Environment-friendly degradable plastic packaging bag and preparation method thereof

Abstract

The invention discloses an environment-friendly degradable plastic packaging bag and a preparation method thereof, belongs to the technical field of packaging bag preparation, and is used for solving the technical problem that the degradation capability and the mechanical property of an environment-friendly packaging bag in the prior art need to be further improved. According to the invention, the prepared carbonic acid bridged compact polyester is used as a main body skeleton to provide strength and film-forming property, silica acetal hybrid polysaccharide is introduced to form a compact and complex diffusion path inside and reduce gas and moisture permeation, and then active side chain polyamino acid is added to adjust interfacial compatibility and enhance structural stability, so that the film-forming property is improved. Through reasonable combination of the three components, the environment-friendly packaging bag keeps high tensile strength and tearing strength, meanwhile, the barrier property is remarkably improved, and gradual complete degradation is achieved in compost and soil environments.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of packaging bag preparation, in particular to an environment-friendly degradable plastic packaging bag and a preparation method thereof. BACKGROUND

[0002] At present, the development of environment-friendly packaging bags mainly focuses on degradation performance and mechanical strength. In terms of degradation ability, early polylactic acid, polybutylene adipate terephthalate and other materials can be quickly decomposed under industrial composting conditions, but the degradation rate in natural soil environment is generally slow, and it often takes months to years to achieve significant decomposition. With the advancement of research, some modified polyesters and composite materials have improved microbial recognition and hydrolysis sensitivity, and can exhibit better biodegradation rate in different environments.

[0003] In terms of mechanical strength, traditional fully biodegradable polymers generally have high brittleness and insufficient toughness, which makes it difficult to meet the actual packaging requirements in terms of longitudinal and transverse tensile strength and tear strength. In recent years, through molecular structure design and composite reinforcement means, the breaking strength, tear strength and use durability of environment-friendly packaging bags have been gradually improved, so that they can meet the degradation requirements while having more extensive application conditions.

[0004] At present, the preparation process of environment-friendly packaging bags still has some deficiencies in the application process: Firstly, the film made of single polyester substrate has certain degradability, but the mechanical strength is insufficient, which can easily cause rupture or tearing during use and transportation, limiting its application in high-strength packaging fields. Secondly, some materials improve the strength through modification, but it often leads to dense molecular chains, which blocks the diffusion of water and gas and inhibits microbial action, causing the degradation speed in soil environment to slow down significantly, showing the problems of difficult to decompose in the early stage and long-term residue; Thirdly, the existing process generally has short boards in barrier performance, with high water vapor transmission rate and oxygen transmission rate, which is difficult to meet the preservation needs of sensitive products such as food, medicine and other products to moisture and oxygen. Overall, how to maintain high mechanical properties and barrier properties while considering effective degradation under composting and soil conditions is a problem that existing technology has not completely solved. SUMMARY

[0005] The present application relates to the technical field of packaging bag preparation, in particular to an environment-friendly degradable plastic packaging bag and a preparation method thereof.

[0006] The application can be achieved by the following technical scheme: an environment-friendly degradable plastic packaging bag, comprising the following raw material components in parts by weight: 50-55 parts of carbonic acid bridged compact polyester, 20-25 parts of siloxane acetal hybrid polysaccharide, 20-25 parts of active side chain polyamino acid, and 4-6 parts of auxiliary materials; Further, the auxiliary materials are a heat stabilizer, a plasticizer and a lubricant mixed in a weight ratio of 0.3-0.5:3.5-5.0:0.2-0.5, wherein the heat stabilizer is one or both of calcium stearate and dibutyltin dilaurate; the plasticizer is one or both of dibutyl phthalate and dioctyl terephthalate; and the lubricant is one or both of zinc stearate and polyethylene wax.

[0007] Further, the preparation method of the carbonic acid bridged compact polyester comprises the following steps: adding star-shaped lactic acid ester grafting body, dimethyl carbonate and tetrabutyl titanate into a reaction kettle, heating to 150-170 DEG C under nitrogen protection, and stirring for 3-5 h, and then post-treating to obtain the carbonic acid bridged compact polyester.

[0008] The reaction principle for preparing the carbonic acid bridged compact polyester is as follows: The hydroxyl groups on the surface of the star-shaped lactic acid ester grafting body and the carbonate groups in the dimethyl carbonate are subjected to nucleophilic substitution under the catalysis of tetrabutyl titanate, gradually generating new -O-CO-O- carbonate bridges and releasing methanol byproducts, and with the progress of the reaction, different molecules are crosslinked and connected through the carbonate bonds, so that the original star-shaped grafting structure evolves into a more compact three-dimensional polyester network structure. The core of the principle lies in using dimethyl carbonate as a bridging agent to realize the crosslinking and densification of polyester molecules through ester exchange polycondensation reaction, and finally preparing the carbonic acid bridged compact polyester.

[0009] Further, in the process of preparing the carbonic acid bridged compact polyester, the amount ratio of the star-shaped lactic acid ester grafting body, dimethyl carbonate and tetrabutyl titanate is 1 g:1.0-1.5 g:0.03-0.05 g, and the post-treatment comprises the following steps: after the reaction is completed, the temperature of the reaction kettle is reduced to room temperature to remove the materials, and then the materials are washed with anhydrous ethanol for 3 times and transferred to a vacuum drying oven, and then vacuum dried at 80 DEG C until the weight is constant to obtain the carbonic acid bridged compact polyester.

[0010] Further, the preparation method of the star-shaped lactic acid ester grafting body comprises the following steps: A1, citric acid, isosorbide, 1,4-butanediol and tetrabutyl titanate are added into a reaction kettle and stirred, the reaction kettle is heated to 180-200 DEG C under nitrogen protection, and then reduced to 200-300 Pa, and then stirred for 4-6 h, and then post-treated to obtain a polyhydroxyl highly branched polyester core; A2, the polyhydroxy highly branched polyester core, lactide and stannous octoate are added into a reaction kettle, and the temperature is raised to 140-160℃ under nitrogen protection, and the temperature is kept for 8-10h, and the star lactate graft body is obtained after post-treatment.

