Preparation method of edible and digestible composite polylactic acid bundling rope for herbivorous animals

Abstract

The invention discloses a preparation method of an edible and digestible composite polylactic acid bundling rope for herbivorous animals, belongs to the technical field of bundling rope processing, and aims to solve the technical problem that the breaking strength and the edible and digestible performance of a polylactic acid bundling rope for animals need to be further improved in the prior art. The method comprises the following steps: under the protection of inert gas, mixing polyethylene glycol, lactide, glycerol, a catalyst and toluene, preparing polylactic acid composite filaments through mutual cooperation, melt mixing and drafting of hybrid polylactic acid, polyglycolic acid, modified straw powder and epoxidized cellulose, and then performing multi-strand weaving, so that the breaking strength of the bundling rope is effectively improved, and the tensile strength of the bundling rope is improved. And the feed can be eaten and digested by herbivorous animals, so that the digestion burden of the herbivorous animals is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of tying rope processing, and in particular to a method for preparing a composite polylactic acid tying rope which is edible and digestible for herbivorous animals. Background Art

[0002] In modern agriculture and animal husbandry, baling ropes are widely used as an important tool to fix, protect and transport various agricultural products and forage. However, traditional baling rope materials, such as plastic, straw rope, hemp rope, etc., are often difficult to degrade after use, causing serious pollution to the environment. Straw products such as straw rope and hemp rope are made of natural plant fibers, and their strength and toughness are relatively limited. In scenarios where they need to withstand large tension or be used for a long time, these natural fibers may not meet the requirements and are prone to breakage or wear.

[0003] In the prior art, polylactic acid is a biodegradable polymer material derived from renewable resources, which has good biocompatibility and bioabsorbability. Although polylactic acid has strong rigidity, it lacks toughness and is prone to brittle fracture. Pure polylactic acid ropes may not meet the requirements of certain specific application scenarios in terms of strength and toughness. In order to improve the mechanical properties and degradation controllability of polylactic acid, fiber is used as a reinforcing material and composited with polylactic acid, which can effectively improve the mechanical strength of the rope.

[0004] However, the interfacial bonding between the fiber and polylactic acid is poor, resulting in the need to further improve the strength of the polylactic acid rope. Secondly, although pure polylactic acid rope can be degraded after being accidentally ingested by animals, the degradation rate may be slow, and substances that are harmful to animals may be produced during the degradation process, posing a threat to their health when accidentally ingested by animals.

[0005] In view of the technical defects in this aspect, a solution is now proposed. Summary of the invention

[0006] The object of the present invention is to provide a method for preparing a composite polylactic acid tying rope that is edible and digestible for herbivorous animals, so as to solve the technical problem in the prior art that the breaking strength and animal edible and digestible performance of the polylactic acid tying rope need to be further improved.

[0007] The purpose of the present invention can be achieved by the following technical scheme: A method for preparing a composite polylactic acid rope that is edible and digestible for herbivorous animals comprises the following steps:

[0008] S1. Under the protection of inert gas, polyethylene glycol, lactide, glycerol, a catalyst and toluene are mixed, the temperature of the reaction system is raised to 70-80°C, the reaction is kept warm for 6-8h, and post-processed to obtain hybrid polylactic acid;

[0009] The synthetic reaction mechanism of hybrid polylactic acid is:

[0010] During the reaction, lactide is ring-opened under the catalysis of stannous octoate to form lactic acid monomer units. The lactic acid monomer units are combined with hydroxyl groups on glycerol or polyethylene glycol molecules through esterification reaction to form polylactic acid chains with polyethylene glycol block copolymers. The multiple hydroxyl groups of the glycerol molecules increase the cross-linking degree of the polylactic acid chains to prepare hybrid polylactic acid.

[0011] S2, mixing hybrid polylactic acid, polyglycolic acid, modified straw powder, epoxidized cellulose and additives, adding the mixture into a twin-screw extruder, and melt-extruding the mixture into thin strips, and then stretching the strips while hot to obtain polylactic acid composite filaments with a diameter of 5±0.5 mm;

[0012] S3, weaving 6-8 polylactic acid composite filaments into multiple strands to obtain a composite polylactic acid rope.

[0013] Furthermore, in step S1, the amount ratio of the polyethylene glycol, lactide, glycerol, catalyst and toluene is 4-5g:6-8g:0.8-1.2g:0.1g:50mL, the polyethylene glycol is polyethylene glycol 400, and the catalyst is stannous octoate. The post-treatment includes: after the reaction is completed, the reaction system is kept warm at 70-80°C, the low boiling point is removed by decompression, the temperature of the reaction system is lowered to 50°C, acetone is added to the reaction system, and stirred until the system is dissolved. The temperature of the reaction system is lowered to room temperature, methanol is added to the reaction system, stirred and dispersed for 10-15min, filtered, the filter cake is washed with methanol 3 times and then dried, and the filter cake is transferred to a drying oven at a temperature of 50-60°C, and vacuum dried to constant weight to obtain hybrid polylactic acid.

