Intumescent flame retardant for thermoplastic vulcanizate (TPV) as well as synthesis method and application of intumescent flame retardant

Abstract

The invention discloses an intumescent flame retardant for thermoplastic vulcanized rubber (TPV), namely anacardol glycidyl polyphosphate melamine salt as well as synthesis and application thereof. The preparation method comprises the following steps: pouring polyphosphoric acid into a solvent, adding acid to regulate the pH value of a system to 2.5-6.5 after polyphosphoric acid is completely dissolved, adding cardanol glycidyl ether and melamine, heating to 40-130 DEG C, carrying out reflux stirring for 0.5-12 hours, cooling, carrying out suction filtration, washing with the solvent, and drying to obtain the cardanol glycidyl polyphosphate melamine salt. The intumescent flame retardant has a carbon source, an acid source and a gas source, the synthesis process is simple, unsaturated alkane long chains of cardanol derivatives in the structure can shield polyphosphoric acid and improve the dispersion of the flame retardant in TPV, unsaturated bonds can be cross-linked with rubber in the dynamic vulcanization process of TPV to form a network structure, and the intumescent flame retardant has a good flame retardant property. The interaction effect of the rubber phase and the plastic phase is enhanced. Therefore, the flame retardant can maintain the physical properties of the TPV while being highly filled.

Description

Technical Field

[0001] The invention belongs to the technical field of flame retardancy of thermoplastic vulcanized rubber, and specifically relates to a cardanol glycidyl polyphosphate melamine salt, a synthesis method and application of the same in thermoplastic vulcanized rubber. Background Art

[0002] Thermoplastic vulcanizate (TPV) is a type of thermoplastic material that is a blend of plastic and rubber. In its internal structure, plastic is a continuous phase and highly cross-linked rubber is a dispersed phase. This special "sea-island" structure makes TPV not only have the good processability and recyclability of plastic, but also the elasticity of rubber. Therefore, it is widely used in the fields of automobiles, home appliances, wires and cables, etc. However, due to the characteristics of the TPV substrate, its flame retardant performance is poor, so in actual applications, TPV is often filled with flame retardants to make it practical.

[0003] In recent years, intumescent flame retardants have been widely used for their halogen-free, low smoke, low toxicity, environmental friendliness, and good flame retardant effects. The intumescent flame retardant synergistic system includes a carbon source, an acid source, and a gas source. During combustion, the acid source decomposes to form a strong acid dehydrating agent to catalyze the carbon source to form a continuous carbon layer that is difficult to burn. At the same time, the gas source decomposes to produce non-flammable gas, which causes the carbon layer to expand continuously while cooling, ultimately achieving the purpose of efficient flame retardancy. At present, the most widely used intumescent flame retardant synergistic system is ammonium polyphosphate (acid source), pentaerythritol (carbon source), and melamine (gas source) system, which can provide good flame retardant effects for TPV. However, due to the poor compatibility between polyphosphates, pentaerythritol, etc. and TPV substrates, the processing difficulty of filled TPV and the physical properties of the composite material are affected. Therefore, while ensuring the flame retardant effect of the intumescent flame retardant synergistic system, improving its affinity with TPV has become an important development direction for TPV flame retardancy.

[0004] The single-component intumescent flame retardant connects the carbon source, acid source, and gas source on the same molecule through chemical bonds to form a "three-source-in-one" structure, which can effectively overcome the shortcomings of multi-component intumescent flame retardants, such as poor compatibility between the components and the substrate, separation between the components, and inability to fully cooperate. It is an ideal flame retardant in the field of polymer materials. In addition, since the current intumescent flame retardants basically rely on chemical synthesis, carbon emissions and environmental pollution are inevitable in the manufacturing process, so the use of renewable biomass materials as a substitute is also in line with the current concept of sustainable development.

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

[0006] For example, in the patent publication "A method for preparing a modified waterborne polyurethane coating (CN 202410789728.0)", a waterborne chain extender of cardanol is synthesized using cardanol glycidyl ether, a derivative of cardanol. The triphenyl triazine structure contained in its structure significantly improves the tensile strength and elongation at break of polyurethane while improving the water absorption of polyurethane. Moreover, this structure also acts as a carbonizing agent when the material burns, and forms an expansion flame retardant system with sodium phytate in the system, thereby improving the fire retardant properties of polyurethane coatings. In the patent publication "A phosphorus-containing cardanol-based polyurethane prepolymer modified phenolic foam and its preparation method (CN201610188926.7)", cardanol glycidyl ether is synthesized, and phosphorus is introduced into the unsaturated double bond of cardanol glycidyl ether to improve the flame retardancy of phenolic foam. At the same time, the long fatty chain structure with good flexibility on cardanol glycidyl ether is used to improve the defects of high elongation and slag drop rate of phenolic foam. Summary of the invention

