Preparation of Metalloporphyrin-Lactic Acid Compound and Flame Retardant and Anti-Dripping PLA Material

Abstract

The present invention discloses a preparation of a metal porphyrin-lactic acid compound and a flame-retardant and anti-melting-dripping PLA material, which relates to the technical field of functional modification of polylactic acid. The present invention designs and synthesizes a metal porphyrin-lactic acid compound with a novel structure. Using amino tetraphenyl porphyrin and a metal compound as raw materials, metal porphyrin is first synthesized, and then the metal porphyrin-lactic acid compound is synthesized. The reaction conditions are mild; the metal porphyrin-lactic acid compound has good compatibility with PLA. Adding it to the polylactic acid material can endow the polylactic acid material with excellent flame-retardant and anti-melting-dripping properties.

Description

Technical Field:

[0001] The present invention relates to the technical field of functional modification of polylactic acid, and particularly relates to a preparation method of a metal porphyrin-lactic acid compound and its application in a flame-retardant and anti-dripping PLA material. Background Art:

[0002] Polylactic acid (PLA) is an environmentally friendly polymer material with good biocompatibility and degradability, and is considered a green bio-based material with broad development prospects to replace petroleum-based polyesters. However, the elemental composition (carbon, hydrogen, oxygen) and molecular chain structure of PLA (ester bonds are easily destroyed at high temperatures to generate volatile combustibles) determine that it, like general polymers, has the defect of being easily combustible. The flammability of polylactic acid limits its application in some special occasions.

[0003] To improve the flame retardancy of PLA, a large number of studies have been carried out by researchers, such as using phosphorus-containing flame retardants such as ammonium polyphosphate, aluminum hypophosphite, phosphazene, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and their compounded flame retardant systems or using these as acid sources to prepare intumescent flame retardant systems, synthesizing new phosphorus-nitrogen flame retardants, using phosphorus-containing bio-based flame retardants and nano flame retardants, etc. However, there are few solutions for PLA flame retardancy and anti-dripping in existing studies, and the common method of adding flame retardants to PLA materials by blending will have a negative impact on the physical and mechanical properties of PLA. Summary of the Invention:

[0004] Aiming at the problems that PLA is flammable and produces a large amount of drips during combustion, the existing flame retardant systems for PLA do not have the function of anti-dripping, and the common method of adding flame retardants to PLA materials by blending has poor compatibility with PLA, the present invention provides a preparation method of a metal porphyrin-lactic acid compound with both flame retardant and anti-dripping functions and good compatibility with PLA, and a flame retardant and anti-dripping PLA material is prepared therefrom.

[0005] The technical problems to be solved by the present invention are realized by adopting the following technical solutions:

[0006] One of the purposes of the present invention is to provide a preparation method of a metal porphyrin-lactic acid compound, comprising the following steps:

[0007] (1) Dissolve aminotetraphenylporphyrin in a solvent, then add a metal compound, and stir and react to obtain a metal porphyrin;

[0008] (2) Mix the metal porphyrin prepared in step (1) with lactic acid and a solvent uniformly, and add a catalyst and a dehydrating agent, and stir and react to obtain a metal porphyrin-lactic acid compound.

[0009] In step (1), the metal compound is an oxide, chloride or sulfate of divalent or polyvalent metal, preferably copper chloride, zinc chloride or ferric trichloride; the mass ratio of the metal compound to aminotetraphenylporphyrin is (1-2):(1-2); the temperature of the stirring reaction is 40-60 °C, and the time is 2-4 h; the solvent is chloroform.

[0010] In step (2), the lactic acid is L-lactic acid, D-lactic acid, DL-lactic acid, lactide or lactic acid oligomer with a polymerization degree of 3-10; the mass ratio of the metal porphyrin to lactic acid is 1:(1-4); the catalyst is 1-hydroxybenzotriazole (HOBt) or p-dimethylaminopyridine (DMAP); the dehydrating agent is dicyclohexylcarbodiimide (DCC); the mass ratio of the catalyst to the metal porphyrin is 1:(50-100); the mass ratio of the dehydrating agent to the metal porphyrin is 1:(5-10); the temperature of the stirring reaction is 60-80 °C, and the time is 4-8 h; the solvent is chloroform.

