A phosphorus-containing flame retardant and its preparation method and application

Abstract

The present invention relates to the field of flame retardant technology, particularly to the field of IPC C08L, and more specifically to a phosphorus-containing flame retardant, its preparation method, and application. The present invention utilizes epoxy curing and chlorination reactions to graft long carbon-chain perfluorocarbon chains onto phosphorus-containing structures to produce a highly cross-linked phosphorus-containing flame retardant. The phosphorus-containing flame retardant is then added to a system containing raw materials such as polyethylene terephthalate, nanofillers, chain extenders, and antioxidants to produce a flame-retardant polyester foam material with excellent pore size and flame retardant properties.

Description

Technical Field

[0001] The present invention relates to the field of flame retardant technology, in particular to the field of IPC C08L, and more specifically to a phosphorus-containing flame retardant and a preparation method and application thereof. Background Art

[0002] Polyethylene terephthalate (PET) is an engineering plastic with excellent performance. Its regular molecular chain structure and strong intermolecular forces give it exceptional properties, such as high mechanical strength and mechanical properties, high temperature resistance, good optical and insulating properties, excellent chemical stability, and good recyclability. PET foam materials not only possess these properties, but also have the advantages of low density and high specific strength. They are currently widely used in wind power, transportation, construction, and automotive industries. However, the PET foaming process places high demands on the melt viscoelasticity of PET, making it difficult to produce high-yield PET foam products using conventional commercial PET. With the country's increasing emphasis on fire protection, these applications are also placing higher demands on the flame retardant properties of PET. Commercial PET has poor fire resistance, with a limiting oxygen index of only around 21. Furthermore, due to the nature of molten dripping, it is highly susceptible to secondary combustion.

[0003] Conventional flame retardants, such as ammonium polyphosphate (APP) and phosphate ester (BDP), have low thermal decomposition temperatures and decompose at PET processing temperatures. This not only causes PET degradation but also significantly reduces its melt viscoelasticity and melt strength, thereby reducing its foaming properties. Furthermore, because flame retardants have low flame retardant efficiency when used alone, higher addition levels are required to achieve a good flame retardant effect. However, high addition levels can also significantly reduce PET's foaming properties. However, different flame retardants, when used in appropriate proportions, can exhibit a synergistic effect, significantly improving their flame retardant efficiency and thereby reducing their addition level and impact on PET's melt viscoelasticity and melt strength.

[0004] Chinese invention patent CN106554605A discloses a phosphorus-bromine synergistic high-expansion flame-retardant PET material and its preparation method. The method uses diethyl aluminum hypophosphite to synergize with polypentabromobenzyl acrylate to flame retard PET. The two flame retardants form a good synergistic effect due to their high expansion properties. However, polypentabromobenzyl acrylate has a significant plasticizing effect on PET, causing a significant reduction in the viscoelasticity of the PET melt and seriously damaging the foamability of PET. In addition, diethyl aluminum hypophosphite has poor compatibility with PET, which will reduce the mechanical properties of the foam.

[0005] Chinese invention patent CN114621488A discloses a method for preparing a halogen-free, highly flame-retardant PET foam material. This method produces a functional, flame-retardant, chain-extended polymer that reacts with the carboxyl groups of PET, exhibiting good compatibility with the material and thus eliminating the effects of traditional flame retardant blends on PET's mechanical properties. However, the preparation process for this functional, flame-retardant, chain-extended polymer is complex and has yet to be commercialized, making it unsuitable for large-scale industrial production of flame-retardant PET foam materials.

[0006] Chinese invention patent CN114479383A discloses a method for preparing a flame-retardant PET foam material with good melt strength. The method uses an organic aluminum hypophosphite flame retardant and a nitrogen-based compound for synergistic flame retardancy, and uses an isocyanate chain extender for chain extension before injection molding and foaming. The PET foam material prepared by this method has a small pore size and good uniformity. However, the presence of the nitrogen-based flame retardant inhibits the PET chain extension reaction, making it difficult to effectively improve the viscoelasticity of the PET melt, making it unsuitable for preparing a high-expansion-ratio foam material.

