Modified talc powder, preparation method thereof, and high-water-resistant and aging-resistant biodegradable PBAT mulching film and preparation method thereof

Abstract

The application provides a modified talcum powder and a preparation method thereof, first synthesizes a coupling agent with a hydroxyl group, then reacts the coupling agent with a long carbon chain carboxylic acid to generate a coupling agent with an ester group, and then grafts the coupling agent with the ester group to the surface of the talcum powder, so that a long carbon chain hydrophobic layer is formed on the surface of the talcum powder. The application also provides a high-water-resistance and aging-resistant biodegradable PBAT mulching film and a preparation method thereof, which comprises PBAT, PLA, calcium carbonate, modified talcum powder, antioxidant, ultraviolet absorber, chain extender and slip agent, and can strengthen the aging resistance of the PBAT mulching film and prolong the induction period of the mulching film. The prepared PBAT composite mulching film is easy to process, uniformly dispersed, high in water resistance and long in induction period, and can be used in crops with long growth periods such as cotton.

Description

Technical Field

[0001] This invention belongs to the field of biodegradable materials, and particularly relates to a modified talc powder and its preparation method, and a highly water-resistant and aging-resistant biodegradable PBAT mulch film and its preparation method. Background Technology

[0002] Mulch film, also known as ground cover film, is usually transparent or black PE film, but green or silver films are also available. It is used to cover the ground to increase soil temperature, retain soil moisture, maintain soil structure, prevent pests from attacking crops and diseases caused by certain microorganisms, and promote plant growth. Although mulch film appears thin, its effects are considerable. It not only increases soil temperature, retains water, conserves soil, and retains fertilizer to improve fertilizer efficiency, but also has multiple functions such as weed control, pest and disease prevention, drought and flood resistance, salt suppression and seedling protection, improvement of near-surface light and heat conditions, and ensuring product hygiene. Because mulch film is very thin, it is extremely difficult to recycle after plant growth and harvest, resulting in the formation of microplastics that remain in the soil. Over time, this accumulation can damage soil fertility and significantly impact crop yields.

[0003] Polybutylene terephthalate (PBAT) is a fully biodegradable polyester material that can be metabolized and broken down by microorganisms into carbon dioxide and water, without burdening the land. PBAT has good ductility and elongation at break, and its film also has a certain strength. However, PBAT itself has poor water resistance and decomposes quickly in the soil, which cannot meet the needs of crop growth cycles.

[0004] Currently, companies like Dawn and Hesemi focus their research on antibacterial and filler types, which doesn't significantly improve the induction period of materials on mulch films. There's also research on PBAT structures or fillings with non-biodegradable materials like PE, which contradicts the original intention of promoting biodegradability nationwide. Therefore, significantly improving PBAT films to meet the requirements of crop growth cycles and full biodegradability is of great research significance. Summary of the Invention

[0005] In view of the above-mentioned problems in the prior art, the purpose of the present invention is to provide a modified talc powder and its preparation method. First, a coupling agent with hydroxyl groups is synthesized, and then it is reacted with a long carbon chain carboxylic acid to generate a coupling agent with ester groups. Then, the coupling agent with ester groups is grafted onto the surface of talc powder to form a long carbon chain hydrophobic layer on the surface of talc powder.

[0006] The present invention also aims to provide a highly water-resistant and aging-resistant biodegradable PBAT mulch film and its preparation method. The present invention introduces the aforementioned modified talc powder into the PBAT mulch film. After a modified coupling agent is grafted onto the surface of the talc powder, on the one hand, a hydrophobic layer is formed on the surface of the talc powder to improve the water-resistant performance of the mulch film; on the other hand, the dispersibility and compatibility of the talc powder in the PBAT mulch film are improved, giving the mulch film excellent tensile strength, elongation at break, puncture strength, and other properties, and further enhancing the water-resistant properties of the mulch film.

[0007] Furthermore, due to the presence of ester bonds in the talc-grafted coupling agent, the mulch film material can preferentially hydrolyze these small molecule ester bonds after absorbing water. The long carbon chains generated by hydrolysis precipitate onto the film surface, further enhancing the film's water-blocking ability and extending its water-blocking time. Reduced contact between water and resin also slows down film disintegration and prolongs the induction period.

[0008] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0009] This invention provides a method for preparing modified talc powder, comprising the following steps:

[0010] 1) Under nitrogen protection, acrylate, vinylsilane, solvent A and initiator are mixed and heated to react. Then the solvent is removed by vacuum distillation to obtain a colorless and transparent liquid.

[0011] 2) Mix the colorless transparent liquid from step 1), long-chain carboxylic acid, and solvent B, heat to react, and then obtain the modified coupling agent by rotary evaporation, washing, and drying.

