Schiff base-DOPO-based composite reaction type flame-retardant unsaturated polyester resin and synthesis method thereof

Abstract

The invention provides Schiff base-DOPO (9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide)-based composite reaction type flame-retardant unsaturated polyester resin and a synthesis method thereof.The synthesis method comprises the steps that an intermediate A is prepared from diprimary amine and 5-hydroxymethylfurfural under the acidic condition, and then a comonomer B is prepared from the intermediate A and DOPO through reaction; finally, the Schiff base-DOPO-based composite reaction type flame-retardant unsaturated polyester resin can be obtained through polymerization and chain extension of a comonomer B, unsaturated anhydride, ethylene glycol and a catalyst, DOPO serves as a flame-retardant monomer and is branched to a macromolecular chain, the distribution uniformity of the flame-retardant monomer in a resin matrix is improved, and the flame-retardant property of the resin matrix is improved. By introducing a large number of aromatic rings into a macromolecular chain segment, the hardness and compressive strength of the unsaturated polyester resin can be remarkably improved after the resin is cured, the resin can still keep excellent mechanical properties after being placed for a long time, and the unsaturated polyester resin has the advantages of easiness in industrial production, low implementation cost and convenience in popularization and implementation.

Description

Technical Field

[0001] The present application belongs to the technical field of chemical raw material production, and specifically relates to a Schiff base-DOPO based composite reaction type flame retardant unsaturated polyester resin and a synthesis method thereof. Background Art

[0002] In the prior art, unsaturated polyester resin (UPR) is one of the most widely used thermosetting resins. It has the advantages of easy availability of raw materials, low price, good chemical corrosion resistance, excellent mechanical properties and a wide processing temperature range, and can be cured at room temperature and pressure. It can be widely used in chemical industry, transportation, construction, electricity, national defense and other fields. However, UPR is mainly composed of carbon and hydrogen elements, and its limiting oxygen index (LOI) is usually only 20%-50%. It is very flammable, and has poor flame retardant and heat resistance. It is easy to cause fire accidents, and a large amount of harmful smoke will be generated during combustion, which will pose a serious threat to life and property safety. Therefore, flame retardant modification of UPR materials is an inevitable measure to reduce its flammability and broaden its application breadth.

[0003] In the prior art, in order to impart flame retardant properties to UPR, the following two methods are generally used: one is additive flame retardant modification, i.e., adding flame retardants during the UPR molding process; the other is reactive flame retardant modification, i.e., using intermediates containing flame retardant elements as raw materials to synthesize flame retardant UPR. In the actual implementation process, traditional flame retardant additives and UPR matrix rely on physical mixing and bonding, and have poor compatibility. Moreover, flame retardant additives are easy to migrate out of the matrix, reducing flame retardant efficiency and destroying the mechanical properties of the material. At the same time, traditional additive flame retardants can only make UPR achieve higher flame retardant properties when added in large amounts, which makes its defects of easy migration and poor compatibility more obvious, the product has a shorter service life, and the actual use experience is poor. Therefore, improvements are urgently needed. Summary of the invention

[0004] In order to solve the technical problem in the prior art that the existing flame-retardant unsaturated polyester resin is usually formed by physically mixing a flame-retardant additive with a UPR matrix, the flame-retardant additive has poor compatibility with the UPR matrix, the bonding strength is low, the flame-retardant additive is easy to migrate out of the matrix, and a large amount of flame-retardant additives need to be added to improve the flame retardant performance. During long-term use, the resin is prone to flame retardant migration and agglomeration, which will reduce the flame retardant performance and mechanical properties of the resin, the present application proposes a Schiff base-DOPO based composite reactive flame-retardant unsaturated polyester resin.

[0005] In order to solve the technical problem raised by the present application, the present application also provides a method for synthesizing a Schiff base-DOPO based composite reaction type flame retardant unsaturated polyester resin.

