A preparation process for automobile lampshade

Abstract

The present invention relates to the technical field of automobile lampshades, and specifically to a process for preparing automobile lampshades, comprising the following steps: S1, using polycarbonate as the main material to integrally injection-mold a mounting ring, a first cover shell, and a fixing plate, and integrally injection-mold a second cover shell and a refractive protrusion; S2, using carbon wire weaving to make a reinforcement layer; S3, providing an annular groove on the inner side of the first hardened layer, and installing a drying wire into the annular groove; S4, preparing a bonding mold for an inner cover body, a reinforcement layer, and an outer cover body; and S5, preparing a high-transmittance adhesive. The present invention increases the rigidity of the inner and outer cover bodies by using the reinforcement layer, and the refractive protrusion is located on the inner side of the inner and outer cover bodies, so that the surface of the automobile lampshade exposed to the outside is smooth and flat. A polyester composite film is used to resist oxidation, prevent ultraviolet rays, and reduce light refraction. A high-transmittance adhesive is used to bond the inner cover body, the reinforcement layer, and the outer cover body, thereby preventing the automobile lampshade from yellowing after long-term use. The second hardened layer is used for protection, thereby improving the hardness of the automobile lampshade.

Description

Technical Field

[0001] The invention relates to the technical field of automobile lampshades, in particular to a preparation process of an automobile lampshade. Background Art

[0002] Car lights are various traffic lights installed on cars to ensure safe driving. They are divided into two categories: lighting lamps and signal lights. The light transmittance of car lampshades and the impact resistance of car lights are also very important. Compared with traditional glass lampshades, plastic products have the advantages of being easy to manufacture and lightweight. They are gradually replacing glass in the manufacturing of car lamp covers. In addition, the impact strength of plastic is greater than that of glass, which effectively improves the impact resistance of car lampshades.

[0003] A Chinese patent (authorization publication number CN106641953B) discloses a process for preparing an automotive headlight cover. This patented technology utilizes a high-transmittance silicone material instead of the traditional PMMA material. The resulting headlight cover exhibits excellent high-temperature and impact resistance, preventing damage from collisions. However, the aforementioned process utilizes an integral injection-molded structure, resulting in poor impact resistance and the cover being easily broken and shattered under impact, compromising safety. Furthermore, the refractive bumps, typically located on the inside of the headlight cover, easily accumulate dust, causing the headlight cover to yellow over time, impacting its light transmittance. Furthermore, in rainy weather, the headlight cover is susceptible to water mist, which can damage the lamp head. Therefore, those skilled in the art have provided a process for preparing an automotive headlight cover to address the issues raised in the aforementioned background art. Summary of the Invention

[0004] The object of the present invention is to provide a process for preparing an automobile lampshade to solve the problems raised in the above background technology.

[0005] To achieve the above-mentioned object, the present invention provides the following technical solution: a process for preparing an automobile lampshade, comprising the following steps:

[0006] S1. Using polycarbonate as the main material, the mounting ring, the first cover, and the fixing plate are integrally injection-molded. The second cover and the refractive bump are integrally injection-molded. After the inner and outer cover bodies solidify, they are removed and trimmed.

[0007] S2. The reinforcement layer is made of braided carbon wire, and the reinforcement layer has a mesh structure;

[0008] S3. Open an annular groove on the inner side of the first hardened layer and install the drying wire into the annular groove;

[0009] S4. Prepare a bonding mold for the inner cover, the reinforcement layer, and the outer cover. The reinforcement layer is placed on the corresponding sides of the inner cover and the outer cover. The distances between the inner cover and the reinforcement layer, and between the reinforcement layer and the outer cover are consistent.

