CN101260227B - A kind of preparation method of halogen-free flame-retardant polylactic acid - Google Patents

Abstract

The present invention belongs to the technical field of polymer materials, and specifically relates to a method for preparing halogen-free flame-retardant polylactic acid. The specific preparation steps are: firstly, a flame retardant, a flame retardant auxiliary agent, and an antioxidant are stirred in a certain proportion to obtain a flame retardant mixture, and then polylactic acid, the flame retardant mixture, a compatibilizer, and a coupling agent are mixed in a certain proportion and melt-blended, and the material is cooled, pelletized, and dried to obtain flame-retardant polylactic acid. The flame-retardant polylactic acid has good flame retardant properties, can pass the UL94 test, and has less molten dripping, and can be used in fields such as aircraft, automobiles, and electronics that have strict requirements on the flame retardant properties of materials.

Description

A kind of preparation method of halogen-free flame-retardant polylactic acid

technical field

The invention belongs to the technical field of polymer material modification, and in particular relates to a preparation method of halogen-free flame-retardant polylactic acid. the

Background technique

Energy issues and environmental issues have promoted the development and application of biomaterials. Polylactic acid is a "green polymer" material whose raw material is derived from renewable non-staple agricultural products (such as cassava) starch and can be completely degraded into carbon dioxide and water. Polylactic acid is not only degradable, but also has many good mechanical properties and processing properties, and is known as the most promising "green plastic". However, polylactic acid, like other polymers, is easy to burn, which limits the application of polylactic acid in aviation, electronics, automobiles and other fields. It is necessary to endow polylactic acid with flame retardant properties by modification. the

The blending of additive flame retardants and polymer materials is a common method for flame retardancy modification of materials. Halogenated flame retardants have high flame retardant properties and are often used in the flame retardant modification of thermoplastic polymer materials. However, with the development of flame retardant technology, it has been found that toxic gases such as hydrogen halides are generated when the flame retardant materials are re-burned. At the same time, the halogen-containing flame retardants and their combustion products have carcinogenic effects. Therefore, at present Developed countries such as Europe and the United States have issued bans on some halogenated flame retardants. The non-halogenation of flame retardant technology is the development direction of flame retardant modification of materials in the future. the

Halogen-free flame retardants that can flame-retardant polyester materials include: phosphorus-based flame retardants, such as red phosphorus, ammonium polyphosphate, melamine phosphate; inorganic hydroxides, such as aluminum hydroxide, magnesium hydroxide, etc.; silicon-based flame retardants Burning agent, such as layered silicate, etc. Galina F et al. (Polym Int, 2000, 49: 1095-1100) mixed the phosphorus-containing flame retardant and butylene terephthalate in a high mixer, and melted the mixture at 230-240°C, and finally The obtained product is hot-pressed at 230-240° C. and a pressure of 30 tons. The flame retardancy of the obtained product can reach UL94 V-0 level. In China, Harbin Institute of Technology, Sichuan University and other universities have conducted research on halogen-free flame-retardant polyester polymers. Although some progress has been made in flame-retardant, the biggest disadvantage is the difficulty in industrial production. Junfeng Xiao et al. (Polymer Degradation and Stability, 2006, 91: 2093-2100) melt-blended the flame retardant melamine, triphenyl phosphate and butylene terephthalate particles through a two-roll mill (temperature: 235°C , number of revolutions: 100). When the content of melamine and triphenyl phosphate in the composite material is 10wt%, 20wt%, it can pass the UL94V-0 level test. In 2002, Sichuan University applied for a patent "Phosphorus-containing flame-retardant polyethylene terephthalate/layered silicate nanocomposite material and its preparation method and application" (CN1396206), which mentioned the application of layered silicate , Reactive phosphorus-containing flame retardants and other additives flame retardant dimethyl terephthalate. The resulting product has flame retardant and mechanical properties, but the disadvantage of this patent is that it uses a reactive phosphorus-containing flame retardant and uses an in-situ intercalation polymerization method, which is not conducive to industrial production. Halogen-free flame-retardant thermoplastic materials are accompanied by a large amount of molten material dripping when burning, especially when phosphoric ester flame retardants are used, as the amount of flame retardants increases, the dripping phenomenon becomes quite serious, which is extremely large. The application range of the material is limited. the