[0014] Furthermore, in step S2, the weight ratio of the hybrid polylactic acid, polyglycolic acid, modified straw powder, epoxidized cellulose and additives is 70-80:15-18:28-32:23-25:6-8, the additives are composed of zinc stearate, polyethylene glycol 800, antioxidants and plasticizers in a weight ratio of 2:1:2:5, the antioxidant is any one of butylated hydroxybenzoate, butylated hydroxyanisole and tert-butylated hydroxyphenyl ether, the plasticizer is acetyl tributyl citrate, the temperatures of the six temperature sections of the twin-screw extruder from the feed end to the discharge end are 230°C, 235°C, 235°C, 235°C, 235°C and 240°C, respectively, the spindle speed of the twin-screw extruder is 18-20r / min, and the stretching temperature is 170-180°C.

[0015] Furthermore, the modified straw powder is obtained by processing the following steps:

[0016] A1. Mix straw powder and deionized water, raise the temperature of the reaction system to 60-70°C, add hydrogen peroxide solution to the reaction system, keep the temperature for 2-3 hours, and post-treat to obtain activated straw powder;

[0017] A2. Mix the activated straw powder, tannic acid, epoxidized soybean oil and dichloromethane, stir and disperse for 30-50 minutes at room temperature, increase the temperature of the reaction system by 50-60° C., reflux and separate to remove the solvent at room temperature, and post-treat to obtain modified straw powder.

[0018] The synthetic reaction mechanism of activated straw powder is:

[0019] Hydrogen peroxide is an oxidant. During the reaction, hydrogen peroxide can oxidize lignin and hemicellulose in the straw, destroy their structure, form active groups such as hydroxyl and carboxyl groups on the surface of the straw powder, increase the surface activity of the straw powder, and prepare activated straw powder.

[0020] In the process of preparing the modified straw powder, dichloromethane is used as a solvent to help tannic acid and epoxy soybean oil be evenly dispersed on the surface of the straw powder. The large number of phenolic hydroxyl groups contained in the tannic acid molecules can hydrogen bond or chemically bond with the active groups (such as hydroxyl groups) on the surface of the straw powder. The epoxy soybean oil contains epoxy groups, which can undergo a ring-opening reaction with the hydroxyl groups on the surface of the straw powder or the phenolic hydroxyl groups of tannic acid to form chemical bonds, forming a coating on the outside of the straw powder to prepare the modified straw powder.

[0021] Furthermore, in step A1, the amount ratio of the straw powder, deionized water and hydrogen peroxide solution is 1g:7mL:3mL, and the straw powder is composed of 100-mesh straw powder, 60-mesh straw powder and straw fiber in a weight ratio of 1:2:3; the mass fraction of the hydrogen peroxide solution is 7-9%, and the pH is 9. The post-treatment includes: after the reaction is completed, the temperature of the reaction system is lowered to room temperature, filtered, the filter cake is washed with purified water until it is neutral and then dried, and the filter cake is transferred to a drying oven at a temperature of 70-80°C, and vacuum dried to constant weight to obtain activated straw powder.

[0022] Furthermore, in step A2, the amount ratio of the activated straw powder, tannic acid, epoxidized soybean oil and dichloromethane is 7g:3g:1g:30mL, and the post-treatment includes: after the reaction is completed, the temperature of the reaction system is lowered to room temperature, the reaction system is transferred to a drying oven at a temperature of 70-80°C, and dried for 6-8h to obtain modified straw powder.

[0023] Furthermore, the epoxidized cellulose is obtained by processing the following steps:

[0024] B1, mixing hydroxymethyl cellulose and sodium hydroxide solution, raising the temperature of the reaction system to 40-50°C, ultrasonically dispersing for 4-6 hours, and post-treating to obtain sodium hydroxymethyl cellulose;

[0025] B2. Under the protection of inert gas, sodium hydroxymethyl cellulose, epichlorohydrin, sodium hydroxide and tetrabutylammonium bromide are mixed and stirred until the system is dissolved. The temperature of the reaction system is raised to 65-75°C, and the reaction is kept warm for 6-7 hours. After post-treatment, epoxidized cellulose is obtained.

[0026] The synthetic reaction mechanism of epoxidized cellulose is:

[0027] During the reaction, sodium hydroxide reacts with hydroxyl groups in hydroxymethyl cellulose to generate sodium hydroxymethyl cellulose, and then ethanol is used as a poor solvent to promote the precipitation of sodium hydroxymethyl cellulose from the solution to prepare sodium hydroxymethyl cellulose. Epichlorohydrin can undergo a ring-opening reaction with the hydroxyl groups in the sodium hydroxymethyl cellulose and then cyclize in an alkaline environment to form an epoxy group. Then, excess epichlorohydrin is removed by washing to prepare epoxidized cellulose.

