Halogen-free cyclophosphazene flame-retardant modified epoxy resin method

Abstract

The invention discloses a method for flame-retardant modification of epoxy resin through halogen-free cyclophosphazene. Unsaturated alcohol (cinnamyl alcohol and derivatives thereof and the like) and hexachlorocyclotriphosphazene (HCCP) are adopted as raw materials, cinnamyl alcohol is preferentially selected as the unsaturated alcohol, and the cinnamyl alcohol substituted halogen-free cyclophosphazene flame retardant CACP is prepared by adopting a one-step method; cACP and epoxy resin E-51 are uniformly mixed, a curing agent DDM is added for curing, and the halogen-free cyclophosphazene flame-retardant modified epoxy resin is prepared. The flame retardance of the modified epoxy resin E-51 is remarkably improved by adding a small amount of the phosphazene flame retardant CACP, the UL 94 grade is V-0 grade, and the modified epoxy resin E-51 has good transparency.

Description

Technical Field

[0001] The invention discloses a method for synthesizing a halogen-free cyclophosphazene flame retardant and flame-retardantly modifying an epoxy resin. The flame retardant significantly improves the flame retardancy of the modified epoxy resin E-51 with a relatively small addition amount and enables the modified epoxy resin E-51 to have good transparency. Technical Background

[0002] Epoxy resin (EP) is an important type of thermosetting plastic, which is widely used in various fields due to its excellent mechanical properties, good corrosion resistance, high electrical insulation performance, etc. However, the limiting oxygen index of EP is about 18%, which is a flammable material and cannot meet the fire safety requirements, so it needs flame retardant treatment.

[0003] The main flame retardants used for EP are inorganic flame retardants and bromine flame retardants. Among them, hydrated metal oxide inorganic flame retardants (such as Mg(OH)2, Al(OH)3, etc.) need to be added in large amounts to achieve a certain flame retardant effect, which greatly reduces the transparency and other performance of EP. Bromine flame retardants (such as tetrabromobisphenol A, decabromodiphenyl ether, etc.) are added in small amounts and have significant flame retardant effects, but they will produce dioxins and other harmful substances when burned, which are harmful to the environment and human health. The corresponding halogen-containing flame retardants have been banned by the European Union.

[0004] In response to this problem, there are some reports on flame-retardant modified EP of cyclotriphosphazene. For example, CN101967268A discloses a halogen-free flame-retardant epoxy resin and its preparation method; adding 17.3wt% hexa-(phosphaphenanthrene hydroxymethylphenoxy)-cyclotriphosphazene, the modified epoxy resin UL 94 grade is V-0. Zhou Lisheng et al. synthesized an α-hydroxyphosphonic acid cyclotriphosphazene compound, hexa-(4-diethylphosphazene-hydroxymethyl-phenoxy)-cyclotriphosphazene (HDHPCP), adding 20wt% HDHPCP, and the modified epoxy resin UL 94 grade is V-0. (Zhou, L., Zhang, G., Li, J. et al. The flame retardancy and thermal stability properties of flame-retarded epoxy resins based on α-hydroxyphosphonate cyclotriphosphazene. J Therm Anal Calorim 129, 1667–1678 (2017).). Some studies on flame-retardant modified EP with additive cyclotriphosphazene flame retardant have solved the problem of balancing flame retardancy and mechanical properties. However, it is still a difficult problem for flame-retardant modified EP to maintain its transparency while improving the flame retardancy of EP with a lower amount of phosphazene added.

[0005] The present invention prepares a novel halogen-free cinnamyl alcohol oxy or cinnamyl alcohol derivative substituted cyclophosphazene flame retardant. Compared with other additive phosphazene flame retardants, the flame retardant imparts excellent flame retardant effect to epoxy resin E-51 with a relatively small addition amount, and the modified epoxy resin E-51 has good transparency. Summary of the invention

[0006] The present invention uses cinnamyl alcohol or cinnamyl alcohol derivative unsaturated alcohol and sodium hydride (NaH) as raw materials. The structural formula of cinnamyl alcohol unsaturated alcohol is as shown in the appendix. Figure 1 As shown, R is one of -H, -CH3, -OCH3, -COOCH3, -COOCH2CH3 and -Ph. Halogen-free cinnamyl alcohol or cinnamyl alcohol derivative-substituted cyclophosphazene flame retardant is prepared by one-step reaction of unsaturated sodium cinnamyl alcohol and HCCP. The synthesized flame retardant is cinnamyl alcohol derivative-based cyclophosphazene, and the structural formula is shown in the attachment Figure 2 shown.

