Modified starch, preparation method and application of modified starch in degradable materials

Abstract

The invention discloses modified starch, a preparation method and application of the modified starch in degradable materials. The preparation method of the modified starch comprises the following steps: (1) extracting high-acid-value sub-brand PBAT in an alcohol-water solution, and separating to obtain a PBAT prefabricated solution and PBAT particles; 2) putting starch into the PBAT prefabricated solution for acidolysis, separation and drying to obtain PBAT prefabricated starch; and 3) mixing the PBAT prefabricated starch, an alcohol plasticizer and an optional chain extender, and stirring to obtain the modified starch. The starch is plasticized and modified by utilizing the acidity of PBAT, PBAT degradation and aging resistance reduction caused by additional acid are avoided, a degradable material with low odor, few crystal points and excellent aging resistance can be comprehensively obtained, and meanwhile, resource recycling is carried out on an auxiliary board PBAT with a high acid value.

Description

TECHNICAL FIELD

[0001] The present application relates to a modified starch, in particular to a modified starch, a preparation method and its application in degradable materials. BACKGROUND

[0002] Fully biodegradable plastics can be degraded by microorganisms in the natural environment such as soil, and finally become CO2 and organic matter without heavy metal pollution, and no harm to soil microorganisms. Among them, PBAT (polybutylene terephthalate) is a biodegradable resin whose raw materials can all come directly from petrochemical raw materials. PLA (polylactic acid) is directly obtained by fermenting biological materials such as starch to obtain lactide, and then ring-opening polymerization to obtain polylactic acid. At present, these two are the most widely used biodegradable plastics on the market, especially in the field of biodegradable film products.

[0003] Starch is a green and renewable fully biodegradable material, which is widely available and inexpensive. It is often filled into PBAT and / or PLA materials to reduce the cost of composite materials. However, starch is a strong polar crystalline material with strong intermolecular and intramolecular hydrogen bonds, poor thermoplasticity, difficult to disperse, and difficult to be filled into composite materials at high content, and will show crystal points. The traditional way is to add acid plasticizers and alcohol plasticizers to plasticize the original starch. Among them, the acid plasticizer can hydrolyze the starch to a certain extent, reduce the viscosity and improve its compatibility with PBAT, and the alcohol plasticizer is used to weaken the intermolecular force of starch, increase the mobility and plasticity of the molecules, and the two are usually used together to reduce the problems of film surface crystal points, molding difficulties, etc.

[0004] For example, patent CN117645748A discloses a high-filled starch modified PBAT film and a preparation method. In the preparation process of the modified starch, glacial acetic acid and maleic anhydride are added as acylation reagents to prepare acetylated modified starch. Patent CN117603402A adds acid substances such as 1,4-succinic acid and maleic acid during the preparation of modified starch, which improves the compatibility of the composite modified starch with the degradation material resin, and can increase the addition amount of the composite modified starch in the degradation plastic.

[0005] However, the above patents all add small molecule acid substances in the plasticizing process of starch, which will cause the coking of starch during shearing, resulting in strong odor and yellow color of the product. At the same time, the above acid substances will also cause the rapid degradation of PBAT during shearing, affecting the aging resistance of the material, etc. SUMMARY

[0006] In order to solve the above technical problems, the present application provides a modified starch, a preparation method and its application in degradable materials.

[0007] The direct esterification method or the ester exchange method produces a large amount of high-acid-value by-product PBAT under unstable polymerization process, and the by-product PBAT contains a large amount of low-molecular-weight PBAT, which does not meet the product indicators of the normal product PBAT, and the market selling price thereof is much lower than that of the normal product, and the resource recycling of the by-product PBAT can significantly improve the market value of the PBAT industrial chain. The present application uses the high-acid-value by-product PBAT as a raw material, separates the low-molecular-weight PBAT, and acid hydrolyzes the starch to obtain modified starch, which has the advantages of few crystal points and good aging resistance when applied to degradable materials.

