Foamed polypropylene composite material and preparation method thereof

Abstract

The invention discloses a foamed polypropylene composite material and a preparation method thereof, and belongs to the technical field of foamed materials. The material comprises the following raw materials in parts by weight: 90-110 parts of polypropylene resin, 5-20 parts of multi-effect flame retardant, 0.1-0.3 parts of initiator, and 3-9 parts of antioxidant. The foamed polypropylene composite material prepared by the invention takes polypropylene as a matrix, which gives the material light and heat-resistant properties; the material prepared by supercritical nitrogen microporous foaming technology has better performance; wherein the antioxidant can greatly enhance the antioxidant performance of the material; wherein the various groups in the multi-effect flame retardant molecule play a synergistic role, greatly enhancing the flame retardant and smoke suppression performance of the material and a certain degree of heat resistance, and the performance is long-term and stable; therefore, the foamed polypropylene composite material prepared by the invention has good antioxidant performance, and has stable and efficient flame retardant, smoke suppression and heat resistance, and has important application value in the technical field of foamed materials.

Description

Technical Field

[0001] The invention belongs to the technical field of foaming materials, and in particular relates to a foamed polypropylene composite material and a preparation method thereof. Background Art

[0002] In recent years, with the increasing awareness of environmental protection, the development of low-carbon and environmentally friendly materials has become the mainstream, and the development of automotive materials towards comfort, safety and lightweight has also become an inevitable trend.

[0003] Polypropylene (PP) is a common plastic with excellent heat resistance, corrosion resistance, low cost and light weight. The advantages of PP for foaming materials are also very obvious. Foaming PP usually uses physical or chemical methods to produce microporous structures inside PP, so the density of its products can often reach a lower level, thereby greatly reducing the weight. Foaming PP also has the characteristics of thermal insulation, cushioning, and light weight of foaming materials and the characteristics of anti-corrosion and low price of PP materials. In addition, foamed polypropylene has a high heat deformation temperature, and the maximum use temperature can reach 130°C, which is much higher than the 80°C of polyethylene foaming materials. More importantly, it is easy to recycle and reuse, easy to degrade, and its products do not contain substances harmful to the human body and the environment. It can achieve a significant weight reduction while maintaining high mechanical properties, so it can improve the acceleration performance and safety performance of the car, and can effectively reduce the weight of automotive parts. It has become one of the important materials for lightweighting cars.

[0004] However, polypropylene is a polymer material with a low oxygen index and is easy to burn. It is easier to ignite after being made into a foam material. When it encounters an open flame, it burns rapidly, endangering people's lives and property safety, and posing a major safety hazard. Commonly used flame retardants on the market have poor compatibility with polypropylene matrix, are easy to precipitate, and have unstable performance. Therefore, it is urgent to solve the above problems to meet the higher requirements in the field of foam material technology. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects of the prior art and provide a foamed polypropylene composite material and a preparation method thereof.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A method for preparing a foamed polypropylene composite material comprises the following steps:

[0008] The polypropylene resin, multi-effect flame retardant, initiator and antioxidant are mixed, added to a high-speed mixer and stirred for 3 hours, poured into a twin-screw extruder, melt blended, extruded, added to the barrel of an injection molding machine, and micro-foaming injection molding is performed using supercritical nitrogen to obtain a foamed polypropylene composite material.

[0009] Furthermore, the raw materials are calculated in parts by weight as follows: 90-110 parts of polypropylene resin, 5-20 parts of multi-effect flame retardant, 0.1-0.3 parts of initiator, and 3-9 parts of antioxidant.

[0010] Furthermore, the antioxidant is prepared by compounding antioxidant 1010 and antioxidant 168 in a mass ratio of 2:1.

[0011] Furthermore, the initiator is one of benzoyl peroxide and lauroyl peroxide.

[0012] The use of supercritical nitrogen microporous foaming technology makes the pore size smaller, the pores more numerous, and the distribution more uniform, which improves the performance of the material to a certain extent; polypropylene is used as the matrix, giving the material light weight and heat resistance; the added antioxidants are hindered phenol antioxidants and phosphite auxiliary antioxidants, the two can play a synergistic role and greatly enhance the material's antioxidant properties.

