An unsaturated polyester resin for fiberglass reinforced plastics (FRP), its preparation method, and FRP.

Abstract

This application relates to the technical field of fiberglass reinforced plastics (FRP), and in particular to an unsaturated polyester resin for FRP, a method for preparing the same, and FRP. The unsaturated polyester resin comprises the following raw materials in parts by weight: diols: neopentyl glycol 22-30 parts, 2,2-diallyl bisphenol A 2-4 parts, and bisphenol fluorene 5-9 parts; diacids: isophthalic acid 5-15 parts, terephthalic acid 5-15 parts; acid anhydrides: phthalic anhydride 3-15 parts, maleic anhydride 5-17 parts; toughening agent: double-ended hydrogen-capped silicone oil 5-9 parts; platinum catalyst: the amount of platinum catalyst added is 30-150 ppm of the total mass of 2,2-diallyl bisphenol A and double-ended hydrogen-capped silicone oil; diluent 25-45 parts; polymerization inhibitor 0.01-0.06 parts. It has the advantage of improving the hardness and toughness of the unsaturated polyester resin, thus enhancing its corrosion resistance.

Description

Technical Field

[0001] This application relates to the technical field of fiberglass, and in particular to an unsaturated polyester resin for fiberglass, a method for preparing the same, and fiberglass. Background Technology

[0002] Unsaturated polyester resin, due to its excellent mechanical properties, good process adaptability, and relatively low cost, has become the core matrix material for manufacturing fiberglass reinforced plastics (FRP), and is widely used in chemical corrosion protection, environmental engineering, shipbuilding, transportation, and building structures. The performance of FRP products largely depends on the characteristics of the matrix resin. In harsh corrosive environments, the balance between the resin's corrosion resistance, toughness, and hardness is crucial and represents a prominent technological challenge.

[0003] In applications such as chemical corrosion protection and flue gas desulfurization, FRP (fiberglass reinforced plastic) equipment is exposed to complex media such as acids, alkalis, salts, and organic solvents for extended periods. To improve corrosion resistance, the industry standard practice is to use high levels of monomers such as isophthalic acid and neopentyl glycol to synthesize resins, creating denser polyester molecular chains with higher chemical stability. While the extensive use of these rigid monomers effectively increases the resin's crosslinking density, hardness, and chemical resistance, it often leads to a sharp decrease in material toughness, resulting in increased brittleness and insufficient impact strength. Microcracks are prone to develop during installation, use, or under stress. These microcracks can become channels for corrosive media penetration, accelerating material damage and ultimately shortening the equipment's lifespan. On the other hand, while introducing flexible segments (such as long-chain diols) or blending with elastomers to improve toughness can enhance impact resistance to some extent, it inevitably sacrifices the material's rigidity, hardness, and heat resistance. This can lead to product deformation under high temperatures or heavy loads, similarly affecting its long-term dimensional stability and durability in corrosion-resistant applications. Furthermore, traditional toughening modification methods (such as adding rubber particles) often cause process problems such as increased resin viscosity and poorer wettability with glass fibers, and may result in a sticky surface after curing, affecting product quality.

[0004] Therefore, developing an unsaturated polyester resin that is corrosion resistant while also possessing hardness and toughness is of great significance for its application in high-end corrosion protection fields. Summary of the Invention

[0005] To improve the hardness and toughness of unsaturated polyester resin with improved corrosion resistance, this application provides an unsaturated polyester resin for fiberglass, a method for preparing the resin, and fiberglass.

[0006] In a first aspect, this application provides an unsaturated polyester resin for fiberglass, employing the following technical solution: An unsaturated polyester resin for use in fiberglass reinforced plastics (FRP) comprises the following raw materials in parts by weight: Diols: 22-30 parts neopentyl glycol, 2-4 parts 2,2-diallyl bisphenol A and 5-9 parts bisphenol fluorene; Dicarboxylic acids: 5-15 parts isophthalic acid, 5-15 parts terephthalic acid; Acid anhydrides: 3-15 parts phthalic anhydride, 5-17 parts maleic anhydride; Toughening agent: 5-9 parts of double-ended hydrogen-sealed silicone oil; Platinum catalyst: The amount of platinum catalyst added is 30-150 ppm of the total mass of 2,2-diallylbisphenol A and double-ended hydrogen-capped silicone oil. 25-45 parts diluent; Polymerization inhibitor 0.01-0.06 parts.

