P / N / S type flame retardant, synthetic method and application of P / N / S type flame retardant in epoxy resin

Abstract

The invention 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 of the P / N / S type flame retardant in epoxy resin. 2-aminobenzothiazole and phenylphosphonic acid react in an alcohol solvent system under the heating condition, white crystals are separated out after cooling, and the novel flame retardant is synthesized. In the chemical structural formula of the flame retardant, 2-aminobenzothiazole and phenylphosphonic acid are combined by electrostatic attraction to form an ionic compound. The flame retardant is directly mixed with a bisphenol A diglycidyl ether monomer and is used for preparing an epoxy resin material. The synthesized novel flame retardant is high in flame retardant efficiency, when the adding amount is 5 wt%, the oxygen index of epoxy resin cured products can be increased to 36.4%, and vertical combustion passes the UL-94V-0 level. More importantly, the mechanical strength of the EP material is 1.7 times higher than that of pure EP.

Description

Technical Field

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

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

[0003] Adding flame retardants is the most common and economical method to improve the flame retardant properties of epoxy resins. Traditional additives are mostly halogen compounds. However, halogen compounds release a large amount of smoke and toxic gases when burned, posing 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 retardant properties of epoxy resins, they are often accompanied by a decrease in mechanical properties and / or a decrease in transparency; in addition, the preparation process of flame retardants is relatively complicated, which also limits their industrial application.

[0004] Therefore, flame retardants with high flame retardant properties while maintaining or improving other properties and with a simpler preparation process have become one of the current research hotspots. Summary of the invention

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

[0006] The present invention is achieved by a P / N / S type flame retardant comprising a compound of the following structural formula:

[0007]

[0008] The present invention also provides a method for synthesizing the P / N / S type flame retardant as described above, comprising: 2-aminobenzothiazole and phenylphosphonic acid are combined by electrostatic attraction to form an ionic compound, wherein the amino group in the 2-aminobenzothiazole molecule is combined with H + , positively charged, phenylphosphonic acid loses the hydrogen atom on the phosphorus hydroxyl group and becomes negatively charged. The chemical equation is as follows:

[0009]

[0010] Further, 2-aminobenzothiazole and phenylphosphonic acid react in an alcohol solvent system under heating conditions, and a white crystalline product is precipitated after cooling. After the crystals are filtered, they are washed several times with anhydrous ethanol or deionized water, and vacuum dried and ground to obtain a white powder.

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

[0012] Furthermore, 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 for reaction.

[0013] Furthermore, 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. Preferably, the reaction temperature is 80°C and the reaction time is 8 hours.

[0014] The present invention also provides the use of the above-mentioned P / N / S type flame retardant in the preparation of epoxy resin.

[0015] Furthermore, the epoxy resin is selected from any one of glycidyl ether epoxy resin, glycidyl ester epoxy resin and glycidyl amine epoxy resin, preferably bisphenol A epoxy resin.

[0016] Furthermore, after the 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. The curing agent is preferably 4,4'-diaminodiphenylmethane (DDM).

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

[0018] The present invention uses 2-aminobenzothiazole and phenylphosphonic acid as main raw materials, and synthesizes a new compound PPS through a one-step reaction. The structural characteristics are that it contains primary amines and combines a hydrogen ion with phenylphosphonic acid by ionic bonding. When used for flame retardant epoxy resin, when the addition amount is only 2.5wt%, the best flame retardant effect UL-V0 level can be achieved, and the mechanical properties are greatly improved compared with pure EP. Due to its unique properties and simple preparation method, it has considerable potential application value.

[0019] In summary, the advantages and positive effects of the present invention are:

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

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

[0022] Figure 1 is the infrared image of the phosphorus, nitrogen and sulfur compounds of the present invention, 1 H NMR and 31 P NMR spectra;

[0023] Figure 2 This is a diagram of the epoxy resin material prepared by adding 5% flame retardant according to the present invention. DETAILED DESCRIPTION

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

[0025] Based on the information contained in this application, it is easy for those skilled in the art to make various changes to the precise description of the present invention without departing from the spirit and scope of the appended claims. It should be understood that the scope of the present invention is not limited to the defined process, properties or components, because these embodiments and other descriptions are only for illustrating specific aspects of the present invention. In fact, various changes that the technicians in this field or related fields can obviously make to the embodiments of the present invention are all covered within the scope of the appended claims.

