CN114479273A - High-performance polypropylene flame retardant and preparation method thereof - Google Patents
High-performance polypropylene flame retardant and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a high-performance polypropylene flame retardant and a preparation method thereof; the preparation method of the high-performance polypropylene flame retardant comprises the following steps: the starch is mixed with the modified metal oxide powder. The invention takes soluble starch as a substrate, chemically combines components containing nitrogen and phosphorus in the soluble starch, then carries out surface modification treatment on metal oxide, and combines the two to prepare the high-performance polypropylene flame retardant; the preparation process has simple steps and low cost, and simultaneously enhances the compatibility of the flame retardant system and the polypropylene and the water resistance of the polypropylene flame retardant.
Description
Technical Field
The invention belongs to the technical field, and particularly relates to a high-performance polypropylene flame retardant and a preparation method thereof.
Background
Polypropylene, one of the most common general-purpose plastics in today's society, has excellent mechanical properties and processability, and is remarkably excellent in electrical insulation properties, and thus is widely used in electrical and electronic product accessories such as electrical insulation materials, insulation layers and sheaths of wires and cables. In the use process of the electronic and electric products, phenomena such as overheating, short circuit, spark, electric arc and the like sometimes occur. The polypropylene generates a large amount of micromolecular hydrocarbon in the thermal decomposition process, is easy to burn, has a limit oxygen index of only 17 percent, and is accompanied with the phenomena of molten drops and the like in the burning process. Thus the potential fire safety issues of polypropylene in applications are very significant.
At present, the flame retardant mode of polypropylene mainly takes an additive type as a main mode, the flame retardant mode is low in cost and convenient and fast to process, and the type of the adopted flame retardant is not limited greatly. The intumescent flame retardant is a very representative halogen-free flame retardant, is developed rapidly compared with other flame retardants, and has the advantages of low smoke, low toxicity, high flame retardance, high efficiency, good thermal stability and the like, thereby being one of the research hotspots of people. The carbon source, the acid source and the gas source are three parts of the intumescent flame retardant, the carbon source is mainly a multi-light-base carbon-containing compound, such as pentaerythritol and the like, the main function is to provide a char-forming substance, and the quality of the char-forming agent can be evaluated to evaluate the flame retardant quality of the intumescent flame retardant. The acid source is in the form of inorganic acid or inorganic acid salt, such as boric acid, polyphosphoric acid, and the like, and has the function of catalyzing the carbon source to be carbonized into carbon. The gas source is mainly a hinge-containing compound, wherein melamine is common, and the functions are to generate non-combustible gas through thermal decomposition, dilute the combustible gas and oxygen and expand the carbon layer.
The intumescent flame retardant is concerned by people as a halogen-free flame retardant, but some key technical problems still need to be solved. The small molecular components of the intumescent flame retardant system have high polarity, so that the thermal stability and the polymer compatibility of the whole intumescent flame retardant are poor; the components are difficult to uniformly disperse, and the mutual synergistic flame-retardant effect is influenced; the components are easy to separate out, so that the material cannot realize permanent flame retardance, and the insulation, breakdown resistance and other properties of the material are also influenced.
CN 103408837A discloses a composite intumescent flame retardant for polypropylene, which is compounded by the following components in parts by weight: nano montmorillonite modified dipentaerythritol phosphate ester: 20-40 parts; 10-40 parts of ammonium polyphosphate; bisphenol a melamine diphosphate salt: 20-50 parts; flame-retardant synergistic effect: 0-2 parts of the flame retardant, which is a composite intumescent flame retardant for polypropylene with excellent flame retardant property, no halogen, low smoke, low toxicity, anti-dripping and no corrosive gas.
CN 111040293A discloses an intumescent flame-retardant polypropylene and a preparation method thereof. The expanded flame-retardant polypropylene comprises the following components in parts by mass: 70-100 parts of polypropylene, 10-30 parts of intumescent flame retardant, 1-5 parts of modified nano silicon dioxide and 0-0.2 part of antioxidant; the modified nano-silica is nano-silica grafted and modified by triazine derivatives containing phenyl and triazinyl. The preparation method of the expanded flame-retardant polypropylene comprises the following steps: the polypropylene, the intumescent flame retardant, the modified nano silicon dioxide and the antioxidant are mixed according to the proportion, and the mixture is placed in a reactor for melt blending to obtain the flame-retardant polypropylene composite material. The modified nano silicon dioxide composite reinforced expanded flame-retardant polypropylene has excellent flame-retardant performance. However, the intumescent flame retardant in the prior art still has the problems of poor water resistance, large influence on the strength of polypropylene and the like, so that the development of a high-performance flame retardant with small addition amount and small influence on the strength of polypropylene is particularly important.
