Flame-retardant modified glass fiber-containing flame-retardant reinforced polypropylene composite material and preparation method thereof

Abstract

The invention relates to the technical field of flame-retardant polypropylene composite materials, in particular to a flame-retardant reinforced polypropylene composite material containing flame-retardant modified glass fibers and a preparation method of the flame-retardant reinforced polypropylene composite material. The flame-retardant modified glass fiber-containing flame-retardant reinforced polypropylene composite material is prepared from the following raw materials: 30 to 60 parts of polypropylene, 5 to 60 parts of flame-retardant modified glass fiber, 5 to 20 parts of piperazine pyrophosphate, 5 to 20 parts of melamine polyphosphate, 0.5 to 5 parts of flame-retardant synergist, 1 to 6 parts of maleic anhydride ester-grafted polypropylene, 0.5 to 3 parts of coupling agent, 0.3 to 3 parts of lubricant and 0.2 to 0.5 part of antioxidant. The flame-retardant modified glass fibers are glass fibers subjected to surface modification by using a focused piperazine phosphate-melamine polyphosphate random copolymer. According to the technical scheme, the problem that the mechanical property and flame retardant property of glass fiber reinforced polypropylene in the prior art are difficult to optimize at the same time can be solved, and the glass fiber reinforced polypropylene has ideal popularization and application prospects.

Description

Technical Field

[0001] The invention relates to the technical field of flame-retardant polypropylene composite materials, and in particular to a flame-retardant reinforced polypropylene composite material containing flame-retardant modified glass fiber and a preparation method thereof. Background Art

[0002] Polypropylene (PP) is another important plastic variety after polyethylene (PE). It has good heat resistance, excellent dielectric and electrical insulation properties. However, when making some engineering parts, its performance cannot meet the requirements. The existing technology often improves the strength, hardness, heat resistance and dimensional stability of polypropylene resin by adding glass fiber, which can be widely used in automobiles, electrical appliances, motors, machinery, home appliances and other fields.

[0003] Glass fiber (GF) is an inorganic non-metallic material with the advantages of high mechanical strength, strong heat resistance, good chemical resistance, and good insulation performance. It is often used as a polymer reinforcement material and can significantly improve the mechanical properties of polymer composites. Polypropylene is flammable, and polypropylene composites with glass fiber added will have polymer melt infiltrate the glass fiber surface at high temperatures and generate interfacial tension, resulting in a "candle wick effect", that is, the polymer melt will quickly infiltrate, spread and flow through the glass fiber surface to the combustion area, further increasing the fire hazard of polypropylene composites, making the flame retardant modification of polymer composites with glass fiber added much more difficult.

[0004] In order to reduce the flammability of glass fiber reinforced polypropylene composites, the current more widespread solution is to suppress the "wick effect" by adding sufficient high-quality flame retardants to the polymer / glass fiber composites. However, the addition of a large amount of flame retardants will seriously affect the mechanical properties of the polymer material, resulting in a decrease in the gain effect of glass fiber in the polymer material. Therefore, it is urgent to improve the flame retardant properties of glass fiber reinforced polypropylene materials and enhance the flame retardant and mechanical properties of the composite materials. Summary of the invention

[0005] The present invention aims to provide a flame retardant reinforced polypropylene composite material containing flame retardant modified glass fiber, so as to solve the technical problem that the mechanical properties and flame retardant properties of the glass fiber reinforced polypropylene composite material in the prior art are difficult to be optimized at the same time.

[0006] In order to achieve the above object, the present invention adopts the following technical scheme:

[0007] A flame retardant reinforced polypropylene composite material containing flame retardant modified glass fiber comprises the following raw materials in parts by weight: 30-60 parts of polypropylene, 5-60 parts of flame retardant modified glass fiber, 5-20 parts of piperazine pyrophosphate, 5-20 parts of melamine polyphosphate, 0.5-5 parts of flame retardant synergist, 1-6 parts of maleic anhydride esterified polypropylene, 0.5-3 parts of coupling agent, 0.3-3 parts of lubricant and 0.2-0.5 parts of antioxidant.

[0008] The flame retardant modified glass fiber is a glass fiber surface-modified with a focused piperazine phosphate-melamine polyphosphate random copolymer, and the structural formula of the focused piperazine phosphate-melamine polyphosphate random copolymer is shown in formula (10);

[0009]

[0010] Wherein, 500<m<10000, 500<n<10000, x>0, y>0, p>0; in formula (10), MPP represents formula (8), PAPP represents formula (1), and the mass ratio of PAPP to MPP is 1:0.2-5.

[0011] Furthermore, the pyrophosphate piperazine is prepared by the following method: diphosphate piperazine is heat treated for 30-240 minutes under a nitrogen atmosphere, a pressure environment of 0.05-0.3 MPa, and a condition of 120-320° C., and thermally polymerized and dehydrated to form pyrophosphate piperazine.

[0012] Furthermore, the melamine polyphosphate is prepared by the following method: melamine phosphate is heat-treated for 60-300 minutes under a nitrogen atmosphere, a pressure environment of 0.05-0.3 MPa, and a temperature of 220-360° C. to thermally polymerize and dehydrate to condense into melamine polyphosphate.

