Modified high-molecular-weight polylactic acid with efficient flame retardance and toughening and preparation method of modified high-molecular-weight polylactic acid

Abstract

The invention relates to the technical field of modified polylactic acid, in particular to modified high-molecular-weight polylactic acid with efficient flame retardance and toughening and a preparation method of the modified high-molecular-weight polylactic acid. In addition, an ethylene-vinyl acetate copolymer is used as an inner core, caprolactone and octadecyl methacrylate are used as raw materials, a cross-linking agent is added, and under the action of a catalyst, the modified high-molecular-weight polylactic acid with efficient flame retardance and toughening is prepared. The hyperbranched polycaprolactone-octadecyl methacrylate is used as a shell, the hyperbranched polycaprolactone and the octadecyl methacrylate are jointly added into the high-molecular-weight polylactic acid to be blended, the hyperbranched polycaprolactone, the octadecyl methacrylate and the toughening agent B are fused to form an interpenetrating network structure under the high-temperature condition, the toughening agent B contains a large number of cavities, and when the toughening agent B is impacted and stretched, the toughening agent B has a good mechanical property. Part of energy can be quickly absorbed, so that the toughness of the blend is improved. The organic silicon A flame retardant provided by the invention has a very remarkable flame retardant effect on a polylactic acid material, and the polylactic acid material can pass the UL-94V-0 level and the oxygen index can reach 30% or above only by the addition amount of 5wt%.

Description

Technical Field

[0001] This invention relates to the field of modified polylactic acid technology, specifically to a modified high molecular weight polylactic acid with high efficiency in flame retardancy and toughening, and its preparation method. Background Technology

[0002] Polylactic acid (PLA) has a glass transition temperature (Tg) of approximately 55℃ and a melting point (Tm) of approximately 180℃. It exhibits good biocompatibility and is completely biodegradable, with the final degradation products being carbon dioxide (CO2) and water. Therefore, it is non-toxic and does not pollute the environment after use, making it a green plastic. Furthermore, PLA has high tensile strength, high compressive modulus, and good transparency; it is easy to process and can be processed like synthetic polymers such as PP, PS, and PET using general-purpose processing equipment through extrusion, injection molding, blow molding, and thermoforming to produce films, sheets, bottles, and various thermoformed and injection-molded products. In short, PLA is not only environmentally friendly and widely used, but its source also reduces the consumption of non-renewable petroleum resources, earning it the reputation of a "green plastic" and attracting widespread interest.

[0003] However, PLA's main drawbacks are its hardness and brittleness, poor impact resistance, and poor hydrophilicity. This greatly limits its applications, especially in the packaging field. Therefore, the modification of PLA has become a research hotspot, particularly in toughening modification. With the increasing maturity of PLA production processes, many defects have been exposed, such as poor heat resistance and flammability. Patent document CN1662603A discloses a polylactic acid polymer composition, its molded articles, and films. By synthesizing a plasticizer containing polyether and / or polyester segments and adding it to polylactic acid, a polylactic acid polymer composition with sufficient flexibility is formed. US Patent document US2005 / 0159583A1 discloses a polylactic acid toughening modifier and its composite. This method first synthesizes an AB-type block copolymer, then adds this block copolymer to PLA to achieve the purpose of toughening PLA, and obtains the best toughening effect by changing the types and molecular weights of A and B. While these methods can minimize the volatilization, leaching, and loss of plasticizers / toughening agents, as well as whitening and turbidity upon heating, the cost of the plasticizers required for synthesis is relatively high. This can easily increase the cost of the final polylactic acid polymer composition, hindering its market competitiveness. Summary of the Invention

[0004] To overcome the shortcomings and deficiencies of existing technologies, one of the objectives of this invention is to provide a method for preparing modified high molecular weight polylactic acid with high efficiency in flame retardancy and toughening. The method involves a self-made organosilicon A flame retardant. Additionally, using ethylene-vinyl acetate copolymer as the core, caprolactone and octadecyl methacrylate as raw materials, and adding a crosslinking agent, a ring-opening-condensation polymerization method is used to synthesize a core-shell structure B toughening agent with hyperbranched polycaprolactone-octadecyl methacrylate as the outer shell under the action of a catalyst. Both are then blended with high molecular weight polylactic acid. Under high temperature conditions, the three components melt to form an interpenetrating network structure. The B toughening agent itself contains a large number of cavities, which can quickly absorb some energy when subjected to impact and stretching, thereby improving the toughness of the blend. The flame retardant provided by this invention exhibits a significant flame-retardant effect on polylactic acid (PLA) materials. Only 5 wt% of the additive is required to achieve a UL-94V-0 rating with an oxygen index exceeding 30%. This avoids the damage to the substrate performance caused by excessive additives and significantly reduces costs. It also greatly improves the toughness of PLA, solving the technical problem of poor mechanical properties in blended materials caused by additive flame retardants in existing technologies. The preparation method is simple to operate, easy to control, highly efficient, and low in cost, making it suitable for large-scale production.