[0008] A preparation method of modified starch, characterized in that the method comprises the following steps:

[0009] 1) The high-acid-value by-product PBAT is placed in an alcohol aqueous solution for extraction to separate PBAT pre-prepared solution and PBAT particles;

[0010] 2) The starch is placed in the PBAT pre-prepared solution for acid hydrolysis, and then separated and dried to obtain PBAT pre-prepared starch;

[0011] 3) The PBAT pre-prepared starch, an alcohol plasticizer and optionally a chain extender are mixed and stirred to obtain modified starch.

[0012] As a preferred embodiment of the present application, the acid value of the by-product PBAT is 20-38; preferably, the melt flow rate (MFR) of the by-product PBAT at 190℃ and 2.16kg is 7-15g / 10min;

[0013] In the present application, the PBAT particles obtained in step 1) are high-molecular-weight PBAT that is insoluble in the alcohol aqueous solution, which can be generally recycled for the preparation of degradable materials in the following text to realize the comprehensive recycling of the high-acid-value by-product PBAT.

[0014] Preferably, the volume content of the small-molecule alcohol in the alcohol aqueous solution is 30-70%, preferably 40-60%; more preferably, the small-molecule alcohol is one or more of methanol, ethanol, isopropanol and butanol;

[0015] Preferably, the mixing mass ratio of the by-product PBAT to the alcohol aqueous solution is (20-50):(80-50), preferably (25-35):(75-65).

[0016] As a preferred embodiment of the present application, the water bath temperature is maintained at 30-70℃ during the extraction process of step 1), preferably 40-60℃;

[0017] Preferably, the extraction time is 0.3-1h, preferably 0.5-0.8h;

[0018] Preferably, the separation mode after extraction in step 1) is by suction filtration or centrifugal separation; wherein the centrifugal separation is preferably at a speed of 4000-8000 rpm, preferably 5000-7000 rpm, for a time period of 0.1-0.3 h, preferably 0.15-0.25 h.

[0019] As a preferred embodiment of the present application, in step 2), the mixing mass ratio of the starch and the PBAT pre-solution is (10-30):(90-70), preferably (15-25):(85-75).

[0020] Preferably, the starch is selected from one or more of corn starch, cassava starch, wheat starch and potato starch.

[0021] As a preferred embodiment of the present application, in step 2), the acidolysis reaction conditions are: at 30-70°C, preferably 40-60°C, for a time period of 0.25-1.5 h, preferably 0.5-1 h.

[0022] Preferably, the separation mode in step 2) is by suction filtration or centrifugal separation; wherein the centrifugal separation is preferably at a speed of 6000-10000 rpm, preferably 7000-9000 rpm, for a time period of 0.3-1 h, preferably 0.4-0.5 h.

[0023] As a preferred embodiment of the present application, in step 3), the mass ratio of the PBAT pre-starch and the alcohol plasticizer is (60-80):(40-20), preferably (65-75):(35-25).

[0024] Preferably, the amount of the chain extender is 0.05-1%, preferably 0.1-0.7%, of the total mass of the PBAT pre-starch and the alcohol plasticizer.

[0025] Preferably, the alcohol plasticizer is selected from one or more of polyhydric alcohols with a molecular weight <3000, preferably glycerol, ethylene glycol, sorbitol.

[0026] Preferably, the chain extender is an epoxy-functionalized chain extender, preferably one or more of ADR4468, KL-E4370, XY4370, BTCE-9013, RELYN 4468.

[0027] As a preferred embodiment of the present application, in step 3), the mixing reaction conditions are: at 60-90°C, preferably 70-80°C, for a time period of 1-3 h, preferably 1.5-2.5 h.

[0028] Further, when the alcohol plasticizer is added to the acid-decomposed starch for plasticizing modification, a chain extender is simultaneously added to precisely cross-link the low molecular weight PBAT and the starch, further improving the aging resistance of the degradable material and avoiding excessive decomposition of the starch to cause a large odor.