[0028] Furthermore, in step B1, the dosage ratio of the hydroxymethyl cellulose and the sodium hydroxide solution is 1g:3mL, the concentration of the sodium hydroxide solution is 0.3-0.5mol / L, and the post-treatment includes: after the reaction is completed, the temperature of the reaction system is lowered to room temperature, anhydrous ethanol is added to the reaction system, stirred and dispersed for 20-30min, filtered, the filter cake is washed with anhydrous ethanol 3 times and then dried, the filter cake is transferred to a drying oven at a temperature of 60-70°C, and vacuum dried to constant weight to obtain sodium hydroxymethyl cellulose.

[0029] Furthermore, in step B2, the amount ratio of sodium hydroxymethyl cellulose, epichlorohydrin, sodium hydroxide, tetrabutylammonium bromide and is 5g:20mL:2g:0.3g, and the post-treatment includes: after the reaction is completed, the temperature of the reaction system is lowered to room temperature, filtered, the filter cake is washed 3 times with 50vol% ethanol aqueous solution and then dried, the filter cake is transferred to a drying oven at a temperature of 70-80°C, and vacuum dried to constant weight to obtain epoxidized cellulose.

[0030] The present invention has the following beneficial effects:

[0031] 1. The edible and digestible composite polylactic acid baling rope for herbivorous animals of the present invention improves the brittleness of polylactic acid, improves the toughness and impact resistance of the material, and indirectly improves the breaking strength by embedding polyethylene glycol as a flexible chain segment into the polylactic acid molecular chain, and then uses glycerol to enhance the degree of hybrid cross-linking of the polylactic acid molecular chain, enhances the interaction force between the molecular chains, and improves the tensile strength and breaking strength of the material. Then, modified straw powder is used as a reinforcing filler to significantly improve the tensile strength and tear resistance of the composite material. Epoxidized cellulose is used as an interface coupling agent and a reinforcing phase to significantly improve the interface bonding strength and overall mechanical properties of the composite material. Through a melt blending-stretching orientation process, the molecular orientation and filler dispersion of the composite filament are optimized, and the breaking strength of the material is enhanced. In addition, the composite polylactic acid baling rope can be gradually degraded and absorbed in the digestive tract of ruminants, and will not cause a digestive burden or health risk to the animals.

[0032] 2. The edible and digestible composite polylactic acid rope for herbivorous animals of the present invention is characterized in that the lignin and hemicellulose in the straw are oxidized by hydrogen peroxide in an alkaline environment, so that the hydroxyl groups on the surface of the straw powder are exposed, the surface activity of the straw powder is improved, and the synergistic effect of the aspect ratio of the straw powder and the multi-scale filler system significantly improves the tensile strength of the composite material. The straw powder is modified by tannic acid and epoxy soybean oil to form a cross-linked network on the outside of the straw powder. The epoxy soybean oil is used as a plasticizer and coupling agent to improve the compatibility of the straw and the polylactic acid and improve its dispersibility in the polylactic acid matrix. At the same time, the epoxy group reacts with the polylactic acid chain segment to enhance the interfacial bonding force with the polylactic acid and reduce the risk of filler-matrix debonding. The polylactic acid can be gradually degraded in the animal body by hydrolysis and enzymolysis. It is degraded into lactic acid, which is further metabolized into carbon dioxide and water. The addition of polyethylene glycol and glycerol increases the hydrophilicity and degradation rate of polylactic acid, making it easier to decompose in the animal digestive tract. The cellulose and hemicellulose in straw powder are the main food sources for herbivorous animals. The microorganisms in their rumen can secrete cellulase to decompose cellulose into glucose, and hydrogen peroxide activation and tannic acid modification further improve the digestibility of straw powder. Epoxidized cellulose can be gradually degraded into cellulose and hydrolysis products of epoxy groups by hydrolysis in the animal body. The cellulose part can be digested and absorbed by animals. The hydrolysis products of epoxy groups are harmless to animals and can be eaten and digested by herbivorous animals without burdening the animal's digestive system.

