CN101544813A - Rapid crystallization polylactic acid composite material and preparation method thereof - Google Patents

Abstract

The invention relates to a rapid crystallization polylactic acid composite material and its preparation technology. The composition of the composite material is calculated in parts by weight: 59-98 parts of semi-crystalline poly-L-lactic acid, 1-40 parts of organically modified natural minerals, 1-20 parts of organic crystallization accelerator, 0.1-1.0 parts of heat stabilizer, 0.05-1.0 parts of lubricant, the sum of the mass percentages of the above components is 100%. The preparation method of the material: firstly prepare the modified natural mineral, then carry out batching according to the composition of the composite material, stir and mix evenly with a high mixer, put the blend into a twin-screw extruder to extrude and granulate. The invention improves the crystallization rate of the polylactic acid matrix through the synergistic effect of the organic mineral and the crystallization accelerator. While accelerating the crystallization rate of polylactic acid, the addition of organic crystallization accelerators can also enhance the mechanical properties of polylactic acid composites, avoiding the significant increase in the mechanical properties of polylactic acid-based composites due to the addition of a single inorganic mineral nucleating agent. Falling flaws. The filler used in the invention has low price, simple process flow of the whole preparation method, less time-consuming process flow, and large-scale industrial production can be realized.

Description

Rapid crystallization polylactic acid composite material and preparation method thereof

technical field

The invention relates to a modified polylactic acid composite material and a preparation method thereof, in particular to a rapidly crystallizing polylactic acid composite material and a preparation method thereof.

Background technique

With the continuous development of the global economy, the consumption of petroleum resources by industry and agriculture continues to increase. At the same time, the amount of non-degradable plastics that rely on petroleum is increasing, causing serious white pollution and posing a huge challenge to the sustainable development of society. In my country, disposable plastic products that are difficult to recycle account for 20% of the total plastic in my country, and the plastic waste generated reaches 4 million tons every year. These plastic wastes have caused serious damage to the environment, resulting in reduced food production, the death of marine life, damage to hydroelectric power generation, and increased greenhouse effect. Solving white pollution is a major scientific and technological issue, environmental and economic issue, and even political issue facing countries all over the world.

Polylactic acid is a biodegradable polymer material prepared by chemical synthesis using renewable plant resources as raw materials. The raw material lactic acid is fermented from renewable natural materials such as corn. It causes little environmental pollution and has good biodegradability. The carbon dioxide and water produced by degradation can return to nature and re-participate in the photosynthesis of plants, thereby maintaining the carbon cycle balance in nature and meeting the requirements of sustainable development. In addition, polylactic acid The mechanical strength, processability, impermeability, gloss and light transmittance are similar to polypropylene and polystyrene. At present, injection molding grade, film grade, sheet grade, fiber grade, medical grade and other industrial grades have been developed. Polylactic acid has a huge market demand.

The main bottleneck restricting the practical application of polylactic acid at present is the long molding cycle. Due to the slow crystallization rate of polylactic acid, the molding time is too long, resulting in complex process conditions, increased energy consumption, and ultimately increased production costs. Improving the crystallization rate of polylactic acid is an effective way to shorten the molding cycle. Therefore, improving the crystallization rate of polylactic acid has important application value for solving the application problems of polylactic acid.

At present, an effective way to increase the crystallization rate of polylactic acid is to add a crystallization nucleating agent, which can reduce the surface free energy barrier for nucleation, thereby accelerating the crystallization rate of the resin matrix. Patent JP1999-106628 uses wax as polylactic acid crystallization nucleating agent. However, the crystallization nucleating agent has poor compatibility with polylactic acid and is easy to precipitate, resulting in a decrease in actual addition amount and insufficient crystal nucleus formation. Patent US6417294 obtains polylactic acid products with transparency and crystallinity by adding complex nucleating agents such as aliphatic carboxylic acid amines, aliphatic carboxylate salts, fatty alcohols and aliphatic carboxylic acid esters to the polylactic acid matrix. However, since the nucleating agent is an organic compound with a small molecular weight, it is easy to escape after being made into a masterbatch or product with polylactic acid. Talc powder is a widely used nucleating agent. Patent JP1997-25345A adds 15% MWHS-T talcum powder as a crystallization nucleating agent (average particle size 2.75 μm), and then adds erucamide with a mass fraction of 1%. , the difference between the absolute value of the melting enthalpy and the crystallization enthalpy is above 25Jg ^-1 , the crystallinity of the product measured by XRD is greater than 35%, and the half-crystallization time below 130°C is less than 20min.