[0012] 3) Mix the modified coupling agent from step 2) with talc powder, heat and react to obtain modified talc powder.

[0013] In step 1) of the present invention, the acrylate is selected from at least one of hydroxypropyl acrylate, ethylene glycol acrylate, ethylene glycol methacrylate, and propylene glycol methacrylate, preferably hydroxypropyl acrylate and / or ethylene glycol methacrylate.

[0014] The vinyl silane is selected from at least one of vinyltriethoxysilane, methacryloxytrimethylsilane, and vinyltrimethoxyethoxysilane, preferably vinyltriethoxysilane and / or vinyltrimethoxyethoxysilane;

[0015] Preferably, the mass ratio of the acrylate to the vinylsilane is 1-4:1, more preferably 1-2:1.

[0016] In step 1) of this invention, solvent A is selected from at least one of xylene, toluene, and chloroform, preferably xylene and / or toluene;

[0017] The amount of solvent A is 1-5 times the total mass of acrylate and vinylsilane, preferably 2-3 times.

[0018] In step 1) of the present invention, the initiator is selected from at least one of azobisisobutyronitrile and benzoyl peroxide, preferably azobisisobutyronitrile;

[0019] The amount of the initiator is 1-5 wt% of the total mass of acrylate and vinylsilane, preferably 1.5-3.5 wt%.

[0020] Preferably, the initiator is fed continuously, preferably by dripping, and the feeding time is 0.5-3 hours, preferably 1-2 hours.

[0021] In step 1) of this invention, the reaction is carried out at a temperature of 100-150℃, preferably 110-140℃, for a time of 1-5h, preferably 2-3h.

[0022] In step 1) of the present invention, the pressure of the vacuum distillation is 0.01-0.1 MPaG, preferably 0.02-0.05 MPaG; the temperature is 100-200℃, preferably 120-160℃; and the time is 0.5-2h, preferably 1-1.5h.

[0023] In step 2) of the present invention, the long-chain carboxylic acid is selected from carboxylic acids with C10-C20 carbon chains, preferably at least one of dodecanoic acid and tridecanoic acid;

[0024] The mass ratio of the long-chain carboxylic acid to the colorless and transparent liquid is 1-4:1, preferably 1.5-3:1.

[0025] In step 2) of the present invention, the solvent B is selected from at least one of dichloromethane, chloroform, and benzene, preferably dichloromethane and / or chloroform;

[0026] The amount of solvent B is 1-3 times the total mass of the colorless transparent liquid and the long-chain carboxylic acid, preferably 1.5-2 times.

[0027] In step 2) of the present invention, the reaction is carried out under reflux. Preferably, the reaction temperature is 100-150℃, more preferably 110-140℃, and the time is 1-24h, preferably 5-12h.

[0028] In step 2) of this invention, the rotary evaporation, washing, and drying are conventional operations in the field, and there are no special requirements for them in this invention. Preferably, the rotary evaporation temperature is 100-160℃, more preferably 120-140℃, and the time is 0.5-2h, more preferably 1-1.5h; the washing is water washing; and the drying temperature is 80-130℃, more preferably 100-120℃.

[0029] In step 3) of the present invention, the talc powder has a particle size of 1000-10000 mesh, preferably 3000-6000 mesh;

[0030] The mass ratio of the modified coupling agent to talc is 1:1-10, preferably 1:2-5.

[0031] In step 3) of the present invention, the reaction is carried out at a temperature of 70-120°C, preferably 80-100°C, for a time of 0.5-3h, preferably 0.5-1h.

[0032] The present invention also provides modified talc powder prepared by the above method, wherein the particle size of the modified talc powder is 1250-5000 mesh, preferably 2500-4000 mesh.

[0033] The modified talc powder provided by this invention can be used to prepare PBAT mulch film materials. It possesses excellent water-blocking properties and also enhances the water-blocking ability of the mulch film. During the research of PBAT composite films, this invention discovered that current methods of increasing the water-blocking ability of films by adding small-molecule additives alone achieve this effect by precipitating small molecules onto the film surface to form a hydrophobic layer. However, in the water-rich environment of the mulch film, this hydrophobic layer is easily washed away, weakening or even eliminating the film's water-blocking ability and resulting in poor long-term effectiveness. To address this deficiency, the inventors discovered that if, based on the physical barrier properties of talc powder, it is modified and coated with a coupling agent containing ester groups to form long carbon chains before being introduced into the PBAT mulch film, the hydrophobic layer formed by precipitation will not be easily washed away by water. Furthermore, if moisture enters the film, the ester bonds in the coating structure will preferentially break, releasing long-chain small molecules, thereby enhancing and extending the film's water-blocking ability and long-term effectiveness, strengthening its anti-aging ability, and prolonging the induction period of the mulch film.

