Polylactic acid composition with both strength and toughness and preparation method thereof

Abstract

The invention discloses a polylactic acid composition with both strength and toughness and a preparation method thereof. The polylactic acid composition is prepared from 1000 parts by weight of polylactic acid, 30-40 parts by weight of polypropylene glycol, 10-40 parts by weight of triphenyl phosphate, 100-500 parts by weight of a filler, 0.2-2 parts by weight of a coupling agent and 1-10 parts by weight of an antioxidant. According to the polylactic acid composition and the preparation method thereof, the polylactic acid composition obtained by compounding the toughening agent not only has excellent elongation at break, but also has relatively high tensile strength and good toughness and strength, and the application range of polylactic acid is widened.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer material modification, and particularly relates to a polylactic acid composition with both strength and toughness and a preparation method thereof. Background Art

[0002] Polylactic acid (PLA) is a new type of biodegradable material made from starch raw materials extracted from renewable plant resources (such as corn, etc.). The starch raw materials are saccharified to obtain glucose, and then high-purity lactic acid is produced by fermenting glucose with certain strains of bacteria. Subsequently, polylactic acid with a certain molecular weight is synthesized through chemical synthesis methods. Polylactic acid has good biodegradability. After use, it can be completely degraded by microorganisms in nature, and finally carbon dioxide and water are generated, without polluting the environment, which is very beneficial to environmental protection and is a recognized environmentally friendly material. The treatment method of ordinary plastics is still incineration, which causes a large amount of greenhouse gases to be discharged into the air. However, polylactic acid plastics are buried in the soil for degradation, and the generated carbon dioxide directly enters the soil organic matter or is absorbed by plants, without being discharged into the air and without causing the greenhouse effect.

[0003] Although PLA has relatively high tensile strength and flexural strength, its toughness is poor, the elongation at break is less than 10%, and it is brittle. The above-mentioned disadvantages greatly limit the application of PLA in certain specific fields. In order to solve the disadvantages of high brittleness and low toughness of PLA, the currently commonly used method is plasticization modification, which is to mix a high-boiling-point, low-volatility and non-toxic plasticizer into the PLA matrix, so that the flexibility of polylactic acid is significantly improved, the low-temperature brittleness is improved, and the overall processing performance is enhanced. There are mainly two forms: physical plasticization and chemical plasticization. Physical plasticization refers to expanding the molecular chain spacing of PLA through hydrogen bonding or van der Waals forces between the plasticizer and the PLA molecular chain, thereby improving the movement ability of the PLA molecular chain to achieve a toughening effect; while chemical plasticization refers to grafting reactions occurring between the plasticizer and the PLA molecular chain segments, and using its own steric hindrance to expand the PLA molecular chain spacing to exert a toughening effect.

[0004] The current plasticization modification effectively realizes the toughening of PLA, but in the use process, the addition amount of the plasticizer is very high (more than 10%), resulting in a significant reduction in tensile strength. Summary of the Invention

[0005] In view of this, it is necessary for the present invention to provide a polylactic acid composition with both strength and toughness. By adding polypropylene glycol and triphenyl phosphite as a compound plasticizing component to the polylactic acid system, the obtained polylactic acid not only has excellent elongation at break, but also has relatively high tensile strength, and both toughness and strength are excellent.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The first aspect of the present invention discloses a polylactic acid composition with both strength and toughness, which is prepared from 1000 parts of polylactic acid, 30 - 40 parts of polypropylene glycol, 10 - 40 parts of triphenyl phosphite, 100 - 500 parts of filler, 0.2 - 2 parts of coupling agent and 1 - 10 parts of antioxidant by weight.

[0008] In a further embodiment, the melt index of the polylactic acid under the conditions of 230 °C and 2.16 kg is 10 - 30 g / 10 min.

[0009] In a further embodiment, the number average molecular weight of the polypropylene glycol is 5000 - 8000, and the hydroxyl value is 17 - 20.7 mgKOH / g.

