Biomass degradable liquid mulching film and preparation method thereof

Abstract

The invention discloses a biomass degradable liquid mulching film and a preparation method thereof. The biomass degradable liquid mulching film comprises a master batch, a cross-linking agent and water, wherein the master batch is prepared from the following components in parts by weight: 6-10 parts of polyvinyl alcohol, 2-4 parts of dextrin, 0.3-0.8 part of nano silicon dioxide, 1.2-1.8 parts of glycerol, 2-6 parts of citric acid, 0.2-0.5 part of a water repellent agent and 0.8-1.5 parts of an auxiliary material; according to the biomass degradable liquid mulching film, natural biomass is used as a main raw material, the problems that a single biomass film is poor in mechanical property and insufficient in water resistance are solved through a composite modification and cross-linking technology, and meanwhile rapid full biodegradation and no environmental residue of the film material are achieved.

Description

Technical Field

[0001] This invention relates to the field of mulch film technology, specifically to a biodegradable liquid mulch film and its preparation method. Background Technology

[0002] As the problem of "white pollution" becomes increasingly severe, the application of traditional petroleum-based plastic films in agriculture, packaging, and other fields is strictly limited due to their difficulty in degradation. Currently, most biodegradable films on the market are solid films, which have problems such as high transportation costs, complex installation operations, and poor adaptability (such as covering irregular surfaces). On the other hand, existing liquid films are mostly based on synthetic polymers. Although they have a certain film-forming property, their degradation cycle is long (usually more than one year), and they may release toxic small molecules during the degradation process, causing secondary pollution to the environment.

[0003] Previously, liquid membranes made from single biomass sources (such as pure starch) suffered from drawbacks such as low mechanical strength and poor water resistance, making them prone to cracking and failure in humid environments, thus failing to meet practical application requirements. Therefore, developing a biomass liquid membrane that uses environmentally friendly raw materials, exhibits excellent film-forming properties, and is rapidly and completely degradable has become a key direction for solving the problem of replacing traditional plastic films. Summary of the Invention

[0004] The purpose of this invention is to provide a biodegradable liquid mulch film and its preparation method. The biodegradable liquid mulch film of this invention uses natural biomass as the main raw material and solves the problems of poor mechanical properties and insufficient water resistance of single biomass films through composite modification and cross-linking processes. At the same time, it realizes the rapid and complete biodegradation of the membrane material without environmental residue.

[0005] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0006] The first aspect of this invention provides a biodegradable liquid mulch film, the biodegradable liquid mulch film comprising a masterbatch, a crosslinking agent, and water:

[0007] The masterbatch is composed of the following components in parts by weight:

[0008] Polyvinyl alcohol 6-10 parts, dextrin 2-4 parts, nano silica 0.3-0.8 parts, glycerol 1.2-1.8 parts, citric acid 2-6 parts, hydrophobic agent 0.2-0.5 parts, and excipients 0.8-1.5 parts.

[0009] Preferably, the mass ratio of the masterbatch, crosslinking agent and water is (1.8~2.2):1:(40~60).

[0010] Preferably, the biodegradable liquid mulch film further includes fibers; the mass ratio of the fibers to the crosslinking agent is (3~5):1; the fibers are starch residue or plant straw.

[0011] Preferably, the crosslinking agent is a complex of glutaraldehyde and boric acid.

[0012] Preferably, the hydrophobic agent is an aqueous modified polysiloxane; the excipient is a chain extender, which is a polyether linear polymer with a number average molecular weight of 5 million to 8 million, and the molar proportion of ethylene oxide units in the repeating structural units of the polyether linear polymer is ≥90%.

[0013] Preferably, the polyvinyl alcohol is prepared by the following method:

[0014] (a) The biomass is crushed, washed and dried to obtain pretreated biomass;

[0015] (b) Pretreated biomass and yeast were added to water for fermentation, and then purified by distillation to obtain anhydrous ethanol;

[0016] (c) Anhydrous ethanol is dehydrated under the action of a catalyst and then purified to obtain ethylene;

[0017] (d) Ethylene and acetic acid are subjected to gas-phase oxidation reaction under the action of oxygen and palladium-gold catalyst to obtain vinyl acetate. Then, vinyl acetate is polymerized in water or methanol under the action of azobisisobutyronitrile to generate polyethyl acetate.

