CN113004503B - Polyester film-forming aqueous dispersion, liquid mulching film and application thereof - Google Patents

Polyester film-forming aqueous dispersion, liquid mulching film and application thereof Download PDF

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CN113004503B
CN113004503B CN201911333309.1A CN201911333309A CN113004503B CN 113004503 B CN113004503 B CN 113004503B CN 201911333309 A CN201911333309 A CN 201911333309A CN 113004503 B CN113004503 B CN 113004503B
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film
polyester
acid
aqueous dispersion
forming
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CN113004503A (en
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申有青
崔婧
黄璇
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Kefeng Xingtai Biotechnology Co.,Ltd.
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Hangzhou Wolfe Biotechnology Co ltd
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
    • C08G63/02—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds
    • C08G63/60—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds derived from the reaction of a mixture of hydroxy carboxylic acids, polycarboxylic acids and polyhydroxy compounds
    • A—HUMAN NECESSITIES
    • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
    • A01G—HORTICULTURE; CULTIVATION OF VEGETABLES, FLOWERS, RICE, FRUIT, VINES, HOPS OR SEAWEED; FORESTRY; WATERING
    • A01G13/00—Protecting plants
    • A01G13/02—Protective coverings for plants; Coverings for the ground; Devices for laying-out or removing coverings
    • A01G13/0256—Ground coverings
    • A01G13/0268—Mats or sheets, e.g. nets or fabrics
    • A01G13/0275—Films
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
    • C08G63/78—Preparation processes
    • C08G63/82—Preparation processes characterised by the catalyst used
    • C08G63/85—Germanium, tin, lead, arsenic, antimony, bismuth, titanium, zirconium, hafnium, vanadium, niobium, tantalum, or compounds thereof
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
    • C08G63/78—Preparation processes
    • C08G63/82—Preparation processes characterised by the catalyst used
    • C08G63/87—Non-metals or inter-compounds thereof
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D167/00—Coating compositions based on polyesters obtained by reactions forming a carboxylic ester link in the main chain; Coating compositions based on derivatives of such polymers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A40/00—Adaptation technologies in agriculture, forestry, livestock or agroalimentary production
    • Y02A40/10—Adaptation technologies in agriculture, forestry, livestock or agroalimentary production in agriculture
    • Y02A40/28—Adaptation technologies in agriculture, forestry, livestock or agroalimentary production in agriculture specially adapted for farming

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  • Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Organic Chemistry (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Materials Engineering (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • General Health & Medical Sciences (AREA)
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Abstract

A film-forming aqueous dispersion contains polyester, wherein the mass percentage of lactic acid monomers in the polyester is equal to or more than 50%, and also contains dibasic acid and dihydric alcohol. The film is elastic by dissolving the polyester in an organic solvent and dispersing the polyester in an aqueous medium to form an aqueous dispersion. The liquid mulching film is prepared for agricultural production, and can obviously improve the water retention and heat preservation capability of soil. The emergence rate of plants has been significantly increased.

Description

Polyester film-forming aqueous dispersion, liquid mulching film and application thereof
Technical Field
The invention relates to a liquid dispersion system, in particular to a polyester-containing aqueous dispersion, which is prepared by dispersing polyester in an aqueous medium to form a film-forming aqueous dispersion used for degradable packing materials.
Background
The agricultural mulching film is a layer of film covered on the soil, can block water in the soil from volatilizing, plays a role in preserving water and moisture, is beneficial to improving the quality of crops, greatly shortens the growth period of the crops, and improves the land utilization rate, is particularly important for agricultural production in arid areas, and becomes an indispensable production data of modern agriculture. However, a large number of mulching films widely used at present are made of non-degradable vinyl polymer plastics and are difficult to decompose in natural environments. The plastic films are easy to be broken into pieces after use due to low mechanical strength and difficult to recycle, and the scattered pieces can pollute agricultural products (such as cotton) and influence the quality of the products. With the annual rotation of land, the problem of plastic mulching film residue is worse and worse, and the agricultural ecology is seriously influenced. Especially, after the plastic film is used for a plurality of years, the plastic film is remained in the soil to destroy the soil structure, and also causes a serious environmental problem, namely 'white pollution'. Therefore, the problems of residue, pollution and the like of the non-degradable plastic mulching film in agricultural production are urgently needed to be treated.
The liquid (body) mulching film is mainly made of natural polymers such as cellulose, starch, chitosan, humic acid, lignin and the like, and also made of synthetic polymers such as polyvinyl alcohol, polyacrylic acid and the like. In general, these liquid mulching films are prepared by simple emulsification suspension technology or solubilization technology, and the film-forming properties of some materials are also better. However, the molecules of the materials contain a large number of hydrophilic groups (such as hydroxyl, carboxyl and the like), which causes poor water retention performance of the materials as agricultural planting soil coverage.