[0011] The second object of the present invention is to provide a metal porphyrin-lactic acid compound obtained according to the foregoing preparation method.

[0012] The third object of the present invention is to provide the application of the foregoing metal porphyrin-lactic acid compound in the preparation of a flame-retardant and anti-melting-drip PLA material.

[0013] The fourth object of the present invention is to provide a flame-retardant and anti-melting-drip PLA material, which is obtained by melt blending and extrusion granulation of polylactic acid and the foregoing metal porphyrin-lactic acid compound.

[0014] Preferably, the mass ratio of the metal porphyrin-lactic acid compound to polylactic acid is 8-15%.

[0015] Preferably, the temperature of the melt blending is 170-180 °C.

[0016] There is a strong π-π stacking interaction between tetraphenylporphyrin molecules. The existence of this physical network structure can restrict the movement of polymer molecular chains, improve the high-temperature melt viscosity and melt strength of the polymer, and play a role in flame retardancy and suppression of melting drops when the polymer is heated. Moreover, the porphyrin ring has a strong metal ion chelating ability. Metal ions not only help the crosslinking of the polymer, enhance the thermal stability, but also promote the dehydrogenation reaction and increase the amount of char residue. However, how to make the porphyrin compound and polylactic acid well compatible to prepare a polylactic acid material with good flame-retardant and anti-melting-drip properties is a technical difficulty to be solved.

[0017] In the present invention, amino tetraphenylporphyrin is coordinated with a metal compound to generate a metal porphyrin, and the metal porphyrin reacts with lactic acid or a lactic acid oligomer to obtain a metal porphyrin-lactic acid compound. Then, a flame-retardant and anti-melting-dripping polylactic acid material is prepared from the metal porphyrin-lactic acid compound and polylactic acid by melt blending method.

[0018] The beneficial effects of the present invention are as follows: A metal porphyrin-lactic acid compound with a novel structure is designed and synthesized in the present invention. Using amino tetraphenylporphyrin and a metal compound as raw materials, the metal porphyrin is first synthesized, and then the metal porphyrin-lactic acid compound is synthesized. The reaction conditions are mild; the metal porphyrin-lactic acid compound has good compatibility with PLA. Adding it to the polylactic acid material can endow the polylactic acid material with excellent flame-retardant and anti-melting-dripping properties. Specific embodiments:

[0019] In order to make the technical means, creative features, achieved purposes and effects of the present invention easy to understand, the present invention will be further described below in conjunction with specific embodiments.

[0020] Example 1

[0021] Add 10 g of amino tetraphenylporphyrin and 100 mL of chloroform into a three-necked flask, stir at room temperature for 30 min until the amino tetraphenylporphyrin is completely dissolved. Then add 10 g of CuCl2, heat the reaction mixture to 40 °C, stir and react for 4 h, distill off the solvent chloroform to obtain copper porphyrin.

[0022] After mixing 10 g of copper porphyrin, 10 g of D-lactic acid and 400 mL of chloroform evenly, add 0.1 g of catalyst HOBt and 1 g of dehydrating agent DCC, heat the reaction mixture to 60 °C, stir and react for 8 h, distill off the solvent chloroform, and dry to obtain a copper porphyrin-lactic acid compound.

[0023] After mixing 16 g of the copper porphyrin-lactic acid compound and 184 g of PLA particles evenly, add them to a twin-screw extruder and melt blend at 180 °C at a speed of 250 rpm, extrude and pelletize, and then heat press at 180 °C into a strip material with a thickness of 2 mm to obtain a flame-retardant and anti-melting-dripping PLA material with a copper porphyrin-lactic acid compound content of 8%.

