Method for preparing well lid from waste fibers

Abstract

The invention relates to a method for preparing a well lid from waste fibers. The method specifically comprises the following steps: cutting the waste fibers into chopped fiber sheets; an inner cavity of a well lid preparation mold is wiped clean with ethyl acetate, and after an ethyl acetate solvent is completely volatilized, the inner cavity of the mold is evenly smeared with a high-temperature release agent; weighing a certain amount of cut chopped fiber sheets, pouring the chopped fiber sheets into a mold cavity of a well lid preparation mold, detecting the content of raw material resin at the same time, and judging whether the resin needs to be supplemented or not; mold closing and curing are conducted, specifically, the mold is placed on a pressing machine to be subjected to high-temperature heat treatment, and before complete mold closing, gas in the mold needs to be exhausted so as to improve the interlayer compactness of a well lid product; after the mold is completely closed, the mold is subjected to heating, heat preservation and cooling according to a preset curing program, after the temperature is reduced to the room temperature, the mold is taken down, and after demolding treatment, the composite material well lid formed through compression molding is taken out; and testing the performance of the manhole cover according to the current standard of the manhole cover. The method is simple to operate, and the technical requirements on operators are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of manhole covers, and in particular to a method for preparing a manhole cover using waste fibers. Background Art

[0002] The manhole covers widely used in urban roads in my country are mostly cast iron manhole covers and reinforced concrete manhole covers. Among them, cast iron manhole covers are frequently stolen because the materials are recyclable. Composite manhole covers do not contain metal and have no recycling value at all, which effectively avoids the possibility of theft and solves the problem of cast iron manhole covers being lost.

[0003] The aerospace manufacturing industry will generate a large amount of composite waste during the manufacturing process. If the waste is treated as solid waste, the waste treatment fee will be a considerable expense, which will directly lead to an increase in manufacturing costs. If the waste is directly discarded, the continuously discarded waste will continue to pollute the environment, making the ecological environment worse. Waste recycling not only saves waste post-processing fees, but also saves the raw material costs of new manufactured products, creating additional value for the company.

[0004] The waste fiber used to prepare the manhole cover of the present invention not only realizes the recycling and reuse of the waste fiber, but also solves the problem that the cast iron manhole cover is easy to be stolen. Summary of the invention

[0005] Based on the above problems, the present invention provides a method for preparing manhole covers from waste fibers to solve the problems of high cost, difficulty, serious pollution, etc. of existing waste fiber processing, as well as the problem that recyclable cast iron manhole covers are easily lost. A method for preparing manhole covers from waste fibers with simple process operation, mild preparation conditions, wide application range of raw materials, and low preparation cost is realized.

[0006] In order to solve the above technical problems, one of the purposes of the present invention is to provide a method for preparing a manhole cover using waste fibers, comprising the following steps:

[0007] S1: Pretreatment of raw materials, cutting waste fibers into chopped fiber pieces;

[0008] S2: Treatment of the manhole cover preparation mold: wipe the inner cavity of the manhole cover preparation mold clean with ethyl acetate, and after the ethyl acetate solvent is completely evaporated, evenly apply the high-temperature release agent to the inner cavity of the mold;

[0009] S3: Weigh a certain amount of the chopped fiber pieces cut in S1, and pour them into the mold cavity of the manhole cover manufacturing mold, and at the same time test the resin content of the raw materials to determine whether additional resin is needed;

[0010] S4: Mold closing, placing the mold on the press for high-temperature heat treatment (i.e. curing). Before the mold is completely closed, the gas in the mold should be exhausted to improve the tightness between the layers of the manhole cover product; after the mold is completely closed, the mold will be heated, kept warm and cooled according to the pre-set curing program. When the temperature drops to room temperature, the mold is removed, and the molded composite manhole cover is taken out after demoulding;

[0011] S5: Perform a performance test on the manhole cover prepared in S4 according to the current standards for manhole covers.

[0012] Furthermore, the S2 release agent is applied three times in total, with the time interval between each application being about 30 minutes.

[0013] Furthermore, the amount of S3 raw materials is calculated by using Unigraphics NX software or Creo Parametric software to calculate the cavity volume of the manhole cover manufacturing mold and then calculate the mass of the required raw materials.

[0014] Furthermore, the weighed amount can refer to the calculated value, and the actual weighed amount is 1 to 1.2 times the calculated value.

[0015] Furthermore, S3 determines the resin content of the raw material. If the raw material is waste pre-impregnated fiber tape and the resin mass content is above 37%, no resin needs to be added. If the raw material is only waste fiber and has not been pre-impregnated, resin should be added, and the mass content of the added resin should be above 37% of the total mass of the resin and the chopped fiber sheets.