[0034] This invention also provides a highly water-resistant and aging-resistant biodegradable PBAT mulch film, the composition of which includes the following raw materials by weight percentage:

[0035]

[0036]

[0037] The total mass of all the above components is taken as 100%.

[0038] In this invention, the type of PBAT is not particularly limited. Preferably, the molecular weight of the PBAT is 10-15w, more preferably 11-13w; the melting point is 110-125℃, more preferably 115-120℃; and the acid value is 10-25, more preferably 11-18.

[0039] There are no specific requirements for the source of the PBAT; it can be purchased or prepared in-house. The preparation method is existing technology and can be prepared from raw materials adipic acid, terephthalic acid, and butanediol. Preferably, the PBAT is selected from PBAT or a mixture thereof prepared by direct polycondensation or two-step chain extension method, more preferably PBAT prepared by two-step chain extension method, wherein the chain extender is preferably HDI.

[0040] In this invention, the melt index of the PLA (polylactic acid) is 3-20 g / 10 min (190°C, 2.16 kg), preferably 3-10 g / 10 min (190°C, 2.16 kg);

[0041] Furthermore, the PLA has a melting point of 150-200℃, preferably 160-175℃.

[0042] There are no specific requirements for the source of the PLA; it can be purchased or made in-house. The preparation method is existing technology. Preferably, the PLA is selected from PLA or a mixture thereof prepared by ring-opening polymerization or direct polycondensation, and more preferably, PLA prepared by ring-opening polymerization.

[0043] In this invention, the calcium carbonate is selected from powder with a particle size of 1000-8000 mesh, preferably 3000-6000 mesh.

[0044] In this invention, the antioxidant is selected from at least one of hindered phenols, phosphites, and thioesters. The hindered phenols are selected from 2,4-dimethyl-6-styrenephenol and 2,6-di-tert-butylphenol. The phosphites are selected from tris(2,4-di-tert-butylphenyl) phosphites and bis(2,4-di-tert-butylphenyl) pentapentetrene diphosphites. The thioesters are selected from lauryl thiodipropionate and octadecyl thiodipropionate. Preferably, it is a combination of hindered phenols and phosphites.

[0045] In this invention, the ultraviolet absorber is selected from at least one of carbon black, benzotriazoles, triazines, and hindered amines. The benzotriazoles are selected from 2'-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole and 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole. The triazines are selected from 2,4,6-tris(2′-hydroxy-4′-n-butoxyphenyl) and 4-4,6-di(2,4-xylyl)-1,3,5-triazine-2-yl-1,3-phenylene glycol. The hindered amines are selected from carbamates and hydantoin-thiourea tryptophan, preferably hindered amines.

[0046] In this invention, the chain extender is selected from at least one of glycidyl ester copolymers and isocyanates. The glycidyl ester copolymer is selected from ADR4468 and XY4370, and the isocyanate is selected from ADI and HDI, preferably a glycidyl ester copolymer.

[0047] In this invention, the slip agent is selected from at least one of stearamide, erucamide, and oleamide, preferably erucamide.

[0048] This invention also provides a method for preparing the above-mentioned highly water-resistant and aging-resistant biodegradable PBAT mulch film, the steps of which include:

[0049] Calcium carbonate is mixed with slip agent, chain extender, UV absorber and antioxidant, and then added to the main feed port of a twin-screw extruder along with PBAT and PLA. Modified talc powder is fed from the side feed port. The mixture is then melt-extruded, cooled, pelletized and dried to obtain PBAT modified alloy.

[0050] PBAT modified alloys were added to a blown film machine to produce a highly water-resistant and aging-resistant biodegradable PBAT mulch film.

[0051] In this invention, the mixing is performed using a high-speed mixer with a rotation speed of 20-100 rpm, preferably 30-80 rpm; the mixing time is 3-15 min, preferably 5-10 min.

[0052] The screw temperature in the plasticizing section of the twin-screw extruder is 150-210℃, preferably 160-200℃; the screw speed is 100-800rpm, preferably 200-500rpm.

[0053] The screw temperature of the blown film machine is 130-180℃, preferably 140-160℃; the rotation speed is 5-30Hz, preferably 10-20Hz.

[0054] Compared with the prior art, the beneficial effects of the technical solution of the present invention are as follows:

[0055] This invention synthesizes an ester-based coupling agent and grafts it onto the surface of talc. Compared with traditional small molecule modifiers, the small molecules have stronger internal stress due to the coating effect of talc, making them less susceptible to erosion in water-rich environments. Furthermore, its secondary release mechanism can further extend its water-blocking effect.