Contents of the invention

One of the purposes of the present invention is to overcome the defects of slow crystallization rate of polylactic acid in the prior art, and improve the crystallization rate of the polylactic acid matrix through the synergistic effect of organically modified natural minerals and crystallization accelerators, thereby obtaining a fast crystallization polylactic acid composite material.

The second object of the present invention is to provide a preparation method of the composite material.

To achieve the above object, the present invention adopts the following technical solutions:

A kind of rapid crystallization polylactic acid composite material is characterized in that the composition and mass percentage content of this composite material are:

Semi-crystalline poly-L-lactic acid 59～98%

Organic modified natural minerals 1～40%

Organic crystallization accelerator 0.5～20%

Heat stabilizer 0.1～1.0%

Lubricant 0.05～1.0%

Antioxidant 0.2～1.5%

The sum of the mass percentages of the above components is 100%; wherein the semi-crystalline poly-L-lactic acid is L-polylactic acid, wherein the content of mesogenic poly-L-lactic acid is lower than 5wt%, and the viscosity-average molecular weight of polylactic acid is 100,000 to 300,000.

The aforementioned natural minerals are: barite, wollastonite, mica, talc, vermiculite, montmorillonite, kaolin, calcite or serpentine.

The specific modification method of the above-mentioned organically modified natural minerals is as follows: in parts by weight, 5 to 20 parts of natural minerals, 75 to 94 parts of 80% to 95% ethanol aqueous solution, 1 to 5 parts of silane coupling agent, 0.1mol/ 0.01-0.05 part of L concentrated hydrochloric acid is mixed, stirred and mixed at 70-90°C, and then refluxed for 3-5 hours; after suction filtration, deionized water washing, drying at 100-105°C, the modified natural minerals.

The above-mentioned silane coupling agents are 3-(2-aminoethyl)-aminopropylmethyldimethoxysilane, γ-glycidyl ether propyltrimethoxysilane, γ-aminopropyltriethylsiloxane alkane, vinyltrimethoxysilane, vinyltris(β-methoxyethoxy)silane, vinyltriethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane at least one of .

The specific modification method of the above-mentioned organically modified natural minerals is as follows: mix 95-99 parts of natural minerals with a particle size of less than 150 mesh, and 1-5 parts of modifiers in a high-speed collision machine, and the mixing temperature is above 80°C. 30 to 90 minutes to obtain dry modified natural minerals; the modifier is stearic acid, aminopropyltrimethoxysilane or monoalkoxy fatty acid titanate; the high-speed collision machine is a high-speed mixer, pulverizer machine or ball mill.

The above organic crystallization accelerators are: ethylene bisstearamide, erucamide, oleamide, ethylene bisoleamide, phthalate, citrate, lactate, lactide, mineral Oil, Triphenyl Phosphate, Glycerin, Glyceryl Acetate, or Glyceryl Butyrate.

The above-mentioned antioxidant is tetraerythritol ester, stearyl propionate or 1,1,3 three (2-methyl-4-hydroxyl-5 tert-butylphenyl) butane; heat stabilizer is butene dianhydride or epoxidized soybean oil; lubricants are aluminum stearate or calcium stearate.

A method for preparing the above-mentioned rapid crystallization polylactic acid composite material is characterized in that the specific steps of the method are as follows: semi-crystalline poly-L-lactic acid, organically modified natural minerals, organic crystallization accelerator, thermally stable Mixing agent, lubricant and antioxidant, stirring evenly after mixing; then extruding and granulating to obtain rapid crystallization polylactic acid composite material

The polylactic acid is a semi-crystalline L-lactic acid with a crystallinity higher than 20%, wherein the content of mesogenic poly-L-lactic acid is less than 5wt%, the viscosity-average molecular weight of the polylactic acid is 100,000-300,000, and the glass transition The temperature range is 40-60°C, and the melt flow rate is 4-15g/10min at 190°C×2.16Kg.

Compared with prior art, the advantage of the present invention is:

(1) The present invention uses the synergistic effect of inorganic minerals and organic crystallization accelerators to increase the crystallization rate of polylactic acid, and the obtained polylactic acid composite material significantly improves the crystallization rate of the polylactic acid matrix.