[0010] S5. Prepare a high-permeability adhesive, which is composed of the following parts by weight: 20-25 parts of polyvinyl chloride, 40-50 parts of acrylonitrile resin, 20-25 parts of carboxylated nitrile rubber, 5-7 parts of polyvinyl butyral, 5-7 parts of polyvinyl alcohol, 2-5 parts of a nucleating agent, 2-5 parts of stearic acid, 2-5 parts of a metal ion scavenger, and 0.5-1.5 parts of an antioxidant;

[0011] S6. Pour the prepared high-permeability adhesive into the bonding mold, wrap the reinforcing layer with the high-permeability adhesive, bond the inner cover body and the outer cover body, place the bonding mold in a negative pressure tank, and use negative pressure to remove bubbles in the high-permeability adhesive. After 20 to 25 minutes, take it out, replenish the high-permeability adhesive, and place it in the negative pressure tank again. Use negative pressure to remove bubbles in the high-permeability adhesive. After 45 to 50 minutes, take it out and place it in a cool and dry place to wait for the high-permeability adhesive to solidify.

[0012] S7. Remove the bonding mold, cut off the high-transmittance bonding material protruding from the inner cover and the reinforcement layer, grind the sides of the inner cover and the reinforcement layer, and polish them after grinding;

[0013] S8, fixing a polyester composite film on the outer side of the second cover;

[0014] S9, preparing a hardening layer mixture, wherein the hardening layer mixture is composed of the following parts by weight: 20-40 parts of organic resin, 5-15 parts of inorganic particles, 1-5 parts of photoinitiator, 1-5 parts of thermal initiator, 1-5 parts of leveling agent, and 30-70 parts of organic solvent;

[0015] S10, spraying the hardening layer mixture on the outer side of the polyester composite film, the inner side of the mounting ring and the inner side of the first cover to complete the production of the second hardening layer and the first hardening layer, with a spraying thickness of 5 to 7 mm;

[0016] S11. Open a mounting hole on the outer side of the fixing plate, the mounting hole corresponding to the mounting position of the upper lampshade;

[0017] S12. Use polishing equipment to polish the inside and outside of the automobile lampshade with a polishing fineness of 0.008 to 0.016 μm.

[0018] As a further solution of the present invention: the trimming process steps in S1 are as follows:

[0019] S101, grinding the edges and corners of the inner cover and the outer cover body, removing the protrusions generated during the injection molding process, and grinding the edges and corners to a grinding fineness of 20 to 40 μm;

[0020] S102, heat-treating the polished inner cover body and the outer cover body at a temperature of 200-217° C., stopping heating after the polished surfaces of the inner cover body and the outer cover body are smooth, and waiting for the inner cover body and the outer cover body to cool and solidify.

[0021] As a further solution of the present invention: the carbon wire in S2 has a diameter of 0.5 mm, the mesh size of the reinforcement layer mesh structure is 5 to 6 cm², and the intersections of the carbon wires are bonded by UV resin.

[0022] As a further solution of the present invention: the size of the annular groove in S3 is adapted to the size of the drying wire, and the drying wire is fixed inside the annular groove by UV resin.

[0023] As a further solution of the present invention: the connection between the bonding mold and the inner cover body and the outer cover body in S4 is sealed by clay, and the distance between the reinforcement layer and the outer cover body is 5 to 6 cm.

[0024] As a further solution of the present invention: the steps for making the high-transmittance adhesive in S5 are as follows:

[0025] S501, adding 20-25 parts of polyvinyl chloride, 40-50 parts of acrylonitrile resin, and 20-25 parts of carboxylated nitrile rubber to a first container, sealing and stirring for 20-25 minutes to obtain a first mixed solution;

[0026] S502, adding 5-7 parts of polyvinyl butyral and 5-7 parts of polyvinyl alcohol to a second container, stirring for 20-25 minutes to obtain a second mixed solution;

[0027] S503, adding 2 to 5 parts of a nucleating agent, 2 to 5 parts of stearic acid, 2 to 5 parts of a metal ion scavenger, and 0.5 to 1.5 parts of an antioxidant to a third container, and stirring for 20 to 25 minutes to obtain a third mixed solution;

[0028] S504, taking out the second mixed solution and the third mixed solution and placing them in the first container, stirring for 20 to 25 minutes, raising the temperature in the first container to 45 to 52° C., and keeping the temperature constant for 2 to 3 hours to obtain a fourth mixed solution;

[0029] S505, placing the fourth mixed liquid into a negative pressure tank, treating it under negative pressure for 20 to 25 minutes, taking out the fourth mixed liquid, and completing the preparation of the high-transmittance adhesive.

