阅读说明：本技术 一种微发泡高透波增强聚丙烯材料及其制备方法 (Micro-foaming high-wave-permeability reinforced polypropylene material and preparation method thereof ) 是由 王清文 杨杰 刁雪峰 申应军 刘曙光 于 2021-08-12 设计创作，主要内容包括：本发明涉及聚丙烯复合物领域,提供一种微发泡高透波增强聚丙烯材料及其制备方法,材料包括聚丙烯树脂65份～90份、低介电常数增强体6份～30份、增韧剂3份～5份、抗氧剂0.4份～0.8份、润滑剂0.1份～0.3份、UV吸收剂0.1份～0.3份、发泡剂母粒2份～4份；所述的低介电常数增强体为片状纳米碳化硅和滑石粉的混合物。本发明采用片状纳米碳化硅和滑石粉的混合物作为增强体,一方面片状纳米碳化硅和滑石粉的协同作用可以增加聚丙烯材料的刚性,另一方面片状纳米碳化硅具有较低的介电常数,又能降低聚丙烯材料的介电常数。同时由于滑石粉的成核作用以及纳米碳化硅的片状结构对气体的阻隔作用,所制得的微发泡聚丙烯的泡孔尺寸均匀且为微米级,可以进一步降低产品整体的介电常数。(The invention relates to the field of polypropylene compounds, and provides a micro-foaming high-wave-transmission reinforced polypropylene material and a preparation method thereof, wherein the material comprises 65 to 90 parts of polypropylene resin, 6 to 30 parts of low-dielectric-constant reinforcement, 3 to 5 parts of toughening agent, 0.4 to 0.8 part of antioxidant, 0.1 to 0.3 part of lubricant, 0.1 to 0.3 part of UV absorbent and 2 to 4 parts of foaming agent master batch; the low dielectric constant reinforcement is a mixture of flaky nano silicon carbide and talcum powder. The invention adopts the mixture of the flaky nano silicon carbide and the talcum powder as the reinforcement, on one hand, the synergistic effect of the flaky nano silicon carbide and the talcum powder can increase the rigidity of the polypropylene material, and on the other hand, the flaky nano silicon carbide has lower dielectric constant and can reduce the dielectric constant of the polypropylene material. Meanwhile, due to the nucleation effect of the talcum powder and the barrier effect of the flaky structure of the nano silicon carbide on gas, the prepared micro-foamed polypropylene has uniform and micron-sized foam pores, and the integral dielectric constant of the product can be further reduced.)

1. A micro-foaming high-wave-permeability reinforced polypropylene material is characterized in that: by weight, comprises

The low dielectric constant reinforcement is a mixture of flaky nano silicon carbide and talcum powder.

2. The micro-foamed high-wave-transparent reinforced polypropylene material according to claim 1, wherein: the mass ratio of the flaky nano silicon carbide to the talcum powder is 3: 1-6: 1.

3. The micro-foamed high-wave-transparent reinforced polypropylene material according to claim 1, wherein: the polypropylene resin is homopolymerized polypropylene, and the melt index of the polypropylene resin is 0.2-30 g/10min at 230 ℃ under the load of 2.16 kg.

4. The micro-foamed high-wave-transparent reinforced polypropylene material according to claim 1, wherein: the toughening agent is one or more of ethylene propylene rubber, ethylene propylene diene monomer rubber, ethylene-butene copolymer, ethylene-octene copolymer and polyethylene.

5. The micro-foamed high-wave-transparent reinforced polypropylene material according to claim 1, wherein: the lubricant is polytetrafluoroethylene micro powder.

6. The micro-foamed high-wave-transparent reinforced polypropylene material according to claim 1, wherein: the antioxidant is a mixture of 1,3, 5-tri (3, 5-di-tert-butyl-4-hydroxybenzyl) isocyanuric acid, tetra [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid ] pentaerythritol ester, dioctadecyl thiodipropionate and tri [2, 4-di-tert-butylphenyl ] phosphite.

7. The micro-foamed high-wave-transparent reinforced polypropylene material according to claim 6, wherein: the antioxidant is a mixture of 1,3, 5-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) s-triazine, tetra [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid ] pentaerythritol ester, dioctadecyl thiodipropionate and tris [2, 4-di-tert-butylphenyl ] phosphite in a mass ratio of 1:1:2: 1.

8. The micro-foamed high-wave-transparent reinforced polypropylene material according to claim 1, wherein: the foaming agent master batch is a master batch obtained by compounding one or more of sodium bicarbonate, azodicarbonamide and azodiisobutyronitrile with low-density polyethylene.

