Preparation method of flame-retardant PE plastic pipe

Abstract

The invention provides a preparation method of a flame-retardant PE (polyethylene) plastic pipe, and solves the technical problems that generally prepared magnesium hydroxide has relatively strong polarity and hydrophilicity, crystal grains tend to secondary agglomeration, the compatibility between the magnesium hydroxide and a non-polar PE material is poor, the dispersion between the magnesium hydroxide and the non-polar PE material is non-uniform, and good combination and adhesion are difficult to form between interfaces of the magnesium hydroxide and the non-polar PE material. The method can be widely applied to the plastic pipe manufacturing field; the preparation method specifically comprises the following steps: adding magnesium hydroxide modified powder and PE granules into a mixer, adding an antioxidant, an antioxidant aid, a flame retardant accelerator and a synergist, uniformly mixing for 5-60 minutes, and drying at 50-90 DEG C to obtain a mixture; the mixture is granulated at the temperature of 25-85 DEG C, the rotating speed of a main machine is 100-450 r / min, and a modified raw material is obtained; the modified raw materials are added into an extruder for extrusion molding of the plastic pipeline, the extrusion temperature of the extruder is 150-220 DEG C, and the extrusion speed is 2-6 m / min; and cooling, shaping, cutting and drawing to form the PE plastic pipe.

Description

Technical Field

[0001] The invention belongs to the technical field of plastic pipe manufacturing, and in particular relates to a method for preparing a flame-retardant PE plastic pipe. Background Art

[0002] Polyethylene (PE) is the most widely used thermoplastic plastic among plastics. It has excellent electrical insulation, low temperature resistance, easy processing and molding, excellent chemical stability and dielectric properties. It is widely used in films, daily necessities, pipes, wires and cables. Pipes are an indispensable infrastructure in modern society. Common types include inorganic pipes, plastic pipes and metal pipes. As a major category of plastic pipes, PE pipes are widely used in water supply and drainage, heating, gas transmission, electrical and telecommunications protective sleeves, farmland irrigation, etc. due to their unique advantages (good mechanical properties, anti-aging, smooth inner wall, etc.). However, due to the characteristics of PE's own molecular structure (consisting only of C and H atoms), it is easy to burn, and the fire spreads quickly after catching fire, which will cause serious consequences. In order to ensure industrial and agricultural production, reduce abnormal shutdowns and the safety of people's lives and property, it is very important to flame retardant PE pipes.

[0003] At present, adding flame retardants to polymer materials to improve the flame retardant properties of products is a common method. The flame retardants used in my country are still mainly organic halides, phosphorus compounds, and organic brominated aliphatic hydrocarbons, among which hexabromocyclododecane (HBCDA) is the most commonly used. However, these flame retardants have defects. Organic halogenide flame retardants will produce toxic substances with complex components under high temperature when the material burns, which becomes a fatal factor in the fire; the products of phosphides after high temperature have extremely strong radiation effects, which have a great impact on the environment near the fire, human body, and instruments and equipment. Developed countries have expressly banned the use of halogen-containing flame retardants, and there are also great restrictions on the use of phosphorus-containing flame retardants.

[0004] As an additive type high-efficiency smoke suppression flame retardant, magnesium hydroxide absorbs large amounts of heat during decomposition and produces water that can isolate the air. Its decomposed oxide is a high temperature resistant substance. Therefore, this flame retardant can not only play a flame retardant role, but also a filling role. It has the characteristics of not producing corrosive halogen and harmful gases, non-volatile, long-lasting effect, non-toxic, smokeless, and dripless. When magnesium hydroxide decomposes, it can absorb the heat on the surface of the burning object to play a flame retardant role; at the same time, it releases a large amount of water to dilute the oxygen on the surface of the burning object, and the active magnesium oxide generated by the decomposition adheres to the surface of the combustible material to further prevent the combustion. In the entire flame retardant process, magnesium hydroxide not only does not produce any harmful substances, but its decomposition products can also absorb a large amount of harmful gases and smoke produced by the combustion of polymers such as rubber and plastics while being flame retardant. The active magnesium oxide continuously absorbs the incompletely burned molten residues, which quickly stops the combustion while eliminating smoke and preventing molten dripping. It is an emerging environmentally friendly inorganic flame retardant and the main trend of flame retardant development worldwide in the near future. However, the commonly prepared magnesium hydroxide has strong polarity and hydrophilicity, and the crystals tend to be secondary agglomerated. It has poor compatibility with non-polar PE materials, uneven dispersion, and it is difficult to form good bonding and adhesion between their interfaces. As the content of magnesium hydroxide in PE materials increases, its processing performance and mechanical properties drop sharply, so that it cannot be used for flame retardancy. Summary of the invention

[0005] The purpose of the present invention is to solve the deficiencies of the above-mentioned technology and provide a method for preparing a flame-retardant PE plastic pipe.