(2) The present invention can not only accelerate the crystallization rate of polylactic acid owing to adding organic crystallization accelerator, and the mechanical property of polylactic acid composite material is improved, has avoided the addition of single inorganic mineral nucleating agent and causes the decline of composite material mechanical property defect.

(3) The mineral used in the present invention is low in price, and its content in the composite material can be as high as 15 wt% without affecting the mechanical properties of the polylactic acid composite material, which greatly reduces the cost of the product.

(4) The preparation technology of the injection molding grade rapid crystallization polylactic acid-based composite material of the present invention has simple process flow, strong processability, low cost and large-scale industrial production.

Detailed ways

The present invention will be described in detail below in conjunction with the examples.

In the stabilization system of polylactic acid, it is mainly to prevent its thermal degradation, so a thermal stabilizer, such as maleic anhydride or epoxidized soybean oil, is often added.

In order to further enhance the compatibility between natural minerals and PLA matrix, it is usually necessary to use a coupling agent to treat the surface of natural minerals. The coupling agents used are low-molecular compounds containing active functional groups, such as silane coupling agents, titanate coupling agents, aluminate coupling agents, and the like.

Embodiment one: the preparation of pure polylactic acid

100 parts of vacuum-dried polylactic acid (weight-average molecular weight 19.5W) is mixed in a high-speed mixer at room temperature, extruded and granulated in a twin-screw extruder, and the extrusion temperature is 160-185 ° C, and then the composite material particles are injected into impact and tensile splines, to be tested. Its crystallization rate and mechanical properties are listed in Table 1.

Embodiment two: the preparation method of modified talcum powder/ethylene bis stearate amide/polylactic acid composite material

The preparation process of modified talcum powder: by weight, 15 parts of talcum powder, 84 parts of 95% ethanol aqueous solution, 1 part of silane coupling agent γ-glycidyl ether propyl trimethoxysilane, 0.1mol/L concentrated hydrochloric acid 0.03 parts were batched, stirred and mixed at 85°C, and then refluxed for 3 hours; filtered by suction, washed with deionized water, and dried at 105°C.

Vacuum-dried semi-crystalline poly L-lactic acid (weight average molecular weight 19.5W) 81 parts, modified talc powder 15 parts, ethylene bis stearate amide 3 parts, heat stabilizer maleic anhydride 0.2 parts, antioxidant 0.5 part of pentaerythritol ester of agent and 0.3 part of lubricant aluminum stearate were mixed in a high-speed blender at room temperature, extruded and granulated in a twin-screw extruder, and the extrusion temperature was 160-185 ° C, and then the composite material particles Injection molded into impact and tensile splines, to be tested. Its crystallization rate and mechanical properties are listed in Table 1.

Example 3: Preparation method of modified talcum powder/erucamide/polylactic acid composite material

The preparation process of modified talc powder: Mix 97 parts of talc powder with a particle size of less than 150 mesh and 3 parts of stearic acid in a high-speed mixer at a mixing temperature above 80°C for 40 minutes to obtain a dry-process modified talc powder.

Vacuum-dried semi-crystalline poly L-lactic acid (weight average molecular weight 19.5W) 86 parts, modified talc powder 10 parts, ethylene bis stearate amide 3 parts, heat stabilizer maleic anhydride 0.2 parts, antioxidant Agent tetraerythritol ester 0.5 part, lubricant aluminum stearate 0.3 are mixed at room temperature in a high-speed mixer, extruded and granulated in a twin-screw extruder, the extrusion temperature is 160-185 ° C, and then the composite material particles are injected into impact and tensile splines, to be tested. Its crystallization rate and mechanical properties are listed in Table 1.

Embodiment four: the preparation method of modified kaolin/ethylene bisstearamide/polylactic acid composite material

The preparation process of modified kaolin: by weight, 15 parts of kaolin, 84 parts of 95% ethanol aqueous solution, 1 part of silane coupling agent γ-glycidyl ether propyl trimethoxysilane, 0.03 part of 0.1mol/L concentrated hydrochloric acid Perform batching, stir and mix at 85°C, and then reflux for 3 hours; filter with suction, wash with deionized water, and dry at 105°C.

Vacuum-dried semi-crystalline poly-L-lactic acid (weight average molecular weight 19.5W) 89 parts, modified kaolin 6 parts, ethylene bis stearate amide 4 parts, heat stabilizer maleic anhydride 0.2 parts, antioxidant Mix 0.5 parts of tetraerythritol ester and 0.3 parts of lubricant calcium stearate at room temperature in a high-speed mixer, extrude and granulate in a twin-screw extruder at a temperature of 160-185°C, and then inject the composite material particles into impact and tensile splines, to be tested. Its crystallization rate and mechanical properties are listed in Table 1.

