P-n synergistic chitosan bio-based flame retardant and preparation method thereof

Abstract

The application relates to a P-N synergistic chitosan bio-based flame retardant and a preparation method thereof. Chitosan is heated and dissolved in an acetic acid solution, nitrogen is introduced, an initiator is added, then a DOPO derivative with a terminal double bond, MDO and AA are added to carry out polymerization reaction to prepare the flame retardant. The application takes the environment-friendly biological material chitosan as a matrix material, first prepares the DOPO derivative with the terminal double bond and P-N flame retardant performance, then carries out ring-opening polymerization to form degradable MDO and grafts and polymerizes the acrylic acid on the chitosan surface, the macromolecular polymer chain formed has high flame retardancy and can be degraded into a low molecular structure and has biological environmental protection, and when the chitosan-based macromolecule containing PCL and PAA segments is added into degradable plastics such as PLA, good compatibility with the plastic particles can be achieved, therefore, the degradable plastics can be endowed with certain flame retardant performance, and the compatibility with the plastic particles is good, so that the degradation rate is not affected.

Description

Technical Field

[0001] This invention relates to the field of flame retardant technology, specifically to a PN synergistic chitosan bio-based flame retardant and its preparation method. Background Technology

[0002] Flame retardants, as the name suggests, are functional additives that impart flame-retardant properties to polymerized materials. They are classified into additive flame retardants and reactive flame retardants based on their application method. Additive flame retardants are more common, with triazine and phosphononitrile flame retardants being frequently used. These offer good flame retardant properties, but their high molecular weight means they are difficult to degrade. Modern society places greater emphasis on green and sustainable development, and many commonly used plastic products have a certain degree of biodegradability. Adding these flame retardants significantly impacts the degradation performance of these materials. Furthermore, the large dosage of flame retardants used to improve flame retardant performance can lead to poor compatibility with biodegradable polyester materials. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a bio-based flame retardant based on chitosan, a natural biomaterial, which can be used in biodegradable plastics to impart flame retardancy to the materials.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] A method for preparing a PN synergistic chitosan bio-based flame retardant includes the following steps:

[0006] S1. Preparation of DOPO derivatives with terminal double bonds

[0007] S1-1, 1 equivalent of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) was dissolved in xylene. Under nitrogen atmosphere, 1 equivalent of paraformaldehyde was slowly added dropwise. The mixture was heated to 140°C and refluxed. The mixture was washed and filtered with hot water and ethanol, and then dried under vacuum to obtain DOPO-OH.

[0008] S1-2. Dissolve 1 equivalent of glycidyl methacrylate in DMSO, heat to 50-70°C, add 1 equivalent of the DOPO-OH, add a catalytic amount of tetrabutylammonium bromide, stir and mix at 70°C for 6-8 hours, pour into ice water to precipitate solid, filter, wash with ice water, filter and dry to obtain DOPO-GMA.

[0009] S1-3. Dissolve DOPO-GMA in methanol and adjust the pH to 8-9 with sodium hydroxide. Add 2-chloro-4,6-dimethoxy-1,3,5-triazine (CDMT) and methanol to a reaction flask and stir until completely dissolved. Slowly add the methanol solution of DOPO-GMA dropwise to the reaction flask and stir the reaction at room temperature for 4-6 hours. After the reaction is complete, filter, wash, and dry to obtain the final product. ;

[0010] S2. Dissolve chitosan in acetic acid solution by heating, keep the temperature at 60-70℃, purge with nitrogen gas for 30 minutes, add initiator, then add DOPO derivative with terminal double bond, 2-methylene-1,3-dioxane (MDO) and acrylic acid (AA), and react for a certain time.

[0011] S3. After the reaction is complete, cool to room temperature, adjust the pH of the system to neutral, pour the reaction solution into ice-cold methanol, precipitate the solid, filter, wash with water and dry to obtain the final product.

[0012] Furthermore, the degree of deacetylation of the chitosan is 90±5%, the mass concentration of the acetic acid solution is 2~5%, and the mass-volume ratio of chitosan to acetic acid solution is 20~30 g / L.

[0013] Furthermore, the initiator is ammonium persulfate or a mixture of potassium persulfate and sodium sulfite.

[0014] Furthermore, the molar ratio of the terminal double bond DOPO derivative, 2-methylene-1,3-dioxane-heptane, and acrylic acid is 2~5:4~7:1; the mass ratio of chitosan, mixed monomers, and initiator is 1:3~5:0.05~0.1.

[0015] The present invention further provides a PN synergistic chitosan bio-based flame retardant prepared by the preparation method described above.

[0016] In this application, DOPO is a novel halogen-free flame retardant intermediate with superior flame retardant performance compared to traditional organophosphates. It achieves high-efficiency flame retardancy through a dual mechanism of free radical quenching in the gas phase and char formation in the condensed phase. Chitosan is a natural macromolecule with abundant amino groups in its molecular structure; CDMT is a compound containing a triazine structure and abundant nitrogen. Both can absorb heat energy and decompose into non-flammable gases, diluting combustible gases and achieving gas-phase flame retardancy.

