Polylactic acid composite and use thereof

Abstract

The present invention discloses a polylactic acid composite and use thereof. The polylactic acid composite includes the following components: (A) 89 to 98 parts by weight of polylactic acid; (B) 1 to 4 parts by weight of talcum powder; and (C) 1 to 7 parts by weight of a plasticizer. In the component (A), the polylactic acid has a polydispersity index P satisfying the following relationship: 1.55≤P≤2.02. In the component (B), the talcum powder has a particle size D.sub.(50) satisfying: 1 μm≤D.sub.(50)≤2.6 μm. In the component (C), the plasticizer has a relative molecular weight M satisfying: 180≤M≤670. Through research, the present invention has unexpectedly discovered that by using the polylactic acid having the polydispersity index P satisfying the relationship 1.55≤P≤2.02 as a matrix, adding a specific range of content of ultrafine talcum powder as a nucleating agent, and selecting the plasticizer of a specific molecular weight as a crystallization promotion agent, the prepared polylactic acid composite has a light transmittance T≥80%, a haze H≤40%, and a heat deflection temperature HDT≥90° C., having significantly improved heat resistance and transparency.

Claims

1. A polylactic acid composite, comprising: (A) 89 to 98 parts by weight of polylactic acid; (B) 1-4 parts by weight of talcum powder; and (C) 1-7 parts by weight of a plasticizer; wherein in the component (A), a polydispersity index P of the polylactic acid satisfies the following relationship: 1.94≤P≤1.97, and the polylactic acid is synthesized using only lactide as a monomer; in the component (B), a particle size D(50) of the talcum powder satisfies: 1μm≤D(50)≤2.6μm; in the component (C), a relative molecular weight M of he plasticizer satisfies: 180≤M≤670, wherein the plasticizer is one or a mixture of PEG-200, PEG-400, and triacetin.

2. The polylactic acid composite according to claim 1, wherein in parts by weight, the polylactic acid composite further comprises 0 to 10 parts by weight of a flexibilizer, and the flexibilizer is one or a mixture of aliphatic polyester, aliphatic-aromatic copolyester, ethylene-vinyl acetate copolymer, methyl methacrylate-butadiene-styrene terpolymer, and polyvinyl alcohol.

3. The polylactic acid composite according to claim 2, wherein the aliphatic polyester is one or a mixture of polycaprolactone (PCL), poly(butylene succinate) (PBS), and polyhydroxybutyrate (PHB); and the aliphatic-aromatic copolyester is an aliphatic-aromatic copolyester of a diacid-diol type.

4. The polylactic acid composite according to claim 1, wherein in parts by weight, the polylactic acid composite further comprises 0 to 5 parts by weight of an organic filler or an inorganic filler, the organic filler is one or a mixture of natural fiber, straw, and starch; and the inorganic filler is one or a mixture of montmorillonite, kaolin, chalk, calcium carbonate, gypsum, calcium chloride, titanium white, iron oxide, dolomite, silicon dioxide, wollastonite, titanium dioxide, silicate, mica, glass fiber, and mineral fiber.

5. The polylactic acid composite according to claim 1, wherein in parts by weight, the polylactic acid composite further comprises 0 to 4 parts by weight of other additives as follows: release agent, surfactant, wax, antistatic agent, dye or other plastic additives.

6. The polylactic acid composite according to claim 1, wherein the polylactic acid composite has a light transmittance T≥80%, a haze H≤40%, and HDT≥90° C.

7. A heat-resistant transparent product comprising the polylactic acid composite according to claim 1.

8. A heat-resistant transparent product comprising the polylactic acid composite according to claim 2.

9. A heat-resistant transparent product comprising the polylactic acid composite according to claim 3.

10. A heat-resistant transparent product comprising the polylactic acid composite according to claim 4.

Description

DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

(1) The present invention is further described below through specific implementations. The following embodiments are preferred implementations of the present invention, but the implementations of the present invention are not limited by the following embodiments.

(2) Preparation of Polylactic Acid:

(3) Polylactic Acid A1

(4) 20 mol of commercially available L-lactide was taken as a raw material, toluene was used as an organic solution, 0.03 mol of stannous octoate was added as a catalyst, and they were added to a 20 L stainless steel reactor which was depressurized to high vacuum of 0.085 MPa, and was slowly heated to 145° C., stirring was conducted for 1 hour to completely dissolve the lactide. A toluene vapor generated by heating was extracted, the vacuum was maintained at 0.085 MPa, and the reaction was stopped after a thermostatic reaction at 145° C. was conducted for 12 hours. After the pressure in the reactor is normal pressure, ethyl acetate was added to dissolve solids in the reactor to obtain a solution, and then the solution was poured into a container for air dry to obtain a solid, after the solvent ethyl acetate completely evaporated, the solid was put in a vacuum dryer for use.

