Flame-retardant polypropylene and process for its preparation

Abstract

The application provides a kind of flame-retardant polypropylene, using the following components by weight: rare earth flame retardant, including: 1-3 parts of rare earth complex, 5-10 parts of intumescent flame retardant and 1-3 parts of boron compound flame retardant, the rare earth complex is prepared from rare earth salt and phosphorus-based flame retardant; Inorganic filler, including: 25-40 parts of carbonate or silicate and 25-50 parts of inorganic hydroxide, toughening agent 3-12 parts, lubricant 1-3 parts and polypropylene base material 10-15 parts. And its manufacturing method is disclosed, first, the rare earth complex is prepared, then the raw materials are weighed according to the formula to produce flame-retardant polypropylene. Compared with the traditional PP flame-retardant modification method, the application can improve the flame-retardant performance of polypropylene board under the condition of reducing the use amount of aluminum hydroxide, magnesium hydroxide and phosphorus-nitrogen flame retardant, and achieve good flame-retardant effect, while also ensuring that the processing performance and mechanical properties of polypropylene board are not affected.

Description

Technical Field

[0001] This invention belongs to the field of polypropylene polymer material technology, and particularly relates to a flame-retardant polypropylene containing rare earth flame retardants and its preparation method. Background Technology

[0002] With restrictions imposed on halogenated plastic products overseas, PVC flooring, once popular abroad, has been banned. While polypropylene (PP) boasts advantages such as abundant raw material sources, low price, excellent material properties, good electrical insulation and chemical stability, and ease of processing, making it one of the most promising plastic flooring alternatives to PVC, PP also has certain drawbacks. These include poor toughness, low-temperature resistance, and aging resistance, as well as high molding shrinkage and flammability, posing a significant risk of fire and property damage, thus preventing it from directly replacing PVC. Therefore, PP must be modified to improve its performance. Traditional flame-retardant modification methods for PP flooring involve adding large amounts of aluminum hydroxide and magnesium hydroxide, or large amounts of phosphorus-nitrogen flame retardants, leading to increased costs or a significant decrease in mechanical properties.

[0003] Due to the processing characteristics of PP sheets, the amount of flame retardant added during flame retardant modification should be as small as possible to ensure that the product has flame retardant function while ensuring that the mechanical properties of the product are not affected. Summary of the Invention

[0004] The purpose of this invention is to provide a flame-retardant polypropylene and its preparation method, which can produce polypropylene sheets with both high flame retardancy and mechanical properties.

[0005] A flame-retardant polypropylene comprises: a rare earth flame retardant A, an inorganic filler B, a toughening agent C, a lubricant D, and a polypropylene substrate E;

[0006] The weight proportions of each component are as follows:

[0007] The rare earth flame retardant A comprises: 1-3 parts of rare earth complex, 5-10 parts of intumescent flame retardant and 1-3 parts of boron compound flame retardant, wherein the rare earth complex is prepared from rare earth salt and phosphorus-based flame retardant.

[0008] The inorganic filler B comprises: 25-40 parts of carbonate or silicate and 25-50 parts of inorganic hydroxide; 3-12 parts of the toughening agent C, 1-3 parts of the lubricant D and 10-15 parts of the polypropylene substrate E.

[0009] Preferably, the rare earth salt is a rare earth nitrate, and the rare earth element is at least one of neodymium, samarium, holmium, yttrium, lanthanum, and praseodymium.

[0010] Preferably, the phosphorus-based flame retardant is at least one of pyrophosphoric acid, hypophosphoric acid (HA), phytic acid (PA), and hexamethylenediaminetetramethylenephosphonic acid (HDTMPA).

[0011] Preferably, the intumescent flame retardant is at least one of boron phosphate, melamine (MA), and sorbitol, and the boron compound flame retardant is one of boric acid, aluminum borate, and ammonium borate.

[0012] Preferably, the carbonate and silicate are calcium carbonate and talc, respectively, and the inorganic hydroxide is at least one of aluminum hydroxide and magnesium hydroxide.

[0013] Preferably, the toughening agent is at least one of EVA, POE, MBS and SBS.

[0014] Preferably, the lubricant is at least two of polyethylene wax, ethylene bis-stearamide (EBS), silicone powder, epoxidized soybean oil (EBSO), acrylate copolymer (ACR), and cerium stearate.