[0033] 3. The edible and digestible composite polylactic acid tying rope for herbivorous animals of the present invention uses epoxidized cellulose as an interface coupling agent and a reinforcing phase. Under high temperature conditions, the epoxy groups on the epoxidized cellulose molecules undergo ring-opening condensation with active reaction sites such as imine, hydroxyl, and carboxyl groups on other molecules to construct a cross-linked network in the polylactic acid composite yarn. Both polylactic acid and polyglycolic acid are polyester materials with similar chemical structures and good compatibility. The high strength and high modulus of polyglycolic acid can significantly improve the tensile strength of the composite material, and the high crystallinity of polyglycolic acid can induce polylactic acid crystallization and improve the crystallinity of the composite material, thereby enhancing the mechanical properties of the polylactic acid composite yarn. After melt extrusion, heat drawing can be used to further improve the molecular chain and fiber orientation, increase the crystallinity, and thus improve the strength of the polylactic acid composite yarn. The multi-strand braided structure combines multiple composite yarns mechanically to disperse stress, thereby further improving the overall strength of the tying rope. DETAILED DESCRIPTION

[0034] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] In the present application, the diameter of the straw fiber is 15-30 μm and the length is 3-5 mm;

[0036] In the present application, the mass fraction of the hydrogen peroxide solution is 7-9%, and the pH is 9;

[0037] In the present application, polyglycolic acid is selected from Wuhan Kangqiong Biopharmaceutical Technology Co., Ltd., with CAS number 26009-03-0, model number kq-051, and brand name Kangqiong.

[0038] Example 1

[0039] This embodiment provides a method for preparing a composite polylactic acid tying rope that is edible and digestible for herbivorous animals, comprising the following steps:

[0040] S1. Preparation of hybrid polylactic acid

[0041] Weigh: 40g of polyethylene glycol 400, 60g of lactide, 8g of glycerol, 1g of stannous octoate and 500mL of toluene, add them to a three-necked flask protected by nitrogen and stir, raise the temperature of the three-necked flask to 70°C, keep the reaction for 6h, keep the three-necked flask at 70°C, reduce the pressure to remove low boiling points, lower the temperature of the reaction system to 50°C, add 300mL of acetone to the reaction system, stir until the system is dissolved, lower the temperature of the reaction system to room temperature, add 600mL of methanol to the reaction system, stir and disperse for 10min, filter, wash the filter cake with methanol 3 times and then dry it, transfer the filter cake to a drying oven at 50°C, and vacuum dry it to constant weight to obtain hybrid polylactic acid.

[0042] S2. Preparation of modified straw powder

[0043] The 100-mesh straw powder, 60-mesh straw powder and straw fiber are uniformly mixed in a weight ratio of 1:2:3 to obtain straw powder for later use;

[0044] Weigh: 100 g of straw powder and 700 mL of deionized water are added to a three-necked flask and stirred. The temperature of the three-necked flask is raised to 60°C. 300 mL of hydrogen peroxide solution is added to the three-necked flask and kept warm for 2 hours. The temperature of the three-necked flask is lowered to room temperature, and the filter cake is filtered. The filter cake is washed with purified water until it is neutral and then dried. The filter cake is then transferred to a drying oven at a temperature of 70°C and vacuum dried to constant weight to obtain activated straw powder;

[0045] Weigh: 70 g of activated straw powder, 30 g of tannic acid, 10 g of epoxidized soybean oil and 300 mL of dichloromethane, add into a three-necked flask and stir. Stir and disperse for 30 min at room temperature. Raise the temperature of the three-necked flask by 50°C, reflux and separate to remove the solvent at room temperature to obtain a powder-like substance. Lower the temperature of the three-necked flask to room temperature, transfer the powder-like substance in the three-necked flask to a drying oven at 70°C, and dry for 6 h to obtain modified straw powder.

[0046] S3. Preparation of epoxidized cellulose

[0047] Weigh: 100 g of hydroxymethyl cellulose and 300 mL of 0.3 mol / L sodium hydroxide solution are added to a three-necked flask, the temperature of the three-necked flask is raised to 40°C, ultrasonic dispersion is performed for 4 hours, the three-necked flask is fixed on an iron stand with mechanical stirring, the temperature of the three-necked flask is lowered to room temperature, 600 mL of anhydrous ethanol is added to the three-necked flask, stirring and dispersing for 20 minutes, suction filtering, the filter cake is washed with anhydrous ethanol 3 times and then dried, the filter cake is transferred to a drying oven at a temperature of 60°C, and vacuum dried to constant weight to obtain sodium hydroxymethyl cellulose;

[0048] Weigh: 100 g of sodium hydroxymethyl cellulose, 400 mL of epichlorohydrin, 40 g of sodium hydroxide and 6 g of tetrabutylammonium bromide, add into a three-necked flask protected by nitrogen, stir until the system is dissolved, raise the temperature of the three-necked flask to 65° C., keep warm for 6 hours, lower the temperature of the three-necked flask to room temperature, filter, wash the filter cake with 50 vol% ethanol aqueous solution three times and then dry it, transfer the filter cake to a drying oven at a temperature of 70° C., and vacuum dry it to constant weight to obtain epoxidized cellulose.

