Bio-based flame retardant with plasticizing effect as well as preparation method and application of bio-based flame retardant

Abstract

The invention belongs to the technical field of PVA (polyvinyl alcohol) plastic flame-retardant hot processing, and particularly discloses a bio-based flame retardant with a plasticizing effect as well as a preparation method and application thereof, and the method comprises the following steps: weighing a bio-based raw material, an acid binding agent and a solvent, and mixing; putting a trichloromethane solution into a dropping funnel, slowly dropwise adding the trichloromethane solution into the solution A, and introducing nitrogen at the same time; heating the solution B, and continuously reacting; transferring substances in the three-neck flask into a Buchner funnel for suction filtration; carrying out rotary evaporation on the filtrate to remove redundant solvent, and dropwise adding a small amount of liquid after rotary evaporation into a post-treatment solvent for precipitation; and carrying out vacuum drying on the solid. According to the bio-based flame retardant with the plasticizing effect as well as the preparation method and the application of the bio-based flame retardant, a commercial plasticizer, the prepared bio-based flame retardant and the like are added, so that the melting point of PVA (polyvinyl alcohol) can be rapidly reduced, a hot working window of the PVA is widened, controllable hot working of the PVA is realized, and further the plasticizing property and the flame retardance of the PVA are improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of PVA plastic flame-retardant hot processing, and particularly relates to a bio-based flame retardant with plasticizing effect and a preparation method and application thereof. BACKGROUND

[0002] Polyvinyl alcohol (PVA) is a green, renewable, and biodegradable environmentally friendly polymer material. PVA film is widely used in the fields of biological medicine, food packaging, etc. due to its good transparency, high strength, and good biocompatibility. It is odorless, non-toxic, non-polluting, and completely biodegradable, which conforms to the concept of green environmental protection and sustainable development. However, the melting temperature of PVA molecules is close to the decomposition temperature due to the existence of a large number of hydrogen bonds, the processing window is narrow, and it is difficult to melt extrusion blow film, especially high-temperature film, which is prone to plasticizer migration and precipitation during processing, and it is difficult to carry out high-efficiency thermoplastic processing. In order to realize the melt processing of PVA, plasticizing modification must be carried out to reduce the intermolecular force and destroy the regularity of the molecular chain, thereby reducing the melting temperature and increasing the thermal processing window. In addition, the low-temperature PVA water-soluble film is relatively brittle after film formation and has strong flammability, and its limiting oxygen index is only about 18%, once ignited, it will spread rapidly, generate toxic gas and a large amount of heat, and the molten droplets generated during polymer combustion will also cause the combustion of other combustible materials, which also limits its application in many fields.

[0003] Phosphorus / nitrogen-containing flame retardants have flame-retardant ability in both condensed phase and gas phase, and therefore have attracted extensive attention in recent years. In the condensed phase, phosphorus-containing flame retardants promote the formation of carbon to resist heat and mass physical barrier, thereby significantly hindering the transfer of heat and combustible fragments between the underlying polymer and the combustion zone. In the gas phase, phosphorus-containing flame retardants decompose at high temperatures to release many phosphorus-containing free radicals, which can capture high-activity H and HO free radicals, thereby improving the flame retardancy. Nitrogen-containing groups decompose to release inert nitrogen-containing gas during combustion, which enhances the gas phase mechanism by diluting the concentration of oxygen and fuel. Therefore, by reasonably designing the chemical structure of the flame retardant and studying the flame-retardant mechanism of the phosphorus / nitrogen-containing flame retardant, it is expected to develop flame-retardant PVA composites.

[0004] PVA plasticizers generally contain some polar groups such as hydroxyl, carbonyl, amino, etc. By forming new hydrogen bonds between the polar groups and PVA molecules, the intramolecular hydrogen bonds of PVA are destroyed, the melting point of PVA is reduced, and the thermal processing window of PVA is increased. By reasonably introducing some polar groups into the flame retardant, it is expected to achieve plasticization on the basis of flame retardation.

[0005] Therefore, there is a need in the art to develop a bio-based flame retardant with plasticizing effect and a preparation method and application thereof, which can effectively solve the above problems. SUMMARY

[0006] The application aims to provide a bio-based flame retardant with plasticizing effect, a preparation method and application thereof.