[0024] Example 2

[0025] Add 10 g of amino tetraphenylporphyrin and 200 mL of chloroform into a three-necked flask, stir at room temperature for 20 min until the amino tetraphenylporphyrin is completely dissolved. Then add 5 g of ZnCl2, heat the reaction mixture to 60 °C, stir and react for 2 h, distill off the solvent chloroform to obtain zinc porphyrin.

[0026] After uniformly mixing 10 g of zinc porphyrin, 20 g of lactide, and 300 mL of chloroform, 0.2 g of catalyst DMAP and 1 g of dehydrating agent DCC were added. The reaction mixture was heated to 80 °C and stirred for 4 h. The solvent chloroform was removed by distillation, and then dried to obtain a zinc porphyrin-lactic acid compound.

[0027] After uniformly mixing 20 g of the zinc porphyrin-lactic acid compound and 180 g of PLA particles, they were added to a twin-screw extruder and melt-blended at 180 °C at a rotation speed of 250 rpm, then pelletized by extrusion. Subsequently, they were hot-pressed at 180 °C to form a strip material with a thickness of 2 mm, obtaining a flame-retardant and anti-melting-drip PLA material containing 10% of the zinc porphyrin-lactic acid compound.

[0028] Example 3

[0029] 30 g of aminotetraphenylporphyrin and 200 mL of chloroform were added to a three-necked flask and stirred at room temperature for 40 min until the aminotetraphenylporphyrin was completely dissolved. Then 30 g of ZnCl2 was added, and the reaction mixture was heated to 60 °C and stirred for 2 h. The solvent chloroform was removed by distillation to obtain zinc porphyrin.

[0030] After uniformly mixing 10 g of zinc porphyrin, 40 g of oligolactic acid, and 450 mL of chloroform, 0.2 g of catalyst DMAP and 2 g of dehydrating agent DCC were added. The reaction mixture was heated to 80 °C and stirred for 4 h. The solvent chloroform was removed by distillation, and then dried to obtain a zinc porphyrin-lactic acid compound.

[0031] After uniformly mixing 24 g of the zinc porphyrin-lactic acid compound and 176 g of PLA particles, they were added to a twin-screw extruder and melt-blended at 180 °C at a rotation speed of 250 rpm, then pelletized by extrusion. Subsequently, they were hot-pressed at 180 °C to form a strip material with a thickness of 2 mm, obtaining a flame-retardant and anti-melting-drip PLA material containing 12% of the zinc porphyrin-lactic acid compound.

[0032] Example 4

[0033] 20 g of aminotetraphenylporphyrin and 200 mL of chloroform were added to a three-necked flask and stirred at room temperature for 40 min until the aminotetraphenylporphyrin was completely dissolved. Then 20 g of FeCl3 was added, and the reaction mixture was heated to 40 °C and stirred for 4 h. The solvent chloroform was removed by distillation to obtain iron porphyrin.

[0034] After uniformly mixing 20 g of iron porphyrin, 30 g of lactide, and 450 mL of chloroform, 0.3 g of catalyst HOBt and 2 g of dehydrating agent DCC were added. The reaction mixture was heated to 80 °C and stirred for 4 h. The solvent chloroform was removed by distillation, and then dried to obtain an iron porphyrin-lactic acid compound.

[0035] After mixing 24 g of iron porphyrin-lactic acid compound and 176 g of PLA particles evenly, they were added to a twin-screw extruder and melt-blended at 180 °C at a rotation speed of 250 rpm, then pelletized by extrusion, and further hot-pressed at 180 °C into a strip material with a thickness of 2 mm, obtaining a flame-retardant and anti-melting-dripping PLA material with a content of 12% of iron porphyrin-lactic acid compound.

[0036] Example 5

[0037] 20 g of aminotetraphenylporphyrin and 200 mL of chloroform were added to a three-necked flask and stirred at room temperature for 40 min until the aminotetraphenylporphyrin was completely dissolved. Then 20 g of FeCl3 was added, and the reaction mixture was heated to 40 °C and stirred for 4 h. The solvent chloroform was removed by distillation to obtain iron porphyrin.

