Flame-retardant thermoplastic material and expanded beads thereof

Abstract

The invention relates to a flame-retardant thermoplastic material, comprising thermoplastic base resin, a flame retardant, and an optional antioxidant, wherein the flame retardant comprises a complex of phosphine oxide and a transition metal salt. The invention also relates to flame-retardant thermoplastic expanded beads. A foam molding prepared from the flame-retardant thermoplastic expanded beads has good flame-retardant and antistatic properties, has excellent mechanical properties and is widely used.

Claims

1. A flame-retardant thermoplastic material comprising a thermoplastic base resin, a flame retardant, and an optional antioxidant, wherein the flame retardant comprises a complex of a phosphine oxide and a transition metal salt, or a complex of tributyl phosphate and a transition metal salt, or a complex of dibutyl butylphosphate and a transition metal salt, and based on 100 parts by weight of the thermoplastic base resin, the amount of the flame retardant is 5-50 parts by weight; and wherein the flame retardant further comprises a carbon nanofiber antistatic agent and the carbon nanofiber antistatic agent comprises 1-5 wt % of transition metal.

2. The flame-retardant thermoplastic material according to claim 1, characterized in that the phosphine oxide has the following structural formula I: ##STR00004## wherein R.sub.1, R.sub.2 and R.sub.3, identical or different, are independently selected from C.sub.1-C.sub.18 linear alkyl, C.sub.3-C.sub.18 branched alkyl, C.sub.1-C.sub.18 linear alkoxy, C.sub.3-C.sub.18 branched alkoxy, C.sub.6-C.sub.20 substituted or unsubstituted aryl, and C.sub.6-C.sub.20 substituted or unsubstituted aryloxy.

3. The flame-retardant thermoplastic material according to claim 2, characterized in that the phosphine oxide is selected from at least one of triphenylphosphine oxide, bis(4-hydroxyphenyl) phenylphosphine oxide, bis(4-carboxyphenyl) phenylphosphine oxide, tributylphosphine oxide, trihexylphosphine oxide, trioctylphosphine oxide, and tridecylphosphine oxide.

4. The flame-retardant thermoplastic material according to claim 1, characterized in that the transition metal salt is a transition metal organic salt and/or a transition metal inorganic salt; and/or the step of preparing the complex comprises stirring and mixing 1-10 parts by weight of phosphine oxide, or tributyl phosphate, or dibutyl butyl phosphate with 3-15 parts by weight of transition metal salt in an organic solvent, followed by microwave heating and supercritical drying to obtain the complex.

5. The flame-retardant thermoplastic material according to claim 1, characterized in that based on 100 parts by weight of the thermoplastic base resin, the amount of the flame retardant is 10-20 parts by weight.

6. The flame-retardant thermoplastic material according to claim 5, characterized in that the flame retardant further comprises an inorganic flame retardant component; the weight ratio of the complex to the inorganic flame retardant component in the flame retardant is (1-5): 1; the inorganic flame retardant component is selected from hydroxides of the Group 2 and Group 13 metals.

7. A flame-retardant thermoplastic material comprising thermoplastic base resin, a flame retardant, and an optional antioxidant, wherein the flame retardant comprises a complex of phosphine oxide and a transition metal salt, or a complex of tributyl phosphate and a transition metal salt, or a complex of dibutyl butylphosphate and a transition metal salt, and based on 100 parts by weight of the thermoplastic base resin, the amount of the flame retardant is 5-50 parts by weight, wherein the thermoplastic base resin is a polypropylene base resin; the polypropylene base resin comprises a propylene homopolymer component and a propylene-ethylene copolymer component and is characterized in that: the molecular weight distribution M.sub.w/M.sub.n is less than or equal to 10 and greater than or equal to 4; M.sub.z+1/M.sub.w is greater than 10 and less than 20; the content of room-temperature xylene-soluble matters is greater than 10% by weight and less than 30% by weight; the ratio of M.sub.w of room-temperature trichlorobenzene-soluble matters to M.sub.w of room-temperature trichlorobenzene-insoluble matters is greater than 0.4 and less than 1.

8. The flame-retardant thermoplastic material according to claim 7, characterized in that the ethylene content in the room-temperature xylene-soluble matters of the polypropylene base resin is less than 50% by weight and more than 25% by weight; and/or, the ethylene monomer content in the polypropylene base resin is 5-15% by weight; and/or the polypropylene base resin has melt index of 0.1-15 g/10 min, as measured at 230 C. under a load of 2.16 kg.

9. The flame-retardant thermoplastic material according to claim 7, characterized in that the step of preparing the polypropylene base resin comprises: (1) first step: propylene homopolymerization reaction, including: {circle around (1)} first stage: carrying out propylene homopolymerization reaction in the presence or absence of hydrogen under the action of a Ziegler-Natta catalyst comprising a first external electron donor to obtain a reaction stream comprising a first propylene homopolymer; {circle around (2)} second stage: adding a second external electron donor to have complexing reaction with the catalyst in the reaction stream and then carrying out propylene homopolymerization in the presence of the first propylene homopolymer and hydrogen to produce a second propylene homopolymer, thereby obtaining a propylene homopolymer component comprising the first propylene homopolymer and the second propylene homopolymer; wherein the melt indices of the first propylene homopolymer and the propylene homopolymer component comprising the first propylene homopolymer and the second propylene homopolymer are 0.001-0.4 g/10 min and 0.1-15 g/10 min, respectively, as measured at 230 C. under a load of 2.16 kg; and the weight ratio of the first propylene homopolymer to the second propylene homopolymer is 40:60 to 60:40; (2) second step: propylene-ethylene copolymerization reaction: carrying out propylene-ethylene copolymerization reaction in the presence of the propylene homopolymer component and hydrogen to produce a propylene-ethylene copolymer component, thereby obtaining the polypropylene base resin comprising the propylene homopolymer component and the propylene-ethylene copolymer component.

10. The flame-retardant thermoplastic material according to claim 9, characterized in that the weight ratio of the propylene-ethylene copolymer component to the propylene homopolymer component is 11-40:100; and/or the ratio of the melt index of the propylene homopolymer component to the melt index of the polypropylene base resin comprising the propylene homopolymer component and the propylene-ethylene copolymer component, as measured at 230 C. under a load of 2.16 kg, is greater than or equal to 0.6 and less than or equal to 1.

11. Flame-retardant thermoplastic expanded beads prepared by carrying out a batch foaming process on a material comprising 100 parts by weight of the flame-retardant thermoplastic material according to claims 1 and 0.001 to 1 part by weight of a cell nucleating agent.

12. A foam molding prepared from the expanded beads according to claim 11, having surface resistivity of 1.0*10.sup.7 to 1.0*10.sup.9, limiting oxygen index of 20-40, and compressive strength of 170-600 kPa.

13. The flame-retardant thermoplastic material according to claim 2, characterized in that R.sub.1, R.sub.2 and R.sub.3 are independently selected from C.sub.4-C.sub.18 linear or branched alkyl and C.sub.6-C.sub.18 aryl having 1 or 2 carbon rings.

14. The flame-retardant thermoplastic material according to claim 2, characterized in that R.sub.1, R.sub.2 and R.sub.3 are independently selected from C.sub.6-C.sub.12 linear or branched alkyl having 6 or more carbon atoms on the primary carbon chain and substituted or unsubstituted phenyl.

15. The flame-retardant thermoplastic material according to claim 4, characterized in that the transition metal salt is at least one of nitrate, thiocyanate, formate, acetate and oxalate of a metal element from Groups 8-10.

16. The flame retardant thermoplastic material according to claim 1, characterized in that based on 100 parts by weight of the thermoplastic base resin, the amount of the carbon nanofiber antistatic agent is 0.1-10 parts by weight.

17. The flame retardant thermoplastic material according to claim 1, characterized in that based on 100 parts by weight of the thermoplastic base resin, the amount of the carbon nanofiber antistatic agent is 1-3 parts by weight.

18. The flame-retardant thermoplastic material according to claim 1, characterized in that the thermoplastic base resin is selected from at least one of polyolefin base resin, polylactic acid base resin, polyurethane base resin, polyester base resin and polyamide base resin.

19. The flame-retardant thermoplastic material according to claim 18, characterized in that the thermoplastic base resin is selected from at least one of polyethylene base resin, polypropylene base resin, polybutylene base resin, polyurethane base resin, polylactic acid base resin, polyethylene terephthalate base resin, polybutylene terephthalate base resin, polyamide 6 base resin, and poly(butylene succinate) base resin.

20. The flame-retardant thermoplastic material according to claim 1, characterized in that the preparation step of the carbon nanofiber antistatic agent comprises: subjecting a carbon source to acid treatment and then forming a complex with a transition metal catalyst, and subjecting the complex to carbonization treatment at 800-1200 C. under the protection of inert gas.

