Two-support high-strength well lid, SMC composite material and preparation method of two-support high-strength well lid

Abstract

The invention relates to the technical field of material application, in particular to a two-support high-strength well lid, an SMC composite material and a preparation method of the two-support high-strength well lid. The SMC composite material for the two-support high-strength well lid is prepared from the following components in parts by weight: 18 to 25 parts of unsaturated polyester resin, 4 to 8 parts of low-shrinkage additive, 0.2 to 0.4 part of initiator, 0.1 to 0.3 part of auxiliary agent, 0.7 to 1.5 parts of release agent, 1 to 2 parts of color paste, 25 to 35 parts of filler, 0.1 to 0.4 part of antioxidant, 1 to 4.0 parts of active magnesium oxide paste and 35 to 45 parts of glass fiber. A method for preparing the SMC composite material for the two-support high-strength well lid comprises the following steps: S1, adding the unsaturated polyester resin and the low-shrinkage additive into a stirring kettle; a method for preparing the two-support high-strength well lid comprises the following steps that S1, the thickened SMC sheets are cut and stacked according to the 100% size of the projected area of a product; the produced two-support well lid is about 30% lighter than a common SMC two-support well lid of the same specification, and the weight of the product is greatly reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of material application, and in particular to a double-support high-strength manhole cover and SMC composite material and a preparation method thereof. Background Art

[0002] Most of the existing two-support manhole covers are made of cast iron, cement steel, resin casting, BMC plus steel, and ordinary SMC materials. Cast iron materials have high energy consumption, high carbon emissions, and a single color appearance. Because of its recycling value, it is often lost. The inspection well has no manhole cover, which will cause great safety hazards. The cast iron manhole cover is very heavy and inconvenient to carry and use. The weight of cement steel manhole cover is more than twice that of ordinary composite materials. After long-term use, the cement will fall off, the bearing capacity will decrease, and it is easy to cause safety hazards. The composite material used in the BMC plus steel manhole cover is low in strength and inconsistent with the thermal expansion coefficient of the steel bar. After long-term use, the composite material will fall off, causing safety hazards. The bending strength of ordinary SMC composite materials used for manhole covers is only about 300MPa, and the modulus is only about 14000MPa. The thickness of the designed and produced large-span two-support manhole cover is relatively thick, the single pressing time is relatively long, and the required press tons are relatively large.

[0003] At the same time, conventional methods for preparing composite materials for manhole covers or methods for preparing manhole covers are such as the technical solutions mentioned in Chinese Patent 2023115549843. However, for example, the manhole covers prepared by the above patents are relatively weak in strength. If a load of 40T is required, the product needs to be thicker to achieve this, and the energy consumption in the production process is relatively high.

[0004] The currently disclosed SMC composite manhole covers all have certain defects and cannot meet the requirements of low energy consumption, light weight and high strength. Therefore, it is particularly important to develop a preparation method and application of SMC composite materials for two-support high-strength manhole covers. Summary of the invention

[0005] In order to overcome the shortcomings of the prior art, the present invention provides a two-support high-strength manhole cover and SMC composite material with high SMC sheet strength, low mold temperature required for molding, reduced energy consumption, short holding time, and low cost of the pressed manhole cover, and a preparation method thereof. In order to optimize the above technical problems, the present invention provides the following technical solutions:

[0006] A SMC composite material for a double-support high-strength manhole cover, comprising the following components in parts by weight:

[0007] Unsaturated polyester resin 18-25 parts,

[0008] 4-8 parts of low shrinkage additive,

[0009] Initiator 0.2-0.4 parts,

[0010] Additives 0.1-0.3 parts,

[0011] Release agent 0.7-1.5 parts,

[0012] 1-2 parts of color paste,

[0013] 25-35 parts of filler,

[0014] Antioxidant 0.1-0.4 parts,

[0015] 1-4.0 parts of activated magnesium oxide paste,

[0016] 35-45 parts of glass fiber.

[0017] On the basis of adopting the above technical solution, the present invention can also adopt the following further technical solution:

[0018] The unsaturated polyester resin is propylene phthalate resin;

[0019] The low shrinkage additive is one of a polystyrene low shrinkage additive and a polyvinyl acetate low shrinkage additive, or a compound of a polystyrene low shrinkage additive and a polyvinyl acetate low shrinkage additive.

