A halogen-free flame-retardant epoxy resin and a production method thereof

Abstract

The present invention relates to the technical field of polymer materials, and discloses a halogen-free flame-retardant epoxy resin and a production method thereof. The halogen-free flame-retardant epoxy resin is prepared by using epoxy resin, curing agent, diluent and functional additive as raw materials through a blending-curing process. The present invention prepares a polymer with a dendritic branching structure as a functional additive, and utilizes the hydroxyl group in its structure to participate in the curing reaction of the epoxy resin, thereby forming an epoxy resin cured product with a three-dimensional branched network structure in which molecular chains are intertwined, which can effectively improve the mechanical properties of the epoxy resin cured product. In addition, the silicon, nitrogen and phosphorus barrier elements rich in the functional additive structure can form a dense expanded carbon layer of deposited silicon when the epoxy resin cured product burns, which can not only effectively isolate oxygen and heat, but also achieve the effect of locking the smoke generated by combustion inside the material, thereby greatly enhancing the flame retardant properties of the epoxy resin.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, and in particular to a halogen-free flame-retardant epoxy resin and a production method thereof. Background Art

[0002] Epoxy resin is one of the thermosetting resins with the largest output. Due to its excellent physical and mechanical properties, electrical insulation properties and bonding properties, it can be made into coatings, composite materials, adhesives, molding materials and other materials, and is widely used in various fields of the national economy. However, as a polymer material, epoxy resin has poor flame retardancy, with a limiting oxygen index value of only 19.5, and it is accompanied by thick smoke and toxic and harmful gases when burning, which poses a great potential threat to people's lives and property safety. With the frequent occurrence of fire accidents in recent years, flame retardant modification of epoxy resin can make it have a wider range of applications and improve its safety.

[0003] At present, the flame retardant modification of epoxy resin is mainly achieved by adding flame retardants, which include organic flame retardants and inorganic flame retardants. Although organic flame retardants have good flame retardant effects, halogen-based organic flame retardants will produce a large amount of toxic and harmful gases when burned, which is not conducive to environmental protection and has been gradually reduced in use. Inorganic flame retardants have poor flame retardant effects and generally require a larger amount of addition to ensure a certain flame retardant effect. Therefore, the use of organic and inorganic flame retardants alone cannot achieve the desired effect.

[0004] The invention patent with publication number CN112679803B discloses a graphene nanosheet-loaded tin flame retardant, a flame-retardant epoxy resin and a method for preparing the two. The graphene nanosheet-loaded tin flame retardant is mixed with hexa(p-hydroxymethylphenoxy)-cyclotriphosphazene as a composite flame retardant and added to the epoxy resin, which can greatly improve the flame retardant effect of the epoxy resin. However, graphene itself is easy to agglomerate, which has a certain adverse effect on the mechanical properties of the epoxy resin. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] In view of the deficiencies in the prior art, the present invention provides a halogen-free flame-retardant epoxy resin and a production method thereof, which solves the problem of poor flame-retardant performance of the epoxy resin.

[0007] (II) Technical solution

[0008] A halogen-free flame-retardant epoxy resin, comprising the following raw materials by weight: 95-100 parts of epoxy resin, 35-50 parts of curing agent, 5-15 parts of diluent, and 4-8 parts of functional additive;

[0009] The functional additive is a polymer with a dendritic branched structure, and the structure is rich in silicon, nitrogen and phosphorus elements.

[0010] Preferably, the epoxy resin is any one of bisphenol A epoxy resin or bisphenol F epoxy resin.

[0011] Preferably, the curing agent is any one of tetrahydrophthalic anhydride or hexahydrophthalic anhydride.

[0012] Preferably, the diluent is any one of phenyl glycidyl ether, butyl glycidyl ether or hexyl glycidyl ether.