Disclosure of Invention
In view of the defects of the prior art, the invention provides a high-performance polypropylene flame retardant and a preparation method thereof, wherein the flame retardant is prepared by mixing inorganic metal oxide and modified starch, and the flame retardant has good compatibility and stable water resistance when being added into polypropylene; the flame retardant property is excellent, and the flame retardant grade can reach UL94-V0 at the addition amount of 25 wt.%.
In order to realize the purpose, the invention provides a preparation method of a high-performance polypropylene flame retardant, which comprises the following steps: mixing starch and modified metal oxide powder to obtain the final product.
Preferably, the mass ratio of the starch to the modified metal oxide powder is (20-25): (1-1.5).
The existing intumescent flame retardant is single, and most of the existing intumescent flame retardant uses one or a combination of two or more of carbon-rich polyol, melamine/melamine derivatives, ammonium polyphosphate and metal hydroxide to realize a synergistic flame retardant effect. The inventor finds out through a large number of experiments that generally, the more the types or the qualities of substances in the flame retardant are, the lower the compatibility of the flame retardant and the polypropylene is easily caused, the easier the flame retardant is to migrate out, and the durability of the polypropylene material is reduced. Therefore, the flame retardant is prepared by a one-step synthesis method, the type of the flame retardant is reduced, and the method is probably an effective way for improving the service performance of the polypropylene after the flame retardant is added. Currently, ammonium polyphosphate groups are grafted on some natural substances, such as jute fibers, sisal fibers, coconut shells and walnut shell fibers, and the natural substances have shown better flame retardance. However, the application of these natural substances requires complicated pretreatment, and the addition of these natural substances has a certain influence on the appearance of polypropylene. The inventor finds that the soluble starch has high carbon content and a large number of reactive groups and can be used as a flame retardant. In addition, nitrogen-containing and phosphorus-containing components can be chemically combined with soluble starch through simple reaction to prepare modified starch, so that the efficient intumescent flame retardant is prepared. Not only saves the reaction time and the operation steps, but also reduces the cost.
Preferably, the starch is one of soluble starch or modified starch.
Preferably, the preparation method of the modified starch comprises the following steps: uniformly mixing soluble starch and phytic acid, and carrying out solvothermal reaction for 1-3 h at the temperature of 100-120 ℃; and cooling, adding melamine and glycerol, uniformly mixing, heating to 80-90 ℃, stirring, refluxing, reacting for 2-5 hours, cooling, filtering, collecting insoluble substances, washing, drying and crushing to obtain the modified starch.
Further preferably, the preparation method of the modified starch comprises the following steps:
(1) mixing 25-50 parts of soluble starch and 25-75 parts of phytic acid at 25-30 ℃ under stirring to form a solution I; transferring the solution I to an environment with the temperature of 100-120 ℃, carrying out solvothermal reaction for 1-3 hours, and naturally cooling to 25-30 ℃ to obtain a solution II;
(2) mixing 10-15 parts of melamine, 50-60 parts of glycerol and 20-30 parts of the solution II obtained in the step (1) at 25-30 ℃ under stirring to form a solution III; and heating the solution III to 80-90 ℃, stirring, refluxing, reacting for 2-5 h, naturally cooling to 25-30 ℃, filtering and collecting insoluble substances, washing with water at 80-90 ℃ for three times, drying, and crushing to obtain the modified starch.
The soluble starch is a starch derivative obtained by treating starch with oxidant, acid, glycerol, enzyme or other methods, is white or off-white powder, has no odor and odor, is insoluble in cold water, ethanol and diethyl ether, has no reducing substance, and has stable chemical properties.
Phytic acid, also known as inositolHexaphosphoric acid, cyclohexanehexol hexaphosphoric acid, molecular formula C6H18O24P6The organophosphorus compound is extracted from plant seeds, has strong acidity and strong chelating ability.
Melamine, a triazine nitrogen-containing heterocyclic ring organic compound, is a white monoclinic crystal, is slightly soluble in water, and therefore has low hygroscopicity; the addition of the flame retardant to the flame retardant component can reduce the hygroscopicity and the precipitation of the whole flame retardant, and is one of the additives commonly used for the intumescent flame retardant.
After the modified starch prepared by the invention is added into polypropylene, although the modified starch has a better flame retardant effect, the carbon residue rate is not high after combustion, and a carbon layer is not compact. Metal oxides, metal borides, metal hydroxides, and the like have been confirmed to have a promoting effect on the formation of the combustion char layer. The inventors have screened a large number of types of metal oxides and optimized the performance of the metal oxides, and have found that the metal cobalt oxide has a good accelerating effect on the formation of the carbon layer. Other metal elements are introduced in the preparation process to prepare composite metal oxide, particularly cobalt-nickel bimetallic oxide, which can promote the generation of solid acid in the combustion process. The solid acid can further enhance the carbon deposit of the degradation product and the flame retardance of the polyolefin, and the carbon residue rate is improved more obviously. In addition, the structure regulator is further added into the metal oxide precursor, so that the morphology of the metal oxide is regulated and controlled; the silane coupling agent is added to modify the surface of the cobalt-nickel bimetallic oxide, so that the compatibility of the cobalt-nickel bimetallic oxide is improved. It is noted that the addition of the modified cobalt-nickel bimetallic oxide with the modified starch as a flame retardant to polypropylene also improves the release of carbon monoxide produced by combustion.
