Glass fiber reinforced resin well lid and its production process

Abstract

This invention belongs to the field of composite material technology, specifically relating to a fiberglass reinforced resin manhole cover and its manufacturing process. The fiberglass reinforced resin manhole cover is made from the following components by weight: 100 parts unsaturated polyester resin, 3-3.5 parts curing agent, 15-25 parts untwisted fiberglass roving, 1-4 parts pigment, 17-20 parts calcium powder, 8-15 parts talc, 2.5-6 parts alumina, 3-5 parts anti-shrinkage agent, 9-15 parts prepolymer material, 0.5-1 part release agent, and 0.1-0.7 parts anti-aging agent; wherein the prepolymer material is obtained from 1,5-hexadiene-3,4-diol, trimellitic anhydride, 4-acetoxy-3-methoxybenzoic acid, and 4'-(acetoxy)biphenyl-4-carboxylic acid. The manufacturing process involves two rounds of blending, sheet compaction, and molding curing of the required raw materials to obtain the fiberglass reinforced resin manhole cover. The manhole cover produced by this invention exhibits excellent toughness in low-temperature environments and is not prone to cracking.

Description

Technical Field

[0001] This invention belongs to the field of composite material technology, specifically relating to a glass fiber reinforced resin manhole cover and its manufacturing process. Background Technology

[0002] Resin manhole covers are manhole cover products made primarily of resin and reinforcing materials, cured and molded through a high-temperature, high-pressure process. They are widely used in urban municipal works, telecommunications, chemical, and power industries. The reinforcing material is mainly glass fiber, which provides the resin manhole cover with tensile strength and impact resistance. The resin material can be selected based on different application scenarios. For example, unsaturated polyester resin (UPR) has the characteristics of easy curing, good flowability, and good bonding performance with materials such as glass fiber, and is often used in general scenarios such as municipal works.

[0003] To compensate for the load-bearing capacity of resin and achieve lightweight manhole covers, a high amount of glass fiber is often added to unsaturated polyester resin. Glass fiber has high specific strength and specific modulus, and can effectively bear the load as a reinforcing skeleton. However, this further highlights the insufficient wettability of unsaturated polyester, which easily forms internal stress at the resin-reinforcing fiber interface. In addition, polyester will still harden and become brittle in the low-temperature environment of the north. These two factors lead to a decrease in the toughness of resin manhole covers in low-temperature environments, and the surface of resin manhole covers is prone to brittle cracking under heavy load and impact conditions.

[0004] Chinese patent CN106243623A discloses a method for producing manhole covers, comprising the following steps: 1) adding paraformaldehyde to ethanol, adjusting the pH to 8-10, heating to depolymerize the paraformaldehyde; adding melamine and dicyandiamide to react, distilling to remove ethanol, and obtaining a prepolymer of melamine-dicyandiamide formaldehyde resin; 2) mixing the prepolymer with urea-formaldehyde resin evenly, then adding cloth and / or cotton yarn, curing agent and stone powder, mixing evenly to obtain a mixture, wherein the curing agent is selected from one or more of ammonium chloride, ammonium sulfate, p-toluenesulfonic acid or ammonium formate; 3) pre-pressing the mixture to obtain a manhole cover blank; the manhole cover blank is hot-pressed and cooled to obtain a manhole cover.

[0005] When the curing agent is an acidic ammonium salt such as ammonium chloride or ammonium sulfate, the curing agent may decompose prematurely and release ammonia gas in a concentrated manner when the prepolymer is prepared under alkaline conditions during the preparation of the mixture in step 2), which will affect the low-temperature brittleness of the material. Summary of the Invention

