A PBAT / bamboo powder biodegradable composite masterbatch, its preparation method and composite film

Abstract

The present invention belongs to the technical field of biodegradable materials, and relates to a PBAT / bamboo powder biodegradable composite masterbatch, its preparation method and composite film. The composite masterbatch comprises the following raw materials in parts by mass: 100 parts of PBAT, 10 - 30 parts of modified bamboo powder, 5 - 10 parts of compatibilizing grafting agent, 0.5 - 1 part of retarder, 20 - 30 parts of barrier agent, and 0.2 - 0.4 part of chain extender; the modified bamboo powder is obtained by impregnating bamboo powder with an inorganic alkali solution and modifying it with an acyl halide reagent; the compatibilizing grafting agent is obtained by subjecting PBAT to ultraviolet grafting modification with a grafting agent, and the grafting agent is a compound of a carboxyl-containing acrylate and glycidyl unsaturated fatty acid ester in a mass ratio of 1:(1 - 2). The present invention modifies bamboo powder and introduces a novel compatibilizing grafting agent, improving the hydrophobicity, dispersibility and compatibility with PBAT of bamboo powder. The obtained composite film has good appearance, high water and oxygen barrier properties and good mechanical properties.

Description

Technical Field

[0001] The present invention belongs to the technical field of biodegradable materials, and particularly relates to a PBAT / bamboo powder biodegradable composite masterbatch, a preparation method thereof, and a composite film. Background Art

[0002] Poly(butylene adipate-co-terephthalate) (PBAT), as a biodegradable aliphatic-aromatic copolyester, has attracted much attention due to its good processing properties, mechanical properties, and biocompatibility. In many fields, especially in the packaging and agricultural mulch film industries, PBAT has shown considerable application prospects. However, the manufacturing cost of PBAT is relatively high. Constructing a composite system with other low-cost and environmentally friendly materials is an effective way to reduce costs. Bamboo powder has the advantages of wide sources, renewability, and degradability. Using bamboo powder to compound with PBAT to prepare PBAT-based composites can effectively reduce costs and also make full use of the remaining bamboo forest resources. However, there are still the following problems in the compounding of bamboo powder and PBAT: 1) For the matrix PBAT, the compatibility and dispersibility of bamboo powder are poor, which affects the mechanical properties of the composite material; 2) Bamboo powder is prone to thermal-oxidative degradation during high-temperature processing, and a series of complex reactions occur to generate brown polymers, making the color of the prepared PBAT-based composite material darker, seriously affecting the appearance quality of the product; 3) Bamboo powder has good water absorption, while PBAT itself has poor water and oxygen barrier properties, and the water and oxygen barrier properties of the product prepared by compounding bamboo powder and PBAT are even worse; 4) In view of the above problems, the effective addition amount of bamboo powder in the prior art is generally low, and the real comprehensive utilization of bamboo powder has not been achieved.

[0003] Patent CN111548611A discloses a high-density bamboo powder / PBAT / polylactic acid biodegradable plastic and a preparation method thereof, which uses a high-speed grinder to prepare ultra-fine bamboo powder with a particle size of 5000-7000 meshes to improve its dispersibility and compatibility in PBAT, but does not give quantitative particle size distribution data of bamboo powder, and the appearance quality and mechanical properties of the prepared composite material are poor; secondly, the process of grinding bamboo powder to 5000-7000 meshes in this patent is energy-consuming and will increase the manufacturing cost. Patent CN118599297A discloses a degradable plastic prepared from marine recycled plastics and a preparation method thereof, and this patent does not pay attention to the compatibility problem of bamboo powder. Summary of the Invention