Preferably, the preparation method of the modified metal oxide powder comprises the following steps:
s1, uniformly mixing cobalt nitrate hexahydrate, water and urea at 20-30 ℃, carrying out hydrothermal reaction at 160-180 ℃ for 6-8 h, naturally cooling, filtering and collecting insoluble substances, washing and drying to obtain powder; calcining the powder at 500-550 ℃, naturally cooling, crushing and sieving to obtain metal oxide powder;
or uniformly mixing cobalt nitrate hexahydrate, water, benzoic acid and fructose at the temperature of 60-80 ℃, carrying out hydrothermal reaction at the temperature of 160-180 ℃ for 6-8 h, naturally cooling, filtering and collecting insoluble substances, washing and drying to obtain powder; calcining the powder at 500-550 ℃, naturally cooling, crushing and sieving to obtain metal oxide powder;
or uniformly mixing cobalt nitrate hexahydrate, nickel acetate tetrahydrate, water, benzoic acid and fructose at 60-80 ℃, carrying out hydrothermal reaction at 160-180 ℃ for 6-8 h, naturally cooling, filtering and collecting insoluble substances, washing and drying to obtain powder; calcining the powder at 500-550 ℃, naturally cooling, crushing and sieving to obtain metal oxide powder;
s2, ultrasonically dispersing metal oxide powder in xylene, adding 3-aminopropyltriethoxysilane, heating to 60-80 ℃, stirring and refluxing for reaction for 2-5 hours, filtering and collecting insoluble substances, washing, drying, crushing and sieving to obtain modified metal oxide powder.
Further preferably, the preparation method of the modified metal oxide powder comprises the following steps:
s1, mixing 2-3 parts of cobalt nitrate hexahydrate and 50-100 parts of water at 25-30 ℃, stirring for 30-60 min, adding 2-5 parts of urea by weight, and continuously stirring for 10-30 min to obtain a solution; carrying out hydrothermal reaction on the solution at 160-180 ℃ for 6-8 h, naturally cooling to 25-30 ℃, filtering and collecting insoluble substances, washing with absolute ethyl alcohol and water for three times respectively, and drying to obtain powder; calcining the powder at 500-550 ℃, naturally cooling to 25-30 ℃, and crushing and sieving the powder to obtain metal oxide powder;
s2, ultrasonically dispersing 2-5 parts of the metal oxide powder obtained in the step S1 in 100-150 parts by weight of dimethylbenzene at 25-30 ℃, adding 5-10 parts of 3-aminopropyltriethoxysilane, heating to 60-80 ℃, stirring, refluxing, reacting for 2-5 hours, filtering, collecting insoluble substances, washing with acetone for three times, drying, crushing and sieving the powder to obtain the modified metal oxide powder.
Further preferably, the preparation method of the modified metal oxide powder comprises the following steps:
s1, mixing 2-3 parts of cobalt nitrate hexahydrate and 50-100 parts of water at 60-80 ℃, stirring for 30-60 min, adding 1-1.5 parts of benzoic acid and 0.5-1 part of fructose, and continuously stirring for 10-30 min to obtain a solution; carrying out hydrothermal reaction on the solution at 160-180 ℃ for 6-8 h, naturally cooling to 25-30 ℃, filtering and collecting insoluble substances, washing with absolute ethyl alcohol and water for three times respectively, and drying to obtain powder; calcining the powder at 500-550 ℃, naturally cooling to 25-30 ℃, and crushing and sieving the powder to obtain metal oxide powder;
s2, ultrasonically dispersing 2-5 parts of the metal oxide powder obtained in the step S1 in 100-150 parts of dimethylbenzene at 25-30 ℃, adding 5-10 parts of 3-aminopropyltriethoxysilane, heating to 60-80 ℃, stirring, refluxing and reacting for 2-5 hours, filtering to collect insoluble substances, washing with acetone for three times, drying, crushing and sieving the powder to obtain the modified metal oxide powder.
