Colorless transparent anti-yellowing glass fiber reinforced epoxy resin prepreg and preparation method thereof

Abstract

The invention discloses a colorless transparent yellowing-resistant glass fiber reinforced epoxy resin prepreg and a preparation method thereof. The preparation method comprises the following steps: reacting thiol with isocyanate to prepare a sulfydryl-terminated oligomer, adding an alkenylated epoxy compound to react to prepare a sulfydryl-terminated epoxy compound, adding epoxy resin and an anhydride compound to obtain an epoxy resin prepolymer, adding a thermal initiator, a light stabilizer and an ultraviolet light absorber, and reacting to obtain the heat-resistant polyurethane resin. And coating the colorless transparent anti-yellowing epoxy resin system, and compounding with glass fibers to obtain the glass fiber reinforced epoxy resin prepreg. The prepreg provided by the invention can be cured at medium temperature, the light transmittance of a cured product is greater than or equal to 89%, and the prepreg can not become yellow outdoors for a long time, has good impact performance, and can be applied to the field of replacing glass, such as a front panel and a back panel of a photovoltaic panel.

Description

Technical Field

[0001] The invention belongs to the technical field of composite materials, and particularly relates to a colorless, transparent, yellowing-resistant glass fiber reinforced epoxy resin prepreg and a preparation method thereof. Background Art

[0002] Photovoltaic panels are mostly placed in open-air environments with sufficient sunlight, so strict requirements are placed on the front and back panels of photovoltaic modules in terms of transparency and yellowing resistance. The front and back panels made of tempered glass used in traditional photovoltaic modules are heavy and brittle, and are easily broken in bad weather, affecting power generation efficiency. In contrast, epoxy composite materials have a low density, excellent processing performance, corrosion resistance and mechanical properties, and are not easily deformed or damaged. They can ensure the stability of photovoltaic modules and are suitable for replacing tempered glass for photovoltaic panels.

[0003] Traditional epoxy prepregs mostly use bisphenol A epoxy resin (refractive index 1.55-1.60) and amine curing system (such as dicyandiamide, tertiary amine accelerator). The benzene ring structure in its molecule easily absorbs ultraviolet light to produce oxidation reaction, and the material has poor yellowing resistance. In addition, the free amines remaining in the amine curing agent react with oxygen to generate quinone chromophores under a hot and humid environment, further aggravating yellowing, resulting in poor yellowing resistance of epoxy prepreg. In order to improve the yellowing resistance of epoxy prepreg resin, the prior art attempts to use epoxy resin without benzene rings, because it has good ultraviolet resistance, but the resin refractive index does not match glass fiber (refractive index 1.54), and light undergoes Fresnel reflection loss at the interface, and the transmittance is low; at the same time, the system has low viscosity at room temperature, and it is difficult to prepare prepreg; in addition, the cured product of the above-mentioned epoxy resin after curing with a thermal cationic system is brittle, and the composite material has poor impact resistance.

[0004] Therefore, there is still a need to develop an epoxy resin thermal cationic curing system that matches the refractive index of glass fiber. This system must not only meet the prepreg preparation process requirements, but also have the characteristics of excellent impact performance, colorless and transparent, and good yellowing resistance of the composite materials prepared thereby, so as to break through the performance bottleneck of lightweight materials for photovoltaic modules. Summary of the invention

[0005] In order to solve at least some of the technical problems existing in the above-mentioned prior art, the present invention adopts two technical innovation routes:

[0006] First, mercaptan and isocyanate are reacted to generate mercapto-terminated oligomers, which are then reacted with olefinated epoxy compounds to obtain mercapto-terminated epoxy compounds. The reaction does not use tertiary amine accelerators, and the sulfur-containing groups are introduced into the epoxy resin structure through a specific reaction path to achieve matching of the resin refractive index with the glass fiber refractive index. The prepared composite material has good transparency and yellowing resistance. At the same time, the polythiocarbamate generated by the reaction has good toughness, and the prepared composite material has good impact resistance.

[0007] Secondly, using terminal mercapto groups as promoters and using acid anhydride to pre-crosslink epoxy resin, a resin system with suitable viscosity is prepared, which is suitable for the prepreg preparation process.

[0008] Based on the above technology, the present invention successfully prepares a colorless, transparent, and yellowing-resistant glass fiber reinforced epoxy resin prepreg for photovoltaic panels, and the specific contents are as follows.

