Construction strategy and preparation method of low-softening-point phosphorus-containing epoxy resin for carbon fibers

Abstract

The invention relates to a construction strategy and a preparation method of phosphorus-containing epoxy resin with a low softening point for carbon fibers, and belongs to the technical field of preparation of halogen-free flame-retardant high polymer materials. According to the material, basic epoxy resin, a reaction type phosphorus-containing flame retardant, 1, 4-naphthoquinone and 1, 4-benzoquinone are used as basic raw materials, a phosphorus-containing diphenol compound is synthesized in a segmented reaction mode and then subjected to chain extension with the basic epoxy resin under the action of a catalyst, finally, novolac epoxy resin is added to adjust the molecular weight, and an epoxy diluent is added to improve the viscosity of a resin system, so that the material is obtained. The low-softening-point phosphorus-containing epoxy resin is obtained. According to the preparation method, the phosphorus content and molecular weight of the product are effectively controlled in a formula design and segmented reaction mode, so that the phosphorus-containing epoxy resin with low softening point and good flame retardance is prepared and can be applied to carbon fiber halogen-free flame-retardant prepreg.

Description

Technical Field

[0001] The present application relates to the technical field of preparation of halogen-free flame-retardant polymer materials, and specifically to a construction strategy and preparation method of a low softening point phosphorus-containing epoxy resin for carbon fiber. Background Art

[0002] Carbon fiber prepreg is a composite material woven from carbon fibers pre-impregnated with organic resin. After curing, it has good durability and mechanical strength and is widely used in aerospace, automotive, electrical and electronic fields. Carbon fiber prepreg often has high requirements for flame retardancy during application, and methods such as adding flame retardants often damage the mechanical properties of composite materials. Therefore, the development of flame retardant epoxy resin for carbon fiber prepreg is particularly important. Since the EU fully implemented the two major directives WEEE (waste electrical and electronic equipment) and RoHS (prohibition of the use of certain hazardous substances in electrical and electronic equipment) in July 2006, flame retardant epoxy resins have developed towards halogen-free and lead-free. At present, halogen-free flame retardant epoxy resins for prepregs often require a large amount of solvents for production, and solvent-free flame retardant epoxy resins often have problems such as processing difficulties in the preparation of prepregs, which greatly limits their application. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a construction strategy and preparation method of a low softening point phosphorus-containing epoxy resin for carbon fiber.

[0004] In order to solve the above technical problems, the technical solution of the present invention is: a low softening point phosphorus-containing epoxy resin for carbon fiber, the innovation of which is to use basic epoxy resin, reactive phosphorus-containing flame retardant, 1,4-naphthoquinone, 1,4-benzoquinone as basic raw materials, synthesize phosphorus-containing diphenol compound by staged reaction, and then complete chain extension with basic epoxy resin under the action of catalyst, and finally adjust molecular weight by adding phenolic epoxy resin and improve viscosity of resin system by epoxy diluent, so as to obtain low softening point phosphorus-containing epoxy resin. The method effectively controls the phosphorus content and molecular weight of the product by formula design and staged reaction, so as to prepare phosphorus-containing epoxy resin with low softening point and good flame retardancy.

[0005] Furthermore, the low softening point phosphorus-containing epoxy resin has a softening point of 55±10° C., an epoxy equivalent of 300±50 g / eq, and a phosphorus content of 2.5±1%.

[0006] A method for preparing a low softening point phosphorus-containing epoxy resin for carbon fiber, the innovation of which is that it comprises the following steps: S1: Add 50-70 parts by mass of a base epoxy resin, 10-20 parts by mass of a reactive phosphorus-containing flame retardant, 2-8 parts by mass of 1,4-naphthoquinone, and 2-8 parts by mass of 1,4-benzoquinone into a reactor, and heat to 80° C. until dissolved and transparent; S2: First-order reaction: heating to 80-90°C and reacting for 2-3 hours; S3: The second-order reaction is heated to 100-120°C and reacted for 2-3 hours; S4: Continue to add 0.02 parts by mass of catalyst into the reactor, raise the temperature to 150-170° C., and react for 3-4 hours; S5: Finally, 5 to 10 parts by weight of phenolic epoxy resin and 5 to 10 parts by weight of epoxy diluent are added into the reactor and stirred evenly to obtain a phosphorus-containing epoxy resin having a softening point of 50±5°C.

[0007] Furthermore, the basic epoxy resin in S1 is: in parts by mass, 20 to 30 parts by mass of bisphenol A epoxy resin and 30 to 40 parts by mass of bisphenol F epoxy resin.

[0008] Furthermore, the reactive phosphorus-containing flame retardant in S1 is one or both of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and diphenylphosphine oxide (DPO).

[0009] Furthermore, the catalyst in S4 is one or two of triphenylphosphine, ethyltriphenylphosphine bromide, ethyltriphenylphosphine acetate, tetraethylammonium bromide, and tetramethylammonium chloride.

