Polylactic acid-based foaming material and preparation method thereof

Abstract

The invention provides a polylactic acid-based foaming material and a preparation method thereof, and relates to the technical field of foaming materials. The polylactic acid-based foaming material comprises the following raw materials in parts by mass: 100 parts of polylactic acid, 20-30 parts of a flame retardant, 3-5 parts of a modified lignin-talcum powder composite material and 3-5 parts of a foaming agent, the flame retardant is prepared from modified ammonium polyphosphate and a triazine charring agent CFA. The polylactic acid-based foaming material provided by the invention has excellent mechanical properties, flame retardance and foaming performance.

Description

Technical Field

[0001] The present invention relates to the technical field of foaming materials, and in particular to a polylactic acid-based foaming material and a preparation method thereof. Background Art

[0002] Polylactic acid (PLA) is a biodegradable material extracted from plant materials such as sugar cane, potatoes, and corn starch. It has the advantages of easy processing, high transparency, and environmentally friendly degradation. In recent years, polylactic acid-based foam materials have attracted attention due to their light weight, heat insulation, and cushioning properties, but their flame retardant properties still need to be further improved. By adding flame retardants, optimizing foaming processes, and developing new flame retardant systems, the application potential of polylactic acid-based foam materials in the field of flame retardancy has gradually emerged, providing a new direction for the sustainable development of green and environmentally friendly materials. Summary of the invention

[0003] Based on the technical problems existing in the background technology, the present invention proposes a polylactic acid-based foaming material and a preparation method thereof.

[0004] The present invention provides a polylactic acid-based foaming material, comprising the following raw materials in parts by weight: 100 parts of polylactic acid, 20-30 parts of a flame retardant, 3-5 parts of a modified lignin-talcum powder composite material, and 3-5 parts of a foaming agent; the flame retardant comprises modified ammonium polyphosphate and a triazine carbonizing agent CFA.

[0005] Preferably, the mass ratio of modified ammonium polyphosphate and triazine carbonizing agent CFA in the flame retardant is (1-3): (1-2).

[0006] More preferably, the mass ratio of modified ammonium polyphosphate to triazine carbonizing agent CFA in the flame retardant is (1-2):1.

[0007] Preferably, the preparation method of the modified ammonium polyphosphate comprises the following steps: mixing ammonium polyphosphate and magnesium hydroxide and ball-milling them, uniformly dispersing them with methanol and a silane coupling agent by ultrasonication, filtering, washing and drying to obtain the modified ammonium polyphosphate.

[0008] More preferably, the mass ratio of the ammonium polyphosphate, magnesium hydroxide, methanol and silane coupling agent is 10:(0.5-3):40:(1-3).

[0009] More preferably, the ball-to-material ratio of the ball mill is 1:(1-1.1), the rotation speed of the ball mill is 1000-2000 r / min, and the ball milling time is 20-60 min.

[0010] More preferably, the ultrasonic frequency is 40-60 kHz and the ultrasonic time is 5-20 min.

[0011] More preferably, the silane coupling agent is selected from one or more of KH550, KH792, and KH602.

[0012] Preferably, the preparation method of the modified lignin-talc composite material comprises the following steps: mixing lignin with urea solution and then heating to obtain pretreated lignin; and uniformly mixing the pretreated lignin with talc and trimethyl citrate to obtain the modified lignin-talc composite material.

[0013] More preferably, the mass ratio of lignin to urea in the urea solution is 1:(0.5-1).

[0014] More preferably, the concentration of the urea solution is 20-30%.

[0015] More preferably, the heating treatment comprises heating to 80-120°C at a rate of 10-20°C / min for reaction for 0.5-1h, and then heating to 300-350°C at a rate of 5-10°C / min for reaction for 0.5-1h.

[0016] More preferably, the mass ratio of the pretreated lignin to talc and trimethyl citrate is 100:(30-50):(2-4).

[0017] More preferably, the lignin is lignin extracted from biomass; the biomass includes crops and straw.

[0018] More preferably, the method for extracting lignin from biomass comprises the following steps: heating the biomass and acidified tetrahydrofurfuryl alcohol to obtain a mixture; filtering the mixture to obtain a filtrate, adding water to the filtrate, filtering, and drying.

[0019] More preferably, the mass volume ratio of the biomass to the acidified tetrahydrofurfuryl alcohol is 1:(5-15).

[0020] More preferably, the acidified tetrahydrofurfuryl alcohol is obtained by acidifying tetrahydrofurfuryl alcohol with an acidic substance; the acidic substance is selected from one or more of hydrochloric acid, sulfuric acid and acetic acid.

[0021] More preferably, the heating treatment comprises reacting at 80-140° C. for 1-2 hours.

[0022] The present invention also provides a method for preparing a polylactic acid-based foam material, comprising the following steps: S1, after kneading polylactic acid, flame retardant, and modified lignin-talc composite material evenly, adding foaming agent and kneading evenly to obtain a mixture; S2, hot-pressing and foaming the mixture, releasing the pressure, and cooling.