[0016] Furthermore, the resin type can be selected from epoxy resin, phenolic resin or a mixture of the two types of resins according to the performance requirements of the manhole cover.

[0017] Furthermore, the raw materials selected in S1 include but are not limited to waste carbon fiber prepregs and waste high-silica fiber prepregs, and the side length of the chopped fiber pieces is 10 to 15 mm.

[0018] Furthermore, the high temperature heat treatment temperature in S4 is from room temperature to 100°C, with a heating rate of 3°C / min; kept at 100°C for 1 hour; from 100°C to 170°C, with a heating rate of 3°C / min; kept at 170°C for 4 hours.

[0019] Furthermore, the curing temperature in S4 is 170-180° C., and the temperature holding time is 3.5-4 hours.

[0020] The above one or more technical solutions of the present invention have at least one or more of the following technical effects:

[0021] Compared with other composite material manhole cover preparation processes, the present invention is simple to operate and reduces the technical requirements for operators.

[0022] Compared with conventional recycled fiber recycling technology, the present invention has a more far-reaching significance. Conventional recycled fiber recycling often uses solvent cleaning or high-temperature roasting to remove the resin on the surface of the waste fiber, which not only pollutes the environment, but also reduces the performance and recycling value of the fiber. The waste fiber prepreg tape in the present invention does not require the removal of resin, which greatly reduces the manufacturing cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 : Flow chart of preparing manhole covers from waste fibers. Specific implementation plan

[0024] A method for preparing a manhole cover using waste fibers, the specific steps of which are: selecting raw materials, prepreg tapes or prepreg cloths of waste fibers; processing raw materials, i.e. using a cutting machine to cut the selected waste fibers into short-cut fiber pieces, wherein the side length of the short-cut fiber pieces can be between 10 and 15 mm; processing a mold for preparing the manhole cover, wherein the inner cavity of the mold for preparing the manhole cover is wiped clean with ethyl acetate, and after the ethyl acetate solvent is completely volatilized, a high-temperature release agent is evenly applied to the inner cavity of the mold, and the release agent is applied three times in total, with a time interval of about 30 minutes between each application. To ensure smooth demoulding of the prepared manhole cover, a release agent should be applied to every corner of the inner cavity of the female and male molds of the mold; the amount of raw materials used is calculated by using Unigraphics NX software or Creo Parametric software to calculate the cavity volume of the manhole cover preparation mold, and then the mass of the required raw materials is calculated. The mass of the raw materials is calculated using the formula, i.e., mass = density * volume; for the preparation of the manhole cover, the cut short fiber sheets are weighed and poured into the cavity of the manhole cover preparation mold. The weighed amount refers to the calculated value, and the actual weighed amount may fluctuate between 1 and 1.2 times the calculated value.

[0025] The amount of resin added depends on the actual situation, and then the mold is closed and placed on the press for curing. At first, the mold could not be completely closed because the height of the chopped fiber sheets was slightly higher than the inner cavity size of the mold. As the curing temperature increased, the fiber tape gradually became soft, and under the pressurized state, the mold gradually closed completely. Before the mold is completely closed, the gas in the mold should be removed to improve the tightness between the layers of the manhole cover product. After the mold is completely closed, the manhole cover product will be heated, kept warm and cooled according to the pre-set curing program. When the temperature drops to room temperature, the mold is removed, and the molded composite manhole cover is taken out after demolding. The manhole cover prepared as above is subjected to performance testing according to the current national standard for inspection manhole covers GB / T23858-2009.

[0026] The material selection of the present invention has low requirements on raw materials and a wide range of selection. In terms of materials, any waste fiber can be used, including but not limited to waste carbon fiber prepreg and waste high-silica fiber prepreg; in terms of specifications, any specifications can be used, such as fiber cloth, fiber tape, and fiber filament.

[0027] During the process of adding raw materials for the preparation of manhole covers, the amount of resin added depends on the actual situation. If the raw material is waste pre-impregnated fiber tape and the resin mass content is above 37%, no resin needs to be added. If the raw material is only waste fiber and has not been pre-impregnated, resin should be added, and the mass content of the resin added should be above 37% of the total mass of the resin and the chopped fiber sheets. The type of resin can be selected from epoxy resin, phenolic resin or a mixture of the two types of resins according to the performance of the prepared manhole cover.

[0028] The maximum curing temperature during mold curing is 170-180°C, and the maximum temperature holding time is 3.5-4h.

[0029] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in combination with the embodiments of the present invention and the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the obtained embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0030] Embodiment 1:

[0031] 1) Waste carbon fiber prepreg tapes were selected as raw materials for preparing manhole covers. The prepreg tapes had a resin content of 37% and a density of 1.52 g / cm3.