[0010] In a further embodiment, the filler is selected from at least one of talc, calcium carbonate, barium sulfate, calcium sulfate, mica powder, wollastonite, diatomaceous earth, carbon black.

[0011] In a further embodiment, the average particle size of the filler is 1000 - 3000 mesh.

[0012] In a further embodiment, there is no particular limitation on the coupling agent in the present invention. Specific examples that can be mentioned include silane coupling agents, aluminate coupling agents, titanate coupling agents, etc., all of which can be used in the present invention. In some specific embodiments of the present invention, the coupling agent is silane coupling agent KH550.

[0013] In a further embodiment, the antioxidant is selected from at least one of hindered phenols, phosphites, thio compounds, hindered amines.

[0014] In a further embodiment, the antioxidant is at least one of antioxidant 1010, antioxidant 1076, antioxidant 1098, antioxidant 300, antioxidant 168.

[0015] In a further embodiment, the antioxidant is a mixture of antioxidant 1010 and antioxidant 168 compounded in a mass ratio of 1:1.

[0016] The second aspect of the present invention discloses a preparation method of a polylactic acid composition with both strength and toughness as described in the first aspect of the present invention, comprising the following steps:

[0017] Mix the polylactic acid, polypropylene glycol, triphenyl phosphite, filler, coupling agent and antioxidant thoroughly according to the weight ratio to obtain a uniform mixed material;

[0018] Add the mixed material into a twin-screw extruder, and carry out melt extrusion granulation to obtain the polylactic acid composition.

[0019] For a further solution, the processing temperatures of each zone of the twin-screw extruder are as follows: the temperature of zone 1 is 120 - 160 °C, the temperature of zone 2 is 170 - 190 °C, the temperature of zone 3 is 180 - 200 °C, the temperature of zone 4 is 190 - 200 °C, and the temperature of the die head is 200 - 210 °C.

[0020] Advantages of the present invention:

[0021] The present invention uses polypropylene glycol and triphenyl phosphite as a compound plasticizer, with a small overall addition amount, which can promote the crystallization of polylactic acid resin. The finally prepared polylactic acid composition not only has excellent elongation at break, but also has high tensile strength. Specific embodiments

[0022] The embodiments of the present invention are described in detail below. The following described embodiments are exemplary and are only used to explain the present invention, and should not be construed as a limitation to the present invention.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the description of the present invention in this specification are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. Additionally, unless otherwise specified, the methods without specific recorded conditions or steps are all conventional methods, and the reagents and materials used can be obtained from commercial channels.

[0024] The raw material information in the examples and comparative examples is specifically as follows:

[0025] Polylactic acid, Total L105 from Thailand, with a melt index of 14 g / 10 min, elongation at break of 2.5%, and tensile strength of 58 MPa.

[0026] Polypropylene glycol, supplied by Mitsui Chemicals (Shandong), with a number average molecular weight of 6000 and a hydroxyl value of 18 mg KOH / g.

[0027] Triphenyl phosphite, supplied by Wuhan Jixin Yibang Biotechnology Co., Ltd.

[0028] Calcium carbonate and talcum powder have a mesh number of 2000, and the supplier is Shanghai Liangjiang Titanium White Chemical Products Co., Ltd.

[0029] The antioxidant is a mixture of antioxidant 1010 and antioxidant 168 compounded in a mass ratio of 1:1, and the supplier is DuPont Company of the United States.

[0030] Example 1

[0031] 1000 parts of polylactic acid, 38 parts of polypropylene glycol, 32 parts of triphenyl phosphite, 310 parts of filler calcium carbonate, 1 part of silane coupling agent KH550 and 3 parts of antioxidant were poured into a high-speed mixer. After mixing evenly, they were added to a twin-screw extruder and granulated after melt extrusion to obtain a polylactic acid composition. Among them, the temperature of the first zone of the twin-screw extruder was 140 °C, the temperature of the second zone was 180 °C, the temperature of the third zone was 190 °C, the temperature of the fourth zone was 200 °C, and the temperature of the die head was 210 °C.

