Functional aid with plasticizing-chain extension function, preparation method and application of functional aid in PVA-PBAT (polyvinyl alcohol-poly (butylene adipate-co-terephthalate))

Abstract

The invention discloses a functional auxiliary agent with plasticizing-chain extension, a preparation method and application of the functional auxiliary agent in PVA-PBAT, and relates to the technical field of PVA-PBAT modified.The preparation method comprises the steps that firstly, 1, 3-bis (2-isocyano-2-propyl) benzene is dissolved in chloroform; then, triethanolamine and a catalyst cobalt acetylacetonate (III) are added into the solution for a reaction, then precipitation, washing and drying are performed, and a plasticizing-chain extension multifunctional auxiliary agent is obtained; and finally, applying the auxiliary agent to PVA / PBAT, and carrying out melt extrusion to obtain the master batch. The hydroxyl group on the functional auxiliary agent weakens Van der Waals force between PVA molecules, increases the mobility of a molecular chain and reduces the crystallinity of the molecular chain, so that the functions of plasticizing the PVA and extending the chain of PBAT are achieved.

Description

Technical Field

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

[0002] PVA is a water-soluble polymer that is biodegradable, non-toxic, harmless, and has good film-forming properties, barrier properties, biocompatibility, and mechanical properties. However, the polyhydroxy structure of PVA easily forms hydrogen bonds within and between molecules, making the melting point of PVA very close to its decomposition temperature, making it difficult to thermoplastically process PVA. The thermoplastic processing window of PVA is obtained and its thermoplastic processing is achieved mainly through grafting modification, copolymerization modification, control of PVA polymerization degree and alcoholysis degree, blending modification, plasticization modification, etc.

[0003] PBAT is a fully biodegradable material, which contains flexible fatty chains and rigid aromatic segments in its structure, which makes it have some excellent properties of polybutylene adipate (PBA) and polybutylene terephthalate (PBT). However, PBAT's performance in mechanical properties, thermal stability and durability is poor, and still needs to be improved to meet the needs of a wider range of applications. At present, the performance of PBAT and its blended materials is improved through chain extension modification, blending modification, filler modification and in-situ polymerization modification.

[0004] In order to improve the thermoplasticity of PVA and improve the mechanical properties of PVA and PBAT blended composite materials, the current method is to add plasticizers. For example, the use of plasticizers such as water, glycerol, and ethylene glycol to plasticize PVA can reduce the melting point of PVA and improve the thermoplastic processing properties of PVA; however, plasticizers with single functions have disadvantages such as unsatisfactory plasticizing effect and easy precipitation of plasticizer molecules from the PVA matrix. For another example, thermoplastic PVA is prepared first, and then the blended composite material of thermoplastic PVA and PBAT is prepared, and the effect of PBAT dosage on the thermal properties, thermoplastic processing properties, microstructure and mechanical properties of PVA / PBAT composite materials is studied. However, the synergistic effect of the physical blending and extrusion of PVA and PBAT is not good. PBAT and thermoplastic PVA are phase separated 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 technology, the present invention proposes a functional additive with plasticizing and chain extending properties, a preparation method and its application in PVA-PBAT. The hydroxyl group on the functional additive weakens the van der Waals force between PVA molecules, increases the mobility of the molecular chain, and reduces the crystallinity of the molecular chain, thereby plasticizing PVA and chain extending PBAT.

[0006] The invention provides a method for preparing a functional additive with plasticizing and chain extending properties, and the method comprises the following steps: 1,3-bis(2-isocyano-2-propyl)benzene and triethanolamine are reacted under the action of a catalyst, cobalt (III) acetylacetonate, to prepare the functional additive with plasticizing and chain extending properties.

[0007] Preferably, 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.

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

[0009] The functional auxiliary agent with plasticizing and chain extension provided by the present invention is prepared by the above method.

[0010] The present invention proposes the use of the above-mentioned functional additive with plasticizing and chain extension in PVA-PBAT composite materials.

[0011] The present invention provides a method for preparing a PVA-PBAT composite material, and the method steps are as follows: polyvinyl alcohol, polybutylene terephthalate-adipate and the above-mentioned functional additives are mixed at high speed and then melt-extruded to obtain the PVA-PBAT composite material.

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

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

[0014] Beneficial technical effects of the present invention: In the present invention, triethanolamine and 1,3-bis(2-isocyano-2-propyl)benzene undergo addition reaction under the action of a catalyst to generate a multifunctional additive with plasticizing and chain extension. The additive has unreacted isocyanate and hydroxyl groups. During the melt extrusion process, the isocyanate groups on the additive and the hydroxyl groups on the PVA undergo 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 force between PVA molecules, increase the mobility of the molecular chain, and reduce the crystallinity of the molecular chain, thereby playing a role in plasticizing the PVA.

