A kind of anti-regeneration thermoplastic starch masterbatch and its preparation method and application

Abstract

The application discloses a kind of thermoplastic starch masterbatch of resistance to retrogradation and preparation method and application thereof, including the components in mass fraction as follows: 68-75 parts of raw starch, 2-5 parts of water, 22.5-29.8 parts of composite plasticizer, 0.2-0.5 parts of acid stabilizer;The composite plasticizer includes glycerol, sorbitol, and the obtained thermoplastic starch masterbatch is resistant to retrogradation, and has good plasticizing property.

Description

Technical Field

[0001] This invention relates to the field of thermoplastic starch technology, and in particular to a retrogradation-resistant thermoplastic starch masterbatch, its preparation method, and its application. Background Technology

[0002] In recent years, with the improvement of people's living standards and the increasing awareness of environmental protection, traditional plastic packaging materials have had a significant impact on the living environment. These include disposable lunch boxes, shopping bags, and express delivery bags. Landfill or recycling costs are also rising. To alleviate the pollution caused by traditional plastics, the government has introduced a number of plastic bans, providing strong support for the vigorous development of biodegradable materials. There are many types of biodegradable plastics, among which PLA, PBAT, and PBS are currently the main biodegradable plastics used. However, their prices are far higher than traditional plastic packaging materials. A common cost-reduction method is blending modification. While ensuring the material meets performance requirements, fillers are added to the biodegradable plastic matrix to reduce costs. Starch is one of the commonly used biodegradable fillers. However, its molecules contain a large number of hydroxyl groups, and there are glycosidic bonds within and between structural units, forming numerous intramolecular and intermolecular hydrogen bonds. This causes the decomposition temperature of starch to be lower than its melting temperature, preventing it from melting during processing. To lower the melting temperature of starch, small-molecule plasticizers that can form hydrogen bonds are added to break the hydrogen bonds in the starch molecules, resulting in thermoplastic starch with plasticizing properties.

[0003] In related technologies, plasticizers are blended with starch granules to obtain thermoplastic starch. However, even with high-speed stirring, it is impossible to achieve molecular-level contact between the plasticizer and starch granules, resulting in poor plasticizing effect. Therefore, the proportion of powdered thermoplastic starch added as a filler in biodegradable plastics is small, and the cost remains high. To further solve the cost problem, powdered thermoplastic starch needs to be further processed in an extruder to become thermoplastic starch masterbatch. Its plasticizing effect is far superior to that of powdered thermoplastic starch, and its filling percentage in the biodegradable material can be increased accordingly, thereby effectively reducing costs.

[0004] However, in thermoplastic starch masterbatches, the hydrogen bonds between plasticizers and starch molecules are not strong. Over time, these hydrogen bonds easily break, leading to plasticizer precipitation. This not only affects the plasticizing properties but also causes retrogradation in the thermoplastic starch masterbatches. In retrograded thermoplastic starch masterbatches, the damaged crystalline regions recrystallize, resulting in a significantly increased melting temperature. This leads to poor dispersibility in the biodegradable material matrix, which is irreversible and ultimately affects the performance of the biodegradable material. Therefore, a method is needed to solve the problem of poor retrogradation resistance and reduced plasticizing effect in thermoplastic starch masterbatches caused by plasticizer precipitation. Summary of the Invention

[0005] In view of this, this application provides a retrogradation-resistant thermoplastic starch masterbatch, its preparation method and application, which has good retrogradation resistance and plasticizing properties.

[0006] To achieve the above technical objectives, this application adopts the following technical solution:

[0007] In a first aspect, this application provides a thermoplastic starch masterbatch resistant to retrogradation, comprising the following components in parts by weight: 68-75 parts native starch, 2-5 parts water, 22.5-29.8 parts composite plasticizer, and 0.2-0.5 parts acid stabilizer; the composite plasticizer includes glycerol and sorbitol.

[0008] Preferably, the acid stabilizer includes one or more of anhydrous citric acid, anhydrous oxalic acid, and maleic acid.

[0009] Preferably, the mass ratio of glycerol to sorbitol is 1:(0.25-0.3).

[0010] Preferably, the native starch includes one or more of corn starch, sweet potato starch or potato starch with a moisture content of 14%.