[0009] The first aspect of the present invention provides a method for preparing a colorless, transparent, yellowing-resistant glass fiber reinforced epoxy resin prepreg, which comprises the following steps:

[0010] (1) reacting a thiol compound with an isocyanate at 40-100° C. for 2-6 hours, and then adding an olefinic epoxy compound and reacting for 3-5 hours to obtain a thiol-terminated epoxy compound, wherein the molar ratio of the thiol group, the isocyanate group, and the double bond in the olefinic epoxy compound is (2.05-2.10):1:0.8;

[0011] (2) adding an epoxy resin and an acid anhydride compound to the thiol-terminated epoxy compound obtained in step (1) in sequence, and reacting at 60-140° C. to make the viscosity of the material reach 50,000-100,000 cps at 70° C., wherein the molar ratio of the thiol group in the thiol-terminated epoxy compound, the anhydride group in the acid anhydride compound, and the epoxy group in the epoxy resin is (0.020-0.050):(0.2-0.4):1;

[0012] (3) controlling the temperature of the material obtained in step (2) to be 40-90° C., adding a thermal initiator, a light stabilizer, and an ultraviolet absorber, and mixing them uniformly to obtain a colorless, transparent, and yellowing-resistant epoxy resin system, wherein the thermal initiator accounts for 0.1-1.0% of the total amount of the colorless, transparent, and yellowing-resistant epoxy resin system, the light stabilizer accounts for 0.01-1.0% of the total amount of the colorless, transparent, and yellowing-resistant epoxy resin system, and the ultraviolet absorber accounts for 0.01-1.0% of the total amount of the colorless, transparent, and yellowing-resistant epoxy resin system;

[0013] (4) The colorless, transparent, yellowing-resistant epoxy resin system coating obtained in step (3) is compounded with glass fiber prepreg to obtain a colorless, transparent, yellowing-resistant glass fiber reinforced epoxy resin prepreg.

[0014] In certain embodiments, according to the method for preparing the colorless, transparent, yellowing-resistant glass fiber reinforced epoxy resin prepreg of the present invention, the refractive index of the thiol compound is greater than 1.5200.

[0015] In certain embodiments, according to the method for preparing the colorless, transparent, yellowing-resistant glass fiber reinforced epoxy resin prepreg of the present invention, the thiol compound includes one or more of pentaerythritol tetrakis(3-mercaptopropionate), thiodiglycol mercaptan, 2,3-dithio(2-mercapto)-1-propanethiol and other thiols without aromatic rings; the isocyanate includes one or more of isophorone diisocyanate, dicyclohexylmethane diisocyanate, 1,6-hexamethylene diisocyanate, trimethylhexane diisocyanate and other isocyanates without aromatic rings.

[0016] In certain embodiments, according to the method for preparing the colorless, transparent, yellowing-resistant glass fiber reinforced epoxy resin prepreg of the present invention, the general structural formula of the olefinated epoxy compound is CH2=CR-XE, wherein R includes hydrogen or an alkyl group, X includes hydrogen, an alkyl group, an alkenyl group, an ester group or an ether bond, and E includes an alicyclic epoxy group or an aliphatic epoxy group.

[0017] In certain embodiments, according to the method for preparing the colorless, transparent, yellowing-resistant glass fiber reinforced epoxy resin prepreg of the present invention, the epoxy resin includes one or more of 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexylcarboxylate, 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester, dicyclopentadiene diepoxide, 1,4-cyclohexanedimethanol bis(3,4-epoxycyclohexanecarboxylic acid) ester, and hydrogenated bisphenol A epoxy resin.

[0018] In certain embodiments, according to the method for preparing the colorless, transparent, yellowing-resistant glass fiber reinforced epoxy resin prepreg of the present invention, the acid anhydride compound includes one or more of maleic anhydride and its adducts, methyl hexahydrophthalic anhydride, hydrogenated methyl nadic anhydride, methyl tetrahydrophthalic anhydride and other anhydrides without aromatic rings;

[0019] In certain embodiments, according to the method for preparing the colorless, transparent, yellowing-resistant glass fiber reinforced epoxy resin prepreg of the present invention, the thermal initiator is selected from one or more of iodonium salt initiators and sulfonium salt initiators; the light stabilizer includes one or more of hindered amines and hindered phenol light stabilizers; and the ultraviolet absorber includes one or more of benzophenone and benzotriazole ultraviolet absorbers.

[0020] In certain embodiments, according to the method for preparing the colorless, transparent, yellowing-resistant glass fiber reinforced epoxy resin prepreg of the present invention, the glass fiber includes at least one of E glass fiber and S glass fiber.

[0021] The second aspect of the present invention provides a colorless, transparent, yellowing-resistant glass fiber reinforced epoxy resin prepreg, which is obtained by the preparation method of the present invention.

[0022] The third aspect of the present invention provides the use of the colorless, transparent, yellowing-resistant glass fiber reinforced epoxy resin prepreg of the present invention in replacing glass in photovoltaic panel front panels, back panels, etc.

[0023] The composite material prepared by the present invention has the following advantages:

[0024] 1. High transparency. The present invention designs a reaction route to introduce sulfur atoms into the epoxy resin structure, so that the refractive index of the resin system reaches 1.5350-1.5450, which is consistent with the refractive index of glass fiber. The prepared composite material has high light transmittance.