[0004] In view of the problems of poor compatibility, low effective addition amount of bamboo powder, dark color of products, and poor water and oxygen barrier properties of the composite of bamboo powder and PBAT in the prior art, the present invention provides a PBAT / bamboo powder biodegradable composite masterbatch, a preparation method thereof, and a composite film. By modifying bamboo powder and introducing a new compatibilizing grafting agent, and through the synergistic effect with other additives, a PBAT / bamboo powder biodegradable composite masterbatch with a high addition amount of bamboo powder is prepared, and then a film product with good mechanical properties, appearance, and high water and oxygen barrier rate is prepared.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A PBAT / bamboo powder biodegradable composite masterbatch, comprising the following raw materials in parts by mass:

[0007] 100 parts of PBAT,

[0008] 10 - 30 parts of modified bamboo powder,

[0009] 5 - 10 parts of compatibilizing grafting agent,

[0010] 0.5 - 1 part of retarder,

[0011] 20 - 30 parts of barrier agent,

[0012] 0.2 - 0.4 part of chain extender,

[0013] The modified bamboo powder is obtained by sequentially impregnating ultrafine bamboo powder with an inorganic alkali solution and modifying it with an acyl halide reagent; the compatibilizing grafting agent is obtained by grafting modification of PBAT with ultraviolet light using a grafting agent, and the grafting agent is a compound of an acrylate containing a carboxyl group and a glycidyl unsaturated fatty acid ester in a mass ratio of 1:(1 - 2).

[0014] Furthermore, the particle size of the ultrafine bamboo powder is 800 - 1000 mesh, the inorganic alkali solution is an aqueous solution of NaOH and / or KOH, the concentration is 4 - 7 wt%, and the mass ratio of the ultrafine bamboo powder to the inorganic alkali solution is 1:(2 - 5); the conditions for the impregnation treatment are: impregnation at 20 - 30 °C for 10 - 30 min, then filtration, washing with water until neutral, and drying at 60 - 80 °C to constant weight. After the impregnation and etching of the inorganic alkali solution, the surface active sites of the ultrafine bamboo powder increase, which is beneficial to the subsequent modification with the acyl halide reagent.

[0015] Further, the ultrafine bamboo powder is obtained by successively impregnating bamboo raw powder with an inorganic salt solution, steam explosion, and pulverization; the particle size D50 of the bamboo raw powder is 100-200 mesh, the inorganic salt solution is an aqueous NaCl solution with a concentration of 0.5-2.0 wt%, the solid-liquid ratio of the bamboo powder to the inorganic salt solution is 1 g:(10-15) mL, and the conditions for impregnating with the inorganic salt solution are: impregnating at 20-30 °C for 1-2 h; the conditions for steam explosion are: explosion pressure 1.5-2.0 MPa, holding pressure time 10-25 min; the pulverization is jet milling. After steam explosion and pulverization treatment, the surface roughness and specific surface area of the bamboo powder increase.

[0016] Further, the dosage of the acyl halide reagent is 4-6 wt% of the ultrafine bamboo powder; the acyl halide reagent is at least one of benzoyl chloride, 2-isopropoxybenzoyl chloride, 4-chlorobenzoyl bromide, 3-bromo-5-trifluoromethylbenzoyl chloride, 2-bromo-4,5-dimethoxy-benzoyl chloride, trifluoromethylbenzoyl chloride, p-trifluoromethoxybenzenesulfonyl chloride, 5-bromo-2-isopropoxybenzoyl chloride.

[0017] Further, the conditions for modifying with the acyl halide reagent are: reacting at 80-100 °C for 2-4 h under a vacuum environment of 0.05-0.08 Mpa. The acyl halide group in the acyl halide reagent undergoes an acylation reaction with the hydroxyl group in the bamboo powder to form an ester group, thereby introducing the acyl halide reagent into the side chain of the bamboo powder, improving the hydrophobicity and dispersibility of the bamboo powder, and increasing the effective addition amount of the bamboo powder in PBAT; at the same time, the graft modification destroys the regularity of the cellulose molecular chain of the bamboo powder, reduces the crystallinity and imparts partial thermoplasticity. At the same time, the ester group generated by the acylation reaction during modification has a better polarity match with the main chain of PBAT, enhancing the interfacial compatibility; in addition, other groups in the bamboo powder such as acetyl groups are easily oxidized to form aldehydes and ketones during hot processing, and quinone substances are generated, resulting in color deepening. However, the acyl halide reagent can cover the active sites or react with these groups to reduce oxidation discoloration during hot processing and act synergistically with the blocker to solve the serious problem of color change during the processing of bamboo powder-based composites.

