Water-resistant low-smoke intumescent flame-retardant polyethylene composite material and preparation method thereof

Abstract

The invention discloses a water-resistant low-smoke intumescent flame-retardant polyethylene composite material and a preparation method thereof, relates to the field of high polymer materials, and aims to solve the problems of relatively large flame retardant addition amount and relatively poor water resistance and smoke suppression performance in the modification process of an existing polyethylene flame retardant. The composite material comprises polyethylene matrix resin, a flame retardant, a synergist, a compatibilizer, a lubricant and an antioxidant. The method comprises the following steps: 1, mixing the flame retardant, the synergist, the compatibilizer, the lubricant and the antioxidant, then adding the polyethylene matrix resin, and continuously mixing to obtain a mixed material; and 2, adding the mixed material into a twin-screw extruder, carrying out melt blending, extrusion, cooling, air drying and granulation through the extruder, and then preparing the water-resistant low-smoke intumescent flame-retardant polyethylene composite material through an injection molding machine. The polyethylene composite material prepared by the invention has excellent flame retardance, water resistance and smoke suppression performance. The method is used for preparing the high-performance polyethylene material.

Description

Technical Field

[0001] The invention relates to the field of polymer materials, and in particular to a water-resistant, low-smoke swelling, flame-retardant polyethylene composite material and a preparation method thereof. Background Art

[0002] Polyethylene resin has the characteristics of easy processing, corrosion resistance, electrical insulation and good mechanical strength, and is widely used in packaging, construction, transportation, electronic and electrical, wire and cable and other fields. However, it is flammable and accompanied by severe molten droplets and large smoke release, which poses a threat to people's life and property safety. Therefore, it needs to be flame retardant and at the same time inhibit dripping and smoke release during combustion.

[0003] At present, the flame retardant modification of polyethylene is mainly achieved by adding inorganic metal hydroxides (such as magnesium hydroxide and aluminum hydroxide, etc.) to improve its flame retardant properties and reduce smoke release. However, this type of flame retardant has the problems of low flame retardant efficiency and large addition amount, which leads to a significant reduction in the mechanical properties of the material. Intumescent flame retardant (IFR) has better flame retardant efficiency and the effect of inhibiting molten droplets for polyethylene, but due to the high melt viscosity of polyethylene, the current addition amount of IFR usually needs to be added to more than 30wt% for the material to obtain better flame retardant properties, which will reduce the mechanical properties of the material and increase the cost. At the same time, the core component of the existing IFR, ammonium polyphosphate, has strong polarity and strong water absorption properties. The carbon layer formed when the material burns is insufficient in strength and density, and is prone to cracking under continuous combustion and high temperature conditions, which makes the material's water resistance and smoke suppression performance poor. Summary of the invention

[0004] The present invention aims to solve the problems of large amount of flame retardant added, poor water resistance and smoke suppression performance in the existing polyethylene flame retardant modification process, and provide a water-resistant, low-smoke expansion, flame-retardant polyethylene composite material and a preparation method thereof.

[0005] The invention provides a water-resistant, low-smoke, swelling, flame-retardant polyethylene composite material, which comprises, by mass percentage, 75-82wt% of polyethylene matrix resin, 15-25wt% of flame retardant, 1-5wt% of synergist, 1-3wt% of compatibilizer, 0.1-1wt% of lubricant, and the balance of antioxidant.

[0006] Furthermore, the flame retardant includes piperazine pyrophosphate and a compounding agent, wherein the compounding agent is one of dimelamine pyrophosphate, melamine polyphosphate, melamine cyanurate, triazine carbon-forming foaming agent, polyphenylene ether, or a mixture of any of them.

[0007] Furthermore, the polyethylene matrix resin is one of high-density polyethylene, low-density polyethylene, linear low-density polyethylene, or a mixture of any of them.

[0008] Furthermore, the synergist is one of polycarbosilane, MQ silicone resin, zinc oxide, nickel oxide, manganese oxide, copper oxide, lanthanum oxide, nickel aluminum hydrotalcite, nickel iron hydrotalcite, nickel aluminum magnesium hydrotalcite, kaolin, talc, diatomaceous earth, fly ash, molecular sieve or a mixture of any of them.