In response to this situation, this patent provides a method for preparing environmentally friendly and biodegradable polylactic acid flame-retardant materials suitable for industrial production, and reduces material combustion by adding flame-retardant additives such as montmorillonite and zinc stearate When the melt drips. This method has the characteristics of simple process and high production capacity, and has important practical application value. the

Contents of the invention

The purpose of the present invention is to provide a method for preparing halogen-free flame-retardant polylactic acid suitable for industrial production. the

The preparation method of the halogen-free flame-retardant polylactic acid proposed by the present invention is to firstly modify the surface of the flame retardant, and then blend and extrude the modified flame retardant, polylactic acid and other additives to obtain a product. the

The preparation method of the halogen-free flame-retardant polylactic acid that the present invention proposes, concrete steps are as follows:

(1) Vacuum dry the polylactic acid and the flame retardant respectively at 30-120°C for 1-24 hours to remove moisture;

(2) Stir the treated flame retardant obtained in step (1) with flame retardant aids and antioxidants in a dry container according to the weight ratio to mix them evenly to obtain a flame retardant mixture; its components The weight percentage is:

Flame retardant 69～98.5wt%

Flame retardant additive 0.5～30wt%

Antioxidant 1～10wt%

Its total weight satisfies 100%;

(3) Add the treated polylactic acid obtained in step (1), the flame retardant mixture obtained in step (2), coupling agent, and compatibilizer into a dry container by weight ratio, mix well, and then melt blend ; Adopt extruder or two-roll mill to obtain required product; Wherein the weight percent of each composition is:

Polylactic acid 59.4～95wt%

Flame retardant mixture 2～40wt%

Coupling agent 0.5～8wt%

The rest are compatibilizers, the total weight of which satisfies 100%;

In the present invention, an extruder is used as described in step (3), the screw speed of which is 15-280 rpm, and the extrusion temperature is 100-190° C. After the material is extruded, it can be cooled, pelletized and dried. the

In the present invention, the two-roll mill is adopted as described in step (3), the temperature of the front roll of the two-roll mill is 80-180°C, and the temperature of the rear roll is 60-170°C. the

In the present invention, the polylactic acid has a weight average molecular weight of 1×10 ⁵ to 3×10 ⁵ .

In the present invention, the flame retardant is a halogen-free flame retardant, specifically montmorillonite, aluminum hydroxide, phosphoric acid, phosphorous acid, ammonium polyphosphate, triphenyl phosphate, trioctyl phosphate, phosphoric acid One or more of tributyl phosphate, tris(2,3-dichloropropyl) phosphate, triphenyl phosphite, phosphate, melamine cyanurate, expanded graphite or red phosphorus are used in combination. the

In the present invention, the flame retardant additives are pentaerythritol, melamine, starch, titanium dioxide, calcium stearate, zinc stearate, calcium carbonate, zinc borate, antimony oxide, zeolite, silicon dioxide, magnesium hydroxide, antidripping One or more of falling agents or cross-linking agents. the

In the present invention, the coupling agent is one or more of titanate or silane coupling agents. the

In the present invention, the compatibilizer is one or more of polycaprolactone (PCL), polyhydroxyalkanoate (PHA), polyethylene glycol (PEG) or epoxy resin. the

In the present invention, the antioxidant is tris(2,4-di-tert-butylphenyl) phosphite, tris(2,4-di-tert-butylphenyl) phosphite, diisophenylene phosphite Decyl ester, tris(nonylphenyl)phosphite or tris(nonylphenyl)phosphite, pentaerythritol bisphosphite bis(2,4-di-tert-butylphenyl)ester, polyalkylbisphenol One or more of the dimer or trimer complex of A phosphite. the