[0013] Furthermore, the polypropylene has a melt index of any one or a mixture of melt index >0g / 10min and <100g / 10min under the conditions of temperature 230°C and load 2.16kg; the 1% thermal weight loss of melamine polyphosphate is ≥360°C; the flame retardant synergist includes at least one of anhydrous zinc borate, 3.5-water zinc borate, zinc oxide, and zirconium phosphate; the coupling agent is a silane coupling agent, including at least one of KH-9120, KT-930, KH-1006 and KH-9130; the lubricant includes at least one of white oil, silicone oil, polyethylene wax, ethylene bis stearamide, pentaerythritol stearate, silicone and amide wax; the antioxidant includes at least one of antioxidant 168, antioxidant 1010 and antioxidant 1098.

[0014] The technical solution also provides a method for preparing a flame retardant reinforced polypropylene composite material containing flame retardant modified glass fiber, comprising the following steps performed in sequence:

[0015] S1: focusing piperazine phosphate and melamine polyphosphate are subjected to thermal polymerization and dehydration to obtain a focusing piperazine phosphate-melamine polyphosphate random copolymer;

[0016] S2: dispersing glass fibers in an alcohol solution, adding an amino coupling agent under stirring conditions, washing and drying after activation reaction, to obtain amino glass fibers;

[0017] S3: dispersing the amino glass fiber in an organic solvent, adding the focused piperazine phosphate-melamine polyphosphate random copolymer, washing and drying after the reaction, to obtain the flame retardant modified glass fiber.

[0018] S4: Using polypropylene, flame retardant modified glass fiber, piperazine pyrophosphate, melamine polyphosphate, flame retardant synergist, maleic anhydride ester polypropylene, coupling agent, lubricant and antioxidant as raw materials, after extrusion through a twin-screw extruder, drawing, pelletizing and screening and dehydration, flame retardant reinforced polypropylene composite material particles containing flame retardant modified glass fiber are obtained.

[0019] Further, in S1, focusing piperazine phosphate and melamine polyphosphate are reacted at a mass ratio of 1:0.2-5 at 200-280° C., 0.1-1.5 MPa, in a nitrogen atmosphere, for 30-180 min, and thermally polymerized and dehydrated to obtain a focusing piperazine phosphate-melamine polyphosphate random copolymer;

[0020] Preferably, the focused piperazine phosphate and melamine polyphosphate are reacted in a mass ratio of 1:0.6 at 270° C., 0.2 MPa, in a nitrogen atmosphere, for 180 min, and thermally polymerized and dehydrated to obtain a focused piperazine phosphate-melamine polyphosphate random copolymer.

[0021] Furthermore, in S2, the alcohol solution is an ethanol solution; the usage ratio of glass fiber to alcohol solution is 100g:250-750ml; the usage of amino coupling agent is 1-5% of the mass of glass fiber; and the activation reaction conditions are 60-100°C for 4-8h.

[0022] Further, in S3, the organic solvent includes any one of ethanol, water, DMF, DMSO, acetonitrile and an aqueous solution of ethanol; and the usage ratio of the amino glass fiber to the organic solvent is 80-160 g: 200-1000 mL.

[0023] Further, in S3, the usage ratio of the focused piperazine phosphate-melamine polyphosphate random copolymer and the amino glass fiber is 0.1-5g:80-160g; and the reaction conditions of the focused piperazine phosphate-melamine polyphosphate random copolymer and the amino glass fiber are 20-50°C and 2-12h.

[0024] Further, in S4, piperazine pyrophosphate, melamine polyphosphate and flame retardant synergist are added to a mixer and stirred at room temperature for 5-30 minutes; the temperature of the mixer is increased to 80-160°C, and the coupling agent is added and stirred for 10-30 minutes; after cooling to room temperature, polypropylene, lubricant, nucleating agent and antioxidant are added and stirred for 5-30 minutes to obtain a material mixture; the material mixture is extruded by a twin-screw extruder at an extrusion temperature of 170-250°C, and flame retardant modified glass fiber is added through side feeding, and after extrusion, drawing, pelletizing and screening dehydration, flame retardant reinforced polypropylene granules are obtained.

[0025] In summary, the present invention modifies the surface of the glass fiber and coats the macromolecular intumescent flame retardant with excellent carbonization effect on the surface of the glass fiber, so that the polymer / glass fiber composite material quickly forms an expanded, dense and hard carbon layer on the surface of the glass fiber at high temperature, thereby greatly suppressing the "wick effect". In addition, after the surface of the glass fiber is modified with a focused piperazine phosphate-melamine polyphosphate random copolymer (PAPP-co-MPP) with a certain molecular chain, the compatibility of the glass fiber and flame-retardant polypropylene can be improved. It plays a bridge and anchoring role between the glass fiber and other flame retardants / polypropylene, thereby improving the mechanical properties of its flame-retardant reinforced polypropylene. Conventional flame-retardant polypropylene has poor mechanical properties, and the glass fiber after surface modification with the focused piperazine phosphate-melamine polyphosphate random copolymer can improve the mechanical properties of polypropylene. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the amino modification and flame retardant modification of the glass fiber of Example 1.

[0027] Figure 2 This is the appearance of the glass fiber surface modified by random copolymer after combustion treatment.

[0028] Figure 3 This is the appearance of glass fiber without surface modification after combustion treatment. DETAILED DESCRIPTION

[0029] The present invention is further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto. Unless otherwise specified, the technical means used in the following examples and experimental examples are conventional means well known to those skilled in the art, and the materials, reagents, etc. used can be obtained from commercial sources.

