Bio-based intumescent flame retardant for TPV (thermoplastic vulcanizate) as well as synthesis method and application of bio-based intumescent flame retardant

Abstract

The invention discloses a bio-based intumescent flame retardant for TPV (thermoplastic vulcanizate) as well as a synthesis method and application of the bio-based intumescent flame retardant. The preparation method comprises the following steps: pouring phytic acid into a solvent, uniformly mixing, adding cardanol glycidyl ether and melamine, heating to 40-80 DEG C, carrying out reflux stirring for 1-24 hours, cooling, carrying out suction filtration, washing with the solvent, and drying to obtain the cardanol glycidyl phytate melamine salt. The main components of the intumescent flame retardant are derived from biomass, so that the intumescent flame retardant is green, environment-friendly and renewable, and conforms to the current idea of resource recycling. Meanwhile, the intumescent flame retardant integrates three sources and is simple in synthesis process, unsaturated alkane long chains of the cardanol derivatives in the structure can shield phytic acid and improve dispersion of the flame retardant in TPV, unsaturated bonds in the cardanol derivatives can be cross-linked with rubber in the dynamic vulcanization process of TPV to form a three-dimensional network structure, and the flame retardant property is improved. The interaction between the rubber phase and the plastic phase is enhanced. The flame retardant has the advantages of simple synthesis process and controllable cost, and can effectively maintain the physical properties of TPV during high filling.

Description

Technical Field

[0001] The invention belongs to the technical field of flame retardancy of thermoplastic vulcanized rubber, and specifically relates to a bio-based intumescent flame retardant (cardanol glycidyl phytate melamine salt) for thermoplastic vulcanized rubber TPV, and its synthesis and application in thermoplastic vulcanized rubber. Background Art

[0002] Thermoplastic vulcanizate (TPV) is a type of thermoplastic material that is a blend of plastic and rubber. It not only has the good processability and recyclability of plastic, but also has the elasticity of rubber, so it is widely used in the fields of automobiles, home appliances, wires and cables, etc. However, due to the limitation of the base material, its flame retardant performance is poor, so in actual applications, it needs to be filled with flame retardants to make it practical.

[0003] Intumescent flame retardants are widely used in polymer materials because of their halogen-free, low smoke, low toxicity, environmental friendliness, and good flame retardant effects. The flame retardant effect of intumescent flame retardants is mainly achieved by carbon sources, acid sources, and gas sources. 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 effect for TPV. However, polyphosphates, pentaerythritol, etc. have poor compatibility with TPV, which affects the processing difficulty and physical properties of TPV after filling. Therefore, ensuring the flame retardant effect of intumescent flame retardants while improving the affinity with polymer materials such as TPV has become an important direction for the development of intumescent flame retardants.

[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, the current mainstream intumescent flame retardants all rely on chemical synthesis, and carbon emissions and environmental pollution are inevitable in the manufacturing process. Therefore, the use of renewable biomass materials as a substitute is in line with the current concept of sustainable development.

[0005] Phytic acid, also known as cyclohexanehexol hexaphosphate, has strong acidity and strong chelating ability. It is mainly found in the seeds, roots and stems of plants, among which the highest content is found in the seeds of leguminous plants, bran and germ of cereals. The phosphorus content in its molecule is as high as 28%, which is an excellent acid source for bio-based flame retardants. In the public invention "A modified melamine phytate flame retardant and its preparation method and application (CN202110235327.7)", phytic acid, melamine and metal salts are used to synthesize a layered melamine phytate containing metal salts for use in polymer materials. However, filling this type of "three-source-in-one" expansion flame retardant into TPV or other rubber and elastomer materials only plays a flame retardant role, and because they affect the interaction effect between polymer molecules, the physical and mechanical properties of the material are often significantly reduced, which is a major disadvantage in its application process.

[0006] 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. In view of the problem that it is difficult to achieve both flame retardancy and physical and mechanical properties of TPV, it is proposed to use cardanol as the core of the intumescent flame retardant. On the one hand, a "three-source-in-one" intumescent flame retardant can be achieved to obtain better flame retardant effect. On the other hand, the unsaturated long alkyl chain of cardanol can be cross-linked with the TPV rubber phase to form a three-dimensional network structure, thereby improving the physical and mechanical properties of TPV. Summary of the invention

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

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] The present invention provides a bio-based intumescent flame retardant for thermoplastic vulcanized rubber TPV, which is cardanol glycidyl phytate melamine salt, and the molecular structure is as follows:

[0010]

[0011] The present invention also provides a method for synthesizing a bio-based intumescent flame retardant for thermoplastic vulcanized rubber TPV, namely, cardanol glycidyl phytate melamine salt, the steps of which are as follows: first, phytic acid is added to a solvent and stirred evenly, then cardanol glycidyl ether and melamine are added, then the temperature is raised to 40 to 80° C., refluxed and stirred for 1 to 24 hours, and finally cooled, filtered, washed with a solvent and dried to obtain cardanol glycidyl phytate melamine salt.