[0015] The preparation method of the above flame-retardant polypropylene includes the following steps:

[0016] (1) Preparation of rare earth complexes

[0017] First, the rare earth salt is dissolved in deionized water to obtain solution a. The complex is then dissolved in deionized water, and the pH is adjusted to around 7 to obtain solution b. Solution a is then gradually added dropwise to solution b over a period of 15 to 60 minutes to obtain solution c. Solution c is then transferred to a high-pressure reactor and reacted at 100–130°C for 6–48 hours. Finally, the mixture is washed with deionized water and dried at 90–120°C for 4–24 hours to obtain the desired rare earth complex.

[0018] (2) Preparation of flame-retardant polypropylene

[0019] First, weigh the rare earth flame retardant, inorganic filler, toughening agent, lubricant, and polypropylene matrix according to the above-mentioned weight proportions, and premix them at high speed in a high-speed mixer to obtain a uniformly mixed mixture. Then, add the mixture to a torque rheometer and melt-blend it at 170-260°C for 3-8 minutes to obtain a blend. Next, pour the blend into a mold, place it on the hot plate of a flat vulcanizing machine, and press it at 170-260°C and 15-20 MPa for 3-5 minutes. Then, transfer it to the cold plate of the flat vulcanizing machine for cooling to produce flame-retardant polypropylene.

[0020] Preferably, in step (1), the ratio of rare earth salt to deionized water in solution a is 1 mmol: 10-30 ml; and the ratio of complex to deionized water in solution b is 0.5-5 mmol: 10-100 ml.

[0021] Preferably, in step (1), the pH of solution b is adjusted to about 7 by adding a weakly alkaline substance, such as ammonia, ammonium hydroxide, or phenol.

[0022] Preferably, in step (2), the thickness of the mold cavity is 3 mm.

[0023] After adopting the above solution, the beneficial effects of the present invention are as follows:

[0024] (1) The rare earth flame retardant used in this invention generates phosphoric acid or polyphosphoric acid at high temperatures, which can catalyze the rapid formation of a dense char layer in polypropylene during combustion, thereby isolating it from oxygen and preventing further combustion. Simultaneously, rare earth ions can scavenge OH· and H· free radical ions generated during polypropylene combustion, thus preventing further combustion and decomposition. Because rare earth flame retardants possess the dual capabilities of catalyzing char formation and scavenging free radicals, compared to traditional PP flame retardant modification methods, this invention achieves good flame retardant effects with only a small amount of halogen-free flame retardant, realizing the goal of improving the flame retardant performance of polypropylene with minimal addition, while ensuring that the processing performance and mechanical properties of polypropylene are not affected.

[0025] (2) The present invention adopts a premixed and melt blending processing method, and improves the thermal stability and flame retardant properties of polypropylene by adding rare earth flame retardants, which can simply and quickly prepare flame retardant polypropylene.

[0026] (3) The present invention uses halogen-free flame retardants and none of the components contain toxic substances, which is less harmful to the environment and human body and meets environmental protection requirements. Detailed Implementation

[0027] To better understand the present invention, specific embodiments are provided below to further illustrate the technical solutions and effects of the present invention. It should be noted that the following embodiments are for illustrative purposes only and should not be construed as limiting the present invention.

[0028] This invention provides a flame-retardant polypropylene, comprising: a rare earth flame retardant A, an inorganic filler B, a toughening agent C, a lubricant D, and a polypropylene substrate E; the weight proportions of the above five raw materials are as follows: rare earth flame retardant A, composed of 1-3 parts of rare earth complex R, 5-10 parts of intumescent flame retardant and 1-3 parts of boron compound flame retardant; inorganic filler B, composed of 25-40 parts of carbonate or silicate and 25-50 parts of inorganic hydroxide; 3-12 parts of toughening agent; 1-3 parts of lubricant; and 10-15 parts of polypropylene substrate. In this invention, the polypropylene substrate E is made from PP chips.

[0029] The rare earth complex R is prepared from rare earth salts and phosphorus-based flame retardants. Considering the environmental friendliness of the product and the uniform elemental composition of the rare earth complex, the rare earth salts used in this case are water-soluble rare earth nitrates, and the rare earth elements are at least one of neodymium, samarium, holmium, yttrium, lanthanum, and praseodymium; the phosphorus-based flame retardant is at least one of pyrophosphoric acid, hypophosphorous acid (HA), phytic acid (PA), and hexamethylenediaminetetramethylenephosphonic acid (HDTMPA).