(5) The polydispersity index P of the prepared polylactic acid was measured by GPC measurement to be 1.76, with two decimal places retained.

(6) Polylactic Acid A2

(7) 20 mol of commercially available L-lactide was taken as a raw material, toluene was used as an organic solution, 0.02 mol of stannous octoate was added as a catalyst, and they were added to a 20 L stainless steel reactor which was depressurized to high vacuum of 0.010 MPa, and was slowly heated to 140° C., stirring was conducted for 1 hour to completely dissolve the lactide. A toluene vapor generated by heating was extracted, the vacuum was maintained at 0.150 MPa, and the reaction was stopped after a thermostatic reaction at 130° C. was conducted for 9 hours. After the pressure in the reactor is normal pressure, ethyl acetate was added to dissolve solids in the reactor to obtain a solution, and then the solution was poured into a container for air dry to obtain a solid, after the solvent ethyl acetate completely evaporated, the solid was put in a vacuum dryer for use.

(8) The polydispersity index P of the prepared polylactic acid was measured by GPC measurement to be 1.94, with two decimal places retained.

(9) Polylactic Acid A3

(10) 20 mol of commercially available L-lactide was taken as a raw material, toluene was used as an organic solution, 0.015 mol of stannous octoate was added as a catalyst, and they were added to a 20L stainless steel reactor which was depressurized to high vacuum of 0.150 MPa, and was slowly heated to 130° C., stirring was conducted for 1 hour to completely dissolve the lactide. A toluene vapor generated by heating was extracted, the vacuum was maintained at 0.150 MPa, and the reaction was stopped after a thermostatic reaction at 130° C. was conducted for 8 hours. After the pressure in the reactor is normal pressure, ethyl acetate was added to dissolve solids in the reactor to obtain a solution, and then the solution was poured into a container for air dry to obtain a solid, after the solvent ethyl acetate completely evaporated, the solid was put in a vacuum dryer for use.

(11) The polydispersity index P of the prepared polylactic acid was measured by GPC measurement to be 1.97, with two decimal places retained.

(12) Polylactic Acid B1

(13) 20 mol of commercially available L-lactide was taken as a raw material, toluene was used as an organic solution, 0.035 mol of stannous octoate was added as a catalyst, and they were added to a 20 L stainless steel reactor which was depressurized to high vacuum of 0.065 MPa, and was slowly heated to 145° C., stirring was conducted for 1 hour to completely dissolve the lactide. A toluene vapor generated by heating was extracted, the vacuum was maintained at 0.065 MPa, and the reaction was stopped after a thermostatic reaction at 145° C. was conducted for 15 hours. After the pressure in the reactor is normal pressure, ethyl acetate was added to dissolve solids in the reactor to obtain a solution, and then the solution was poured into a container for air dry to obtain a solid, after the solvent ethyl acetate completely evaporated, the solid was put in a vacuum dryer for use.

(14) The polydispersity index P of the prepared polylactic acid was measured by GPC measurement to be 1.50, with two decimal places retained.

(15) Polylactic Acid B2

(16) 20 mol of commercially available L-lactide was taken as a raw material, toluene was used as an organic solution, 0.01 mol of stannous octoate was added as a catalyst, and they were added to a 20 L stainless steel reactor which was depressurized to high vacuum of 0.50 MPa, and was slowly heated to 120° C., stirring was conducted for 1 hour to completely dissolve the lactide. A toluene vapor generated by heating was extracted, the vacuum was maintained at 0.50 MPa, and the reaction was stopped after a thermostatic reaction at 120° C. was conducted for 5 hours. After the pressure in the reactor is normal pressure, ethyl acetate was added to dissolve solids in the reactor to obtain a solution, and then the solution -was poured into a container for air dry to obtain a solid, after the solvent ethyl acetate completely evaporated, the solid was put in a vacuum dryer for use.

(17) The polydispersity index P of the prepared polylactic acid was measured by GPC measurement to be 2.12, with two decimal places retained.