[0025] 2. Excellent yellowing resistance. It adopts alicyclic epoxy thermal cationic curing system and abandons tertiary amine accelerators, which effectively avoids the yellowing problem caused by the participation of amine substances in the reaction. The prepared product has good yellowing resistance. Under the synergistic effect of specific ultraviolet absorbers and light stabilizers, the composite material is not easy to yellow under long-term light.

[0026] 3. Outstanding impact performance: The polythiocarbamate generated by the reaction of thiol and isocyanate has good toughness. The prepared composite material has good impact performance, which improves the durability and reliability of the material.

[0027] Fourth, to meet the prepreg preparation process, terminal mercapto groups are used as promoters, and acid anhydrides are used to pre-crosslink epoxy resins, thereby preparing a resin system with suitable viscosity that meets the prepreg preparation process. DETAILED DESCRIPTION

[0028] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0029] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that the upper and lower limits of the scope and each intermediate value therebetween are specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0030] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art to which the invention belongs. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0031] Preparation method

[0032] One aspect of the present invention provides a method for preparing a colorless, transparent, yellowing-resistant glass fiber reinforced epoxy resin prepreg. In a preferred embodiment, the preparation method of the present invention comprises the following steps:

[0033] (1) reacting a thiol compound with an isocyanate at 40-100° C., 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100° C.; adding an olefinic epoxy compound, and continuing the reaction to obtain a thiol-terminated epoxy compound, wherein the molar ratio of the thiol group, the isocyanate group, and the double bond in the olefinic epoxy compound is (2.05-2.10):1:0.8; for example, 2.05:1:0.8, 2.06:1:0.8, 2.07:1:0.8, 2.08:1:0.8, 2.09:1:0.8, 2.10:1:0.8;

[0034] (2) reacting the anhydride compound, the epoxy resin and the mercapto-terminated epoxy compound at 60-140° C., for example, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140° C., so that the viscosity of the material at 70° C. reaches 50,000-100,000 cps, preferably 55,000-100,000 cps, and more preferably 60,000-100,000 cps, for example, 60,000, 65,000, 70,000, 75,000, 76,000, 77,000, 78,000 , 79000, 80000, 81000, 82000, 83000, 84000, 85000, 86000, 87000, 88000, 89000, 90000, 91000, 92000, 93000, 94000, 95000, 96000, 97000, 98000, 99000, 100000 cps to obtain an epoxy prepolymer, wherein the molar ratio of the thiol group in the thiol-terminated epoxy compound, the anhydride group in the anhydride compound, and the epoxy group in the epoxy resin is (0.020-0.050): (0.2-0 .4):1; preferably (0.02-0.04): (0.2-0.4):1; for example 0.02:0.2:1, 0.02:0.3:1, 0.02:0.4:1, 0.022:0.2:1, 0.022:0.3:1, 0.022:0.4:1, 0.024:0.2:1, 0.024:0.3:1, 0.024:0.4:1, 0.026:0.2:1, 0.026:0.3:1, 0.026:0.4:1, 0.028:0.2:1, 0.028:0.3:1, 0.028:0.4:1 , 0.03:0.2:1, 0.03:0.3:1, 0.03:0.4:1, 0.032:0.2:1, 0.032:0.3:1, 0.032:0.4:1, 0.034:0.2:1, 0.034:0.3:1, 0.034:0.4:1, 0.036:0.2:1, 0.036:0.3:1, 0.036:0.4:1, 0.038:0.2:1, 0.038:0.3:1, 0.038:0.4:1, 0.04:0.2:1, 0.04:0.3:1, 0.04:0.4:1;

[0035] (3) mixing the epoxy prepolymer with a light stabilizer and an ultraviolet absorber at 40-90° C., for example, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90° C., adding a thermal initiator for reaction, preferably stirring, to obtain a colorless, transparent, yellowing-resistant epoxy resin system, wherein the thermal initiator accounts for 0.1-1.0%, preferably 0.1-0.9%, more preferably 0.1-0.8%, more preferably 0.1-0.7%, for example 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7% of the total amount of the colorless, transparent, yellowing-resistant epoxy resin system; the light stabilizer accounts for 0.1% to 1.0%, preferably 0.1% to 0.9%, more preferably 0.1% to 0.8%, more preferably 0.1% to 0.7%, for example 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7% of the total amount of the colorless, transparent, yellowing-resistant epoxy resin system; The amount of the colorless, transparent, yellowing-resistant epoxy resin system is 0.01-1.0%, preferably 0.01-0.9%, also preferably 0.01-0.8%, more preferably 0.01-0.7%, such as 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7%; the ultraviolet absorber accounts for 0.01-1.0% of the total amount of the colorless, transparent, yellowing-resistant epoxy resin system, preferably 0.01-0.9%, also preferably 0.01-0.8%, more preferably 0.01-0.7%, such as 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7%;

[0036] (4) The colorless, transparent, yellowing-resistant epoxy resin system coating obtained in step (3) is compounded with glass fiber prepreg to obtain a colorless, transparent, yellowing-resistant glass fiber reinforced epoxy resin prepreg.

