1. The corrosion-resistant lignin epoxy resin/carbon fiber composite material is obtained by crosslinking and curing modified lignin epoxy resin and carbon fibers, and the modified lignin epoxy resin is prepared from the following raw materials: the composite material comprises enzymatic hydrolysis lignin, dihydric alcohol, hyperbranched polyol, aliphatic dibasic acid and/or dibasic acid anhydride, fluorine-containing aromatic dibasic acid/acid anhydride, an epoxy diluent and an epoxy-containing silane coupling agent.

2. The lignin epoxy resin/carbon fiber composite material according to claim 1, characterized by comprising the following raw materials in parts by mass: 20-30 parts of modified lignin epoxy resin, 40-60 parts of carbon fiber material, 8-15 parts of curing agent and 0.1-0.3 part of curing accelerator.

3. The lignin epoxy resin/carbon fiber composite material according to claim 2, wherein the curing agent is an anhydride curing agent, specifically selected from at least one of tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, phthalic anhydride, and maleic anhydride; the accelerator is an amine accelerator, and is specifically selected from at least one of N, N-dimethylformamide, N-dimethylacetamide, N-dimethylaniline and N, N-dimethylbenzylamine; the carbon fiber material is selected from carbon fiber cloth, carbon fiber yarn or carbon fiber felt.

4. The lignin epoxy resin/carbon fiber composite material according to claim 1, wherein the modified lignin epoxy resin comprises the following raw materials in parts by mass: 100 parts of enzymatic hydrolysis lignin, 80-120 parts of dihydric alcohol, 5-10 parts of hyperbranched polyol, 100-140 parts of aliphatic dibasic acid/anhydride, 20-30 parts of fluorine-containing aromatic dibasic acid/anhydride, 300-500 parts of epoxy diluent and 15-30 parts of epoxy silane-containing coupling agent.

5. The lignin epoxy/carbon fiber composite according to claim 1, wherein the epoxy-containing silane coupling agent is selected from at least one of 3-glycidoxypropyltrimethoxysilane and 3-glycidoxypropyltriethoxysilane.

6. The lignin epoxy resin/carbon fiber composite material according to claim 1, wherein the hyperbranched polyol is a hyperbranched polyether polyol and/or a hyperbranched polyester polyol, preferably a hyperbranched polyester polyol, having a molecular weight of 1000-3000 and a hydroxyl value of 400-700mg KOH/g.

7. The lignin epoxy/carbon fiber composite according to claim 1, wherein the glycol is selected from at least one of ethylene glycol, propylene glycol, butylene glycol, pentylene glycol, hexylene glycol, 3-methyl-1, 5-pentylene glycol, cyclohexanediol; and/or

The aliphatic dibasic acid/anhydride is at least one selected from oxalic acid, malonic acid and glutaric anhydride; and/or

The fluorine aromatic dibasic acid/anhydride is at least one selected from tetrafluorophthalic anhydride, tetrafluorophthalic acid and tetrafluoroterephthalic acid; and/or

The epoxy diluent is at least one selected from ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1, 4-butanediol diglycidyl ether, neopentyl glycol diglycidyl ether and 1, 6-hexanediol diglycidyl ether.

8. The lignin epoxy/carbon fiber composite material according to any one of claims 1 to 7, wherein the lignin epoxy is prepared by a preparation method comprising the following steps:

(S1) adding dihydric alcohol into a reaction container according to the proportion, adding hyperbranched polyol, aliphatic dibasic acid/anhydride, fluorine-containing aromatic dibasic acid/anhydride and enzymatic hydrolysis lignin into the reaction container under the stirring condition, and reacting for 2-4 hours at 90-130 ℃ by taking a sulfuric acid aqueous solution as a catalyst until the enzymatic hydrolysis lignin is completely dissolved;

(S2) continuing to add an epoxy diluent and an epoxy-containing silane coupling agent into the reaction container, and reacting for 2-4 hours at 70-100 ℃ to obtain the lignin epoxy resin.

9. The method for preparing the lignin epoxy resin/carbon fiber composite material according to claim 8, comprising the steps of:

(T1) uniformly mixing the lignin epoxy resin, the accelerator and the curing agent according to the proportion;

(T2) uniformly coating the prepared lignin epoxy resin mixture on a carbon fiber material;

(T3) putting the carbon fiber material uniformly coated with the epoxy resin into an oven, and curing at the temperature of 110-150 ℃ for 2-6 hours to finish curing to obtain the reinforced composite material.