The advantages of the present invention are:

(1) Select an environment-friendly halogen-free flame retardant to compound with polylactic acid, and the obtained product fully meets the requirements of environmental protection. the

(2) Composite halogen-free flame retardants and polylactic acid, the resulting products have good flame retardant properties, and the products meet UL 94V0 or UL 94V1 standards, and can be used in aviation, automobiles, electronics, etc., which have strict requirements on flame retardant properties field of. the

(3) The preparation method is simple and effective, the process conditions are mild, and it is suitable for industrial production. the

(4) The dosage and formula of the flame retardant can be adjusted according to the requirements of the product to control the production cost;

Detailed ways

The present invention is further described below by way of examples. the

Example 1

1. Vacuum dry polylactic acid and ammonium polyphosphate at 30°C for 24 hours to remove moisture. the

2. The dried flame retardant ammonium polyphosphate and flame retardant additives pentaerythritol, melamine, zinc stearate, antioxidant tris (2,4-di-tert-butylphenyl) phosphite are dried by weight Stir and mix evenly in a container at high speed to obtain a flame retardant mixture. Wherein ammonium polyphosphate is 3 parts, pentaerythritol is 2 parts, melamine is 1 part, zinc stearate is 1 part, and antioxidant is 0.5 part. the

3. Mix the dried polylactic acid with the flame retardant mixture obtained in step (2), compatibilizer polycaprolactone, and coupling agent titanate LD-101 in a dry container according to a certain weight ratio, and then mix them in a dry container Blending and extrusion were carried out in an extruder, wherein the screw rotation speed was 250 rpm, and the extrusion temperature was 180°C. Among them, 90 parts of polylactic acid, 8.5 parts of flame retardant mixture, 0.5 parts of coupling agent, and 1 part of compatibilizer. After the material is extruded, it is cooled, pelletized and dried to obtain flame-retardant polylactic acid. the

Flame retardant UL-94V test:

UL-94V specification: place a test piece with a length of 127 mm, a width of 12.7 mm, and a thickness of 1.6 mm vertically, ignite it in the test furnace for 10 seconds, then remove the flame, and measure the self-extinguishing time of the test piece on fire. Secondly, immediately re-ignite for 10 seconds when the flame is extinguished, and also test the flame self-extinguishing time. At the same time, check whether the falling tinder can ignite the absorbent cotton. The fire grade of the material is evaluated by the time of the first and second fires and the presence or absence of fires of absorbent cotton. The combustion grade V-0 is the highest, followed by V-1 and V-2 respectively. the

The limiting oxygen index of the product is greater than 29, which can pass the V-1 level combustion test. the

Example 2

1. Vacuum dry polylactic acid, montmorillonite, and ammonium polyphosphate at 80°C for 3 hours to remove moisture. the

2. the dried flame retardant montmorillonite, ammonium polyphosphate and flame retardant additives pentaerythritol, melamine, antioxidant tris (2,4-di-tert-butylphenyl) ester in dry Stir and mix evenly in the container at high speed to obtain a flame retardant mixture. Wherein montmorillonite is 15 parts, ammonium polyphosphate is 8 parts, pentaerythritol is 4 parts, melamine is 3 parts, and antioxidant is 1 part. the

3. Mix the dried polylactic acid with the flame-retardant mixture obtained in step (2), compatibilizer polycaprolactone, and coupling agent silane coupling agent KH550 in a dry container according to a certain weight ratio, and then Blending and extrusion were carried out in the extruder, wherein the screw rotation speed was 30 rpm, and the extrusion temperature was 150°C. Among them, polylactic acid is 64 parts, flame retardant mixture is 31 parts, coupling agent is 4 parts, and compatibilizer is 1 part. After the material is extruded, it is cooled, pelletized and dried to obtain flame-retardant polylactic acid. the

