A high-strength flame-retardant polypropylene foam material and preparation method thereof

Abstract

The present invention relates to the field of foaming materials, and in particular to a high-strength flame-retardant polypropylene foaming material and a preparation method thereof. The polypropylene foaming material is calculated by weight and comprises: 75-95 parts of polypropylene resin, 5-10 parts of toughening agent, 6-12 parts of composite flame retardant, 1.8-4.2 parts of foaming agent, 1-3 parts of lubricant and 0.2-0.8 parts of antioxidant. The flame retardant used in the present invention is a composite flame retardant. Compared with conventional flame retardants, which need to be added to polypropylene materials in an amount of more than 20%, the composite flame retardant of the present invention only needs about 10% to achieve excellent flame retardant effect, which not only solves the problem of insufficient foaming ratio of polypropylene materials, but also improves the mechanical properties of polypropylene materials to a certain extent.

Description

Technical Field

[0001] The invention relates to the field of foaming materials, and in particular to a high-strength flame-retardant polypropylene foaming material and a preparation method thereof. Background Art

[0002] Foam plastics have the advantages of light weight, heat insulation, cushioning, insulation, corrosion resistance, and low price. Therefore, they are widely used in daily necessities, packaging, industry, agriculture, transportation, military industry, and aerospace industry. Since the 1990s, the development of foam plastics in my country has been very rapid, among which the main varieties are polyurethane foam plastics, polystyrene foam plastics and polyethylene foam plastics. In the foaming process of polyurethane foam, there are isocyanate residues that are harmful to the human body, and the foaming material cannot be recycled; chlorofluorocarbons or butane are usually used in the foaming process of polystyrene, which have adverse effects on the environment, and the product is difficult to degrade and easily forms white pollution; while the use temperature and rigidity of cross-linked polyethylene foam plastics are both low.

[0003] Polypropylene is a thermoplastic synthetic resin with excellent performance, which has the advantages of chemical resistance, heat resistance, electrical insulation, high strength mechanical properties and good high wear resistance processing performance. Polypropylene (PP) is more rigid than polyethylene (PE), so it is expected to replace polyethylene and be developed and applied in many fields.

[0004] Under normal circumstances, the flame retardant properties of foamed polypropylene are poor, and there are safety hazards when used in the fields of high-rise building exterior wall insulation, automobiles, home appliances, power batteries, etc. Therefore, it is necessary to add flame retardants during the preparation of foamed polypropylene masterbatch to achieve a flame retardant effect. However, in the existing flame-retardant foamed polypropylene materials, the amount of flame retardant added is relatively large, usually needing to reach more than 20%, and the addition of a large amount of flame retardant will cause polypropylene to have problems such as void collapse, not only the foaming effect is insufficient, but also the mechanical properties are greatly affected, which seriously limits the application of foamed polypropylene materials. Therefore, it is necessary to develop a polypropylene foam material with good foaming effect, excellent mechanical properties and flame retardant effect. Summary of the invention

[0005] In view of the problems existing in the prior art, the object of the present invention is to provide a high-strength flame-retardant polypropylene foam material and a preparation method thereof.

[0006] The purpose of the present invention is achieved by the following technical solutions:

[0007] In a first aspect, the present invention provides a high-strength flame-retardant polypropylene foam material, calculated by weight, comprising:

[0008] 75-95 parts of polypropylene resin, 5-10 parts of toughening agent, 6-12 parts of composite flame retardant, 1.8-4.2 parts of foaming agent, 1-3 parts of lubricant and 0.2-0.8 parts of antioxidant.

[0009] Preferably, the density of the polypropylene resin is 0.90-0.92 g / cm 3 , the melt index is 3.5-7.5g / 10min (190℃ / 2.16kg).

[0010] Preferably, the toughening agent is a mixture of one or more of styrene-butadiene-styrene block copolymer (SBS), ethylene-methyl acrylate copolymer (EMA) and ethylene-vinyl acetate copolymer (EVA).

[0011] More preferably, the toughening agent is ethylene-methyl acrylate copolymer (EMA), with a methyl acrylate content of 24% and a density of 0.94 g / cm 3 , the melt index is 3g / 10min (190℃ / 2.16kg).