[0006] To this end, the present invention provides a method for preparing a flame retardant PE plastic pipe, comprising the following steps: Adding magnesium hydroxide modified powder and PE pellets into a mixer, and then adding antioxidant, auxiliary antioxidant, flame retardant promoter and synergist, mixing and drying, the mixing time is 5 to 60 minutes, and the temperature is maintained at 50 to 90° C. to obtain a mixture; Granulate the mixed material at a granulation temperature of 25 to 85° C. and a main engine speed of 100 to 450 r / min to obtain a modified raw material; The modified raw materials are added into the extruder for extrusion molding of plastic pipes. The extrusion temperature of the extruder is 150-220°C and the extrusion speed is 2-6m / min. Then, the PE plastic pipe is formed after cooling and shaping, cutting and pulling.

[0007] Furthermore, the mass ratio of PE pellets, magnesium hydroxide modified powder, antioxidant, auxiliary antioxidant, flame retardant promoter and synergist is 60: (6-21): (0.4-1.3): (0.1-1.15): (0.8-2.25): (0.35-1.5).

[0008] Furthermore, the antioxidant may be one or more of Antioxidant CA, Antioxidant 1076, and Antioxidant 1010.

[0009] Furthermore, the flame retardant synergist uses one or more of red phosphorus, phosphorus pentoxide, sodium pyrophosphate, ammonium pyrophosphate, ammonium polyphosphate, expanded graphite, melamine urea cyanate, layered metal double hydroxide, organic clay, rubber, and multi-walled carbon nanotubes.

[0010] Furthermore, the flame retardant promoter uses one or more of aluminum hydroxide, antimony oxide, zinc borate, molybdenum trioxide, zinc molybdate, ammonium phosphate, titanium dioxide, organic silicon compound, talc, mica, pyrophyllite, kaolin, bentonite, vermiculite, and serpentine.

[0011] Further, the preparation steps of magnesium hydroxide modified powder are: Mix magnesium hydroxide and an inert dispersant to form a dispersion with a concentration of 5% to 45%, and stir evenly; Adding a surfactant to the dispersion and modifying it in a high-speed mixer at 25 to 90° C. for 10 to 120 minutes to obtain a mixed material; The mixed material is filtered, dried, and ball-milled to obtain a preliminary modified magnesium hydroxide powder; The preliminary magnesium hydroxide modified powder is mixed with the inert dispersant again and stirred evenly; then a coupling agent is added, and the mixture is modified at 30 to 90° C. for 10 to 120 minutes, and filtered, dried, and ball-milled to obtain magnesium hydroxide modified powder.

[0012] Furthermore, the mass ratio of magnesium hydroxide, surfactant and coupling agent is 20:(0.8-1.7):(0.2-1.4).

[0013] Furthermore, the inert dispersant uses one or more of xylene, diesel, kerosene, liquid paraffin, low-viscosity methyl silicone oil, and N,N-dimethylformamide.

[0014] Furthermore, the surfactant uses one or more of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium stearate, sodium palmitate, polyoxyethylene sorbitan monooleate 85, polyoxyethylene sorbitan monooleate 83, polyoxyethylene sorbitan monooleate 80, polyoxyethylene sorbitan monooleate 65, polyoxyethylene sorbitan monooleate 60, polyoxyethylene sorbitan monooleate 40, polyoxyethylene sorbitan monooleate 20, emulsifier OP10, sodium polyoxyethylene fatty alcohol ether sulfate, peregal, Turkey red oil, propylene glycol alginate, and cocamidopropyl betaine.

[0015] Furthermore, the coupling agent uses ethyl silicate, aminopropyl trimethoxysilane, glycidyloxypropyl trimethoxysilane, methacryloxypropyl trimethoxysilane, methacryloxypropyl methyl dimethoxysilane, vinyl triethoxysilane, aminopropyl methyl diethoxysilane, urea propyl triethoxysilane, 3-glycidoxypropyl trimethoxysilane, isopropyl dioleyl acyloxy (dioctyl phosphate acyloxy) titanate, isopropyl trioleyl acyloxy titanium Acid ester, isopropyl tri (dioctyl pyrophosphate acyloxy) titanate, bis (dioctyl pyrophosphate ester) ethylene titanate, tetraisopropyl di (dioctyl phosphite acyloxy) titanate), dioctyl phosphate phthalate, stearic acid, palmitic acid, oleic acid, linoleic acid, glyceryl trioleate, glyceryl tripalmitate, glyceryl tristearate, methyl stearate, ethyl stearate, stearyl alcohol phosphate, methyl palmitate, ethyl palmitate, hexadecanol, octadecyl alcohol, tetradecyl alcohol, one or more thereof.