[0026] In order to better understand the present invention but not to limit the scope of the present invention, all the numbers used in this application to express the amount, percentage, and other numerical values ​​should be understood as modified by the word "about" in all cases. Therefore, unless otherwise specified, the numerical parameters listed in the specification and the appended claims are approximate values, which may be changed according to the different ideal properties attempted to be obtained. Each numerical parameter should at least be regarded as obtained based on the reported significant figures and by conventional rounding methods.

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

[0028] It should be noted that the material parts in the following embodiments are all weight parts. The limiting oxygen index in the embodiments is tested using an HC-2C oxygen index tester in accordance with GB / T 2406-1993, and the vertical combustion is tested using a CZF-2 vertical combustion instrument in accordance with GB / T2408-1996. The technical solution of the present invention is described clearly and completely below in conjunction with the embodiments of the present invention.

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

[0030] First, take 4.5060g (0.03mol) of 2-aminobenzothiazole and place it in a three-necked flask, add 80mL of anhydrous ethanol and stir until completely dissolved. Then, weigh 3.1618g (0.02mol) of phenylphosphonic acid, dissolve it in 40mL of anhydrous ethanol, transfer it to a constant pressure funnel, and add it to 2-aminobenzothiazole at a rate of 1 drop / s, and a white precipitate gradually appears. Reflux and stir at 80°C for 8h. Cool to room temperature to precipitate crystals, filter and wash several times with anhydrous ethanol. The filter cake is vacuum dried at 80°C for 6h, and after grinding, 6.1382g of white powder is obtained, with a yield of 80%. The melting range of PPS is: 188-190°C. The chemical equation for 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 graph. The analysis of infrared spectrum, nuclear magnetic resonance hydrogen spectrum and nuclear magnetic resonance phosphorus spectrum showed that PPS was successfully synthesized. The compound PPS is formed by 2-aminobenzothiazole and phenylphosphonic acid in the form of ionic bonds, in which the amino group in the 2-aminobenzothiazole molecule is combined with H + , positively charged, while phenylphosphonic acid loses the hydrogen atom on the phosphorus hydroxyl group and becomes negatively charged. The two combine to form an ionic compound due to electrostatic attraction.

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

[0034] Under vacuum conditions, 77.8% of bisphenol A diglycidyl ether (DGEBA) was pumped at 135°C until there were no bubbles, then 1% of powdered PPS was quickly added, and the mixture was stirred quickly to allow the PPS and EP to react fully. The mixture was cooled to 95°C and stirred evenly, and 20.4% of curing agent DDM was added. The resulting liquid was poured into a polytetrafluoroethylene (PTFE) mold, and cured at 100°C and 150°C for 2 hours each to obtain epoxy resin. After being made into standard specimens, oxygen index and vertical combustion tests were performed. The test results showed that the oxygen index was 30.6% and the vertical combustion grade was UL-94V-1.

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

[0036] Under vacuum conditions, 77.4% of bisphenol A diglycidyl ether (DGEBA) was pumped at 130°C until there were no bubbles, then 2.5% of powdered PPS was quickly added, and the mixture was stirred quickly to allow the PPS and EP to react fully, then cooled to 95°C and stirred, and 20.1% of curing agent DDM was added, and the obtained liquid was poured into a polytetrafluoroethylene (PTFE) mold, and cured at 100°C and 150°C for 2 hours to obtain epoxy resin. The test results showed that the oxygen index was 32.5% and the vertical combustion rating was UL-94V-0.