[0006] The present application adopts the following scheme, a method for synthesizing a Schiff base-DOPO-based composite reactive flame-retardant unsaturated polyester resin, comprising the following steps:

[0007] In an inert gas atmosphere and acidic conditions, an aqueous solution of a diprimary amine and an aqueous solution of 5-hydroxymethylfurfural are placed in a reaction kettle, and heated and condensed under reflux for 1 hr to 2 hr to obtain an intermediate A.

[0008] Adding DOPO ethanol solution to the intermediate A, stirring and reacting for 9-12 hours under heating conditions, and after the reaction, evaporating the solvent, washing with water and drying to obtain the comonomer B;

[0009] The comonomer B, unsaturated acid anhydride, ethylene glycol and catalyst are sequentially put into a reaction kettle, and reacted for 7-12 hours at 110° C.-225° C. under an inert gas atmosphere to obtain a high-purity Schiff base-DOPO-based composite reactive flame-retardant unsaturated polyester resin;

[0010] The high-purity Schiff base-DOPO-based composite reactive flame-retardant unsaturated polyester resin is cooled and transferred to a dilution tank and diluted with styrene to obtain a finished Schiff base-DOPO-based composite reactive flame-retardant unsaturated polyester resin.

[0011] In a possible embodiment, the synthesis method of the Schiff base-DOPO based composite reactive flame retardant unsaturated polyester resin comprises the following steps:

[0012] Step 101. Under a nitrogen atmosphere, an aqueous solution of a diprimary amine, an aqueous solution of 5-hydroxymethylfurfural and 10% acetic acid are put into a reaction kettle, and condensed and refluxed for 1 hr to 2 hr in a water bath at 50° C. to 85° C. to obtain an intermediate A. During the reaction, the progress of the reaction is monitored by HPLC;

[0013] Step 102. Add DOPO ethanol solution to the intermediate A prepared in step 101, and stir the mixture under heating conditions for 9-12 hours. After the reaction is completed, evaporate the solvent, wash with water, and dry to obtain comonomer B.

[0014] Step 103. The comonomer B, unsaturated acid anhydride, ethylene glycol and catalyst prepared in step 102 are sequentially put into a reaction kettle, and in a nitrogen atmosphere, sequentially go through a first heating stage, a first heat preservation reaction stage, a second heating stage, a second heat preservation reaction stage, a third heating stage, a third heat preservation reaction stage and a cooling stage in chronological order to obtain a high-purity Schiff base-DOPO-based composite reactive flame-retardant unsaturated polyester resin;

[0015] The first heating stage is: heating the temperature of the reaction system from room temperature to 110°C;

[0016] The first heat preservation reaction stage is: the temperature of the reaction system is stabilized to 110°C and reacted for 50min-60min;

[0017] The second heating stage is: raising the temperature of the reaction system from 110°C to 180°C;

[0018] The second heat preservation reaction is: the temperature of the reaction system is stabilized at 180°C and reacted for 3.8hr-4hr;

[0019] The three heating stages are: raising the temperature of the reaction system from 180°C to 225°C;

[0020] The three heat preservation reaction stages are: stabilizing the temperature of the reaction system to 225°C for 2.5hr-3hr;

[0021] The cooling stage is as follows: lowering the temperature of the reaction system from 225°C to 145°C;

[0022] In the actual implementation process, comonomer B, unsaturated anhydride, ethylene glycol and catalyst are added to the reactor in sequence, and the reaction is carried out under a nitrogen atmosphere through a gradual heating and heat preservation reaction, and finally a high-purity Schiff base-DOPO-based composite reactive flame-retardant unsaturated polyester resin is prepared. The specific steps include: first, the reaction system is heated from room temperature to 110°C for a preliminary reaction, and then kept at 110°C for 50-60 minutes; then the temperature is raised from 110°C to 180°C for a second time, and then kept at 180°C for 3.8-4 hours; then the temperature is raised from 180°C to 225°C for a third time, and finally kept at 225°C for 2.5-3 hours, and finally the temperature of the reaction system is controlled to drop to 145°C. The whole process ensures the purity and performance of the product. Through multi-stage heating and heat preservation reactions, chain extension can be effectively carried out, which is conducive to the embedding of DOPO flame retardant groups into resin segments, improving the uniformity of the distribution of DOPO flame retardant groups in the resin, and significantly improving the stability and flame retardancy of flame retardant resins.

