Biodegradable foaming material and preparation method thereof

Abstract

The invention discloses a biodegradable foaming material and a preparation method thereof, and belongs to the technical field of foaming materials. The foaming material is prepared from the following substances in parts by weight: 60-90 parts of aromatic-aliphatic copolyester with side chains, 10-30 parts of blended resin, 0.2-5 parts of a nucleating agent, 40-80 parts of a plasticizer, 0.1-2 parts of a chain extender and 0.1-0.5 part of an antioxidant, the plasticizer is aconitate, the structural general formula of the aconitate is as shown in formula I: # imgabs0 #, R1, R2 and R3 can be one of straight-chain alkyl, branched-chain alkyl and naphthenic base, and the number of carbon atoms in R1, R2 and R3 is 4-8. The aromatic-aliphatic copolyester with a side chain is used as a matrix material, the aconite is used as a plasticizer, and the matrix material, the plasticizer, the blended resin, the nucleating agent, the chain extender and the antioxidant have a synergistic effect, so that the prepared biodegradable foaming material has excellent processability, foaming performance and mechanical performance and can be applied to a wider range of scenes.

Description

Technical Field

[0001] The present application relates to a biodegradable foaming material and a preparation method thereof, belonging to the technical field of foaming materials. Background Art

[0002] With the development of polymer foaming material preparation and molding processing technologies, the application of lightweight, high-performance, and functional polymer composites with bubble / pore structures is becoming increasingly extensive. They are not only widely used in traditional industrial fields such as packaging building materials, refrigerated transportation, electronic appliances, footwear and textile, chemical engineering, etc., but also increasingly extended to high-end industrial fields such as intelligent sensing, biomedicine, environmental energy, vehicles, ships, aviation, military aerospace, etc.

[0003] Under the "dual carbon" strategy and the "plastic ban" policy, biodegradable plastics have attracted much attention due to their excellent biodegradable properties, and the industry has developed rapidly. Currently, the main research and application of biodegradable foaming materials focus on polymers such as polylactic acid (PLA), polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), and starch. Among them, the product performance of foaming materials prepared from PBAT, PLA, or PBAT / PLA blend materials as substrates can reach or approach the performance standards of PE, EVA, and PET foaming materials, and they already fully possess the ability to replace petroleum-based plastic products.

[0004] However, there are certain problems when PBAT or PLA is used alone as the substrate of the foaming material. For example, PBAT-based foaming materials often have problems such as relatively large and unevenly distributed pores, and PBAT-based foaming materials have poor strength and toughness. Therefore, in order to improve the performance of biodegradable foaming materials, a PBAT / PLA blend foaming system is generally used. However, due to the thermodynamic incompatibility between PBAT and PLA, there are fewer entanglements between different material segments, resulting in a decrease in the melt strength of the mixed material system, and then causing problems such as uneven foaming and low foaming ratio in the PBAT / PLA blend system, which limits the development and application of biodegradable foaming materials.

[0005] Therefore, in order to promote the development of the biodegradable foaming material field, it is urgent to develop biodegradable polyester materials and corresponding blend resin foaming systems with high foaming efficiency and foaming stability, so as to improve the strength and toughness of the foaming materials and widely meet the consumption needs of the public. Summary of the Invention

[0006] In order to solve the above problems, the present application proposes a biodegradable foaming material and a preparation method thereof. By mixing a side-chain aromatic-aliphatic copolyester with a blend resin, and using aconitate as a plasticizer in combination with an epoxy chain extender and other components, the foaming efficiency of the polyester foaming material is improved, and the strength and toughness of the foaming material are also improved.

[0007] According to one aspect of the present application, a biodegradable foaming material is provided, which is prepared from the following substances in parts by weight: 60-90 parts of a side-chain aromatic-aliphatic copolyester, 10-30 parts of a blend resin, 0.2-5 parts of a nucleating agent, 1-10 parts of a plasticizer, 0.1-2 parts of a chain extender, and 0.1-0.5 parts of an antioxidant;

[0008] The plasticizer is aconitate, and the general structural formula of the aconitate is shown in Formula I:

[0009]

[0010] Wherein, R 1 、R 2 、R 3 can each be one of a straight-chain alkyl group, a branched-chain alkyl group, and a cycloalkyl group, and the number of carbon atoms of R 1 、R 2 、R 3 is 4-8.

