P / n / s type flame retardant, synthesis method and application thereof in epoxy resin

Abstract

The present application belongs to the technical field of epoxy resin materials, and particularly relates to a P / N / S type flame retardant, a synthesis method and application thereof in epoxy resin. In the present application, 2-amino benzothiazole and phenyl phosphonic acid are reacted in an alcohol solvent system under heating conditions, and white crystals are separated out after cooling, thus synthesizing a novel flame retardant. In the chemical structural formula of the flame retardant, 2-amino benzothiazole and phenyl phosphonic acid are combined to form an ionic compound by electrostatic attraction. The flame retardant is directly mixed with bisphenol A diglycidyl ether monomer and used for preparing epoxy resin materials. The novel flame retardant synthesized in the present application has high flame retardant efficiency, when the addition amount is 5wt%, the oxygen index of the epoxy resin cured product can be increased to 36.4%, and the vertical burning passes UL-94 V-0 level. More importantly, the mechanical strength is increased by 1.7 times compared with pure EP.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of epoxy resin materials, and particularly relates to a P / N / S type flame retardant, a synthesis method thereof and application of the flame retardant in epoxy resin. BACKGROUND

[0002] Epoxy resin (EP) is a widely used thermosetting polymer material, which has excellent electrical insulation, corrosion resistance, high thermal stability, low shrinkage, strong adhesion and mechanical durability, and has been applied to the fields of electronic appliances, packaging, printed circuit boards, automobiles, adhesives and surface coatings. However, due to the highly flammable nature of EP, its application in many fields is limited. Therefore, enhancing the flame retardance of EP has been an important issue of concern.

[0003] Adding a flame retardant is the most common and economical method to improve the flame retardance of epoxy resin. Traditional additives are mostly halogen compounds. However, halogen compounds release a large amount of smoke and toxic gases during combustion, which poses a serious threat to personal safety. Therefore, halogen flame retardants are gradually replaced by halogen-free flame retardants. Although a large number of external flame retardants reported in the prior art have improved the flame retardance of epoxy resin, they often accompany with the decrease of mechanical properties or / and the weakening of transparency; in addition, the preparation process of the flame retardant is relatively complicated, which also limits its application in industry.

[0004] Therefore, a flame retardant with high flame retardance, while maintaining or improving other properties, and a simple preparation process has become one of the research hotspots. SUMMARY

[0005] In view of the problems in the prior art, the application provides a P / N / S type flame retardant, a synthesis method thereof and application of the flame retardant in epoxy resin, aiming to solve some problems in the prior art or at least alleviate some problems in the prior art.

[0006] The application is implemented as follows: a P / N / S type flame retardant includes a compound with the following structural formula:

[0007]

[0008] The application further provides a synthesis method of the P / N / S type flame retardant, which includes: 2-amino benzothiazole and phenyl phosphonic acid are combined by electrostatic attraction to form an ionic compound, wherein the amino group in the 2-amino benzothiazole molecule is combined with H + , which is positively charged, and the phenyl phosphonic acid loses a hydrogen atom on the phosphorus hydroxyl group, which is negatively charged, and the chemical equation is as follows:

[0009]

[0010] Further, the 2-amino benzothiazole and phenyl phosphonic acid are reacted in an alcohol solvent system under heating condition, and white crystal product is separated out after cooling. The crystal is filtered, washed with anhydrous ethanol or deionized water for several times, dried in vacuum, and grinded to obtain white powder.

[0011] Further, the alcohol solvent is a low carbon alcohol solvent, which is selected from any one of methanol, ethanol, propanol or butanol.

[0012] Further, the 2-amino benzothiazole and phenyl phosphonic acid are respectively dissolved in an alcohol solvent, and then the liquid of phenyl phosphonic acid is added dropwise into the liquid of 2-amino benzothiazole to react.

[0013] Further, the molar ratio of 2-amino benzothiazole to phenyl phosphonic acid is 1.5-1:1-1.2, the reaction temperature is 60-100℃, and the reaction time is 5-10h. Preferably, the reaction temperature is 80℃, and the reaction time is 8h.

[0014] The application also provides an application of the P / N / S type flame retardant as described above in preparation of an epoxy resin.

