Flame-retardant starch-kaolin flame retardant modified polylactic acid membrane material and preparation method thereof

Abstract

The invention relates to the technical field of polylactic acid, and discloses a flame-retardant starch-kaolin flame retardant modified polylactic acid membrane material, which is prepared by taking glycerol as a plasticizer, taking a phosphorus-containing starch-kaolin composite flame retardant as a filling modifier, carrying out melt blending with polylactic acid, and carrying out blow molding to form a membrane. A starch molecular chain is grafted to kaolin nanometre, so that the starch is used as a compatilizer, the dispersity of kaolin in polylactic acid is improved, the reinforcing effect of kaolin is better played, and the elongation at break and tensile strength of the polylactic acid membrane material are improved; the expression-modified phosphabicyclo octane compound is used as an organic phosphorus flame-retardant component, promotes starch pyrolysis to form an expanded carbon layer under high-temperature combustion, and is compounded with kaolin to form a continuous inorganic barrier layer, so that the effects of isolating oxygen and inhibiting smoke escape are achieved, and an excellent flame-retardant effect is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of polylactic acid, in particular to a flame-retardant starch-kaolin flame retardant modified polylactic acid film material and a preparation method thereof. Background Art

[0002] As a biodegradable polymer material, polylactic acid has a wide range of raw material sources, is cheap and easy to obtain, and has good mechanical strength, biocompatibility, non-toxicity and pollution-free advantages, making polylactic acid widely used in packaging, agriculture and forestry industries, medical fields, etc. However, polylactic acid has some obvious disadvantages, such as low tensile properties, poor toughness, easy burning, and poor flame retardant properties. In recent years, toughening modification and flame retardant modification of polylactic acid have been hot research areas.

[0003] In recent years, starch, as a swelling carbon source, has been combined with organophosphorus flame retardants such as 1-oxyphospha-4-hydroxymethyl-2,6,7-trioxabicyclo[2.2.2]octane, and has broad application prospects in the field of flame retardancy. Kaolin (Kaol) is a natural nanomaterial that can be used as a filler and reinforcer in polymer materials. Therefore, combining kaolin with starch and organophosphorus flame retardants to obtain a composite flame retardant and applying it to polylactic acid to improve the flame retardancy and tensile properties of polylactic acid is an effective and feasible strategy. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a flame-retardant starch-kaolin flame retardant modified polylactic acid film material and a preparation method, which solves the problem of low tensile properties and flame retardancy of polylactic acid.

[0005] To achieve the above object, the present invention provides the following technical solution: a flame retardant starch-kaolin flame retardant modified polylactic acid film material, the preparation method of the flame retardant starch-kaolin flame retardant modified polylactic acid film material is as follows: (1) Add kaolin (Kaol) and γ-aminopropyltriethoxysilane to a mixed solution of toluene and dichloromethane, heat to 70-85 °C, react for 3-8 h, then lower the temperature to 20-35 °C, add triethylamine and succinyl chloride, react for 12-24 h, filter to remove the solvent, wash with dichloromethane and acetone to obtain acyl chloride-modified kaolin.

[0006] (2) Add starch and acyl chloride-modified kaolin to dimethyl sulfoxide solvent, stir evenly and then add catalyst, react at 25-50 °C for 10-20 h, remove the solvent by centrifugation, wash with deionized water and ethanol to obtain starch-grafted kaolin.

[0007] (3) Starch-grafted kaolin and isocyanate-based phosphabicyclooctane compound are added to toluene and dimethyl sulfoxide solvents, stirred and dissolved, and then a catalyst dibutyltin dilaurate (DBTDL) is added in a nitrogen atmosphere to react. The solvent is removed by centrifugation, and the mixture is washed with acetone and ethanol to obtain a flame-retardant phosphorus-containing starch-kaolin composite flame retardant.