[0029] A modified starch prepared according to the method described above.

[0030] Use of a modified starch prepared according to the method described above in a degradable material or a film product thereof.

[0031] A degradable material comprising the modified starch prepared according to the method described above, comprising the following components by weight:

[0032] PBAT resin 50-90 parts, preferably 65-85 parts,

[0033] PLA resin 0-10 parts, preferably 3-8 parts,

[0034] Modified starch 10-35 parts, preferably 15-30 parts,

[0035] Chain extender 0-0.5 parts, preferably 0.1-0.3 parts,

[0036] Antioxidant 0-1 part, preferably 0.2-0.4 parts,

[0037] Lubricant 0-1 part, preferably 0.2-0.4 parts;

[0038] Preferably, the PBAT resin has a melt index of 3-10 g / 10 min at 190°C, 2.16 kg, and an acid value of 10-18; and / or,

[0039] The PLA resin has a melt index of 3-10 g / 10 min at 190°C, 2.16 kg; and / or,

[0040] The chain extender is an epoxy-functionalized chain extender, preferably one or more of ADR4468, KL-E4370, XY4370, BTCE-9013, RELYN 4468; and / or,

[0041] The antioxidant is selected from one or more of amine antioxidants, hindered phenolic antioxidants, thioester antioxidants, and phosphite antioxidants, preferably one or both of antioxidant 1010 and antioxidant 168; and / or,

[0042] The lubricant is selected from one or more of erucamide, zinc stearate, and ethylene bis-stearamide.

[0043] A method for preparing a degradable material as described above, comprising the following steps:

[0044] The PBAT resin, modified starch and optionally PLA resin, chain extender, antioxidant, lubricant are mixed and fed into a twin-screw extruder for melt extrusion, and after cooling, the pellets are cut, dried to obtain a degradable material.

[0045] Preferably, the barrel temperature of the twin-screw extruder is not higher than 150℃, preferably 50-150℃.

[0046] Preferably, the temperature of the first 6 zones of the barrel of the twin-screw extruder is 80-110℃, preferably 90-100℃; the temperature of the last 6 zones is 130-150℃, preferably 135-145℃; and / or,

[0047] The barrel rotation speed of the twin-screw extruder is 200-400 rpm, preferably 250-350 rpm.

[0048] Preferably, the modified starch and optionally the chain extender, antioxidant, lubricant are mixed and fed into the main feeding port of the twin-screw extruder, and the PBAT resin and optionally the PLA resin are mixed and fed into the side feeding port of the twin-screw extruder for melt extrusion.

[0049] The present application utilizes the acidity of PBAT itself to plasticize and modify starch, avoids the degradation of PBAT and the decrease of aging resistance caused by external acid, and the precise crosslinking of the chain extender further improves the aging resistance of the degradable material, and avoids the problems of coking and strong odor caused by excessive decomposition of starch, and can comprehensively obtain a degradable material with low odor, few crystal points and excellent aging resistance, and at the same time, the high-acid-value secondary PBAT is recycled and utilized. DETAILED DESCRIPTION

[0050] The present application will be further described below by specific examples, and the examples described in the present application are only used to illustrate the present application and do not limit the scope of the present application.

[0051] The main raw material sources in the examples of the present application are shown in Table 1:

[0052] Table 1

[0053] In Table 1, MFR represents the melt index of the polymer at 190℃, 2.16kg, unit g / 10min.

[0054] Other raw materials and reagents can be purchased through market channels if not specifically mentioned.

[0055] In each example of the present application, the main performance test method of the degradable material is shown in Table 2:

[0056] Table 2

[0057]

[0058] In addition, the test method of odor grade is as follows:

[0059] The film sample is cut into a size of 5cm*10cm, 10 pieces are taken into a 1L glass bottle, and placed in a constant temperature and humidity room in the dark environment for 24h, and 5 people test 3 groups of samples to obtain the average value. Among them, odor grade 1 represents a basic slight odor, 2 represents a moderate non-stimulating odor, 3 represents a stimulating odor, and 4 represents a severe stimulating odor.

