A coordination polymer based on pyridine carboxylic acid and its preparation method and application
By using the coordination polymer based on pyridine carboxylic acid as a flame retardant, combined with inorganic fillers, tougheners, etc., the problem of large amount of halogen-free flame retardant added and poor flame retardant effect in the prior art is solved, and high efficiency is achieved , the preparation of environmentally friendly flame retardant polypropylene materials has good flame retardant properties and mechanical properties.
Patent Information
- Application Number
- CN202410355496.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-03-27
- Publication Date
- 2025-02-18
- Estimated Expiration
- 2044-03-27
AI Technical Summary
After adding halogen-free flame retardant polypropylene, the flame retardant effect is poor and the mechanical properties are deteriorated, making it difficult to meet the needs of both green and environmental protection and performance.
The coordination polymer based on pyridine carboxylic acid is used as the flame retardant, and the coordination polymer is synthesized by hydrothermal reaction method, and combined with inorganic fillers, tougheners, lubricants, etc. to prepare good flame retardant properties. and mechanical properties of flame retardant polypropylene.
The environmentally friendly flame retardant effect is achieved, and only a small amount of flame retardant is required to significantly improve the flame retardant performance of polypropylene, while maintaining good mechanical properties, including tensile strength and bending strength.
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Figure CN118126342B_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of flame retardant materials, and in particular to a coordination polymer based on pyridine carboxylic acid, and a preparation method and application thereof. Background Art
[0002] Polypropylene is a polymer material that is non-toxic, low in density, light in weight, and has excellent mechanical, electrical insulation, and chemical resistance properties. It is widely used in electronics, construction, textiles, decoration, machinery, and other fields. Since polypropylene is a flammable material, it will release toxic and corrosive gases and a large amount of smoke when burned, posing a hidden danger to life and property. Therefore, it is necessary to perform flame retardant modification on polypropylene to meet its use needs in more fields.
[0003] Flame retardant polypropylene is often achieved by directly adding flame retardants. Commonly used polypropylene flame retardants include: halogen flame retardants, inorganic flame retardants, phosphorus flame retardants, and intumescent flame retardants. Although halogen-based organic flame retardants can guarantee the performance of polymer materials, they release toxic and carcinogenic substances when burned, which is not in line with the current green and environmental development concept. Therefore, halogen-free flame retardant systems have become the current development trend. However, halogen-free flame retardants usually need to reach more than 25wt% to have a flame retardant effect. The large amount of flame retardant added results in a significant decrease in the tensile strength and impact strength of flame retardant polypropylene. Summary of the invention
[0004] One of the purposes of the present invention is to provide an environmentally friendly and flame retardant coordination polymer.
[0005] In order to achieve the above purpose, the present invention adopts the following technical scheme: a coordination polymer based on pyridine carboxylic acid, the chemical formula is: [Zn2(C6H4NO2)2(C7H5N4)2] n ; Crystallographic data: belongs to monoclinic system, space group C2 / c, unit cell parameters: β=118.254(4)°, Dc=1.704g / cm 3 , Z=8, F(000)=1336, final deviation factor R1=0.0453, wR2=0.0854.
[0006] Wherein, the crystal molecular structure of the above coordination polymer is as follows:
[0007]
[0008] The second object of the present invention is to provide a method for preparing a coordination polymer based on pyridinecarboxylic acid, which comprises the following steps:
[0009] Add appropriate amount of 4-pyridinecarboxylic acid, 3-(2-pyridyl)-1,2,4-triazole and zinc salt to a reaction container, add appropriate amount of water as solvent, stir for a period of time, add alkaline solution to adjust the pH value, heat to 90-180°C, react for a period of time, cool to room temperature, and obtain light yellow granular crystals, which are the target product.
[0010] Preferably, the molar ratio of the 4-pyridinecarboxylic acid, 3-(2-pyridyl)-1,2,4-triazole and zinc salt is (1-6):(1-4):(1-3).
[0011] Preferably, the zinc salt is at least one (preferably one) of zinc chloride, zinc sulfate, zinc hydroxide, zinc acetate, zinc nitrate, zinc perchlorate, zinc fluoride, and basic zinc carbonate.
