CN110746646B

CN110746646B - Biomass-based flame retardant and preparation method thereof

Info

Publication number: CN110746646B
Application number: CN201910871693.4A
Authority: CN
Inventors: 黄子群; 谢成根; 常文贵; 李淮芬; 金俊成; 杨雷
Original assignee: West Anhui University
Current assignee: West Anhui University
Priority date: 2019-09-16
Filing date: 2019-09-16
Publication date: 2021-05-18
Anticipated expiration: 2039-09-16
Also published as: CN110746646A

Abstract

The invention discloses a biomass-based flame retardant and a preparation method thereof. The preparation method steps are as follows: S1: under magnetic stirring, dissolve vanillin in tetrahydrofuran, and the concentration of the prepared vanillin solution is 0.1-0.5mol/L , drip dichlorodimethylsilane under nitrogen, react at 50-80 ℃ for 2-8h to obtain product I; S2: under magnetic stirring, mix product I with aminophenol/primary aminophenol in a molar ratio of 1 : 2-5 is mixed and dissolved in absolute ethanol, the product is filtered out after reacting at 50-80 ℃ for 4-8 h, the obtained product is washed with deionized water, and vacuum-dried to constant weight at 50-80 ℃ to obtain the product II; S3: Dissolving DOPO in dichloromethane, then adding azobisisobutyl cyanide, and then adding the product in S2 under the protection of inert gas to obtain biomass-based flame retardant III. The preparation method of the invention has the advantages of simple process and green and renewable raw materials, is beneficial to reduce the consumption of the organic phosphorus flame retardant for non-renewable petroleum and coal resources, and has application prospects.

Description

Biomass-based flame retardant and preparation method thereof

Technical Field

The invention relates to the technical field of organic chemistry, in particular to a biomass-based flame retardant and a preparation method thereof.

Background

The polymer material is one of three traditional materials, and is applied to various fields of national economy and people's life. With the high concern of people on safety and sustainable development, the high molecular flame retardant material becomes an important content of material research and development. However, the polymer material itself does not have good flame retardancy.

The Intumescent Flame Retardant (IFR) is a flame retardant taking phosphorus and nitrogen as main components, and the flame retardant foams and expands when being heated, so the intumescent flame retardant is called as the intumescent flame retardant and is an environment-friendly flame retardant with higher flame retardant efficiency. Due to the unique flame retardant mechanism, good flame retardant, smoke suppression and anti-dripping effects, the IFR has wide application prospect and is one of the most active research fields of flame retardants since the 90 s of the 20 th century. However, most of the production raw materials of the flame retardant are from non-renewable petrochemical resources, and if the raw materials are partially replaced by chemicals derived from biomass resources, the sustainable development of 'green' in the field of flame retardance is facilitated.

The flame retardant prepared by using biomass as a raw material just meets the trend of safety, environmental protection and sustainability, but most biomass materials have insufficient heat resistance, and most of biomass-based flame retardants have low efficiency and cannot meet the use requirement of the flame retardant.

Disclosure of Invention

Based on the technical problems in the background art, the invention provides the biomass-based flame retardant and the preparation method thereof, so that the flame retardant is green and renewable, and the flame retardant efficiency of high polymer materials such as polycarbonate, epoxy resin and the like can be effectively improved.

The biomass-based flame retardant provided by the invention comprises the following chemical structures of a flame retardant (III):

the preparation method of the biomass-based flame retardant provided by the invention comprises the following steps:

s1: dissolving vanillin in tetrahydrofuran, and then adding dichlorodimethylsilane for reaction to obtain a product (I);

s2: dissolving the product in S1 in absolute ethyl alcohol, and then adding aminophenol or primary aminophenol to react to obtain a product (II);

s3: dissolving 9, 10-dihydro-9, 10-oxa-10-phosphaphenanthrene-10-oxide (DOPO) in dichloromethane, adding Azodiisobutyronitrile (AIBN), and adding the product in S2 under the protection of inert gas to obtain the biomass-based flame retardant (III).

Preferably, the vanillin in S1 is derived from a biomass resource.

Preferably, the specific steps of S1 are: under magnetic stirring, dissolving vanillin in tetrahydrofuran to prepare vanillin solution with the concentration of 0.1-0.5mol/L, adding dichlorodimethylsilane dropwise under the condition of introducing nitrogen, and reacting at 50-80 ℃ for 2-8h to obtain the product (I).