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

[0038] Under vacuum conditions, 74.6% of bisphenol A diglycidyl ether (DGEBA) was pumped at 132°C until there were no bubbles, then 5% of powdered PPS was quickly added, and the mixture was stirred quickly to allow the PPS and EP to react fully, then the mixture was cooled to 95°C and stirred, and 19.6% of curing agent DDM was added, and the obtained liquid was poured into a polytetrafluoroethylene (PTFE) mold, and cured at 100°C and 150°C for 2 hours to obtain epoxy resin. The test results showed that the oxygen index was 36.4% and the vertical combustion rating was UL-94V-0.

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

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

[0041] Under vacuum conditions, 73.4% of bisphenol A diglycidyl ether (DGEBA) was pumped at 128°C until there were no bubbles, then 7.5% of powdered PPS was quickly added, and the mixture was stirred quickly to allow the PPS and EP to react fully, then the mixture was cooled to 95°C and stirred, and 19.1% of curing agent DDM was added, and the obtained liquid was poured into a polytetrafluoroethylene (PTFE) mold, and cured at 100°C and 150°C for 2 hours to obtain epoxy resin. The test results showed that the oxygen index was 34.6% and the vertical combustion rating was UL-94V-1.

[0042] Comparative Example Preparation of Pure EP

[0043] Under vacuum conditions, 79.4% of bisphenol A diglycidyl ether (DGEBA) was pumped at 120°C until there were no bubbles, cooled to 95°C and stirred evenly, 20.6% of curing agent DDM was added, and the obtained liquid was poured into a polytetrafluoroethylene (PTFE) mold, and cured at 100°C and 150°C for 2 hours to obtain epoxy resin. The test results showed that the oxygen index was 26.5% and the vertical combustion grade was UL-94 without grade.

[0044] The mechanical properties of the epoxy resins prepared in the examples and comparative examples are also tested in this application by: tensile test and three-point bending test are performed on a CMT6103 universal testing machine according to the methods of GB / T 1040.2-2006 and GB / T 9341-2008, respectively. 3 The dumbbell-shaped specimen of the three-point bending test has a specimen size of 80×10×4mm 3 The value of each test is taken as the average of three tests. The test results are shown in Table 1 below.

[0045] Table 1: Effect of the phosphorus, nitrogen and sulfur compounds (PPS) of the present invention on the mechanical properties of epoxy resin

[0046]

[0047] As can be seen from the above table, the tensile strength, elongation at break, flexural strength and flexural modulus of the new epoxy resin obtained by adding the new flame retardant containing phosphorus, nitrogen and sulfur prepared in the present invention to the epoxy resin all increase with the increase of the amount of PPS compound added in EP, and when the addition amount is 5%, its flexural strength reaches 1.7 times that of pure EP, and it has the characteristics of high flame retardant efficiency and excellent mechanical properties. The present invention provides a preparation method for 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 invention, as well as the upper and lower limits and interval values ​​of the raw materials of the present invention, and the upper and lower limits and interval values ​​of the process parameters (such as temperature, time, etc.) can all achieve the present invention, and the embodiments are not listed one by one here. In addition to the synthesis method, it also includes additives with the same structure synthesized by other methods.

[0049] The above description is only a preferred embodiment of the present invention and is 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 P / N / S type flame retardant, characterized in that: Including compounds with the following structural formula:

2. A method for synthesizing the P / N / S type flame retardant as claimed in claim 1, 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 equation is as follows:

3. The method for synthesizing a P / N / S type flame retardant according to claim 2, characterized in that: 2-Aminobenzothiazole and phenylphosphonic acid react in an alcohol solvent system under heating conditions, and a white crystalline product is precipitated after cooling.

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

5. The method for synthesizing a P / N / S type flame retardant according to claim 3, characterized in that: 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.

6. The method for synthesizing a P / N / S type flame retardant according to claim 3, characterized in that: 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 h.

7. Use of the P / N / S type flame retardant as claimed in claim 1 in the preparation of epoxy resin.

8. The use according to claim 7, 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.

9. The use according to claim 8, 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.

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

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