21. The flame-retardant thermoplastic material according to claim 20, characterized in that the carbon source is selected from at least one of carbon pitch, petroleum pitch, coal tar pitch, coal tar, natural graphite, artificial graphite, bamboo charcoal, carbon black, activated carbon and graphene with carbon content of 80 wt % or higher; the transition metal catalyst is selected from at least one of sulfate, nitrate, acetate and a menthyl compound of a transition metal; the transition metal is selected from at least one of iron, cobalt, nickel and chromium; and/or the mass ratio of the transition metal catalyst to the carbon source is 35-70:100, based on the transition metal.

22. The flame-retardant thermoplastic material according to claim 7, characterized in that the phosphine oxide has the following structural formula I: ##STR00005## wherein R.sub.1, R.sub.2 and R.sub.3, identical or different, are independently selected from C.sub.1-C.sub.18 linear alkyl, C.sub.3-C.sub.18 branched alkyl, C.sub.1-C.sub.18 linear alkoxy, C.sub.3-C.sub.18 branched alkoxy, C.sub.6-C.sub.20 substituted or unsubstituted aryl, and C.sub.6-C.sub.20 substituted or unsubstituted aryloxy.

23. The flame-retardant thermoplastic material according to claim 22, characterized in that the phosphine oxide is selected from at least one of triphenylphosphine oxide, bis(4-hydroxyphenyl) phenylphosphine oxide, bis(4-carboxyphenyl) phenylphosphine oxide, tributylphosphine oxide, trihexylphosphine oxide, trioctylphosphine oxide, and tridecylphosphine oxide.

24. The flame-retardant thermoplastic material according to claim 7, characterized in that the transition metal salt is a transition metal organic salt and/or a transition metal inorganic salt; and/or, the step of preparing the complex comprises stirring and mixing 1-10 parts by weight of phosphine oxide, or tributyl phosphate, or dibutyl butylphosphate with 3-15 parts by weight of transition metal salt in an organic solvent, followed by microwave heating and supercritical drying to obtain the complex.

25. The flame-retardant thermoplastic material according to claim 7, characterized in that based on 100 parts by weight of the thermoplastic base resin, the amount of the flame retardant is 10-20 parts by weight.

26. The flame-retardant thermoplastic material according to claim 25, characterized in that the flame retardant further comprises an inorganic flame retardant component; wherein the weight ratio of the complex to the inorganic flame retardant component in the flame retardant is (1-5): 1, and the inorganic flame retardant component is selected from hydroxides of the Group 2 and Group 13 metals.

27. Flame-retardant thermoplastic expanded beads prepared by carrying out an batch foaming process on a material comprising 100 parts by weight of the flame-retardant thermoplastic material according to claims 7 and 0.001 to 1 part by weight of a cell nucleating agent.

28. A foam molding prepared from the expanded beads according to claim 27, having surface resistivity of 1.0*10.sup.7 to 1.0*10.sup.9, limiting oxygen index of 20-40, and compressive strength of 170-600 kPa.

29. The flame-retardant thermoplastic material according to claim 22, characterized in that R.sub.1, R.sub.2 and R.sub.3 are independently selected from C.sub.4-C.sub.18 linear or branched alkyl and C.sub.6-C.sub.18 aryl having 1 or 2 carbon rings.

30. The flame-retardant thermoplastic material according to claim 22, characterized in that R.sub.1, R.sub.2 and R.sub.3 are independently selected from C.sub.6-C.sub.12 linear or branched alkyl having 6 or more carbon atoms on the primary carbon chain and substituted or unsubstituted phenyl.

31. The flame-retardant thermoplastic material according to claim 24, characterized in that the transition metal salt is at least one of nitrate, thiocyanate, formate, acetate and oxalate of a metal element from Groups 8-10.

Description

DESCRIPTION OF DRAWINGS

(1) The invention is further described in detail with reference to the drawings, in which like parts are designated by like reference numerals.

(2) FIG. 1 shows the infrared spectra of triphenylphosphine oxide and complex Co(OPPh.sub.3).sub.2(NO.sub.3).sub.2;

(3) FIG. 2 shows the scanning electron micrograph of the microscopic morphology of the complex Co(OPPh.sub.3).sub.2(NO.sub.3).sub.2;

(4) FIG. 3 shows the scanning electron micrograph of the microscopic morphology of carbon nanofibers;

(5) FIG. 4 shows the surface electron micrograph of the flame-retardant antistatic expanded polypropylene beads prepared in Example 2;

(6) FIG. 5 shows the cross-sectional electron micrograph of the flame-retardant antistatic expanded polypropylene beads prepared in Example 2;

(7) FIG. 6 shows the surface electron micrograph of the expanded polypropylene beads prepared in Comparative Example 2;

(8) FIG. 7 shows the cross-sectional electron micrograph of the expanded polypropylene beads prepared in Comparative Example 2.

EMBODIMENTS

(9) The invention is further described with reference to the following examples, but it is noted that the invention is not limited to these examples.

(10) The raw materials in the following Examples and Comparative Examples are shown below. Ordinary polypropylene base resin: Qilu Company of China Petroleum & Chemical Corporation, Trademark EPS30R; Polyethylene base resin: Yangzi Petrochemical Company Limited of China Petroleum & Chemical Corporation, Trademark 7042; Polyethylene base resin: Yanshan Company of China Petroleum & Chemical Corporation, Trademark LD100ac; Polyethylene base resin: Beijing Research Institute of Chemical Industry of China Petroleum & Chemical Corporation, Trademark HPE1, HPE2; Polylactic acid base resin: Natureworks; TPU base resin: BASF; PBT base resin: ChiMei Chemical Corporation; PET base resin: Japan Toray; PA 6 base resin: BASF; PBS base resin: Beijing Research Institute of Chemical Industry of China Petroleum & Chemical Corporation; Kaolin: J&K Scientific Ltd., ACROS, Analytical purity; Triphenylphosphine oxide: J&K Scientific Ltd., ACROS, Analytical purity; Cobalt nitrate: J&K Scientific Ltd., ACROS, Analytical purity; Nickel nitrate: J&K Scientific Ltd., ACROS, Analytical purity; Coal tar pitch: Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences, Carbon content of higher than 80 wt %, Industrial grade; Petroleum pitch: Sinopec, Carbon content of higher than 80 wt %, Industrial grade; Bamboo charcoal: Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences, Carbon content of higher than 80 wt %, Industrial grade; Magnesium hydroxide: J&K Scientific Ltd., ACROS, Analytical purity; Aluminum hydroxide: J&K Scientific Ltd., ACROS, Analytical purity; Ethanol: J&K Scientific Ltd., ACROS, Analytical purity; Sodium dodecylbenzene sulfonate: Tianjin Guangfu Fine Chemical Research Institute, Analytical purity; Aluminum sulfate: Tianjin Guangfu Technology Development Co., Ltd., Analytical purity; Zinc borate: Tianjin Guangfu Fine Chemical Research Institute, Analytical purity; Carbon nanofibers: Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences, Purity greater than 80 wt %, Industrial grade; Antistatic agent Atmer129: Croda Company, Industrial grade; Trioctylphosphine oxide, trihexylphosphine oxide, tridecylphosphine oxide, tributyl phosphate and dibutyl butylphosphate are all prepared by conventionally known preparation methods.

(11) Other used raw materials are commercially available.

(12) The production and test apparatus and equipment used in the Examples and Comparative Examples are shown below. Underwater granulation system: Labline 1000, Germany BKG Company; Melt Tensile Tester: Rheotens71.97, Germany Goettfert Company; Density Tester: CPA225D, Density Accessories YDK01, Germany Satorius Company; Molding Machine: Germany Kurtz Ersa Company Kurtz T-Line; Universal material testing machine: 5967, the US Instron Corporation; Oxygen Index Instrument: 6448, Italy ceast Company; Cone calorimeter: FTT200, British FTT Company; Surface resistance meter: 4339B, the US Agilent company.

(13) The polymer-related data in the examples were obtained according to the following test methods.

(14) (1) the content of the room-temperature xylene-soluble matters and the ethylene content in the room-temperature xylene-soluble matters (i.e., the content of the rubber phase and the ethylene content of the rubber phase) were measured by the CRYSTEX method using CRYST-EX (CRYST-EX EQUIPMENT, IR4+detector) manufactured by Spain Polymer Char Company, a series of samples with different content of the room-temperature xylene-soluble matters were selected as standard samples for calibration, and the content of the room-temperature xylene-soluble matters in the standard samples was measured by ASTM D5492. The infrared detector provided by the instrument itself can test the weight content of propylene in the soluble matters, which is used to characterize the ethylene content in the room-temperature xylene-soluble matters (ethylene content in the rubber phase) by substracting the weight content of propylene from 100%.

(15) (2) the tensile strength of the resin was measured according to the method described in GB/T 1040.2 (ISO 527).