[0007] To achieve the above-mentioned purpose, the application provides a preparation method of a bio-based flame retardant with plasticizing effect, comprising the following steps: Step S1, weigh the bio-based raw material, acid-binding agent and solvent into a three-necked flask for mixing to obtain solution A; Step S2, mix phenylphosphonic dichloride with chloroform to obtain a chloroform solution; place the chloroform solution in a dropping funnel and drop it into solution A at a speed of 1 drop per second while introducing nitrogen to obtain solution B; Step S3, after the dropping is completed, heat solution B to 60-70°C and continue to react for 12 hours to stop the reaction; Step S4, transfer the substances in the three-necked flask to a Buchner funnel for suction filtration to obtain a filtrate; Step S5, perform rotary evaporation of the filtrate under the conditions of vacuum-0.1 Mpa, water bath 60°C and rotation speed 40 rpm to remove excess solvent, drop one fourth of the rotary evaporated liquid into a post-treatment solvent for precipitation to obtain a solid; Step S6, vacuum dry the solid at a temperature of 60°C for 24 hours to obtain the bio-based flame retardant with plasticizing effect.

[0008] Preferably, in step S1, the bio-based raw material is one of alanine, phenylalanine, glycine, tyrosine and tryptophan; The acid-binding agent is one of triethylamine, N,N-diisopropyl ethylamine, pyridine, potassium carbonate and potassium hydroxide; The solvent is one of chloroform, dichloromethane and tetrahydrofuran.

[0009] Preferably, in step S1, the bio-based raw material is 8.909-17.818 g, the acid-binding agent is 10.119-20.238 g and the solvent is 150-200 mL; The three-necked flask is provided with two gas guides and a dropping funnel.

[0010] Preferably, in step S2, the mass of phenylphosphonic dichloride is 9.307-18.614 g and the chloroform is 30-50 mL.

[0011] Preferably, in step S5, the post-treatment solvent is one of n-hexane, n-heptane and petroleum ether.

[0012] The application also provides a bio-based flame retardant prepared by the preparation method of the bio-based flame retardant with plasticizing effect.

[0013] The application also provides application of the bio-based flame retardant in preparation of PVA composite materials.

[0014] Preferably, the preparation of the PVA composite material comprises the following steps: Step S1, placing polyvinyl alcohol and commercial plasticizer in a beaker, while being equipped with an electric stirring device and a stirring rod, stirring until the solution is translucent, the particles are swollen, and the whole is uniform, so as to fully swell and obtain solution C (swollen PVA); Step S2, adding the solution C and the bio-based flame retardant with plasticizing effect into a banbury mixer and mixing for 5 min to obtain a sample, and then taking out the sample and placing it into a press to be pressed for 5 min to form a PVA composite material.

[0015] Preferably, the weight ratio of polyvinyl alcohol (PVA) to commercial plasticizer is 10:3; and the weight ratio of solution C to the bio-based flame retardant with plasticizing effect is 10:(2-3). Preferably, the weight ratio of solution C to the bio-based flame retardant with plasticizing effect is 10:2, 10:2.5 or 10:3.

[0016] Preferably, the commercial plasticizer is composed of two of glycerol, tributyl citrate, triethyl citrate, acetyl tributyl citrate, acetyl triethyl citrate, glyceryl triacetate, epoxy soybean oil, flaxseed oil, castor oil and polycaprolactone triol, and the weight ratio of the two is 1:1.

[0017] The bio-based flame retardant with plasticizing effect, the preparation method and the application thereof have the following beneficial effects: 1. The bio-based flame retardant with plasticizing effect is successfully prepared through molecular design and structure regulation, realizes hot processing of PVA at a lower temperature, and proposes an environmentally friendly flame-retardant PVA preparation technology.

[0018] 2. The bio-based flame-retardant plasticizer is prepared by reaction of active amino functional groups (such as alanine, glycine and phenylalanine) in the bio-based material with traditional flame retardants (such as phosphorus oxychloride, phenoxy phosphorus oxychloride and phenyl phosphorus oxychloride). The P-N structure in the molecule plays a flame-retardant role in the condensed phase and the gas phase, respectively, and the polar groups such as carboxyl in the molecular structure can form new hydrogen bonds with PVA molecules, break the intramolecular hydrogen bonds of PVA, reduce the melting point of PVA, and realize the purpose of hot processing of PVA.