[0030] Because rare earth elements have a special atomic electronic structure and abundant electronic transition energy levels, they can capture and quench free radicals, thus catalyzing char formation during combustion. Furthermore, these four phosphorus-based flame retardant complexes themselves possess certain flame retardant properties and good coordination ability, enabling them to form a good synergistic flame retardant effect with rare earth ions. Therefore, the rare earth flame retardant described in this case has a dual function of catalyzing char formation and scavenging free radicals, achieving a highly efficient flame retardant effect.

[0031] To further ensure the product's environmental friendliness, all components in the polypropylene are non-toxic and harmless substances. All flame retardants in the formulation are environmentally friendly flame retardants. Specifically, the intumescent flame retardant is at least one of boron phosphate, melamine (MA), and sorbitol; the boron compound flame retardant is one of boric acid, aluminum borate, and ammonium borate; the carbonate or silicate is calcium carbonate or talc; the inorganic hydroxide is at least one of aluminum hydroxide and magnesium hydroxide; the toughening agent is at least one of EVA, POE, MBS, and SBS; and the lubricant is at least two of polyethylene wax, ethylene bis-stearamide (EBS), silicone powder, epoxidized soybean oil (EBSO), acrylate copolymers (ACR), and cerium stearate.

[0032] Therefore, compared with traditional PP flame retardant modification methods, this invention can achieve good flame retardant effect while reducing the amount of aluminum hydroxide, magnesium hydroxide and phosphorus-nitrogen flame retardants used. It realizes the goal of improving the flame retardant performance of polypropylene with a small amount of addition, while ensuring that the processing performance and mechanical properties of polypropylene are not affected.

[0033] The preparation method of the above flame-retardant polypropylene includes the following steps:

[0034] (1) Preparation of rare earth complexes

[0035] First, dissolve 1 mmol of rare earth salt in 10–30 ml of deionized water to obtain solution a. Dissolve 0.5–5 mmol of the complex in 10–100 ml of deionized water and add a weakly alkaline substance, such as ammonia, ammonium hydroxide, or phenol, to adjust the pH to around 7 to obtain solution b. Then, gradually add solution a dropwise to solution b over a period of 15–60 minutes to obtain solution c. Transfer solution c to a high-pressure reactor and react at 100–130 °C for 6–48 hours. Finally, wash with deionized water 3–5 times and dry at 90–120 °C for 4–24 hours to obtain the desired rare earth complex R.

[0036] During the process of slowly adding solution a to solution b, there is sufficient time for rare earth ions and phosphorus-based flame retardants to pre-coordinate and form rare earth complexes. To ensure that the elemental composition of the rare earth complexes is uniform and stable, after obtaining solution c, it is transferred to a high-pressure reactor so that the rare earth complex crystals grow during the reaction.

[0037] (2) Preparation of flame-retardant polypropylene

[0038] First, weigh out the five raw materials—rare earth flame retardant A, inorganic filler B, toughening agent C, lubricant D, and polypropylene substrate E—according to the above-mentioned weight proportions. Premix them at high speed in a high-speed mixer to obtain a uniformly mixed material. Then, add the mixture to a torque rheometer and melt-blend at 170–260°C for 3–8 minutes to obtain a blend. Pour the blend into a mold with a 3mm thickness, place it on the hot plate of a flat vulcanizing machine, and press it at 170–260°C and 15–20 MPa for 3–5 minutes. Afterward, transfer it to the cold plate of the flat vulcanizing machine for cooling. Finally, remove the sample to obtain a 3mm thick flame-retardant polypropylene.

[0039] Different rare earth complexes R1 to R4 were prepared through Examples 1 to 4.

[0040] Example 1

[0041] Preparation of rare earth complex R1

[0042] First, 1 mmol of samarium nitrate was dissolved in 10 ml of deionized water and labeled as a1. 0.5 mmol of PA was added to 20 ml of deionized water, and the pH was adjusted to about 7 and labeled as b1. Then, a1 was gradually added dropwise to b1 over a period of 15 min to obtain c1. c1 was then transferred to a high-pressure reactor and reacted at 100 °C for 6 h. Finally, the mixture was washed three times with deionized water and dried at 90 °C for 24 h to obtain rare earth complex R1 (samarium@PA) or (samarium phytate).