[0020] The filler is 1250 mesh calcium carbonate whisker, the auxiliary agent is an anti-phase separation agent, the initiator is tert-butyl peroxide-2-ethylhexanoate, the release agent is zinc stearate, the black slurry has a viscosity of less than 10000 mPa.s, and the carbon black content is greater than or equal to 30%.

[0021] The antioxidant is one or a combination of BHT and TBHQ; the magnesium oxide paste contains 50% magnesium oxide, and the viscosity of the magnesium oxide paste is less than 10000 mPa.s; and the glass fiber is alkali-free glass fiber roving.

[0022] Furthermore, the present invention also provides the following technical solutions:

[0023] A method for preparing the above-mentioned two-support high-strength SMC composite material for manhole covers comprises the following steps:

[0024] S1. Add unsaturated polyester resin and low shrinkage additive into a stirring kettle, start stirring automatically, and add curing agent, auxiliary agent and antioxidant in sequence;

[0025] S2, adding zinc stearate and calcium carbonate whiskers to the stirring tank of step S1 and continuing stirring until the temperature reaches 35°C;

[0026] S3, after stopping stirring, the mixed paste in the stirring kettle of step S2 is transferred to the intermediate barrel A, and the mixed resin paste, color paste barrel B, and magnesium oxide paste barrel C in the intermediate barrel A are simultaneously pumped into the high-speed mixer according to a certain proportion by using an online mixing device, and as the online device continuously enters the high-speed mixer from the bottom, the stirred mixture finally overflows from the top trough and flows into the upper and lower paste areas of the SMC sheet molding compound molding machine respectively;

[0027] S4, adjusting the height of the upper and lower paste gates to 0.9-1.0 mm, ensuring that the weight of the paste flowing out of the upper and lower paste gates of the SMC sheet molding compound molding machine in step S3 on the supporting PP film is 2.4-2.6 kg per square meter;

[0028] S5, the mixed paste in the upper pasting area is evenly coated on the PP carrier film through the pasting door, and a yarn cutting device is started. In addition, 40 continuous basalt fibers are passed through the pipeline between the two layers of film. The sheet pulling speed is 10 m / min. The resin paste is coated on the two PP carrier films and transported to the conveyor belt respectively. The yarn cutter cuts the alkali-free glass fiber roving and lays it on the resin paste of the lower PP carrier film. The two layers of film are closed again to form a sandwich layer of paste, continuous alkali-free glass fiber, short alkali-free glass fiber, and paste;

[0029] S6, the sandwich layer is continuously rolled by 20 sets of offset rollers through the upper and lower mesh belts of the SMC unit, and the compacted sheets are collected in ton packaging bags with high barrier nylon bags to obtain SMC sheets;

[0030] S7. Put the full box of SMC materials into the constant temperature curing room;

[0031] S8. After the thickened SMC sheets are tested and qualified, they are placed in a cold storage for future use.

[0032] In step S1, the stirring time is 6 minutes and the stirring speed is 1200 rpm; in step S2, the stirring time is 15-20 minutes and the stirring speed is 1200-1500 rpm; in step S3, the rotation speed is 2000 rpm; and in step S5, the rotation speed is 50-60 rpm.

[0033] The yarn cutter in step S5 cuts the alkali-free glass fiber roving into 25.4 mm roving.

[0034] In step S7, the temperature of the constant temperature aging chamber is 45° C. and the time is 24 hours.

[0035] Furthermore, the present invention also provides the following technical solutions:

[0036] A method for preparing the above-mentioned two-support high-strength manhole cover comprises the following steps:

[0037] S1. Weigh the thickened SMC sheet according to the weight of the manhole cover, cut it according to 100% of the projected area of ​​the product and stack it;

[0038] S2, after the mold reaches the preset temperature, the stacked materials are placed into the mold;

[0039] S3, the press moves downward, and the product pressing pressure is 10MPa;

[0040] S4. The holding time is the product thickness multiplied by 25S / mm. When the holding time is reached, the machine automatically starts to open the mold and drives to the top. Press the ejection button to eject the product and take it out and place it at the trimming area for trimming.