Most preferably, the preparation method of the modified metal oxide powder comprises the following steps:
s1, mixing 1-2.5 parts of cobalt nitrate hexahydrate, 0.5-1 part of nickel acetate tetrahydrate and 50-100 parts of water at 60-80 ℃, stirring for 30-60 min, adding 1-1.5 parts of benzoic acid and 0.5-1 part of fructose, and continuously stirring for 10-30 min to obtain a solution; carrying out hydrothermal reaction on the solution at 160-180 ℃ for 6-8 h, naturally cooling to 25-30 ℃, filtering and collecting insoluble substances, washing with absolute ethyl alcohol and water for three times respectively, and drying to obtain powder; calcining the powder at 500-550 ℃, naturally cooling to 25-30 ℃, and crushing and sieving the powder to obtain metal oxide powder;
s2, ultrasonically dispersing 2-5 parts of metal oxide powder in 100-150 parts of dimethylbenzene at 25-30 ℃, adding 5-10 parts of 3-aminopropyltriethoxysilane, heating to 60-80 ℃, stirring, refluxing, reacting for 2-5 hours, filtering, collecting insoluble substances, washing, drying, crushing and sieving to obtain superfine metal oxide powder, soaking the superfine metal oxide powder in 1-1.2 mol/L ammonium persulfate aqueous solution, standing at room temperature for 10-12 hours, filtering, drying a filter cake, grinding the filter cake into powder, roasting in a muffle furnace, and cooling to obtain the required modified metal oxide powder; the volume mass ratio of the ammonium persulfate aqueous solution to the superfine metal oxide powder is (10-15): 1 mL/g.
The invention also provides a high-performance polypropylene flame retardant prepared by the preparation method.
The invention has the beneficial effects that:
(1) the invention takes soluble starch as a substrate, and can chemically combine nitrogen-containing and phosphorus-containing components in the soluble starch through simple reaction to prepare modified starch, thereby preparing the efficient intumescent flame retardant; the preparation method not only saves reaction time and operation steps, but also can reduce cost, and the preparation method similar to one-pot preparation reduces the types of the flame retardant and enhances the compatibility of a flame retardant system and polypropylene.
(2) According to the invention, the modified metal oxide and the modified starch are compounded to prepare the efficient flame retardant, so that the flame retardant property of the polypropylene is effectively improved, and the release of toxic gas carbon monoxide in the combustion process of the polypropylene is reduced.
(3) The flame retardant disclosed by the invention is good in compatibility with polypropylene, has little influence on the mechanical property of the polypropylene after being added, and is good in water resistance.
Drawings
FIGS. 1A to C are scanning electron micrographs of modified metal oxides according to examples 1 to 3 of the present invention, respectively.
FIGS. 2A-B are scanning electron micrographs of inorganic-washed carbon layers of conical combustion heat tests of examples 5-6, respectively, in accordance with the present invention.
Detailed Description
Example 1
A high-performance polypropylene flame retardant is prepared by mixing 23.5kg of soluble starch and 1.5kg of modified metal oxide powder.
The preparation method of the modified metal oxide powder comprises the following steps:
s1 mixing 3kg of cobalt nitrate hexahydrate and 50kg of water at 25 ℃, stirring at the rotating speed of 400r/min for 30min, adding 5kg of urea, and continuously stirring for 15min to obtain a solution; transferring the solution to a reaction kettle, carrying out hydrothermal reaction at 180 ℃ for 8h, naturally cooling to 25 ℃, filtering and collecting insoluble substances, washing with absolute ethyl alcohol and water for three times respectively, and drying at 80 ℃ for 8h to obtain powder; calcining the powder at 550 ℃ for 2h, naturally cooling to 25 ℃, crushing the powder and sieving to obtain 325-mesh metal oxide powder;
s2 dispersing 5kg of metal oxide powder obtained in step S1 in 100kg of dimethylbenzene at the ultrasonic power of 80W and the frequency of 50kHz for 30min at 25 ℃, adding 10kg of 3-aminopropyltriethoxysilane, heating to 80 ℃, stirring at the rotating speed of 350r/min for reflux reaction for 2h, filtering and collecting insoluble substances, washing with acetone for three times, drying at 80 ℃ for 8h to obtain powder, crushing and sieving the powder to obtain 325-mesh modified metal oxide powder.
Example 2
A high-performance polypropylene flame retardant is prepared by mixing 23.5kg of soluble starch and 1.5kg of modified metal oxide powder.
The preparation method of the modified metal oxide powder comprises the following steps:
s1 mixing 3kg of cobalt nitrate hexahydrate and 50kg of water at 80 ℃, stirring at the rotating speed of 400r/min for 30min, adding 1kg of benzoic acid and 0.5kg of fructose, and continuously stirring for 15min to obtain a solution; transferring the solution to a reaction kettle, carrying out hydrothermal reaction at 180 ℃ for 8h, naturally cooling to 25 ℃, filtering and collecting insoluble substances, washing with absolute ethyl alcohol and water for three times respectively, and drying at 80 ℃ for 8h to obtain powder; calcining the powder at 550 ℃ for 2h, naturally cooling to 25 ℃, crushing the powder and sieving to obtain 325-mesh metal oxide powder;
s2 dispersing 5kg of metal oxide powder obtained in step S1 in 100kg of dimethylbenzene at the ultrasonic power of 80W and the frequency of 50kHz for 30min at 25 ℃, adding 10kg of 3-aminopropyltriethoxysilane, heating to 80 ℃, stirring at the rotating speed of 350r/min for reflux reaction for 2h, filtering and collecting insoluble substances, washing with acetone for three times, drying at 80 ℃ for 8h to obtain powder, crushing and sieving the powder to obtain 325-mesh modified metal oxide powder.