10. Use of the lignin epoxy/carbon fiber composite material according to any one of claims 1 to 9 for structural reinforcement of aerospace, industrial equipment, transportation means, pressure vessels, fan blades, medical devices, sporting goods, in particular for materials that are in contact with aqueous media for a long time, such as marine vessels, marine engineering equipment, etc.

Background

The carbon fiber/epoxy resin composite material has the advantages of light specific gravity and high specific strength, can reduce the structural weight and the cost in many fields, and is widely applied to the fields of medical appliances, traffic, energy, buildings and the like. The applicant's prior patent CN201910258445.2, CN201910446281.6, discloses a lignin epoxy/carbon fiber reinforced composite. Compared with the conventional epoxy resin, the lignin epoxy resin and carbon fiber composite material has the advantages that the same strength can be achieved under the condition of extremely low carbon fiber using amount, the use of expensive carbon fiber materials is saved, the cost is reduced, the epoxy resin/carbon fiber composite material is made to be practical, and the basis is established in marketization.

In a carbon fiber/epoxy resin composite material system, a reinforcement such as carbon fiber has very high corrosion resistance, and in contrast, the corrosion resistance of the epoxy resin used as a matrix is unsatisfactory; in a humid environment, corrosive media such as water and the like can slowly permeate and diffuse into the epoxy resin, so that the epoxy resin is corroded to cause structural damage, the performance of the whole composite material is greatly reduced, and great potential safety hazards are formed. Therefore, researches on further improving the corrosion resistance of the epoxy resin are very significant for prolonging the service life of the epoxy resin and the composite material thereof.

Thangzhou et al (research on acid and alkali resistance of a siloxane-terminated oligomer/epoxy resin composite system, Material engineering, 7. 2005) found that the acid and alkali resistance of the cured epoxy resin was improved by blending the epoxy resin with trimethylolpropane, polycaprolactone triol and a silane coupling agent containing isocyanate after the reaction. But the document only evaluates the acid and alkali resistance by the rate of mass reduction in the acid and alkali. The applicant finds out through practical tests that according to the method disclosed by the document, although the system quality is not changed greatly after the acid-base soaking, the mechanical strength is reduced obviously in practice. The reason for this is probably that the acid and alkali destroy the internal molecular structure of the epoxy resin, but due to crosslinking or intermolecular forces, the destroyed structural units do not fall off from the epoxy resin bulk material, so the corrosion resistance of the composite material cannot be truly reflected by the use mass change rate.

Therefore, the development of epoxy resin composite materials with beneficial corrosion resistance, particularly epoxy resin/carbon fiber composite materials, has important significance and industrial value.

Disclosure of Invention

In order to overcome the defect that the corrosion resistance of the lignin epoxy resin/carbon fiber composite material is unsatisfactory, the invention provides the corrosion-resistant lignin epoxy resin/carbon fiber composite material and a preparation method thereof.

In order to solve the technical problems, the invention provides the following technical scheme:

the first purpose of the invention is to provide a corrosion-resistant lignin epoxy resin/carbon fiber composite material, which is obtained by crosslinking and curing modified lignin epoxy resin and carbon fiber, wherein the modified lignin epoxy resin is prepared from the following raw materials: the composite material comprises enzymatic hydrolysis lignin, dihydric alcohol, hyperbranched polyol, aliphatic dibasic acid and/or dibasic acid anhydride, fluorine-containing aromatic dibasic acid/acid anhydride, an epoxy diluent and an epoxy-containing silane coupling agent.

Further, the corrosion-resistant lignin epoxy resin/carbon fiber composite material comprises the following raw materials in parts by mass: 20-30 parts of modified lignin epoxy resin, 40-60 parts of carbon fiber material, 8-15 parts of curing agent and 0.1-0.3 part of curing accelerator.

The curing agent is an anhydride curing agent, and is specifically selected from at least one of tetrahydrophthalic anhydride, methyl tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyl hexahydrophthalic anhydride, phthalic anhydride and maleic anhydride; the accelerator is an amine accelerator, and is specifically selected from at least one of N, N-dimethylformamide, N-dimethylacetamide, N-dimethylaniline and N, N-dimethylbenzylamine; the carbon fiber material is selected from carbon fiber cloth, carbon fiber yarn or carbon fiber felt.