(16) (3) the melt mass flow rate MFR (also known as melt index) was measured at 230 C. under a load of 2.16 kg using the 7026 Melt Indexer from the CEAST Company according to the method described in ASTM D1238.

(17) (4) the flexural modulus was measured according to the method described in GB/T 9341 (ISO178).

(18) (5) the notched impact strength of simply supported beam was measured according to the method described in GB/T 1043.1 (ISO179).

(19) (6) the ethylene content was measured by an infrared spectroscopy (IR) method, in which the standard sample measured by a nuclear magnetic resonance method was used for calibrating. In the nuclear magnetic resonance method, an AVANCE III 400 MHz nuclear magnetic resonance (NMR) spectrometer from Swiss Bruker Company and a 10 mm probe were adopted for measuring. The solvent was deuterated o-dichlorobenzene, and about 250 mg of the sample was placed in 2.5 ml of deuterated solvent and dissolved by heating in a 140 C. oil bath to form a homogeneous solution. .sup.13C-NMR was collected, the probe temperature was 125 C., 90 pulse was adopted, the sampling time AQ was 5 seconds, the delay time D1 was 10 seconds, and the scanning frequency was more than or equal to 5000 times. Other operations, peak identification and the like were implemented according to the commonly used NMR experimental requirements.

(20) (7) polydispersity index of relative molecular weight (PI): a resin sample was molded into a 2 mm sheet at 200 C. and subjected to dynamic frequency scanning at 190 C. under the protection of nitrogen by using an ARES (Advanced Rheometer Extension System) rheometer from the USA Rheometric Scientific Inc. The parallel plate clamps were adopted, and the appropriate strain amplitude was determined to ensure that the experiment was carried out in the linear region. The changes of the energy storage modulus (G), the energy consumption modulus (G) and the like of the samples along with the frequency were measured. The PI=10.sup.5/G, where G (Pa) is the modulus value at the intersection of the G-frequency curve and the G-frequency curve.

(21) (8) the melt strength was measured by using a Rheotens melt strength meter manufactured by the Germany Geottfert Werkstoff Pruefmaschinen Company. The polymer was melted and plasticized by the single-screw extruder and downward extruded through a 90 steering head with a die having aspect ratio of 30/2 to form melt strips, which were clamped in a group of two rollers oppositely rotating at constant acceleration to be uniaxially drawn, the force of the melt drawing process was measured and recorded by means of a force measuring unit connected to the drawing rollers, and the maximum force value measured at the time of melt fracture was defined as the melt strength.

(22) (9) molecular weight (M.sub.w, M.sub.n) and molecular weight distribution (M.sub.w/M.sub.n, M.sub.z+1/M.sub.w) were measured by using a PL-GPC 220 gel permeation chromatograph manufactured by the British Polymer Laboratories, Inc. or a GPCIR instrument (IR5 concentration detector) manufactured by the Spain Polymer Char Company. The chromatographic column was three serial PLgel 13 um Olexis columns, the solvent and mobile phase were 1,2,4-trichlorobenzene (containing 250 ppm of antioxidant 2,6-dibutyl p-cresol), the column temperature was 150 C., the flow rate was 1.0 ml/min, and the EasiCal PS-1 narrowly distributed polystyrene standard sample from the PL Company was used for universal calibration. The preparation process of room-temperature trichlorobenzene-soluble matters comprises accurately weighing the sample and trichlorobenzene solvent, dissolving at 150 C. for 5 hours, standing at 25 C. for 15 hours, and filtering by use of quantitative glassfiber filter paper to get the solution of the room-temperature trichlorobenzene-soluble matters used for the determination. The GPC curve area was corrected by using polypropylene with known concentration to determine the content of the room-temperature trichlorobenzene-soluble matters. The molecular weight data of the room-temperature trichlorobenzene-insoluble matters were calculated according to the GPC data of the original sample and the GPC data of the soluble matters.

(23) (10) density measurement: according to GB/T 1033.1-2008 (ISO1183), the densities of the polypropylene base resin and the expanded polypropylene beads were obtained by the drainage method using the density accessories of the Satorius balance. The foaming ratio of the obtained polypropylene foamed material was calculated by the formula: b=1/2, wherein b is the foaming ratio, 1 is the density of the polypropylene base resin, and 2 is the apparent density of the foamed material.

(24) (11) the oxygen index was tested according to the method described in GB/T 2406.2-2009 (ISO4589).

(25) (12) the surface resistivity was tested according to the method described in GB/T 1410-2006 (International Electrotechnical Commission (IEC) 60167).

(26) (13) test of compressive strength: a 50*50*25 mm sample was cut from the foam molding of the expanded beads and tested on a universal material testing machine 5967 based on US ASTM D3575-08 at a compression rate of 10 mm/min, and the compression strength when the foam molding was compressed by 50% was obtained.

(27) Preparation of Polypropylene Base Resin HMSPP

(28) Preparation of Polypropylene Base Resin HMSPP601

(29) Propylene polymerization reaction was carried out in a polypropylene device, and the device mainly comprises a prepolymerization reactor, a first loop reactor, a second loop reactor and a third gas phase reactor. The polymerization method and the steps were as follows.

(30) (1) Prepolymerization Reaction

(31) The main catalyst (DQC-401 catalyst, provided by Beijing Oda Branch of Sinopec Catalyst Company), cocatalyst (triethylaluminum), and the first external electron donor (dicyclopentyl-dimethoxysilane, DCPMS) were precontacted at 6 C. for 20 min, and then continuously added to the continuous stirred tank prepolymerization reactor for prepolymerization reaction. The flow rate of triethylaluminum (TEA) entering the prepolymerisation reactor was 6.33 g/hr, the flow rate of dicyclopentyl-dimethoxysilane was 0.3 g/hr, the flow rate of the main catalyst was 0.6 g/hr, and the TEA/DCPMS ratio was 50 (mol/mol). The prepolymerization was carried out in the propylene liquid phase bulk environment at the temperature of 15 C. and residence time of about 4 min. The prepolymerization ratio of the catalyst was about 80-120 times.

(32) (2) The First Step: Propylene Polymerization Reaction

(33) The first stage: the catalyst after prepolymerization continuously entered the first loop reactor to complete propylene homopolymerization reaction of the first stage, the polymerization reaction temperature in the first loop reactor was 70 C., and the reaction pressure was 4.0 MPa; the feed of the first loop reactor was free of hydrogen, the hydrogen concentration was less than 10 ppm, measured through online chromatography, and the first propylene homopolymer A was obtained.

(34) The second stage: the propylene homopolymerization reaction of the second stage was carried out in the second loop reactor connected in series with the first loop reactor. 0.63 g/hr of tetraethoxysilane (TEOS) was added along with propylene in the second loop reactor to be mixed with the reaction stream from the first loop reactor, the TEA/TEOS ratio was 5 (mol/mol), and TEOS was the second external electron donor. The polymerization temperature of the second loop reactor was 70 C. and the reaction pressure was 4.0 MPa. A certain amount of hydrogen was added along with the propylene feed, and the concentration of hydrogen in the feed was 3,000 ppm, measured through online chromatography, and the second propylene homopolymer B was generated in the second loop reactor, so that the propylene homopolymer component comprising the first propylene homopolymer and the second propylene homopolymer was obtained.

(35) (3) The Second Step: Ethylene/Propylene Copolymerization Reaction

(36) A certain amount of hydrogen was added to the third reactor, and H.sub.2/(C.sub.2+C.sub.3)=0.06 (mol/mol), and C.sub.2/(C.sub.2+C.sub.3)=0.3 (mol/mol) (C.sub.2 and C.sub.3 respectively refer to ethylene and propylene). The ethylene/propylene copolymerization reaction was further initiated in the third reactor at the reaction temperature of 75 C. to produce the propylene-ethylene copolymer component C.

(37) The final product contains the first propylene homopolymer, the second propylene homopolymer and the propylene-ethylene copolymer component, the unreacted catalyst was deactivated by wet nitrogen and the final product was dried by heating to obtain polymer powder. 0.1 wt % of IRGAFOS 168 additive, 0.1 wt % of IRGANOX 1010 additive and 0.05 wt % of calcium stearate were added to the resulting powder and granulated with the twin-screw extruder. The analysis results of the polymer and the physical properties of the polymers were shown in Tables 1 and 2.

(38) Preparation of Polypropylene Base Resin HMSPP602

(39) The catalyst, the prepolymerization and polymerization process conditions for the preparation of HMSPP602 were the same as those for the preparation of HMSPP601. The differences from the preparation of the HMSPP601 were that the amount of hydrogen in the second reactor in the second stage was 13,000 ppm, the H.sub.2/(C.sub.2+C.sub.3) in the gas phase reactor of the second step was 0.49 (mol/mol), the first external electron donor was methyl-isopropyl-dimethoxysilane (MIPMS), and the addition amount was unchanged. The analysis results of the polymer and the physical properties of the polymer were shown in Tables 1 and 2.