[0023] Step 104: Cooling the high-purity Schiff base-DOPO-based composite reactive flame-retardant unsaturated polyester resin and transferring it to a dilution tank for dilution with styrene to obtain a finished Schiff base-DOPO-based composite reactive flame-retardant unsaturated polyester resin.

[0024] In a possible implementation, the reaction formula of step 101 is as follows:

[0025]

[0026] In one possible embodiment, the structural formula of intermediate A in step 101 is as follows:

[0027]

[0028] In one possible implementation, the reaction formula of step 102 is as follows:

[0029]

[0030] In one possible implementation, the structural formula of comonomer B in step 102 is as follows:

[0031]

[0032] In a possible embodiment, in the method for synthesizing a Schiff base-DOPO-based composite reactive flame-retardant unsaturated polyester resin, the diprimary amine in the aqueous solution of the diprimary amine is any one or more of methylethylamine, phenylenediamine, cyclohexylmethylamine, dicyclohexylamine, triphenylmethylamine, adamantane, and 3-ethoxybutylamine.

[0033] In a possible embodiment, in the method for synthesizing a Schiff base-DOPO-based composite reactive flame-retardant unsaturated polyester resin, in step 101, the aqueous solution of diprimary amine is a saturated aqueous solution of phenylenediamine, and the aqueous solution of 5-hydroxymethylfurfural is a saturated aqueous solution of 5-hydroxymethylfurfural.

[0034] In a possible embodiment, in the method for synthesizing a Schiff base-DOPO-based composite reactive flame-retardant unsaturated polyester resin, in step 101, HPLC is used to detect that during the reaction, the molar ratio of the diprimary amine to 5-hydroxymethylfurfural in the reaction system is maintained at 1:2-6.2.

[0035] In a possible implementation, in the method for synthesizing a Schiff base-DOPO based composite reactive flame retardant unsaturated polyester resin, in step 102, the DOPO ethanol solution is prepared by mixing DOPO and anhydrous ethanol at a mass ratio of 1:10-12.5.

[0036] In a possible implementation, in the method for synthesizing a Schiff base-DOPO based composite reactive flame retardant unsaturated polyester resin, in step 103, the molar ratio of comonomer B, unsaturated acid anhydride, and ethylene glycol is 1:1.17-1.2:1.07-1.15.

[0037] In a possible embodiment, in the method for synthesizing a Schiff base-DOPO-based composite reactive flame-retardant unsaturated polyester resin, in step 103, during the reaction, the reaction system is sampled and the acid value of the sample is detected every 10 minutes to 30 minutes, and when the acid value of the sample is within the standard interval, p-methoxyphenol is added to the reaction system to terminate the reaction.

[0038] In order to solve the technical problem proposed by the present application, the present application also provides a Schiff base-DOPO based composite reactive flame retardant unsaturated polyester resin, which is prepared by the above-mentioned synthesis method of a Schiff base-DOPO based composite reactive flame retardant unsaturated polyester resin, and its general structural formula is as follows:

[0039]

[0040] The value range of n is 2480-6721.

[0041] Compared with the prior art, this application has the following beneficial effects:

[0042] The present application provides a Schiff base-DOPO based composite reactive flame retardant unsaturated polyester resin and a synthesis method thereof. An intermediate A is prepared under acidic conditions by reacting a diprimary amine with 5-hydroxymethylfurfural, and a comonomer B is prepared by reacting the intermediate A with DOPO. Finally, the Schiff base-DOPO based composite reactive flame retardant unsaturated polyester resin is obtained after chain extension through polymerization of the comonomer B, an unsaturated acid anhydride, ethylene glycol and a catalyst. By using DOPO as a flame retardant monomer and curing it on a polymer chain, not only the uniformity of the distribution of the flame retardant monomer in the resin matrix is ​​improved, but also the flame retardant effect of the unsaturated polyester resin is improved. By introducing a large number of aromatic rings into the polymer chain segment, the hardness and compressive strength of the resin can be significantly improved after curing. After the resin is placed for a long time, it can still maintain excellent mechanical properties. The resin has the advantages of being easy for industrial production, low implementation cost, and easy to promote and implement. DETAILED DESCRIPTION

[0043] The present technical solution is further explained in conjunction with Examples 1-3.