[0009] Furthermore, the compatibilizer is one or a mixture of maleic anhydride grafted polyethylene and silane grafted polyethylene.

[0010] Furthermore, the lubricant is polyethylene wax, polypropylene wax or a mixture of both.

[0011] Furthermore, the antioxidant is one of antioxidant 1010, antioxidant 1076, antioxidant 168, or a mixture of any of them.

[0012] The present invention also provides a method for preparing the water-resistant, low-smoke swelling, flame-retardant polyethylene composite material, comprising the following steps:

[0013] 1. Firstly, add the flame retardant, synergist, compatibilizer, lubricant and antioxidant into a high-speed mixer for mixing, and then add the polyethylene matrix resin and continue mixing to obtain a mixed material;

[0014] 2. Add the mixed material into a twin-screw extruder, melt blend, extrude, cool, air-dry and granulate through the extruder, and then prepare a water-resistant, low-smoke expansion and flame-retardant polyethylene composite material through an injection molding machine.

[0015] Furthermore, the mixing time of the two mixing steps in step 1 is 5 to 10 minutes.

[0016] Furthermore, the heating temperatures of each zone of the twin-screw extruder in step 2 are: zone 1 140-150°C; zone 2 145-155°C; zone 3 150-160°C; zone 4 155-165°C; zone 5 160-170°C; the die head temperature is 160-170°C, and the screw speed is 350-500 rpm.

[0017] Furthermore, in step 2, the temperatures of the various zones of the injection molding machine are: zone 1 150-160°C; zone 2 155-165°C; zone 3 160-170°C; and the head temperature 165-170°C.

[0018] Beneficial effects of the present invention:

[0019] The invention departs from the ammonium polyphosphate expansion flame retardant system and adopts a new flame retardant material to obtain a flame retardant system with excellent expansion and charring properties, plays an excellent expansion charring role in polyethylene materials with high melt viscosity, reduces the amount of flame retardant added, and improves the flame retardant efficiency.

[0020] By introducing flame retardant synergists into the intumescent flame retardant system, the carbonization is effectively catalyzed and the carbon layer is reinforced; the water resistance of the composite material is improved through the surface migration of hydrophobic silicone resin. During the combustion process, polycarbosilane plays a role in bonding and reinforcing the formed carbon layer, thus forming a stronger, better heat-resistant and denser carbon layer, thereby more effectively suppressing the release of smoke and heat.

[0021] The invention can meet the demand for high-performance polyethylene materials in the fields of wires and cables, electronic and electrical equipment, etc. DETAILED DESCRIPTION

[0022] The technical solution of the present invention is not limited to the specific implementation modes listed below, but also includes any combination of the specific implementation modes.

[0023] Specific embodiment 1: The water-resistant, low-smoke, intumescent, flame-retardant polyethylene composite material of this embodiment comprises, by mass percentage: 75-82wt% of polyethylene matrix resin, 15-25wt% of flame retardant, 1-5wt% of synergist, 1-3wt% of compatibilizer, 0.1-1wt% of lubricant, and the remainder of antioxidant; wherein the flame retardant comprises piperazine pyrophosphate and a compounding agent, wherein the compounding agent is one or a mixture of any of dimelamine pyrophosphate, melamine polyphosphate, melamine cyanurate, triazine carbon-forming foaming agent, and polyphenylene ether.

[0024] The piperazine structure in piperazine pyrophosphate and the benzene ring structure in polyphenylene ether in the flame retardant of the present invention have excellent charring performance. During heating or combustion, compounds containing melamine functional groups such as polymelamine phosphate, dimelamine pyrophosphate and melamine cyanurate decompose to generate sufficient flame-retardant gas with excellent expansion performance. The triazine charring foaming agent has both charring and expansion performance. After the flame retardant components are compounded, an intumescent flame retardant with excellent charring and expansion performance is obtained, which plays an excellent expansion charring role in polyethylene materials with high melt viscosity, thereby improving the flame retardant efficiency.