[0037] In a preferred embodiment, after adding the isocyanate compound in step (1), stirring is continued for 1-10 hours, preferably 2-10 hours, and preferably 2-6 hours, such as 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6 hours. After adding the olefinated epoxy compound, the reaction time is 1-10 hours, preferably 2-10 hours, and preferably 2-6 hours, and more preferably 3-5 hours, such as 3, 3.5, 4, 4.5, 5 hours.

[0038] In a preferred embodiment, in step (2), the reaction is carried out for 1-10 h, preferably 1-9 h, further preferably 1-8 h, more preferably 1-6 h, for example 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6 h.

[0039] In a preferred embodiment, the thiol compound includes one or more of pentaerythritol tetrakis (3-mercaptopropionic acid) ester, thiodiglycol mercaptan, 2,3-dithio (2-mercapto)-1-propanethiol, 1,5-pentanedithiol, trimethylolpropane tris (3-mercaptopropionate), and other thiols without aromatic rings. In a specific embodiment, the thiol compound is pentaerythritol tetrakis (3-mercaptopropionic acid) ester. In another specific embodiment, the thiol compound is thiodiglycol mercaptan. In another specific embodiment, the thiol compound is 2,3-dithio (2-mercapto)-1-propanethiol.

[0040] In a preferred embodiment, the isocyanate includes one or more of isophorone diisocyanate, dicyclohexylmethane diisocyanate, 1,6-hexamethylene diisocyanate, trimethylhexane diisocyanate and other isocyanates without aromatic rings. In a specific embodiment, the isocyanate is isophorone diisocyanate. In another specific embodiment, the isocyanate is dicyclohexylmethane diisocyanate. In another specific embodiment, the isocyanate is 1,6-hexamethylene diisocyanate.

[0041] In a preferred embodiment, the refractive index of the thiol compound is >1.5200.

[0042] In a preferred embodiment, the structural formula of the olefinated epoxy compound is CH2=CR-XE, wherein R includes hydrogen or an alkyl group, X includes hydrogen, an alkyl group, an alkenyl group, an ester group or an ether bond, and E includes an alicyclic epoxy group or an aliphatic epoxy group.

[0043] In a specific embodiment, the alkenylated epoxy compound is glycidyl methacrylate. In another specific embodiment, the alkenylated epoxy compound is allyl glycidyl ether. In yet another specific embodiment, the alkenylated epoxy compound is 3,4-epoxycyclohexyl methacrylate.

[0044] In a preferred embodiment, the anhydride compound includes one or more of maleic anhydride and its adduct, methyl hexahydrophthalic anhydride, hydrogenated methyl nadic anhydride, methyl tetrahydrophthalic anhydride and other anhydrides without aromatic rings. In a specific embodiment, the anhydride compound is methyl hexahydrophthalic anhydride. In another specific embodiment, the anhydride compound is hydrogenated methyl nadic anhydride. In another specific embodiment, the anhydride compound is methyl tetrahydrophthalic anhydride.

[0045] In a preferred embodiment, the epoxy resin includes two or more of 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexylcarboxylate, 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester, dicyclopentadiene diepoxide, and 1,4-cyclohexanedimethanol bis(3,4-epoxycyclohexanecarboxylic acid) ester, one of which is selected from dicyclopentadiene diepoxide. In a specific embodiment, the epoxy resin is hydrogenated bisphenol A epoxy resin, and in another specific embodiment, the epoxy resin is 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester and hydrogenated bisphenol A epoxy resin. In another specific embodiment, the epoxy resin is 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexylcarboxylate and hydrogenated bisphenol A epoxy resin.

[0046] In a preferred embodiment, the thermal initiator includes a thermal cationic initiator (for example, but not limited to diphenyliodonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, etc.); the light stabilizer includes hindered amine and hindered phenol light stabilizers (for example, but not limited to hindered amine light stabilizers UV-123, UV-292, UV-622, UV-765, UV-770, UV-783, UV-791, UV-944); the ultraviolet absorber includes one or more of benzophenones and benzotriazoles, for example, but not limited to ultraviolet absorbers UV-81, UV-234, UV-327, UV-328, UV-571.

[0047] In a preferred embodiment, the glass fiber includes at least one of E glass fiber and S glass fiber.

[0048] Glass fiber reinforced epoxy resin prepreg

[0049] One aspect of the present invention provides a colorless, transparent, yellowing-resistant glass fiber reinforced epoxy resin prepreg, which is obtained by the preparation method of the present invention. The colorless, transparent, yellowing-resistant glass fiber reinforced epoxy resin of the present invention has a refractive index of 1.5350-1.5450 (consistent with the refractive index of glass fiber), has good bending strength and impact strength, and has excellent yellowing resistance, and can persist for a long time outdoors without yellowing. The detection of the performance of the glass fiber reinforced epoxy resin prepreg of the present invention can be carried out by methods and devices known in the art, without particular limitation.