Example 3
A high-performance polypropylene flame retardant is prepared by mixing 23.5kg of soluble starch and 1.5kg of modified metal oxide powder.
The preparation method of the modified metal oxide powder comprises the following steps:
s1 mixing 2kg of cobalt nitrate hexahydrate, 1kg of nickel acetate tetrahydrate and 50kg of water at 80 ℃, stirring at the rotating speed of 400r/min for 30min, adding 1kg of benzoic acid and 0.5kg of fructose, and continuously stirring for 15min to obtain a solution; transferring the solution to a reaction kettle, carrying out hydrothermal reaction at 180 ℃ for 8h, naturally cooling to 25 ℃, filtering and collecting insoluble substances, washing with absolute ethyl alcohol and water for three times respectively, and drying at 80 ℃ for 8h to obtain powder; calcining the powder at 550 ℃ for 2h, naturally cooling to 25 ℃, crushing the powder and sieving to obtain 325-mesh metal oxide powder;
s2 dispersing 5kg of metal oxide powder obtained in step S1 in 100kg of dimethylbenzene at the ultrasonic power of 80W and the frequency of 50kHz for 30min at 25 ℃, adding 10kg of 3-aminopropyltriethoxysilane, heating to 80 ℃, stirring at the rotating speed of 350r/min for reflux reaction for 2h, filtering and collecting insoluble substances, washing with acetone for three times, drying at 80 ℃ for 8h to obtain powder, crushing and sieving the powder to obtain 325-mesh modified metal oxide powder.
Example 4
A high-performance polypropylene flame retardant is prepared by mixing 23.5kg of modified starch and 1.5kg of modified metal oxide powder.
The preparation method of the modified starch comprises the following steps:
(1) mixing 25kg of soluble starch and 75kg of phytic acid at 25 ℃ under stirring to form a solution I; transferring the solution I to a reaction kettle, carrying out solvothermal reaction for 2h at 120 ℃, and naturally cooling to 25 ℃ to obtain a solution II;
(2) mixing 15kg of melamine, 60kg of glycerol and 30kg of the solution II obtained in step (1) at 25 ℃ with stirring to form a solution III; heating the solution III to 90 ℃, stirring and refluxing at the rotating speed of 350r/min for 2 hours, naturally cooling to 25 ℃, filtering and collecting insoluble substances, washing with 90 ℃ water for three times, drying at 80 ℃ for 8 hours to obtain powder, and crushing and sieving the powder to obtain 325-mesh modified starch.
The preparation method of the modified metal oxide powder comprises the following steps:
s1 mixing 3kg of cobalt nitrate hexahydrate and 50kg of water at 25 ℃, stirring at the rotating speed of 400r/min for 30min, adding 5kg of urea, and continuously stirring for 15min to obtain a solution; transferring the solution to a reaction kettle, carrying out hydrothermal reaction at 180 ℃ for 8h, naturally cooling to 25 ℃, filtering and collecting insoluble substances, washing with absolute ethyl alcohol and water for three times respectively, and drying at 80 ℃ for 8h to obtain powder; calcining the powder at 550 ℃ for 2h, naturally cooling to 25 ℃, crushing the powder and sieving to obtain 325-mesh metal oxide powder;
s2 dispersing 5kg of metal oxide powder obtained in step S1 in 100kg of dimethylbenzene at the ultrasonic power of 80W and the frequency of 50kHz for 30min at 25 ℃, adding 10kg of 3-aminopropyltriethoxysilane, heating to 80 ℃, stirring at the rotating speed of 350r/min for reflux reaction for 2h, filtering and collecting insoluble substances, washing with acetone for three times, drying at 80 ℃ for 8h to obtain powder, crushing and sieving the powder to obtain 325-mesh modified metal oxide powder.
Example 5
A high-performance polypropylene flame retardant is prepared by mixing 23.5kg of modified starch and 1.5kg of modified metal oxide powder.
The preparation method of the modified starch is the same as that of the modified starch in example 4; the modified metal oxide powder was prepared in the same manner as in example 2.
Example 6
A high-performance polypropylene flame retardant is prepared by mixing 23.5kg of modified starch and 1.5kg of modified metal oxide powder.