[0016] The present invention provides a method for preparing a flame-retardant PE plastic pipe, which has the following beneficial effects: The present invention greatly improves the compatibility and dispersibility of MH in PE and the bonding force between MH and PE substrate by performing secondary surface modification on magnesium hydroxide. The flame retardant synergist and accelerator are added to show synergistic effect. The product generally reduces the amount of flame retardant, improves the flame retardant performance of the product, and is more environmentally friendly. DETAILED DESCRIPTION

[0017] The present invention is further described below in conjunction with specific examples to help understand the content of the present invention. The methods used in the present invention are all conventional methods unless otherwise specified; the raw materials and devices used are all conventional commercially available products unless otherwise specified. Example 1

[0018] Add 100 kg of xylene, 20 kg of magnesium hydroxide flame retardant and 1 kg of sodium dodecyl sulfate to the mixer, start stirring, stir evenly, heat to 75°C, and keep warm for 80 minutes; stop stirring and heating to obtain a mixed material. Filter, dry and ball-mill the mixed material to obtain magnesium hydroxide powder modified in the first step. Add 100 kg of xylene, 20 kg of magnesium hydroxide flame retardant powder modified in one step and 0.5 kg of ethyl silicate to the mixer again, start stirring, stir evenly, heat to 85°C, and keep warm for 60 minutes; stop stirring and heating to obtain a reaction material. Filter, dry and ball-mill the reaction material to obtain magnesium hydroxide powder modified in the second step.

[0019] 10 kg of magnesium hydroxide powder modified in the second step, 60 kg of polyethylene, 1 kg of montmorillonite, 0.6 kg of red phosphorus, 0.6 kg of antioxidant CA, and 0.3 kg of antioxidant DLTP are added to a mixer for mixing and drying; the mixing time is 30 minutes, and the temperature is maintained at 70°C to obtain a mixture. The mixed and dried mixture is granulated at a granulation temperature of 70-75°C and a main engine speed of 250-300r / min. The manufactured modified granules are added to an extruder for extrusion molding of plastic pipes. The extrusion temperature of the extruder is 195°C and the extrusion speed is 4m / min. After cooling and shaping, cutting and pulling form a PE plastic pipe. Example 2

[0020] Add 350 kg of low-viscosity methyl silicone oil, 20 kg of magnesium hydroxide flame retardant and 1.2 kg of polyoxyethylene sorbitan monooleate 85 (Tween85) to the mixer, start stirring, stir evenly, heat to 80°C, and keep warm for 60 minutes; stop stirring and heating to obtain a mixed material. Filter, dry and ball-mill the mixed material to obtain magnesium hydroxide powder modified in the first step. Add 350 kg of low-viscosity methyl silicone oil, 20 kg of magnesium hydroxide flame retardant powder modified in one step and 0.8 kg of aminopropyltrimethoxysilane to the mixer again, start stirring, stir evenly, heat to 90°C, and keep warm for 50 minutes; stop stirring and heating to obtain a reaction material. Filter, dry and ball-mill the reaction material to obtain magnesium hydroxide powder modified in the second step.

[0021] 12 kg of magnesium hydroxide powder modified in the second step, 60 kg of polyethylene, 1.2 kg of antimony oxide, 0.8 kg of phosphorus pentoxide, 0.8 kg of antioxidant 1076, and 0.5 kg of antioxidant 168 are added to a mixer for mixing and drying; the mixing time is 30 minutes, and the temperature is maintained at 75°C to obtain a mixture. The mixed and dried mixture is granulated at a granulation temperature of 75-80°C and a main engine speed of 250-300r / min. The manufactured modified granules are added to an extruder for extrusion molding of plastic pipes. The extrusion temperature of the extruder is 195°C and the extrusion speed is 4m / min. After cooling and shaping, cutting and pulling form a PE plastic pipe. Example 3

[0022] Add 150 kg of liquid paraffin, 20 kg of magnesium hydroxide flame retardant and 1.4 kg of sodium dodecylbenzene sulfonate to the mixer, start stirring, stir evenly, heat to 50°C, and keep warm for 90 minutes; stop stirring and heating to obtain a mixed material. Filter, dry and ball-mill the mixed material to obtain magnesium hydroxide powder modified in the first step. Add 150 kg of liquid paraffin, 20 kg of magnesium hydroxide flame retardant powder modified in one step and 1 kg of stearic acid to the mixer again, start stirring, stir evenly, heat to 70°C, and keep warm for 80 minutes; stop stirring and heating to obtain a reaction material. Filter, dry and ball-mill the reaction material to obtain magnesium hydroxide powder modified in the second step.