[0049] S4. Preparation of polylactic acid composite yarn

[0050] Mix zinc stearate, polyethylene glycol 800, butyl hydroxybenzoate and acetyl tributyl citrate in a weight ratio of 2:1:2:5 to obtain an additive, which is set aside;

[0051] Weigh by weight: 70 parts of hybrid polylactic acid, 15 parts of polyglycolic acid, 28 parts of modified straw powder, 23 parts of epoxidized cellulose and 6 parts of additives, mix and add to a twin-screw extruder, the temperatures of the 6 temperature zones of the twin-screw extruder from the feed end to the discharge end are set to 230°C, 235°C, 235°C, 235°C, 235°C, and 240°C, respectively, the main shaft speed of the twin-screw extruder is 18r / min, and after melt-extrusion into thin strips by the twin-screw extruder, they are stretched while hot at 170°C to obtain polylactic acid composite filaments with a diameter of 5±0.5mm.

[0052] S5. Preparation of composite polylactic acid rope

[0053] The six polylactic acid composite filaments are braided into multiple strands to obtain a composite polylactic acid rope.

[0054] Example 2

[0055] This embodiment provides a method for preparing a composite polylactic acid tying rope that is edible and digestible for herbivorous animals, comprising the following steps:

[0056] S1. Preparation of hybrid polylactic acid

[0057] Weigh: 40045g polyethylene glycol, 70g lactide, 10g glycerol, 1g stannous octoate and 500mL toluene, add to a nitrogen-protected three-necked flask and stir, raise the temperature of the three-necked flask to 75°C, keep warm for 7h, keep the three-necked flask at 75°C, reduce the pressure to remove low-boiling substances, lower the temperature of the reaction system to 50°C, add 300mL of acetone to the reaction system, stir until the system is dissolved, lower the temperature of the reaction system to room temperature, add 600mL of methanol to the reaction system, stir and disperse for 13min, filter, wash the filter cake with methanol 3 times and then dry it, transfer the filter cake to a drying oven at 55°C, and vacuum dry it to constant weight to obtain hybrid polylactic acid.

[0058] S2. Preparation of modified straw powder

[0059] The 100-mesh straw powder, 60-mesh straw powder and straw fiber are uniformly mixed in a weight ratio of 1:2:3 to obtain straw powder for later use;

[0060] Weigh: 100 g of straw powder and 700 mL of deionized water are added to a three-necked flask and stirred. The temperature of the three-necked flask is raised to 65°C. 300 mL of hydrogen peroxide solution is added to the three-necked flask and kept warm for 2.5 hours. The temperature of the three-necked flask is lowered to room temperature, and the filter cake is filtered. The filter cake is washed with purified water until it is neutral and then dried. The filter cake is then transferred to a drying oven at a temperature of 75°C and vacuum dried to constant weight to obtain activated straw powder;

[0061] Weigh: 70 g of activated straw powder, 30 g of tannic acid, 10 g of epoxidized soybean oil and 300 mL of dichloromethane, add into a three-necked flask and stir. Stir and disperse for 40 min at room temperature. Raise the temperature of the three-necked flask to 55°C, reflux and separate to remove the solvent at room temperature to obtain a powder-like substance. Lower the temperature of the three-necked flask to room temperature, transfer the powder-like substance in the three-necked flask to a drying oven at 75°C, and dry for 7 h to obtain modified straw powder.

[0062] S3. Preparation of epoxidized cellulose

[0063] Weigh: 100 g of hydroxymethyl cellulose and 300 mL of 0.4 mol / L sodium hydroxide solution are added to a three-necked flask, the temperature of the three-necked flask is raised to 45°C, ultrasonic dispersion is performed for 5 hours, the three-necked flask is fixed on an iron stand with mechanical stirring, the temperature of the three-necked flask is lowered to room temperature, 600 mL of anhydrous ethanol is added to the three-necked flask, stirring and dispersing for 25 minutes, suction filtering, the filter cake is washed with anhydrous ethanol 3 times and then dried, the filter cake is transferred to a drying oven at a temperature of 65°C, and vacuum dried to constant weight to obtain sodium hydroxymethyl cellulose;

[0064] Weigh: 100 g of sodium hydroxymethyl cellulose, 400 mL of epichlorohydrin, 40 g of sodium hydroxide and 6 g of tetrabutylammonium bromide, add into a three-necked flask protected by nitrogen, stir until the system is dissolved, raise the temperature of the three-necked flask to 70° C., keep warm for 6.5 hours, lower the temperature of the three-necked flask to room temperature, filter, wash the filter cake with 50 vol% ethanol aqueous solution three times and then dry it, transfer the filter cake to a drying oven at a temperature of 75° C., and vacuum dry it to constant weight to obtain epoxidized cellulose.