[0056] Adding it to PBAT mulch film can strengthen and extend the film's water-blocking ability and lifespan, enhance its anti-aging ability, and prolong the induction period of the mulch film, thus making it suitable for more demanding crop growth cycle requirements. Detailed Implementation

[0057] The present invention will be further illustrated below with specific embodiments. These embodiments are merely illustrative and do not limit the scope of the invention.

[0058] The main sources of raw materials in the various embodiments and comparative examples of this invention are as follows:

[0059]

[0060]

[0061] Unless otherwise specified, all other raw materials and reagents were obtained through ordinary commercial channels.

[0062] The processing equipment used was: a twin-screw extruder, Coperon, model ZSK 26Mc 18, with an aspect ratio of 52 and a screw diameter of 26cm; and a blown film extruder, Zhangjiagang Lianjiang Machinery Co., Ltd., model SCM 25, with an aspect ratio of 30 and a screw diameter of 25cm.

[0063] The main performance characteristics of the PBAT mulch film in this embodiment of the invention were tested using the following methods:

[0064] Percolation strength: GB / T 21302-2007;

[0065] Tensile strength: ISO 527.3;

[0066] Initial elongation at break: ISO 527.3;

[0067] Xenon lamp aging 100h elongation at break retention rate: After aging for 100h under PV3930 standard, the elongation at break is tested according to ISO527.3, and the ratio of the elongation at break to the initial elongation at break is the retention rate;

[0068] Elongation at break retention rate after 30 days of damp heat aging: Take 5 films of 25×25cm, put them in a damp heat aging chamber at 60℃ and 60% humidity, take them out after 30 days and test the elongation at break according to ISO 527.3. The ratio of the elongation at break to the initial elongation at break is the retention rate.

[0069] Water resistance coefficient: GB / T 1037;

[0070] Water resistance coefficient after soaking in water for 5 days: Take 5 sheets of 25×25cm film, lay them flat in a sufficiently large water container, place them in a constant temperature and humidity room for 5 days, and then test them according to GB / T 1037.

[0071] Example 1

[0072] The steps for preparing modified talc are as follows:

[0073] 1) Weigh 130g of hydroxypropyl acrylate and 100g of vinyltriethoxysilane and add them to a three-necked flask. Add 460g of xylene, purge with nitrogen for protection, heat to 120℃, and then add 3.5g of initiator azobisisobutyronitrile dropwise over 1 hour. Keep the reaction at this temperature for 2 hours. Distill the product under reduced pressure at 0.02 MPaG, 120℃, and for 1 hour to obtain a colorless and transparent liquid.

[0074] 2) Add 50g of the above colorless transparent liquid and 70g of dodecanoic acid to a three-necked flask containing 180g of dichloromethane, reflux at 130℃ for 5h, rotary evaporate at 120℃ for 1h, wash with water, and dry at 110℃ to obtain a yellow powder modified coupling agent (M-VTMOS).

[0075] 3) Weigh 30g of modified coupling agent (M-VTMOS) and 60g of talc powder and add them to a grinder. Mix and react at 80℃ for 30min to obtain modified talc powder (M-Talc) with a particle size of 3000 mesh.

[0076] Preparation of highly water-resistant and aging-resistant biodegradable PBAT mulch film:

[0077] Using the modified talc powder and the formulation components in Table 1 as raw materials, and referring to the raw material dosages in Table 1, PBAT mulch film was prepared according to the following method:

[0078] First, dry the pure PBAT and PLA materials separately in a dehumidifying drying oven at 80°C for 4 hours;

[0079] Calcium carbonate was mixed with slip agent, chain extender, UV absorber, and antioxidant in a high-speed mixer at 90 rpm for 7 minutes. Then, it was added to the main feed port of a twin-screw extruder along with PBAT and PLA, while modified talc was fed through the side feed port. The mixture was then melt-extruded under the following conditions: screw speed 300 rpm, and screw temperatures from the feed port to the die head set in segments of 160℃, 160℃, 170℃, 170℃, 170℃, 180℃, 180℃, 180℃, 190℃, 190℃, 190℃. The mixture was then cooled, pelletized, and dried at 90℃ for 4 hours to obtain the PBAT-modified alloy.

[0080] PBAT modified alloy was added to a blown film machine with a screw temperature of 160℃ and a rotation speed of 10Hz to produce a biodegradable PBAT mulch film with high water resistance and aging resistance. The performance test results are shown in Table 2.