[0043] Example 2

[0044] Preparation of rare earth complex R2

[0045] First, 1 mmol of lanthanum nitrate was dissolved in 20 ml of deionized water and labeled a2. 2 mmol of HA was dissolved in 30 ml of deionized water, and the pH was adjusted to about 7 and labeled b2. Then, a2 was gradually added dropwise to b2 over 30 min to obtain c2. c2 was then transferred to a high-pressure reactor and reacted at 120 °C for 24 h. Finally, the mixture was washed three times with deionized water and dried at 120 °C for 4 h to obtain rare earth complex R2 (lanthanum@HA) or (lanthanum hypophosphite).

[0046] Example 3

[0047] Preparation of rare earth complex R3

[0048] First, 1 mmol of yttrium oxalate was dissolved in 30 ml of deionized water and labeled a3. 1 mmol of pyrophosphate and 2 mmol of PA were dissolved in 40 ml of deionized water, and the pH was adjusted to about 7 and labeled b3. Then, a3 was gradually added dropwise to b3 over a period of 45 min to obtain c3. c3 was then transferred to a high-pressure reactor and reacted at 130 °C for 48 h. Finally, the mixture was washed 5 times with deionized water and dried at 110 °C for 12 h to obtain rare earth complex R3 (yttrium@pyrophosphate@PA) or (yttrium pyrophosphate phytate).

[0049] Example 4

[0050] Preparation of rare earth complex R4

[0051] First, 0.5 mmol of praseodymium nitrate and 0.5 mmol of lanthanum nitrate were dissolved in 20 ml of deionized water and labeled a4. 5 mmol of HDTMPA was dissolved in 50 ml of deionized water, and the pH was adjusted to approximately 7 and labeled b4. Then, a4 was gradually added dropwise to b4 over a period of 60 min to obtain c4. c4 was then transferred to a high-pressure reactor and reacted at 120 °C for 24 h. Finally, the mixture was washed four times with deionized water and dried at 110 °C for 24 h to obtain rare earth complex R4 (lanthanum praseodymium@HDTMPA) or (lanthanum praseodymium hexamethylenediaminetetramethylenephosphonate).

[0052] As can be seen from Examples 1 to 4 above, the preparation method of rare earth complex R in this invention is simple.

[0053] Table 1: Formulation composition of Examples 5-9 and Comparative Examples 1-5

[0054]

[0055]

[0056] Example 5

[0057] Preparation of flame-retardant polypropylene PP1

[0058] After preparing the raw materials according to the weight proportions of A, B, C, D, and E in Table 1, they were placed in a high-speed mixer for high-speed premixing to obtain a uniformly mixed mixture F1. Then, F1 was added to a torque rheometer and melt-blended at 220°C for 5 minutes to obtain a blend G1. G1 was then placed in a mold with a cavity thickness of 3 mm and placed together in the hot plate of a flat vulcanizing machine. After pressing at 220°C and 15 MPa for 3 minutes, it was quickly placed in the cold plate of the flat vulcanizing machine for cooling. Finally, the sample was removed to obtain the desired flame-retardant polypropylene sheet PP1.

[0059] Example 6

[0060] Preparation of flame-retardant polypropylene PP2

[0061] After preparing the raw materials according to the weight proportions of A, B, C, D, and E in Table 1, they were placed in a high-speed mixer for high-speed premixing to obtain a uniformly mixed material F2. Then, F2 was added to a torque rheometer and melt-blended at 260°C for 8 minutes to obtain a blend G2. G2 was then placed in a mold with a cavity thickness of 3 mm and placed together in the hot plate of a flat vulcanizing machine. After pressing at 240°C and 15 MPa for 3 minutes, it was quickly placed in the cold plate of the flat vulcanizing machine for cooling. Finally, the sample was removed to obtain the desired flame-retardant polypropylene sheet PP2.