[0050] In the present invention, the colorless, transparent, yellowing-resistant glass fiber reinforced epoxy resin prepreg is prepared from the following raw materials: 5-30 parts by mass of a thiol compound, 1-20 parts by mass of an isocyanate, 5-20 parts by mass of an olefinic epoxy compound, 20-50 parts by mass of an anhydride compound, 50-150 parts by mass of an epoxy resin, 0.01-5 parts by mass of an initiator, 0.01-5 parts by mass of a light stabilizer, and 0.01-5 parts by mass of an ultraviolet absorber. Also preferably, the colorless, transparent, yellowing-resistant glass fiber reinforced epoxy resin prepreg is prepared from the following raw materials: 5-30 parts by mass (e.g., 5, 10, 15, 20, 25, 30 parts by mass) of a thiol compound, 1-20 parts by mass (e.g., 1, 5, 10, 15, 20 parts by mass) of an isocyanate, 5-20 parts by mass (e.g., 5, 10, 15, 20 parts by mass) of an olefinic epoxy compound, 20-80 parts by weight of anhydride compound (e.g., 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80 parts by weight), 50-150 parts by weight (e.g., 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 15 0 mass parts) of epoxy resin, 0.01-5 mass parts (e.g., 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 mass parts) of initiator, 0.01-5 mass parts (e.g., 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5 , 0.6, 0.7, 0.8, 0.9, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 mass parts) of light stabilizer, 0.01-5 mass parts (e.g., 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 mass parts) of ultraviolet absorber. Unless otherwise specified, the viscosity values ​​mentioned herein are the viscosity values ​​measured at 70°C. The viscosity value can be measured by a viscosity measurement method and apparatus known in the art, and is not particularly limited thereto.

[0051] Example 1

[0052] This embodiment shows a method for preparing a colorless, transparent, yellowing-resistant glass fiber reinforced epoxy resin prepreg.

[0053] (1) Preparation of a mercapto-terminated epoxy compound: 20.00 g of pentaerythritol tetrakis (3-mercaptopropionic acid) ester was placed in a three-necked flask, the temperature was raised to 100° C., 8.88 g of isophorone diisocyanate was added, stirring was continued for 2 h, 9.08 g of glycidyl methacrylate was added, and the reaction was continued for 3 h to obtain a mercapto-terminated epoxy compound;

[0054] (2) Preparation of epoxy prepolymer: 31.58 g of methyl hexahydrophthalic anhydride and 100 g of hydrogenated bisphenol A epoxy resin were weighed and added to the thiol-terminated epoxy compound prepared in step (1) in sequence, and the temperature was raised to 60° C. and stirred for 5 h. The viscosity of the material at 70° C. reached 82175 cps, thereby obtaining an epoxy prepolymer;

[0055] (3) Preparation of colorless, transparent, yellowing-resistant prepreg epoxy resin: The material obtained in step (2) was cooled to 90° C., 0.01 g of light stabilizer and 1.00 g of ultraviolet absorber were added, and 0.10 g of thermal cationic initiator was added after stirring evenly. The material was stirred evenly again and then discharged to obtain a colorless, transparent, yellowing-resistant epoxy resin;

[0056] (4) The colorless, transparent, yellowing-resistant epoxy resin is coated with a film coating machine, and finally compounded with glass fiber, and cured according to a curing process of 140° C.*40 min to obtain the colorless, transparent, yellowing-resistant glass fiber reinforced epoxy resin prepreg, wherein the glass fiber is 108 g / m 2 E-glass fiber.

[0057] Example 2

[0058] This embodiment shows a method for preparing a colorless, transparent, yellowing-resistant glass fiber reinforced epoxy resin prepreg.

[0059] (1) Preparation of a thiol-terminated epoxy compound: 15.00 g of thiodiglycol mercaptan was placed in a three-necked flask, the temperature was raised to 40° C., 12.15 g of dicyclohexylmethane diisocyanate was added, stirring was continued for 6 h, 8.46 g of allyl glycidyl ether was added, and the reaction was continued for 5 h to obtain a thiol-terminated epoxy compound;

[0060] (2) Preparation of epoxy prepolymer: Weigh 22.39 g of hydrogenated methyl nadic anhydride, 40 g of 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester and 60 g of hydrogenated bisphenol A epoxy resin and add them to the thiol-terminated epoxy compound prepared in step (1) in sequence, raise the temperature to 140° C., and continue stirring for 1.5 hours. The viscosity of the material at 70° C. reaches 99117 cps, thereby obtaining an epoxy prepolymer;

[0061] (3) Preparation of colorless, transparent, yellowing-resistant prepreg epoxy resin: The material obtained in step (2) was cooled to 40° C., 1.00 g of light stabilizer and 0.01 g of ultraviolet absorber were added, and 1.00 g of thermal cationic initiator was added after stirring evenly. The material was stirred evenly again and then discharged to obtain a colorless, transparent, yellowing-resistant epoxy resin;

[0062] (4) The colorless, transparent, yellowing-resistant epoxy resin is coated with a film coating machine, and finally compounded with glass fiber, and cured according to a curing process of 120° C.*60 min, wherein the glass fiber is 108 g / m 2 E-glass fiber.