[0007] By adopting the above technical solution, in the preparation of unsaturated polyester resin, neopentyl glycol in the diol provides corrosion resistance to the unsaturated polyester resin. Simultaneously, the diol is compounded with 2,2-diallylbisphenol A and bisphenol fluorene. Both substances contain large benzene ring structures, and their inherent rigidity and stability provide a solid skeletal structure for the unsaturated polyester resin. This directly results in higher flexural strength, rigidity, and heat distortion temperature after resin curing. The unique Cardo (fluorene ring) structure of bisphenol fluorene provides significant steric hindrance and rigidity, synergistically enhancing the rigidity of the molecular chain with the benzene ring structure of 2,2-diallylbisphenol A. Based on this, a hydrogen-terminated silicone oil is introduced. Due to steric hindrance, it preferentially undergoes hydrosilylation with the double bonds on 2,2-diallylbisphenol A, allowing the hydrogen-terminated silicone oil to act as a side link, branching onto the main chain of the unsaturated polyester. These flexible side chains are highly efficient energy buffer centers, significantly improving impact toughness and elongation at break. On the other hand, when both ends of the hydrogen-capped silicone oil react with the double bonds of the side chains on different main chains, its large molecular weight can also reduce the local crosslinking density. These sites with low crosslinking density can further buffer external forces, thereby further improving the toughness of the unsaturated polyester. Furthermore, the large molecular weight of the hydrogen-capped silicone oil results in a lower degree of crosslinking to the main chain, forming weak crosslinks that do not affect the viscosity of the uncured unsaturated polyester or its actual application.

[0008] Therefore, this application constructs a strong rigid framework with neopentyl glycol, 2,2-diallylbisphenol A and bisphenol fluorene, providing a solid support platform for flexible siloxane segments. By grafting double-ended hydrogen-capped silicone oil as a side chain, the toughness is adjusted without affecting the strength of the main chain, and an unsaturated polyester with high corrosion resistance, high strength, high heat resistance and excellent toughness is synergistically prepared.

[0009] Preferably, the viscosity of the double-ended hydrogen-sealed silicone oil is 500-5000 mPa·s.

[0010] By adopting the above technical solution, this range corresponds to medium molecular weight silicone oil, which can provide a significant toughening effect, while having good compatibility with the polyester matrix and helping to maintain the transparency of the resin.

[0011] Preferably, the viscosity of the double-ended hydrogen-sealed silicone oil is 2000-5000 mPa·s.

[0012] By adopting the above technical solution, within this range, the siloxane segments are long enough to achieve the most significant toughening effect, while their molecular weight is insufficient to cause severe microphase separation. This allows for the achievement of high toughness while maintaining the rigidity and compatibility of the material.

[0013] Preferably, the diol further comprises 0.001-1 parts by weight of a dihydroxysilane coupling agent.

[0014] Preferably, the dihydroxysilane coupling agent is 3-[bis(2-hydroxyethyl)amino]propane-triethoxysilane.

[0015] By adopting the above technical solution, the dihydroxysilane coupling agent contains two hydroxyl groups, which can participate in the main chain reaction of unsaturated polyester and "embed" into the polyester main chain. The silane group contained in the dihydroxysilane coupling agent has good compatibility with the molecular chain of the hydrogen-terminated silicone oil. Therefore, it can act as a "molecular bridge," effectively improving the interfacial bonding force between the hydrophobic organosilicon phase and the relatively hydrophilic polyester phase. This can reduce micro-phase separation, allowing stress to be transferred more effectively between the two phases, thereby simultaneously improving toughness and strength, and also helping to maintain the uniformity and transparency of the resin. In addition, as a silane coupling agent, the dihydroxysilane coupling agent contains silicon-oxygen bonds that can react with the glass fiber of fiberglass, thereby improving the wettability of unsaturated polyester and glass fiber, and improving the performance of fiberglass products.