The flame retardancy UL-94V test is the same as that in Example 1. the

The limiting oxygen index of the product is greater than 30, which can pass the V-1 level combustion test. the

Example 3

1. Dry polylactic acid and calcium stearate in vacuum at 80°C for 3 hours to remove moisture. the

2. Stir and mix the flame retardant tripenyl phosphate, the flame retardant additive calcium stearate, and the antioxidant phenylene diisodecyl phosphite in a dry container at high speed according to the weight ratio to obtain a flame retardant mixture. Among them, 15 parts of tripenyl phosphate, 3 parts of calcium stearate, and 1 part of antioxidant. the

3. Mix the dry polylactic acid with the flame retardant mixture obtained in step (2), the compatibilizer polyethylene glycol, and the coupling agent silane coupling agent KH550 in a dry container according to a certain weight ratio, and then extrude Blending and extrusion were carried out in the extruder, wherein the screw rotation speed was 130 rpm, and the extrusion temperature was 190°C. Among them, the polylactic acid is 77.9 parts, the flame retardant mixture is 19 parts, the coupling agent is 3 parts, and the compatibilizer is 0.1 part. After the material is extruded, it is cooled, pelletized and dried to obtain flame-retardant polylactic acid. the

Flame retardancy UL-94V test is the same as Example 1. the

The limiting oxygen index of the product is greater than 29, which can pass the V-2 level combustion test. the

Example 4

1. Vacuum dry polylactic acid and ammonium polyphosphate at 70°C for 10 hours to remove moisture. the

2. Mix the dry flame retardant ammonium polyphosphate with flame retardant additives magnesium hydroxide, pentaerythritol, and antioxidant phenylene diisodecyl phosphite at high speed in a dry container according to the weight ratio to obtain a flame retardant mixture . Wherein magnesium hydroxide is 5 parts, ammonium polyphosphate is 12 parts, pentaerythritol is 6 parts, and antioxidant is 1 part. the

3. Mix the dried polylactic acid with the flame retardant mixture obtained in step (2), compatibilizer polyethylene glycol, and coupling agent silane coupling agent KH560 in a dry container according to a certain weight ratio, and then extrude Blending and extrusion were carried out in the extruder, wherein the screw rotation speed was 150 rpm, and the extrusion temperature was 170°C. Among them, the polylactic acid is 75.5 parts, the flame retardant mixture is 24 parts, the coupling agent is 2 parts, and the compatibilizer is 0.5 parts. After the material is extruded, it is cooled, pelletized and dried to obtain flame-retardant polylactic acid. the

The flame retardancy UL-94V test is the same as that in Example 1. the

The limiting oxygen index of the sample is greater than 31, which can pass the V-0 level combustion test. the

Example 5

1. Vacuum dry polylactic acid and expanded graphite at 60°C for 20 hours to remove moisture. the

2. With dry flame retardant expanded graphite and flame retardant red phosphorus, flame retardant additive pentaerythritol, antioxidant pentylene glycol bisphosphite bis (2,4-di-tert-butylphenyl) ester, press Stir and mix evenly at high speed in a dry container to obtain a flame retardant mixture. Among them, 5 parts of expanded graphite, 3 parts of red phosphorus, 1 part of pentaerythritol, and 1 part of antioxidant. the

3. Mix the dried polylactic acid with the flame retardant mixture obtained in step (2), compatibilizer polyethylene glycol, and coupling agent silane coupling agent KH560 in a dry container according to a certain weight ratio, and then extrude Blending and extrusion were carried out in the extruder, wherein the screw rotation speed was 70 rpm, and the extrusion temperature was 180°C. Among them, 88.9 parts of polylactic acid, 10 parts of flame retardant mixture, 1 part of coupling agent, and 0.1 part of compatibilizer. After the material is extruded, it is cooled, pelletized and dried to obtain flame-retardant polylactic acid. the