[0011] Secondly, this application provides a method for preparing a thermoplastic starch masterbatch resistant to retrogradation, comprising the following steps:

[0012] S1. Mix water, composite plasticizer, and acid stabilizer according to the mass fraction to obtain a mixture;

[0013] S2. Mix the mixture with the original starch according to the mass fraction to obtain the mixture;

[0014] S3. The mixture is kneaded and extruded, then air-cooled and pelletized to obtain the thermoplastic starch masterbatch resistant to retrogradation.

[0015] Preferably, in step S1, the stirring speed is 20-30 r / min and the stirring time is 5-10 min, and in step S2, the stirring speed is 1500-2000 r / min and the stirring time is 3-5 min.

[0016] Preferably, in step S3, the screw length-to-diameter ratio L / D of the compounding extrusion is 58-60, the temperature of zones 1-10 during compounding extrusion is 125-135℃, the main machine speed is 300-400 r / min, and the feeding speed is 1-4 r / min.

[0017] Preferably, the air-cooled temperature is -2 to -5℃.

[0018] Thirdly, please provide an application of a regress-resistant thermoplastic starch masterbatch in biodegradable plastics.

[0019] Preferably, the regenerating thermoplastic starch masterbatch accounts for 30-40% of the biodegradable plastic by mass.

[0020] The beneficial effects of this application are as follows:

[0021] In this application, by compounding raw materials, acid stabilizers, composite plasticizers and native starch are bonded together to form a stable whole, which inhibits the precipitation of small plasticizer molecules and reduces the hydrogen bond content of native starch, thereby improving the resistance to retrogradation of thermoplastic starch masterbatch and maintaining good thermoplastic properties.

[0022] In this application, the combination of composite plasticizer with high-speed mixing and high screw long-diameter compounding extrusion process allows the small molecules of plasticizer to be fully mixed with the native starch, effectively destroying starch crystals and enhancing the plasticizing effect of native starch. Then, the molten starch is rapidly cooled by low-temperature air cooling to prevent the molten starch from recrystallizing due to natural cooling, thereby reducing the crystallinity of starch and enhancing its resistance to retrogradation. Attached Figure Description

[0023] Figure 1 This is the process flow for this solution. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0025] This application provides a thermoplastic starch masterbatch resistant to retrogradation, comprising the following components in parts by weight: 68-75 parts native starch, 2-5 parts water, 22.5-29.8 parts composite plasticizer, and 0.2-0.5 parts acid stabilizer; the composite plasticizer includes a mixture of glycerol and sorbitol.

[0026] In this scheme, native starch is used as the main raw material. By adjusting the ratio of raw materials and additives, a thermoplastic starch masterbatch resistant to retrogradation is obtained. This method inhibits the precipitation of small plasticizer molecules and reduces the hydrogen bond content of native starch. The mechanism is that the acid stabilizer dehydrates to form acid anhydride when heated. The acid anhydride reacts with native starch to form esterified starch, thus reducing the hydrogen bonds in the starch. Meanwhile, the composite plasticizer forms stronger hydrogen bonds with the unreacted carboxyl groups of the acid stabilizer. At the same time, the composite plasticizer also forms hydrogen bonds with the hydroxyl groups in the starch. Thus, the acid stabilizer, native starch, and composite plasticizer are bonded together to form a stable whole. This reduces the precipitation of plasticizer, lowers the glass transition temperature and melting temperature of the thermoplastic starch masterbatch to ensure good thermoplasticity, and reduces the initial crystallinity and slows down the rate of crystallinity change to improve the retrogradation resistance of the thermoplastic starch masterbatch and extend its durability.

[0027] The composite plasticizer contains glycerol and sorbitol. Both glycerol and sorbitol have plasticizing properties, with glycerol having a better plasticizing effect than sorbitol. However, glycerol is too hygroscopic, which will increase the hygroscopicity of thermoplastic starch and is not conducive to its application. In this solution, sorbitol can reduce the hygroscopicity of glycerol without weakening the plasticizing effect of the composite plasticizer. The composite plasticizer and acid stabilizer work together to inhibit the retrogradation of thermoplastic starch masterbatch.

[0028] This method limits the amount of acid stabilizer. If the amount exceeds the limit of this application, the high content of acid substances will cause the thermoplastic starch masterbatch to turn yellowish, which is not conducive to application. If the amount is lower than the limit of this application, the effective combination of acid stabilizer, compound plasticizer and original starch cannot be guaranteed, and a good retrogradation resistance effect cannot be achieved.