[0044] Example 1

[0045] The synthesis method of the Schiff base-DOPO based composite reactive flame retardant unsaturated polyester tree comprises the following steps:

[0046] Step 101. Under a nitrogen atmosphere, a saturated aqueous solution of phenylenediamine, a saturated aqueous solution of 5-hydroxymethylfurfural and 10% acetic acid are put into a reaction kettle, and condensed and refluxed for 1.2 hours in a water bath at 52.5° C. to obtain an intermediate A. During the reaction, the progress of the reaction is monitored by HPLC, and the molar ratio of phenylenediamine to 5-hydroxymethylfurfural in the reaction system is maintained at 1:2.5, and the pH value of the reaction system is maintained at 5;

[0047] Step 102. Add DOPO ethanol solution to the intermediate A prepared in step 101, and stir the mixture under heating conditions for 9 hours. After the reaction is completed, evaporate the solvent, wash with water, and dry to obtain comonomer B;

[0048] Among them, DOPO and anhydrous ethanol were compounded at a mass ratio of 1:10.2;

[0049] Step 103. The comonomer B, unsaturated acid anhydride, ethylene glycol and catalyst prepared in step 102 are sequentially put into a reaction kettle, and in a nitrogen atmosphere, sequentially go through a first heating stage, a first heat preservation reaction stage, a second heating stage, a second heat preservation reaction stage, a third heating stage, a third heat preservation reaction stage and a cooling stage in chronological order to obtain a high-purity Schiff base-DOPO-based composite reactive flame-retardant unsaturated polyester resin;

[0050] Wherein, the molar ratio of comonomer B, unsaturated anhydride and ethylene glycol is 1:1.17:1.07;

[0051] The first heating stage is: heating the temperature of the reaction system from room temperature to 110°C;

[0052] The first heat preservation reaction stage is: the temperature of the reaction system is stabilized at 110°C and reacted for 50 minutes;

[0053] The second heating stage is: raising the temperature of the reaction system from 110°C to 180°C;

[0054] The second heat preservation reaction is: the temperature of the reaction system is stabilized at 180°C for 3.8 hours;

[0055] The three heating stages are: raising the temperature of the reaction system from 180°C to 225°C;

[0056] The three heat preservation reaction stages are: stabilizing the temperature of the reaction system to 225°C for 2.5 hours;

[0057] The cooling stage is as follows: lowering the temperature of the reaction system from 225°C to 145°C;

[0058] During the reaction, the reaction system was sampled every 12 minutes and the acid value of the sample was tested. When the acid value of the sample was within the standard interval, p-methoxyphenol was added to the reaction system to terminate the reaction.

[0059] Step 104: Cooling the high-purity Schiff base-DOPO-based composite reactive flame-retardant unsaturated polyester resin and transferring it to a dilution tank for dilution with styrene to obtain a finished Schiff base-DOPO-based composite reactive flame-retardant unsaturated polyester resin.

[0060] The general structure of the finished product of Schiff base-DOPO composite reactive flame retardant unsaturated polyester resin is as follows:

[0061]

[0062] Among them, n is 5121, and its acid value is 28.7 mgKOH / g.