[0023] 15 kg of magnesium hydroxide powder modified in the second step, 60 kg of polyethylene, 1.5 kg of molybdenum trioxide, 1 kg of ammonium pyrophosphate, 1 kg of antioxidant 1010, and 0.7 kg of antioxidant DSTP are added to the mixer for mixing and drying; the mixing time is 30 minutes, and the temperature is maintained at 80°C to obtain a mixture. The mixed and dried mixture is granulated at a granulation temperature of 80-85°C and a main engine speed of 250-300r / min. The manufactured modified granules are added to the extruder for extrusion molding of plastic pipes. The extrusion temperature of the extruder is 195°C and the extrusion speed is 4m / min. After cooling and shaping, cutting and pulling form PE plastic pipes. Example 4

[0024] Add 180 kg of kerosene, 20 kg of magnesium hydroxide flame retardant and 1.6 kg of polyoxyethylene sorbitan monooleate 80 (Tween80) to the mixer, start stirring, stir evenly, heat to 90°C, and keep warm for 25 minutes; stop stirring and heating to obtain a mixed material. Filter, dry and ball-mill the mixed material to obtain magnesium hydroxide powder modified in the first step. Add 180 kg of kerosene, 20 kg of magnesium hydroxide flame retardant powder modified in one step and 1.2 kg of methyl palmitate to the mixer again, start stirring, stir evenly, heat to 85°C, and keep warm for 50 minutes; stop stirring and heating to obtain a reaction material. Filter, dry and ball-mill the reaction material to obtain magnesium hydroxide powder modified in the second step.

[0025] 18 kg of magnesium hydroxide powder modified in the second step, 60 kg of polyethylene granules, 2 kg of bentonite, 0.6 kg of expanded graphite, 0.6 kg of antioxidant CA, and 0.45 kg of antioxidant 1010 are added to the mixer for mixing and drying; the mixing time is 50 minutes, and the temperature is maintained at 70°C to obtain a mixture. The mixed and dried mixture is granulated at a granulation temperature of 75-80°C and a main engine speed of 350-400r / min. The manufactured modified granules are added to the extruder for extrusion molding of plastic pipes. The extrusion temperature of the extruder is 195°C and the extrusion speed is 4m / min. After cooling and shaping, cutting and pulling form PE plastic pipes.

[0026] The flame-retardant PE plastic pipes prepared in Examples 1-4 of the present invention were compared with the PE plastic pipes containing conventional organic flame retardants in performance tests. The results are shown in Table 1.

[0027] Table 1 Performance test results

[0028] The flame-retardant PE plastic pipe finally prepared has a good flame retardant effect compared with the traditional organic flame retardant PE plastic pipe. At the same time, due to the use of magnesium hydroxide modifier formula and modification method, the mechanical properties of this product are better, and the elongation at break, longitudinal shrinkage rate and tensile strength are significantly improved.

[0029] However, what is described above is only a specific embodiment of the present invention and should not be used to limit the scope of implementation of the present invention. Therefore, the replacement of equivalent components, or equivalent changes and modifications made according to the scope of protection of the present invention should still fall within the scope covered by the claims of the present invention.

Claims

1. A method for preparing a flame-retardant PE plastic pipe, characterized in that: The following steps are involved: Adding magnesium hydroxide modified powder and PE pellets into a mixer, and then adding antioxidant, auxiliary antioxidant, flame retardant promoter and synergist, mixing and drying, the mixing time is 5 to 60 minutes, and the temperature is maintained at 50 to 90° C. to obtain a mixture; Granulate the mixed material at a granulation temperature of 25 to 85° C. and a main engine speed of 100 to 450 r / min to obtain a modified raw material; The modified raw materials are added into the extruder for extrusion molding of plastic pipes. The extrusion temperature of the extruder is 150-220°C and the extrusion speed is 2-6m / min. Then, the PE plastic pipe is formed after cooling and shaping, cutting and pulling.

