Intumescent flame-retardant polypropylene material and preparation method thereof

Abstract

The invention provides an intumescent flame-retardant polypropylene material. The intumescent flame-retardant polypropylene material comprises the following materials in parts by weight: 60-80 parts of polypropylene resin, 6-10 parts of ammonium polyphosphate, 2-8 parts of a charring foaming agent, 2-6 parts of a synergist, 1-2 parts of a vulcanizing agent, 0.1-1 part of an antioxidant and 0.1-1 part of a lubricant, wherein the synergist comprises a 4A molecular sieve core-shell material and boron-doped titanium dioxide powder in a weight ratio of 1: (1-4); the preparation method of the boron-doped titanium dioxide comprises the following steps: dissolving 5-20 g of boric acid in 60-80 mL of absolute ethyl alcohol, adding a hydrochloric acid solution into the mixed solution, uniformly stirring, slowly dropwise adding 15-25 mL of butyl titanate into the solution, continuously stirring, adding 5-12 mL of distilled water until a sol state appears, and drying to obtain the boron-doped titanium dioxide. And naturally aging at room temperature, drying, and grinding to obtain the boron-doped titanium dioxide powder. According to the intumescent flame-retardant polypropylene material provided by the invention, the mixed material of the 4A molecular sieve core-shell material and the boron-doped titanium dioxide powder is used as the flame-retardant synergist, so that the flame-retardant property of the polypropylene material can be effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of flame retardant materials, and in particular to an expanded flame retardant polypropylene material and a preparation method thereof. Background Art

[0002] Polypropylene is a thermoplastic synthetic resin with excellent performance. It is one of the five general-purpose resins. It has excellent characteristics such as low price, light weight, easy processing, and strong chemical resistance. It is widely used in chemical, electrical, packaging and other industrial fields. In some application fields, it has replaced or partially replaced engineering plastics. It is one of the most promising plastic varieties under the trend of general plastic engineering. In recent years, the continuous development of production technology and the continuous expansion of application fields have further promoted the rapid development of the world's polypropylene industry. According to data, the world's demand for polypropylene in 2007 was 47 million tons, and China's was 9.6 million tons. By 2020, the world's demand for polyethylene is expected to increase by more than 1 times, reaching about 100 million tons, with an average annual growth rate of 5-7%. China's growth rate will be faster, with an annual growth rate of about 8-10%.

[0003] Polypropylene is a general-purpose thermoplastic resin, which is widely used in various aspects of production and life because of its excellent comprehensive properties. However, polypropylene is a flammable material, which greatly limits its further application. Intumescent flame retardants have the advantages of low smoke, non-toxicity, no corrosive gas, and reusability. Therefore, new intumescent flame retardant systems are constantly being developed for the flame retardancy of polypropylene, becoming a hot spot in the research and application of polypropylene flame retardants.

[0004] In terms of the variety and sales of flame retardants, halogen flame retardants, especially Australian flame retardants, still occupy a pivotal position in the flame retardant system. Halogen flame retardants have good flame retardant effects. Its flame retardant mechanism is also relatively clear. As a commodity, it has a history of many years, but while it is flame retardant, it also brings some serious problems. It releases a large amount of toxic gases such as, etc., and hydrogen halide gas easily absorbs moisture in the air to form hydrohalic acid, which has a strong corrosive effect, causing secondary public hazards, generating a large amount of smoke, and is also seriously corrosive to processing equipment. Among the people who died in fire accidents in the world, the above are because the smoke and toxic gases emitted when the materials burn make people suffocate to death, not open flames. These smoke, toxic gases and corrosive gases bring great difficulties to fire extinguishing, escape and recovery work. In addition, more seriously, in the last century, it was found that the combustion products of halogen-containing flame retardants contain carcinogens such as dihydrogen phosphate, so the use of halogen-containing flame retardants has caused widespread controversy and concern worldwide. As people pay more and more attention to their own health and environmental protection, the current campaign to discard halogen-containing flame retardants is being carried out intensively around the world, especially in Europe. The promulgation of two directives published by the European Union in 2017, the Waste Electrical and Electronic Equipment Directive and the Directive on the Restriction of Hazardous Substances in Electrical and Electronic Equipment, further accelerated this process. The directives clearly stipulate that electronic and electrical products placed on the EU market after January 2017 shall not contain six types of hazardous substances. Two of them are odorous flame retardants. Although other types of halogen-containing flame retardants have not been banned for the time being, their future is also precarious. In view of the above situation, this application proposes an intumescent flame-retardant polypropylene material. Summary of the invention

[0005] The purpose of the present invention is to provide an expanded flame-retardant polypropylene material and a preparation method thereof. The prepared expanded flame-retardant polypropylene material has excellent flame-retardant properties.