[0060] The equipment used in the application mainly includes:

[0061] A twin-screw extruder, Kobe Long, model ZSK 26Mc 18, length-diameter ratio 52, screw diameter 26cm;

[0062] A film blowing machine, Zhangjiagang Lianjiang Machinery Co., Ltd., model SCM 25, length-diameter ratio 30, screw diameter 25cm;

[0063] A German Gottfert melt index instrument, test conditions 190℃, 2.16kg;

[0064] A German ZWICK universal material testing machine, tensile test conditions 500mm / min, angle tear test conditions 200mm / min;

[0065] Jinan Lan light FDI-01 dart impact instrument;

[0066] A heat aging oven, Espeke Environmental Instruments (Shanghai) Co., Ltd.

[0067] The following examples 1-3 are used to prepare modified starches A-C:

[0068]

Example 1

[0069] A method for preparing a modified starch, comprising the following steps:

[0070] 1) Take 210g of ethanol and 490g of deionized water to prepare an alcohol-water solution; 300g The vice card PBAT of T16 is placed in the above alcohol-water solution, heated to 30℃ in a water bath and stirred for 30min, fully extracted, filtered and dried to obtain a PBAT pre-solution and PBAT particles;

[0071] 2) Put 100g of wheat starch into 900g of PBAT pre-solution, heat the water bath to 40℃ and stir for 60min to fully acidify, filter and dry to obtain a PBAT pre-starch;

[0072] 3) Mix 800g PBAT pre-starch, 200g glycerol and 3g ADR4468, stir at 600 rpm for 4 min, then put into a water bath and heat and stir, react at 60℃ for 1 h, cool down, get modified starch A.

[0073] Example 2

[0074] A method for preparing a modified starch, comprising the following steps:

[0075] 1) Take 300g ethanol and 300g deionized water to make an alcohol-water solution; put 400g PBAT of MGJH901S into the alcohol-water solution, heat the water bath to 50℃ and stir for 45 min for sufficient extraction, dry after suction filtration, get PBAT pre-solution and PBAT particles;

[0076] 2) Put 200g corn starch into 800g PBAT pre-solution, heat the water bath to 50℃ and stir for 45 min for sufficient acidolysis, dry after suction filtration, get PBAT pre-starch;

[0077] 3) Mix 700g PBAT pre-starch, 300g ethylene glycol and 5g ADR4468, stir at 600 rpm for 4 min, then put into a water bath and heat and stir, react at 75℃ for 2 h, cool down, get modified starch B.

[0078] Example 3

[0079] Prepare modified starch C according to the method basically same as example 2, the only difference is that step 3) does not add ADR4468.

[0080] Example 4

[0081] A method for preparing a modified starch, comprising the following steps:

[0082] 1) Take 300g ethanol and 200g deionized water to make an alcohol-water solution; put 500g PBAT of DT-10A into the alcohol-water solution, heat the water bath to 70℃ and stir for 60 min for sufficient extraction, dry after suction filtration, get PBAT pre-solution and PBAT particles;

[0083] 2) Put 300g cassava starch into 700g PBAT pre-solution, heat the water bath to 60℃ and stir for 30 min for sufficient acidolysis, dry after suction filtration, get PBAT pre-starch;

[0084] 3) 600 g of the pre-prepared starch PBAT, 400 g of sorbitol and 6 g of KL-E4370 were mixed and stirred at 600 rpm for 4 min, then placed in a water bath and heated and stirred, reacted at 90°C for 3 h, and cooled to obtain modified starch D.