[0063] Example 3

[0064] This embodiment shows a method for preparing a colorless, transparent, yellowing-resistant glass fiber reinforced epoxy resin prepreg.

[0065] (1) Preparation of a thiol-terminated epoxy compound: 10.00 g of 2,3-dithio(2-thiol)-1-propanethiol was placed in a three-necked flask, the temperature was raised to 70° C., 4.68 g of 1,6-hexamethylene diisocyanate was added, stirring was continued for 3.5 h, 8.74 g of 3,4-epoxycyclohexyl methacrylate was added, and the reaction was continued for 4 h to obtain a thiol-terminated epoxy compound;

[0066] (2) Preparation of epoxy prepolymer: 31.47 g of methyltetrahydrophthalic anhydride, 60 g of 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexylcarboxylate and 40 g of hydrogenated bisphenol A epoxy resin were weighed and added to the thiol-terminated epoxy compound prepared in step (1) in sequence, and the temperature was raised to 100° C. and stirred for 3 h. The viscosity of the material at 70° C. reached 79314 cps, thereby obtaining an epoxy prepolymer;

[0067] (3) Preparation of colorless, transparent, yellowing-resistant prepreg epoxy resin: The material obtained in step (2) was cooled to 70° C., 0.30 g of light stabilizer and 0.20 g of ultraviolet absorber were added, and 0.30 g of thermal cationic initiator was added after stirring evenly. The material was stirred evenly again and then discharged to obtain a colorless, transparent, yellowing-resistant epoxy resin;

[0068] (4) The colorless, transparent, yellowing-resistant epoxy resin is coated with a film coating machine, and finally compounded with glass fiber, and cured according to a curing process of 130° C.*50 min, wherein the glass fiber is 108 g / m 2 E-glass fiber.

[0069] Comparative Example 1

[0070] This comparative example shows a method for preparing a modified epoxy resin prepreg.

[0071] Put 20.00g of pentaerythritol tetrakis (3-mercaptopropionic acid) into a three-necked flask, heat it to 60℃, add 30g of 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexylcarboxylate and 70g of hydrogenated bisphenol A epoxy resin, stir continuously for 3.5h, raise the material temperature to 90℃, add 0.01g of light stabilizer and 1.00g of ultraviolet absorber, stir evenly, add 0.10g of thermal cationic initiator, stir evenly again and discharge the material to obtain modified epoxy resin. Since the obtained resin is a viscous liquid at room temperature, it is impossible to coat the prepreg. The obtained resin is compounded with glass fiber by hand lay-up process, and cured at 140℃*40min according to the curing process. Among them, the glass fiber adopts 108g / m 2 E-glass fiber.

[0072] Comparative Example 2

[0073] This comparative example shows a method for preparing a modified epoxy resin prepreg.

[0074] Put 15.00g of thiodiglycol mercaptan into a three-necked flask, heat it to 40°C, add 12.15g of dicyclohexylmethane diisocyanate, and continue stirring for 6h; 22.39g of hydrogenated methyl nadic anhydride, 60g of 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester and 40g of hydrogenated bisphenol A epoxy resin, heat it to 140°C, and continue stirring for 0.5h until the viscosity of the material at 70°C reaches 90918cps, thereby obtaining an epoxy prepolymer; reduce the temperature of the obtained material to 40°C, add 1.00g of light stabilizer and 0.01g of ultraviolet absorber, stir evenly, then add 1.00g of thermal cationic initiator, stir evenly again, and then discharge the material to obtain a modified epoxy resin. The colorless, transparent, yellowing-resistant epoxy resin is coated with a film coating machine, and finally compounded with glass fiber, and cured according to the curing process of 120°C*60min, wherein the glass fiber is 108g / m 2 E-glass fiber.

[0075] Comparative Example 3

[0076] This comparative example shows a method for preparing a modified epoxy resin prepreg.

[0077] Put 10.00g of 2,3-dithio (2-mercapto)-1-propanethiol into a three-necked flask, heat it to 70°C, add 50g of 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexyl carboxylate and 50g of hydrogenated bisphenol A epoxy resin, add 0.05g of triethylamine, react for 6 hours, the viscosity of the material at 70°C reaches 82771cps, add 0.30g of light stabilizer and 0.20g of ultraviolet absorber, stir evenly, add 0.30g of thermal cationic initiator, stir evenly again and discharge the material to obtain the modified epoxy resin. Since the obtained resin is a viscous liquid at room temperature, it is impossible to coat the prepreg. The obtained resin is compounded with glass fiber by hand lay-up process, and cured according to the curing process of 130°C*50min. Among them, the glass fiber adopts 108g / m 2 The alkali-free glass fiber is added to obtain a modified epoxy resin prepreg.