[0012] Preferably, the alkaline solution is at least one (preferably one) of sodium hydroxide, potassium hydroxide, aqueous ammonia, triethylamine, and ethylenediamine.
[0013] Preferably, the pH value after adjustment with the alkaline solution is 4-9.
[0014] In addition, the pyridine carboxylic acid-based coordination polymer can be used as a flame retardant.
[0015] In addition, another object of the present invention is to provide a flame retardant polypropylene, to which the above-mentioned pyridine carboxylic acid-based coordination polymer is added.
[0016] The flame retardant polypropylene can be prepared by the following steps:
[0017] An appropriate amount of a pyridine carboxylic acid-based coordination polymer, an inorganic filler, a toughening agent, a lubricant and a polypropylene base material are mixed, melt-blended and then pressed to obtain a target product.
[0018] Preferably, the mass ratio of the pyridine carboxylic acid-based coordination polymer, inorganic filler, toughening agent, lubricant, and polypropylene substrate is (7-13): (69-75): 3: 3: 12. The mass contents of the pyridine carboxylic acid-based coordination polymer, inorganic filler, toughening agent, lubricant, and polypropylene substrate may be 7%-13% (e.g., 7%, 10%, 13%), 69%-75% (e.g., 75%, 72%, 69%), 3%, 3%, and 12%, respectively.
[0019] Preferably, the inorganic filler is at least one (preferably one) of calcium carbonate, sodium silicate, talc, aluminum hydroxide and magnesium hydroxide.
[0020] Preferably, the toughening agent is at least one (preferably one) of EVA, POE, MBS and SBS.
[0021] Preferably, the lubricant is at least two of polyethylene wax, ethylene bisstearamide, silicone powder, epoxy soybean oil, acrylic acid ester copolymer and cerium stearate.
[0022] Preferably, the mass content of the pyridinecarboxylic acid-based coordination polymer is 7% to 13% (preferably 13%).
[0023] The coordination polymer of the present invention is environmentally friendly, contains transition metal element zinc, which is an inorganic flame retardant element, and the triazole compound in the molecular structure belongs to an intumescent flame retardant, which decomposes to generate NH3, N2, N x O y , H2O and other non-flammable gases, dilute the flammable gas and oxygen concentration, take away heat, reduce the surface temperature of the polymer, so that the coordination polymer has good flame retardancy. Moreover, the coordination polymer of the present invention has good thermal stability and no decomposition is observed at a temperature of 260°C. According to tests, the coordination polymer of the present invention has good flame retardancy when used as a flame retardant. Only a small amount of flame retardant needs to be added to make polypropylene have strong flame retardancy and good mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Figure 1 Schematic diagram of the crystal molecular structure of a coordination polymer based on pyridine carboxylic acid;
[0025] Figure 2 is a one-dimensional chain diagram of a coordination polymer based on pyridine carboxylic acid;
[0026] Figure 3 is a three-dimensional network diagram of a coordination polymer based on pyridine carboxylic acid;
[0027] Figure 4 TG diagram of the coordination polymer based on pyridine carboxylic acid. DETAILED DESCRIPTION
[0028] In order to facilitate the understanding of those skilled in the art, the present invention is further described below in conjunction with the examples, and the contents mentioned in the examples are not limitations of the present invention. It should be noted in advance that the following examples were completed in the laboratory, and those skilled in the art should understand that the amounts of the components given in the examples only represent the ratio relationship between the components, rather than specific limitations.
[0029] Example 1
[0030] 3mmol 4-pyridinecarboxylic acid, 2mmol 3-(2-pyridyl)-1,2,4-triazole and 2mmol zinc salt (zinc chloride is selected in this embodiment) are added to a 30mL hydrothermal reaction kettle, a certain amount of water is added as a solvent, and the mixture is stirred in a greenhouse with a magnetic stirrer for 1 to 3 hours (2 hours in this embodiment), and an alkaline solution (sodium hydroxide is selected in this embodiment) is added to adjust the pH to 4 to 9 (pH to 6 in this embodiment); then the reaction kettle is heated to 90 to 180°C (130°C in this embodiment), reacted for 36 to 72 hours (48 hours in this embodiment), slowly cooled to room temperature by program temperature control, and a large amount of light yellow granular crystals are obtained by opening the kettle, thus obtaining a coordination polymer based on pyridinecarboxylic acid.