[0008] (4) Add polylactic acid, phosphorus-containing starch-kaolin composite flame retardant, plasticizer propylene glycol, and antioxidant 1076 into a twin-screw extruder, blend the materials at 165-175°C, extrude granules at 160-170°C, and then blow mold into a film using a blow molding machine to obtain a flame-retardant starch-kaolin flame retardant modified polylactic acid film material.

[0009] Preferably, in step (1), the dosage ratio of toluene, dichloromethane, kaolin (Kaol), γ-aminopropyltriethoxysilane, triethylamine and succinyl chloride is 30-400 mL: 12-150 mL: 0.5-5 g: 0.02-0.3 g: 0.15-2.5 g: 0.35-6 g.

[0010] Preferably, in step (2), the usage ratio of dimethyl sulfoxide solvent, starch, acyl chloride-modified kaolin, and catalyst is 60-1000 mL: 0.8-10 g: 0.5-5 g: 0.02-0.35 g.

[0011] Preferably, the catalyst in step (2) is pyridine.

[0012] Preferably, in step (3), the mass ratio of toluene, dimethyl sulfoxide, starch-grafted kaolin, isocyanate-based phosphabicyclooctane compound, and dibutyltin dilaurate is 15-200 mL: 25-300 mL: 1.2-15 g: 0.25-3.5 g: 0.01-0.2 g.

[0013] Preferably, the reaction temperature in step (3) is 65-90°C and the reaction time is 4-10 h.

[0014] Preferably, in the step (4), the dosage ratio of polylactic acid, phosphorus-containing starch-kaolin composite flame retardant, plasticizer glycerol, and antioxidant 1076 is 200-2500 g: 4-150 g: 6-200 g: 0.5-12 g.

[0015] Compared with the prior art, the present invention has the following beneficial technical effects: The flame-retardant starch-kaolin flame retardant modified polylactic acid film material comprises the following steps: treating kaolin with gamma-aminopropyltriethoxysilane, causing the introduced amino group to undergo amidation reaction with an acyl chloride functional group of succinyl chloride to obtain acyl chloride modified kaolin, thereby introducing acyl chloride functional groups; then, under the catalytic action of pyridine, causing the acyl chloride functional groups of the modified kaolin to undergo esterification reaction with hydroxyl groups of starch to obtain starch grafted kaolin, thereby grafting the starch onto the surface of the kaolin; further, under the catalytic action of dibutyltin dilaurate, causing the isocyanate functional groups of an isocyanate-based phosphabicyclooctane compound to react with hydroxyl groups in the kaolin grafted starch, further chemically grafting the phosphabicyclooctane compound onto the starch molecular chain, thereby obtaining a flame-retardant phosphorus-containing starch-kaolin composite flame retardant.

[0016] The flame-retardant starch-kaolin flame retardant modified polylactic acid film material uses glycerol as a plasticizer, and a phosphorus-containing starch-kaolin composite flame retardant as a filling modifier to be melt-blended with polylactic acid and blown into a film to obtain a modified polylactic acid film material. Since starch and polylactic acid have good compatibility, and kaolin is nano-grafted with starch molecular chains, starch is used as a compatibilizer to improve the dispersibility of kaolin in polylactic acid, better exert the reinforcing effect of kaolin, further improve the elongation at break and tensile strength of the polylactic acid film material, and show better tensile properties. At the same time, starch is used as an expansion carbon source, and an expression-modified phosphabicyclooctane compound is used as an organic phosphorus flame retardant component, which promotes the pyrolysis of starch to form an expansion carbon layer under high-temperature combustion, and is compounded with kaolin to form a continuous inorganic barrier layer, which has the effect of isolating oxygen and inhibiting smoke escape, thereby achieving an excellent flame retardant effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is the reaction diagram of starch and acyl chloride modified kaolin; Figure 2 This is the reaction diagram of starch grafted with kaolin and isocyanate-based phosphabicyclooctane compound. DETAILED DESCRIPTION

