CN110003677A - A kind of halogen-free polypropylene flame redardant wood plastic composite and preparation method thereof - Google Patents

Abstract

The invention discloses a halogen-free flame-retardant polypropylene wood-plastic composite material and a preparation method thereof, comprising the following components in mass fractions: 10-50 parts of waste epoxy resin, 20-60 parts of polypropylene and 20-60 parts of wood powder 60 parts, flame retardant system 15-40 parts, antistatic agent 10-40 parts, coupling agent 2-10 parts, compatibilizer 5-15 parts, heat stabilizer 2-5 parts, antioxidant 1-4 parts , 1-4 parts of lubricant. The invention uses the "two-step melting method" to prepare the wood-plastic composite material, and the method can effectively improve the interface compatibility and improve the flame-retardant effect of the wood-plastic composite material on the premise of maintaining good mechanical properties. The polypropylene wood-plastic composite material prepared by the invention has the advantages of simple production process and good flame retardant effect, and can effectively reduce environmental pollution and protect forest resources while realizing the reuse of waste epoxy resin.

Description

A halogen-free flame-retardant polypropylene wood-plastic composite material and preparation method thereof

technical field

The invention relates to a wood-plastic composite material and a preparation method thereof, in particular to a halogen-free flame-retardant polypropylene wood-plastic composite material and a preparation method thereof.

Background technique

Wood Plastic Composite (WPC) is a kind of green composite material made of low-cost, natural wood, hemp and other natural fibers or powder materials and thermoplastics (including PE, PP, PVC, etc.) as the main raw materials. Environmentally friendly and environmentally friendly new materials. WPC has good processing properties and mechanical properties, and the market potential is huge. In recent years, with the vigorous development of the electronics industry, epoxy resin has been widely used in the housing of electronic products because of its good electrical insulation properties and sealing properties. However, epoxy resins are difficult to reuse due to their special three-dimensional network structure and insolubility. Adding waste epoxy resin obtained by mechanical crushing as a filler to organic polymer materials to make recycled polymer materials can not only reduce the cost of products, but also alleviate the environmental pressure caused by waste landfill and incineration. In addition, because wood fibers and plastics are hydrocarbons, wood-plastic materials can burn in the presence of an open flame or under heating, and it is difficult to self-extinguish after burning. Therefore, it is difficult for WPC to achieve interior decoration without flame retardant treatment. In principle, it is not allowed to be directly used as relevant building decoration materials according to the requirements of the design fire protection code.

At present, most of the flame retardant properties of wood-plastic composites are improved by adding flame retardants at home and abroad. The patent with the application number of 201811153485.2 discloses a high-strength flame-retardant wood-plastic material and a preparation method thereof. It is found that the flame-retardant performance of the wood-plastic material can be significantly improved by adding antimony trioxide (Sb ₂ O ₃ ), but Sb ₂ O ₃ has been listed by the World Health Organization (WHO) as a Class 2B carcinogen in October 2017, which is harmful to human health. The patent with the application number of 201810046114.8 discloses a flame-retardant polypropylene-based wood-plastic composite board and a preparation method. However, the flame-retardant modification process is complicated and the cost is high, which is not conducive to industrial production. The patent with the application number of 201010235935.X discloses a flame-retardant wood-plastic composite material and a preparation method thereof. It fires the wood-plastic composite material by adding red phosphorus with a mass fraction of 2% to 10%, and obtains better results. However, red phosphorus itself is easy to absorb moisture, has poor thermal stability, and is prone to generate extremely toxic phosphine (PH ₃ ) during processing, which limits its application. Deka (Journal of Applied Polymer Science, 2012, 124(4): 2919-2929) prepared polyethylene wood-plastic composites and found that nanoclay and ZnO could improve the flame retardant properties of wood-plastic materials, but only a small amount of clay and ZnO were added. The flame retardant efficiency is not high, and too much addition will reduce the mechanical properties of wood-plastic materials. The patent of 201711279323.9 discloses a preparation method of high-strength flame-retardant PE wood-plastic floor. The PE wood-plastic floor is flame-retardant by adding a self-made flame-retardant function mother liquor, and the flame-retardant effect is good, but the disclosed flame retardant preparation process It is complicated and expensive, which is not conducive to the industrial production of flame-retardant wood-plastic.