[0005] The second objective of this invention is to provide a modified high molecular weight polylactic acid with high efficiency in flame retardancy and toughening.

[0006] One of the objectives of this invention is achieved through the following technical solution: a method for preparing modified high molecular weight polylactic acid with high efficiency flame retardancy and toughening, comprising the following steps: (S1) Mix siloxane A, alkoxysilane and solvent, add acid catalyst A, and carry out hydrolysis reaction for 4-12 hours under certain temperature conditions. Then add siloxane B and continue the reaction for 1 hour. Then add an appropriate amount of base neutralizer to neutralize the product to neutralize it. Wash the product with water, separate the layers, filter to remove water and solvent, and obtain organosilicon A flame retardant. (S2) Mix ethylene-vinyl acetate copolymer, water, caprolactone, octadecyl methacrylate and crosslinking agent, add catalyst B, react at 80-90℃ under nitrogen atmosphere for 2-6h, then react at 140-160℃ under vacuum for 3-5h, then heat to 170-180℃ and continue to react for 5-7h to form a transparent viscous liquid, then add precipitant methanol, take the light yellow precipitate and wash it repeatedly with chloroform to remove monomers, dry it under vacuum at 60-80℃ to obtain toughening agent B; (S3) Add organosilicon flame retardant A and toughening agent B to high molecular weight polylactic acid for physical and mechanical blending to obtain modified high molecular weight polylactic acid with high efficiency flame retardancy and toughening.

[0007] Preferably, in step (S1), the weight parts of each raw material are: 80-125 parts of siloxane A, 3-30 parts of alkoxysilane, 80-130 parts of solvent, 0.35-6 parts of acid catalyst A and 0-5 parts of siloxane B.

[0008] Preferably, in step (S1), the siloxane A is at least one of octaphenylcyclotetrasiloxane, 1,1,3,3-tetramethyldisiloxane, hexamethyldisiloxane, and dimethylsiloxane; and the siloxane B is at least one of octaphenylcyclotetrasiloxane, 1,1,3,3-tetramethyldisiloxane, hexamethyldisiloxane, and dimethylsiloxane.

[0009] Preferably, in step (S1), the alkoxysilane is at least one of diisopropoxydimethylsilane, phenyltrimethoxysilane, phenyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, methyltrimethoxysilane, and methyltriethoxysilane.

[0010] Preferably, in step (S1), the solvent is at least one of toluene, xylene, cyclohexane, and acetone; and the acid catalyst A is at least one of concentrated sulfuric acid, trifluoromethanesulfonic acid, trifluoroacetic acid, formic acid, acetic acid, and concentrated hydrochloric acid.

[0011] Preferably, in step (S1), the temperature of the hydrolysis reaction is 15℃-115℃; the alkali neutralizing agent is at least one of sodium bicarbonate, sodium carbonate, sodium hydroxide, potassium hydroxide, ammonia, and calcium carbonate.

[0012] Preferably, in step (S2), the weight parts of each raw material are: 15-28 parts ethylene-vinyl acetate copolymer, 35-47 parts water, 80-110 parts caprolactone, 20-50 parts octadecyl methacrylate, 5-8 parts crosslinking agent and 0.2-0.9 parts catalyst B.

[0013] Preferably, in step (S2), the vinyl acetate content in the ethylene-vinyl acetate copolymer is less than 30%; the crosslinking agent is methyl propylene glycol and / or diethylpentane glycol; and the catalyst B is at least one of dibutyltin dilaurate, stannous octoate, bismuth laurate, bismuth neocaprate, bismuth isocyanate, bismuth neocaprate, and bismuth naphthenate.