[0016] Preferably, the diluent is a mixture of styrene and methyl methacrylate.

[0017] By adopting the above technical solution, styrene and methyl methacrylate (MMA) are used as a diluent. Styrene is a highly efficient and low-cost crosslinking monomer; the introduction of MMA can significantly improve the resin's UV resistance and reduce yellowing, which is crucial for outdoor fiberglass products (such as skylights and equipment housings). Simultaneously, MMA can also regulate the curing shrinkage rate and reactivity.

[0018] Secondly, this application provides a method for preparing unsaturated polyester resin for fiberglass, employing the following technical solution: A method for preparing an unsaturated polyester resin for fiberglass reinforced plastics (FRP) comprises the following steps: S1. Under nitrogen atmosphere protection, diol, isophthalic acid and phthalic anhydride are added to the reactor for esterification and polycondensation reaction. When the acid value reaches below 40 mg KOH / g, the system is cooled to 90-120℃, and double-ended hydrogen-capped silicone oil and platinum catalyst are added to carry out hydrosilylation reaction to obtain the first reaction system. S2. Heat the first reaction system to 180-195℃, continue to add terephthalic acid and maleic anhydride, and continue the esterification and polycondensation reaction. When the acid value drops to below 25mg KOH / g, cool the reaction system to 75-110℃, add the polymerization inhibitor, stir evenly, cool it to below 70℃, add the pre-mixed styrene and methyl methacrylate, stir for 1.5h, and obtain a completely uniform and transparent unsaturated polyester resin.

[0019] By employing the above technical solution, a prepolymer with side-chain double bonds and an acid value of 40 mg KOH / g or lower is first synthesized. Then, a hydrosilylation reaction is carried out at a relatively low temperature. The low temperature suppresses side reactions, ensuring that the silicone oil reacts only with the highly reactive side-chain double bonds. After grafting, the temperature is increased to allow chain growth and introduce cross-linked double bonds (maleic anhydride) into the main chain. This preparation process ensures the regularity and predictability of the final product structure, enabling the realization of the desired molecular design and control of product performance.

[0020] A type of fiberglass, wherein the raw material of the fiberglass includes the unsaturated polyester resin used for fiberglass.

[0021] In summary, this application includes at least one of the following beneficial technical effects: 1. In the preparation of unsaturated polyester resin, neopentyl glycol in the diol provides corrosion resistance. Simultaneously, the diol is compounded with 2,2-diallylbisphenol A and bisphenol fluorene. Both substances contain large benzene ring structures, and their inherent rigidity and stability provide a robust skeletal structure for the unsaturated polyester resin. This directly contributes to higher flexural strength, rigidity, and heat distortion temperature after resin curing. The unique Cardo (fluorene ring) structure of bisphenol fluorene provides significant steric hindrance and rigidity, synergistically enhancing the rigidity of the molecular chain with the benzene ring structure of 2,2-diallylbisphenol A. Furthermore, a hydrogen-terminated silicone oil is introduced. Due to steric hindrance, it preferentially undergoes hydrosilylation with the double bonds on 2,2-diallylbisphenol A, allowing the hydrogen-terminated silicone oil to act as a side link, branching onto the main chain of the unsaturated polyester. These flexible side chains are highly efficient energy buffer centers, significantly improving impact toughness and elongation at break. On the other hand, when both ends of the hydrogen-capped silicone oil react with the double bonds of the side chains on different main chains, its large molecular weight can also reduce the local crosslinking density. These sites with low crosslinking density can further buffer external forces, thereby further improving the toughness of the unsaturated polyester. Furthermore, the large molecular weight of the hydrogen-capped silicone oil results in a lower degree of crosslinking to the main chain, forming weak crosslinks that do not affect the viscosity of the uncured unsaturated polyester or its actual application.