[0007] Therefore, how to use better technology to prepare high-performance and highly flame-retardant PET foam materials needs further research. Summary of the Invention

[0008] In order to solve the above problems, the present invention provides a phosphorus-containing flame retardant in the first aspect, which has the structural formula Where R is R F CF3(CF2) m COO-; m=2-8; further preferably, m=4.

[0009] Preferably, the number average relative molecular weight of the phosphorus-containing flame retardant is 1000-3000.

[0010] In a second aspect, the present invention provides a method for preparing the phosphorus-containing flame retardant, comprising the following steps:

[0011] S1. Epoxy ring-opening reaction: Add the epoxy compound, fluorinated organic acid, solvent, and catalyst I into a four-necked flask equipped with a condenser and a magnetic stirrer. Stirring is started under nitrogen protection. The temperature is increased. After reacting at 70-120° C. for 8-12 h, the reaction is stopped to obtain a solution containing reactant I.

[0012] S2. Purification by distillation: placing the solution containing reactant I in a distillation apparatus, and performing reduced pressure distillation at 150° C. and −0.098 MPa to obtain reactant I;

[0013] S3, chlorination reaction: 15-30 parts of reactant I and 0-0.5 parts of catalyst II are added to a four-necked flask equipped with a condenser and a magnetic stirrer, stirring is started under nitrogen protection, 15-80 parts of phosphorus oxychloride solution are added dropwise using a constant pressure dropping funnel, and the temperature is raised. After reacting at 150-180°C for 6-10 hours, the reaction is stopped to obtain Solution II;

[0014] S4. Purification by distillation: placing the second solution in a distillation apparatus, and removing dichloromethane by reduced pressure distillation at 100° C. and −0.098 MPa to obtain a reaction product, which is a phosphorus-containing flame retardant.

[0015] Preferably, the epoxy compound contains a hydroxyl group.

[0016] Preferably, the epoxy compound includes but is not limited to glycidol.

[0017] Preferably, the structural formula of the fluorine-containing organic acid is CF3(CF2) m COOH; wherein m=2~8.

[0018] Preferably, the weight ratio of the epoxy compound to the fluorine-containing organic acid is (1-2): (1-2).

[0019] Preferably, the solvent includes but is not limited to one or more of N,N-dimethylformamide, dimethyl sulfoxide, acetonitrile, and hexamethylphosphoric triamide.

[0020] Preferably, the catalyst I includes but is not limited to one or more of a chloroplatinic acid catalyst, a platinum catalyst, a palladium catalyst, and a rhodium catalyst.

[0021] Preferably, the amount of catalyst I added is 0-0.5 wt% of the total raw materials in step S1.

[0022] Preferably, when the epoxy compound is glycidol, the reaction equation of reaction S1 is as follows:

[0023]

[0024] Preferably, the structural formula of the reactant I is where R F CF3(CF2) m Any one of COO-; m=2 to 8; more preferably, m=4.

[0025] The inventors have creatively discovered that by using epoxy compounds and long-chain fluorinated organic acids for an epoxy ring-opening reaction, a phosphorus-containing flame retardant with excellent flame retardancy can be obtained. This is likely due to the use of epoxy curing and chlorination reactions to graft long carbon-chain perfluorocarbon chains onto the phosphorus-containing structure. The glycidol polyhydroxy structures are continuously interwoven, forming a dense and compact network structure in the product, thereby achieving the flame retardant effects of heat absorption, covering, and inhibiting chain reactions. The longer the carbon chain, the greater the number-average relative molecular weight, and the greater the intermolecular forces. Although the melting and boiling points will increase, the chemical properties are unstable, and the carbon chain is easily broken at high temperatures, which in turn affects its flame retardancy.

[0026] Preferably, the catalyst II includes but is not limited to one or more of chloroplatinic acid catalyst, platinum catalyst, palladium catalyst, and rhodium catalyst.

[0027] Preferably, the amount of catalyst II added is 0-0.5 wt% of the total raw materials in step S3.

[0028] Preferably, the solvent of the phosphorus oxychloride solution includes but is not limited to one or more of dichloromethane, chloroform, and carbon tetrachloride.