[0030] Example 1: Preparation process of flame retardant modified glass fiber reinforced polypropylene composite material

[0031] The flame retardant modified glass fiber reinforced polypropylene composite material comprises the following raw materials in parts by weight:

[0032] 30-60 parts of polypropylene, 5-60 parts of GF-NH2-FR (flame-retardant modified glass fiber), 5-20 parts of piperazine pyrophosphate (i.e., focused piperazine phosphate, commercially available or prepared according to the method of this scheme), 5-20 parts of melamine polyphosphate (commercially available or prepared according to the method of this scheme), 0.5-5 parts of flame retardant synergist, 1-6 parts of maleic anhydride ester PP, 0.5-3 parts of coupling agent, 0.3-3 parts of lubricant, and 0.2-0.5 parts of antioxidant. In addition to having good flame retardant properties, the flame retardant polypropylene composition also has very excellent precipitation resistance and mechanical properties.

[0033] Wherein, the polypropylene is any one or a mixture of the following: a melt index of >0 g / 10 min and <100 g / 10 min under the conditions of a temperature of 230° C. and a load of 2.16 kg.

[0034] The melamine polyphosphate has a 1% heat loss of greater than or equal to 300° C. The preparation method of the melamine polyphosphate can be specifically referred to in Example 2. In addition, the preparation method of piperazine pyrophosphate can also be referred to in Example 2.

[0035] The flame retardant synergist is any one of anhydrous zinc borate, zinc sulfide, 3.5-hydrate zinc borate, zinc oxide, and zirconium phosphate, or a mixture of several of them.

[0036] The coupling agent is a silane coupling agent, which can be any one of aminosilane coupling agent KH-9120, isocyanate silane coupling agent KT-930, epoxy silane coupling agent KH-1006 and KH-9130, or a mixture of several of the silane coupling agents.

[0037] The lubricant is one or more of white oil, silicone oil, polyethylene wax, ethylene bis stearamide (EBS), pentaerythritol stearate, silicone and amide wax.

[0038] The antioxidant is antioxidant 168, antioxidant 1010 or antioxidant 1098.

[0039] The flame retardant modified glass fiber reinforced polypropylene composite material is prepared according to the following process:

[0040] Step 1: Add piperazine pyrophosphate, melamine polyphosphate and flame retardant synergist into a mixer and stir at room temperature for 5-30 minutes;

[0041] Step 2: In the mixture of step 1, increase the temperature of the mixer to 80-160°C, ensure that the temperature of the material in the mixer also reaches the set temperature, then add the coupling agent and continue stirring for 10-30 minutes;

[0042] Step 3: After the mixture of step 2 is cooled to room temperature, polypropylene, lubricant, maleic anhydride ester PP and antioxidant are added and stirred for 5 to 30 minutes;

[0043] Step 4: The mixture of step 3 is extruded by a twin-screw extruder at a temperature of 170-250°C. GF-NH2-FR is added through side feeding, and then through the process of drawing and pelletizing, the flame-retardant reinforced polypropylene granules are obtained after screening and dehydration.

[0044] Example 2: Preparation of flame retardant modified glass fiber

[0045] (1) Focus on the synthesis of piperazine phosphate (PAPP)

[0046] The structure of the focused piperazine phosphate is shown in formula (1), n=500-10000, and it is synthesized from piperazine diphosphate (formula (4)). The synthesis of piperazine diphosphate is a conventional method in the prior art (using a conventional reactor in the prior art), specifically, phosphoric acid (formula (2)) and piperazine (formula (3)) are used in a molar ratio of 2.0-2.2:1, under reaction conditions of 60-150°C and 0.1-1.0MPa (in a reaction system with water or alcohol as solvent), and the reaction is carried out for 30-300 minutes to obtain. The reaction equation is shown in formula (5).

[0047] The piperazine diphosphate obtained and purified by the above-mentioned chemical reaction is heat-treated in a nitrogen atmosphere, a pressure environment of 0.05-0.3 MPa, and a temperature of 120-320° C. for 30-240 min to undergo thermal polymerization, dehydration, and condensation to obtain piperazine phosphate (Formula (1)). The reaction equation is shown in Formula (6).

[0048]

[0049]

[0050] (2) Synthesis of melamine polyphosphate (MPP)

[0051] Using deionized water as solvent, melamine (ME) and H3PO4 are reacted by acid-base neutralization to prepare melamine phosphate (MP) with high purity, high whiteness and high thermal stability, and then MP is subjected to high-temperature thermal polymerization to obtain melamine polyphosphate (MPP). The above synthesis process can be found in the inventor's previously published paper "Zhong Zhiqiang, Synthesis of Melamine Polyphosphate and Properties of Flame-Retardant Polypropylene, Engineering Plastics Application, 2018". Specifically, in this embodiment, the method for preparing melamine phosphate is: the molar ratio of ME to H3PO4 is 1:1.05, the reaction time is 2.0h, the reaction temperature is 95°C, and the molar ratio of ME to deionized water is 3:97. Melamine phosphate (Formula (7)) was synthesized under the above conditions.

[0052] Then, melamine phosphate is used to synthesize melamine polyphosphate (MPP). Melamine phosphate is heat treated at 220-360° C. for 60-300 min, in an inert gas environment (such as nitrogen) and under a pressure of 0.05-0.3 MPa, and thermally polymerized and dehydrated to form melamine polyphosphate (MPP, formula (8), 500<m<10000), and the reaction formula is shown in formula (9).