[0081] Example 2

[0082] The steps for preparing modified talc are as follows:

[0083] 1) Weigh 180g of ethylene glycol methacrylate and 100g of vinyltrimethoxyethoxysilane and add them to a three-necked flask. Add 800g of toluene, purge with nitrogen for protection, heat to 140℃, and then add 9.8g of initiator azobisisobutyronitrile dropwise over 2 hours. Keep the reaction at this temperature for 3 hours. Distill the product under reduced pressure at 0.05 MPaG, 160℃, and 1.5 hours to obtain a colorless and transparent liquid.

[0084] 2) Add 50g of the above colorless transparent liquid and 150g of tridecanoic acid to a three-necked flask containing 400g of chloroform solvent. Reflux at 140°C for 12h, rotary evaporate at 140°C for 1.5h, wash with water, and dry at 110°C to obtain a yellow powder modified coupling agent.

[0085] 3) Weigh 30g of modified coupling agent and 150g of talc powder and add them to a grinder. Mix and react at 100℃ for 1 hour to obtain modified talc powder with a particle size of 3000 mesh.

[0086] Preparation of highly water-resistant and aging-resistant biodegradable PBAT mulch film:

[0087] Using the modified talc powder and the formulation components in Table 1 as raw materials, and referring to the raw material dosages in Table 1, PBAT mulch film was prepared according to the following method:

[0088] First, dry the pure PBAT and PLA materials separately in a dehumidifying drying oven at 80°C for 4 hours;

[0089] Calcium carbonate was mixed with slip agent, chain extender, UV absorber, and antioxidant in a high-speed mixer at 50 rpm for 10 minutes. Then, it was added to the main feed port of a twin-screw extruder along with PBAT and PLA, while modified talc was fed through the side feed port. The mixture was then melt-extruded under the following conditions: screw speed 300 rpm, and screw temperatures from the feed port to the die head set in segments of 160℃, 160℃, 170℃, 170℃, 170℃, 180℃, 180℃, 180℃, 190℃, 190℃, 190℃. The mixture was then cooled, pelletized, and dried at 90℃ for 4 hours to obtain the PBAT-modified alloy.

[0090] PBAT modified alloy was added to a blown film machine with a screw temperature of 170℃ and a rotation speed of 14Hz to produce a biodegradable PBAT mulch film with high water resistance and aging resistance. The performance test results are shown in Table 2.

[0091] Example 3

[0092] The steps for preparing modified talc are as follows:

[0093] 1) Weigh 130g of hydroxypropyl acrylate and 100g of vinyltriethoxysilane and add them to a three-necked flask. Add 580g of xylene, purge with nitrogen for protection, heat to 130℃, and then add 4.6g of initiator azobisisobutyronitrile dropwise over 1.5h. Keep the reaction at this temperature for 2.5h. Distill the product under reduced pressure at 0.03MPaG, 140℃, and 1.2h to obtain a colorless and transparent liquid.

[0094] 2) Add 50g of the above colorless transparent liquid and 70g of dodecanoic acid to a three-necked flask containing 200g of dichloromethane, reflux at 130℃ for 8h, rotary evaporate at 130℃ for 1h, wash with water, and dry at 110℃ to obtain a yellow powder modified coupling agent (M-VTMOS).

[0095] 3) Weigh 30g of modified coupling agent (M-VTMOS) and 60g of talc powder and add them to a grinder. Mix and react at 90℃ for 50min to obtain modified talc powder (M-Talc) with a particle size of 3000 mesh.

[0096] Preparation of highly water-resistant and aging-resistant biodegradable PBAT mulch film:

[0097] Using the modified talc powder and the formulation components in Table 1 as raw materials, and referring to the raw material dosages in Table 1, PBAT mulch film was prepared according to the following method:

[0098] First, dry the pure PBAT and PLA materials separately in a dehumidifying drying oven at 80°C for 4 hours;

[0099] Calcium carbonate was mixed with slip agent, chain extender, UV absorber, and antioxidant in a high-speed mixer at 90 rpm for 7 minutes. Then, it was added to the main feed port of a twin-screw extruder along with PBAT and PLA, while modified talc was fed through the side feed port. The mixture was then melt-extruded under the following conditions: screw speed 300 rpm, and screw temperatures from the feed port to the die head set in segments of 160℃, 160℃, 170℃, 170℃, 170℃, 180℃, 180℃, 180℃, 190℃, 190℃, 190℃. The mixture was then cooled, pelletized, and dried at 90℃ for 4 hours to obtain the PBAT-modified alloy.