At present, polyester materials such as polylactic acid and the like are advocated to replace vinyl refractory materials in the field of traditional plastic films, but the technology needs to overcome the bottlenecks of high production cost (polyester molecules need to reach the molecular weight meeting the requirements of extrusion and stretching), difficult film forming, uneven degradation and the like of the polyester materials.
Chinese patent application 201910361218.2 discloses a degradable agricultural composite plastic mulching film, which takes polylactic acid as matrix resin and is added with bamboo fibers, so that crops can fully contact with sunlight, moisture conduction and absorption and desorption are facilitated, and the degradable agricultural composite plastic mulching film has good permeability and excellent moisture absorption and permeability. The adsorption layer formed by the roughness and activity of the surface of the bamboo fiber is entangled on polylactic acid molecules to form a network structure, so that the mechanical strength and the interface mechanical capacity of the composite membrane are effectively enhanced.
Chinese patent application 201810560800.7 discloses a biodegradable polylactic acid agricultural mulching film which is prepared from 100-120 parts by weight of polylactic acid resin, 15-30 parts by weight of light calcium carbonate, 5-10 parts by weight of polypropylene carbonate, 5-10 parts by weight of carboxyl, methyl-beta-cyclodextrin, 1-5 parts by weight of PEG-60 hydrogenated castor oil, 1-5 parts by weight of hexamethylol melamine hexa methyl ether, 1-5 parts by weight of ultraviolet screening agent, 0.5-2 parts by weight of antioxidant and the like. The prepared polylactic acid film is nontoxic and harmless, has strong use environmental protection performance and excellent use performance, and meets the use requirement of agricultural mulching films.
Chinese patent application 201811121875.1 discloses a degradable moisture-preserving mulching film and a preparation method thereof, wherein the degradable moisture-preserving mulching film comprises 20-30 parts of chitosan, 4-5 parts of acrylamide, 3-4 parts of sulfanilic acid, 1-2 parts of alumina, 45-50 parts of tetrahydrofuran, 20-25 parts of polylactic acid, 6-7 parts of polyvinyl alcohol, 5-6 parts of polycaprolactone, 3-4 parts of polyethylene glycol, 40-50 parts of petroleum ether, 4-5 parts of low-density polyethylene, 3-4 parts of dodecanol ester, 2-3 parts of traditional Chinese medicine extracting solution and 1-2 parts of nano titanium dioxide. The dodecenol ester modified polylactic acid is used for preparing the moisture-keeping mulching film, so that the moisture-keeping mulching film has good water absorption and moisture keeping performance, also has good biodegradability and cannot cause pollution to the environment.
In the prior art, polylactic acid is mostly used as a base material, and is mainly prepared into an agricultural mulching film in a mode of mixing a plurality of substances, so that the defect of singly using the lactic acid to prepare the mulching film is overcome, or more performances are endowed to the mulching film.
Disclosure of Invention
The invention aims to provide a polyester which is prepared by synthesizing a low-molecular-weight copolyester material from lactic acid and short-chain aliphatic dibasic acid/alcohol by a conventional polyester condensation technology, and is dispersed in an aqueous medium to prepare a film-forming aqueous dispersion for a degradable packaging material.
The invention also aims to provide polyester which is prepared by synthesizing a low-molecular-weight copolyester material by using lactic acid and short-chain aliphatic dibasic acid/alcohol through a conventional polyester condensation technology, and is dispersed in an aqueous medium to prepare a liquid mulching film for covering crops, so that the mulching film is automatically degraded, and soil residue is avoided.
The invention also aims to provide a liquid mulching film, which is prepared by synthesizing a low-molecular-weight copolyester material by using lactic acid and short-chain aliphatic dibasic acid/alcohol through a conventional polyester condensation technology and preparing the liquid mulching film with a smaller particle size through an emulsification process so as to facilitate agricultural spraying operation.
The invention also aims to provide a liquid mulching film, which is prepared by synthesizing a low-molecular-weight copolyester material by using lactic acid and short-chain aliphatic dibasic acid/alcohol through a conventional polyester condensation technology, and further improving the solid content through an emulsification process, so that the liquid mulching film is convenient to store stably.
The fifth purpose of the invention is to provide a liquid mulching film, wherein the liquid film has elasticity; the degradation period is controllable.