In addition, because wood fibers and plastics are both insulating substances, static electricity is easily generated during use. The electrostatic action will cause the products to absorb dust in the air, which will easily lead to distortion of precision instruments, failure of electronic components, and even more, static electricity will cause fire or explosion, etc. The patent with the application number of 201711315715.6 discloses an antistatic PVC wood-plastic composite material and a preparation method thereof. The PVC wood-plastic composite material obtained by using layered graphene powder as an antistatic agent has excellent mechanical properties and has Good antistatic properties. The patent with the application number of 201410723764.3 discloses a conductive/antistatic polyethylene wood-plastic composite material and a preparation method thereof. The antistatic agent used in it is a multi-walled carbon nanotube with a diameter of 20-100 nm and a length of 10-50 μm. The wood-plastic material has good antistatic effect. However, the antistatic agent used in the above method is expensive, which leads to the high production cost of the antistatic wood-plastic composite material, which is not conducive to the realization of industrialized production.

SUMMARY OF THE INVENTION

The invention discloses a halogen-free flame-retardant polypropylene wood-plastic composite material and a preparation method thereof in order to solve the problems of poor fire resistance, high anti-static cost and unfavorable industrialized production of the existing wood-plastic composite material.

In the invention, waste epoxy resin and thermoplastic plastic are blended, and then compounded with wood powder, ammonium polyphosphate (APP) is used as a flame retardant, and iron powder is used as an antistatic agent, and the wood-plastic composite material is prepared by a two-step melt extrusion process. Due to the pretreatment of wood powder and the use of secondary melting process, the interfacial bonding properties between resin, wood fiber and blended resin are effectively improved, and the impact toughness of the composite material is improved. Moreover, the present invention effectively reduces environmental pollution while realizing the recycling and reuse of waste epoxy resin, and provides a sustainable development approach for building a resource-saving and environment-friendly society in my country.

The halogen-free flame-retardant polypropylene wood-plastic composite material of the invention is obtained by processing main materials and auxiliary materials.

Described main material includes each component of following mass parts:

10-50 parts of waste epoxy resin

Thermoplastic 20-60 copies

20-60 servings of wood flour.

Described auxiliary material comprises each component of following mass parts:

The waste epoxy resin is the waste epoxy resin powder after crushing, grinding and sieving, and the particle size is 40-100 mesh.

The thermoplastic is polypropylene (PP), and the polypropylene has a melt flow rate of 0.5-5 g/10min.

The particle size of the wood flour is 40-80 mesh.

The flame retardant system includes a flame retardant and a synergist, wherein the flame retardant is ammonium polyphosphate with a degree of polymerization of 1000-4000, and the synergist is one of pentaerythritol, melamine, magnesium hydroxide, aluminum hydroxide, or the like. The mass ratio of the flame retardant and the synergist in the flame retardant system is 1:2-4:1.

The antistatic agent is one or more of metal powders such as iron powder, copper powder, aluminum powder, etc.; and the particle size of the metal powder is 20-100 μm.

The coupling agent is any one of a silane coupling agent, an aluminate coupling agent, a zirconate coupling agent, a titanate coupling agent, a phosphorus-containing coupling agent, and the like.

The compatibilizer is maleic anhydride branched polypropylene (MAH-g-PP), and the graft ratio of MAH is greater than or equal to 0.8%.

The heat stabilizer is a calcium-zinc composite heat stabilizer, and its function is to thermally stabilize the blended resin.

The antioxidant is selected from any one of hindered phenols, phosphites, thioesters, composite antioxidants, and the like.

The lubricant is selected from any one of liquid paraffin, stearic acid, calcium stearate, zinc stearate, chlorinated ethylene wax, and ethylene oxide wax.

Further, the mass ratio of the waste epoxy resin and thermoplastic is 1:1-1:3.

Further, the mass ratio of the coupling agent to the wood powder is 1:10-1:20.

The preparation method of halogen-free flame-retardant polypropylene wood-plastic composite material of the present invention comprises the following steps:

Step 1: Drying of Waste Epoxy Resin and Wood Flour

Dry the waste epoxy resin and wood powder in an oven at 60-90 ℃ for 4-8 hours, so that the moisture content is lower than 2%;

Step 2: Pretreatment of Wood Flour

Soak the wood powder in ethanol containing a coupling agent, disperse it ultrasonically for 1-3 hours, heat and stir until it solidifies, and put it in an oven to dry for 1-2 hours to obtain the pretreated wood powder;

Step 3: One Melt Mixing and Extrusion Pelletizing

Add waste epoxy resin, thermoplastic, antistatic agent, compatibilizer, heat stabilizer, antioxidant and lubricant to a high-speed mixer and stir evenly to obtain a primary mixture; add the primary mixture to a twin-screw extruder , carry out the first melt blending, extrusion granulation to obtain pellet A;

Step 4: Secondary Melt Mixing and Extrusion

Add the pellets A, pretreated wood powder, flame retardant and synergist into a high-speed mixer to stir and mix evenly to obtain a secondary mixture; add the secondary mixture to a twin-screw extruder, and carry out the second melt co-coagulation. Mixed and extruded to obtain halogen-free flame retardant polypropylene wood-plastic composite material.

