An intumescent flame retardant for thermoplastic vulcanizate (TPV) and a synthesis method and application thereof

Abstract

The application discloses an intumescent flame retardant for thermoplastic vulcanizate (TPV), cashew phenol glycidyl polyphosphate melamine salt and a synthesis and application thereof. First, polyphosphoric acid is poured into a solvent, after being completely dissolved, acid is added to control the pH of the system to 2.5-6.5, then cashew phenol glycidyl ether and melamine are added, the temperature is increased to 40-130 DEG C, reflux stirring is carried out for 0.5-12 h, cooling, suction filtration, washing with a solvent and drying are carried out, and cashew phenol glycidyl polyphosphate melamine salt is obtained. The intumescent flame retardant has carbon source, acid source and gas source, and the synthesis process is simple, meanwhile, the unsaturated alkane long chain of the cashew phenol derivative in the structure can shield polyphosphoric acid, improve the dispersion of the flame retardant in the TPV, and the unsaturated bond can also crosslink with the rubber in the TPV dynamic vulcanization process to form a network structure, enhance the interaction effect between the rubber phase and the plastic phase. Therefore, the flame retardant can be highly filled while maintaining the physical properties of the TPV.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of flame-retardant thermoplastic vulcanizate, and particularly relates to a cardanol glycidyl polyphosphate melamine salt, a synthesis method thereof and application thereof in thermoplastic vulcanizate. BACKGROUND

[0002] Thermoplastic vulcanizate (TPV) is a kind of thermoplastic material formed by blending plastic and rubber, in which the plastic is the continuous phase and the highly cross-linked rubber is the dispersed phase. This special "sea-island" structure makes TPV not only have good processability and recyclability of plastic, but also have the elasticity of rubber, so it is widely used in the fields of automobiles, household appliances, wires and cables. However, due to the characteristics of TPV substrate, its flame retardant performance is poor, so in practical application, TPV is often filled with flame retardant to have practical value.

[0003] In recent years, intumescent flame retardant has been widely used due to its halogen-free, low smoke, low toxicity, environmental friendliness, good flame retardant effect and other characteristics. The intumescent flame retardant synergistic system includes carbon source, acid source and gas source. During combustion, the acid source decomposes to form a strong acidic dehydrating agent to catalyze the carbon source to form a continuous carbon layer that is difficult to burn, and the gas source decomposes to produce non-combustible gas, which lowers the temperature and promotes the continuous expansion of the carbon layer, ultimately achieving high-efficiency flame retardation. The most widely used intumescent flame retardant synergistic system is the ammonium polyphosphate (acid source), pentaerythritol (carbon source), melamine (gas source) system, which can provide good flame retardant effect for TPV. However, due to the poor compatibility between polyphosphate, pentaerythritol and TPV substrate, the processing difficulty of TPV after filling and the physical properties of the composite material are affected, so it is an important development direction for TPV flame retardant to ensure the flame retardant effect of the intumescent flame retardant synergistic system while improving its affinity with TPV.

[0004] Single-component intumescent flame retardant connects carbon source, acid source and gas source in the same molecule to form a "three-source-in-one" structure, which can effectively overcome the shortcomings of multi-component intumescent flame retardant, such as poor compatibility of components with the substrate, separation of components from each other and insufficient synergy. It is an ideal flame retardant in the field of polymer materials. In addition, since the current intumescent flame retardant basically relies on chemical synthesis, carbon emissions and environmental pollution are inevitable during the manufacturing process, so using renewable biomass materials for substitution also conforms to the current concept of sustainable development.

[0005] Cardanol is extracted and prepared from natural cashew nut shell oil, and is one of the by-products in the cashew industry with low cost and easy to obtain in large quantities. Among many renewable natural bio-based resources, cardanol is considered as an important bio-based raw material due to its unique chemical structure, abundant content and low cost. The molecular structure of cardanol contains phenolic hydroxyl, benzene ring and long alkyl chain containing olefin structure. Among them, the chemical reactivity of phenolic hydroxyl is high, which can undergo esterification, etherification and epoxidation reactions; the benzene ring is a rigid six-membered ring, which can undergo substitution reactions such as sulfonation; the long-chain alkyl containing olefin structure also provides multiple reaction sites; it is these chemical structures that distinguish cardanol from other natural bio-based resources, and show excellent plasticity, which has important application value in the field of polymer material flame retardation.