The film-forming aqueous dispersion provided by the invention is prepared by stably dispersing low-molecular-weight polyester in an aqueous medium through an intermolecular condensation technology and a nano self-assembly technology. The liquid mulching film is directly sprayed on the soil surface to form a film, namely, the liquid mulching film, so that the characteristics of moisture preservation and heat preservation of the traditional agricultural film can be met, and the environmental problems of residual fragments and the like of the traditional mulching film are solved. Meanwhile, the liquid mulching film can mix the herbicide required by crops into the liquid film for spraying, so that the labor intensity is greatly reduced compared with manual mulching film, and the labor efficiency is improved; after spraying, the crops can naturally emerge, manual seedling guiding and seedling releasing are not needed, labor force is saved, and adaptability to landforms and landforms is stronger.
From the technical application, the polyester of the invention not only can be used as a liquid (body) mulching film, but also can be compounded into a film aqueous dispersion through a polyester molecule design and dispersion system, and can be used as a packaging material for sand-fixing agents/dust depressants, fertilizer coating, film-forming agents for seed coating technology, product packaging adhesives, pesticide carriers, papermaking processing and other fields.
A polyester having a structure represented by the following formula I,
Figure GDA0002374295220000021
wherein n and x are integers of 1 or more, R 1 And R 2 Independently selected from C2 to C10 substituted or unsubstituted alkyl groups such as: but are not limited to, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, and decyl.
The weight average molecular weight of the polyester is 2,000-30,000, and 12,000 +/-2,000 is preferred to be favorable for large-scale polyester synthesis.
The mass ratio of the lactic acid monomer in the polyester is equal to or more than 50 percent, and the molar ratio of the dibasic acid to the dihydric alcohol is equal.
The other polyester is formed by the polycondensation of lactic acid, dibasic acid and dihydric alcohol, the mass percentage of lactic acid monomer is equal to or more than 50 percent, and the molar ratio of the dibasic acid to the dihydric alcohol is equal.
The dibasic acids used in the synthesis of the polyesters contain from 2 to 10 carbon atoms in the alkane carbon chain backbone, such as: but are not limited to, oxalic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, and the like. The alkane carbon chain skeleton should also contain substituents such as: methyl, ethyl, propyl and the like.
The diols used in the synthesis of the polyesters contain from 2 to 10 carbon atoms in the alkane carbon chain backbone, such as: but are not limited to, ethylene glycol, propylene glycol, butylene glycol, and the like. The alkane carbon chain skeleton should also contain substituents such as: methyl, ethyl, propyl and the like.
The other polyester is prepared by the condensation polymerization of lactic acid/dibasic acid/dihydric alcohol, and the molar ratio is 40-75: 10-30, especially the molar ratio is 50-75: 25.
The other polyester is prepared by the polycondensation of lactic acid/adipic acid/dihydric alcohol, and the molar ratio is 40-75: 10-30, especially 50-75: 25.
The other polyester is prepared by the condensation polymerization of lactic acid/succinic acid/dihydric alcohol, the molar ratio is 40-75: 10-30, especially the molar ratio is 50-75: 25.
The other polyester is prepared by the polycondensation of lactic acid/dibasic acid/glycol, and the molar ratio is 40-75: 10-30, especially 50-75: 25.
The other polyester is prepared by the condensation polymerization of lactic acid/dibasic acid/butanediol, and the molar ratio is 40-75: 10-30, especially the molar ratio is 50-75: 25.
The other polyester is prepared by the polycondensation of lactic acid/adipic acid/ethylene glycol, and the molar ratio is 40-75: 10-30, especially 50-75: 25.
The other polyester is prepared by the polycondensation of lactic acid/adipic acid/butanediol, and the molar ratio is 40-75: 10-30, especially 50-75: 25.
The other polyester is prepared by the condensation polymerization of lactic acid/succinic acid/ethylene glycol, the molar ratio is 40-75: 10-30, especially the molar ratio is 50-75: 25.
The other polyester is prepared by the condensation polymerization of lactic acid/succinic acid/butanediol, the mol ratio is 40-75: 10-30, especially the mol ratio is 50-75: 25.
The polyesters of the invention are prepared by an alkyd condensation reaction, such as: placing lactic acid, dibasic acid and dihydric alcohol in a condensation reaction kettle, setting the temperature at 130 ℃, stirring under normal pressure (collecting condensed water until the weight is not increased any more), then heating to 160 ℃, and continuing stirring; adding catalyst (such as stannous chloride), heating (such as 205 deg.C), polymerizing under reduced pressure (such as maintaining pressure at-0.095 MPa), and stopping reaction after 4 hr.