[0022] 2. Dihydroxysilane coupling agents contain two hydroxyl groups, enabling them to participate in the main chain reaction of unsaturated polyesters and "embed" into the polyester backbone. The silane groups in these agents exhibit good compatibility with the molecular chains of hydrogen-terminated silicone oils, thus acting as "molecular bridges." This effectively improves the interfacial bonding between the hydrophobic organosilicon phase and the relatively hydrophilic polyester phase, reducing micro-phase separation and allowing for more effective stress transfer between the two phases. This simultaneously enhances toughness and strength, and also helps maintain resin uniformity and transparency. Furthermore, as a silane coupling agent, the siloxane bonds in these agents can react with the glass fibers of fiberglass reinforced plastics (FRP), thereby improving the wettability of the unsaturated polyester and glass fibers, and enhancing the performance of FRP products. Detailed Implementation

[0023] The following provides a more detailed description of this application in conjunction with specific details.

[0024] raw material All raw materials used in the embodiments of this application are commercially available products, and their purity is analytical grade. Specifically, the platinum mass fraction in the isopropanol chloroplatinic acid solution is 0.5%; the double-ended hydrogen-capped silicone oil is purchased from Hoshine Silicon Industry Co., Ltd., and its different viscosities are custom-made products. Example

[0025] Examples 1-3 An unsaturated polyester resin for fiberglass reinforced plastics (FRP) is provided, the raw materials of which are shown in Table 1, and the preparation method is as follows: S1. Under nitrogen atmosphere protection, neopentyl glycol, 2,2-diallylbisphenol A, bisphenol fluorene, isophthalic acid and phthalic anhydride were added to the reactor, heated to 185℃ for esterification polycondensation reaction, and the acid value was monitored in real time. When the acid value decreased to 40mg KOH / g, the system was cooled to 110℃, and double-ended hydrogen-capped silicone oil and platinum catalyst were added. The reaction was stirred for 8h to obtain the first reaction system. S2. Heat the first reaction system to 190℃, continue to add terephthalic acid and maleic anhydride, and continue the esterification and polycondensation reaction. When the acid value drops to 25mg KOH / g, cool the reaction system to 100℃, add the polymerization inhibitor, stir evenly, cool it to 70℃, add the pre-mixed styrene and methyl methacrylate, stir for 1.5h, and obtain a completely uniform and transparent unsaturated polyester resin.

[0026] The amount of platinum catalyst used is calculated based on platinum metal, and the amount of platinum catalyst added is 100 ppm of the total mass of 2,2-diallylbisphenol A and double-ended hydrogen-sealed silicone oil. The viscosity of the double-ended hydrogen-sealed silicone oil is 500 mPa·s.

[0027] Table 1. Raw materials and dosage (kg) for Examples 1-3

[0028] Example 4 An unsaturated polyester resin for fiberglass, which differs from Example 2 in that the viscosity of its double-ended hydrogen-capped silicone oil is 1000 mPa·s, while the other steps are the same as in Example 2.

[0029] Example 5 An unsaturated polyester resin for fiberglass, which differs from Example 2 in that the viscosity of its double-ended hydrogen-capped silicone oil is 2000 mPa·s, while the other steps are the same as in Example 2.

[0030] Example 6 An unsaturated polyester resin for fiberglass, which differs from Example 2 in that the viscosity of its double-ended hydrogen-sealed silicone oil is 3000 mPa·s, while the other steps are the same as in Example 2.

[0031] Example 7 An unsaturated polyester resin for fiberglass, which differs from Example 2 in that the viscosity of its double-ended hydrogen-capped silicone oil is 5000 mPa·s, while the other steps are the same as in Example 2.

[0032] Example 8 An unsaturated polyester resin for fiberglass, which differs from Example 6 in that the amount of double-ended hydrogen-capped silicone oil added is 5 kg, while the remaining steps are the same as in Example 6.

[0033] Example 9 An unsaturated polyester resin for fiberglass, which differs from Example 6 in that the amount of double-ended hydrogen-capped silicone oil added is 9 kg, while the remaining steps are the same as in Example 6.

