Preparation process of integral SMC glass fiber reinforced plastic inspection well

Abstract

The invention belongs to the technical field of underground pipe network inspection wells, and particularly discloses a preparation process of an integral SMC (Sheet Molding Compound) glass fiber reinforced plastic inspection well, which comprises the following steps: (1) raw material preparation: the raw materials comprise the following components in parts by mass: 30-60 parts of a resin system, 22-30 parts of a reinforcing material, 10-30 parts of a filler and 0.5-3 parts of a release agent; (2) flaking: adding the raw materials into an extruder, and extruding into sheets; (3) plasticizing: placing the sheet in a transfer box for standing and plasticizing to obtain a sheet molding composite material; and (4) compression molding: coating a lower die of a die with the plastified sheet-shaped molding composite material, closing and pressing the die, and opening the die to take out a product after compression molding. Through process control, the overall SMC glass fiber reinforced plastic inspection well stable in performance can be prepared, the tensile strength can reach 60-100 MPa, the bending strength can reach 120-200 MPa, and the industrial application requirement is met.

Description

Technical Field

[0001] The invention belongs to the technical field of underground pipe network inspection wells, and specifically is a preparation process of an integral SMC glass fiber reinforced plastic inspection well. Background Art

[0002] In underground pipe networks in the fields of municipal administration, water supply, electricity, communications, and chemical industry, inspection wells are installed at certain intervals, intersections, bends, and slope changes on the straight sections of the pipelines to facilitate inspection and installation of valves.

[0003] Manholes typically serve as diversion and convergence points, connecting different water flows. They also help discharge harmful gases from pipelines and prevent their accumulation. Furthermore, manholes provide convenient access to underground pipe networks for regular inspections. Some manholes can also be equipped with sensors, flow meters, and other equipment to monitor pipeline status in real time.

[0004] Common inspection wells currently include brick, reinforced concrete, plastic, and ductile iron. Plastic inspection wells are typically manufactured using processes such as injection molding and are widely used due to their lightweight, acid and alkali resistance, aging resistance, and long service life. However, conventional plastic inspection wells are often spliced ​​together, prone to leakage and deformation, resulting in poor load-bearing capacity.

[0005] SMC fiberglass inspection well refers to an inspection well made of sheet molding compound (SMC) through a molding process. Traditional SMC fiberglass inspection wells need to be assembled after molding to obtain the finished product, so leakage will occur at the assembly connection, affecting the use of underground pipelines.

[0006] Therefore, it is necessary to design an integral SMC glass fiber reinforced plastic inspection well to solve the above technical problems. Summary of the Invention

[0007] In order to solve the problems raised in the above background technology, the present invention provides a preparation process for an integral SMC glass fiber reinforced plastic inspection well.

[0008] To achieve the above object, the present invention provides the following technical solution: a preparation process of an integral SMC glass fiber reinforced plastic inspection well, comprising the following steps:

[0009] (1) Raw material preparation: The raw materials include, by mass:

[0010] Resin system 30-60 parts, reinforcing material 22-30 parts, filler 10-30 parts, release agent 0.5-3 parts;

[0011] (2) Sheeting: Add the raw materials into the extruder and extrude into sheets;

[0012] (3) Plasticization: The sheet is placed in a transfer box and plasticized to obtain a sheet molding compound;

[0013] (4) Compression molding: The plasticized sheet molding compound is coated on the lower mold of the mold, the mold is closed and pressed, and after compression molding, the mold is opened and the product is taken out.

[0014] Furthermore, the resin system comprises, by weight, 30-45 parts of unsaturated polyester resin, 0.5-1.5 parts of initiator, 10-20 parts of low shrinkage additive, and 2-5 parts of thickener.

[0015] Furthermore, the reinforcing material is selected from chopped glass fibers with a length of 25-50 mm.

[0016] Furthermore, the filler is selected from one or more of calcium carbonate, aluminum hydroxide, talc, mica powder, glass beads, and wollastonite; and the release agent is selected from one or more of fatty acid esters, fatty alcohol phosphates, and zinc stearate.