The polyester of the invention has elasticity after film forming, and is prepared into a film forming aqueous dispersion by matching with an aqueous dispersion system (containing one or more of an emulsifier and a dispersant). Specifically, for example: dissolving polyester in organic solvent, and dispersing in aqueous medium, wherein the weight ratio of the organic solvent to the aqueous medium is less than or equal to 1, preferably 0.5, which is favorable for increasing the solid content of the aqueous dispersion.
Unlike the prior known liquid mulching films, the present invention applies the degradable synthetic polyester material to the liquid mulching film technology for the first time, and also applies the polyester material to other application fields (such as aqueous dispersion coating) or is called by the concept of "polyester", and the typical technologies are briefly introduced and distinguished.
CN1113247A discloses a preparation method of a polyester aqueous dispersion, wherein a polyester material is polyacrylic acid, and a polyester composition is prepared by an emulsification-back extraction technology. It should be noted that this material is not a polyester material in the field of materials science (i.e., a polymer obtained by a synthetic method has a plurality of repeating structural units having ester bonds in the main chain).
CN107001815A discloses a method for preparing polyester and low acidity polyamide aqueous dispersion coating, and proposes that polymer resin (such as polyamide and polyester) is dispersed in water or aqueous medium and used as primer composition. The materials used are mostly polyester and polyamide with the prior trade mark, and the polyester is obtained by the reaction of at least one monocarboxylic acid with the carbon number of 12-24 and at least one diol and polyol, which is essentially different from the lactic acid copolyester material in the invention in structure.
CN1168899a discloses a method for preparing an aqueous polyester resin dispersion, which provides excellent processability, water resistance, corrosion resistance, weather resistance, etc., and is used as a coating film for adhesion to various substrates. The polyester is prepared by condensing aliphatic and aromatic dibasic acid and dihydric alcohol.
CN1239470A discloses a polyester aqueous dispersion for coating a granular fertilizer, wherein the polyester is prepared from aliphatic/aromatic dicarboxylic acid and dihydric alcohol, and is applied to coating the granular fertilizer, and the coating effect of a coating material on the fertilizer is improved through the viscosity of the polyester material.
The polyester prepared by the invention is dispersed in an aqueous medium to prepare a liquid mulching film (with the solid content of 20wt% -60 wt%) for covering crops, so that the mulching film is automatically degraded, and the soil residue is avoided. The polyester material is dissolved by environment-friendly non-limited organic solvent, such as: but are not limited to, acetone, methyl ethyl ketone, cyclohexanone, methyl isobutyl ketone, isophorone, ethyl acetate, butyl acetate, and the like, which are used alone or in combination in the present invention. The weight ratio of the organic solvent to the aqueous medium is preferably not more than 1, more preferably 0.5.
The invention also adopts an emulsification process to prepare the liquid mulching film with the micelle particle size of 100-1000 nanometers (especially 200-600 nanometers) so as to facilitate agricultural spraying operation. Emulsifiers such as: but not limited to, ethylene oxide propylene oxide block copolymer, alkyl polyether nonionic surfactant, alkyl glycoside, polyvinyl alcohol, organic ammonium cationic surfactant, sulfonate anionic surfactant and the like, and the substances are singly or in combination applied to the invention, wherein the dosage of the substances is 2-20% of the mass of the polyester material, and preferably 5-10%.
In the emulsification process of the present invention, dispersants such as: but not limited to polyacrylate, cross-linked cellulose, chelating functional dispersant, etc., and the dosage is 0-3 w/w%.
One embodiment of a method for preparing a liquid mulch film according to the present invention comprises:
firstly, dissolving polyester in an organic solvent (low-toxicity non-limited solvent) with a low boiling point to obtain a polyester solution;
then, slowly adding the polyester solution into an aqueous medium (aqueous solution containing an emulsifier/dispersant) under the condition of stirring and dispersing for emulsification (for example, stirring or high-speed shearing equipment is adopted);
then, recovering the organic solvent under reduced pressure to obtain the compound.
When dispersing polyester solutions in aqueous media, it is desirable to increase the shear rate as much as possible, and generally high rotational speeds are preferred, such as: greater than 1,000rpm.
According to the requirement, the liquid mulching film disclosed by the invention is also added with the following components: but are not limited to, thickeners, fillers, color enhancers, stabilizers, film forming aids, anti-freeze agents, defoamers, and wetting agents.
Thickeners such as: but are not limited to bentonite, xanthan gum, cellulose ether, and the like, alone or in combination, are useful in the present invention.
The fillers are: but are not limited to, alumina powder, calcium carbonate powder, kaolin powder, diatomaceous earth powder, and the like, which are used alone or in combination in the present invention.