[0018] (e) Polyvinyl acetate is saponified under sodium hydroxide catalysis to obtain polyvinyl alcohol, which is then precipitated, washed and dried to obtain the polyvinyl alcohol.

[0019] Preferably, the biomass is corn, cassava, sugarcane bagasse, or plant straw;

[0020] The molecular weight of the polyvinyl alcohol is 100,000 to 150,000.

[0021] Preferably, when the biomass is sugarcane bagasse or plant straw, step (a) further includes enzymatic hydrolysis of the biomass using cellulase.

[0022] Preferably, the dextrin is prepared by the following method:

[0023] (1) According to the mass ratio of starch to hydrochloric acid solution of 1: (0.1~0.2), add hydrochloric acid solution with a concentration of 0.1%~0.3% to starch and mix well. Then dry at low temperature of 50~60℃ until the moisture content is 8%~12% to obtain starch mixture;

[0024] (2) Preheat the starch mixture to 100~120℃, then heat it to 120~180℃ for 30~140min. After the reaction is complete, add sodium bicarbonate until the pH is neutral. Then, cool and crush to obtain the dextrin.

[0025] A second aspect of the present invention provides a method for preparing the above-mentioned biomass biodegradable liquid mulch film, the method comprising the following steps:

[0026] (1) Polyvinyl alcohol, dextrin and nano silica are stirred and mixed to obtain a mixture;

[0027] (2) Add glycerol to the mixture and stir evenly, then add citric acid, hydrophobic agent and excipients and stir for 20-30 minutes to obtain the masterbatch;

[0028] (3) Add some water to the masterbatch and stir into a paste. Then, add the remaining water and stir thoroughly. Then, add the crosslinking agent and stir at high speed into a foam to obtain the biodegradable liquid mulch film.

[0029] Compared with the prior art, the beneficial effects of the present invention include at least the following:

[0030] The raw materials of the biodegradable liquid mulch film of this invention are all natural biomass or green chemicals. In the natural environment, it can be completely degraded by microorganisms into CO2 and H2O. The degradation cycle is only 3-6 months, which is much shorter than that of existing biodegradable films. It leaves no environmental residues or secondary pollution.

[0031] Through modification and cross-linking processes, the biodegradable liquid mulch film of this invention achieves a tensile strength of 10-15 MPa and an elongation at break of 120%-140% after film formation, while also improving water resistance (water absorption ≤15%, 24h), thus meeting the practical needs of agricultural applications.

[0032] The biodegradable liquid mulch of this invention exists in liquid form and can be applied to the surface of any shaped substrate by direct spraying or by mixing with liquid fertilizer or pesticides for spraying. It is especially suitable for irregular soil surfaces and has lower transportation costs than traditional solid films. In addition, the main raw materials are crops (corn, cassava) and agricultural waste (such as starch residue and straw), which are abundant and inexpensive. The preparation process does not require high-temperature and high-pressure equipment, making it easy to industrialize and giving it significant economic advantages. Detailed Implementation

[0033] The embodiments of the technical solution of the present invention will be described in detail below with reference to the examples. The following embodiments are only used to illustrate the technical solution of the present invention more clearly, and are therefore only examples, and should not be used to limit the scope of protection of the present invention.

[0034] It should be noted that, unless otherwise stated, the technical or scientific terms used in this application should have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0035] This invention provides a biodegradable liquid mulch film, which comprises a masterbatch, a crosslinking agent, and water.

[0036] The masterbatch is composed of the following components in parts by weight:

[0037] Polyvinyl alcohol 6-10 parts, dextrin 2-4 parts, nano silica 0.3-0.8 parts, glycerol 1.2-1.8 parts, citric acid 2-6 parts, hydrophobic agent 0.2-0.5 parts, and excipients 0.8-1.5 parts.

[0038] In one embodiment, the mass ratio of the masterbatch, crosslinking agent and water is (1.8~2.2):1:(40~60).

[0039] In one embodiment, depending on site requirements, the biomass biodegradable liquid mulch film further includes fibers; the mass ratio of the fibers to the crosslinking agent is (3~5):1; the fibers are starch residue or plant straw.