[0062] Example 7

[0063] Preparation of flame-retardant polypropylene PP3

[0064] After preparing the raw materials according to the weight proportions of A, B, C, D, and E in Table 1, they were placed in a high-speed mixer for high-speed premixing to obtain a uniformly mixed mixture F3. Then, F3 was added to a torque rheometer and melt-blended at 200°C for 6 minutes to obtain a blend G3. G3 was then placed in a mold with a cavity thickness of 3 mm and placed together in the hot plate of a flat vulcanizing machine. After pressing at 210°C and 15 MPa for 5 minutes, it was quickly placed in the cold plate of the flat vulcanizing machine for cooling. Finally, the sample was removed to obtain the desired flame-retardant polypropylene sheet PP3.

[0065] Example 8

[0066] Preparation of flame-retardant polypropylene PP4

[0067] After preparing the raw materials according to the weight proportions of A, B, C, D, and E in Table 1, they were placed in a high-speed mixer for high-speed premixing to obtain a uniformly mixed compound F4. Then, F4 was added to a torque rheometer and melt-blended at 210°C for 8 minutes to obtain a blend G4. G4 was then placed in a mold with a cavity thickness of 3 mm and placed together in the hot plate of a flat vulcanizing machine. After pressing at 210°C and 15 MPa for 3 minutes, it was quickly placed in the cold plate of the flat vulcanizing machine for cooling. Finally, the sample was removed to obtain the desired flame-retardant polypropylene sheet PP4.

[0068] Example 9

[0069] Preparation of flame-retardant polypropylene PP5

[0070] After preparing the raw materials according to the weight proportions of A, B, C, D, and E in Table 1, they were placed in a high-speed mixer for high-speed premixing to obtain a uniformly mixed mixture F5. Then, F5 was added to a torque rheometer and melt-blended at 210°C for 8 minutes to obtain a blend G5. G5 was then placed in a mold with a cavity thickness of 3 mm and placed together in the hot plate of a flat vulcanizing machine. After pressing at 210°C and 15 MPa for 3 minutes, it was quickly placed in the cold plate of the flat vulcanizing machine for cooling. Finally, the sample was removed to obtain the desired flame-retardant polypropylene sheet PP5.

[0071] To investigate the compatibility of the five raw materials A, B, C, D, and E, as well as the synergistic effect between A and B and C, and to obtain a flame-retardant PP material with excellent comprehensive performance, this case uses Example 9 as a control and conducts the following five sets of comparative experiments.

[0072] Comparative Example 1

[0073] Preparation of polypropylene sheet PP6

[0074] In Example 9, R3, boron phosphate, sorbitol, and boric acid in raw material A were replaced with 7 parts of conventional filler calcium carbonate. The remaining raw materials B, C, D, and E were prepared according to the weight proportions in Table 1. They were then placed in a high-speed mixer for high-speed premixing to obtain a uniformly mixed mixture F6. F6 was then added to a torque rheometer and melt-blended at 210°C for 8 minutes to obtain a blend G6. G6 was then placed in a mold with a cavity thickness of 3 mm and placed together in the hot plate of a flat vulcanizing machine. After pressing at 210°C and 15 MPa for 3 minutes, it was quickly placed in the cold plate of the flat vulcanizing machine for cooling. Finally, the sample was removed to obtain the desired flame-retardant polypropylene sheet PP6.

[0075] Comparative Example 2

[0076] Preparation of polypropylene sheet PP7

[0077] In Example 9, R3, boron phosphate, sorbitol, and boric acid in raw material A were replaced with 5 parts aluminum hydroxide and 2 parts magnesium hydroxide. The remaining raw materials B, C, D, and E were prepared according to the weight proportions in Table 1. They were then placed in a high-speed mixer for high-speed premixing to obtain a uniformly mixed mixture F7. Then, F7 was added to a torque rheometer and melt-blended at 210°C for 8 minutes to obtain a blend G7. G7 was then placed in a mold with a cavity thickness of 3 mm and placed together in the hot plate of a flat vulcanizing machine. After pressing at 210°C and 15 MPa for 3 minutes, it was quickly placed in the cold plate of the flat vulcanizing machine for cooling. Finally, the sample was removed to obtain the desired flame-retardant polypropylene sheet PP7.