[0023] Preferably, in S1, the banburying temperature is 160-190°C.

[0024] Preferably, in S2, the temperature of hot pressing foaming is 190-210° C., the pressure is 10-25 MPa, and the holding time is 2-8 min.

[0025] Preferably, in S2, after the pressure is released, heat treatment is further performed, the heat treatment temperature is 90° C.-150° C., and the heat treatment time is 10-30 min.

[0026] The beneficial effects of the present invention are: The polylactic acid, flame retardant, modified lignin-talc composite material and foaming agent in the polylactic acid-based foaming material provided by the present invention work synergistically, so that the obtained lactic acid-based foaming material has excellent flame retardant properties, mechanical properties and foaming effect. Among them, the synergistic effect of the flame retardant and the modified lignin-talc composite material helps to further improve the flame retardant effect of the polylactic acid-based foaming material.

[0027] The modified lignin-talc composite material contains a variety of functional groups, such as methoxy, alcohol hydroxyl, phenolic hydroxyl, benzene, aldehyde, carbonyl, etc., which provide abundant active sites for further chemical modification, which is beneficial to improve its flame retardant properties. Lignin has a high carbon content and a multi-hydroxy structure, thus having excellent carbon-forming properties. The modified lignin-talc composite material and the flame retardant work synergistically to form a porous foam char layer on the surface of the material during the combustion process, making it difficult for heat to penetrate the condensed phase, preventing oxygen from entering the combustion area, and preventing the gaseous or liquid products generated by degradation from overflowing the surface of the material, thereby achieving a flame retardant effect. DETAILED DESCRIPTION

[0028] The technical solution of the present invention is described in detail through specific embodiments.

[0029] Unless otherwise specified, the materials, reagents, etc. used in the following examples and comparative examples can be obtained from commercial sources. Example 1

[0030] A polylactic acid-based foaming material comprises the following raw materials in parts by mass: 100 parts of polylactic acid, 26 parts of a flame retardant, 4 parts of a modified lignin-talcum powder composite material, and 4 parts of a foaming agent; the flame retardant comprises modified ammonium polyphosphate and a triazine carbonizing agent CFA in a mass ratio of 2:1.

[0031] The preparation method of modified ammonium polyphosphate comprises the following steps: Ammonium polyphosphate and magnesium hydroxide were mixed and ball-milled for 30 minutes to obtain a mixture, the ball-to-material ratio was 1:1.1, the rotation speed of the ball mill was 2000 r / min, the mixture was treated with methanol and KH550 silane coupling agent at a frequency of 60 kHz and ultrasound for 15 minutes, filtered, washed, and dried to obtain the product; the mass ratio of ammonium polyphosphate, magnesium hydroxide, methanol, and KH550 silane coupling agent was 10:2:40:1.5.

[0032] The preparation method of the modified lignin-talc composite material comprises the following steps: After mixing lignin with 20% urea solution, the temperature was raised to 110°C at a rate of 15°C / min for reaction for 1 hour, and then the temperature was raised to 320°C at a rate of 5°C / min for reaction for 0.5 hour to obtain pretreated lignin; the pretreated lignin was evenly mixed with talcum powder and trimethyl citrate in a mass ratio of 100:40:3 to obtain; the mass ratio of urea in lignin and urea solution was 1:0.5.

[0033] The lignin is lignin extracted from corn stalks. The method for extracting lignin from corn stalks comprises the following steps: mixing corn stalks with acidified tetrahydrofurfuryl alcohol in a mass volume ratio of 1:10, and reacting at 120°C for 1.5 hours to obtain a mixture; filtering the mixture to obtain a filtrate, adding 5 times the volume of water to the filtrate, filtering, and drying to obtain the acidified tetrahydrofurfuryl alcohol. The acidified tetrahydrofurfuryl alcohol is obtained by acidifying tetrahydrofurfuryl alcohol with hydrochloric acid.

[0034] A method for preparing a polylactic acid-based foam material comprises the following steps: S1. After the polylactic acid, flame retardant and modified lignin-talc composite material are uniformly kneaded, a foaming agent is added and uniformly kneaded to obtain a mixture; the kneading temperature is 175° C.; S2, the mixture is maintained at 200°C, 15MPa, and pressure for 5 minutes, then pressure is released, heat-treated at 110°C for 20 minutes, and cooled to obtain the mixture. Heat treatment helps to improve the crystal network of the polylactic acid-based foaming material and improve the heat resistance of the polylactic acid-based foaming material. Example 2

[0035] A polylactic acid-based foaming material comprises the following raw materials in parts by mass: 100 parts of polylactic acid, 26 parts of a flame retardant, 4 parts of a modified lignin-talcum powder composite material, and 4 parts of a foaming agent; the flame retardant comprises modified ammonium polyphosphate and a triazine carbonizing agent CFA in a mass ratio of 1:1.