(40) Preparation of Polypropylene Base Resin HMSPP603

(41) The catalyst, the prepolymerization and polymerization process conditions for the preparation of HMSPP603 were the same as those for the preparation of HMSPP601. The differences from the preparation of the HMSPP601 were that the second external electron donor was 2,2-diisobutyl-1,3-dimethoxypropane (DIBMP), the addition amount was unchanged and the amount of hydrogen in the second reactor in the second stage was 3,600 ppm. The analysis results of the polymer and the physical properties of the polymer were shown in Tables 1 and 2.

(42) TABLE-US-00001 TABLE 1 Polymerization Process Conditions and Analysis Results of the Polypropylene Base Resin Hydrogen concentration (ppm) H.sub.2/(C.sub.2 + C.sub.3) (v/v) C.sub.2/(C.sub.2 + C.sub.3) (v/v) External electron donor Homopolymerization Homopolymerization Copolymerization Copolymerization Trademark DONOR-1 DONOR-2 of the first stage of the second stage of the second step of the second step HMSPP601 DCPMS TEOS 0 3000 0.06 0.3 HMSPP602 MIPMS TEOS 0 13000 0.49 0.3 HMSPP603 DCPMS DIBMP 0 3600 0.06 0.3 Size and distribution of Size and distribution of MFR molecular weight molecular weight (g/10 min) (Polymer A + B) (Polymer A + B + C) Polymer Polymer M.sub.w 10.sup.4 M.sub.w 10.sup.4 Trademark (A + B) (A + B + C) (g/mol) M.sub.w/M.sub.n M.sub.n+1/M.sub.w (g/mol) M.sub.w/M.sub.n M.sub.n+1/M.sub.w HMSPP601 0.4 0.43 96.8 10.5 106 71.8 7.9 12 HMSPP602 0.4 0.43 97.2 10.4 107 70.6 7.0 12.7 HMSPP603 0.38 0.4 98.0 10.8 110 73.2 8.1 12.3 Note: DONOR-1 was the first external electron donor, and DONOR-2 was the second external electron donor.

(43) TABLE-US-00002 TABLE 2 Physical Properties of the Polypropylene Base Resin M.sub.w(room-temperature M.sub.w of M.sub.w of trichlorobenzene- room-temperature room-temperature soluble matters)/ Content of Ethylene content trichlorobenzene- trichlorobenzene- M.sub.w(room-temperature room-temperature of the base soluble matters insoluble matters trichlorobenzene- xylene-soluble Trademark resin wt % (10.sup.4 g/mol) (10.sup.4 g/mol) insoluble matters) matters wt % HMSPP601 10.0 56.7 81.2 0.70 19.8 HMSPP602 10.5 55.2 80.6 0.68 21.8 HMSPP603 9.2 54.3 82.1 0.66 17.5 Ethylene content of Izod notched room-temperature Tensile flexural Melt strength Melt strength impact strength xylene-soluble Polydispersity strength modulus (die temperature (die temperature at 23 C. Trademark matters wt % index (PI) MPa GPa 200 C.) N 220 C.) N KJ/m.sup.2 HMSPP601 42.9 5.27 24.4 0.93 >2 1.3 82.6 HMSPP602 46.7 5.2 23.5 0.91 >2 1.3 88.4 HMSPP603 42.5 5.1 25.8 1.01 >2 1.4 77.6

Example 1

(44) The raw material ratio and the reaction conditions for the preparation of the flame retardant, the polypropylene composition, the expanded beads and other products in this Example were shown in Tables 3 and 4, and the performance parameters of the expanded beads were also listed in Table 4. In the tables, the flame-retardant component A was phosphine oxide, the flame-retardant component B was the transition metal salt, and the flame-retardant component C was the inorganic flame-retardant component.

(45) (1) Preparation of the (Halogen-Free) Flame Retardant

(46) Triphenylphosphine oxide and cobalt nitrate were added to ethanol and stirred at a rate of 100 rpm. The mixture was then heated at 40 C. for 4 h under microwave irradiation with heating power of 50 W while stirring. The complex Co(OPPh.sub.3).sub.2(NO.sub.3).sub.2 formed by triphenylphosphine oxide and cobalt nitrate was obtained by supercritical drying of the material after microwave heating. The structures and microscopic morphology of the complexes were characterized by infrared spectroscopy and scanning electron microscopy. The results were shown in FIG. 1 and FIG. 2.

(47) The prepared complex Co(OPPh.sub.3).sub.2(NO.sub.3).sub.2 was mechanically stirred with magnesium hydroxide at a rate of 10 rpm to obtain the flame retardant.

(48) FIG. 1 shows the infrared spectrum of the complex Co(OPPh.sub.3).sub.2(NO.sub.3).sub.2. It can be seen from the figure that in the infrared spectrum of the complex, the peaks at 1143 cm.sup.1 and 1070 cm.sup.1 correspond to the PO stretching vibration and move toward the direction of low wave number compared with triphenylphosphine oxide, proving the formation of the complex. The peaks at 1258 cm.sup.1, 1024 cm.sup.1 and 812 cm.sup.1 correspond to coordination of O.NO.sub.2, thus demonstrating the tetrahedral structure of the complex.

(49) (2) Preparation of Carbon Nanofiber Antistatic Agent

(50) A pretreated material was obtained by carrying out grinding pretreatment on coal tar pitch having carbon content of 85 wt % as the carbon source with mixed acid of phosphoric acid/nitric acid/hydrochloric acid (volume ratio 1:1:1).

(51) The above-mentioned pretreated material and the catalyst cobalt nitrate were mixed in a ball mill to obtain a complex.

(52) The complex was subjected to carbonization reaction under the high-purity nitrogen at 950 C. for 1.5 hours and then cooled to room temperature to obtain self-assembled carbon nanofibers. Post-treatment for removing catalyst metal impurities was not needed, and the carbon nanofibers contain 2 wt % of cobalt, as measured. The microscopic morphology of the carbon nanofibers was shown in FIG. 3.

(53) (3) Preparation of (Halogen-Free) Flame-Retardant Polypropylene Composition

(54) The HMSPP601, the above-prepared carbon nanofiber antistatic agent, the cell nucleating agent zinc borate, the antioxidant 1010 (BASF Company) and the antioxidant 168 (BASF Company) were evenly mixed with the above-prepared flame retardant in the high-speed stirrer. The mixed material was then added into the feeder of the twin-screw extruder manufactured by the Coperion Company, the material entered the twin screws via the feeder and the temperature of the screws was maintained at 170-200 C. during processing. The material was melted and mixed evenly by the screws, and then entered the Labline100 micropellet preparation system, the torque was controlled at about 65%, and the rotation speed was controlled at 300 rpm. The flame-retardant antistatic polypropylene composition micropellets were obtained. The Izod notched impact strength of the composition material at 23 C. was 25.8 KJ/m.sup.2.

(55) (4) Preparation of (Halogen-Free) Flame-Retardant Antistatic Expanded Polypropylene Beads

(56) 1. The above-prepared flame-retardant polypropylene composition, the dispersing medium water, the surfactant sodium dodecylbenzene sulfonate, the dispersant kaolin, the dispersant enhancer aluminum sulfate and other additives were mixed in the autoclave to obtain a dispersion.

(57) 2. The residual air in the autoclave was removed by using the inert blowing agent carbon dioxide and the inert blowing agent was further introduced, and the pressure inside the autoclave was initially adjusted until it was stable. The dispersion in the autoclave was then stirred.

(58) 3. Then, the pressure inside the autoclave was adjusted to achieve the pressure required for foaming. The temperature was raised to the foaming temperature at an average heating rate of 0.1 C./min, and the foaming temperature was 0.5-1 C. lower than the melting temperature of the micropellets. At the foaming temperature and pressure, stirring was continued for 0.25-0.5 hour.

(59) 4. The outlet of the autoclave was then opened and the materials in the autoclave were discharged into the collection tank to obtain the expanded polypropylene beads. The carbon dioxide gas was fed while the discharge is being carried out so that the pressure in the autoclave was maintained near the foaming pressure before all the particles were completely foamed and entered into the collection tank. Then the expanded beads were washed and dried at 60 C. for 5 hours.

(60) 5. The density of the expanded beads was measured and the results were shown in Table 4. The surface and cross-sectional morphologies of the expanded beads were characterized by scanning electron microscope, and the results were shown in FIG. 4 and FIG. 5, respectively.

(61) (5) Preparation and Performance Test of the Foam Molding of the Expanded Beads

(62) The dried expanded beads were allowed to stand for aging at room temperature for about 12 hours, then added to the molding machine, and molded into the foam molding of the expanded beads by using water vapor at molding pressure of 0.22 MPa. The resulting foam molding was allowed to stand in an oven at 80 C. for 12 hours. The oxygen index, the carbon residue rate, the flame height, the smoke condition, the surface resistivity, the compressive strength and other parameters of the foam molding were measured according to the method described above. The surface resistivity of the foam molding was measured when the foam molding was just prepared, and the surface resistivity of the foam molding was measured again after the foam molding was allowed to stand for 30 days in the absence of special protective measures. The test results were shown in Table 4.