[0011] The reaction principle for preparing the star lactate graft body is as follows: Firstly, citric acid is used as a multifunctional carboxylic acid, and isosorbide and 1,4-butanediol are used as polyhydroxy alcohol monomers, and a polycondensation reaction is carried out under the catalysis of titanate, and -COO- bonds are continuously generated between carboxyl and hydroxyl through esterification reaction, and a highly branched polyester core with multiple branching points and rich terminal hydroxyl is formed, wherein the citric acid molecules provide a tri-carboxyl structure, so that a large number of branching points appear in the network, isosorbide as a rigid diol gives the skeleton a certain spatial structure stability, and 1,4-butanediol plays a flexible adjusting role, and the polycondensation reaction is carried out under reduced pressure, which is helpful for the timely removal of by-product water and promotes the reaction to convert to high molecular compounds; On this basis, the obtained polyhydroxy highly branched polyester core is used as a multifunctional initiation center, and lactide is introduced for ring-opening polymerization, and under the catalysis of stannous octoate, the ester bond in the lactide ring is activated, and cationic or coordination insertion type ring-opening reaction occurs, and the terminal hydroxyl of the polyester core serves as an active initiation point, and is connected with the new chain segments generated by the ring-opening of lactide, so that the poly-lactic acid branches are gradually extended on each hydroxyl site, and finally a star-shaped graft structure is formed in space, with the highly branched polyester core as the center and a plurality of poly-lactic acid arm chains as the periphery, and finally the star lactate graft body is prepared.

[0012] Further, in step A1, the amount ratio of the citric acid, isosorbide, 1,4-butanediol and tetrabutyl titanate is 1g:0.8-1.2g:2.0-2.5g:0.05g, and the post-treatment includes: after the reaction is completed, the material is removed when the temperature of the reaction kettle is reduced to room temperature, and then washed with anhydrous ethanol for 3 times, and then transferred to a vacuum drying box, and dried at 80℃ under vacuum until the weight is constant, to obtain the polyhydroxy highly branched polyester core; Further, in step A2, the amount ratio of the polyhydroxy highly branched polyester core, lactide and stannous octoate is 1g:3-6g:0.01g, and the post-treatment includes: after the reaction is completed, the material is removed when the temperature of the reaction kettle is reduced to room temperature, and then washed with anhydrous ethanol for 3 times, and then transferred to a vacuum drying box, and dried at 80℃ under vacuum until the weight is constant, to obtain the star lactate graft body.

[0013] Further, the preparation method of the siloxane acetal hybrid polysaccharide comprises the following steps: B1, starch and deionized water are added to the reaction kettle and stirred, 1M hydrochloric acid aqueous solution is used to adjust the pH of the reaction system to 3-4, and then glyoxal is added, the temperature of the reaction kettle is raised to 40-60℃, and the reaction is stirred for 6-8h, and then the acetal polysaccharide cross-linked skeleton is obtained by post-treatment; B2, the acetal polysaccharide cross-linked skeleton, 3-aminopropyl triethoxysilane, anhydrous ethanol and deionized water are added to the reaction kettle, the temperature of the reaction kettle is raised to 40-60℃ under nitrogen protection, and the reaction is carried out for 6-8h, and then the silicon-oxygen acetal hybrid polysaccharide is obtained by post-treatment.

[0014] The reaction principle for preparing the silicon-oxygen acetal hybrid polysaccharide is as follows: First, under acidic conditions, the hydroxyl groups in the starch can react with glyoxal to form acetal, and glyoxal, as a bifunctional cross-linking agent, can react with the hydroxyl groups on the polysaccharide chain to form stable -O-CH2-CH2-O- acetal bridge bonds, which introduces covalent cross-linking points between molecules, thereby forming an acetal polysaccharide cross-linked skeleton with a certain spatial network structure, significantly improving the structural stability and hydrolysis resistance of the polysaccharide; On this basis, 3-aminopropyl triethoxysilane is introduced, which has both organic amine groups and hydrolyzable triethoxysilane groups in its molecular structure. In the reaction, the ethoxyl groups of the silane are hydrolyzed to Si-OH in the presence of water, and then form Si-O-Si bonds through condensation reaction, and further bond with the hydroxyl groups on the polysaccharide molecules through Si-O-C bond, so that the polysaccharide skeleton and the silicon-oxygen network are coupled through covalent bonds and hydrogen bonds in a dual manner, forming an organic-inorganic hybrid cross-linked system, and finally obtaining the silicon-oxygen acetal hybrid polysaccharide.

[0015] Further, in step B1, the amount ratio of starch, deionized water and glyoxal is 1g:50mL:1.0-1.5g, and the post-treatment includes: after the reaction is completed, the reaction solution is filtered to collect the filter cake, which is then washed with deionized water and anhydrous ethanol for 3 times each, and then transferred to a vacuum drying oven for drying at 60℃ until the weight is constant, to obtain the acetal polysaccharide cross-linked skeleton; Further, in step B2, the amount ratio of the acetal polysaccharide cross-linked skeleton, 3-aminopropyl triethoxysilane, anhydrous ethanol and deionized water is 1g:1.0-1.2g:80mL:20mL, and the post-treatment includes: collecting the product by filtration, and then placing the product in a curing environment at 40-60℃ and 60-80% humidity for 16h, and then drying at 60℃ under vacuum until the weight is constant, to obtain the silicon-oxygen acetal hybrid polysaccharide.

[0016] Further, the preparation method of the active side-chain polyamino acid comprises the following steps: C1, 5-benzyl glutamate and dioxane are added to the reaction kettle, n-butylamine is added under nitrogen protection, and stirring is carried out at room temperature for 24h, and then the protected polyglutamic acid is obtained by post-treatment. C2, the protective group polyglutamic acid, palladium carbon and tetrahydrofuran are added into the reaction kettle, after hydrogen is introduced, the temperature of the reaction kettle is increased to 35-40℃, after incubation for 6-8h, epichlorohydrin is added and the temperature of the reaction kettle is increased to 40-50℃, incubation stirring for 4-6h, and then the active side chain polyamino acid is obtained by post-treatment.