[0041] S5, repeat the operations of S1-S4;

[0042] S6. Trim and process the pressed manhole covers and manhole seats.

[0043] In the step S2, the upper mold temperature is 115-120°C, and the lower mold temperature is 120-125°C.

[0044] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0045] 1) The use of dipropylene glycol resin, whose heat deformation temperature is 140°C, solves the problem that the heat deformation temperature of ordinary resin is only 60-120°C and the heat resistance temperature of the product is low;

[0046] 2) The use of polystyrene low shrinkage additives and polyvinyl acetate low shrinkage additives solves the problems of product impact toughness and coloring;

[0047] 3) Use calcium carbonate whiskers to improve the strength and impact toughness of the product;

[0048] 4) When using new fully automated online equipment to produce SMC composite materials for two-support high-strength manhole covers, the stirring is more uniform, the temperature is constant, and magnesium oxide paste is added online. The viscosity of the system increases rapidly (from 20,000 mPa.s to 500,000 mPa.s in 10 minutes), which is conducive to the stability of each phase in the system and will not separate. In addition, the airbag pressure is large, which is more conducive to the infiltration of long fibers, greatly improving the appearance and mechanical properties of the product;

[0049] 5) Using tert-butyl peroxy-2-ethylhexanoate as the initiator, the mold temperature required for molding is reduced from about 150°C to about 120°C, and the curing speed is reduced from about 45S / mm to about 20S / mm, which greatly reduces energy consumption and improves efficiency;

[0050] 6) Using one or a combination of BHT and TBHQ as antioxidants can increase the storage period of SMC sheets and extend the service life of the sheets;

[0051] 7) The use of continuous alkali-free glass fiber doubles the bending strength of the product and improves the impact toughness of the product;

[0052] 8) The two-support manhole cover produced by the present invention is about 30% lighter than the ordinary SMC two-support manhole cover of the same specification, which greatly reduces the weight of the product. DETAILED DESCRIPTION

[0053] The present invention provides a double-support high-strength manhole cover and SMC composite material and a preparation method thereof.

[0054] In the following examples, the above raw materials are selected from the following models and manufacturers:

[0055] 1. Unsaturated polyester resin: preferably Palapreg P17-902 produced by Jinling Aliancy Resin Co., Ltd.

[0056] 2. Low shrinkage additives: EL-8114 (25 kg) and 8117C (25 kg) from Zhenjiang Lidel Composite Materials Co., Ltd. are preferred.

[0057] 3. Filler: 1250 mesh calcium carbonate whiskers from Hebei Senade Nanomaterial Technology Co., Ltd. are preferred.

[0058] 4. Additives: German BYK W972 anti-phase separation agent is preferred.

[0059] 5. Initiator: preferably Nouryon Trigonox 21S tert-butyl peroxy-2-ethylhexanoate.

[0060] 6. Release agent: Zinc stearate from Jiangsu Taihu New Materials Holding Yancheng Co., Ltd. is preferred.

[0061] 7. Color paste: Ecoleader PT-0118-9M produced by Zhenjiang Lidel Composite Materials Co., Ltd. is preferred.

[0062] 8. Antioxidant: BHT (0.3 kg) and TBHQ (0.3 kg) from Jiangsu Maida New Materials Co., Ltd. are preferred.

[0063] 9. Magnesium oxide paste: Ecoleader GT560H produced by Zhenjiang Lidel Composite Materials Co., Ltd. is preferred.

[0064] 10. Glass fiber: SMC T949QZ-4800 alkali-free glass fiber roving produced by Taishan Glass Fiber Co., Ltd. is preferred.

[0065] 11. Continuous glass fiber: SMC T949QZ-4800 alkali-free glass fiber roving produced by Taishan Glass Fiber Co., Ltd. is preferred.

[0066] 12. Carrying film: preferably 1150*0.35mm PP film produced by Hangzhou Bennett Composite Materials Co., Ltd.

[0067] Embodiment 1, a method for preparing a SMC composite material for a double-support high-strength manhole cover, comprising the following steps:

[0068] S1. Add 200 kg of unsaturated polyester resin and 50 kg of low shrinkage additive into a stirring kettle, start stirring automatically, add 2.5 kg of curing agent, 2 kg of auxiliary agent, and 0.6 kg of antioxidant in sequence, and stir for 6 minutes at a stirring speed of 1200 rpm.