[0040] In one embodiment, the crosslinking agent is a glutaraldehyde and boric acid complex, wherein the mass ratio of glutaraldehyde to boric acid is 100:(2~4).

[0041] In one embodiment, the hydrophobic agent is an aqueous modified polysiloxane; the excipient is a chain extender, which is a polyether linear polymer with a number average molecular weight of 5 million to 8 million, and the molar proportion of ethylene oxide units in the repeating structural units of the polyether linear polymer is ≥90%.

[0042] In one embodiment, the polyvinyl alcohol is prepared by the following method:

[0043] (a) The biomass is crushed, washed and dried to obtain pretreated biomass;

[0044] (b) Pretreated biomass and yeast were added to water for fermentation, and then purified by distillation to obtain anhydrous ethanol;

[0045] (c) Anhydrous ethanol is dehydrated under the action of a catalyst and then purified to obtain ethylene;

[0046] (d) Ethylene and acetic acid are subjected to gas-phase oxidation reaction under the action of oxygen and palladium-gold catalyst to obtain vinyl acetate. Then, vinyl acetate is polymerized in water or methanol under the action of azobisisobutyronitrile to generate polyethyl acetate.

[0047] (e) Polyvinyl acetate is saponified under sodium hydroxide catalysis to obtain polyvinyl alcohol, which is then precipitated, washed and dried to obtain the polyvinyl alcohol.

[0048] In one embodiment, the biomass is corn, cassava, sugarcane bagasse, or plant straw;

[0049] The molecular weight of the polyvinyl alcohol is 100,000 to 150,000.

[0050] In one embodiment, when the biomass is sugarcane bagasse or plant straw, step (a) further includes enzymatic hydrolysis of the biomass using cellulase.

[0051] In one embodiment, the dextrin is prepared by the following method:

[0052] (1) According to the mass ratio of starch to hydrochloric acid solution of 1: (0.1~0.2), add hydrochloric acid solution with a concentration of 0.1%~0.3% to starch and mix well. Then dry at low temperature of 50~60℃ until the moisture content is 8%~12% to obtain starch mixture;

[0053] (2) Preheat the starch mixture to 100~120℃, then heat it to 120~180℃ for 30~140min. After the reaction is complete, add sodium bicarbonate until the pH is neutral. Then, cool and crush to obtain the dextrin.

[0054] In the above preparation method, reaction temperature and time are the primary factors for controlling the DE value. The DE value corresponds to the degree of hydrolysis, and the temperature must be strictly controlled between 120 and 140°C, and the reaction time must be shortened to 30 to 60 minutes. Every 5°C increase in temperature or 10-minute extension of time may cause the DE value to exceed the upper limit. Therefore, a reactor with a precise temperature control system (such as a jacketed reactor) must be used to monitor and stabilize the temperature in real time.

[0055] Acid concentration and dosage: Acid is a hydrolysis catalyst, and excessive concentration will accelerate the reaction. The concentration of dilute hydrochloric acid should be controlled at 0.1%~0.3% (mass fraction), and the mixing ratio of starch to acid solution should be accurate to 1:0.1~1:0.2 (dry weight of starch: volume of acid solution) to ensure uniform acid distribution but mild catalytic intensity and avoid local over-hydrolysis.

[0056] Raw material moisture content: The moisture content of the starch after acidification needs to be stabilized at 8%~10%. Too high a moisture content will dilute the acid concentration, resulting in insufficient reaction (DE value <1); too low a moisture content will cause the acid concentration to be too high in some areas. Therefore, the moisture content at the endpoint must be strictly controlled during the drying process.

[0057] Another embodiment of the present invention provides a method for preparing the above-mentioned biomass biodegradable liquid mulch film, the method comprising the following steps:

[0058] (1) Polyvinyl alcohol, dextrin and nano silica are stirred and mixed to obtain a mixture;

[0059] (2) Add glycerol to the mixture and stir evenly, then add citric acid, hydrophobic agent and excipients and stir for 20-30 minutes to obtain the masterbatch;

[0060] (3) Add some water to the masterbatch and stir into a paste. Then, add the remaining water and stir thoroughly. Then, add the crosslinking agent and stir at high speed into a foam to obtain the biodegradable liquid mulch film.