9. The method for preparing the micro-foamed high-wave-transparent reinforced polypropylene material according to any one of claims 1 to 8, wherein:

s100, adding polypropylene resin, a low dielectric constant reinforcement, a toughening agent, an antioxidant, a lubricant and a UV (ultraviolet) absorbent into a high-speed mixer, uniformly mixing, putting the mixed material into a double-screw extruder, and carrying out melt extrusion and granulation to obtain a reaction product;

s200, uniformly mixing the reaction product obtained in the step S100 with the foaming agent master batch, and performing injection molding to obtain the micro-foaming high-wave-transmission reinforced polypropylene material.

10. The method for preparing the micro-foaming high-wave-transparent reinforced polypropylene material according to claim 9, wherein the method comprises the following steps:

the length-diameter ratio of a screw of the double-screw extruder is 30-48, the first zone temperature is 150-170 ℃, the second zone temperature is 170-190 ℃, the third zone temperature is 170-200 ℃, the fourth zone temperature is 190-210 ℃, the fifth zone temperature is 190-210 ℃, the sixth zone temperature is 190-210 ℃, the seventh zone temperature is 190-210 ℃, the eighth zone temperature is 200-210 ℃, the ninth zone temperature is 200-210 ℃, the tenth zone temperature is 200-210 ℃, the head temperature is 200-210 ℃, the screw rotation speed is 300-500 r/min, and the mixture stays for 2-3 min after granulation to obtain a reaction product;

the temperature of the charging barrel of the injection molding machine is 180-240 ℃, the injection molding pressure is 30-60 MPa, the injection molding speed is 30-70 mm/s, and the cooling time is 10-30 s.

Technical Field

The invention relates to the field of polypropylene composites, in particular to a micro-foaming high-wave-permeability reinforced polypropylene material and a preparation method thereof.

Background

The wave-transmitting material can transmit electromagnetic waves and hardly changes the properties (including energy) of the electromagnetic waves, and is mainly applied to various fields such as guiding radomes, hypersonic aircraft radomes, space shuttle radomes, satellite radomes, warning radomes, weather radomes, ground radomes with thin-wall structures, radomes of mobile communication base stations, vehicle radomes and the like. In practical application, the dielectric constant and the loss factor are two important indexes for measuring the wave-transmitting capacity of the wave-transmitting material, and according to the use environment of the wave-transmitting material, other properties besides the wave-transmitting rate, such as long-time high-temperature resistance, high rigidity, stable size, toughness, chemical corrosion, wear resistance, specific gravity and the like, need to be considered.

On the premise of ensuring key use performance, the smaller the specific gravity of the wave-transmitting material is, particularly for parts such as airborne radars and the like, on the premise of certain airborne weight, the lighter the weight of the parts is, which means that more airborne equipment can be carried. Therefore, the light weight of the wave-transmitting material of the housing is important. However, the existing antenna housing material mainly comprises glass fiber reinforced plastic material, and the specific gravity reaches about 2.4g/cm³. Meanwhile, the thermosetting resin is mainly prepared by a hand pasting process at present, and the problems of long and complicated product processing process, low efficiency and even environmental pollution generally exist. Therefore, a lightweight antenna housing material is urgently needed, and a preparation method of the material needs to be simple and efficient.

The micro-foaming material is a material with a unique compact surface layer and a foaming core layer structure, and the weight of a finished piece is obviously reduced on the premise of ensuring the basic performance of the material.

The polypropylene material is thermoplastic synthetic resin with excellent performance, the high-frequency electrical performance of the polypropylene is excellent, the polypropylene is hardly influenced by the environmental humidity, and the polypropylene has the advantages of high dielectric strength, low dielectric constant (2.20-2.60), small specific gravity, no toxicity, easiness in processing, impact strength and the like, but the polypropylene also has some defects, such as large molding shrinkage rate, poor cold resistance, low heat distortion temperature and the like. In order to improve the overall performance of polypropylene materials, a great deal of research has been conducted by researchers. CN109206734A discloses a preparation method of a glass fiber reinforced polypropylene composite material, the production process of the invention is simple, the rigidity of polypropylene is effectively enhanced, and the prepared material has higher strength, but the dielectric property and the light weight of polypropylene are not improved. CN111073148A discloses a low-dielectric-constant micro-foamed glass fiber reinforced polypropylene compound and a preparation method thereof, wherein the dielectric property and the light weight of polypropylene are improved through the microcosmic composition and topological structure design of materials, but the whole dielectric property of the polypropylene is affected by adding continuous alkali-free glass fiber (the dielectric constant is 6-7) with higher dielectric constant. CN1444621 discloses a dielectric resin foam and a lens for radio waves using the same, wherein the lens is prepared by using a dielectric resin, but the dielectric alkaline earth metal salt used in the foam has poor thermal stability and affects the thermal stability of the resin; the adopted titanate and lead salt have certain toxicity and can affect the environmental friendliness of the resin.