[0032] Example 2

[0033] 1000 parts of polylactic acid, 32 parts of polypropylene glycol, 18 parts of triphenyl phosphite, 150 parts of filler talc powder, 0.5 part of silane coupling agent KH550 and 3 parts of antioxidant were poured into a high-speed mixer. After mixing evenly, they were added to a twin-screw extruder and granulated after melt extrusion to obtain a polylactic acid composition. Among them, the temperature of the first zone of the twin-screw extruder was 140 °C, the temperature of the second zone was 170 °C, the temperature of the third zone was 180 °C, the temperature of the fourth zone was 190 °C, and the temperature of the die head was 200 °C.

[0034] Example 3

[0035] 1000 parts of polylactic acid, 40 parts of polypropylene glycol, 38 parts of triphenyl phosphite, 400 parts of filler talc powder, 1.5 parts of silane coupling agent KH550 and 6 parts of antioxidant were poured into a high-speed mixer. After mixing evenly, they were added to a twin-screw extruder and granulated after melt extrusion to obtain a polylactic acid composition. Among them, the temperature of the first zone of the twin-screw extruder was 130 °C, the temperature of the second zone was 170 °C, the temperature of the third zone was 180 °C, the temperature of the fourth zone was 190 °C, and the temperature of the die head was 200 °C.

[0036] Example 4

[0037] 1000 parts of polylactic acid, 30 parts of polypropylene glycol, 10 parts of triphenyl phosphite, 100 parts of filler calcium carbonate, 0.2 part of silane coupling agent KH550 and 2 parts of antioxidant were poured into a high-speed mixer. After mixing evenly, they were added to a twin-screw extruder and granulated after melt extrusion to obtain a polylactic acid composition. Among them, the temperature of the first zone of the twin-screw extruder was 150 °C, the temperature of the second zone was 180 °C, the temperature of the third zone was 190 °C, the temperature of the fourth zone was 200 °C, and the temperature of the die head was 200 °C.

[0038] Example 5

[0039] 1000 parts of polylactic acid, 35 parts of polypropylene glycol, 25 parts of triphenyl phosphite, 250 parts of filler talc, 0.6 part of silane coupling agent KH550, and 5 parts of antioxidant were poured into a high-speed mixer. After mixing evenly, they were added to a twin-screw extruder, melt-extruded, and pelletized to obtain a polylactic acid composition. Among them, the temperature of the first zone of the twin-screw extruder was 130 °C, the temperature of the second zone was 170 °C, the temperature of the third zone was 180 °C, the temperature of the fourth zone was 190 °C, and the temperature of the die head was 200 °C.

[0040] Comparative Example 1

[0041] This comparative example adopted the same implementation method as in Example 5, with the only difference being that "35 parts of polypropylene glycol and 25 parts of triphenyl phosphite" was replaced with "60 parts of polypropylene glycol". The specific steps are as follows:

[0042] 1000 parts of polylactic acid, 60 parts of polypropylene glycol, 250 parts of filler talc, 0.6 part of silane coupling agent KH550, and 5 parts of antioxidant were poured into a high-speed mixer. After mixing evenly, they were added to a twin-screw extruder, melt-extruded, and pelletized to obtain a polylactic acid composition. Among them, the temperature of the first zone of the twin-screw extruder was 130 °C, the temperature of the second zone was 170 °C, the temperature of the third zone was 180 °C, the temperature of the fourth zone was 190 °C, and the temperature of the die head was 200 °C.

