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CN-121975281-A - Nanometer montmorillonite reinforced PBAT/PLA high heat-resistant degradable mulch film and preparation method thereof

CN121975281ACN 121975281 ACN121975281 ACN 121975281ACN-121975281-A

Abstract

The invention discloses a PBAT/PLA high heat-resistant degradable mulch film reinforced by nano montmorillonite and a preparation method thereof, relating to the technical field of material science and engineering, wherein the method comprises the steps of preparing a multifunctional dynamic cross-linking agent containing aldehyde groups, catechol structures and coordinated metal ions; the preparation method comprises the steps of carrying out end group functionalization on PBAT and PLA to obtain an amino-terminated product, carrying out self-polymerization on the modified sodium montmorillonite by dopamine, injecting a cross-linking agent after the fusion of the PBAT, the PLA and the PLA, forming in-situ dynamic cross-linking master batch through multistage reaction, blending the master batch with unmodified PLA, casting a cast sheet, carrying out low-temperature biaxial stretching, short-wave ultraviolet irradiation and mild thermal curing to obtain a finished product, wherein the mulching film comprises a PBAT/PLA matrix, the modified montmorillonite and a dynamic cross-linking network (dynamic imine bond and coordination bond), the thermal deformation temperature is more than or equal to 110 ℃, and the cross-linking network can be dissociated and degraded under a composting environment.

Inventors

  • WU GUANGHUA

Assignees

  • 四川麦古实业有限公司

Dates

Publication Date
20260505
Application Date
20260324

Claims (10)

  1. 1. The preparation method of the PBAT/PLA high heat-resistant degradable mulch film reinforced by nano montmorillonite is characterized by comprising the following steps: Preparing a multifunctional dynamic cross-linking agent which is a molecule containing aldehyde groups at two ends and catechol structures and coordinated metal ions in the middle; performing end group functionalization treatment on the PBAT and the PLA to respectively prepare an amino-terminated PBAT and an amino-terminated PLA; adopting the dopamine self-polymerization-adhesion principle to carry out surface modification on sodium montmorillonite to prepare catechol modified montmorillonite; Adding amino-terminated PBAT, amino-terminated PLA and catechol modified montmorillonite into a double-screw extruder, injecting a multifunctional dynamic crosslinking agent after melting, and realizing in-situ dynamic crosslinking blending through a multi-stage reaction to obtain dynamic crosslinking master batches; blending the dynamic crosslinking master batch with unmodified PLA, and casting to obtain a thick sheet; And sequentially carrying out short wave ultraviolet irradiation and thermal curing treatment to obtain the PBAT/PLA high heat-resistant degradable mulch film reinforced by nano montmorillonite.
  2. 2. The preparation method of the multifunctional dynamic cross-linking agent according to claim 1 is characterized by comprising the steps of taking 3, 4-dihydroxybenzaldehyde as a starting material, conducting hydroxyl protection, long-chain extension, deprotection and introduction of a second aldehyde group reaction to obtain catechol ligands with aldehyde groups at two ends, and carrying out coordination reaction on the catechol ligands and degradable metal salt to obtain the multifunctional dynamic cross-linking agent, wherein the degradable metal salt is ferric ammonium citrate.
  3. 3. The preparation method of the terminal amino group PBAT according to claim 1, wherein the preparation of the terminal amino group PLA is characterized in that dihydric alcohol containing primary amino groups is introduced as a capping agent in the later stage of PBAT polycondensation, and the preparation of the terminal amino group PLA is characterized in that ethanolamine is used as an initiator in the ring-opening polymerization of PLA.
  4. 4. The preparation method of the catechol modified montmorillonite is characterized in that the preparation method comprises the steps of dispersing sodium-based montmorillonite in Tris-HCl buffer solution, adding dopamine hydrochloride, stirring, oxidizing and polymerizing for 24-48 hours at room temperature, and enabling polydopamine to be coated on the surface and edges of a montmorillonite sheet layer.
  5. 5. The method of claim 1, wherein the multi-stage reaction to achieve in situ dynamic cross-linking blending comprises: melting a first area of feeding, namely physically melting the amino-terminated PBAT, the amino-terminated PLA and the catechol modified montmorillonite at 170-180 ℃; The two-zone preliminary reaction is that a liquid multifunctional dynamic cross-linking agent is injected at 180-185 ℃ to enable aldehyde groups and polymer terminal amino groups to form dynamic imine bonds, and metal ions are coordinated with the polydopamine layer; three-zone high shear dynamic crosslinking, namely forming a dynamic crosslinking network through screw elements with high shear kneading blocks and reverse thread elements alternately at 185-190 ℃; and (5) devolatilizing and forming in four regions, namely vacuum removing small molecule byproducts at 175-180 ℃ and forming.
  6. 6. The method according to claim 1, wherein the temperature of the low-temperature synchronous biaxial stretching is 60-65 ℃, the temperature is 10-15 ℃ lower than that of the conventional stretching process, the short-wave ultraviolet irradiation is short-time irradiation by using UVC, and the mild thermosetting is heat treatment at 70 ℃ for 5-10 minutes.
  7. 7. The method of claim 1, wherein the cross-links of the dynamic cross-linked network comprise dynamic imine bonds formed by the reaction of aldehyde groups of the multifunctional dynamic cross-linking agent with terminal amino groups of the polymer and dynamic coordination bonds formed by coordination of metal ions of the multifunctional dynamic cross-linking agent with polydopamine layers of catechol-modified montmorillonite.
  8. 8. The preparation method of claim 1, wherein the blending mass ratio of the dynamic crosslinking master batch to the unmodified PLA is (80-95): 5-20, and the degradation rate of the mulching film is regulated and controlled by adjusting the addition amount of the unmodified PLA.
  9. 9. The preparation method of any one of claims 1 to 8, wherein the mulch film has stable dynamic imine bonds and coordination bonds in the service period, the thermal deformation temperature is not lower than 110 ℃, and the imine bonds are hydrolyzed and broken and the coordination bonds are decomposed due to ion competition under the composting environment, so that the dynamic crosslinking network dissociation is realized.
  10. 10. The nano montmorillonite reinforced PBAT/PLA high heat-resistant degradable mulch film is characterized by being prepared by adopting the preparation method as claimed in any one of claims 1-9, wherein the mulch film comprises a PBAT/PLA blending matrix, catechol modified montmorillonite and a dynamic cross-linking network, the dynamic cross-linking network is formed by connecting a polymer chain with montmorillonite sheets through a multifunctional dynamic cross-linking agent, the cross-linking bond is a dynamic imine bond and a dynamic coordination bond, the heat distortion temperature of the mulch film is more than or equal to 110 ℃, and the dissociative degradation of the dynamic cross-linking network can be realized in a composting environment.

