阅读说明：本技术 一种星型聚酯改性木质素环氧树脂及其碳纤维复合预浸料 (Star-shaped polyester modified lignin epoxy resin and carbon fiber composite prepreg thereof ) 是由 方品文 王燚 郭宏 于 2020-07-01 设计创作，主要内容包括：本发明提供了一种星型聚酯改性木质素环氧树脂,包括以下原料：三元以上的多元醇,内酯,二元醇,二元酸酐,酶解木质素,环氧稀释剂,有机金属催化剂,硫酸水溶液催化剂。本发明还提供了一种包括星型聚酯改性木质素环氧树脂为原料的木质素环氧树脂/碳纤维预浸料。本发明制得的星型聚酯改性的木质素环氧树脂,韧性显著增强,同时黏度减小,有利于和碳纤维复合材料的浸润性,增强了复合材料的界面强度。所得预浸料耐候性优异,固化后在各种紫外,高温,冷冻模拟老化环境下,各项力学性能的保持率高,保证了在各种苛刻环境下使用的稳定性和安全性。(The invention provides star polyester modified lignin epoxy resin which comprises the following raw materials: more than three-component polyhydric alcohol, lactone, dihydric alcohol, dibasic acid anhydride, enzymatic hydrolysis lignin, epoxy diluent, organic metal catalyst and sulfuric acid aqueous solution catalyst. The invention also provides a lignin epoxy resin/carbon fiber prepreg which takes the star-shaped polyester modified lignin epoxy resin as a raw material. The star polyester modified lignin epoxy resin prepared by the invention has the advantages of obviously enhanced toughness, reduced viscosity, contribution to wettability with carbon fiber composite materials and enhanced interface strength of the composite materials. The obtained prepreg has excellent weather resistance, and has high retention rate of various mechanical properties in various ultraviolet, high-temperature and freezing simulated aging environments after curing, thereby ensuring the stability and safety of use in various harsh environments.)

1. A star-shaped polyester modified lignin epoxy resin comprises the following raw materials: more than three-component polyhydric alcohol, lactone, dihydric alcohol, dibasic acid anhydride, enzymatic hydrolysis lignin, epoxy diluent, organic metal catalyst and sulfuric acid aqueous solution catalyst; wherein, the polyhydric alcohol with more than three elements and the lactone react in the presence of an organotin catalyst to obtain a star polymer with the polyester as a branched chain, and then the star polymer reacts with other materials in the presence of a sulfuric acid catalyst to obtain the star polyester modified lignin epoxy resin.

2. The lignin epoxy resin according to claim 1, comprising the following raw materials in parts by weight: 1-1.5 parts of polyhydric alcohol, 5-8 parts of lactone, 20-30 parts of dihydric alcohol, 30-50 parts of dibasic acid anhydride, 80-120 parts of epoxy diluent, 10-20 parts of enzymatic hydrolysis lignin, 0.01-0.02 part of organic metal catalyst and 1-3 parts of sulfuric acid aqueous solution catalyst.

3. The lignin epoxy resin according to claim 1, wherein the ternary or higher polyol is a combination of an aliphatic polyol and a urea-containing polyol, and preferably, the mass ratio of the aliphatic polyol to the urea-containing polyol is 5-8: 1-2.

4. The lignin epoxy resin according to claim 3, wherein the aliphatic polyol is at least one of glycerol, pentaerythritol, sorbitol, trimethylolpropane, mannitol; the polyol containing urea groups is one or a combination of two of tri (2-hydroxyethyl) isocyanurate and tetramethylol glycoluril.

5. The lignin epoxy resin according to claim 3, wherein the trihydric or higher polyol is selected from pentaerythritol, sorbitol and tetramethylolglycoluril in a mass ratio of 2-3:3-5: 1-2.