[0063] Example 2

[0064] The synthesis method of the Schiff base-DOPO based composite reactive flame retardant unsaturated polyester tree comprises the following steps:

[0065] Step 101. Under a nitrogen atmosphere, a saturated aqueous solution of phenylenediamine, a saturated aqueous solution of 5-hydroxymethylfurfural and 10% acetic acid are put into a reaction kettle, and condensed and refluxed for 1.5 hours in a water bath at 65° C. to obtain an intermediate A. During the reaction, the progress of the reaction is monitored by HPLC, and the molar ratio of phenylenediamine to 5-hydroxymethylfurfural in the reaction system is maintained at 1:4.7, and the pH value of the reaction system is maintained at 6;

[0066] Step 102. Add DOPO ethanol solution to the intermediate A prepared in step 101, and stir the mixture under heating conditions for 11 hours. After the reaction is completed, evaporate the solvent, wash with water, and dry to obtain comonomer B;

[0067] Among them, DOPO and anhydrous ethanol were compounded at a mass ratio of 1:11.5;

[0068] Step 103. The comonomer B, unsaturated acid anhydride, ethylene glycol and catalyst prepared in step 102 are sequentially put into a reaction kettle, and in a nitrogen atmosphere, sequentially go through a first heating stage, a first heat preservation reaction stage, a second heating stage, a second heat preservation reaction stage, a third heating stage, a third heat preservation reaction stage and a cooling stage in chronological order to obtain a high-purity Schiff base-DOPO-based composite reactive flame-retardant unsaturated polyester resin;

[0069] Wherein, the molar ratio of comonomer B, unsaturated anhydride and ethylene glycol is 1:1.18:1.11;

[0070] The first heating stage is: heating the temperature of the reaction system from room temperature to 110°C;

[0071] The first heat preservation reaction stage is: the temperature of the reaction system is stabilized at 110°C and reacted for 55 minutes;

[0072] The second heating stage is: raising the temperature of the reaction system from 110°C to 180°C;

[0073] The second heat preservation reaction is: the temperature of the reaction system is stabilized at 180°C for 3.9 hours;

[0074] The three heating stages are: raising the temperature of the reaction system from 180°C to 225°C;

[0075] The three heat preservation reaction stages are: stabilizing the temperature of the reaction system to 225°C for 2.7 hours;

[0076] The cooling stage is as follows: lowering the temperature of the reaction system from 225°C to 145°C;

[0077] During the reaction, the reaction system was sampled every 20 minutes and the acid value of the sample was tested. When the acid value of the sample was within the standard interval, p-methoxyphenol was added to the reaction system to terminate the reaction.

[0078] Step 104: Cooling the high-purity Schiff base-DOPO-based composite reactive flame-retardant unsaturated polyester resin and transferring it to a dilution tank for dilution with styrene to obtain a finished Schiff base-DOPO-based composite reactive flame-retardant unsaturated polyester resin.

[0079] The general structure of the finished product of Schiff base-DOPO composite reactive flame retardant unsaturated polyester resin is as follows:

[0080]

[0081] Among them, the value of n is 5331 and its acid value is 29.1 mgKOH / g.

[0082] Example 3

[0083] The synthesis method of the Schiff base-DOPO based composite reactive flame retardant unsaturated polyester tree comprises the following steps:

[0084] Step 101. Under a nitrogen atmosphere, a saturated aqueous solution of phenylenediamine, a saturated aqueous solution of 5-hydroxymethylfurfural and 10% acetic acid are put into a reaction kettle together, and condensed and refluxed for 2 hours in a water bath at 85° C. to obtain an intermediate A. During the reaction, the progress of the reaction is monitored by HPLC, and the molar ratio of phenylenediamine to 5-hydroxymethylfurfural in the reaction system is maintained at 1:6, and the pH value of the reaction system is maintained at 5;

[0085] Step 102. Add DOPO ethanol solution to the intermediate A prepared in step 101, and stir the mixture under heating conditions for 12 hours. After the reaction is completed, evaporate the solvent, wash with water, and dry to obtain comonomer B;

[0086] Among them, DOPO and anhydrous ethanol were compounded at a mass ratio of 1:12.5;

[0087] Step 103. The comonomer B, unsaturated acid anhydride, ethylene glycol and catalyst prepared in step 102 are sequentially put into a reaction kettle, and in a nitrogen atmosphere, sequentially go through a first heating stage, a first heat preservation reaction stage, a second heating stage, a second heat preservation reaction stage, a third heating stage, a third heat preservation reaction stage and a cooling stage in chronological order to obtain a high-purity Schiff base-DOPO-based composite reactive flame-retardant unsaturated polyester resin;