[0025] Specific implementation method 2: The polyethylene matrix resin in this implementation method is one of high-density polyethylene, low-density polyethylene, linear low-density polyethylene, or a mixture of any of the above. Other steps and parameters are the same as those in specific implementation method 1.

[0026] Specific embodiment 3: The synergist of this embodiment is one or a mixture of any of polycarbosilane, MQ silicone resin, zinc oxide, nickel oxide, manganese oxide, copper oxide, lanthanum oxide, nickel aluminum hydrotalcite, nickel iron hydrotalcite, nickel aluminum magnesium hydrotalcite, kaolin, talc, diatomaceous earth, fly ash, molecular sieve. Other steps and parameters are the same as those of specific embodiment 1 or 2.

[0027] The polycarbosilane in the synergist of the present invention is a ceramic precursor, which can effectively improve the strength of the carbon layer and the thermal stability at high temperature; MQ silicone resin forms nano silicon dioxide when burning, which improves the strength of the carbon layer; at the same time, polycarbosilane and MQ silicone resin are both low surface energy and hydrophobic substances, which can migrate to the surface of the material during material processing, thereby improving the water resistance of the polyolefin material. Metal oxides, hydrotalcites, and silicates can effectively catalyze the carbonization of the flame retardant during the combustion process, and at the same time play a role in reinforcing the carbon layer; fly ash and molecular sieves are porous materials, which play a role of supporting points in the carbonization process of the intumescent flame retardant, thereby effectively improving the strength of the carbon layer.

[0028] Specific embodiment 4: The compatibilizer of this embodiment is one or a mixture of maleic anhydride grafted polyethylene and silane grafted polyethylene. Other steps and parameters are the same as those of specific embodiments 1 to 3.

[0029] Compatibilizers can improve the compatibility of flame retardants with matrix resins and their dispersibility in resins, thereby improving the flame retardant efficiency of materials and maintaining good mechanical properties of composite materials.

[0030] Specific implementation method 5: The lubricant in this implementation method is polyethylene wax, polypropylene wax, or a mixture of the two. Other steps and parameters are the same as those in specific implementation methods 1 to 4.

[0031] Lubricants are used to improve the gloss and processing performance of materials.

[0032] Specific embodiment 6: The antioxidant in this embodiment is one of the antioxidants 1010, 1076, and 168, or a mixture of any of them. Other steps and parameters are the same as those in specific embodiments 1 to 5.

[0033] During the high-temperature melt processing and use of polyethylene composite materials, polymer materials are prone to oxidative degradation. The addition of flame retardants often accelerates the aging and degradation of materials, and the degraded polyethylene is more flammable. Therefore, antioxidants are added to improve the material's long-lasting flame retardancy and safe service life.

[0034] Specific embodiment 7: The preparation method of the water-resistant low-smoke swelling flame-retardant polyethylene composite material in this embodiment comprises the following steps:

[0035] 1. Firstly, add the flame retardant, synergist, compatibilizer, lubricant and antioxidant into a high-speed mixer for mixing, and then add the polyethylene matrix resin and continue mixing to obtain a mixed material;

[0036] 2. Add the mixed material into a twin-screw extruder, melt blend, extrude, cool, air-dry and granulate through the extruder, and then prepare a water-resistant, low-smoke expansion and flame-retardant polyethylene composite material through an injection molding machine.

[0037] Specific implementation example eight: In step one of this implementation example, the mixing time for the two times is 5 to 10 minutes. Other steps and parameters are the same as those of specific implementation example seven.

[0038] Specific implementation method 9: In step 2 of this implementation method, the heating temperature of each zone of the twin-screw extruder is: zone 1 140-150°C; zone 2 145-155°C; zone 3 150-160°C; zone 4 155-165°C; zone 5 160-170°C; die head temperature 160-170°C, screw speed 350-500 rpm. Other steps and parameters are the same as those of specific implementation method 7 or 8.

[0039] Specific embodiment 10: In step 2 of this embodiment, the temperature of each zone of the injection molding machine is: zone 1 150-160° C.; zone 2 155-165° C.; zone 3 160-170° C.; head temperature 165-170° C. Other steps and parameters are the same as those of specific embodiments 7 to 9.