In step 3, the temperature of the high-speed mixer is set to 40-60° C., the rotational speed is 300-500 rpm, and the mixing time is 10-20 min.

In step 3, the extrusion temperature of the twin-screw extruder is 190-215° C., and the screw speed is 80-120 rpm.

In step 4, the temperature of the high-speed mixer is set to 40-60° C., the rotational speed is 300-500 rpm, and the mixing time is 10-20 min.

In step 4, the extrusion temperature of the twin-screw extruder is 185-210° C., and the screw speed is 70-110 rpm.

The invention uses the "two-step melting" process to prepare the wood-plastic composite material, the method can effectively improve the interface compatibility, and the prepared composite material can have good flame retardant performance and antistatic property on the premise of maintaining good mechanical properties. performance. The technological process of the invention is simple, and is favorable for realizing industrialized production.

Description of drawings

FIG. 1 is a scanning electron microscope photograph of the cross section of the sample of Example 1. FIG.

FIG. 2 is a scanning electron microscope photograph of the cross section of the sample in Example 2. FIG.

FIG. 3 is a scanning electron microscope photograph of a cross section of a comparative example.

Detailed ways

The present invention is further described below in conjunction with specific embodiments, but the scope of the present invention is not limited by these embodiments.

Example 1:

1. Ingredients

Waste epoxy resin: 300g

PP plastic: 300g

Wood flour: 600g

APP: 150g

Mg(OH) ₂ : 50g

Fe powder: 150g

Aluminate coupling agent: 70g

MAH-g-PP: 50g

Calcium zinc heat stabilizer: 20g

Antioxidant 168: 20g

Stearic acid: 15g

2. Preparation

(1) Dry the waste epoxy resin and wood powder in an oven at 80°C for 5 hours, so that the moisture content is lower than 2%;

(2) Soak the wood powder in ethanol containing aluminate coupling agent, disperse by ultrasonic for 2 hours, heat and stir to solidify, and put it in an oven to dry for 1 hour;

(3) Add waste epoxy resin, PP plastic, Fe powder, MAH-g-PP, calcium zinc heat stabilizer, antioxidant 168 and stearic acid into the high-speed mixer, and mix at 40°C and 400rpm. 15min to obtain primary compound A; add primary compound A to the twin-screw extruder for the first melt blending and granulation to obtain pellet A, the extrusion temperature is 210 ° C, and the screw speed is 120 rpm;

(4) adding above-mentioned pellets A and pretreated wood powder, APP and Mg(OH) into the high _- speed mixer, and mixing for 15min at 40° C. and rotating speed 400rpm to obtain secondary mixture; The material is added to a twin-screw extruder, and the second melt blending is carried out at a temperature of 205 ° C and a screw speed of 105 rpm, and the halogen-free flame retardant polypropylene wood-plastic composite material is obtained by extrusion.

Example 2:

1. Ingredients

Waste epoxy resin: 180g

PP plastic: 420g

Wood flour: 600g

APP: 150g

Mg(OH) ₂ : 50g

Fe powder: 150g

Aluminate coupling agent: 70g

MAH-g-PP: 50g

Calcium zinc heat stabilizer: 20g

Antioxidant 168: 20g

Stearic acid: 15g

2. Preparation

(1) Dry the waste epoxy resin and wood powder in an oven at 80°C for 5 hours, so that the moisture content is lower than 2%;

(2) Soak the wood powder in ethanol containing aluminate coupling agent, disperse by ultrasonic for 2 hours, heat and stir to solidify, and put it in an oven to dry for 1 hour;

(3) Add waste epoxy resin, PP plastic, Fe powder, MAH-g-PP, calcium zinc heat stabilizer, antioxidant 168 and stearic acid into the high-speed mixer, at 40 ° C and 400 rpm under the condition of Mix for 15min to obtain primary compound A; add primary compound A to the twin-screw extruder for the first melt blending and granulation to obtain pellet A, the extrusion temperature is 210 ° C, and the screw speed is 120 rpm;

(4) adding above-mentioned pellets A and pretreated wood powder, APP and Mg(OH) into the high _- speed mixer, and mixing for 15min at 40° C. and rotating speed 400rpm to obtain secondary mixture; The material is added to a twin-screw extruder, and the second melt blending is carried out at a temperature of 205 ° C and a screw speed of 105 rpm, and the halogen-free flame retardant polypropylene wood-plastic composite material is obtained by extrusion.