[0015] Further, the epoxy resin is selected from any one of glycidyl ether type epoxy resin, glycidyl ester type epoxy resin, glycidyl amine type epoxy resin. Preferably, the epoxy resin is bisphenol A type epoxy resin.

[0016] Further, after the bisphenol A diglycidyl ether is fully reacted with the P / N / S type flame retardant, a curing agent is added to obtain an epoxy resin with improved performance. The curing agent is preferably 4,4'-diamino diphenyl methane (DDM).

[0017] Further, the adding amount of the P / N / S type flame retardant is 0.5-10wt%, preferably 1.0-7.5wt%.

[0018] The application synthesizes a new compound PPS by one-step reaction with 2-amino benzothiazole and phenyl phosphonic acid as main raw materials. The structural feature is that it contains primary amine, and combines a hydrogen ion with phenyl phosphonic acid by ionic bond. When the adding amount is only 2.5wt%, the flame retardant for epoxy resin can achieve the best effect of UL-V0 level, and the mechanical performance is greatly improved compared with pure EP. Due to its unique performance and simple preparation method, it has considerable potential application value.

[0019] In summary, the advantages and positive effects of the application are as follows:

[0020] 1. Compared with the prior art, the synthesis reaction method is simple, has high yield, no other by-products, mild reaction condition, safe operation and low cost, and has great industrial value.

[0021] 2. Compared with the prior art, the phosphorus, nitrogen and sulfur compound flame retardant prepared by the present application has higher flame retardant efficiency. When the addition amount of the flame retardant is 5wt%, the oxygen index of the epoxy resin cured product can be increased to 36.4%, and the vertical combustion passes the UL-94 V-0 level. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is an infrared spectrum of the phosphorus, nitrogen and sulfur compound of the present application, 1 H NMR and 31 P NMR spectrum of the present application;

[0023] Figure 2 is an epoxy resin material prepared by adding 5% of the flame retardant of the present application. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below in combination with examples. The equipment and reagents used in each example and test example can be obtained from commercial channels unless otherwise specified. The specific examples described herein are only used to explain the present application and do not limit the present application.

[0025] According to the information contained in the present application, various changes to the precise description of the present application can be easily made by those skilled in the art without departing from the spirit and scope of the appended claims. It should be understood that the scope of the present application is not limited to the defined processes, properties or components, as these embodiments and other descriptions are only illustrative of certain aspects of the present application. In fact, various changes to the embodiments of the present application that are apparent to those skilled in the art or related fields are encompassed within the scope of the appended claims.

[0026] In order to better understand the present application without limiting the scope of the present application, all numbers, percentages and other numerical values used in this application to express amounts, percentages and other numerical values should be understood as being modified by the word "about" in all cases. Therefore, unless specifically stated otherwise, the numerical parameters listed in the specification and attached claims are approximations. They can vary depending on different desired properties sought to be obtained by the use of the present application. Each numerical parameter should be considered as being at least as precise as the reporting of the effective digits and the rounding methods commonly used by those skilled in the art.

[0027] The present application discloses a P / N / S type flame retardant, a synthesis method and its application in epoxy resin.

[0028] It should be noted that the material parts in the following examples are all by weight. The limiting oxygen index in the examples is tested according to GB / T 2406-1993 by using HC-2C type oxygen index tester, and the vertical burning is tested according to GB / T 2408-1996 by using CZF-2 type vertical burning tester. The technical solutions of the present application will be clearly and completely described in combination with the embodiments of the present application.

[0029] Synthesis of P / N / S-containing flame retardant PPS in Example 1

[0030] First, 4.5060 g (0.03 mol) of 2-aminobenzothiazole was taken into a three-necked flask, 80 mL of anhydrous ethanol was added and stirred until completely dissolved. Then, 3.1618 g (0.02 mol) of phenylphosphonic acid was weighed, dissolved in 40 mL of anhydrous ethanol, and then transferred to a constant pressure funnel, and added dropwise to the 2-aminobenzothiazole at a rate of 1 drop / s, and white precipitate gradually appeared. Stirring was carried out at 80°C for 8 h. The crystals were precipitated after cooling to room temperature, filtered and washed with anhydrous ethanol several times. The filter cake was dried at 80°C under vacuum for 6 h, and after grinding, 6.1382 g of white powder was obtained, with a yield of 80%, and the melting range of PPS was 188-190°C. The chemical equation of the synthesis reaction is as follows:

