CN-121975289-A - High-foaming-rate high-stability fully-degradable biomass-based foaming material

Abstract

The invention relates to a high-foaming-rate high-stability fully-degradable biomass-based foaming material, which takes PLLA, PDLA, bio-polyester, microcrystalline cellulose and surface epoxy grafted carbon nano tubes as main raw materials, and comprehensively regulates and controls melt characteristics and crystallization characteristics through free radical reaction crosslinking, chain extension and three-dimensional complex promotion among matrixes, and adopts a two-stage melt conveying and extrusion continuous supercritical foaming process to realize the high foaming rate of a foaming body, a high-density closed cell structure with pore diameters in bimodal distribution, and the foaming body has the advantages of high foaming rate, high strength and toughness, excellent morphological stability, low thermal conductivity and full degradation, and can be applied to the lightweight buffering fields such as packaging, industry, building and the like.

Inventors

• CHEN YI
• LIAO XIZHI
• LU JIAWEI
• LIU JIATING
• CHEN YING

Assignees

• 湖南工业大学

Dates

Publication Date

20260505

Application Date

20260408

Claims (10)

1. 1. The fully-degradable biomass-based foaming material with high foaming rate and high stability is prepared by a batch feeding, extrusion granulation and extrusion continuous supercritical CO 2 foaming process, and the specific preparation process comprises the following steps: the preparation method of the blend A comprises the steps of uniformly mixing PLLA, a special melt reinforcing agent, second biopolyester, microcrystalline cellulose and BPO at a high speed, and then putting the mixture into an extruder for extrusion and granulation to obtain the blend A, wherein the blend A comprises the following components in parts by mass: Calculated by taking the mass of PLLA as 100 parts: 30-60 parts of second biological polyester 3-6 Parts of special melt reinforcing agent 2-4 Parts of microcrystalline cellulose 0.5-1.2 Parts of BPO The preparation method comprises the following steps of (I) uniformly mixing a blend A, PDLA, a chain extender, a three-dimensional accelerator and a surface epoxy grafted carbon nano tube at a high speed, putting the mixture into a double-screw extrusion foaming device, and extruding and foaming by taking supercritical CO 2 as a foaming agent to obtain a product, wherein the mass ratio of each component put into the extrusion foaming device is as follows: Based on 100 parts by mass of blend A, The mass parts of other components are as follows: PDLA 15-40 parts 1-4 Parts of a stereoaccelerator 3-8 Parts of chain extender 2-4 Parts of surface epoxy grafted carbon nano tube.
2. 2. The high-foaming-rate high-stability fully-degradable biomass-based foaming material of claim 1, wherein the double-screw extrusion foaming equipment adopted in the preparation process II is of a double-stage serial structure and consists of a first-stage melt extrusion conveying section and a second-stage extrusion foaming section, wherein one of a vertical-horizontal two-stage double-stage serial form or a horizontal-horizontal two-stage double-stage serial form can be adopted, the first-stage melt extrusion conveying section adopts a general screw extrusion device for mixing and chain extension of the composite material, and the second-stage extrusion foaming section is matched with a supercritical fluid conveying device and a foaming auxiliary device in the screw extrusion device for extrusion foaming of the composite material; it is also characterized in that: the technological conditions of the first-order melt extrusion conveying section are as follows: the extrusion temperature is between 160 and 200 ℃, and the material residence time is between 45 and 120 seconds; The technological conditions of the second-order extrusion foaming section are as follows: 1) The supercritical CO 2 is injected at the beginning end of the extrusion screw by constant flow, and the mass dosage of the supercritical CO 2 is between 5 and 9 percent of the foaming material; 2) The initial temperature of the extrusion foaming section is between 90 and 140 ℃, and the temperature from the initial section to a die opening is uniformly reduced to 70 to 90 ℃; 3) The rotating speed of the screw is between 150 and 250rpm, and the time of the material from the feeding to the output mould is between 45 and 120 s; 4) The pressure of the whole foaming section is between 15 and 30 MPa; 5) And after the melt is output from the die, a heat exchange area is arranged, the temperature is gradually reduced, and the cooling time is 15-30 s.
3. 3. The high-foaming-rate high-stability fully-degradable biomass-based foaming material according to claim 2, wherein the auxiliary device of the second-order extrusion foaming section in the double-screw extrusion foaming equipment comprises a supercritical CO 2 introducing device arranged at the initial position of the extrusion section, a reverse screw element arranged at the upstream of the supercritical CO 2 introducing port and used for dynamic melt sealing so as to maintain the supercritical CO 2 pressure at the rear part of the extruder, and a gear pump arranged at the tail end of the extrusion foaming section so as to maintain the pressure level at the tail end of the extruder.
4. 4. The high-foaming-rate high-stability fully-degradable biomass-based foaming material as claimed in claim 1, wherein the molecular weight of PLLA and PDLA is between 100,000 and 250,000 g/mol.
5. 5. The high-foaming-rate high-stability fully-degradable biomass-based foaming material of claim 1, wherein the special melt enhancer is selected from commercial PLA special melt enhancers and is at least one of commercial Paraloid TM BPMS250、Paraloid TM BPMS260、Paraloid TM BPMS265 and Biostrength 700.
6. 6. The high-foaming-rate high-stability fully-degradable biomass-based foaming material of claim 1, wherein the second bio-polyester is one of polycaprolactone, polybutylene succinate, polybutylene terephthalate-adipate and poly 3-hydroxybutyrate-4-hydroxybutyrate.
7. 7. The high-foaming-rate high-stability fully-degradable biomass-based foaming material of claim 1, wherein the accelerator is a polyhydroxy compound selected from one of PEG, D-sorbitol and D-mannitol with molecular weight between 200 and 400.
8. 8. The high-foaming-rate high-stability fully-degradable biomass-based foaming material of claim 1, wherein the surface epoxy grafted carbon nano tube is a carbon nano tube with an epoxy group connected to the surface, and the epoxy value is between 0.02 and 0.06 mol/100 g.
9. 9. The high-foaming-rate high-stability fully-degradable biomass-based foaming material of claim 1, wherein the chain extender is a small molecular substance containing di-functional or multi-functional epoxy groups.
10. 10. The high-foaming-rate high-stability fully-degradable biomass-based foaming material as claimed in claim 1, wherein the foaming material has a cell size of 10-100 μm, a cell density of 7 x 10 8 -9*10 10 cells/cm 3 , a foaming ratio of 15-30 by volume and a cell closure rate of 80% -95%.