[0088] Wherein, the molar ratio of comonomer B, unsaturated acid anhydride and ethylene glycol is 1:1.2:1.15;

[0089] The first heating stage is: heating the temperature of the reaction system from room temperature to 110°C;

[0090] The first heat preservation reaction stage is: the temperature of the reaction system is stabilized at 110°C and reacted for 60 minutes;

[0091] The second heating stage is: raising the temperature of the reaction system from 110°C to 180°C;

[0092] The second heat preservation reaction is: the temperature of the reaction system is stabilized at 180°C for 4 hours;

[0093] The three heating stages are: raising the temperature of the reaction system from 180°C to 225°C;

[0094] The three heat preservation reaction stages are: stabilizing the temperature of the reaction system to 225°C for 3 hours;

[0095] The cooling stage is as follows: lowering the temperature of the reaction system from 225°C to 145°C;

[0096] During the reaction, the reaction system was sampled every 30 minutes and the acid value of the sample was tested. When the acid value of the sample was within the standard interval, p-methoxyphenol was added to the reaction system to terminate the reaction.

[0097] Step 104: Cooling the high-purity Schiff base-DOPO-based composite reactive flame-retardant unsaturated polyester resin and transferring it to a dilution tank for dilution with styrene to obtain a finished Schiff base-DOPO-based composite reactive flame-retardant unsaturated polyester resin.

[0098] The general structure of the finished product of Schiff base-DOPO composite reactive flame retardant unsaturated polyester resin is as follows:

[0099]

[0100] Among them, the value of n is 5581 and its acid value is 28.4 mgKOH / g.

[0101] The Schiff base-DOPO based composite reactive flame retardant unsaturated polyester resin prepared in Examples 1-3 was subjected to the following tests:

[0102] Test 1: The Schiff base-DOPO-based composite reactive flame-retardant unsaturated polyester resins prepared in Examples 1-3 were sampled respectively, and after being made into test pieces of the same specifications according to GB / T8924 standard, the corresponding limiting oxygen indexes were measured respectively;

[0103] Test 2: The Schiff base-DOPO-based composite reactive flame-retardant unsaturated polyester resins prepared in Examples 1-3 were sampled, and after being made into test pieces of the same specifications, their corresponding UL-94 flame retardancy ratings were measured respectively;

[0104] Test 3: Stability test, after the Schiff base-DOPO-based composite reactive flame-retardant unsaturated polyester resin samples prepared in Examples 1-3 were left to stand and aged, experimental pieces of the same specifications were made, the appearance of the resin samples was observed, and the corresponding UL-94 flame retardancy ratings were measured respectively;

[0105] The aging treatment includes placing the Schiff base-DOPO-based composite reactive flame-retardant unsaturated polyester resin prepared in Examples 1-3 under ultraviolet light, and measuring the corresponding UL-94 flame retardancy rating after 24 hours, 72 hours and 120 hours at a temperature of 50°C;

[0106] Test 4: Mechanical properties test. After the Schiff base-DOPO-based composite reactive flame-retardant unsaturated polyester resin prepared in Examples 1-3 was made into resin castings of the same specifications, the corresponding mechanical properties were measured according to GB / T2567-2008 and GB / T3854-2005, respectively. The test results are shown in Table 1 below.

[0107] Table 1 Test results of examples 1-3

[0108]

[0109] It can be seen from the test results in Table 1 that the Schiff base-DOPO-based composite reactive flame-retardant unsaturated polyester resin prepared in Examples 1-3 is prepared by reacting the intermediate A with DOPO to obtain the comonomer B. The phosphorus-containing flame-retardant group in DOPO can be effectively embedded in the polymer chain segment. Compared with the traditional flame-retardant additive type flame-retardant resin, the binding ability of the chemical bond is significantly higher than that of the physical blending. After standing for a long time, the Schiff base-DOPO-based composite reactive flame-retardant unsaturated polyester resin can still maintain a high mechanical stability and flame retardant performance, which greatly extends the service life of the resin. Furthermore, in this scheme, the intermediate A contains a large number of aromatic rings. By introducing a large number of aromatic rings into the unsaturated polyester resin, its own tensile and compressive mechanical properties are significantly improved. Compared with the traditional additive unsaturated polyester resin, it not only effectively reduces the amount of flame retardant additives and reduces the preparation cost, but also significantly improves the flame retardant and mechanical properties of the resin, which is in line with the concept of green chemical production.