Disclosure of Invention

In order to solve the problem of poor overall performance of the dielectric constant reinforcement in the prior art, the invention provides a micro-foaming high-wave-permeability reinforced polypropylene material, which comprises

The low dielectric constant reinforcement is a mixture of flaky nano silicon carbide and talcum powder.

In one embodiment, the mass ratio of the flaky nano silicon carbide to the talcum powder is 3: 1-6: 1.

In one embodiment, the polypropylene resin is homo-polypropylene, and the melt index of the homo-polypropylene resin is 0.2-30 g/10min at 230 ℃ under a load of 2.16 kg.

In one embodiment, the toughening agent is one or more of ethylene propylene rubber, ethylene propylene diene monomer, ethylene-butene copolymer, ethylene-octene copolymer and polyethylene.

Preferably, the toughening agent is ethylene-octene copolymer or ethylene propylene diene monomer.

In one embodiment, the lubricant is polytetrafluoroethylene micropowder.

In one embodiment, the antioxidant is a mixture of 1,3, 5-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) isocyanuric acid, pentaerythritol tetrakis [ β - (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ], dioctadecyl thiodipropionate, and tris [2, 4-di-tert-butylphenyl ] phosphite.

Preferably, the antioxidant is a mixture of 1,3, 5-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) isocyanuric acid, pentaerythritol tetrakis [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ], dioctadecyl thiodipropionate and tris [2, 4-di-tert-butylphenyl ] phosphite in a mass ratio of 1:1:2: 1.

In one embodiment, the foaming agent master batch is a master batch obtained by compounding one or more of sodium bicarbonate, azodicarbonamide and azodiisobutyronitrile with low-density polyethylene.

The invention also provides a preparation method of the micro-foaming high-wave-transparent reinforced polypropylene material in the technical scheme, which comprises the following specific steps:

s100, adding polypropylene resin, a low dielectric constant reinforcement, a toughening agent, an antioxidant, a lubricant and a UV (ultraviolet) absorbent into a high-speed mixer, uniformly mixing, putting the mixed material into a double-screw extruder, and carrying out melt extrusion and granulation to obtain a reaction product;

s200, uniformly mixing the reaction product obtained in the step S100 with the foaming agent master batch, and performing injection molding to obtain the micro-foaming high-wave-transmission reinforced polypropylene material.

In one embodiment, the preparation method of the micro-foamed high-wave-transparent reinforced polypropylene material comprises the following process parameters:

the length-diameter ratio of a screw of the double-screw extruder is 30-48, the first zone temperature is 150-170 ℃, the second zone temperature is 170-190 ℃, the third zone temperature is 170-200 ℃, the fourth zone temperature is 190-210 ℃, the fifth zone temperature is 190-210 ℃, the sixth zone temperature is 190-210 ℃, the seventh zone temperature is 190-210 ℃, the eighth zone temperature is 200-210 ℃, the ninth zone temperature is 200-210 ℃, the tenth zone temperature is 200-210 ℃, the head temperature is 200-210 ℃, the screw rotation speed is 300-500 r/min, and the mixture stays for 2-3 min after granulation to obtain a reaction product;

the temperature of the charging barrel of the injection molding machine is 180-240 ℃, the injection molding pressure is 30-60 MPa, the injection molding speed is 30-70 mm/s, and the cooling time is 10-30 s.

Based on the above, compared with the prior art, the micro-foaming high-wave-transparent reinforced polypropylene material provided by the invention has the following beneficial effects:

the invention adopts the mixture of the flaky nano silicon carbide and the talcum powder as the reinforcement, on one hand, the synergistic effect of the flaky nano silicon carbide and the talcum powder can increase the rigidity of the polypropylene material, and on the other hand, the flaky nano silicon carbide has lower dielectric constant and can reduce the dielectric constant of the polypropylene material. Due to the sheet structure of the sheet nano silicon carbide, the surface area is increased, the interface polarization is enhanced, and the dielectric constant is greatly increased. The silicon carbide has excellent thermal stability, is beneficial to improving the overall thermal stability of the polypropylene composite material, and is non-toxic and environment-friendly. Meanwhile, due to the nucleation effect of the talcum powder and the barrier effect of the flaky structure of the nano silicon carbide on gas, the gas overflow can be reduced, the foaming performance is improved, the size of the foam pores of the prepared micro-foaming polypropylene is uniform, and the uniform micron-sized foam pores in the micro-foaming product can further reduce the overall dielectric constant of the product.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the features particularly pointed out in the written description and claims hereof.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments; the technical features designed in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other; all other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the description of the present invention, it is to be noted that all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs, and are not to be construed as limiting the present invention; it will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

The present invention provides examples 1 to 3 and comparative examples 1 to 6.