[0078] Comparative Example 4

[0079] This comparative example shows a method for preparing a modified epoxy resin prepreg.

[0080] 40g of 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexyl carboxylate and 60g of hydrogenated bisphenol A epoxy resin were placed in a three-necked flask, heated to 90°C, 0.01g of light stabilizer and 1.00g of ultraviolet absorber were added, stirred evenly, 0.10g of thermal cationic initiator was added, stirred evenly again, and the modified epoxy resin was discharged. Since the obtained resin was a viscous liquid at room temperature, it was impossible to coat the prepreg, so the obtained resin was compounded with glass fiber by hand lay-up process, and cured at 140°C*40min according to the curing process. The glass fiber was 108g / m 2 The alkali-free glass fiber is added to obtain a modified epoxy resin prepreg.

[0081] test:

[0082] Resin storage period test: The epoxy resin system is allowed to stand at 25°C and 50% RH. During this process, samples are taken to test the viscosity at a constant temperature of 70°C. When the viscosity reaches twice the initial viscosity, the material is considered expired.

[0083] Resin refractive index test: Use Abbe refractometer to test the resin refractive index.

[0084] Composite material transmittance test: Tested according to ASTM D1003 standard.

[0085] Composite double 85 test: According to the test standard: GB / T 9535, the obtained prepreg composite material is placed in a hot and humid environment with a temperature of 85±2℃ and a relative humidity of 85±5% for 1000h, and the bending performance retention rate is tested, and the performance retention rate is required to be ≥70%.

[0086] Composite material bending performance test: Tested in accordance with standard GB / T3356.

[0087] Composite material impact performance test: Tested in a standard pendulum electronic impact tester according to ASTM D7136.

[0088] Composite UV aging test: Tested according to ISO4892-2, the acceleration rate is set to 62.57, and 1 year of outdoor UV irradiation time is equivalent to 70 hours of UV indoor irradiation time.

[0089] The performance data of the resins and composite materials of Examples 1, 2 and 3 and Comparative Examples 2, 3 and 4 are shown in Table 1 below, wherein Comparative Example 1 is not cured and still not cured after the curing time is extended.

[0090] Table 1 Properties of resin and composite materials

[0091]

[0092]

[0093] By comparing Examples 1, 2 and 3 with Comparative Example 2, it can be seen that the temperature storage period of the resins in Examples 1, 2 and 3 is ≥ 25 days, which has a good storage period. In comparison, the storage period of the resin in Comparative Example 2 is only two days. This is because the epoxy resin anhydride system forms a trimolecular complex when there is a mercapto group, and the viscosity of the resin increases rapidly at room temperature. The resin cannot be stored for a long time, which affects subsequent use.

[0094] By comparing Examples 1, 2 and 3 with Comparative Example 3, it can be seen that the catalyst of tertiary amines is not added to the resin of the embodiment of the present invention, and its initial yellowing index (YI) is ≤1.40, which meets the requirement of the initial yellowing index (YI) of photovoltaic glass ≤1.50. Relatively speaking, the catalyst of tertiary amines is added to Comparative Example 3, and its initial yellowing index (YI) reaches 4.61, which far exceeds the requirement of the initial yellowing index of photovoltaic glass. After the subsequent simulated accelerated aging test, the increment (ΔYI) of the yellowing index of Examples 1, 2 and 3 is only 2.93, 2.97 and 3.00 in 30 days, which meets the technical requirement of the increment (ΔYI) of the yellowing index of the photovoltaic panel after the accelerated aging test ≤3, which is equivalent to that it can persist in the outdoors for 10 years without yellowing, and can ensure the light transmittance of the photovoltaic panel. The ΔYI (30 days) of Comparative Example 3 has reached 18.35, the sample is seriously yellowed, and the light transmittance is significantly reduced.

[0095] Through detailed comparative analysis of Examples 1, 2 and 3 and Comparative Example 4, it can be seen that the light transmittance of the embodiments of the present invention is ≥89% when the refractive index of the resin system is between 1.5350-1.5450, which meets the requirements of high light transmittance of the front and rear panels of the photovoltaic panel. It can be seen from the test results of the mechanical properties of the composite materials that the bending strength of Examples 1, 2 and 3 is ≥350MPa and the impact strength is ≥43.0kJ·m -2 , excellent mechanical properties. In comparison, the comparative example 4 does not meet the prepreg preparation process, and the composite material has a bending strength of only 210MPa and an impact strength of only 17.0kJ·m -2 , the performance is poor.

[0096] It can be seen that the prepreg composite material of the present invention has high transparency, excellent yellowing resistance, and good impact resistance, and can be used to replace the front plate and back plate glass of photovoltaic modules, etc., and has broad application prospects.