[0031] Example 2
[0032] 1mmol 4-pyridinecarboxylic acid, 1mmol 3-(2-pyridyl)-1,2,4-triazole and 1mmol zinc salt (zinc hydroxide is selected in this embodiment) are added to a 30mL hydrothermal reactor, a certain amount of water is added as a solvent, and the mixture is stirred in a greenhouse with a magnetic stirrer for 1 to 3 hours (1 hour in this embodiment), and an alkaline solution (potassium hydroxide is selected in this embodiment) is added to adjust the pH to 4 to 9 (pH = 4 in this embodiment); then the reactor is heated to 90 to 180°C (90°C in this embodiment), reacted for 36 to 72 hours (36 hours in this embodiment), slowly cooled to room temperature by program temperature control, and a large amount of light yellow granular crystals are obtained by opening the reactor, thus obtaining a coordination polymer based on pyridinecarboxylic acid.
[0033] Example 3
[0034] 6mmol 4-pyridinecarboxylic acid, 4mmol 3-(2-pyridyl)-1,2,4-triazole and 3mmol zinc salt (zinc nitrate is selected in this embodiment) are added to a 30mL hydrothermal reaction kettle, a certain amount of water is added as a solvent, and the mixture is stirred in a greenhouse with a magnetic stirrer for 1 to 3 hours (3 hours in this embodiment), and an alkaline solution (triethylamine is selected in this embodiment) is added to adjust the pH to 4 to 9 (pH = 9 in this embodiment); then the reaction kettle is heated to 90 to 180°C (180°C in this embodiment), reacted for 36 to 72 hours (72 hours in this embodiment), slowly cooled to room temperature by program temperature control, and a large amount of light yellow granular crystals are obtained by opening the kettle, i.e., a coordination polymer based on pyridinecarboxylic acid is obtained.
[0035] The chemical formula of the pyridine carboxylic acid-based coordination polymer prepared in the above embodiment is: [Zn2(C6H4NO2)2(C7H5N4)2] n ; Crystallographic data: belongs to monoclinic system, space group C2 / c, unit cell parameters: β=118.254(4)°, Dc=1.704g / cm3 , Z=8, F(000)=1336, final deviation factor R1=0.0453, wR2=0.0854.
[0036] The molecular structure of the pyridine carboxylic acid-based coordination polymer prepared in the above example is shown in Figure 1 The main bond lengths and bond angles are listed in Table 1. Figure 1 It can be seen that each independent unit structure is composed of two 4-pyridine carboxylic acids, two 3-(2-pyridyl)-1,2,4-triazole molecules and two zinc (II) ions, and the two central atoms are bridged by two 3-(2-pyridyl)-1,2,4-triazole molecules to form a binuclear structure. The central zinc (II) ion is in a hexacoordinated environment, forming a deformed octahedral tetragonal bipyramidal structure, in which the four coordinated nitrogen atoms come from two 3-(2-pyridyl)-1,2,4-triazole molecules and one 4-pyridine carboxylic acid molecule, and the other two coordinated oxygen atoms come from one 4-pyridine carboxylic acid root. Among them, O(1) and N(5) are in axial position, located at the two vertices of the tetrahedral bipyramid, and N(1), N(4), O(2) and N(2i) are in equatorial position, among which N(1)-Zn(1)-N(4), O(2)-Zn(1)-N(4), O(2)-Zn(1)-N(2 i ) and N(2 i The bond angles of )-Zn(1)-N(1) are 80.546(2), 92.155(3), 89.823(2), 97.362(3)°, and the total bond angle is 359.886°, which is close to 360°, indicating that N(1), N(4), O(2), N(2i) and Zn(1) are almost on the same plane. Figure 2 ,3 It can be seen that every four unit structures of the coordination polymer constitute a large ring, which is bridged by 4-pyridinecarboxylic acid to form a spatial network structure. The polymer formed by this structure has very good stability.