[0100] PBAT modified alloy was added to a blown film machine with a screw temperature of 150℃ and a rotation speed of 9Hz to produce a biodegradable PBAT mulch film with high water resistance and aging resistance. The performance test results are shown in Table 2.

[0101] Table 1. Raw materials and dosage (%) of PBAT mulch film in Examples 1-3

[0102] raw material Example 1 Example 2 Example 3 PBAT(801T) 85.8 82.8 77.8 PLA (LX575) 3 3 3 Calcium carbonate 3 3 3 Modified talc M-Talc 7 10 15 Antioxidant 1010 0.4 0.3 0.4 Antioxidant 168 0.2 0.15 0.2 UV absorber UV-944 0.3 0.4 0.2 Chain extender ADR4468 0.1 0.15 0.2 Erucamide 0.2 0.2 0.2

[0103] Comparative Example 1

[0104] The PBAT mulch film was prepared according to the method in Example 1, with the only difference being that the talc powder was not modified and was used directly to prepare the PBAT mulch film. Other parameters and operations remained unchanged. The mulch film performance test results are shown in Table 2.

[0105] Comparative Example 2

[0106] The PBAT mulch film was prepared according to the method in Example 1, except that when preparing modified talc, step 1) was omitted, and vinyltriethoxysilane was directly added to step 2) to react with dodecanoic acid. Other parameters and operations remained unchanged. The mulch film performance test results are shown in Table 2.

[0107] Comparative Example 3

[0108] The PBAT mulch film was prepared according to the method in Example 1, except that hydroxypropyl acrylate was replaced with glyceryl monostearate when preparing modified talc powder. Other parameters and operations remained unchanged. The mulch film performance test results are shown in Table 2.

[0109] Comparative Example 4

[0110] The PBAT mulch film was prepared according to the method in Example 1, except that when preparing the modified talc powder, step 1) was omitted, and hydroxypropyl acrylate was directly added to step 2) to react with dodecanoic acid. Other parameters and operations remained unchanged. The mulch film performance test results are shown in Table 2.

[0111] Comparative Example 5

[0112] The PBAT mulch film was prepared according to the method in Example 1, except that when preparing the modified talc powder, vinyltriethoxysilane was replaced with γ-glycidoxypropyltrimethoxysilane. Other parameters and operations remained unchanged. The mulch film performance test results are shown in Table 2.

[0113] Comparative Example 6

[0114] The PBAT mulch film was prepared according to the method in Example 1, with the only difference being that when preparing modified talc, step 2) of modification was omitted, and the reaction product of step 1) was directly used in step 3). Other parameters and operations remained unchanged, and the mulch film performance test results are shown in Table 2.

[0115] Comparative Example 7

[0116] The PBAT mulch film was prepared according to the method in Example 1, except that when preparing the modified talc powder, dodecanoic acid was replaced with short-chain carboxylic acid (acetic acid), while other parameters and operations remained unchanged. The mulch film performance test results are shown in Table 2.

[0117] The modified PBAT alloys obtained in Examples 1-3 and Comparative Examples 1-7 were blown into film in an extrusion blown film machine. The screw temperature was set to 150°C, 170°C, 170°C, 170°C, and 175°C, and the screw speed was 12 Hz. The film was blown into a film with a thickness of 10 micrometers.

[0118] Table 2. Thin film performance results of Examples 1-3 and Comparative Examples 1-7

[0119]

[0120] As can be seen from Comparative Examples 1-7 and Examples 1-3, compared with the prior art, the aging resistance and hydrophobicity of the present invention are significantly improved, thus meeting the stringent requirements of crops.

[0121] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing modified talc powder, characterized in that the steps include... include: 1) Under nitrogen protection, acrylate, vinylsilane, solvent A and initiator are mixed and heated to react. Then the solvent is removed by vacuum distillation to obtain a colorless and transparent liquid. 2) Mix the colorless transparent liquid from step 1), long-chain carboxylic acid, and solvent B, heat to react, and then obtain the modified coupling agent by rotary evaporation, washing, and drying. 3) Mix the modified coupling agent from step 2) with talc powder, heat and react to obtain modified talc powder; The acrylate is selected from at least one of hydroxypropyl acrylate, ethylene glycol acrylate, ethylene glycol methacrylate, and propylene glycol methacrylate; The vinylsilane is selected from at least one of vinyltriethoxysilane and vinyltrimethoxyethoxysilane; The long-chain carboxylic acid is selected from carboxylic acids with C10-C20 carbon chains.