[0053]

[0054] (3) Focus on the synthesis of piperazine phosphate (PAPP)-melamine polyphosphate (MPP) random copolymer (PAPP-co-MPP)

[0055] Focused piperazine phosphate and melamine polyphosphate are reacted at a mass ratio of 1:0.2-5 under reaction conditions of 200-280°C and 0.1-1.5MPa (nitrogen atmosphere) for 30-180 minutes, and then thermally polymerized and dehydrated to obtain a focused piperazine phosphate-melamine polyphosphate random copolymer (PAPP-co-MPP), the structural formula of which is shown in Formula (10), and the reaction equation of which is shown in Formula (11). The polymerization degrees of focused piperazine phosphate (PAPP, Formula (6)) and melamine polyphosphate (MPP, Formula (8)) are both greater than 500 and less than 10000, that is, 500<m<10000, and 500<n<10000. In Formula (10), x>0, y>0, and p>0, and in PAPP-co-MPP, the mass ratio of PAPP to MPP is 1:0.2-5.

[0056]

[0057] (4) Amide modification of glass fiber (GF-NH2)

[0058] Disperse 100g of chopped glass fiber (GF, ECS301CL model glass fiber can be used) in ethanol / water (250-750ml, for example, 450:50 ethanol solution), add 1-5wt% of amino coupling agent (for example, KH550, etc.) under high-speed stirring (200-1500rpm), raise the temperature from room temperature to 60-100℃ and react for 4-8h. After the reaction is completed, filter, wash and dry at 80℃ to obtain GF-NH2.

[0059] (5) Preparation of flame retardant modified glass fiber (GF-NH2-FR)

[0060] GF-NH2 (80-160 g) was dispersed in 200-1000 mL of solvent (ethanol, water, DMF, DMSO, acetonitrile and other organic solvents), PAPP-co-MPP (0.1-5 g) was added to the solution, and the reaction was continued at 20-50 ° C for 2-12 h while maintaining a stirring speed of 50-1500 rpm. After the reaction was completed, GF-NH2-FR was obtained by filtering, washing and drying at 80 ° C.

[0061] The schematic diagram of the synthesis process of steps (4) and (5), the schematic diagram of the amino modification of glass fiber (GF-NH2) and its flame retardant modification (GF-NH2-FR) are shown in detail. Figure 1 The glass fiber surface is modified with PAPP-co-MPP, and then the modified glass fiber is burned, and a carbon layer is formed on the surface of the glass fiber (see typical pictures Figure 2 If the glass fiber surface is not modified in any way and the glass fiber is burned, the carbon layer will not appear on the surface of the glass fiber (see the typical picture). Figure 3 ). Figure 2 and Figure 3 Long glass fibers are used in this study. Although this scheme uses short glass fibers to make flame-retardant reinforced composite materials, it is not convenient to intuitively display the PAPP-co-MPP modification effect on short fibers. Therefore, long fibers are used in this experiment to observe the state of glass fibers modified with PAPP-co-MPP after combustion.

[0062] Experimental Example 1

[0063] Melamine polyphosphate was prepared as follows: melamine phosphate was synthesized according to the method described in Example 2, melamine phosphate was heat treated at 320°C for 240 min, and melamine polyphosphate (MPP, 500<m<10000) was synthesized by thermal polymerization and dehydration condensation in a nitrogen environment and a pressure environment of 0.15 MPa.

[0064] Phosphoric acid and piperazine are mixed in a molar ratio of 2.05:1, reacted at 80°C and 0.1MPa for 210min in an ethanol aqueous solution environment (ethanol volume fraction 50%, phosphoric acid mass fraction of ethanol aqueous solution can be selected to be 5%-30%, 15% in specific experimental operation), and then purified and dried by conventional methods to obtain the intermediate piperazine diphosphate. The intermediate piperazine diphosphate is heat treated at 290°C and 0.1MPa nitrogen atmosphere for 240min, and thermally polymerized and dehydrated to obtain focused piperazine phosphate (PAPP, 500<n<10000).

[0065] The focused piperazine phosphate obtained in the above steps and melamine polyphosphate were mixed (according to the mass ratio of PAPP:MPP = 1:0.6), and thermally polymerized at 270°C for 180min under a nitrogen atmosphere of 0.2MPa to obtain PAPP-co-MPP. After a large number of experimental studies, the PAPP-co-MPP prepared according to the above technical parameters was applied to glass fiber modification, and a polypropylene composite material was prepared. The polypropylene composite material can obtain more excellent effects in mechanical properties and flame retardant properties, which is the optimal parameter for preparing PAPP-co-MPP for glass fiber modification and preparing polypropylene composite materials adopted in this scheme. As a comparison, for example, a polypropylene composite material prepared by a PAPP:MPP mass ratio of 1:0.5 and a pressure environment of 0.5MPa (except for the above differences, the rest is prepared by referring to the method of Experimental Example 1), and its flame retardancy UL 94 (1.0mm) is V-1 level.

[0066] Disperse 100g GF (ECS301CL-4.5, chopped GF) of glass fiber in ethanol / water (500ml, 450:50), add 1wt% (1g) of amino coupling agent KH550 under high-speed stirring (about 1000rpm), raise the temperature from room temperature to 90℃ for 6h, after the reaction is completed, filter, wash and dry at 80℃ to obtain GF-NH2.