[0012] Preferably, the foaming agent is one of 4,4'-oxybisbenzenesulfonyl hydrazide, p-toluenesulfonyl semicarbazide and azodicarbonamide.

[0013] Preferably, the composite flame retardant is prepared by a click chemistry reaction between mercapto-functionalized calcium borate and a triazine compound containing a phenylphosphoryl group.

[0014] Preferably, the lubricant is a mixture of one or more of stearic acid, calcium stearate, and ethylene bisstearamide.

[0015] Preferably, the antioxidant is a mixture of one or more of antioxidant 168, antioxidant 1010, antioxidant 1024, antioxidant 1076, and antioxidant 1098.

[0016] Preferably, the preparation method of the composite flame retardant comprises:

[0017] S1. Mix calcium borate powder and anhydrous ethanol, add 3-mercaptopropylmethyldimethoxysilane, and perform ultrasonic treatment at room temperature for 0.2-0.6h, then heat to 70-80°C, reflux and stir for 4-6h, collect the powder by suction filtration, and dry to obtain mercapto-functionalized calcium borate;

[0018] S2, adding 2-vinyl-4,6-diamino-1,3,5-triazine to anhydrous ethanol, stirring thoroughly in an ice-water bath, then adding 3-hydroxyphenylphosphoryl propionic acid, and then dropping triethylamine, heating to 70-90° C., stirring and preserving for 3-5 hours, and then distilling off the solvent under reduced pressure, and drying in vacuo to obtain a triazine compound containing a phenylphosphoryl group;

[0019] S3. Mix a triazine compound containing a phenyl phosphoryl group and N-methylpyrrolidone, add thiol-functionalized calcium borate, stir thoroughly, then add a photoinitiator, irradiate with ultraviolet light under a nitrogen atmosphere, stir for 1-2 hours, then filter and collect the solid, and dry under reduced pressure to obtain a composite flame retardant.

[0020] Preferably, in S1, the particle size of the calcium borate powder is 10±2 μm, and the mass ratio of the calcium borate powder, 3-mercaptopropylmethyldimethoxysilane and anhydrous ethanol is 1:0.1-0.3:10-30.

[0021] Preferably, in S2, the mass ratio of 2-vinyl-4,6-diamino-1,3,5-triazine, 3-hydroxyphenylphosphorylpropionic acid and anhydrous ethanol is 0.21-0.42:0.68-1.36:10-20.

[0022] Preferably, in S2, the amount of triethylamine added is 2.5%-5.5% of the mass of 3-hydroxyphenylphosphatidyl propionic acid.

[0023] Preferably, in S3, the mass ratio of mercapto-functionalized calcium borate, the triazine compound containing phenylphosphoryl group and N-methylpyrrolidone is 1:0.34-0.68:15-35.

[0024] Preferably, in S3, the photoinitiator is photoinitiator 651 or photoinitiator 184, and the added amount is 2%-6% of the mass of the triazine compound containing phenylphosphoryl group.

[0025] Preferably, in S3, the ultraviolet light power is 25-75W, and the wavelength is 250-420nm. More preferably, the ultraviolet light power is 55W, and the wavelength is 365nm.

[0026] In a second aspect, the present invention provides a method for preparing a high-strength flame-retardant polypropylene foam material, comprising the following steps:

[0027] Step 1, taking a certain amount of polypropylene resin, a toughening agent and a composite flame retardant, mixing them in a mixer, heating and mixing, and obtaining a polypropylene mixture;

[0028] Step 2, taking lubricant and antioxidant according to the amount and mixing them with the polypropylene mixture in a twin-screw extruder, and performing melt extrusion and granulation to obtain polypropylene masterbatch;

[0029] Step 3, placing the polypropylene masterbatch in an extruder and heating it to melt, then adding a foaming agent in a certain amount, and extruding it into a mold after foaming to obtain a high-strength flame-retardant polypropylene foam material.

[0030] Preferably, in step 1, the heating temperature is 165-185° C., the stirring time is 20-40 min, and the stirring speed is 500-600 r / min.

[0031] Preferably, in step 2, the temperature range of the twin-screw extruder is 170-210° C., and the aspect ratio of the screw is 20-25.