[0014] Preferably, in step (S3), the weight ratio of organosilicon A flame retardant, B toughening agent and high molecular weight polylactic acid is 1-5:1-10:75-95; the weight average molecular weight of high molecular weight polylactic acid is 100,000-750,000. High molecular weight polylactic acid provides a good mechanical basis for the blend, which greatly increases the overall mechanical strength.

[0015] The second objective of this invention is achieved through the following technical solution: a modified high molecular weight polylactic acid with high efficiency flame retardancy and toughening is prepared by the above-mentioned preparation method of modified high molecular weight polylactic acid with high efficiency flame retardancy and toughening.

[0016] The beneficial effects of this invention are as follows: The preparation method of the modified high molecular weight polylactic acid with high efficiency flame retardancy and toughening of this invention involves the organosilicon A flame retardant generating a silicon-containing inorganic protective layer through high-temperature pyrolysis. This layer simultaneously achieves flame retardancy through synergistic char formation and smoke suppression. The pyrolysis at high temperature generates an inorganic network structure containing Si-O bonds. This protective layer covers the material surface, forming a physical barrier that blocks the exchange of oxygen and combustible gases and inhibits further thermal decomposition of the material. During combustion, it promotes carbonization of the material surface, forming a dense char layer. This char layer not only insulates against heat but also adsorbs free radicals generated during combustion, delaying the combustion chain reaction. Simultaneously, the introduction of silicon-oxygen bonds improves the char layer structure, preventing cracking or peeling and enhancing flame retardancy durability. Furthermore, the blending of organosilicon A flame retardant with high molecular weight polylactic acid, with its Si-O-Si chains and phenyl, methyl, and other groups, improves compatibility with polylactic acid, reduces phase separation, promotes uniform stress distribution, and to a certain extent enhances the toughness of the material.

[0017] Furthermore, in the core-shell structure of toughening agent B, the vinyl acetate content in the core ethylene-vinyl acetate copolymer is less than 30%, giving it excellent flexibility and making it easy to integrate with plastic products. In the outer shell, the long-chain hyperbranched polycaprolactone-octadecyl methacrylate blended with high-molecular-weight polylactic acid (PLA) results in strong molecular chain entanglement and hydrogen bonding between the flexible polycaprolactone-octadecyl methacrylate molecular chains and the rigid PLA molecular chains, forming a cross-linked structure. Because the hyperbranched outer shell itself contains numerous cavities, it can quickly absorb some energy under impact and tension, further enhancing the toughness of the PLA. The outer shell contains a large number of hydroxyl groups at the ends of hyperbranched polycaprolactone-octadecyl methacrylate formed by adding a crosslinking agent. These hydroxyl groups can form strong hydrogen bonds with the carboxyl and hydroxyl groups at the ends of polylactic acid, forming a three-dimensional network structure. This enhances the interaction and compatibility between the blended polymer polylactic acid and the organosilicon A flame retardant, improves the dispersibility of the organosilicon A flame retardant in polylactic acid, and better promotes the formation of an inorganic protective layer containing Si-O bonds at high temperatures. This blocks oxygen and inhibits PLA decomposition, resulting in a highly efficient flame retardant effect. At the same time, it promotes the formation of a char layer to reduce the release of smoke and toxic gases. Detailed Implementation

[0018] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to embodiments. The content mentioned in the embodiments is not intended to limit the present invention.

[0019] Example 1 A method for preparing modified high molecular weight polylactic acid with high flame retardancy and toughening properties includes the following steps: (S1) Mix 95 parts of siloxane A, 22.5 parts of alkoxysilane and 125 parts of solvent by weight, add 3.45 parts of acid catalyst A, and carry out hydrolysis reaction at 70°C for 6 hours. Then add 3 parts of siloxane B and continue the reaction for 1 hour. Then add an appropriate amount of alkali neutralizer to neutralize the product to neutral. Wash the product with water, separate the layers, filter to remove water and solvent, and obtain organosilicon A flame retardant. (S2) Mix 27.95 parts by weight of ethylene-vinyl acetate copolymer, 38.49 parts by weight of water, 108.48 parts by weight of caprolactone, 42.37 parts by weight of octadecyl methacrylate and 7.86 parts by weight of crosslinking agent, add 0.71 parts by weight of catalyst B, react at 85°C under nitrogen atmosphere for 4 hours, then react at 150°C under vacuum for 4 hours, and continue to react at 175°C for 6 hours to form a transparent viscous liquid. Then add methanol as precipitant, take the pale yellow precipitate and wash it repeatedly with chloroform to remove monomers, and dry it under vacuum at 80°C to obtain toughening agent B. (S3) Add organosilicon flame retardant A and toughening agent B together to high molecular weight polylactic acid and melt blend in a torque rheometer at 180℃ and 60 r / min to obtain modified high molecular weight polylactic acid with high efficiency flame retardancy and toughening.