Description

Nanometer montmorillonite reinforced PBAT/PLA high heat-resistant degradable mulch film and preparation method thereof Technical Field The invention relates to the technical field of material science and engineering, in particular to a PBAT/PLA high heat-resistant degradable mulch film reinforced by nano montmorillonite and a preparation method thereof. Background In the industrialized application process of the degradable mulch, the PBAT/PLA blending system has flexibility and mechanical strength, so that the PBAT/PLA blending system becomes a mainstream choice for replacing the traditional plastic mulch, but the system faces the technical bottleneck of unbalanced heat resistance and degradability for a long time, the thermal deformation temperature of the existing PBAT/PLA mulch is generally lower than 70 ℃, heat shrinkage, adhesion and even melting occur in a field exposure field Jing Xiayi in summer, the functions of soil moisture conservation, weeding and the like fail in advance, and when the heat resistance is improved by simply adding inorganic filler or crosslinking modification, the embrittlement and degradation rate of the material are greatly reduced, and a vicious circle with enhanced heat resistance, namely blocked degradation is formed. In the prior art, the inorganic filler (such as montmorillonite) is poor in interfacial compatibility with a PBAT/PLA matrix, is easy to agglomerate to form a stress concentration point, cannot effectively transfer load to achieve enhancement effect, and can damage continuity of a degradation process, the traditional cross-linking agent is mostly formed into an irreversible covalent cross-linking network, although heat resistance can be improved, but materials are difficult to degrade in natural environment, residual fragments pollute soil, meanwhile, a conventional stretching process is required to be carried out at a high temperature of 75-80 ℃, PLA phase crystallization unbalance is easy to be caused, the problem of insufficient heat resistance stability of the materials is further aggravated, in addition, the existing modification scheme lacks a dynamic regulation and control mechanism for long-period service requirement and environmental friendliness requirement of a mulching film in a field complex environment, and a set of collaborative technical system for fusion dynamic cross-linking, interface modification and low-temperature molding is required to be constructed, so that the precise balance of heat resistance, mechanical property and degradability is realized. Disclosure of Invention In order to solve the problems of poor heat resistance, low interface compatibility, degradation and enhancement unbalance and the like of the PBAT/PLA mulching film in the prior art, the invention discloses a nano montmorillonite-enhanced PBAT/PLA high heat resistance degradable mulching film and a preparation method thereof, which can effectively solve the technical problems. In order to solve the technical problems, the technical scheme of the invention is as follows: a preparation method of a nano montmorillonite reinforced PBAT/PLA high heat-resistant degradable mulch film comprises the following steps: Preparing a multifunctional dynamic cross-linking agent which is a molecule containing aldehyde groups at two ends and catechol structures and coordinated metal ions in the middle; performing end group functionalization treatment on the PBAT and the PLA to respectively prepare an amino-terminated PBAT and an amino-terminated PLA; adopting the dopamine self-polymerization-adhesion principle to carry out surface modification on sodium montmorillonite to prepare catechol modified montmorillonite; Adding amino-terminated PBAT, amino-terminated PLA and catechol modified montmorillonite into a double-screw extruder, injecting a multifunctional dynamic crosslinking agent after melting, and realizing in-situ dynamic crosslinking blending through a multi-stage reaction to obtain dynamic crosslinking master batches; blending the dynamic crosslinking master batch with unmodified PLA, and casting the mixture into a thick sheet by casting; Carrying out low-temperature synchronous biaxial stretching treatment on the thick sheet; And sequentially carrying out short wave ultraviolet irradiation and thermal curing treatment to obtain the PBAT/PLA high heat-resistant degradable mulch film reinforced by nano montmorillonite. Preferably, the multifunctional dynamic cross-linking agent is prepared by taking 3, 4-dihydroxybenzaldehyde as an initial raw material, carrying out hydroxyl protection, long-chain extension, deprotection and introduction of a second aldehyde group reaction to obtain catechol ligands with aldehyde groups at two ends, and carrying out coordination reaction on the catechol ligands and degradable metal salt to obtain the multifunctional dynamic cross-linking agent, wherein the degradable metal salt is ferric ammonium citrate. Preferably, the preparation of the amino