[0013] Furthermore, the multi-effect flame retardant is prepared by the following steps:

[0014] S1. In a three-necked flask equipped with a stirring device, tris(hydroxymethyl)aminomethane hydrochloride, triethylamine and DMF were mixed at room temperature, placed in an ice-water bath at 2°C, and stirred for 50 min. Then, phosphorus oxychloride was slowly added dropwise, and the temperature was controlled not to exceed 20°C during the addition. After the addition was completed, the temperature was raised to 95°C and the reaction was kept warm for 8 h. After the reaction was completed, the solvent was removed by filtration under reduced pressure, and the filter cake was washed three times with anhydrous ethanol, vacuum dried, and ground to obtain intermediate 1; the ratio of tris(hydroxymethyl)aminomethane hydrochloride, triethylamine, DMF, and phosphorus oxychloride was 16.1 g:14.4 g:150 mL:15.3 g;

[0015] Tris(hydroxymethyl)aminomethane hydrochloride reacts with phosphorus oxychloride to obtain intermediate 1; the specific reaction process is as follows:

[0016] ;

[0017] S2, the intermediate 1 and toluene were mixed, added to a three-necked round-bottom flask equipped with a thermometer, a magnetic stirring system and a spherical condenser, and formaldehyde solution (mass fraction 18%) was added dropwise under ice-water bath conditions, and stirring was continued for 30 minutes, and then hydroquinone was added, and the reaction temperature was controlled to 65°C, and the reflux reaction was carried out for 5 hours. After the reaction was completed, it was cooled to room temperature, and the solvent was removed by rotary evaporation, and toluene and deionized water were added to separate the layers, and the upper organic phase was taken, and washed with saturated sodium carbonate, saturated sodium bicarbonate and saturated brine in turn, and vacuum dried to obtain intermediate 2; the ratio of the amount of intermediate 1, toluene, formaldehyde solution and hydroquinone was 16.5g:100mL:20mL:12.1g;

[0018] Intermediate 1, hydroquinone and formaldehyde undergo a Mannich condensation reaction, and hydroquinone is slightly in excess to obtain intermediate 2; the specific reaction process is as follows:

[0019] ;

[0020] S3. In a three-necked flask equipped with a stirring device, add cyanuric chloride, sodium hydroxide, triethylamine and toluene in sequence, stir at room temperature for 15 minutes, add intermediate 2, control the reaction temperature to 50°C, keep the reaction for 3 hours, and complete the reaction. Filter, wash the filtrate with saturated brine 3 times, dry the organic phase with anhydrous magnesium sulfate, and then purify by column chromatography (the eluent is a mixed solvent of benzene / ethyl acetate, the volume ratio of the two is 3:2), and remove the eluent by rotary evaporation to obtain intermediate 3; the ratio of cyanuric chloride, sodium hydroxide, triethylamine, toluene and intermediate 2 is 19.1g:8.1g:30mL:100mL:59.8g;

[0021] Sodium hydroxide reacts with the hydroxyl group on the intermediate 2 to form sodium phenolate with stronger nucleophilicity. Sodium phenolate, as a nucleophilic reagent, attacks the carbon atom connected to the chlorine atom on cyanuric chloride, so that the chlorine atom is replaced, thereby generating an ether bond; by controlling the molar ratio of intermediate 2 to cyanuric chloride to be close to 2:1 and the cyanuric chloride to be slightly excessive, only two chlorine groups on the cyanuric chloride participate in the reaction, and triethylamine removes the hydrogen chloride generated by the reaction to obtain intermediate 3; the structure of intermediate 3 is shown below:

[0022] ;

[0023] S4. In a three-necked flask equipped with a stirring device, the intermediate 3, 3-butene-1-ol and N,N-dimethylformamide (DMF) were mixed and stirred for 10 minutes under ice bath conditions. Then, sodium hydroxide was mixed with distilled water and slowly added to the three-necked flask. The reaction temperature was controlled to be 55°C and the reaction was carried out for 6 hours. After the reaction was completed, the residue was filtered and washed with distilled water and ethanol in turn. After repeating twice, it was purified by column chromatography (the eluent was a mixed solvent of ethyl acetate / benzene in a volume ratio of 4:3), and the mixture was dried in an oven to obtain a multi-effect flame retardant. The ratio of the amount of the intermediate 3, 3-butene-1-ol, N,N-dimethylformamide, sodium hydroxide and distilled water was 70.9g:7.2g:150mL:4.1g:30mL.