[0006] The purpose of this invention is to provide a fiberglass reinforced resin manhole cover, which exhibits excellent toughness in low-temperature environments and is not prone to cracking; this invention also provides a manufacturing process for the fiberglass reinforced resin manhole cover.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The fiberglass reinforced resin well cover of the present invention is made from the following components by weight: 100 parts unsaturated polyester resin, 3-3.5 parts curing agent, 15-25 parts untwisted fiberglass roving, 1-4 parts pigment, 17-20 parts calcium powder, 8-15 parts talc powder, 2.5-6 parts alumina, 3-5 parts anti-shrinkage agent, 9-15 parts prepolymer material, 0.5-1 part release agent, and 0.1-0.7 parts anti-aging agent; wherein the preparation process of the prepolymer material is as follows: S1. Preparation of 4-acetoxy-3-methoxybenzoic acid; S2. 1,5-Hexadien-3,4-diol, trimellitic anhydride, 4-acetoxy-3-methoxybenzoic acid, 4'-(acetoxy)biphenyl-4-carboxylic acid are mixed with an organic solvent, and a catalyst is added. The mixture is reacted under an inert atmosphere, and the organic solvent is removed to obtain the prepolymer material.

[0008] in: The curing agent is composed of cyclohexanone peroxide and cobalt naphthenate in a mass ratio of 1:(0.1~0.2), the calcium powder is heavy calcium carbonate, the anti-shrinkage agent is polytetrahydrofuran ether glycol, the release agent is zinc stearate, and the anti-aging agent is UV-531.

[0009] In S1, the preparation process involves mixing vanillin, acetic anhydride, toluene, and pyridine in a ratio of 2:(2~2.5):(9~12):(0.1~0.15) and refluxing the mixture. After concentration under reduced pressure, filtration, and recrystallization, 4-acetoxy-3-methoxybenzoic acid is obtained. Vanillin is expressed in kg, and acetic anhydride, toluene, and pyridine are expressed in L. The refluxing reaction time is 2.5~3.5 h.

[0010] In S2, the organic solvent is toluene, and the catalysts are N-methylimidazolium and tetrabutyl titanate; the ratio of 1,5-hexadiene-3,4-diol, trimellitic anhydride, N-methylimidazolium, tetrabutyl titanate, and a portion of the organic solvent is 220:(320~400):10:(9.5~11.5):(6~11); the ratio of 1,5-hexadiene-3,4-diol, 4-acetoxy-3-methoxybenzoic acid, 4'-(acetoxy)biphenyl-4-carboxylic acid, and the remaining organic solvent is 220:(200~250):140:(2~5), wherein 1,5-hexadiene-3,4-diol, trimellitic anhydride, 4-acetoxy-3-methoxybenzoic acid, and 4'-(acetoxy)biphenyl-4-carboxylic acid are expressed in g, N-methylimidazolium and tetrabutyl titanate in mL, and toluene in L.

[0011] In the S2 process, the blending temperature is 70~80℃, the primary reaction temperature is 125~130℃, and the primary reaction time is 1.5~2.5h; the inert atmosphere is argon, the inert atmosphere pressure is 0.5~0.6MPa, the secondary reaction temperature is 165~175℃, and the secondary reaction time is 4~5h.

[0012] The manufacturing process of the fiberglass reinforced resin manhole cover of the present invention includes the following steps: (1) Unsaturated polyester resin, anti-shrinkage agent, and prepolymer material are stirred once, and calcium powder, talc powder, pigment, alumina, release agent, anti-aging agent and curing agent are added for a second stirring. Finally, the mixture is allowed to stand and mature to obtain a premix. (2) The premix is ​​coated on the polyethylene carrier film to form a resin paste. Glass fiber untwisted roving is cut and added to the resin paste. The two layers of resin paste are combined and compacted to obtain the sheet to be molded. (3) Add the sheet to be molded into the preheated mold, press, cure and cool to obtain the finished product, and then process the finished product to obtain the glass fiber reinforced resin well cover.

[0013] in: In step (1), the first stirring rate is 600~800 rpm and the first stirring time is 3~5 min; the second stirring rate is 600~800 rpm and the second stirring time is 20~30 min; the standing maturation time is 12~24 h and the standing maturation temperature is 20~30℃.

[0014] In step (2), the resin paste has a unit area weight of 2.4~2.6 kg / m². 2 .

[0015] In step (3), the preheating temperature of the mold is 160~180℃, and the pressure of mold closing and pressing is 22~25MPa.

[0016] In step (3), the curing temperature is 160~180℃ and the curing time is 30~40min.

[0017] In step (3), the cooling rate is 5~8℃ / min, and the temperature is reduced to 50~60℃. Post-processing includes trimming, punching, and packaging.