[0007] In order to solve the problems of processing difficulties and affected physical properties of composite materials encountered when existing intumescent flame retardants are used in TPV, the present invention provides a method for preparing cardanol glycidyl polyphosphate melamine salt for TPV. Its "three-source-in-one" feature can effectively overcome the shortcomings of poor compatibility between multi-component intumescent flame retardant components and TPV substrates, separation of various components, and lack of full synergy, thereby maintaining the physical properties of TPV under high filling.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

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

[0010]

[0011] The present invention also provides a method for synthesizing an intumescent flame retardant for thermoplastic vulcanizate (TPV) - cardanol glycidyl polyphosphate melamine salt, the steps of which are as follows: firstly, polyphosphoric acid is added into a solvent to be 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 with stirring for 0.5-12 hours, finally cooled, filtered, washed with a solvent and dried to obtain cardanol glycidyl polyphosphate melamine salt.

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

[0013]

[0014] in

[0015] The molecular weight of the polyphosphoric acid described in the step is between 1000 and 10000.

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

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

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

[0019] The cardanol glycidyl polyphosphate melamine salt prepared by the present invention is suitable for all TPV materials synthesized by dynamic vulcanization.

[0020] In the dynamically vulcanized TPV, the mass proportion of the intumescent flame retardant, cardanol glycidyl polyphosphate melamine salt, is 10% to 50%.

[0021] In the dynamically vulcanized TPV, the dynamic vulcanizing agent used in the TPV is one or more of sulfur, sulfur-containing compounds, peroxides, amines, and metal oxides; the mass proportion of the dynamic vulcanizing agent is 0.1% to 2.0%.

[0022] The present invention adopts the above technical scheme, and utilizes the bridging effect of cardanol glycidyl ether on polyphosphoric acid and melamine to realize the synthesis of "three-source-in-one" intumescent flame retardant. This scheme is not only simple in process, but also the unsaturated alkane long chain of cardanol derivatives in the flame retardant structure can shield polyphosphoric acid, improve the dispersion performance of the flame retardant in TPV, and the unsaturated bonds therein can also cross-link with the rubber phase during the dynamic vulcanization process of TPV to form a network structure, enhance the interaction effect between the rubber phase and the plastic phase, and thereby achieve the maintenance of the physical properties of TPV under high filling. Specifically, the beneficial effects of the present invention are as follows:

[0023] 1. The present invention constructs a "three-in-one" intumescent flame retardant - cardanol glycidyl polyphosphate melamine salt through cardanol glycidyl ether.

[0024] 2. In the intumescent flame retardant system of cardanol glycidyl polyphosphate melamine salt, cardanol glycidyl ether is used as a carbon source with a carbon content of up to 80%, which has a better and faster carbonization effect. At present, the carbon content of pentaerythritol carbon source commonly used in multi-component intumescent flame retardant systems is only 44%. In comparison, cardanol glycidyl ether has obvious advantages in carbonization.

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

[0026] 4. During the dynamic vulcanization process of TPV, the unsaturated bonds in the intumescent flame retardant cardanol glycidyl polyphosphate melamine salt can be cross-linked with the rubber phase through the vulcanizer to form a network structure, enhance the interaction between the rubber phase and the plastic phase, and improve the physical properties of TPV.

[0027] 5. The cardanol described in the present invention is a natural phenolic compound extracted from cashew nut shells, which are agricultural and forestry residues. It is one of the most commonly used bio-based resources and has the unique advantages of being environmentally friendly, renewable, low-priced and abundant in resources. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below with reference to the embodiments.

[0029] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in the present invention.

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

[0031] Example 1

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

[0033] Add polyphosphoric acid with a relative molecular weight of 1000 to an appropriate amount of ethanol and completely dissolve it, add dilute sulfuric acid to adjust the pH to 5.5, and then add cardanol glycidyl ether and melamine, wherein the molar ratio of polyphosphoric acid, cardanol glycidyl ether and melamine is 3:1:2. Then heat to 65°C, reflux and stir for 3.5 hours, then cool, filter, wash with ethanol 3 times and dry 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] Add polyphosphoric acid with a relative molecular weight of 2000 to an appropriate amount of toluene to completely dissolve it, add dilute sulfuric acid to adjust the pH to 5.5, and then add cardanol glycidyl ether and melamine, wherein the molar ratio of polyphosphoric acid, cardanol glycidyl ether and melamine is 3:1:2. Then heat to 100°C, reflux and stir for 3.5h, then cool, filter, wash with toluene 3 times and dry to obtain cardanol glycidyl polyphosphate melamine salt.

[0037] Example 3

[0038] Application of cardanol glycidyl polyphosphate melamine salt in dynamically vulcanized TPV.