[0019] 3. The PVA composite prepared by the method has good compatibility with several plasticizers, high plasticizing effect, good flame-retardant effect, and carbonization property, and can be applied to plasticizing and fire protection of PVA and other materials.

[0020] 4. The preparation process is simple and widely applicable, and the bio-based flame-retardant PVA prepared by using bio-based raw materials is green and environmentally friendly, which can effectively improve production efficiency and save energy. The bio-based flame retardant with dual functions of flame retardation and plasticization obtained in the application realizes controllable thermal processing of PVA and PVA flame retardation by synergistic effect with commercial plasticizers.

[0021] The technical solutions of the application will be further described in detail below with reference to the drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The synthesis route and structural formula of the bio-based flame retardant with plasticizing effect in the application are shown in Example 1. Figure 2 The nuclear magnetic resonance spectrum of the bio-based flame retardant with plasticizing effect in the application is shown in Example 1. (a) is a nuclear magnetic hydrogen spectrum, and (b) is a nuclear magnetic phosphorus spectrum. Figure 3 The DSC test graphs of p-PVA20, p-PVA25, p-PVA30 and p-PVA in the experimental example of the application are shown in Example 1. Figure 4 The cone calorimetry test graphs of p-PVA20, p-PVA25, p-PVA30 and p-PVA in the experimental example of the application are shown in Example 1. (a) is a heat release rate curve, and (b) is a total heat release curve. Figure 5 The thermal stability test graphs of p-PVA20, p-PVA25, p-PVA30 and p-PVA in the experimental example of the application are shown in Example 1. (a) is a thermal stability TGA curve and DTG curve graph of Ala-BPOD, and (b) is a TGA curve graph of the thermal stability of p-PVA20, p-PVA25, p-PVA30 and p-PVA. DETAILED DESCRIPTION

[0023] The technical solutions of the application will be further described in detail below with reference to the drawings and examples.

[0024] Unless otherwise defined, technical terms or scientific terms used in the present application shall have the meanings that are commonly understood by a person of ordinary skill in the art to which the present application belongs.

[0025] Example 1 As shown in Figure 1 A method for preparing a bio-based plasticizer having a plasticizing effect, comprising the following steps: Step S1, 17.818 g of alanine, 20.238 g of triethylamine and 150 ml of chloroform were put into a 250 ml three-necked flask for mixing to obtain solution A; Step S2, at the same time, the three-necked flask was equipped with two gas inlets and a dropping funnel; 18.614 g of phenylphosphoryl dichloride was mixed with 50 mL of chloroform to obtain a chloroform solution; the chloroform solution was placed in the dropping funnel and added to solution A at a rate of 1 drop per second while nitrogen was introduced, to obtain solution B; Step S3, after the addition was completed, solution B was warmed to 65°C and the reaction was continued for 12 h before stopping; Step S4, the contents of the three-necked flask were transferred to a Buchner funnel for suction filtration to obtain a filtrate; Step S5, the filtrate was subjected to rotary evaporation under the conditions of vacuum-0.1 Mpa, water bath 60°C, and rotation speed 40 rpm to remove excess solvent, and one quarter of the rotary evaporated liquid was dropped into n-hexane for precipitation to obtain a solid; Step S6, the solid was vacuum dried at 60°C for 24 h to obtain the bio-based plasticizer having a plasticizing effect (Ala-BPOD), as shown in Figure 2 .

[0026] The obtained Ala-BPOD was used as a raw material to prepare a PVA composite material, comprising the following steps: Step S1, 35 g of PVA, 5.25 g of glycerol and 5.25 g of tributyl citrate were placed in a beaker, and an electric stirring device and a stirring rod were equipped to stir to make them fully swell, and the stirring was continued until the mixture became translucent, the particles swelled and the whole was uniform, to obtain solution C.

[0027] Step S2, solution C and Ala-BPOD were added to a Banbury mixer in the weight ratio of 100:20, 100:25 and 100:30 respectively and mixed for 5 min, and then the mixed samples in the Banbury mixer were taken out and placed in a press to be pressed for 5 min to form a PVA composite material, which was named p-PVA20, p-PVA25 and p-PVA30 in turn.