[0007] 1. A method for flame retardantly modifying epoxy resin by halogen-free cyclophosphazene, characterized in that it comprises the steps of:

[0008] a. A certain amount of unsaturated alcohol and NaH were reacted in tetrahydrofuran (THF) at a molar ratio at 0-10°C for 30 min to prepare unsaturated sodium alcohol.

[0009] b. A certain amount of HCCP and unsaturated sodium alcohol were reacted in THF at a molar ratio at 30-60°C for 12-24 hours, by-products were removed by centrifugation, and after distillation, the mixture was washed several times with n-heptane and dried in a vacuum oven at 50-70°C for 12 hours to obtain a light yellow cyclophosphazene flame retardant powder.

[0010] c. Dissolve 3% to 12% of the mass fraction of cyclophosphazene flame retardant in THF, add 100g of E-51 epoxy resin, stir evenly, remove bubbles in a vacuum oven, add curing agent DDM to cure, and obtain a cyclophosphazene-modified transparent epoxy resin with high flame retardant properties.

[0011] The unsaturated alcohol described in the above synthesis is preferably cinnamyl alcohol, that is, when R is -H, the synthetic product is hexacinnamyloxy cyclotriphosphazene (CACP), the structural formula of which is shown in the attached Figure 3 shown.

[0012] The present invention has the following advantages and effects:

[0013] a. The phosphazene flame retardant CACP of the present invention has a relatively high content of P and N flame retardant elements, which can impart good flame retardant properties to the composite material at a relatively low addition amount.

[0014] b. The phosphazene flame retardant CACP of the present invention does not contain halogen and meets the requirements of halogen-free flame retardancy.

[0015] c. The phosphazene flame retardant CACP of the present invention has good compatibility with EP, so that the modified EP has good transparency. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a synthetic unsaturated alcohol structural formula of cinnamyl alcohol.

[0017] Figure 2 It is a synthetic halogen-free cinnamyl alcohol or cinnamyl alcohol derivative substituted cyclophosphazene flame retardant structural formula, wherein R is one of -H, -CH3, -OCH3, -COOCH3, -COOCH2CH3 and -Ph.

[0018] Figure 3 It is the structural formula of synthetic hexacinnamyloxy cyclotriphosphazene (CACP). DETAILED DESCRIPTION

[0019] In order to better understand the present invention, the present invention is described in detail through examples, but the protection scope of the present invention is not limited to the following implementation cases.

[0020] Implementation Case 1:

[0021] Take 7.2g NaH in a 500ml three-necked flask, add 50ml THF to dissolve. Add a magnet to the three-necked flask, place the three-necked flask in a water pot, and install a condenser; take 24.15g cinnamyl alcohol and dissolve it in 150ml THF, add the THF solution containing cinnamyl alcohol dropwise to the THF suspension containing NaH under magnetic stirring, react at 0-10℃ for 30min, and prepare sodium cinnamyl alcohol; take 8.69g HCCP and dissolve it in 50ml THF, add the THF solution containing HCCP dropwise to the THF suspension containing sodium cinnamyl alcohol under magnetic stirring, and react at 30-60℃ for 12-24h. After the reaction is completed, centrifuge to remove by-products, distill, wash with n-heptane several times, and dry in a vacuum oven at 50-70℃ for 12h to obtain a light yellow cyclophosphazene flame retardant CACP.

[0022] Take 3.9g CACP and dissolve it in 15ml THF. After CACP is fully dissolved in THF, add 100g epoxy resin E-51, stir evenly, stir at 70-90℃ to remove most of the THF in the mixed system, and then move to a vacuum oven to remove the remaining small amount of THF. Add curing agent DDM to the system, continue stirring, wait until DDM is fully dissolved, remove bubbles in a vacuum oven, cure at 100℃ for 2h, and cure at 140℃ for 2h. Cool naturally at room temperature and take out the sample. The initial decomposition temperature of the obtained product is 319.8℃, the residual carbon rate at 800℃ is 20.8%, the LOI is 23.5%, the UL 94 grade is V-2, and the average transmittance in the visible light band of 400-800nm ​​is 90.5%.

[0023] Implementation Case 2:

[0024] The synthesis of CACP in Example 2 is the same as that in Example 1.

