Functional Auxiliary Agent with Plasticizing-Chain Extending Function, Preparation Method Thereof and Application Thereof in PVA-PBAT

Abstract

The present invention discloses a functional additive with plasticizing - chain - extending functions, a preparation method thereof, and its application in PVA - PBAT, which relates to the technical field of PVA - PBAT modification. First, 1,3 - bis(2 - isocyanato - 2 - propyl)benzene is dissolved in chloroform; then, triethanolamine and a catalyst cobalt(III) acetylacetonate are added to the above - mentioned solution for reaction, and after precipitation, washing, and drying, a plasticizing - chain - extending multifunctional additive is obtained; finally, the above - mentioned additive is applied to PVA / PBAT, and masterbatch is obtained by melt extrusion. The hydroxyl groups on the functional additive of the present invention weaken the van der Waals forces between PVA molecules, increase the mobility of molecular chains, and reduce the crystallinity of molecular chains, thereby playing the role of plasticizing PVA and chain - extending PBAT.

Description

Technical Field

[0001] The present invention relates to the technical field of PVA-PBAT modification, and particularly to a functional additive with plasticizing-chain extending functions, a preparation method thereof, and an application thereof in PVA-PBAT. Background Art

[0002] PVA is a water-soluble polymer, which is biodegradable, non-toxic, harmless, and has good film-forming property, barrier property, biocompatibility, mechanical properties, etc. However, the multi-hydroxyl structure of PVA is prone to form intramolecular and intermolecular hydrogen bond interactions, making the melting point of PVA very close to its decomposition temperature, resulting in difficulty in thermoplastic processing and forming of PVA. To obtain the thermoplastic processing window of PVA and realize its thermoplastic processing, it is mainly through graft modification, copolymerization modification, controlling the degree of polymerization and alcoholysis degree of PVA, blending modification, plasticization modification, etc.

[0003] PBAT is a fully biodegradable material, and its structure contains flexible aliphatic chains and rigid aromatic chain segments, which makes it have some excellent properties of poly(butylene adipate) (PBA) and poly(butylene terephthalate) (PBT). However, PBAT shows poor performance in terms of mechanical properties, thermal stability, and durability, and still needs to be improved to meet wider application requirements. At present, for PBAT materials, chain extension modification, blending modification, filler modification, and in-situ polymerization modification, etc. are used to improve the properties of PBAT and its blend materials.

[0004] In order to improve the thermoplasticity of PVA and the mechanical properties of PVA / PBAT blend composites, the current method is to add plasticizers. For example, using plasticizers such as water, glycerol, and ethylene glycol to plasticize PVA can reduce the melting point of PVA and improve the thermoplastic processing performance of PVA; however, plasticizers with single functions have disadvantages such as unsatisfactory plasticization effect and easy precipitation of plasticizer molecules from the PVA matrix. Another example is to first prepare thermoplastic PVA, and then prepare a blend composite of thermoplastic PVA and PBAT, and study the effects of the amount of PBAT on the thermal properties, thermoplastic processing performance, microstructure, and mechanical properties of PVA / PBAT composites. However, the compounding synergistic effect of physical blending and extrusion of PVA and PBAT is not good, and PBAT and thermoplastic PVA undergo phase separation and exist in PVA in the form of defects, resulting in a decrease in the mechanical properties of the composite material. Summary of the Invention

[0005] Based on the technical problems existing in the background art, the present invention proposes a functional additive with plasticizing-chain extending functions, a preparation method thereof, and an application thereof in PVA-PBAT. The hydroxyl groups on the functional additive weaken the van der Waals forces between PVA molecules, increase the mobility of molecular chains, and reduce the crystallinity of molecular chains, thereby playing the role of plasticizing PVA and chain extending PBAT.

[0006] The preparation method of the functional additive with plasticizing and chain - extending functions proposed by the present invention is as follows: React 1,3 - bis(2 - isocyanato - 2 - propyl)benzene and triethanolamine under the action of the catalyst cobalt(III) acetylacetonate to obtain the functional additive with plasticizing and chain - extending functions.

[0007] Preferably, the molar ratio of 1,3 - bis(2 - isocyanato - 2 - propyl)benzene, triethanolamine and cobalt(III) acetylacetonate is 1:0.2 - 0.5:0.0002 - 0.004.

[0008] Preferably, the reaction temperature is 45 - 55 °C and the reaction time is 3 - 5 h.

[0009] The functional additive with plasticizing and chain - extending functions proposed by the present invention is prepared by the above - mentioned method.