[0069] S2. Add 10 kg of zinc stearate and 336 kg of calcium carbonate whisker to the stirring kettle which has already started stirring. Continue stirring for 15-20 minutes after adding. The speed is 1200-1500 rpm. The temperature is stirred to 35° C. and the stirring is completed automatically.

[0070] S3. After stopping stirring, the raw materials in the stirring kettle are loaded into the middle barrel A. The mixed resin paste, color paste barrel B, and magnesium oxide paste barrel C in the middle barrel A are simultaneously pumped into a high-speed mixer with a rotation speed of 2000 revolutions per minute according to a certain ratio of 60.11:1:0.89 by using an online mixing device. As the online equipment continuously enters the high-speed mixer from the bottom, the stirred mixture finally overflows from the top trough and flows into the upper and lower paste areas of the SMC sheet molding compound molding machine respectively.

[0071] S4. Adjust the height of the upper and lower glue doors to 0.9-1.0mm to ensure that the weight of the glue flowing out of the upper and lower glue doors on the supporting PP film is 2.4-2.6 kg per square.

[0072] S5. The mixed paste in the upper pasting area is evenly coated on the PP carrier film through the pasting door, and a yarn cutting device is started with a rotation speed of 50-60 rpm. In addition, 40 continuous glass fibers are passed through the pipeline between the two layers of film. The sheet pulling speed is 10 m / min. The resin paste is coated on two PP carrier films and transported to the conveyor belt respectively. The yarn cutter cuts them into 25.4 mm alkali-free glass fiber roving and lays them on the resin paste of the lower PP carrier film. The two layers of film are closed again to form a sandwich layer of paste, continuous alkali-free glass fiber, chopped alkali-free glass fiber, and paste. Finally, the consumption of 25.4 mm chopped glass fiber and continuous alkali-free glass fiber are 140 kg and 240 kg respectively, with a total consumption of 380 kg.

[0073] S6. The sandwich layer passes through the upper and lower mesh belts of the SMC unit and is continuously rolled by 20 sets of offset rollers. The compacted sheets are collected in ton packaging bags with high barrier nylon bags to obtain SMC sheets.

[0074] S7. Place the full box of SMC materials into a constant temperature curing room at 45°C for 24 hours.

[0075] S8. After the thickened SMC sheets are tested and qualified, they are placed in a cold storage for future use.

[0076] A method for preparing a two-support high-strength manhole cover, comprising the following steps:

[0077] S1. Weigh the thickened SMC sheets according to the weight of the manhole cover, cut and stack them according to 100% size of the projected area of ​​the product.

[0078] S2. The upper mold temperature is 115-120℃, and the lower mold temperature is 120-125℃. After the mold reaches the temperature, put the folded materials into the mold.

[0079] S3. The press moves downward and the product pressing pressure is 10MPa.

[0080] S4. The holding time is the product thickness multiplied by 25S / mm. When the holding time is reached, the machine automatically starts to open the mold and moves to the top. Press the ejection button to eject the product and take the product out and place it at the trimming area for trimming.

[0081] S5. Repeat steps S1-S4.

[0082] S6. Trim and process the pressed manhole covers and manhole seats.

[0083] Embodiment 2, a method for preparing a two-support high-strength SMC composite material for a manhole cover, comprising the following steps:

[0084] S1. Add 212 kg of unsaturated polyester resin and 50 kg of low shrinkage additive into a stirring kettle, start stirring automatically, add 2.5 kg of curing agent, 2 kg of auxiliary agent, and 0.6 kg of antioxidant in sequence, and stir for 6 minutes at a stirring speed of 1200 rpm.

[0085] S2. Add 10 kg of zinc stearate and 321 kg of calcium carbonate whisker to the stirring kettle which has already started stirring. Continue stirring for 15-20 minutes at a speed of 1200-1500 rpm and stir until the temperature reaches 35°C. The stirring is completed automatically.