[0013] Preferably, the preparation method of the functional additive comprises the following steps:

[0014] Step 1: Stir and mix tetraisocyanatosilane, glycidol and toluene to form a uniform solution, pass nitrogen to deoxygenate, add catalyst A and stir evenly, start stirring, keep at 70-80°C for 4-8h, cool and discharge, separate the solid material, wash and vacuum dry to obtain an intermediate product;

[0015] Step 2: Mix the intermediate product, flame retardant DDP and 1,4-dioxane, stir mechanically to form a uniform solution, add catalyst B to the solution, mix well, pass nitrogen protection, increase the temperature to 80-90°C, stir at a constant temperature for 12-24 hours, discharge the material, filter out the solid material, wash it, and then place it in a vacuum drying oven for vacuum drying to obtain a functional additive.

[0016] Preferably, in step 1, the molar ratio of tetraisocyanatosilane to glycidol is 1:4.

[0017] Preferably, in step 1, the catalyst A is any one of stannous octoate or dibutyltin dilaurate.

[0018] Preferably, in step 2, the molar ratio of the intermediate product to the flame retardant DDP is 1:1-2.

[0019] Preferably, in step 2, the catalyst B is any one of tetrabutylammonium bromide, tetrabutylammonium hydrogen sulfate or N,N-dimethylbenzylamine.

[0020] The present invention uses tetraisocyanatosilane and glycidol as raw materials. Under the catalytic action of catalyst A, the isocyanate group in the tetraisocyanatosilane structure can undergo amine esterification reaction with the active hydroxyl group in the glycidol structure. By controlling the molar ratio of the two, an intermediate product containing four equivalent epoxy groups in the structure can be generated. Under the action of catalyst B, the epoxy group can undergo ring-opening esterification reaction with the active carboxyl group in the flame retardant DDP structure to form a dendritic polymer with the intermediate product as the core. The structure is rich in silicon, nitrogen and phosphorus flame retardant elements and contains a large number of hydroxyl functional groups generated by the ring-opening esterification reaction, i.e., a functional auxiliary agent.

[0021] A method for producing a halogen-free flame-retardant epoxy resin comprises the following steps:

[0022] Step 1: Accurately weigh the raw materials of each component according to the dosage of the formula and set aside;

[0023] Step 2: Put the epoxy resin, diluent and functional additive into a stirring tank, and stir them mechanically to obtain a premix;

[0024] Step 3: Add the curing agent into a stirring kettle, stir and mix well, then pour into a mold, raise the temperature to 120-140°C, and cure for 2-4 hours to obtain a halogen-free flame-retardant epoxy resin.

[0025] (III) Beneficial technical effects

[0026] The present invention prepares a polymer with a dendritic branching structure as a functional auxiliary agent, and utilizes the hydroxyl group in the structure to participate in the curing reaction of the epoxy resin, thereby forming an epoxy resin cured product with a three-dimensional branched network structure in which molecular chains are intertwined, which can effectively improve the mechanical properties of the epoxy resin cured product. In addition, the silicon, nitrogen, and phosphorus barrier elements rich in the functional auxiliary agent structure can form a dense expanded carbon layer of deposited silicon when the epoxy resin cured product burns, which can not only effectively isolate oxygen and heat, but also achieve the effect of locking the smoke generated by combustion inside the material, thereby greatly enhancing the flame retardant properties of the epoxy resin. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0028] Figure 1 This is the infrared characterization diagram of the functional additive. DETAILED DESCRIPTION

[0029] In order to facilitate the understanding of the present invention, the present invention will be described more fully below. Preferred embodiments of the present invention are given below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0030] The functional additives used in the following examples were prepared by the following method:

[0031] Step 1: 1.2 g of tetraisocyanatosilane, 1.8 g of glycidol and toluene were stirred and mixed to form a uniform solution, nitrogen was passed to deoxygenate, 0.1 g of dibutyltin dilaurate was added and stirred evenly, stirring was started, and the mixture was kept at 75° C. for 6 h, then the temperature was lowered and the solid material was separated, washed, and vacuum dried to obtain an intermediate product;

[0032] Step 2: Mix 1.5 g of the intermediate product, 2 g of the flame retardant DDP and 1,4-dioxane, and mechanically stir to form a uniform solution. Add 0.2 g of tetrabutylammonium bromide to the solution, mix well, pass nitrogen protection, increase the temperature to 85°C, stir at a constant temperature for 16 hours, discharge the material, filter out the solid material, wash it, and then place it in a vacuum drying oven for vacuum drying to obtain a functional additive.

