Halogen-free flame-retardant polypropylene film and preparation method thereof

Abstract

The present invention provides a halogen-free flame-retardant polypropylene film and a preparation method thereof, wherein the halogen-free flame-retardant polypropylene film comprises the following raw materials in parts by weight: 60-100 parts of polypropylene resin, 20-40 parts of halogen-free flame retardant, 3-10 parts of high thermal conductivity filler, 1-3 parts of antioxidant, 0.1-3 parts of anti-dripping agent, and 1-3 parts of smoke suppressant, wherein the halogen-free flame retardant is compounded by piperazine pyrophosphate and melamine polyphosphate, and the mass ratio of piperazine pyrophosphate to melamine polyphosphate is 1:1-3:1. The present invention compounds piperazine pyrophosphate and melamine polyphosphate to form a halogen-free flame retardant, which can significantly improve the limiting oxygen index of the polypropylene flame retardant film. The synergistic effect between the high thermal conductivity filler, the anti-dripping agent and the halogen-free flame retardant can significantly improve the thermal conductivity, anti-dripping performance, flame retardant performance and mechanical properties of the polypropylene material.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, in particular to a halogen-free flame-retardant polypropylene film and a preparation method thereof. Background Art

[0002] Polypropylene is a crystalline polymer with a regular structure, which is polymerized with propylene as a monomer. It is a white granular, odorless, non-toxic, lightweight thermoplastic resin. As a hydrocarbon, polypropylene has an oxygen index of only 17.4, is easy to burn, has poor flame retardancy, generates high heat when burning, and is prone to fires when dripping, posing a threat to life and property. In the field of electronics and electrical appliances, the flammable nature of polypropylene limits its wider application, so many researchers have begun to work on the flame retardant development of PP materials.

[0003] Although traditional polypropylene materials have excellent mechanical properties and processing properties, polypropylene materials themselves have weak oxygen barrier properties and are low-barrier polymer materials. In addition, polypropylene is a non-self-supporting, flammable polymer with a fast flame propagation speed and a low limiting oxygen index, which seriously affects its safety during use. At present, most of the flame retardants used in reported PP flame-retardant films contain halogens, which do not meet the requirements of green environmental protection. Therefore, developing a halogen-free flame-retardant polypropylene film is one of the current research hotspots. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the present invention provides a halogen-free flame-retardant polypropylene film and a preparation method thereof, which not only has good thermal conductivity but also can achieve the purpose of halogen-free flame retardancy.

[0005] The technical solution provided by the present invention is: a halogen-free flame retardant polypropylene film, comprising the following raw materials in parts by weight: 60-100 parts of polypropylene resin, 20-40 parts of halogen-free flame retardant, 3-10 parts of high thermal conductivity filler, 1-3 parts of antioxidant, 0.1-3 parts of anti-dripping agent, 1-3 parts of smoke suppressant, the halogen-free flame retardant is obtained by compounding piperazine pyrophosphate and melamine polyphosphate, the mass ratio of piperazine pyrophosphate to melamine polyphosphate is between 1:1-3:1, and the high thermal conductivity filler is any one of non-oxide ceramic fillers.

[0006] Furthermore, the polypropylene resin is a mixture of homopolymer polypropylene resin and copolymer polypropylene resin, wherein the mass ratio of the homopolymer polypropylene resin to the copolymer polypropylene resin is 1:1-5:1.

[0007] Furthermore, the oxide ceramic filler is selected from one or more of boron nitride, aluminum nitride, silicon boride, silicon carbide, and titanium carbide, and the particle size of the non-oxide ceramic filler particles is 0.2um≤D50≤10um, more preferably 3um≤D50≤7um, and most preferably 4.5um≤D50≤5.5um.

[0008] Furthermore, the antioxidant is selected from at least one of antioxidant 168 and antioxidant 1010.

[0009] Furthermore, the anti-dripping agent is selected from any one of polytetrafluoroethylene powder and modified polytetrafluoroethylene powder.

[0010] Furthermore, the smoke suppressant is selected from any one of molybdenum trioxide, ammonium octamolybdate, aluminum hypophosphite, antimony trioxide, zinc hydroxystannate, and montmorillonite.