[0086] S3. After stopping stirring, the raw materials in the stirring kettle are loaded into the middle barrel A. The mixed resin paste, color paste barrel B, and magnesium oxide paste barrel C in the middle barrel A are simultaneously pumped into a high-speed mixer with a rotation speed of 2000 revolutions per minute according to a certain ratio of 60.11:1:0.89 by using an online mixing device. As the online equipment continuously enters the high-speed mixer from the bottom, the stirred mixture finally overflows from the top trough and flows into the upper and lower paste areas of the SMC sheet molding compound molding machine respectively.

[0087] S4. Adjust the height of the upper and lower glue doors to 0.9-1.0mm to ensure that the weight of the glue flowing out of the upper and lower glue doors on the supporting PP film is 2.4-2.6 kg per square.

[0088] S5. The mixed paste in the upper pasting area is evenly coated on the PP carrier film through the paste gate, and a yarn cutting device is started with a rotation speed of 50-60 rpm. In addition, 40 continuous basalt fibers are passed through the pipeline between the two layers of film. The sheet pulling speed is 10 m / min. The resin paste is coated on two PP carrier films and transported to the conveyor belt respectively. The yarn cutter cuts them into 25.4 mm alkali-free glass fiber roving and lays them on the resin paste of the lower PP carrier film. The two layers of film are closed again to form a sandwich layer of paste, continuous alkali-free glass fiber, chopped alkali-free glass fiber, and paste. Finally, the consumption of 25.4 mm chopped glass fiber and continuous alkali-free glass fiber is 140 kg and 240 kg respectively, with a total consumption of 380 kg.

[0089] S6. The sandwich layer passes through the upper and lower mesh belts of the SMC unit and is continuously rolled by 20 sets of offset rollers. The compacted sheets are collected in ton packaging bags with high barrier nylon bags to obtain SMC sheets.

[0090] S7. Place the full box of SMC materials into a constant temperature curing room at 45°C for 24 hours.

[0091] S8. After the thickened SMC sheets are tested and qualified, they are placed in a cold storage for future use.

[0092] A method for preparing a two-support high-strength manhole cover, comprising the following steps:

[0093] S1. Weigh the thickened SMC sheets according to the weight of the manhole cover, cut and stack them according to 100% size of the projected area of ​​the product.

[0094] S2. The upper mold temperature is 115-120℃, and the lower mold temperature is 120-125℃. After the mold reaches the temperature, put the folded materials into the mold.

[0095] S3. The press moves downward and the product pressing pressure is 10MPa.

[0096] S4. The holding time is the product thickness multiplied by 25S / mm. When the holding time is reached, the machine automatically starts to open the mold and moves to the top. Press the ejection button to eject the product and take it out and place it at the trimming area.

[0097] S5. Repeat the operations of steps S1-S4.

[0098] S6. Trim and process the pressed manhole covers and manhole seats.

[0099] Embodiment 3, a method for preparing a two-support high-strength SMC composite material for a manhole cover, comprising the following steps:

[0100] S1. Add 200 kg of unsaturated polyester resin and 50 kg of low shrinkage additive into a stirring kettle, start stirring automatically, add 2.5 kg of curing agent, 2 kg of auxiliary agent, and 0.6 kg of antioxidant in sequence, and stir for 6 minutes at a stirring speed of 1200 rpm.

[0101] S2. Add 10 kg of zinc stearate and 316 kg of calcium carbonate whisker to the stirring kettle which has already started stirring. Continue stirring for 15-20 minutes at a speed of 1200-1500 rpm and stir until the temperature reaches 35°C. The stirring is completed automatically.

[0102] S3. After stopping stirring, the raw materials in the stirring kettle are loaded into the middle barrel A. The mixed resin paste, color paste barrel B, and magnesium oxide paste barrel C in the middle barrel A are simultaneously pumped into a high-speed mixer with a rotation speed of 2000 revolutions per minute according to a certain ratio of 58.11:1:0.89 by using an online mixing device. As the online equipment continuously enters the high-speed mixer from the bottom, the stirred mixture finally overflows from the top trough and flows into the upper and lower paste areas of the SMC sheet molding compound molding machine respectively.

[0103] S4. Adjust the height of the upper and lower glue doors to 0.9-1.0mm to ensure that the weight of the glue flowing out of the upper and lower glue doors on the supporting PP film is 2.4-2.6 kg per square.