[0018] The beneficial effects of this invention are as follows: In the preparation of prepolymer materials, trimellitic anhydride contains anhydride and carboxyl groups; 1,5-hexadien-3,4-diol contains hydroxyl groups and terminal carbon-carbon double bonds; 4-acetoxy-3-methoxybenzoic acid and 4'-(acetoxy)biphenyl-4-carboxylic acid contain carboxyl groups and acetoxy groups. Under the action of catalysts N-methylimidazolium and tetrabutyl titanate, trimellitic anhydride and 1,5-hexadien-3,4-diol react to generate ester compounds. Further, as the temperature increases, the acetoxy groups in 4-acetoxy-3-methoxybenzoic acid and 4'-(acetoxy)biphenyl-4-carboxylic acid gradually react with the carboxyl groups, and the resulting molecular chains contain aliphatic flexible segments and aromatic rigid segments (containing benzene rings and biphenyls). The branching points in the molecular chains are introduced by the trifunctionality of trimellitic anhydride, and terminal carbon-carbon double bonds are also introduced. During molding and curing, the C=C at the end of the prepolymer can participate in the curing and crosslinking process of the unsaturated polyester resin, and together form a grafted crosslinking network.

[0019] This invention constructs a grafted crosslinking network comprising a hard phase and a soft phase. The hard phase consists of a UPR backbone and rigid aromatic (benzene, biphenyl) segments of the prepolymer; the soft phase consists of aliphatic flexible segments containing 1,5-hexadiene. By constructing the grafted crosslinking network, the UPR backbone and the prepolymer grafted chains intertwine and entangle, hindering relative slippage between molecular chains. Through the design of multi-site crosslinking at branching points and a two-stage crosslinking reaction process, and the simultaneous formation of hydrogen bonds between the residual carboxyl and hydroxyl groups of the prepolymer and the silanol groups on the glass fiber surface, the glass fiber and the grafted crosslinking network are integrated into a composite system. Phase separation is less likely to occur at the glass fiber, resulting in simultaneous improvement in rigidity and toughness, and eliminating creep and interface failure issues. This significantly improves the heavy-load performance and impact resistance of the resulting resin manhole cover under external stress. Detailed Implementation

[0020] The present invention will now be described and illustrated in detail with reference to the embodiments.

[0021] The raw materials used in the following examples and comparative examples are all commercially available products. Among them, the unsaturated polyester resin, model TM-191RS, was provided by Changzhou Tianma Group Co., Ltd.; the glass fiber roving, model ERS240-T949M, was provided by Taishan Glass Fiber Co., Ltd.; the heavy calcium carbonate, 400 mesh, was provided by Jiangxi Bairui Calcium Carbonate Co., Ltd.; the polytetrahydrofuran ether diol, model PTMEG650, was provided by Guangzhou Jingbo New Material Technology Co., Ltd.; and the polycarbonate, model A1077, was provided by Wanhua Chemical.

[0022] Example 1 Weigh out 10,000g of unsaturated polyester resin, 320g of curing agent (pre-mixed with cyclohexanone peroxide and cobalt naphthenate in a mass ratio of 1:0.2), 2,500g of glass fiber roving, 400g of pigment, 2,000g of heavy calcium carbonate, 1,200g of talc, 400g of alumina, 300g of polytetrahydrofuran ether diol, 900g of prepolymer material, 50g of zinc stearate, and 10g of UV-531; the prepolymer material needs to be prepared in advance.

[0023] Preparation of prepolymer materials 2 kg vanillin, 2.2 L acetic anhydride, 9 L toluene and 0.15 L pyridine were added to a reaction vessel and refluxed for 2.5 h. The reaction solution was concentrated under reduced pressure and filtered. The filter residue was recrystallized with petroleum ether to obtain 4-acetoxy-3-methoxybenzoic acid with a yield of 49.5%.