[0032] Preferably, in step 3, the foaming temperature is 155-175° C., the foaming pressure is 0.6-1.2 MPa, and the foaming time is 1-3 min.

[0033] The beneficial effects of the present invention are:

[0034] 1. The present invention prepares a polypropylene foam material, which uses polypropylene resin as the main raw material and adds a copolymer as a toughening agent to enhance the toughness and strength of the polypropylene resin. In addition, the flame retardant used in the present invention is a composite flame retardant. Compared with conventional flame retardants that need to be added to the polypropylene material in an amount of more than 20%, the composite flame retardant of the present invention only needs about 10% to achieve excellent flame retardant effects, which not only solves the problem of insufficient foaming ratio of polypropylene materials, but also improves the mechanical properties of polypropylene materials to a certain extent.

[0035] 2. Calcium borate is an inorganic boron flame retardant with excellent flame retardant properties and environmental protection characteristics; 3-hydroxyphenylphosphoryl propionic acid is a phosphorus-based environmentally friendly flame retardant, commonly used in flame retardant materials for polyester. The present invention combines calcium borate and 3-hydroxyphenylphosphoryl propionic acid by chemical crosslinking to prepare a new type of composite flame retardant, which not only combines the advantages of boron and phosphorus flame retardants, but also has a good improvement on the mechanical properties of polypropylene foam materials.

[0036] 3. The preparation process of the composite flame retardant prepared by the present invention is to first treat the calcium borate powder with a thiol coupling agent to obtain thiol-functionalized calcium borate; then use 3-hydroxyphenylphosphoryl propionic acid and 2-vinyl-4,6-diamino-1,3,5-triazine to react with amide to obtain a triazine compound containing phenyl phosphoryl; then use the triazine compound containing phenyl phosphoryl to combine with thiol-functionalized calcium borate, and after a thiol-vinyl click chemistry reaction, a composite flame retardant is obtained. The composite flame retardant prepared by the present invention contains not only phenyl phosphoryl groups and triazine groups, but also generated amide groups and thioether groups, which not only greatly improves the flame retardant effect, but also has good improvements on the mechanical properties of polypropylene materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The present invention is further described using the accompanying drawings, but the embodiments in the accompanying drawings do not constitute any limitation to the present invention. A person skilled in the art can obtain other drawings based on the following drawings without creative work.

[0038] Figure 1 is a scanning electron microscope (SEM) schematic diagram of the high-strength flame-retardant polypropylene foam material product prepared in Example 1 of the present invention;

[0039] Figure 2 This is a physical picture of the high-strength flame-retardant polypropylene foam material product prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0040] In order to better understand the above technical scheme, the exemplary embodiments of the present invention are described in more detail below. Although exemplary embodiments of the present invention are shown, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to enable the scope of the present invention to be fully communicated to those skilled in the art.

[0041] The present invention will be further described below in conjunction with the following examples.

[0042] Example 1

[0043] A high-strength flame-retardant polypropylene foam material, calculated by weight, comprising:

[0044] 85 parts of polypropylene resin, 8 parts of toughening agent, 9 parts of composite flame retardant, 2.8 parts of foaming agent, 2 parts of lubricant and 0.5 parts of antioxidant.

[0045] Among them, the density of polypropylene resin is 0.91g / cm 3 , melt index is 5.5g / 10min (190℃ / 2.16kg); toughening agent is ethylene-methyl acrylate copolymer (EMA), methyl acrylate content is 24%, density is 0.94g / cm 3 , the melt index is 3g / 10min (190℃ / 2.16kg); the foaming agent is 4,4'-oxybisbenzenesulfonyl hydrazide (OBSH, 98% purity); the lubricant is ethylenebisstearamide (EBS); and the antioxidant is antioxidant 168.