Embodiment five: the preparation method of modified talcum powder/acetyl tri-n-butyl citrate/polylactic acid composite material

The preparation process of modified talcum powder: by weight, 15 parts of talcum powder, 84 parts of 95% ethanol aqueous solution, 1 part of silane coupling agent γ-glycidyl ether propyl trimethoxysilane, 0.1mol/L concentrated hydrochloric acid 0.03 parts were batched, stirred and mixed at 85°C, and then refluxed for 3 hours; filtered by suction, washed with deionized water, and dried at 105°C.

Vacuum-dried semi-crystalline poly L-lactic acid (weight average molecular weight 19.5W) 74 parts, modified talc powder 10 parts, acetyl tri-n-butyl citrate 15 parts, heat stabilizer maleic anhydride 0.2 parts, antioxidant Agent tetraerythritol ester 0.5 part, lubricant aluminum stearate 0.3 are mixed at room temperature in a high-speed mixer, extruded and granulated in a twin-screw extruder, the extrusion temperature is 160-185 ° C, and then the composite material particles are injected into impact and tensile splines to be tested, and their crystallization rate and mechanical properties are shown in Table 1.

Embodiment 6: Preparation method of modified barite/ethylene bisstearate amide/polylactic acid composite material

The preparation process of modified barite: by weight, 15 parts of barite, 84 parts of 95% ethanol aqueous solution, 1 part of silane coupling agent γ-glycidyl ether propyl trimethoxysilane, 0.1mol/L 0.03 part of concentrated hydrochloric acid is used for batching, stirred and mixed at 85°C, and then refluxed for 3 hours; filtered with suction, washed with deionized water, and dried at 105°C.

Vacuum-dried semi-crystalline poly L-lactic acid (weight average molecular weight 19.5W) 89 parts, modified barite 5 parts, ethylene bis stearate amide 5 parts, heat stabilizer maleic anhydride 0.2 parts, anti Mix 0.5 parts of tetraerythritol ester of oxygen agent and 0.3 parts of aluminum stearate of lubricant in a high-speed blender at room temperature, extrude and granulate in a twin-screw extruder, and the extrusion temperature is 160-185 ° C, and then the composite material The particles were injection molded into impact and tensile splines to be tested. The crystallization rate and mechanical properties are shown in Table 1.

Embodiment 7: the preparation method of modified talcum powder/ethylene bis stearate amide/polylactic acid composite material

The preparation process of modified talcum powder: by weight, 15 parts of talcum powder, 84 parts of 95% ethanol aqueous solution, 1 part of silane coupling agent γ-glycidyl ether propyl trimethoxysilane, 0.1mol/L concentrated hydrochloric acid 0.03 parts were batched, stirred and mixed at 85°C, and then refluxed for 3 hours; filtered by suction, washed with deionized water, and dried at 105°C.

Vacuum-dried semi-crystalline poly L-lactic acid 88 parts (weight average molecular weight is 12.87W), modified talcum powder 10 parts, ethylene bis stearate amide 1 part, thermal stabilizer maleic anhydride 0.2 part, anti- Mix 0.5 parts of tetraerythritol ester of oxygen agent and 0.3 parts of aluminum stearate of lubricant in a high-speed blender at room temperature, extrude and granulate in a twin-screw extruder, and the extrusion temperature is 160-185 ° C, and then the composite material The particles were injection molded into impact and tensile splines to be tested. The crystallization rate and mechanical properties are shown in Table 1.

Table 1: Properties of the polylactic acid composition prepared in Examples 1-7

example Half crystallization time (min) Unnotched impact strength (Kj/m ² ) Tensile strength MPa 1 15(110℃) 10 60 2 1.8(101℃) twenty three 55 3 2(108℃) 20 57 4 5.1(110℃) 19 55 5 1.5(100℃) 16 40 6 7.8(115℃) 18 62 7 1.7(110℃) twenty two 61

As can be seen from the table, compared with pure polylactic acid, the rapid crystallization type polylactic acid-based composite material prepared by the invention under the synergistic effect of inorganic mineral/organic crystallization accelerator has fast crystallization rate and good mechanical properties, especially Its rapid crystallization performance significantly shortens the processing and molding cycle of polylactic acid, improves production efficiency, and reduces production costs. The above description of the examples is to facilitate the understanding and application of the present invention by those of ordinary skill in the technical field. Those skilled in the art can easily make various modifications to these implementation examples, and apply the general principles described here to other application examples without creative efforts. Therefore, the present invention is not limited to the implementation examples here, and the improvements and modifications made by those skilled in the art according to the disclosure of the present invention should be within the protection scope of the present invention.