6. The lignin epoxy resin according to claim 1, wherein the lactone is selected from lactones with 5-10 carbon atoms, in particular at least one of valerolactone, caprolactone and octalactone;

in the organic metal catalyst, the metal is at least one of Zn, Sn and Al, and the organic group is organic acid and organic alcohol;

the dihydric alcohol is at least one of ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol and cyclohexanediol;

the binary anhydride is at least one of maleic anhydride, phthalic anhydride, maleic anhydride and glutaric anhydride;

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 sulfuric acid catalyst is a sulfuric acid aqueous solution with the mass concentration of 40-70%.

7. The preparation method of the star-shaped polyester modified lignin epoxy resin as claimed in any one of claims 1 to 6, comprising the following steps:

(S1) adding the star polymer of the polyester branched chain, dihydric alcohol, dibasic acid anhydride and enzymatic hydrolysis lignin according to the proportion, and reacting under the stirring condition by taking a sulfuric acid aqueous solution as a catalyst until the enzymatic hydrolysis lignin is completely dissolved;

(S2) adding an epoxy diluent, and continuing to react to obtain the star-shaped polyester modified lignin epoxy resin.

8. A lignin epoxy resin/carbon fiber prepreg comprises the following raw materials in parts by weight: 20-30 parts of bisphenol A epoxy resin, 12-18 parts of star-shaped polyester modified lignin epoxy resin as described in any one of claims 1-6, 40-70 parts of carbon fiber, 1-2 parts of latent curing agent and 0.4-0.7 part of accelerator.

9. The lignin epoxy/carbon fiber prepreg according to claim 8, wherein the bisphenol a type epoxy resin is selected from at least one of E20, E36, E41;

the latent curing agent is at least one selected from dicyandiamide, methyl tetrahydrophthalic anhydride, benzoyl hydrazine and adipic dihydrazide;

the accelerator is an imidazole accelerator, preferably a cyanuric acid modified imidazole accelerator, and is specifically selected from imidazole cyanurate, 2-methylimidazole cyanurate, 2-ethyl cyanurate, and 2-phenylimidazole cyanurate.

10. A method of making a lignin epoxy/carbon fiber prepreg according to claim 8 or 9, comprising the steps of:

(M1) heating and melting the star polyester modified lignin epoxy resin, adding the bisphenol A epoxy resin, the latent curing agent and the accelerator according to the proportion, and melting at 90-120 ℃;

(M2) adding the molten mixed resin into a glue groove of a hot-melt glue spreader, cooling and rolling to obtain a glue film;

(M3) placing the prepared adhesive film in a compound machine, synchronously feeding the carbon fiber yarns and the adhesive film into a compound roller of the compound machine, heating for compounding, cooling and rolling to obtain the carbon fiber resin prepreg.

Technical Field

The invention belongs to the field of composite materials, and particularly relates to star-shaped polyester modified lignin epoxy resin and a carbon fiber composite prepreg thereof.

Background

Carbon fiber reinforced composite materials are widely used in modern industries, such as aerospace, automotive, marine heavy industry, and deep sea oil fields, due to their high strength, high rigidity, and light weight. With the progress of global science and technology and production technology and the expansion of application fields, the requirements on material performance are higher and higher, and carbon fiber prepregs using carbon fibers as main reinforcing materials become research hotspots in the reinforcing field of composite materials at present.

Prepreg is commonly called as molding compound, is a combination body made by impregnating fiber and fabric thereof under the condition of strictly controlling resin, and is a sheet-shaped laminated material made by impregnating matrix resin in carbon fiber, which is a product prepared by corresponding laminating mode and process of fiber and resin before the curing state is achieved. The prepreg and the fiber reinforced composite material are combined better to embody the advantages of the fiber reinforced composite material. The performance of the prepreg directly affects the performance of the composite material, so that the carbon fiber prepreg is required to have good performance advantages such as toughness and modulus besides good bonding performance. For the design of composite materials, the prepreg is a structural unit with certain mechanical properties, and can be structurally designed. As a representative thermosetting resin, epoxy resin is widely used as a matrix material for preparing carbon fiber prepreg in the prior art due to its excellent mechanical properties, dielectric properties, corrosion resistance, adhesiveness, wettability, low curing shrinkage and moderate price. However, the thermosetting epoxy resin system has a certain defect, and generally, the thermosetting epoxy resin has low toughness, and internal defects such as fracture lines, silver lines and the like exist after curing according to the material fracture theory. Therefore, the epoxy resin is toughened and modified, and the toughening method in the prior art comprises the steps of toughening thermoplastic resin, toughening inorganic nano particles and toughening rubber. However, these methods belong to the methods of adding toughening agents, whether inorganic substances, nanoparticles or polymers, theoretically belong to the methods of physically modifying and toughening. Although this toughening method can increase the toughness of the material to some extent, the compatibility of the material is not good. The retention of the respective properties with time is not high, and particularly, mechanical properties relating to toughness are not high, and stress is generated in a certain place in long-term use, and such defects are gradually diffused into the entire material with time, resulting in deterioration of the properties of the material.