[0017] The reaction principle for preparing the active side chain polyamino acid is as follows: Firstly, 5-benzyl ester glutamic acid N-carboxyanhydride is a typical N-carboxyanhydride monomer, and its cyclic structure can undergo ring-opening polymerization in the presence of a primary amine initiator. In the reaction, the amino group attacks the carbonyl carbon atom of the N-carboxyanhydride monomer ring, causing the anhydride ring to break and a new amino end to be generated, thereby continuously initiating the next monomer molecule, gradually forming a high molecular chain. Through this process, the main chain is polyglutamic acid, and the benzyl protection exists on the side chain carboxyl, thereby generating a protective group polyglutamic acid; Subsequently, the palladium carbon catalytic hydrogenation reaction can selectively remove the benzyl protecting group on the glutamic acid side chain. In the hydrogenation process, the benzyloxy group is hydrogenated to release toluene or benzyl alcohol as a byproduct, while exposing the originally protected -COOH side chain functional group. This process realizes the conversion from the protective group polyglutamic acid to poly-L-glutamic acid, giving the polymer side chain good reactivity; On this basis, epichlorohydrin is introduced, and the side chain carboxyl acts as a nucleophile to attack the epoxide ring, generating an ester bond and simultaneously introducing a new hydroxyl or chloro functional group on the side chain. This reaction not only realizes the chemical activation of the side chain, but also may form intermolecular crosslinking to some extent, thereby giving the polymer higher reactivity and functional expansion ability, and finally preparing the active side chain polyamino acid.

[0018] Further, in step C1, the amount ratio of 5-benzyl ester glutamic acid, dioxane and n-butylamine is 1g:40-50mL:0.05-0.06g, and the post-treatment includes: after the reaction is completed, the reaction liquid is poured into 5 times the volume of anhydrous methanol, after the precipitation is completely precipitated, the filter cake is collected by suction filtration, and then the filter cake is washed with deionized water and anhydrous ethanol for 3 times, and then transferred to a vacuum drying oven, dried at 60℃ under vacuum until constant weight, to obtain the acetal polysaccharide cross-linked skeleton, and the protective group polyglutamic acid is obtained. Further, in step C2, the amount ratio of protective group polyglutamic acid, palladium carbon, tetrahydrofuran and epichlorohydrin is 1g:0.08g:50mL:0.1-0.2g, and the post-treatment includes: after the reaction is completed, the reaction liquid is poured into 5 times the volume of anhydrous ether, after the precipitation is completely precipitated, the filter cake is collected by suction filtration, and then the filter cake is washed with deionized water and anhydrous ethanol for 3 times, and then transferred to a vacuum drying oven, dried at 60℃ under vacuum until constant weight, to obtain the acetal polysaccharide cross-linked skeleton, and the active side chain polyamino acid is obtained.

[0019] The application further discloses a preparation method of the environment-friendly degradable plastic packaging bag.

[0020] The application has the following advantages: 1. The carbonic acid bridged compact polyester prepared by the application forms a compact three-dimensional network structure through carbonate bond crosslinking, so that stress can be uniformly distributed in the stress process, thereby significantly enhancing the overall carrying capacity and toughness. The silicon-oxygen-acetal hybrid polysaccharide introduces Si-O-Si and Si-O-C bonds between molecules to build a rigid skeleton structure, effectively hinders the initiation and expansion of cracks, and provides excellent tear resistance for the film. Meanwhile, the active side chain polyamino acid contains polar groups such as carboxyl and hydroxyl groups, which can form hydrogen bonds or ester bonds with the polyester and polysaccharide, significantly improving the interfacial bonding strength, reducing the accumulation of microcracks and the risk of interfacial debonding. Ultimately, through the combined action of chemical crosslinking, hydrogen bonding and physical entanglement between multiple components, the film is endowed with a balanced structure of rigidity and toughness, so that it is superior to conventional degradable films in terms of longitudinal and transverse tensile strength and right-angle tear strength, and exhibits excellent mechanical stability and application reliability.

[0021] 2. The carbonic acid bridged compact polyester prepared by the application forms a compact three-dimensional network structure between molecules, effectively reducing free volume and penetration channels, so that the diffusion of oxygen and water molecules is limited. The silicon-oxygen-acetal hybrid polysaccharide builds an inorganic silicon-oxygen skeleton in the system to form a "labyrinth effect", greatly extending the penetration path of small molecules and further improving the barrier ability of gas and water vapor. At the same time, the active side chain polyamino acid contains a large number of polar groups, which can reversibly combine with small penetrating molecules through hydrogen bonding, thereby playing the role of adsorption and diffusion delay. Ultimately, through the combined action of chemical crosslinking, hydrogen bonding and structure complementation between the three, an organic-inorganic hybrid multiple barrier system is built, which not only significantly reduces the oxygen transmission rate, but also effectively inhibits the water vapor transmission rate.

[0022] 3、 In the compost environment, the carbonic acid bridging dense polyester molecular chain rapidly hydrolyzes and ester bond breaks under the action of high temperature, high humidity and microorganisms, forming low molecular weight fragments, which are easily further utilized by microorganisms; the siloxane acetal hybrid polysaccharide gradually breaks under acidic and enzymatic conditions, while releasing low molecular polysaccharides that can promote microbial growth, further accelerating the overall degradation process; the active side chain polyamino acid realizes a high decomposition rate in a relatively short time because its polar side group is easily recognized and metabolized by compost bacteria; in the natural soil environment, although the temperature and humidity are lower, the above multi-component material can still gradually undergo hydrolysis, oxidation and biological metabolism reaction under the premise of good interfacial bonding, showing a slow first and then gradually accelerated degradation trend. The synergistic effect between the three in terms of chemical structure and biocompatibility enables the film to achieve high disintegration rate and high biodegradation rate in a short period under composting conditions, and also enables the film to achieve complete degradation in a long period under soil conditions, taking into account both rapid treatment and environmental adaptability. DETAILED DESCRIPTION

[0023] The technical solutions of the present application will be clearly and completely described below in combination with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0024] In the present application, the starch is purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., with the product code S104454; the starch is purchased from Shanghai Macklin Biochemical Technology Co., Ltd., with the product code P821217; the calcium stearate is purchased from Shanghai Macklin Biochemical Technology Co., Ltd., with the product code C805417; and the polyethylene wax is purchased from Shanghai Macklin Biochemical Technology Co., Ltd., with the product code P903666.