[0017] Furthermore, the initiator is selected from one or more of benzoyl peroxide, methyl ethyl ketone peroxide, dicumyl peroxide, diisopropyl peroxydicarbonate, and tert-butyl perbenzoate; the low shrinkage additive is selected from one or more of polystyrene, polymethyl methacrylate, and polyvinyl acetate; and the thickener is selected from one or both of magnesium oxide and calcium hydroxide.

[0018] Furthermore, in the film forming process of step (2),

[0019] Before forming into sheets, first prepare the resin paste: add unsaturated polyester resin, initiator, and low shrinkage additive into a disperser, stir evenly, then slowly add filler, thickener, and release agent, and continue stirring until uniform and free of particles; during this process, control the temperature to ≤35°C and the initial viscosity to 200-500mPa·s;

[0020] Then, resin paste is applied on the lower polyethylene film, and after preliminary curing, chopped glass fibers are evenly spread on the surface of the resin paste;

[0021] Finally, the upper polyethylene film coated with resin paste is laminated and compacted on top of the chopped glass fibers, and then rolled up after compaction.

[0022] Furthermore, in the plasticizing process of step (3), the plasticizing time is 24-72 hours and the plasticizing temperature is 40-45°C.

[0023] Furthermore, the viscosity of the plasticized material is 10 5 -10 6 mpa·s, and the product is in a dry state after plasticization.

[0024] Furthermore, during the compression molding process of step (4), the mold is first preheated, and then the cut and plasticized sheet molding compound is coated on the lower mold of the mold, and the mold is closed for compression molding and then opened to take out the product.

[0025] Furthermore, during the compression molding process, the compression parameters are: pressure 10-20 MPa, temperature 140-160°C, pressing time 1-3 min / mm thickness, and mold closing speed 10-20 mm / s; demolding: the mold is opened after the ejection temperature drops below 80°C.

[0026] Compared with the prior art, the preparation process of the integral SMC glass fiber reinforced plastic inspection well of the present invention has the following advantages:

[0027] Beneficial effects:

[0028] (1) The molding process of the integral SMC glass fiber reinforced plastic inspection well of the present invention is simple and easy to operate, and has strong repeatability. Through the process control of the present invention, an integral SMC glass fiber reinforced plastic inspection well with stable performance can be prepared, with a tensile strength of 60-100 MPa and a bending strength of 120-200 MPa, which meets the needs of industrial applications.

[0029] (2) The integral SMC glass fiber reinforced plastic inspection well prepared by the process of the present invention is integrally formed and has no joints, which greatly improves the occurrence of leakage.

[0030] (3) In the present invention, the inspection well is based on unsaturated polyester resin and added with short-cut glass fiber as reinforcement material. It is acid- and alkali-resistant and corrosion-resistant, and no additional anti-corrosion materials are required. The product has stable performance and a long service life of more than 50 years. DETAILED DESCRIPTION

[0031] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0032] A preparation process of an integral SMC glass fiber reinforced plastic inspection well comprises the following steps:

[0033] (1) Raw material preparation: by mass, including:

[0034] The resin system specifically includes: 38 parts of unsaturated polyester resin, 1 part of initiator tert-butyl perbenzoate, 15 parts of low shrinkage additive polystyrene, and 2.5 parts of thickener magnesium oxide.

[0035] Reinforcement material: chopped glass fiber, length 25-50mm, 25 parts.

[0036] Filler calcium carbonate, 20 parts.

[0037] Release agent zinc stearate, 1.5 parts.

[0038] Then, prepare the resin paste: add the unsaturated polyester resin, initiator, and low shrinkage additive into a high-speed disperser and stir at 500-800 rpm for 10-15 minutes. Then slowly add the filler, thickener, and release agent and continue stirring for 20-30 minutes to make the resin paste uniform and free of particles.

[0039] During this process, the temperature was controlled to be ≤35°C to prevent premature thickening, and the initial viscosity was controlled to be 200-500 mPa·s (25°C).

[0040] In other embodiments, pigments such as green masterbatch, yellow masterbatch, etc. may also be added to the raw materials to make the finished inspection wells appear in different colors for use in different application scenarios.