[0018] Further, the dosage of the grafting agent is 10-20 wt% of PBAT.

[0019] Further, the carboxyl-containing acrylate can be commercially available or self-made, and is selected from at least one of mono(2-acryloyloxyethyl) succinate, mono-2-(methacryloyloxy)ethyl succinate, mono-2-acryloyloxyethyl maleate, mono-2-(methacryloyloxy)ethyl maleate, mono-2-acryloyloxyethyl fumarate, mono-2-(methacryloyloxy)ethyl fumarate, mono-2-(methacryloyloxy)ethyl itaconate.

[0020] Furthermore, the unsaturated fatty acid glycidyl ester is at least one of glycidyl acrylate and glycidyl methacrylate. The carboxyl-containing acrylate and the unsaturated fatty acid glycidyl ester are used to carry out ultraviolet grafting reaction on PBAT to form a novel PBAT-based compatibilizing grafting agent containing carboxyl and epoxy groups. This compatibilizing grafting agent has good reaction compatibility with PBAT. At the same time, the active carboxyl and epoxy groups in this compatibilizing grafting agent can interact or react with the active groups on the surface of bamboo powder, significantly improving the compatibility of bamboo powder in the composite material system, enhancing the interfacial adhesion force, and further increasing the effective addition amount of bamboo powder in PBAT.

[0021] Furthermore, the conditions for the ultraviolet grafting are: ultraviolet irradiation with a wavelength of 200 - 400 nm for 10 - 30 min.

[0022] Furthermore, the compatibilizing grafting agent is prepared by a preparation method including the following steps: PBAT, a grafting agent, and an initiator are dissolved in a solvent together, and a grafting reaction is carried out under ultraviolet irradiation. After the reaction is completed, it is filtered, washed, and dried to obtain the compatibilizing grafting agent.

[0023] Preferably, the dosage of the initiator is 5 - 8 wt% of PBAT, and the initiator is at least one of benzophenone, α-dimethoxybenzil ketal, 1-hydroxycyclohexyl phenyl ketone, and 2-hydroxy-2-methyl-1-phenyl-1-propanone; the solvent is chloroform or tetrahydrofuran, and its dosage is 4 - 6 times the mass of PBAT; the washing is carried out with ethanol and / or pure water, and the drying is vacuum drying at 50 - 70 °C until constant weight.

[0024] Furthermore, the weight-average molecular weight of the PBAT is 200,000 - 400,000.

[0025] Furthermore, the retarder is at least one of calcium sulfite, sodium sulfite, magnesium sulfite, and sodium bisulfite. The retarder has strong reducibility and preferentially reacts with oxygen during the hot processing to block the oxidation path of phenolic substances in bamboo powder. Secondly, the metal ions in the retarder help to improve the thermal stability of bamboo powder and weaken the color change during processing. The synergistic effect of the retarder and the bamboo powder modifier solves the problem of color change during the processing of bamboo powder-based composites.

[0026] Furthermore, the barrier agent is a polycarbonate copolymer, such as PPC-P can be selected; the chain extender is at least one of 2,4-toluene diisocyanate, pyromellitic dianhydride, glycidyl methacrylate, and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane.

[0027] Further, the raw materials further include 0.1 to 1 part of weather resistance agent and 0.1 to 1 part of mildew preventive; the weather resistance agent is at least one of bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, 3-benzotriazole-5-tert-butyl-4-hydroxyphenyl propionate, 2-(2-hydroxy-3-cumyl-5-tert-octylphenyl) benzotriazole, 2-(3,5-di-tert-butyl-2-hydroxyphenyl)-5-chlorobenzotriazole, 2-hydroxy-4-n-octyloxybenzophenone; the mildew preventive is at least one of dimethyl fumarate, iodopropynyl butylcarbamate, dodecyl dimethyl benzyl ammonium chloride, dichlorodidecyldimethylammonium chloride.