[0065] S4. Preparation of polylactic acid composite yarn

[0066] Zinc stearate, polyethylene glycol 800, butylated hydroxyanisole and acetyl tributyl citrate are uniformly mixed in a weight ratio of 2:1:2:5 to obtain an additive, which is set aside;

[0067] Weigh by weight: 75 parts of hybrid polylactic acid, 17 parts of polyglycolic acid, 30 parts of modified straw powder, 24 parts of epoxidized cellulose and 7 parts of additives, mix and add to a twin-screw extruder, the temperatures of the 6 temperature zones of the twin-screw extruder from the feed end to the discharge end are set to 230°C, 235°C, 235°C, 235°C, 235°C, and 240°C, respectively, the main shaft speed of the twin-screw extruder is 19r / min, and after melt-extrusion into thin strips by the twin-screw extruder, they are stretched while hot at 175°C to obtain polylactic acid composite filaments with a diameter of 5±0.5mm.

[0068] S5. Preparation of composite polylactic acid rope

[0069] Seven polylactic acid composite filaments are braided into multiple strands to obtain a composite polylactic acid binding rope.

[0070] Example 3

[0071] This embodiment provides a method for preparing a composite polylactic acid tying rope that is edible and digestible for herbivorous animals, comprising the following steps:

[0072] S1. Preparation of hybrid polylactic acid

[0073] Weigh: 50 g of polyethylene glycol 400, 80 g of lactide, 12 g of glycerol, 1 g of stannous octoate and 500 mL of toluene, add them to a three-necked flask protected by nitrogen and stir, raise the temperature of the three-necked flask to 80 ° C, keep the reaction for 8 hours, keep the three-necked flask at 80 ° C, reduce the pressure to remove low boiling points, lower the temperature of the reaction system to 50 ° C, add 300 mL of acetone to the reaction system, stir until the system is dissolved, lower the temperature of the reaction system to room temperature, add 600 mL of methanol to the reaction system, stir and disperse for 15 minutes, filter, wash the filter cake with methanol 3 times and then dry it, transfer the filter cake to a drying oven at a temperature of 60 ° C, and vacuum dry it to constant weight to obtain hybrid polylactic acid.

[0074] S2. Preparation of modified straw powder

[0075] The 100-mesh straw powder, 60-mesh straw powder and straw fiber are uniformly mixed in a weight ratio of 1:2:3 to obtain straw powder for later use;

[0076] Weigh: 100 g of straw powder and 700 mL of deionized water are added to a three-necked flask and stirred. The temperature of the three-necked flask is raised to 70°C. 300 mL of hydrogen peroxide solution is added to the three-necked flask and kept warm for 3 hours. The temperature of the three-necked flask is lowered to room temperature, and the filter cake is filtered. The filter cake is washed with purified water until it is neutral and then dried. The filter cake is then transferred to a drying oven at a temperature of 80°C and vacuum dried to constant weight to obtain activated straw powder;

[0077] Weigh: 70 g of activated straw powder, 30 g of tannic acid, 10 g of epoxidized soybean oil and 300 mL of dichloromethane, add into a three-necked flask and stir. Stir and disperse for 50 min at room temperature. Raise the temperature of the three-necked flask by 60°C, reflux and separate to remove the solvent at room temperature to obtain a powder-like substance. Lower the temperature of the three-necked flask to room temperature, transfer the powder-like substance in the three-necked flask to a drying oven at 80°C, and dry for 8 h to obtain modified straw powder.

[0078] S3. Preparation of epoxidized cellulose

[0079] Weigh: 100 g of hydroxymethyl cellulose and 300 mL of 0.5 mol / L sodium hydroxide solution are added to a three-necked flask, the temperature of the three-necked flask is raised to 50° C., ultrasonic dispersion is performed for 6 h, the three-necked flask is fixed on an iron stand with mechanical stirring, the temperature of the three-necked flask is lowered to room temperature, 600 mL of anhydrous ethanol is added to the three-necked flask, stirring and dispersing for 30 min, suction filtering, the filter cake is washed with anhydrous ethanol 3 times and then dried, the filter cake is transferred to a drying oven at a temperature of 70° C., and vacuum dried to constant weight to obtain sodium hydroxymethyl cellulose;

[0080] Weigh: 100 g of sodium hydroxymethyl cellulose, 400 mL of epichlorohydrin, 40 g of sodium hydroxide and 6 g of tetrabutylammonium bromide, add into a three-necked flask protected by nitrogen, stir until the system is dissolved, raise the temperature of the three-necked flask to 75° C., keep warm for 7 hours, lower the temperature of the three-necked flask to room temperature, filter, wash the filter cake with 50 vol% ethanol aqueous solution three times and then dry it, transfer the filter cake to a drying oven at 80° C., and vacuum dry it to constant weight to obtain epoxidized cellulose.

