A bio-based intumescent flame retardant for thermoplastic vulcanizate (TPV) and its synthesis method and application

Abstract

The application discloses a kind of for thermoplastic vulcanizate TPV bio-based intumescent flame retardant and synthesis method and application.First, phytic acid is poured into solvent, after mixing evenly, add cashew phenol glycidyl ether and melamine, temperature is increased to 40~80 ℃, reflux stirring 1~24h, cooling, filtration, after washing with solvent, dry, obtain cashew phenol glycidyl phytic acid ester melamine salt.The main component of the intumescent flame retardant is derived from biomass, green and environmentally friendly renewable, in line with the current resource recycling concept.At the same time, the intumescent flame retardant "three sources in one", simple synthesis process, unsaturated alkane long chain of cashew phenol derivative can shield phytic acid, improve the dispersion of flame retardant in TPV, unsaturated bond in cashew phenol derivative can also crosslink with rubber in TPV dynamic vulcanization process, form three-dimensional network structure, enhance the interaction of rubber phase and plastic phase.The synthesis process of the flame retardant is simple, cost controllable, can be effectively maintained while high filling TPV physical performance.

Description

Technical Field

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

[0002] Thermoplastic vulcanizate (TPV) is a thermoplastic material formed by blending plastic and rubber. It combines the good processability and recyclability of plastic with the elasticity of rubber, making it widely used in automobiles, home appliances, wire and cable, and other fields. However, due to limitations in its base material, its flame retardancy is poor, so in practical applications, it requires flame retardant addition to enhance its practical value.

[0003] Intumescent flame retardants (IFRs) are widely used in polymer materials due to their halogen-free, low-smoke, low-toxicity, environmentally friendly, and effective flame retardancy. Their flame retardancy is primarily achieved through the use of carbon, acid, and gas sources. During combustion, the acid decomposes to form a strongly acidic dehydrating agent, which catalyzes the carbon source to form a continuous, difficult-to-burn char layer. Simultaneously, the gas source decomposes to produce non-flammable gases, which cool the material while causing the char layer to expand continuously, ultimately achieving effective flame retardancy. Currently, the most widely used synergistic IFR system is ammonium polyphosphate (acid source), pentaerythritol (carbon source), and melamine (gas source), which provide excellent flame retardancy for TPVs. However, polyphosphates and pentaerythritol have poor compatibility with TPVs, compromising processing and physical properties of the filled TPVs. Therefore, maintaining the flame retardant effectiveness of IFRs while improving their compatibility with polymers like TPV has become a key development direction for IFRs.

[0004] Single-component intumescent flame retardants chemically link a carbon source, acid source, and gas source into a single molecule, creating a "three-in-one" structure. This effectively overcomes the shortcomings of multi-component intumescent flame retardants, which suffer from poor compatibility with substrates, separation between components, and lack of synergy, making them an ideal flame retardant in the polymer materials field. Furthermore, currently mainstream intumescent flame retardants rely on chemical synthesis, inevitably generating carbon emissions and environmental pollution during the manufacturing process. Therefore, using renewable biomass materials as an alternative aligns with current sustainable development concepts.

[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, the bran and germ of cereals. The phosphorus content in its molecule is as high as 28%, making it an excellent acid source for bio-based flame retardants. In the public invention “A modified melamine phytate flame retardant, its preparation method and application (CN202110235327.7)”, phytic acid, melamine and metal salts were 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 or 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 and prepared from natural cashew nut shell liquid and is one of the cashew industry's low-cost and readily available by-products. Among the numerous renewable natural bio-based resources, cardanol is considered an important bio-based raw material due to its unique chemical structure, abundant content, and low cost. The molecular structure of cardanol consists of a phenolic hydroxyl group, a benzene ring, and a long alkyl chain containing an olefin structure. The phenolic hydroxyl group is highly chemically reactive and can undergo reactions such as esterification, etherification, and epoxidation; the benzene ring is a rigid six-membered ring that can undergo substitution reactions such as sulfonation; and the long-chain alkyl group containing an olefin structure can also provide multiple reaction sites. It is precisely these chemical structures that distinguish cardanol from other natural bio-based resources, exhibiting excellent plasticity and important application value in the field of flame retardant polymer materials. In order to solve 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 is realized to obtain better flame retardant effect. On the other hand, the unsaturated long alkyl chain of cardanol is 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 affected physical and mechanical properties of materials encountered when existing intumescent flame retardants are used in TPV, the present invention provides a preparation method of cardanol glycidyl phytate melamine salt for TPV. Its "three-source-in-one" feature can effectively overcome the shortcomings of poor compatibility between the components of the multi-component intumescent flame retardant and the TPV substrate, separation between the components, 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 solutions adopted by the present invention are as follows:

[0009] The present invention provides a bio-based intumescent flame retardant for thermoplastic vulcanizate (TPV), which is cardanol glycidyl phytate melamine salt, and has the following molecular structure:

[0010]

[0011] The present invention also provides a method for synthesizing a bio-based intumescent flame retardant for thermoplastic vulcanizate (TPV) - 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 40-80°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.