[0043] Comparative Example 2

[0044] This comparative example adopted the same implementation method as in Example 5, with the only difference being that "35 parts of polypropylene glycol and 25 parts of triphenyl phosphite" was replaced with "60 parts of triphenyl phosphite". The specific steps are as follows:

[0045] 1000 parts of polylactic acid, 60 parts of triphenyl phosphite, 250 parts of filler talc, 0.6 part of silane coupling agent KH550, and 5 parts of antioxidant were poured into a high-speed mixer. After mixing evenly, they were added to a twin-screw extruder, melt-extruded, and pelletized to obtain a polylactic acid composition. Among them, the temperature of the first zone of the twin-screw extruder was 130 °C, the temperature of the second zone was 170 °C, the temperature of the third zone was 180 °C, the temperature of the fourth zone was 190 °C, and the temperature of the die head was 200 °C.

[0046] Comparative Example 3

[0047] This comparative example adopted the same implementation method as in Example 5, with the only difference being that "35 parts of polypropylene glycol and 25 parts of triphenyl phosphite" was replaced with "60 parts of diphenyl phthalate". The specific steps are as follows:

[0048] 1000 parts of polylactic acid, 60 parts of diphenyl phthalate, 250 parts of filler talc powder, 0.6 part of silane coupling agent KH550 and 5 parts of antioxidant were poured into a high-speed mixer. After mixing evenly, they were added into a twin-screw extruder, melt-extruded and granulated to obtain a polylactic acid composition. Among them, the temperature of the first zone of the twin-screw extruder was 130 °C, the temperature of the second zone was 170 °C, the temperature of the third zone was 180 °C, the temperature of the fourth zone was 190 °C, and the temperature of the die head was 200 °C.

[0049] Comparative Example 4

[0050] This comparative example adopted the same implementation method as in Example 5, with the only difference being that "35 parts of polypropylene glycol" was replaced by "35 parts of polyethylene glycol". The specific steps are as follows:

[0051] 1000 parts of polylactic acid, 35 parts of polyethylene glycol, 25 parts of triphenyl phosphite, 250 parts of filler talc powder, 0.6 part of silane coupling agent KH550 and 5 parts of antioxidant were poured into a high-speed mixer. After mixing evenly, they were added into a twin-screw extruder, melt-extruded and granulated to obtain a polylactic acid composition. Among them, the temperature of the first zone of the twin-screw extruder was 130 °C, the temperature of the second zone was 170 °C, the temperature of the third zone was 180 °C, the temperature of the fourth zone was 190 °C, and the temperature of the die head was 200 °C.

[0052] Comparative Example 5

[0053] This comparative example adopted the same implementation method as in Example 5, with the only difference being that "25 parts of triphenyl phosphite" was replaced by "25 parts of diphenyl phthalate". The specific steps are as follows:

[0054] 1000 parts of polylactic acid, 35 parts of polypropylene glycol, 25 parts of diphenyl phthalate, 250 parts of filler talc powder, 0.6 part of silane coupling agent KH550 and 5 parts of antioxidant were poured into a high-speed mixer. After mixing evenly, they were added into a twin-screw extruder, melt-extruded and granulated to obtain a polylactic acid composition. Among them, the temperature of the first zone of the twin-screw extruder was 130 °C, the temperature of the second zone was 170 °C, the temperature of the third zone was 180 °C, the temperature of the fourth zone was 190 °C, and the temperature of the die head was 200 °C.

[0055] Performance Test

[0056] The polylactic acid compositions prepared in the examples and comparative examples were subjected to relevant performance tests. Specifically, the tests were carried out according to the ISO standard. The polylactic acid compositions were injection-molded into standard specimens using an injection molding machine. After the specimens were stabilized for 24 h at 23 °C and a relative humidity of 50%, performance tests were carried out. The physical and mechanical performance tests carried out were:

[0057] (1) Tensile strength: The specimens were prepared and tested according to the ISO 527 standard, and the test speed was 50 mm / min;

[0058] (2) Elongation at break: Specimens were prepared and tested in accordance with ISO 527 standard, and the test speed was 50 mm / min.

[0059] The test results are shown in Table 1.