[0011] Specifically, the molecular weight of the side-chain aromatic-aliphatic copolyester is 3×10 4 g / mol to 12×10 4 g / mol; the molecular weight of the blend resin is 5×10 4 g / mol to 10×10 4 g / mol.

[0012] In this solution, a side-chain aromatic-aliphatic copolyester is mixed with a blend resin, and aconitate is added as a plasticizer, which acts synergistically with a nucleating agent, an epoxy chain extender, and an antioxidant to improve the foaming controllability of the foaming material and enhance the mechanical properties of the foaming material.

[0013] By limiting the number of carbon atoms of R 1 、R 2 、R 3 in the aconitate to 4-8, the aconitate plasticizer has a relatively low molecular weight and a relatively active molecular chain. It can not only achieve effective plasticization, but also allow the molecular chains of the blend resin to stretch, reduce the entanglement degree of the resin chains, increase the effective contact area between the blend resin and the matrix polyester, and facilitate the improvement of the compatibility between the blend resin and the matrix polyester; further, the improvement of the compatibility promotes the controlled degree of the foaming process and ultimately improves the performance of the foaming material.

[0014] If the carbon number of the ester chain of aconitic acid ester and the corresponding molecular weight are too low, although the plasticizing effect and foaming effect are good, there is a problem that the plasticizer is likely to migrate out; if the carbon number of the ester chain of aconitic acid ester and the corresponding molecular weight are too high, the migration of the plasticizer is reduced, but the too-long ester chain will reduce the activity of aconitic acid ester, and the effect of improving the compatibility between different resins is average, so it will also have an adverse impact on the foaming process and the performance of the foamed material.

[0015] Optionally, the monomers of the copolyester are a side-chain-containing aliphatic dicarboxylic acid, terephthalic acid, and an aliphatic diol. The molar ratio of terephthalic acid to the side-chain-containing aliphatic dicarboxylic acid is 1:1 to 5, and the molar ratio of the total amount of terephthalic acid and the side-chain-containing aliphatic dicarboxylic acid to the alcohol is 1:1 to 2.

[0016] By limiting the ratio of the copolyester monomers, both the foaming ratio of the polyester foamed material and the mechanical strength of the material can be improved. When the addition ratio of the soft-segment polymerization monomer is too low, the strength of the obtained foamed material is too high, and the crystallization rate of the polyester material is too high, which will inhibit the progress of the entire foaming process, resulting in a decrease in the foaming ratio, a decrease in the cell pore size and cell density, and at the same time, the shrinkage rate and compression set of the foamed material also decrease; when the addition ratio of the soft-segment monomer is too high, the strength of the polyester material will decrease, and at the same time, the crystallization rate of the polyester material slows down. Correspondingly, the degree of control of the foaming process decreases, resulting in too large cell pore sizes in the obtained foamed material, and there may be a phenomenon of cell collapse, resulting in a decrease in the foaming ratio and cell density, and the compression ratio and compression set performance deteriorate accordingly.

[0017] Optionally, the structural general formula of the side-chain-containing aliphatic dicarboxylic acid is shown in Formula II, and the structural general formula of the aliphatic diol is shown in Formula Ш:

[0018]

[0019] Among them, for the side-chain-containing aliphatic dicarboxylic acid, the side chain X is 1 to 4, the main chain Y is 1 to 5, and for the diol Z is 0 to 4.

[0020] Limiting the number of carbon atoms in the aliphatic chains of the side-chain-containing aliphatic dicarboxylic acid and the diol can balance the strength and foaming degree of the polyester material. When the main chain length of the soft-segment monomer is too low, the strength of the polyester material is too high, which will inhibit the entire foaming process; when the main chain length of the soft-segment monomer is too high, the strength of the polyester material becomes low, and there may be a phenomenon of cell collapse during the foaming process, and the performance of the foamed material is affected.