[0024] The reactor was purged with argon gas to remove oxygen. 220g of 1,5-hexadien-3,4-diol, 350g of trimellitic anhydride, 10mL of N-methylimidazole, 9.5mL of tetrabutyl titanate, and 11L of toluene were added to a sealed reactor. The reactor was stirred, heated to 70℃, and stirred until dissolved. The reaction was carried out at 128℃ for 2 hours. Then, argon gas was introduced until the gauge pressure reached 0.5MPa. 250g of 4-acetoxy-3-methoxybenzoic acid, 140g of 4'-(acetoxy)biphenyl-4-carboxylic acid, and 2L of toluene were added. The temperature was raised to 170℃, and the reaction continued for 4 hours. After the reaction was completed, the toluene was evaporated, and the mixture was cooled to room temperature to obtain the prepolymer material, which was then sealed and stored for later use.

[0025] Preparation of glass fiber reinforced resin manhole covers Weigh out the unsaturated polyester resin, polytetrahydrofuran ether glycol and prepolymer materials and add them to a mixing tank. Turn on the stirring in the tank at a speed of 700 rpm and stir for 3 minutes. Then, while stirring, add the weighed out heavy calcium carbonate, talc, pigment, alumina, zinc stearate, UV-531 and curing agent. Continue stirring at 700 rpm for 30 minutes. Stop stirring and let it stand at 30°C for 12 hours to obtain the premix.

[0026] The premixed material is coated onto a polyethylene carrier film to form a resin paste, with a unit area weight of 2.6 kg / m³. 2 Cut the untwisted fiberglass roving and evenly spread it onto the resin paste; then, use rollers to press the two layers of resin paste together to obtain the sheet to be molded. The structure of the sheet to be molded, from top to bottom, consists of a polyethylene carrier film, resin paste, cut untwisted fiberglass roving, resin paste, and a polyethylene carrier film. The polyethylene carrier films on both sides need to be removed before molding.

[0027] Preheat the mold to 160°C, put the sheet material to be molded with the polyethylene bearing film removed into the mold, close the mold and press it. When the pressure reaches 25MPa, lock the mold and keep it at 160°C for 40 minutes to cure. After curing, reduce the temperature to 50°C at a constant rate of 7°C / min, take out the finished product, cool it to room temperature, trim, punch holes and package it to obtain the glass fiber reinforced resin well cover.

[0028] Example 2 Weigh out 10,000g of unsaturated polyester resin, 300g of curing agent (pre-mixed with cyclohexanone peroxide and cobalt naphthenate in a mass ratio of 1:0.12), 1,500g of glass fiber roving, 100g of pigment, 1,700g of heavy calcium carbonate, 1,500g of talc, 600g of alumina, 500g of polytetrahydrofuran ether diol, 1,200g of prepolymer material, 75g of zinc stearate, and 70g of UV-531; the prepolymer material needs to be prepared in advance.

[0029] Preparation of prepolymer materials 2 kg vanillin, 2.5 L acetic anhydride, 10.2 L toluene and 0.1 L pyridine were added to a reaction vessel and refluxed for 3 h. The reaction solution was concentrated under reduced pressure and filtered. The filter residue was recrystallized with petroleum ether to obtain 4-acetoxy-3-methoxybenzoic acid with a yield of 51.8%.

[0030] The reactor was purged with argon gas to remove oxygen. 220g of 1,5-hexadien-3,4-diol, 320g of trimellitic anhydride, 10mL of N-methylimidazole, 10mL of tetrabutyl titanate, and 8.5L of toluene were added to a sealed reactor. The reactor was stirred, heated to 80℃, and stirred until dissolved. The reaction was carried out at 125℃ for 2.5h. Then, argon gas was introduced until the gauge pressure reached 0.6MPa. 200g of 4-acetoxy-3-methoxybenzoic acid, 140g of 4'-(acetoxy)biphenyl-4-carboxylic acid, and 5L of toluene were added. The temperature was raised to 165℃, and the reaction continued for 4.5h. After the reaction was completed, the toluene was evaporated, and the mixture was cooled to room temperature to obtain the prepolymer material, which was then sealed and stored for later use.

