阅读说明：本技术 一种全生物降解改性pbat发泡板材及其制备方法、应用 (Full-biodegradable modified PBAT foamed sheet and preparation method and application thereof ) 是由 杨晋涛 张恺亮 毛世华 郑司雨 于 2021-06-04 设计创作，主要内容包括：本发明涉及发泡材料技术领域,尤其涉及一种全生物降解改性PBAT发泡板材及其制备方法、应用,所述全生物降解改性PBAT发泡板材包括以下重量份的组分：70～100份PBAT,20～30份刚性聚合物,10～20份成核剂,2.5～5份相容剂,0.4～0.6份抗氧剂,1.2～3份润滑剂和3～6份扩链剂。本发明各配方组分之间协同增效,创造性通过引入刚性聚合物,在PBAT基体的分子结构中引入硬段,并在PBAT上接枝扩链剂,提高PBAT材料的熔体强度,提高其在发泡后的尺寸稳定性。(The invention relates to the technical field of foaming materials, in particular to a full-biodegradation modified PBAT foaming board, a preparation method and application thereof, wherein the full-biodegradation modified PBAT foaming board comprises the following components in parts by weight: 70-100 parts of PBAT, 20-30 parts of rigid polymer, 10-20 parts of nucleating agent, 2.5-5 parts of compatilizer, 0.4-0.6 part of antioxidant, 1.2-3 parts of lubricant and 3-6 parts of chain extender. The components of the formula are synergistic synergistically, a rigid polymer is creatively introduced, a hard segment is introduced into the molecular structure of the PBAT matrix, and a chain extender is grafted on the PBAT, so that the melt strength of the PBAT material is improved, and the dimensional stability of the PBAT material after foaming is improved.)

1. A full-biodegradable modified PBAT foamed sheet is characterized by comprising the following components in parts by weight:

70-100 parts of PBAT, 20-30 parts of rigid polymer, 10-20 parts of nucleating agent, 2.5-5 parts of compatilizer, 0.4-0.6 part of antioxidant, 1.2-3 parts of lubricant and 3-6 parts of chain extender.

2. The fully biodegradable modified PBAT foamed sheet material according to claim 1,

the rigid polymer is selected from one or two of levorotatory polylactic acid PLLA, dextrorotatory polylactic acid PDLA, low-density polyethylene LDPE and polypropylene PP;

the mass ratio of the rigid polymer to the PBAT is (5-30): 100.

3. The fully biodegradable modified PBAT foamed sheet according to claim 1, wherein the nucleating agent is at least one of carbon nanotubes, graphene, talcum powder, modified calcium carbonate, carbon black and montmorillonite; the modified calcium carbonate is silane coupling agent modified calcium carbonate.

4. The fully biodegradable modified PBAT foamed sheet material according to claim 1,

the compatilizer is one or more of maleic anhydride, citric acid ester, tributyl citrate and ammonia acid triisocyanate;

the mass ratio of the compatilizer to the PBAT is (0.1-5) to 100;

the chain extender is one or two of multifunctional active epoxy polymer and acrylic polymer with polyepoxy group;

the mass ratio of the chain extender to the PBAT is (0.5-10) to 100;

the lubricant is one or two selected from zinc stearate, calcium stearate, silicone powder and erucamide;

the mass ratio of the lubricant to the PBAT is (1-10) to 100;

the antioxidant is selected from one or two of antioxidant 1010, antioxidant 168 and antioxidant DLTP;

the ratio of the antioxidant to the PBAT is (0.3-0.9): 100.

5. A method for preparing the fully biodegradable modified PBAT foamed sheet material according to any one of claims 1 to 4, which comprises the following steps:

(1) according to the proportion, the PBAT, the rigid polymer and the nucleating agent are subjected to heat treatment, and then are pre-blended with the compatilizer, the antioxidant, the lubricant and the chain extender to obtain a mixture;

(2) extruding and granulating the mixture obtained in the step (1) to obtain modified PBAT granules;

(3) and (3) carrying out supercritical mould pressing foaming on the modified PBAT granules obtained in the step (2) to obtain the full-biodegradable modified PBAT foaming board.

