A pbs modified pbat foamed polyester and a method for preparing the same

Abstract

The application discloses a kind of PBS modified PBAT foamed polyester and its preparation method, polyester includes PBS and PBAT, the PBS is high melt index PBS, and the melt index is 10-55 g / 10 min under the condition of 190 DEG C, 2.16kg;The PBAT is low melt index PBAT, and the melt index is 1-8 g / 10 min under the condition of 230 DEG C, 2.16kg, the density of the foamed polyester is less than 0.08 g·cm ‑3 , cell density is greater than 5×10 7 cm ‑3 -10 , and the foaming ratio is greater than 15;Its preparation method includes the following steps: raw material is mixed, and modified PBAT granules are obtained by melt granulation, then the granules are foamed to obtain;High melt index PBS is introduced into low melt index PBAT, which improves the strength and modulus of PBAT polyester, improves the cell wall strength, reduces the shrinkage and deformation of the material, and improves the foaming ratio of PBAT.

Description

Technical Field

[0001] This invention relates to a polyester and its preparation method, and particularly to a PBS-modified PBAT foamed polyester and its preparation method. Background Technology

[0002] PBAT, a novel aliphatic-aromatic biodegradable copolyester, combines the excellent mechanical properties of aromatic polyesters with the superior biodegradability of aliphatic polyesters, making it a leader in the field of biodegradable materials. PBAT exhibits excellent toughness and good elasticity. When foamed, PBAT can be used to prepare foamed materials for applications such as cushioning foams, foamed food containers, and packaging supplies, showing broad application prospects.

[0003] CN110498939A discloses a method for long-chain branching modification of biodegradable polyester using radiation technology, which can prepare long-chain branched biodegradable polyester compositions with no initiator residue, low gel content, and improved melt strength. However, radiation technology is costly and inefficient, with a foaming ratio of only 5-10 times. CN109721714A discloses a method for preparing high melt strength foamed polyester through esterification, branching, and solid-state polycondensation, which can prepare materials with large molecular weight, wide molecular weight distribution, and high melt strength. However, it involves complex polymerization equipment and processes, and the foaming ratio is only 6-15 times.

[0004] After PBAT foaming and depressurization, due to the low glass transition temperature of PBAT (~33℃), the soft segments of the foamed particles still have the ability to move at room temperature. At this time, carbon dioxide diffuses outward while air diffuses inward, causing the volume of the foamed particles to shrink. The higher the swelling temperature, the more severe the deformation and shrinkage, resulting in a low foaming ratio. Summary of the Invention

[0005] Objectives of the invention: The first objective of this invention is to provide a PBS-modified PBAT foamed polyester with improved foaming ratio; the second objective of this invention is to provide a method for preparing the polyester.

[0006] Technical Solution: The modified PBAT foamed polyester of this invention contains PBS and PBAT. The PBS is high melt index PBS, with a melt index of 10–55 g / 10 min at 190°C and 2.16 kg. The PBAT is low melt index PBAT, with a melt index of 1–8 g / 10 min at 230°C and 2.16 kg. The density of the foamed polyester is less than 0.08 g·cm³. -3 Pore ​​density greater than 5×10 7 1 cm -3 The foaming ratio is greater than 15.

[0007] PBAT has a glass transition temperature of approximately 33°C. After depressurization, the chain segments of the foamed particles still retain mobility at room temperature, causing the volume of the foamed particles to shrink. The addition of high melt flow index (HFRI) PBS improves the strength and modulus of the PBAT polyester, increases cell wall strength, significantly reduces material shrinkage and deformation, enhances the dimensional stability of the foam, and increases the foaming ratio of PBAT. However, excessive addition of HFRI PBS affects the melt strength of the copolyester, making the cells prone to cross-cell collapse and failing to improve shrinkage. Insufficient addition of HFRI PBS does not improve strength and modulus.

[0008] Preferably, the mass ratio of PBS to PBAT is 10-40:50-80.

[0009] The method for preparing the modified foamed polyester of the present invention includes the following steps:

[0010] (1) Mix 10-40 parts of PBS, 50-80 parts of PBAT, 10-30 parts of thermoplastic starch, 0.5-3 parts of nucleating agent and 0.1-1 parts of chain extender by weight, and melt granulate to obtain modified PBAT granules;

[0011] (2) The granules from step (1) are foamed to obtain PBS-modified PBAT foamed polyester.