Example 2

(63) The flame retardant, the carbon nanofiber antistatic agent, the flame-retardant polypropylene composition and the expanded beads were prepared in a manner similar to that of Example 1, except that the starting materials and the reaction conditions shown in Tables 3 and 4 were different. For example, in this example, HMSPP602 was adopted, the formed halogen-free flame retardant was the complex Ni(OPOt.sub.3).sub.2(NO.sub.3).sub.2 formed by trioctyl phosphine oxide and nickel nitrate, and the prepared carbon nanofiber antistatic agent contains 3 wt % of nickel.

Example 3

(64) The flame retardant, the carbon nanofiber antistatic agent, the flame-retardant polypropylene composition and the expanded beads were prepared in a manner similar to that of Example 1, except that the starting materials and the reaction conditions shown in Tables 3 and 4 were different. For example, in this example, HMSPP603 was adopted, and the formed halogen-free flame retardant was the complex Co(OPOt.sub.3).sub.2(NO.sub.3).sub.2 formed by trioctylphosphine oxide and cobalt nitrate.

Example 4

(65) The flame retardant, the carbon nanofiber antistatic agent, the flame-retardant polypropylene composition and the expanded beads were prepared in a manner similar to that of Example 1, except that the starting materials and the reaction conditions shown in Tables 3 and 4 were different. For example, in this example, the formed halogen-free flame retardant was the complex Ni(OPPh.sub.3).sub.2(NO.sub.3).sub.2 formed by triphenyl phosphine oxide and nickel nitrate.

Example 5

(66) The flame retardant, the carbon nanofiber antistatic agent, the flame-retardant polypropylene composition and the expanded beads were prepared in a manner similar to that of Example 1, except that the starting materials and the reaction conditions shown in Tables 3 and 4 were different. For example, in this example, HMSPP602 was adopted, and the formed halogen-free flame retardant was the complex Ni(OPHx.sub.3).sub.2(NO.sub.3).sub.2 formed by trihexyl phosphine oxide and nickel nitrate.

Example 6

(67) The flame retardant, the carbon nanofiber antistatic agent, the flame-retardant polypropylene composition and the expanded beads were prepared in a manner similar to that of Example 1, except that the starting materials and the reaction conditions shown in Tables 3 and 4 were different. For example, in this example, HMSPP603 was adopted, and the formed halogen-free flame retardant was the complex Co(OPDe.sub.3).sub.2(NO.sub.3).sub.2 formed by tridecylphosphine oxide and cobalt nitrate.

Example 7

(68) The test process similar to that of Example 1 was implemented, except that the carbon nanofiber antistatic agent was not prepared or used. The specific raw material formula, the reaction conditions and the performance of the final foamed material were shown in Table 3 and Table 4.

Example 8

(69) The test process similar to that of Example 1 was implemented, except that tributyl phosphate instead of triphenylphosphine oxide was used to prepare the complex. The specific raw material formula, the reaction conditions and the performance of the final foamed material were shown in Table 3 and Table 4.

Example 9

(70) The test process similar to that of Example 1 was implemented, except that dibutyl butylphosphonate instead of triphenylphosphine oxide was used to prepare the complex, and the inorganic flame-retardant component was not used. The specific raw material formula, the reaction conditions and the performance of the final foamed material were shown in Table 3 and Table 4.

Example 10

(71) The test process similar to that of Example 1 was implemented, except that ordinary impact copolypropylene EPS30R instead of polypropylene base resin HMSPP601 with high melt strength was adopted. The specific raw material formula, the reaction conditions and the performance of the final foamed material were shown in Table 3 and Table 4.

Example 11

(72) The test process similar to that of Example 1 was implemented, except that the process (2) was not implemented, and in the preparation of the flame-retardant polypropylene composition in the process (3), the antistatic agent was carbon black. The specific raw material formula, the reaction conditions and the performance of the final foamed material were shown in Table 3 and Table 4.

Example 12

(73) The test process similar to that of Example 1 was implemented, except that the process (2) was not implemented, and in the preparation of the flame-retardant polypropylene composition in the process (3), the antistatic agent was Atmer129. The specific raw material formula, the reaction conditions and the performance of the final foamed material were shown in Table 3 and Table 4.

Example 13

(74) The test process similar to that of Example 1 was implemented, except that linear low-density polyethylene 7042 with 1-butene as the comonomer instead of polypropylene base resin HMSPP601 with high melt strength was adopted. The specific raw material formula, the reaction conditions and the performance of the final foamed material were shown in Table 3 and Table 4.

Example 14

(75) The test process similar to that of Example 1 was implemented, except that the metallocene catalyst was adopted, and polyethylene HPE001 with 1-hexene as the comonomer instead of polypropylene base resin HMSPP601 with high melt strength was adopted. The specific raw material formula, the reaction conditions and the performance of the final foamed material were shown in Table 3 and Table 4.

Example 15

(76) The test process similar to that of Example 1 was implemented, except that the Ziegler-natta catalyst was adopted, and polyethylene HPE002 with 1-hexene as the comonomer instead of polypropylene base resin HMSPP601 with high melt strength was adopted. The specific raw material formula, the reaction conditions and the performance of the final foamed material were shown in Table 3 and Table 4.

Example 16

(77) The test process similar to that of Example 1 was implemented, except that low-density polyethylene LD100AC instead of polypropylene base resin HMSPP601 with high melt strength was adopted. The specific raw material formula, the reaction conditions and the performance of the final foamed material were shown in Table 3 and Table 4.

Example 17

(78) The test process similar to that of Example 1 was implemented, except that foaming-grade polylactic acid PLA instead of polypropylene base resin HMSPP601 with high melt strength was adopted. The specific raw material formula, the reaction conditions and the performance of the final foamed material were shown in Table 3 and Table 4.

Example 18

(79) The test process similar to that of Example 1 was implemented, except that foaming-grade thermoplastic polyurethane TPU instead of polypropylene base resin HMSPP601 with high melt strength was adopted. The specific raw material formula, the reaction conditions and the performance of the final foamed material were shown in Table 3 and Table 4.

Example 19

(80) The test process similar to that of Example 1 was implemented, except that foaming-grade polybutylene terephthalate PBT instead of polypropylene base resin HMSPP601 with high melt strength was adopted. The specific raw material formula, the reaction conditions and the performance of the final foamed material were shown in Table 3 and Table 4.

Example 20

(81) The test process similar to that of Example 1 was implemented, except that foaming-grade polyethylene terephthalate PET instead of polypropylene base resin HMSPP601 with high melt strength was adopted. The specific raw material formula, the reaction conditions and the performance of the final foamed material were shown in Table 3 and Table 4.

Example 21

(82) The test process similar to that of Example 1 was implemented, except that foaming-grade polyamide 6 PA6 instead of polypropylene base resin HMSPP601 with high melt strength was adopted. The specific raw material formula, the reaction conditions and the performance of the final foamed material were shown in Table 3 and Table 4.

Example 22

(83) The test process similar to that of Example 1 was implemented, except that foaming-grade poly(butylene succinate) PBS instead of polypropylene base resin HMSPP601 with high melt strength was adopted. The specific raw material formula, the reaction conditions and the performance of the final foamed material were shown in Table 3 and Table 4.

Comparative Example 1

(84) The test process similar to that of Example 1 was implemented, except that the flame retardant was triphenylphosphine oxide and magnesium hydroxide. The specific raw material formula, the reaction conditions and the performance of the final foamed material were shown in Table 3 and Table 4.

Comparative Example 2

(85) The test process similar to that of Example 1 was implemented, except that the process (1) was not implemented, and in the preparation of the flame-retardant polypropylene composition in the process (3), the flame retardant was red phosphorus. The specific raw material formula, the reaction conditions and the performance of the final foamed material were shown in Table 3 and Table 4.

Comparative Example 3

(86) The test process similar to that of Example 1 was implemented, except that the process (1) was not implemented, and in the preparation of the flame-retardant polypropylene composition in the process (3), the flame retardant was a composition of hexabromocyclododecane and antimony trioxide (weight ratio about 2.5:1). The specific raw material formula, the reaction conditions and the performance of the final foamed material were shown in Table 3 and Table 4.

Comparative Example 4

(87) The test process similar to that of Example 1 was implemented, except that the flame retardant was cobalt phosphate. The specific raw material formula, the reaction conditions and the performance of the final foamed material were shown in Table 3 and Table 4.