Preferably, the chemical structure of the product (i) is:

preferably, the vanillin solution further comprises an amine acid scavenger.

Preferably, the acid scavenger is an organic amine acid scavenger.

Preferably, the organic amine acid-binding agent is one or more of triethylamine, diethylamine, pyridine and aminopyridine.

Preferably, the molar ratio of dichlorodimethylsilane to vanillin in S1 is 1: 2-5.

Preferably, the specific steps of S2 are: under magnetic stirring, mixing the product (I) and aminophenol/primary aminophenol in a molar ratio of 1:2-5, dissolving in absolute ethanol, reacting at 50-80 ℃ for 4-8h, filtering out the product, washing the obtained product with deionized water, and drying at 50-80 ℃ in vacuum to constant weight to obtain the product (II).

Preferably, the aminophenol is 4-hydroxyaniline and the primary aminophenol is dopamine;

preferably, the chemical structure of the product (ii) is:

preferably, the specific steps of S3 are: under the protection of nitrogen, the DOPO and the product (II) are dissolved according to the mol ratio of 2-5:1In CH₂Cl₂Adding AIBN with the concentration of 0.001-0.01mol/L, and reacting for 2-8h at the temperature of 50-80 ℃ to obtain the biomass-based flame retardant (III).

The invention provides an application of a biomass-based flame retardant in a thermoplastic polymer.

Preferably, the thermoplastic polymer comprises polypropylene, polyethylene, polyvinyl chloride, polystyrene, polymethylmethacrylate, polyamide, polycarbonate, or a terephthalate-based thermoplastic polyester.

The invention provides an application of a biomass-based flame retardant in thermosetting resin.

Preferably, the thermosetting resin is epoxy resin or polyurethane, and the biomass-based flame retardant and the epoxy resin or the polyurethane can be used as a curing agent or an auxiliary agent.

Compared with the prior art, the invention has the beneficial technical effects that:

(1) the invention provides a biomass phosphorus-nitrogen-silicon-containing multi-element intumescent flame retardant, which combines the excellent reaction performance of vanillin, aminophenol/primary aminophenol and the flame retardant advantages of intumescent flame retardant elements, can be independently used as an intumescent flame retardant for application without being compounded with other flame retardants, and can be used as an additive type and reactive type flame retardant with good compatibility and an ideal adhesive flame retardant coating due to the existence of catechol groups in molecules.

(2) The flame retardant formed by mixing a plurality of components in the prior art has the limitations of uneven dispersion of each component, insufficient compatibility of each component with a matrix material and the like, but the flame retardant combining a plurality of elements into one molecule only needs to consider the compatibility of one flame retardant component with the matrix material, and has relatively stronger operability.

(3) The invention provides a multi-element intumescent flame retardant based on biomass resources, which has better market prospect and sustainable development advantage compared with the flame retardant derived from non-renewable petrochemical resources.

(4) The flame retardant of the invention has hydroxyl groups, is particularly suitable for polylactic acid, epoxy resin and similar systems, and has better flame retardant property.

Drawings

FIG. 1 is a nuclear magnetic resonance hydrogen spectrum (a) and a phosphorus spectrum (b) of a biomass-based flame retardant in example 1 of the present invention;

FIG. 2 is an infrared spectrum of a biomass-based flame retardant in example 1 of the present invention;

FIG. 3 is an SEM image of a carbon layer of a biomass-based flame retardant composite epoxy resin after combustion in example 1 of the invention;

FIG. 4 is a digital photograph of a residual carbon layer from combustion of biomass-based flame retardant composite epoxy resin in example 1 of the present invention;

FIG. 5 is a pressure-tension curve diagram of the biomass-based flame retardant composite epoxy resin in example 1 of the present invention.

Detailed Description

The present invention will be further illustrated with reference to the following specific examples.

Example 1

First, 15mmol of vanillin was dissolved in 150mL of THF at room temperature, 3mL of triethylamine was injected into the flask using a syringe, and after stirring for 10min, 7.5mmol of dichlorodimethylsilane was slowly injected into the flask using a syringe. Stirring and reacting at 50 ℃ for 2 hours, pouring the reaction mixture into n-hexane at 0 ℃, filtering, washing the precipitate with deionized water, and drying in vacuum at 50 ℃ to obtain an intermediate product (I).