[0024] Sodium hydroxide reacts with the hydroxyl group on the intermediate 3 to form sodium phenol, which then undergoes nucleophilic substitution with 3-butene-1-ol to obtain a multi-effect flame retardant. The structure of the multi-effect flame retardant is shown below:

[0025] ;

[0026] The prepared multi-effect flame retardant molecules contain caged phosphonate, triazine, benzoxazine and carbon-carbon double bond structures, among which the caged phosphonate structure is a green and environmentally friendly flame retardant with strong stability. When burned, it will promote the formation of a carbon layer, inhibit smoke release, and improve the flame retardant and smoke suppression properties of the polypropylene matrix. In addition, the introduced triazine structure will produce nitrogen-containing gas when burned, which dilutes and reduces the smoke density, and self-condenses at high temperature to form melem to make the carbon layer tight, which can play a synergistic role with the caged phosphonate to greatly enhance the flame retardant and smoke suppression properties of the matrix. In addition, the introduced benzoxazine can enhance the heat resistance of the matrix. Finally, the introduced carbon-carbon double bond can cross-link with the polypropylene matrix, which can significantly enhance the migration resistance and exudation resistance of the multi-effect flame retardant, so that the multi-effect flame retardant can perform its performance stably for a long time.

[0027] Beneficial effects of the present invention:

[0028] 1. The foamed polypropylene composite material prepared by the present invention uses polypropylene as a matrix, which gives the material light weight and heat resistance;

[0029] 2. The material produced by supercritical nitrogen microporous foaming technology has better performance;

[0030] 3. The added antioxidants are hindered phenol antioxidants and phosphite auxiliary antioxidants, which can play a synergistic role and greatly enhance the antioxidant properties of the material;

[0031] 4. The various groups in the prepared multi-effect flame retardant molecules work synergistically, greatly enhancing the flame retardant and smoke suppression properties of the material and a certain degree of heat resistance, and the performance is long-lasting and stable;

[0032] Therefore, the foamed polypropylene composite material prepared by the present invention has good antioxidant properties, and has stable and efficient flame retardant, smoke suppression and heat resistance properties, and has important application value in the field of foaming material technology. DETAILED DESCRIPTION

[0033] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] Embodiment 1

[0035] Preparation of multi-effect flame retardant:

[0036] S1. In a three-necked flask equipped with a stirring device, 16.1 g of tris(hydroxymethyl)aminomethane hydrochloride, 14.4 g of triethylamine and 150 mL of DMF were mixed at room temperature, placed in an ice-water bath at 2°C, and stirred for 50 min. Then, 15.3 g of phosphorus oxychloride was slowly added dropwise, and the temperature was controlled not to exceed 20°C during the addition. After the addition was completed, the temperature was raised to 95°C and kept for reaction for 8 h. After the reaction was completed, the solvent was removed by filtration under reduced pressure, and the filter cake was washed three times with anhydrous ethanol, dried in vacuo, and ground to obtain intermediate 1.