Description

High-foaming-rate high-stability fully-degradable biomass-based foaming material Technical Field The invention relates to a fully degradable foaming material, in particular to a fully degradable foaming material with uniform micropore structure, higher foaming multiplying power and good compression resistance and tensile resistance. Background The foaming material is widely applied to a plurality of fields such as packaging, construction, transportation, daily consumer products, biological medicine and the like due to the outstanding characteristics of light weight, high porosity, buffering, heat insulation, sound insulation, high specific strength and the like. Currently, the most mainstream foaming materials in the market still take petroleum-based foaming materials as polystyrene foam (EPS), polyethylene foam (EPE), polyurethane foam (EPU), polypropylene foam (EPP) and the like. Although these materials have a more excellent cell structure, good mechanical properties and processing characteristics based on the characteristics of the matrix, they are not degradable and difficult to recycle, resulting in their inability to dissipate after disposal, and also are easily formed into microplastic, thus causing great impact and persistent pollution to the environment and human health. With the unprecedented rise in environmental awareness and the increasing severity of the problem of "white pollution" worldwide, the development of biodegradable green materials derived from renewable resources has become an important direction and urgent need in the field of material science. Among the numerous biomass-based degradable materials, polylactic acid (PLA) is recognized as one of the most promising and representative green polymeric materials due to its excellent processability, biocompatibility, compostability and mechanical properties. After the product is used, industrial composting treatment can be carried out, and the product is finally degraded into carbon dioxide and water, and the product returns to natural circulation again, so that green closed loop is truly realized. PLA has been proved to have foamability like other thermoplastic resins, and the preparation of PLA can be realized by adopting common processes such as extrusion, kettle pressure, injection and the like, and the PLA foaming material perfectly inherits the degradability and biocompatibility of the PLA material, and simultaneously has the light weight, heat insulation and buffering characteristics of the porous material. The degradable PLA foaming material is developed to replace the traditional petroleum-based plastic foaming material, so that the degradable PLA foaming material can be applied to industrial and civil fields, and has great strategic significance and application value for relieving environmental pressure and promoting the development of recycling economy. Nevertheless, the use of PLA for the preparation of high performance foamed materials still faces a number of challenges. For example, pure PLA has low melt strength, slow crystallization speed and low crystallinity, which results in a narrow foaming temperature window, and the lower melt strength is difficult to effectively wrap the gas generated during bubble growth, so that the cells are easy to merge or collapse, and a uniform, fine and high-density cell structure is difficult to form. Meanwhile, the brittleness, easy hydrolyzability and poor crystallinity of PLA themselves also cause the defects of brittleness, poor stability and the like of the foamed material after being molded, thereby severely limiting the application thereof. In recent years, research on PLA modified foaming is getting more and more popular, such as developing special materials for PLA foaming by using some PLA tap enterprises, such as Nature works, marine organisms and the like, widely exploring ways of adding nano fillers to promote PLA crystallization, chain extension, branching and the like and improving PLA melt strength, and also intensively researching ways of promoting PLLA and PDLA to form stereocomplex to improve crystallization and the like. In practical application and development, patent 202210534929.7 of Wanhua chemistry adopts PLA and PBAT-g-PDLA as modifiers, and inorganic filler is used for realizing high-foaming-rate kettle-pressure foaming PLA bead foaming to obtain a foaming material with the cell density of 6 multiplied by 10 8/cm < 3 > and the foaming rate of 30 times, and patent 202211692137.9 of Geling new material adopts toughening-grade PLA, acrylic acid grafting modified nano SiO 2 and thermoplastic starch as raw materials, and the foaming material with the closed porosity of 99% is obtained through kettle-pressure supercritical foaming. Although progress has been made, in the preparation of a large-scale continuous extrusion foamed product, there still remains a bottleneck how to comprehensively improve the strength even if the homogenization and high density of cells are r