A phosphorus-containing epoxy curing agent and preparation method thereof

Abstract

The present invention discloses a phosphorus-containing epoxy curing agent and a preparation method thereof. After the epoxy curing agent and epoxy resin are cured into a polymer, the flame retardant effect can be improved because the phosphorus is in the main chain. The epoxy curing agent has multiple functions, a simple preparation process, high product purity, a non-toxic and harmless production process, and is easy to carry out large-scale production.

Description

Technical Field

[0001] The invention belongs to the technical field of curing agents, and specifically relates to a phosphorus-containing epoxy curing agent and a preparation method thereof. Background Art

[0002] Epoxy resins are widely known for their excellent adhesion, chemical and heat resistance, good to excellent mechanical properties, and good electrical insulation properties. Cured epoxy resin systems have a wide range of applications, including adhesives, coatings, inks, and composite materials. For example: protective coatings for metal surfaces, and building products for concrete, cement, or ceramic substrates, commonly known as civil engineering applications; sealants for electronic 3C products or for LEDs. The industries involved include construction, chemicals, automobiles, ships, electrical insulation, etc.

[0003] Epoxy resin itself is a linear compound with very stable performance. It must be used together with a curing agent to have practical value. Therefore, the curing agent is an indispensable and important component of epoxy resin during use. There are many types of curing agents for epoxy resin, the most common ones are: aliphatic diamines and polyamines, aromatic polyamines, other nitrogen-containing compounds and modified aliphatic amines, anhydrides, polyamides, organic acids, boron trifluoride, etc. Among them, diamine polyamine and anhydride curing agents are the most common.

[0004] Epoxy resin is widely used in many fields, but its limiting oxygen index is very low, usually below 20, and it is very easy to burn, which greatly limits its application. In the electronic packaging industry and transportation equipment industry, the epoxy resin used must be flame retardant, so the research and development of flame retardant epoxy resin is urgent.

[0005] Most organophosphorus flame retardants have the advantages of low smoke, non-toxicity, low halogen, and halogen-free, which are in line with the development direction of flame retardants and have good development prospects. Organophosphorus flame retardants include phosphates, phosphites, phosphonates, organophosphorus salts, phosphorus heterocyclic compounds and polymer phosphate (phosphonate) esters, etc., but the most widely used are phosphates and phosphonates. The research and development of phosphorus flame retardants is in full swing, and many reports are reported every year. For example, patent application 202011344498.5 discloses a method for preparing a low-halogen, high-polymerization degree phosphate flame retardant, comprising the following steps: (1) preparing an oligomeric phosphate solution using dihydroxy or diamine compounds and phosphorus dichloride compounds as raw materials; (2) concentrating the oligomeric phosphate solution until it is a viscous mixture, adding a solvent to the viscous mixture to dissolve it into a solution state, then heating it to the boiling point of the solvent, and keeping it warm at this temperature for a polymerization reaction for 1 to 6 hours, filtering to obtain a polyphosphate agglomerate; (3) polymerizing the polyphosphate agglomerate at high temperature, and then cooling it to obtain a low-halogen, high-polymerization degree phosphate flame retardant. Patent application 201910314499.6 discloses a nitrogen-containing phosphonate flame retardant and a synthesis method thereof. The chemical name of the nitrogen-containing phosphonate flame retardant is polymethylpiperazine phosphonate; preparation method: take dimethyl methyl phosphate in a reaction container, add piperazine and a catalyst, stir thoroughly to dissolve it, heat and react for several hours, collect the methanol fraction; after the reaction is completed, cool down to obtain the product polymethylpiperazine phosphonate.

[0006] The mechanism of action of organophosphorus flame retardants is that when heated, they can produce cross-linked solid substances or carbonized layers with more stable structures. The formation of the carbonized layer can prevent the polymer from further pyrolysis on the one hand, and prevent the thermal decomposition products inside it from entering the gas phase and participating in the combustion process on the other hand.