[0020] In step (S1), siloxane A is octaphenylcyclotetrasiloxane; siloxane B is 1,1,3,3-tetramethyldisiloxane.

[0021] In step (S1), the alkoxysilane is phenyltrimethoxysilane.

[0022] In step (S1), the solvent is toluene; the acid catalyst A is concentrated sulfuric acid.

[0023] The alkali neutralizing agent is sodium bicarbonate.

[0024] In step (S2), the vinyl acetate content in the ethylene-vinyl acetate copolymer is 25 wt%; the crosslinking agent is methyl propylene glycol; and the catalyst B is dibutyltin dilaurate.

[0025] In step (S3), the weight ratio of organosilicon A flame retardant, B toughening agent and high molecular weight polylactic acid is 5:7:88; the weight average molecular weight of high molecular weight polylactic acid is 150,000.

[0026] Example 2 A method for preparing modified high molecular weight polylactic acid with high flame retardancy and toughening properties includes the following steps: (S1) Mix 95 parts of siloxane A, 22.5g parts of alkoxysilane and 113.6g parts of solvent by weight, add 4.5 parts of acid catalyst A, and carry out hydrolysis reaction at 60℃ for 5h. Then add 3 parts of siloxane B and continue the reaction for 1h. Then add an appropriate amount of alkali neutralizer to neutralize the product to neutral. Wash the product with water, separate the layers, filter to remove water and solvent, and obtain organosilicon A flame retardant. (S2) Mix 18.76 parts by weight of ethylene-vinyl acetate copolymer, 40 parts of water, 108.45 parts of caprolactone, 43.5 parts of octadecyl methacrylate and 8 parts of crosslinking agent, add 0.68 parts of catalyst B, react at 90°C under nitrogen atmosphere for 6 hours, then react at 150°C under vacuum for 4 hours, and continue to react at 175°C for 6 hours to form a transparent viscous liquid. Then add methanol as precipitant, take the light yellow precipitate and wash it repeatedly with chloroform to remove the monomer, and dry it under vacuum at 80°C to obtain toughening agent B. (S3) Add organosilicon flame retardant A and toughening agent B together to high molecular weight polylactic acid and melt blend in a torque rheometer at 180℃ and 60 r / min to obtain modified high molecular weight polylactic acid with high efficiency flame retardancy and toughening.

[0027] In step (S1), siloxane A is octaphenylcyclotetrasiloxane; siloxane B is 1,1,3,3-tetramethyldisiloxane.

[0028] In step (S1), the alkoxysilane is phenyltriethoxysilane.

[0029] In step (S1), the solvent is cyclohexane; the acid catalyst A is concentrated hydrochloric acid.

[0030] The alkali neutralizing agent is sodium bicarbonate.

[0031] In step (S2), the vinyl acetate content in the ethylene-vinyl acetate copolymer is 25 wt%; the crosslinking agent is diethylpentanediol; and the catalyst B is dibutyltin dilaurate.

[0032] In step (S3), the weight ratio of organosilicon A flame retardant, B toughening agent and high molecular weight polylactic acid is 5:7:88; the weight average molecular weight of high molecular weight polylactic acid is 150,000.

[0033] Example 3 A method for preparing modified high molecular weight polylactic acid with high flame retardancy and toughening properties includes the following steps: (S1) Mix 100 parts by weight of siloxane A, 3.5 parts by weight of alkoxysilane and 86.6 parts by weight of solvent, add 0.5 parts by weight of acid catalyst A, and carry out hydrolysis reaction at 25°C for 12 hours. Then add an appropriate amount of alkali neutralizer to neutralize the product to neutralize it. Wash the product with water, separate the layers, filter to remove water and solvent, and obtain organosilicon A flame retardant. (S2) Mix 15 parts by weight of ethylene-vinyl acetate copolymer, 35 parts of water, 80 parts of caprolactone, 50 parts of octadecyl methacrylate and 5 parts of crosslinking agent, add 0.57 parts of catalyst B, react at 85°C under nitrogen atmosphere for 2 hours, then react at 150°C under vacuum for 4 hours, and continue to react at 175°C for 6 hours to form a transparent viscous liquid. Then add methanol as precipitant, take the pale yellow precipitate and wash it repeatedly with chloroform to remove the monomer, and dry it under vacuum at 80°C to obtain toughening agent B. (S3) Add organosilicon flame retardant A and toughening agent B together to high molecular weight polylactic acid and melt blend in a torque rheometer at 180℃ and 60 r / min to obtain modified high molecular weight polylactic acid with high efficiency flame retardancy and toughening.