[0046] The preparation method of the composite flame retardant comprises:

[0047] S1. Mix calcium borate powder with a particle size of 10±2 μm and anhydrous ethanol, add 3-mercaptopropylmethyldimethoxysilane, the mass ratio of calcium borate powder, 3-mercaptopropylmethyldimethoxysilane and anhydrous ethanol is 1:0.2:20, ultrasonicate at room temperature for 0.4 h, heat to 75°C, reflux and stir for 5 h, filter and collect the powder, and dry to obtain thiol-functionalized calcium borate;

[0048] S2, adding 2-vinyl-4,6-diamino-1,3,5-triazine to anhydrous ethanol, stirring thoroughly under ice-water bath conditions, then adding 3-hydroxyphenylphosphoryl propionic acid, the mass ratio of 2-vinyl-4,6-diamino-1,3,5-triazine, 3-hydroxyphenylphosphoryl propionic acid and anhydrous ethanol is 0.4:1.02:15, and then dripping triethylamine as a catalyst, the addition amount is 3.5% of the mass of 3-hydroxyphenylphosphoryl propionic acid, heating to 80°C, reflux stirring for 4h, removing the solvent by reduced pressure distillation, and vacuum drying to obtain a triazine compound containing phenylphosphoryl;

[0049] S3. Mix a triazine compound containing a phenyl phosphoryl group and N-methylpyrrolidone, add mercapto-functionalized calcium borate, the mass ratio of mercapto-functionalized calcium borate, the triazine compound containing a phenyl phosphoryl group and N-methylpyrrolidone is 1:0.51:25, after sufficient stirring, add photoinitiator 651, the added amount is 4% of the mass of the triazine compound containing a phenyl phosphoryl group, irradiate with ultraviolet light in a nitrogen atmosphere, the ultraviolet light power is 55 W, the wavelength is 365 nm, stir for 1.5 hours, then filter and collect the solid, and dry under reduced pressure to obtain a composite flame retardant.

[0050] The preparation method of the high-strength flame-retardant polypropylene foam material comprises the following steps:

[0051] Step 1, taking a certain amount of polypropylene resin, a toughening agent and a composite flame retardant, mixing them in a mixer, heating them to 175° C., and mixing and stirring them at a speed of 550 r / min for 30 minutes to obtain a polypropylene mixture;

[0052] Step 2, mixing the lubricant and antioxidant with the polypropylene mixture in a twin-screw extruder at a temperature range of 170-210° C. and a screw aspect ratio of 22, and obtaining polypropylene masterbatch through melt extrusion and granulation;

[0053] Step 3, placing the polypropylene masterbatch in an extruder and heating it to melt, then adding a foaming agent in an appropriate amount, and extruding it into a mold after foaming. The foaming temperature is 165° C., the foaming pressure is 0.8 MPa, and the foaming time is 2 min to obtain a high-strength flame-retardant polypropylene foam material.

[0054] Example 2

[0055] A high-strength flame-retardant polypropylene foam material, calculated by weight, comprising:

[0056] 75 parts of polypropylene resin, 5 parts of toughening agent, 6 parts of composite flame retardant, 1.8 parts of foaming agent, 1 part of lubricant and 0.2 parts of antioxidant.

[0057] Among them, the density of polypropylene resin is 0.91g / cm 3 , the melt index is 5.5g / 10min (190℃ / 2.16kg); the toughening agent is styrene-butadiene-styrene block copolymer (SBS); the foaming agent is p-toluenesulfonyl semicarbazide; the lubricant is stearic acid; and the antioxidant is antioxidant 1010.

[0058] The preparation method of the composite flame retardant is the same as that of Example 1.

[0059] The preparation method of the high-strength flame-retardant polypropylene foam material comprises the following steps:

[0060] Step 1, taking a certain amount of polypropylene resin, a toughening agent and a composite flame retardant, mixing them in a mixer, heating them to 165° C., and mixing and stirring them at a speed of 500 r / min for 20 minutes to obtain a polypropylene mixture;

[0061] Step 2, taking lubricant and antioxidant according to the amount and mixing with polypropylene mixture in a twin-screw extruder, the temperature range is 170° C., the screw aspect ratio is 20, and the polypropylene masterbatch is obtained by melt extrusion and granulation;

[0062] Step 3, placing the polypropylene masterbatch in an extruder and heating it to melt, then adding a foaming agent in an appropriate amount, and extruding it into a mold after foaming. The foaming temperature is 155° C., the foaming pressure is 0.6 MPa, and the foaming time is 1 min to obtain a high-strength flame-retardant polypropylene foam material.