[0041] (2) Film:

[0042] In the SMC unit equipped with film unwinding, resin paste coating, fiber cutting and pressing devices, resin paste is first coated on the lower polyethylene film with a thickness of 1-3mm;

[0043] Then, the glass fibers are cut into short glass fibers by a cutting machine and evenly spread on the surface of the resin paste;

[0044] Then, the upper polyethylene film coated with resin paste is laminated and compacted on top of the chopped glass fibers, and rolled up after compaction. The pressure is controlled at 0.1-0.3 MPa to ensure that the chopped glass fibers are completely impregnated.

[0045] Finally, the fiber is reeled in at a speed of 1-3 m / min to avoid segregation of the chopped glass fibers.

[0046] The resulting sheet is two layers of resin with glass fiber reinforcement sandwiched between them, which is squeezed to remove the air inside.

[0047] (3) Plasticization:

[0048] The sheet obtained in step (2) is placed in a transfer box and plasticized to obtain a sheet molding compound. The plasticizing temperature is 40-45°C and the plasticizing time is 24-72 hours. The product is thickened to a viscosity of 10 5 -10 6 mpa·s, and ensure that the product is dry after plasticization to facilitate the next step of cutting.

[0049] (4) Compression molding:

[0050] First, preheat the mold to 140-160°C;

[0051] Then, cut the SMC sheet according to 70-80% of the product volume, cover it on the lower mold, and then close the mold for pressing;

[0052] During the molding process, the molding parameters are: pressure 10-20MPa (adjusted according to the complexity of the product); temperature 140-160℃; pressing time: 1-3 minutes / mm thickness (such as 3-9 minutes for a 3mm thick product); mold closing speed 10-20mm / s to prevent resin overflow; demolding: open the mold only after the ejection temperature drops below 80℃ to avoid product deformation.

[0053] During molding, the lower mold is first removed, the sheet is wrapped around the surface of the lower mold, and then the mold is closed. After the sheet melts at high temperature, it has a certain fluidity and flows in the gap between the upper and lower molds. It is then kept warm under high temperature and high pressure for 10 minutes before forming; then the temperature is lowered and the mold is opened to take the product out of the mold.

[0054] Finally, the products taken out after mold opening are post-processed, including trimming, deburring, and removing flash using files and angle grinders, and then stacking and placing them.

[0055] In the preparation process of the present invention,

[0056] The key quality control points are:

[0057] (1) Resin paste uniformity: avoid filler sedimentation or fiber agglomeration; (2) Thickening speed: adjust the plasticizing time by the MgO / Ca(OH)2 ratio; (3) Molding venting: a short pressure relief (0.5-1 second) is required at the initial stage of mold closing to expel bubbles; (4) Fiber orientation: control the mechanical properties by optimizing the layup design.

[0058] Common process problems and solutions include:

[0059] (1) Bubble defects: Increase the molding pressure or extend the holding time; (2) Surface ripples: Adjust the resin viscosity or reduce the mold closing speed; (3) Fiber exposure: Increase the thickness of the resin paste coating or reduce the fiber content.

[0060] At the same time, in the present invention, during the production process, attention should be paid to VOC control. Since the raw materials contain styrene, a ventilation system should be installed in a closed workshop. At the same time, attention should be paid to dust protection. Due to the use of fillers and chopped glass fibers, professional dust masks should be installed in the operation area.

[0061] By controlling the above process and adopting the process method of the present invention, SMC glass fiber reinforced plastic products with stable performance can be produced, with a tensile strength of up to 60-100 MPa and a bending strength of 120-200 MPa, which can fully meet the needs of industrial applications.

[0062] In a specific embodiment, the inspection well obtained by the process of the present invention weighs 65-100 kilograms and can be carried and installed manually. It can be directly hoisted to the pre-buried foundation pit in the excavated pipeline of the foundation pit or well, and can be completed manually; it has a low thermal expansion coefficient and is not easy to crack or deform when used in the range of -30°C to 80°C; the load capacity can reach 50 tons.