[0025] Take 8.0g CACP and dissolve it in 20ml THF. After CACP is fully dissolved in THF, add 100g epoxy resin E-51, stir evenly, stir at 70-90℃ to remove most of the THF in the mixed system, and then move to a vacuum oven to remove the remaining small amount of THF. Add curing agent DDM to the system, continue stirring, wait until DDM is fully dissolved, remove bubbles in a vacuum oven, cure at 100℃ for 2h, and cure at 140℃ for 2h. Cool naturally at room temperature and take out the sample. The initial decomposition temperature of the obtained product is 314.8℃, the residual carbon rate at 800℃ is 20.2%, the LOI is 26.1%, the UL 94 grade is V-1, and the average transmittance in the visible light band of 400-800nm ​​is 88.1%.

[0026] Implementation Case 3:

[0027] The synthesis of CACP in Example 3 is the same as that in Example 1.

[0028] Take 12.4g CACP and dissolve it in 25ml THF. After CACP is fully dissolved in THF, add 100g epoxy resin E-51, stir evenly, stir at 70-90℃ to remove most of the THF in the mixed system, and then move to a vacuum oven to remove the remaining small amount of THF. Add curing agent DDM to the system, continue stirring, wait until DDM is fully dissolved, remove bubbles in a vacuum oven, cure at 100℃ for 2h, and cure at 140℃ for 2h. Cool naturally at room temperature and take out the sample. The initial decomposition temperature of the obtained product is 309.3℃, the residual carbon rate at 800℃ is 20.6%, the LOI is 27.5%, the UL 94 grade is V-1, and the average transmittance in the visible light band of 400-800nm ​​is 86.5%.

[0029] Implementation Case 4:

[0030] The synthesis of CACP in Example 4 is the same as that in Example 1.

[0031] Take 17.1g CACP and dissolve it in 30ml THF. After CACP is fully dissolved in THF, add 100g epoxy resin E-51, stir evenly, stir at 70-90℃ to remove most of the THF in the mixed system, and then move to a vacuum oven to remove the remaining small amount of THF. Add curing agent DDM to the system, continue stirring, wait until DDM is fully dissolved, remove bubbles in a vacuum oven, cure at 100℃ for 2h, and cure at 140℃ for 2h. Cool naturally at room temperature and take out the sample. The initial decomposition temperature of the obtained product is 302.7℃, the residual carbon rate at 800℃ is 21.0%, the LOI is 29.5%, the UL 94 grade is V-0, and the average transmittance in the 800nm ​​visible light band is 85.3%.

Claims

1. A method for flame-retardantly modifying epoxy resin by halogen-free cyclophosphazene, characterized in that: The steps include: a. A quantitative amount of unsaturated alcohol and sodium hydride (NaH) are reacted in tetrahydrofuran (THF) at a molar ratio at 0 to 10°C for 30 min to prepare unsaturated sodium alcohol. b. A certain amount of HCCP and unsaturated sodium alcohol were reacted in THF at a molar ratio at 30-60°C for 12-24 hours, by-products were removed by centrifugation, and after distillation, the mixture was washed several times with n-heptane and dried in a vacuum oven at 50-70°C for 12 hours to obtain a light yellow cyclophosphazene flame retardant powder. c. Dissolve 3% to 12% of the mass fraction of cyclophosphazene flame retardant in THF, add 100g of E-51 epoxy resin, stir evenly, remove bubbles in a vacuum oven, add curing agent DDM to cure, and obtain a cyclophosphazene-modified transparent epoxy resin with high flame retardant properties.

2. The method for preparing a halogen-free cyclophosphazene flame-retardant modified EP according to claim 1, characterized in that: The unsaturated alcohol in step a is a cinnamyl alcohol derivative, wherein R is one of -H, -CH3, -OCH3, -COOCH3, -COOCH2CH3 and -Ph; the molar ratio of the unsaturated alcohol to NaH is 1:1 to 1.2, preferably 1:1.2 in the present invention.

3. The method for preparing a halogen-free cyclophosphazene flame-retardant modified EP according to claim 1, characterized in that: The molar ratio of HCCP to unsaturated sodium alcoholate in step b is 1:6-7.2, preferably 1:7.2 in the present invention.

4. The method for preparing a halogen-free cyclophosphazene flame-retardant modified EP according to claim 1, characterized in that: The light yellow cyclophosphazene flame retardant obtained in step c is a cinnamyl alcohol derivative-based cyclophosphazene flame retardant. In the above synthesis process, the unsaturated alcohol is preferably cinnamyl alcohol (R is -H), and the synthetic product is hexacinnamyl alcoholoxy cyclotriphosphazene (CACP).

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