The preparation method of the modified starch is the same as that of the modified starch in example 4; the modified metal oxide powder was prepared in the same manner as in example 3.
Example 7
A high-performance polypropylene flame retardant is prepared by mixing 23.5kg of modified starch and 1.5kg of modified metal oxide powder.
The preparation method of the modified starch is the same as that of the modified starch in example 4; the preparation method of the modified metal oxide powder comprises the following steps:
s1 mixing 2kg of cobalt nitrate hexahydrate, 1kg of nickel acetate tetrahydrate and 50kg of water at 80 ℃, stirring at the rotating speed of 400r/min for 30min, adding 1kg of benzoic acid and 0.5kg of fructose, and continuously stirring for 15min to obtain a solution; transferring the solution to a reaction kettle, carrying out hydrothermal reaction at 180 ℃ for 8h, naturally cooling to 25 ℃, filtering and collecting insoluble substances, washing with absolute ethyl alcohol and water for three times respectively, and drying at 80 ℃ for 8h to obtain powder; calcining the powder at 550 ℃ for 2h, naturally cooling to 25 ℃, crushing the powder and sieving to obtain 325-mesh metal oxide powder;
s2 dispersing 5kg of metal oxide powder obtained in the step S1 in 100kg of dimethylbenzene at an ultrasonic power of 80W and a frequency of 50kHz for 30min at 25 ℃, adding 10kg of 3-aminopropyltriethoxysilane, heating to 80 ℃, stirring at a rotating speed of 350r/min for reflux reaction for 2h, filtering and collecting insoluble substances, washing with acetone for three times, drying at 80 ℃ for 8h to obtain powder, crushing and sieving the powder to obtain 325-mesh ultrafine metal oxide powder, soaking in 1mol/L ammonium persulfate aqueous solution, standing at room temperature for 12h according to the volume of the solution calculated by 15mL/g of ultrafine metal oxide powder, filtering, drying a filter cake at 100 ℃ for 10h, grinding into powder, roasting at 550 ℃ in a muffle furnace for 3h, and cooling to obtain the required modified metal oxide powder.
Comparative example 1
A high-performance polypropylene flame retardant is 25kg of modified starch.
The modified starch was prepared as described in example 4.
Comparative example 2
A high-performance polypropylene flame retardant is 25kg of soluble starch.
Test example 1
Scanning electron microscopy was used to characterize the modified metal oxide powders prepared in examples 1-3 of the present invention, and the results are shown in fig. 1A-C. As can be seen from fig. 1A, the modified metal oxide prepared in example 1 is a spherical mass-agglomerated structure; after the benzoic acid and the fructose are added, the metal oxide is changed into a porous nanosheet from a spherical and largely-agglomerated structure (example 2, figure 1B); the structure of the modified metal oxide was not significantly changed after the introduction of nickel element (example 3, fig. 1C). The modified metal oxide porous flaky structures prepared in examples 2 and 3 may be more beneficial to the dispersion of the modified metal oxide porous flaky structures in polypropylene, and the stability of forming a carbon layer by combustion is improved.
The specific surface area of the modified metal oxides prepared according to the present invention 1 to 3 was tested, and the results are shown in table 1.
| BET specific surface area (m)2/g) | |
| Example 1 | 38.7 |
| Example 2 | 123.6 |
| Example 3 | 128.3 |
The large specific surface area is advantageous for providing compatibility with the polypropylene matrix in combination with other components of the flame retardant.
Test example 2
After the flame retardant is added into polypropylene to prepare flame-retardant polypropylene, the improvement of the flame-retardant performance of the polypropylene and the evaluation of the influence on the mechanical performance of the polypropylene material are particularly important.
The preparation process of the sample for testing the flame retardant property of the flame retardant polypropylene is as follows:
(1) putting the flame retardant and the polypropylene into a vacuum oven at 80 ℃ for drying for 12h for later use;
(2) putting 75kg of polypropylene and 25kg of flame retardant into an internal mixer, and carrying out melt blending for 5min at 190 ℃ and at the rotating speed of 60 r/min;
(3) and (3) placing the molten blend obtained in the step (2) on a flat vulcanizing machine, hot-pressing for 2min at the pressure of 10MPa, exhausting for 10 times, and cold-pressing for 2min to obtain a plate sample.
The limit oxygen index of the flame-retardant polypropylene is measured by a limit oxygen index measuring instrument according to the combustion behavior standard determined by an oxygen index method of GB/T2406.2-2009; the size of the sample was 120X 7X 4mm3Each groupThe samples were tested in parallel five times, the average value was taken; generally, materials with a limiting oxygen index of less than 22% are flammable; the flame retardant is combustible at 22-27%; 27% -34% of the fuel is difficult to burn; above 34% is non-combustible.