[0006] For example, in the published patent "Preparation method of modified waterborne polyurethane coating (CN202410789728.0)", a cardanol waterborne chain extender is synthesized by using cardanol glycidyl ether, which contains a triphenyl s-triazine structure in its structure. The structure significantly improves the water absorption, tensile strength and elongation at break of polyurethane while improving the water absorption of polyurethane, and the structure also acts as a charring agent when the material burns, forming an intumescent flame retardant system with sodium phytate in the system, and improving the fire retardant performance of polyurethane coating. In the published patent "Phosphorus-containing cardanol-based polyurethane prepolymer modified phenolic foam plastic and preparation method thereof (CN201610188926.7)", by synthesizing cardanol glycidyl ether, phosphorus element is introduced on the unsaturated double bond of cardanol glycidyl ether, which improves the flame retardance of phenolic foam plastic, and the long fatty chain structure with good flexibility of cardanol glycidyl ether is used to improve the elongation and high dropping rate of phenolic foam plastic. SUMMARY

[0007] To solve the problems of processing difficulty and the influence of physical properties of the composite material when the existing intumescent flame retardant is applied in TPV, the present application provides a preparation method of cardanol glycidyl polyphosphate melamine salt for TPV. The "three sources in one body" feature can effectively overcome the poor compatibility between the components of the multi-component intumescent flame retardant and the TPV substrate, the separation between the components, and the insufficient synergy, so as to maintain the physical properties of TPV under high filling.

[0008] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0009] The present application provides an intumescent flame retardant for thermoplastic vulcanized rubber (TPV), which is cardanol glycidyl polyphosphate melamine salt, and the molecular structure formula is as follows:

[0010]

[0011] The application also provides a synthesis method of intumescent flame retardant - cashew phenol glycidyl polyphosphate melamine salt for thermoplastic vulcanizate (TPV), which comprises the following steps: first, polyphosphoric acid is added into a solvent to be completely dissolved, and an acid is added to adjust the pH to 2.5-6.5, then cashew phenol glycidyl ether and melamine are added, and then the temperature is raised to 40-130 DEG C, and reflux stirring is carried out for 0.5-12 h, finally, cooling, suction filtration, washing with a solvent and drying are carried out to obtain cashew phenol glycidyl polyphosphate melamine salt.

[0012] The reaction formula of the synthesis method is as follows:

[0013]

[0014] Among them

[0015] The polyphosphoric acid in the step has a molecular weight of 1000-10000.

[0016] The solvent in the step is one or more of ethanol, toluene, xylene, acetone, DMF and THF.

[0017] The acid for adjustment in the step is one or more of sulfuric acid, hydrochloric acid, formic acid and acetic acid.

[0018] The molar ratio among the polyphosphoric acid, cashew phenol glycidyl ether and melamine in the step is 1.8-3.8:1:1.8-3.8.

[0019] The cashew phenol glycidyl polyphosphate melamine salt prepared by the application is suitable for all TPV materials synthesized by dynamic vulcanization.

[0020] In the dynamic vulcanization TPV, the mass ratio of the intumescent flame retardant - cashew phenol glycidyl polyphosphate melamine salt is 10%-50%.

[0021] In the dynamic vulcanization TPV, the dynamic vulcanizing agent used by the TPV is one or more of sulfur, sulfur-containing compounds, peroxides, amines and metal oxides, and the mass ratio of the dynamic vulcanizing agent is 0.1%-2.0%.

[0022] The application adopts the technical scheme, and utilizes the bridging effect of cardanol glycidyl ether on the polyphosphoric acid and melamine to realize the synthesis of the "three-source integrated" intumescent flame retardant. The scheme is simple in process, and the unsaturated alkane long chain of the cardanol derivative in the structure of the flame retardant can shield the polyphosphoric acid, improve the dispersion performance of the flame retardant in the TPV, the unsaturated bond in the flame retardant can be crosslinked with the rubber phase in the dynamic vulcanization process of the TPV to form a network structure, enhance the interaction effect between the rubber phase and the plastic phase, and realize the maintenance of the physical performance of the TPV under high filling. Specifically, the beneficial effects of the application are as follows:

[0023] 1. The application constructs an intumescent flame retardant, i.e., cardanol glycidyl polyphosphoric acid ester melamine salt, by using cardanol glycidyl ether.

[0024] 2. In the intumescent flame retardant system of the cardanol glycidyl polyphosphoric acid ester melamine salt, the cardanol glycidyl ether serves as a carbon source, and the carbon content is as high as 80%, which has better and faster carbon formation effect. The carbon content of the commonly used pentaerythritol carbon source in the current multi-component intumescent flame retardant system is only 44%, and the carbon formation advantage of the cardanol glycidyl ether is obvious.