[0029] Preferably, the concentration of phosphorus oxychloride in the phosphorus oxychloride solution is 0.1-40 wt %.

[0030] Preferably, the weight ratio of the reactant I to the phosphorus oxychloride in the phosphorus oxychloride solution is 1:(1-2).

[0031] The reaction equation of reaction S3 is as follows:

[0032]

[0033] In a third aspect, the present invention provides an application of the phosphorus-containing flame retardant for preparing a flame-retardant polyester foam material. The flame-retardant polyester foam material comprises, by weight, 70-90 parts of polyethylene terephthalate (PET), 5-30 parts of the phosphorus-containing flame retardant, 0.5-5 parts of a nanofiller, 0.3-4 parts of a chain extender, and 0.1-0.5 parts of an antioxidant.

[0034] Preferably, the ash content of the PET is 30-40 wt%.

[0035] In some preferred embodiments, the PET is purchased from MacLean Reagents.

[0036] Preferably, the chain extender is one or more of an epoxy chain extender, an anhydride chain extender, an oxazoline chain extender and an isocyanate chain extender.

[0037] Preferably, the nanofiller includes one or more of nano-silicon dioxide, nano-wollastonite, nano-montmorillonite, nano-titanium oxide, and nano-calcium carbonate; more preferably, it is nano-silicon dioxide.

[0038] Preferably, the surface of the nano-silica is treated with an alkoxysilane coupling agent.

[0039] Preferably, the particle size of the nano-silicon dioxide is 1-10 mm; more preferably, it is 1.2-2.5 mm.

[0040] In some preferred embodiments, the nano-silicon dioxide is purchased from quartz chips produced by Aladdin, with CAS number 14808-60-7 and serial number 124528.

[0041] The antioxidant is not particularly limited, and any antioxidant available on the market can be used.

[0042] In some preferred embodiments, the antioxidant is one or both of diphenylamine and phosphite.

[0043] The inventors have creatively discovered that a flame-retardant polyester foam material prepared by combining the phosphorus-containing flame retardant prepared in this application with PET and other raw materials not only exhibits excellent flame retardancy but also has uniform pores with large diameters. This is likely due to the good compatibility between the phosphorus-containing flame retardant prepared in this application and PET, and the addition of fluorine-containing carbon chains that can overcome both the inherent combustion effects of the PET material and the effects of gases in the pores. This not only improves the flame retardancy of the resulting flame-retardant polyester foam material, but also improves its pore properties and ensures uniform pores.

[0044] The preparation method of the flame retardant polyester foam material is:

[0045] S1, mixing PET, a phosphorus-containing flame retardant, a nanofiller, a chain extender, and an antioxidant in parts by weight, and melting the mixture at 240-280° C. to obtain a polyester composition;

[0046] S2. Inject a physical foaming agent into the extruder and mix it evenly with the polyester composition melt in the extruder, cool the polyester composition melt containing the physical foaming agent to 220° C.-260° C., adjust the extrusion process so that the melt pressure at the die is ≥4 MPa, and obtain a flame-retardant polyester foam material after foaming, cooling and shaping at the die.

[0047] The physical foaming agent includes but is not limited to one or more of petroleum ether, n-hexane, n-heptane, and n-pentane.

[0048] The mass ratio of the physical foaming agent to the polyester composition is 1:(10-20).

[0049] Beneficial effects:

[0050] 1. The present invention can obtain a phosphorus-containing flame retardant with excellent flame retardancy by selecting an epoxy compound and a long carbon chain fluorine-containing organic acid to carry out an epoxy ring-opening reaction.

[0051] 2. The flame-retardant polyester foam material is prepared by selecting the phosphorus-containing flame retardant prepared by the present invention and raw materials such as PET. The flame-retardant polyester foam material has good flame retardancy and uniform pores with large diameters.

[0052] 3. The present invention utilizes epoxy curing and chlorination reactions to graft long carbon chain perfluorocarbon chains into phosphorus-containing structures to obtain a highly cross-linked phosphorus-containing flame retardant; and adds the phosphorus-containing flame retardant to a system containing raw materials such as polyethylene terephthalate, nanofiller, chain extender and antioxidant to prepare a flame-retardant polyester foam material, which has good foaming properties and flame retardant properties. DETAILED DESCRIPTION

[0053] Example

[0054] Example 1

[0055] Example 1 provides a phosphorus-containing flame retardant, the structural formula of which is wherein m=4; and the number average relative molecular weight of the phosphorus-containing flame retardant is 1000 to 3000.