[0025] Embodiment 1 The present embodiment provides a preparation method of carbonic acid bridging dense polyester, comprising the following steps: Step I, preparation of a polyhydroxyl highly branched polyester core Weigh 10.0 g of citric acid, 8.0 g of isosorbide, 20.0 g of 1,4-butanediol and 0.5 g of tetrabutyl titanate into a reaction kettle and stir. After the reaction kettle is heated to 180℃ under nitrogen protection, it is reduced to 200 Pa, and then kept stirring for 4 h. After the reaction is completed, the material is removed when the temperature of the reaction kettle is reduced to room temperature, washed with anhydrous ethanol for 3 times, and then transferred to a vacuum drying oven for drying at 80℃ until the weight is constant. Thus, a polyhydroxyl highly branched polyester core is obtained.

[0026] Step II, preparation of a star-shaped lactic acid ester grafting body Weighing: 10.0 g of the star-shaped lactic acid ester grafting body, 15.0 g of dimethyl carbonate and 0.5 g of tetrabutyl titanate are added into a reaction kettle, and the temperature is raised to 170°C under nitrogen protection, and stirring is performed for 5 h. After the reaction is completed, the materials are removed after the temperature of the reaction kettle is reduced to room temperature, washed with anhydrous ethanol for 3 times, and then transferred to a vacuum drying box for drying at 80°C until the weight is constant, to obtain the carbonic acid bridged dense polyester.

[0027] Step III, preparation of carbonic acid bridged dense polyester Weighing: 10.0 g of the star-shaped lactic acid ester grafting body, 15.0 g of dimethyl carbonate and 0.5 g of tetrabutyl titanate are added into a reaction kettle, and the temperature is raised to 170°C under nitrogen protection, and stirring is performed for 5 h. After the reaction is completed, the materials are removed after the temperature of the reaction kettle is reduced to room temperature, washed with anhydrous ethanol for 3 times, and then transferred to a vacuum drying box for drying at 80°C until the weight is constant, to obtain the carbonic acid bridged dense polyester.

[0028] Example 2 The embodiment provides a preparation method of carbonic acid bridged dense polyester, which comprises the following steps. Step I, preparation of a multi-hydroxyl highly branched polyester core Weighing: 10.0 g of the star-shaped lactic acid ester grafting body, 15.0 g of dimethyl carbonate and 0.5 g of tetrabutyl titanate are added into a reaction kettle, and the temperature is raised to 170°C under nitrogen protection, and stirring is performed for 5 h. After the reaction is completed, the materials are removed after the temperature of the reaction kettle is reduced to room temperature, washed with anhydrous ethanol for 3 times, and then transferred to a vacuum drying box for drying at 80°C until the weight is constant, to obtain the carbonic acid bridged dense polyester.

[0029] Step II, preparation of a star-shaped lactic acid ester grafting body Weighing: 10.0 g of the star-shaped lactic acid ester grafting body, 15.0 g of dimethyl carbonate and 0.5 g of tetrabutyl titanate are added into a reaction kettle, and the temperature is raised to 170°C under nitrogen protection, and stirring is performed for 5 h. After the reaction is completed, the materials are removed after the temperature of the reaction kettle is reduced to room temperature, washed with anhydrous ethanol for 3 times, and then transferred to a vacuum drying box for drying at 80°C until the weight is constant, to obtain the carbonic acid bridged dense polyester.

[0030] Step III, preparation of carbonic acid bridged dense polyester Weighing: 10.0 g of the star-shaped lactic acid ester grafting body, 15.0 g of dimethyl carbonate and 0.5 g of tetrabutyl titanate are added into a reaction kettle, and the temperature is raised to 170°C under nitrogen protection, and stirring is performed for 5 h. After the reaction is completed, the materials are removed after the temperature of the reaction kettle is reduced to room temperature, washed with anhydrous ethanol for 3 times, and then transferred to a vacuum drying box for drying at 80°C until the weight is constant, to obtain the carbonic acid bridged dense polyester.

[0031] Example 3 The embodiment provides a preparation method of carbonic acid bridged compact polyester, which comprises the following steps: Step I, preparation of a polyhydroxyl highly branched polyester core Take 10.0 g of citric acid, 10.0 g of isosorbide, 24.0 g of 1,4-butanediol and 0.5 g of tetrabutyl titanate into a reaction kettle and stir, then the reaction kettle is heated to 190 DEG C under nitrogen protection, and then reduced pressure is applied to 250 Pa, and the reaction is stirred for 5 h; after the reaction is completed, the material is removed when the temperature of the reaction kettle is reduced to room temperature, and then the material is washed with anhydrous ethanol for three times and then transferred to a vacuum drying box, and vacuum drying is carriedated at 80 DEG C until the weight is constant, so as to obtain the polyhydroxyl highly branched polyester core.

[0032] Step II, preparation of a star-shaped lactic acid ester grafting body Take 10.0 g of the polyhydroxyl highly branched polyester core, 40.0 g of lactic acid lactide and 0.1 g of stannous octoate into a reaction kettle, and then the reaction kettle is heated to 150 DEG C under nitrogen protection, and then the reaction is stirred for 9 h; after the reaction is completed, the material is removed when the temperature of the reaction kettle is reduced to room temperature, and then the material is washed with anhydrous ethanol for three times and then transferred to a vacuum drying box, and vacuum drying is carriedated at 80 DEG C until the weight is constant, so as to obtain the star-shaped lactic acid ester grafting body.