[0067] GF-NH2 (100 g) was evenly dispersed in an ethanol solution (500 ml, 400:100), PAPP-co-MPP (1 g) was added to the solution, and the reaction was continued at 50°C for 11 h (while stirring at about 500 rpm). After the reaction was completed, GF-NH2-FR was obtained by filtering, washing and drying at 80°C.

[0068] The raw material composition of the flame retardant modified glass fiber reinforced polypropylene composite material is:

[0069] 57 parts of polypropylene Z30S, 20 parts of GF-NH2-FR, 12 parts of piperazine pyrophosphate (synthesized by the above method), 6 parts of melamine polyphosphate (synthesized by the above method), 1 part of zinc sulfide, 2 parts of maleic anhydride ester PP (KT-1), 1 part of coupling agent KH1006, 0.5 parts of ethylene bis stearic acid amide, 0.2 parts of antioxidant 1010, and 0.3 parts of antioxidant 168. Among them, the addition amount of flame retardant is 18% of flame retardant (piperazine pyrophosphate + melamine polyphosphate).

[0070] The preparation method is as follows:

[0071] Step 1: Add piperazine pyrophosphate, melamine polyphosphate and flame retardant synergist into a mixer and stir at room temperature for 30 minutes;

[0072] Step 2: In the mixture of step 1, increase the temperature of the mixer to 140°C, ensure that the temperature of the material in the mixer also reaches the set temperature, then add the coupling agent and continue stirring for 30 minutes;

[0073] Step 3: After the mixture in step 2 is cooled to room temperature, polypropylene, lubricant, maleic anhydride ester PP and antioxidant are added and stirred for 30 minutes;

[0074] Step 4: The mixture of step 3 is extruded by a conventional twin-screw extruder in the prior art, GF-NH2-FR is added by side feeding, and then through the process of drawing and pelletizing, screening and dehydration, flame retardant reinforced polypropylene granules are obtained. The temperature of the twin-screw extruder is set to 170-250°C (preferably 180-220°C). More specifically, it can be set as follows: the twin-screw extruder is divided into 10 temperature zones, and the temperatures of each temperature zone are 180, 190, 200, 210, 220, 220, 210, 200, 190, 180°C in the order of material movement.

[0075] Experimental Example 2

[0076] This experimental example is basically the same as the experimental example 1, except that the amount of the flame retardant added is 15% (piperazine pyrophosphate + melamine polyphosphate).

[0077] The specific formula of the flame retardant reinforced polypropylene composition is: 60 parts of PP Z30S; 20 parts of GF-NH2-FR; 10 parts of piperazine pyrophosphate; 5 parts of melamine phosphate; 1 part of zinc sulfide; 2 parts of maleic anhydride ester PP; 1 part of coupling agent KH1006; 0.5 parts of EBS; 0.2 parts of antioxidant 1010 and 0.3 parts of antioxidant 168. The flame retardant modified glass fiber reinforced polypropylene composite material is prepared according to the above formula

[0078] Comparative Experiment Example 1

[0079] The same method as in Experimental Example 1 was used, but an equal amount of untreated chopped GF was used instead of GF-NH2-FR to prepare a flame retardant modified glass fiber reinforced polypropylene composite material.

[0080] Comparative Experiment Example 2

[0081] The same method as in Experimental Example 2 was used, but an equal amount of untreated chopped GF was used instead of GF-NH2-FR to prepare a flame retardant modified glass fiber reinforced polypropylene composite material.

[0082] Comparative Experiment 3

[0083] The same method as in Experimental Example 1 was used, but GF-NH2 was used in equal amounts to replace GF-NH2-FR to prepare a flame retardant modified glass fiber reinforced polypropylene composite material. The specific preparation method of GF-NH2 is shown in Experimental Example 1.

[0084] Comparative Experiment Example 4

[0085] The same method as in Experimental Example 1 is used, but an equal amount of PAPP-modified GF (GF-NH2-PAPP) is used to replace GF-NH2-FR to prepare a flame retardant reinforced polypropylene composite material. The preparation method of GF-NH2-PAPP is as in Experimental Example 1, except that an equal amount of PAPP-co-MPP in Experimental Example 1 is replaced by focused piperazine phosphate (PAPP), and the preparation method of focused piperazine phosphate is also the same as in Experimental Example 1.

[0086] Comparative Experiment Example 5

[0087] The same method as in Experimental Example 1 is used, but an equal amount of MPP-modified GF (GF-NH2-MPP) is used to replace GF-NH2-FR to prepare a flame-retardant reinforced polypropylene composite material. The preparation method of GF-NH2-MPP is as in Experimental Example 1, except that an equal amount of PAPP-co-MPP in Experimental Example 1 is replaced by melamine polyphosphate (MPP), and the preparation method of melamine polyphosphate is also the same as in Experimental Example 1.

[0088] Comparative Experiment Example 6

[0089] The same method as in Experimental Example 1 is used, but GF (GF-NH2-PAPP / MPP) modified with PAPP and MPP is used in equal amounts to replace GF-NH2-FR to prepare a flame retardant reinforced polypropylene composition. The preparation method of GF-NH2-PAPP / MPP is similar to that in Experimental Example 1, except that 1 g of PAPP-co-MPP in Experimental Example 1 is replaced with a mixture of PAPP and MPP in a mass ratio of 1:0.6, and the preparation method of focused piperazine phosphate and melamine polyphosphate is also the same as that in Experimental Example 1.

