwent geometric proliferation after adapting to the environment; the OD600 absorbance of the culture medium in Example 1 remained stable at a low baseline of around 0.05, indicating that the proliferation of the fungi was blocked.

[0077] The polyhexamethylene guanidine hydrochloride molecule contains densely packed positively charged guanidine groups. The lipid bilayer of fungal cell membranes is usually negatively charged. The guanidine groups are adsorbed onto the outer wall of pathogenic fungal cells by electrostatic attraction, disrupting the cell membrane structure, causing osmotic pressure imbalance in the cytoplasm and leakage of contents, thus inducing cell death.

[0078] The preparation process used in Example 1 induces a condensation addition reaction in the molecular network, anchoring and intercalating the long polymer chains of polyhexamethylene guanidine hydrochloride within the hydrophobic silica network.

[0079] The cross-linked three-dimensional mesh restricts the free desorption of water-soluble guanidine salt components in aqueous solutions, resisting the hydrodynamic shear stress peeling effect caused by heavy rainfall. After prolonged immersion in water, the active structure immobilized on the surface of the modified mesh can still kill spores of Phytophthora licheniformis attached to the edges of the mesh openings, reducing the probability of fruit rot caused by the proliferation of pathogenic microorganisms during the ripening period.

[0080] Test Example 5: Cut the lower modified polyamide mesh 2 prepared in Examples 1, 2, and 3, as well as the lower modified polyamide mesh 2 prepared in Comparative Example 1 and the original polyamide mesh in Comparative Example 4, to obtain a long strip test sample with a size of 30cm×5cm.

[0081] Some test samples were installed on the test sample rack inside the UV accelerated aging test chamber. The equipment was turned on, and the light source was set to a UVA-340 fluorescent ultraviolet lamp with an irradiance of 0.76 W / m². 2 The blackboard temperature was set to 60℃, and it was subjected to continuous ultraviolet light irradiation for 500 hours.

[0082] The test sample that had undergone 500 hours of UV aging was removed from the equipment and placed in a standard environment with a temperature of 20°C and a relative humidity of 65% for 24 hours to adjust the humidity.

[0083] The longitudinal fracture strength of unexposed test specimens before aging and the test specimens after aging were tested using an electronic universal testing machine. The initial distance between the upper and lower clamps was set to 20 cm, the tensile rate was set to 100 mm / min, the equipment was started, and the maximum load value at the moment of specimen fracture was recorded as the fracture strength.

[0084] Divide the maximum load value measured after fracture by the maximum load value measured before aging to calculate the percentage of fracture strength retention.

[0085] Test samples from Example 1 and Comparative Example 1 were collected at 0, 100, 200, 300, 400, and 500 hours of UV aging. The fracture strength was measured according to the same procedure, and the mechanical data of the change with aging time were obtained and plotted.

[0086] Table 5. Mechanical test data for UV aging resistance

[0087] Figure 6 The horizontal axis represents UV aging time in hours (h); the vertical axis represents fracture strength in nanometers (N). Figure 6 The solid line represents Example 1, and the dashed line represents Comparative Example 1.

[0088] The test results are as follows: Based on the data in Table 5 and Figure 6 The results show that the original polyamide mesh of Comparative Example 4 retained 47.6% of its tensile strength after 500 hours of continuous ultraviolet irradiation. Comparative Example 1, which did not add sodium lignosulfonate during preparation, retained 51.4% of its tensile strength after aging. The modified polyamide mesh 2 prepared in Examples 1 to 3 retained between 85.0% and 90.5% of its tensile strength under the same aging conditions.

[0089] Combination Figure 6 Analysis of the curve data shows that as the UV aging time increases, the fracture strength of Comparative Example 1 exhibits an exponential decline, and the tensile properties of the material are lost at an accelerated rate; the fracture strength curve of Example 1 shows a gentle downward slope, retaining a higher load-bearing capacity.

[0090] Polyamide polymer chains contain amide bonds. Under the action of high-energy ultraviolet radiation with a wavelength of 340 nm, the main chain structure undergoes photo-oxidative degradation, leading to the breakage and separation of the macromolecular chains. The macroscopic manifestations are that the fibers become yellow and brittle, and the mechanical strength is reduced.

[0091] The sodium lignosulfonate contained in the formulation of Example 1 is a natural polyphenol cross-linked macromolecule with abundant aromatic conjugated groups such as benzene rings and phenolic hydroxyl groups in its molecular structure. After absorbing ultraviolet photons, the electrons inside the molecule undergo energy level transition reactions, converting the absorbed light energy into low-energy state heat energy and dissipating it into the surrounding environment.

[0092] This process embeds sodium lignosulfonate into the cross-linked network on the surface of the mesh, blocking the penetration path of ultraviolet energy into the underlying polyamide fiber matrix. This reduces the number of main chain breaks and slows down the aging and degradation process of the mesh bag in open-field environments. Comparative Example 1 lacks this ultraviolet-absorbing component, and the mesh directly absorbs light radiation energy, resulting in a rapid decline in its mechanical properties.