[0006] The present invention adopts the following technical solutions to solve the above technical problems: An expanded flame-retardant polypropylene material, characterized in that it comprises the following materials in parts by weight: 60-80 parts of polypropylene resin, 6-10 parts of ammonium polyphosphate, 2-8 parts of carbon-forming foaming agent, 2-6 parts of synergist, 1-2 parts of vulcanizing agent, 0.1-1 parts of antioxidant, and 0.1-1 parts of lubricant; The synergist comprises a 4A molecular sieve core-shell material and a boron-doped titanium dioxide powder in a weight ratio of 1:1-4; the preparation method of the boron-doped titanium dioxide comprises: taking 5-20g of boric acid and dissolving it in 60-80mL of anhydrous ethanol, adding a hydrochloric acid solution to the mixed solution and stirring evenly, then slowly dripping 15-25mL of butyl titanate into the solution, continuing to stir and then adding 5-12mL of distilled water until a sol appears, and naturally aging, drying, and grinding at room temperature to obtain the boron-doped titanium dioxide powder.

[0007] Furthermore, the preparation method of the 4A molecular sieve core-shell material includes: modifying NiO using a polyelectrolyte solution, washing the polyelectrolyte solution remaining on the surface with deionized water after modification, placing the modified NiO in a 4A molecular sieve solution prepared using kaolin, standing for 20-40 hours, and obtaining a 4A molecular sieve core-shell material after centrifugation and washing.

[0008] Furthermore, the method for modifying NiO using a polyelectrolyte solution is: prepare a 0.1-1 mol / L sodium chloride solution, add a positive polyelectrolyte PDDA and a negative polyelectrolyte PSS to prepare a solution with a concentration of 0.5-1 wt%, and disperse NiO in the polyelectrolyte solution for 30-60 minutes.

[0009] Furthermore, the specific steps of preparing the 4A molecular sieve solution using kaolin include: calcining kaolin at 400-600°C and then soaking it in a sodium hydroxide solution with a concentration of 0.5-1 mol / L, heating it to 60-70°C and gelling it under stirring, and after gelling for 30-40 minutes, heating it to 100-120°C and crystallizing it for 4-5 hours, and obtaining a 4A molecular sieve solution after crystallization.

[0010] Furthermore, the amount of hydrochloric acid added is 2-5 mL, and the concentration is 1-2 mol / L.

[0011] Furthermore, the drying temperature is 40-80°C.

[0012] Furthermore, the structural formula of the carbon-forming foaming agent is .

[0013] Furthermore, the vulcanizing agent is sulfur.

[0014] The preparation method of the expanded flame-retardant polypropylene material comprises the following steps: weighing materials in proportion, mixing the materials evenly, feeding the mixed materials into a twin-screw extruder, melting and blending and extruding, and obtaining the expanded flame-retardant polypropylene material after cooling.

[0015] The advantages of the present invention are: (1) The present invention uses 4A molecular sieve core-shell material and boron-doped titanium dioxide powder in a weight ratio of 1:1-4 as synergists to effectively improve the flame retardant properties of polypropylene materials; (2) The electron-deficient property of B can change the electron density in the energy band of TiO2 crystal, thus enhancing its surface acidity and adsorbing OH - The number increases, which enables TiO2 to better achieve flame retardant synergy after B doping. In addition, TiO2 material is also a commonly used whitening agent. After adding, it makes the material white and beautiful, further expanding its application range; (3) A core-shell material is prepared by wrapping NiO with 4A molecular sieve crystals. The specific surface area of ​​the outer layer of 4A molecular sieve material is increased. This core-shell material is generally used in the fields of alcohol-ammonia separation and organic carbonate synthesis. In the present invention, it is used as a flame retardant synergist with excellent effect and can better improve the flame retardant effect. This has not been reported in existing literature. DETAILED DESCRIPTION

[0016] The present invention will be further described below in conjunction with specific implementation modes. The following examples are intended to illustrate the present invention rather than to further limit the present invention.