6. The production method according to claim 5,

in the step (1), the heat treatment temperature is 60-80 ℃, and the time is 6-8 h;

in the step (2), the granulation temperature is 180-200 ℃;

in the step (3), supercritical die pressing foaming is carried out in a die pressing foaming machine, and the specific steps are as follows:

and (3) placing the modified PBAT granules obtained in the step (2) in a supercritical mould pressing foaming machine, raising the temperature of the mould pressing foaming machine to 50-150 ℃ in advance, closing the mould, introducing a physical foaming agent, keeping the pressure of the foaming agent at 5-20 MPa for 0.5-6 h, quickly releasing the pressure for 0.1-20 s, and opening the mould after the pressure in the mould cavity is completely released to obtain the fully biodegradable modified PBAT foaming board.

7. The method of claim 6, wherein the physical blowing agent is selected from CO₂And N₂One or two of them.

8. The method of manufacturing according to claim 6, wherein the supercritical die-pressing foaming machine comprises a die and a control system, the die comprises an upper die and a lower die, and a cavity between the upper die and the lower die forms a cavity; the upper die is provided with an air inlet valve and an air outlet valve.

9. The production method according to claim 6,

the control system comprises a pressure maintaining system, and the pressure maintaining system is a PCT automatic control system;

and a metal flow guide layer is arranged in the die, and is made of foam copper or foam nickel.

10. Use of the fully biodegradable modified PBAT foamed sheet according to any of claims 1-4 in fitness equipment.

Technical Field

The invention relates to the technical field of foaming materials, in particular to a full-biodegradable modified PBAT foaming board and a preparation method and application thereof.

Background

The polymer foam material is widely applied to various industries at present due to the advantages of excellent mechanical property and light weight. At present, PE foaming materials, PS foaming materials, PVC foaming materials and the like are widely applied. As a country with a large population base, China consumes a large amount of foaming materials every year. At present, along with the enhancement of national environmental protection consciousness, the nation puts forward further environmental protection requirements on plastic products, and the biodegradable plastic products are required to be greatly popularized to replace disposable plastic products.

The PBAT material (poly adipic acid/butylene terephthalate) is used as a thermoplastic biodegradable material, and due to the excellent ductility and elongation and the processing temperature close to that of PE, most PE production manufacturers can switch raw materials without replacing equipment, so that the PBAT material has higher universality. However, PBAT as an ester polymer is very easy to be subjected to thermal oxidative degradation in the thermal processing process, and due to the linear structure of PBAT, no branch chain exists, and the melt strength of PBAT is low, so that the application of PBAT in the foaming field is restricted.

Chinese patent literature discloses a polyethylene heat-insulating foaming plate and a preparation method thereof, and the application publication number is CN111100354A, PBAT is used as a partial modifier to be filled in a PE foaming material, although the PBAT can provide the material with certain biodegradation performance, most of the material matrix is PE, and no biodegradation performance exists.

The Chinese patent literature discloses 'a degradable chemical foaming master batch and a preparation method thereof', the application publication number of the degradable chemical foaming master batch is CN109762309A, the invention uses a chemical foaming agent in the foaming process, substances such as formamide or the foaming agent and the like can be remained in a finished product, namely, the product performance is influenced, and the remained chemical substances can have certain influence on a human body.

Disclosure of Invention

The invention provides a full-biodegradation modified PBAT foaming sheet material with high melt strength, wide foaming range, and excellent comprehensive performances of ductility and tensile strength, aiming at overcoming the problems of insufficient melt strength and incomplete degradation of the existing PBAT material.

The invention also provides a preparation method of the full-biodegradable modified PBAT foaming board, which is simple to operate, controllable in process conditions and easy to industrialize.

The invention also provides application of the full-biodegradable modified PBAT foaming board in fitness equipment.

In order to achieve the purpose, the invention adopts the following technical scheme:

a full-biodegradable modified PBAT foamed sheet comprises the following components in parts by weight: 70-100 parts of PBAT, 20-30 parts of rigid polymer, 10-20 parts of nucleating agent, 2.5-5 parts of compatilizer, 0.4-0.6 part of antioxidant, 1.2-3 parts of lubricant and 3-6 parts of chain extender.