Claims

1. A novel hybrid net bag suitable for litchi and longan, characterized in that, It includes a translucent polyethylene waterproof film (1) and a lower modified polyamide mesh (2) with a cross-linked network covalently bonded to its surface. The lower modified polyamide mesh (2) with a cross-linked network covalently bonded to its surface is obtained by treating polyamide mesh with a composite cross-linking working solution, wherein the composite cross-linking working solution contains polyhexamethylene guanidine hydrochloride, sodium lignosulfonate, hydroxyl-terminated polydimethylsiloxane emulsion and γ-glycidoxypropyltrimethoxysilane. The transverse edge of the translucent polyethylene waterproof film (1) is continuously heat-fused to the transverse edge of the lower modified polyamide mesh (2) whose surface is covalently bonded with a cross-linked network. The translucent polyethylene waterproof film (1) and the lower modified polyamide mesh (2) with a cross-linked network covalently bonded to the surface are folded longitudinally. The side edges (4) of the translucent polyethylene waterproof film (1) and the lower modified polyamide mesh (2) with a cross-linked network covalently bonded to the surface are pressed and sealed to form a tubular bag. The lower edge is folded and covered and a drawstring (6) is threaded through it as the lower closure.

2. The novel hybrid net bag for lychee and longan according to claim 1, characterized in that, The transverse edge of the transparent polyethylene waterproof film (1) is continuously heat-fused to the transverse edge of the lower modified polyamide mesh (2) whose surface is covalently bonded with a cross-linked network using an ultrasonic welding machine. The translucent polyethylene waterproof film (1) and the lower modified polyamide mesh (2) with a cross-linked network on the surface are pressed and sealed at the side overlap (4) to form a tubular bag. The lower edge is folded and wrapped and a drawstring (6) is threaded through it as the lower closure.

3. The novel hybrid net bag for litchi and longan according to claim 1, characterized in that, The lower modified polyamide mesh (2) with a surface covalently bonded to a crosslinked network is obtained through the following steps: The polyamide mesh is continuously drawn through the composite crosslinking working liquid and then pre-dried and cured.

4. A novel hybrid net bag suitable for litchi and longan according to claim 3, characterized in that, The continuous traction through the composite crosslinking working fluid and the pre-drying process include: The polyamide mesh impregnated with the composite crosslinking working solution is extruded using a twin-roll mill. The physical liquid film bridges in the polyamide mesh are broken by blowing away the mesh openings using a high-pressure air knife system. The polyamide mesh, after the physical liquid film bridges have been broken, is conveyed to a drying room for pre-drying.

5. A novel hybrid net bag suitable for litchi and longan according to claim 4, characterized in that, The baking and curing process includes: The pre-dried polyamide mesh is transported to a high-temperature drying room for baking and curing. The polyamide mesh after baking and curing is cooled and wound up to obtain the lower modified polyamide mesh (2) with a cross-linked network covalently bonded to its surface.

6. A novel hybrid net bag suitable for litchi and longan according to claim 1, characterized in that, The raw materials for preparing the composite crosslinking working fluid also include room temperature deionized water, citric acid, and fatty alcohol polyoxyethylene ether.

7. A novel hybrid net bag for litchi and longan according to claim 6, characterized in that, The composite crosslinking working solution is prepared by a method comprising the following steps: Add the room temperature deionized water to the reaction vessel; The citric acid and the fatty alcohol polyoxyethylene ether were added sequentially to the reaction vessel and stirred.

8. A novel hybrid net bag for litchi and longan according to claim 7, characterized in that, The method for preparing the composite crosslinking working solution further includes: Slowly add the aqueous solution of polyhexamethylene guanidine hydrochloride to the reaction vessel and let it stand; After standing, the sodium lignosulfonate is uniformly sprinkled into the reaction vessel, and the stirring speed of the reaction vessel is increased to perform high-shear dispersion, thereby obtaining a submicron-sized pre-complexed microcolloid dispersion.

9. A novel hybrid net bag for litchi and longan according to claim 8, characterized in that, The method for preparing the composite crosslinking working solution further includes: Reduce the stirring speed of the reactor; The terminal hydroxyl polydimethylsiloxane emulsion and the γ-glycidoxypropyltrimethoxysilane were slowly added sequentially to the submicron-scale pre-complexed microcolloid dispersion, and the mixture was stirred.

10. A novel hybrid net bag for litchi and longan according to claim 9, characterized in that, The method for preparing the composite crosslinking working solution further includes: After stirring, deionized water is added to the reaction vessel to make up the total mass of the composite crosslinking working solution, and stirring is maintained. After stirring, the composite crosslinking working solution is obtained.

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