[0007] At present, the most commonly used methods are additive and reactive flame retardants. The additive type uses physical dispersion, which not only has poor compatibility and low flame retardant efficiency, but also affects the physical properties of the material. Reactive halogen-containing materials have been widely used due to their excellent flame retardant and mechanical and electrical properties, but they will produce toxic and harmful substances and are banned in many countries. Therefore, it is very necessary to develop a high-performance, multifunctional halogen-free flame retardant epoxy curing agent. Summary of the invention

[0008] To solve the above problems, the primary purpose of the present invention is to provide a phosphorus-containing epoxy curing agent and a preparation method thereof. The epoxy curing agent and the preparation method thereof can improve the flame retardant effect and have multiple functions because the short-chain phosphorus-containing or cyclic phosphorus-containing epoxy curing agent and the preparation method thereof are in the main chain.

[0009] Another object of the present invention is to provide a phosphorus-containing epoxy curing agent and a preparation method thereof. The epoxy curing agent and the preparation method thereof have a simple preparation process, high product purity, a non-toxic and harmless production process, and are easy to carry out large-scale production.

[0010] To achieve the above objectives, the technical solution of the present invention is as follows.

[0011] A phosphorus-containing epoxy curing agent, the molecular structure of the phosphorus-containing epoxy curing agent is as follows:

[0012]

[0013] Among them, R is alkyl, alkoxy, aryl, aryloxy; R' is alkyl chain, ether chain, aryl chain.

[0014] The invention improves the performance of the curing agent by using short-chain phosphorus or cyclic phosphorus, so that the curing agent has excellent flame retardant performance, and can increase the hardness of the product, waterproof and other functions.

[0015] The preparation process of the phosphorus-containing epoxy curing agent is as follows:

[0016]

[0017] Dissolve the divinyl phosphate (one equivalent) representing C or D in water or ethanol, then add dropwise to the aqueous solution of hydroxylamine hydrochloride at 0°C within three hours. After the addition is complete, warm the mixture to room temperature and react overnight at room temperature. Monitor the end point of the reaction by TLC (thin layer chromatography). After the reaction is complete, remove the low-boiling point substances under reduced pressure to obtain a transparent viscous liquid.

[0018] Furthermore, the concentration of the hydroxylamine solution is 30%.

[0019] Furthermore, the dosage of the divinyl phosphate representing C or D and the hydroxylamine solution is: divinyl phosphate 14-25mmol (this dosage is summarized according to the examples, please confirm), 30% hydroxylamine solution 120ml.

[0020] Furthermore, after confirming that the reaction is complete, the reaction system is decompressed to remove the residual ammonia and water or ethanol, and finally a colorless, transparent, viscous liquid is obtained.

[0021] After the epoxy curing agent of the present invention is cured with the epoxy resin into a polymer, due to the short-chain phosphorus or cyclic phosphorus, phosphorus is in the main chain, which can improve the hardness of the product, and the coating has no blistering, wrinkling, obvious discoloration, shedding and the like within 240 hours; at the same time, in terms of the limiting oxygen index, the limiting oxygen index is all above 27, and the flame retardant effect is greatly improved.

[0022] Moreover, the preparation process is simple, the product purity is high, the production process is non-toxic and harmless, and it is easy to carry out large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the H NMR spectrum of compound A2 achieved in the present invention. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0025] The phosphorus-containing epoxy curing agent realized by the present invention has a molecular structure as follows:

[0026]

[0027] Among them, R is alkyl, alkoxy, aryl, aryloxy; R' is alkyl chain, ether chain, aryl chain.

[0028] The preparation of the phosphorus-containing epoxy curing agent is as follows:

[0029]

[0030] The divinyl phosphate (one equivalent) representing C or D is dissolved in water or ethanol, and then added dropwise to an aqueous solution of hydroxylamine hydrochloride (30%) at 0°C over a few hours. After the addition is complete, the temperature is raised to room temperature and the reaction is allowed to proceed overnight at room temperature. The reaction endpoint is monitored by TLC. After the reaction is completed, ammonia and water or ethanol are evaporated under reduced pressure to obtain a transparent viscous liquid.

[0031] The implementation of the present invention is described below in conjunction with specific embodiments.