Table 1: composition ratio of materials of examples and comparative examples

Wherein, the polypropylene resin is preferably homo-polypropylene, and the melt index of the polypropylene resin is 0.2-30 g/10min at 230 ℃ under the load of 2.16 kg.

Preferably, the toughening agent is one or more of ethylene propylene rubber, ethylene propylene diene monomer, ethylene-butene copolymer, ethylene-octene copolymer and polyethylene.

Preferably, the antioxidant is a mixture of 1,3, 5-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) isocyanuric acid, pentaerythritol tetrakis [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ], dioctadecyl thiodipropionate and tris [2, 4-di-tert-butylphenyl ] phosphite in a mass ratio of 1:1:2: 1.

Preferably, the foaming agent master batch is a master batch obtained by compounding one or more of sodium bicarbonate, azodicarbonamide and azodiisobutyronitrile with low-density polyethylene.

The preparation methods of the above examples and comparative examples include:

(1) adding polypropylene resin, a low dielectric constant reinforcement, a toughening agent, an antioxidant, polytetrafluoroethylene micro powder and a UV (ultraviolet) absorbent into a high-speed mixer, uniformly mixing, putting the mixed material into a double-screw extruder for extrusion and granulation, wherein the length-diameter ratio of screws of the double-screw extruder is 30-48, and performing melt extrusion and granulation; the processing technology is as follows: the temperature of a first area of the double-screw extruder is 150-170 ℃, the temperature of a second area is 170-190 ℃, the temperature of a third area is 170-200 ℃, the temperature of a fourth area is 190-210 ℃, the temperature of a fifth area is 190-210 ℃, the temperature of a sixth area is 190-210 ℃, the temperature of a seventh area is 190-210 ℃, the temperature of an eighth area is 200-210 ℃, the temperature of a ninth area is 200-210 ℃, the temperature of a tenth area is 200-210 ℃, the temperature of a machine head is 200-210 ℃, the rotating speed of a screw is 300-500 r/min, and the retention time is 2-3 min, so as to obtain a reaction product;

(2) and (2) uniformly mixing the reaction product obtained in the step (1) with the foaming agent master batch, and performing injection molding to obtain the micro-foaming high-wave-transmission reinforced polypropylene material, wherein the temperature of a charging barrel of an injection molding machine is 180-240 ℃, the injection pressure is 30-60 MPa, the injection speed is 30-70 mm/s, and the cooling time is 10-30 s.

The grade and other technical indexes of the raw materials adopted in the preparation method, the examples and the comparative examples can be selected according to the prior art, and if the technical indexes are specified in the invention, the technical indexes are selected within the range specified in the invention, so that the technical effect of the invention is not influenced.

The following experiments were carried out under the same test conditions for each set of test samples obtained in the examples and comparative examples shown in Table 1:

the density was measured according to ISO1183 standard, the dipping method.

Tensile strength was measured according to ISO527-2 standard.

The bending strength and the bending modulus are tested according to the ISO 178 standard; the dielectric constant is tested according to GB/T1409-2006, the test frequency is 1MHz, the size of the test sample strip is 8mm multiplied by 3.2mm multiplied by 1.6mm, and the dielectric constant is tested after the surface of the test sample strip is uniformly coated with a silver electrode.

Weathering test was carried out according to SAE J2527-2004, with an illumination amplitude of 0.55W/m²@340nm, the blackboard temperature in the illumination stage is 70 +/-2 ℃, the relative humidity is 50%, the blackboard temperature in the dark stage is 38 +/-2 ℃, the relative humidity is 95%, and the test time is 1000h, and the weather resistance of the material is evaluated by testing the color difference change of the material.

Cell size testing: the scanning electron microscope photographs the sample sections, the diameter of the cells is counted using software, and the average is calculated.