[0060] Table 1 Test Results of the Properties of the Polylactic Acid Composition

[0061] Tensile strength (MPa) Elongation at break (%) Example 1 58.5 86 Example 2 59.1 134 Example 3 56.5 62 Example 4 58.3 219 Example 5 59.8 103 Comparative Example 1 58.2 21 Comparative Example 2 51.6 8 Comparative Example 3 54.7 6 Comparative Example 4 57.1 14 Comparative Example 5 56.4 13

[0062] It can be seen from the test results in Table 1 that in the polylactic acid system, the addition content of the plasticizer generally needs to reach more than 10% to have an obvious plasticizing effect. The test results in the comparative examples show that when the addition content of the plasticizer is low, the normal effect of the plasticizer cannot be fully exerted, and the elongation at break of the polylactic acid compositions in each comparative example is relatively low. However, in this application, a plasticizer composed of a compound of polypropylene glycol and triphenyl phosphite can significantly improve the elongation at break of the polylactic acid composition with a small addition amount, and ensure that the tensile strength of the system is maintained at a high level.

[0063] In summary, it can be seen that a polylactic acid with both strength and toughness is obtained through the polylactic acid formulation system in the present invention, which provides a new idea for the modification of polylactic acid and at the same time expands the application scope of polylactic acid.

[0064] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0065] The above-described embodiments only represent several implementation manners of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the invention patent should be subject to the appended claims.

Claims

1. A polylactic acid composition with both strength and toughness, characterized in that, It is prepared from 1000 parts of polylactic acid, 30 - 40 parts of polypropylene glycol, 10 - 40 parts of triphenyl phosphite, 100 - 500 parts of filler, 0.2 - 2 parts of coupling agent and 1 - 10 parts of antioxidant by weight.

2. The polylactic acid composition having both strength and toughness according to claim 1, wherein The melt index of the polylactic acid under the conditions of 230 °C and 2.16 kg is 10 - 30 g / 10 min.

3. The polylactic acid composition with both strength and toughness according to claim 1, characterized in that, The number-average molecular weight of the polypropylene glycol is 5000 - 8000, and the hydroxyl value is 17 - 20.7 mgKOH / g.

4. The polylactic acid composition with both strength and toughness as described in claim 1, wherein The filler is selected from at least one of talc powder, calcium carbonate, barium sulfate, calcium sulfate, mica powder, wollastonite, diatomaceous earth, carbon black.

5. The polylactic acid composition with both strength and toughness according to claim 1 or 4, characterized in that, The average particle size of the filler is 1000 - 3000 mesh.

6. The polylactic acid composition with both strength and toughness as described in claim 1, wherein The antioxidant is selected from at least one of hindered phenols, phosphites, thio compounds, hindered amines.

7. The polylactic acid composition with both strength and toughness according to claim 6, wherein The antioxidant is at least one of antioxidant 1010, antioxidant 1076, antioxidant 1098, antioxidant 300, antioxidant 168.

8. The polylactic acid composition with both strength and toughness according to claim 7, characterized in that, The antioxidant is a mixture obtained by compounding antioxidant 1010 and antioxidant 168 in a mass ratio of 1:

1.

9. A method for preparing a polylactic acid composition having both strength and toughness as described in any one of claims 1-8, characterized in that, It includes the following steps: Fully mix polylactic acid, polypropylene glycol, triphenyl phosphite, filler, coupling agent and antioxidant according to the weight ratio to obtain a uniform mixed material; Add the mixed material into a twin-screw extruder, and carry out melt extrusion granulation to obtain a polylactic acid composition.

10. The preparation method according to claim 9, characterized in that, The processing temperatures of each zone of the twin-screw extruder are in sequence: the temperature of the first zone is 120 - 160 °C, the temperature of the second zone is 170 - 190 °C, the temperature of the third zone is 180 - 200 °C, the temperature of the fourth zone is 190 - 200 °C, and the temperature of the die head is 200 - 210 °C.