[0018] To achieve the above object, the present invention provides the following embodiments and examples: A method for preparing a flame-retardant starch-kaolin flame retardant modified polylactic acid film material is as follows: (1) Add 0.5-5 g of kaolin (Kaol) and 0.02-0.3 g of γ-aminopropyltriethoxysilane to a mixed solution of 30-400 mL of toluene and 12-150 mL of dichloromethane, heat to 70-85 °C, react for 3-8 h, then lower the temperature to 20-35 °C, add 0.15-2.5 g of triethylamine and 0.35-6 g of succinyl chloride, react for 12-24 h, filter to remove the solvent, wash with dichloromethane and acetone to obtain acyl chloride-modified kaolin.

[0019] (2) Add 0.8-10 g starch and 0.5-5 g acyl chloride-modified kaolin to 60-1000 mL dimethyl sulfoxide solvent, stir evenly, add 0.02-0.35 g catalyst pyridine, react at 25-50 °C for 10-20 h, centrifuge to remove the solvent, wash with deionized water and ethanol to obtain starch-grafted kaolin.

[0020] (3) Add 1.2-15 g of starch-grafted kaolin and 0.25-3.5 g of isocyanate-based phosphabicyclooctane compound to 15-200 mL of toluene and 25-300 mL of dimethyl sulfoxide solvent, stir to dissolve, then add 0.01-0.2 g of catalyst dibutyltin dilaurate in a nitrogen atmosphere, react at 65-90 °C for 4-10 h, centrifuge to remove the solvent, wash with acetone and ethanol to obtain a flame-retardant phosphorus-containing starch-kaolin composite flame retardant.

[0021] (4) Add 200-2500 g of polylactic acid, 4-150 g of phosphorus-containing starch-kaolin composite flame retardant, 6-200 g of plasticizer propylene glycol, and 0.5-12 g of antioxidant 1076 into a twin-screw extruder, blend the materials at 165-175 °C, extrude granules at 160-170 °C, and then blow mold into a film using a blow molding machine to obtain a flame-retardant starch-kaolin flame retardant modified polylactic acid film material. Example 1

[0022] (1) Add 0.5 g kaolin and 0.02 g γ-aminopropyltriethoxysilane to a mixed solution of 30 mL toluene and 12 mL dichloromethane, heat to 70 °C, react for 3 h, then lower the temperature to 20 °C, add 0.15 g triethylamine and 0.35 g succinyl chloride, react for 12 h, filter to remove the solvent, wash with dichloromethane and acetone to obtain acyl chloride-modified kaolin.

[0023] (2) Add 0.8 g starch and 0.5 g acyl chloride-modified kaolin to 60 mL dimethyl sulfoxide solvent, stir evenly, then add 0.02 g catalyst pyridine, react at 25 °C for 10 h, centrifuge to remove the solvent, wash with deionized water and ethanol to obtain starch-grafted kaolin.

[0024] (3) 1.2 g of starch-grafted kaolin and 0.25 g of isocyanate-based phosphabicyclooctane compound were added to 15 mL of toluene and 25 mL of dimethyl sulfoxide solvent. After stirring to dissolve, 0.01 g of catalyst dibutyltin dilaurate was added in a nitrogen atmosphere. The mixture was reacted at 65 °C for 4 h. The solvent was removed by centrifugation and the mixture was washed with acetone and ethanol to obtain a flame-retardant phosphorus-containing starch-kaolin composite flame retardant.