[0029] The raw materials for this scheme are further specified: the acid stabilizers include one or more of anhydrous citric acid, anhydrous oxalic acid, and maleic acid. The acid stabilizers in this application have high carboxyl content and strong reactivity, which is beneficial for better binding with native starch and composite plasticizers. The mass ratio of glycerol to sorbitol is 1:(0.25-0.3). Within this range, the plasticizing effect of starch can be guaranteed, and the hygroscopicity of thermoplastic starch masterbatch can be significantly reduced. The native starch includes one or more of corn starch, sweet potato starch, or potato starch with a moisture content of 14%. The 14% moisture content is the natural moisture content of edible starch, and the amount of moisture used in this scheme is beneficial for starch plasticization.

[0030] This application provides a method for preparing a thermoplastic starch masterbatch resistant to retrogradation, comprising the following steps:

[0031] S1. Mix water, composite plasticizer and acid stabilizer according to the mass parts to obtain a mixture. The equipment used for mixing is a low-speed mixer.

[0032] S2. Mix the mixture with the original starch according to the mass fraction to obtain a mixture. The equipment used for mixing is a high-speed mixer.

[0033] S3. The mixture is kneaded and extruded, then air-cooled and pelletized to obtain the thermoplastic starch masterbatch resistant to regeneration. The equipment used for kneading and extrusion is a twin-screw extruder.

[0034] Through the above steps, a thermoplastic starch masterbatch resistant to retrogradation can be obtained. To further improve the retrogradation resistance and plasticizing properties of the thermoplastic starch masterbatch, in this scheme, the stirring speed in step S1 is 20-30 r / min, and the stirring time is 5-10 min; in step S2, the stirring speed is 1500-2000 r / min, and the stirring time is 3-5 min. In step S3, the screw length-to-diameter ratio (L / D) of the compounding extrusion is 58-60, the temperature of zones 1-10 during compounding extrusion is 125-135℃, the main machine speed is 300-400 r / min, and the feeding speed is 1-4 r / min. The combination of composite plasticizer and high-speed mixing and high screw length-to-diameter compounding extrusion process allows the small molecules of plasticizer to be fully mixed with the native starch, effectively breaking down starch crystals, reducing the glass transition temperature and melting temperature, and enhancing the plasticizing effect of the native starch. In step S3, the air-cooling temperature is -2 to -5℃. Rapid cooling at low temperature prevents the molten starch from recrystallizing due to natural cooling, reducing the starch's crystallinity and enhancing its resistance to retrogradation. Under the process conditions of this scheme, the initial crystallinity of starch can be effectively reduced, the resistance to retrogradation can be improved, and the plasticizing effect of the original starch can be maximized.

[0035] Please provide a biodegradable plastic containing a regenerating thermoplastic starch masterbatch, wherein the regenerating thermoplastic starch masterbatch is used as a filler, and the main material in the biodegradable plastic includes, but is not limited to, one or more of PLA, PBAT, PE, and PP.

[0036] The thermoplastic starch masterbatch that is resistant to regeneration accounts for 30-40% of the mass of biodegradable plastics, with the remainder being the main material and other additives. The thermoplastic starch masterbatch prepared in this scheme can be added in large quantities as a filler, which can effectively reduce the cost of biodegradable plastics. The thermoplastic starch masterbatch and the main biodegradable plastic material have good dispersibility.

[0037] The following specific embodiments further illustrate this solution.

[0038] Example 1

[0039] A thermoplastic starch masterbatch resistant to retrogradation comprises the following components in parts by weight: 68 parts of native starch with a moisture content of 14%, 2 parts of water, 29.8 parts of composite plasticizer, and 0.2 parts of acid stabilizer; the composite plasticizer contains glycerol to sorbitol in a mass ratio of 1:0.3, the acid stabilizer is anhydrous citric acid, and the native starch is corn starch.

[0040] A method for preparing a retrogradation-resistant thermoplastic starch masterbatch includes the following steps:

[0041] S1. Prepare water, composite plasticizer, and acid stabilizer as described above, and pour them into a low-speed mixer to pre-stir until uniform to obtain a mixed liquid. The stirring speed is 20 r / min and the stirring time is 5 min to obtain the mixed liquid.

[0042] S2. Mix the above mixture with the original starch using a high-speed mixer to obtain a mixture. The mixing speed of the high-speed mixer is 1500 r / min and the mixing time is 3 min.