[0034] In step (S1), the siloxane A is dimethylsiloxane.

[0035] In step (S1), the alkoxysilane is diisopropoxydimethylsilane.

[0036] In step (S1), the solvent is xylene; the acid catalyst A is trifluoromethanesulfonic acid.

[0037] The alkali neutralizing agent is sodium bicarbonate.

[0038] In step (S2), the vinyl acetate content in the ethylene-vinyl acetate copolymer is 25 wt%; the crosslinking agent is methyl propylene glycol; and the catalyst B is dibutyltin dilaurate.

[0039] In step (S3), the weight ratio of organosilicon A flame retardant, B toughening agent and high molecular weight polylactic acid is 5:7:88; the weight average molecular weight of high molecular weight polylactic acid is 150,000.

[0040] Comparative Example 1 The difference between this comparative example and Example 1 is as follows: A method for preparing modified high molecular weight polylactic acid includes the following steps: (S1) Mix 95 parts of siloxane A, 22.5 parts of alkoxysilane and 125 parts of solvent by weight, add 3.45 parts of acid catalyst A, and carry out hydrolysis reaction at 70°C for 6 hours. Then add 3 parts of siloxane B and continue the reaction for 1 hour. Then add an appropriate amount of alkali neutralizer to neutralize the product to neutral. Wash the product with water, separate the layers, filter to remove water and solvent, and obtain organosilicon A flame retardant. (S2) Add organosilicon A flame retardant to high molecular weight polylactic acid and melt blend it in a torque rheometer at 180℃ and 60 r / min to obtain modified high molecular weight polylactic acid.

[0041] In step (S1), siloxane A is octaphenylcyclotetrasiloxane; siloxane B is 1,1,3,3-tetramethyldisiloxane.

[0042] In step (S1), the alkoxysilane is phenyltrimethoxysilane.

[0043] In step (S1), the solvent is toluene; the acid catalyst A is concentrated sulfuric acid.

[0044] The alkali neutralizing agent is sodium bicarbonate.

[0045] In step (S2), the weight ratio of organosilicon A flame retardant to high molecular weight polylactic acid is 4:96; the weight average molecular weight of high molecular weight polylactic acid is 150,000.

[0046] Comparative Example 2 The difference between this comparative example and Example 3 is as follows: A method for preparing modified high molecular weight polylactic acid includes the following steps: (S1) Mix 15 parts by weight of ethylene-vinyl acetate copolymer, 35 parts of water, 80 parts of caprolactone, 50 parts of octadecyl methacrylate and 5 parts of crosslinking agent, add 0.57 parts of catalyst B, react at 85°C under nitrogen atmosphere for 2 hours, then react at 150°C under vacuum for 4 hours, and continue to react at 175°C for 6 hours to form a transparent viscous liquid. Then add methanol as precipitant, take the pale yellow precipitate and wash it repeatedly with chloroform to remove the monomer, and dry it under vacuum at 80°C to obtain toughening agent B. (S2) Add toughening agent B to high molecular weight polylactic acid and melt blend it in a torque rheometer at 180℃ and 60 r / min to obtain modified high molecular weight polylactic acid.

[0047] In step (S1), the vinyl acetate content in the ethylene-vinyl acetate copolymer is 25 wt%; the crosslinking agent is methyl propylene glycol; and the catalyst B is dibutyltin dilaurate.

[0048] In step (S2), the weight ratio of toughening agent B to high molecular weight polylactic acid is 6:94; the weight average molecular weight of high molecular weight polylactic acid is 150,000.