Table 2: test results of examples and comparative examples

As can be seen from Table 2, the materials of the examples have light density, moderate cell size, good mechanical properties, low dielectric constant and good weather resistance after foaming, and are suitable for being used as communication equipment materials, especially as manufacturing materials of 5G products. When comparative example 1 lacks the flaky nano-silicon carbide, the dielectric constant is high and the cell size is too large (the cell size is too large to cause a further increase in the dielectric constant). When comparative example 2 lacked the polytetrafluoroethylene micropowder for adhesion promotion and auxiliary nucleation, the dielectric constant increased and the cell size was too large (too large cell size resulted in further increase of dielectric constant). When comparative example 3 lacks the blowing agent, the density is large and the dielectric constant is high due to the absence of cells. When comparative example 4 lacks the antioxidant and the UV absorber, the weather resistance is decreased and the color difference is increased. When the mass ratio of the flaky nano silicon carbide to the talcum powder in the comparative examples 5 and 6 is not in the range of 3: 1-6: 1, the dielectric constant is increased, and the mechanical property is reduced.

In summary, compared with the prior art, the micro-foaming high-wave-transparent reinforced polypropylene material provided by the invention has the following beneficial effects:

1. the invention adopts the mixture of the flaky nano silicon carbide and the talcum powder as the reinforcement, on one hand, the synergistic effect of the flaky nano silicon carbide and the talcum powder can increase the rigidity of the polypropylene material, and on the other hand, the flaky nano silicon carbide has lower dielectric constant and can reduce the dielectric constant of the polypropylene material. Due to the sheet structure of the sheet nano silicon carbide, the surface area is increased, the interface polarization is enhanced, and the dielectric constant is greatly increased. The silicon carbide has excellent thermal stability, is beneficial to improving the overall thermal stability of the polypropylene composite material, and is non-toxic and environment-friendly. Meanwhile, due to the nucleation effect of the talcum powder and the barrier effect of the flaky structure of the nano silicon carbide on gas, the gas overflow can be reduced, the foaming performance is improved, the size of the foam pores of the prepared micro-foaming polypropylene is uniform, and the uniform micron-sized foam pores in the micro-foaming product can further reduce the overall dielectric constant of the product.

2. The polytetrafluoroethylene micro powder is beneficial to the micro-foaming process, and the dielectric constant of the polytetrafluoroethylene micro powder is only 2.1 and is lower than that of polypropylene (2.3); the polytetrafluoroethylene has low dielectric constant, and can further reduce the dielectric constant of the product by serving as a lubricant.

3. The invention uses the synergistic cooperation of the high-efficiency antioxidant and the light stabilizing system, and the prepared composite material has excellent weather resistance and high thermal oxidation resistance. 1,3, 5-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) isocyanuric acid, tetra [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid ] pentaerythritol ester, dioctadecyl thiodipropionate and tris [2, 4-di-tert-butylphenyl ] phosphite can prevent different stages of chain-lock reaction of composite oxidation, respectively, 1,3, 5-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) isocyanuric acid and tetra [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid ] pentaerythritol ester as main antioxidant, by capturing the free radicals generated in the degradation process of the polypropylene to generate inactive free radicals, the chain reaction is terminated, and the antioxidant effect is continuously exerted for a long time; the composite material is prepared by taking dioctadecyl thiodipropionate and tris [2, 4-di-tert-butylphenyl ] phosphite as auxiliary antioxidants, decomposing oxidative degradation products into non-radical products, interrupting chain reaction to achieve the purpose of antioxidation, mainly providing thermal processing stability, and preventing the antioxidants from losing efficacy due to photothermal decomposition by using a UV absorbent, so that the antioxidants and a photostable system are synergistically matched, and the composite material has excellent weather resistance.

4. The micro-foaming high-frequency wave-transparent reinforced polypropylene product has the characteristics of low density, high strength, high weather resistance, low dielectric constant and the like, and is a material very suitable for 5G products, in particular to similar applications such as 5G base station antenna housing and the like.

In addition, it will be appreciated by those skilled in the art that, although there may be many problems with the prior art, each embodiment or aspect of the present invention may be improved only in one or several respects, without necessarily simultaneously solving all the technical problems listed in the prior art or in the background. It will be understood by those skilled in the art that nothing in a claim should be taken as a limitation on that claim.

Although terms such as polypropylene resin, low dielectric constant reinforcement, toughening agent, antioxidant, lubricant, UV absorber, blowing agent masterbatch … …, etc., are used more often herein, the possibility of using other terms is not excluded. These terms are used merely to more conveniently describe and explain the nature of the present invention; they are to be construed as being without limitation to any additional limitations that may be imposed by the spirit of the present invention; the terms "first," "second," and the like in the description and in the claims, if any, of the embodiments of the invention are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.