Comparative ratio:

1. Ingredients

Waste epoxy resin: 300g

PP plastic: 300g

Wood flour: 600g

Aluminate coupling agent: 70g

MAH-g-PP: 50g

Calcium zinc heat stabilizer: 20g

Antioxidant 168: 20g

Stearic acid: 15g

2. Preparation

(1) Dry the waste epoxy resin and wood powder in an oven at 80°C for 5 hours, so that the moisture content is lower than 2%;

(2) Soak the wood powder in ethanol containing aluminate coupling agent, disperse by ultrasonic for 2 hours, heat and stir to solidify, and put it in an oven to dry for 1 hour;

(3) Add waste epoxy resin, PP plastic, MAH-g-PP, calcium zinc heat stabilizer, antioxidant 168 and stearic acid into the high-speed mixer, and mix at 40°C and 400rpm for 15min, The primary compound A was obtained; the primary compound A was added to the twin-screw extruder for the first melt blending and granulation to obtain pellet A, and the extrusion temperature was 210 ° C and the screw speed was 120 rpm;

(4) adding above-mentioned pellets A and wood powder into a high-speed mixer, and mixing for 15 minutes at 40° C. and a rotating speed of 400rpm to obtain a secondary mixture; adding the secondary mixture into a twin-screw extruder, at a temperature of 205 ℃ Under the conditions of ℃ and screw speed of 105 rpm, the second melt blending is carried out, and the halogen-free flame retardant polypropylene wood-plastic composite material is obtained by extrusion.

Combustion properties, antistatic properties and mechanical properties of the composite materials prepared in the examples and comparative examples were tested. The result is as follows:

Table 1. Performance test parameters of PP wood-plastic composites

Combustion parameters Example 1 Example 2 Comparative ratio Thermal decomposition temperature (℃) 477.3 478.6 472.9 Ignition time (s) 31 32 26 Extinguishing time (s) 300 331 336 Total heat release (MJ/m²) 64.5 66.0 69.6 Average heat release rate (kW/m²) 239.7 220.8 224.5 Peak heat release rate (kW/m²) 375.2 384.6 504.2 Average mass loss rate (g/s) 0.072 0.062 0.071 Peak mass loss rate (g/s) 0.267 0.275 0.867 Average yield of CO (kg/kg) 0.001 0.001 0.002 Average yield of CO₂ (kg/kg) 1.141 1.692 2.120 Carbonization rate (%) 29.2 27.9 26.7 Volume resistivity (Ω·m) 4.13E+07 3.94E+07 1.19E+08 Notched impact strength (kJ/m²) 4.5 4.9 3.9

Note: Cone calorimetry test is performed according to ASTM E1354, ISO 5560 standard; volume resistivity is tested according to GB/T1410-2006 standard; Notched impact strength is tested according to GB/T 1043.1-2008 standard.

It can be seen from Table 1 that the total heat release amount and the peak heat release rate of the comparative example (without flame retardant) are as high as 69.6MJ/m ² and 224.5MJ/m ² , while after adding the flame retardant, Example 1 and Example Both the heat release amount and the heat release rate of 2 were significantly reduced. In addition, the yields of CO and CO ₂ of the composite material decreased, and the char formation rate increased, indicating that the wood-plastic composite material obtained by this implementation method has good flame retardant properties. After adding the antistatic agent Fe, the volume resistivity of Examples 1 and 2 decreased by an order of magnitude compared with the comparative example, which effectively improved the antistatic performance of the material. Figures 1-3 are scanning electron microscope photographs of the three samples. It is not difficult to see that in the samples prepared by wood powder pretreatment and "two-step melting" process, both wood powder particles and ammonium polyphosphate APP particles show good uniform dispersion, which effectively promotes the reasonable dispersion of fillers in the phase interface. , to achieve the improvement of impact strength.

To sum up, the present invention can obviously improve the flame retardant performance and antistatic performance of the wood-plastic composite material on the premise of ensuring good mechanical properties, and the process is simple and suitable for industrial production.

The above only exemplifies the present invention. It should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacements that those skilled in the art can do without creative effort are all within the scope of the present invention. within the scope of protection.