[0032] Example 1

[0033]

[0034] Preparation of phosphorus-containing epoxy curing agent A1 using divinyl butanediol diphosphate C1: Dissolve C1 (2.18 g, 7.3 mmol) in 120 mL of water, control the temperature to 0°C, and add the C1 solution dropwise to a three-necked flask with mechanical stirring containing 120 mL of hydroxylamine solution (30%) within three hours. After the addition is complete, the temperature of the reaction system is raised to room temperature and the reaction is allowed to proceed overnight. The reaction is monitored by TLC to confirm that the reaction is complete. The reaction system is decompressed to remove residual ammonia and water. Finally, 2.39 g of A1 is obtained as a colorless, transparent, viscous liquid with a yield of 98.8%.

[0035] Example 2

[0036]

[0037] Preparation of A2 using C2: C2 (1.97 g, 7.3 mmol) was dissolved in 120 mL of water, and the temperature was controlled at 0°C. Within three hours, the C2 solution was added dropwise to a three-necked flask with mechanical stirring and 120 mL of hydroxylamine solution (30%). After the addition was completed, the temperature of the reaction system was raised to room temperature and the reaction was allowed to proceed overnight. The reaction was monitored by TLC to confirm the completion of the reaction. The reaction system was decompressed to remove the residual ammonia and water. Finally, 2.20 g of A2 was obtained as a colorless, transparent, viscous liquid with a yield of 99.1%.

[0038] Example 3

[0039]

[0040] Preparation of A3 using C3: C3 (2.18 g, 7.3 mmol) was dissolved in 120 mL of water, and the temperature was controlled at 0°C. Within three hours, the C3 solution was added dropwise to a three-necked flask with mechanical stirring and 120 mL of hydroxylamine solution (30%). After the addition was completed, the temperature of the reaction system was raised to room temperature and the reaction was allowed to proceed overnight. The reaction was monitored by TLC to confirm the completion of the reaction. The reaction system was decompressed to remove the residual ammonia and water. Finally, 2.40 g of A2 was obtained as a colorless, transparent, viscous liquid with a yield of 99.2%.

[0041] Example 4

[0042]

[0043] Preparation of A4 using C4: C4 (3.29 g, 7.3 mmol) was dissolved in 120 mL of water, and the temperature was controlled at 0°C. Within three hours, the C4 solution was added dropwise to a three-necked flask with mechanical stirring and 120 mL of hydroxylamine solution (30%). After the addition was completed, the temperature of the reaction system was raised to room temperature and the reaction was allowed to proceed overnight. The reaction was monitored by TLC to confirm the completion of the reaction. The reaction system was decompressed to remove the residual ammonia and water. Finally, 3.45 g of A4 was obtained as a colorless, transparent, viscous liquid with a yield of 97.7%.

[0044] Example 5

[0045]

[0046] Preparation of A5 using C5: C5 (2.82 g, 7.3 mmol) was dissolved in 120 mL of water, and the temperature was controlled at 0°C. Within three hours, the C5 solution was added dropwise to a three-necked flask with mechanical stirring and 120 mL of hydroxylamine solution (30%). After the addition was completed, the temperature of the reaction system was raised to room temperature and the reaction was allowed to proceed overnight. The reaction was monitored by TLC to confirm the completion of the reaction. The reaction system was decompressed to remove the residual ammonia and water. Finally, 3 g of A5 was obtained as a colorless, transparent, viscous liquid with a yield of 97.7%.

[0047] Example 6

[0048]

[0049] Preparation of A6 using C6: C6 (2.69 g, 7.3 mmol) was dissolved in 120 mL of water, and the temperature was controlled at 0°C. The mixture was added dropwise to a three-necked flask with a mechanical stirrer containing 120 mL of hydroxylamine solution (30%) over three hours. After the addition was complete, the temperature of the reaction system was raised to room temperature and the reaction was allowed to proceed overnight. The reaction was monitored by TLC to confirm the completion of the reaction. The reaction system was decompressed to remove the residual ammonia and water. Finally, 3 g of A6 was obtained as a colorless, transparent, viscous liquid with a yield of 98.7%.