The UL-94 vertical burning test of the flame-retardant polypropylene is determined by a vertical burner according to the standards of GB/T2408-2008 plastic burning performance determination horizontal method and vertical method, and the size of a sample is 125 multiplied by 13 multiplied by 3mm3Each group of samples is tested in parallel for five times, and the average value is taken; generally, the UL-94 vertical burning test results of the material are evaluated by burning grades V-0 to V-2 and NR, which has the worst flame retardant effect and the best V-0 grade effect.
And (3) testing the water resistance: the quality of the flame-retardant polypropylene sample strip for testing vertical combustion is measured at normal temperature after being dried at 100 ℃ and is recorded as W0(ii) a Boiling the sample in 70 deg.C water bath for 168 hr, oven drying at 100 deg.C for 48 hr, measuring the mass at room temperature, and recording as W1Weight loss ratio (W)x) The calculation formula is as follows:
the results of the flame retardant property test of the flame retardant polypropylene are shown in table 2.
TABLE 2 flame retardancy test results
As can be seen from the test results in Table 2, pure polypropylene is flammable, and the flame retardant property of comparative example 2 is improved after the soluble starch is added, because the soluble starch has a large amount of hydroxyl groups, the soluble starch can be used as a carbon source in the combustion process and has a certain flame retardant property. From the results of examples 1 to 3, it can be seen that the flame retardant property can be improved by adding the modified metal oxide, probably because the metal oxide can promote the formation of the carbon layer and improve the strength of the carbon layer, and the metal oxide also has a certain radical trapping capability. The modified starch is added in the comparative example 1, so that the flame retardant effect is obviously improved, because the modified starch can be used as an intumescent flame retardant. Example 4 the flame retardant property is further improved by adding modified starch and modified metal oxide, and the addition of the modified metal oxide promotes the generation of the carbon layer and enhances the compactness of the carbon layer.
The flame retardant performance of example 5 was further improved and the UL-94 vertical burn rating reached a V-0 rating. This is probably because the structure of the metal oxide is successfully adjusted by adding benzoic acid and fructose, the metal oxide with larger specific surface area and three-dimensional structure can be used as a template for carbon growth, and a part of cobalt oxide is more easily reduced at high temperature to form low-price cobalt species, thereby enhancing the formation of a carbon layer. The flame retardant effect of examples 6 and 7 is the best, which may be that the composite metal oxide formed by introducing the nickel element has a larger specific surface area, and at the same time, the effect of catalyzing the formation of the carbon layer is better, and the crystallinity of the carbon layer is improved, so that the carbon layer is more compact.
Using a conical combustion heat tester to test the thickness of 100 multiplied by 3mm3The flame retardant polypropylene samples were heated from 30 ℃ to 600 ℃ at a heating rate of 1 ℃/min and the combustion behavior of the flame retardant polypropylene was recorded. The results are shown in Table 3.
TABLE 3 flame behaviour of flame retardant polypropylenes
As can be seen from the results in Table 3, the total heat release of the flame retardant polypropylene is reduced after the addition of the modified metal oxide. This is probably because the modified metal oxide promotes the decomposition product of polypropylene to form a carbonaceous protective layer, preventing further combustion of polypropylene; the introduction of nickel promotes the carbon layer to be more compact, and further inhibits the combustion of polypropylene.
Carbon monoxide can suffocate people and it is also important to evaluate the release of carbon monoxide from polypropylene materials during combustion. The peak carbon monoxide release rate results in table 3 show that the flame retardant polypropylene prepared from the flame retardant of example 6 has the lowest peak carbon monoxide release rate. This is probably because the carbon layer inhibits the release of carbon monoxide.
The carbon residue rate shows that the carbon layer is not easy to decompose after the modified metal oxide is added, and the existence of the stable carbon layer improves the combustion performance of the flame-retardant polypropylene. Carbon layers of the flame-retardant polypropylene prepared by the flame retardant of the embodiment 5 and the embodiment 6 are respectively soaked in 2mol/L nitric acid aqueous solution and 10 wt.% hydrofluoric acid aqueous solution for 24 hours, inorganic substances are washed off, the carbon layers are washed with water for three times, the carbon layers are dried in an oven at 80 ℃ for 12 hours, and the appearance characterization result of the carbon layers by a scanning electron microscope is shown in figure 2. The spherical materials in FIGS. 2A-B are carbon. The modified metal oxide can promote the decomposition products of the polypropylene to form carbon balls to be filled on the surface of the formed carbon layer, inhibit the combustion of the polypropylene and reduce the release of carbon monoxide. The carbon spheres of fig. 2B are finer and more uniform, which indicates that the introduction of nickel promotes the formation of carbon spheres, further stabilizing the carbon layer structure.