[0030] As a further solution of the present invention: the steps for preparing the hardened layer mixture in S9 are as follows:

[0031] S901, adding 20-40 parts of organic resin, 5-15 parts of inorganic particles, and 30-70 parts of organic solvent into a fourth container, sealing and stirring for 20-25 minutes to obtain a fifth mixed solution;

[0032] S902, adding 1 to 5 parts of a photoinitiator, 1 to 5 parts of a thermal initiator, and 1 to 5 parts of a leveling agent to the fourth container, and stirring for 20 to 25 minutes to obtain a sixth mixed solution;

[0033] S903, taking out the sixth mixed solution and placing it in the fourth container, stirring for 20 to 25 minutes to obtain a seventh mixed solution;

[0034] S904, placing the seventh mixed liquid into a negative pressure tank, treating it under negative pressure for 20 to 25 minutes, taking out the seventh mixed liquid, and completing the preparation of the hardened layer mixture.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] The manufacturing process of the automobile lampshade of the present invention increases the rigidity of the inner cover body and the outer cover body through the reinforcement layer, thereby improving the impact resistance of the automobile lampshade, preventing it from breaking and falling under collision and impact, and improving the safety of the automobile lampshade.

[0037] The refractive bumps are located on the inner side of the inner cover and the outer cover, making the surface of the car lampshade exposed to the outside smooth and flat, avoiding dust accumulation, and improving the light transmittance of the car lampshade. The polyester composite film is anti-oxidation, anti-ultraviolet, and reduces light refraction. The inner cover, reinforcement layer and outer cover are bonded with high-transmittance adhesive to avoid yellowing of the car lampshade after long-term use and maintain the light transmittance of the car lampshade. The second hardened layer is used for protection to improve the hardness of the car lampshade. The inner side of the car lampshade is dried by the drying wire to avoid water mist in the car lampshade in rainy weather and damage to the lamp head. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 The figure is a schematic diagram of the structure of a car lampshade;

[0039] Figure 2 This is a disassembled diagram of a car lampshade;

[0040] Figure 3 This is a schematic structural diagram of an inner cover body in a car lampshade;

[0041] Figure 4 The figure is a schematic diagram of the structure of the inner and outer covers of a car lampshade.

[0042] In the figure: 1. Inner cover; 2. Reinforcement layer; 3. Outer cover; 4. Mounting ring; 5. First cover shell; 6. Drying wire; 7. Fixing plate; 8. First hardened layer; 9. Second cover shell; 10. Refractive bump; 11. Second hardened layer; 12. Polyester composite film. DETAILED DESCRIPTION

[0043] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the 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.

[0044] See also Figures 1 to 4 In an embodiment of the present invention, a process for preparing a car lampshade comprises the following steps:

[0045] S1. Use polycarbonate as the main material to integrally mold the mounting ring 4, the first cover 5, and the fixing plate 7. In addition, integrally mold the second cover 9 and the refractive bump 10. After the inner cover 1 and the outer cover 3 are solidified, remove them and perform trimming. The trimming steps are as follows:

[0046] S101, grinding the edges and corners of the inner cover 1 and the outer cover 3, removing the protrusions generated during the injection molding process, and grinding the edges and corners to a grinding fineness of 20 to 40 μm;

[0047] S102, heat-treating the polished inner cover 1 and outer cover 3 at a temperature of 200-217° C., stopping heating after the polished surfaces of the inner cover 1 and outer cover 3 are smooth, and waiting for the inner cover 1 and outer cover 3 to cool and solidify;

[0048] S2. Use carbon wire to weave a reinforcement layer 2, and the reinforcement layer 2 has a mesh structure. The diameter of the carbon wire is 0.5 mm, and the mesh size of the reinforcement layer 2 is 5 to 6 cm². The intersections of the carbon wires are bonded with UV resin.

[0049] S3. An annular groove is formed inside the first hardened layer 8, and the drying wire 6 is installed in the annular groove. The size of the annular groove is adapted to the size of the drying wire 6, and the drying wire 6 is fixed inside the annular groove by UV resin.