[0037] S2, 16.5g of intermediate 1 and 100mL of toluene were mixed, and added to a three-necked round-bottom flask equipped with a thermometer, a magnetic stirring system and a spherical condenser. Under an ice-water bath, 20mL of formaldehyde solution was added dropwise, and stirring was continued for 30min, and then 12.1g of hydroquinone was added. The reaction temperature was controlled to 65°C, and the reaction was refluxed for 5h. After the reaction was completed, the mixture was cooled to room temperature, and the solvent was removed by rotary evaporation. Toluene and deionized water were added to separate the layers, and the upper organic phase was taken, and washed with saturated sodium carbonate, saturated sodium bicarbonate and saturated brine in sequence, and dried in vacuo to obtain intermediate 2;

[0038] S3, in a three-necked flask equipped with a stirring device, 19.1g of cyanuric chloride, 8.1g of sodium hydroxide, 30mL of triethylamine and 100mL of toluene were added in sequence, and the mixture was stirred at room temperature for 15min, and then 59.8g of intermediate 2 was added, and the reaction temperature was controlled to 50°C, and the reaction was kept warm for 3h. After the reaction was completed, the mixture was filtered, and the filtrate was washed 3 times with saturated brine, and the organic phase was dried over anhydrous magnesium sulfate, and then purified by column chromatography (the eluent was a mixed solvent of benzene / ethyl acetate, and the volume ratio of the two was 3:2), and the eluent was removed by rotary evaporation to obtain intermediate 3;

[0039] S4. In a three-necked flask equipped with a stirring device, mix 70.9 g of intermediate 3, 7.2 g of 3-butene-1-ol and 150 mL of N,N-dimethylformamide, and stir in an ice bath for 10 min. Then, mix 4.1 g of sodium hydroxide with 30 mL of distilled water, and slowly add them to the three-necked flask. Control the reaction temperature to 55 ° C. React for 6 hours. After the reaction is completed, filter, wash the filter residue with distilled water and ethanol in turn, repeat twice, and then purify by column chromatography (the eluent is a mixed solvent of ethyl acetate / benzene, and the volume ratio of the two is 4:3), put it in an oven for drying, and obtain a multi-effect flame retardant.

[0040] Embodiment 2

[0041] 90 g of polypropylene resin, 5 g of the multi-effect flame retardant prepared in Example 1, 0.1 g of benzoyl peroxide and 3 g of antioxidant (prepared by compounding 2 g of antioxidant 1010 and 1 g of antioxidant 168) were mixed, added to a high-speed mixer and stirred for 3 h, poured into a twin-screw extruder, melt blended, extruded, added to the barrel of an injection molding machine, and micro-foaming injection molding was performed using supercritical nitrogen to obtain a foamed polypropylene composite material.

[0042] Embodiment 3

[0043] 100 g of polypropylene resin, 12.5 g of the multi-effect flame retardant prepared in Example 1, 0.2 g of lauroyl peroxide and 6 g of antioxidant (prepared by compounding 4 g of antioxidant 1010 and 2 g of antioxidant 168) were mixed, added to a high-speed mixer and stirred for 3 h, poured into a twin-screw extruder, melt blended, extruded, added to the barrel of an injection molding machine, and micro-foaming injection molding was performed using supercritical nitrogen to obtain a foamed polypropylene composite material.

[0044] Embodiment 4

[0045] 110 g of polypropylene resin, 20 g of the multi-effect flame retardant prepared in Example 1, 0.3 g of lauroyl peroxide and 9 g of antioxidant (prepared by compounding 6 g of antioxidant 1010 and 3 g of antioxidant 168) were mixed, added to a high-speed mixer and stirred for 3 hours, poured into a twin-screw extruder, melt blended, extruded, added to the barrel of an injection molding machine, and micro-foaming injection molding was performed using supercritical nitrogen to obtain a foamed polypropylene composite material.

[0046] Comparative Example 1

[0047] A commercially available flame retardant BPDP (produced by Guangzhou Shanghe Chemical Technology Co., Ltd.) of equal quality was used to replace the multi-effect flame retardant in Example 5, and the remaining steps were the same as in Example 5 to obtain a composite material.

[0048] Comparative Example 2

[0049] A commercially available foamed polypropylene material was used.

[0050] Embodiments 2, 3, 4, and comparative examples 1 and 2 were made into corresponding shapes according to different test standards, and the following performance tests were performed:

[0051] The notched impact strength was determined using the national standard GB / T 1843-2008 "Determination of Izod Impact Strength of Plastics" and the notched impact strength was determined before and after the sample was placed in an environment of 180°C and hot air oxidized for 72 hours.