The components of all the formulas of the full-biodegradable modified PBAT foaming board are synergized, rigid polymers are creatively introduced, hard sections are introduced into the molecular structure of a PBAT matrix, and chain extenders are grafted on the PBAT, so that the melt strength of the PBAT material is improved, and the dimensional stability of the PBAT material after foaming is improved.

Preferably, the rigid polymer is selected from one of polylactic acid (PLA), Low Density Polyethylene (LDPE) and polypropylene (PP); the mass ratio of the rigid polymer to the PBAT is (5-30): 100.

The PBAT and the rigid polymer are blended to prepare the PBAT modified material with high melt strength, wherein a stereo composite crystal formed by the interaction of PLLA and PDLA is introduced, and the characteristics of rigidity and high temperature resistance of the stereo composite crystal are utilized to ensure that the PBAT modified material serves as a physical crosslinking point and a heterogeneous nucleation point, thereby overcoming the defects of soft hardness and poor tensile strength of the PBAT.

Preferably, the nucleating agent is at least one of carbon nano tube, graphene, talcum powder, modified calcium carbonate, carbon black and montmorillonite; the modified calcium carbonate is silane coupling agent modified calcium carbonate. If unmodified calcium carbonate is directly used as a nucleating agent, the defects of poor interface bonding force and poor dispersion between PBAT and rigid polymer are existed; the silane coupling agent modified calcium carbonate used as the nucleating agent has the following effects: (1) making the phase size of the rigid polymer smaller; (2) the interface bonding force among the PBAT, the rigid polymer and the modified calcium carbonate is stronger, the modified calcium carbonate has better dispersion effect, is more beneficial to foaming, and simultaneously improves the mechanical property.

Preferably, the preparation method of the modified calcium carbonate is that under the condition of normal temperature, the calcium carbonate is stirred at high speed and is dropwise added with a silane coupling agent for activation treatment, so as to obtain the modified calcium carbonate; the silane coupling agent is added in an amount of 4-6 wt% based on the total mass of calcium carbonate.

Preferably, the compatibilizer is maleic anhydride; the mass ratio of the compatilizer to the PBAT is (0.1-5): 100.

Preferably, the chain extender is one or both of a multifunctional reactive epoxy polymer and an acrylic polymer having a polyepoxy group.

Preferably, the chain extender is multifunctional active epoxy oligomer ADR-4370 s; the mass ratio of the chain extender to the PBAT is (0.5-10): 100. The grafting of the epoxy chain extender on the PBAT can effectively improve the melt strength of the PBAT material and improve the dimensional stability of the PBAT material after foaming.

Preferably, the lubricant is one or two of zinc stearate, zinc oxide, silicone powder and erucamide; the mass ratio of the lubricant to the PBAT is (1-10): 100.

Preferably, the antioxidant is selected from one or two of antioxidant 1010, antioxidant 168 and antioxidant DLTP; the ratio of the antioxidant to the PBAT is (0.3-0.9): 100.

A preparation method of a full-biodegradable modified PBAT foaming board comprises the following steps:

(1) according to the proportion, the PBAT, the rigid polymer and the nucleating agent are subjected to heat treatment, and then are pre-blended with the compatilizer, the antioxidant, the lubricant and the chain extender to obtain a mixture;

(2) extruding and granulating the mixture obtained in the step (1) to obtain modified PBAT granules; in the process, the melt strength of the PBAT material can be effectively improved by grafting the epoxy chain extender on the PBAT through granulation treatment, and the dimensional stability of the PBAT material after foaming is improved;

(3) and (3) carrying out supercritical mould pressing foaming on the modified PBAT granules obtained in the step (2) to obtain the full-biodegradable modified PBAT foaming board. The supercritical die pressing foaming has the advantages of environmental protection, cleanness, no pollution and the like, and no waste water and waste gas is generated in the production process.

Preferably, in the step (1), the heat treatment temperature is 60-80 ℃ and the time is 6-8 h; the heat treatment serves to remove water and prevent degradation of the PBAT during extrusion.

Preferably, in the step (2), the granulation temperature is 180 to 200 ℃.

