Modified montmorillonite with nucleation and compatibilization functions as well as preparation and application of modified montmorillonite

Abstract

The invention discloses modified montmorillonite with nucleation and compatibilization functions, preparation and application, and relates to the technical field of composites.The preparation method comprises the following steps that S1, isocyanate propyl triethoxy silane is dissolved in an ethanol water solution, then the solution and montmorillonite are mixed to be uniform, and alkylated montmorillonite is obtained; s2, dissolving cyanuric chloride in methylbenzene, and then adding allinol for reaction; s3, the alkylated montmorillonite is dissolved in acetone, then a product obtained in the S2 and a catalyst are added for a reaction, precipitation, washing and drying are conducted after the reaction, and the modified montmorillonite with the nucleation and compatibilization functions is obtained. The obtained modified montmorillonite plays a role in heterogeneous nucleation, and can improve the crystallization property of the PBAT composite material; meanwhile, the hydrophobic property is high, the reaction activity is high, and compatibilization with PBAT (poly (butylene adipate-co-terephthalate)) can be realized; in addition, as a two-dimensional layered material, montmorillonite can improve the barrier property and mechanical property of the PBAT composite material.

Description

Technical Field

[0001] The present invention relates to the technical field of composite materials, and particularly to a modified montmorillonite with nucleation and compatibilization functions, its preparation and application. Background Art

[0002] Poly(butylene adipate-co-terephthalate) (PBAT) is an aliphatic-aromatic biodegradable copolyester with good ductility, heat resistance and impact resistance. However, PBAT has poor water vapor and oxygen barrier properties, and it is difficult to meet the requirements of moisture-proof, moisture-retention and food preservation when used in fields such as food wrap. Therefore, in the large-scale application of PBAT, how to improve its gas barrier performance is a key problem that needs to be solved urgently. At present, filling modification of PBAT is a common method to improve the barrier performance, and the modification method is simple and economical.

[0003] Montmorillonite (MMT) is a hydrated aluminosilicate layered clay, which is one of the most commonly used layered silicates and is used to enhance the mechanical and barrier properties of some polymers. Compared with other inorganic nanoparticles, MMT has many good properties, such as its large aspect ratio, high surface area, good mechanical strength and high delamination ability. In addition, they are abundant in nature, have low cost, and have the potential to improve the mechanical strength of biopolymers. Due to these characteristics, MMT is widely used in the packaging field to enhance the performance of biopolymers and is used as a food packaging material. However, montmorillonite has poor hydrophobicity and is prone to agglomeration and the formation of stress concentration parts during the polymer modification process, resulting in its inability to exert the maximum advantage of the structure. Therefore, effective hydrophobic modification treatment of montmorillonite is an effective method to solve this problem.

[0004] For example, using a cationic surfactant to intercalate montmorillonite can expand the montmorillonite layer spacing, reduce the number of surface hydroxyl groups at the same time, and improve the hydrophobicity and dispersibility of montmorillonite. Using a silane coupling agent for organic coating to reduce the number of surface hydroxyl groups can improve the compatibility between the polymer and montmorillonite and reduce the agglomeration phenomenon in the polymer matrix. At present, the above-mentioned montmorillonite modification methods still have problems such as poor modification effect, poor dispersibility, easy agglomeration and poor thermal stability when blended with polymers, and cannot effectively improve the crystallization performance, barrier performance and 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 modified montmorillonite with nucleation and compatibilization functions, its preparation and application, solves the problems of poor hydrophobicity and poor dispersibility of montmorillonite, and uses it for PBAT modification, thereby improving the barrier performance, mechanical properties and crystallization performance of the PBAT composite material.

[0006] A preparation method of modified montmorillonite with both nucleating and compatibilizing functions proposed by the present invention is characterized in that the method steps are as follows:

[0007] S1: Dissolve isocyanatopropyltriethoxysilane in an ethanol aqueous solution, and then mix it evenly with montmorillonite to obtain alkylated montmorillonite;

[0008] S2: Dissolve cyanuric chloride in toluene, and then add allyl alcohol for reaction;

[0009] S3: Dissolve the alkylated montmorillonite in acetone, then add the product of S2 and a catalyst for reaction. After the reaction, precipitate, wash, and dry to obtain modified montmorillonite with both nucleating and compatibilizing functions.