Further, the modified lignin epoxy resin comprises the following raw materials in parts by mass: 100 parts of enzymatic hydrolysis lignin, 80-120 parts of dihydric alcohol, 5-10 parts of hyperbranched polyol, 100-140 parts of aliphatic dibasic acid/anhydride, 20-30 parts of fluorine-containing aromatic dibasic acid/anhydride, 300-500 parts of epoxy diluent and 15-30 parts of epoxy silane-containing coupling agent.

Further, the epoxy-containing silane coupling agent is selected from at least one of 3-glycidoxypropyltrimethoxysilane and 3-glycidoxypropyltriethoxysilane.

Further, the hyperbranched polyol is hyperbranched polyether polyol and/or hyperbranched polyester polyol, preferably hyperbranched polyester polyol, the molecular weight of which is 3000-. Hyperbranched polyester polyols can be made by themselves, for example by polycondensation of polyols (such as trimethylolpropane, pentaerythritol, castor oil) and polyacids/anhydrides (such as phthalic acid, adipic acid, phthalic anhydride, 2-dimethylolpropionic acid); also commercially available, such as Boltorn H20, Boltorn H2004, Boltorn P500.

The dihydric alcohol is at least one selected from ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, 3-methyl-1, 5-pentanediol and cyclohexanediol; the aliphatic dibasic acid/anhydride is at least one selected from oxalic acid, malonic acid and glutaric anhydride.

The fluorine aromatic dibasic acid/anhydride is at least one selected from tetrafluorophthalic anhydride, tetrafluorophthalic acid and tetrafluoroterephthalic acid.

The epoxy diluent is at least one selected from ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1, 4-butanediol diglycidyl ether, neopentyl glycol diglycidyl ether and 1, 6-hexanediol diglycidyl ether.

The lignin epoxy resin is prepared by the preparation method comprising the following steps:

(S1) adding dihydric alcohol into a reaction container according to the proportion, adding hyperbranched polyol, aliphatic dibasic acid/anhydride, fluorine-containing aromatic dibasic acid/anhydride and enzymatic hydrolysis lignin into the reaction container under the stirring condition, and reacting for 2-4 hours at 90-130 ℃ by taking a sulfuric acid aqueous solution as a catalyst until the enzymatic hydrolysis lignin is completely dissolved;

(S2) continuing to add an epoxy diluent and an epoxy-containing silane coupling agent into the reaction container, and reacting for 2-4 hours at 70-100 ℃ to obtain the lignin epoxy resin.

The invention also provides a preparation method of the corrosion-resistant lignin epoxy resin/carbon fiber composite material, which comprises the following steps:

(T1) uniformly mixing the lignin epoxy resin, the accelerator and the curing agent according to the proportion;

(T2) uniformly coating the prepared lignin epoxy resin mixture on a carbon fiber material;

(T3) putting the carbon fiber material uniformly coated with the epoxy resin into an oven, and curing at the temperature of 110-150 ℃ for 2-6 hours to finish curing to obtain the reinforced composite material.

The invention also provides application of the corrosion-resistant lignin epoxy resin/carbon fiber composite material, which is used for structural reinforcement materials of aerospace, industrial equipment, transportation tools, pressure vessels, fan blades, medical instruments and sports goods, in particular to materials which are in contact with aqueous media for a long time, such as marine ships, offshore engineering equipment and the like.

Detailed Description

The technical solution of the present invention is further explained with reference to the following embodiments, but it should be noted that the embodiments are only an embodiment and explanation of the technical solution of the present invention, and should not be construed as a limitation to the scope of the present invention.

The reagents and instruments used in the examples are commercially available and the detection methods are conventional methods well known in the art.

The lignin used in the invention is enzymatic lignin, which is obtained by separating and extracting the lignocellulose raw materials such as straws and the like after the enzymolysis of cellulase, and the lignin is not treated by alkaline acid in the preparation process, so that the ash content in the enzymatic lignin is low, and the chemical activity and the molecular structure of the enzymatic lignin are well reserved. The extraction of the enzymatic hydrolysis lignin can be made by referring to the method of the inventor in the previous patent ZL201710091949, and specifically, the enzymatic hydrolysis lignin is prepared by crushing crop straws (such as corn straws), pretreating, performing solid-liquid separation (such as filtration and centrifugal separation) after enzymolysis by using compound cellulase, washing and drying, wherein the content of lignin in the enzymatic hydrolysis lignin is more than 85 wt%.