Preferably, in the step (3), the supercritical die pressing foaming is carried out in a die pressing foaming machine, and the specific steps are as follows: and (3) placing the modified PBAT granules obtained in the step (2) in a supercritical mould pressing foaming machine, raising the temperature of the mould pressing foaming machine to 50-150 ℃ in advance, closing the mould, introducing a physical foaming agent, keeping the pressure of the foaming agent at 5-20 MPa for 0.5-6 h, quickly releasing the pressure for 0.1-20 s, and opening the mould after the pressure in the mould cavity is completely released to obtain the fully biodegradable modified PBAT foaming board.

Preferably, the physical blowing agent is selected from CO₂And N₂One or two of them.

Preferably, the supercritical die-pressing foaming machine comprises a die and a control system, wherein the die comprises an upper die and a lower die, and a cavity between the upper die and the lower die forms a cavity; the upper die is provided with an air inlet valve and an air outlet valve; the air inlet valve can realize the rapid inlet of the supercritical fluid, the air outlet valve can realize the rapid outlet of the supercritical fluid, and the volume ratio of the mold cavity to the PBAT foaming board to be molded is 6: 5-5: 1. The pressure relief time is regulated and controlled by regulating the size of a nozzle of the pressure relief valve.

Preferably, the control system comprises a pressure maintaining system, and the pressure maintaining system is a PCT automatic control system; the pressure change in the die cavity is monitored in real time through a PCT automatic control system, and the booster pump is controlled to be opened or closed in real time to achieve the purpose of keeping the pressure.

Preferably, a metal flow guide layer is arranged in the die, and the metal flow guide layer is made of foamed copper or foamed nickel, so that the diffusion of supercritical gas (physical foaming agent) is facilitated.

An application of a full-biodegradable modified PBAT foaming board in fitness equipment, wherein the fitness equipment is preferably a yoga mat.

Therefore, the invention has the following beneficial effects:

(1) the components of all the formulas of the full-biodegradable modified PBAT foaming board are synergized, rigid polymers are creatively introduced, hard sections are introduced into the molecular structure of a PBAT substrate, and chain extenders are grafted on the PBAT, so that the melt strength of the PBAT material is improved, and the dimensional stability of the PBAT material after foaming is improved;

(2) the preparation method is simple to operate, controllable in process conditions and easy to industrialize; by adopting the supercritical foaming technology, the method has the advantages of environmental protection, cleanness, no pollution and the like, and no waste water or waste gas is generated in the production process;

(3) the full-biodegradable modified PBAT foaming board has the characteristics of high melt strength and wide foaming interval, and can be widely applied to fitness equipment.

Drawings

FIG. 1 is a SEM image of a cross section of a fully biodegradable modified PBAT foamed sheet prepared in example 1.

FIG. 2 is a SEM image of a cross section of a fully biodegradable modified PBAT foamed sheet prepared in example 6.

FIG. 3 is a SEM image of a cross section of a fully biodegradable modified PBAT foamed sheet prepared in example 7.

FIG. 4 is a sectional SEM photograph of the foamed material prepared in comparative example 1.

FIG. 5 is a sectional SEM photograph of the foamed material prepared in comparative example 2.

FIG. 6 is a sectional SEM photograph of the foamed material prepared in comparative example 3.

Detailed Description

The technical solution of the present invention is further specifically described below by using specific embodiments and with reference to the accompanying drawings.

In the present invention, all the equipment and materials are commercially available or commonly used in the art, and the methods in the following examples are conventional in the art unless otherwise specified.

Example 1

(1) According to the following mixture ratio, 80kg of PBAT, 20kg of PP and 10kg of modified calcium carbonate are subjected to heat treatment at 60 ℃ for 8h, and then are pre-blended with 4kg of maleic anhydride, 10106 kg of antioxidant, 1.2kg of zinc stearate and 5kg of chain extender (such as ADR-4370s) to obtain a mixture;

(2) carrying out double-screw extrusion granulation on the mixture obtained in the step (1), wherein the granulation temperature is 190 ℃, and obtaining modified PBAT granules;