[0063] Example 3

[0064] A high-strength flame-retardant polypropylene foam material, calculated by weight, comprising:

[0065] 95 parts of polypropylene resin, 10 parts of toughening agent, 12 parts of composite flame retardant, 4.2 parts of foaming agent, 3 parts of lubricant and 0.8 parts of antioxidant.

[0066] Among them, the density of polypropylene resin is 0.91g / cm 3 , the melt index is 5.5g / 10min (190℃ / 2.16kg); the toughening agent is ethylene-vinyl acetate copolymer (EVA); the foaming agent is azodicarbonamide; the lubricant is calcium stearate; and the antioxidant is antioxidant 1024.

[0067] The preparation method of the composite flame retardant is the same as that of Example 1.

[0068] The preparation method of the high-strength flame-retardant polypropylene foam material comprises the following steps:

[0069] Step 1, taking a certain amount of polypropylene resin, a toughening agent and a composite flame retardant, mixing them in a mixer, heating them to 185° C., and mixing and stirring them at a speed of 600 r / min for 40 minutes to obtain a polypropylene mixture;

[0070] Step 2, taking lubricant and antioxidant according to the amount and mixing with polypropylene mixture in a twin-screw extruder, the temperature range is 210° C., the screw aspect ratio is 25, and the polypropylene masterbatch is obtained by melt extrusion and granulation;

[0071] Step 3, placing the polypropylene masterbatch in an extruder and heating it to melt, then adding a foaming agent in an appropriate amount, and extruding it into a mold after foaming. The foaming temperature is 175° C., the foaming pressure is 1.2 MPa, and the foaming time is 3 minutes to obtain a high-strength flame-retardant polypropylene foam material.

[0072] Example 4

[0073] A high-strength flame-retardant polypropylene foam material is different from Example 1 only in that the preparation method of the composite flame retardant is different from that of Example 1.

[0074] The preparation method of the composite flame retardant comprises:

[0075] S1. Mix calcium borate powder with a particle size of 10±2 μm and anhydrous ethanol, add 3-mercaptopropylmethyldimethoxysilane, the mass ratio of calcium borate powder, 3-mercaptopropylmethyldimethoxysilane and anhydrous ethanol is 1:0.3:30, ultrasonicate at room temperature for 0.6 h, heat to 80°C, reflux and stir for 6 h, filter and collect the powder, and dry to obtain thiol-functionalized calcium borate;

[0076] S2, adding 2-vinyl-4,6-diamino-1,3,5-triazine to anhydrous ethanol, stirring thoroughly under ice-water bath conditions, then adding 3-hydroxyphenylphosphoryl propionic acid, the mass ratio of 2-vinyl-4,6-diamino-1,3,5-triazine, 3-hydroxyphenylphosphoryl propionic acid and anhydrous ethanol is 0.42:1.36:20, and then dripping triethylamine as a catalyst, the addition amount is 5.5% of the mass of 3-hydroxyphenylphosphoryl propionic acid, heating to 90°C, keeping warm and stirring for 5h, removing the solvent by distillation under reduced pressure, and vacuum drying to obtain a triazine compound containing phenylphosphoryl;

[0077] S3. Mix a triazine compound containing a phenyl phosphoryl group and N-methylpyrrolidone, add mercapto-functionalized calcium borate, the mass ratio of mercapto-functionalized calcium borate, the triazine compound containing a phenyl phosphoryl group and N-methylpyrrolidone is 1:0.68:35, and after sufficient stirring, add photoinitiator 651 in an amount of 6% of the mass of the triazine compound containing a phenyl phosphoryl group. Under a nitrogen atmosphere, use ultraviolet light for irradiation, the ultraviolet light power is 55 W, the wavelength is 365 nm, stir for 2 hours, then filter and collect the solid, and dry under reduced pressure to obtain a composite flame retardant.

[0078] Example 5

[0079] A high-strength flame-retardant polypropylene foam material is different from Example 1 only in that the preparation method of the composite flame retardant is different from that of Example 1.