The inventor previously applied for a method for synthesizing lignin epoxy resin by using enzymatic hydrolysis lignin, application number is 201910258445.2, and biological epoxy resin is obtained by condensation reaction by using enzymatic hydrolysis lignin, polyhydric alcohol, diacid anhydride and epoxy diluent as raw materials. The biological epoxy resin synthesized by the method is combined with the carbon fiber material, and the strength of the obtained composite material is higher than that of the common bisphenol A epoxy resin/carbon fiber composite material. However, the obtained lignin epoxy resin/carbon fiber is suitable for winding processes, such as cylindrical products of pipelines, gas cylinders and the like, the application field is limited, the application field of the lignin epoxy resin needs to be further expanded, and the lignin epoxy resin has high viscosity, insufficient wettability of the carbon fiber and inconvenient processing.

Disclosure of Invention

The method aims to solve the problem that the cost is high due to high carbon fiber consumption of an epoxy resin/carbon fiber prepreg material in the prior art; the interface bonding property of the resin and the carbon fiber is poor, so that the performance of the resin is influenced even a certain potential safety hazard is caused after long-term use. The invention provides a star-shaped polyester modified lignin epoxy resin prepreg, the mechanical strength of a composite material obtained by combining the prepreg resin and a carbon fiber material is higher than that of a common hot-melt prepreg resin composite material, the mechanical property retention rate is high over time, the long service life and the stability of the composite material are shown, the comprehensive performance is excellent, the cost of the carbon fiber composite material is reduced, the raw materials are more environment-friendly, and the star-shaped polyester modified lignin epoxy resin prepreg is suitable for industrial production and commercial popularization.

The invention provides a star polyester modified lignin epoxy resin, which comprises the following raw materials: more than three-component polyhydric alcohol, lactone, dihydric alcohol, dibasic acid anhydride, enzymatic hydrolysis lignin, epoxy diluent, organic metal catalyst and sulfuric acid aqueous solution catalyst; wherein, the polyhydric alcohol with more than three elements and the lactone react in the presence of an organotin catalyst to obtain a star polymer with the polyester as a branched chain, and then the star polymer reacts with other materials in the presence of a sulfuric acid catalyst to obtain the star polyester modified lignin epoxy resin.

Further, the star polyester modified lignin epoxy resin comprises the following raw materials in parts by weight: 1-1.5 parts of polyhydric alcohol, 5-8 parts of lactone, 20-30 parts of dihydric alcohol, 30-50 parts of dibasic acid anhydride, 80-120 parts of epoxy diluent, 10-20 parts of enzymatic hydrolysis lignin, 0.01-0.02 part of organic metal catalyst and 1-3 parts of sulfuric acid aqueous solution catalyst.

The trihydric or higher polyhydric alcohol refers to an organic compound having three or more alcoholic hydroxyl groups. Preferably, the aliphatic polyol and the urea-containing polyol are compounded. The aliphatic polyhydric alcohol is glycerol, pentaerythritol, sorbitol, trimethylolpropane and mannitol; the urea group-containing polyol is at least one selected from tris (2-hydroxyethyl) isocyanurate and tetramethylol glycoluril.

Preferably, the mass ratio of the aliphatic polyol to the urea-containing polyol is 5-8: 1-2.