[0040] The embodiments of the present invention are described in detail below. The following embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation schemes and specific operation processes are given, but the protection scope of the present invention is not limited to the following embodiments.

[0041] Embodiment 1:

[0042] The method for preparing the expanded flame-retardant polyethylene composite material of this embodiment comprises the following steps:

[0043] 13wt% of piperazine pyrophosphate, 7wt% of melamine polyphosphate, 1wt% of maleic anhydride grafted polyethylene, 1wt% of polycarbosilane, 0.5wt% of polyethylene wax and 0.5wt% of antioxidant 1010 are mixed in a high-speed mixer for 5 minutes, and then 77wt% of linear low-density polyethylene is added to the high-speed mixer and mixed evenly before being taken out to obtain a mixed material. The mixed material is added to a twin-screw extruder, melt-blended, extruded, cooled, air-dried and granulated by the extruder, and then a water-resistant, low-smoke expansion and flame-retardant polyethylene composite material is prepared by an injection molding machine.

[0044] The heating temperatures of each zone of the twin-screw extruder are: zone 1 140°C; zone 2 145°C; zone 3 150°C; zone 4 155°C; zone 5 160°C; the die head temperature is 160°C, and the screw speed is 350 rpm.

[0045] The temperatures of each zone of the injection molding machine are: Zone 1 150°C; Zone 2 155°C; Zone 3 160°C; and the head temperature is 165°C.

[0046] Embodiment 2:

[0047] The method for preparing the expanded flame-retardant polyethylene composite material of this embodiment comprises the following steps:

[0048] 10wt% of piperazine pyrophosphate, 4wt% of triazine carbon-forming foaming agent, 4wt% of melamine polyphosphate, 1wt% of maleic anhydride grafted polyethylene, 1wt% of MQ silicone resin, 0.5wt% of polyethylene wax and 0.5wt% of antioxidant 1076 are mixed in a high-speed mixer for 5 minutes, and then 79wt% of low-density polyethylene is added to the high-speed mixer and mixed evenly before being taken out to obtain a mixed material. The mixed material is added to a twin-screw extruder, melt-blended, extruded, cooled, air-dried and granulated by the extruder, and then a water-resistant, low-smoke, intumescent and flame-retardant polyethylene composite material is prepared by an injection molding machine.

[0049] The heating temperatures of each zone of the twin-screw extruder are: zone 1 140°C; zone 2 145°C; zone 3 150°C; zone 4 155°C; zone 5 160°C; the die head temperature is 160°C, and the screw speed is 350 rpm.

[0050] The temperatures of each zone of the injection molding machine are: Zone 1 150°C; Zone 2 155°C; Zone 3 160°C; and the head temperature is 165°C.

[0051] Embodiment 3:

[0052] The method for preparing the expanded flame-retardant polyethylene composite material of this embodiment comprises the following steps:

[0053] 12wt% of piperazine pyrophosphate, 4wt% of dimelamine pyrophosphate, 1wt% of silane grafted polyethylene, 1wt% of nickel aluminum hydrotalcite, 1wt% of polycarbosilane, 0.5wt% of polypropylene wax and 0.5wt% of antioxidant 1010 are mixed in a high-speed mixer for 5 minutes, and then 80wt% of linear low-density polyethylene is added to the high-speed mixer and mixed evenly before being taken out to obtain a mixture. The mixture is added to a twin-screw extruder, melt-blended, extruded, cooled, air-dried and granulated, and then a water-resistant, low-smoke expansion and flame-retardant polyethylene composite material is prepared by an injection molding machine.

[0054] The heating temperatures of each zone of the twin-screw extruder are: zone 1 140°C; zone 2 145°C; zone 3 150°C; zone 4 155°C; zone 5 160°C; the die head temperature is 160°C, and the screw speed is 350 rpm.

[0055] The temperatures of each zone of the injection molding machine are: Zone 1 150°C; Zone 2 155°C; Zone 3 160°C; and the head temperature is 165°C.