[0085] Comparative Example 1

[0086] A method for preparing a modified starch, comprising the following steps:

[0087] 1) 300 g of ethanol and 300 g of deionized water were weighed and mixed to form an alcohol-water solution; 400 g of maleic anhydride was placed in the alcohol-water solution, heated to 50°C in a water bath and stirred for 45 min, then filtered and dried to obtain a pre-prepared solution;

[0088] 2) 200 g of corn starch was placed in 800 g of the pre-prepared solution, heated to 50°C in a water bath and stirred for 45 min to fully acidify, then filtered and dried to obtain a pre-prepared starch;

[0089] 3) 700 g of the pre-prepared starch, 300 g of ethylene glycol and 5 g of ADR4468 were mixed and stirred at 600 rpm for 4 min, then placed in a water bath and heated and stirred, reacted at 75°C for 2 h, and cooled to obtain modified starch M.

[0090] Comparative Example 2

[0091] A method for preparing a modified starch, comprising the following steps:

[0092] 1) 300 g of ethanol and 300 g of deionized water were weighed and mixed to form an alcohol-water solution; 400 g of maleic anhydride was placed in the alcohol-water solution, heated to 50°C in a water bath and stirred for 45 min, then filtered and dried to obtain a pre-prepared solution;

[0093] 2) 200 g of corn starch was placed in 800 g of the pre-prepared solution, heated to 50°C in a water bath and stirred for 45 min to fully acidify, then filtered and dried to obtain a pre-prepared starch;

[0094] 3) 700 g of the pre-prepared starch, 300 g of ethylene glycol were mixed and stirred at 600 rpm for 4 min, then placed in a water bath and heated and stirred, reacted at 75°C for 2 h, and cooled to obtain modified starch N.

[0095] Comparative Example 3

[0096] A method for preparing a modified starch, comprising the following steps:

[0097] 1) 300 g of ethanol and 300 g of deionized water were weighed and mixed to form an alcohol-water solution; 400 g of maleic anhydride was placed in the alcohol-water solution, heated to 50°C in a water bath and stirred for 45 min, then filtered and dried to obtain a pre-prepared solution; The vice card PBAT of T16 is placed in the above alcohol aqueous solution to obtain a PBAT pre-prepared solution;

[0098] 2) 200g of corn starch is placed in 800g of the PBAT pre-prepared solution, and the water bath is heated to 50°C and stirred for 45min to make it fully acidolysis, and after filtration and drying, a PBAT pre-prepared starch is obtained;

[0099] 3) 700g of the PBAT pre-prepared starch, 300g of ethylene glycol and 5g of ADR4468 are mixed, stirred at 600rpm for 4min, then heated and stirred in a water bath, reacted at 75°C for 2h, and cooled to obtain modified starch P.

[0100]

Comparative Example 4

[0101] A method for preparing a modified starch, comprising the following steps:

[0102] 1) 300g of ethanol and 300g of deionized water are weighed to form an alcohol aqueous solution; 400g of T16 is placed in the above alcohol aqueous solution, and the water bath is heated to 50°C and stirred for 45min to make it fully extracted, and after filtration and drying, a PBAT pre-prepared solution and PBAT particles are obtained;

[0103] 2) 200g of corn starch is placed in 800g of the PBAT pre-prepared solution, and the water bath is heated to 50°C and stirred for 45min to make it fully acidolysis, and after filtration and drying, a PBAT pre-prepared starch is obtained;

[0104] 3) 700g of the PBAT pre-prepared starch, 300g of ethylene glycol and 5g of ADR4468 are mixed, stirred at 600rpm for 4min, then heated and stirred in a water bath, reacted at 75°C for 2h, and cooled to obtain modified starch Q.