[0021] Optionally, the chain extender is an epoxy chain extender.

[0022] The epoxy chain extender can react with the terminal hydroxyl groups or terminal carboxyl groups in the polymer molecular chain on the basis of increasing the molecular weight of the polyester and the mechanical strength of the polymer, thereby significantly improving the stability of the foamed material.

[0023] Optionally, the chain extender is an epoxy chain extender with a bio-based aconitic acid backbone, and its structural general formula is shown in Formula IV:

[0024]

[0025] Among them, p is an integer from 1 to 4.

[0026] The epoxy chain extender with a bio-based aconitic acid backbone contains three epoxy groups, which can undergo a polymerization reaction with the carboxyl groups at the ends of the polyester chains. It can not only increase the molecular weight of the polyester but also crosslink linear polymers into a network structure, improving the mechanical properties and stability of the foamed material.

[0027] Optionally, the blend resin is one or more of PLA, PBS, and PPC.

[0028] The addition of the blend resin can improve the comprehensive properties of the foamed material, enhancing strength, toughness, and degradability. By specifying a specific ratio of the blend resin and the side-chain aromatic-aliphatic copolyester, the strength and toughness of the foamed material can be greatly improved, giving full play to the advantages of both materials.

[0029] Optionally, the nucleating agent is one or more of calcium carbonate, talcum powder, silica, titanium dioxide, hydrotalcite, and nanocellulose.

[0030] Optionally, the antioxidant is one or more of antioxidant 168, antioxidant 1010, antioxidant 1076, and antioxidant 2246.

[0031] The antioxidant can effectively quench the generation of active oxygen species in the plastic film, thus playing a role in inhibiting the oxidative degradation of the polyester material and extending the service life of the foamed material.

[0032] According to another aspect of the present application, a method for preparing a biodegradable foamed material is provided, which is characterized by including the following steps:

[0033] (1) Put the side-chain aromatic-aliphatic copolyester and the blend resin into an oven and dry them for later use;

[0034] (2) Weigh the epoxy chain extender, the dried side-chain aromatic-aliphatic copolyester, and the blend resin according to the amount, add them together to a high-speed mixer and mix evenly, and then add the nucleating agent and the plasticizer and mix evenly;

[0035] (3) Add the above-mentioned uniformly mixed materials to a screw extruder for extrusion granulation, and obtain a composite material by blowing film after extrusion granulation;

[0036] (4) Thermally press the obtained composite material into a mold, place it in a foaming kettle, heat the foaming kettle and inject CO at a certain pressure 2A gas is used, and after maintaining pressure for a period of time, the pressure is rapidly released to obtain a low-foaming ratio foam material;

[0037] (5) The obtained foam material is placed in a vacuum drying oven and heated, the vacuum is pumped and the pressure is maintained for a period of time, and then the pressure is released to obtain a high-foaming ratio foaming material.

[0038] Optionally, in step (1), the drying temperature is 30-60 °C and the drying time is 5 h;

[0039] In step (2), the speed of the high-speed mixer is set to first stir at a low speed of 150 r / min for 4-10 min, and then stir at a high speed of 1000 r / min for 10-30 min;

[0040] For the twin-screw extruder in step (3), the main machine temperature is 160-200 °C, the head temperature is 170-190 °C, and the screw rotation speed is 300 r / min.

[0041] Optionally, in step (4), the foaming kettle temperature is 60-150 °C, the foaming pressure is 10-30 MPa; the pressure maintaining time is 1-6 h;

[0042] In step (5), the temperature of the vacuum drying oven is 80-120 °C, the vacuum degree is -0.01 MPa to -0.1 MPa, and the true pressure maintaining time is 20-120 min.

[0043] The polymer composite material is vacuum-pressurized for a period of time after foaming treatment under high pressure, which is beneficial to maintaining the foaming ratio, improving the stability of the foaming material, reducing the shrinkage rate of the foaming material, and improving the mechanical properties of the material.