[0017] Example 1

[0018] This embodiment provides an expanded flame-retardant polypropylene material, and the specific preparation method is as follows: (1) Prepare a 0.5 mol / L sodium chloride solution, add positive polyelectrolyte PDDA and negative polyelectrolyte PSS to prepare a solution with a concentration of 0.5 wt%, disperse NiO in the polyelectrolyte solution and keep it for 40 min to obtain a polyelectrolyte solution-modified NiO material; (2) After calcining kaolin at 500°C, soaking it in a 1 mol / L sodium hydroxide solution, heating it to 65°C and gelling it under stirring, heating it to 110°C for 30 minutes and crystallizing it for 4 hours, and obtaining a 4A molecular sieve solution after crystallization; (3) Modifying NiO with a polyelectrolyte solution, washing the polyelectrolyte solution remaining on the surface with deionized water, placing the modified NiO in a 4A molecular sieve solution prepared using kaolin, standing for 30 hours, and obtaining a 4A molecular sieve core-shell material after centrifugation and washing; (4) Dissolve 10 g of boric acid in 70 mL of anhydrous ethanol, add 3 mL of 1 mol / L hydrochloric acid solution to the mixed solution and stir evenly, then slowly drop 20 mL of butyl titanate into the solution, continue stirring, and then add 10 mL of distilled water until a sol appears, naturally age at room temperature, dry at 60 ° C, and grind to obtain boron-doped titanium dioxide powder; (5) Weigh the following materials in proportion: 70 parts of polypropylene resin, 8 parts of ammonium polyphosphate, 4 parts of carbon-forming foaming agent, 4 parts of synergist, 2 parts of sulfur, 0.5 parts of antioxidant, and 0.5 parts of lubricant. Mix the materials evenly and feed the mixed materials into a twin-screw extruder for melt blending and extrusion. After cooling, an expanded flame-retardant polypropylene material is obtained; wherein the synergist comprises a 4A molecular sieve core-shell material and a boron-doped titanium dioxide powder in a weight ratio of 1:2; the structural formula of the carbon-forming foaming agent is .

[0019] Example 2

[0020] This embodiment provides an expanded flame-retardant polypropylene material, and the specific preparation method is as follows: (1) Prepare a 1 mol / L sodium chloride solution, add positive polyelectrolyte PDDA and negative polyelectrolyte PSS to prepare a solution with a concentration of 0.8 wt%, disperse NiO in the polyelectrolyte solution and keep it for 50 min to obtain a polyelectrolyte solution-modified NiO material; (2) After calcining kaolin at 500°C, soaking it in a 0.5 mol / L sodium hydroxide solution, heating it to 60°C and gelling it under stirring, heating it to 120°C and crystallizing it for 4 hours after gelling it for 40 minutes, and obtaining a 4A molecular sieve solution after crystallization; (3) Modifying NiO with a polyelectrolyte solution, washing the polyelectrolyte solution remaining on the surface with deionized water, placing the modified NiO in a 4A molecular sieve solution prepared using kaolin, standing for 20 hours, and obtaining a 4A molecular sieve core-shell material after centrifugation and washing; (4) Take 5 g of boric acid and dissolve it in 80 mL of anhydrous ethanol, add 2 mL of 1 mol / L hydrochloric acid solution into the mixed solution and stir evenly, then slowly drop 15 mL of butyl titanate into the solution, continue stirring, and then add 5 mL of distilled water until a sol appears, naturally age at room temperature, dry at 4 ° C, and grind to obtain boron-doped titanium dioxide powder; (5) Weigh the following materials in proportion: 60 parts of polypropylene resin, 10 parts of ammonium polyphosphate, 5 parts of carbon-forming foaming agent, 5 parts of synergist, 1 part of sulfur, 0.1 parts of antioxidant, and 0.1 parts of lubricant. Mix the materials evenly and feed the mixed materials into a twin-screw extruder for melt blending and extrusion. After cooling, an expanded flame-retardant polypropylene material is obtained; wherein the synergist comprises a 4A molecular sieve core-shell material and a boron-doped titanium dioxide powder in a weight ratio of 1:3; the structural formula of the carbon-forming foaming agent is .