[0025] (4) 200 g of polylactic acid, 4 g of phosphorus-containing starch-kaolin composite flame retardant, 6 g of plasticizer propylene glycol, and 0.5 g of antioxidant 1076 were added to a twin-screw extruder, the materials were blended at 165 °C, extruded into granules at 160 °C, and then blown into films by a blow molding machine to obtain flame-retardant starch-kaolin flame retardant modified polylactic acid film materials. Example 2

[0026] (1) Add 1 g of kaolin and 0.05 g of γ-aminopropyltriethoxysilane to a mixed solution of 60 mL of toluene and 25 mL of dichloromethane, heat to 70 °C, react for 5 h, then lower the temperature to 20 °C, add 0.4 g of triethylamine and 0.8 g of succinyl chloride, react for 12 h, filter to remove the solvent, wash with dichloromethane and acetone to obtain acyl chloride-modified kaolin.

[0027] (2) Add 1.5 g starch and 1.2 g acyl chloride-modified kaolin to 150 mL dimethyl sulfoxide solvent, stir evenly, then add 0.05 g catalyst pyridine, react at 50 °C for 10 h, centrifuge to remove the solvent, wash with deionized water and ethanol to obtain starch-grafted kaolin.

[0028] (3) Add 2.5 g of starch-grafted kaolin and 0.5 g of isocyanate-based phosphabicyclooctane compound to 30 mL of toluene and 60 mL of dimethyl sulfoxide solvent, stir to dissolve, then add 0.025 g of catalyst dibutyltin dilaurate in a nitrogen atmosphere, react at 65 °C for 4 h, centrifuge to remove the solvent, wash with acetone and ethanol to obtain a flame-retardant phosphorus-containing starch-kaolin composite flame retardant.

[0029] (4) 500 g of polylactic acid, 15 g of phosphorus-containing starch-kaolin composite flame retardant, 18 g of plasticizer propylene glycol, and 1.2 g of antioxidant 1076 were added into a twin-screw extruder, the materials were blended at 165 °C, extruded into granules at 165 °C, and then blown into film by a blow molding machine to obtain a flame-retardant starch-kaolin flame retardant modified polylactic acid film material. Example 3

[0030] (1) Add 2 g of kaolin and 0.12 g of γ-aminopropyltriethoxysilane to a mixed solution of 200 mL of toluene and 80 mL of dichloromethane, heat to 80 °C, react for 5 h, then lower the temperature to 30 °C, add 1.2 g of triethylamine and 2.5 g of succinyl chloride, react for 18 h, filter to remove the solvent, wash with dichloromethane and acetone to obtain acyl chloride-modified kaolin.

[0031] (2) Add 4 g starch and 2 g acyl chloride-modified kaolin to 500 mL dimethyl sulfoxide solvent, stir evenly, then add 0.15 g catalyst pyridine, react at 40 °C for 12 h, centrifuge to remove the solvent, wash with deionized water and ethanol to obtain starch-grafted kaolin.

[0032] (3) 7 g of starch-grafted kaolin and 1.5 g of isocyanate-based phosphabicyclooctane compound were added to 80 mL of toluene and 120 mL of dimethyl sulfoxide solvent. After stirring to dissolve, 0.1 g of catalyst dibutyltin dilaurate was added in a nitrogen atmosphere. The mixture was reacted at 80 °C for 6 h. The solvent was removed by centrifugation and the mixture was washed with acetone and ethanol to obtain a flame-retardant phosphorus-containing starch-kaolin composite flame retardant.

[0033] (4) 1200 g of polylactic acid, 70 g of phosphorus-containing starch-kaolin composite flame retardant, 100 g of plasticizer propylene glycol, and 6 g of antioxidant 1076 were added to a twin-screw extruder, the materials were blended at 165 °C, extruded into granules at 170 °C, and then blown into films by a blow molding machine to obtain flame-retardant starch-kaolin flame retardant modified polylactic acid film materials. Example 4

[0034] (1) Add 3.5 g kaolin and 0.22 g γ-aminopropyltriethoxysilane to a mixed solution of 320 mL toluene and 110 mL dichloromethane, heat to 85 °C, react for 8 h, then lower the temperature to 35 °C, add 1.8 g triethylamine and 4.5 g succinyl chloride, react for 18 h, filter to remove the solvent, wash with dichloromethane and acetone to obtain acyl chloride-modified kaolin.