[0033] Step III, preparation of carbonic acid bridged compact polyester Take 10.0 g of the star-shaped lactic acid ester grafting body, 12.0 g of dimethyl carbonate and 0.4 g of tetrabutyl titanate into a reaction kettle, and then the reaction kettle is heated to 160 DEG C under nitrogen protection, and then the reaction is stirred for 4 h; after the reaction is completed, the material is removed when the temperature of the reaction kettle is reduced to room temperature, and then the material is washed with anhydrous ethanol for three times and then transferred to a vacuum drying box, and vacuum drying is carriedated at 80 DEG C until the weight is constant, so as to obtain the carbonic acid bridged compact polyester.

[0034] Embodiment 4 The embodiment provides a preparation method of siloxane acetal hybrid polysaccharide, which comprises the following steps: Step 1, preparation of acetal polysaccharide crosslinked skeleton Take 10.0 g of starch and 500.0 mL of deionized water into a reaction kettle and stir, then the pH of the reaction system is adjusted to 3 by using 1M hydrochloric acid aqueous solution, and then 10.0 g of glyoxal is added; the temperature of the reaction kettle is increased to 40 DEG C, and then the reaction is stirred for 6 h; after the reaction is completed, the reaction liquid is collected by filtration, and then the filter cake is washed with deionized water and anhydrous ethanol for three times respectively, and then the filter cake is transferred to a vacuum drying box and vacuum dried at 60 DEG C until the weight is constant, so as to obtain the acetal polysaccharide crosslinked skeleton.

[0035] Step 2, preparation of siloxane acetal hybrid polysaccharide Take: 10.0 g of acetal polysaccharide cross-linked skeleton, 12.0 g of 3- aminopropyl triethoxysilane, 800.0 mL of anhydrous ethanol and 200.0 mL of deionized water into the reaction kettle, and the temperature of the reaction kettle is raised to 40℃ under nitrogen protection, and after 6h of incubation, the product is collected by suction filtration, and the product is placed in a 40℃, humidity 60% condition for 16h, after the completion of the curing, vacuum drying at 60℃ to constant weight, to obtain a siloxane acetal hybrid polysaccharide.

[0036] Example 5 The present embodiment provides a method for preparing a siloxane acetal hybrid polysaccharide, comprising the following steps: Step ①, preparation of acetal polysaccharide cross-linked skeleton Take: 10.0 g of starch and 500.0 mL of deionized water into the reaction kettle, and stir, adjust the pH of the reaction system to 4 using 1M hydrochloric acid solution, and add 15.0 g of glyoxal, then raise the temperature of the reaction kettle to 60℃, and incubate for 8h, after the completion of the reaction, collect the filter cake by suction filtration, wash the filter cake with deionized water and anhydrous ethanol for 3 times respectively, and then transfer to a vacuum drying oven, and vacuum dry at 60℃ to constant weight, to obtain an acetal polysaccharide cross-linked skeleton.

[0037] Step ②, preparation of siloxane acetal hybrid polysaccharide Take: 10.0 g of acetal polysaccharide cross-linked skeleton, 12.0 g of 3- aminopropyl triethoxysilane, 800.0 mL of anhydrous ethanol and 200.0 mL of deionized water into the reaction kettle, and the temperature of the reaction kettle is raised to 40℃ under nitrogen protection, and after 6h of incubation, the product is collected by suction filtration, and the product is placed in a 40℃, humidity 60% condition for 16h, after the completion of the curing, vacuum drying at 60℃ to constant weight, to obtain a siloxane acetal hybrid polysaccharide.

[0038] Example 6 The present embodiment provides a method for preparing a siloxane acetal hybrid polysaccharide, comprising the following steps: Step ①, preparation of acetal polysaccharide cross-linked skeleton Take: 10.0 g of starch and 500.0 mL of deionized water into the reaction kettle, and stir, adjust the pH of the reaction system to 4 using 1M hydrochloric acid solution, and add 15.0 g of glyoxal, then raise the temperature of the reaction kettle to 60℃, and incubate for 8h, after the completion of the reaction, collect the filter cake by suction filtration, wash the filter cake with deionized water and anhydrous ethanol for 3 times respectively, and then transfer to a vacuum drying oven, and vacuum dry at 60℃ to constant weight, to obtain an acetal polysaccharide cross-linked skeleton.

[0039] Step ②, preparation of siloxane acetal hybrid polysaccharide Take: 10.0 g of acetal polysaccharide cross-linked skeleton, 12.0 g of 3-aminopropyl triethoxysilane, 800.0 mL of anhydrous ethanol and 200.0 mL of deionized water into the reaction kettle, and the temperature of the reaction kettle is raised to 45℃ under nitrogen protection, and after 7h of incubation, the product is collected by suction filtration, and the product is placed in a 50℃, humidity 70% condition for 16h, after the completion of the curing, vacuum drying at 60℃ to constant weight, to obtain a silicon-oxygen acetal hybrid polysaccharide.

[0040] Example 7 The present embodiment provides a preparation method of an environmentally friendly degradable plastic packaging bag, comprising the following steps: Step one, preparation of protecting group polyglutamic acid Take: 10.0 g of 5-benzyl glutamate and 400.0 mL of dioxane into the reaction kettle, and 0.5 g of n-butylamine is added under nitrogen protection, and stirred at room temperature for 24 h, after the reaction is completed, the reaction solution is poured into 5 times the volume of anhydrous methanol, and after the precipitation is completed, the filter cake is collected by suction filtration, and then washed with deionized water and anhydrous ethanol for 3 times respectively, and then transferred to a vacuum drying oven, and dried at 60℃ under vacuum to constant weight, to obtain an acetal polysaccharide cross-linked skeleton, and obtain a protecting group polyglutamic acid.