In a more preferable technical scheme of the invention, the polyhydric alcohol with more than three elements is selected from pentaerythritol, sorbitol and tetramethylolglycoluril according to the mass ratio of 2-3:3-5: 1-2.

The lactone is selected from lactone with carbon atom of 5-10, specifically at least one of valerolactone, caprolactone and octalactone, preferably caprolactone.

In the organometallic catalyst, the metal is at least one of Zn, Sn and Al, and the organic group is organic acid and organic alcohol. Such as aluminum isopropoxide, stannous trifluoromethanesulfonate, stannous octoate, stannous laurate, preferably stannous octoate.

The dihydric alcohol is selected from aliphatic dihydric alcohol, specifically selected from ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, and cyclohexanediol. The position of the hydroxyl group is not particularly limited, and the hydroxyl group of the diol is generally in two stages of the molecule, such as 1, 3-propanediol, but may be in other positions, such as 1, 2-propanediol, 1, 3-butanediol.

The binary anhydride is at least one of maleic anhydride, phthalic anhydride, maleic anhydride and glutaric anhydride.

The enzymatic hydrolysis lignin is a product obtained by carrying out enzymatic hydrolysis separation on lignocellulose raw materials such as straws and the like by using cellulase. The ash content is low without acid and alkali treatment, and the chemical activity and the molecular structure are well reserved. In particular, the lignin-rich corn stalk cellulose is prepared by crushing crop stalks (such as corn stalks), pretreating, performing enzymolysis by using composite cellulase, performing solid-liquid separation, washing by using water and drying, wherein the lignin content is more than 85 wt%.

The epoxy diluent is selected from the group consisting of ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1, 4-butanediol diglycidyl ether, neopentyl glycol diglycidyl ether, 1, 6-hexanediol diglycidyl ether.

The sulfuric acid catalyst is a sulfuric acid aqueous solution with the mass concentration of 40-70%.

The invention uses polyhydric alcohol with more than three elements as an initiator, and the polyhydric alcohol and lactone are subjected to ring opening polymerization under the action of a catalyst to obtain the polyester branched chain star polymer. The number of the upper arms of the star polymer can be adjusted by the number of the hydroxyl groups of the polyol, and the length of the arms can be controlled by adjusting polymerization reaction conditions such as the dosage of the catalyst, the feed ratio and the reaction temperature. Finally, a proper star polymer is obtained, a certain inter-transmission network structure (IPN) can be formed with lignin macromolecules, on one hand, the toughness of a system after curing of lignin epoxy resin is improved, on the other hand, the system has very good weather resistance after curing, can resist chemical corrosion, is high in temperature and humidity, cannot lose mechanical properties under the harsh condition of an ultraviolet lamp, and guarantees the use stability and safety of the epoxy resin/carbon fiber prepreg composite material.

The inventor also unexpectedly discovers that in the preparation of the star polymer, the polyol of the initiator is selected from the compound of aliphatic polyol and urea-containing polyol, and the two polyols are used as the initiators to play a synergistic role, so that the thermal stability, the mechanical property and the viscosity of the obtained epoxy resin simultaneously meet the requirements, and the comprehensive performance is optimal.

In one embodiment of the invention, the polyester branched star polymer is prepared by a preparation method comprising the following steps: the polyhydric alcohol with more than three elements, caprolactone and organic metal catalyst react for 30-50h at the temperature of 140 ℃ under the inert atmosphere. Reference may be made in particular to the literature (M.Lang, R.P.Wong, C. -C.Chu, J.Polym.Sci.part A: Polym.chem.40(2002) 1127.).

The second purpose of the invention is to provide a preparation method of the star polyester modified lignin epoxy resin, which comprises the following steps:

(S1) adding the star polymer of the polyester branched chain, dihydric alcohol, dibasic acid anhydride and enzymatic hydrolysis lignin according to the proportion, and reacting under the stirring condition by taking a sulfuric acid aqueous solution as a catalyst until the enzymatic hydrolysis lignin is completely dissolved;

(S2) adding an epoxy diluent, and continuing to react to obtain the star-shaped polyester modified lignin epoxy resin.