[0050] S4. Prepare a bonding mold for the inner cover 1, the reinforcing layer 2, and the outer cover 3. Place the reinforcing layer 2 on the corresponding sides of the inner cover 1 and the outer cover 3. The distances between the inner cover 1 and the reinforcing layer 2, and between the reinforcing layer 2 and the outer cover 3 are consistent. Seal the joints between the bonding mold and the inner cover 1 and the outer cover 3 with clay. The distance between the reinforcing layer 2 and the outer cover 3 is 5 to 6 cm.

[0051] S5. Prepare a high-permeability adhesive, which is composed of the following parts by weight: 20-25 parts of polyvinyl chloride, 40-50 parts of acrylonitrile resin, 20-25 parts of carboxylated nitrile rubber, 5-7 parts of polyvinyl butyral, 5-7 parts of polyvinyl alcohol, 2-5 parts of nucleating agent, 2-5 parts of stearic acid, 2-5 parts of metal ion scavenger, and 0.5-1.5 parts of antioxidant;

[0052] S6. Pour the prepared high-permeability adhesive into the bonding mold, wrap the reinforcing layer 2 with the high-permeability adhesive, and bond the inner cover 1 and the outer cover 3. Place the bonding mold in a negative pressure tank and treat it with negative pressure to remove bubbles in the high-permeability adhesive. After 20 to 25 minutes, take it out, replenish the high-permeability adhesive, and place it in the negative pressure tank again. Treat it with negative pressure to remove bubbles in the high-permeability adhesive. After 45 to 50 minutes, take it out and place it in a cool and dry place to wait for the high-permeability adhesive to solidify.

[0053] S7, remove the bonding mold, cut off the high-transmittance bonding material protruding from the inner cover body 1 and the reinforcement layer 2, grind the side edges of the inner cover body 1 and the reinforcement layer 2, and polish them after grinding;

[0054] S8, fixing the polyester composite film 12 on the outer side of the second cover 9;

[0055] S9, preparing a hardening layer mixture, the hardening layer mixture is composed of the following parts by weight: 20-40 parts of organic resin, 5-15 parts of inorganic particles, 1-5 parts of photoinitiator, 1-5 parts of thermal initiator, 1-5 parts of leveling agent, and 30-70 parts of organic solvent;

[0056] S10, the outer side of the polyester composite film 12, the inner side of the mounting ring 4 and the inner side of the first cover 5 are all sprayed with the hardening layer mixture to complete the production of the second hardening layer 11 and the first hardening layer 8, with a spraying thickness of 5 to 7 mm;

[0057] S11, opening a mounting hole on the outer side of the fixing plate 7, the mounting hole corresponding to the mounting position of the upper lampshade;

[0058] S12. Use polishing equipment to polish the inside and outside of the automobile lampshade with a polishing fineness of 0.008 to 0.016 μm.

[0059] The content in the embodiment also includes:

[0060] The steps for making high-transmittance adhesive are as follows:

[0061] S501, adding 20-25 parts of polyvinyl chloride, 40-50 parts of acrylonitrile resin, and 20-25 parts of carboxylated nitrile rubber to a first container, sealing and stirring for 20-25 minutes to obtain a first mixed solution;

[0062] S502, adding 5-7 parts of polyvinyl butyral and 5-7 parts of polyvinyl alcohol to a second container, stirring for 20-25 minutes to obtain a second mixed solution;

[0063] S503, adding 2 to 5 parts of a nucleating agent, 2 to 5 parts of stearic acid, 2 to 5 parts of a metal ion scavenger, and 0.5 to 1.5 parts of an antioxidant to a third container, and stirring for 20 to 25 minutes to obtain a third mixed solution;

[0064] S504, taking out the second mixed solution and the third mixed solution and placing them in the first container, stirring for 20 to 25 minutes, raising the temperature in the first container to 45 to 52° C., and keeping the temperature constant for 2 to 3 hours to obtain a fourth mixed solution;

[0065] S505, placing the fourth mixed liquid into a negative pressure tank, treating it under negative pressure for 20 to 25 minutes, taking out the fourth mixed liquid, and completing the preparation of the high-transmittance adhesive.