[0080] The preparation method of the composite flame retardant comprises:

[0081] S1. Mix calcium borate powder with a particle size of 10±2 μm and anhydrous ethanol, add 3-mercaptopropylmethyldimethoxysilane, the mass ratio of calcium borate powder, 3-mercaptopropylmethyldimethoxysilane and anhydrous ethanol is 1:0.1:10, ultrasonicate at room temperature for 0.2 h, heat to 70°C, reflux and stir for 4 h, filter and collect the powder, and dry to obtain thiol-functionalized calcium borate;

[0082] S2, adding 2-vinyl-4,6-diamino-1,3,5-triazine to anhydrous ethanol, stirring thoroughly under ice-water bath conditions, then adding 3-hydroxyphenylphosphoryl propionic acid, the mass ratio of 2-vinyl-4,6-diamino-1,3,5-triazine, 3-hydroxyphenylphosphoryl propionic acid and anhydrous ethanol is 0.21:0.68:10, and then dripping triethylamine as a catalyst, the addition amount is 2.5% of the mass of 3-hydroxyphenylphosphoryl propionic acid, heating to 70°C, keeping warm and stirring for 3h, removing the solvent by reduced pressure distillation, and vacuum drying to obtain a triazine compound containing phenylphosphoryl;

[0083] S3. Mix a triazine compound containing a phenyl phosphoryl group and N-methylpyrrolidone, add mercapto-functionalized calcium borate, the mass ratio of mercapto-functionalized calcium borate, the triazine compound containing a phenyl phosphoryl group and N-methylpyrrolidone is 1:0.34:15, and after sufficient stirring, add photoinitiator 184 in an amount of 2% of the mass of the triazine compound containing a phenyl phosphoryl group. Under a nitrogen atmosphere, use ultraviolet light for irradiation, the ultraviolet light power is 55 W, the wavelength is 365 nm, stir for 1 hour, then filter and collect the solid, and dry under reduced pressure to obtain a composite flame retardant.

[0084] Comparative Example 1

[0085] A polypropylene foam material, which is different from Example 1 only in that the composite flame retardant in Example 1 is replaced by calcium borate powder with a particle size of 10±2 μm.

[0086] Comparative Example 2

[0087] A polypropylene foam material, which is different from Example 1 only in that the composite flame retardant in Example 1 is replaced by 3-hydroxyphenylphosphatidyl propionic acid.

[0088] Comparative Example 3

[0089] A polypropylene foam material is different from Example 1 only in that the composite flame retardant in Example 1 is replaced by a mixture of calcium borate powder and 3-hydroxyphenylphosphoryl propionic acid, and the mass ratio of calcium borate powder to 3-hydroxyphenylphosphoryl propionic acid is 1:0.34.

[0090] Experimental testing

[0091] The properties of the polypropylene foam materials prepared in Example 1 and Comparative Examples 1-3 were tested, including density (Quarrz density tester AU-300S), tensile strength (reference GB / T 1040-2006), impact resistance (reference GB / T 1843-2008), oxygen index (reference GB / T 2406.2-2009), and vertical burning grade (reference US UL9‎4 fire protection standard).

[0092] The test results are shown in Table 1:

[0093] Table 1 Performance of different polypropylene foam materials

[0094] Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 <![CDATA[Density (g / cm 3 ).]]> 0.56 0.59 0.53 0.57 Surface quality No air marks, no dents There are obvious air marks and pits No air marks, no dents There are air marks but no dents Cross-sectional foaming effect Uniform and dense Uneven and severe pores Uniform and dense More uniform but coarse pores Tensile strength (MPa) 24.7 18.1 20.4 18.9 <![CDATA[Notched impact strength (kJ / m 2 )]]> 29.5 19.3 23.0 21.5 Oxygen index (%) 31 23 27 26 Vertical burning UL94 grade (grade) V-0 V-2 V-1 V-1

[0095] It can be seen from Table 1 that the polypropylene foam material prepared in Example 1 of the present invention has high surface quality, good foaming effect, and better tensile strength and impact strength. In addition, under the condition of the same addition amount of flame retardant, the oxygen index of the polypropylene foam material prepared in Example 1 of the present invention reaches 31%, and the flame retardant grade reaches V-0, indicating that its flame retardant performance is more excellent.

[0096] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms should not be understood as necessarily being directed to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification.