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

[0013]

[0014] The phytic acid described in the steps is derived from seeds, roots, stems and tubers of plants.

[0015] The solvent described in the step is one or more of water, ethanol and acetone.

[0016] The molar ratio of phytic acid, cardanol glycidyl ether and melamine in the step is 1.8-3.8:1:1.8-3.8.

[0017] The cardanol glycidyl phytate melamine salt prepared by the present invention is suitable for all TPV materials synthesized by dynamic vulcanization.

[0018] In the dynamically vulcanized TPV, the mass proportion of the intumescent flame retardant, cardanol glycidyl phytate melamine salt, is 10% to 50%.

[0019] 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%.

[0020] The present invention adopts the above technical scheme, and utilizes the bridging effect of cardanol glycidyl ether on phytic 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 phytic acid, improve the dispersion performance of the flame retardant in TPV, and the unsaturated bonds in the cardanol derivatives can also cross-link with the rubber phase during the dynamic vulcanization process of TPV to form a three-dimensional network structure, enhance the interaction effect between the flame retardant and the rubber phase and the plastic phase, and realize the maintenance of the physical properties of TPV under high filling. Specifically, the beneficial effects of the present invention are as follows:

[0021] 1. The present invention constructs a "three-in-one" bio-based intumescent flame retardant - cardanol glycidyl phytate melamine salt through cardanol glycidyl ether and phytic acid.

[0022] 2. In the system of cardanol glycidyl phytate melamine salt, cardanol glycidyl ether as a carbon source has a carbon content of up to 80%, which has a better and faster carbonization effect. At present, the carbon content of pentaerythritol commonly used in multi-component intumescent flame retardant systems is only 44%. In comparison, cardanol glycidyl ether has obvious advantages in carbonization.

[0023] 3. In the structure of the bio-based intumescent flame retardant cardanol glycidyl phytate melamine salt, the unsaturated alkane long chain of cardanol derivatives can also shield phytic acid, thereby increasing the filling amount and dispersion performance of the flame retardant in TPV.

[0024] 4. During the dynamic vulcanization process of TPV, the unsaturated bonds in the bio-based intumescent flame retardant cardanol glycidyl phytate melamine salt can be cross-linked with the rubber phase through the vulcanizer to form a three-dimensional network structure, thereby enhancing the interaction between the flame retardant and the rubber phase and the plastic phase, thereby improving the physical properties of TPV.

[0025] 5. One of the bio-based materials used in the present invention, phytic acid, is an organic phosphorus compound extracted from the seeds, roots, and stems of plants; the second bio-based material used in the present invention, the cardanol derivative, is a secondary processed product of cardanol extracted from cashew nut shells, which are agricultural and forestry residues. These two bio-based materials are commonly used and easily accessible resources, and have the unique advantages of being environmentally friendly, renewable, low-priced, and abundant in resources. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below with reference to the embodiments.

[0027] 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.

[0028] The raw materials used in the examples are all commercially available.

[0029] Example 1

[0030] The preparation method of cardanol glycidyl phytate melamine salt comprises the following steps:

[0031] Phytic acid was added to an appropriate amount of ethanol and completely dissolved, and then cardanol glycidyl ether and melamine were added, wherein the molar ratio of phytic acid, cardanol glycidyl ether and melamine was 2:1:2. The temperature was then raised to 70°C, refluxed and stirred for 3.5 hours, then cooled, filtered, washed with ethanol 3 times and dried to obtain cardanol glycidyl phytate melamine salt.

[0032] Example 2

[0033] The preparation method of cardanol glycidyl phytate melamine salt comprises the following steps:

[0034] Phytic acid is added to an appropriate amount of ethanol and completely dissolved, and then cardanol glycidyl ether and melamine are added, wherein the molar ratio of phytic acid, cardanol glycidyl ether and melamine is 2:1:4. Then the temperature is raised to 70°C, refluxed and stirred for 5 hours, then cooled, filtered, washed with ethanol 3 times and dried to obtain cardanol glycidyl phytate melamine salt.

