CN-122011694-A - Mineral-based degradable plastic and preparation method thereof

CN122011694ACN 122011694 ACN122011694 ACN 122011694ACN-122011694-A

Abstract

The invention discloses a mineral-based degradable plastic and a preparation method thereof, wherein the plastic is prepared by taking PLA, PBAT and the like as matrixes, introducing modified mineral filler taking nano calcium carbonate as a substrate and combining an extrusion process, and starch fragments are loaded in the nano calcium carbonate and on the surface through physical adsorption and in-situ polymerization, so that the interface bonding energy between the nano calcium carbonate and the matrixes is greatly improved, and the problems of phase separation, mechanical property attenuation and starch thermal decomposition of the plastic under high mineral filling are effectively solved. The plastic disclosed by the invention has the advantages of high mechanical property, excellent processing fluidity, controllable degradation rate and high recovery retention rate, and is suitable for the fields of degradable packages, agricultural films and injection molding products with higher requirements on performance and processing.

Inventors

MA LANYU
HUANG YIFENG
ZHENG YIHUA
LIU ZHONGLIN
XU MENGXUE
XIAO NING

Assignees

广西科学院

Dates

Publication Date: 20260512
Application Date: 20260228

Claims (5)

1. The mineral-based degradable plastic is characterized by being prepared from the following components in parts by weight: 60-85 parts of biological resin matrix, 15-40 parts of modified mineral filler, 0.5-3 parts of cross-linking agent, 0.05-0.5 part of initiator, 0.2-1 part of heat stabilizer and 0.5-2 parts of lubricant; the biological resin matrix is one or the combination of more than two of polylactic acid, poly adipic acid/polybutylene terephthalate and poly butylene succinate; The modified mineral filler is a composite material taking nano calcium carbonate as a core, and the surface and the pores of the composite material are loaded with enzymolysis starch fragments and coated with polylactic acid shells, wherein the pore diameter of the nano calcium carbonate is 2-50nm, and the specific surface area is more than or equal to 30m 2 /g; the cross-linking agent is one or two of dicumyl peroxide and divinylbenzene; The initiator is one of benzoyl peroxide and dicumyl peroxide; The heat stabilizer is one of triphenyl phosphite and triphenyl phosphate; The lubricant is one of polyethylene wax, oxidized polyethylene wax, glyceryl stearate and pentaerythritol stearate.
2. The mineral-based degradable plastic according to claim 1, wherein the polylactic acid and polybutylene adipate/terephthalate composition is obtained by mixing (4-8) and (2-6) by weight.
3. The mineral-based degradable plastic according to claim 1, wherein the modified mineral filler is prepared by the following steps: A1, preparing corn starch into suspension with the mass concentration of 10% -30%, regulating the pH value to 6.0-6.5, adding alpha-amylase with the dry weight of 0.1% -0.5% of the corn starch, hydrolyzing for 30-90min at 60-75 ℃, and then heating to 90-100 ℃ to inactivate enzyme for 10-20min to obtain starch hydrolysate solution with the molecular weight of 1000-10000 Da; A2, dispersing nano calcium carbonate in the starch hydrolysate solution according to the dry weight ratio of the calcium carbonate to the starch hydrolysate solution of (70-80) (20-30), stirring and adsorbing for 2-4 hours at 50-65 ℃, controlling the starch load to be 20-30 wt%, and then performing centrifugal separation and vacuum drying at 60-80 ℃ to obtain the load type calcium carbonate with starch fragments adsorbed on the surface; a3, mixing the supported calcium carbonate, the L-lactic acid monomer and the stannous octoate catalyst according to the weight ratio of 100 (50-150) (0.1-0.3), carrying out prepolymerization dehydration for 2-3 hours at 120-140 ℃ under the protection of nitrogen, then raising the system temperature to 150-170 ℃ for 4-8 hours under the vacuum degree of <100Pa, controlling the shell thickness to 5-20nm, and after the reaction is finished, crushing and sieving the product to obtain the modified mineral filler.
4. A method for the preparation of a mineral-based degradable plastic according to any one of claims 1-3, comprising the steps of: B1, mixing a biological resin matrix, modified mineral filler, a heat stabilizer and a lubricant according to the weight part ratio to obtain a premix, and putting the premix into a high-speed mixer to be mixed for 8-10min at 800-1000rpm to obtain the premix; B2, melting and mixing the premix in a double-screw extruder, and simultaneously dissolving a cross-linking agent and an initiator in acetone and then injecting the mixture into the extruder, wherein the mixing temperature of the double-screw extruder is 150-185 ℃, and the screw rotating speed is 200-350rpm; And B3, immediately cooling and shaping the material strips extruded by the double-screw extruder in water at the temperature of 25 ℃, airing the surface moisture, feeding the material strips into a granulator, cutting the material strips into cylindrical particles with the diameter of 5-6mm and the length of 8-10mm, and vacuum drying the particles for 6 hours at the temperature of 75-80 ℃ to obtain the mineral-based degradable plastic.
5. The method of producing a mineral-based degradable plastic according to claim 4, wherein the twin-screw extruder has a first zone temperature of 105-155 ℃, a second zone temperature of 156-168 ℃, a third zone temperature of 169-173 ℃, a fourth zone temperature of 174-178 ℃, and a head temperature of 178-185 ℃.