[0037] Table 1 Main bond lengths of coordination polymer materials Bond angle (°)
[0038]
[0039] Thermal stability test of coordination polymer based on pyridine carboxylic acid: Test results are as follows Figure 4As can be seen from the figure, the whole decomposition process is divided into two stages. The first stage is the loss of two 3-(2-pyridyl)-1,2,4-triazole molecules, the temperature is 264-352℃, and the weight loss rate is about 32.0% (theoretical value: 31.99%); the second stage is the loss of two 4-pyridine carboxylate ions, the temperature is 352-536℃, and the weight loss rate is about 50.0% (theoretical value: 49.917%); the final ZnO is about 18.00% (theoretical value: 17.93%). Because the coordination compound forms a spatial network structure, it has good stability, which is reflected in the high starting temperature of the thermal decomposition process, reaching above 260℃.
[0040] The decomposition process is:
[0041]
[0042] The coordination polymer based on pyridine carboxylic acid can be used in polymer flame retardancy. For example, the coordination polymer based on pyridine carboxylic acid is used as a flame retardant to prepare flame retardant polypropylene, as follows:
[0043] Weigh flame retardant A (mass content of 7%) (flame retardant A is a coordination polymer based on pyridine carboxylic acid), inorganic filler B (mass content of 75%) (inorganic filler B is selected from at least one of calcium carbonate, sodium silicate, talc, aluminum hydroxide, and magnesium hydroxide, and calcium carbonate is selected as inorganic filler B in this preparation step), toughener C (mass content of 3%) (toughener C is selected from at least one of EVA, POE, MBS and SBS, and EVA is selected as toughener C in this preparation step), lubricant D (mass content of 3%) (lubricant D is selected from at least two of polyethylene wax, ethylene bis stearamide, silicone powder, epoxy soybean oil, acrylate copolymer and cerium stearate, and this preparation step In the first step, five raw materials, including polyethylene wax and ethylene bisstearamide as lubricants D) and polypropylene substrate E (mass content is 12%) (polypropylene substrate E uses PP slices), are premixed at high speed in a high-speed mixer to obtain a uniformly mixed mixture; then, the mixture is added to a torque rheometer, melt-blended at 170-260° C. for 3-8 minutes to obtain a blend; then, the blend is poured into a mold with a membrane cavity thickness of 3 mm, placed on a hot plate of a flat vulcanizer, pressed at 170-260° C. and 15-20 MPa for 3-5 minutes, and then moved to a cold plate of the flat vulcanizer for cooling, and finally the sample is taken out to make a flame-retardant polypropylene with a thickness of 3 mm, which is numbered 1.
[0044] Under the same conditions, two other flame-retardant polypropylene samples were prepared. The only difference in the mass content of flame retardant A and inorganic filler B was in each sample. In one sample, the mass contents of flame retardant A and inorganic filler B were 10% and 72%, respectively, and it was numbered 2; in the other sample, the mass contents of flame retardant A and inorganic filler B were 13% and 69%, respectively, and it was numbered 3.
[0045] The critical thermal radiation flux test was carried out with reference to ASTM E648 standard; the tensile strength test was carried out with reference to GB / T1040.1-2006. The results are shown in Table 2.
[0046] Table 2 Results of thermal radiation flux and mechanical properties of flame-retardant polypropylene composites
[0047] Test No. <![CDATA[Thermal radiation flux / (Kw / m 2 )]]> Tensile strength MPa Bending strength MPa 1 10.0 23 26 2 12.0 25 28 3 14.0 24 30
[0048] From the data in Table 2, it can be seen that the present invention adopts a transition metal coordination polymer as the flame retardant A, and through the reasonable design of the formula compatibility of the flame retardant A, the inorganic filler B, the toughening agent C, the lubricant D, and the polypropylene E, the tensile strength of the modified polypropylene sheet (flame retardant polypropylene) is maintained above 23MPa, and the bending strength is maintained above 26MPa. While maintaining its mechanical properties basically unchanged, the flame retardant properties of polypropylene can be significantly improved, and the thermal radiation flux of the flame retardant PP material is maintained at 10Kw / m 2 Among them, PP No. 3 is the best flame retardant polypropylene material, and its heat radiation flux is 14Kw / m 2 , tensile strength is 24MPa and flexural strength is 30MPa.