[0011] Another technical solution provided by the present invention is a method for preparing a halogen-free flame-retardant polypropylene film, comprising the following steps:

[0012] Step 1: According to the ratio of raw materials, polypropylene resin, halogen-free flame retardant, high thermal conductivity filler, antioxidant, anti-dripping agent and smoke suppressant are added into a high-speed mixer and mixed evenly to obtain a mixed material;

[0013] Step 2: putting the mixed material obtained in step 1 into the hopper of the extruder, and obtaining a flame retardant polypropylene film semi-finished product after melt extrusion and casting roll forming;

[0014] Step 3: Cool and shape the flame-retardant polypropylene film semi-finished product obtained in step 2, then stretch it through a traction system, and then roll it up and package it to obtain a halogen-free flame-retardant polypropylene film.

[0015] Furthermore, in the step 2, the operating temperature of the extruder is 180-230°C, and the casting temperature is 30-60°C.

[0016] Furthermore, the stretching ratio of the traction system in step three is 1.0-2.0.

[0017] Furthermore, the thickness of the halogen-free flame-retardant polypropylene film is 30-100 um.

[0018] Beneficial effects of the present invention:

[0019] (1) The film obtained by the present invention has good thermal conductivity under the action of thermal conductive filler, and the thermal conductive filler has the characteristics of small particle size, uniform distribution, large specific surface area, and high surface activity, and has good matching with polypropylene raw materials, and can also improve the mechanical properties and thermal conductive dielectric properties of the composite material.

[0020] (2) The present invention forms a halogen-free flame retardant by compounding piperazine pyrophosphate and melamine polyphosphate, and the mass ratio of the two is between 1:1-3:1, which can significantly improve the limiting oxygen index of the polypropylene flame retardant film. The synergistic effect between the high thermal conductivity filler, the anti-dripping agent and the halogen-free flame retardant can significantly improve the thermal conductivity, anti-dripping performance, flame retardant performance and mechanical properties of the polypropylene material.

[0021] (3) The halogen-free flame-retardant polypropylene film provided by the present invention is environmentally friendly, has good mechanical properties, and excellent processing properties. At the same time, the halogen-free flame-retardant polypropylene film of the present invention can reduce the frequency of fire accidents during use and ensure personal and property safety. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of the present invention more clear, the technical solutions of the present invention are further explained with specific implementation cases below.

[0023] Example 1

[0024] A method for preparing a halogen-free flame-retardant polypropylene film comprises the following steps:

[0025] (1) Add polypropylene resin, halogen-free flame retardant (piperazine pyrophosphate, melamine polyphosphate), high thermal conductivity filler boron nitride, antioxidant 1010, anti-dripping agent polytetrafluoroethylene powder, and smoke suppressant aluminum hypophosphite into a high-speed mixer and stir evenly to obtain a mixed material.

[0026] (2) putting the mixture obtained in step (1) into the hopper of an extruder, subjecting it to melt extrusion (extrusion temperature of 200° C.), and casting it on a casting roll at a temperature of 40° C. to obtain a flame-retardant polypropylene film semi-finished product;

[0027] (3) The semi-finished polypropylene film obtained in step (2) is cooled and shaped, and the traction stretching ratio is 1.1, and then the flame-retardant polypropylene film is obtained after winding and packaging.

[0028] The raw material ratios in Example 1 are calculated by weight: 90 weight parts of polypropylene resin, 30 weight parts of halogen-free flame retardant, 5 weight parts of high thermal conductivity filler boron nitride, 1.5 weight parts of antioxidant 1010, 0.5 weight parts of anti-drip agent polytetrafluoroethylene powder, and 1.2 weight parts of smoke suppressant aluminum hypophosphite. The weight ratio of homopolymer polypropylene resin to copolymer polypropylene resin in the polypropylene resin is 3:1; the weight ratio of piperazine pyrophosphate to melamine polyphosphate in the halogen-free flame retardant is 2:1.

[0029] Example 2

[0030] (1) Add polypropylene resin, halogen-free flame retardant (piperazine pyrophosphate, melamine polyphosphate), high thermal conductivity filler aluminum nitride, antioxidant 1010, anti-dripping agent modified polytetrafluoroethylene powder, and smoke suppressant aluminum hypophosphite into a high-speed mixer and stir evenly to obtain a mixed material.

[0031] (2) putting the mixture obtained in step (1) into the hopper of an extruder, subjecting it to melt extrusion (extrusion temperature 210° C.), and casting it on a casting roll at a temperature of 55° C. to obtain a flame retardant polypropylene film semi-finished product;

[0032] (3) The semi-finished polypropylene film obtained in step (2) is cooled and shaped, and the traction stretching ratio is 1.1, and then the flame-retardant polypropylene film is obtained after winding and packaging.