[0031]

[0032] Figure 1 is the infrared spectrum of the prepared compound PPS, 1 H NMR and 31 P NMR diagram. Through the analysis of infrared spectrum, nuclear magnetic resonance hydrogen spectrum and nuclear magnetic resonance phosphorus spectrum, it is shown that PPS is successfully synthesized. The compound PPS is formed by 2-aminobenzothiazole and phenylphosphonic acid in the form of ionic bond, in which the amino group in the 2-aminobenzothiazole molecule combines H + with positive electricity, and the phenylphosphonic acid loses the hydrogen atom on the phosphorus hydroxyl group with negative electricity, and the two are combined into ionic compound due to electrostatic attraction.

[0033] Preparation of epoxy resin EP / 1 PPS in Example 2

[0034] The bisphenol A diglycidyl ether (DGEBA) with a mass fraction of 77.8% was vacuumed to be bubble-free at 135°C, then the powdered PPS with a mass fraction of 1% was quickly added, the PPS was fully reacted with the EP by fast stirring, the temperature was decreased to 95°C and stirred uniformly, the curing agent DDM with a mass fraction of 20.4% was added, the obtained liquid was poured into a polytetrafluoroethylene (PTFE) mold, and was cured at 100°C and 150°C for 2h respectively, to obtain an epoxy resin. After being made into a standard sample, the oxygen index and vertical burning test were carried out. The test results show that the oxygen index is 30.6%, and the vertical burning level is UL-94 V-1 level.

[0035] Example 3 Preparation of epoxy resin EP / 2.5PPS

[0036] The bisphenol A diglycidyl ether (DGEBA) with a mass fraction of 77.4% was vacuumed to be bubble-free at 130°C, then the powdered PPS with a mass fraction of 2.5% was quickly added, the PPS was fully reacted with the EP by fast stirring, the temperature was decreased to 95°C and stirred, the curing agent DDM with a mass fraction of 20.1% was added, the obtained liquid was poured into a polytetrafluoroethylene (PTFE) mold, and was cured at 100°C and 150°C for 2h respectively, to obtain an epoxy resin. The test results show that the oxygen index is 32.5%, and the vertical burning level is UL-94 V-0 level.

[0037] Example 4 Preparation of epoxy resin EP / 5PPS

[0038] The bisphenol A diglycidyl ether (DGEBA) with a mass fraction of 74.6% was vacuumed to be bubble-free at 132°C, then the powdered PPS with a mass fraction of 5% was quickly added, the PPS was fully reacted with the EP by fast stirring, the temperature was decreased to 95°C and stirred, the curing agent DDM with a mass fraction of 19.6% was added, the obtained liquid was poured into a polytetrafluoroethylene (PTFE) mold, and was cured at 100°C and 150°C for 2h respectively, to obtain an epoxy resin. The test results show that the oxygen index is 36.4%, and the vertical burning level is UL-94 V-0 level.

[0039] Figure 2 The figure of the epoxy resin formed by adding 5% of the PPS compound clearly shows that the obtained epoxy resin has good light transmittance, and the following Wuhan University of Technology logo pattern is clearly visible.

[0040] Example 5 Preparation of epoxy resin EP / 7.5PPS

[0041] The bisphenol A diglycidyl ether (DGEBA) with a mass fraction of 73.4% was degassed to be bubble-free at 128°C under vacuum, then the powdered PPS with a mass fraction of 7.5% was quickly added, the PPS was fully reacted with the EP by fast stirring, the temperature was lowered to 95°C and stirred, the curing agent DDM with a mass fraction of 19.1% was added, the obtained liquid was poured into a polytetrafluoroethylene (PTFE) mold, and was cured at 100°C and 150°C for 2h respectively, to obtain an epoxy resin. The test results show that the oxygen index is 34.6%, and the vertical burning level is UL-94 V-1 level.