[0025] 3. In the structure of the intumescent flame retardant cardanol glycidyl polyphosphoric acid ester melamine salt, the unsaturated alkane long chain of the cardanol derivative can shield the polyphosphoric acid, and improve the filling amount and dispersion performance of the flame retardant in the TPV.

[0026] 4. In the dynamic vulcanization process of the TPV, the unsaturated bond in the intumescent flame retardant cardanol glycidyl polyphosphoric acid ester melamine salt can be crosslinked with the rubber phase through the vulcanizing agent to form a network structure, enhance the interaction effect between the rubber phase and the plastic phase, and improve the physical performance of the TPV.

[0027] 5. The cardanol used in the application is a natural phenolic compound extracted from the agroforestry residues cashew nut shell, and is one of the most commonly used bio-based resources, which has the unique advantages of environmental protection, renewability, low price and rich resources. DETAILED DESCRIPTION

[0028] The application will be further described in detail below in combination with the embodiments.

[0029] The endpoints of the ranges and any values disclosed in this document are not limited to the precise values stated. These ranges and values should be construed and interpreted as being inclusive of values adjacent to the recited ranges and / or values. For values whose distributions are not known exactly, for example, measured or determined values, the exact values are either disclosed or can be inferred from context, and those exact values are hereby incorporated into this specification as if expressly stated in this specification. For numerical values that represent ranges, the endpoints of each range are combined with each other, the endpoints of each range are combined with individual points, and individual points are combined with each other to produce one or more new ranges of values that are specifically disclosed.

[0030] The raw materials used in the examples are commercially available.

[0031] Example 1

[0032] The preparation method of cardanol glycidyl polyphosphate melamine salt comprises the following steps:

[0033] Polyphosphoric acid with a relative molecular weight of 1000 is completely dissolved in a proper amount of ethanol, and dilute sulfuric acid is added to adjust the pH to 5.5. Then cardanol glycidyl ether and melamine are added, and the molar ratio of polyphosphoric acid, cardanol glycidyl ether and melamine is 3:1:2. Then the temperature is raised to 65°C, and reflux stirring is carried out for 3.5h. Then it is cooled, filtered, washed with ethanol for 3 times and dried to obtain cardanol glycidyl polyphosphate melamine salt.

[0034] Example 2

[0035] The preparation method of cardanol glycidyl polyphosphate melamine salt comprises the following steps:

[0036] Polyphosphoric acid with a relative molecular weight of 2000 is completely dissolved in a proper amount of toluene, and dilute sulfuric acid is added to adjust the pH to 5.5. Then cardanol glycidyl ether and melamine are added, and the molar ratio of polyphosphoric acid, cardanol glycidyl ether and melamine is 3:1:2. Then the temperature is raised to 100°C, and reflux stirring is carried out for 3.5h. Then it is cooled, filtered, washed with toluene for 3 times and dried to obtain cardanol glycidyl polyphosphate melamine salt.

[0037] Example 3

[0038] Application of cardanol glycidyl polyphosphate melamine salt in dynamic vulcanization TPV.

[0039] In order to verify the application effect of cardanol glycidyl polyphosphate melamine salt in dynamic vulcanization TPV, two types of dynamic vulcanization TPV, low filling and high filling, are set up for experimental demonstration.

[0040] Low filling dynamic vulcanization TPV: EPDM / PP rubber-plastic ratio is 45 / 55, mass ratio is 70%; mass ratio of intumescent flame retardant is 25%; mass ratio of dynamic vulcanization agent DCP is 0.3%; mass ratio of other additives is 4.7%.

[0041] High filling dynamic vulcanization TPV: EPDM / PP rubber-plastic ratio is 45 / 55, mass ratio is 56%; mass ratio of intumescent flame retardant is 40%; mass ratio of dynamic vulcanization agent DCP is 0.25%; mass ratio of other additives is 3.75%.

[0042] The preparation method of the dynamically vulcanized TPV composite material is as follows: PP and EPDM are mixed in a 60 rpm stirring speed, 180℃ internal mixer for 5 min, then the intumescent flame retardant is mixed for 3 min, finally the dynamic vulcanizing agent DCP and other additives are mixed for 6 min, and the material is discharged to complete the preparation.

[0043] Test sample 1: the cashew phenol glycidyl polyphosphate melamine salt prepared in Example 1 is compounded with a low-filled dynamically vulcanized TPV to obtain test sample 1.

[0044] Test sample 2: the cashew phenol glycidyl polyphosphate melamine salt prepared in Example 1 is compounded with a high-filled dynamically vulcanized TPV to obtain test sample 2.