[0081] S4. Preparation of polylactic acid composite yarn

[0082] Mix zinc stearate, polyethylene glycol 800, tert-butyl hydroxyphenyl ether, and acetyl tributyl citrate in a weight ratio of 2:1:2:5 to obtain an additive, which is set aside;

[0083] Weigh by weight: 80 parts of hybrid polylactic acid, 18 parts of polyglycolic acid, 32 parts of modified straw powder, 25 parts of epoxidized cellulose and 8 parts of additives, mix and add to a twin-screw extruder, the temperatures of the 6 temperature zones of the twin-screw extruder from the feed end to the discharge end are set to 230°C, 235°C, 235°C, 235°C, 235°C, and 240°C, respectively, the main shaft speed of the twin-screw extruder is 20r / min, and after melt-extrusion into thin strips by the twin-screw extruder, they are stretched while hot at 180°C to obtain polylactic acid composite filaments with a diameter of 5±0.5mm.

[0084] S5. Preparation of composite polylactic acid rope

[0085] Eight polylactic acid composite filaments are braided into multiple strands to obtain a composite polylactic acid binding rope.

[0086] Comparative Example 1

[0087] The difference between this comparative example and Example 3 is that in step S1, glycerol is not added.

[0088] Comparative Example 2

[0089] The difference between this comparative example and Example 3 is that the modified straw powder in step S4 is replaced by the activated straw powder in step S2.

[0090] Comparative Example 3

[0091] The difference between this comparative example and Example 3 is that the epoxidized cellulose in step S4 is replaced by hydroxymethyl cellulose in step S3.

[0092] Performance Test:

[0093] The average breaking strength and minimum breaking strength of the composite polylactic acid rope samples prepared in Examples 1-3 and Comparative Example 1-x were measured with reference to the standard GB / T 21328-2024 “General Requirements for Fiber Ropes”. The specific test results are shown in Table 1 below.

[0094] Table 1-Performance test data of samples

[0095]

[0096]

[0097] Data Analysis:

[0098] A comparative analysis of the data in Table 1 above shows that the average breaking strength of the composite polylactic acid rope prepared by the present invention reaches 286 kN, the minimum breaking strength reaches 269 kN, and the composite polylactic acid rope can be eaten and digested by herbivorous animals. The performance test data are all better than those of the comparative example, indicating that the present invention cooperates with hybrid polylactic acid, polyglycolic acid, modified straw powder, and epoxidized cellulose, melts and mixes, and then stretches to prepare polylactic acid composite filaments, which are then braided into multiple strands, which not only effectively improves the breaking strength of the rope, but also can be eaten and digested by herbivorous animals, thereby reducing the digestive burden on herbivorous animals.

[0099] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to only specific implementation methods. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing a composite polylactic acid tying rope that is edible and digestible for herbivorous animals, characterized in that: The following steps are involved: S1. Under the protection of inert gas, polyethylene glycol, lactide, glycerol, a catalyst and toluene are mixed, the temperature of the reaction system is raised to 70-80°C, the reaction is kept warm for 6-8h, and post-processed to obtain hybrid polylactic acid; S2, mixing hybrid polylactic acid, polyglycolic acid, modified straw powder, epoxidized cellulose and additives, adding the mixture into a twin-screw extruder, and melt-extruding the mixture into thin strips, and then stretching the strips while hot to obtain polylactic acid composite filaments with a diameter of 5±0.5 mm; S3, weaving 6-8 polylactic acid composite filaments into multiple strands to obtain a composite polylactic acid rope.

2. The method for preparing the edible and degradable composite polylactic acid tying rope for herbivorous animals according to claim 1, characterized in that: In step S1, the amount ratio of the polyethylene glycol, lactide, glycerol, catalyst and toluene is 4-5g:6-8g:0.8-1.2g:0.1g:50mL, the polyethylene glycol is polyethylene glycol 400, and the catalyst is stannous octoate. The post-treatment includes: after the reaction is completed, the reaction system is kept at 70-80°C, the low-boiling substances are removed under reduced pressure, the temperature of the reaction system is reduced to 50°C, acetone is added to the reaction system, and stirred until the system is dissolved. The temperature of the reaction system is reduced to room temperature, methanol is added to the reaction system, stirred and dispersed for 10-15min, filtered, the filter cake is washed with methanol 3 times and then dried, and the filter cake is transferred to a drying oven at a temperature of 50-60°C, and vacuum dried to constant weight to obtain hybrid polylactic acid.