[0049] In general, the present invention uses zinc salt, 4-pyridine carboxylic acid and 3-(2-pyridyl)-1,2,4-triazole as raw materials to synthesize a transition metal coordination polymer [Zn2(C6H4NO2)2(C7H5N4)2] n (Its crystal molecular structure can be seen in Figure 1 The polymer has good thermal stability and no decomposition at 260°C. When applied to PP materials, it has good flame retardant effect. Its flame retardant mechanism is mainly reflected in two aspects. First, the polymer contains transition metal element zinc, which is currently a good inorganic flame retardant element; second, the triazole compound in the molecular structure is an intumescent flame retardant, which decomposes into NH3, N2, N x O y , H2O and other non-flammable gases, dilute the concentration of flammable gases and oxygen, take away heat, and reduce the surface temperature of the polymer. The polymer synthesis process is simple, does not use organic solvents, is environmentally friendly, has a stable structure, good repeatability, and has a shorter crystal period than the solvent method and diffusion method. It is a flame retardant polymer material worthy of promotion.
[0050] In addition, it is worth mentioning that the present invention has the following advantages: (1) The coordination polymer is prepared by a hydrothermal reaction method using water as a solvent. No organic solvent is used in the synthesis process, and there is no organic solvent volatilization, which will not cause pollution to the environment. (2) The product is stable and has good repeatability. The crystal period obtained is shorter than that of the solvent method and the diffusion method. (3) Single crystals were cultured and the structure was determined. (4) No decomposition was observed at a temperature of 260°C. The coordination polymer has a stable structure and is a polymer material with good thermal stability. (5) The coordination polymer can be used as a flame retardant material in PP, and has a good flame retardant effect.
[0051] The above embodiments are preferred implementation schemes of the present invention. In addition, the present invention may also be implemented in other ways. Any obvious replacement without departing from the concept of the present technical solution is within the protection scope of the present invention.
[0052] Finally, it should be emphasized that in order to allow ordinary technicians in the field to more easily understand the improvements of the present invention over the prior art, some descriptions of the present invention have been simplified, and for the sake of clarity, some other elements are omitted in this application document. Those skilled in the art should realize that these omitted elements may also constitute the content of the present invention.
Claims
1. Application of a coordination polymer based on pyridine carboxylic acid as a flame retardant, characterized in that: The chemical formula of the pyridine carboxylic acid-based coordination polymer is: [Zn2(C6H4NO2)2(C7H5N4)2] n ; Among them, C6H4NO2 is 4-pyridinecarboxylic acid, C7H5N4 is 3-(2-pyridyl)-1,2,4-triazole molecule; crystallographic data are: belongs to monoclinic system, space group C2 / c , unit cell parameters: a =17.472(2)Å, b = 10.214(2)Å, c = 16.420(2)Å, β = 118.254(4)º, V = 2558.5(4)Å 3 , Dc =1.704g / cm 3 , Z =8, F (000) = 1336, final deviation factor R 1= 0.0453, wxya 2= 0.0854.
2. The use of the pyridinecarboxylic acid-based coordination polymer as a flame retardant according to claim 1, characterized in that: The pyridine carboxylic acid-based coordination polymer is prepared by the following steps: Add appropriate amount of 4-pyridinecarboxylic acid, 3-(2-pyridyl)-1,2,4-triazole and zinc salt to a reaction container, add appropriate amount of water as solvent, stir for a period of time, add alkaline solution to adjust the pH value, heat to 90-180°C, react for a period of time and cool to room temperature to obtain light yellow granular crystals, which are the target product.
3. The use of the pyridinecarboxylic acid-based coordination polymer as a flame retardant according to claim 2, characterized in that: The molar ratio of the 4-pyridinecarboxylic acid, 3-(2-pyridyl)-1,2,4-triazole and zinc salt is (1-6): (1-4): (1-3).