[0045] Test sample 3: the cashew phenol glycidyl polyphosphate melamine salt prepared in Example 2 is compounded with a low-filled dynamically vulcanized TPV to obtain test sample 3.

[0046] Test sample 4: the cashew phenol glycidyl polyphosphate melamine salt prepared in Example 2 is compounded with a high-filled dynamically vulcanized TPV to obtain test sample 4.

[0047] Control sample 1: polyphosphoric acid with a relative molecular weight of 1000, cashew phenol glycidyl ether and melamine are compounded with a low-filled dynamically vulcanized TPV at a molar ratio of 3:1:2 to obtain control sample 1.

[0048] Control sample 2: polyphosphoric acid with a relative molecular weight of 1000, cashew phenol glycidyl ether and melamine are compounded with a high-filled dynamically vulcanized TPV at a molar ratio of 3:1:2 to obtain control sample 2.

[0049] The performance tests of the test samples and the control samples are carried out to obtain Table 1.

[0050] Table 1 Performance test of dynamically vulcanized TPV composite material

[0051] Item Test Sample 1 Test Sample 2 Test Sample 3 Test Sample 4 Control Sample 1 Control Sample 2 Tensile Strength (MPa) 10.33 9.78 10.02 9.11 8.42 8.03 Elongation at Break (%) 276 232 249 204 120 81 Oxygen Index (%) 28.4 30.5 27.8 29.2 26.0 28.9 UL94 (3 mm) V-0 V-0 V-0 V-0 V-1 V-1

[0052] It can be known by comparing test sample 1, test sample 3 and control sample 1 that the TPV filled with the “three-source-in-one” intumescent flame retardant cashew phenol glycidyl polyphosphate melamine salt is superior to the TPV filled with the traditional multi-component intumescent flame retardant in physical and flame-retardant properties, which indicates that the affinity of the cashew phenol glycidyl polyphosphate melamine salt with the TPV is better and the flame-retardant effect is better.

[0053] It can be known by comparing test sample 2, test sample 4 and control sample 2 that the cashew phenol glycidyl polyphosphate melamine salt is more suitable for high filling in the TPV than the traditional multi-component intumescent flame retardant.

[0054] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including that each technical feature is combined in any other suitable manner. These simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. An intumescent flame retardant for thermoplastic vulcanizate (TPV), characterized in that It is cardanol glycidyl polyphosphate melamine salt, and its molecular structure is as follows: or or or in, 2. The method for synthesizing an intumescent flame retardant for thermoplastic vulcanizate (TPV) according to claim 1, characterized in that The steps are as follows: first, polyphosphoric acid is added to a solvent and completely dissolved, acid is added to adjust the pH to 2.5-6.5, then cardanol glycidyl ether and melamine are added, then the temperature is raised to 40-130° C., refluxed and stirred for 0.5-12 hours, and finally cooled, filtered, washed with a solvent and then dried to obtain cardanol glycidyl polyphosphate melamine salt.

3. The method for synthesizing an intumescent flame retardant for thermoplastic vulcanizate (TPV) according to claim 2, characterized in that The molecular weight of the polyphosphoric acid described in the step is 1000 to 10000.

4. The method for synthesizing an intumescent flame retardant for thermoplastic vulcanizate (TPV) according to claim 2, characterized in that The solvent described in the step is one or more of ethanol, toluene, xylene, acetone, DMF, and THF.

5. The method for synthesizing an intumescent flame retardant for thermoplastic vulcanizate (TPV) according to claim 2, characterized in that The regulating acid described in the step is one or more of sulfuric acid, hydrochloric acid, formic acid and acetic acid.

6. The method for synthesizing an intumescent flame retardant for thermoplastic vulcanizate (TPV) according to claim 2, characterized in that The molar ratio of polyphosphoric acid, cardanol glycidyl ether and melamine in the step is 1.8-3.8:1:1.8-3.

8.

7. The use of an intumescent flame retardant for thermoplastic vulcanizate (TPV) according to claim 1, characterized in that Applicable to all dynamically vulcanized TPV materials.

8. The use of an intumescent flame retardant for thermoplastic vulcanizate (TPV) according to claim 7, characterized in that In the dynamically vulcanized TPV, the mass proportion of cardanol glycidyl polyphosphate melamine salt is 10% to 50%.

9. The use of an intumescent flame retardant for thermoplastic vulcanizate (TPV) according to claim 7, characterized in that In the dynamically vulcanized TPV, the dynamic vulcanizing agent is one or more of sulfur, sulfur-containing compounds, peroxides, amines, and metal oxides; and the mass proportion of the dynamic vulcanizing agent is 0.1% to 2.0%.

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