[0028] In the second aspect, the present invention also provides a preparation method of the above PBAT / bamboo powder biodegradable composite masterbatch, comprising the following steps: mixing the above raw materials and then performing melt extrusion, followed by water cooling, pelletizing, and drying to obtain the PBAT / bamboo powder biodegradable composite masterbatch.

[0029] Further, the conditions of the melt extrusion are: melting and pelletizing in a twin-screw extruder, with a melting temperature of 150 to 250 °C and a screw speed of 150 to 300 rpm; the drying is carried out at 60 to 80 °C for 12 to 24 h.

[0030] In the third aspect, the present invention also provides a composite film, which is formed by blowing the aforementioned PBAT / bamboo powder biodegradable composite masterbatch with a blown film machine.

[0031] Further, the rotational speed of the blown film machine is 70 to 120 rpm, the temperature is set at 165 to 185 °C, the blow-up ratio is 2 to 3.5, and the traction speed is 3 to 7 m / min. Adjust the above parameters according to the required thickness of the composite film.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] 1. By modifying the bamboo powder and introducing a new compatibilizing grafting agent, the present invention improves the dispersibility and compatibility of the bamboo powder in the PBAT matrix through polarity matching and chemical reactions, enhances the interfacial adhesion between the bamboo powder and PBAT, breaks through the technical bottleneck of the bamboo powder addition amount, and the composite film products can still maintain excellent comprehensive performance and good appearance when the bamboo powder addition amount is as high as 30%.

[0034] 2. By modifying the bamboo powder, the present invention is beneficial to improving the color of the products, and through the synergistic effect with the blocker, solves the discoloration problem during the processing of the bamboo powder-based composite materials, thereby obtaining products with a lighter color.

[0035] 3. By modifying the bamboo powder to improve its hydrophobicity and combining with the synergistic effect of the barrier agent, the finally prepared film products have good water and oxygen barrier properties. Detailed implementation manners

[0036] The present invention will be further described below in conjunction with specific embodiments. In the following embodiments, unless otherwise specified, the parts are by mass.

[0037] The bamboo raw powder is selected from Lu'an Xingzhu New Material Technology Co., Ltd., and the particle size is 100 mesh.

[0038] The PBAT powder is selected from Dongguan Kadar Plastic Raw Materials Co., Ltd., the particle size is about 400 mesh, and the weight average molecular weight is about 248,000.

[0039] The polycarbonate copolymer PPC-P is selected from Shandong Lianxin Environmental Protection Technology Co., Ltd., and the weight average molecular weight is about 152,000.

[0040] Example 1

[0041] (S1) The bamboo raw powder is placed into an aqueous NaCl solution (concentration 1 wt%) at a solid-liquid ratio of 1 g: 10 mL and impregnated at 25 °C for 1.5 h to form a mixed material. Then the mixed material is placed into a steam explosion tank, and saturated steam is introduced for steam explosion. The explosion pressure is 1.7 MPa, and the pressure maintaining time is 15 min. After explosion, the material is collected, washed with water, dried at 90 °C for 12 h to obtain dry material, and then the dry material is pulverized by air flow to a particle size of 800 - 1000 mesh, thus obtaining ultrafine bamboo powder;

[0042] (S2) 100 parts of ultrafine bamboo powder are placed into 400 parts of an aqueous KOH solution (concentration 4 wt%) and impregnated under ultrasonic wave at 25 °C for 20 min. The ultrasonic frequency is 50 kHz. After impregnation, it is filtered, washed with pure water until neutral, and dried at 60 °C for 24 h to obtain pretreated ultrafine bamboo powder. The pretreated ultrafine bamboo powder and 4 parts of 4-chlorobenzoyl bromide are put into a vacuum high-speed mixer, the vacuum degree is set to 0.05 Mpa, and they are kneaded and modified at 80 °C and a rotation speed of 200 rpm for 2 h. After the reaction ends, modified bamboo powder is obtained;