[0031] Preparation of glass fiber reinforced resin manhole covers Weigh out the unsaturated polyester resin, polytetrahydrofuran ether glycol and prepolymer materials and add them to a mixing tank. Turn on the stirring in the tank at a speed of 800 rpm and stir for 5 minutes. Then, while stirring, add the weighed out heavy calcium carbonate, talc, pigment, alumina, zinc stearate, UV-531 and curing agent. Continue stirring at 800 rpm for 20 minutes. Stop stirring and let it stand at 25°C for 16 hours to obtain the premix.

[0032] The premixed material is coated onto a polyethylene carrier film to form a resin paste, with a unit area weight of 2.4 kg / m³. 2Cut the untwisted fiberglass roving and evenly spread it onto the resin paste; then, use rollers to press the two layers of resin paste together to obtain the sheet to be molded. The structure of the sheet to be molded, from top to bottom, consists of a polyethylene carrier film, resin paste, cut untwisted fiberglass roving, resin paste, and a polyethylene carrier film. The polyethylene carrier films on both sides need to be removed before molding.

[0033] Preheat the mold to 168°C, put the sheet material to be molded with the polyethylene bearing film removed into the mold, close the mold and press, lock the mold when the pressure reaches 22MPa, and keep the pressure at 168°C for 30 minutes to cure; after curing, reduce the temperature to 60°C at a constant rate of 8°C / min, take out the finished product, cool it to room temperature, trim, punch holes and package it to obtain the glass fiber reinforced resin well cover.

[0034] Example 3 Weigh out 10,000g of unsaturated polyester resin, 350g of curing agent (pre-mixed with cyclohexanone peroxide and cobalt naphthenate in a mass ratio of 1:0.15), 2,000g of glass fiber roving, 250g of pigment, 1,800g of heavy calcium carbonate, 800g of talc, 250g of alumina, 400g of polytetrahydrofuran ether diol, 1,500g of prepolymer material, 100g of zinc stearate, and 60g of UV-531; the prepolymer material needs to be prepared in advance.

[0035] Preparation of prepolymer materials 2 kg vanillin, 2 L acetic anhydride, 12 L toluene and 0.13 L pyridine were added to a reactor and refluxed for 3.5 h. The reaction solution was concentrated under reduced pressure and filtered. The filter residue was recrystallized with petroleum ether to obtain 4-acetoxy-3-methoxybenzoic acid with a yield of 53.4%.

[0036] The reactor was purged with argon gas to remove oxygen. 220g of 1,5-hexadien-3,4-diol, 400g of trimellitic anhydride, 10mL of N-methylimidazole, 11.5mL of tetrabutyl titanate, and 6L of toluene were added to a sealed reactor. The reactor was stirred, heated to 75℃, and stirred until dissolved. The reaction was carried out at 130℃ for 1.5h. Then, argon gas was introduced until the gauge pressure reached 0.58MPa. 230g of 4-acetoxy-3-methoxybenzoic acid, 140g of 4'-(acetoxy)biphenyl-4-carboxylic acid, and 4L of toluene were added. The temperature was raised to 175℃, and the reaction continued for 5h. After the reaction was completed, the toluene was evaporated, and the mixture was cooled to room temperature to obtain the prepolymer material, which was then sealed and stored for later use.

[0037] Preparation of glass fiber reinforced resin manhole covers Weigh out the unsaturated polyester resin, polytetrahydrofuran ether glycol and prepolymer materials and add them to a mixing tank. Turn on the stirring in the tank at a speed of 600 rpm and stir for 4 minutes. Then, while stirring, add the weighed out heavy calcium carbonate, talc, pigment, alumina, zinc stearate, UV-531 and curing agent. Continue stirring at 600 rpm for 25 minutes. Stop stirring and let it stand at 20°C for 24 hours to obtain the premix.

[0038] The premixed material is coated onto a polyethylene carrier film to form a resin paste, with a unit area weight of 2.5 kg / m³. 2 Cut the untwisted fiberglass roving and evenly spread it onto the resin paste; then, use rollers to press the two layers of resin paste together to obtain the sheet to be molded. The structure of the sheet to be molded, from top to bottom, consists of a polyethylene carrier film, resin paste, cut untwisted fiberglass roving, resin paste, and a polyethylene carrier film. The polyethylene carrier films on both sides need to be removed before molding.