[0104] S5. The mixed paste in the upper pasting area is evenly coated on the PP carrier film through the pasting door, and a yarn cutting device is started with a rotation speed of 50-60 rpm. In addition, 40 continuous alkali-free glass fibers are passed through the pipeline between the two layers of film. The sheet pulling speed is 10 m / min. The resin paste is coated on two PP carrier films and transported to the conveyor belt respectively. The yarn cutter cuts them into 25.4 mm alkali-free glass fiber rovings and lays them on the resin paste of the lower PP carrier film. The two layers of film are closed again to form a sandwich layer of paste, continuous alkali-free glass fiber, chopped alkali-free glass fiber, and paste. Finally, the consumption of 25.4 mm chopped glass fiber and continuous alkali-free glass fiber are 160 kg and 240 kg respectively, with a total consumption of 400 kg.

[0105] S6. The sandwich layer passes through the upper and lower mesh belts of the SMC unit and is continuously rolled by 20 sets of offset rollers. The compacted sheets are collected in ton packaging bags with high barrier nylon bags to obtain SMC sheets.

[0106] S7. Place the full box of SMC materials into a constant temperature curing room at 45°C for 24 hours.

[0107] S8. After the thickened SMC sheets are tested and qualified, they are placed in a cold storage for future use.

[0108] A method for preparing a two-support high-strength manhole cover, comprising the following steps:

[0109] S1. Weigh the thickened SMC sheets according to the weight of the manhole cover, cut and stack them according to 100% size of the projected area of ​​the product.

[0110] S2. The upper mold temperature is 115-120℃, and the lower mold temperature is 120-125℃. After the mold reaches the temperature, put the folded materials into the mold.

[0111] S3. The press moves downward and the product pressing pressure is 10MPa.

[0112] S4. The holding time is the product thickness multiplied by 25S / mm. When the holding time is reached, the machine automatically starts to open the mold and moves to the top. Press the ejection button to eject the product and take it out and place it at the trimming area.

[0113] S5. Repeat the operations of steps S1-S4.

[0114] S6. Trim and process the pressed manhole covers and manhole seats.

[0115] Comparative Example: A method for preparing a two-support high-strength SMC composite material for a manhole cover, comprising the following steps:

[0116] S1. Add 200 kg of unsaturated polyester resin and 50 kg of low shrinkage additive into a stirring kettle, start stirring automatically, add 2.5 kg of curing agent, 2 kg of auxiliary agent, and 0.6 kg of antioxidant in sequence, and stir for 6 minutes at a stirring speed of 1200 rpm.

[0117] S2. Add 10 kg of zinc stearate and 336 kg of calcium carbonate to the stirring kettle which has already started stirring. Continue stirring for 15-20 minutes after adding. The speed is 1200-1500 rpm. The temperature is stirred to 35°C and the stirring is completed automatically.

[0118] S3. After stopping stirring, the raw materials in the stirring kettle are loaded into the middle barrel A. The mixed resin paste, color paste barrel B, and magnesium oxide paste barrel C in the middle barrel A are simultaneously pumped into a high-speed mixer with a rotation speed of 2000 revolutions per minute according to a certain ratio of 60.11:1:0.89 by using an online mixing device. As the online equipment continuously enters the high-speed mixer from the bottom, the stirred mixture finally overflows from the top trough and flows into the upper and lower paste areas of the SMC sheet molding compound molding machine respectively.

[0119] S4. Adjust the height of the upper and lower glue doors to 0.9-1.0mm to ensure that the weight of the glue flowing out of the upper and lower glue doors on the supporting PP film is 2.4-2.6 kg per square.

[0120] S5. The mixed paste in the upper pasting area is evenly coated on the PP carrier film through the pasting door, and a yarn cutting device is started with a rotation speed of 95-115 rpm and a sheet pulling speed of 10 m / min. The resin paste is coated on two PP carrier films and transported to the conveyor belt respectively. The yarn cutter cuts them into 25.4 mm alkali-free glass fiber rovings and lays them on the resin paste of the lower PP carrier film. The two layers of film are then closed to form a sandwich layer of paste, chopped alkali-free glass fiber and paste; the final amount of 25.4 mm chopped glass fiber is 380 kg.