[0052] The smoke density is measured using the national standard GB / T 8323.2-2008 "Plastic smoke generation Part 2: Single chamber method for determination of smoke density test method";

[0053] The national standard GB / T 2406-2008 "Test method for combustion performance of plastics" is used to determine the limiting oxygen index;

[0054] After the sample is placed at room temperature for 180 days, the smoke density and limiting oxygen index of the sample are measured using the same standard;

[0055] The measured results are shown in the following table:

[0056] ;

[0057] It can be seen from the above table that the flame retardancy, smoke suppression and heat resistance of the foamed polypropylene composite material prepared in the embodiment of the present invention are higher than those of the comparative example, and the performance is long-lasting and stable, which has important application value in the field of foaming material technology.

[0058] In the description of the specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0059] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A method for preparing a foamed polypropylene composite material, characterized in that: The following steps are involved: The polypropylene resin, multi-effect flame retardant, initiator and antioxidant are mixed, added into a high-speed mixer for stirring, poured into a twin-screw extruder, melt blended, extruded, added into the barrel of an injection molding machine, and micro-foaming injection molding is performed using supercritical nitrogen to obtain a foamed polypropylene composite material; Wherein, the multi-effect flame retardant is prepared by the following steps: S1. Mix tris(hydroxymethyl)aminomethane hydrochloride, triethylamine and DMF, place in an ice-water bath at 2°C, stir thoroughly for 50 min, then add phosphorus oxychloride dropwise until the addition is complete, react at 95°C for 8 h, and after the reaction is complete, filter under reduced pressure, wash, vacuum dry, and grind to obtain intermediate 1; the ratio of tris(hydroxymethyl)aminomethane hydrochloride, triethylamine, DMF, and phosphorus oxychloride is 16.1 g:14.4 g:150 mL:15.3 g; S2, the intermediate 1 and toluene were mixed, and formaldehyde solution was added dropwise under ice water bath condition, and the mixture was stirred for 30 min, and then hydroquinone was added, and the mixture was reacted at 65°C for 5 h. After the reaction was completed, the mixture was cooled to room temperature, and the mixture was evaporated by rotary evaporation. Toluene and deionized water were added to separate the layers, and the upper organic phase was taken, washed, and vacuum dried to obtain the intermediate 2; the ratio of the amount of the intermediate 1, toluene, formaldehyde solution, and hydroquinone was 16.5 g: 100 mL: 20 mL: 12.1 g; S3, cyanuric chloride, sodium hydroxide, triethylamine and toluene were mixed, stirred at room temperature for 15 min, intermediate 2 was added, and the mixture was reacted at 50°C for 3 h. After the reaction was completed, the mixture was filtered, dried, purified by column chromatography, and rotary evaporated to obtain intermediate 3; the ratio of cyanuric chloride, sodium hydroxide, triethylamine, toluene and intermediate 2 was 19.1 g: 8.1 g: 30 mL: 100 mL: 59.8 g; S4. In a three-necked flask, mix the intermediate 3, 3-butene-1-ol and N,N-dimethylformamide, stir in an ice bath for 10 minutes, then mix sodium hydroxide and distilled water, add them to the three-necked flask, and react at 55°C for 6 hours. After the reaction is completed, filter and wash, repeat twice, and purify by column chromatography to obtain a multi-effect flame retardant; the dosage ratio of the intermediate 3, 3-butene-1-ol, N,N-dimethylformamide, sodium hydroxide, and distilled water is 70.9g:7.2g:150mL:4.1g:30mL.

2. The method for preparing the foamed polypropylene composite material according to claim 1, characterized in that: The raw materials are calculated in parts by weight as follows: 90-110 parts of polypropylene resin, 5-20 parts of multi-effect flame retardant, 0.1-0.3 parts of initiator, and 3-9 parts of antioxidant.

3. The method for preparing the foamed polypropylene composite material according to claim 1, characterized in that: The antioxidant is prepared by compounding antioxidant 1010 and antioxidant 168 in a mass ratio of 2:

1.

4. A foamed polypropylene composite material, characterized in that: Prepared according to the method according to any one of claims 1 to 3.