[0039] Preheat the mold to 180°C, put the sheet material to be molded with the polyethylene bearing film removed into the mold, close the mold and press, lock the mold when the pressure reaches 24MPa, and keep it at 180°C for 35 minutes to cure. After curing, reduce the temperature to 55°C at a constant rate of 5°C / min, take out the finished product, cool it to room temperature, trim, punch holes and package it to obtain the glass fiber reinforced resin well cover.

[0040] Comparative Example 1 Without adding 4-acetoxy-3-methoxybenzoic acid, the remaining steps are the same as in Example 1 to obtain a glass fiber reinforced resin well cover.

[0041] Comparative Example 2 Without adding 4'-(acetoxy)biphenyl-4-carboxylic acid, the remaining steps are the same as in Example 1 to obtain a glass fiber reinforced resin well cover.

[0042] Comparative Example 3 Without adding 1,5-hexadien-3,4-diol, the remaining steps are the same as in Example 1 to obtain a glass fiber reinforced resin well cover.

[0043] Comparative Example 4 Without adding trimellitic anhydride, the remaining steps are the same as in Example 1 to obtain a glass fiber reinforced resin manhole cover.

[0044] Implementation effect evaluation Referring to the relevant inspection items and standards of CJ / T 211-2005 "Polymer-based Composite Manhole Covers", the resin manhole covers prepared in the examples and comparative examples were tested. The heavy load bearing capacity test and impact strength test processes are as follows: Heavy-duty load-bearing capacity test: The manufactured fiberglass reinforced resin manhole cover and matching support are installed. The manhole cover specification is D500, with an embedding thickness of 50mm. It is kept in an environment of -30℃ for 72 hours, then removed and loaded with a test load of 280kN. After maintaining the test load for 25 minutes, it is unloaded. The manhole cover and support are visually inspected for cracks, fissures, or obvious permanent deformation. Loading continues until the manhole cover breaks, collapses, or can no longer bear the load. The maximum destructive load value is recorded. Requirements: No cracks, fissures, or obvious permanent deformation under a 280kN load; a destructive load ≥420kN is considered excellent.

[0045] Impact strength testing: Refer to Section 6.2 of CJ / T 211-2005 and GB / T 1043-1993 "Impact Test Method for Simply Supported Beams of Rigid Plastics" for the testing process. The requirements are: for each example and comparative example, take 5 samples of the glass fiber reinforced resin manhole cover, and the average unnotched impact strength should be ≥18.0 kJ / m. 2 And the minimum value of one of them is ≥15.0 kJ / m 2 Excellent. See Table 1 for detailed test results.

[0046] Table 1 Test Results

[0047] As shown in Table 1, the low-temperature heavy-load bearing capacity and impact resistance of the embodiments of the present invention are excellent, fully meeting the requirements for heavy-duty manhole covers in municipal and industrial applications, and exhibiting excellent impact resistance and crack resistance. All four comparative examples were based on Example 1, except for the removal of one core functional monomer from the prepolymer material; the remaining raw materials and process parameters were identical. The final performance of all examples showed a significant decrease, indicating that without the core functional monomer, the synergistic effect between the soft phase, hard phase, and branching points cannot be formed, thus preventing the formation of a complete graft crosslinking network.

Claims

1. A fiberglass reinforced resin manhole cover, characterized in that, The product, by weight, is prepared from the following components: 100 parts unsaturated polyester resin, 3-3.5 parts curing agent, 15-25 parts untwisted glass fiber roving, 1-4 parts pigment, 17-20 parts calcium powder, 8-15 parts talc, 2.5-6 parts alumina, 3-5 parts anti-shrinkage agent, 9-15 parts prepolymer material, 0.5-1 part release agent, and 0.1-0.7 parts anti-aging agent; the preparation process of the prepolymer material is as follows: S1. Preparation of 4-acetoxy-3-methoxybenzoic acid; S2. 1,5-hexadien-3,4-diol, trimellitic anhydride, catalyst and part of organic solvent are mixed and reacted once. Then 4-acetoxy-3-methoxybenzoic acid, 4'-(acetoxy)biphenyl-4-carboxylic acid and the remaining organic solvent are added and reacted twice under an inert atmosphere to remove the organic solvent and obtain the prepolymer material.