[0010] The application of the above - mentioned functional additive with plasticizing and chain - extending functions proposed by the present invention in PVA - PBAT composites.

[0011] The preparation method of a PVA - PBAT composite material proposed by the present invention is as follows: Mix polyvinyl alcohol, poly(butylene adipate - co - terephthalate) and the above - mentioned functional additive at high speed and then carry out melt extrusion to obtain the PVA - PBAT composite material.

[0012] Preferably, the mass ratio of polyvinyl alcohol, poly(butylene adipate - co - terephthalate) and the functional additive is 5:1:0.025 - 0.075.

[0013] Preferably, the conditions for melt extrusion are: the screw speed is 200 - 300 rpm, the feeding speed is 5 - 7 Hz, and the extrusion temperature zones are set as 165 °C, 170 °C, 170 °C, 175 °C, 180 °C, 185 °C, 190 °C, 190 °C, 190 °C, 185 °C, 180 °C.

[0014] The beneficial technical effects of the present invention:

[0015] In the present invention, triethanolamine and 1,3 - bis(2 - isocyanato - 2 - propyl)benzene undergo an addition reaction under the action of the catalyst to generate a multifunctional additive with plasticizing and chain - extending functions. There are unreacted isocyanate and hydroxyl groups on the additive. During the melt extrusion processing, the isocyanate groups on the additive and the hydroxyl groups on PVA undergo a cross - linking reaction, reducing the number of hydroxyl groups on the PVA molecular chain; at the same time, the hydroxyl groups on the additive weaken the van der Waals forces between PVA molecules, increase the mobility of the molecular chain, and reduce the crystallinity of the molecular chain, thereby playing a role in plasticizing PVA.

[0016] During the melt extrusion process of the present invention, the isocyanate groups on the additive react with the terminal carboxyl groups of PBAT, which plays a role in chain extension of PBAT; at the same time, the amide bonds formed by the interaction between the terminal carboxyl groups and isocyanate groups have physical hydrogen bond interactions with the hydroxyl groups of PVA. Under the combined action of chemical reactions and physical hydrogen bonds, the mechanical properties of the PVA-PBAT blend system are improved. Description of the Drawings

[0017] Figure 1 It is a FTIR comparison chart of TMXDI, TEA and additive TCA-1 proposed by the present invention;

[0018] Figure 2 It is a schematic diagram of the synthesis mechanism of additive TCA proposed by the present invention;

[0019] Figure 3 It is a schematic diagram of the mechanism of action of additive TCA for chain extension of PBAT proposed by the present invention;

[0020] Figure 4 It is a schematic diagram of the mechanism of action of additive TCA for plasticizing PVA proposed by the present invention. Detailed Embodiments

[0021] The present invention will be further explained below in conjunction with specific embodiments.

[0022] Example 1

[0023] First, weigh 3 g of 1,3-bis(2-isocyanato-2-propyl)benzene (TMXDI) and add it to 20 mL of chloroform. Heat it to 50 °C until it is completely dissolved; then, add 8 mL of triethanolamine (TEA) and 0.02 g of catalyst cobalt(III) acetylacetonate (Co(acac) 3 ) to the above solution and react for 4 h to obtain a product solution.

[0024] Pour the product solution into a beaker containing 110 mL of methanol and stir it continuously with a glass rod to precipitate the product; then, filter the suspension to obtain a pre-product. Place the pre-product in an oven at 80 °C and dry it for 4 h to obtain a functional additive with plasticizing-chain extension function, denoted as TCA-1.

[0025] Weigh 1 kg of polyvinyl alcohol (PVA), 0.2 kg of poly(butylene adipate-co-terephthalate) (PBAT) and 10 g of TCA-1, and perform high-speed mixing to obtain a mixture; melt-extrude the mixture, with a screw speed of 200 rpm, a feeding speed of 5 Hz, and the extrusion temperature zones set at 165 °C, 170 °C, 170 °C, 175 °C, 180 °C, 185 °C, 190 °C, 190 °C, 190 °C, 185 °C, 180 °C to obtain a composite material, denoted as PVA-PBAT-1.

[0026] Example 2

[0027] First, weigh 3 g of TMXDI and add it to 20 mL of chloroform. Heat it to 50 °C until it is completely dissolved. Then, add 15 mL of TEA and 0.02 g of the catalyst Co(acac) to the above solution. 3 React for 4 h to obtain a product solution.