[0121] S6. The sandwich layer passes through the upper and lower mesh belts of the SMC unit and is continuously rolled by 20 sets of offset rollers. The compacted sheets are collected in ton packaging bags with high barrier nylon bags to obtain SMC sheets.

[0122] S7. Place the full box of SMC materials into a constant temperature curing room at 45°C for 24 hours.

[0123] S8. After the thickened SMC sheets are tested and qualified, they are placed in a cold storage for future use.

[0124] A method for preparing a two-support high-strength manhole cover, comprising the following steps:

[0125] S1. Weigh the thickened SMC sheets according to the weight of the manhole cover, cut and stack them according to 100% size of the projected area of ​​the product.

[0126] S2. The upper mold temperature is 145-150℃, and the lower mold temperature is 140-145℃. After the mold reaches the temperature, put the folded materials into the mold.

[0127] S3. The press moves downward and the product pressing pressure is 15MPa.

[0128] S4. The holding time is the product thickness multiplied by 45S / mm. When the holding time is reached, the machine automatically starts to open the mold and moves to the top. Press the ejection button to eject the product and take it out and place it at the trimming area.

[0129] S5. Repeat the operations of steps S1-S4.

[0130] S6. Trim and process the pressed manhole covers and manhole seats.

[0131] The weight parts of the above examples 1 to 3 and the comparative example are as follows:

[0132]

[0133] The sheet materials and manhole cover products of Examples 1 to 3 and the comparative example were tested, and the results are as follows:

[0134] Table 1 shows the material properties of the sheet, as shown below:

[0135]

[0136] Table 2 is the weight comparison data of the D250 double-support manhole cover with a size of 1200 mm*500 mm produced according to Examples 1 to 3 and the comparative example, as shown in the following table:

[0137]

[0138] The 1200mm*500mm D250 double-support manhole covers produced in Examples 1 to 3 and the comparative cases all meet the requirements of the D250 load-bearing grade test in the GB / T23858-2009 standard, and the product thickness is reduced by 30%, the weight is lighter by more than 30%, the press pressure required for product production is reduced by about 30%, the required mold temperature is reduced by 20%, and the holding time is reduced by more than 50%, which greatly reduces energy consumption and greatly reduces the overall cost of the final product.

[0139] In summary, the present invention not only increases the strength of the material and the manhole cover by using some continuous fibers, but also greatly reduces the thickness of the manhole cover product while ensuring the same load-bearing capacity as the prior art. On the other hand, the curing system of the present invention is different from the prior art, and the mold temperature required in the production process is lower than that of the prior art, and the curing time is shorter, thereby greatly reducing the energy consumption in the production process.

[0140] The present invention has been described with reference to preferred embodiments, but it will be understood by those skilled in the art that various changes in form and details may be made therein within the scope of the claims.

Claims

1. A two-support high-strength SMC composite material for manhole covers, characterized in that The composition comprises the following components in parts by weight: Unsaturated polyester resin 18-25 parts, 4-8 parts of low shrinkage additive, Initiator 0.2-0.4 parts, Additives 0.1-0.3 parts, Release agent 0.7-1.5 parts, 1-2 parts of color paste, 25-35 parts of filler, Antioxidant 0.1-0.4 parts, 1-4.0 parts of activated magnesium oxide paste, 35-45 parts of glass fiber.

2. The SMC composite material for double-support high-strength manhole cover according to claim 1, characterized in that The unsaturated polyester resin is propylene phthalate resin; The low shrinkage additive is one of a polystyrene low shrinkage additive and a polyvinyl acetate low shrinkage additive, or a compound of a polystyrene low shrinkage additive and a polyvinyl acetate low shrinkage additive.

3. The SMC composite material for double-support high-strength manhole cover according to claim 1, characterized in that The filler is 1250 mesh calcium carbonate whisker, the auxiliary agent is an anti-phase separation agent, the initiator is tert-butyl peroxide-2-ethylhexanoate, the release agent is zinc stearate, the black slurry has a viscosity of less than 10000 mPa.s, and the carbon black content is greater than or equal to 30%.