[0033] The functional additive was characterized by infrared spectroscopy. Figure 1 , after analysis, we know that 3462cm -1 NH stretching vibration peak, 3344 cm -1 is the hydroxyl stretching vibration peak, 3000~3100cm -1 The peak of CH stretching vibration on the benzene ring is 1745 cm -1 is the C=O stretching vibration peak in the ester group, 1681 cm -1 is the C=O stretching vibration peak in the amide group, 1257 cm -1 It is the characteristic absorption peak of P=O, 1155~1190cm -1 It is the characteristic absorption peak of Si-N.

[0034] Example 1

[0035] A halogen-free flame-retardant epoxy resin, comprising the following raw materials by weight: 95 parts of E51 epoxy resin, 35 parts of curing agent tetrahydrophthalic anhydride, 5 parts of diluent phenyl glycidyl ether, and 4 parts of functional additives;

[0036] The halogen-free flame retardant epoxy resin is prepared by the following method:

[0037] Step 1: Accurately weigh the raw materials of each component according to the dosage of the formula and set aside;

[0038] Step 2: Add E51 epoxy resin, diluent phenyl glycidyl ether and functional additives into a stirring kettle, and stir mechanically to obtain a premix;

[0039] Step 3: Add the curing agent tetrahydrophthalic anhydride into a stirring kettle, stir and mix well, pour into a mold, increase the temperature to 120°C, and cure for 2 hours to obtain a halogen-free flame-retardant epoxy resin.

[0040] Example 2

[0041] A halogen-free flame-retardant epoxy resin, comprising the following raw materials by weight: 96 parts of E51 epoxy resin, 45 parts of hexahydrophthalic anhydride curing agent, 10 parts of butyl glycidyl ether diluent, and 6.5 parts of functional additives;

[0042] The halogen-free flame retardant epoxy resin is prepared by the following method:

[0043] Step 1: Accurately weigh the raw materials of each component according to the dosage of the formula and set aside;

[0044] Step 2: Add E51 epoxy resin, diluent butyl glycidyl ether and functional additives into a stirring kettle, and stir mechanically to obtain a premix;

[0045] Step 3: Add the curing agent hexahydrophthalic anhydride into a stirring kettle, stir and mix well, pour into a mold, increase the temperature to 130°C, and cure to obtain a halogen-free flame-retardant epoxy resin.

[0046] Example 3

[0047] A halogen-free flame-retardant epoxy resin, comprising the following raw materials by weight: 100 parts of E51 epoxy resin, 50 parts of curing agent tetrahydrophthalic anhydride, 15 parts of diluent hexyl glycidyl ether, and 8 parts of functional additives;

[0048] The halogen-free flame retardant epoxy resin is prepared by the following method:

[0049] Step 1: Accurately weigh the raw materials of each component according to the dosage of the formula and set aside;

[0050] Step 2: Add E51 epoxy resin, diluent hexyl glycidyl ether and functional additives into a stirring kettle, and stir mechanically to obtain a premix;

[0051] Step 3: Add the curing agent tetrahydrophthalic anhydride into a stirring kettle, stir and mix well, pour into a mold, increase the temperature to 140°C, and cure for 3 hours to obtain a halogen-free flame-retardant epoxy resin.

[0052] Comparative Example 1

[0053] A halogen-free flame-retardant epoxy resin, comprising the following raw materials by weight: 96 parts of E51 epoxy resin, 45 parts of tetrahydrophthalic anhydride as a curing agent, and 10 parts of hexyl glycidyl ether as a diluent;

[0054] The halogen-free flame retardant epoxy resin is prepared by the following method:

[0055] Step 1: Accurately weigh the raw materials of each component according to the dosage of the formula and set aside;

[0056] Step 2: Add E51 epoxy resin, diluent hexyl glycidyl ether and into a stirring kettle, and stir mechanically to obtain a premix;

[0057] Step 3: Add the curing agent tetrahydrophthalic anhydride into a stirring kettle, stir and mix well, pour into a mold, increase the temperature to 130°C, and cure for 4 hours to obtain a halogen-free flame-retardant epoxy resin.