Comparative Example 5

(88) The test process similar to that of Example 2 was implemented, except that the process (1) was not implemented, and in the preparation of the flame-retardant polypropylene composition in the process (3), the flame retardant was aluminum hydroxide. The specific raw material formula, the reaction conditions and the performance of the final foamed material were shown in Table 3 and Table 4.

Comparative Example 6

(89) The test process similar to that of Example 3 was implemented, except that the process (1) was not implemented, and in the preparation of the flame-retardant polypropylene composition in the process (3), the flame retardant was ammonium polyphosphate. The specific raw material formula, the reaction conditions and the performance of the final foamed material were shown in Table 3 and Table 4.

Comparative Example 7

(90) The test process similar to that of Example 1 was implemented, except that the flame retardant was trihydroxymethyl phosphine oxide. The specific raw material formula, the reaction conditions and the performance of the final foamed material were shown in Table 3 and Table 4.

Comparative Example 8

(91) The test process similar to that of Example 13 was implemented, except that the process (1) and the process (2) were not implemented, and in the preparation of the flame-retardant polypropylene composition in the process (3), the flame retardant was red phosphorus. The specific raw material formula, the reaction conditions and the performance of the final foamed material were shown in Table 3 and Table 4.

Comparative Example 9

(92) The test process similar to that of Example 14 was implemented, except that the process (1) and the process (2) were not implemented, and in the preparation of the flame-retardant polypropylene composition in the process (3), the flame retardant was red phosphorus. The specific raw material formula, the reaction conditions and the performance of the final foamed material were shown in Table 3 and Table 4.

Comparative Example 10

(93) The test process similar to that of Example 15 was implemented, except that the process (1) and the process (2) were not implemented, and in the preparation of the flame-retardant polypropylene composition in the process (3), the flame retardant was red phosphorus. The specific raw material formula, the reaction conditions and the performance of the final foamed material were shown in Table 3 and Table 4.

Comparative Example 11

(94) The test process similar to that of Example 16 was implemented, except that the process (1) and the process (2) were not implemented, and in the preparation of the flame-retardant polypropylene composition in the process (3), the flame retardant was red phosphorus. The specific raw material formula, the reaction conditions and the performance of the final foamed material were shown in Table 3 and Table 4.

Comparative Example 12

(95) The test process similar to that of Example 17 was implemented, except that the process (1) and the process (2) were not implemented, and in the preparation of the flame-retardant polypropylene composition in the process (3), the flame retardant was red phosphorus. The specific raw material formula, the reaction conditions and the performance of the final foamed material were shown in Table 3 and Table 4.

Comparative Example 13

(96) The test process similar to that of Example 18 was implemented, except that the process (1) and the process (2) were not implemented, and in the preparation of the flame-retardant polypropylene composition in the process (3), the flame retardant was red phosphorus. The specific raw material formula, the reaction conditions and the performance of the final foamed material were shown in Table 3 and Table 4.

Comparative Example 14

(97) The test process similar to that of Example 19 was implemented, except that the process (1) and the process (2) were not implemented, and in the preparation of the flame-retardant polypropylene composition in the process (3), the flame retardant was red phosphorus. The specific raw material formula, the reaction conditions and the performance of the final foamed material were shown in Table 3 and Table 4.

Comparative Example 15

(98) The test process similar to that of Example 20 was implemented, except that the process (1) and the process (2) were not implemented, and in the preparation of the flame-retardant polypropylene composition in the process (3), the flame retardant was red phosphorus. The specific raw material formula, the reaction conditions and the performance of the final foamed material were shown in Table 3 and Table 4.

Comparative Example 16

(99) The test process similar to that of Example 21 was implemented, except that the process (1) and the process (2) were not implemented, and in the preparation of the flame-retardant polypropylene composition in the process (3), the flame retardant was red phosphorus. The specific raw material formula, the reaction conditions and the performance of the final foamed material were shown in Table 3 and Table 4.

Comparative Example 17

(100) The test process similar to that of Example 22 was implemented, except that the process (1) and the process (2) were not implemented, and in the preparation of the flame-retardant polypropylene composition in the process (3), the flame retardant was red phosphorus. The specific raw material formula, the reaction conditions and the performance of the final foamed material were shown in Table 3 and Table 4.

(101) TABLE-US-00003 TABLE 3 The formula of the flame-retardant thermoplastic material used in Examples and Comparative Examples Flame-retardant Flame-retardant Flame-retardant Amount component A component B component C Parts by Flame Parts by Parts by Parts by Item Base resin weight retardant Type weight Type weight Type weight Example 1 HMSPP601 100 triphenyl- 7 cobalt 3 magnesium 5 phosphine nitrate hydroxide oxide Example 2 HMSPP602 100 Trioctyl- 6 nickel 4 aluminum 4 phosphine nitrate hydroxide oxide Example 3 HMSPP603 100 trioctyl- 6.5 cobalt 4.5 aluminum 4.5 phosphine nitrate hydroxide oxide Example 4 HMSPP601 100 triphenyl- 8.4 nickel 3.6 magnesium 3 phosphine nitrate hydroxide oxide Example 5 HMSPP602 100 trihexyl- 7.5 nickel 3.5 aluminum 3.5 phosphine nitrate hydroxide oxide Example 6 HMSPP603 100 tridecyl- 6.5 cobalt 2.5 magnesium 4 phosphine nitrate hydroxide oxide Example 7 HMSPP601 100 triphenyl- 7 cobalt 3 magnesium 5 phosphine nitrate hydroxide oxide Example 8 HMSPP601 100 tributyl 8 nickel 2.5 magnesium 4 phosphate nitrate hydroxide Example 9 HMSPP601 100 dibutyl 7 nickel 3 butylphosphate nitrate Example 10 EPS30R 100 triphenyl- 7 cobalt 3 magnesium 5 phosphine nitrate hydroxide oxide Example 11 HMSPP601 100 triphenyl- 7 cobalt 3 magnesium 5 phosphine nitrate hydroxide oxide Example 12 HMSPP601 100 triphenyl- 7 cobalt 3 magnesium 5 phosphine nitrate hydroxide oxide Example 13 LLDPE7042 100 triphenyl- 7 cobalt 3 magnesium 5 phosphine nitrate hydroxide oxide Example 14 HPE001 100 triphenyl- 7 cobalt 3 magnesium 5 phosphine nitrate hydroxide oxide Example 15 HPE002 100 triphenyl- 7 cobalt 3 magnesium 5 phosphine nitrate hydroxide oxide Example 16 LD100AC 100 triphenyl- 7 cobalt 3 magnesium 5 phosphine nitrate hydroxide oxide Example 17 PLA 100 triphenyl- 7 cobalt 3 magnesium 5 phosphine nitrate hydroxide oxide Example 18 TPU 100 triphenyl- 7 cobalt 3 magnesium 5 phosphine nitrate hydroxide oxide Example 19 PBT 100 triphenyl- 7 cobalt 3 magnesium 5 phosphine nitrate hydroxide oxide Example 20 PET 100 triphenyl- 7 cobalt 3 magnesium 5 phosphine nitrate hydroxide oxide Example 21 PA6 100 triphenyl- 7 cobalt 3 magnesium 5 phosphine nitrate hydroxide oxide Example 22 PBS 100 triphenyl- 7 cobalt 3 magnesium 5 phosphine nitrate hydroxide oxide Comparative HMSPP601 100 triphenyl- 7 magnesium 5 example 1 phosphine hydroxide oxide Comparative HMSPP601 100 red phosphorus 20 example 2 Comparative HMSPP601 100 composition of example 3 hexabromo- cyclododecane and antimony trioxide Comparative HMSPP601 100 cobalt 25 example 4 phosphate Comparative HMSPP602 100 aluminum 12 example 5 hydroxide Comparative HMSPP603 100 ammonium 35 example 6 polyphosphate Comparative HMSPP601 100 trihydroxymethyl 25 example 7 phosphine oxide Comparative LLDPE7042 100 red phosphorus 20 example 8 Comparative HPE001 100 red phosphorus 20 example 9 Comparative HPE002 100 red phosphorus 20 example 10 Comparative LD100AC 100 red phosphorus 20 example 11 Comparative PLA 100 red phosphorus 20 example 12 Comparative TPU 100 red phosphorus 20 example 13 Comparative PBT 100 red phosphorus 20 example 14 Comparative PET 100 red phosphorus 20 example 15 Comparative Polyamide 6 100 red phosphorus 20 example 16 Comparative PBS 100 red phosphorus 20 example 17 Preparation and amount of antistatic agent Carbonization Heat Cell nucleating agent Carbon Catalyst temperature insulation Parts by Parts by Item source type C. time/hr Type weight Type weight Example 1 coal tar cobalt 950 1.5 carbon 1 zinc 0.5 pitch nitrate nanofibers borate Example 2 coal tar nickel 1050 2.5 carbon 1.5 zinc 0.4 pitch nitrate nanofibers borate Example 3 petroleum nickel 1000 2 carbon 1.5 zinc 0.5 pitch nitrate nanofibers borate Example 4 coal tar nickel 1050 2.5 carbon 1 zinc 0.4 pitch nitrate nanofibers borate Example 5 bamboo nickel 1150 1.5 carbon 1.5 zinc 0.5 charcoal nitrate nanofibers borate Example 6 bamboo cobalt 1000 2 carbon 1 zinc 0.3 charcoal nitrate nanofibers borate Example 7 coal tar cobalt 950 1.5 zinc 0.5 pitch nitrate borate Example 8 bamboo nickel 1150 1.5 carbon 1.5 zinc 0.3 charcoal nitrate nanofibers borate Example 9 petroleum nickel 1000 2 carbon 1.5 calcium 0.3 pitch nitrate nanofibers carboante Example 10 coal tar cobalt 950 1.5 carbon 1 zinc 0.5 pitch nitrate nanofibers borate Example 11 carbon 6 zinc 0.5 black borate Example 12 Atmer129 3 zinc 0.5 borate Example 13 coal tar cobalt 950 1.5 carbon 1 zinc 0.5 pitch nitrate nanofibers borate Example 14 coal tar cobalt 950 1.5 carbon 1 zinc 0.5 pitch nitrate nanofibers borate Example 15 coal tar cobalt 950 1.5 carbon 1 zinc 0.5 pitch nitrate nanofibers borate Example 16 coal tar cobalt 950 1.5 carbon 1 zinc 0.5 pitch nitrate nanofibers borate Example 17 coal tar cobalt 950 1.5 carbon 1 zinc 0.5 pitch nitrate nanofibers borate Example 18 coal tar cobalt 950 1.5 carbon 1 zinc 0.5 pitch nitrate nanofibers borate Example 19 coal tar cobalt 950 1.5 carbon 1 zinc 0.5 pitch nitrate nanofibers borate Example 20 coal tar cobalt 950 1.5 carbon 1 zinc 0.5 pitch nitrate nanofibers borate Example 21 coal tar cobalt 950 1.5 carbon 1 zinc 0.5 pitch nitrate nanofibers borate Example 22 coal tar cobalt 950 1.5 carbon 1 zinc 0.5 pitch nitrate nanofiber borate Comparative coal tar cobalt 950 1.5 carbon 1 zinc 0.5 example 1 pitch nitrate nanofibers borate Comparative coal tar cobalt 950 1.5 carbon 1 zinc 0.5 example 2 pitch nitrate nanofibers borate Comparative coal tar cobalt 950 1.5 carbon 1 zinc 0.5 example 3 pitch nitrate nanofibers borate Comparative coal tar cobalt 950 1.5 carbon 1 zinc 0.5 example 4 pitch nitrate nanofibers borate Comparative coal tar nickel 1050 2.5 carbon 1.5 zinc 0.5 example 5 pitch nitrate nanofibers borate Comparative petroleum nickel 1000 2 carbon 1.5 zinc 0.5 example 6 pitch nitrate nanofibers borate Comparative coal tar cobalt 950 1.5 carbon 1 zinc 0.5 example 7 pitch nitrate nanofibers borate Comparative coal tar cobalt 950 1.5 carbon 1 zinc 0.5 example 8 pitch nitrate nanofibers borate Comparative coal tar cobalt 950 1.5 carbon 1 zinc 0.5 example 9 pitch nitrate nanofibers borate Comparative coal tar cobalt 950 1.5 carbon 1 zinc 0.5 example 10 pitch nitrate nanofibers borate Comparative coal tar cobalt 950 1.5 carbon 1 zinc 0.5 example 11 pitch nitrate nanofibers borate Comparative coal tar cobalt 950 1.5 carbon 1 zinc 0.5 example 12 pitch nitrate nanofibers borate Comparative coal tar cobalt 950 1.5 carbon 1 zinc 0.5 example 13 pitch nitrate nanofibers borate Comparative coal tar cobalt 950 1.5 carbon 1 zinc 0.5 example 14 pitch nitrate nanofibers borate Comparative coal tar cobalt 950 1.5 carbon 1 zinc 0.5 example 15 pitch nitrate nanofibers borate Comparative coal tar cobalt 950 1.5 carbon 1 zinc 0.5 example 16 pitch nitrate nanofibers borate Comparative coal tar cobalt 950 1.5 carbon 1 zinc 0.5 example 17 pitch nitrate nanofibers borate