[0033] The proportions of the raw materials in Example 2 are calculated by weight: 90 weight parts of polypropylene resin, 30 weight parts of halogen-free flame retardant, 5 weight parts of aluminum nitride, a high thermal conductivity filler, 1.5 weight parts of antioxidant 1010, 0.5 weight parts of polytetrafluoroethylene powder, an anti-drip agent, and 1.2 weight parts of aluminum hypophosphite, a smoke suppressant. The weight ratio of homopolymer polypropylene resin to copolymer polypropylene resin in the polypropylene resin is 3:1; the weight ratio of piperazine pyrophosphate to melamine polyphosphate in the halogen-free flame retardant is 1.5:1.

[0034] Example 3

[0035] A method for preparing a halogen-free flame-retardant polypropylene film comprises the following steps:

[0036] (1) Add polypropylene resin, halogen-free flame retardant (piperazine pyrophosphate, melamine polyphosphate), high thermal conductivity filler borosilicate, antioxidant 168, anti-dripping agent modified polytetrafluoroethylene powder, and smoke suppressant montmorillonite into a high-speed mixer and stir evenly to obtain a mixed material.

[0037] (2) putting the mixture obtained in step (1) into the hopper of an extruder, subjecting it to melt extrusion (extrusion temperature 210° C.), and casting it on a casting roll at a temperature of 50° C. to obtain a flame retardant polypropylene film semi-finished product;

[0038] (3) The semi-finished polypropylene film obtained in step (2) is cooled and shaped, and the traction stretching ratio is 1.2, and then the flame-retardant polypropylene film is obtained after winding and packaging.

[0039] The proportions of the raw materials in Example 3 are calculated by weight: 100 weight parts of polypropylene resin, 25 weight parts of halogen-free flame retardant, 3 weight parts of borosilicate, a high thermal conductivity filler, 1.8 weight parts of antioxidant 168, 0.6 weight parts of anti-drip agent modified polytetrafluoroethylene powder, and 1.1 weight parts of smoke suppressant montmorillonite. The weight ratio of homopolymer polypropylene resin to copolymer polypropylene resin in the polypropylene resin is 4:1; the weight ratio of piperazine pyrophosphate to melamine polyphosphate in the halogen-free flame retardant is 2:1.

[0040] Example 4

[0041] A method for preparing a halogen-free flame-retardant polypropylene film comprises the following steps:

[0042] (1) Add polypropylene resin, halogen-free flame retardant (piperazine pyrophosphate, melamine polyphosphate), high thermal conductivity filler silicon carbide, antioxidant 1010, anti-dripping agent modified polytetrafluoroethylene powder, and smoke suppressant zinc hydroxystannate into a high-speed mixer and stir evenly to obtain a mixed material.

[0043] (2) putting the mixture obtained in step (1) into the hopper of an extruder, subjecting it to melt extrusion (extrusion temperature 205° C.), and casting it on a casting roll at a temperature of 45° C. to obtain a flame retardant polypropylene film semi-finished product;

[0044] (3) The semi-finished polypropylene film obtained in step (2) is cooled and shaped, and the traction stretching ratio is 1.3, and then the flame-retardant polypropylene film is obtained after winding and packaging.

[0045] The raw material ratios in Example 4 are calculated by weight: 100 weight parts of polypropylene resin, 35 weight parts of halogen-free flame retardant, 7 weight parts of high thermal conductivity filler silicon carbide, 2 weight parts of antioxidant 1010, 0.8 weight parts of anti-drip agent modified polytetrafluoroethylene powder, and 2 weight parts of smoke suppressant zinc hydroxystannate. The weight ratio of homopolymer polypropylene resin to copolymer polypropylene resin in the polypropylene resin is 5:1; the weight ratio of piperazine pyrophosphate to melamine polyphosphate in the halogen-free flame retardant is 1:1.

[0046] Comparative Example 1

[0047] A flame retardant film, the specific implementation manner of which is the same as that of Example 1, except that the halogen-free flame retardant is only piperazine pyrophosphate, and there is no high thermal conductivity filler boron nitride.

[0048] Comparative Example 2

[0049] A flame retardant film, the specific implementation manner of which is the same as that of Example 1, except that the halogen-free flame retardant is only melamine polyphosphate, and there is no high thermal conductivity filler aluminum nitride.

[0050] Comparative Example 3

[0051] A flame retardant film, the specific implementation manner of which is the same as that of Example 2, except that the mass ratio of piperazine pyrophosphate to melamine polyphosphate in the halogen-free flame retardant is 4:1.