(18) Talcum powder:

(19) Plustalc H10 D.sub.(50)=2.2 μm, MONDO MINERALS B.V;

(20) TYT-8875B D.sub.(50)=7˜9 μm, Haicheng Tianyuan Chemical Co., Ltd.;

(21) self-made talcum powder D.sub.(50)<1 μm obtained by crushing and sieving talcum powder Plustalc H10 by a pulverizer.

(22) Plasticizer:

(23) ATBC n-butyl acetyl citrate M=402, Wuxi Kailai Biotechnology Co., Ltd.;

(24) PEG 400 M=360˜440, Jiangsu Haian Petroleum Chemical Factory;

(25) PEG 800 M=720˜880, Jiangsu Haian Petroleum Chemical Factory.

(26) Performance Test Method:

(27) 1. Test methods for light transmittance and haze of polylactic acid composite, refer to GBT 2410-2008 “Test Methods for Light Transmittance and Haze of Transparent Plastics”.

(28) 2. Test method for heat deflection temperature (HDT) of polylactic acid composite, refers to ASTM D648, and the test conditions are 0.45 MPa, 6.4 mm, and side placement.

(29) Preparation of HDT test splines: injection temperature at 170 to 230° C., mold temperature at 90 to 120° C., cooling time of 60 to 90 seconds, injection molding was performed to prepare the splines required for testing HDT according to ASTM D648.

(30) 3. The measurement method for polydispersity index P of polylactic acid is as follows:

(31) 15 mg of polylactic acid was dissolved in 10 ml of tetrahydrofuran (THF), and 125 μl of this solution was analyzed by gel permeation chromatography (GPC). Measurement was conducted at room temperature, and pure tetrahydrofuran was used as a mobile phase for elution, and an elution rate is 1 ml/min. Polystyrene standards of various molecular weights were used to calibrate the curve, and an elution range outside the curve was determined by extrapolation.

(32) 4. The test method for particle size of talcum powder is carried out by referring to the method of GB/T 19077.1 “Particle Size Analysis Laser Diffraction Method”.

(33) Embodiments 1-8 and comparative examples 1-6:

(34) According to the formula of Table 1, polylactic acid, talcum powder and plasticizer were mixed uniformly, put into a twin-screw extruder, and then extruded and pelletized at 160° C. to 190° C. to obtain polylactic acid composite.

(35) TABLE-US-00001 TABLE 1 Ratio and performance test results of polylactic acid composite (parts by weight) Compa. Compa. Compa. Compa. Compa. Compa. embodi- embodi- embodi- embodi- embodi- embodi- embodi- embodi- ex. 1 ex. 2 ex. 3 ex. 4 ex. 5 ex. 6 ment 1 ment 2 ment 3 ment 4 ment 5 ment 6 ment 7 ment 8 polylactic 93 93 93 93 93 95 89 90 95 93 acid A1 polylactic 93 acid A2 polylactic 93 acid A3 polylactic 93 acid B1 polylactic 93 acid B2 Plustalc 2 2 10 2 2 2 4 4 3 2 4 H10 self-made 2 talcum powder TYT-8875B 2 ATBC 1 6 5 3 3 PEG 400 5 5 5 5 5 5 5 5 PEG 800 5 light 76.4 70.5 67.0 68.4 66.4 48.2 88.5 86.7 85.1 84.1 80.8 82.9 89.7 86.6 transmittance T % haze H % 45.82 51.75 55.35 48.33 56.93 67.5 12.92 20.85 22.34 19.38 23.45 22.01 11.54 17.56 HDT ° C. 78 112 96 117 101 109 110 101 92 105 107 101 116 110

(36) From the results in Table 1, it can be seen that in the embodiments of the present invention, by using the polylactic acid having a polydispersity index P satisfying the relationship 1.55≤P≤2.02 as a matrix, adding a specific range of content of ultrafine talcum powder having a particle size D.sub.(50) satisfying 1 μm≤D.sub.(50)<2.6 μm as a nucleating agent, and selecting a plasticizer of a specific molecular weight as a crystallization promotion agent, the prepared polylactic acid composite has a light transmittance T≥80%, a haze H≤40%, and a heat deflection temperature HDT≥90° C. The polylactic acid composite has significantly improved heat resistance while maintaining good transparency. In the comparative examples 2 to 6, although the heat deflection temperature of the composites has increased, their transparency has severely decreased.