(102) TABLE-US-00004 TABLE 4 Comparison of the process parameters for preparation of flame-retardant thermoplastic expanded beads and product performance in Examples and Comparative Examples Melting 50% Combustion Foaming Foaming Sample pressure of Compressive extinguishing temperature pressure density cell density/ expanded beads strength time Item C. MPa g/cm.sup.3 cm.sup.3 MPa kPa s Example 1 160 2 0.21 2.5 10.sup.8 0.22 579 2 Example 2 162 2.5 0.18 3.4 10.sup.8 0.23 578 2 Example 3 161 3 0.15 3.7 10.sup.8 0.21 576 2 Example 4 159 3.5 0.11 3.9 10.sup.8 0.22 575 2 Example 5 160 4 0.09 5.5 10.sup.8 0.23 573 1 Example 6 162 4.5 0.07 5.1 10.sup.8 0.22 571 2 Example 7 161 4 0.10 4.9 10.sup.8 0.22 572 1 Example 8 160 4 0.09 4.8 10.sup.8 0.23 573 1 Example 9 161 4 0.11 5.0 10.sup.8 0.23 574 1 Example 10 165 3 0.15 8.5 10.sup.7 0.29 575 4 Example 11 159 2.5 0.13 9.2 10.sup.4 0.36 178 3 Example 12 165 3 0.15 8.5 10.sup.7 0.29 177 4 Example 13 124 3.5 0.12 4.1 10.sup.8 0.15 395 2 Example 14 126 4 0.11 2.5 10.sup.8 0.18 405 2 Example 15 126 3.5 0.1 3.2 10.sup.8 0.17 408 2 Example 16 110 3.5 0.11 1.8 10.sup.8 0.18 259 2 Example 17 145 3 0.08 1.5 10.sup.8 0.16 368 2 Example 18 80 5 0.19 1.6 10.sup.8 0.35 515 2 Example 19 180 5 0.18 2.1 10.sup.8 0.45 408 1 Example 20 200 3.5 0.15 2.5 10.sup.8 0.32 509 1 Example 21 220 3.5 0.19 3.4 10.sup.8 0.64 575 1 Example 22 120 4 0.22 2.5 10.sup.8 0.19 495 1 Comparative 160 2 0.23 9.4 10.sup.5 0.22 395 4 example 1 Comparative 162 2.5 0.16 3.5 10.sup.4 0.28 180 5 example 2 Comparative 161 2 0.13 8.4 10.sup.5 0.35 181 3 example 3 Comparative 162 2.5 0.21 8.5 10.sup.5 0.23 421 5 example 4 Comparative 162 2.5 0.17 3.8 10.sup.5 0.35 179 5 example 5 Comparative 161 3 0.14 4.9 10.sup.5 0.37 176 4 example 6 Comparative 161 3 0.18 8.6 10.sup.5 0.21 412 4 example 7 Comparative 124 3.5 0.15 2.3 10.sup.6 0.15 318 5 example 8 Comparative 126 4 0.19 4.2 10.sup.6 0.18 352 6 example 9 Comparative 126 3.5 0.18 9.1 10.sup.6 0.17 235 5 example 10 Comparative 110 3.5 0.19 2.4 10.sup.6 0.18 205 6 example 11 Comparative 145 3 0.21 3.5 10.sup.6 0.16 345 6 example 12 Comparative 80 5 0.45 4.5 10.sup.6 0.35 399 4 example 13 Comparative 180 5 0.46 5.8 10.sup.6 0.45 358 5 example 14 Comparative 200 3.5 0.25 1.5 10.sup.6 0.44 398 6 example 15 Comparative 220 3.5 0.34 2.4 10.sup.6 0.55 415 5 example 16 Comparative 120 4 0.41 1.6 10.sup.6 0.53 296 4 example 17 Residual Limiting Surface Surface Mass Flame oxygen Surface Resistivity Resistivity Fraction Height index Smoke and Cell Item % mm LOI Condition Structure (0th day) (30th day) Example 1 3.2 15 29.5 6.0*10.sup.8 6.1*10.sup.8 Example 2 3.5 14 29.6 3.4*10.sup.8 3.5*10.sup.8 Example 3 3.3 13 28.6 4.2*10.sup.8 4.3*10.sup.8 Example 4 3.4 13 30.1 1.1*10.sup.8 1.2*10.sup.8 Example 5 3.3 15 30.2 4.4*10.sup.8 4.6*10.sup.8 Example 6 3.6 14 28.9 9.3*10.sup.8 9.4*10.sup.8 Example 7 3.3 13 29.2 .sup.1.2*10.sup.13 .sup.1.3*10.sup.13 Example 8 3.4 12 30.2 5.4*10.sup.8 5.6*10.sup.8 Example 9 3.5 14 29.9 4.3*10.sup.8 4.4*10.sup.8 Example 10 3.2 19 25.1 x 2.6*10.sup.8 2.7*10.sup.8 Example 11 4.3 20 21.2 x 1.3*10.sup.9 1.4*10.sup.9 Example 12 3.2 19 25.1 x 3.5*10.sup.9 .sup.2.8*10.sup.13 Example 13 3.2 13 29.6 3.4*10.sup.8 3.5*10.sup.8 Example 14 3.1 14 29.5 4.0*10.sup.8 4.1*10.sup.8 Example 15 3.5 13 30.1 3.3*10.sup.8 3.4*10.sup.8 Example 16 3.1 15 29.2 2.5*10.sup.8 2.6*10.sup.8 Example 17 3.2 15 28.5 4.4*10.sup.8 4.5*10.sup.8 Example 18 3.2 14 28.3 5.6*10.sup.8 5.7*10.sup.8 Example 19 3.1 13 28.4 4.7*10.sup.8 4.8*10.sup.8 Example 20 3.5 13 28.2 2.1*10.sup.8 2.2*10.sup.8 Example 21 3.3 14 28.5 3.5*10.sup.8 3.6*10.sup.8 Example 22 3.1 12 29.8 4.2*10.sup.8 4.3*10.sup.8 Comparative 5.5 21 22.1 x .sup.5.3*10.sup.11 .sup.5.4*10.sup.11 example 1 Comparative 5.5 27 17.0 x .sup.3.4*10.sup.11 .sup.3.5*10.sup.11 example 2 Comparative 4.9 21 22.9 x .sup.5.2*10.sup.10 .sup.5.3*10.sup.10 example 3 Comparative 4.2 20 24.4 x .sup.2.4*10.sup.11 .sup.2.5*10.sup.11 example 4 Comparative 4.7 21 20.1 x .sup.9.3*10.sup.11 .sup.9.4*10.sup.11 example 5 Comparative 3.8 16 22.3 x .sup.1.5*10.sup.11 .sup.1.5*10.sup.11 example 6 Comparative 5.3 22 23.7 x .sup.6.5*10.sup.11 .sup.6.6*10.sup.11 example 7 Comparative 5.2 21 20.5 x .sup.4.3*10.sup.11 .sup.4.4*10.sup.11 example 8 Comparative 6.1 19 21.6 x .sup.2.5*10.sup.11 .sup.2.6*10.sup.11 example 9 Comparative 5.5 21 24.5 x .sup.6.5*10.sup.11 .sup.6.6*10.sup.11 example 10 Comparative 6.1 18 25.1 x .sup.7.4*10.sup.11 .sup.7.5*10.sup.11 example 11 Comparative 7.2 19 23.5 x .sup.6.5*10.sup.11 .sup.6.6*10.sup.11 example 12 Comparative 5.2 25 23.4 x .sup.4.2*10.sup.11 .sup.4.3*10.sup.11 example 13 Comparative 4.1 21 25.2 x .sup.5.7*10.sup.11 .sup.5.8*10.sup.11 example 14 Comparative 6.1 27 24.3 .sup.6.3*10.sup.11 .sup.6.4*10.sup.11 example 15 Comparative 5.5 26 21.6 .sup.8.2*10.sup.11 .sup.8.3*10.sup.11 example 16 Comparative 6 25.5 20.1 .sup.2.3*10.sup.11 .sup.2.4*10.sup.11 example 17 smoke, no smoke, dense and uniform cells, x sparse and nonuniform cells