[0010] Preferably, the mass ratio of isocyanatopropyltriethoxysilane to montmorillonite in S1 is (2 - 5):100.

[0011] Preferably, the mixing temperature in S1 is 60 - 80 °C.

[0012] Preferably, the mass ratio of cyanuric chloride to allyl alcohol in S2 is (2 - 3):(1 - 1.5).

[0013] Preferably, the reaction temperature in S2 is 100 - 120 °C, and the reaction time is 1 - 2 h.

[0014] Preferably, the catalyst in S3 is triethylamine; the mass ratio of the alkylated montmorillonite, the product of S2, and the catalyst is (50 - 60):(1.5 - 1.8):(0.05 - 0.1).

[0015] Preferably, the reaction temperature in S3 is 120 - 140 °C, and the reaction time is 2 - 3 h.

[0016] A modified montmorillonite with both nucleating and compatibilizing functions proposed by the present invention is prepared by the above preparation method.

[0017] A preparation method of a PBAT composite material proposed by the present invention, the method steps are as follows: Mix poly(butylene adipate-co-terephthalate) and the above-mentioned modified montmorillonite and then melt-extrude to obtain the composite material.

[0018] Preferably, the mass ratio of the modified montmorillonite to poly(butylene adipate-co-terephthalate) is (10 - 20):100; the melt-extrusion conditions are: the screw speed is 200 - 300 rpm, the feeding speed is 6 - 8 Hz, and the extrusion temperature zones are set at 140, 140, 145, 160, 150, 155, 140, 145 °C.

[0019] The beneficial technical effects of the present invention:

[0020] (1) The present invention proposes a chlorine substitution reaction based on cyanuric chloride and aliphenyl alcohol, and the reaction product is used for grafting modification of montmorillonite. The product has the characteristics of multiple reaction sites, high reaction activity and stable chemical properties, so that the modified montmorillonite has excellent hydrophobicity and thermal stability.

[0021] (2) The modified montmorillonite designed in the present invention has active functional groups such as isocyanate, double bonds and chlorine atoms on its surface, and can generate multiple hydrogen bonds with PBAT, thereby achieving capacity expansion with PBAT.

[0022] (3) The modified montmorillonite proposed in the present invention, as an inorganic layered material, can play a role in heterogeneous nucleation and improve the crystallization performance and barrier performance of the PBAT composite material. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Infrared spectra of the MMT, S-MMT-1, CA-1 and GS-MMT-1 samples proposed in the present invention;

[0024] Figure 2 The crystallization / melting curve comparison diagram of the PBAT and PBAT / GS-MMT-2 samples proposed in the present invention; wherein (a) is the crystallization process of cooling, and (b) is the melting process of heating;

[0025] Figure 3 Schematic diagram of the preparation mechanism of the GS-MMT sample proposed in the present invention. DETAILED DESCRIPTION

[0026] The present invention will be further explained below in conjunction with specific embodiments.

[0027] Example 1

[0028] 5 g of isocyanatepropyltriethoxysilane (IPTS) was weighed and prepared into a solution with water and ethanol as a mixed solvent. The mass ratio of the components in the solution was IPTS: water: ethanol = 10: 8: 72. The solution was evenly sprayed on the surface of 0.2 kg of montmorillonite (MMT), fully mixed in a high-speed mixer at 60 ° C and 200 rpm for 5 min, and vacuum dried at 85 ° C for 8 h to obtain alkylated montmorillonite, recorded as S-MMT-1.

[0029] Under room temperature conditions, 10 g of cyanuric chloride (CC) was dissolved in 100 g of toluene solution and stirred at 150 rpm / min for 0.2 h. After complete dissolution, 5 g of aliphenyl alcohol was slowly added into a three-necked flask and reacted at 120 °C for 1.5 h. After the reaction was completed, the product was obtained by rotary evaporation and recorded as CA-1.