[0056] Embodiment 4:

[0057] The method for preparing the expanded flame-retardant polyethylene composite material of this embodiment comprises the following steps:

[0058] 13wt% of piperazine pyrophosphate, 1wt% of polyphenylene ether, 3wt% of melamine cyanurate, 1wt% of dimelamine pyrophosphate, 1wt% of MQ silicone resin, 1wt% of silane grafted polyethylene, 1wt% of fly ash, 0.5wt% of polyethylene wax and 0.5wt% of antioxidant 1010 are mixed in a high-speed mixer for 5 minutes, and then 78wt% of low-density polyethylene is added to the high-speed mixer and mixed evenly before being taken out to obtain a mixed material. The mixed material is added to a twin-screw extruder, melt-blended, extruded, cooled, air-dried and granulated by the extruder, and then a water-resistant, low-smoke, intumescent and flame-retardant polyethylene composite material is prepared by an injection molding machine.

[0059] The heating temperatures of each zone of the twin-screw extruder are: zone 1 140°C; zone 2 145°C; zone 3 150°C; zone 4 155°C; zone 5 160°C; the die head temperature is 160°C, and the screw speed is 350 rpm.

[0060] The temperatures of each zone of the injection molding machine are: Zone 1 150°C; Zone 2 155°C; Zone 3 160°C; and the head temperature is 165°C.

[0061] The performance of the expanded flame-retardant polyethylene composite material prepared in the above example was tested as follows:

[0062] (1) According to ASTM D3801, the vertical burning rating of polyethylene materials was tested using a CZF-2 instrument (China Jiangning Analytical Instrument Co., Ltd.). The sample size was 130 mm × 13 mm × 3.2 mm.

[0063] (2) According to ASTM D2863, the limiting oxygen index of polyethylene was tested using a JF-3 instrument (Jiangning Analytical Instrument Co., Ltd., China). The sample size was 130 mm × 6.5 mm × 3 mm.

[0064] The test results are shown in Table 1: when the flame retardant addition amount is only about 20wt%, the modified polyethylene composite materials can pass the UL-94V-0 level in the vertical burning test, and the limiting oxygen index (LOI) value exceeds 30.0%, indicating that the above-mentioned intumescent flame retardant system has excellent flame retardant efficiency for polyethylene materials.

[0065] Table 1 Vertical combustion (UL-94) and limiting oxygen index (LOI) test results of LLDPE materials

[0066]

[0067] (3) According to ISO-5660 standard, polyethylene material was tested by cone calorimetry test. The test results of ignition time (TTI), heat release rate (HRR), total heat release (THR), smoke release rate (SPR) and total smoke release (TSP) are shown in Table 2. The sample size is 100 mm × 100 mm × 4 mm, and the thermal radiation intensity is 50 kW / m 2 .

[0068] Table 2 Cone calorimetry test data of polyethylene materials

[0069]

[0070]

[0071] Under a thermal radiation intensity of 50 kW, pure polyethylene material burns violently until it is completely burned out after being ignited. It has no carbon-forming properties. The peak heat release rate (pHRR) and peak smoke release rate (pSPR) are 1042.9 kW / m 2 and 0.07m 2 / s, the total heat release (THR) and total smoke release (TSP) reached 176.5MJ / m 2 and 14.5m 2 .

[0072] Compared with the unmodified polyethylene material, the combustion parameters of the flame retardant modified polyethylene material have been significantly reduced. Among them, polycarbosilane has an excellent synergistic flame retardant effect in the expansion flame retardant system. During the combustion process, polycarbosilane plays a role in bonding and reinforcing the formed carbon layer, thus forming a stronger, better heat-resistant and denser carbon layer, thereby more effectively suppressing the release of smoke and heat.

[0073] (4) Water resistance test

[0074] To evaluate the water resistance of the polyethylene composite material prepared above, the initial mass was recorded as m0, and then the specimen was immersed in a constant temperature water bath for 168 hours at 70°C, and the distilled water was replaced every 24 hours. After the test, the surface moisture of the specimen was removed with filter paper, and the mass was weighed and recorded as m1. The specimen was dried in an oven at 105°C to constant weight, and the mass was recorded as m2.