[0017] MDO is a compound that can undergo ring-opening polymerization to form PCL-like segments. Its polymer chains are easily hydrolyzed by microorganisms, enzymes, or acids and alkalis. Reacting it with DOPO derivatives with terminal double bonds provides degradation sites, allowing the macromolecule to degrade into smaller molecules. Chitosan itself is biodegradable, forming a dual degradation pathway with PCL. Acrylic acid provides free radical active sites to promote the polymerization reaction, while the similarity and compatibility between the polyester segments and PLA reduces interfacial defects and avoids localized non-degradable regions caused by phase separation.

[0018] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention uses chitosan, an environmentally friendly biomaterial, as the matrix material. First, a DOPO derivative with terminal double bonds possessing PN flame-retardant properties is prepared. Then, it is grafted onto the chitosan surface with ring-opening polymerization to form degradable MDO and acrylic acid. The resulting macromolecular polymer chain has high flame retardancy. Since the ring-opening polymerization of MDO forms a degradable PCL chain, the macromolecular polymer chain can be degraded into a low molecular weight structure, possessing bio-environmental friendliness. When chitosan-based macromolecules containing PCL and PAA segments are added to degradable plastics such as PLA, they can also achieve good compatibility with plastic particles. Therefore, it can endow degradable plastics with certain flame-retardant properties, while maintaining good compatibility with plastic particles and thus keeping the degradation rate unaffected. Detailed Implementation

[0019] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0021] Example 1: A PN-synergistic chitosan bio-based flame retardant

[0022] S1. Preparation of DOPO derivatives with terminal double bonds

[0023] S1-1, 1 equivalent of DOPO is dissolved in xylene. Under nitrogen atmosphere, 1 equivalent of paraformaldehyde is slowly added dropwise. The mixture is heated to 140°C and refluxed. The mixture is washed and filtered with hot water and ethanol, and then dried under vacuum to obtain DOPO-OH.

[0024] S1-2. Dissolve 1 equivalent of glycidyl methacrylate in DMSO, heat to 50-70°C, add 1 equivalent of the DOPO-OH, add a catalytic amount of tetrabutylammonium bromide, stir and mix at 70°C for 6-8 hours, pour into ice water to precipitate solid, filter, wash with ice water, filter and dry to obtain DOPO-GMA.

[0025] S1-3. Dissolve DOPO-GMA in methanol and adjust the pH to 8-9 with sodium hydroxide. Add CDMT and methanol to the reaction flask and stir until completely dissolved. Slowly add the methanol solution of DOPO-GMA dropwise to the reaction flask and stir the reaction at room temperature for 4-6 hours. After the reaction is complete, filter, wash, and dry to obtain the final product. ;

[0026] S2. Dissolve 10g of chitosan in 500ml of acetic acid solution by heating, keep the temperature at 60-70℃, purge with nitrogen gas for 30min, add 0.8g of a mixture of ammonium persulfate and sodium sulfite as initiators, then add 16g of DOPO derivative with terminal double bonds, 12.8g of MDO and 1.2g of AA (monomer molar ratio of approximately 2:7:1), and react for a certain time;

[0027] S3. After the reaction is complete, cool to room temperature, adjust the pH of the system to neutral, pour the reaction solution into ice-cold methanol, precipitate the solid, filter, wash with water and dry to obtain the final product.

[0028] Example 2: A PN-synergistic chitosan bio-based flame retardant

[0029] S1. Preparation of DOPO derivatives with terminal double bonds

[0030] Same as Example 1;

[0031] S2. Dissolve 10g of chitosan in 500ml of acetic acid solution by heating, keep the temperature at 60-70℃, purge with nitrogen gas for 30min, add 0.8g of a mixture of ammonium persulfate and sodium sulfite as initiators, then add 25g of DOPO derivative with terminal double bonds, 4.3g of MDO and 0.7g of AA (monomer molar ratio of 5:4:1), and react for a certain time;

[0032] S3. After the reaction is complete, cool to room temperature, adjust the pH of the system to neutral, pour the reaction solution into ice-cold methanol, precipitate the solid, filter, wash with water and dry to obtain the final product.

[0033] Example 3: A PN-synergistic chitosan bio-based flame retardant

[0034] S1. Preparation of DOPO derivatives with terminal double bonds

[0035] Same as Example 1;

[0036] S2. Dissolve 10g of chitosan in 500ml of acetic acid solution by heating, keep the temperature at 60-70℃, purge with nitrogen gas for 30min, add 0.8g of a mixture of ammonium persulfate and sodium sulfite as initiators, then add 26g of DOPO derivative with terminal double bonds, 21.3g of MDO and 1.9g of AA (monomer molar ratio of 3:6:1), and react for a certain time;

[0037] S3. After the reaction is complete, cool to room temperature, adjust the pH of the system to neutral, pour the reaction solution into ice-cold methanol, precipitate the solid, filter, wash with water and dry to obtain the final product.