[0030] Weigh 200 g of S-MMT-1 and dissolve it in acetone. First, ultrasonically treat it for 0.5 h at 60 °C under nitrogen protection, and then ultrasonically treat it for 0.5 h at 100 °C under nitrogen protection to make it uniformly dispersed in acetone, obtaining a montmorillonite suspension; weigh 6.0 g of C-A-1 and add it to the montmorillonite suspension. Weigh 0.2 g of triethylamine as a reaction catalyst and carry out the reaction at 140 °C for 2.5 h. After the reaction is complete, obtain the initial product by rotary evaporation, and obtain the grafted-alkylated modified montmorillonite through washing and drying, denoted as G-S-MMT-1.

[0031] Weigh 0.2 kg of G-S-MMT-1 and 1 kg of PBAT, mix them thoroughly to obtain a mixture; put the mixture into a twin-screw extruder and melt-extrude it to obtain a composite material, denoted as PBAT / G-S-MMT-1. The screw speed is 200 rpm, the feeding speed is 6 Hz, and the extrusion temperature zones of the twin-screw extruder are set at 140, 140, 145, 150, 160, 155, 150, 145 °C.

[0032] Example 2

[0033] Weigh 200 g of S-MMT-1 and dissolve it in acetone. First, ultrasonically treat it for 0.5 h at 60 °C under nitrogen protection, and then ultrasonically treat it for 0.5 h at 100 °C under nitrogen protection to make it uniformly dispersed; weigh 6.5 g of C-A-1 and add it to the montmorillonite suspension. Weigh 0.2 g of triethylamine as a reaction catalyst and carry out the reaction at 140 °C for 2.5 h. After the reaction is complete, obtain the initial product by rotary evaporation, and obtain the grafted-alkylated modified montmorillonite through washing and drying, denoted as G-S-MMT-2.

[0034] Weigh 0.2 kg of G-S-MMT-2 and 1 kg of PBAT, mix them thoroughly to obtain a mixture; put the mixture into a twin-screw extruder and melt-extrude it to obtain a composite material, denoted as PBAT / G-S-MMT-2. The screw speed is 200 rpm, the feeding speed is 6 Hz, and the extrusion temperature zones of the twin-screw extruder are set at 140, 140, 145, 150, 160, 155, 150, 145 °C.

[0035] Example 3

[0036] Weigh 200 g of S-MMT-1 and dissolve it in acetone. First, ultrasonically treat it at 60 °C for 0.5 h under nitrogen protection, and then ultrasonically treat it at 100 °C for 0.5 h under nitrogen protection to make it uniformly dispersed in acetone. Weigh 7.0 g of C-A-1 and add it to the montmorillonite suspension. Weigh 0.2 g of triethylamine and use it as a reaction catalyst, and carry out the reaction at 140 °C for 2.5 h. After the reaction is complete, obtain the initial product by rotary evaporation, and obtain the grafted-alkylated modified montmorillonite by washing and drying, denoted as G-S-MMT-3.

[0037] Weigh 0.2 kg of G-S-MMT-3 and 1 kg of PBAT, mix them thoroughly to obtain a mixture. Put the mixture into a twin-screw extruder and melt-extrude it to obtain a composite material, denoted as PBAT / G-S-MMT-3. The screw speed is 200 rpm, the feeding speed is 6 Hz, and the extrusion temperature zones of the twin-screw extruder are set at 140, 140, 145, 150, 160, 155, 150, 145 °C.

[0038] Comparative Example 1

[0039] Weigh 200 g of MMT and dissolve it in acetone. First, ultrasonically treat it at 60 °C for 0.5 h under nitrogen protection, and then ultrasonically treat it at 100 °C for 0.5 h under nitrogen protection to make it uniformly dispersed in acetone. Weigh 6.5 g of C-A-1 and add it to the montmorillonite suspension. Weigh 0.2 g of triethylamine and use it as a reaction catalyst, and carry out the reaction at 140 °C for 2.5 h. After the reaction is complete, obtain the initial product by rotary evaporation operation, and obtain the grafted modified montmorillonite by washing and drying, denoted as G -MMT-1.

[0040] Weigh 0.2 kg of G- MMT-1 and 1 kg of PBAT, mix them thoroughly to obtain a mixture. Put the mixture into a twin-screw extruder and melt-extrude it to obtain a composite material, denoted as PBAT / G- MMT-1. The screw speed is 200 rpm, the feeding speed is 6 Hz, and the extrusion temperature zones of the twin-screw extruder are set at 140, 140, 145, 150, 160, 155, 150, 145 °C.