[0034] Example 10 An unsaturated polyester resin for fiberglass, differing from Example 6 in that its diol further includes 0.5 kg of 3-[bis(2-hydroxyethyl)amino]propane-triethoxysilane, with the remaining steps being the same as in Example 6.

[0035] Example 11 An unsaturated polyester resin for fiberglass, which differs from Example 2 in that the viscosity of its double-ended hydrogen-capped silicone oil is 10000 mPa·s, while the other steps are the same as in Example 2.

[0036] Example 12 An unsaturated polyester resin for fiberglass reinforced plastics differs from that in Example 2 in that its preparation method is different, as detailed below: S1. Under a nitrogen atmosphere, neopentyl glycol, 2,2-diallylbisphenol A, bisphenol fluorene, isophthalic acid and maleic anhydride were added to a reactor, and the temperature was raised to 185℃ for esterification polycondensation reaction. The acid value was monitored in real time. When the acid value decreased to 40 mg KOH / g, the system was cooled to 110℃, and double-ended hydrogen-capped silicone oil and platinum catalyst were added. The reaction was stirred for 8 hours to obtain the first reaction system. S2. Heat the first reaction system to 190°C, add terephthalic acid and phthalic anhydride, and continue the esterification and polycondensation reaction. When the acid value drops to 25 mg KOH / g, cool the reaction system to 100°C, add the polymerization inhibitor, stir evenly, cool it to 70°C, add the pre-mixed styrene and methyl methacrylate, stir for 1.5 h, and obtain a completely uniform and transparent unsaturated polyester resin.

[0037] Comparative Example Comparative Example 1 An unsaturated polyester resin for fiberglass, which differs from Example 2 in that, in its diol, bisphenol fluorene is replaced with an equal mass of neopentyl glycol, while the remaining steps are the same as in Example 2.

[0038] Comparative Example 2 An unsaturated polyester resin for fiberglass, differing from Example 2 in that the double-ended hydrogen-capped silicone oil is replaced with hydroxyl-capped silicone oil of equal viscosity and mass, while the remaining steps are the same as in Example 2.

[0039] Performance testing Detection methods / test methods Unsaturated polyester resins were prepared according to the preparation methods of Examples 1-12 and Comparative Examples 1-2, and then tested according to the following testing methods. The test results are shown in Table 2.

[0040] Viscosity: The viscosity of the prepared unsaturated polyester resin was tested, and the test method was in accordance with GB / T7193-2008.

[0041] The curing process for unsaturated polyester resin is as follows: Mix 100g of unsaturated polyester resin, 0.3g of cobalt isooctanoate and 2.5g of methyl ethyl ketone peroxide evenly, degas under vacuum, cure the silicone mold at room temperature for 5 hours, and then test its mechanical properties after 24 hours.

[0042] Tensile strength and elongation at break: tested according to the test methods in GB / T2567-2001; Barthel hardness: Tested according to the test method in GB / T3854-2017; Heat distortion temperature: Tested according to the test method in GB / T1634-2019.

[0043] Table 2 Test Results

[0044] As can be seen from the test data in Table 2, the viscosity of the unsaturated polyester resin prepared in this application is all 740 mPa·s and below, which is consistent with actual construction conditions; the tensile strength can all reach 82.0 MPa and above, with a maximum of 89.6 MPa; at the same time, its elongation at break can all reach 4.6-6.4%; and the Barcol hardness can reach 45-55 as tested. This indicates that the unsaturated polyester resin prepared in this application has excellent tensile strength, toughness and hardness.