Claims (10)

1. a halogen-free flame-retardant polypropylene wood-plastic composite material is characterized in that the halogen-free flame-retardant polypropylene wood-plastic composite material is processed and obtained by main material and auxiliary material; Described main material includes each component of following mass parts: 10-50 parts of waste epoxy resin Thermoplastic 20-60 copies 20-60 servings of wood flour; Described auxiliary material comprises each component of following mass parts: 2. halogen-free flame-retardant polypropylene wood-plastic composite material according to claim 1, is characterized in that: The waste epoxy resin is the waste epoxy resin powder after crushing, grinding and sieving, and the particle size is 40-100 mesh; The thermoplastic is polypropylene, and the melt flow rate of the polypropylene is 0.5-5 g/10min; The particle size of the wood flour is 40-80 mesh. 3. halogen-free flame retardant polypropylene wood-plastic composite material according to claim 1, is characterized in that: The flame retardant system includes a flame retardant and a synergist, wherein the flame retardant is ammonium polyphosphate with a degree of polymerization of 1000-4000, and the synergist is one of pentaerythritol, melamine, magnesium hydroxide, aluminum hydroxide, or the like. Several; the mass ratio of flame retardant and synergist in the flame retardant system is 1:2-4:1; The antistatic agent is one or more of metal powders such as iron powder, copper powder, aluminum powder, etc., and the particle size of the metal powder is 20-100 μm; The coupling agent is any one of a silane coupling agent, an aluminate coupling agent, a zirconate coupling agent, a titanate coupling agent, a phosphorus-containing coupling agent, and the like; The compatibilizer is maleic anhydride grafted polypropylene MAH-g-PP, and the graft ratio of MAH is ≥0.8%; The heat stabilizer is a calcium-zinc composite heat stabilizer; The antioxidant is selected from any one of hindered phenols, phosphites, thioesters, composite antioxidants, etc.; The lubricant is selected from any one of liquid paraffin, stearic acid, calcium stearate, zinc stearate, chlorinated ethylene wax, and ethylene oxide wax. 4. halogen-free flame-retardant polypropylene wood-plastic composite material according to claim 1, is characterized in that: The mass ratio of the waste epoxy resin and the thermoplastic is 1:1-1:3. 5. halogen-free flame-retardant polypropylene wood-plastic composite material according to claim 1, is characterized in that: The mass ratio of the coupling agent to the wood powder is 1:10-1:20. 6. a preparation method of any halogen-free flame retardant polypropylene wood-plastic composite material in claim 1-5, is characterized in that comprising the steps: Step 1: Drying of Waste Epoxy Resin and Wood Flour Dry the waste epoxy resin and wood powder in an oven at 60-90 ℃ for 4-8 hours, so that the moisture content is lower than 2%; Step 2: Pretreatment of Wood Flour Soak the wood powder in ethanol containing a coupling agent, disperse it ultrasonically for 1-3 hours, heat and stir until it solidifies, put it in an oven to dry for 1-2 hours, and obtain the pretreated wood powder; Step 3: One Melt Mix Extrusion Add waste epoxy resin, thermoplastic, antistatic agent, compatibilizer, heat stabilizer, antioxidant and lubricant into a high-speed mixer and stir evenly to obtain a primary mixture; add the primary mixture into a twin-screw extruder, Carry out melt blending for the first time, extrude and granulate to obtain pellet A; Step 4: Secondary Melt Mixing Extrusion Add the pellets A, pretreated wood powder, flame retardant and synergist into a high-speed mixer to stir and mix evenly to obtain a secondary mixture; add the secondary mixture to a twin-screw extruder, and carry out the second melt co-coagulation. Mixed and extruded to obtain halogen-free flame retardant polypropylene wood-plastic composite material. 7. preparation method according to claim 6, is characterized in that: In step 3, the temperature of the high-speed mixer is set to 40-60° C., the rotational speed is 300-500 rpm, and the mixing time is 10-20 min. 8. preparation method according to claim 6, is characterized in that: In step 3, the extrusion temperature of the twin-screw extruder is 190-215° C., and the screw speed is 80-120 rpm. 9. preparation method according to claim 6, is characterized in that: In step 4, the temperature of the high-speed mixer is set to 40-60° C., the rotational speed is 300-500 rpm, and the mixing time is 10-20 min. 10. preparation method according to claim 6, is characterized in that: In step 4, the extrusion temperature of the twin-screw extruder is 185-210° C., and the screw speed is 70-110 rpm.