[0050] Example 7

[0051]

[0052] Preparation of A7 using C7: C7 (3.27 g, 7.3 mmol) was dissolved in 120 mL of water, and the temperature was controlled at 0°C. The mixture was added dropwise to a three-necked flask with mechanical stirring and 120 mL of hydroxylamine solution (30%) over three hours. After the addition was complete, the temperature of the reaction system was raised to room temperature and the reaction was allowed to proceed overnight. The reaction was monitored by TLC to confirm the completion of the reaction. The reaction system was decompressed to remove the residual ammonia and water. Finally, 3.45 g of A7 was obtained as a colorless, transparent, viscous liquid with a yield of 98.0%.

[0053] Example 8

[0054]

[0055] Preparation of B using D: D (2.04 g, 7.3 mmol) was dissolved in 120 mL of water, the temperature was controlled at 0°C, and the mixture was added dropwise to a three-necked flask with mechanical stirring and 120 mL of hydroxylamine solution (30%) within three hours. After the addition was completed, the temperature of the reaction system was raised to room temperature and the reaction was allowed to proceed overnight. The reaction was monitored by TLC to confirm the completion of the reaction. The reaction system was decompressed to remove the residual ammonia and water. Finally, 2.28 g of B was obtained as a colorless, transparent, viscous liquid with a yield of 99.6%.

[0056] Take A2 as an example. Figure 1 As shown, the H-NMR carbon spectrum data of compound A2 are as follows:

[0057] 1 H NMR (500 MHz, CDCl 3 )δ4.40(td,J=3.9,1.5Hz,2H),3.65(d,J=21.8Hz,3H),2.96(t,J=16.6Hz,2H),2.03(dt,J=23.8,16.6Hz,2H),1.18(s,2H). 13CNMR (125MHz, CDCl 3 )δ63.95(t,J=6.2Hz),53.21(d,J=6.7Hz),38.90(d,J=6.7Hz),30.93(s),30.17(s).

[0058] Refer to Table 1 again.

[0059]

[0060] Table 1

[0061] It can be seen from Table 1 that the flame-retardant epoxy curing agents A1, A7, and D prepared in Examples 1, 7, and 8 were added at an amount of 10% (mass fraction, curing agent 1) to the traditional epoxy curing agent polyetheramine D230 (curing agent 2), and then a leveling agent and an accelerator were added to form component B of Example 9, Example 10, and Example 11, respectively. Comparative Example 1 and Comparative Example 2 only have a single curing agent 2 (D230), and no flame retardant is added to Comparative Example 1, while 2% of the traditional flame retardant tetrabutylphosphine chloride is added to Comparative Example 2. Component A resin 1 uses Nan Ya epoxy resin 128, and component A resin 2 uses alicyclic epoxy 821E from Jiangsu Taitel New Materials Technology Co., Ltd. The above-mentioned leveling agent is selected from Dongguan Moen Chemical Co., Ltd. The accelerator used was JSC-1120 from Hangzhou Jessica Chemical Co., Ltd.

[0062] The above embodiment was subjected to performance characterization test, and the test results are shown in Table 2:

[0063] 1. Adhesion: The coating samples provided in the examples were tested for adhesion according to the pull-off method of GB / T5210-85. The results are shown in Table 2.

[0064] 2. Pencil hardness: The pencil hardness of the coating sample provided in the embodiment was tested according to GB / T6739-86. The results are shown in Table 2.

[0065] 3. Limiting oxygen index: The limiting oxygen index of the coating sample provided in the embodiment was tested according to GB / T2406-2008. The results are shown in Table 2.

[0066] 4. Water-impermeability: The coating samples provided in the examples were tested for water-impermeability according to GB / T16777-2008, 0.4 MPa, 2 hours. The results are shown in Table 2.

[0067] 5. Water resistance: The coating samples provided in the examples were tested for water resistance according to GB / T1733-1993. The water resistance was tested for 240 hours, and the coating was observed for blistering, wrinkling, obvious discoloration, and shedding.