[0012] Preferably, the thermoplastic starch is at least one of thermoplastic potato starch, thermoplastic corn starch, thermoplastic cassava starch, or thermoplastic wheat starch. Thermoplastic starch has a polyhydroxy structure, which can form branched structures with PBAT and PBS, improving melt strength. Furthermore, the addition of thermoplastic starch reduces the degree of crystallinity of PBAT, thereby lowering the melting temperature of the material, broadening the melting peak, and widening the foaming process window. Simultaneously, the reduced degree of crystallinity means fewer crystalline regions, which is beneficial for the wetting and diffusion of supercritical gases, thus facilitating high-ratio foaming.

[0013] Preferably, the chain extender is one or more selected from glycidyl ether, triglycidyl isocyanurate, bis(3,4-epoxycyclohexylmethyl)adipate, and glycidyl ester epoxy polyesters. The chain extender is a reactive difunctional or polyfunctional substance that can react with the terminal carboxyl and hydroxyl groups of the polyester, thereby increasing the relative molecular mass of the polyester several times over.

[0014] Preferably, the nucleating agent is one or more of talc, calcium carbonate, montmorillonite, and silica.

[0015] Preferably, in step (1), the melt granulation temperature is 130–210°C. During the melt granulation process, the terminal hydroxyl and carboxyl groups of PBAT and PBS react with the epoxy groups of the chain extender. The epoxy groups on the epoxy chain extender are opened, generating ether bonds and ester bonds, resulting in a chain extension effect and increasing the relative molecular mass. The PBAT molecular chains that react with the chain extender act as long branches, increasing the branching degree of the extended PBAT. The terminal hydroxyl or carboxyl groups of the branches can further undergo esterification reactions or inter-chain entanglement, increasing the chemical and physical cross-linking degree between molecular chains and improving the melt strength of the extended PBAT.

[0016] Preferably, in step (2), the foaming is supercritical carbon dioxide autoclave foaming, which includes swelling and foaming. The swelling temperature is 90-110°C, the swelling pressure is 7-15 MPa (gauge pressure), and the swelling time is 2-3 hours. Then, the pressure inside the autoclave is quickly released, and after cooling, PBS-modified PBAT foamed polyester is obtained.

[0017] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) By introducing high melt index PBS into low melt index PBAT, the strength and modulus of PBST polyester are improved, the cell wall strength is increased, the shrinkage and deformation of the material are significantly reduced, the dimensional stability of the foam is enhanced, and the foaming ratio of PBAT is increased; (2) This method can realize continuous production of extrusion, granulation and foaming, with high production efficiency. Detailed Implementation

[0018] The technical solution of the present invention will be further described below with reference to the embodiments.

[0019] Example 1

[0020] The PBS-modified PBAT foamed polyester of the present invention comprises the following raw material composition: 40 parts of high melt index PBS, 50 parts of low melt index PBAT, 10 parts of thermoplastic potato starch, 3 parts of nucleating agent talc, and 1 part of chain extender glycidyl ether; the low melt index PBAT resin has a melt index of 8 g / 10 min at 230°C and 2.16 kg; the high melt index PBS resin has a melt index of 10 g / 10 min at 190°C and 2.16 kg.

[0021] Its preparation method includes the following steps:

[0022] (1) High melt index PBS, low melt index PBAT, thermoplastic potato starch, nucleating agent talc powder and chain extender glycidyl ether are mixed and melt-granulated by twin screw at 210℃ to obtain modified PBAT granules;

[0023] (2) Place the granules from step (1) into a high-pressure reactor, introduce high-pressure carbon dioxide fluid into the reactor, raise the temperature to 90°C, adjust the pressure inside the reactor to 15 MPa, and keep it warm and pressurized for 2 hours; then open the high-pressure reactor, quickly release the pressure inside the reactor, and obtain PBS-modified PBAT foamed polyester after cooling.

[0024] Example 2

[0025] The PBS-modified PBAT foamed polyester of the present invention comprises the following raw material composition: 10 parts of high melt index PBS, 70 parts of low melt index PBAT, 20 parts of thermoplastic corn starch, 0.5 parts of nucleating agent calcium carbonate, and 0.1 parts of chain extender triglycidyl isocyanurate; the low melt index PBAT resin has a melt index of 1 g / 10 min at 230°C and 2.16 kg; the high melt index PBS resin has a melt index of 55 g / 10 min at 190°C and 2.16 kg.