Then, under the protection of nitrogen, 0.1mol (12.21g) of the intermediate product (I) is dissolved in 500m1 of absolute ethyl alcohol, 0.2mo1 of dopamine is slowly dropped into the solution prepared above, the product is filtered after heating reflux reaction for 4 hours, the obtained solid is washed by deionized water and dried in vacuum at 50 ℃ to constant weight, and the product (II) is obtained;

finally, product (II) (0.1mol) was dissolved in absolute ethanol (100 ml) in N₂Adding 0.2mol of DOPO and 0.1mmol of AIBN under protection, stirring and refluxing at 50 ℃ for 2h, and cooling to room temperature. Filtration and washing of the precipitate with dichloromethane followed by vacuum drying at 50 ℃ for 12 hours gave biomass-based flame retardant (III).

Referring to a in FIG. 1, which is a nuclear magnetic resonance hydrogen spectrum of the biomass-based flame retardant prepared in this example, 8.92ppm was assigned to phenolic hydroxyl groups (Ar-OH), 7.30ppm, 6.73ppm and 6.69ppm were assigned to H on benzene rings, 3.74ppm was assigned to H on methoxy groups, and 1.13ppm was assigned to H on methyl groups on silanes.

Referring to b in FIG. 1, which is the NMR spectrum of the biomass-based flame retardant prepared in this example, a sharp peak at 15.83ppm was observed, indicating that there is only one phosphorus atom in the molecular structure, consistent with theory.

See FIG. 2, 3571cm^-1Belongs to N-H, 3219-3342cm^-1Belongs to phenolic hydroxyl Ar-OH, 3106cm^-1Belonging to the aromatic ring C-H), 2962and2869cm^-1Belong to-

CH

₃1612,1580,1515 and 1359cm^-1Belongs to an aromatic ring; 1466cm^-1Belongs to (P-C); 1247cm^-1To (P ═ O); 1153cm^-1Belongs to (Si-O-C); 912 and 914cm^-1Belongs to (P-O-C).

As can be seen from the above figures, the product prepared in this example is the target product.

In order to determine the morphology of the carbon residue, SEM analysis was performed on the carbon residue, and it can be seen from FIG. 3 that the carbon layer was not sufficiently formed without adding the flame retardant of the present invention and was macroporous. In contrast, the coverage and continuity of the char layer with 5% flame retardant addition was improved. The carbon layer has good compactness and continuity, and is beneficial to reducing the transfer of gas and heat in the combustion process. These results again demonstrate the effectiveness of the flame retardant application of the present invention in carbon layer formation, ultimately improving the flame retardant effectiveness of the polymeric substrate.

The expansion by heating is the most obvious characteristic of the intumescent flame retardant, a porous foam carbon layer formed by the expansion by heating can play a flame retardant role in a condensed phase, and the expansion degree is one of the main bases of the flame retardant effect of the intumescent flame retardant. As can be seen from FIG. 4, the addition of the flame retardant of the present invention achieves a greater swell height and the expanded residue not only better inhibits the release of volatile fuels, but also further insulates and protects the interior substrate from fire.

FIG. 5 illustrates that the addition of the flame retardant of the present invention reduces the elongation at break of the substrate, increasing and then decreasing the tensile strength to the substrate.

The limiting oxygen index refers to the minimum oxygen content necessary to maintain stable combustion of the target material in an oxygen-nitrogen mixture under specified conditions. The high oxygen index indicates that the material is not easy to burn, so that the measurement of the oxygen index of the material can theoretically determine the flame retardant effect of the flame retardant material.

The flammability UL-94 rating is widely used, and is often used as a flammability standard for plastic materials to evaluate the ability of the material to extinguish after being ignited, which is a test method for vertical burning. UL-94V-O assessment method: the sample quickly self-extinguished after the flame was removed from the ignition until no flaming melt dropped within a certain time interval (i.e., the flaming melt dropped on a cotton pad located one foot below the test sample and did not bow | burn the cotton). UL-94V-1 is similar to the assessment method for V-0, except that the self-extinguishing time is different. The required self-extinguishing time of V-1 is relatively long. This test requires that the droplets falling on the cotton pad do not ignite the cotton. UL-94V-2 is identical to V-1 except that it allows burning droplets to ignite the cotton below.