[0090] Comparative Experiment Example 7

[0091] Basically the same as comparative experimental example 1, but without adding any flame retardant, the specific formula is:

[0092] PP Z30S 75 parts, short-cut GF 20 parts, zinc sulfide 1 part, maleic anhydride ester PP (KT-1) 2 parts, coupling agent KH1006 1 part, ethylene bis stearic acid amide 0.5 parts, antioxidant 1010 0.2 parts, antioxidant 168 0.3 parts. According to the above formula, a glass fiber reinforced polypropylene composite material was prepared.

[0093] The formula compositions of the experimental examples and comparative experimental examples are summarized in Table 1, and the experimental results are shown in Table 2.

[0094] Table 1: Composition of the formula of the experimental example and the comparative experimental example

[0095]

[0096] The flame retardant glass fiber reinforced polypropylene composites synthesized in the experimental examples and the comparative experimental examples were tested for performance. The performance indicators include flame retardancy test, oxygen index (LOI) test, tensile strength, and notched impact strength. The flame retardancy test was carried out according to Test for Flammability of Plastic Materials for Parts in Devices and Appliances-UL 94. The reference standard for oxygen index (LOI) test is GB / T 2406. The reference standard for tensile strength is GB / T1040. The reference standard for notched impact strength is GB / T1843.

[0097] Table 2: Test results of various properties of flame-retardant glass fiber reinforced polypropylene composites synthesized in experimental examples and comparative experimental examples (the experimental results are the average values ​​of three independent repeated experiments)

[0098]

[0099] Experimental Example 1 uses the flame-retardant modified glass fiber (GF-NH2-FR) of this scheme to prepare a polypropylene composite material. When less flame retardant is added, a relatively ideal flame retardant effect can be achieved, and the mechanical properties of the material are guaranteed. Experimental Example 2 has a reduced amount of flame retardants (melamine polyphosphate and diethyl aluminum phosphinate) added compared to Experimental Example 1, and the flame retardant performance has a certain decrease. Comparative Experimental Example 1 does not use flame-retardant modified glass fiber (GF-NH2-FR), but uses ordinary glass fiber that has not been surface-modified. Compared with Comparative Experimental Example 1, Experimental Example 2 is similar in flame retardant performance indicators (flame retardancy UL 94), but the amount of flame retardants (melamine polyphosphate and diethyl aluminum phosphinate) added in Experimental Example 2 is less. When the amount of flame retardant added is less, Experimental Example 2 can maintain a certain flame retardant effect, which shows that the flame retardant modified glass fiber (GF-NH2-FR) of this scheme has the function of increasing the flame retardant effect of polypropylene composite materials, and a smaller amount of flame retardant can be added to the polypropylene composite material to save flame retardant raw materials and reduce the impact of flame retardants on the performance of polypropylene composite materials.

[0100] This scheme adopts the scheme of synthesizing random copolymer (PAPP-co-MPP) by focusing piperazine phosphate PAPP and melamine polyphosphate MPP, and uses this new material to modify the surface of glass fiber. The modified glass fiber is added to the polypropylene composite material to eliminate or inhibit the "candle wick effect" and enhance the flame retardant performance. The glass fiber in comparative experimental example 1 is not modified, the glass fiber in comparative experimental example 3 is only modified by amino group, the glass fiber in comparative experimental example 4 is modified by PAPP, and the glass fiber in comparative experimental example 5 is modified by MPP. The flame retardant properties of these polypropylene composite materials are not ideal, and there is a relatively large gap between the composite material synthesized in experimental example 1. In addition, the inventor also tried to use PAPP and MPP for the modification of glass fiber at the same time, but did not synthesize PAPP-co-MPP (Comparative Experimental Example 6), and found that this operation mode has little effect on improving the flame retardant effect of the composite material (comparable to the flame retardant properties of the composite materials of comparative experimental examples 4 and comparative experimental examples 5). From the flame retardant test results of Comparative Experimental Example 1, Comparative Experimental Example 4, and Comparative Experimental Example 5, it can be seen that the combined modification of glass fiber with PAPP and MPP can effectively improve the flame retardant properties of the composite material and produce a certain synergistic effect. Moreover, this combined use must be achieved in the form of a synthetic random copolymer in order to achieve an effective and significant improvement in the flame retardant effect.

[0101] In addition, based on comparative experimental example 4, the inventors also made the following attempts: focused piperazine phosphate (PAPP) was not directly used for compounding with amino-modified glass fiber, but the PAPP obtained in comparative experimental example 4 was placed in a 0.2MPa nitrogen atmosphere and heat-treated at 270°C for 180min (the same condition as that of obtaining PAPP-co-MPP by thermal polymerization). Under this condition, PAPP spontaneously copolymerized to a certain extent to form heat-treated PAPP. The heat-treated PAPP was replaced with PAPP-co-MPP in equal amounts to prepare a heat-treated PAPP-modified GF, and then a flame-retardant reinforced polypropylene composite material was prepared according to the method of comparative experimental example 4. The flame retardant properties of the composite material were tested, and the flame retardancy UL 94 (3.2mm) was V-0, and the flame retardancy UL 94 (1.6mm) was V-1. It can be seen that even if PAPP is heat-treated, it is difficult to effectively improve the flame retardant properties of the composite material as a whole, which is consistent with the flame retardant material properties of comparative experimental example 4.