[0010] Furthermore, the novolac epoxy resin in S5 is phenol novolac epoxy resin.

[0011] Furthermore, the epoxy diluent in S5 is one or two of alkylene glycidyl ether, butyl glycidyl ether, phenyl glycidyl ether, and benzyl glycidyl ether.

[0012] The advantages of the present invention are as follows: the phosphorus-containing epoxy resin with a low softening point is synthesized into a phosphorus-containing diphenol compound through a staged reaction process, and then reacted with an epoxy resin under the action of a catalyst to generate a phosphorus-containing epoxy resin; the phosphorus content and molecular weight of the product are effectively controlled through simple formula design and staged reaction, thereby preparing a phosphorus-containing epoxy resin with a low softening point, good flame retardancy and easy processing.

[0013] After the carbon fiber prepreg prepared by the product of the present invention is cured with cyanate, when the phosphorus content is as low as 2.5%, the flame retardancy passes the UL94-V0 grade and reaches a limiting oxygen index of 48%, meeting the performance requirements in the fields of aerospace, automobile, electronics and electrical. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The present invention is a flow chart for the preparation of low softening point phosphorus-containing epoxy resin for carbon fiber. DETAILED DESCRIPTION

[0015] The low-softening-point phosphorus-containing epoxy resin for carbon fiber of the present invention uses basic epoxy resin, reactive phosphorus-containing flame retardant, 1,4-naphthoquinone and 1,4-benzoquinone as basic raw materials, synthesizes phosphorus-containing diphenol compound in a staged reaction mode, and then completes chain extension with the basic epoxy resin under the action of a catalyst, and finally adjusts the molecular weight by adding phenolic epoxy resin and improves the viscosity of the resin system by adding epoxy diluent, so as to obtain the low-softening-point phosphorus-containing epoxy resin.

[0016] The method for preparing the above-mentioned low softening point phosphorus-containing epoxy resin for carbon fiber comprises the following steps: S1: Add 50-70 parts by mass of a base epoxy resin, 10-20 parts by mass of a reactive phosphorus-containing flame retardant, 2-8 parts by mass of 1,4-naphthoquinone, and 2-8 parts by mass of 1,4-benzoquinone into a reactor, and heat to 80° C. until dissolved and transparent; S2: First-order reaction: heating to 80-90°C and reacting for 2-3 hours; S3: The second-order reaction is heated to 100-120°C and reacted for 2-3 hours; S4: Continue to add the catalyst to the reactor, raise the temperature to 150-170° C., and react for 3-4 hours; S5: Finally, 10 to 20 parts by weight of phenolic epoxy resin is added into the reactor and stirred to obtain a phosphorus-containing epoxy resin having a softening point of 50±5°C.

[0017] Furthermore, the basic epoxy resin in S1 is: in parts by mass, 20 to 30 parts by mass of bisphenol A epoxy resin and 30 to 40 parts by mass of bisphenol F epoxy resin.

[0018] Furthermore, the reactive phosphorus-containing flame retardant in S1 is one or both of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and diphenylphosphine oxide (DPO).

[0019] Furthermore, the catalyst in S4 is one or two of triphenylphosphine, ethyltriphenylphosphine bromide, ethyltriphenylphosphine acetate, tetraethylammonium bromide, and tetramethylammonium chloride.

[0020] Furthermore, the novolac epoxy resin in S5 is phenol novolac epoxy resin.

[0021] Furthermore, the epoxy diluent in S5 is one or two of alkylene glycidyl ether, butyl glycidyl ether, phenyl glycidyl ether, and benzyl glycidyl ether.

[0022] The prepared low-softening-point phosphorus-containing epoxy resin has a softening point of 55±10°C, an epoxy equivalent of 300±50 g / eq, a phosphorus content of 2.5±1%, and is a yellow-brown transparent solid. Embodiment 1:

[0023] 20 parts by mass of bisphenol A epoxy resin (Shandong Aimonte EMTE128), 40 parts by mass of bisphenol F epoxy resin (Shandong Aimonte EMTE170), 15 parts by mass of DOPO, 5 parts by mass of 1,4-naphthoquinone and 2 parts by mass of 1,4-benzoquinone were added into a reactor, heated to 80°C to dissolve, and then kept warm for reaction for 2 hours; the temperature was continued to be raised to 110°C and kept warm for reaction for 2 hours; 0.02 parts by mass of ethyl triphenylphosphine acetate was added and the temperature was raised to 160°C and kept warm for reaction for 3 hours; finally, 10 parts by mass of phenol novolac epoxy resin (Shandong Aimonte EMTE638S) and 8 parts by mass of phenyl glycidyl ether (TV690) were added and stirred evenly. The obtained low softening point phosphorus-containing epoxy resin had a softening point of 48.3°C, an epoxy equivalent of 312.5 g / eq, a phosphorus content of 2.1%, and was a yellow-brown transparent solid. Embodiment 2:

[0024] 30 parts by mass of bisphenol A epoxy resin (Shandong Aimonte EMTE128), 30 parts by mass of bisphenol F epoxy resin (Shandong Aimonte EMTE170), 12 parts by mass of DOPO, 5 parts by mass of DPO, 5 parts by mass of 1,4-naphthoquinone and 5 parts by mass of 1,4-benzoquinone were added into a reactor, heated to 80°C to dissolve, and then kept warm for reaction for 2 hours; the temperature was continued to be raised to 120°C and kept warm for reaction for 2 hours; 0.02 parts by mass of ethyl triphenylphosphine bromide was added and the temperature was raised to 165°C and kept warm for reaction for 3 hours; finally, 8 parts by mass of phenol novolac epoxy resin (Shandong Aimonte EMTE638) and 5 parts by mass of phenyl glycidyl ether (TV690) were added and stirred evenly. The obtained low softening point phosphorus-containing epoxy resin had a softening point of 53.8°C, an epoxy equivalent of 324.7 g / eq, a phosphorus content of 2.5%, and was a yellow-brown transparent solid. Embodiment 3:

[0025] The carbon fiber prepreg is prepared using a low-softening point phosphorus-containing epoxy resin. The prepreg contains 30 parts by mass of a low-softening point phosphorus-containing epoxy resin. After being cured with cyanate ester, it has good durability and mechanical strength. Its flame retardancy passes the UL94-V0 grade and reaches a limiting oxygen index of 48%, meeting its performance requirements in the fields of aerospace, automobiles, electronics and electrical.

[0026] Finally, it should be noted that the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may be subject to various changes and improvements, and these changes and improvements shall all fall within the scope of the present invention claimed for protection.

Claims

1. A low softening point phosphorus-containing epoxy resin for carbon fiber, characterized in that: The phosphorus-containing epoxy resin is based on a basic epoxy resin, a reactive phosphorus-containing flame retardant, 1,4-naphthoquinone and 1,4-benzoquinone. The phosphorus-containing diphenol compound is synthesized by a staged reaction, and then the chain is extended with the basic epoxy resin under the action of a catalyst. Finally, a phenolic epoxy resin is added to adjust the molecular weight and an epoxy diluent is added to improve the viscosity of the resin system to obtain a phosphorus-containing epoxy resin with a low softening point.

2. The low softening point phosphorus-containing epoxy resin for carbon fiber according to claim 1, characterized in that: The phosphorus-containing epoxy resin has a softening point of 55±10° C., an epoxy equivalent of 300±50 g / eq, and a phosphorus content of 2.5±1%.

3. A method for preparing a low softening point phosphorus-containing epoxy resin for carbon fiber, characterized in that: The following steps are involved: S1: Add 50-70 parts by mass of a base epoxy resin, 10-20 parts by mass of a reactive phosphorus-containing flame retardant, 2-8 parts by mass of 1,4-naphthoquinone, and 2-8 parts by mass of 1,4-benzoquinone into a reactor, and heat to 80° C. until dissolved and transparent; S2: First-order reaction: heating to 80-90°C and reacting for 2-3 hours; S3: The second-order reaction is heated to 100-120°C and reacted for 2-3 hours; S4: Continue to add 0.02 parts by mass of catalyst into the reactor, raise the temperature to 150-170° C., and react for 3-4 hours; S5: Finally, 5 to 10 parts by weight of phenolic epoxy resin and 5 to 10 parts by weight of epoxy diluent are added into the reactor and stirred evenly to obtain a phosphorus-containing epoxy resin having a softening point of 55±10°C.

4. The method for preparing a low softening point phosphorus-containing epoxy resin for carbon fiber according to claim 3, characterized in that: The basic epoxy resin in S1 is: 20 to 30 parts by mass of bisphenol A epoxy resin and 30 to 40 parts by mass of bisphenol F epoxy resin.

5. The method for preparing a low softening point phosphorus-containing epoxy resin for carbon fiber according to claim 3, characterized in that: The reactive phosphorus-containing flame retardant in S1 is one or two of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and diphenylphosphine oxide (DPO).

6. The method for preparing a low softening point phosphorus-containing epoxy resin for carbon fiber according to claim 3, characterized in that: The catalyst in S4 is one or two of triphenylphosphine, ethyltriphenylphosphine bromide, ethyltriphenylphosphine acetate, tetraethylammonium bromide and tetramethylammonium chloride.

7. The method for preparing a low softening point phosphorus-containing epoxy resin for carbon fiber according to claim 3, characterized in that: The novolac epoxy resin in S5 is phenol novolac epoxy resin.

8. The method for preparing a low softening point phosphorus-containing epoxy resin for carbon fiber according to claim 3, characterized in that: The epoxy diluent in S5 is one or two of alkylene glycidyl ether, butyl glycidyl ether, phenyl glycidyl ether and benzyl glycidyl ether.

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