[0058] The following performance tests were performed on the halogen-free flame retardant epoxy resins prepared in Examples 1 to 3 of the present invention and Comparative Example 1:

[0059] Refer to standard GB / T 7124-1008 for tensile performance test;

[0060] Refer to UL94-2009 and conduct UL-94 grade test;

[0061] Refer to standard GB / T 2406.2-2009 to conduct limiting oxygen index test; the test results are recorded in the following table:

[0062] Tensile strength / MPa Limiting oxygen index / % UL-94 Rating Example 1 18.4 32.0 V-0 Example 2 19.0 32.4 V-0 Example 3 18.8 32.3 V-0 Comparative Example 1 11.3 19.6 -

[0063] Note: “-” in the table means the level was not tested.

[0064] From the test results in the table, it can be seen that the epoxy resin with added functional additives not only has good mechanical properties, but also has excellent flame retardant properties.

[0065] Based on the ideal embodiment of the present invention, through the above description, relevant personnel can make various changes and modifications without departing from the technical concept of the present invention. The technical scope of the present invention is not limited to the content in the specification, and the technical scope must be determined according to the scope of the claims.

Claims

1. A halogen-free flame-retardant epoxy resin, characterized in that: The following raw materials are included by weight: 95-100 parts of epoxy resin, 35-50 parts of curing agent, 5-15 parts of diluent, and 4-8 parts of functional additive; The functional additive is a polymer with a dendritic branched structure, and the structure is rich in silicon, nitrogen and phosphorus elements; The preparation method of the functional additive comprises the following steps: Step 1: Stir and mix tetraisocyanatosilane, glycidol and toluene to form a uniform solution, pass nitrogen to deoxygenate, add catalyst A and stir evenly, start stirring, keep at 70-80°C for 4-8h, cool and discharge, separate the solid material, wash and vacuum dry to obtain an intermediate product; Step 2: Mix the intermediate product, flame retardant DDP and 1,4-dioxane, mechanically stir to form a uniform solution, add catalyst B to the solution, mix well, pass nitrogen protection, increase the temperature to 80-90°C, stir at a constant temperature for 12-24 hours, discharge the material, filter out the solid material, wash it, and then place it in a vacuum drying oven for vacuum drying to obtain a functional additive; the molar ratio of the intermediate product to the flame retardant DDP is 1:1-2.

2. The halogen-free flame-retardant epoxy resin according to claim 1, characterized in that: The epoxy resin is any one of bisphenol A epoxy resin and bisphenol F epoxy resin.

3. The halogen-free flame-retardant epoxy resin according to claim 1, characterized in that: The curing agent is any one of tetrahydrophthalic anhydride or hexahydrophthalic anhydride.

4. The halogen-free flame-retardant epoxy resin according to claim 1, characterized in that: The diluent is any one of phenyl glycidyl ether, butyl glycidyl ether or hexyl glycidyl ether.

5. The halogen-free flame-retardant epoxy resin according to claim 1, characterized in that: In step 1, the molar ratio of tetraisocyanatosilane to glycidol is 1:

4.

6. The halogen-free flame-retardant epoxy resin according to claim 1, characterized in that: In step 1, the catalyst A is any one of stannous octoate or dibutyltin dilaurate.

7. The halogen-free flame-retardant epoxy resin according to claim 1, characterized in that: In step 2, the catalyst B is any one of tetrabutylammonium bromide, tetrabutylammonium hydrogen sulfate or N,N-dimethylbenzylamine.

8. The method for producing a halogen-free flame-retardant epoxy resin according to claim 1, characterized in that: The following steps are involved: Step 1: Accurately weigh the raw materials of each component according to the dosage of the formula and set aside; Step 2: Put the epoxy resin, diluent and functional additive into a stirring tank, and stir them mechanically to obtain a premix; Step 3: Add the curing agent into the stirring kettle, stir and mix well, then pour into the mold, increase the temperature to 120-140℃, and cure for 2-4h to obtain halogen-free flame-retardant epoxy resin.

Images