[0042] Preparation of pure EP

[0043] The bisphenol A diglycidyl ether (DGEBA) with a mass fraction of 79.4% was degassed to be bubble-free at 120°C under vacuum, the temperature was lowered to 95°C and stirred uniformly, the curing agent DDM with a mass fraction of 20.6% was added, the obtained liquid was poured into a polytetrafluoroethylene (PTFE) mold, and was cured at 100°C and 150°C for 2h respectively, to obtain an epoxy resin. The test results show that the oxygen index is 26.5%, and the vertical burning level is UL-94 no level.

[0044] In the present application, the mechanical properties of the epoxy resins prepared in each embodiment and the comparative example are also tested, and the method is that the tensile test and the three-point bending test are respectively carried out on a CMT6103 universal testing machine according to the methods of GB / T 1040.2-2006 and GB / T 9341-2008. The dumbbell-shaped sample with a size of 75x4x2mm 3 is used for the tensile test, and the sample size for the three-point bending test is 80x10x4mm 3 . The value of each test is taken as the average value of three tests. The test results are shown in Table 1.

[0045] Table 1: Influence of the phosphorus, nitrogen and sulfur-containing compound (PPS) of the present application on the mechanical properties of the epoxy resin

[0046]

[0047] From the above table, it can be seen that the tensile strength, elongation at break, bending strength and bending modulus of the new epoxy resin obtained by adding the new phosphorus, nitrogen and sulfur-containing flame retardant prepared in the present application to the epoxy resin are all increased with the increase of the addition amount of the PPS compound in the EP, and when the addition amount is 5%, the bending strength is 1.7 times that of the pure EP, which has the characteristics of high flame retardant efficiency and excellent mechanical properties. The present application provides a preparation method of an epoxy resin flame retardant with low cost, simple operation and high reaction efficiency, and has potential application value.

[0048] The raw materials listed in the present application, and the upper and lower limits, interval values of each raw material of the present application, and the upper and lower limits, interval values of process parameters (such as temperature, time, etc.) can realize the present application, and examples are not listed here. In addition to the synthesis method, the same structure of the additive synthesized by other methods is also included.

[0049] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for synthesizing a P / N / S type flame retardant, characterized in that: 2-Aminobenzothiazole and phenylphosphonic acid combine by electrostatic attraction to form an ionic compound, in which the amino group in the 2-aminobenzothiazole molecule combines with H + , positively charged, phenylphosphonic acid loses the hydrogen atom on the phosphorus hydroxyl group and becomes negatively charged. The chemical formula is as follows: 。 2. The method for synthesizing a P / N / S type flame retardant according to claim 1, wherein: 2-Aminobenzothiazole reacts with phenylphosphonic acid in an alcohol solvent system under heating conditions, and a white crystalline product is precipitated after cooling.

3. The method for synthesizing a P / N / S type flame retardant according to claim 2, wherein: The alcohol solvent is a low-carbon alcohol solvent, selected from any one of methanol, ethanol, propanol or butanol.

4. The method for synthesizing a P / N / S type flame retardant according to claim 2, wherein: 2-aminobenzothiazole and phenylphosphonic acid are dissolved in an alcohol solvent respectively, and then the phenylphosphonic acid liquid is added dropwise to the 2-aminobenzothiazole liquid to react.

5. The method for synthesizing a P / N / S type flame retardant according to claim 2, wherein: The molar ratio of 2-aminobenzothiazole to phenylphosphonic acid is 1.5-1:1-1.2; the reaction temperature is 60-100° C.; and the reaction time is 5-10 hours.

6. Use of a P / N / S type flame retardant in the preparation of epoxy resin, wherein the P / N / S type flame retardant comprises a compound of the following structural formula: 。 7. The use according to claim 6, characterized in that: The epoxy resin is selected from any one of glycidyl ether epoxy resin, glycidyl ester epoxy resin and glycidyl amine epoxy resin.

8. The use according to claim 7, characterized in that: After bisphenol A diglycidyl ether and the P / N / S type flame retardant are fully reacted, a curing agent is added to obtain an epoxy resin with improved performance.

9. The use according to claim 8, characterized in that: The addition amount of the P / N / S type flame retardant is 0.5-10 wt%.

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