[0110] In actual implementation, the phosphorus in the comonomer B prevents further combustion by capturing free radicals and combustion products during the combustion process to form a dense carbon layer. During the combustion process, phosphoric anhydride and volatile phosphides (such as PO·, etc.) are generated. Phosphoric anhydride can dehydrate and carbonize the polymer during the combustion of the material, forming a carbonized layer on the surface of the polymer, which can both isolate the external heat and prevent the combustion of the polymer; secondly, the thermal decomposition of phosphoric anhydride will form a glass-like melt on the surface of the polymer. Most organophosphorus flame retardants generate volatile PO·, which will capture the H· generated by the combustion of the polymer to form a stable HPO, which can effectively slow down or prevent further combustion of the polymer.

[0111] The present application provides a Schiff base-DOPO based composite reactive flame retardant unsaturated polyester resin and a synthesis method thereof. An intermediate A is prepared under acidic conditions by reacting a diprimary amine with 5-hydroxymethylfurfural, and a comonomer B is prepared by reacting the intermediate A with DOPO. Finally, the Schiff base-DOPO based composite reactive flame retardant unsaturated polyester resin is obtained after chain extension through polymerization of the comonomer B, an unsaturated acid anhydride, ethylene glycol and a catalyst. By using DOPO as a flame retardant monomer and curing it on a polymer chain, not only the uniformity of the distribution of the flame retardant monomer in the resin matrix is ​​improved, but also the flame retardant effect of the unsaturated polyester resin is improved. By introducing a large number of aromatic rings into the polymer chain segment, the hardness and compressive strength of the resin can be significantly improved after curing. After the resin is placed for a long time, it can still maintain excellent mechanical properties. The resin has the advantages of being easy for industrial production, low implementation cost, and easy to promote and implement.

[0112] The above are only embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for synthesizing a Schiff base-DOPO based composite reactive flame retardant unsaturated polyester resin, characterized in that: The following steps are involved: In an inert gas atmosphere and acidic conditions, an aqueous solution of a diprimary amine and an aqueous solution of 5-hydroxymethylfurfural are placed in a reaction kettle, and heated and condensed under reflux for 1 hr to 2 hr to obtain an intermediate A. Adding DOPO ethanol solution to the intermediate A, stirring and reacting for 9-12 hours under heating conditions, and after the reaction, evaporating the solvent, washing with water and drying to obtain the comonomer B; The comonomer B, unsaturated acid anhydride, ethylene glycol and catalyst are sequentially put into a reaction kettle, and reacted for 7-12 hours at 110° C.-225° C. under an inert gas atmosphere to obtain a high-purity Schiff base-DOPO-based composite reactive flame-retardant unsaturated polyester resin; The high-purity Schiff base-DOPO-based composite reactive flame-retardant unsaturated polyester resin is cooled and transferred to a dilution tank and diluted with styrene to obtain a finished Schiff base-DOPO-based composite reactive flame-retardant unsaturated polyester resin.