[0061] The technical solution of the present invention will be further described in detail below through specific embodiments.

[0062] Example 1

[0063] This embodiment describes a method for preparing polyvinyl alcohol from biomass as raw material, which includes the following steps:

[0064] (a) The corn is crushed, washed and dried to obtain pretreated biomass;

[0065] (b) Pretreated biomass and yeast (Saccharomyces cerevisiae SHBCCD13642, from Shanghai Ruichu Biotechnology Co., Ltd.) were added to water for fermentation, and then purified by distillation to obtain anhydrous ethanol.

[0066] (c) Anhydrous ethanol was dehydrated at 350°C in the presence of a catalyst (alumina), and then purified to obtain ethylene;

[0067] (d) Ethylene and acetic acid were subjected to a gas-phase oxidation reaction under the action of oxygen and palladium-gold catalyst to obtain vinyl acetate. Then, vinyl acetate was polymerized in water under the action of azobisisobutyronitrile to generate polyethyl acetate. The gas-phase oxidation reaction temperature was 170℃ and the reaction pressure was 1MPa; the polymerization reaction temperature was 65℃ and the polymerization reaction time was 3h.

[0068] (e) Polyvinyl acetate was saponified under sodium hydroxide catalysis to obtain polyvinyl alcohol, which was then precipitated, washed and dried to obtain polyvinyl alcohol with a molecular weight of 120,000.

[0069] Example 2

[0070] This embodiment describes a method for preparing dextrin from starch, which includes the following steps:

[0071] (1) According to the mass ratio of corn starch to hydrochloric acid solution of 1:0.15, add 0.2% hydrochloric acid solution to starch and mix well, then dry at low temperature at 55℃ until the moisture content is 10% to obtain starch mixture;

[0072] (2) Preheat the starch mixture to 120°C, then heat it to 140°C for 60 min. After the reaction is complete, add sodium bicarbonate until the pH is neutral. Then, cool and crush to obtain the dextrin.

[0073] Example 3

[0074] This embodiment is a biodegradable liquid mulch film, which includes masterbatch, crosslinking agent and water, wherein the mass ratio of masterbatch, crosslinking agent and water is 2:1:50; the crosslinking agent is a glutaraldehyde and boric acid complex with a mass ratio of 100:3.

[0075] The masterbatch is composed of the following components in parts by weight:

[0076] Example 1: 8 parts polyvinyl alcohol; Example 2: 3 parts dextrin, 0.5 parts nano-silica, 1.5 parts glycerol, 4 parts citric acid, 0.3 parts hydrophobic agent, and 1.2 parts excipients; the hydrophobic agent is a water-based modified polysiloxane (polyether-modified silicone oil, Dow Corning DC-190, sourced from Dow Chemical); the excipients are chain extenders, which are polyether linear polymers with a number average molecular weight of 5 million to 8 million, and the molar percentage of ethylene oxide units in the repeating structural units of the polyether linear polymer is ≥90% (the polyether linear polymer is Sumitomo Chemical Co., Ltd., Japan, trade name PEO-27, CAS No. 25322-68);

[0077] The preparation method of the above-mentioned biodegradable liquid mulch film includes the following steps:

[0078] (1) Polyvinyl alcohol, dextrin and nano silica are stirred and mixed to obtain a mixture;

[0079] (2) Add glycerol to the mixture and stir evenly, then add citric acid, hydrophobic agent and excipients and stir for 25 minutes to obtain the masterbatch;

[0080] (3) Add some water to the masterbatch and stir into a paste. Then, add the remaining water and stir thoroughly. Then, add the crosslinking agent and stir at high speed into a foam to obtain the biodegradable liquid mulch film.