[0044] The beneficial effects that this application can produce include but are not limited to:

[0045] 1. The biodegradable foaming material provided by this application uses aconitate bio-based products as plasticizers, which have no toxic side effects and will not pose a threat to human health; the structure is more stable, the migration is lower, and the plasticizing effect and foaming promoting effect are excellent; at the same time, limiting the molecular weight of the aconitate plasticizer is beneficial to improving the compatibility between the base polyester and the blend resin, thereby improving the controllability of the foaming process and making the properties of the foaming material better.

[0046] 2. The biodegradable foaming material provided by this application uses a copolyester matrix material synthesized with a fatty dibasic acid with side chains as the polymerization monomer. Due to the existence of its side chain structure, the strength of the copolyester material is enhanced, the crystallization rate is effectively regulated, the structural stability of the polyester material is higher, and it can provide more effective support during the foaming process, and there will be no phenomenon of cell collapse. Finally, the properties of the obtained foaming material are all better.

[0047] 3. The biodegradable foaming material provided by this application is prepared by blending a side-chain aromatic-aliphatic copolyester with a resin, adding aconitate as a plasticizer, and synergistically using a nucleating agent, an aconitic acid skeleton epoxy chain extender, and an antioxidant. The obtained biodegradable foaming material has good mechanical properties, and at the same time, the cell pore size is smaller and more uniform, and the cell density is higher. Its performance characteristics have broad application prospects in the field of foaming materials. Detailed Embodiments

[0048] The following describes this application in detail with reference to embodiments, but this application is not limited to these embodiments.

[0049] Unless otherwise defined, all professional and scientific terms used herein have the same meaning as those familiar to persons skilled in the art. The reagents or raw materials used in the present invention can be obtained through conventional channels. Unless otherwise specified, the reagents or raw materials used in the present invention are used in accordance with the conventional methods in the art or in accordance with the product instructions. In addition, any methods and materials similar or equivalent to the described content can be applied to the method of the present invention. The preferred implementation methods and materials described in this patent are for illustrative purposes only.

[0050] In the following preparation method of the biodegradable foaming material, the preparation method of the epoxy chain extender used is as follows:

[0051] T1. React aconitic acid with thionyl chloride at 100 °C to obtain an acyl chloride intermediate;

[0052] T2. React the acyl chloride intermediate with epoxy alcohol at 20 °C to obtain an epoxy chain extender with a bio-based aconitic acid skeleton;

[0053] The structural formula of the obtained epoxy alcohol is shown as follows,

[0054]

[0055] wherein, p is an integer from 1 to 4, and p depends on the type of epoxy alcohol.

[0056] Example 1

[0057] The preparation method of the biodegradable foaming material includes the following steps:

[0058] (1) Put the side-chain aromatic-aliphatic copolyester and the blend resin into an oven and dry them at 40 °C for 5 h for later use;

[0059] (2) Add 1.2 parts of the epoxy chain extender, 80 parts of dried poly(butylene succinate-co-terephthalate), and 15 parts of PLA to a high-speed mixer and stir at a low speed of 150 r / min for 6 min. Then add 3.5 parts of calcium carbonate, 5 parts of tributyl aconitate, and 0.3 part of antioxidant 1010, and stir at a high speed of 1000 r / min for 15 min to mix evenly;

[0060] Among them, the molar ratio of terephthalic acid to methylsuccinic acid in the poly(butylene methylsuccinate-co-terephthalate) is 1:1, and the molar ratio of methylsuccinic acid, terephthalic acid to 1,4-butanediol is 1:1.5; the epoxy chain extender is an epoxy chain extender with a bio-based aconitic acid backbone, the number of carbon atoms in its aliphatic chain n = 3, and the type of epoxy alcohol used is epoxy pentanol;

[0061] (3) Add the above-mentioned uniformly mixed materials into a screw extruder for extrusion granulation. After extrusion granulation, blow molding is carried out to obtain a composite material. The main body temperature of the twin-screw extruder is 170 °C, the head temperature is 180 °C, and the screw rotation speed is 300 r / min;

[0062] (4) Thermally press the obtained composite material into a mold, place it in a foaming kettle, heat the foaming kettle to 120 °C and inject CO 2 gas at 20 MPa. After maintaining the pressure for 3 h, quickly release the pressure to obtain a low-foaming ratio foam material;

[0063] (5) Place the obtained foam material in a vacuum drying oven and heat it to 100 °C, evacuate to -0.05 MPa, maintain the pressure for 60 min, and release the pressure to obtain a high-foaming ratio biodegradable foam material 1#.