[0041] Comparative Example 2

[0042] Weigh 0.2 kg of S-MMT-1 and 1 kg of PBAT, mix them thoroughly to obtain a mixture. Put the mixture into a twin-screw extruder and melt-extrude it to obtain a composite material, denoted as PBAT / S-MMT-1. The screw speed is 200 rpm, the feeding speed is 6 Hz, and the extrusion temperature zones of the twin-screw extruder are set at 140, 140, 145, 150, 160, 155, 150, 145 °C.

[0043] The present invention conducted mechanical property tests on the samples prepared in Examples 1-3 and Comparative Examples 1-2, as well as the pure PBAT sample. The results are shown in Table 1. Among them, the standards for tensile strength and elongation at break tests are GB / T 1040.1-2018 "Plastics - Determination of tensile properties".

[0044] Table 1 Mechanical properties of the samples

[0045] As can be seen from Table 1, the sample PBAT / G-S-MMT-2 prepared in Example 2 has the best mechanical properties, with a tensile strength of 33.14 MPa and an elongation at break of 622%. Compared with pure PBAT, the PBAT / G-S-MMT-2 filled with 20% modified montmorillonite shows a certain degree of decrease in both tensile strength and elongation at break. This is because excessive fillers are prone to agglomeration in PBAT, resulting in stress concentration, thus leading to a decrease in tensile strength. In addition, the elongation at break also decreases to a certain extent. This is because the incorporation of a large amount of inorganic fillers makes the PBAT composite material have a certain rigidity, resulting in a decrease in its toughness. Generally speaking, the PBAT / G-S-MMT-2 sample still has good mechanical properties. At the same time, after filling and modification, the composite material has excellent properties and a lower cost. Among them, the mechanical properties of the sample in Example 2 are better than those in Examples 1 and 3. This may be due to the poor modification effect caused by the low grafting rate of modified montmorillonite or the excessive cross-linking with the polymer due to the high grafting rate. However, it can be seen from the two groups of comparative examples that the mechanical properties of the PBAT composite materials obtained from graft-modified montmorillonite and silane-modified montmorillonite are both poor. This is because there are problems such as low grafting rate and poor modification effect in graft-modified and silane-modified montmorillonite, and the compatibility with PBAT is poor, resulting in low mechanical properties. Therefore, the multiple modification method proposed in the present invention has better effects than single silane modification and graft modification. The intermolecular binding force between the modified montmorillonite and PBAT obtained is stronger, the compatibility is better, and the properties of the composite material are more superior.

[0046] The present invention conducted water vapor and oxygen permeability tests on the samples prepared in Examples 1-3 and Comparative Examples 1-2, as well as the pure PBAT sample. The results are shown in Table 2. Among them, the test standard for water vapor transmission rate is GB / T 1037-2021 "Determination of water vapor transmission properties of plastic films"; the test standard for oxygen transmission rate is GB / T 1038.1-2022 "Determination of oxygen transmission properties of plastic films".

[0047] Table 2 Water vapor and oxygen barrier properties of the samples

[0048] As can be seen from Table 2, the water vapor transmission rate of pure PBAT is 148 g / (m 2 ·24 h), and the oxygen transmission rate is 1300 cm 3 / (m 2 ·24 h·0.1 MPa); it can be seen from each example and comparative example that, compared with pure PBAT, both the water vapor transmission rate and the oxygen transmission rate have decreased significantly, which is caused by the flaky structure of montmorillonite. Using montmorillonite as a filler in PBAT can form a multi-layer barrier layer, expand the diffusion path of water vapor and oxygen, and reduce the transmission rate of water vapor and oxygen; it can be seen from the three groups of examples that the montmorillonite after multiple modifications has a good barrier effect, because the montmorillonite after multiple modifications is more uniformly dispersed in the PBAT matrix, making the gas diffusion path longer and more tortuous, which is more beneficial to improving the barrier performance of the PBAT composite material. Among them, the barrier performance of the sample in Example 2 is the best, which indicates that the modified montmorillonite obtained by this method has the best dispersion effect, which is consistent with the above mechanical test results. However, the water vapor transmission rate and oxygen transmission rate of the film samples in Comparative Examples 1 and 2 are both high, which indicates that the modified montmorillonite obtained by single silane modification or graft modification still has problems such as poor hydrophobicity and easy agglomeration, and cannot be uniformly dispersed in PBAT, resulting in poor barrier performance of the PBAT / modified montmorillonite composite film. Therefore, the multiple modified montmorillonite proposed in the present invention has strong hydrophobicity and good dispersibility, and can significantly improve its barrier performance when modifying PBAT.