Determination of epoxy value of lignin epoxy resin: the acid acetone method, which is well known in the art, is used; the viscosity measurement adopts the Shanghai Square Stomer viscometer for testing, and the test conditions are as follows: at 25 ℃.

Preparation examplePreparation of modified lignin epoxy resin

Preparation example 1

(S1) adding 90 parts of ethylene glycol into a reaction container, adding 8 parts of Boltorn P500, 110 parts of glutaric anhydride, 20 parts of tetrafluorophthalic anhydride and 100 parts of enzymatic lignin, adding into the reaction container under the stirring condition, reacting for 4 hours at 130 ℃ by taking 60 wt% sulfuric acid aqueous solution as a catalyst until the enzymatic lignin is completely dissolved;

(S2) continuously adding 400 parts of ethylene glycol diglycidyl ether and 20 parts of KH-560 into a reaction vessel, reacting for 3 hours at 80 ℃, and cooling to room temperature to obtain the modified lignin epoxy resin 1 with viscosity of 12500cps and epoxy value of 0.41.

Preparation example 2

(S1) adding 120 parts of butanediol into a reaction container, adding 5 parts of Boltorn P500, 140 parts of oxalic acid, 30 parts of tetrafluoroterephthalic acid and 100 parts of enzymatic lignin, adding into the reaction container under the stirring condition, reacting for 4 hours at 120 ℃ by taking a 60 wt% sulfuric acid aqueous solution as a catalyst until the enzymatic lignin is completely dissolved;

(S2) continuously adding 460 parts of ethylene glycol diglycidyl ether and 30 parts of KH-560 into a reaction vessel, reacting for 3 hours at 80 ℃, and cooling to room temperature to obtain the modified lignin epoxy resin 2 with viscosity of 11700cps and epoxy value of 0.42.

Preparation example 3

(S1) adding 80 parts of cyclohexanediol into a reaction container, then adding 10 parts of Boltorn P500, 100 parts of oxalic acid, 30 parts of tetrafluoroterephthalic acid and 100 parts of enzymatic lignin, adding into the reaction container under the stirring condition, taking a 60 wt% sulfuric acid aqueous solution as a catalyst, and reacting for 4 hours at 120 ℃ until the enzymatic lignin is completely dissolved;

(S2) adding 550 parts of propylene glycol diglycidyl ether and 15 parts of KH-560 into the reaction vessel, and reacting at 80 ℃ for 3 hours to obtain the modified lignin epoxy resin 3 with viscosity of 13200cps and epoxy value of 0.42.

Preparation example 4

The other conditions and procedures were the same as in preparation example 1 except that 3 parts of Boltorn P500 was added, and the resulting modified lignin epoxy resin 4 had a viscosity of 10300cps and an epoxy value of 0.42.

Preparation example 5

The other conditions and procedure were the same as in preparation example 1 except that 15 parts of Boltorn P500 was added, and the resulting modified lignin epoxy resin 5 had a viscosity of 16300cps and an epoxy value of 0.42.

Preparation example 6

The other conditions and procedure were the same as in preparation example 1 except that the amount of tetrafluorophthalic anhydride added was 15 parts, and the resulting modified lignin epoxy resin 6 had a viscosity of 12600cps and an epoxy value of 0.43.

Preparation example 7

The other conditions and procedure were the same as in preparation example 1 except that the amount of tetrafluorophthalic anhydride added was 40 parts, and the resulting modified lignin epoxy resin 7 had a viscosity of 11800cps and an epoxy value of 0.40.

Preparation example 8

The other conditions and procedures were the same as in preparation example 1 except that 10 parts of KH-560 was added, and the resulting modified lignin epoxy resin 8 had a viscosity of 12600cps and an epoxy value of 0.42.

Preparation example 9

The other conditions and procedures were the same as in preparation example 1 except that the amount of KH-560 added was 40 parts, and the resulting modified lignin epoxy resin 9 had a viscosity of 14200cps and an epoxy value of 0.42.