[0043] S3. The above mixture is added to a twin-screw extruder for compounding and extrusion, and then conveyed to a pelletizer via an air-cooled conveyor belt for pelletizing to obtain a thermoplastic starch masterbatch resistant to regeneration. The temperature of zones 1 to 10 of the twin-screw extruder is 130°C, the main extruder speed is 300 r / min, the feed speed is 3 r / min, the air-cooled conveyor belt is cooled by -2°C cold air, and the screw length-to-diameter ratio L / D of the twin-screw extruder is 58.

[0044] Example 2

[0045] A thermoplastic starch masterbatch resistant to retrogradation comprises the following components in parts by weight: 68 parts of native starch with a moisture content of 14%, 2 parts of water, 29.5 parts of composite plasticizer, and 0.5 parts of acid stabilizer; the composite plasticizer contains glycerol to sorbitol in a mass ratio of 1:0.3, the acid stabilizer is anhydrous citric acid, and the native starch is corn starch.

[0046] A method for preparing a retrogradation-resistant thermoplastic starch masterbatch includes the following steps:

[0047] S1. Prepare water, composite plasticizer, and acid stabilizer as described above, and pour them into a low-speed mixer to pre-stir until uniform to obtain a mixed liquid. The stirring speed is 20 r / min and the stirring time is 5 min to obtain the mixed liquid.

[0048] S2. Mix the above mixture with the original starch using a high-speed mixer to obtain a mixture. The mixing speed of the high-speed mixer is 1500 r / min and the mixing time is 3 min.

[0049] S3. The above mixture is added to a twin-screw extruder for compounding and extrusion, and then conveyed to a pelletizer via an air-cooled conveyor belt for pelletizing to obtain a thermoplastic starch masterbatch resistant to regeneration. The temperature of zones 1 to 10 of the twin-screw extruder is 130°C, the main extruder speed is 300 r / min, the feed speed is 3 r / min, the air-cooled conveyor belt is cooled by -2°C cold air, and the screw length-to-diameter ratio L / D of the twin-screw extruder is 58.

[0050] Example 3

[0051] A thermoplastic starch masterbatch resistant to retrogradation comprises the following components in parts by weight: 75 parts of native starch with a moisture content of 14%, 2 parts of water, 22.5 parts of composite plasticizer, and 0.5 parts of acid stabilizer; the composite plasticizer contains glycerol to sorbitol in a mass ratio of 1:0.3, the acid stabilizer is anhydrous citric acid, and the native starch is corn starch.

[0052] A method for preparing a retrogradation-resistant thermoplastic starch masterbatch includes the following steps:

[0053] S1. Prepare water, composite plasticizer, and acid stabilizer as described above, and pour them into a low-speed mixer to pre-stir until uniform to obtain a mixed liquid. The stirring speed is 20 r / min and the stirring time is 5 min to obtain the mixed liquid.

[0054] S2. Mix the above mixture with the original starch using a high-speed mixer to obtain a mixture. The mixing speed of the high-speed mixer is 1500 r / min and the mixing time is 3 min.

[0055] S3. The above mixture is added to a twin-screw extruder for compounding and extrusion, and then conveyed to a pelletizer via an air-cooled conveyor belt for pelletizing to obtain a thermoplastic starch masterbatch resistant to regeneration. The temperature of zones 1 to 10 of the twin-screw extruder is 130°C, the main extruder speed is 300 r / min, the feed speed is 3 r / min, the air-cooled conveyor belt is cooled by -2°C cold air, and the screw length-to-diameter ratio L / D of the twin-screw extruder is 58.

[0056] Example 4

[0057] A thermoplastic starch masterbatch resistant to retrogradation comprises the following components in parts by weight: 75 parts of native starch with a moisture content of 14%, 2 parts of water, 22.5 parts of composite plasticizer, and 0.5 parts of acid stabilizer; the composite plasticizer contains glycerol to sorbitol in a mass ratio of 1:0.3, the acid stabilizer is anhydrous oxalic acid, and the native starch is corn starch.

[0058] A method for preparing a retrogradation-resistant thermoplastic starch masterbatch includes the following steps:

[0059] S1. Prepare water, composite plasticizer, and acid stabilizer as described above, and pour them into a low-speed mixer to pre-stir until uniform to obtain a mixed liquid. The stirring speed is 20 r / min and the stirring time is 5 min to obtain the mixed liquid.