(3) with CO₂Placing the modified PBAT granules obtained in the step (2) into a supercritical mould pressing foaming machine as a physical foaming agent, wherein the supercritical mould pressing foaming machine comprises a mould and a PCT automatic control system, the mould comprises an upper mould and a lower mould, and a cavity is formed by a cavity between the upper mould and the lower mould; a metal flow guide layer is arranged in the die, and is made of foam copper or foam nickel; the upper die is provided with an air inlet valve and an air outlet valve; and (3) heating the temperature of a mould pressing foaming machine to 120 ℃ in advance, introducing a physical foaming agent after mould assembly, keeping the pressure of the foaming agent at 9MPa for 3h, quickly releasing the pressure for 2s, and opening the mould after the pressure in the mould cavity is completely released to obtain the fully biodegradable modified PBAT foaming board.

The section of the fully biodegradable modified PBAT foamed sheet prepared in this example is shown in fig. 1, and it can be seen from fig. 1 that the addition of rigid polymer PP makes the cell wall thickness of the material slightly thicker, the addition of nucleating agent modified calcium carbonate makes the cell pore diameter significantly smaller, the average pore diameter is 26 microns, which is half of the cell pore diameter of comparative example 1, and the cell density is about twice of that of comparative example 1, which is attributed to the fact that the addition of rigid polymer PP makes the melt strength of PBAT composite material improved, and makes the cell pore diameter reduced. The nucleating agent brings more nucleation sites and thus more micropores are formed. The smaller bubble size under the same multiplying power enables the material to absorb more energy, so that the material has excellent mechanical properties.

Example 2

(1) According to the following mixture ratio, 80kg of PBAT, 20kg of PLA and 10kg of modified calcium carbonate are subjected to heat treatment at 80 ℃ for 6h, and then are pre-blended with 4kg of maleic anhydride, 0.6kg of antioxidant DLTP, 1.2kg of silicone powder and 5kg of chain extender (ADR-4370s) to obtain a mixture;

(2) carrying out double-screw extrusion granulation on the mixture obtained in the step (1), wherein the granulation temperature is 180 ℃, and obtaining modified PBAT granules;

(3) with N₂Placing the modified PBAT granules obtained in the step (2) into a supercritical mould pressing foaming machine as a physical foaming agent, wherein the supercritical mould pressing foaming machine comprises a mould and a PCT automatic control system, the mould comprises an upper mould and a lower mould, and a cavity is formed by a cavity between the upper mould and the lower mould; a metal flow guide layer is arranged in the die, and is made of foam copper or foam nickel; the upper die is provided with an air inlet valve and an air outlet valve; and (3) heating the temperature of a mould pressing foaming machine to 110 ℃, closing the mould, introducing a physical foaming agent, keeping the pressure of the foaming agent at 12MPa for 2 hours, quickly releasing the pressure for 3 seconds, and opening the mould after the pressure in the mould cavity is completely released to obtain the fully biodegradable modified PBAT foaming board.

Example 3

(1) According to the following mixture ratio, 80kg of PBAT, 20kg of LDPE and 15kg of montmorillonite are subjected to heat treatment at 75 ℃ for 7 hours, and then are pre-blended with 5kg of maleic anhydride, 1681.8 kg of antioxidant, 2kg of erucamide and 3kg of chain extender (ADR-4370s) to obtain a mixture;

(2) carrying out double-screw extrusion granulation on the mixture obtained in the step (1), wherein the granulation temperature is 190 ℃, and obtaining modified PBAT granules;

(3) with N₂Placing the modified PBAT granules obtained in the step (2) into a supercritical mould pressing foaming machine as a physical foaming agent, wherein the supercritical mould pressing foaming machine comprises a mould and a PCT automatic control system, the mould comprises an upper mould and a lower mould, and a cavity is formed by a cavity between the upper mould and the lower mould; gold is arranged in the dieBelongs to a flow guide layer, and the metal flow guide layer is foamed copper or foamed nickel; the upper die is provided with an air inlet valve and an air outlet valve; and (3) raising the temperature of a mould pressing foaming machine to 115 ℃ in advance, introducing a physical foaming agent after mould assembly, keeping the pressure of the foaming agent at 10MPa for 2.5 hours, quickly relieving the pressure for 3.5 seconds, and opening the mould after the pressure in the mould cavity is completely released to obtain the fully biodegradable modified PBAT foaming board.