[0052] Comparative Example 4

[0053] A flame retardant film, the specific implementation manner of which is the same as that of Example 2, except that the mass ratio of piperazine pyrophosphate to melamine polyphosphate in the halogen-free flame retardant is 1:5.

[0054] Performance Testing:

[0055]

[0056]

[0057] It can be seen from the above table that the limiting oxygen index of the materials obtained in comparative examples 1-4 is less than 22%, which is a flammable material; in Examples 1-4, the compound system of piperazine pyrophosphate and melamine polyphosphate forms a halogen-free flame retardant, and the mass ratio of the two is between 1:1-3:1, which can significantly improve the limiting oxygen index of the polypropylene flame retardant film. The synergistic effect between the high thermal conductivity filler and the halogen-free flame retardant can significantly improve the thermal conductivity, anti-dripping performance, flame retardant performance and mechanical properties of the polypropylene material. The data in the table show that the halogen-free flame retardant polypropylene film prepared by the present invention has stable performance. In summary, the halogen-free flame retardant polypropylene film and its preparation method provided by the present invention not only have environmental protection, good mechanical properties and excellent processing properties, but also have excellent flame retardant properties and anti-dripping properties. During use, the halogen-free flame retardant polypropylene film of the present invention can reduce the frequency of fire accidents and ensure personal and property safety.

[0058] The above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. A halogen-free flame-retardant polypropylene film, characterized in that: The invention comprises the following raw materials in parts by weight: 60-100 parts of polypropylene resin, 20-40 parts of halogen-free flame retardant, 3-10 parts of high thermal conductivity filler, 1-3 parts of antioxidant, 0.1-3 parts of anti-dripping agent and 1-3 parts of smoke suppressant. The halogen-free flame retardant is compounded by piperazine pyrophosphate and melamine polyphosphate, the mass ratio of piperazine pyrophosphate to melamine polyphosphate is between 1:1-3:1, and the high thermal conductivity filler is any one of non-oxide ceramic fillers.

2. The halogen-free flame-retardant polypropylene film according to claim 1, characterized in that: The polypropylene resin is a mixture of homopolymer polypropylene resin and copolymer polypropylene resin, wherein the mass ratio of the homopolymer polypropylene resin to the copolymer polypropylene resin is 1:1-5:

1.

3. The halogen-free flame-retardant polypropylene film according to claim 1, characterized in that: The oxide ceramic filler is selected from one or more of boron nitride, aluminum nitride, silicon boride, silicon carbide, and titanium carbide. The particle size of the non-oxide ceramic filler particles is 0.2um≤D50≤10um.

4. The halogen-free flame-retardant polypropylene film according to claim 1, characterized in that: The antioxidant is selected from at least one of antioxidant 168 and antioxidant 1010.

5. The halogen-free flame-retardant polypropylene film according to claim 1, characterized in that: The anti-dripping agent is selected from any one of polytetrafluoroethylene powder and modified polytetrafluoroethylene powder.

6. The halogen-free flame-retardant polypropylene film according to claim 1, characterized in that: The smoke suppressant is selected from any one of molybdenum trioxide, ammonium octamolybdate, aluminum hypophosphite, antimony trioxide, zinc hydroxystannate, and montmorillonite.

7. The method for preparing a halogen-free flame-retardant polypropylene film according to claim 1, characterized in that: The steps include: Step 1: According to the ratio of raw materials, polypropylene resin, halogen-free flame retardant, high thermal conductivity filler, antioxidant, anti-dripping agent and smoke suppressant are added into a high-speed mixer and mixed evenly to obtain a mixed material; Step 2: putting the mixed material obtained in step 1 into the hopper of the extruder, and obtaining a flame retardant polypropylene film semi-finished product after melt extrusion and casting roll forming; Step 3: Cool and shape the flame-retardant polypropylene film semi-finished product obtained in step 2, then stretch it through a traction system, and then roll it up and package it to obtain a halogen-free flame-retardant polypropylene film.

8. The method for preparing a halogen-free flame-retardant polypropylene film according to claim 7, characterized in that: In the step 2, the operating temperature of the extruder is 180°C-230°C, and the casting temperature is 30°C-60°C.

9. The method for preparing a halogen-free flame-retardant polypropylene film according to claim 7, characterized in that: The stretching ratio of the traction system in step 3 is 1.0-2.

0.

10. The method for preparing a halogen-free flame-retardant polypropylene film according to claim 7, characterized in that: The thickness of the halogen-free flame-retardant polypropylene film is 30-100 um.

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