(103) As can be seen from Table 1 and Table 2, the HMSPP601, HMSPP602 and HMSPP603 polypropylenes prepared by the invention have high melt strength, tensile strength and flexural modulus, and higher notched impact strength.

(104) The flame-retardant antistatic composition is prepared by taking the impact polypropylene with high melt strength, prepared by the invention as the base resin, and adding the flame retardant compounded by the complex of phosphine oxide and the transition metal salt with an inorganic hydroxide, and the carbon nanofibers or carbon nanotubes containing nickel or cobalt as the antistatic agent. Subsequently, the flame-retardant antistatic expanded beads are prepared according to the batch foaming method provided by the invention. From Table 3, Table 4 and FIGS. 4 and 5, it can be seen that the expanded beads having density of 0.07-0.21 g/cm.sup.3 can be obtained by adjusting the conditions such as foaming pressure and temperature, and when non-supercritical carbon dioxide is used as the blowing agent, the foaming effect is good, the cell density is higher, the cells are dense and uniform, the cell size is smaller, the cell walls are thin, and the bead surfaces are smooth.

(105) From the result of Example 10, it can be seen that compared with the expanded beads taking the impact polypropylene PPSPP601, HMSPP602 and HMSPP603 with high melt strength as the base resin, the expanded beads obtained by taking the ordinary impact copolypropylene EPS30R as the base resin have higher density, nonuniform cells and not flat bead surfaces. This is mainly caused by lower melt strength of EPS30R, and the required foaming temperature is higher, resulting in higher molding pressure. Due to the above structural characteristics, the impact resistance of the foam molding of the expanded beads taking EPS30R as the base resin is inferior to that of the foam molding of the expanded beads using the impact polypropylene (e.g., HMSPP601, 602 and 603) with high melt strength provided by the invention. In addition, the molding pressure of the expanded beads obtained by using the conventional impact copolypropylene is high, and thus the production energy consumption is increased.

(106) Table 4 shows that the foam molding prepared from the expanded beads provided according to the invention has excellent mechanical properties, flame retardancy and antistatic properties, has oxygen index higher than 28 and can be used in the field requiring higher flame-retardant level, while the surface resistivity reaches 10.sup.8 antistatic level. The expanded beads have good cell structure, so that the foam molding is excellent in compressive properties. The results of the oxygen index and correlated flame retardant tests of the foam molding show that the flame retardant and the antistatic agent can play a synergistic effect, which can effectively reduce the amount of flame retardant, as evidenced by the results of Examples 1 and 7.

(107) From the results shown in Table 4, particularly the results of Comparative Examples 2-7, it can be seen that the flame retardant such as conventional red phosphorus, brominated flame retardants, individual aluminum hydroxide or individual phosphine oxide is used in combination with carbon nanofibers containing nickel or cobalt and the like to serve as a complex flame-retardant antistatic agent for the preparation of the polypropylene composition, the flame retardancy and electrostatic resistance of the foam molding of the expanded beads prepared from such polypropylene composition are inferior to those of the foam molding of the expanded beads prepared from the compositions described in Examples 1-22, and the addition of the flame retardants and the antistatic agents in the comparative examples generates a negative effect on the foaming property, resulting in nonuniform cells and damaged cell walls.

(108) In the examples of the invention, in a flame-retardant antistatic system composed of the flame retardant compounded by the complex of organophosphorus and the transition metal such as nickel or cobalt with magnesium hydroxide or aluminum hydroxide and carbon nanofibers, the transition metal and the flame retardant generate a synergistic catalytic effect, so that the flame-retardant efficiency of the phosphorus flame retardant is improved. The carbon nanofibers can build an effective conductive network inside the resin, thereby forming a long-lasting antistatic network system, and effectively reducing the surface resistivity of the foam molding of the expanded beads, and when the storage or use time is 30 days or longer, the antistatic capability of the foam molding is almost unchanged. The residual nickel or cobalt catalyst in the carbon fibers also has a good synergistic effect with the complex to promote the improvement of flame-retardant efficiency. In Comparative Example 2, in the composition obtained by using the system formed by the conventional red phosphorus flame retardant and the antistatic agent, a synergistic effect is not generated, but the flame retardant and the antistatic agent affect each other to reduce the flame retardancy and the antistatic property, a negative effect is generated on the cell structure of the beads, and thus the resulting expanded beads have low cell density, larger cell diameter, and cell wall breakage (as shown in FIG. 6 and FIG. 7).

(109) In addition, it can be found from Tables 3 and 4 that, in addition to being applied to the polypropylene resin, the flame retardant also has excellent mechanical properties, flame-retardant properties, foaming performance and antistatic performance when applied to polyethylene, polyester, polyamide, and degradable thermoplastic materials of various densities and comonomers.

(110) While the invention has been described in detail, modifications within the spirit and scope of the invention will be apparent to those skilled in the art. In addition, it is to be understood that various aspects, and various parts and various recited characteristics of the various embodiments of the invention may be combined or fully or partially interchangeable. In the above embodiments, those embodiments which refer to another embodiment may be suitably combined with other embodiments, as will be understood by those skilled in the art. Furthermore, it will be understood by those skilled in the art that the foregoing description is by way of examples only and is not intended to limit the invention.