[0041] Step two, preparation of active side chain polyamino acid Take: 10.0 g of protecting group polyglutamic acid, 0.8 g of palladium-carbon and 500.0 mL of tetrahydrofuran into the reaction kettle, and after hydrogen is introduced, the temperature of the reaction kettle is raised to 35℃, and after 6h of incubation, 1.0 g of epichlorohydrin is added and the temperature of the reaction kettle is raised to 40℃, and after 4h of incubation and stirring, the reaction is completed, the reaction solution is poured into 5 times the volume of anhydrous ether, and after the precipitation is completed, the filter cake is collected by suction filtration, and then washed with deionized water and anhydrous ethanol for 3 times respectively, and then transferred to a vacuum drying oven, and dried at 60℃ under vacuum to constant weight, to obtain an acetal polysaccharide cross-linked skeleton, and obtain an active side chain polyamino acid.

[0042] Step three, preparation of environmentally friendly packaging bag Mix calcium stearate, dioctyl terephthalate and polyethylene wax according to the weight ratio of 0.3:3.5:0.2, and collect for standby, to obtain an auxiliary material; According to the weight part, take: 50 parts of carbonic acid bridged dense polyester prepared in example 1, 20 parts of silicon-oxygen acetal hybrid polysaccharide prepared in example 4, 20 parts of active side chain polyamino acid and 4 parts of auxiliary material into the melt extruder, melt blend and granulation at 180℃, and then the granules are formed by casting process to obtain a primary film with a thickness of 50μm, and the primary film is cured at 40℃, humidity 60% for 16h, and then the environmentally friendly packaging bag is processed according to the specification.

[0043] Example 8 The embodiment provides a preparation method of an environment-friendly degradable plastic packaging bag, and comprises the following steps: Step one, preparation of a protected polyglutamic acid Take 10.0 g of 5-benzyl ester glutamic acid and 500.0 mL of dioxane, and add them into a reaction kettle, then add 0.6 g of n-butylamine under the protection of nitrogen, and stir at room temperature for 24 hours, after the reaction is completed, pour the reaction liquid into 5 times the volume of anhydrous methanol, and after the precipitation is completely separated out, collect the filter cake by suction filtration, wash the filter cake with deionized water and anhydrous ethanol for three times respectively, and then transfer the filter cake to a vacuum drying box, and vacuum dry at 60 DEG C until the weight is constant, so as to obtain an acetal polysaccharide cross-linked skeleton, and obtain the protected polyglutamic acid.

[0044] Step two, preparation of an active side chain polyamino acid Take 10.0 g of the protected polyglutamic acid, 0.8 g of palladium-carbon and 500.0 mL of tetrahydrofuran, and add them into a reaction kettle, then increase the temperature of the reaction kettle to 40 DEG C after hydrogen is introduced, and keep the temperature for 8 hours, then add 2.0 g of epichlorohydrin and increase the temperature of the reaction kettle to 50 DEG C, and keep stirring for 6 hours, after the reaction is completed, pour the reaction liquid into 5 times the volume of anhydrous diethyl ether, and after the precipitation is completely separated out, collect the filter cake by suction filtration, wash the filter cake with deionized water and anhydrous ethanol for three times respectively, and then transfer the filter cake to a vacuum drying box, and vacuum dry at 60 DEG C until the weight is constant, so as to obtain an acetal polysaccharide cross-linked skeleton, and obtain the active side chain polyamino acid.

[0045] Step three, preparation of an environment-friendly packaging bag Mix calcium stearate, dioctyl terephthalate and polyethylene wax according to a weight ratio of 0.5:5.0:0.2, and collect the mixture for standby, so as to obtain an auxiliary material; According to weight parts, take 55 parts of the carbonic acid bridged dense polyester prepared in example 2, 25 parts of the siloxane acetal hybrid polysaccharide prepared in example 5, 25 parts of the active side chain polyamino acid and 6 parts of the auxiliary material, and add them into a melt extruder, so as to be melt blended and granulated at 200 DEG C, then the granules are formed through a flow casting process, so as to obtain a preliminary film with a thickness of 50 microns, and after the preliminary film is maintained at 55 DEG C and humidity of 75% for 16 hours, the environment-friendly packaging bag is obtained through specification processing.

[0046] Example 9 The embodiment provides a preparation method of an environment-friendly degradable plastic packaging bag, and comprises the following steps: Step one, preparation of a protected polyglutamic acid Take: 10.0 g of 5-benzyl ester glutamic acid and 450.0 mL of dioxane into the reaction kettle, under the protection of nitrogen, add 0.6 g of n-butylamine, and stir at room temperature for 24 h, after the reaction is completed, pour the reaction liquid into 5 times the volume of anhydrous methanol, after the precipitation is completely precipitated, collect the filter cake by suction filtration, wash the filter cake with deionized water and anhydrous ethanol for 3 times respectively, and then transfer to a vacuum drying oven, vacuum drying at 60℃ until constant weight, to obtain the acetal polysaccharide cross-linked skeleton, and obtain the protected polyglutamic acid.

[0047] Step two, preparation of active side chain polyamino acid Take: 10.0 g of 5-benzyl ester glutamic acid and 450.0 mL of dioxane into the reaction kettle, under the protection of nitrogen, add 0.6 g of n-butylamine, and stir at room temperature for 24 h, after the reaction is completed, pour the reaction liquid into 5 times the volume of anhydrous methanol, after the precipitation is completely precipitated, collect the filter cake by suction filtration, wash the filter cake with deionized water and anhydrous ethanol for 3 times respectively, and then transfer to a vacuum drying oven, vacuum drying at 60℃ until constant weight, to obtain the acetal polysaccharide cross-linked skeleton, and obtain the protected polyglutamic acid.