[0081] Experimental Example

[0082] The biodegradable liquid mulch film prepared in Example 3 above was obtained and poured into a foam spraying machine for direct spraying onto the surface of farmland. It immediately bonded with the soil surface to form a heat-insulating film. Experiments have verified that the biodegradable liquid mulch film of the present invention can achieve 100% degradation in 180 days. At the same time, it can increase the temperature of the soil layer at a depth of 5-15 cm by 1-6°C. The tensile strength, elongation at break, and water resistance of the liquid mulch film of the present invention were tested. The test results showed that the tensile strength was 14.6 MPa, the elongation at break was 127%, and the water absorption rate after 24 hours of soaking was 7.3%.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A biodegradable liquid mulch film, characterized in that, The biomass-degradable liquid mulch film comprises masterbatch, crosslinking agent, and water: The masterbatch is composed of the following components in parts by weight: Polyvinyl alcohol 6-10 parts, dextrin 2-4 parts, nano silica 0.3-0.8 parts, glycerol 1.2-1.8 parts, citric acid 2-6 parts, hydrophobic agent 0.2-0.5 parts, and excipients 0.8-1.5 parts.

2. The biomass-degradable liquid mulch film according to claim 1, characterized in that, The mass ratio of the masterbatch, crosslinking agent and water is (1.8~2.2):1:(40~60).

3. The biomass-degradable liquid mulch film according to claim 1, characterized in that, The biodegradable liquid mulch film also includes fibers; the mass ratio of the fibers to the crosslinking agent is (3~5):1; the fibers are starch residue or plant straw.

4. The biomass-degradable liquid mulch film according to claim 1, characterized in that, The crosslinking agent is a complex of glutaraldehyde and boric acid.

5. The biomass-degradable liquid mulch film according to claim 1, characterized in that, The hydrophobic agent is an aqueous modified polysiloxane; the excipient is a chain extender, which is a polyether linear polymer with a number average molecular weight of 5 million to 8 million, and the molar proportion of ethylene oxide units in the repeating structural units of the polyether linear polymer is ≥90%.

6. The biomass-degradable liquid mulch film according to claim 1, characterized in that, The polyvinyl alcohol is prepared by the following method: (a) The biomass is crushed, washed and dried to obtain pretreated biomass; (b) Pretreated biomass and yeast were added to water for fermentation, and then purified by distillation to obtain anhydrous ethanol; (c) Anhydrous ethanol is dehydrated under the action of a catalyst and then purified to obtain ethylene; (d) Ethylene and acetic acid are subjected to gas-phase oxidation reaction under the action of oxygen and palladium-gold catalyst to obtain vinyl acetate. Then, vinyl acetate is polymerized in water or methanol under the action of azobisisobutyronitrile to generate polyethyl acetate. (e) Polyvinyl acetate is saponified under sodium hydroxide catalysis to obtain polyvinyl alcohol, which is then precipitated, washed and dried to obtain the polyvinyl alcohol.

7. The biomass-degradable liquid mulch film according to claim 6, characterized in that, The biomass is corn, cassava, sugarcane bagasse, or plant straw; The molecular weight of the polyvinyl alcohol is 100,000 to 150,000.

8. The biomass-degradable liquid mulch film according to claim 6, characterized in that, When the biomass is sugarcane bagasse or plant straw, step (a) further includes enzymatic hydrolysis of the biomass using cellulase.

9. The biomass-degradable liquid mulch film according to claim 1, characterized in that, The dextrin is prepared by the following method: (1) According to the mass ratio of starch to hydrochloric acid solution of 1: (0.1~0.2), add hydrochloric acid solution with a concentration of 0.1%~0.3% to starch and mix well. Then dry at low temperature of 50~60℃ until the moisture content is 8%~12% to obtain starch mixture; (2) Preheat the starch mixture to 100~120℃, then heat it to 120~180℃ for 30~140min. After the reaction is complete, add sodium bicarbonate until the pH is neutral. Then, cool and crush to obtain the dextrin.

10. The method for preparing the biomass-degradable liquid mulch film according to any one of claims 1 to 9, characterized in that, The preparation method includes the following steps: (1) Polyvinyl alcohol, dextrin and nano silica are stirred and mixed to obtain a mixture; (2) Add glycerol to the mixture and stir evenly, then add citric acid, hydrophobic agent and excipients and stir for 20-30 minutes to obtain the masterbatch; (3) Add some water to the masterbatch and stir into a paste. Then, add the remaining water and stir thoroughly. Then, add the crosslinking agent and stir at high speed into a foam to obtain the biodegradable liquid mulch film.