[0028] Example 2 The Ala-BPOD obtained in Example 1 is used as a raw material to prepare a PVA composite, including the following steps: Step S1, 35g PVA, 5.25g glycerol, 5.25g triacetin are placed in a beaker, and an electric stirring device and a stirring rod are provided at the same time, stirring is carried out to make it fully swell, and the solution C is obtained when the stirring is semi-transparent, the particles are expanded, and the whole is uniform.

[0029] Step S2, solution C and Ala-BPOD are added to the internal mixer in the weight ratio of 100:20, 100:25, 100:30 respectively, mixed for 5 min, then the mixed sample in the internal mixer is taken out and put into a press to form a sheet for 5 min, and the PVA composite is obtained, which is named p1-PVA20, p1-PVA25, p1-PVA30 in turn.

[0030] Comparative Example A method for preparing a PVA composite, including the following steps: Step S1, 35g PVA, 5.25g glycerol, 5.25g tributyl citrate are placed in a beaker, and an electric stirring device and a stirring rod are provided at the same time, stirring is carried out to make it fully swell, and the solution C is obtained.

[0031] Step S2, solution C is added to the internal mixer and mixed for 5 min, then the mixed sample in the internal mixer is taken out and put into a press to form a sheet for 5 min, and the PVA composite is obtained, which is named p-PVA.

[0032] Experimental Example (I) DSC test of p-PVA20, p-PVA25, p-PVA30 prepared in Example 1 and p-PVA prepared in the comparative example.

[0033] As shown in Figure 3 , the melting point of p-PVA is 176°C, and the melting points of p-PVA20, p-PVA25 and p-PVA30 are reduced to 142°C, 127°C and 123°C respectively.

[0034] (II) Melting point change test of p-PVA20, p-PVA25, p-PVA30 prepared in Example 1 and p-PVA prepared in the comparative example by using a differential scanning calorimeter.

[0035] It is found by differential scanning calorimetry test that the melting point of p-PVA with only commercial plasticizer added is reduced by about 10°C, and the melting points of p-PVA20, p-PVA25, p-PVA30 after adding flame retardant are obviously reduced.

[0036] This further demonstrates the feasibility of successfully preparing flame-retardant PVA composite materials by using the bio-based flame retardant with dual flame-retardant and plasticizing effects in Example 1 in synergy with other plasticizers via thermal processing.

[0037] (III) Vertical combustion tests were conducted on p-PVA20, p-PVA25, p-PVA30 prepared in Example 1 and p-PVA prepared in the comparative example.

[0038] First, the NR (Normally Induced Rating) of p-PVA was tested using vertical combustion, with an oxygen index of 25. Adding 20% ​​Ala-BPOD increased the vertical combustion rating to V-1 with an oxygen index of 27. Adding 25% Ala-BPOD increased the vertical combustion rating to V-0 with an oxygen index of 29. Adding 30% Ala-BPOD further increased the oxygen index to 30.

[0039] (iv) The flame retardant properties of the p-PVA20, p-PVA25, p-PVA30 prepared in Example 1 and the p-PVA coating prepared in the comparative example were tested using a cone calorimeter.

[0040] like Figure 4 As shown, it exhibits a significantly higher heat release rate compared to p-PVA, with a maximum heat release of 396 KJ / m³. 2 With the addition of Ala-BPOD, the heat release rate of the coating continuously decreased. Specifically, the heat release rate of p-PVA30 decreased by 30.3% compared to p-PVA, and the total heat release rate also decreased by 30.9%.

[0041] This demonstrates that in Example 1, a bio-based flame retardant with dual flame retardant and plasticizing properties was successfully used in conjunction with other plasticizers to prepare PVA composite materials using a thermal processing method, thus improving their flame retardant properties.

[0042] (v) The thermal stability properties of the p-PVA20, p-PVA25, p-PVA30 prepared in Example 1 and the p-PVA coating prepared in the comparative example were tested using a thermogravimetric analyzer.

[0043] like Figure 5 As shown, the synthesized p-PVA has a char residue of almost 0 at 800℃. The maximum thermal decomposition temperature increases with the introduction of the flame retardant Ala-BPOD, and this increase is accompanied by an earlier maximum thermal decomposition temperature.