2. The preparation method according to claim 1, characterized in that, In step 1), the mass ratio of the acrylate to the vinylsilane is 1-4:1; Solvent A is selected from at least one of xylene, toluene, and chloroform; Solvent A is used in an amount of 1-5 times the total mass of acrylate and vinylsilane; The initiator is selected from at least one of azobisisobutyronitrile and benzoyl peroxide; The amount of initiator used is 1-5 wt% of the total mass of acrylate and vinylsilane; In step 1), the reaction is carried out at a temperature of 100-150℃ for 1-5 hours. The vacuum distillation is carried out at a pressure of 0.01-0.1 MPaG, a temperature of 100-200℃, and a time of 0.5-2 h.

3. The preparation method according to claim 2, characterized in that, The mass ratio of the acrylate to the vinylsilane is 1-2:

1.

4. The preparation method according to claim 2, characterized in that, The amount of solvent A used is 2-3 times the total mass of acrylate and vinylsilane.

5. The preparation method according to claim 2, characterized in that, The amount of initiator used is 1.5-3.5 wt% of the total mass of acrylate and vinylsilane.

6. The preparation method according to claim 2, characterized in that, The reaction is carried out at a temperature of 110-140℃ for 2-3 hours.

7. The preparation method according to claim 2, characterized in that, The vacuum distillation is carried out at a pressure of 0.02-0.05 MPaG, a temperature of 120-160℃, and a time of 1-1.5 h.

8. The preparation method according to claim 1, characterized in that, In step 1), the initiator is fed continuously for 0.5-3 hours.

9. The preparation method according to claim 8, characterized in that, The feeding time is 1-2 hours.

10. The preparation method according to claim 8, characterized in that, The initiator is added dropwise.

11. The preparation method according to claim 1, characterized in that, In step 2), the long-chain carboxylic acid is selected from at least one of dodecanoic acid and tridecanoic acid; The mass ratio of the long-chain carboxylic acid to the colorless and transparent liquid is 1-4:1; Solvent B is selected from at least one of dichloromethane, trichloromethane, and benzene; The amount of solvent B used is 1-3 times the total mass of the colorless transparent liquid and the long-chain carboxylic acid; In step 2), the reaction is carried out under reflux. The rotary evaporation temperature is 100-160℃, and the time is 0.5-2h; the washing is water washing; the drying temperature is 80-130℃.

12. The preparation method according to claim 11, characterized in that, The mass ratio of the long-chain carboxylic acid to the colorless and transparent liquid is 1.5-3:

1.

13. The preparation method according to claim 11, characterized in that, The amount of solvent B used is 1.5-2 times the total mass of the colorless transparent liquid and the long-chain carboxylic acid.

14. The preparation method according to claim 11, characterized in that, The reaction is carried out at a temperature of 100-150℃ for 1-24 hours.

15. The preparation method according to claim 14, characterized in that, The reaction is carried out at a temperature of 110-140℃ for 5-12 hours.

16. The preparation method according to claim 11, characterized in that, The rotary evaporation temperature is 120-140℃, and the time is 1-1.5h.

17. The preparation method according to claim 11, characterized in that, The drying temperature is 100-120℃.

18. The preparation method according to claim 1, characterized in that, In step 3), the talc powder has a particle size of 1000-10000 mesh; The mass ratio of the modified coupling agent to talc is 1:1-10; In step 3), the reaction is carried out at a temperature of 70-120℃ for a time of 0.5-3h.

19. The preparation method according to claim 18, characterized in that, The talc powder has a particle size of 3000-6000 mesh.

20. The preparation method according to claim 18, characterized in that, The mass ratio of the modified coupling agent to talc is 1:2-5.

21. The preparation method according to claim 18, characterized in that, The reaction is carried out at a temperature of 80-100℃ for a time of 0.5-1h.

22. A modified talc powder prepared by the preparation method according to any one of claims 1-21, characterized in that, The modified talc powder has a particle size of 1250-5000 mesh.

23. The modified talc powder according to claim 22, characterized in that, The modified talc powder has a particle size of 2500-4000 mesh.

24. A highly water-resistant and aging-resistant biodegradable PBAT mulch film, characterized in that, The raw material composition by weight percentage includes: PBAT 60-85%; PLA5-30%; Calcium carbonate 1-10%; Modified talc powder 5-30%; Antioxidant 0.05-2%; UV absorber 0.05-2%; Chain extender 0.05-2%; Lubricant 0.05-2%; Based on the total mass of all the above components being 100%; The modified talc powder is prepared by the preparation method according to any one of claims 1-21.

25. The biodegradable PBAT mulch film according to claim 24, characterized in that, The raw material composition by weight percentage includes: PBAT 65-80%; PLA8-20%; Calcium carbonate 3-7%; Modified talc powder 8-20%; Antioxidant 0.1-1%; UV absorber 0.1-0.6%; Chain extender 0.1-1%; Lubricant 0.1-1%; The total mass of all the above components is taken as 100%.