[0097] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A high-strength flame-retardant polypropylene foam material, characterized in that: Calculated by weight, including: 75-95 parts of polypropylene resin, 5-10 parts of toughening agent, 6-12 parts of composite flame retardant, 1.8-4.2 parts of foaming agent, 1-3 parts of lubricant and 0.2-0.8 parts of antioxidant; wherein the composite flame retardant is prepared by a click chemical reaction between mercapto-functionalized calcium borate and a triazine compound containing a phenylphosphoryl group; The preparation method of the composite flame retardant comprises: S1. Mix calcium borate powder and anhydrous ethanol, add 3-mercaptopropylmethyldimethoxysilane, and perform ultrasonic treatment at room temperature for 0.2-0.6h, then heat to 70-80°C, reflux and stir for 4-6h, collect the powder by suction filtration, and dry to obtain mercapto-functionalized calcium borate; S2, adding 2-vinyl-4,6-diamino-1,3,5-triazine to anhydrous ethanol, stirring thoroughly in an ice-water bath, then adding 3-hydroxyphenylphosphoryl propionic acid, and then dropping triethylamine, heating to 70-90° C., stirring and preserving for 3-5 hours, and then distilling off the solvent under reduced pressure, and drying in vacuo to obtain a triazine compound containing a phenylphosphoryl group; S3. Mix a triazine compound containing a phenyl phosphoryl group and N-methylpyrrolidone, add thiol-functionalized calcium borate, stir thoroughly, then add a photoinitiator, irradiate with ultraviolet light under a nitrogen atmosphere, stir for 1-2 hours, then filter and collect the solid, and dry under reduced pressure to obtain a composite flame retardant.

2. A high-strength flame-retardant polypropylene foam material according to claim 1, characterized in that: The density of the polypropylene resin is 0.90-0.92 g / cm 3 The melt index is 3.5-7.5 g / 10 min at 190°C and 2.16 kg.

3. The high-strength flame-retardant polypropylene foam material according to claim 1, characterized in that: The toughening agent is a mixture of one or more of styrene-butadiene-styrene block copolymer, ethylene-methyl acrylate copolymer and ethylene-vinyl acetate copolymer.

4. The high-strength flame-retardant polypropylene foam material according to claim 1, characterized in that: The foaming agent is one of 4,4'-oxybisbenzenesulfonyl hydrazide, p-toluenesulfonyl semicarbazide and azodicarbonamide.

5. The high-strength flame-retardant polypropylene foam material according to claim 1, characterized in that: The lubricant is a mixture of one or more of stearic acid, calcium stearate and ethylene bis stearic acid amide.

6. The high-strength flame-retardant polypropylene foam material according to claim 1, characterized in that: The antioxidant is a mixture of one or more of antioxidant 168, antioxidant 1010, antioxidant 1024, antioxidant 1076, and antioxidant 1098.

7. The high-strength flame-retardant polypropylene foam material according to claim 1, characterized in that: In S2, the mass ratio of 2-vinyl-4,6-diamino-1,3,5-triazine, 3-hydroxyphenylphosphoryl propionic acid and anhydrous ethanol is 0.21-0.42:0.68-1.36:10-20; and the amount of triethylamine added is 2.5%-5.5% of the mass of 3-hydroxyphenylphosphoryl propionic acid.

8. The high-strength flame-retardant polypropylene foam material according to claim 1, characterized in that: In S3, the mass ratio of mercapto-functionalized calcium borate, the triazine compound containing phenyl phosphoryl and N-methylpyrrolidone is 1:0.34-0.68:15-35; the photoinitiator is photoinitiator 651 or photoinitiator 184, and the added amount is 2%-6% of the mass of the triazine compound containing phenyl phosphoryl.

9. A method for preparing the high-strength flame-retardant polypropylene foam material according to claim 1, characterized in that: The following steps are involved: Step 1, taking a certain amount of polypropylene resin, a toughening agent and a composite flame retardant, mixing them in a mixer, heating and mixing, and obtaining a polypropylene mixture; Step 2, taking lubricant and antioxidant according to the amount and mixing them with the polypropylene mixture in a twin-screw extruder, and performing melt extrusion and granulation to obtain polypropylene masterbatch; Step 3, placing the polypropylene masterbatch in an extruder and heating it to melt, then adding a foaming agent in a certain amount, and extruding it into a mold after foaming to obtain a high-strength flame-retardant polypropylene foam material.

Images