[0032] 2) Using a cutting machine, the prepreg tape in step 1) is cut into short-cut fiber sheets with a specification of 10 mm*10 mm.

[0033] 3) Treatment of the manhole cover mold: wipe the inner cavity of the manhole cover mold clean with ethyl acetate. After the ethyl acetate has evaporated, evenly apply the high-temperature release agent to the inner cavity of the mold and the bolt holes and other corners. Apply it 3 times in total, with an interval of 30 minutes.

[0034] 4)Using Unigraphics NX software to calculate the mold cavity volume, the manhole cover mold cavity volume is 1791074.0571mm 3 , the cavity volume of the well seat is 1888170.3126mm 3 , it is calculated that the mass of waste carbon fiber required for preparing manhole covers is 2686.6g, and the mass of waste fiber required for preparing well bases is 2832g.

[0035] 5) According to the mass value calculated in step 4), weigh the chopped fiber pieces cut in step 2) and place them in the inner cavity of the mold for preparing the manhole cover. After closing the mold, put the mold on the press, set the curing program, and perform curing. Remember to perform exhaust treatment before the mold is completely closed. When the curing program is completed and the temperature drops to room temperature, demold and take out the manhole cover product.

[0036] The preparation process of the well base is the same as that of the well cover.

[0037] 6) The manhole cover product prepared in step 5) was subjected to a mechanical property test. The results are shown in Table 1.

[0038] Table 1 Mechanical properties of composite manhole covers

[0039]

[0040] Obviously, those skilled in the art can make various changes and modifications to the embodiments of the present invention without departing from the spirit and scope of the embodiments of the present invention. Thus, if these modifications and variations of the embodiments of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for preparing a manhole cover using waste fibers, characterized in that: The steps include: S1: Pretreatment of raw materials, cutting waste fibers into chopped fiber pieces; S2: Treatment of the manhole cover preparation mold: wipe the inner cavity of the manhole cover preparation mold clean with ethyl acetate, and after the ethyl acetate solvent is completely evaporated, evenly apply the high-temperature release agent to the inner cavity of the mold; S3: Weigh a certain amount of the chopped fiber pieces cut in S1, and pour them into the mold cavity of the manhole cover manufacturing mold, and at the same time test the resin content of the raw materials to determine whether additional resin is needed; S4: Mold closing and curing. The mold is placed on a press for high-temperature heat treatment. Before the mold is completely closed, the gas in the mold should be removed to improve the tightness between the layers of the manhole cover product. After the mold is completely closed, the mold will be heated, kept warm and cooled according to the pre-set curing program. When the temperature drops to room temperature, the mold is removed, and the molded composite manhole cover is taken out after demoulding. S5: Perform a performance test on the manhole cover prepared in S4 according to the current standards for manhole covers.

2. The method for preparing a manhole cover using waste fibers according to claim 1, characterized in that: The S2 release agent was applied three times, with the time interval between each application being about 30 minutes.

3. The method for preparing a manhole cover using waste fibers according to claim 1, characterized in that: S3 Calculation of raw material usage: Unigraphics NX software or Creo Parametric software is used to calculate the cavity volume of the manhole cover manufacturing mold, and then the mass of the required raw materials is calculated.

4. The method for preparing a manhole cover using waste fibers according to claim 3, characterized in that: The weighed amount can refer to the calculated value, and the actual weighed amount is 1 to 1.2 times the calculated value.

5. The method for preparing a manhole cover using waste fibers according to claim 1, characterized in that: The S3 determines the resin content of the raw material. If the raw material is waste pre-impregnated fiber tape and the resin mass content is above 37%, no resin needs to be added. If the raw material is only waste fiber and has not been pre-impregnated, resin should be added, and the mass content of the added resin should be above 37% of the total mass of the resin and the chopped fiber sheets.

6. The method for preparing a manhole cover using waste fibers according to claim 5, characterized in that: The resin type can be selected from epoxy resin, phenolic resin or a mixture of the two types of resins according to the performance requirements of the manhole cover.

7. The method for preparing a manhole cover using waste fibers according to claim 1, characterized in that: The raw materials selected in S1 include but are not limited to waste carbon fiber prepregs and waste high-silica fiber prepregs, and the side length of the chopped fiber pieces is 10 to 15 mm.

8. The method for preparing a manhole cover using waste fibers according to claim 1, characterized in that: The high temperature heat treatment temperature in S4 is as follows: room temperature is increased to 100°C, the heating rate is 3°C / min; 100°C is kept for 1 hour; 100°C is increased to 170°C, the heating rate is 3°C / min; 170°C is kept for 4 hours.

9. The method for preparing a manhole cover using waste fibers according to claim 1, characterized in that: The curing temperature in S4 is 170-180°C, and the temperature holding time is 3.5-4h.

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