4. The use of the pyridinecarboxylic acid-based coordination polymer as a flame retardant according to claim 2, characterized in that: The zinc salt is at least one of zinc chloride, zinc sulfate, zinc hydroxide, zinc acetate, zinc nitrate, zinc perchlorate, zinc fluoride and basic zinc carbonate.
5. The use of the pyridinecarboxylic acid-based coordination polymer as a flame retardant according to claim 2, characterized in that: The alkaline solution is at least one of sodium hydroxide, potassium hydroxide, ammonia water, triethylamine and ethylenediamine.
6. The use of the pyridinecarboxylic acid-based coordination polymer as a flame retardant according to claim 2, characterized in that: The pH value after adjustment with alkaline solution is 4-9.
7. A flame retardant polypropylene, characterized in that: A pyridine carboxylic acid-based coordination polymer is added, and the chemical formula of the pyridine carboxylic acid-based coordination polymer is: [Zn2(C6H4NO2)2(C7H5N4)2] n ; Among them, C6H4NO2 is 4-pyridinecarboxylic acid, C7H5N4 is 3-(2-pyridyl)-1,2,4-triazole molecule; crystallographic data are: belongs to monoclinic system, space group C2 / c , unit cell parameters: a =17.472(2)Å, b = 10.214(2)Å, c = 16.420(2)Å, β = 118.254(4)º, V = 2558.5(4)Å 3 , Dc =1.704g / cm 3 , Z =8, F (000) = 1336, final deviation factor R 1= 0.0453, wxya 2= 0.0854.
8. The flame retardant polypropylene according to claim 7, characterized in that: The pyridine carboxylic acid-based coordination polymer is prepared by the following steps: Add appropriate amount of 4-pyridinecarboxylic acid, 3-(2-pyridyl)-1,2,4-triazole and zinc salt to a reaction container, add appropriate amount of water as solvent, stir for a period of time, add alkaline solution to adjust the pH value, heat to 90-180°C, react for a period of time and cool to room temperature to obtain light yellow granular crystals, which are the target product.
9. The flame retardant polypropylene according to claim 8, characterized in that: The molar ratio of the 4-pyridinecarboxylic acid, 3-(2-pyridyl)-1,2,4-triazole and zinc salt is (1-6): (1-4): (1-3).
10. The flame retardant polypropylene according to claim 8, characterized in that: The zinc salt is at least one of zinc chloride, zinc sulfate, zinc hydroxide, zinc acetate, zinc nitrate, zinc perchlorate, zinc fluoride and basic zinc carbonate.
11. The flame retardant polypropylene according to claim 8, characterized in that: The alkaline solution is at least one of sodium hydroxide, potassium hydroxide, ammonia water, triethylamine and ethylenediamine.
12. The flame retardant polypropylene according to claim 8, characterized in that: The pH value after adjustment with alkaline solution is 4-9.
13. The flame retardant polypropylene according to claim 7, characterized in that: The flame retardant polypropylene is prepared by the following steps: An appropriate amount of a pyridine carboxylic acid-based coordination polymer, an inorganic filler, a toughening agent, a lubricant and a polypropylene base material are mixed, melt-blended and then pressed to obtain a target product.
14. The flame retardant polypropylene according to claim 13, characterized in that: The mass ratio of the pyridine carboxylic acid-based coordination polymer, the inorganic filler, the toughening agent, the lubricant, and the polypropylene substrate is (7-13): (69-75): 3: 3:
12.
15. The flame retardant polypropylene according to claim 13, characterized in that: The inorganic filler is at least one of calcium carbonate, sodium silicate, talcum powder, aluminum hydroxide and magnesium hydroxide.
16. The flame retardant polypropylene according to claim 13, characterized in that: The toughening agent is at least one of EVA, POE, MBS and SBS.
17. The flame retardant polypropylene according to claim 13, characterized in that: The lubricant is at least two of polyethylene wax, ethylene bis stearic acid amide, silicone powder, epoxy soybean oil, acrylic acid ester copolymer and cerium stearate.
18. The flame retardant polypropylene according to any one of claims 7 to 17, characterized in that: The mass content of the pyridine carboxylic acid-based coordination polymer is 7% to 13%.