[0043] (S3) 100 parts of PBAT powder, 10 parts of grafting agent [a compound of succinic acid mono(2-acryloyloxyethyl ester) and glycidyl acrylate in a mass ratio of 1:1], and 6 parts of initiator benzophenone are jointly dissolved in 400 parts of chloroform, and then placed into an ultraviolet reactor and irradiated with ultraviolet light of 360 nm for 20 min. After the reaction ends, it is filtered, washed with absolute ethanol, and vacuum dried at 70 °C for 12 h to obtain a compatibilizing grafting agent;

[0044] (S4) The modified bamboo powder, compatibilizing grafting agent and other raw materials prepared in the above steps are mixed evenly according to the following parts by mass:

[0045] PBAT 100 parts,

[0046] Modified bamboo powder 10 parts,

[0047] 5 parts of compatibilizing grafting agent,

[0048] 0.5 part of calcium sulfite as a retarder,

[0049] 20 parts of PPC-P as a barrier agent,

[0050] 0.2 part of 2,4-toluene diisocyanate as a chain extender,

[0051] 0.1 part of bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate as a weathering agent,

[0052] 0.1 part of dimethyl fumarate as a mildew-proof agent,

[0053] Put the above-mentioned mixed raw materials into a twin-screw extruder, melt and extrude, cool with water, and pelletize. The melting temperature is set at 165 °C, the extrusion temperature is set at 155 °C, the screw extrusion speed is 150 rpm, and the degreasing vacuum degree is set at 0.06 Mpa; the pelletized material is dried at 60 °C for 24 h to obtain PBAT / bamboo powder biodegradable composite masterbatch.

[0054] Example 2

[0055] The rest is the same as in Example 1, except that: in step (S2), 4.5 parts of p-trifluoromethoxybenzenesulfonyl chloride are used to replace 4 parts of 4-chlorobenzoyl bromide; in step (S3), succinic acid mono(2-acryloyloxyethyl ester) and glycidyl acrylate are compounded at a mass ratio of 1:1.5; in step (S4), 0.6 part of sodium sulfite is used to replace 0.5 part of calcium sulfite.

[0056] Example 3

[0057] The rest is the same as in Example 1, except that: in step (S2), 6 parts of 3-bromo-5-trifluoromethylbenzoyl chloride are used to replace 4 parts of 4-chlorobenzoyl bromide; in step (S3), succinic acid mono(2-acryloyloxyethyl ester) and glycidyl acrylate are compounded at a mass ratio of 1:2; in step (S4), 0.7 part of magnesium sulfite is used to replace 0.5 part of calcium sulfite.

[0058] Example 4

[0059] The rest is the same as in Example 1, except that: in step (S3), the dosage of the grafting agent is 15 parts.

[0060] Example 5

[0061] The rest is the same as in Example 1, except that: in step (S3), the dosage of the grafting agent is 20 parts.

[0062] Example 6

[0063] The rest is the same as in Example 1, except that: in step (S3), the grafting agent is a compound of fumaric acid mono-2-(methacryloyloxy)ethyl ester and glycidyl methacrylate in a mass ratio of 1:1.

[0064] Example 7

[0065] The rest is the same as in Example 1, except that in step (S4), the mass parts of each raw material are:

[0066] 100 parts of PBAT,

[0067] 20 parts of modified bamboo powder,

[0068] 8 parts of compatibilizing grafting agent,

[0069] 0.8 part of sodium sulfite as a retarder,

[0070] 25 parts of PPC-P as a barrier agent,

[0071] 0.4 part of 2,4-toluene diisocyanate as a chain extender,

[0072] 0.5 part of bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate as a weathering agent,

[0073] 0.5 part of dimethyl fumarate as a mildew-proof agent.