[0049] The present invention respectively performs infrared detection and analysis on the MMT, S-MMT-1, G-S-MMT-1, and C-A-1 samples, and the results are as Figure 1 shown. As can be seen from the figure, the absorption peaks of the infrared spectra of the MMT, S-MMT-1, and G-S-MMT-1 samples at 1000 cm -1 are the stretching vibration peaks of the Si-O-Si bond, which are the characteristic absorption peaks of montmorillonite; 3600 cm -1 is the characteristic absorption peak of the surface hydroxyl group of montmorillonite. The infrared spectrum of the S-MMT-1 sample shows a group of strong absorption peaks at 2270 cm -1 , which are the characteristic peaks of the -NCO group, proving that IPTS is successfully grafted onto the surface of MMT; the characteristic absorption peak of the C=O group appears at 1706 cm -1 , further proving the successful preparation of S-MMT-1. The infrared spectrum of the C-A-1 sample shows a strong C-Cl absorption peak at 850 cm -1 ; a strong absorption peak appears at 1700 cm -1 , which is the characteristic absorption peak of the C=O group; at the same time, a strong absorption peak appears at 1600 cm -1The characteristic absorption peak of the strong C=C group appears, proving the successful preparation of product C-A-1. No obvious characteristic absorption peak of the -NCO group was observed in the infrared spectrum of G-S-MMT-1, indicating that further reaction occurred in the montmorillonite modified by silane; meanwhile, at 850 cm -1 A strong C-Cl absorption peak appears, and the characteristic absorption peak of the C=O group shifts to the left compared with G-MMT-1, at 1600 cm -1 No obvious characteristic absorption peak of the C=C group was observed, proving the preparation of G-S-MMT-1.

[0050] In this invention, differential scanning calorimetry was performed on PBAT and PBAT / G-S-MMT-2 samples respectively to evaluate the influence of the modified montmorillonite on the thermal properties and crystallization properties of the PBAT composite materials, and the results are as Figure 2 shown.

[0051] As Figure 2 shown in (a), the crystallization peak of the PBAT / G-S-MMT-2 composite material has changed compared with PBAT. Due to the addition of the modified montmorillonite, the crystallization peak shifts towards the high-temperature direction; as Figure 2 shown in (b), at the same time, the melting peak of the PBAT / G-S-MMT-2 composite material has changed compared with PBAT. Due to the addition of the modified montmorillonite, the melting peak also shifts towards the high-temperature direction.

[0052] Table 3 shows the crystallization parameters of the samples. It can be seen that the melting temperature of PBAT is 120.81 °C, and the melting temperature of the PBAT / G-S-MMT-2 composite material is 127.98 °C; the crystallization temperature of PBAT is 37.62 °C, and the crystallization temperature of the PBAT / G-S-MMT-2 composite material is 85.46 °C. After filling with the modified montmorillonite, the crystallinity, crystallization temperature and melting temperature of the modified PBAT composite material all show an increase. This is because after filling with the modified montmorillonite, the montmorillonite has a heterogeneous nucleation effect, which improves the nucleation rate of PBAT and increases the crystallinity and crystallization temperature. As can be seen from Figure 2 (b), the melting point of the PBAT / G-S-MMT-2 composite material is higher than that of pure PBAT, indicating that the thermal stability of the composite material is improved after filling with the modified montmorillonite. When montmorillonite is added to the polymer, the crystallinity increases, and materials with high crystallinity usually have higher melting points. The added montmorillonite acts as a crystal nucleus, refining the grains of PBAT and increasing the melting point; the interfacial interaction increases the energy requirement for melting. Therefore, the PBAT / G-S-MMT-2 composite material has better thermal stability and crystallization properties.