[0066] The steps for preparing the hardened layer mixture are as follows:

[0067] S901, adding 20-40 parts of organic resin, 5-15 parts of inorganic particles, and 30-70 parts of organic solvent into a fourth container, sealing and stirring for 20-25 minutes to obtain a fifth mixed solution;

[0068] S902, adding 1 to 5 parts of a photoinitiator, 1 to 5 parts of a thermal initiator, and 1 to 5 parts of a leveling agent to a fourth container, and stirring for 20 to 25 minutes to obtain a sixth mixed solution;

[0069] S903, taking out the sixth mixed solution and placing it in a fourth container, stirring for 20 to 25 minutes to obtain a seventh mixed solution;

[0070] S904, placing the seventh mixed liquid into a negative pressure tank, treating it under negative pressure for 20 to 25 minutes, taking out the seventh mixed liquid, and completing the preparation of the hardened layer mixture.

[0071] The working principle of the present invention is as follows: the mounting ring 4 on the automobile lampshade is clamped into the inside of the lamp mounting groove and fixed to the automobile through the fixing plate 7. During use, when the lamp is on, the refractive protrusion 10 refracts the light, and the polyester composite film 12 and the high-transmittance adhesive prevent the automobile lampshade from yellowing prematurely. When water mist enters the inner side of the automobile lampshade in rainy weather, the drying wire 6 runs to dry the water mist inside the automobile lampshade, and the reinforcing layer 2 increases the rigidity of the inner cover body 1 and the outer cover body 3.

[0072] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

[0073] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A process for preparing an automobile lampshade, characterized in that: Here are the steps: S1. Using polycarbonate as the main material, integrally mold the mounting ring (4), the first cover shell (5) and the fixing plate (7), integrally mold the second cover shell (9) and the refractive protrusion (10), and after the main bodies of the inner cover body (1) and the outer cover body (3) are solidified, remove them and perform trimming treatment; S2, using carbon wire weaving to make a reinforcement layer (2), and the reinforcement layer (2) has a mesh structure; S3, opening an annular groove on the inner side of the first hardened layer (8), and installing the drying wire (6) into the annular groove; S4, preparing a bonding mold for the inner cover body (1), the reinforcing layer (2) and the outer cover body (3), wherein the reinforcing layer (2) is placed on the corresponding sides of the inner cover body (1) and the outer cover body (3), and the distances between the inner cover body (1) and the reinforcing layer (2), and between the reinforcing layer (2) and the outer cover body (3) are consistent; S5. Prepare a high-permeability adhesive, which is composed of the following parts by weight: 20-25 parts of polyvinyl chloride, 40-50 parts of acrylonitrile resin, 20-25 parts of carboxylated nitrile rubber, 5-7 parts of polyvinyl butyral, 5-7 parts of polyvinyl alcohol, 2-5 parts of a nucleating agent, 2-5 parts of stearic acid, 2-5 parts of a metal ion scavenger, and 0.5-1.5 parts of an antioxidant; S6. Pour the prepared high-permeability adhesive into the bonding mold, wrap the reinforcing layer (2) with the high-permeability adhesive, bond the inner cover (1) and the outer cover (3), place the bonding mold in a negative pressure tank, and use negative pressure to remove bubbles in the high-permeability adhesive. After 20 to 25 minutes, take it out, replenish the high-permeability adhesive, and place it in the negative pressure tank again. Use negative pressure to remove bubbles in the high-permeability adhesive. After 45 to 50 minutes, take it out and place it in a cool and dry place to wait for the high-permeability adhesive to solidify. S7, removing the bonding mold, cutting off the high-transmittance bonding material protruding from the inner cover body (1) and the reinforcing layer (2), grinding the side edges of the inner cover body (1) and the reinforcing layer (2), and polishing them after grinding; S8, fixing a polyester composite film (12) on the outer side of the second cover (9); S9, preparing a hardening layer mixture, wherein the hardening layer mixture is composed of the following parts by weight: 20-40 parts of organic resin, 5-15 parts of inorganic particles, 1-5 parts of photoinitiator, 1-5 parts of thermal initiator, 1-5 parts of leveling agent, and 30-70 parts of organic solvent; S10, the outer side of the polyester composite film (12), the inner side of the mounting ring (4) and the inner side of the first cover (5) are all sprayed with the hardening layer mixture to complete the production of the second hardening layer (11) and the first hardening layer (8), with the spraying thickness of 5 to 7 mm; S11, opening a mounting hole on the outer side of the fixing plate (7), the mounting hole corresponding to the mounting position of the upper lampshade; S12. Use polishing equipment to polish the inside and outside of the automobile lampshade with a polishing fineness of 0.008 to 0.016 μm.