The color-enhancing agent is as follows: but are not limited to, carbon black, water-based pigments, and the like, which are used alone or in combination in the present invention.
Stabilizers such as: but are not limited to, titanium dioxide, pH modifiers (alkaline), phosphates, and the like, alone or in combination, are useful in the present invention.
Defoamers such as: but are not limited to silicone based defoamers.
The liquid mulching film prepared by the invention is used for agricultural production, and can obviously improve the water retention and heat preservation capability of soil. The emergence rate of plants has been significantly increased.
According to practical requirements, the liquid mulching film can be applied to soil together with chemical fertilizers, micro-fertilizers, growth regulators, pesticides, herbicides and the like, so that the mulching film has more characteristics and can be used in various scenes.
The polyester can also be compounded with a dispersion system to be applied to fertilizer coating, seed coating, papermaking, product packaging, sand fixation and forestation, saline-alkali soil improvement, tree and grass planting, water and soil conservation, road slope protection and the like.
Drawings
FIG. 1 is an infrared spectrum of the lactic acid copolyester of the present invention, which characterizes ester bond functional groups contained in the polyester material;
FIG. 2 is a drawing showing the preparation of the lactic acid/succinic acid/ethylene glycol (75/25/25) copolyester of the present invention 1 HNMR map (deuterated reagent is CDCl) 3 )；
FIG. 3 is a drawing showing the preparation of the lactic acid/adipic acid/ethylene glycol (60/25/25) copolyester of the present invention 1 HNMR spectrum (deuterated reagent is CDCl) 3 )；
FIG. 4 is a dynamic light scattering diagram of a liquid mulch film made by dispersing the polyester of the present invention in an aqueous medium;
FIG. 5 is a transmission electron microscope (negative dyeing with uranyl acetate) picture of a liquid mulching film prepared by dispersing the polyester of the present invention in an aqueous medium;
FIG. 6 is a graph of stress-strain curves after coating a liquid mulch film made of the polyester of the present invention;
FIG. 7 is an optical microscope picture of the weather resistance investigation of a liquid mulching film made of the polyester of the present invention;
FIG. 8 is a graph showing the degradation profile of a liquid mulch film made of the polyester of the present invention in various media;
FIG. 9 is a graph showing the result of using the liquid mulching film made of polyester of the present invention for cotton cultivation to increase the number of cotton seedlings;
FIG. 10 is a graph showing the results of using the liquid mulching film made of polyester of the present invention for cotton cultivation to increase the crop emergence rate.
Detailed Description
The technical solution of the present invention is described in detail below. The embodiments of the present invention are only for illustrating the technical solutions of the present invention and not for limiting the same. Although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the spirit and scope of the invention as defined in the appended claims.
Example 1
Weighing lactic acid (the content is about 85%;7.5mol,795 g), adipic acid (2.5 mol,365 g) and ethylene glycol (2.6 mol, 162g) in a condensation reaction kettle, setting the temperature at 130 ℃, and stirring for 2 hours under normal pressure (collecting condensed water until the weight is not increased any more); the temperature is increased to 160 ℃, and the stirring is continued for 1.5 hours; adding 5g of stannous chloride catalyst, starting reduced pressure polymerization (the pressure is maintained at about-0.095 MPa) after the temperature is increased to 205 ℃, stopping the reaction after 4 hours, and discharging when the temperature of the materials is reduced to a safe temperature range. The infrared spectrum of the obtained polyester is detected and shown in figure 1, which shows that the product prepared by the method of the embodiment has ester bond functional group and is a polyester material.
Dissolving polyester with 1.5L methyl ethyl ketone (dissolving can be accelerated by moderate ultrasound), slowly adding into 2L water solution dissolved with 80 g poloxamer under high-speed shearing action, stirring for 20 min, adding appropriate amount of defoamer and dispersant, evaporating out methyl ethyl ketone under reduced pressure, and barreling with liquid mulching film. Through dynamic light scattering analysis, detailed in figure 4, the particle size of the liquid mulching film is 400 nanometers, and the distribution PDI is 0.2. The morphology of the particles was also observed by transmission electron microscopy, as detailed in FIG. 5.
Example 2
Weighing lactic acid (the content is about 85 percent; 7.5mol, 795g), adipic acid (2.5mol, 365g) and ethylene glycol (2.6mol, 162g) in a condensation reaction kettle, setting the temperature at 130 ℃, and stirring for 2 hours under normal pressure (collecting condensed water until the weight is not increased any more); the temperature is increased to 160 ℃, and the stirring is continued for 1.5 hours; adding 2g of stannous chloride and 2g of p-toluenesulfonic acid as catalysts, starting reduced pressure polymerization (the pressure is maintained at about-0.095 MPa) after the temperature is raised to 205 ℃, stopping reaction after 4 hours, and discharging when the temperature of the materials is reduced to a safe temperature range.