Further, in the step (S1), the reaction is carried out for 1-4h at 90-140 ℃; the reaction condition in the step (S2) is reaction for 2-6h at 70-100 ℃.

The third purpose of the invention is to provide a lignin epoxy resin/carbon fiber prepreg, which comprises the following raw materials in parts by weight: 20-30 parts of bisphenol A epoxy resin, 12-18 parts of star polyester modified lignin epoxy resin and 40-70 parts of

Carbon fiber, 1-2 parts of latent curing agent and 0.4-0.7 part of accelerator.

Preferably, the carbon fiber is used in an amount of 47 to 60 parts.

The bisphenol a type epoxy resin is not particularly limited and is well known in the art, such as at least one of E20, E36, E41.

The carbon fiber is not particularly limited, and a carbon fiber material is generally used in the art.

The latent curing agent is at least one selected from dicyandiamide, methyl tetrahydrophthalic anhydride, benzoyl hydrazine and adipic dihydrazide.

The accelerator is an imidazole accelerator, preferably a cyanuric acid modified imidazole accelerator, and is specifically selected from imidazole cyanurate, 2-methylimidazole cyanurate, 2-ethyl cyanurate, and 2-phenylimidazole cyanurate. The cyanuric acid modified imidazole is adopted, so that the compatibility with epoxy resin can be further improved, certain latency is provided, and convenience is provided for construction.

The invention also provides a preparation method of the lignin epoxy resin/carbon fiber prepreg, which comprises the following steps:

(M1) heating and melting the prepared star polyester modified lignin epoxy resin, adding bisphenol A epoxy resin, a latent curing agent and an accelerator according to a proportion, and melting at 90-120 ℃;

(M2) adding the molten mixed resin into a glue groove of a hot-melt glue spreader, cooling and rolling to obtain a glue film;

(M3) placing the prepared adhesive film in a compound machine, synchronously feeding the carbon fiber yarns and the adhesive film into a compound roller of the compound machine, heating for compounding, cooling and rolling to obtain the carbon fiber resin prepreg.

Compared with the prior art, the invention achieves the following excellent technical effects:

according to the invention, the star polymer taking polyester as a branched chain is prepared by taking polyalcohol as an initiator, the terminal of the branched chain of the star polymer is hydroxyl, so that a part of polyalcohol used in the traditional lignin epoxy resin preparation process can be replaced, and the prepared star polyester modified lignin epoxy resin has the advantages of obviously enhanced toughness, reduced viscosity and favorable wettability with carbon fiber composite materials.

The inventor unexpectedly finds that the polyol of the initiator is selected from the compound of aliphatic polyol and urea-containing polyol, and the two polyols play a synergistic cooperation role as the initiator, so that the mechanical property and viscosity of the obtained epoxy resin meet the requirements at the same time, and the comprehensive performance is optimal. And the weather resistance is excellent, the retention rate of various mechanical properties is very high under various ultraviolet, high temperature and freezing simulated aging environments, and the stability and the safety of the product used in various harsh environments are ensured.

Detailed Description

The reagents used in the present invention are all commercially available reagents unless otherwise specified.

The lignin epoxy resin used in the invention is self-made, the preparation method refers to the method described in the inventor's prior patent application No. 201710091949, the epoxy value is 0.43, and the carbon fiber used in the examples of the invention is purchased from Shanghai petrochemical SCF35S-12K (the strength is the same as T300). In the examples of the present invention, the term "part" means part by weight unless otherwise specified.

Preparation example 1a

According to the mass ratio, 0.3 part of pentaerythritol, 0.5 part of sorbitol, 0.2 part of tetramethylolglycoluril, 5 parts of caprolactone and 0.01 part of stannous octoate are added and reacted for 40 hours at 120 ℃ in a nitrogen atmosphere, the system is added with chloroform to be dissolved, then excessive petroleum ether precipitation products are poured, the ethanol and the water are respectively used for washing, and vacuum drying is carried out to obtain 5.6 parts of star-shaped polyester with the number average molecular weight of 13.2 × 10³g/mol, molecular weight dispersity (PDI ═ Mw/Mn) 1.46.