[0021] Comparative Example 1 This embodiment provides an expanded flame-retardant polypropylene material, and the specific preparation method is as follows: (1) Prepare a 0.5 mol / L sodium chloride solution, add positive polyelectrolyte PDDA and negative polyelectrolyte PSS to prepare a solution with a concentration of 0.5 wt%, disperse NiO in the polyelectrolyte solution and keep it for 40 min to obtain a polyelectrolyte solution-modified NiO material; (2) After calcining kaolin at 500°C, soaking it in a 1 mol / L sodium hydroxide solution, heating it to 65°C and gelling it under stirring, heating it to 110°C for 30 minutes and crystallizing it for 4 hours, and obtaining a 4A molecular sieve solution after crystallization; (3) Modifying NiO with a polyelectrolyte solution, washing the polyelectrolyte solution remaining on the surface with deionized water, placing the modified NiO in a 4A molecular sieve solution prepared using kaolin, standing for 30 hours, and obtaining a 4A molecular sieve core-shell material after centrifugation and washing; (4) Weigh the following materials in proportion: 70 parts of polypropylene resin, 8 parts of ammonium polyphosphate, 4 parts of carbon-forming foaming agent, 4 parts of synergist, 2 parts of sulfur, 0.5 parts of antioxidant, and 0.5 parts of lubricant. Mix the materials evenly and feed the mixed materials into a twin-screw extruder for melt blending and extrusion. After cooling, an expanded flame-retardant polypropylene material is obtained; wherein the synergist is a 4A molecular sieve core-shell material; and the structural formula of the carbon-forming foaming agent is: .

[0022] Different from Example 1, in Comparative Example 1, only 4A molecular sieve core-shell material is used as a synergist.

[0023] Comparative Example 2 This embodiment provides an expanded flame-retardant polypropylene material, and the specific preparation method is as follows: (1) Dissolve 10 g of boric acid in 70 mL of anhydrous ethanol, add 3 mL of 1 mol / L hydrochloric acid solution to the mixed solution and stir evenly, then slowly drop 20 mL of butyl titanate into the solution, continue stirring, then add 10 mL of distilled water until a sol appears, naturally age at room temperature, dry at 60 ° C, and grind to obtain boron-doped titanium dioxide powder; (2) Weigh the following materials in proportion: 70 parts of polypropylene resin, 8 parts of ammonium polyphosphate, 4 parts of carbon-forming foaming agent, 4 parts of synergist, 2 parts of sulfur, 0.5 parts of antioxidant, and 0.5 parts of lubricant. Mix the materials evenly and feed the mixed materials into a twin-screw extruder for melt blending and extrusion. After cooling, an expanded flame-retardant polypropylene material is obtained. The synergist is boron-doped titanium dioxide powder. The structural formula of the carbon-forming foaming agent is: .

[0024] Different from Example 1, in Comparative Example 2, only boron-doped titanium dioxide powder core-shell material is used as a synergist.

[0025] Test method: The vertical combustion test was conducted using a CZF-3 horizontal vertical combustion tester in accordance with the method of GB4609-84. The sample size was 130.0 mm in length, 13.0 mm in width, and 1.6 mm in thickness.

[0026] Test method: Place the sample vertically, with the upper end of the sample clamped by 6 mm, and the lower end 300 mm away from the horizontally laid medical absorbent cotton. Light a Bunsen burner about 150 mm away from the sample, and adjust the gas to ensure that the Bunsen burner produces a 20 mm high blue flame. Aim the flame at the center of the lower end of the sample 10 mm away from the lower end of the sample, and start timing. Immediately after applying the flame for 10 seconds, record the time the sample has flame burning after the flame is removed. After the flame of the sample goes out, immediately apply the flame for 10 seconds, and record the time the sample has flame burning and flameless burning (bright but no flame) after the flame is removed.

[0027] The flammability of materials is divided into three levels according to UL-94 V0, V1 and V2. The criteria for judging the three levels are as follows: For V0 grade, the total time of flaming after flame application and fire removal for each sample is not more than 10s. The total time of flaming after flame application 10 times and fire removal for each group of 5 samples is not more than 50s. In addition, the flaming or flameless burning of each sample does not spread to the fixture, and the sample will not ignite medical cotton when dripping.

[0028] For grade V1, the total time of flaming after flame application for 2 times and fire removal for each sample is not more than 30s. The total time of flaming after flame application for 10 times and fire removal for each group of 5 samples is not more than 250s. In addition, the flaming or flameless burning of each sample does not spread to the fixture. Each sample will not ignite medical cotton wool when dripping.

[0029] For grade V2, the total time of flaming after flame application for 2 times and fire removal for each sample is not more than 30s. The total time of flaming after flame application for 10 times and fire removal for each group of 5 samples is not more than 250s. There is also the phenomenon of flaming or flameless burning of each sample without spreading to the fixture. However, when samples drip, they will ignite medical cotton wool.

[0030] The average burning time of splines is mentioned many times in the following experimental results. The calculation method is to add up the burning time of 10 ignitions of 5 splines in each group, and then take the average burning time of each spline. If there are splines in individual groups that do not burn out, the burning time of this spline is calculated as 50s.