The flame retardancy UL-94V test is the same as that in Example 1. the

The limiting oxygen index of the product is greater than 27, which can pass the V-2 level combustion test. the

Example 6

1. Dry polylactic acid, ammonium polyphosphate, and montmorillonite in vacuum at 50°C for 10 hours to remove moisture. the

2. Mix the dried ammonium polyphosphate, montmorillonite, pentaerythritol, melamine, compatibilizer polycaprolactone, and antioxidant phenylene diisodecyl phosphite at a high speed in a dry container by weight ratio to obtain Flame retardant compound. Wherein 25 parts of montmorillonite, 45 parts of ammonium polyphosphate, 18 parts of pentaerythritol, 8 parts of melamine, 3 parts of polycaprolactone, and 1 part of antioxidant phenylene diisodecyl phosphite. the

3. the dry polylactic acid is blended with the flame retardant mixture obtained in step (2), compatibilizer polyethylene glycol, coupling agent silane coupling agent KH560 on a two-roll mill according to a certain weight ratio, to obtain Flame retardant polylactic acid. Among them, the temperature of the front roll is 140°C, the temperature of the back roll is 100°C, the polylactic acid is 60.2 parts, the flame retardant mixture is 38 parts, the compatibilizer is 0.8 parts, and the coupling agent is 1 part. the

The flame retardancy UL-94V test is the same as that in Example 1. the

The limiting oxygen index of the product is greater than 27, and the sample can pass the V-0 level combustion test. the

Example 7

1. Dry polylactic acid, ammonium polyphosphate, and montmorillonite in vacuum at 100°C for 5 hours to remove moisture. the

2. Stir and mix the dried ammonium polyphosphate, montmorillonite and pentaerythritol, compatibilizer polyhydroxyalkanoate (PHA), antioxidant phenylene diisodecyl phosphite at high speed in a dry container according to the weight ratio , to obtain a flame retardant premix. Wherein 15 parts of montmorillonite, 55 parts of ammonium polyphosphate, 23 parts of pentaerythritol, 5 parts of polyhydroxyalkanoate, and 2 parts of antioxidant phenylene diisodecyl phosphite. the

3. Dry polylactic acid and the flame-retardant premixed flame-retardant mixture obtained in step (2), compatibilizer polyethylene glycol, and coupling agent silane coupling agent KH550 are carried out on a double-roll mill according to a certain weight ratio Blending to obtain flame-retardant polylactic acid. Among them, the temperature of the front roll is 130°C, the temperature of the back roll is 120°C, the polylactic acid is 65 parts, the flame retardant mixture is 33.2 parts, the compatibilizer is 1 part, and the coupling agent is 0.8 parts. the

The flame retardancy UL-94V test is the same as that in Example 1. the

The limiting oxygen index of the sample is greater than 28, and the sample can pass the V-0 level combustion test. the

Example 8

1. Dry polylactic acid, melamine cyanurate, and montmorillonite in vacuum at 120°C for 1 hour to remove moisture. the

2. Stir and mix the dried melamine cyanurate, montmorillonite and pentaerythritol, compatibilizer polyhydroxyalkanoate (PHA), antioxidant phenylene diisodecyl phosphite at high speed in a dry container according to the weight ratio , to obtain a flame retardant premix. Wherein 20 parts of montmorillonite, 46 parts of melamine cyanurate, 24 parts of pentaerythritol, 8 parts of polyhydroxyalkanoate, and 2 parts of antioxidant phenylene diisodecyl phosphite. the

3. the dry polylactic acid is blended with the flame retardant mixture obtained in step (2), compatibilizer polyethylene glycol, coupling agent silane coupling agent KH570 on a two-roll mill according to a certain weight ratio, to obtain Flame retardant polylactic acid. The temperature of the front roll is 135°C, the temperature of the back roll is 125°C, the polylactic acid is 85 parts, the flame retardant mixture is 15 parts, the compatibilizer is 0.9 parts, and the coupling agent is 0.9 parts. the