[0015] In the melt extrusion process of the present invention, the isocyanate group on the auxiliary agent chemically reacts with the terminal carboxyl group of PBAT to extend the chain of PBAT; at the same time, the amide bond generated by the interaction between the terminal carboxyl group and the isocyanate group generates a physical hydrogen bond with the hydroxyl group of PVA. Under the combined action of the chemical reaction and the physical hydrogen bond, the mechanical properties of the PVA-PBAT blending system are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 FTIR comparison chart of TMXDI, TEA and auxiliary agent TCA-1 proposed in the present invention; Figure 2 This is a schematic diagram of the synthesis mechanism of the auxiliary agent TCA proposed in the present invention; Figure 3 This is a schematic diagram of the mechanism of action of the auxiliary agent TCA to extend the PBAT chain proposed in the present invention; Figure 4 Schematic diagram of the mechanism of action of the auxiliary agent TCA proposed in the present invention in plasticizing PVA. DETAILED DESCRIPTION

[0017] The present invention will be further explained below in conjunction with specific embodiments.

[0018] Example 1 First, 3 g of 1,3-bis(2-isocyano-2-propyl)benzene (TMXDI) was weighed and added to 20 mL of chloroform, and the temperature was raised to 50°C until it was completely dissolved; then, 8 mL of triethanolamine (TEA) and 0.02 g of catalyst cobalt (III) acetylacetonate (Co(acac)3) were added to the above solution and reacted for 4 hours to obtain a product solution.

[0019] The resulting solution was poured into a beaker containing 110 mL of methanol and stirred continuously with a glass rod to precipitate the product; then, the suspension was filtered to obtain a pre-product. The pre-product was placed in an oven at 80°C and dried for 4 hours to obtain a functional additive with plasticization and chain extension, which was recorded as TCA-1.

[0020] 1 kg of polyvinyl alcohol (PVA), 0.2 kg of polybutylene terephthalate-adipate (PBAT) and 10 g of TCA-1 were weighed and mixed at high speed to obtain a mixture; the mixture was melt-extruded, the screw speed was 200 rpm, the feeding rate was 5 Hz, and the extrusion temperature zones were set to 165°C, 170°C, 170°C, 175°C, 180°C, 185°C, 190°C, 190°C, 190°C, 185°C, and 180°C to obtain a composite material, which was recorded as PVA-PBAT-1.

[0021] Example 2 First, 3 g of TMXDI was weighed and added to 20 mL of chloroform, and the temperature was raised to 50°C until it was completely dissolved; then, 15 mL of TEA and 0.02 g of catalyst Co(acac)3 were added to the above solution and reacted for 4 hours to obtain a product solution.

[0022] The resulting solution was poured into a beaker containing 110 mL of methanol and stirred continuously with a glass rod to precipitate the product; then, the suspension was filtered to obtain a pre-product. The pre-product was placed in an oven at 80°C and dried for 4 hours to obtain a functional additive with plasticization and chain extension, which was recorded as TCA-2.

[0023] 1 kg of PVA, 0.2 kg of PBAT and 10 g of TCA-2 were weighed and mixed at high speed to obtain a mixture; the mixture was melt-extruded, the screw speed was 200 rpm, the feeding rate was 5 Hz, and the extrusion temperature zones were set to 165°C, 170°C, 170°C, 175°C, 180°C, 185°C, 190°C, 190°C, 190°C, 185°C, and 180°C to obtain a composite material, recorded as PVA-PBAT-2.

[0024] Example 3 1 kg of PVA, 0.2 kg of PBAT and 15 g of TCA-1 were weighed and mixed at high speed to obtain a mixture; the mixture was melt-extruded, the screw speed was 200 rpm, the feeding rate was 5 Hz, and the extrusion temperature zones were set to 165°C, 170°C, 170°C, 175°C, 180°C, 185°C, 190°C, 190°C, 190°C, 185°C, and 180°C to obtain a composite material, recorded as PVA-PBAT-3.

[0025] Comparative Example 1 1 kg of PVA and 0.2 kg of PBAT were weighed and mixed at high speed to obtain a mixture; the mixture was melt-extruded, the screw speed was 200 rpm, the feeding rate was 5 Hz, and the extrusion temperature zones were set to 165°C, 170°C, 170°C, 175°C, 180°C, 185°C, 190°C, 190°C, 190°C, 185°C, and 180°C to obtain a composite material, recorded as PVA-PBAT-4.