Dissolving polyester with 1.2L ethyl acetate (dissolving can be accelerated by moderate ultrasound), slowly adding into 2L water solution dissolved with 80 g poloxamer under high-speed shearing action, stirring for 20 min, adding appropriate amount of defoamer and dispersant, evaporating ethyl acetate under reduced pressure, and barreling with liquid mulching film.
Example 3
Weighing lactic acid (the content is about 85%;7.5mol,795 g), adipic acid (2.5 mol,365 g) and ethylene glycol (2.6 mol, 162g) in a condensation reaction kettle, setting the temperature at 130 ℃, and stirring for 2 hours under normal pressure (collecting condensed water until the weight is not increased any more); the temperature is increased to 160 ℃, and the stirring is continued for 1.5 hours; adding 5g of tetrabutyl titanate serving as a catalyst, starting reduced pressure polymerization (the pressure is maintained at about-0.095 MPa) after the temperature is increased to 205 ℃, stopping the reaction after 4 hours, and discharging when the temperature of the materials is reduced to a safe temperature range.
Dissolving polyester with 1.5L methyl ethyl ketone (dissolving can be accelerated by moderate ultrasound), slowly adding into 2L water solution dissolved with 80 g polyvinyl alcohol under high-speed shearing action, continuously stirring for 20 minutes, adding appropriate amount of defoamer and dispersant, evaporating out methyl ethyl ketone under reduced pressure, and barreling with liquid mulching film.
Example 4
Weighing lactic acid (the content is about 85%;6.0mol, 635g), adipic acid (2.5mol, 365g), and ethylene glycol (2.6mol, 162g) in a condensation reaction kettle, setting the temperature at 130 ℃, and stirring for 2 hours under normal pressure (collecting condensed water until the weight is not increased any more); the temperature is increased to 160 ℃, and the stirring is continued for 1.5 hours; adding catalyst stannous chloride 1.8g and p-toluenesulfonic acid 1.8g, starting reduced pressure polymerization (pressure is maintained at about-0.095 Mpa) after the temperature is raised to 205 ℃, stopping reaction after 4 hours, and discharging when the material is reduced to a safe temperature range. The hydrogen nuclear magnetic spectrum of the prepared polyester is detected, and the detail is shown in figure 3, which shows that the polyester composition is lactic acid/adipic acid/ethylene glycol (60/25/25) copolyester.
Dissolving polyester with 1.3L ethyl acetate (dissolving can be accelerated by moderate ultrasound), slowly adding into 2L water solution dissolved with 80 g poloxamer under high-speed shearing action, stirring for 20 min, adding appropriate amount of defoamer and dispersant, evaporating ethyl acetate under reduced pressure, and barreling with liquid mulching film.
Example 5
Weighing lactic acid (the content is about 85%;6.0mol, 635g), succinic acid (2.5 mol, 295g), ethylene glycol (2.6 mol, 162g) in a condensation reaction kettle, setting the temperature at 130 ℃, and stirring for 2 hours under normal pressure (collecting condensed water until the weight is not increased any more); the temperature is increased to 180 ℃, and the stirring is continued for 1.5 hours; adding 1.8g of stannous chloride and 1.8g of p-toluenesulfonic acid as catalysts, starting reduced pressure polymerization (the pressure is maintained at about-0.095 MPa) after the temperature is raised to 208 ℃, stopping reaction after 4 hours, and discharging when the temperature of the materials is lowered to a safe temperature range. The hydrogen nuclear magnetic spectrum of the prepared polyester is detected, and detailed shown in figure 2, which shows that the polyester is composed of lactic acid/succinic acid/ethylene glycol (70/25/25) copolyester.
Dissolving polyester with 0.5L of mixed solution of methyl ethyl ketone and 1L of ethyl acetate (the dissolving can be accelerated by moderate ultrasound), slowly adding the polyester into 2L of aqueous solution in which 80 g of poloxamer is dissolved under the action of high-speed shearing, continuously stirring for 20 minutes, adding a proper amount of antifoaming agent and dispersing agent, decompressing, steaming out the organic solvent, and barreling the liquid mulching film.