3. The method for preparing the edible and degradable composite polylactic acid tying rope for herbivorous animals according to claim 1, characterized in that: In step S2, the weight ratio of the hybrid polylactic acid, polyglycolic acid, modified straw powder, epoxidized cellulose and additives is 70-80:15-18:28-32:23-25:6-8, the additives are composed of zinc stearate, polyethylene glycol 800, antioxidants and plasticizers in a weight ratio of 2:1:2:5, the antioxidant is any one of butylated hydroxybenzoate, butylated hydroxyanisole and tert-butylated hydroxyphenyl ether, the plasticizer is acetyl tributyl citrate, the temperatures of the six temperature sections of the twin-screw extruder from the feed end to the discharge end are 230°C, 235°C, 235°C, 235°C, 235°C and 240°C, respectively, the spindle speed of the twin-screw extruder is 18-20r / min, and the stretching temperature is 170-180°C.

4. The method for preparing the edible and degradable composite polylactic acid tying rope for herbivorous animals according to claim 1, characterized in that: The modified straw powder is obtained by processing the following steps: A1. Mix straw powder and deionized water, raise the temperature of the reaction system to 60-70°C, add hydrogen peroxide solution to the reaction system, keep the temperature for 2-3 hours, and post-treat to obtain activated straw powder; A2. Mix the activated straw powder, tannic acid, epoxidized soybean oil and dichloromethane, stir and disperse for 30-50 minutes at room temperature, increase the temperature of the reaction system by 50-60° C., reflux and separate to remove the solvent at room temperature, and post-treat to obtain modified straw powder.

5. The method for preparing the edible and degradable composite polylactic acid tying rope for herbivorous animals according to claim 4, characterized in that: In step A1, the amount ratio of the straw powder, deionized water and hydrogen peroxide solution is 1g:7mL:3mL, and the straw powder is composed of 100-mesh straw powder, 60-mesh straw powder and straw fiber in a weight ratio of 1:2:3; the mass fraction of the hydrogen peroxide solution is 7-9%, and the pH is 9. The post-treatment includes: after the reaction is completed, the temperature of the reaction system is lowered to room temperature, filtered, the filter cake is washed with purified water until it is neutral and then dried, and the filter cake is transferred to a drying oven at a temperature of 70-80°C, and vacuum dried to constant weight to obtain activated straw powder.

6. The method for preparing the edible and degradable composite polylactic acid tying rope for herbivorous animals according to claim 4, characterized in that: In step A2, the amount ratio of the activated straw powder, tannic acid, epoxidized soybean oil and dichloromethane is 7g:3g:1g:30mL, and the post-treatment includes: after the reaction is completed, the temperature of the reaction system is lowered to room temperature, the reaction system is transferred to a drying oven at a temperature of 70-80°C, and dried for 6-8h to obtain modified straw powder.

7. The method for preparing the edible and degradable composite polylactic acid tying rope for herbivorous animals according to claim 1, characterized in that: The epoxidized cellulose is obtained by processing the following steps: B1, mixing hydroxymethyl cellulose and sodium hydroxide solution, raising the temperature of the reaction system to 40-50°C, ultrasonically dispersing for 4-6 hours, and post-treating to obtain sodium hydroxymethyl cellulose; B2. Under the protection of inert gas, sodium hydroxymethyl cellulose, epichlorohydrin, sodium hydroxide and tetrabutylammonium bromide are mixed and stirred until the system is dissolved. The temperature of the reaction system is raised to 65-75°C, and the reaction is kept warm for 6-7 hours. After post-treatment, epoxidized cellulose is obtained.

8. The method for preparing the edible and degradable composite polylactic acid tying rope for herbivorous animals according to claim 7, characterized in that: In step B1, the dosage ratio of the hydroxymethyl cellulose and the sodium hydroxide solution is 1g:3mL, the concentration of the sodium hydroxide solution is 0.3-0.5mol / L, and the post-treatment includes: after the reaction is completed, the temperature of the reaction system is lowered to room temperature, anhydrous ethanol is added to the reaction system, stirred and dispersed for 20-30min, filtered, the filter cake is washed with anhydrous ethanol for 3 times and then dried, the filter cake is transferred to a drying oven at a temperature of 60-70°C, and vacuum dried to constant weight to obtain sodium hydroxymethyl cellulose.

9. The method for preparing the edible and digestible composite polylactic acid tying rope for herbivorous animals according to claim 7, characterized in that: In step B2, the amount ratio of sodium hydroxymethyl cellulose, epichlorohydrin, sodium hydroxide and tetrabutylammonium bromide is 5g:20mL:2g:0.3g, and the post-treatment includes: after the reaction is completed, the temperature of the reaction system is lowered to room temperature, filtered, the filter cake is washed three times with 50vol% ethanol aqueous solution and then dried, the filter cake is transferred to a drying oven at a temperature of 70-80°C, and vacuum dried to constant weight to obtain epoxidized cellulose.

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