[0105] The following examples 5-10 are used to prepare a degradable material:

[0106]

Example 5

[0107] A degradable material, comprising the following components in parts by weight:

[0108]

[0109] The preparation method of the above degradable material, comprising the following steps:

[0110] The modified starch A, the chain extender ADR4468, the antioxidant 1010, the antioxidant 168, and the ethylene bis stearyl amide were mixed in a low-speed mixer for 2 minutes, and were added to a main feeding port of a twin-screw extruder. The T16 and the LX175 were mixed in a low-speed mixer for 2 minutes, and were added to a side feeding port of the twin-screw extruder. Melt extrusion was performed. The extrusion conditions were as follows: the screw rotation speed was 200 rpm, and the screw temperature was set in sections from the feeding port to the die head as follows: 50℃, 50℃, 50℃, 50℃, 50℃, 50℃, 110℃, 130℃, 110℃, 110℃, 110℃, and 100℃. The extruded material was cooled and pelletized in a water tank of the extruder, and was dried to obtain the degradable material A.

[0111] Example 6

[0112] A degradable material includes the following components by weight:

[0113]

[0114] A preparation method of the degradable material includes the following steps:

[0115] The modified starch B, the chain extender ADR4468, the antioxidant 1010, the antioxidant 168, and the zinc stearate were mixed in a low-speed mixer for 2 minutes, and were added to a main feeding port of a twin-screw extruder. The MGJH901S and the LX575 were mixed in a low-speed mixer for 2 minutes, and were added to a side feeding port of the twin-screw extruder. Melt extrusion was performed. The extrusion conditions were as follows: the screw rotation speed was 200 rpm, and the screw temperature was set in sections from the feeding port to the die head as follows: 60℃, 60℃, 60℃, 60℃, 60℃, 60℃, 120℃, 140℃, 120℃, 120℃, 120℃, and 100℃. The extruded material was cooled and pelletized in a water tank of the extruder, and was dried to obtain the degradable material B.

[0116] Example 7

[0117] The degradable material C was prepared according to the same method as in Example 6, except that the modified starch B was replaced by the modified starch C.

[0118] Example 8

[0119] A degradable material includes the following components by weight:

[0120]

[0121] A preparation method of the degradable material includes the following steps:

[0122] The modified starch D, the chain extender KL-E4370, the antioxidant 1010, the antioxidant 168 and the erucamide were mixed in a low-speed mixer for 2 min, and were added to a main feeding port of a twin-screw extruder. The DT-10A and the LX175 were mixed in a low-speed mixer for 2 min, and were added to a side feeding port of the twin-screw extruder. Melt extrusion was performed. The extrusion conditions were as follows: the screw rotation speed was 200 rpm, and the screw temperature was set in sections from the feeding port to the die head as follows: 70℃, 70℃, 70℃, 70℃, 70℃, 70℃, 130℃, 140℃, 130℃, 130℃, 130℃, and 100℃. The extruded material was cooled and pelletized in a water tank of the extruder, and was dried to obtain the degradable material D.

[0123] Example 9

[0124] A degradable material comprises the following components in parts by weight:

[0125]

[0126] A preparation method of the degradable material comprises the following steps:

[0127] The modified starch A, the chain extender BTCE-9013, the antioxidant 1010, the antioxidant 168 and the erucamide were mixed in a low-speed mixer for 2 min, and were added to a main feeding port of a twin-screw extruder. The T16 was mixed in a low-speed mixer for 2 min, and was added to a side feeding port of the twin-screw extruder. Melt extrusion was performed. The extrusion conditions were as follows: the screw rotation speed was 200 rpm, and the screw temperature was set in sections from the feeding port to the die head as follows: 70℃, 70℃, 70℃, 70℃, 70℃, 70℃, 130℃, 140℃, 130℃, 130℃, 130℃, and 100℃. The extruded material was cooled and pelletized in a water tank of the extruder, and was dried to obtain the degradable material E.