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

[0040] Low-filled dynamically vulcanized TPV: EPDM / PP rubber-plastic ratio is 45 / 55, accounting for 70% by mass; the mass proportion of intumescent flame retardant is 25%; the mass proportion of dynamic vulcanizer DCP is 0.3%; the mass proportion of other additives is 4.7%.

[0041] Highly filled dynamically vulcanized TPV: EPDM / PP rubber-plastic ratio is 45 / 55, accounting for 56% by mass; the mass proportion of intumescent flame retardant is 40%; the mass proportion of dynamic vulcanizer DCP is 0.25%; the mass proportion of other additives is 3.75%.

[0042] The preparation method of dynamically vulcanized TPV composite materials is as follows: add PP and EPDM to an internal mixer at 180°C and mix for 5 minutes while maintaining a stirring speed of 60 rpm, then add an intumescent flame retardant and mix for 3 minutes, and finally add a dynamic vulcanizer DCP and other additives and mix for 6 minutes, discharge the materials, and complete the production.

[0043] Test sample 1: The cardanol glycidyl polyphosphate melamine salt prepared in Example 1 was compounded with low-filled dynamically vulcanized TPV to obtain test sample 1.

[0044] Test sample 2: Test sample 2 was obtained by compounding the cardanol glycidyl polyphosphate melamine salt prepared in Example 1 with a highly filled dynamically vulcanized TPV.

[0045] Test sample 3: Test sample 3 was obtained by compounding the cardanol glycidyl polyphosphate melamine salt prepared in Example 2 with low-filled dynamically vulcanized TPV.

[0046] Test sample 4: Test sample 4 was obtained by compounding the cardanol glycidyl polyphosphate melamine salt prepared in Example 2 with a high-filled dynamically vulcanized TPV.

[0047] Control sample 1: Polyphosphoric acid with a relative molecular weight of 1000, cardanol glycidyl ether, and melamine were compounded with low-filled dynamically vulcanized TPV in 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, cardanol glycidyl ether, and melamine were compounded with a highly filled dynamically vulcanized TPV in a molar ratio of 3:1:2 to obtain control sample 2.

[0049] The test samples and control samples were tested for performance, and the results are shown in Table 1.

[0050] Table 1 Dynamically vulcanized TPV composite material performance test

[0051] project 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(3mm) V-0 V-0 V-0 V-0 V-1 V-1

[0052] By comparing test sample 1, test sample 3 and control sample 1, it can be seen that the TPV filled with the "three-in-one" intumescent flame retardant cardanol 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 cardanol glycidyl polyphosphate melamine salt has better affinity with TPV and better flame retardant effect.

[0053] By comparing test sample 2, test sample 4 and control sample 2, it can be seen that cardanol glycidyl polyphosphate melamine salt is more suitable for high filling in TPV than traditional multi-component intumescent flame retardants.

[0054] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

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:

2. An intumescent flame retardant for thermoplastic vulcanizate (TPV) as claimed in claim 1, characterized in that The steps of the synthesis method 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, and then cardanol glycidyl ether and melamine are added, followed by heating to 40-130° C., reflux stirring for 0.5-12 hours, and finally cooling, filtering, washing with a solvent and drying to obtain cardanol glycidyl polyphosphate melamine salt.

3. An intumescent flame retardant for thermoplastic vulcanizate (TPV) as claimed in claim 2, characterized in that The reaction formula of the synthesis method is as follows: in 4. An intumescent flame retardant for thermoplastic vulcanizate (TPV) as claimed in claim 2, characterized in that The molecular weight of the polyphosphoric acid described in the steps of the synthesis method is between 1000 and 10000.

5. An intumescent flame retardant for thermoplastic vulcanizate (TPV) as claimed in claim 2, characterized in that The solvent described in the steps of the synthesis method is one or more of ethanol, toluene, xylene, acetone, DMF, and THF.

6. An intumescent flame retardant for thermoplastic vulcanizate (TPV) as claimed in claim 2, characterized in that The regulating acid described in the steps of the synthesis method is one or more of sulfuric acid, hydrochloric acid, formic acid and acetic acid.

7. An intumescent flame retardant for thermoplastic vulcanizate (TPV) as claimed in claim 2, characterized in that In the steps of the synthesis method, the molar ratio of polyphosphoric acid, cardanol glycidyl ether and melamine is 1.8-3.8:1:1.8-3.

8.

8. An intumescent flame retardant for thermoplastic vulcanizate (TPV) as claimed in claim 1, characterized in that Applicable to all dynamically vulcanized TPV materials.

9. An intumescent flame retardant for thermoplastic vulcanizate (TPV) as claimed in claim 8, characterized in that In the dynamically vulcanized TPV, the mass proportion of cardanol glycidyl polyphosphate melamine salt is 10% to 50%.

10. An intumescent flame retardant for thermoplastic vulcanizate (TPV) as claimed in claim 8, 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; the mass proportion of the dynamic vulcanizing agent is 0.1% to 2.0%.

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