Preparation example 2a

The other steps and conditions were the same as in preparation example 1 except that the amount of caprolactone used was 8 parts, to finally obtain 8.4 parts of star-shaped polyester having a number average molecular weight of 15.4 × 10³g/mol, molecular weight dispersity (PDI ═ Mw/Mn) of 1.53.

Preparation example 3a

The other steps and conditions were the same as in preparation example 1 except that 10 parts of caprolactone was used to obtain 10.2 parts of star-shaped polyester having a number average molecular weight of 18.4 × 10³g/mol, molecular weight dispersity (PDI ═ Mw/Mn) of 1.61.

Preparation example 4a

The other steps and conditions were the same as in preparation example 1 except that the polyol was replaced with 0.4 parts of pentaerythritol and 0.6 parts of sorbitol to finally obtain 5.4 parts of star-shaped polyester having a number average molecular weight of 14.3 × 10³g/mol, molecular weight dispersity (PDI ═ Mw/Mn) of 1.51.

Preparation example 5a

The other steps and conditions were the same as in preparation example 1 except that 1 part of tetramethylolglycoluril was substituted for the polyol, to finally obtain 5.2 parts of a star-shaped polyester having a number average molecular weight of 12.1 × 10³g/mol, molecular weight dispersity (PDI ═ Mw/Mn) of 1.58.

Preparation example 6a

The other procedures and conditions were the same as in preparation example 1 except that tetramethylol glycoluril was replaced with tris (2-hydroxyethyl) isocyanurate to finally obtain 5.5 parts of a star-shaped polyester having a number average molecular weight of 12.8 × 10³g/mol, molecular weight dispersity (PDI ═ Mw/Mn) was 1.52.

Preparation example 1b

(S1) adding 5.6 parts of the polyester branched star polymer prepared in preparation example 1, 25 parts of ethylene glycol, 40 parts of maleic anhydride and 15 parts of enzymatic lignin, and reacting at 110 ℃ for 4 hours by using 1.5 parts of 60 wt% sulfuric acid aqueous solution as a catalyst under the stirring condition until the enzymatic lignin is completely dissolved;

(S2) adding 120 parts of ethylene glycol diglycidyl ether, and continuing to react to obtain the star polyester modified lignin epoxy resin, wherein the viscosity is 6000mpa.s, and the epoxy value is 0.44.

Preparation example 2b

The other steps and conditions were the same as those in preparation example 1b, except that the star polymer branched by the polyester in step (S1) was replaced with 8.4 parts of the star polymer prepared in preparation example 2a, to finally obtain a star polyester-modified lignin epoxy resin having a viscosity of 5500mpa.s and an epoxy value of 0.43.

Preparation example 3b

The other steps and conditions were the same as those in preparation example 1b, except that the star polymer branched by the polyester in step (S1) was replaced with 10.2 parts of the star polymer prepared in preparation example 3a, to finally obtain a star polyester-modified lignin epoxy resin having a viscosity of 5000mPa.s and an epoxy value of 0.42.

Preparation example 4b

The other steps and conditions were the same as those in preparation example 1b, except that the star polymer branched by the polyester in step (S1) was replaced with 5.4 parts of the star polymer prepared in preparation example 4a, to finally obtain a star polyester-modified lignin epoxy resin having a viscosity of 6500mpa.s and an epoxy value of 0.43.

Preparation example 5b

The other steps and conditions were the same as those in preparation example 1b, except that the star polymer branched by the polyester in step (S1) was replaced with 5.2 parts of the star polymer prepared in preparation example 5a, to finally obtain a star polyester-modified lignin epoxy resin having a viscosity of 7000mpa.s and an epoxy value of 0.42.

Preparation example 6b

The other steps and conditions were the same as those in preparation example 1b, except that the star polymer branched by the polyester in step (S1) was replaced with 5.5 parts of the star polymer prepared in preparation example 6a, to finally obtain a star polyester-modified lignin epoxy resin having a viscosity of 6800mpa.s and an epoxy value of 0.43.