[0060] S2. Mix the above mixture with the original starch using a high-speed mixer to obtain a mixture. The mixing speed of the high-speed mixer is 1500 r / min and the mixing time is 3 min.

[0061] S3. The above mixture is added to a twin-screw extruder for compounding and extrusion, and then conveyed to a pelletizer via an air-cooled conveyor belt for pelletizing to obtain a thermoplastic starch masterbatch resistant to regeneration. The temperature of zones 1 to 10 of the twin-screw extruder is 130°C, the main extruder speed is 300 r / min, the feed speed is 3 r / min, the air-cooled conveyor belt is cooled by -2°C cold air, and the screw length-to-diameter ratio L / D of the twin-screw extruder is 58.

[0062] Example 5

[0063] A thermoplastic starch masterbatch resistant to retrogradation, which is otherwise the same as in Example 1, except that the mass ratio of glycerol to sorbitol in the composite plasticizer is 1:0.25.

[0064] Comparative Example 1

[0065] A thermoplastic starch masterbatch resistant to regression, which is otherwise the same as in Example 1, except that it does not include an acid stabilizer.

[0066] Comparative Example 2

[0067] A thermoplastic starch masterbatch resistant to regeneration, which is otherwise the same as in Example 1, except that the length-to-diameter ratio of the twin-screw extruder is L / D = 25, and the mixing speed in step S2 is 800 r / min.

[0068] Comparative Example 3

[0069] A type of thermoplastic starch masterbatch resistant to reversion, which is otherwise the same as in Example 1, except that the twin-screw extruder has a screw length-to-diameter ratio L / D = 25 and the raw material does not include acid stabilizers.

[0070] Comparative Example 4

[0071] A thermoplastic starch masterbatch resistant to regression, which is otherwise the same as in Example 1, except that the air-cooling temperature is set to 20°C.

[0072] Comparative Example 5

[0073] A thermoplastic starch masterbatch resistant to regression, which is otherwise the same as in Example 1, except that sorbitol in the composite plasticizer is replaced with ethylene glycol.

[0074] Comparative Example 6

[0075] A thermoplastic starch masterbatch resistant to regression, which is otherwise the same as in Example 1, except that the stabilizer is stearic acid.

[0076] Comparative Example 7

[0077] A thermoplastic starch masterbatch resistant to retrogradation, which is otherwise the same as in Example 1, except that the mass fraction of the acid stabilizer is 0.8 parts.

[0078] Comparative Example 8

[0079] A thermoplastic starch masterbatch resistant to regression, which is otherwise the same as in Example 1, except that the mass fraction of the acid stabilizer is 0.1 parts.

[0080] Evaluation Test

[0081] The thermoplastic starch masterbatches obtained in Examples 1-4 and Comparative Examples 1-8 were directly tested using a DSC instrument. The Lab value was tested using a colorimeter under a D65 light source. The larger the L value, the whiter the sample; the larger the b value, the yellower the sample. The results are shown in Table 1.

[0082] Table 1 Test Results

[0083]

[0084]

[0085] As can be seen from Table 1, the thermoplastic starch masterbatches obtained in Examples 1-4 of this invention have low glass transition and melting temperatures, indicating good plasticizing performance; the initial crystallinity is low, and the increase in crystallinity is small over time, indicating that the thermoplastic starch masterbatches obtained by this scheme have strong durability and good resistance to retrogradation.

[0086] Compared to Examples 1 and 2, Comparative Example 1, which did not use a stabilizer, showed a nearly 10-fold increase in crystallinity after 30 days of settling. In contrast, the crystallinity of the retrogradation-resistant thermoplastic starch masterbatch in Examples 1 and 2 increased by less than 0.5 times, indicating that the acidic stabilizer in this formulation has a strong inhibitory effect on retrogradation. However, when the acidic stabilizer was replaced with stearic acid in Comparative Example 6, the glass transition temperature and melting temperature of Comparative Example 1 increased significantly, and the crystallinity also increased rapidly over time. Not only did the obtained starch masterbatch lack retrogradation resistance, but the plasticizing effect was also poor. This is because the acidic stabilizers in the formulation of this invention have fewer than 7 carbon atoms in their molecular structure and are soluble in water, while stearic acid has 18 carbon atoms and a carboxyl group in its structure. As a long-chain fatty acid, it is insoluble in water and cannot effectively break the hydrogen bonds in starch.