[0035] Example 3

[0036] Application of Cardanol Glycidyl Phytate Melamine Salt in Dynamic Vulcanized TPV

[0037] In order to verify the application effect of cardanol glycidyl phytate melamine salt in dynamically vulcanized TPV, two types of dynamically vulcanized TPV with low filling and high filling were set up for experimental demonstration.

[0038] 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%.

[0039] 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%.

[0040] 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.

[0041] Test sample 1: The cardanol glycidyl phytate melamine salt prepared in Example 1 was compounded with low-filled dynamically vulcanized TPV to obtain test sample 1.

[0042] Test sample 2: Test sample 2 was obtained by compounding the cardanol glycidyl phytate melamine salt prepared in Example 1 with a high-filled dynamically vulcanized TPV.

[0043] Test sample 3: Test sample 3 was obtained by compounding the cardanol glycidyl phytate melamine salt prepared in Example 2 with low-filled dynamically vulcanized TPV.

[0044] Test sample 4: Test sample 4 was obtained by compounding the cardanol glycidyl phytate melamine salt prepared in Example 2 with a high-filled dynamically vulcanized TPV.

[0045] Control sample 1: Phytic acid, cardanol glycidyl ether, and melamine were compounded with low-filled dynamically vulcanized TPV in a molar ratio of 2:1:2 to obtain control sample 1.

[0046] Control sample 2: Phytic acid, cardanol glycidyl ether, and melamine were compounded with a highly filled dynamically vulcanized TPV at a molar ratio of 2:1:2 to obtain control sample 2.

[0047] The test samples and control samples were tested for performance, and the results are shown in Table 1.

[0048] Table 1 Dynamically vulcanized TPV composite material performance test

[0049] project Test sample 1 Test sample 2 Test sample 3 Test sample 4 Control sample 1 Control sample 2 Tensile strength(MPa) 9.27 8.56 9.40 9.03 7.16 5.49 Elongation at break (%) 205 181 227 199 155 92 Oxygen index (%) 27.1 29.4 26.6 28.5 24.7 25.7 UL94(3mm) V-0 V-0 V-0 V-0 V-1 V-1

[0050] 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 phytate melamine salt has better physical and flame retardant properties, which indicates that cardanol glycidyl phytate melamine salt has better affinity with TPV and flame retardant effect.

[0051] By comparing test sample 2, test sample 4 and control sample 2, it can be seen that cardanol glycidyl phytate melamine salt is more suitable for high filling in TPV than the same type of flame retardant added in multiple components.

[0052] 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. A bio-based intumescent flame retardant for thermoplastic vulcanizate (TPV), characterized in that It is cardanol glycidyl phytate melamine salt, and its molecular structure is as follows:

2. A bio-based intumescent flame retardant for thermoplastic vulcanizate (TPV) according to claim 1, characterized in that The steps of the synthesis method are as follows: first, phytic acid is added to a solvent and stirred evenly, then cardanol glycidyl ether and melamine are added, then the temperature is raised to 40-80° C., refluxed and stirred for 1-24 hours, and finally cooled, filtered, washed with a solvent and dried to obtain cardanol glycidyl phytate melamine salt.

3. A bio-based 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. A bio-based intumescent flame retardant for thermoplastic vulcanizate (TPV) as claimed in claim 2, characterized in that The phytic acid described in the synthesis method steps is derived from seeds, roots, stems and tubers of plants.

5. A bio-based intumescent flame retardant for thermoplastic vulcanizate (TPV) as claimed in claim 2, characterized in that The solvent described in the synthesis method steps is one or more of water, ethanol and acetone.

6. A bio-based intumescent flame retardant for thermoplastic vulcanizate (TPV) as claimed in claim 2, characterized in that The molar ratio of phytic acid, cardanol glycidyl ether and melamine in the synthesis method step is 1.8-3.8:1:1.8-3.

8.

7. A bio-based intumescent flame retardant for thermoplastic vulcanizate (TPV) according to claim 1, characterized in that Applicable to all dynamically vulcanized TPV materials.

8. A bio-based intumescent flame retardant for thermoplastic vulcanizate (TPV) as claimed in claim 7, characterized in that In the dynamically vulcanized TPV, the mass proportion of cardanol glycidyl phytate melamine salt is 10% to 50%.

9. A bio-based intumescent flame retardant for thermoplastic vulcanizate (TPV) according to claim 7, characterized in that In the dynamically vulcanized TPV, the dynamic vulcanizing agent used is one or more of sulfur, sulfur-containing compounds, peroxides, amines, and metal oxides.

10. A bio-based intumescent flame retardant for thermoplastic vulcanizate (TPV) according to claim 9, characterized in that: The mass proportion of the dynamic vulcanizing agent is 0.1% to 2.0%.

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