[0035] (2) Add 7.5 g starch and 4 g acyl chloride-modified kaolin to 800 mL dimethyl sulfoxide solvent, stir evenly, then add 0.28 g catalyst pyridine, react at 50 °C for 12 h, centrifuge to remove the solvent, wash with deionized water and ethanol to obtain starch-grafted kaolin.

[0036] (3) Add 12 g of starch-grafted kaolin and 2.5 g of isocyanate-based phosphabicyclooctane compound to 120 mL of toluene and 200 mL of dimethyl sulfoxide solvent, stir to dissolve, then add 0.15 g of catalyst dibutyltin dilaurate in a nitrogen atmosphere, react at 90 °C for 8 h, centrifuge to remove the solvent, wash with acetone and ethanol to obtain a flame-retardant phosphorus-containing starch-kaolin composite flame retardant.

[0037] (4) 1800 g of polylactic acid, 120 g of phosphorus-containing starch-kaolin composite flame retardant, 125 g of plasticizer propylene glycol, and 8.5 g of antioxidant 1076 were added into a twin-screw extruder, the materials were blended at 175 °C, extruded into granules at 170 °C, and then blown into film by a blow molding machine to obtain a flame-retardant starch-kaolin flame retardant modified polylactic acid film material. Example 5

[0038] (1) Add 5 g of kaolin and 0.3 g of γ-aminopropyltriethoxysilane to a mixed solution of 400 mL of toluene and 150 mL of dichloromethane, heat to 85 °C, react for 8 h, then lower the temperature to 35 °C, add 2.5 g of triethylamine and 6 g of succinyl chloride, react for 24 h, filter to remove the solvent, wash with dichloromethane and acetone to obtain acyl chloride-modified kaolin.

[0039] (2) Add 10 g starch and 5 g acyl chloride-modified kaolin to 1000 mL dimethyl sulfoxide solvent, stir evenly, then add 0.35 g catalyst pyridine, react at 50 °C for 20 h, centrifuge to remove the solvent, wash with deionized water and ethanol to obtain starch-grafted kaolin.

[0040] (3) Add 15 g of starch-grafted kaolin and 3.5 g of isocyanate-based phosphabicyclooctane compound to 200 mL of toluene and 300 mL of dimethyl sulfoxide solvent, stir to dissolve, then add 0.2 g of catalyst dibutyltin dilaurate in a nitrogen atmosphere, react at 90 °C for 10 h, centrifuge to remove the solvent, wash with acetone and ethanol to obtain a flame-retardant phosphorus-containing starch-kaolin composite flame retardant.

[0041] (4) 2500 g of polylactic acid, 150 g of phosphorus-containing starch-kaolin composite flame retardant, 200 g of plasticizer propylene glycol, and 12 g of antioxidant 1076 were added to a twin-screw extruder, the materials were blended at 175 °C, extruded into granules at 170 °C, and then blown into films by a blow molding machine to obtain flame-retardant starch-kaolin flame retardant modified polylactic acid film materials.

[0042] Comparative Example 1 (1) Add 2 g of kaolin and 0.12 g of γ-aminopropyltriethoxysilane to a mixed solution of 200 mL of toluene and 60 mL of dichloromethane, heat to 70 °C, react for 4 h, then lower the temperature to 35 °C, add 1 g of triethylamine and 2.5 g of succinyl chloride, react for 24 h, filter to remove the solvent, wash with dichloromethane and acetone to obtain acyl chloride-modified kaolin.

[0043] (2) 1000 g of polylactic acid, 65 g of acyl chloride-modified kaolin, 80 g of plasticizer propylene glycol, and 3 g of antioxidant 1076 were added into a twin-screw extruder, the materials were blended at 170 °C, extruded into granules at 170 °C, and then blown into a film by a blow molding machine to obtain a kaolin-modified polylactic acid film material.