[0028] Pour the product solution into a beaker containing 110 mL of methanol, and continuously stir it with a glass rod to precipitate the product. Then, filter the suspension to obtain a pre-product. Place the pre-product in an oven at 80 °C and dry it for 4 h to obtain a plasticizing-chain extending functional additive, denoted as TCA-2.

[0029] Weigh 1 kg of PVA, 0.2 kg of PBAT, and 10 g of TCA-2, and perform high-speed mixing to obtain a mixture. Melt-extrude the mixture with a screw speed of 200 rpm, a feeding speed of 5 Hz, and the extrusion temperature zones set at 165 °C, 170 °C, 170 °C, 175 °C, 180 °C, 185 °C, 190 °C, 190 °C, 190 °C, 185 °C, 180 °C to obtain a composite material, denoted as PVA-PBAT-2.

[0030] Example 3

[0031] Weigh 1 kg of PVA, 0.2 kg of PBAT, and 15 g of TCA-1, and perform high-speed mixing to obtain a mixture. Melt-extrude the mixture with a screw speed of 200 rpm, a feeding speed of 5 Hz, and the extrusion temperature zones set at 165 °C, 170 °C, 170 °C, 175 °C, 180 °C, 185 °C, 190 °C, 190 °C, 190 °C, 185 °C, 180 °C to obtain a composite material, denoted as PVA-PBAT-3.

[0032] Comparative Example 1

[0033] Weigh 1 kg of PVA and 0.2 kg of PBAT, and perform high-speed mixing to obtain a mixture. Melt-extrude the mixture with a screw speed of 200 rpm, a feeding speed of 5 Hz, and the extrusion temperature zones set at 165 °C, 170 °C, 170 °C, 175 °C, 180 °C, 185 °C, 190 °C, 190 °C, 190 °C, 185 °C, 180 °C to obtain a composite material, denoted as PVA-PBAT-4.

[0034] The present invention conducts infrared tests on TMXDI, TEA, and the additive TCA-1, and the results are as Figure 1 shown. As can be seen from the figure, TMXDI is at 2934 and 2874 cm -1 for -CH 3 and -CH2 Stretching vibration absorption peak; 2240 cm -1 The stretching vibration absorption peak of -NCO is at 2240 cm; The stretching vibration peaks of the benzene ring skeleton are at 1603 and 1587 cm -1 The stretching vibration absorption peak of C-C-C is at 1172 cm -1 The stretching vibration absorption peak of C-C-C is at 1080 cm -1 The stretching vibration peak of C-O-C is at 779 and 708 cm -1 The stretching vibration absorption peak of meta-substituted C-H in the benzene ring is at 779 and 708 cm; The peaks of TEA at 2947, 2875, and 2813 cm -1 are caused by carbon-hydrogen bond vibration, and the 4 peaks between 1500 - 1200 cm -1 are caused by hydroxyl vibration, and the doublet at 1152 and 1029 cm -1 is caused by carbon-oxygen bond vibration, while the peaks at 907 and 880 cm -1 are caused by carbon-nitrogen vibration. In addition to the infrared characteristic absorption peaks of TMXDI and TEA, the plasticizer-chain extender multifunctional additive TCA-1 has a carbonyl stretching vibration absorption peak of carbamate at 1700 cm -1 The stretching vibration absorption peak of CO of carbamate is at 1700 cm; Meanwhile, a new absorption peak appears at 1530 cm -1 which is attributed to the characteristic absorption peak of -NH- in carbamate, indicating that the isocyanate group and the hydroxyl group have fully participated in the reaction, and the plasticizer-chain extender multifunctional additive TCA-1 has been successfully synthesized.

[0035] Figure 2 is the schematic diagram of the synthesis mechanism of the additive TCA proposed by the present invention. The isocyanate group on TMXDI and the hydroxyl group on TEA undergo an addition polymerization reaction under the action of the catalyst cobalt(III) acetylacetonate. First, cobalt(III) acetylacetonate complexes with the hydroxyl hydrogen on TEA, thereby activating the hydroxyl oxygen and enhancing its nucleophilicity to generate a catalytic intermediate; then, the highly unsaturated group -N=C=O in the isocyanate molecule of TMXDI undergoes an addition polymerization reaction with the intermediate containing active hydrogen to generate the additive TCA.