The preparation process of the sample for testing the mechanical strength of the flame-retardant polypropylene comprises the following steps:
(1) putting the flame retardant and the polypropylene into a vacuum oven at 80 ℃ for drying for 12h for later use;
(2) and putting 75kg of polypropylene and 25kg of flame retardant into an internal mixer, melting and blending for 5min at 200 ℃ and a rotating speed of 60r/min, extruding to a die at 40 ℃, and keeping for 10s under the pressure of 0.6MPa to obtain a sample.
The tensile strength is determined according to the determination standard of GB/T1040.1-2018 plastic tensile property on a universal tester, and the sample is 62.5 multiplied by 3.25 multiplied by 0.7mm3Dumbbell-shaped, each group of samples was tested five times and the average was taken;
the impact strength is measured by a cantilever beam impact tester according to the measuring standard of GB/T1843-2008 plastic cantilever beam impact strength, and the sample size is 10 multiplied by 1.5mm3Each set of samples was tested five times and averaged.
The mechanical strength results of the flame retardant polypropylene are shown in table 4.
TABLE 4 mechanical Property test results
| Tensile Strength (MPa) | Impact strength (kJ/m)2) | |
| Polypropylene | 36.3 | 5.2 |
| Example 5 | 32.8 | 4.6 |
| Example 6 | 33.4 | 4.8 |
| Comparative example 1 | 34.2 | 4.8 |
The test results in Table 4 show that the flame retardant of the present invention has good compatibility with polypropylene and little influence on the mechanical properties of polypropylene materials.
The results of the water resistance test of the flame retardant polypropylene are shown in table 5.
TABLE 5 Water resistance test results
| Weight loss ratio (%) | |
| Example 6 | 3.4 |
| Example 7 | 1.8 |
| Comparative example 1 | 5.2 |
As can be seen from the test results in table 5, the water resistance of the flame retardant polypropylene is improved after the metal oxide is further modified in example 7, and it is found that the subsequent modification step changes the surface roughness of the metal oxide powder and reduces the weight loss rate of the flame retardant polypropylene in the water resistance test as compared with example 6 and example 7.
Claims (5)
1. The preparation method of the high-performance polypropylene flame retardant is characterized by comprising the following steps of (20-25) mixing modified starch and modified metal oxide powder in a mass ratio: (1-1.5);
the preparation method of the modified starch comprises the following steps: uniformly mixing soluble starch and phytic acid, and carrying out solvothermal reaction for 1-3 h at the temperature of 100-120 ℃; cooling, adding melamine and glycerol, uniformly mixing, heating to 80-90 ℃, stirring, refluxing, reacting for 2-5 hours, cooling, filtering, collecting insoluble substances, washing, drying and crushing to obtain modified starch;
the modified metal oxide powder is prepared by the following method:
s1, uniformly mixing cobalt nitrate hexahydrate, nickel acetate tetrahydrate, water, benzoic acid and fructose at 60-80 ℃, carrying out hydrothermal reaction at 160-180 ℃ for 6-8 h, naturally cooling, filtering and collecting insoluble substances, washing and drying to obtain powder; calcining the powder at 500-550 ℃, naturally cooling, crushing and sieving to obtain metal oxide powder;
s2, ultrasonically dispersing metal oxide powder in xylene, adding 3-aminopropyltriethoxysilane, heating to 60-80 ℃, stirring and refluxing for 2-5 h, filtering and collecting insoluble substances, washing, drying, crushing and sieving to obtain superfine metal oxide powder, soaking the superfine metal oxide powder in 1-1.2 mol/L ammonium persulfate aqueous solution, standing at room temperature for 10-12 h, filtering, drying a filter cake, grinding into powder, roasting in a muffle furnace, and cooling to obtain the required modified metal oxide powder.
2. The method for preparing high-performance polypropylene flame retardant according to claim 1, wherein: the volume mass ratio of the ammonium persulfate aqueous solution to the ultrafine metal oxide powder in the step S2 is (10-15): 1 mL/g.
3. The method for preparing high-performance polypropylene flame retardant according to claim 1, wherein: the roasting condition in the step S2 is roasting for 2-3 h at 530-550 ℃.
4. The method for preparing high-performance polypropylene flame retardant according to claim 1, wherein: and the drying condition in the step S2 is drying for 8-12 h at 100-105 ℃.
5. A high-performance polypropylene flame retardant is characterized in that: the preparation method of any one of claims 1 to 4.
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| JP2020084024A (en) * | 2018-11-26 | 2020-06-04 | 住友化学株式会社 | Molded body and gasket for building component |
| CN113461950A (en) * | 2021-07-02 | 2021-10-01 | 长春工业大学 | Preparation method of green sustainable chemical-physical synergistic intumescent flame retardant system |
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| US20090035365A1 (en) * | 2007-07-30 | 2009-02-05 | Lewis Michael Popplewell | Density Controlled Capsule Particles and Methods of Making the Same |
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