The flame retardancy UL-94V test is the same as that in Example 1. the

The limiting oxygen index of the product is greater than 28, and the sample can pass the V-1 level combustion test, and the molten material drips very little when burning. the

In addition, compared with polylactic acid flame-retardant only with halogen-free flame retardants (such as ammonium polyphosphate, triphenyl phosphate, etc.), the samples prepared with the present invention have less molten drips during combustion. the

Claims (7)

1. a preparation method of halogen-free flame-retardant polylactic acid, is characterized in that concrete steps are as follows: (1) Vacuum dry the polylactic acid and the flame retardant respectively at 30-120°C for 1-24 hours to remove moisture; (2) Stir the treated flame retardant obtained in step (1) with flame retardant aids and antioxidants in a dry container according to the weight ratio to mix them evenly to obtain a flame retardant mixture; its components The weight percentage is: Flame retardant 69～98.5wt% Flame retardant additive 0.5～30wt% Antioxidant 1～10wt% Its total weight satisfies 100%; (3) Add the treated polylactic acid obtained in step (1), the flame retardant mixture obtained in step (2), coupling agent, and compatibilizer into a dry container by weight ratio, mix well, and then melt blend ; Adopt extruder or two-roll mill to obtain required product; Wherein the weight percent of each composition is: Polylactic acid 59.4～95wt% Flame retardant mixture 2～40wt% Coupling agent 0.5～8wt% The rest are compatibilizers, the total weight of which satisfies 100%; The flame retardant is montmorillonite, aluminum hydroxide, phosphoric acid, phosphorous acid, ammonium polyphosphate, triphenyl phosphate, trioctyl phosphate, tributyl phosphate, tris(2,3-dichloropropyl) phosphate , triphenyl phosphite, phosphate, melamine cyanurate, expanded graphite or red phosphorus, or one or more mixed use; the flame retardant additives are pentaerythritol, melamine, starch, titanium dioxide, calcium stearate, One or more of zinc stearate, calcium carbonate, zinc borate, antimony oxide, zeolite, silicon dioxide, magnesium hydroxide, anti-dripping agent or cross-linking agent. 2. The preparation method of halogen-free flame-retardant polylactic acid according to claim 1, characterized in that an extruder is used in step (3), the screw speed is 15-280rpm, and the extrusion temperature is 100-190°C , After the material is extruded, it can be cooled, pelletized and dried. 3. The preparation method of halogen-free flame-retardant polylactic acid according to claim 1, characterized in that the temperature of the front rolls of the double-roll mill used in the step (3) is 80 to 180 ° C, and the temperature of the rear rolls is 60 ° C. ~170°C. 4. The preparation method of halogen-free flame-retardant polylactic acid according to claim 1, characterized in that the weight average molecular weight of the polylactic acid is 1×10 ⁵ to 3×10 ⁵ . 5. The preparation method of halogen-free flame-retardant polylactic acid according to claim 1, characterized in that the coupling agent is one or more of titanate or silane coupling agent. 6. the preparation method of halogen-free flame-retardant polylactic acid according to claim 1 is characterized in that described compatibilizer is polycaprolactone, polyhydroxyalkanoate, polyethylene glycol or epoxy resin at least one kind. 7. the preparation method of halogen-free flame-retardant polylactic acid according to claim 1 is characterized in that described antioxidant is phosphite tris (2,4-di-tert-butylphenyl) ester, phosphite tris ( 2,4-di-tert-butylphenyl) ester, phenylene diisodecyl phosphite, tris(nonylphenyl) phosphite or tris(nonylphenyl) phosphite or pentaerythritol bisphosphite di( One or more of 2,4-di-tert-butylphenyl) esters.