[0049] Comparative Example 3 The difference between this comparative example and Example 1 is as follows: A method for preparing modified high molecular weight polylactic acid includes the following steps: (S1) Mix 95 parts of siloxane A, 22.5 parts of alkoxysilane and 125 parts of solvent by weight, add 3.45 parts of acid catalyst A, and carry out hydrolysis reaction at 70°C for 6 hours. Then add 3 parts of siloxane B and continue the reaction for 1 hour. Then add an appropriate amount of alkali neutralizer to neutralize the product to neutral. Wash the product with water, separate the layers, filter to remove water and solvent, and obtain organosilicon A flame retardant. (S2) The organosilicon A flame retardant and toughening agent EVA were added to high molecular weight polylactic acid and melt-blended in a torque rheometer at 180℃ and 60 r / min to obtain modified high molecular weight polylactic acid.

[0050] In step (S1), siloxane A is octaphenylcyclotetrasiloxane; siloxane B is 1,1,3,3-tetramethyldisiloxane.

[0051] In step (S1), the alkoxysilane is phenyltrimethoxysilane.

[0052] In step (S1), the solvent is toluene; the acid catalyst A is concentrated sulfuric acid.

[0053] The alkali neutralizing agent is sodium bicarbonate.

[0054] In step (S2), the vinyl acetate content in the toughening agent EVA is 25 wt%.

[0055] In step (S2), the weight ratio of organosilicon A flame retardant, toughening agent EVA and high molecular weight polylactic acid is 5:7:88; the weight average molecular weight of high molecular weight polylactic acid is 150,000.

[0056] Comparative Example 4 The difference between this comparative example and Example 1 is as follows: A method for preparing modified high molecular weight polylactic acid includes the following steps: (S1) Mix 27.95 parts by weight of ethylene-vinyl acetate copolymer, 38.49 parts by weight of water, 108.48 parts by weight of caprolactone, 42.37 parts by weight of octadecyl methacrylate and 7.86 parts by weight of crosslinking agent, add 0.71 parts by weight of catalyst B, react at 85°C under nitrogen atmosphere for 4 hours, then react at 150°C under vacuum for 4 hours, and continue to react at 175°C for 6 hours to form a transparent viscous liquid. Then add methanol as precipitant, take the pale yellow precipitate and wash it repeatedly with chloroform to remove monomers, and dry it under vacuum at 80°C to obtain toughening agent B. (S2) The organosilicon flame retardant and toughening agent B were added to the high molecular weight polylactic acid and melt-blended in a torque rheometer at 180°C and 60 r / min to obtain modified high molecular weight polylactic acid.

[0057] In step (S1), the vinyl acetate content in the ethylene-vinyl acetate copolymer is 25 wt%; the crosslinking agent is methyl propylene glycol; and the catalyst B is dibutyltin dilaurate.

[0058] In step (S2), the organosilicon flame retardant is selected from Dow Corning FCA-107.

[0059] In step (S2), the weight ratio of organosilicon flame retardant, B toughening agent and high molecular weight polylactic acid is 5:7:88; the weight average molecular weight of high molecular weight polylactic acid is 150,000.

[0060] Performance testing High molecular weight polylactic acid with a weight-average molecular weight of 150,000 was used as a blank sample.

[0061] Blank samples and modified high molecular weight polylactic acid from Examples 1-3 and Comparative Examples 1-4 were taken and pressed into samples with dimensions of 0.5 mm × 10 cm × 10 cm using a hot press. The temperature of both the upper and lower plates of the hot press was set to 185°C, the pressure was 8 MPa, and the hot pressing was carried out for 6 min. After removal, the samples were cooled to room temperature for 3 min to form tensile specimens of 150 mm × 10 mm × 0.5 mm and impact specimens of 80 mm × 10 mm × 4 mm.

[0062] The test results are shown in Table 1 below:

[0063] As shown in Table 1 above, the present invention uses a blend of special organosilicon A flame retardant, B toughening agent and high molecular weight polylactic acid, which significantly improves the toughness and flame retardancy of high molecular weight polylactic acid.

[0064] The above embodiments are preferred implementations of the present invention. In addition, the present invention can be implemented in other ways. Any obvious substitutions without departing from the concept of the present invention are within the protection scope of the present invention.