[0102] The inventors also tried that on the basis of comparative experimental example 5, melamine polyphosphate (MPP) was not directly used for compounding with amino-modified glass fiber, but the MPP obtained in comparative experimental example 5 was placed in a 0.2MPa nitrogen atmosphere and heat treated at 270°C for 180min (the same condition as the thermal polymerization to obtain PAPP-co-MPP). Under this condition, MPP spontaneously copolymerized to a certain extent to form a heat-treated MPP. The heat-treated MPP was replaced with PAPP-co-MPP in equal amounts to prepare a heat-treated MPP-modified GF, and then a flame-retardant reinforced polypropylene composite material was prepared according to the method of comparative experimental example 5. The flame retardant properties of the composite material were tested, and the flame retardancy UL 94 (3.2mm) was V-0, and the flame retardancy UL 94 (1.6mm) was V-2. It can be seen that even if the MPP is heat-treated, it is difficult to effectively improve the flame retardant properties of the composite material as a whole, which is consistent with the flame retardant material performance of comparative experimental example 5.

[0103] It can be seen that only by adopting the method of this scheme to thermally polymerize MPP and PAPP to form a random copolymer can the synergistic effect of MPP and PAPP on the flame retardant effect be achieved. Although MPP and PAPP can form their own copolymers by heat treatment alone, the improvement effect on the flame retardant properties of the composite material is limited because MPP and PAPP cannot coexist.

[0104] Oxygen index (LOI) refers to the minimum oxygen concentration required for a material to burn with a flame in an oxygen-nitrogen mixed gas flow under specified conditions. It is expressed as a numerical value of the volume percentage occupied by oxygen. A high oxygen index indicates that the material is not easy to burn, and a low oxygen index indicates that the material is easy to burn. Comparing the experimental data of Example 1, Comparative Experimental Example 1, Comparative Experimental Example 4, Comparative Experimental Example 5 and Comparative Experimental Example 6, a synergistic effect can be clearly observed in the oxygen index (LOI) index. Adding PAPP-co-MPP surface modification, the gain effect of the oxygen index is: 32.2-27.3=4.9 (Example 1-Comparative Experimental Example 1); adding PAPP surface modification, the gain effect of the oxygen index is: 28.9-27.3=1.6 (Comparative Experimental Example 4-Comparative Experimental Example 1); adding MPP surface modification, the gain effect of the oxygen index is: 28.4-27.3=1.1 (Comparative Experimental Example 5-Comparative Experimental Example 1). It can be seen that the oxygen index gain effect (4.9) brought about by the addition of PAPP-co-MPP surface modification is greater than the sum of the oxygen index gain effect brought about by the surface modification of PAPP alone and the oxygen index gain effect brought about by the surface modification of MPP alone (1.6+1.1=2.7). PAPP and MPP produce a synergistic effect of improving the flame retardancy of the composite material in the form of a random copolymer. If PAPP and MPP do not form a random copolymer, the synergistic effect of PAPP and MPP cannot occur.

[0105] The polypropylene composite material of Experimental Example 1 has significantly improved mechanical properties compared to Comparative Experimental Example 1. Although the glass fiber can be improved to varying degrees by amino modification (Comparative Experimental Example 3), PAPP modification (Comparative Experimental Example 4), MPP modification (Comparative Experimental Example 5), and PAPP and MPP combined modification (without random copolymer synthesis, Comparative Experimental Example 6) (when the glass fiber is not used in Comparative Experimental Example 1), the mechanical property improvement effect after the glass fiber is modified with random copolymer (Experimental Example 1) is more significant. It can be seen that after the surface of the glass fiber is modified with PAPP-co-MPP having a certain molecular chain, the compatibility of the glass fiber and polypropylene can be improved, which plays a bridge and anchoring role between the glass fiber and other flame retardants / polypropylene, thereby improving the mechanical properties of its flame retardant reinforced polypropylene composite material.

[0106] In addition, Comparative Experiment 7 used unmodified glass fiber and did not add any flame retardant. Compared with Comparative Experiment 1 (using unmodified glass fiber but adding flame retardant), it shows that the piperazine pyrophosphate and melamine polyphosphate flame retardants prepared in this scheme have a certain flame retardant effect, but in the case where the glass fiber is not modified with PAPP-co-MPP, the amount of flame retardant added in Comparative Experiment 1 is not enough to improve the flame retardant effect of the composite material to an ideal level.

[0107] The above is only an embodiment of the present invention, and the common knowledge such as the known specific technical solutions and / or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several modifications and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A flame retardant reinforced polypropylene composite material containing flame retardant modified glass fiber, characterized in that: The invention comprises the following raw materials in parts by weight: 30-60 parts of polypropylene, 5-60 parts of flame retardant modified glass fiber, 5-20 parts of piperazine pyrophosphate, 5-20 parts of melamine polyphosphate, 0.5-5 parts of flame retardant synergist, 1-6 parts of maleic anhydride grafted polypropylene, 0.5-3 parts of coupling agent, 0.3-3 parts of lubricant and 0.2-0.5 parts of antioxidant. The flame retardant modified glass fiber is a glass fiber surface-modified with a focused piperazine phosphate-melamine polyphosphate random copolymer, and the structural formula of the focused piperazine phosphate-melamine polyphosphate random copolymer is shown in formula (10); Wherein, 500<m<10000, 500<n<10000, x>0, y>0, p>0; in formula (10), MPP represents formula (8), PAPP represents formula (1), and the mass ratio of PAPP to MPP is 1:0.2-5.