[0045] Combining Examples 2 and 4-7, as well as Example 11, the siloxane chain segments are sufficiently long, resulting in the most significant toughening effect. However, this can also easily reduce the mechanical properties of the unsaturated polyester resin. Simultaneously, its molecular weight is insufficient to cause severe microphase separation. By controlling the viscosity of the siloxane chain within the range of 2000-5000 mPa·s, high toughness can be achieved while maintaining the rigidity and hardness of the material relatively well. In conjunction with Example 10, the dihydroxysilane coupling agent contains two hydroxyl groups, enabling it to participate in the main chain reaction of the unsaturated polyester and "embed" itself into the polyester backbone. The silane groups in the dihydroxysilane coupling agent have good compatibility with the molecular chains of the hydrogen-terminated silicone oil. Therefore, it can act as a "molecular bridge," effectively improving the interfacial bonding force between the hydrophobic organosilicon phase and the relatively hydrophilic polyester phase. This can reduce microphase separation, allowing stress to be transferred more effectively between the two phases, thereby simultaneously improving toughness and strength, and also helping to maintain the uniformity and transparency of the resin. In addition, as a silane coupling agent, the dihydroxysilane coupling agent contains silicon-oxygen bonds that can react with the glass fibers of fiberglass, thereby improving the wettability of unsaturated polyester and glass fibers and enhancing the performance of fiberglass products.

[0046] Combining Examples 2 and 12, a prepolymer with side-chain double bonds and an acid value of 40 mg KOH / g or lower was first synthesized. Then, a hydrosilylation reaction was carried out at a low temperature. The low temperature suppressed side reactions, ensuring that the silicone oil reacted only with the highly reactive side-chain double bonds. After grafting, the temperature was increased to allow chain growth and introduce cross-linked double bonds (maleic anhydride) into the main chain. This preparation process ensures the regularity and predictability of the final product structure, enabling the realization of the desired molecular design and control over product performance.

[0047] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. An unsaturated polyester resin for fiberglass reinforced plastics, characterized in that: It comprises the following raw materials in parts by weight: Diols: 22-30 parts neopentyl glycol, 2-4 parts 2,2-diallyl bisphenol A and 5-9 parts bisphenol fluorene; Dicarboxylic acids: 5-15 parts isophthalic acid, 5-15 parts terephthalic acid; Acid anhydrides: 3-15 parts phthalic anhydride, 5-17 parts maleic anhydride; Toughening agent: 5-9 parts of double-ended hydrogen-sealed silicone oil; Platinum catalyst: The amount of platinum catalyst added is 30-150 ppm of the total mass of 2,2-diallylbisphenol A and double-ended hydrogen-capped silicone oil. 25-45 parts diluent; Polymerization inhibitor 0.01-0.06 parts.

2. The unsaturated polyester resin for fiberglass as described in claim 1, characterized in that: The viscosity of the double-ended hydrogen-sealed silicone oil is 500-5000 mPa·s.

3. The unsaturated polyester resin for fiberglass as described in claim 1, characterized in that: The viscosity of the double-ended hydrogen-sealed silicone oil is 2000-5000 mPa·s.

4. The unsaturated polyester resin for fiberglass as described in claim 1, characterized in that: The diol also includes 0.001-1 parts by weight of a dihydroxysilane coupling agent.

5. The unsaturated polyester resin for fiberglass as described in claim 4, characterized in that: The dihydroxysilane coupling agent is 3-[bis(2-hydroxyethyl)amino]propane-triethoxysilane.

6. The unsaturated polyester resin for fiberglass as described in claim 1, characterized in that: The diluent is a mixture of styrene and methyl methacrylate.

7. A method for preparing an unsaturated polyester resin for fiberglass as described in any one of claims 1-6, characterized in that: It includes the following steps: S1. Under nitrogen atmosphere protection, diol, isophthalic acid and phthalic anhydride are added to the reactor for esterification and polycondensation reaction. When the acid value reaches below 40 mg KOH / g, the system is cooled to 90-120℃, and double-ended hydrogen-capped silicone oil and platinum catalyst are added to carry out hydrosilylation reaction to obtain the first reaction system. S2. Heat the first reaction system to 180-195℃, continue to add terephthalic acid and maleic anhydride, and continue the esterification and polycondensation reaction. When the acid value drops to below 25mg KOH / g, cool the reaction system to 75-110℃, add the polymerization inhibitor, stir evenly, cool it to below 70℃, add the pre-mixed styrene and methyl methacrylate, stir for 1.5h, and obtain a completely uniform and transparent unsaturated polyester resin.

8. A type of fiberglass, characterized in that: The raw materials for the fiberglass include the unsaturated polyester resin for fiberglass as described in any one of claims 1-6.

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