[0078] Comparative Example 3

[0079] Preparation of polypropylene sheet PP8

[0080] In Example 9, one part of R3 in raw material A was replaced with one part of calcium carbonate. The remaining raw materials B, C, D, and E were prepared according to the weight proportions in Table 1 and then placed in a high-speed mixer for high-speed premixing to obtain a uniformly mixed mixture F8. Then, F8 was added to a torque rheometer and melt-blended at 210°C for 8 minutes to obtain a blend G8. G8 was then placed in a mold with a cavity thickness of 3 mm and placed together in the hot plate of a flat vulcanizing machine. After pressing at 210°C and 15 MPa for 3 minutes, it was quickly placed in the cold plate of the flat vulcanizing machine for cooling. Finally, the sample was removed to obtain the desired flame-retardant polypropylene sheet PP8.

[0081] Comparative Example 4

[0082] Preparation of polypropylene sheet PP9

[0083] Remove 33 parts of calcium carbonate from raw material B in Example 9. Prepare the remaining raw materials A, C, D, and E according to the weight proportions in Table 1, and put them into a high-speed mixer for high-speed premixing to obtain a uniformly mixed mixture F9. Then, add F9 to a torque rheometer and melt-blend at 210°C for 8 minutes to obtain a blend G9. Then, place G9 in a mold with a cavity thickness of 3 mm and place it together in the hot plate of a flat vulcanizing machine. After pressing at 210°C and 15 MPa for 3 minutes, quickly place it in the cold plate of the flat vulcanizing machine for cooling. Finally, take out the sample to obtain the desired flame-retardant polypropylene sheet PP9.

[0084] Comparative Example 5

[0085] Polypropylene sheets (PP) 10 Preparation

[0086] Ce@DDP (selected from the rare earth flame retardant complex in existing patent technology CN114874265A) was used to replace the rare earth complex R3 in Example 9. The remaining components were prepared according to the weight parts in Table 1, and then put into a high-speed mixer for high-speed premixing to obtain a uniformly mixed mixture F. 10 Then, F 10 The mixture was added to a torque rheometer and melt-blended at 210°C for 8 minutes to obtain blend F. 10 Then, F 10 The mixture was added to a torque rheometer and melt-blended at 210°C for 8 minutes to obtain blend G. 10 Then, G 10 The sample is placed in a mold with a cavity thickness of 3mm, and then placed on the hot plate of a flat vulcanizing machine. After pressing at 210℃ and 15MPa for 3 minutes, it is quickly placed on the cold plate of the flat vulcanizing machine for cooling. Finally, the sample is removed to obtain the desired flame-retardant polypropylene sheet (PP). 10 .

[0087] The flame-retardant PP materials prepared in Examples 5-9 and Comparative Examples 1-5 were subjected to corresponding performance tests:

[0088] The critical thermal flux was tested according to ASTM E648 standard; the tensile strength was tested according to GB / T1040.1-2006, and the results are shown in Table 2.

[0089] Table 2: Summary of performance of Examples 5-9 and Comparative Examples 1-5

[0090]

[0091] As shown in Table 2, the rare earth complex R prepared by the present invention using rare earth nitrates and phosphorus-based flame retardants, as a component of rare earth flame retardant A, can produce a good synergistic effect with phosphorus-based flame retardants, achieving a highly efficient flame retardant effect. Furthermore, by rationally designing the compatibility of the formulation of rare earth flame retardant A, inorganic filler B, toughening agent C, lubricant D, and polypropylene E, the tensile strength of the modified polypropylene sheet is maintained above 22 MPa, and the flexural strength is maintained above 26 MPa. While maintaining its basic mechanical properties, the flame retardant performance of polypropylene can be significantly improved, and the heat radiation flux of the flame-retardant PP material is maintained at 10 kW / m². 2 The above. Among them, the PP4 prepared in Example 8 is the flame-retardant polypropylene material with the best performance, and its heat radiation flux is 13 kW / m². 2 The tensile strength is 23 MPa and the flexural strength is 28 MPa.

[0092] Furthermore, a comparison between Example 9 and Comparative Example 5 shows that the rare earth complex R prepared in this case has a better flame retardant effect in the application of polypropylene sheets compared with the rare earth flame retardant complex Ce@DDP prepared by the prior patent technology.