[0087] Compared with Example 1, Comparative Example 2 used a combination of a screw with a smaller length-to-diameter ratio and low-speed stirring. The resulting starch masterbatch had significantly increased Tg and Tm, poor plasticizing effect, increased initial crystallinity, and low resistance to retrogradation. However, due to the presence of stabilizer, the crystallinity of the thermoplastic starch masterbatch in Comparative Example 2 did not increase significantly with increasing standing time.

[0088] Compared with Example 1, Comparative Example 3 did not use a stabilizer or a screw assembly with a large length-to-diameter ratio. The increase in Tg, Tm, and initial crystallinity compared with Example 1 was much greater than the sum of the increases in Comparative Example 1 and Comparative Example 2 compared with Example 1. Furthermore, the crystallinity in Comparative Example 3 also increased rapidly over time. This indicates that the stabilizer and the high length-to-diameter ratio screw process in this scheme have a combined effect, synergistically improving the plasticizing properties and resistance to retrogradation of thermoplastic starch.

[0089] Compared with Example 1, Comparative Example 4 uses a room temperature air-cooled conveying device, so its crystallinity is slightly larger than that of the thermoplastic starch masterbatch prepared by the low temperature air-cooled Example 1, and Tg and Tm are also larger, resulting in poor thermoplasticity and resistance to regression.

[0090] In Comparative Example 5, when sorbitol was replaced with ethylene glycol, the glass transition temperature and melting temperature increased significantly, and the plasticizing effect deteriorated significantly. This indicates that not all alcohols can be combined with sorbitol to improve the plasticizing effect.

[0091] After the acid stabilizer content in Comparative Example 7 exceeded the standard, the color turned significantly black and yellow. In Comparative Example 8, the stabilizer dosage was insufficient, and the crystallinity still increased over time, failing to achieve the desired anti-retrogradation effect.

[0092] In this application, by compounding raw materials, acid stabilizers, composite plasticizers and native starch are bonded together to form a stable whole, which inhibits the precipitation of small plasticizer molecules and reduces the hydrogen bond content of native starch, thereby improving the resistance to retrogradation of thermoplastic starch masterbatch and maintaining good thermoplastic properties.

[0093] In this application, the combination of composite plasticizer with high-speed mixing and high screw long-diameter compounding extrusion process allows the small molecules of plasticizer to be fully mixed with the native starch, effectively destroying starch crystals and enhancing the plasticizing effect of native starch. Then, the molten starch is rapidly cooled by low-temperature air cooling to prevent the molten starch from recrystallizing due to natural cooling, thereby reducing the crystallinity of starch and enhancing its resistance to retrogradation.

[0094] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A thermoplastic starch masterbatch resistant to retrogradation, characterized in that, The product comprises the following components in parts by weight: 68-75 parts native starch, 2-5 parts water, 22.5-29.8 parts compound plasticizer, and 0.2-0.5 parts acid stabilizer; wherein the compound plasticizer includes glycerol and sorbitol; The acid stabilizers include one or more of anhydrous citric acid, anhydrous oxalic acid, and maleic acid. The mass ratio of glycerol to sorbitol is 1:(0.25-0.3). The original starch includes one or more of corn starch, sweet potato starch or potato starch with a moisture content of 14%. The method for preparing the aforementioned resistant thermoplastic starch masterbatch is characterized by comprising the following steps: S1. Mix water, composite plasticizer, and acid stabilizer according to the mass fraction to obtain a mixture; S2. Mix the mixture with the original starch according to the mass ratio to obtain a mixture; S3. The mixture is kneaded and extruded, then air-cooled and pelletized to obtain the resistant thermoplastic starch masterbatch; In step S1, the stirring speed is 20-30 r / min and the stirring time is 5-10 min. In step S2, the stirring speed is 1500-2000 r / min and the stirring time is 3-5 min. In step S3, the screw length-to-diameter ratio L / D of the compounding extrusion is 58-60, the temperature of zones 1-10 during compounding extrusion is 125-135℃, the main machine speed is 300-400r / min, and the feeding speed is 1-4r / min. The air-cooled temperature is -2 to -5℃.

2. The application of the resistant thermoplastic starch masterbatch as described in claim 1 in biodegradable plastics.

3. The application according to claim 2, characterized in that, The regress-resistant thermoplastic starch masterbatch accounts for 30-40% of the mass of the biodegradable plastic.

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