[0036] Figure 3 is the schematic diagram of the mechanism of the additive TCA proposed by the present invention for chain-extending PBAT. Figure 4Schematic diagram of the action mechanism of plasticizer TCA plasticizing PVA proposed by the present invention. As can be seen from the figure, the plasticizing-chain extending multifunctional additive TCA also has hydroxyl groups and isocyanate groups with high reactivity. During the process of melt extrusion granulation of the PVA / PBAT system, the isocyanate groups react with the hydroxyl groups on the PVA molecular chain to form crosslinking reactions, which can increase the molecular weight and reduce the number of hydroxyl groups on the PVA molecular chain, thereby enhancing the strength of PVA. At the same time, physical hydrogen bond interactions occur between the hydroxyl groups on TCA and the hydroxyl groups on PVA, enabling PVA to have thermoplastic processing properties. In addition, the isocyanate on TCA reacts with the terminal carboxyl groups on PBAT to form amide bonds, thus playing a chain extension role, and the generated amide bonds have physical hydrogen bond interactions with the PVA / PBAT system. Physical and chemical interactions occur between the thermoplastic PVA and the chain-extended PBAT, and the tensile strength of the PVA / PBAT composite material also increases accordingly.

[0037] The present invention conducts mechanical property tests on PVA samples, Comparative Example 1 samples, and Examples 1, 2, and 3 samples. The results are shown in Table 1. As can be seen from the table, after adding PBAT, the tensile strength and elongation at break of the PVA / PBAT-4 composite material decrease. Due to the strong hydrogen bond interactions within and between the PVA molecular chains, the melting point of PVA is very close to its decomposition temperature, resulting in difficulty in thermoplastic processing of PVA, and phase separation occurs during the co-extrusion of PVA and PBAT. PBAT exists as defects in the composite material, causing stress concentration and leading to a decrease in both the tensile strength and elongation at break of the material. The mechanical properties of the PVA / PBAT-1 composite material added with the plasticizing-chain extending multifunctional additive TCA-1 are the best. Its maximum tensile strength can reach 27.03 Mpa, and the maximum elongation at break can reach 643%. This is because the additive plasticizes PVA to form a crosslinked structure, reducing the melting point of thermoplastic PVA, increasing the molecular weight, and raising the tensile strength. At the same time, the polar groups on PBAT after chain extension form hydrogen bond interactions with the hydroxyl groups of PVA, increasing the intermolecular forces of the blend system as physical crosslinking points, resulting in an increase in the tensile strength of the composite material. Due to the existence of hydrogen bond interactions, there is a certain compatibility at the interface between PBAT and thermoplastic PVA, and PBAT plays a toughening role, increasing the ductility of the composite material, thereby increasing the tensile strength and elongation at break.

[0038] Table 1 Mechanical property tests of samples

[0039]

Claims

1. A method for preparing a functional additive having plasticizing and chain extension, characterized in that: The method comprises the following steps: 1,3-bis(2-isocyano-2-propyl)benzene and triethanolamine are reacted under the action of cobalt (III) acetylacetonate as a catalyst to prepare a functional additive with plasticizing and chain extension; The structural formula of the functional additive is as follows: 。 2. The method for preparing a functional additive having plasticizing and chain extension according to claim 1, characterized in that: The molar ratio of 1,3-bis(2-isocyano-2-propyl)benzene, triethanolamine and cobalt(III) acetylacetonate is 1:0.2-0.5:0.0002-0.

004.

3. The method for preparing a functional additive having plasticizing and chain extension according to claim 1, characterized in that: The reaction temperature is 45-55°C and the reaction time is 3-5 h.

4. A functional additive with plasticizing and chain extension, characterized in that: The method is prepared according to any one of claims 1 to 3.

5. Use of the functional additive with plasticizing and chain extending properties as claimed in claim 4 in a PVA-PBAT composite material.

6. A method for preparing a PVA-PBAT composite material, characterized in that: The method comprises the following steps: polyvinyl alcohol, polybutylene terephthalate-adipate and the functional additive as claimed in claim 4 are mixed at high speed and then melt-extruded to obtain a PVA-PBAT composite material.

7. The method for preparing the PVA-PBAT composite material according to claim 6, characterized in that: The mass ratio of polyvinyl alcohol, polybutylene terephthalate-adipate and functional additive is 5:1:0.025-0.

075.

8. The method for preparing the PVA-PBAT composite material according to claim 6, characterized in that: The conditions for melt extrusion were: screw speed of 200-300 rpm, feed rate of 5-7 Hz, and extrusion temperature zones of 165 °C, 170 °C, 170 °C, 175 °C, 180 °C, 185 °C, 190 °C, 190 °C, 190 °C, 185 °C, and 180 °C.

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