[0048] Step three, preparation of environment-friendly packaging bag Mix calcium stearate, dioctyl terephthalate and polyethylene wax according to the weight ratio of 0.4:3.7.0:0.3, collect and reserve, to obtain the auxiliary material; According to the weight part, take: 54 parts of carbonic acid bridged dense polyester prepared in example 3, 24 parts of siloxane acetal hybrid polysaccharide prepared in example 6, 24 parts of active side chain polyamino acid and 5 parts of auxiliary material into the melt extruder, melt blending and granulation at 190℃, then the granules are formed by casting process, to obtain the initial film with a thickness of 50μm, and the initial film is cured at 50℃ and humidity of 70% for 16h, then the environment-friendly packaging bag is processed according to the specification.

[0049] Comparative example 1 The difference between this comparative example and example 9 is that the siloxane acetal hybrid polysaccharide is not used in step three.

[0050] Comparative example 2 The difference between this comparative example and example 9 is that the carbonic acid bridged dense polyester used in step three cancels step III in the preparation process.

[0051] Comparative example 3 The difference between this comparative example and example 9 is that the active side chain polyamino acid is not used in step three.

[0052] Performance test: The breaking force, right-angle tear strength, water vapor transmission rate and oxygen transmission rate of the environmentally friendly packaging bags prepared from Examples 7-9 and Comparative Examples 1-3 were tested according to the standard GB / T 28117-2011 "Multilayer co-extrusion film and bag for food packaging", and the specific data are shown in Table 1. The disintegration rate under industrial composting conditions for 12 weeks and the biodegradation rate for 180 days of the packaging bag samples prepared from Examples 7-9 and Comparative Examples 1-3, and the biodegradation rate under soil conditions for 180 days, 1 year and 2 years were tested according to the standard GB / T 41010-2021 "Biodegradable plastics and products degradation performance and identification requirements", and the specific data are shown in Table 2. Table 1 - Performance test data table of each sample

[0053] Table 2 - Biodegradation performance test data table of each sample

[0054] Data analysis: After comparing and analyzing the data in Table 1, it can be found that the longitudinal breaking force of the environmentally friendly packaging bag prepared by the present application is 21N, the transverse breaking force is 17N, the longitudinal right-angle tear strength is 51N·mm, the transverse right-angle tear strength is 48N·mm, the water vapor transmission rate is 10g·(m 2 ·24h) -1 , and the oxygen transmission rate is 10cm 3 ·(m 2 ·24h·0.1MPa) -1 After comparing and analyzing the data in Table 2, it can be found that the disintegration rate under industrial composting conditions for 12 weeks of the environmentally friendly packaging bag prepared by the present application is 98.6%, the biodegradation rate is 94.8%, the soil condition material degradation rate for 180 days is 19.1%, the soil condition material degradation rate for 1 year is 45.2%, and the soil condition material degradation rate for 2 years is 97.9%, all of which are better than those of the comparative examples, which shows that: Comparative Example 1 cancels the use of siloxane acetal hybrid polysaccharide, so that the material lacks the inorganic rigid skeleton constructed by Si-O-Si and Si-O-C bonds. Due to the role of this skeleton in prolonging the diffusion path of gas and water molecules in the original system, the lack of this skeleton leads to the directness of the diffusion channel, and the oxygen and water vapor transmission rates increase significantly. At the same time, the lack of the support of the rigid phase makes the crack initiation and propagation more rapid under external force, and the tear energy and fracture toughness of the material decrease significantly. Further, due to the lack of inorganic skeleton, the overall network structure tends to be loose, the intermolecular bonding force is weakened, and the barrier and mechanical properties decrease simultaneously. The comparative example 2 directly replaces the carbonic acid bridging product with a star-shaped lactic acid ester grafting body, so that the dense three-dimensional network formed by the carbonic acid ester crosslinking is no longer present in the system, the lack of this network structure reduces the binding force between the polymer segments, the free volume increases, the diffusion resistance of gas and water molecules is significantly reduced, thereby showing a decrease in barrier property, at the same time, the stress is not uniformly dispersed in the stress process, and the local segments are prone to concentrated fracture, resulting in insufficient tensile force and toughness, further, due to the decrease in the density of the system, the material is prone to produce interface voids and micro-cracks under external environment, and the durability and stability are significantly weakened; The comparative example 3 cancels the use of active side chain polyamino acid, so that the bridging effect of the polar carboxyl and hydroxyl side chains on the interface of the multi-component is lacking in the system, resulting in a decrease in the interfacial binding force, a decrease in the compatibility of the polyester and polysaccharide, and an easier production of micro-cracks or voids at the micro-interface, which become stress concentration points when stressed, thereby causing a decrease in the tearing strength and overall mechanical properties, in addition, the lack of polar groups also weakens the reversible adsorption and hysteresis effect of the material on water molecules, making the diffusion process of gas and water vapor lack effective resistance, and in the degradation process, the recognition efficiency and metabolic rate of microorganisms to the material are reduced, showing a significant slowdown in the degradation process in the compost and soil environment; Finally, it is pointed out that the environmental protection packaging bag introduces carbonic acid bridging dense polyester, siloxane acetal hybrid polysaccharide and active side chain polyamino acid in the preparation process, so that the obtained film forms an advantage complementary in structure and performance, the polyester part ensures the overall strength and film forming property, the polysaccharide provides a rigid skeleton and effectively prolongs the diffusion path of gas and water molecules, and the amino acid side chain produces a stable effect between the interfaces, avoiding defects and brittle fracture caused by component incompatibility, so that the environmental protection packaging bag not only reaches a high level in the longitudinal and transverse tensile force and right angle tearing strength, but also shows extremely low water vapor and oxygen transmission, under environmental conditions, the material can be quickly decomposed in the compost, and presents a stable first and then gradually accelerated decomposition process in the soil, taking into account the reliability during use and the environmental friendliness after disposal, the overall performance is excellent and the application prospect is broad.

[0055] The preferred embodiments disclosed above are only used to help explain the present application. The preferred embodiments do not describe all the details, nor limit the present application to the specific embodiments. Obviously, many modifications and changes can be made according to the content of the present application. The embodiments are selected and described in detail in order to better explain the principles and practical applications of the present application, so that those skilled in the art can well understand and utilize the present application. The present application is limited only by the claims and their entire scope and equivalents.