[0064] Example 2

[0065] The preparation method of the biodegradable foam material includes the following steps:

[0066] (1) Put the side-chain aromatic-aliphatic copolyester and the blend resin into an oven and dry them at 30 °C for 5 h for later use;

[0067] (2) Add 0.1 part of the epoxy chain extender, 60 parts of dried poly(pentylene ethylsuccinate-co-terephthalate), and 10 parts of PBS into a high-speed mixer and stir at a low speed of 150 r / min for 4 min. Then add 0.2 part of talcum powder, 3 parts of tributyl pentyl aconitate, and 0.1 part of antioxidant 168, and stir at a high speed of 1000 r / min for 10 min to mix evenly;

[0068] Among them, the molar ratio of terephthalic acid to ethylsuccinic acid in the poly(pentylene ethylsuccinate-co-terephthalate) is 1:1, and the molar ratio of ethylsuccinic acid, terephthalic acid to 1,5-pentanediol is 1:1; the epoxy chain extender is an epoxy chain extender with a bio-based aconitic acid backbone, the number of carbon atoms in its aliphatic chain n = 1, and the type of epoxy alcohol used is epoxy propanol;

[0069] (3) Add the above-mentioned uniformly mixed materials into a screw extruder for extrusion granulation. After extrusion granulation, blow molding is carried out to obtain a composite material. The main body temperature of the twin-screw extruder is 160 °C, the head temperature is 170 °C, and the screw rotation speed is 300 r / min;

[0070] (4) Thermally press the obtained composite material into a mold, place it in a foaming kettle, heat the foaming kettle to 60 °C and inject CO 2 gas at 10 MPa. After maintaining the pressure for 1 h, quickly release the pressure to obtain a low-foaming ratio foam material;

[0071] (5) Place the obtained foam material in a vacuum drying oven and heat it to 80 °C. Evacuate to -0.01 MPa, maintain the pressure for 20 min, and release the pressure to obtain a high-foaming ratio biodegradable foam material 2#.

[0072] Example 3

[0073] The preparation method of the biodegradable foam material comprises the following steps:

[0074] (1) Put the side-chain aromatic-aliphatic copolyester and the blend resin into an oven and dry them at 60 °C for 5 h for standby;

[0075] (2) Add 2 parts of epoxy chain extender, 90 parts of dried poly(2-propylglutaric acid / ethylene terephthalate), and 30 parts of PPC into a high-speed mixer and stir at a low speed of 150 r / min for 10 min. Then add 5 parts of titanium dioxide, 5 parts of tributyl aconitate, and 0.5 part of antioxidant 1076, and stir at a high speed of 1000 r / min for 30 min to mix evenly; The epoxy chain extender is an epoxy chain extender based on biobased aconitic acid, the number of carbon atoms n in its aliphatic chain is 4, and the type of epoxy alcohol used is epoxyhexanol;

[0076] Among them, the molar ratio of terephthalic acid to 2-propylglutaric acid in the poly(2-propylglutaric acid / ethylene terephthalate) is 1:5, and the molar ratio of 2-propylglutaric acid, terephthalic acid, and ethylene glycol is 1:2;

[0077] (3) Add the above-mentioned uniformly mixed materials into a screw extruder for extrusion granulation. After extrusion granulation, blow molding is carried out to obtain a composite material. The main body temperature of the twin-screw extruder is 200 °C, the head temperature is 190 °C, and the screw rotation speed is 300 r / min;

[0078] (4) Thermally press the obtained composite material into a mold, place it in a foaming kettle, heat the foaming kettle to 150 °C and inject CO 2 gas at 30 MPa. After maintaining the pressure for 6 h, quickly release the pressure to obtain a low-foaming ratio foam material;

[0079] (5) Place the obtained foam material in a vacuum drying oven, heat it to 120 °C, evacuate to -0.1 MPa, hold the pressure for 120 min, and release the pressure to obtain the highly foamed biodegradable foam material 3#.