Example 4

(1) According to the following mixture ratio, 70kg of PBAT, 30kg of PP and 10kg of talcum powder are subjected to heat treatment at 65 ℃ for 7h, and then are pre-blended with 2.5kg of maleic anhydride, 1680.3 kg of antioxidant, 0.3kg of antioxidant DLTP, 1kg of zinc oxide, 1kg of silicone powder and 6kg of chain extender (ADR-4370s) to obtain a mixture;

(2) carrying out double-screw extrusion granulation on the mixture obtained in the step (1), wherein the granulation temperature is 200 ℃, and obtaining modified PBAT granules;

(3) with CO₂Placing the modified PBAT granules obtained in the step (2) into a supercritical mould pressing foaming machine as a physical foaming agent, wherein the supercritical mould pressing foaming machine comprises a mould and a PCT automatic control system, the mould comprises an upper mould and a lower mould, and a cavity is formed by a cavity between the upper mould and the lower mould; a metal flow guide layer is arranged in the die, and is made of foam copper or foam nickel; the upper die is provided with an air inlet valve and an air outlet valve; and (3) heating the temperature of a mould pressing foaming machine to 150 ℃, closing the mould, introducing a physical foaming agent, keeping the pressure of the foaming agent at 5MPa for 0.5h, quickly releasing the pressure for 0.1s, and opening the mould after the pressure in the mould cavity is completely released to obtain the fully biodegradable modified PBAT foaming board.

Example 5

(1) According to the following mixture ratio, 80kg of PBAT, 20kg of PP and 20kg of modified calcium carbonate are subjected to heat treatment at 68 ℃ for 7h, and then are pre-blended with 5kg of maleic anhydride, 1680.6 kg of antioxidant, 3kg of calcium stearate and 4.5kg of chain extender (ADR-4370s) to obtain a mixture;

(2) carrying out double-screw extrusion granulation on the mixture obtained in the step (1), wherein the granulation temperature is 190 ℃, and obtaining modified PBAT granules;

(3) with CO₂As a physical foaming agent, the modified PBAT granules obtained in the step (2) are placed in a supercritical mould pressing foaming machine,the supercritical mould pressing foaming machine comprises a mould and a PCT automatic control system, wherein the mould comprises an upper mould and a lower mould, and a cavity between the upper mould and the lower mould forms a cavity; a metal flow guide layer is arranged in the die, and is made of foam copper or foam nickel; the upper die is provided with an air inlet valve and an air outlet valve; and (3) heating the temperature of a mould pressing foaming machine to 50 ℃, introducing a physical foaming agent after mould assembly, keeping the pressure of the foaming agent at 20MPa for 6h, quickly releasing the pressure for 2s, and opening the mould after the pressure in the mould cavity is completely released to obtain the fully biodegradable modified PBAT foaming board.

Example 6

(1) According to the following mixture ratio, 80kg of PBAT, 15kg of PLLA, 5kg kg of PDLA and 6kg of modified calcium carbonate are subjected to heat treatment at 70 ℃ for 8h, and then are pre-blended with 3kg of maleic anhydride, 0.4kg of antioxidant DLTP, 1kg of silicone powder and 3kg of chain extender (ADR-4370s) to obtain a mixture;

(2) carrying out double-screw extrusion granulation on the mixture obtained in the step (1), wherein the granulation temperature is 200 ℃, and obtaining modified PBAT granules;

(3) with CO₂Placing the modified PBAT granules obtained in the step (2) into a supercritical mould pressing foaming machine as a physical foaming agent, wherein the supercritical mould pressing foaming machine comprises a mould and a PCT automatic control system, the mould comprises an upper mould and a lower mould, and a cavity is formed by a cavity between the upper mould and the lower mould; a metal flow guide layer is arranged in the die, and is made of foam copper or foam nickel; the upper die is provided with an air inlet valve and an air outlet valve; and (3) raising the temperature of a mould pressing foaming machine to 125 ℃, closing the mould, introducing a physical foaming agent, keeping the pressure of the foaming agent at 20MPa for 6 hours, quickly releasing the pressure for 2s, and opening the mould after the pressure in the mould cavity is completely released to obtain the fully biodegradable modified PBAT foaming board.