2. The fiberglass reinforced resin manhole cover according to claim 1, characterized in that, The curing agent is a mixture of cyclohexanone peroxide and cobalt naphthenate in a mass ratio of 1:(0.1~0.2), the calcium powder is heavy calcium carbonate, the anti-shrinkage agent is polytetrahydrofuran ether glycol, the release agent is zinc stearate, and the anti-aging agent is UV-531.

3. The fiberglass reinforced resin manhole cover according to claim 1, characterized in that, In S1, the preparation process involves mixing vanillin, acetic anhydride, toluene, and pyridine in a ratio of 2:(2~2.5):(9~12):(0.1~0.15) and refluxing the mixture. After concentration under reduced pressure, filtration, and recrystallization, 4-acetoxy-3-methoxybenzoic acid is obtained. Vanillin is expressed in kg, while acetic anhydride, toluene, and pyridine are expressed in L. The refluxing time is 2.5~3.5 h.

4. The fiberglass reinforced resin manhole cover according to claim 1, characterized in that, In S2, the organic solvent is toluene, and the catalysts are N-methylimidazolium and tetrabutyl titanate. The ratio of 1,5-hexadiene-3,4-diol, trimellitic anhydride, N-methylimidazolium, tetrabutyl titanate, and a portion of the organic solvent is 220:(320~400):10:(9.5~11.5):(6~11). The ratio of 1,5-hexadiene-3,4-diol, 4-acetoxy-3-methoxybenzoic acid, 4'-(acetoxy)biphenyl-4-carboxylic acid, and the remaining organic solvent is 220:(200~250):140:(2~5). Among these, 1,5-hexadiene-3,4-diol, trimellitic anhydride, 4-acetoxy-3-methoxybenzoic acid, and 4'-(acetoxy)biphenyl-4-carboxylic acid are expressed in g, N-methylimidazolium and tetrabutyl titanate in mL, and toluene in L.

5. The fiberglass reinforced resin manhole cover according to claim 1, characterized in that, In S2, the blending temperature is 70~80℃, the primary reaction temperature is 125~130℃, and the primary reaction time is 1.5~2.5h; the inert atmosphere is argon, the inert atmosphere pressure is 0.5~0.6MPa, the secondary reaction temperature is 165~175℃, and the secondary reaction time is 4~5h.

6. A manufacturing process for a fiberglass reinforced resin manhole cover according to any one of claims 1-5, characterized in that, Includes the following steps: (1) Unsaturated polyester resin, anti-shrinkage agent, and prepolymer material are stirred once, and calcium powder, talc powder, pigment, alumina, release agent, anti-aging agent and curing agent are added for a second stirring. Finally, the mixture is allowed to stand and mature to obtain a premix. (2) The premix is ​​coated on the polyethylene carrier film to form a resin paste. Glass fiber untwisted roving is cut and added to the resin paste. The two layers of resin paste are combined and compacted to obtain the sheet to be molded. (3) Add the sheet to be molded into the preheated mold, press, cure and cool to obtain the finished product, and then process the finished product to obtain the glass fiber reinforced resin well cover.

7. The manufacturing process of the fiberglass reinforced resin manhole cover according to claim 6, characterized in that, In step (1), the first stirring rate is 600~800 rpm and the first stirring time is 3~5 min; the second stirring rate is 600~800 rpm and the second stirring time is 20~30 min.

8. The manufacturing process of the fiberglass reinforced resin manhole cover according to claim 6, characterized in that, In step (2), the unit area weight of the resin paste is 2.4 to 2.6 kg / m 2 .

9. The manufacturing process of the fiberglass reinforced resin manhole cover according to claim 6, characterized in that, In step (3), the preheating temperature of the mold is 160~180℃, the pressure of mold closing and pressing is 22~25MPa, the curing temperature is 160~180℃, and the curing time is 30~40min.

10. The manufacturing process of the fiberglass reinforced resin manhole cover according to claim 6, characterized in that, In step (3), the cooling rate is 5~8℃ / min, and the temperature is reduced to 50~60℃.

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