The flame retardant effect of the product prepared in the embodiment in polycarbonate and DGEBA epoxy resin is examined through oxygen index and vertical combustion performance, wherein the oxygen index is less than 21 and is flammable material, the oxygen index has self-extinguishing property between 22 and 26, the oxygen index is more than 27 and is nonflammable material, the vertical combustion method comprises three grades V-0, V-1 and V-2, the grade V-0 is the best grade which can be achieved by the material, and the evaluation standard of the grade of the material is based on the combustion time from the moment that a vertically placed sample is removed to the moment that the sample is self-extinguished.

And testing the limiting oxygen index of the sample according to GB/T2406-2008 'Plastic burning performance test method-oxygen index method'. The flame retardant and the polymer base material are uniformly mixed in different proportions, extruded by an extruder to prepare a sample strip with the diameter of 3mm, and the flame retardant property of the sample strip is tested, wherein the test result is shown in table 1.

TABLE 1 flame retardant Effect of flame retardant polycarbonate

TABLE 2 flame retardant DGEBA epoxy resin combustion parameters

TABLE 3 thermal Properties of flame retardant DGEBA epoxy resin

TABLE 4 mechanical Properties of flame retardant DGEBA epoxy resin

As can be seen from tables 1-4, the flame retardant of the present application exhibits very good tensile strength (80MPa) and modulus (2709MPa) when applied to an epoxy resin, which are much higher than those of a bisphenol A epoxy resin (Dow DER331) measured under the same conditions (76MPa) and modulus (1893 MPa). The flame retardant property is excellent, two applied base materials (polycarbonate and epoxy resin) reach the UL-94V-0 industrial flame retardant level, and the limited oxygen index reaches 30%; meanwhile, no black smoke is generated in the epoxy resin in a combustion experiment, and a large amount of black smoke is generated by the bisphenol A epoxy resin, so that the flame retardant disclosed by the invention has a smoke suppression effect. Through a thermal weight loss experiment and analysis of the morphology and structural components of the carbon layer after a flame-retardant experiment, the excellent flame retardance of the carbon layer is mainly found out as follows: the biomass-based multi-element flame retardant has excellent expansion char forming capability, and a formed char layer is very compact, so that the flame retardant can play a very good role in heat insulation and oxygen isolation, and further combustion of internal materials is prevented.

Example 2

First, 75mmol of vanillin was dissolved in 150mL of THF at room temperature, 3mL of triethylamine was injected into the flask using a syringe, and after stirring for 10min, 15mmol of dichlorodimethylsilane was slowly injected into the flask using a syringe. Stirring and reacting at 80 ℃ for 8 hours, pouring the reaction mixture into n-hexane at 0 ℃, filtering, washing the precipitate with deionized water, and drying in vacuum at 80 ℃ to obtain an intermediate product (I).

Then, under the protection of nitrogen, 0.1mol (12.21g) of the intermediate product (I) is dissolved in 500m1 of absolute ethyl alcohol, 0.5mo1 of 4-hydroxyaniline is slowly dropped into the prepared solution, the product is filtered after heating reflux reaction for 8 hours, the obtained solid is washed by deionized water and dried in vacuum at 80 ℃ to constant weight, and the product structure (II) is obtained;

finally, product (II) (0.1mol) was dissolved in absolute ethanol (100 ml) in N₂Adding 0.5mol of DOPO and 1mmol of AIBN under protection, stirring and refluxing at 80 ℃ for 8h, and cooling to room temperature. Filtration and washing of the precipitate with dichloromethane followed by vacuum drying at 50 ℃ for 12 hours gave biomass-based flame retardant (III).

Example 3

First, 20mmol of vanillin was dissolved in 100mL of THF at room temperature, 3mL of triethylamine was injected into the flask using a syringe, and after stirring for 10min, 5mmol of dichlorodimethylsilane was slowly injected into the flask using a syringe. Stirring and reacting at 60 ℃ for 5 hours, pouring the reaction mixture into n-hexane at 0 ℃, filtering, washing the precipitate with deionized water, and drying in vacuum at 60 ℃ to obtain an intermediate product (I).