[0063] When the bottom diameter and height of the inspection well are both 1.2 meters, the cost is less than one thousand yuan, while concrete costs more than 1,500-2,000 yuan. Therefore, the cost is low and the price is more advantageous.

[0064] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0065] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A preparation process for an integral SMC glass fiber reinforced plastic inspection well, characterized by: The steps include: (1) Raw material preparation: The raw materials include, by mass: Resin system 30-60 parts, reinforcing material 22-30 parts, filler 10-30 parts, release agent 0.5-3 parts; (2) Sheeting: Add the raw materials into the extruder and extrude into sheets; (3) Plasticization: The sheet is placed in a transfer box and plasticized to obtain a sheet molding compound; (4) Compression molding: The plasticized sheet molding compound is coated on the lower mold of the mold, the mold is closed and pressed, and after compression molding, the mold is opened and the product is taken out.

2. The preparation process of the integral SMC glass fiber reinforced plastic inspection well according to claim 1, characterized in that: Calculated by weight, the resin system includes: 30-45 parts of unsaturated polyester resin, 0.5-1.5 parts of initiator, 10-20 parts of low shrinkage additive, and 2-5 parts of thickener.

3. The preparation process of the integral SMC glass fiber reinforced plastic inspection well according to claim 1 is characterized in that: The reinforcing material is selected from chopped glass fibers with a length of 25-50 mm.

4. The preparation process of the integral SMC glass fiber reinforced plastic inspection well according to claim 1 is characterized in that: The filler is selected from one or more of calcium carbonate, aluminum hydroxide, talc, mica powder, glass beads, and wollastonite; and the release agent is selected from one or more of fatty acid esters, fatty alcohol phosphates, and zinc stearate.

5. The preparation process of the integral SMC glass fiber reinforced plastic inspection well according to claim 2, characterized in that: The initiator is selected from one or more of benzoyl peroxide, methyl ethyl ketone peroxide, dicumyl peroxide, diisopropyl peroxydicarbonate, and tert-butyl perbenzoate; the low shrinkage additive is selected from one or more of polystyrene, polymethyl methacrylate, and polyvinyl acetate; and the thickener is selected from one or both of magnesium oxide and calcium hydroxide.

6. The preparation process of the integral SMC glass fiber reinforced plastic inspection well according to claim 2, characterized in that: During the film forming process of step (2), Before forming into sheets, first prepare the resin paste: add unsaturated polyester resin, initiator, and low shrinkage additive into a disperser, stir evenly, then slowly add filler, thickener, and release agent, and continue stirring until uniform and free of particles; during this process, control the temperature to ≤35°C and the initial viscosity to 200-500mPa·s; Then, resin paste is applied on the lower polyethylene film, and after preliminary curing, chopped glass fibers are evenly spread on the surface of the resin paste; Finally, the upper polyethylene film coated with resin paste is laminated and compacted on top of the chopped glass fibers and then rolled up after compaction.

7. The preparation process of the integral SMC glass fiber reinforced plastic inspection well according to claim 1, characterized in that: During the plasticizing process of step (3), the plasticizing time is 24-72 hours and the plasticizing temperature is 40-45°C.

8. The process for preparing the integral SMC glass fiber reinforced plastic inspection well according to claim 7, characterized in that: The viscosity of the plasticized material is 10 5 -10 6 mpa·s, and the product is in a dry state after plasticization.

9. The preparation process of the integral SMC glass fiber reinforced plastic inspection well according to claim 1, characterized in that: During the compression molding process of step (4), the mold is first preheated, and then the cut and plasticized sheet molding compound is coated on the lower mold of the mold. After the mold is closed for compression molding, the mold is opened to take out the product.

10. The process for preparing the integral SMC glass fiber reinforced plastic inspection well according to claim 9, characterized in that: During the compression molding process, the compression parameters are: pressure 10-20MPa, temperature 140-160℃, pressing time 1-3min / mm thickness, and mold closing speed 10-20mm / s; demolding: the mold is opened only after the ejection temperature drops below 80℃.