[0053] Table 3 Crystallization parameters of the samples

[0054] Figure 3 This is a schematic diagram of the preparation mechanism of grafting-silylation modified montmorillonite (G-S-MMT) proposed by the present invention. As Figure 3 shown, first, step ① is carried out. Isocyanatopropyltriethoxysilane (IPTS) is used to alkylate montmorillonite. The silicon-oxygen bond undergoes a hydrolysis reaction in an ethanol aqueous solution to generate silanol groups. The silanol groups can destroy the polar groups on the surface of montmorillonite and produce hydrogen bond interactions. At the same time, the isocyanate group at the other end of the Si atom can increase the surface polarity of montmorillonite and improve its hydrophobic property. Secondly, step ② is the synthesis of modifier C-A. Cyanuric chloride (CC) and allyl alcohol (AB) undergo a chlorine substitution reaction under alkaline conditions. The chlorine atoms on cyanuric chloride attack the hydrogen atoms on the hydroxyl groups of allyl alcohol, resulting in chlorine atom substitution and generating a chloroether compound. Finally, step ③ is the reaction of C-A with S-MMT. The chlorine atoms and double bonds on C-A undergo a graft copolymerization reaction with the surface of alkylated montmorillonite under certain conditions, forming a complex structure on the surface of montmorillonite, changing the surface polarity of montmorillonite, improving its hydrophobic property, and further enhancing the compatibility with PBAT.

[0055] Although the embodiments of the present application have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principle and spirit of the present application. The scope of the present application is defined by the appended claims and their equivalents, and all of them should be included within the protection scope of the present application.

Claims

1. A preparation method of modified montmorillonite with nucleation and compatibilization functions, characterized in that, The method steps are as follows: S1: Dissolve 3-isocyanatopropyltriethoxysilane in an ethanol aqueous solution, and then mix it evenly with montmorillonite to obtain alkylated montmorillonite; S2: Dissolve cyanuric chloride in toluene, and then add allyl alcohol for reaction; S3: Dissolve the alkylated montmorillonite in acetone, then add the product of S2 and a catalyst for reaction. After the reaction, precipitate, wash, and dry to obtain modified montmorillonite with nucleation and compatibilization functions.

2. The preparation method of the modified montmorillonite with nucleation and compatibilization functions according to claim 1, characterized in that, In S1, the mass ratio of 3-isocyanatopropyltriethoxysilane to montmorillonite is (2 - 5):

100.

3. The preparation method of the modified montmorillonite with nucleation and compatibilization functions according to claim 1, characterized in that, In S1, the mixing temperature is 60 - 80 °C.

4. The preparation method of the modified montmorillonite with nucleation and compatibilization functions according to claim 1, characterized in that, In S2, the mass ratio of cyanuric chloride to allyl alcohol is (2 - 3):(1 - 1.5).

5. The preparation method of the modified montmorillonite with nucleation and compatibilization functions according to claim 1, characterized in that, In S2, the reaction temperature is 100 - 120 °C, and the reaction time is 1 - 2 h.

6. The preparation method of the modified montmorillonite with nucleation and compatibilization functions according to claim 1, characterized in that, In S3, the catalyst is triethylamine; the mass ratio of the alkylated montmorillonite, the product of S2, and the catalyst is (50 - 60):(1.5 - 1.8):(0.05 - 0.1).

7. The preparation method of the modified montmorillonite with nucleation and compatibilization functions according to claim 1, characterized in that, In S3, the reaction temperature is 120 - 140 °C, and the reaction time is 2 - 3 h.

8. A modified montmorillonite with both nucleating and compatibilizing functions, characterized in that, Prepared by the preparation method described in any one of claims 1 - 7.

9. A method for preparing a PBAT composite material, characterized in that, The method steps are as follows: Mix polybutylene adipate / terephthalate and the modified montmorillonite described in claim 8, and then melt - extrude to obtain a composite material.

10. The preparation method of the PBAT composite material according to claim 9, characterized in that, The mass ratio of the modified montmorillonite to polybutylene adipate / terephthalate is (10 - 20):100; the melt - extrusion conditions are: the screw speed is 200 - 300 rpm, the feeding speed is 6 - 8 Hz, and the extrusion temperature zones are set at 140, 140, 145, 160, 150, 155, 140, 145 °C.

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