[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 and stems 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 solution and utilizes the bridging effect of cardanol glycidyl ether on phytic acid and melamine to achieve the synthesis of a "three-source-in-one" intumescent flame retardant. This solution is not only simple in process, but the long unsaturated alkane chain of the cardanol derivative in the flame retardant structure can also shield phytic acid, improving the dispersion performance of the flame retardant in TPV. The unsaturated bonds in the cardanol derivative can also cross-link with the rubber phase during the dynamic vulcanization process of TPV to form a three-dimensional network structure, thereby enhancing the interaction effect between the flame retardant and the rubber phase and the plastic phase, and achieving 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 cardanol glycidyl phytate melamine salt system, cardanol glycidyl ether, with a carbon content of up to 80%, exhibits superior and faster charring. Compared to the pentaerythritol carbon source commonly used in multi-component intumescent flame retardant systems, which has a carbon content of only 44%, cardanol glycidyl ether exhibits a significant charring advantage.

[0023] 3. In the structure of the bio-based intumescent flame retardant cardanol glycidyl phytate melamine salt, the long unsaturated alkane chain of the cardanol derivative 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. Phytic acid, one of the bio-based materials used in this invention, is an organophosphorus compound extracted from plant seeds, roots, and stems. A second bio-based material used in this invention, a cardanol derivative, is a secondary processed product of cardanol extracted from cashew nut shells, a source of agricultural and forestry residues. These two bio-based materials are commonly available and readily available resources, offering unique advantages such as environmental friendliness, reproducibility, affordability, and abundance. DETAILED DESCRIPTION

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

[0027] The endpoints of the ranges disclosed herein and any values ​​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 endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered to be 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 completely dissolved in an appropriate amount of ethanol, followed by the addition of cardanol glycidyl ether and melamine, wherein the molar ratio of phytic acid, cardanol glycidyl ether, and melamine was 2:1:2. The mixture was then heated to 70°C and refluxed with stirring for 3.5 hours. The mixture was then cooled, filtered, washed three times with ethanol, 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 was completely dissolved in an appropriate amount of ethanol, followed by the addition of cardanol glycidyl ether and melamine, wherein the molar ratio of phytic acid, cardanol glycidyl ether, and melamine was 2:1:4. The temperature was then raised to 70°C, refluxed and stirred for 5 hours, and then cooled, filtered, washed three times with ethanol, and dried to obtain cardanol glycidyl phytate melamine salt.

[0035] Example 3

[0036] Application of Cardanol Glycidyl Phytate Melamine Salt in Dynamically 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: The EPDM / PP rubber-plastic ratio is 45 / 55, accounting for 70% by mass; the intumescent flame retardant accounts for 25% by mass; the dynamic vulcanizing agent DCP accounts for 0.3% by mass; and other additives account for 4.7% by mass.

[0039] Highly filled dynamically vulcanized TPV: The EPDM / PP rubber-plastic ratio is 45 / 55, accounting for 56% by mass; the intumescent flame retardant accounts for 40% by mass; the dynamic vulcanizing agent DCP accounts for 0.25% by mass; and other additives account for 3.75% by mass.

[0040] The preparation method of dynamically vulcanized TPV composite materials is as follows: PP and EPDM are added to an internal mixer at 180°C and mixed for 5 minutes, then an intumescent flame retardant is added and mixed for 3 minutes, and finally a dynamic vulcanizer DCP and other additives are added and mixed for 6 minutes, and the material is discharged to 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: The cardanol glycidyl phytate melamine salt prepared in Example 1 was compounded with a highly filled dynamically vulcanized TPV to obtain test sample 2.

[0043] Test sample 3: The cardanol glycidyl phytate melamine salt prepared in Example 2 was compounded with low-filled dynamically vulcanized TPV to obtain test sample 3.

[0044] Test sample 4: The cardanol glycidyl phytate melamine salt prepared in Example 2 was compounded with a highly filled dynamically vulcanized TPV to obtain test sample 4.

[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 performance of the test samples and the control samples was tested 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 have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection 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 synthesis method comprises the following steps: firstly adding phytic acid into a solvent and stirring evenly, then adding cardanol glycidyl ether and melamine, then heating to 40-80° C., reflux stirring for 1-24 hours, finally cooling, filtering, washing with a solvent and drying to obtain cardanol glycidyl phytate melamine salt.

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

5. A bio-based intumescent flame retardant for thermoplastic vulcanizate (TPV) according to 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) according to claim 2, characterized in that The molar ratio of phytic acid, cardanol glycidyl ether and melamine in the synthesis method steps 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) according to 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. The 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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