[0044] The kaolin-modified polylactic acid film material was pressed into a film material with a thickness of 2 mm, and the flame retardancy was tested according to the UL-94 fire rating using a BJY horizontal and vertical combustion tester.

[0045]

[0046] The tensile properties of modified polylactic acid film materials were tested using a CTM universal testing machine in accordance with GB / T 1040.1-2018 standard.

[0047]

Claims

1. A flame retardant starch-kaolin flame retardant modified polylactic acid film material, characterized in that: The preparation method of the flame-retardant starch-kaolin flame retardant modified polylactic acid film material is as follows: (1) Add kaolin and γ-aminopropyltriethoxysilane to a mixed solution of toluene and dichloromethane, heat to 70-85°C, react for 3-8 hours, then lower the temperature to 20-35°C, add triethylamine and succinyl chloride, react for 12-24 hours, filter to remove the solvent, wash with dichloromethane and acetone to obtain acyl chloride-modified kaolin; (2) Add starch and acyl chloride-modified kaolin to dimethyl sulfoxide solvent, stir evenly, add catalyst, react at 25-50° C. for 10-20 h, remove the solvent by centrifugation, wash with deionized water and ethanol, and obtain starch-grafted kaolin; (3) Adding starch-grafted kaolin and isocyanate-based phosphabicyclooctane compound to toluene and dimethyl sulfoxide solvents, stirring and dissolving, adding catalyst dibutyltin dilaurate in a nitrogen atmosphere to react, centrifuging to remove the solvent, washing with acetone and ethanol, and obtaining a flame-retardant phosphorus-containing starch-kaolin composite flame retardant; (4) Add polylactic acid, phosphorus-containing starch-kaolin composite flame retardant, plasticizer propylene glycol, and antioxidant 1076 into a twin-screw extruder, blend the materials at 165-175°C, extrude granules at 160-170°C, and then blow mold into a film using a blow molding machine to obtain a flame-retardant starch-kaolin flame retardant modified polylactic acid film material.

2. The flame retardant starch-kaolin flame retardant modified polylactic acid film material according to claim 1, characterized in that: In the step (1), the dosage ratio of toluene, dichloromethane, kaolin, γ-aminopropyltriethoxysilane, triethylamine and succinyl chloride is 30-400 mL: 12-150 mL: 0.5-5 g: 0.02-0.3 g: 0.15-2.5 g: 0.35-6 g.

3. The flame retardant starch-kaolin flame retardant modified polylactic acid film material according to claim 1, characterized in that: In the step (2), the usage ratio of dimethyl sulfoxide solvent, starch, acyl chloride-modified kaolin, and catalyst is 60-1000 mL: 0.8-10 g: 0.5-5 g: 0.02-0.35 g.

4. The flame retardant starch-kaolin flame retardant modified polylactic acid film material according to claim 1, characterized in that: The catalyst in step (2) is pyridine.

5. The flame retardant starch-kaolin flame retardant modified polylactic acid film material according to claim 1, characterized in that: In the step (3), the mass ratio of toluene, dimethyl sulfoxide, starch-grafted kaolin, isocyanate-based phosphabicyclooctane compound, and dibutyltin dilaurate is 15-200 mL: 25-300 mL: 1.2-15 g: 0.25-3.5 g: 0.01-0.2 g.

6. The flame retardant starch-kaolin flame retardant modified polylactic acid film material according to claim 1, characterized in that: The reaction temperature in step (3) is 65-90°C and the reaction time is 4-10 h.

7. The flame retardant starch-kaolin flame retardant modified polylactic acid film material according to claim 1, characterized in that: In the step (4), the dosage ratio of polylactic acid, phosphorus-containing starch-kaolin composite flame retardant, plasticizer propylene glycol, and antioxidant 1076 is 200-2500 g: 4-150 g: 6-200 g: 0.5-12 g.

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