2. The method for synthesizing a Schiff base-DOPO based composite reactive flame retardant unsaturated polyester resin according to claim 1, characterized in that: The following steps are involved: Step 101. Under a nitrogen atmosphere, an aqueous solution of a diprimary amine, an aqueous solution of 5-hydroxymethylfurfural and 10% acetic acid are put into a reaction kettle, and condensed and refluxed for 1 hr to 2 hr in a water bath at 50° C. to 85° C. to obtain an intermediate A. During the reaction, the progress of the reaction is monitored by HPLC; Step 102. Add DOPO ethanol solution to the intermediate A prepared in step 101, and stir the mixture under heating conditions for 9-12 hours. After the reaction is completed, evaporate the solvent, wash with water, and dry to obtain comonomer B. Step 103. The comonomer B, unsaturated acid anhydride, ethylene glycol and catalyst prepared in step 102 are sequentially put into a reaction kettle, and in a nitrogen atmosphere, sequentially go through a first heating stage, a first heat preservation reaction stage, a second heating stage, a second heat preservation reaction stage, a third heating stage, a third heat preservation reaction stage and a cooling stage in chronological order to obtain a high-purity Schiff base-DOPO-based composite reactive flame-retardant unsaturated polyester resin; The first heating stage is: heating the reaction system temperature from room temperature to 110°C; The first heat preservation reaction stage is: the temperature of the reaction system is stabilized to 110°C and reacted for 50min-60min; The second heating stage is: raising the temperature of the reaction system from 110°C to 180°C; The second heat preservation reaction is: the temperature of the reaction system is stabilized at 180°C and reacted for 3.8hr-4hr; The three heating stages are: raising the temperature of the reaction system from 180°C to 225°C; The three heat preservation reaction stages are: stabilizing the temperature of the reaction system to 225°C for 2.5hr-3hr; The cooling stage is: lowering the temperature of the reaction system from 225°C to 145°C; Step 104: Cooling the high-purity Schiff base-DOPO-based composite reactive flame-retardant unsaturated polyester resin and transferring it to a dilution tank for dilution with styrene to obtain a finished Schiff base-DOPO-based composite reactive flame-retardant unsaturated polyester resin.

3. The method for synthesizing a Schiff base-DOPO based composite reactive flame retardant unsaturated polyester resin according to claim 2, characterized in that: The diprimary amine in the aqueous solution of diprimary amine is any one or more of methylethylamine, phenylenediamine, cyclohexylmethylamine, dicyclohexylamine, triphenylmethylamine, adamantane, and 3-ethoxybutylamine.

4. The method for synthesizing a Schiff base-DOPO based composite reactive flame retardant unsaturated polyester resin according to claim 2, characterized in that: In step 101, the aqueous solution of diprimary amine is a saturated aqueous solution of phenylenediamine, and the aqueous solution of 5-hydroxymethylfurfural is a saturated aqueous solution of 5-hydroxymethylfurfural.

5. The method for synthesizing a Schiff base-DOPO based composite reactive flame retardant unsaturated polyester resin according to claim 2, characterized in that: In step 101, HPLC was used to detect that during the reaction, the molar ratio of the diprimary amine to 5-hydroxymethylfurfural in the reaction system was maintained at 1:2-6.

2.

6. The method for synthesizing a Schiff base-DOPO based composite reactive flame retardant unsaturated polyester resin according to claim 2, characterized in that: In step 102, the ethanol solution of DOPO is prepared by mixing DOPO and anhydrous ethanol at a mass ratio of 1:10-12.

5.

7. The method for synthesizing a Schiff base-DOPO based composite reactive flame retardant unsaturated polyester resin according to claim 2, characterized in that: In step 103, the molar ratio of comonomer B, unsaturated acid anhydride, and ethylene glycol is 1:1.17-1.2:1.07-1.

15.

8. The method for synthesizing a Schiff base-DOPO based composite reactive flame retardant unsaturated polyester resin according to claim 2, characterized in that: In step 103, during the reaction, the reaction system is sampled every 10 minutes to 30 minutes and the acid value of the sample is detected. When the acid value of the sample is within the standard interval, p-methoxyphenol is added to the reaction system to terminate the reaction.

9. A Schiff base-DOPO based composite reactive flame retardant unsaturated polyester resin, characterized in that: It is prepared by the synthesis method of a Schiff base-DOPO-based composite reactive flame-retardant unsaturated polyester resin as described in any one of claims 1 to 8, and its general structural formula is as follows: The value range of n is 2480-6721.

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