2. The flame retardant reinforced polypropylene composite material containing flame retardant modified glass fiber according to claim 1, characterized in that: The pyrophosphate piperazine is prepared by the following method: diphosphate piperazine is heat treated for 30-240 minutes under a nitrogen atmosphere, a pressure environment of 0.05-0.3 MPa, and a condition of 120-320° C., and thermally polymerized and dehydrated to condense into pyrophosphate piperazine.

3. The flame retardant reinforced polypropylene composite material containing flame retardant modified glass fiber according to claim 1, characterized in that: The melamine polyphosphate is prepared by the following method: melamine phosphate is heat-treated for 60-300 minutes under a nitrogen atmosphere, a pressure environment of 0.05-0.3 MPa, and a temperature of 220-360° C. to thermally polymerize and dehydrate to condense into melamine polyphosphate.

4. The flame retardant reinforced polypropylene composite material containing flame retardant modified glass fiber according to claim 1, characterized in that: The polypropylene has a melt index of any one or a mixture of melt index>0g / 10min and <100g / 10min under the conditions of temperature 230°C and load 2.16kg; the 1% thermal weight loss of melamine polyphosphate is ≥360°C; the flame retardant synergist includes at least one of anhydrous zinc borate, 3.5-water zinc borate, zinc oxide, and zirconium phosphate; the coupling agent is a silane coupling agent, including at least one of KH-9120, KT-930, KH-1006 and KH-9130; the lubricant includes at least one of white oil, silicone oil, polyethylene wax, ethylene bis stearamide, pentaerythritol stearate, silicone and amide wax; the antioxidant includes at least one of antioxidant 168, antioxidant 1010 and antioxidant 1098.

5. A method for preparing a flame retardant reinforced polypropylene composite material containing flame retardant modified glass fiber according to any one of claims 1 to 4, characterized in that: The method includes the following steps in sequence: S1: focusing piperazine phosphate and melamine polyphosphate are subjected to thermal polymerization and dehydration to obtain a focusing piperazine phosphate-melamine polyphosphate random copolymer; S2: dispersing glass fibers in an alcohol solution, adding an amino coupling agent under stirring conditions, washing and drying after activation reaction, and obtaining amino glass fibers; S3: The amino-modified glass fiber is dispersed in an organic solvent, and the focused piperazine phosphate-melamine polyphosphate random copolymer is added. After the reaction, the flame-retardant modified glass fiber is obtained by washing and drying. S4: Using polypropylene, flame retardant modified glass fiber, piperazine pyrophosphate, melamine polyphosphate, flame retardant synergist, maleic anhydride ester polypropylene, coupling agent, lubricant and antioxidant as raw materials, after extrusion through a twin-screw extruder, drawing, pelletizing and screening and dehydration, flame retardant reinforced polypropylene composite material particles containing flame retardant modified glass fiber are obtained.

6. The method for preparing a flame retardant reinforced polypropylene composite material containing flame retardant modified glass fiber according to claim 5, characterized in that: In S1, focusing piperazine phosphate and melamine polyphosphate in a mass ratio of 1:0.2-5, under reaction conditions of 200-280° C., 0.1-1.5 MPa, in a nitrogen atmosphere, after 30-180 min of reaction, thermal polymerization and dehydration are performed to obtain a focusing piperazine phosphate-melamine polyphosphate random copolymer; Preferably, the focused piperazine phosphate and melamine polyphosphate are reacted in a mass ratio of 1:0.6 at 270° C., 0.2 MPa, in a nitrogen atmosphere, for 180 min, and thermally polymerized and dehydrated to obtain a focused piperazine phosphate-melamine polyphosphate random copolymer.

7. The method for preparing a flame retardant reinforced polypropylene composite material containing flame retardant modified glass fiber according to claim 5, characterized in that: In S2, the alcohol solution is ethanol solution; the usage ratio of glass fiber to alcohol solution is 100g:250-750ml; the usage of amino coupling agent is 1-5% of the mass of glass fiber; the activation reaction condition is 60-100°C for 4-8h.

8. The method for preparing a flame retardant reinforced polypropylene composite material containing flame retardant modified glass fiber according to claim 5, characterized in that: In S3, the organic solvent includes any one of ethanol, water, DMF, DMSO, acetonitrile and an aqueous solution of ethanol; and the usage ratio of the amino glass fiber to the organic solvent is 80-160 g: 200-1000 mL.

9. The method for preparing a flame retardant reinforced polypropylene composite material containing flame retardant modified glass fiber according to claim 8, characterized in that: In S3, the amount ratio of the piperazine phosphate-melamine polyphosphate random copolymer and the amino glass fiber is 0.1-5g:80-160g; the reaction conditions of the piperazine phosphate-melamine polyphosphate random copolymer and the amino glass fiber are 20-50°C and 2-12h.

10. The method for preparing a flame retardant reinforced polypropylene composite material containing flame retardant modified glass fiber according to claim 5, characterized in that: In S4, piperazine pyrophosphate, melamine polyphosphate and flame retardant synergist are added to a mixer and stirred at room temperature for 5-30 minutes; the temperature of the mixer is increased to 80-160°C, and a coupling agent is added and stirred for 10-30 minutes; after cooling to room temperature, polypropylene, lubricant, nucleating agent and antioxidant are added and stirred for 5-30 minutes to obtain a material mixture; the material mixture is extruded by a twin-screw extruder at an extrusion temperature of 170-250°C, flame retardant modified glass fiber is added through side feeding, and flame retardant reinforced polypropylene granules are obtained after extrusion, drawing, pelletizing and screening dehydration.

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