[0031] Oxygen index refers to the minimum oxygen concentration required for a sample to maintain stable combustion in a mixed flow of oxygen and nitrogen under specified conditions, expressed as the volume percentage of oxygen. The size of LOI indicates the relative combustion difficulty of the material. Due to the simplicity of the method and good data reproducibility, it is widely used. However, the combustion performance information provided by this method is relatively single, and its results cannot be used to assess the fire hazard of the material under actual use conditions.

[0032] The oxygen index test was conducted using a JF-3 oxygen index tester. The oxygen index was determined according to the method of GB / T 2406-1993. The size of the oxygen index specimen was 120 mm long, 6.5 mm wide and 3.0 mm thick.

[0033] The tensile strength was tested by making standard specimens according to GB1040-1992 standard on a RGT-20A electronic universal testing machine at a tensile speed of 20 mm / min.

[0034] The bending strength was tested on a RGT-20A electronic universal testing machine at a speed of 2 mm / min.

[0035] The above tests were performed on the materials prepared in Examples 1-2 and Comparative Examples 1-2, respectively, and the experimental results are summarized in Table 2 below:

[0036]

[0037] Finally, it should be noted that the above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention. Those skilled in the art should understand that the present invention can still be modified or replaced by equivalents. All technical solutions and improvements that do not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. An expanded flame-retardant polypropylene material, characterized in that: The invention comprises the following materials in parts by weight: 60-80 parts of polypropylene resin, 6-10 parts of ammonium polyphosphate, 2-8 parts of carbon-forming foaming agent, 2-6 parts of synergist, 1-2 parts of vulcanizing agent, 0.1-1 parts of antioxidant and 0.1-1 parts of lubricant; The synergist comprises a 4A molecular sieve core-shell material and a boron-doped titanium dioxide powder in a weight ratio of 1:1-4; the preparation method of the boron-doped titanium dioxide comprises: taking 5-20g of boric acid and dissolving it in 60-80mL of anhydrous ethanol, adding a hydrochloric acid solution to the mixed solution and stirring evenly, then slowly dripping 15-25mL of butyl titanate into the solution, continuing to stir and then adding 5-12mL of distilled water until a sol appears, and naturally aging, drying, and grinding at room temperature to obtain the boron-doped titanium dioxide powder.

2. The intumescent flame-retardant polypropylene material according to claim 1, characterized in that: The preparation method of the 4A molecular sieve core-shell material comprises: modifying NiO with a polyelectrolyte solution, washing the polyelectrolyte solution remaining on the surface with deionized water after the modification, placing the modified NiO in a 4A molecular sieve solution prepared by using kaolin, standing for 20-40 hours, and obtaining the 4A molecular sieve core-shell material after centrifugation and washing.

3. The intumescent flame-retardant polypropylene material according to claim 2, characterized in that: The method for modifying NiO using a polyelectrolyte solution is as follows: preparing a 0.1-1 mol / L sodium chloride solution, adding positive polyelectrolyte PDDA and negative polyelectrolyte PSS to prepare a solution with a concentration of 0.5-1 wt%, and dispersing NiO in the polyelectrolyte solution for 30-60 minutes.

4. The intumescent flame-retardant polypropylene material according to claim 2, characterized in that: The specific steps of preparing the 4A molecular sieve solution using kaolin include: calcining kaolin at 400-600° C. and then soaking it in a sodium hydroxide solution with a concentration of 0.5-1 mol / L, heating it to 60-70° C. and gelling it under stirring, and after gelling for 30-40 minutes, heating it to 100-120° C. and crystallizing it for 4-5 hours, and obtaining the 4A molecular sieve solution after crystallization.

5. The intumescent flame-retardant polypropylene material according to claim 1, characterized in that: The amount of hydrochloric acid added is 2-5 mL, and the concentration is 1-2 mol / L.

6. The intumescent flame-retardant polypropylene material according to claim 1, characterized in that: The drying temperature is 40-80°C.

7. The intumescent flame-retardant polypropylene material according to claim 1, characterized in that: The structural formula of the carbon-forming foaming agent is .

8. An intumescent flame-retardant polypropylene material according to claim 1, characterized in that: The vulcanizing agent is sulfur.

9. A method for preparing the expanded flame-retardant polypropylene material according to any one of claims 1 to 8, characterized in that the steps include: The materials are weighed in proportion, mixed evenly, and the mixed materials are fed into a twin-screw extruder for melt blending and extrusion. After cooling, the expanded flame-retardant polypropylene material is obtained.

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