[0080] Example 4

[0081] The difference from Example 1 is that the molar ratio of terephthalic acid to methylsuccinic acid in poly(methylsuccinic acid / butylene terephthalate) copolymer is changed from 1:3 to 1:0.5, and the foam material 4# is prepared.

[0082] Example 5

[0083] The difference from Example 1 is that the molar ratio of terephthalic acid to methylsuccinic acid in poly(methylsuccinic acid / butylene terephthalate) copolymer is 1:3, and the molar ratio of the sum of the molar numbers of methylsuccinic acid and terephthalic acid to 1,4-butanediol is 1:1.5, which is replaced by the molar ratio of terephthalic acid to methylsuccinic acid being 1:7, and the molar ratio of the sum of the molar numbers of methylsuccinic acid and terephthalic acid to 1,4-butanediol being 1:5, and the foam material 5# is prepared.

[0084] Example 6

[0085] The difference from Example 1 is that poly(methylsuccinic acid / butylene terephthalate) copolymer is replaced by poly(2-methylheptanedioic acid / butylene terephthalate) copolymer, and the foam material 6# is prepared.

[0086] Example 7

[0087] The difference from Example 1 is that poly(methylsuccinic acid / butylene terephthalate) copolymer is replaced by poly(methylsuccinic acid / hexylene terephthalate) copolymer, and the foam material 7# is prepared.

[0088] Example 8

[0089] The difference from Example 1 is that poly(methylsuccinic acid / butylene terephthalate) copolymer is replaced by PBAT, and the foam material 8# is prepared.

[0090] The difference between Example 9 and Example 1 is that calcium carbonate is replaced by sodium stearate, and the foam material 9# is prepared.

[0091] The difference between Example 10 and Example 1 is that the epoxy chain extender with a bio-based aconitic acid backbone and a fatty chain carbon number n = 3 is replaced by the epoxy chain extender with a bio-based aconitic acid backbone and a fatty chain carbon number n = 8, and the foam material 10# is prepared.

[0092] Comparative Example 1

[0093] The difference from Example 1 is that 80 parts of poly(butylene methyl succinate / terephthalate) are replaced with 40 parts to prepare the foamed material D1#.

[0094] Comparative Example 2

[0095] The difference from Example 1 is that 80 parts of poly(butylene methyl succinate / terephthalate) are replaced with 120 parts to prepare the foamed material D2#.

[0096] Comparative Example 3

[0097] The difference from Example 1 is that tributyl aconitate is replaced with trimethyl aconitate to prepare the foamed material D3#.

[0098] Comparative Example 4

[0099] The difference from Example 1 is that tributyl aconitate is replaced with tridecyl aconitate to prepare the foamed material D4#.

[0100] Comparative Example 5

[0101] The difference from Example 1 is that tributyl aconitate is replaced with tributyl citrate to prepare the foamed material D5#.

[0102] Comparative Example 6

[0103] The difference from Example 1 is that poly(butylene methyl succinate / terephthalate) is replaced with PBAT to prepare the foamed material D6#.

[0104] Comparative Example 7

[0105] The difference from Example 1 is that after high-pressure foaming, vacuum pressure holding is not carried out to prepare the foamed material D7#.

[0106] Test Example

[0107] The microcellular foamed materials 1#-10# and 1#-7# prepared in the above examples and comparative examples were tested for foaming ratio, cell diameter, cell density, shrinkage rate and compression set. The test results are shown in Table 1 and Table 2.