Example 6
Weighing lactic acid (the content is about 85 percent; 7.5mol, 795g), succinic acid (2.5mol, 295g) and ethylene glycol (2.6mol, 162g) in a condensation reaction kettle, setting the temperature at 130 ℃, and stirring for 2 hours under normal pressure (collecting condensed water until the weight is not increased any more); the temperature is increased to 180 ℃, and the stirring is continued for 1.5 hours; adding catalyst stannous chloride 1.9g and p-toluenesulfonic acid 1.9g, starting reduced pressure polymerization (pressure is maintained at about-0.095 Mpa) after the temperature is raised to 208 ℃, stopping reaction after 4 hours, and discharging when the material is reduced to a safe temperature range. The hydrogen nuclear magnetic spectrum of the prepared polyester is detected, and the detail is shown in figure 3, which shows that the polyester is composed of lactic acid/succinic acid/ethylene glycol (75/25/25) copolyester.
Dissolving polyester with 1.2L ethyl acetate (dissolving can be accelerated by moderate ultrasound), slowly adding into 2L water solution dissolved with 80 g tween 80 under high-speed shearing action, stirring for 20 min, adding appropriate amount of defoamer and dispersant, evaporating ethyl acetate under reduced pressure, and canning with liquid mulching film.
Example 7
Weighing lactic acid (the content is about 85%;6.0mol, 635g), succinic acid (2.5mol, 295g), and butanediol (2.6mol, 234g) in a condensation reaction kettle, setting the temperature at 130 ℃, and stirring for 2 hours under normal pressure (collecting condensed water until the weight is not increased any more); the temperature is increased to 180 ℃, and the stirring is continued for 1.5 hours; adding catalyst stannous chloride 1.9g and p-toluenesulfonic acid 1.9g, starting reduced pressure polymerization (pressure is maintained at about-0.095 Mpa) after the temperature is raised to 208 ℃, stopping reaction after 4 hours, and discharging when the material is reduced to a safe temperature range.
Dissolving polyester with 1.5L methyl ethyl ketone (dissolving can be accelerated by moderate ultrasound), slowly adding into 2L water solution dissolved with 30 g poloxamer/30 g polyethylene glycol under high-speed shearing action, stirring for 20 min, adding appropriate amount of defoamer and dispersant, evaporating out methyl ethyl ketone under reduced pressure, and canning with liquid mulching film.
Example 8
Weighing lactic acid (the content is about 85%;6.0mol, 635g), adipic acid (2.5mol, 365g), butanediol (2.6mol, 234g) in a condensation reaction kettle, setting the temperature at 130 ℃, and stirring for 2 hours under normal pressure (collecting condensed water until the weight is not increased any more); the temperature is increased to 160 ℃, and the stirring is continued for 1.5 hours; adding catalyst stannous chloride 1.9g and p-toluenesulfonic acid 1.9g, starting reduced pressure polymerization (pressure is maintained at about-0.095 Mpa) after the temperature is raised to 208 ℃, stopping reaction after 4 hours, and discharging when the material is reduced to a safe temperature range.
Dissolving polyester with 1.2L ethyl acetate (dissolving can be accelerated by moderate ultrasound), slowly adding into 2L water solution dissolved with 30 g poloxamer/50 g polyethylene glycol under high-speed shearing action, continuously stirring for 20 min, adding appropriate amount of defoamer and dispersant, evaporating methyl ethyl ketone under reduced pressure, and barreling with liquid film.
Example 9
The characteristics of the prepared lactic acid copolyester samples of the components are measured, and the specific results are detailed in table 1.
TABLE 1 characterization data for samples of lactic acid copolyester of different compositions
Figure GDA0002374295220000081
Note: the products in table 1, catalysts all adopt stannous chloride/p-toluenesulfonic acid composite catalytic system; lactic acid, la; succinic acid, su; adipic acid, ad; ethylene glycol, go; butanediol, bo.
Example 10
The liquid mulching films obtained in example two, example four, example five and example six were directly coated on a teflon film plate as sample 1, sample 2, sample 3, sample 4 and sample 5 to obtain liquid film dry film samples having an average film thickness of 100 μm (including a group of commercially available aqueous dispersion products as a control). 5 groups of dry film samples are adopted to prepare samples according to the tensile property test national standard, a tensile test is carried out at the speed of 10mm/min, the stress-strain change condition is recorded, and the result is shown in figure 6, wherein the comparison is a commercial emulsion sample.
Example 11
The liquid mulching film prepared in embodiment 8 is coated on a glass slide, 5 samples are repeatedly prepared, the liquid mulching film is placed in an incubator for weather resistance detection, the time period is 1 year, and sampling observation is carried out at time points of 0 month, 1 month, 2 months, 3 months, 6 months and 1 year respectively, and the result is shown in detail in fig. 7.