[0056] The preparation method of the phosphorus-containing flame retardant comprises the following steps, in parts by weight:

[0057] S1. Epoxy ring-opening reaction: 20 parts of glycidol, 25 parts of perfluorohexanoic acid, 54.5 parts of N,N-dimethylformamide, and 0.5 parts of chloroplatinic acid catalyst were added to a four-necked flask equipped with a condenser and a magnetic stirrer. Stirring was started under nitrogen protection, and the temperature was increased. After reacting at 100° C. for 10 h, the reaction was stopped to obtain a solution containing reactant I;

[0058] S2. Purification by distillation: placing the solution containing reactant I in a distillation apparatus, and performing reduced pressure distillation at 150° C. and −0.098 MPa to obtain reactant I;

[0059] S3, chlorination reaction: 19.5 parts of reactant I and 0.5 parts of chloroplatinic acid catalyst were added to a four-necked flask equipped with a condenser and a magnetic stirrer, and stirring was started under nitrogen protection. 80 parts of a 37.5 wt% phosphorus oxychloride dichloromethane solution was added dropwise using a constant pressure dropping funnel and the temperature was raised. After reacting at 160° C. for 7 h, the reaction was stopped to obtain Solution 2;

[0060] S4. Purification by distillation: placing the second solution in a distillation apparatus, and removing dichloromethane by reduced pressure distillation at 100° C. and −0.098 MPa to obtain a reaction product, which is a phosphorus-containing flame retardant.

[0061] Example 2

[0062] Example 2 provides a phosphorus-containing flame retardant, the structural formula of which is Wherein m=2; the number average relative molecular weight of the phosphorus-containing flame retardant is 1000-3000.

[0063] The preparation method of the phosphorus-containing flame retardant is the same as that of Example 1, except that the fluorine-containing organic acid is perfluorobutyric acid.

[0064] Example 3

[0065] Example 3 provides a phosphorus-containing flame retardant, the structural formula of which is wherein m=6; and the number average relative molecular weight of the phosphorus-containing flame retardant is 1000 to 3000.

[0066] The preparation method of the phosphorus-containing flame retardant is the same as that of Example 1, except that the fluorine-containing organic acid is perfluorooctanoic acid.

[0067] Example 4

[0068] Example 4 provides a phosphorus-containing flame retardant, the structural formula of which is wherein m=8; and the number average relative molecular weight of the phosphorus-containing flame retardant is 1000 to 3000.

[0069] The preparation method of the phosphorus-containing flame retardant is the same as that of Example 1, except that the fluorine-containing organic acid is perfluorodecanoic acid.

[0070] Comparative Example 1

[0071] Comparative Example 1 provides a phosphorus-containing flame retardant, the structural formula of which is wherein m=0; and the number average relative molecular weight of the phosphorus-containing flame retardant is 1000 to 3000.

[0072] The preparation method of the phosphorus-containing flame retardant comprises the following steps, in parts by weight:

[0073] S1. Epoxy ring-opening reaction: 20 parts of glycidol, 25 parts of formic acid, 54.5 parts of N,N-dimethylformamide, and 0.5 parts of chloroplatinic acid catalyst were added to a four-necked flask equipped with a condenser and a magnetic stirrer. Stirring was started under nitrogen protection, and the temperature was increased. After reacting at 100° C. for 10 hours, the reaction was stopped to obtain a solution containing reactant I;

[0074] S2. Purification by distillation: placing the solution containing reactant I in a distillation apparatus, and performing reduced pressure distillation at 150° C. and −0.098 MPa to obtain reactant I;

[0075] S3, chlorination reaction: 19.5 parts of reactant I and 0.5 parts of chloroplatinic acid catalyst were added to a four-necked flask equipped with a condenser and a magnetic stirrer, and stirring was started under nitrogen protection. 80 parts of a 37.5 wt% phosphorus oxychloride dichloromethane solution was added dropwise using a constant pressure dropping funnel and the temperature was raised. After reacting at 160° C. for 7 h, the reaction was stopped to obtain Solution 2;

[0076] S4. Purification by distillation: placing the second solution in a distillation apparatus, and removing dichloromethane by reduced pressure distillation at 100° C. and −0.098 MPa to obtain a reaction product, which is a phosphorus-containing flame retardant.