[0026] Its preparation method includes the following steps:

[0027] (1) Mix high melt index PBS, low melt index PBAT, thermoplastic corn starch, nucleating agent calcium carbonate and chain extender triglycidyl isocyanurate, and then melt-granulate by twin screw extruder at 130°C to obtain modified PBAT granules.

[0028] (2) Place the granules from step (1) into a high-pressure reactor, introduce high-pressure carbon dioxide fluid into the reactor, raise the temperature to 110°C, adjust the pressure inside the reactor to 7 MPa, and keep it warm and pressurized for 3 hours; then open the high-pressure reactor, quickly release the pressure inside the reactor, and obtain PBS-modified PBAT foamed polyester after cooling.

[0029] Example 3

[0030] The PBS-modified PBAT foamed polyester of the present invention comprises the following raw material composition: 15 parts of high melt index PBS, 55 parts of low melt index PBAT, 30 parts of thermoplastic wheat starch, 2 parts of nucleating agent montmorillonite, and 0.5 parts of chain extender triglycidyl isocyanurate; the low melt index PBAT resin has a melt index of 4 g / 10 min at 230°C and 2.16 kg; the high melt index PBS resin has a melt index of 20 g / 10 min at 190°C and 2.16 kg.

[0031] Its preparation method includes the following steps:

[0032] (1) High melt index PBS, low melt index PBAT, thermoplastic wheat starch, nucleating agent montmorillonite and chain extender triglycidyl isocyanurate are mixed and melt-granulated by twin screw extruder at 150°C to obtain modified PBAT granules.

[0033] (2) Place the granules from step (1) into a high-pressure reactor, introduce high-pressure carbon dioxide fluid into the reactor, raise the temperature to 100°C, adjust the pressure inside the reactor to 12 MPa, and keep it at the pressure for 2.2 hours. Then open the high-pressure reactor and quickly release the pressure inside the reactor. After cooling, PBS-modified PBAT foamed polyester is obtained.

[0034] Example 4

[0035] The PBS-modified PBAT foamed polyester of the present invention comprises the following raw material composition: 10 parts of high melt index PBS, 80 parts of low melt index PBAT, 10 parts of thermoplastic cassava starch, 1 part of nucleating agent silica, and 0.6 parts of chain extender glycidyl ether; the low melt index PBAT resin has a melt index of 6 g / 10 min at 230°C and 2.16 kg; the high melt index PBS resin has a melt index of 15 g / 10 min at 190°C and 2.16 kg.

[0036] Its preparation method includes the following steps:

[0037] (1) Mix high melt index PBS, low melt index PBAT, thermoplastic cassava starch, nucleating agent silica and chain extender glycidyl ether, and then melt-granulate by twin screw extruder at 180°C to obtain modified PBAT granules.

[0038] (2) Place the granules from step (1) into a high-pressure reactor, introduce high-pressure carbon dioxide fluid into the reactor, raise the temperature to 100°C, adjust the pressure inside the reactor to 10 MPa, and keep it at the pressure for 2.5 hours. Then open the high-pressure reactor and quickly release the pressure inside the reactor. After cooling, PBS-modified PBAT foamed polyester is obtained.

[0039] Comparative Example 1

[0040] Based on Example 3, PBS with a high melt index was not added, and other conditions remained unchanged.

[0041] Comparative Example 2

[0042] Based on Example 3, 50 portions of PBS were added, while other conditions remained unchanged.

[0043] Comparative Example 3

[0044] Based on Example 3, the melt index of the added PBS was changed to 5 g / 10 min at 190°C and 2.16 kg, while other conditions remained unchanged.

[0045] Comparative Example 4

[0046] Based on Example 3, the melt index of the added PBS was changed to 80 g / 10 min at 190°C and 2.16 kg, while other conditions remained unchanged.