[0093] The reaction mechanism of this invention lies in the fact that the degradation products such as phosphoric acid and polyphosphoric acid produced by the decomposition of rare earth flame retardant A at high temperatures catalyze the formation of a char layer, which remains in the char layer in the form of P=O and POC, isolating it from contact with oxygen and preventing further combustion of polypropylene sheets. In addition, rare earth ions can scavenge OH· and H· free radical ions generated during the combustion of polypropylene, thereby interrupting and inhibiting combustion and slowing down the degradation process of polypropylene. Therefore, under the dual action of rare earth flame retardant A catalyzing char formation and scavenging free radicals, continuous and dense highly graphitized char residue is produced, which helps reduce heat and oxygen transfer, ultimately slowing down or even preventing the combustion process and achieving a highly efficient flame retardant effect.

[0094] The above description is only a preferred embodiment of the present invention and is not intended to limit the design of this case. All equivalent changes made based on the key design features of this case shall fall within the protection scope of this case.

Claims

1. A flame-retardant polypropylene, characterized in that: The following components are used by weight fraction: The rare earth flame retardant is composed of 1-3 parts of a rare earth complex, 5-10 parts of an intumescent flame retardant, and 1-3 parts of a boron compound flame retardant, wherein the rare earth complex is formed by a coordination reaction between a rare earth salt and a phosphorus-based flame retardant; The rare earth salt is a rare earth nitrate, and the rare earth element is at least one of neodymium, samarium, holmium, yttrium, lanthanum, and praseodymium, and the phosphorus-based flame retardant is at least one of pyrophosphoric acid, hypophosphorous acid, phytic acid, and hexamethylene diamine tetra-methylene phosphonic acid; The intumescent flame retardant is at least one of boron phosphate, melamine, and sorbitol, and the boron compound flame retardant is one of boric acid, aluminum borate, and ammonium borate; The inorganic filler is composed of 25-40 parts of a carbonate or a silicate and 25-50 parts of an inorganic hydroxide; The carbonate and the silicate are calcium carbonate and talcum powder, respectively, and the inorganic hydroxide is at least one of aluminum hydroxide and magnesium hydroxide; The toughening agent is at least one of EVA, POE, MBS, and SBS, the lubricant is at least two of polyethylene wax, ethylene bis-stearyl amide, silicone powder, epoxy soybean oil, acrylate copolymer, and cerium stearate, and the polypropylene base material is 10-15 parts.

2. A flame retardant polypropylene according to claim 1, characterized in that: The toughening agent is at least one of EVA, POE, MBS, and SBS.

3. A flame retardant polypropylene according to claim 1, characterized in that: The lubricant is at least two of polyethylene wax, ethylene bis-stearyl amide, silicone powder, epoxy soybean oil, acrylate copolymer, and cerium stearate.

4. A process for the preparation of a flame-retardant polypropylene according to any one of claims 1 to 3, characterized in that: The method comprises the following steps: (1) Preparation of a rare earth complex First, a rare earth nitrate is dissolved in deionized water to obtain solution a, and a phosphorus-based flame retardant is dissolved in deionized water and adjusted to a pH value of 7 to obtain solution b; Then, solution a is gradually added to solution b dropwise, the dropwise adding time is 15 min-60 min, to obtain solution c; solution c is then transferred into a high-pressure reaction kettle and reacted at 100-130 ℃ for 6-48 h; finally, it is washed with deionized water and dried at 90-120 ℃ for 4-24 h to obtain the required rare earth complex; In step (1), in solution a, the ratio of the rare earth nitrate to deionized water is 1 mmol:10-30 ml; in solution b, the ratio of the phosphorus-based flame retardant to deionized water is 0.5-5 mmol:10-100 ml; (2) Preparation of a flame-retardant polypropylene First, the rare earth flame retardant, the inorganic filler, the toughening agent, the lubricant, and the polypropylene base material are weighed according to the above weight fractions, and are pre-mixed at high speed in a high-speed mixer to obtain a uniformly mixed mixture; then, the mixture is added to a torque rheometer, and is melt-blended at 170-260 ℃ for 3-8 min to obtain a blended material; the blended material is then poured into a mold, placed on the hot plate of a flat vulcanizing machine, and pressed at 170-260 ℃ and 15-20 MPa for 3-5 min, and then moved to the cold plate of the flat vulcanizing machine for cooling to obtain the flame-retardant polypropylene.

5. A process for the preparation of flame retardant polypropylene as claimed in claim 4, wherein: In step (1), the pH of solution b is adjusted to 7 by adding a weakly alkaline substance.

6. A process for the preparation of a flame retardant polypropylene according to claim 5, characterized in that: The weakly alkaline substance is ammonia.

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