[0077] Example 5

[0078] Example 5 provides a flame-retardant polyester foam material, the raw materials for its preparation include, by weight: 15 parts of the phosphorus-containing flame retardant prepared in Example 1, 80 parts of polyethylene terephthalate, 3 parts of nanofiller, 1.5 parts of chain extender, and 0.5 parts of antioxidant.

[0079] The ash content of the PET is 30-40 wt%.

[0080] The PET was purchased from MacLean Reagents.

[0081] The chain extender is 2,3-butanediol, and its CAS number is 19132-06-0.

[0082] The nano filler is nano silicon dioxide.

[0083] The surface of the nano-silica is treated with an alkoxysilane coupling agent.

[0084] The particle size of the nano silicon dioxide is 1.2-2.5 mm.

[0085] The nano-silicon dioxide was purchased from quartz chips produced by Aladdin, with CAS number 14808-60-7 and serial number 124528.

[0086] The antioxidant is diphenylamine, and its CAS number is 122-39-4.

[0087] The preparation method of the flame retardant polyester foam material is:

[0088] S1, mixing PET, a phosphorus-containing flame retardant, a nanofiller, a chain extender, and an antioxidant in parts by weight, and melting the mixture at 260° C. to obtain a polyester composition;

[0089] S2. Inject a physical foaming agent into the extruder and mix it evenly with the polyester composition melt in the extruder, cool the polyester composition melt containing the physical foaming agent to 230° C., adjust the extrusion process so that the melt pressure at the die is 4 MPa, and obtain a flame-retardant polyester foam material after foaming, cooling and shaping through the die.

[0090] The physical foaming agent is petroleum ether.

[0091] The mass ratio of the physical foaming agent to the polyester composition is 1:15.

[0092] Example 6

[0093] Example 6 provides a flame-retardant polyester foam material. The specific implementation method is the same as that of Example 5, except that the phosphorus-containing flame retardant used is the phosphorus-containing flame retardant prepared in Example 2.

[0094] Example 7

[0095] Example 7 provides a flame-retardant polyester foam material. The specific implementation method is the same as that of Example 5, except that the phosphorus-containing flame retardant used is the phosphorus-containing flame retardant prepared in Example 3.

[0096] Example 8

[0097] Example 8 provides a flame-retardant polyester foam material. The specific implementation method is the same as that of Example 5, except that the phosphorus-containing flame retardant used is the phosphorus-containing flame retardant prepared in Example 4.

[0098] Comparative Example 2

[0099] Comparative Example 2 provides a flame-retardant polyester foam material, and the specific implementation method is the same as Example 5, except that the phosphorus-containing flame retardant used is the phosphorus-containing flame retardant prepared in Comparative Example 1.

[0100] Performance Testing

[0101] 1. Performance test of phosphorus-containing flame retardants

[0102] Limiting Oxygen Index (LOI) testing method: The phosphorus-containing flame retardants prepared in Examples 1-4 and Comparative Example 1 were tested according to the method specified in GB / T 2406.2-2009, with a flame retardant addition level of 6%. Materials with an LIO greater than 27% are considered flame-retardant, with a higher LIO indicating better flame retardancy. UL-94 grades are based on the LIO: 33.0 or higher is designated V-0, 31.0-33.0 is designated V-1, 27.0-31.0 is designated V-2, and 27.0 or lower is designated NR. The results are recorded in Table 1.

[0103] Table 1

[0104] Limiting oxygen index / % UL-94 rating Example 1 34.6 V-0 Example 2 33.0 V-0 Example 3 33.5 V-0 Example 4 31.6 V-1 Comparative Example 1 26.4 NR

[0105] It can be seen from Table 1 that in the presence of a fluorine-containing carbon chain, the flame retardant properties of the phosphorus-containing flame retardant are improved, and the flame retardant properties are optimal when the number of carbon atoms in the fluorine-containing carbon chain is 6.