[0047] Performance Characterization

[0048] The properties of the foamed polyesters prepared in Examples 1 to 1 and Comparative Example 1 were tested using the following methods:

[0049] Expansion ratio test: calculated using the density ratio of the original PBAT particles to the expanded particles;

[0050] Pore ​​density testing: The foamed sample was immersed in liquid nitrogen, cooled, and quenched. The fracture surface was sprayed with gold. The structure of the foam was observed at 200x magnification, and the pore density was calculated. The pore density was analyzed using the computer software Image Tool and calculated using the following formula:

[0051]

[0052] In the formula, Nc is the cell density, cells / cm³. 3 ;n b A represents the number of bubbles in the statistical area, in units; A represents the selected statistical area in the scanning electron microscope image, in cm². 2 ;ρ f The density of the foamed sample is in g / cm³. 3 ρ is the density of the unfoamed sample, in g / cm³. 3 ;

[0053] Test method for compressive strength: Compressive performance is determined according to GB / T 8813—2008;

[0054] Bubble shrinkage rate: V=(H0-H 24 ) / H0

[0055] In the formula, H0 is the initial foaming ratio, H 24 The foaming ratio after 24 hours.

[0056] The test results are shown in Table 1.

[0057] Table 1. Polyester performance test results

[0058]

[0059] As can be seen from Table 1, in Examples 1-4, by adding high melt index PBS, the cell density increased, the foaming ratio increased significantly, the cell shrinkage after 24 hours decreased, and the compressive strength of the foamed polyesters prepared in Examples 1-4 was good.

[0060] Comparative Example 1, without the addition of high melt index PBS as in Example 3, showed a significant decrease in cell density, a reduction in foaming ratio, and substantial cell shrinkage over 24 hours.

[0061] Comparative Example 2, based on Example 3, added an excessive amount of high melt index PBS, which significantly reduced the cell density, foaming ratio, cell shrinkage after 24 hours, and compressive strength.

[0062] In Comparative Example 3, the addition of PBS with a lower melt index increased melt strength, resulting in smaller and denser pores, which in turn reduced the foaming ratio. The stronger the inhibitory effect on bubble growth, the more effective the foaming ratio became. Although the pore density and number of bubbles increased, the pores remained small and dense, failing to fully expand, and the foaming ratio actually decreased. Furthermore, significant pore shrinkage occurred after 24 hours.

[0063] In Comparative Example 4, the addition of PBS with a higher melt index reduced the strength, causing cell closure and collapse, resulting in a decrease in foaming ratio.

Claims

1. A PBS-modified PBAT foamed polyester, characterized in that, The polyester comprises, by weight, 10-40 parts PBS, 50-80 parts PBAT, 10-30 parts thermoplastic starch, 0.5-3 parts nucleating agent, and 0.1-1 parts chain extender. The PBS is high melt index PBS, with a melt index of 10-55 g / 10 min at 190°C and 2.16 kg. The PBAT is low melt index PBAT, with a melt index of 1-8 g / 10 min at 230°C and 2.16 kg. The density of the foamed polyester is less than 0.08 g·cm³. -3 Pore ​​density greater than 5×10 7 1 cm -3 The foaming ratio is greater than 15.

2. A method for preparing foamed polyester according to claim 1, characterized in that, Includes the following steps: (1) Mix 10-40 parts of PBS, 50-80 parts of PBAT, 10-30 parts of thermoplastic starch, 0.5-3 parts of nucleating agent and 0.1-1 parts of chain extender by weight, and melt granulate to obtain modified PBAT granules; (2) The granules from step (1) are foamed to obtain PBS-modified PBAT foamed polyester.

3. The method for preparing foamed polyester according to claim 2, characterized in that, The thermoplastic starch is one or more of thermoplastic potato starch, thermoplastic corn starch, thermoplastic cassava starch, and thermoplastic wheat starch.

4. The method for preparing foamed polyester according to claim 2, characterized in that, The chain extender is one or more of glycidyl ether, triglycidyl isocyanurate, bis(3,4-epoxycyclohexylmethyl) adipate, and glycidyl ester epoxy polyester.

5. The method for preparing foamed polyester according to claim 2, characterized in that, The nucleating agent is one or more of talc, calcium carbonate, montmorillonite, and silica.

6. The method for preparing foamed polyester according to claim 2, characterized in that, In step (1), the granulation temperature is 130~210 ℃.

7. The method for preparing foamed polyester according to claim 2, characterized in that, In step (2), the foaming is supercritical carbon dioxide autoclave foaming.

8. The method for preparing foamed polyester according to claim 2, characterized in that, The supercritical carbon dioxide autoclave foaming process includes swelling and foaming. The swelling temperature is 90~110℃, the swelling pressure is 7~15MPa (gauge pressure), and the swelling time is 2~3 hours. Then, the pressure inside the autoclave is rapidly released, and after cooling, PBS-modified PBAT foamed polyester is obtained.

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