[0128] Example 10

[0129] A degradable material comprises the following components in parts by weight:

[0130]

[0131]

[0132] A preparation method of the degradable material comprises the following steps:

[0133] Modified starch B, chain extender Relyon 4468, antioxidant 1010, antioxidant 168, zinc stearate were mixed in a low-speed mixer for 2 min, and were added to the main feeding port of the twin-screw extruder. T16 and 2003D were mixed in a low-speed mixer for 2 min, and were added to the side feeding port of the twin-screw extruder. Melt extrusion was performed. The extrusion conditions were as follows: screw rotation speed 200 rpm, screw temperature from the feeding port to the die head was set in sections as follows: 60°C, 60°C, 60°C, 60°C, 60°C, 60°C, 120°C, 140°C, 120°C, 120°C, 120°C, 100°C. The extruded material was cooled in the extruder sink, pelletized, and dried to obtain the degradable material F.

[0134] Comparative Example 5

[0135] The degradable material M was prepared according to the substantially same method as in Example 6, except that modified starch B was replaced by modified starch M.

[0136] Comparative Example 6

[0137] The degradable material N was prepared according to the substantially same method as in Example 6, except that modified starch B was replaced by modified starch N.

[0138] Comparative Example 7

[0139] The degradable material Q was prepared according to the substantially same method as in Example 6, except that modified starch B was replaced by modified starch P.

[0140] Comparative Example 8

[0141] The degradable material Q was prepared according to the substantially same method as in Example 6, except that modified starch B was replaced by modified starch Q.

[0142] The degradable materials prepared in Examples 5-10 and Comparative Examples 5-8 were respectively extruded and blown into films, to obtain thin films with a film thickness of 25 microns, which were labeled as thin films A-F and M-Q. The crystal point conditions of each thin film were determined by visual judgment (the number of crystal points with a size greater than 0.2 mm in a sample size of 150 mm*150 mm), the mechanical properties of the thin films were tested by a tensile testing machine, the aging of the thin films was accelerated by a damp heat aging oven, and the falling dart performance after aging was tested, and the test results are shown in Table 3.

[0143] Table 3, Performance Test Results

[0144]

[0145] It can be seen from the data in Table 3 that the overall performance of the examples is better than that of the comparative examples, and it can be seen that the degradable material prepared by using the modified starch of the application can fully utilize the acidity of the high-acid-value Zhi-pai PBAT to complete the plasticization of the starch, has few film crystal points, and further realizes precise crosslinking of the starch and low-molecular-weight PBAT through the chain extender, improves the compatibility of the two, has good initial mechanical properties and falling-dart performance, and improves the overall aging performance of the material.

[0146] The above only describes the preferred embodiments of the application, and it should be noted that those skilled in the art can make several improvements and supplements without departing from the method of the application, and these improvements and supplements should also be considered as the protection scope of the application.

Claims

1. A method for preparing a modified starch, characterized by, The method comprises the following steps: 1) placing high-acid-value by-product PBAT in an alcohol aqueous solution for extraction to separate PBAT pre-prepared solution and PBAT particles; 2) placing starch into the PBAT pre-prepared solution for acidolysis, separating and drying to obtain PBAT pre-prepared starch; 3) mixing and stirring the PBAT pre-prepared starch, an alcohol plasticizer and optionally a chain extender to prepare modified starch.

2. The method for producing a modified starch according to claim 1, characterized by, The by-product PBAT has an acid value of 20-38; preferably, the by-product PBAT has a melt index of 7-15 g / 10 min at 190℃ under a load of 2.16 kg; Preferably, the alcohol aqueous solution contains 30-70% of small-molecule alcohol, preferably 40-60%; more preferably, the small-molecule alcohol is one or more of methanol, ethanol, isopropanol and butanol; Preferably, the mixing mass ratio of the by-product PBAT to the alcohol aqueous solution is (20-50):(80-50), preferably (25-35):(75-65).