[0108] Among them, the foaming ratio test was carried out by using a density balance to measure the density of the blend material before and after foaming according to the water displacement method (ASTM-D792). The calculation formula of the foaming ratio ER is as follows:

[0109]

[0110] Where ER is the foaming ratio; ρ m is the density of the modified material before foaming, with the unit of g / cm 3 ; ρ fis the density of the modified material after foaming, with the unit of g / cm 3 ;

[0111] Cell diameter and cell density: After quenching the foamed material with liquid nitrogen and sputtering gold on the cross-section, the cell structure inside the foamed material was observed using a scanning electron microscope (SEM), and the average cell diameter D was statistically analyzed and the cell density N was calculated through Image J software. The calculation formulas are as follows:

[0112]

[0113] where D is the average cell diameter, with the unit of μm; n is the number of cells in the SEM image; d i is the diameter of the i-th cell, with the unit of μm;

[0114]

[0115] where N is the cell density, with the unit of cells / cm 3 ; n is the number of cells in the SEM image; M is the magnification of the SEM image; A is the area of the SEM image, with the unit of cm 2 ; ER is the foaming ratio of the sample. The instrument model of the scanning electron microscope is Phenom Pro desktop scanning electron microscope, and the test conditions are 10KV;

[0116] Dimensional stability: The dimensional stability of different foamed materials was evaluated using the shrinkage rate;

[0117] First, the foaming ratio ER of all foamed materials was measured 1 , and after standing for 1 week, the foaming ratio ER was measured again 2 , and the shrinkage rate S of the foamed material was calculated as follows:

[0118]

[0119] where S is the shrinkage rate of the foamed material, with the unit of %; ER 1 is the foaming ratio when just out of the kettle; ER 2 is the foaming ratio after standing for one week.

[0120] Compression set: It was carried out according to the provisions of Method C of Standard GB / T6669-2008. The specimen size was 50mm×50mm×25mm, the number of specimens was 5, the thickness of the specimen was compressed by 50%, the compression time was 24h, and the compression set CS was calculated as follows:

[0121]

[0122] where CS is the compression set, with the unit of %; d 0is the initial thickness of the specimen, in mm; d r is the final thickness of the specimen, in mm;

[0123] Tensile property test: GB / T 1040-92 "Test Method for Tensile Properties of Plastics" is adopted, and the shape of the test sample is the Type II dumbbell-shaped specimen in the execution standard;

[0124] Volatility test: The volatility of plasticizers involved in the examples and test examples, such as aconitic acid esters and tributyl citrate, in the corresponding foamed materials is tested to reflect the high and low volatility of different types of plasticizers. The test is carried out with reference to HG / T 4458-2012 "Determination of Plasticizer Loss in Plastics - Activated Carbon Method". The test temperature is 70 °C and the test time is 24 h.

[0125] Table 1

[0126]

[0127]

[0128] Table 2

[0129] Number Compression permanent deformation / % Tensile strength / MPa Elongation at break / % Volatility / % 1# 9.4 25.6 597.6 0.72 2# 12.2 22.4 524.5 0.73 3# 14.3 23.2 536.7 0.72 4# 8.2 26.3 432.1 0.72 5# 28.4 14.8 615.2 0.73 6# 26.2 16.3 609.2 0.74 7# 25.9 16.2 603.5 0.74 8# 29.3 12.1 637.0 0.78 9# 10.2 27.3 531.6 0.75 10# 24.6 21.7 607.4 0.73 D1# 25.4 19.2 489.2 0.73 D2# 27.1 21.2 498.4 0.74 D3# 9.6 25.8 492.3. 0.95 D4# 17.9 12.3 462.4 0.27 D5# 24.6 21.4 532.6 0.91 D6# 25.8 22.6 457.8 0.74 D7# 30.4 23.2 542.6 0.74

[0130] According to the test results, it can be known that the biodegradable foamed material of the present invention has a high foaming ratio, a moderate cell diameter, a large cell density and a small shrinkage rate, and the foaming effect is excellent; at the same time, the foamed material also has good tensile properties and low volatility. It can be seen that the obtained foamed material has a high foaming rate and good structural stability, and has a wide range of applications.

[0131] Each embodiment in this specification is described in a progressive manner. For the same or similar parts among the embodiments, reference can be made to each other. The key point of each embodiment is to illustrate the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can refer to the partial description of the method embodiment.

[0132] The above are only the embodiments of the present application and are not used to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the scope of the claims of the present application.