Then, under the protection of nitrogen, 0.1mol (12.21g) of the intermediate product (I) is dissolved in 500m1 of absolute ethyl alcohol, 0.4mo1 of dopamine is slowly dropped into the solution prepared above, the product is filtered after heating reflux reaction for 5 hours, the obtained solid is washed by deionized water and dried in vacuum at 60 ℃ to constant weight, and the product structure (II) is obtained;

finally, product (II) (0.1mol) was dissolved in absolute ethanol (100 ml) in N₂Under protection, 0.5mol of DOPO and1mmol of AIBN, at 80 ℃ under stirring and reflux for 8h, cooling to room temperature. Filtration and washing of the precipitate with dichloromethane followed by vacuum drying at 50 ℃ for 12 hours gave biomass-based flame retardant (III).

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.

Claims

1. Biomass-based flame retardant, characterized in that the chemical structure of the flame retardant III is:

2. a preparation method of biomass-based flame retardant as claimed in claim 1, is characterized in that, method step is as follows:

S1: dissolve vanillin in tetrahydrofuran, then add dichlorodimethylsilane to react to obtain product I;

S2: Dissolving the product in S1 in absolute ethanol, then adding aminophenol or primary aminophenol for reaction to obtain product II;

S3: Dissolve 9,10-dihydro-9,10-oxa-10-phosphaphenanthrene-10-oxide in dichloromethane, then add azobisisobutyl cyanide, and then under the protection of inert gas, The product in S2 is added to obtain biomass-based flame retardant III.

3 . The preparation method of a biomass-based flame retardant according to claim 2 , wherein the vanillin in the S1 is derived from biomass resources. 4 .

4. the preparation method of biomass-based flame retardant according to claim 2, is characterized in that, the concrete step of described S1 is: under magnetic stirring, vanillin is dissolved in tetrahydrofuran, the concentration of the prepared vanillin solution At 0.1-0.5mol/L, dichlorodimethylsilane was added dropwise under nitrogen, and the reaction was carried out at 50-80°C for 2-8h to obtain product I.

5. The preparation method of biomass-based flame retardant according to claim 4, wherein the chemical structure of the product I is:

6 . The method for preparing a biomass-based flame retardant according to claim 4 , wherein the vanillin solution further comprises an amine acid binding agent. 7 .

7 . The method for preparing a biomass-based flame retardant according to claim 6 , wherein the acid binding agent is an organic amine acid binding agent. 8 .

8 . The method for preparing a biomass-based flame retardant according to claim 7 , wherein the organic amine acid binding agent is one or more of triethylamine, diethylamine, pyridine and aminopyridine. 9 .

9 . The method for preparing a biomass-based flame retardant according to claim 2 , wherein the molar ratio of dichlorodimethylsilane to vanillin in the S1 is 1:2-5. 10 .

10. The preparation method of biomass-based flame retardant according to claim 2, it is characterized in that, the concrete step of described S2 is: under magnetic stirring, mix product I and aminophenol/primary aminophenol in a molar ratio of 1 : 2-5 mixed and dissolved in absolute ethanol, reacted at 50-80 ℃ for 4-8 hours, filtered out the product, washed the obtained product with deionized water, and vacuum-dried at 50-80 ℃ to constant weight to obtain the product II.

The method for preparing a biomass-based flame retardant according to claim 10, wherein the aminophenol is 4-hydroxyaniline, and the primary aminophenol is dopamine.

12. The preparation method of biomass-based flame retardant according to claim 10, wherein the chemical structural formula of the product II is:

13. The preparation method of biomass-based flame retardant according to claim 2, wherein the specific step of S3 is: under nitrogen protection, 9,10-dihydro-9,10-oxa -10-phosphaphenanthrene-10-oxide and product II were dissolved in CH ₂ Cl ₂ in a molar ratio of 2-5:1, and the concentration of azobisisobutyl cyanide was added to be 0.001-0.01mol/L, at 50-80 React at ℃ for 2-8h to obtain biomass-based flame retardant III.

14. Use of the biomass-based flame retardant of claim 1 in thermoplastic polymers.

15. The application of biomass-based flame retardant in thermoplastic polymer according to claim 14, wherein the thermoplastic polymer comprises polypropylene, polyethylene, polyvinyl chloride, polystyrene, polymethyl Methyl acrylate, polyamide, polycarbonate, polyterephthalate thermoplastic polyester.

16. The application of biomass-based flame retardant as claimed in claim 1 in thermosetting resin;

17. The application of the biomass-based flame retardant in thermosetting resin according to claim 16, wherein the thermosetting resin is epoxy resin or polyurethane.