[0038] Comparative Example 1:

[0039] S1. Preparation of DOPO derivatives with terminal double bonds

[0040] S1-1, 1 equivalent of DOPO is dissolved in xylene. Under nitrogen atmosphere, 1 equivalent of paraformaldehyde is slowly added dropwise. The mixture is heated to 140°C and refluxed. The mixture is washed and filtered with hot water and ethanol, and then dried under vacuum to obtain DOPO-OH.

[0041] S1-2. Dissolve 1 equivalent of glycidyl methacrylate in DMSO, heat to 50-70°C, add 1 equivalent of the DOPO-OH, add a catalytic amount of tetrabutylammonium bromide, stir and mix at 70°C for 6-8 hours, pour into ice water to precipitate solid, filter, wash with ice water, filter and dry to obtain DOPO-GMA.

[0042] S2. Dissolve 10g of chitosan in 500ml of acetic acid solution by heating, keep the temperature at 60-70℃, purge with nitrogen gas for 30min, add 0.8g of a mixture of ammonium persulfate and sodium sulfite as initiators, then add 14.2g of DOPO-GMA, 14.5g of MDO and 1.3g of AA (monomer molar ratio of approximately 2:7:1), and react for a certain time;

[0043] S3. After the reaction is complete, cool to room temperature, adjust the pH of the system to neutral, pour the reaction solution into ice-cold methanol, precipitate the solid, filter, wash with water and dry to obtain the final product.

[0044] Comparative Example 2:

[0045] The product is obtained by polymerizing a DOPO derivative with terminal double bonds with acrylic acid in a 1:1 molar ratio.

[0046] The flame retardants prepared above were subjected to performance tests. The products obtained in Examples 1-3 and Comparative Examples 1-2 were mixed with polylactic acid and extruded to obtain PLA composite materials. The addition amount was 10 wt% of polylactic acid. The flame retardancy and mechanical properties of the PLA composite materials were investigated, and the results are recorded in Table 1.

[0047] Table 1

[0048]

[0049] Observing Table 1, it can be found that the product obtained in this application can effectively improve the limiting oxygen index of PLA when added to it, that is, this application has successfully prepared a flame retardant. At the same time, the flame retardant of this application also improves the elongation at break when added to PLA, indicating that the flame retardant has good compatibility with PLA, and the flame retardant containing macromolecular polymer chains has little effect on the degradation rate of PLA when added to it.

[0050] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details.

Claims

1. A method for preparing a P-N synergistic chitosan bio-based flame retardant, characterized in that, Includes the following steps: S1. Preparation of DOPO derivatives with terminal double bonds S1-1, 1 equivalent of DOPO is dissolved in xylene. Under nitrogen atmosphere, 1 equivalent of paraformaldehyde is slowly added dropwise. The mixture is heated to 140°C and refluxed. The mixture is washed and filtered with hot water and ethanol, and then dried under vacuum to obtain DOPO-OH. S1-2. Dissolve 1 equivalent of glycidyl methacrylate in DMSO, heat to 50-70°C, add 1 equivalent of the DOPO-OH, add a catalytic amount of tetrabutylammonium bromide, stir and mix at 70°C for 6-8 hours, pour into ice water to precipitate solid, filter, wash with ice water, filter and dry to obtain DOPO-GMA. S1-3. Dissolve DOPO-GMA in methanol and adjust the pH to 8-9 with sodium hydroxide. Add 2-chloro-4,6-dimethoxy-1,3,5-triazine and methanol to the reaction flask and stir until completely dissolved. Slowly add the methanol solution of DOPO-GMA dropwise to the reaction flask and stir the reaction at room temperature for 4-6 hours. After the reaction is complete, filter, wash, and dry to obtain the final product. S2. Dissolve chitosan in acetic acid solution by heating, keep the temperature at 60-70℃, purge with nitrogen gas for 30 minutes, add initiator, then add DOPO derivative with terminal double bond, 2-methylene-1,3-dioxane-heptane and acrylic acid, and react for a certain time. S3. After the reaction is complete, cool to room temperature, adjust the pH of the system to neutral, pour the reaction solution into ice-cold methanol, precipitate the solid, filter, wash with water and dry to obtain the final product.

2. The preparation method of the PN synergistic chitosan bio-based flame retardant as described in claim 1, characterized in that, The degree of deacetylation of the chitosan is 90±5%, the mass concentration of the acetic acid solution is 2~5%, and the mass-volume ratio of chitosan to acetic acid solution is 20~30 g / L.

3. The preparation method of the PN synergistic chitosan bio-based flame retardant as described in claim 1, characterized in that, The initiator is ammonium persulfate or a mixture of potassium persulfate and sodium sulfite.

4. The preparation method of the PN synergistic chitosan bio-based flame retardant as described in claim 1, characterized in that, The molar ratio of the terminal double bond DOPO derivative, 2-methylene-1,3-dioxane-heptane, and acrylic acid is 2~5:4~7:1; the mass ratio of chitosan, mixed monomers, and initiator is 1:3~5:0.05~0.

1.

5. A PN synergistic chitosan bio-based flame retardant prepared by the preparation method according to any one of claims 1-4.

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