[0097] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some of the technical features therein by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a colorless, transparent, yellowing-resistant glass fiber reinforced epoxy resin prepreg, characterized in that: It includes the following steps: (1) reacting a thiol compound with an isocyanate at 40-100° C. for 2-6 hours, and then adding an olefinic epoxy compound and reacting for 3-5 hours to obtain a thiol-terminated epoxy compound, wherein the molar ratio of the thiol group, the isocyanate group, and the double bond in the olefinic epoxy compound is (2.05-2.10):1:0.8; (2) adding an epoxy resin and an acid anhydride compound to the thiol-terminated epoxy compound obtained in step (1) in sequence, and reacting at 60-140° C. to make the viscosity of the material reach 50,000-100,000 cps at 70° C., wherein the molar ratio of the thiol group in the thiol-terminated epoxy compound, the anhydride group in the acid anhydride compound, and the epoxy group in the epoxy resin is (0.020-0.050):(0.2-0.4):1; (3) controlling the temperature of the material obtained in step (2) to be 40-90° C., adding a thermal initiator, a light stabilizer, and an ultraviolet absorber, and mixing them uniformly to obtain a colorless, transparent, and yellowing-resistant epoxy resin system, wherein the thermal initiator accounts for 0.1-1.0% of the total amount of the colorless, transparent, and yellowing-resistant epoxy resin system, the light stabilizer accounts for 0.01-1.0% of the total amount of the colorless, transparent, and yellowing-resistant epoxy resin system, and the ultraviolet absorber accounts for 0.01-1.0% of the total amount of the colorless, transparent, and yellowing-resistant epoxy resin system; (4) The colorless, transparent, yellowing-resistant epoxy resin system coating obtained in step (3) is compounded with glass fiber prepreg to obtain a colorless, transparent, yellowing-resistant glass fiber reinforced epoxy resin prepreg.

2. The method for preparing the colorless, transparent, yellowing-resistant glass fiber reinforced epoxy resin prepreg according to claim 1, characterized in that: The refractive index of the thiol compound is greater than 1.5200.

3. The method for preparing the colorless, transparent, yellowing-resistant glass fiber reinforced epoxy resin prepreg according to claim 1, characterized in that: The thiol compound includes one or more of pentaerythritol tetrakis (3-mercaptopropionate), thiodiglycol mercaptan, 2,3-dithio (2-mercapto)-1-propanethiol and other thiols not containing aromatic rings.

4. The method for preparing the colorless, transparent, yellowing-resistant glass fiber reinforced epoxy resin prepreg according to claim 1, characterized in that: The isocyanate includes one or more of isophorone diisocyanate, dicyclohexylmethane diisocyanate, 1,6-hexamethylene diisocyanate, trimethylhexane diisocyanate and other isocyanates not containing an aromatic ring.

5. The method for preparing the colorless, transparent, yellowing-resistant glass fiber reinforced epoxy resin prepreg according to claim 1, characterized in that: The general structural formula of the alkenyl epoxy compound is CH2=CR-XE, wherein R includes hydrogen or an alkyl group, X includes hydrogen, an alkyl group, an alkenyl group, an ester group or an ether bond, and E includes an alicyclic epoxy group or an aliphatic epoxy group.

6. The method for preparing the colorless, transparent, yellowing-resistant glass fiber reinforced epoxy resin prepreg according to claim 1, characterized in that: The epoxy resin includes one or more of 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexylcarboxylate, 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester, dicyclopentadiene diepoxide, 1,4-cyclohexanedimethanol bis(3,4-epoxycyclohexanecarboxylate), and hydrogenated bisphenol A epoxy resin.

7. The method for preparing the colorless, transparent, yellowing-resistant glass fiber reinforced epoxy resin prepreg according to claim 1, characterized in that: The acid anhydride compounds include one or more of maleic anhydride and its adducts, methylhexahydrophthalic anhydride, hydrogenated methylnadic anhydride, methyltetrahydrophthalic anhydride and other acid anhydrides without aromatic rings.

8. The method for preparing the colorless, transparent, yellowing-resistant glass fiber reinforced epoxy resin prepreg according to claim 1, characterized in that: The thermal initiator includes one or more of an iodonium salt initiator and a sulfonium salt initiator, the light stabilizer includes one or more of a hindered amine and a hindered phenol light stabilizer, and the ultraviolet absorber includes one or more of a benzophenone and a benzotriazole ultraviolet absorber.

9. The method for preparing the colorless, transparent, yellowing-resistant glass fiber reinforced epoxy resin prepreg according to claim 1, characterized in that: The glass fiber includes one or more of E glass fiber and S glass fiber.

10. A colorless, transparent, yellowing-resistant glass fiber reinforced epoxy resin prepreg, characterized in that: It is obtained according to the preparation method according to any one of claims 1 to 9.

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