The cross section of the fully biodegradable modified PBAT foamed sheet prepared in the example is shown in FIG. 2, and it can be seen from FIG. 2 that when the content of PDLA is 5%, the cell size is smaller than 14 microns, which is attributed to that a stereo composite crystal SC is formed by strong interaction between PDLA and PLLA, and the SC simultaneously plays roles of physical cross-linking point and heterogeneous nucleation, so that the melt strength of the modified PBAT material is further improved.

Example 7

(1) According to the following mixture ratio, 80kg of PBAT, 10kg of PLLA, 10kg of PDLA and 4kg of montmorillonite are subjected to heat treatment at 70 ℃ for 8h, and then are pre-blended with 3kg of maleic anhydride, 0.6kg of antioxidant DLTP, 1kg of calcium stearate and 2kg of chain extender (ADR-4370s) to obtain a mixture;

(2) carrying out double-screw extrusion granulation on the mixture obtained in the step (1), wherein the granulation temperature is 200 ℃, and obtaining modified PBAT granules;

(3) with CO₂Placing the modified PBAT granules obtained in the step (2) into a supercritical mould pressing foaming machine as a physical foaming agent, wherein the supercritical mould pressing foaming machine comprises a mould and a PCT automatic control system, the mould comprises an upper mould and a lower mould, and a cavity is formed by a cavity between the upper mould and the lower mould; a metal flow guide layer is arranged in the die, and is made of foam copper or foam nickel; the upper die is provided with an air inlet valve and an air outlet valve; and (3) heating the temperature of a mould pressing foaming machine to 128 ℃ in advance, introducing a physical foaming agent after mould assembly, keeping the pressure of the foaming agent at 20MPa for 6 hours, quickly releasing the pressure for 2s, and opening the mould after the pressure in the mould cavity is completely released to obtain the fully biodegradable modified PBAT foaming board.

The section of the fully biodegradable modified PBAT foamed sheet prepared in the example is shown in FIG. 3, and it can be seen from FIG. 3 that when the content of PDLA is 10%, too much SC causes too high melt strength of the material, which is not favorable for foaming, the cell morphology is poor, and unfoamed regions appear in many places.

Comparative example 1

Comparative example 1 differs from example 1 in that the rigid polymer (PP) and nucleating agent (modified calcium carbonate) are not added and the rest of the process is exactly the same.

The cross section of the fully biodegradable modified PBAT foamed sheet prepared in the comparative example 1 is shown in FIG. 4, and it can be seen from FIG. 4 that the PBAT foamed sheet without adding the rigid polymer and the nucleating agent has thinner cell walls, an average cell size of 52 μm and a cell density of 4.23X 10⁷This is caused by the low melt strength of the PBAT. The relatively thin cell walls and large cell sizes result in poor mechanical properties of pure PBAT foams, thereby limiting their applications.

Comparative example 2

Comparative example 2 differs from example 3 in that the compatibilising agent and chain extender are not added and the rest of the process is exactly the same.

The cross section of the fully biodegradable modified PBAT foamed sheet prepared in the comparative example 2 is shown in FIG. 5, and it can be observed from FIG. 5 that the PBAT foamed material without the addition of the compatilizer and the chain extender has no uniform cell morphology, and some areas are not foamed, because the interfacial bonding force between the PBAT and the PLA is weak due to the incompatibility of the two phases, CO is not foamed, and the PBAT and the PLA are not foamed₂Is easy to escape from the gap between the two phases, resulting in poor foaming appearance, and further obviously reducing the mechanical property of the foam.

Comparative example 3

Comparative example 3 differs from example 1 in that unmodified calcium carbonate is used as the nucleating agent and the rest of the process is exactly the same. This comparative example, which uses unmodified calcium carbonate, has poor interfacial bonding force between PBAT, PP and calcium carbonate during the preparation process and non-uniform dispersion, and it can be seen from fig. 6 that the cell size is non-uniform and there are many dense small cells due to non-uniform dispersion of calcium carbonate, thereby reducing the tensile strength of the foamed material.