Claims (8)

1. rapid crystallization polylactic acid composite material is characterized in that the composition of this matrix material and mass percentage content are:

Half hitch crystal formation poly (l-lactic acid) 59～98%

Organically-modified natural mineral 1～40%

Organic crystal promotor 0.5～20%

Thermo-stabilizer 0.1～1.0%

Lubricant 0.05～1.0%

Oxidation inhibitor 0.2～1.5%

More than the mass percent sum of each component be 100%; Wherein said poly(lactic acid) is that degree of crystallinity is higher than 20% half hitch crystal formation Poly-L-lactic acid, and wherein the content of meso poly (l-lactic acid) is lower than 5wt%, and the viscosity-average molecular weight of poly(lactic acid) is 10～300,000.

2. rapid crystallization polylactic acid composite material according to claim 1 is characterized in that natural mineral is: barite, wollastonite, mica, talcum powder, vermiculite, polynite, kaolin, calcite or serpentine.

3. rapid crystallization polylactic acid composite material according to claim 1, the concrete method of modifying that it is characterized in that described organically-modified natural mineral is: by weight, with 5～20 parts of natural mineral, 75～94 parts of 80%～95% aqueous ethanolic solutions, 1～5 part of silane coupling agent, 0.1mol/L concentrated hydrochloric acid is prepared burden for 0.01～0.05 part, mixes under 70～90 ℃, refluxes 3～5 hours again; Through suction filtration, behind the deionized water wash,, promptly obtain the modified natural mineral 100～105 ℃ of oven dry down.

4. rapid crystallization polylactic acid composite material according to claim 3 is characterized in that described silane coupling agent is at least a in 3-(2-aminoethyl)-aminopropyl methyl dimethoxysilane, γ-glycidyl ether propyl trimethoxy silicane, gamma-amino propyl-triethylsilicane oxygen alkane, vinyltrimethoxy silane, vinyl three (beta-methoxy-oxyethyl group) silane, vinyltriethoxysilane, β-(3,4-epoxycyclohexyl) ethyl trimethoxy silane.

5. rapid crystallization polylactic acid composite material according to claim 1, the concrete method of modifying that it is characterized in that described organically-modified natural mineral is: with particle diameter less than 95～99 parts of 150 purpose natural mineral, properties-correcting agent mixes in the high velocity impact machine for 1～5 part, mixing temperature is more than 80 ℃, mixed 30～90 minutes, and obtained the dry method modification natural mineral; Described properties-correcting agent is hard ester acid, aminopropyl trimethoxysilane or monoalkoxy lipid acid titanic acid ester; The high velocity impact machine is high-speed mixer, pulverizer or ball mill.

6. rapid crystallization polylactic acid composite material according to claim 1 is characterized in that described organic crystal promotor is: the two hard acid ester acid amides of ethylene, erucicamide, amine hydroxybenzene, the two amine hydroxybenzenes of ethylene, phthalic ester, citrate, lactate, rac-Lactide, mineral oil, triphenylphosphate, glycerine, glycerol acetate or butyrin.

7. rapid crystallization polylactic acid composite material according to claim 1 is characterized in that described oxidation inhibitor is pentaerythritol tetrathioglycollate, propionic acid stearyl alcohol ester or 1,1,3 three (2-methyl-4-hydroxyl-5 tert-butyl-phenyl) butane; Thermo-stabilizer is MALEIC ANHYDRIDE or epoxy soybean oil; Lubricant is aluminum stearate or calcium stearate.

8. method for preparing rapid crystallization polylactic acid composite material according to claim 1, the concrete steps that it is characterized in that this method are as follows: by said ratio half hitch crystal formation poly (l-lactic acid), organically-modified natural mineral, organic crystal promotor, thermo-stabilizer, lubricant and oxidation inhibitor are mixed, stir after the mixing; Carry out extruding pelletization again, promptly obtain rapid crystallization polylactic acid composite material.