[0038] After mixing 20 g of iron porphyrin, 30 g of lactide and 450 mL of chloroform evenly, 0.3 g of catalyst HOBt and 2 g of dehydrating agent DCC were added. The reaction mixture was heated to 80 °C and stirred for 4 h. The solvent chloroform was removed by distillation and dried to obtain iron porphyrin-lactic acid compound.

[0039] After mixing 30 g of iron porphyrin-lactic acid compound and 170 g of PLA particles evenly, they were added to a twin-screw extruder and melt-blended at 180 °C at a rotation speed of 250 rpm, then pelletized by extrusion, and further hot-pressed at 180 °C into a strip material with a thickness of 2 mm, obtaining a flame-retardant and anti-melting-dripping PLA material with a content of 15% of iron porphyrin-lactic acid compound.

[0040] Control Example 1

[0041] The difference from Example 4 is that metal porphyrin was not prepared, and aminotetraphenylporphyrin-lactic acid compound was directly prepared and blended with PLA.

[0042] After mixing 20 g of aminotetraphenylporphyrin, 30 g of lactide and 450 mL of chloroform evenly, 0.3 g of catalyst HOBt and 2 g of dehydrating agent DCC were added. The reaction mixture was heated to 80 °C and stirred for 4 h. The solvent chloroform was removed by distillation and dried to obtain porphyrin-lactic acid compound.

[0043] After mixing 24 g of porphyrin-lactic acid compound and 176 g of PLA particles evenly, they were added to a twin-screw extruder and melt-blended at 180 °C at a rotation speed of 250 rpm, then pelletized by extrusion, and further hot-pressed at 180 °C into a strip material with a thickness of 2 mm, obtaining a PLA material with a content of 12% of porphyrin-lactic acid compound.

[0044] Control Example 2

[0045] The difference from Example 4 is that metal porphyrin-lactic acid compound was not prepared, and metal porphyrin was directly blended with PLA.

[0046] Add 20 g of aminotetraphenylporphyrin and 200 mL of chloroform into a three-necked flask, stir at room temperature for 40 min until the aminotetraphenylporphyrin is completely dissolved. Then add 20 g of FeCl3, heat the reaction mixture to 40 °C, stir and react for 4 h, and distill off the solvent chloroform to obtain iron porphyrin.

[0047] After mixing 24 g of iron porphyrin and 176 g of PLA particles evenly, add them to a twin-screw extruder and melt-blend at 180 °C at a rotation speed of 250 rpm, extrude and pelletize, and then hot-press at 180 °C to form a strip material with a thickness of 2 mm. A flame-retardant and anti-melting-dripping PLA material with an iron porphyrin content of 12% is obtained.

[0048] Control Example 3

[0049] Directly melt-blend the polylactic acid particles at 180 °C at a rotation speed of 200 rpm, extrude and pelletize, and then hot-press at 180 °C to form a strip material with a thickness of 2 mm.

[0050] Performance test:

[0051] The tensile properties of the material were tested according to the tensile strength test standard GB / T 1040-2006 using an H5K-S type universal electronic testing machine.

[0052] The limiting oxygen index of the material was tested according to the oxygen index method for combustion performance test standard GB / T 5454-1997 using an FAA type oxygen index instrument.

[0053] The vertical burning performance of the material was tested according to the test method for measuring the comparative burning performance of solid plastics in a vertical position ASTM D3801-2010 using a CZF-1 type vertical burning tester.

[0054] Table 1 shows the physical and mechanical properties and flame-retardant and anti-melting-dripping properties of the PLA materials obtained in Examples 1-5 and Control Examples 1-3.