[0068]

[0069] Table 2

[0070] From Table 2, we can see that the adhesion performance of Examples 9, 10, 11 and Comparative Examples 1, 2 is not much different, all above 2.1 MPa. In the pencil hardness test experiment, the hardness of Examples 9, 10, 11 is 3H, while Comparative Examples 1, 2 are only 2H. This is because the comparative example only has a single polyether amine curing agent D230, which has a longer chain length, resulting in a softer final material. The curing agent of the embodiment is added with a synthetic short-chain phosphorus-containing curing agent A1 or a cyclic phosphorus-containing cyclic curing agent A7, D, so that the hardness is higher than that of the comparative example. In terms of impermeability and water resistance, Examples 9, 10, 11 and Comparative Examples 1 and 2 all perform very well, are all impermeable, and the coating has no blistering, wrinkling, obvious discoloration, shedding, etc. within 240 hours. In terms of limiting oxygen index, the embodiments performed much better than the comparative examples, with limiting oxygen indexes all above 27, while the limiting oxygen index of the coating film of comparative example 1, which had no flame retardant ingredients at all, was only 17, and the limiting oxygen index of comparative example 2, which had two additional flame retardants, was only 20.

[0071] The above are only preferred 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 phosphorus-containing epoxy curing agent, characterized in that The molecular structure of the phosphorus-containing epoxy curing agent is as follows:

2. A method for preparing a phosphorus-containing epoxy curing agent as claimed in claim 1, characterized in that The preparation process is as follows: Preparation of phosphorus-containing epoxy curing agent A1 using divinyl butanediol diphosphate C1: 2.18 g of C1 was dissolved in 120 mL of water, the temperature was controlled at 0°C, and within three hours, the C1 solution was added dropwise to a three-necked flask with a mechanical stirrer containing 120 mL of 30% hydroxylamine solution. After the addition was completed, the temperature of the reaction system was raised to room temperature and the reaction was allowed to proceed overnight. The reaction was monitored by TLC to confirm the completion of the reaction. The reaction system was decompressed to remove the residual ammonia and water, and finally 2.39 g of A1 was obtained as a colorless, transparent, viscous liquid. Preparation of A2 using C2: 1.97 g of C2 was dissolved in 120 mL of water, and the temperature was controlled at 0°C. Within three hours, the C2 solution was added dropwise to a three-necked flask with a mechanical stirrer and filled with 120 mL of a 30% hydroxylamine solution. After the addition was completed, the temperature of the reaction system was raised to room temperature and the reaction was allowed to proceed overnight. The reaction was monitored by TLC. After the reaction was completed, the reaction system was decompressed to remove the residual ammonia and water. Finally, 2.20 g of A2 was obtained as a colorless, transparent, viscous liquid. Preparation of A3 using C3: 2.18 g of C3 was dissolved in 120 mL of water, and the temperature was controlled at 0°C. Within three hours, the C3 solution was added dropwise to a three-necked flask with a mechanical stirrer and filled with 120 mL of a 30% hydroxylamine solution. After the addition was completed, the temperature of the reaction system was raised to room temperature and the reaction was allowed to proceed overnight. The reaction was monitored by TLC to confirm the completion of the reaction. The reaction system was decompressed to remove the residual ammonia and water, and finally 2.40 g of A3 was obtained as a colorless, transparent, viscous liquid. Preparation of A6 using C6: 2.69 g of C6 was dissolved in 120 mL of water, the temperature was controlled at 0°C, and the mixture was added dropwise to a three-necked flask with a mechanical stirrer containing 120 mL of a 30% hydroxylamine solution within three hours; after the addition was completed, the temperature of the reaction system was raised to room temperature and the reaction was allowed to proceed overnight, and the reaction was monitored by TLC to confirm the completion of the reaction; the reaction system was decompressed to remove the residual ammonia and water, and finally 3 g of A6 was obtained as a colorless, transparent, viscous liquid; Preparation of A7 using C7: 3.27 g of C7 was dissolved in 120 mL of water, the temperature was controlled at 0°C, and the solution was added dropwise to a three-necked flask with a mechanical stirrer containing 120 mL of a 30% hydroxylamine solution within three hours. After the addition was complete, the temperature of the reaction system was raised to room temperature and the reaction was allowed to proceed overnight. The reaction was monitored by TLC to confirm the completion of the reaction. The reaction system was decompressed to remove residual ammonia and water, and 3.45 g of A7 was obtained as a colorless, transparent, viscous liquid.

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