Claims

1. A biodegradable foam material, characterized in that: The invention is prepared from the following materials in parts by weight: 60-90 parts of aromatic-aliphatic copolyester with side chain, 10-30 parts of blending resin, 0.2-5 parts of nucleating agent, 40-80 parts of plasticizer, 0.1-2 parts of chain extender, and 0.1-0.5 parts of antioxidant; The plasticizer is aconitate, and the general structural formula of the aconitate is shown in Formula I: Wherein, R1, R2, and R3 can all be one of a straight-chain alkyl group, a branched-chain alkyl group, and a cycloalkyl group, and the number of carbon atoms in R1, R2, and R3 is 4 to 8.

2. The biodegradable foam material according to claim 1, characterized in that: The monomers of the copolyester are fatty dibasic acid with side chains, terephthalic acid and aliphatic diols, the molar ratio of terephthalic acid to fatty dibasic acid with side chains is 1:1-5, and the molar ratio of the total sum of terephthalic acid and fatty dibasic acid with side chains to alcohol is 1:1-2.

3. The biodegradable foam material according to claim 2, characterized in that: The general structural formula of the side chain fatty dibasic acid is shown in Formula II, and the general structural formula of the aliphatic diol is shown in Formula Ш: The side chain X of the fatty dibasic acid with a side chain is 1-4, the main chain Y is 1-5, and the diol Z is 0-4.

4. The biodegradable foam material according to claim 1, characterized in that: The chain extender is an epoxy chain extender.

5. The biodegradable foam material according to claim 4, characterized in that: The epoxy chain extender is an epoxy chain extender with bio-based aconitic acid as the skeleton, and the general structural formula is shown in Formula IV: Here, n is an integer from 1 to 4.

6. The biodegradable foam material according to claim 1, characterized in that: The blended resin is one or more of PLA, PBS and PPC.

7. The biodegradable foam material according to claim 1, characterized in that: The nucleating agent is one or more of calcium carbonate, talc, silicon dioxide, titanium dioxide, hydrotalcite, and nanocellulose; the antioxidant is one or more of antioxidant 168, antioxidant 1010, antioxidant 1076, and antioxidant 2246.

8. A method for preparing the biodegradable foam material according to any one of claims 1 to 7, characterized in that: The steps include: (1) placing the side chain aromatic-aliphatic copolyester and the blended resin in an oven for drying; (2) adding the epoxy chain extender, the dried aromatic-aliphatic copolyester with side chains, and the blended resin into a high-speed mixer according to the weight, and then adding the nucleating agent, the plasticizer, and the antioxidant to mix evenly; (3) adding the above-mentioned uniformly mixed materials into a screw extruder for extrusion granulation, and blowing a film after extrusion granulation to obtain a composite material; (4) hot-pressing the obtained composite material into a shape, placing it in a foaming kettle, heating the foaming kettle and injecting a certain pressure of CO2 gas, maintaining the pressure for a period of time and then rapidly releasing the pressure to obtain a low foaming ratio foam material; (5) placing the obtained foam material in a vacuum drying oven and heating it, evacuating the air and maintaining the pressure for a period of time, and releasing the pressure to obtain a foam material with a high foaming ratio.

9. The method for preparing the biodegradable foam material according to claim 8, characterized in that: In step (1), the drying temperature is 30-60° C. and the drying time is 5 h; In step (2), the speed of the high-speed mixer is set to first stir at a low speed of 150 r / min for 4 to 10 min, and then stir at a high speed of 1000 r / min for 10 to 30 min; The twin-screw extruder in step (3) has a main engine temperature of 160-200° C., a die head temperature of 170-190° C., and a screw rotation speed of 300 r / min.

10. The method for preparing the biodegradable foam material according to claim 8, characterized in that: In step (4), the temperature of the foaming kettle is 60-150° C., the foaming pressure is 10-30 MPa, and the pressure holding time is 1-6 h; In step (5), the temperature of the vacuum drying oven is 80 to 120° C., the vacuum degree is -0.01 MPa to -0.1 MPa, and the vacuum holding time is 20 to 120 min.

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