[0055] Table 1

[0056] Specimen Tensile strength (MPa) Limiting oxygen index (%) Vertical burning rating Example 1 56.4 27.3 V1 Example 2 58.7 28.4 V1 Example 3 60.2 28.7 V0 Example 4 60.7 29.0 V0 Example 5 59.3 30.5 V0 Control Example 1 49.0 27.5 V2 Control Example 2 52.3 27.0 V1 Control Example 3 50.2 20.5 No rating

[0057] As can be seen from Table 1, the metal porphyrin-polylactic acid compound has excellent flame-retardant and anti-melting-dripping effects on PLA. When the addition amount of the metal porphyrin-polylactic acid compound is 8%, the limiting oxygen index of PLA is 27.3%, and the vertical burning grade reaches V1. Increasing the amount of the metal porphyrin-polylactic acid compound further improves the flame-retardant and anti-melting-dripping performance, the limiting oxygen index can reach more than 30%, the vertical burning reaches V0, and the melting-dripping phenomenon is significantly inhibited. During the combustion performance test, it can be clearly seen that a continuous and dense carbon layer is formed after the PLA material burns.

[0058] Comparing Comparative Example 1 and Example 4, it can be seen that the introduction of metal compounds is of great help to the vertical combustion performance of PLA, which indicates that by preparing porphyrin metal complexes according to the present invention, the catalytic carbonization effect of metal compounds is fully exerted.

[0059] Comparing Comparative Example 2 and Example 4, it can be seen that by preparing metal porphyrin-lactic acid compounds, due to the introduction of lactic acid structure, the compatibility between metal porphyrin and PLA is effectively improved, enabling metal porphyrin to fully exert its flame retardant and anti-dripping effects, and due to the introduction of metal, the strength of PLA materials is also enhanced to a certain extent.

[0060] The above results show that by utilizing the unique performance advantages of metal porphyrin and improving its compatibility with polylactic acid by lactic acid modification, the present invention endows polylactic acid with excellent flame retardancy and anti-dripping properties.

[0061] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and what is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A preparation method of a metal porphyrin-lactic acid compound, characterized in that: It includes the following steps: (1) Dissolve amino tetraphenyl porphyrin in a solvent, then add a metal compound, and stir and react to obtain a metal porphyrin; (2) Mix the metal porphyrin prepared in step (1) with lactic acid and a solvent evenly, and add a catalyst and a dehydrating agent, and stir and react to obtain a metal porphyrin-lactic acid compound; The metal compound is copper chloride, zinc chloride or ferric trichloride; The catalyst is 1-hydroxybenzotriazole or p-dimethylaminopyridine; The dehydrating agent is dicyclohexylcarbodiimide; The lactic acid is L-lactic acid, D-lactic acid, DL-lactic acid, lactide or a lactic acid oligomer with a polymerization degree of 3 to 10.

2. The preparation method according to claim 1, characterized in that: In step (1), the mass ratio of the metal compound to amino tetraphenyl porphyrin is (1 to 2):(1 to 2); the temperature of the stirring reaction is 40 to 60 °C, and the time is 2 to 4 h; the solvent is chloroform.

3. The preparation method according to claim 1, characterized in that: In step (2), the mass ratio of the metal porphyrin to lactic acid is 1:(1 to 4); the mass ratio of the catalyst to the metal porphyrin is 1:(50 to 100); the mass ratio of the dehydrating agent to the metal porphyrin is 1:(5 to 10); the temperature of the stirring reaction is 60 to 80 °C, and the time is 4 to 8 h; the solvent is chloroform.

4. A metal porphyrin-lactic acid compound obtained by the preparation method according to any one of claims 1 to 3.

5. Use of the metal porphyrin-lactic acid compound according to claim 4 in the preparation of a flame-retardant and anti-melting-dripping PLA material.

6. A flame-retardant and melt-drop resistant PLA material, characterized in that: It is obtained by melt blending and extrusion granulation of polylactic acid and the metal porphyrin-lactic acid compound according to claim 4.

7. The flame-retardant and anti-dripping PLA material according to claim 6, characterized in that: The mass ratio of the metal porphyrin-lactic acid compound to polylactic acid is 8 to 15%.

8. The flame-retardant and anti-dripping PLA material according to claim 6, wherein: The temperature of the melt blending is 170 to 180 °C.