2. The method for preparing a flame-retardant PE plastic pipe according to claim 1, characterized in that: The mass ratio of PE granules, magnesium hydroxide modified powder, antioxidant, auxiliary antioxidant, flame retardant promoter and synergist is 60: (6-21): (0.4-1.3): (0.1-1.15): (0.8-2.25): (0.35-1.5).

3. The method for preparing a flame-retardant PE plastic pipe according to claim 1, characterized in that: As the antioxidant, one or more of antioxidant CA, antioxidant 1076 and antioxidant 1010 are used.

4. The method for preparing a flame-retardant PE plastic pipe according to claim 1, characterized in that: The flame retardant synergist uses one or more of red phosphorus, phosphorus pentoxide, sodium pyrophosphate, ammonium pyrophosphate, ammonium polyphosphate, expanded graphite, melamine urea cyanate, layered metal double hydroxide, organic clay, rubber, and multi-walled carbon nanotubes.

5. The method for preparing a flame-retardant PE plastic pipe according to claim 1, characterized in that: The flame retardant accelerator uses one or more of aluminum hydroxide, antimony oxide, zinc borate, molybdenum trioxide, zinc molybdate, ammonium phosphate, titanium dioxide, organic silicon compound, talc, mica, pyrophyllite, kaolin, bentonite, vermiculite, and serpentine.

6. The method for preparing a flame-retardant PE plastic pipe according to any one of claims 1 to 5, characterized in that: The preparation steps of magnesium hydroxide modified powder are: Mix the magnesium hydroxide flame retardant with an inert dispersant to prepare a dispersion with a concentration of 5% to 45%, and stir evenly; Adding a surfactant to the dispersion and modifying it in a high-speed mixer at 25 to 90° C. for 10 to 120 minutes to obtain a mixed material; The mixed material is filtered, dried, and ball-milled to obtain a preliminary modified magnesium hydroxide powder; The preliminary magnesium hydroxide modified powder is mixed with the inert dispersant again and stirred evenly; then a coupling agent is added, and the mixture is modified at 30 to 90° C. for 10 to 120 minutes, and filtered, dried, and ball-milled to obtain magnesium hydroxide modified powder.

7. The method for preparing a flame-retardant PE plastic pipe according to claim 6, characterized in that: The mass ratio of magnesium hydroxide, surfactant and coupling agent is 20:(0.8-1.7):(0.2-1.4).

8. The method for preparing a flame-retardant PE plastic pipe according to claim 6, characterized in that: The inert dispersant may be one or more of xylene, diesel, kerosene, liquid paraffin, low-viscosity methyl silicone oil, and N,N-dimethylformamide.

9. The method for preparing a flame-retardant PE plastic pipe according to claim 6, characterized in that: As the surfactant, one or more of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium stearate, sodium palmitate, polyoxyethylene sorbitan monooleate 85, polyoxyethylene sorbitan monooleate 83, polyoxyethylene sorbitan monooleate 80, polyoxyethylene sorbitan monooleate 65, polyoxyethylene sorbitan monooleate 60, polyoxyethylene sorbitan monooleate 40, polyoxyethylene sorbitan monooleate 20, emulsifier OP10, sodium polyoxyethylene fatty alcohol ether sulfate, peregal, Turkey red oil, propylene glycol alginate, and cocamidopropyl betaine are used.

10. The method for preparing a flame-retardant PE plastic pipe according to claim 6, characterized in that: The coupling agent used is ethyl silicate, aminopropyl trimethoxysilane, glycidyloxypropyl trimethoxysilane, methacryloxypropyl trimethoxysilane, methacryloxypropyl methyl dimethoxysilane, vinyl triethoxysilane, aminopropyl methyl diethoxysilane, urea propyl triethoxysilane, 3-glycidoxypropyl trimethoxysilane, isopropyl dioleyl acyloxy (dioctyl phosphate acyloxy) titanate, isopropyl trioleyl acyloxy titanate, One or more of isopropyl tri(dioctyl pyrophosphate) titanate, bis(dioctyl pyrophosphate) ethylene titanate, tetraisopropyl di(dioctyl phosphite) titanate), dioctyl phosphate phthalate, stearic acid, palmitic acid, oleic acid, linoleic acid, glyceryl trioleate, glyceryl tripalmitate, glyceryl tristearate, methyl stearate, ethyl stearate, stearyl alcohol phosphate, methyl palmitate, ethyl palmitate, hexadecanol, octadecyl alcohol, tetradecyl alcohol.

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