The PBAT foamed sheets prepared in examples 1 to 7 and comparative examples 1 to 3 were subjected to performance tests, the test methods and test conditions were as follows: material rate analysis: the magnification (φ) of the PBAT foamed sheet was calculated from the following formula:ρ is the density of the PBAT sheet, ρ_fThe density of the PBAT board after foaming. The above densities are measured by the drainage method according to ASTM D792-00.

Analyzing the appearance of the cells: the morphology of the cells inside the foamed material was observed using a scanning electron microscope (Tescan Vega 3 SBH). The observation is carried out under the conditions that the accelerating voltage is 15kV and the working distance is 8-12 mm. Preparing a sample: and (3) placing the sample in liquid nitrogen for low-temperature brittle fracture, and then carrying out metal spraying treatment on the section by using an ion sputtering instrument to ensure that the sample has better conductivity.

The SEM pictures obtained above were pre-processed using Photoshop software, followed by cell pore size analysis using Digital Micrographs (DM) softwareAnd (4) counting the size and the pore density, and ensuring that each sample has more than 300 pores during counting. The cell density was calculated according to the following formula.Wherein N is cell density (cells/cm)³) N is the number of cells in the statistical region, A is the area (cm) of the statistical region³)。

And (3) testing tensile property: the foamed PBAT sheet was cut into a dumbbell shape, and the tensile properties of the material were characterized at room temperature by a high-low temperature double column tester (Instron 5966) at a tensile rate of 10 mm/min.

The test results are shown in table 1:

TABLE 1 test results

As can be seen from Table 1, with the addition of the rigid polymer, in examples 1 to 3, 20 parts of PP, PLA and LDPE are added respectively, the tensile strength is sequentially improved to 2.35, 2.52 and 2.24MPa, but the elongation at break is slightly reduced to 395, 385 and 427 percent, which shows that the mechanical property of the foam material can be regulated and controlled by adding the rigid polymer. And the addition of PP and LDPE which are lower in price compared with PLA, and the examples 1-3 have no great influence on the mechanical property and the foaming property of the material.

Example 4 the PP content increased and the tensile strength of the foam increased compared to example 1, indicating that increasing the content of rigid polymer can significantly increase the tensile strength of the foam. Compared with the embodiment 1, the embodiment 5 has the advantages that the content of the nucleating agent is increased, and the pore diameter of the obtained foaming material is smaller under the same multiplying power, so that the mechanical property of the material is further improved.

Comparative example 1 the tensile strength of PBAT foamed panels not modified by rigid polymer was significantly reduced compared to example 1. Compared with the example 3, the tensile strength of the PBAT foamed sheet material without adding the compatilizer and the chain extender is only 1/3 of the example 2, in the preparation process of the example 3, one end of maleic anhydride is connected with a rigid polymer chain, and the rigid polymer phase and the PBAT phase are tightly connected together through entanglement of the molecular chain, so that the interfacial bonding force of the two phases is remarkably improved, and the foaming appearance and the mechanical property are remarkably improved.

Examples 6 and 7, compared to example 2, with the introduction of PDLA, strong interaction (hydrogen bonding) between the L-type lactic acid unit and the D-type lactic acid unit occurs to form a Stereocomplex Crystal (SC). SC serves both as a physical cross-linking point and heterogeneous nucleation, resulting in a further reduction of the cells of the modified PBAT foamed sheet, from 5% to 10% with an increase in PDLA content, compared to 23 μm of example 2 to 14 μm, 10 μm, respectively. The strong interaction of the SC and the function of the physical crosslinking point of the SC obviously improve the tensile strength of the modified PBAT foaming board. However, when the PDLA content is 10%, the magnification of the modified PBAT foamed material cannot be further increased due to too high melt strength, the cell morphology also deteriorates, and several unfoamed regions appear.

As can be seen by comparing the data of comparative example 3 with that of example 1, calcium carbonate modified by a siloxane coupling agent can be uniformly dispersed in PBAT and a rigid polymer, thereby forming uniform cells, resulting in an increase in tensile strength of the material.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and other variations and modifications may be made without departing from the spirit of the invention as set forth in the claims.