[0026] The present invention performs infrared testing on TMXDI, TEA and auxiliary agent TCA-1, and the results are as follows: Figure 1 As shown in the figure, TMXDI has a peak at 2934 and 2874 cm -1 The stretching vibration absorption peaks of -CH3 and -CH2 are at 2240cm -1 The -NCO stretching vibration absorption peaks are at 1603 and 1587 cm -1 The peak at 1172cm is the skeleton stretching vibration peak of the benzene ring; -1The stretching vibration absorption peak of CCC is at 1080cm -1 The stretching vibration peaks of COC; 779 and 708 cm -1 The peaks of CH stretching vibration of benzene ring meta-substituted are at 2947, 2875 and 2813 cm -1 The peak at 1500-1200 cm is caused by the vibration of carbon-hydrogen bonds. -1 The four peaks between 1152 and 1029 cm are caused by the vibration of hydroxyl groups. -1 The double peak at 907 cm-1 is caused by the vibration of carbon-oxygen bonds, while the peaks at 880 cm-1 and 907 cm-2 are caused by the vibration of carbon-oxygen bonds. -1 The peak at 1700 cm is caused by carbon-ammonia vibration. -1 The CO stretching vibration absorption peak of carbamate is at 1530cm -1 A new absorption peak appeared, which was attributed to the characteristic absorption peak of -NH- in carbamate, indicating that the isocyanate and hydroxyl groups had fully participated in the reaction, and the multifunctional additive TCA-1 with plasticizing and chain extension was successfully synthesized.

[0027] Figure 2 This is a schematic diagram of the synthesis mechanism of the auxiliary agent TCA proposed in the present invention. The isocyanate group on TMXDI and the hydroxyl group on TEA undergo addition polymerization under the action of the catalyst cobalt (III) acetylacetonate. First, cobalt (III) acetylacetonate complexes with the hydroxyl hydrogen on TEA to activate the hydroxyl oxygen, enhance its nucleophilicity, and generate a catalytic intermediate; then, the highly unsaturated group - N=C=O in the isocyanate molecule of TMXDI undergoes addition polymerization with the intermediate containing active hydrogen to generate the auxiliary agent TCA.

[0028] Figure 3 This is a schematic diagram of the mechanism of action of the auxiliary agent TCA to extend the chain of PBAT proposed in the present invention. Figure 4This is a schematic diagram of the mechanism of action of the additive TCA proposed in the present invention to plasticize PVA. As can be seen from the figure, the multifunctional additive TCA with plasticization and chain extension also has highly reactive hydroxyl groups and isocyanate groups. During the melt extrusion granulation process of the additive TCA in the PVA / PBAT system, the isocyanate groups and the hydroxyl groups on the PVA molecular chain undergo cross-linking reactions, which can increase the molecular weight and reduce the number of hydroxyl groups on the PVA molecular chain, thereby enhancing the strength of the PVA; at the same time, physical hydrogen bonds are generated between the hydroxyl groups on the TCA and the hydroxyl groups on the PVA, so that the PVA has thermoplastic processing properties. In addition, the isocyanate on the TCA reacts with the terminal carboxyl group on the PBAT to form an amide bond, thereby playing a chain extension role, and the generated amide bond produces a physical hydrogen bond with the PVA / PBAT system. A physical and chemical reaction occurs between the thermoplastic PVA and the chain extended PBAT, and the tensile strength of the PVA / PBAT composite material also increases accordingly.

[0029] The present invention conducts mechanical property tests on PVA samples, comparative example 1 samples, and examples 1, 2, and 3 samples, and 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 bonding within and between the PVA molecular chains, the melting point of PVA is very close to its decomposition temperature, which makes PVA difficult to be thermoplastic processed, and phase separation occurs when PVA and PBAT are co-extruded. PBAT exists in the composite material as a defect, causing stress concentration, resulting in a decrease in the tensile strength and elongation at break of the material. The mechanical properties of the PVA / PBAT-1 composite material with the addition of the plasticizer-chain extender multifunctional additive TCA-1 are the best, with a maximum tensile strength of 27.03 MPa and a maximum elongation at break of 643%. This is because the additive plasticizes PVA to form a cross-linked structure, which reduces the melting point of the thermoplastic PVA, increases the molecular weight, and increases the tensile strength. At the same time, after chain extension, the polar groups on the PBAT form hydrogen bonds with the hydroxyl groups of the PVA, which serve as physical cross-linking points to increase the intermolecular force of the blending system, thereby increasing the tensile strength of the composite material. Due to the existence of hydrogen bonding, the interface between PBAT and the thermoplastic PVA has a certain compatibility, and PBAT plays a toughening role, which increases the ductility of the composite material, thereby increasing the tensile strength and elongation at break.

[0030] Table 1 Mechanical properties test of samples

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 catalyst cobalt (III) acetylacetonate to prepare a functional auxiliary agent with plasticizing and chain extension.

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 3-5h.

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 are: screw speed of 200-300 rpm, feed rate of 5-7 Hz, and extrusion temperature zones are set to 165°C, 170°C, 170°C, 175°C, 180°C, 185°C, 190°C, 190°C, 185°C, and 180°C.

Images