Description

Mineral-based degradable plastic and preparation method thereof Technical Field The invention belongs to the technical field of environment-friendly plastics, and particularly relates to a mineral-based degradable plastic and a preparation method thereof. Background With the deep advancement of the plastic-limiting command, degradable plastics represented by polybutylene terephthalate-adipate (PBAT), polylactic acid (PLA) and a blending system thereof are widely applied in the fields of packaging, agriculture and the like. Natural or mineral fillers such as starch, calcium carbonate, etc. are often blended with degradation resins in order to reduce costs and to impart more functionality to the material (e.g., to increase specific gravity, stiffness, degradation rate). However, existing physical blending techniques face significant bottlenecks: 1. The interfacial compatibility is poor, namely the hydrophilicity of starch and the high polarity of calcium carbonate are weak in interfacial bonding with a hydrophobic resin (such as PBAT) matrix, phase separation is easy to cause, and the mechanical properties (particularly impact strength and elongation at break) and the water resistance of the material are seriously damaged. The filler is usually subjected to surface modification by adding silane coupling agents, dopamine and the like, so that the process flow is complex and the cost is increased. 2. The degradation rate of natural fillers such as starch is far faster than that of a resin matrix, so that the materials generate a large number of pores and defects due to rapid loss of the fillers in the initial use period (such as storage or use stage), and the mechanical properties (such as tensile strength and elongation at break) are rapidly attenuated in a short time (1-3 months), so that the reliability and the storage life stability of the products are affected. 3. The processability is deteriorated, at high filling levels (typically >20 wt%), the filler is very prone to agglomeration, resulting in a sharp rise in melt viscosity (e.g. 800 Pa s at 180 ℃) and narrowing of the processing window, increased energy consumption, and the risk of thermal decomposition of starch during high temperature (> 180 ℃) extrusion processing, limiting its application in high temperature processing scenarios (e.g. injection moulding, blown film). Therefore, developing a novel composite material and process capable of synchronously solving three problems of interface compatibility, degradation controllability and processing stability becomes a key to be broken through in the field. Disclosure of Invention Aiming at the defects of the existing mineral-based plastic, the invention provides the mineral-based degradable plastic and the preparation method thereof, and the strong interface combination and interpenetrating network structure is constructed on molecules by combining the filler design and the extrusion process, so that the cooperative promotion of the mechanical property, the long-acting stability, the controllable degradability and the processing rheological property of the mineral-based degradable plastic is realized. The invention is realized by the following technical scheme: a mineral-based degradable plastic is prepared from the following components in parts by weight: 60-85 parts of biological resin matrix, 15-40 parts of modified mineral filler, 0.5-3 parts of cross-linking agent, 0.05-0.5 part of initiator, 0.2-1 part of heat stabilizer and 0.5-2 parts of lubricant; the biological resin matrix is one or the combination of more than two of polylactic acid, poly adipic acid/polybutylene terephthalate and poly butylene succinate; The modified mineral filler is a composite material taking nano calcium carbonate as a core, and the surface and the pores of the composite material are loaded with enzymolysis starch fragments and coated with polylactic acid shells, wherein the pore diameter of the nano calcium carbonate is 2-50nm, and the specific surface area is more than or equal to 30m 2/g; the cross-linking agent is one or two of dicumyl peroxide and divinylbenzene; The initiator is one of benzoyl peroxide and dicumyl peroxide, and is used for activating the cross-linking agent in the extrusion process to generate free radicals. The dicumyl peroxide is well matched with the processing temperature (170-185 ℃) of the invention, and the smell of the decomposed product is small. The heat stabilizer is one of triphenyl phosphite and triphenyl phosphate, and is used for preventing thermooxidative degradation and hydrolysis of PLA and other resins in the high-temperature processing process. The human stabilizer can effectively capture peroxide free radicals and inhibit beta-elimination degradation reaction of PLA. The lubricant is one of polyethylene wax, oxidized polyethylene wax, glyceryl stearate and pentaerythritol stearate. Preferably, the polylactic acid and the composition of the poly (adipic acid)/the polybutylene t