Claims

1. A process for the preparation of a modified high molecular weight polylactic acid having high efficiency flame retardant toughening, characterized in that, It comprises the following steps: (S1), mixing siloxane A, alkoxysilane and solvent, adding acid catalyst A, hydrolysis reaction for 4-12h under certain temperature conditions, then adding siloxane B for 1h, then adding appropriate amount of base neutralizer for neutralization reaction to neutral, then washing, layering, filtering to remove water and solvent, obtaining silicone A flame retardant; (S2), mixing ethylene-vinyl acetate copolymer, water, caprolactone, octadecyl methacrylate and crosslinking agent, adding catalyst B, reacting for 2-6h under 80-90℃ and nitrogen atmosphere, then reacting for 3-5h under vacuum condition at 140-160℃, then heating to 170-180℃ for 5-7h, forming transparent viscous liquid, then adding precipitant methanol, taking light yellow precipitate for several times of washing with chloroform to remove monomer, drying under vacuum condition at 60-80℃, obtaining B toughening agent; (S3), adding silicone A flame retardant and B toughening agent into high molecular weight polylactic acid for physical and mechanical blending, obtaining modified high molecular weight polylactic acid with high efficient flame retardant and toughening.

2. The process for the preparation of modified high molecular weight polylactic acid with high efficiency flame retardant and toughening according to claim 1, characterized in that: In the step (S1), the weight part of each raw material is: 80-125 parts of siloxane A, 3-30 parts of alkoxysilane, 80-130 parts of solvent, 0.35-6 parts of acid catalyst A and 0-5 parts of siloxane B.

3. The process for the preparation of modified high molecular weight polylactic acid with high efficiency flame retardant and toughening according to claim 1, characterized in that: In the step (S1), the siloxane A is at least one of octaphenylcyclotetrasiloxane, 1,1,3,3-tetramethyldisiloxane, hexamethyldisiloxane and dimethylsiloxane; the siloxane B is at least one of octaphenylcyclotetrasiloxane, 1,1,3,3-tetramethyldisiloxane, hexamethyldisiloxane and dimethylsiloxane.

4. The process for the preparation of modified high molecular weight polylactic acid with high efficiency flame retardant and toughening according to claim 1, characterized in that: In the step (S1), the alkoxysilane is at least one of diisopropenyldimethylsilane, phenyltrimethoxysilane, phenyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, methyltrimethoxysilane and methyltriethoxysilane.

5. The process for the preparation of modified high molecular weight polylactic acid with high efficiency flame retardant and toughening according to claim 1, characterized in that: In the step (S1), the solvent is at least one of toluene, xylene, cyclohexane and acetone; the acid catalyst A is at least one of concentrated sulfuric acid, triflic acid, trifluoroacetic acid, formic acid, acetic acid and concentrated hydrochloric acid.

6. The process for the preparation of modified high molecular weight polylactic acid with high efficiency flame retardant and toughening according to claim 1, characterized by the fact that: In the step (S1), the temperature of the hydrolysis reaction is 15-115℃; the base neutralizer is at least one of sodium bicarbonate, sodium carbonate, sodium hydroxide, potassium hydroxide, ammonia and calcium carbonate.

7. The process for the preparation of modified high molecular weight polylactic acid with high efficiency flame retardant and toughening according to claim 1, characterized by the fact that: In the step (S2), the weight part of each raw material is: 15-28 parts of ethylene-vinyl acetate copolymer, 35-47 parts of water, 80-110 parts of caprolactone, 20-50 parts of octadecyl methacrylate, 5-8 parts of crosslinking agent and 0.2-0.9 parts of catalyst B.

8. The process for the preparation of modified high molecular weight polylactic acid with high efficiency flame retardant and toughening according to claim 1, characterized by the fact that: In the step (S2), the content of vinyl acetate in the ethylene-vinyl acetate copolymer is less than 30%; the crosslinking agent is methylpropanediol and / or diethylpentanediol; the catalyst B is at least one of dibutyltin dilaurate, stannous octoate, bismuth laurate, bismuth neodecanoate, bismuth isononanoate, bismuth neodecanoate and bismuth naphthenate.

9. The process for the preparation of modified high molecular weight polylactic acid with high efficiency flame retardant and toughening according to claim 1, characterized by the fact that: The weight ratio of the organosilicon A flame retardant, the B toughening agent and the high molecular weight polylactic acid in the step (S3) is 1-5:1-10:75-95; the weight average molecular weight of the high molecular weight polylactic acid is 100,000-750,000.

10. A modified high molecular weight polylactic acid having high efficiency flame retardant toughening, characterized by: The preparation method of the modified high molecular weight polylactic acid with high-efficiency flame-retardant toughening is prepared by using the method according to any one of claims 1-9.

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