3. The method of producing a modified starch according to claim 1 or 2, characterized in that, In the extraction process of step 1), the water bath temperature is kept at 30-70℃, preferably 40-60℃; Preferably, the extraction time is 0.3-1 h, preferably 0.5-0.8 h; Preferably, the separation mode after extraction in step 1) is suction filtration or centrifugal separation; preferably, the centrifugal separation condition is a centrifugal speed of 4000-8000 rpm, preferably 5000-7000 rpm, and a centrifugal time of 0.1-0.3 h, preferably 0.15-0.25 h.

4. The method of producing a modified starch according to claim 1 or 2, characterized in that, In step 2), the mixing mass ratio of the starch to the PBAT pre-prepared solution is (10-30):(90-70), preferably (15-25):(85-75); Preferably, the starch is selected from one or more of corn starch, cassava starch, wheat starch and potato starch.

5. The method of producing a modified starch according to any one of claims 1 to 4, characterized in that, In step 2), the acidolysis reaction condition is a reaction at 30-70℃, preferably 40-60℃ for 0.25-1.5 h, preferably 0.5-1 h; Preferably, the separation mode in step 2) is suction filtration or centrifugal separation; preferably, the centrifugal separation condition is a centrifugal speed of 6000-10000 rpm, preferably 7000-9000 rpm, and a centrifugal time of 0.3-1 h, preferably 0.4-0.5 h.

6. The method of producing a modified starch according to any one of claims 1 to 5, characterized in that, In step 3), the mass ratio of the PBAT pre-prepared starch to the alcohol plasticizer is (60-80):(40-20), preferably (65-75):(35-25); Preferably, the amount of the chain extender is 0.05-1% of the total mass of the PBAT pre-prepared starch and the alcohol plasticizer, preferably 0.1-0.7%; Preferably, the alcohol plasticizer is selected from one or more of polyhydric alcohols with a molecular weight of less than 3000, preferably glycerol, ethylene glycol and sorbitol; Preferably, the chain extender is an epoxy-functionalized chain extender, preferably one or more of ADR4468, KL-E4370, XY4370, BTCE-9013 and RELYN 4468.

7. The method of producing a modified starch according to any one of claims 1 to 6, characterized in that, In step 3), the mixing reaction condition is a reaction at 60-90℃, preferably 70-80℃ for 1-3 h, preferably 1.5-2.5 h.

8. A modified starch prepared according to the method of any one of claims 1-7.

9. Use of the modified starch prepared according to the method of any one of claims 1-7 in a degradable material or a film product thereof.

10. A degradable material comprising the modified starch produced by the method of any one of claims 1-7, wherein, comprising the following components by weight parts: Preferably, the PBAT resin has a melt index of 3-10 g / 10 min at 190℃, 2.16 kg, and an acid value of 10-18; and / or, the PLA resin has a melt index of 3-10 g / 10 min at 190℃, 2.16 kg; and / or, the chain extender is an epoxy-functionalized chain extender, preferably one or more of ADR4468, KL-E4370, XY4370, BTCE-9013, RELYN 4468; and / or, the antioxidant is selected from one or more of amine antioxidants, hindered phenolic antioxidants, thioester antioxidants, phosphite antioxidants, preferably one or both of antioxidant 1010, antioxidant 168; and / or, the lubricant is selected from one or more of erucamide, zinc stearate, and ethylene bis-stearamide.

11. A method of producing a degradable material as claimed in claim 10, characterised in that, comprising the following steps: mixing the PBAT resin, the modified starch, and optionally the PLA resin, the chain extender, the antioxidant, and the lubricant, and feeding into a twin-screw extruder for melt extrusion, and after cooling, pelletizing and drying to obtain the degradable material; Preferably, the barrel temperature of the twin-screw extruder is not higher than 150℃, preferably 50-150℃; Preferably, the temperature of the first 6 zones of the barrel of the twin-screw extruder is 80-110℃, preferably 90-100℃; the temperature of the last 6 zones is 130-150℃, preferably 135-145℃; and / or, the barrel rotation speed of the twin-screw extruder is 200-400 rpm, preferably 250-350 rpm.

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