2. The process for preparing an automobile lampshade according to claim 1, characterized in that: The trimming process steps in S1 are as follows: S101, grinding the edges and corners of the inner cover body (1) and the outer cover body (3), removing the protrusions generated during the injection molding process, and grinding the edges and corners to a grinding fineness of 20 to 40 μm; S102, heat-treating the polished inner cover body (1) and the outer cover body (3) at a temperature of 200-217°C. After the polished surfaces of the inner cover body (1) and the outer cover body (3) are smooth, heating is stopped and the inner cover body (1) and the outer cover body (3) are allowed to cool and solidify.

3. The process for preparing an automobile lampshade according to claim 1, characterized in that: The carbon wire in S2 has a diameter of 0.5 mm, the mesh size of the mesh structure of the reinforcement layer (2) is 5 to 6 cm², and the intersections of the carbon wires are bonded by UV resin.

4. The process for preparing an automobile lampshade according to claim 1, characterized in that: The size of the annular groove in S3 is adapted to the size of the drying wire (6), and the drying wire (6) is fixed inside the annular groove by UV resin.

5. The process for preparing an automobile lampshade according to claim 1, characterized in that: The connection between the bonding mold and the inner cover body (1) and the outer cover body (3) in S4 is sealed by clay, and the distance between the reinforcement layer (2) and the outer cover body (3) is 5 to 6 cm.

6. The process for preparing an automobile lampshade according to claim 1, characterized in that: The steps for making the high-transmittance adhesive in S5 are as follows: S501, adding 20-25 parts of polyvinyl chloride, 40-50 parts of acrylonitrile resin, and 20-25 parts of carboxylated nitrile rubber to a first container, sealing and stirring for 20-25 minutes to obtain a first mixed solution; S502, adding 5-7 parts of polyvinyl butyral and 5-7 parts of polyvinyl alcohol to a second container, stirring for 20-25 minutes to obtain a second mixed solution; S503, adding 2 to 5 parts of a nucleating agent, 2 to 5 parts of stearic acid, 2 to 5 parts of a metal ion scavenger, and 0.5 to 1.5 parts of an antioxidant to a third container, and stirring for 20 to 25 minutes to obtain a third mixed solution; S504, taking out the second mixed solution and the third mixed solution and placing them in the first container, stirring for 20 to 25 minutes, raising the temperature in the first container to 45 to 52° C., and keeping the temperature constant for 2 to 3 hours to obtain a fourth mixed solution; S505, placing the fourth mixed liquid into a negative pressure tank, treating it under negative pressure for 20 to 25 minutes, taking out the fourth mixed liquid, and completing the preparation of the high-transmittance adhesive.

7. The process for preparing an automobile lampshade according to claim 1, characterized in that: The steps for preparing the hardened layer mixture in S9 are as follows: S901, adding 20-40 parts of organic resin, 5-15 parts of inorganic particles, and 30-70 parts of organic solvent into a fourth container, sealing and stirring for 20-25 minutes to obtain a fifth mixed solution; S902, adding 1 to 5 parts of a photoinitiator, 1 to 5 parts of a thermal initiator, and 1 to 5 parts of a leveling agent to the fourth container, and stirring for 20 to 25 minutes to obtain a sixth mixed solution; S903, taking out the sixth mixed solution and placing it in the fourth container, stirring for 20 to 25 minutes to obtain a seventh mixed solution; S904, placing the seventh mixed liquid into a negative pressure tank, treating it under negative pressure for 20 to 25 minutes, taking out the seventh mixed liquid, and completing the preparation of the hardened layer mixture.

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