4. The SMC composite material for double-support high-strength manhole cover according to claim 1, characterized in that The antioxidant is one or a combination of BHT and TBHQ; the magnesium oxide paste contains 50% magnesium oxide, and the viscosity of the magnesium oxide paste is less than 10000 mPa.s; The glass fiber is alkali-free glass fiber roving.

5. A method for preparing the SMC composite material for double-support high-strength manhole cover according to any one of claims 1 to 4, characterized in that The following steps are involved: S1. Add unsaturated polyester resin and low shrinkage additive into a stirring kettle, start stirring automatically, and add curing agent, auxiliary agent and antioxidant in sequence; S2, adding zinc stearate and calcium carbonate whiskers to the stirring tank of step S1 and continuing stirring until the temperature reaches 35°C; S3, after stopping stirring, the mixed paste in the stirring kettle of step S2 is transferred to the intermediate barrel A, and the mixed resin paste, color paste barrel B, and magnesium oxide paste barrel C in the intermediate barrel A are simultaneously pumped into the high-speed mixer according to a certain proportion by using an online mixing device, and as the online device continuously enters the high-speed mixer from the bottom, the stirred mixture finally overflows from the top trough and flows into the upper and lower paste areas of the SMC sheet molding compound molding machine respectively; S4, adjusting the height of the upper and lower paste gates to 0.9-1.0 mm, ensuring that the weight of the paste flowing out of the upper and lower paste gates of the SMC sheet molding compound molding machine in step S3 on the supporting PP film is 2.4-2.6 kg per square meter; S5, the mixed paste in the upper pasting area is evenly coated on the PP carrier film through the pasting door, and a yarn cutting device is started. In addition, 40 continuous basalt fibers are passed through the pipeline between the two layers of film. The sheet pulling speed is 10 m / min. The resin paste is coated on the two PP carrier films and transported to the conveyor belt respectively. The yarn cutter cuts the alkali-free glass fiber roving and lays it on the resin paste of the lower PP carrier film. The two layers of film are closed again to form a sandwich layer of paste, continuous alkali-free glass fiber, short alkali-free glass fiber, and paste; S6, the sandwich layer is continuously rolled by 20 sets of offset rollers through the upper and lower mesh belts of the SMC unit, and the compacted sheets are collected in ton packaging bags with high barrier nylon bags to obtain SMC sheets; S7. Put the full box of SMC materials into the constant temperature curing room; S8. After the thickened SMC sheets are tested and qualified, they are placed in a cold storage for future use.

6. A method for preparing a double-support high-strength SMC composite material for a manhole cover according to claim 5, characterized in that In step S1, the stirring time is 6 minutes and the stirring speed is 1200 rpm; in step S2, the stirring time is 15-20 minutes and the stirring speed is 1200-1500 rpm; in step S3, the rotation speed is 2000 rpm; and in step S5, the rotation speed is 50-60 rpm.

7. A method for preparing a double-support high-strength SMC composite material for a manhole cover according to claim 5, characterized in that The yarn cutter in step S5 cuts the alkali-free glass fiber roving into 25.4 mm roving.

8. The method for preparing a double-support high-strength SMC composite material for a manhole cover according to claim 5, characterized in that In step S7, the temperature of the constant temperature aging chamber is 45° C. and the time is 24 hours.

9. A method for preparing a two-support high-strength manhole cover as claimed in any one of claims 5 to 8, characterized in that The following steps are involved: S1. Weigh the thickened SMC sheet according to the weight of the manhole cover, cut it according to 100% of the projected area of ​​the product and stack it; S2, after the mold reaches the preset temperature, the stacked materials are placed into the mold; S3, the press moves downward, and the product pressing pressure is 10MPa; S4. The holding time is the product thickness multiplied by 25S / mm. When the holding time is reached, the machine automatically starts to open the mold and drives to the top. Press the ejection button to eject the product and take it out and place it at the trimming area for trimming. S5, repeat the operations of S1-S4; S6. Trim and process the pressed manhole covers and manhole seats.

10. A method for preparing a double-support high-strength manhole cover according to claim 9, characterized in that In the step S2, the upper mold temperature is 115-120°C, and the lower mold temperature is 120-125°C.

Images