26. The biodegradable PBAT mulch film according to claim 24, characterized in that, The PBAT has a molecular weight of 10-15w, a melting point of 110-125℃, and an acid value of 10-25. The PLA has a melt index of 3-20 g / 10 min at 190℃ and 2.16 kg. The PLA has a melting point of 150-200℃.

27. The biodegradable PBAT mulch film according to claim 26, characterized in that, The PBAT has a molecular weight of 11-13w, a melting point of 115-120℃, and an acid value of 15-20.

28. The biodegradable PBAT mulch film according to claim 26, characterized in that, The PBAT is selected from PBAT or a mixture thereof prepared by direct polycondensation or two-step chain extension.

29. The biodegradable PBAT mulch film according to claim 28, characterized in that, The PBAT is selected from PBAT prepared by a two-step chain extension method.

30. The biodegradable PBAT mulch film according to claim 26, characterized in that, The PLA has a melt index of 3-10 g / 10 min at 190℃ and 2.16 kg.

31. The biodegradable PBAT mulch film according to claim 26, characterized in that, The PLA has a melting point of 160-175℃.

32. The biodegradable PBAT mulch film according to claim 26, characterized in that, The PLA is selected from PLA or a mixture thereof prepared by ring-opening polymerization or direct polycondensation.

33. The biodegradable PBAT mulch film according to claim 32, characterized in that, The PLA is selected from PLA prepared by ring-opening polymerization.

34. The biodegradable PBAT mulch film according to claim 24, characterized in that, The calcium carbonate is selected from powder with a particle size of 1000-8000 mesh; The antioxidant is selected from at least one of hindered phenols, phosphites, and thioesters. The hindered phenols are selected from 2,4-dimethyl-6-styrenephenol and 2,6-di-tert-butylphenol. The phosphites are selected from tris(2,4-di-tert-butylphenyl) phosphites and bis(2,4-di-tert-butylphenyl) pentapentetrene diphosphites. The thioesters are selected from lauryl thiodipropionate and octadecyl thiodipropionate. The ultraviolet absorber is selected from at least one of carbon black, benzotriazoles, triazines, and hindered amines. The benzotriazoles are selected from 2'-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole and 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole. The triazines are selected from 2,4,6-tris(2′-hydroxy-4′-n-butoxyphenyl) and 4-4,6-di(2,4-dimethylyl)-1,3,5-triazine-2-yl-1,3-phenylene glycol. The hindered amines are selected from carbamates and hydantoin-thiourea tryptophan. The chain extender is selected from at least one of glycidyl ester copolymer and isocyanate, wherein the glycidyl ester copolymer is selected from ADR4468 and XY4370, and the isocyanate is selected from ADI and HDI. The slip agent is selected from at least one of stearamide, erucamide, and oleamide.

35. The biodegradable PBAT mulch film according to claim 34, characterized in that, The calcium carbonate is selected from powder with a particle size of 3000-6000 mesh.

36. The biodegradable PBAT mulch film according to claim 34, characterized in that, The antioxidant is selected from a combination of hindered phenols and phosphites.

37. A method for preparing a high water-resistant and aging-resistant biodegradable PBAT mulch film according to any one of claims 24-36, characterized in that the steps include... include: Calcium carbonate is mixed with slip agent, chain extender, UV absorber and antioxidant, and then added to the main feed port of a twin-screw extruder along with PBAT and PLA. Modified talc powder is fed from the side feed port. The mixture is then melt-extruded, cooled, pelletized and dried to obtain PBAT modified alloy. PBAT modified alloys were added to a blown film machine to produce a highly water-resistant and aging-resistant biodegradable PBAT mulch film.

38. The preparation method according to claim 37, characterized in that, The mixing is performed using a high-speed mixer with a speed of 20-100 rpm and a mixing time of 3-15 min; The screw temperature in the plasticizing section of the twin-screw extruder is 150-210℃, and the rotation speed is 100-800rpm. The screw temperature of the blown film machine is 130-180℃, and the rotation speed is 5-30Hz.

39. The preparation method according to claim 38, characterized in that, The high-speed mixer has a rotation speed of 30-80 rpm and a mixing time of 5-10 min.

40. The preparation method according to claim 38, characterized in that, The plasticizing section screw temperature of the twin-screw extruder is 160-200℃, and the rotation speed is 200-500rpm.

41. The preparation method according to claim 38, characterized in that, The screw temperature of the blown film machine is 140-160℃, and the rotation speed is 10-20Hz.

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