[0075] Water absorption (%) = (m1-m0) / m0×100% (Formula 1)

[0076] Mass loss rate (%) = (m2-m1) / m1×100% (Formula 2)

[0077] The water absorption rate and mass loss rate were obtained according to the above formula. The samples after water resistance test and drying were tested respectively, and the test results are shown in Table 3.

[0078] It can be seen from Table 3 that the polyethylene composites after the water resistance test for 168 h can all pass the UL-94V-0 level in the vertical burning test, and the LOI value is slightly reduced, indicating that the prepared expanded flame retardant polyethylene composite has excellent water resistance.

[0079] Table 3 Test results of polyethylene composite materials after water resistance test

[0080]

Claims

1. A water-resistant, low-smoke, swelling, flame-retardant polyethylene composite material, characterized in that: The composite material comprises, by mass percentage, 75-82wt% of a polyethylene matrix resin, 15-25wt% of a flame retardant, 1-5wt% of a synergist, 1-3wt% of a compatibilizer, 0.1-1wt% of a lubricant, and the remainder of an antioxidant; wherein the flame retardant comprises piperazine pyrophosphate and a compounding agent, wherein the compounding agent is one of dimelamine pyrophosphate, melamine polyphosphate, melamine cyanurate, a triazine carbon-forming foaming agent, and polyphenylene ether, or a mixture of any of the foregoing.

2. The water-resistant, low-smoke swelling, flame-retardant polyethylene composite material according to claim 1, characterized in that: The polyethylene matrix resin is one of high-density polyethylene, low-density polyethylene, linear low-density polyethylene, or a mixture of any of the above.

3. A water-resistant, low-smoke swelling, flame-retardant polyethylene composite material according to claim 1 or 2, characterized in that: The synergist is one of polycarbosilane, MQ silicone resin, zinc oxide, nickel oxide, manganese oxide, copper oxide, lanthanum oxide, nickel aluminum hydrotalcite, nickel iron hydrotalcite, nickel aluminum magnesium hydrotalcite, kaolin, talc, diatomaceous earth, fly ash, molecular sieve or a mixture of any of them.

4. The water-resistant, low-smoke swelling, flame-retardant polyethylene composite material according to claim 1, characterized in that: The compatibilizer is one of maleic anhydride grafted polyethylene and silane grafted polyethylene or a mixture of both.

5. The water-resistant, low-smoke swelling, flame-retardant polyethylene composite material according to claim 1, characterized in that: The lubricant is polyethylene wax, polypropylene wax or a mixture of the two.

6. The water-resistant, low-smoke swelling, flame-retardant polyethylene composite material according to claim 1, characterized in that: The antioxidant is one of antioxidant 1010, antioxidant 1076, and antioxidant 168, or a mixture of any of them.

7. The method for preparing the water-resistant, low-smoke, swelling, flame-retardant polyethylene composite material according to claim 1, characterized in that: The method comprises the following steps:

1. Firstly, add the flame retardant, synergist, compatibilizer, lubricant and antioxidant into a high-speed mixer for mixing, and then add the polyethylene matrix resin and continue mixing to obtain a mixed material; 2. Add the mixed material into a twin-screw extruder, melt blend, extrude, cool, air-dry and granulate through the extruder, and then prepare a water-resistant, low-smoke expansion and flame-retardant polyethylene composite material through an injection molding machine.

8. The method for preparing the water-resistant, low-smoke swelling, flame-retardant polyethylene composite material according to claim 7, characterized in that: The mixing time of the two times in step 1 is 5 to 10 minutes.

9. The method for preparing the water-resistant, low-smoke swelling, flame-retardant polyethylene composite material according to claim 7 or 8, characterized in that: The heating temperatures of the zones of the twin-screw extruder in step 2 are: zone 1 140-150°C; zone 2 145-155°C; zone 3 150-160°C; zone 4 155-165°C; zone 5 160-170°C; the die head temperature is 160-170°C, and the screw speed is 350-500 rpm.

10. The method for preparing the water-resistant, low-smoke swelling, flame-retardant polyethylene composite material according to claim 9, characterized in that: In step 2, the temperatures of the various zones of the injection molding machine are: zone 1 150-160°C; zone 2 155-165°C; zone 3 160-170°C; and the head temperature 165-170°C.

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