[0036] The rest is the same as Example 1. Example 3

[0037] A polylactic acid-based foaming material comprises the following raw materials in parts by mass: 100 parts of polylactic acid, 26 parts of a flame retardant, 4 parts of a modified lignin-talcum powder composite material, and 4 parts of a foaming agent; the flame retardant comprises modified ammonium polyphosphate and a triazine carbonizing agent CFA in a mass ratio of 1:2.

[0038] The rest is the same as Example 1.

[0039] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that the modified lignin-talc composite material in Example 1 is replaced by a lignin-talc mixture.

[0040] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the modified ammonium polyphosphate in Example 1 is replaced by untreated ammonium polyphosphate.

[0041] The above polylactic acid-based foamed material was tested for its tensile strength (GB / T1040.2-2022), impact strength (GB / T1843-2008), limiting oxygen index test (LOI) (GB / T2406.2-2009), vertical burning test (UL-94), average cell diameter (GB / T12811-1991), and cell density. The test results are shown in Table 1.

[0042] Table 1

[0043] It can be seen from the data in Table 1 that the polylactic acid-based foamed material prepared in Examples 1-2 of the present invention has excellent mechanical properties, flame retardant properties and foaming properties by controlling the raw materials and proportions of the materials. It can be seen from the data of Comparative Example 1 and Example 1 that the vertical combustion grade of the polylactic acid-based foamed material prepared by replacing the modified lignin-talc composite material with a lignin-talc mixture is V-1, and the mechanical properties and foaming effect are also reduced. It can be seen from the data of Comparative Example 2 and Example 1 that the flame retardant properties of the unmodified ammonium polyphosphate are significantly reduced. The raw materials of the polylactic acid-based foaming material of the present invention work synergistically to jointly improve the mechanical properties, flame retardant properties and foaming properties of the material. On the one hand, the modification of ammonium polyphosphate helps to improve the dispersion uniformity and further improve the flame retardant properties, and the magnesium hydroxide in the modified ammonium polyphosphate and the lignin in the modified lignin-talc composite material can further play a synergistic role; on the other hand, the modified lignin-talc composite material is used to improve the charring performance and foaming performance of the polylactic acid-based foaming material. The addition of the modified lignin-talc composite material helps to reduce the pore diameter, increase the pore density, and improve the foaming effect.

[0044] In summary, the polylactic acid-based foam material provided by the present invention has excellent mechanical properties, flame retardant properties and foaming properties.

[0045] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A polylactic acid-based foaming material, characterized in that: The invention comprises the following raw materials in parts by weight: 100 parts of polylactic acid, 20-30 parts of flame retardant, 3-5 parts of modified lignin-talcum powder composite material, and 3-5 parts of foaming agent; the flame retardant comprises modified ammonium polyphosphate and triazine carbonizing agent CFA.

2. The polylactic acid-based foam material according to claim 1, characterized in that: The preparation method of the modified ammonium polyphosphate comprises the following steps: mixing ammonium polyphosphate and magnesium hydroxide, ball-milling, uniformly dispersing with methanol and a silane coupling agent by ultrasonication, filtering, washing and drying to obtain the modified ammonium polyphosphate.

3. The polylactic acid-based foam material according to claim 2, characterized in that: The mass ratio of the ammonium polyphosphate, magnesium hydroxide, methanol and silane coupling agent is 10:(0.5-3):40:(1-3); the silane coupling agent is selected from one or more of KH550, KH792 and KH602.

4. The polylactic acid-based foam material according to claim 1, characterized in that: The preparation method of the modified lignin-talcum powder composite material comprises the following steps: mixing lignin with urea solution and then heating to obtain pretreated lignin; and uniformly mixing the pretreated lignin with talcum powder and trimethyl citrate to obtain the modified lignin-talcum powder composite material.

5. The polylactic acid-based foam material according to claim 4, characterized in that: The mass ratio of lignin to urea in the urea solution is 1:(0.5-1); the concentration of the urea solution is 20-30%; the mass ratio of pretreated lignin to talcum powder and trimethyl citrate is 100:(30-50):(2-4).

6. The polylactic acid-based foam material according to claim 4, characterized in that: The heating treatment includes heating to 80-120°C at a rate of 10-20°C / min and reacting for 0.5-1h, and then heating to 300-350°C at a rate of 5-10°C / min and reacting for 0.5-1h.

7. The polylactic acid-based foam material according to claim 1, characterized in that: The mass ratio of modified ammonium polyphosphate and triazine carbonizing agent CFA in the flame retardant is (1-3): (1-2).

8. A method for preparing the polylactic acid-based foamed material according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1, after kneading polylactic acid, flame retardant, and modified lignin-talc composite material evenly, adding foaming agent and kneading evenly to obtain a mixture; S2, hot-pressing and foaming the mixture, releasing the pressure, and cooling.

9. The preparation method according to claim 8, characterized in that: In the S2, after the pressure is released, heat treatment is further performed, the temperature of the heat treatment is 90° C.-150° C., and the heat treatment time is 10-30 minutes.

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