Comparative preparation example 1

The other conditions and procedures were the same as in preparation example 1 except that no hyperbranched polyol Boltorn P500 was added, to obtain a modified lignin epoxy resin A having a viscosity of 8400cps and an epoxy value of 0.43.

Comparative preparation example 2

The other conditions and procedure were the same as in preparation example 1 except that tetrafluorophthalic anhydride was not added and the amount of glutaric anhydride was changed to 140 parts, to obtain modified lignin epoxy resin B having viscosity 12100cps and epoxy value of 0.41.

Comparative preparation example 3

The other conditions and procedures were the same as in preparation example 1 except that KH-560 was not added, to obtain modified lignin epoxy resin C having a viscosity of 10200cps and an epoxy value of 0.43.

ExamplesPreparation of lignin epoxy resin/carbon fiber composite material

Examples 1 to 9

Respectively heating and melting 24 parts of the lignin epoxy resin prepared in preparation examples 1-9, adding 10 parts of phthalic anhydride curing agent and 0.15 part of gN, N-dimethylformamide accelerator, melting at 90 ℃, mixing and blending; the prepared lignin epoxy resin is uniformly coated on each layer of carbon fiber cloth (16cm multiplied by 16cm), and the total number of the carbon fiber cloth is 12 (the mass of the carbon fiber cloth is about 50 parts). And (3) covering the carbon fiber cloth coated with the lignin epoxy resin with tin foil paper from top to bottom, putting the carbon fiber cloth into a hot press for compression molding, and setting the temperature at 100 ℃ for 1h and pressurizing at 0.6MPa +135 ℃ for 3h and pressurizing at 1MPa to complete curing.

Comparative examples 1 to 3

The other conditions and procedures were the same as in example 1 except that the lignin epoxy resin 1 obtained in production example 1 was replaced with modified lignin epoxy resins A to C obtained in comparative production examples 1 to 3, respectively.

Application example

The carbon fiber plate plates cured in the above examples and comparative examples were taken out, and the outer layer of the tinfoil paper was peeled off. Preparation of three-point bending test specimen: and respectively sawing the two carbon fiber plates into 5 test sample strips with the thickness of 12.7 multiplied by 2.0mm for mechanical property experiments. And (3) carrying out three-point bending test on the breaking load (unit: N) by using a universal tester WSN-5K according to a GB/T1449 method, and taking an average value of 5 times of test results.

The corrosion resistance is expressed in terms of the failure load retention, specifically the acid resistance test: same batch of test bars at 5% H₂SO₄Taking out after soaking for 15 days, washing with water, drying, and testing the breaking load according to the test method, wherein the breaking load retention rate is expressed; alkali resistance test: soaking the same batch of test sample strips in 5% NaOH for 15 days, taking out, washing with water, drying, and testing the breaking load according to the test method, wherein the breaking load retention rate is expressed; and (3) testing salt resistance: soaking the same batch of test sample strips in 15% NaCl at 60 deg.C for 15 days, taking out, washing with water, and oven dryingThe failure load was then tested according to the test method described above and expressed as failure load retention.

Breaking load retention rate (breaking load after immersion in corrosive liquid (acid, alkali, salt)/breaking load before immersion in corrosive liquid

The results are shown in table 1 below:

TABLE 1

	Breaking load (N)	Acid resistance (%)	Alkali resistance (%)	Salt tolerance (%)
					Example 1	3348	99.4	98.7	99.6
Example 2	3287	98.5	97.7	99.1
					Example 3	3360	98.2	97.9	99.2
Example 4	3154	95.7	96.4	98.5
					Example 5	3425	99.8	98.6	99.1
Example 6	3381	98.3	97.1	98.8
					Example 7	2862	99.5	98.2	99.6
Example 8	3362	96.5	96.5	97.4
					Example 9	3248	98.4	98.4	99.3
Comparative example 1	2884	95.8	94.5	98.4
					Comparative example 2	3277	95.6	95.0	97.2
Comparative example 3	3165	94.6	96.1	97.5

The data in table 1 show that the modified epoxy resin of the invention is added with the components of hyperbranched polyol, fluorine-containing aromatic dibasic acid/anhydride and epoxy-containing silane coupling agent, and the three components generate a synergistic compounding effect, and can significantly improve the corrosion resistance of the cured epoxy resin and carbon fiber composite material by matching with each other, thereby ensuring the use of the material in special environments.