Claims

1. An environmentally degradable plastic packaging bag, characterized in that, The raw material composition comprises 50-55 parts of carbonic acid bridged compact polyester, 20-25 parts of siloxane acetal hybrid polysaccharide, 20-25 parts of active side chain polyamino acid, and 4-6 parts of auxiliary materials by weight; The preparation method of the carbonic acid bridged compact polyester comprises the following steps: adding star-shaped lactic acid ester grafting body, dimethyl carbonate and tetrabutyl titanate into a reaction kettle, heating to 150-170 DEG C under nitrogen protection, and stirring for 3-5 h; after the reaction is completed, the temperature of the reaction kettle is reduced to room temperature, the materials are removed, and the obtained product is washed with anhydrous ethanol for 3 times, and then is transferred to a vacuum drying oven, and dried at 80 DEG C under vacuum until the weight is constant to obtain the carbonic acid bridged compact polyester.

2. The environment-friendly degradable plastic packaging bag according to claim 1, characterized in that, The auxiliary materials are mixed by weight ratio of 0.3-0.5:3.5-5.0:0.2-0.5 to obtain heat stabilizers, plasticizers and lubricants; in the preparation process of the carbonic acid bridged compact polyester, the weight ratio of the star-shaped lactic acid ester grafting body, dimethyl carbonate and tetrabutyl titanate is 1g:1.0-1.5g:0.03-0.05g.

3. The environment-friendly degradable plastic packaging bag according to claim 1, characterized in that, The preparation method of the star-shaped lactic acid ester grafting body comprises the following steps: A1, citric acid, isosorbide, 1, 4-butanediol and tetrabutyl titanate are added into a reaction kettle and stirred, the reaction kettle is heated to 180-200 DEG C under nitrogen protection, and then is reduced to 200-300 Pa, and is stirred for 4-6 h, and then is treated to obtain a polyhydroxyl highly branched polyester core; A2, the polyhydroxyl highly branched polyester core, lactic acid lactide and stannous octoate are added into a reaction kettle, the temperature is raised to 140-160 DEG C under nitrogen protection, and is stirred for 8-10 h, and then is treated to obtain a star-shaped lactic acid ester grafting body.

4. The environment-friendly degradable plastic packaging bag according to claim 3, characterized in that, In step A1, the weight ratio of the citric acid, isosorbide, 1, 4-butanediol and tetrabutyl titanate is 1g:0.8-1.2g:2.0-2.5g:0.05g; in step A2, the weight ratio of the polyhydroxyl highly branched polyester core, lactic acid lactide and stannous octoate is 1g:3-6g:0.01g.

5. The environment-friendly degradable plastic packaging bag according to claim 1, characterized in that, The preparation method of the siloxane acetal hybrid polysaccharide comprises the following steps: B1, starch and deionized water are added into a reaction kettle and stirred, 1M hydrochloric acid aqueous solution is used to adjust the pH of the reaction system to 3-4, and then glyoxal is added, the temperature of the reaction kettle is raised to 40-60 DEG C, and is stirred for 6-8 h, and then is treated to obtain an acetal polysaccharide crosslinked skeleton; B2, the acetal polysaccharide crosslinked skeleton, 3-aminopropyl triethoxysilane, anhydrous ethanol and deionized water are added into a reaction kettle, the temperature of the reaction kettle is raised to 40-50 DEG C under nitrogen protection, and is stirred for 6-8 h, and then the product is collected by suction filtration, and is cured at 40-60 DEG C and humidity of 60-80% for 16 h, and then is dried under vacuum at 60 DEG C until the weight is constant to obtain the siloxane acetal hybrid polysaccharide.

6. The environment-friendly degradable plastic packaging bag according to claim 5, characterized in that, In step B1, the weight ratio of the starch, deionized water and glyoxal is 1g:50mL:1.0-1.5g; in step B2, the weight ratio of the acetal polysaccharide crosslinked skeleton, 3-aminopropyl triethoxysilane, anhydrous ethanol and deionized water is 1g:1.0-1.2g:80mL:20mL.

7. The environment-friendly degradable plastic packaging bag according to claim 1, characterized in that, The preparation method of the active side chain polyamino acid comprises the following steps: C1, 5-benzyl glutamate and dioxane were added into a reaction kettle, n-butylamine was added under nitrogen protection, and stirring was carried out at room temperature for 24 h, and then the protective group polyglutamic acid was obtained after post-treatment; C2, the protective group polyglutamic acid, palladium carbon and tetrahydrofuran were added into a reaction kettle, hydrogen was introduced, and then the temperature of the reaction kettle was increased to 35-40℃, and then the reaction was carried out for 6-8 h, then epichlorohydrin was added, and the temperature of the reaction kettle was increased to 40-50℃, and then stirring was carried out for 4-6 h, and then the active side chain polyamino acid was obtained after post-treatment.

8. The environment-friendly degradable plastic packaging bag according to claim 7, characterized in that, In step C1, the amount ratio of 5-benzyl glutamate, dioxane and n-butylamine was 1g:40-50mL:0.05-0.06g; in step C2, the amount ratio of the protective group polyglutamic acid, palladium carbon, tetrahydrofuran and epichlorohydrin was 0.1-0.2g:0.08g:50mL:0.1-0.2g.

9. A method of preparing an environmentally degradable plastic packaging bag according to any one of claims 1 to 8, characterized in that, The method comprises the following steps: 50-55 parts of carbon acid bridged compact polyester, 20-25 parts of siloxane acetal hybrid polysaccharide, 20-25 parts of active side chain polyamino acid and 4-6 parts of auxiliary materials are weighed according to weight parts, and then the materials are added into a melt extruder, and then melt blending and granulation are carried out in the interval of 180-200℃, then the granules are molded by a flow casting process, and then the initial film with a thickness of 50μm is obtained, and then the initial film is cured at 40-55℃ and humidity of 60-75% for 16 h, and then the environment-friendly packaging bag is obtained.

Images