[0044] This demonstrates that in Example 1, a bio-based flame retardant with both flame-retardant and plasticizing properties was successfully used in conjunction with other plasticizers to prepare PVA composite materials using a thermal processing method, thus improving their thermal stability.

[0045] Therefore, the application adopts the above-mentioned biobased plasticizer with plasticizing effect, and its preparation method and application, and by adding commercial plasticizers and the prepared biobased flame retardant, the melting point of PVA can be rapidly reduced, the thermal processing window of PVA is widened, the controllable thermal processing of PVA is realized, and the plasticity and flame retardancy of PVA are improved.

[0046] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit them, although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that: the technical solutions of the present application can still be modified or replaced by equivalents, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. A process for the preparation of a bio-based flame retardant with plasticizing effect, characterized in that, The method comprises the following steps: Step S1, weigh the bio-based raw material, acid-binding agent and solvent into a three-necked flask for mixing to obtain solution A; Step S2, mix phenylphosphonic dichloride with chloroform to obtain a chloroform solution; place the chloroform solution in a dropping funnel and drop it into solution A at a rate of 1 drop per second while nitrogen is introduced to obtain solution B; Step S3, after the dropping is completed, heat solution B to 60-70°C and continue to react for 12 hours to stop the reaction; Step S4, transfer the contents in the three-necked flask to a Buchner funnel for suction filtration to obtain a filtrate; Step S5, perform rotary evaporation on the filtrate under the conditions of vacuum-0.1 Mpa, water bath 60°C and rotation speed 40 rpm to remove excess solvent; drop one fourth of the rotary evaporated liquid into a post-treatment solvent for precipitation to obtain a solid; Step S6, vacuum dry the solid at 60°C for 24 hours to obtain the bio-based flame retardant having plasticizing effect.

2. A process for the preparation of a bio-based plasticizer having flame retardant effect according to claim 1, characterized by: In step S1, the bio-based raw material is one of alanine, phenylalanine, glycine, tyrosine and tryptophan; The acid-binding agent is one of triethylamine, N,N-diisopropylethylamine, pyridine, potassium carbonate and potassium hydroxide; The solvent is one of chloroform, dichloromethane and tetrahydrofuran.

3. A process for the preparation of a bio-based plasticizer having flame retardant effect according to claim 2, characterized by: In step S1, the weight of the bio-based raw material is 8.909-17.818 g, the weight of the acid-binding agent is 10.119-20.238 g and the solvent is 150-200 mL.

4. A process for the preparation of a bio-based plasticizer having flame retardant effect according to claim 1, characterized by: In step S2, the weight of phenylphosphonic dichloride is 9.307-18.614 g and the weight of chloroform is 30-50 mL.

5. A process for the preparation of a bio-based plasticizer having flame retardant effect according to claim 1, characterized by: In step S5, the post-treatment solvent is one of n-hexane, n-heptane and petroleum ether.

6. The bio-based flame retardant having plasticizing effect prepared by the method of any one of claims 1-5.

7. The bio-based flame retardant of claim 6 for use in preparing a PVA composite material.

8. Use according to claim 7, characterized in that, The method for preparing the PVA composite material comprises the following steps: Step S1, place polyvinyl alcohol and commercial plasticizer in a beaker for stirring until the mixture is translucent, the particles are expanded and the whole is uniform to obtain solution C; Step S2, add solution C and the bio-based flame retardant having plasticizing effect into a banbury mixer for mixing for 5 minutes to obtain a sample, and then take out the sample and place it in a press for pressing for 5 minutes to form a PVA composite material.

9. Use according to claim 8, characterized in that: The weight ratio of polyvinyl alcohol to commercial plasticizer is 10:3; and the weight ratio of solution C to the bio-based flame retardant having plasticizing effect is 10:(2-3).

10. Use according to claim 9, characterized in that: The commercial plasticizer is composed of two of glycerol, tributyl citrate, triethyl citrate, acetyl tributyl citrate, acetyl triethyl citrate, triacetin, epoxy soybean oil, linseed oil, castor oil and polycaprolactone triol, and the weight ratio of the two is 1:1.

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