[0106] 2. Performance test of flame retardant polyester foam material

[0107] The limiting oxygen index and UL-94 rating are the same as above.

[0108] Test method for apparent density: Use analytical balance to test the apparent density of foam products according to standard GB1033-86.

[0109] The average cell diameter is determined by immersing the sample in liquid nitrogen, removing it and fracturing it to produce a specimen. The fracture surface is then gold-sprayed and the fracture morphology is observed using a scanning electron microscope (SEM). The SEM images are processed using the image analysis software Image-Pro, and the number of cells counted is greater than 100. Cell size is the average diameter of the cells in the foamed sample, calculated directly by the software. Cell density is the number of cells per cubic centimeter of the foamed sample. The results are recorded in Table 2.

[0110] Table 2

[0111]

[0112] It can be seen from Table 2 that in the presence of fluorine-containing carbon chains, the flame retardant properties of the flame retardant polyester foam material are improved. When the number of carbon atoms in the fluorine-containing carbon chain is 6, the flame retardant property is the best and the pore diameter is the largest. The pore structure is more uniform when the foaming temperature is 235°C.

Claims

1. A phosphorus-containing flame retardant, characterized in that: The preparation method of the phosphorus-containing flame retardant comprises the following steps: S1. Epoxy ring-opening reaction: Add the epoxy compound, fluorinated organic acid, solvent, and catalyst I to a four-necked flask equipped with a condenser and a magnetic stirrer. Stirring is started under nitrogen protection. The temperature is increased. After reacting at 70-120° C. for 8-12 h, the reaction is stopped to obtain a solution containing reactant I. S2. Purification by distillation: placing the solution containing reactant I in a distillation apparatus, and performing reduced pressure distillation at 150° C. and −0.098 MPa to obtain reactant I; S3, chlorination reaction: add reactant I and catalyst II to a four-necked flask equipped with a condenser and a magnetic stirrer, start stirring under nitrogen protection, add phosphorus oxychloride solution dropwise using a constant pressure dropping funnel, start heating, react at 150-180°C for 6-10 hours, and then stop the reaction to obtain solution II; S4, distillation purification: placing the second solution in a distillation apparatus, and removing dichloromethane by reduced pressure distillation at 100°C and -0.098 MPa to obtain a reaction product, which is a phosphorus-containing flame retardant; The epoxy compound contains hydroxyl groups; the structural formula of the fluorine-containing organic acid is CF3(CF2) m COOH; wherein m=2~8; the epoxy compound is glycidol.

2. A phosphorus-containing flame retardant according to claim 1, characterized in that: The number average relative molecular weight of the phosphorus-containing flame retardant is 1000-3000.

3. The phosphorus-containing flame retardant according to claim 1, characterized in that: The weight ratio of the epoxy compound to the fluorine-containing organic acid is (1-2): (1-2).

4. A phosphorus-containing flame retardant according to claim 3, characterized in that: The concentration of phosphorus oxychloride in the phosphorus oxychloride solution is 0.1-40 wt %.

5. The phosphorus-containing flame retardant according to claim 4, characterized in that: The weight ratio of the reactant I to the phosphorus oxychloride in the phosphorus oxychloride solution is 1:(1-2).

6. Use of the phosphorus-containing flame retardant according to any one of claims 1-2, characterized in that: The flame retardant polyester foam material is used to prepare a flame retardant polyester foam material. The raw materials for preparing the flame retardant polyester foam material include, by weight, 70-90 parts of polyethylene terephthalate, 5-30 parts of the phosphorus-containing flame retardant according to any one of claims 1-2, 0.5-5 parts of nanofiller, 0.3-4 parts of chain extender and 0.1-0.5 parts of antioxidant.

7. The use of the phosphorus-containing flame retardant according to claim 6, characterized in that: The nano filler includes one or more of nano silicon dioxide, nano wollastonite, nano montmorillonite, nano titanium oxide, and nano calcium carbonate.

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