[0074] Example 8

[0075] The rest is the same as in Example 1, except that in step (S4), the mass parts of each raw material are:

[0076] 100 parts of PBAT,

[0077] 30 parts of modified bamboo powder,

[0078] 10 parts of compatibilizing grafting agent,

[0079] 1 part of magnesium sulfite as a retarder,

[0080] 30 parts of PPC-P as a barrier agent,

[0081] 0.4 part of 2,4-toluene diisocyanate as a chain extender,

[0082] 0.5 part of bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate as a weathering agent,

[0083] 0.5 part of dimethyl fumarate as a mildew-proof agent.

[0084] Comparative Example 1

[0085] The rest is the same as in Example 1, except that: Steps (S2) and (S3) are omitted, ultrafine bamboo powder is used to replace the modified bamboo powder in Step (S4), and the compatibilizing grafting agent is not used.

[0086] Comparative Example 2

[0087] The rest is the same as in Example 8, except that: Steps (S2) and (S3) are omitted, ultrafine bamboo powder is used to replace the modified bamboo powder in Step (S4), and the compatibilizing grafting agent is not used.

[0088] Comparative Example 3

[0089] The rest is the same as in Example 1, except that: Step (S2) is omitted, and ultrafine bamboo powder is used to replace the modified bamboo powder in Step (S4).

[0090] Comparative Example 4

[0091] The rest is the same as in Example 1, except that: Step (S3) is omitted, and the compatibilizing grafting agent is not used in Step (S4).

[0092] Comparative Example 5

[0093] The rest is the same as in Example 1, except that: maleic anhydride is used to replace the compound of succinic acid mono(2-acryloyloxyethyl ester) and glycidyl acrylate in a mass ratio of 1:1 in Step (S3).

[0094] Application Example 1

[0095] The PBAT / bamboo powder biodegradable composite masterbatch prepared in Example 1 was put into a blown film machine, the processing temperature was set at 175 °C, the blow-up ratio was 2.5, after forming, it was cooled by an air ring, the height of the condensation line was controlled at 2 cm, the traction speed was 4 m / min, and then it was cut and wound to obtain a composite film.

[0096] Application Examples 2 - 8

[0097] The rest is the same as in Application Example 1, except that the composite masterbatches are prepared from Examples 2 - 8 respectively.

[0098] Comparative Application Examples 1 - 5

[0099] The rest is the same as in Application Example 1, except that the composite masterbatches are prepared from Comparative Examples 1 - 5 respectively.

[0100] Testing and Analysis

[0101] The composite films prepared in the above application examples and comparative application examples were respectively subjected to the following performance tests:

[0102] Tensile properties: According to the relevant regulations of GB / T 1040.3-2006 standard, a universal testing machine was used to conduct tensile tests on the prepared composite films, and the tensile strength and elongation at break were tested. Five groups of parallel tests were carried out, and the test results were averaged.

[0103] Color difference: Five samples were cut from different positions on the prepared composite film. The samples were placed on the surface of a white standard plate, and a color difference meter was used to measure the color of the samples. The brightness (L*), chromaticity (a* and b*) of the samples were measured. By comparing with the standard white board, the total color difference (ΔE) of the film samples was calculated. The calculation formula is as follows:

[0104] ;

[0105] where ΔL is the brightness difference, Δa is the color difference on the red-green axis, and Δb is the color difference on the yellow-blue axis. The smaller the total color difference value, the lighter the color of the film product and the better the appearance quality.

[0106] Water vapor transmission rate: Five samples were cut from different positions of the prepared composite film and tested according to the GB / T 26253-2010 standard. A water vapor transmission rate tester was used to determine the water vapor transmission rate of the samples. The test conditions were: 25°C, 90% relative humidity, and the results were the average of the data of 5 samples. The lower the water vapor transmission rate, the better the water barrier property.