Example 12
The liquid mulching film prepared in the embodiment 8 is respectively placed in water and buffer solution media (different pH conditions), the polyester material is periodically sampled and extracted, and the degradation condition of the polyester molecules under different conditions is detected. The change in molecular weight of the polyester is shown in FIG. 8.
Example 13
The liquid mulching film prepared in the embodiment 8 is adopted to carry out a liquid film cultivation test in a Xinjiang cotton test field: the cotton varieties are ZD-619 and ZD-64; each set up 3 test treatments: plastic mulching, liquid mulching and blank bare land cultivation. The emergence conditions of the cotton in each treatment group are statistically investigated in fig. 9 and fig. 10, and the polyester liquid mulching film can promote the emergence of the cotton and ensure the emergence rate.

Claims (18)

1. A film-forming aqueous dispersion characterized by containing a polyester represented by the following formula I
Figure 673702DEST_PATH_IMAGE002
Formula I
Wherein n and x are integers of 1 or more, R 1 And R 2 Independently selected from C2-C10 substituted or unsubstituted alkyl;
the mass percentage of the lactic acid monomer in the polyester is equal to or more than 50%.
2. The film-forming aqueous dispersion is characterized by being formed by polycondensation of lactic acid, dibasic acid and dihydric alcohol, wherein the mass percentage of lactic acid monomers is equal to or more than 50%, the molar ratio of the dibasic acid to the dihydric alcohol is equal, the alkane carbon chain skeleton of the dibasic acid contains 2 to 10 carbon atoms, and the alkane carbon chain skeleton of the dihydric alcohol contains 2 to 10 carbon atoms.
3. The aqueous film-forming dispersion according to claim 2, wherein the dibasic acid is one or more selected from the group consisting of oxalic acid, succinic acid, glutaric acid, adipic acid and sebacic acid.
4. The aqueous film-forming dispersion according to claim 2, wherein the glycol is one or more selected from the group consisting of ethylene glycol, propylene glycol and butylene glycol.
5. The aqueous film-forming dispersion according to claim 2, wherein the carbon chain skeleton of the alkane further comprises a substituent selected from one or more of methyl, ethyl and propyl.
6. The film-forming aqueous dispersion according to claim 2, wherein the polyester is obtained by polycondensation of lactic acid/dibasic acid/diol at a molar ratio of 40 to 75: 10 to 30.
7. The film-forming aqueous dispersion of 1~6 of claim wherein the polyester has a weight average molecular weight of 2,000 to 50,000.
8. The film-forming aqueous dispersion of claim 1~6 wherein said polyester has a weight average molecular weight of 12,000 ± 2,000.
9. The film-forming aqueous dispersion of claim 1~6 wherein said polyester is first dissolved in an organic solvent and redispersed in an aqueous medium, the weight ratio of said organic solvent to said aqueous medium being less than or equal to 1.
10. The film-forming aqueous dispersion of claim 1~6 wherein said polyester is first dissolved in an organic solvent and redispersed in an aqueous medium, the weight ratio of said organic solvent to said aqueous medium being 0.5.
11. Use of the film-forming aqueous dispersion according to any one of claims 1~6 in the preparation of a packaging material.
12. Use of the film-forming aqueous dispersion of claim 1~6 in fertilizer coatings, seed coatings, paper making, product packaging, sand fixation and forestation, saline and alkaline land improvement, tree and grass planting, soil and water conservation, and road slope protection.
13. A liquid mulching film, characterized by comprising the film-forming aqueous dispersion and an emulsifier according to any one of claims 1 to 10, wherein the emulsifier is one or more selected from ethylene oxide propylene oxide block copolymers, alkyl polyether nonionic surfactants, alkyl glycosides, polyvinyl alcohol, organic ammonium cationic surfactants and sulfonate anionic surfactants.
14. The liquid mulching film according to claim 13, wherein the polyester is dissolved in an organic solvent, and the organic solvent is selected from one or more of acetone, methyl ethyl ketone, cyclohexanone, methyl isobutyl ketone, isophorone, ethyl acetate, and butyl acetate.
15. The liquid mulch of claim 13 further comprising a dispersant selected from one or more of polyacrylate, cross-linked cellulose and chelating functional dispersant.
16. The liquid mulching film according to claim 13, wherein the micelles have a particle size of 100 nm to 1000 nm.
17. Use of a liquid mulch film according to claim 13 for improving the water and heat retention capacity of the soil.
18. Use of a liquid mulch film according to claim 13 for increasing the rate of emergence of a plant.
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