[0107] Oxygen transmission rate: Five samples were cut from different positions of the prepared composite film and tested according to the GB / T 19789-2021 standard. An oxygen transmission rate tester was used to determine the oxygen transmission rate of the samples. The test temperature was 23°C, and the results were the average of the data of 5 samples. The lower the oxygen transmission rate, the better the oxygen barrier property.

[0108] The above test results are shown in Table 1.

[0109] Table 1 Performance test of composite film

[0110] 。

[0111] As can be seen from the data in Table 1, the total color difference of the composite film obtained by blow molding the PBAT / bamboo powder biodegradable composite masterbatch prepared by the present invention is small (indicating that the overall color of the product is light), all not exceeding 35, and it has good water and oxygen barrier properties and good mechanical properties. Especially in Example 8, when the addition amount of the modified bamboo powder is as high as 30% of PBAT, the film product still has good comprehensive properties. Comparing with Application Example 1 where the bamboo powder is unmodified (the addition amount of bamboo powder is 10% of PBAT) and no compatibilizing graft is used, the color difference value of its film product is much higher than that of Example 1, and the mechanical properties are much lower than those of Example 1, and the water and oxygen barrier properties are both poor. Comparing with Application Example 2 where the bamboo powder is unmodified (the addition amount of bamboo powder is 30% of PBAT) and no compatibilizing grafting agent is used, both the product color and the mechanical properties of its film product are much worse than those of Example 8, unable to meet the daily use requirements, and the water and oxygen barrier properties are also poor. Comparing with Application Example 3 where the bamboo powder is unmodified, the comprehensive properties of its film product are significantly lower than those of Example 1. Comparing with Application Example 4 where the self-made compatibilizing graft is not used, although the color of its film product is not deep, the mechanical properties are worse than those of Example 1. Comparing with Application Example 5, although the water and oxygen barrier properties of its film product are good and the color is not deep, the mechanical properties are also worse than those of Example 1.

[0112] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A PBAT / bamboo powder biodegradable composite masterbatch, characterized in that, Comprising raw materials in the following parts by mass: 100 parts of PBAT, 10 - 30 parts of modified bamboo powder, 5 - 10 parts of compatibilizing grafting agent, 0.5 - 1 part of retarder, 20 - 30 parts of barrier agent, 0.2 - 0.4 part of chain extender, The modified bamboo powder is obtained by impregnating ultrafine bamboo powder with an inorganic alkali solution and then modifying it with an acyl halide reagent; the compatibilizing grafting agent is obtained by grafting PBAT with a grafting agent under ultraviolet light, and the grafting agent is a compound of an acrylate with carboxyl and glycidyl unsaturated fatty acid ester in a mass ratio of 1:(1 - 2); the retarder is at least one of calcium sulfite, sodium sulfite, magnesium sulfite, and sodium bisulfite; the barrier agent is a polycarbonate copolymer.

2. The PBAT / bamboo powder biodegradable composite masterbatch according to claim 1, wherein The particle size of the ultrafine bamboo powder is 800 - 1000 mesh, the inorganic alkali solution is an aqueous solution of NaOH and / or KOH with a concentration of 4 - 7 wt%, and the mass ratio of the ultrafine bamboo powder to the inorganic alkali solution is 1:(2 - 5); the conditions for the impregnation treatment are: impregnation at 20 - 30 °C for 10 - 30 min, then filtration, washing with water until neutral, and drying at 60 - 80 °C to constant weight; and / or The ultrafine bamboo powder is obtained by successively impregnating bamboo raw powder with an inorganic salt solution, steam explosion, and pulverization.

3. The PBAT / bamboo powder biodegradable composite masterbatch according to claim 1, wherein The dosage of the acyl halide reagent is 4 - 6 wt% of the ultrafine bamboo powder; the acyl halide reagent is at least one of benzoyl chloride, 2 - isopropoxybenzoyl chloride, 4 - chlorobenzoyl bromide, 3 - bromo - 5 - trifluoromethylbenzoyl chloride, 2 - bromo - 4,5 - dimethoxy - benzoyl chloride, trifluoromethylbenzoyl chloride, p - trifluoromethoxybenzenesulfonyl chloride, 5 - bromo - 2 - isopropoxybenzoyl chloride; and / or The conditions for the modification with the acyl halide reagent are: reaction at 80 - 100 °C for 2 - 4 h under a vacuum environment of 0.05 - 0.08 Mpa.

4. The PBAT / bamboo powder biodegradable composite masterbatch according to claim 1, characterized in that, The dosage of the grafting agent is 10 - 20 wt% of PBAT; and / or The acrylate with carboxyl is selected from at least one of mono(2 - acryloyloxyethyl) succinate, mono - 2 - (methacryloyloxy)ethyl succinate, mono - 2 - acryloyloxyethyl maleate, mono - 2 - (methacryloyloxy)ethyl maleate, mono - 2 - (methacryloyloxy)ethyl fumarate, and mono - 2 - (methacryloyloxy)ethyl itaconate; and / or The glycidyl unsaturated fatty acid ester is at least one of glycidyl acrylate and glycidyl methacrylate; and / or The conditions for the ultraviolet light grafting are: ultraviolet light irradiation with a wavelength of 200 - 400 nm for 10 - 30 min.

5. The PBAT / bamboo powder biodegradable composite masterbatch according to claim 1, wherein The compatibilizing grafting agent is prepared by a preparation method including the following steps: dissolving PBAT, the grafting agent, and an initiator in a solvent, and carrying out a grafting reaction under ultraviolet light irradiation. After the reaction is completed, it is filtered, washed, and dried to obtain the compatibilizing grafting agent.

6. The PBAT / bamboo powder biodegradable composite masterbatch according to claim 5, wherein The dosage of the initiator is 5-8 wt% of PBAT, and the initiator is at least one of benzophenone, α-dimethoxybenzil ketal, 1-hydroxycyclohexyl phenyl ketone, and 2-hydroxy-2-methyl-1-phenyl-1-propanone; the solvent is chloroform or tetrahydrofuran, and its dosage is 4-6 times the mass of PBAT; the washing is carried out with ethanol and / or pure water, and the drying is carried out under vacuum at 50-70 °C until constant weight.

7. The PBAT / bamboo powder biodegradable composite masterbatch according to claim 1, wherein The weight-average molecular weight of the PBAT is 200,000-400,000; the chain extender is at least one of 2,4-toluene diisocyanate, pyromellitic dianhydride, glycidyl methacrylate, and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane.

8. The PBAT / bamboo powder biodegradable composite masterbatch according to claim 1, characterized in that, The raw materials further include 0.1-1 part of a weathering agent and 0.1-1 part of a mildew-proof agent; the weathering agent is at least one of bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, 3-benzotriazol-5-tert-butyl-4-hydroxyphenyl propionate, 2-(2-hydroxy-3-cumyl-5-tert-octylphenyl) benzotriazole, 2-(3,5-di-tert-butyl-2-hydroxyphenyl)-5-chlorobenzotriazole, and 2-hydroxy-4-n-octyloxybenzophenone; the mildew-proof agent is at least one of dimethyl fumarate, iodopropynyl butylcarbamate, dodecyl dimethyl benzyl ammonium chloride, and dichlorodidecyl dimethyl ammonium chloride.

9. The preparation method of the PBAT / bamboo powder biodegradable composite masterbatch according to any one of claims 1-8, characterized in that, It includes the following steps: mixing the above raw materials and then carrying out melt extrusion, followed by water cooling, pelletizing, and drying to obtain the PBAT / bamboo powder biodegradable composite masterbatch.

10. A composite film, characterized in that, It is made by blow molding the PBAT / bamboo powder biodegradable composite masterbatch according to any one of claims 1-8 by a blown film machine.