Polyurethane hard foaming process for bottom protective plate of battery box body

Abstract

The invention discloses a battery box body bottom guard plate polyurethane hard foaming process which comprises the following steps: firstly, carrying out shielding pretreatment on a foaming outline of a bottom guard plate, cleaning a mold, fixing the bottom guard plate, and controlling the temperature of the mold to be 50-58 DEG C; the material A and the material B are stored in temperature control tanks respectively, the tank temperature is 25-30 DEG C, the material temperature is 32-36 DEG C, and the material A and the material B are mixed according to the proportion of 100: 103. And the mixed material is injected into a lower mold cavity within 4.3-5.8 seconds through a robot arm, the temperature of the mold is kept after the mold is closed, curing is completed, and finally demolding and edge trimming are conducted. The foaming device has the beneficial effects that the foaming efficiency and the foaming quality are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of battery box protection, and in particular to a polyurethane rigid foaming process for a battery box bottom guard plate. Background Art

[0002] In the manufacturing of underbody panels for new energy vehicle battery cases, the polyurethane rigid foaming process is primarily used to construct a critical layer that combines both protective and functional properties. The rigid foam layer formed through this process significantly improves the underbody panel's impact resistance. Its high-density, cross-linked structure effectively absorbs external forces such as road debris impacts and vehicle jolts, reducing the risk of mechanical damage to the battery compartment. The closed-cell structure of the foam layer also provides excellent thermal insulation, blocking the conduction of heat generated during battery charging and discharging. Furthermore, the rigid foam's low density contributes to the lightweight design of the underbody panel, reducing weight compared to traditional metal panels and improving vehicle endurance. Through process control, its surface can be achieved to be smooth and flat, providing a reliable foundation for the precise installation of subsequent components such as water cooling pipes and sensors.

[0003] The traditional polyurethane rigid foaming process typically uses low-pressure mixing equipment to mix material A and material B in a 1:1 weight ratio. The material temperature is controlled at 25-30°C. After injection into the mold through an injection nozzle, the physical foaming agent vaporizes and expands upon heating, filling the mold cavity and curing through cross-linking to form a rigid foam layer. This process relies on manual monitoring of the pouring time window and requires a 12-24 hour room temperature aging period for complete curing. This traditional process has significant limitations: First, the foaming method in the lower mold cavity causes gas to accumulate in recessed areas that are difficult to escape, resulting in bubbles in the foam layer and high surface roughness, which cannot meet the flatness and sealing requirements of the battery underbody shield. Second, the low-temperature mixing process slows the reaction rate, extending the milky white phase to over 30 seconds, making it difficult to control. Premature foaming of the foam often leads to uneven mold adhesion. In addition, due to the lack of effective edge shielding, the foam easily overflows into non-foamed areas, requiring extensive manual trimming after demolding. This not only increases the processing time of each piece but also leads to high scrap rates due to insufficient trimming accuracy. Summary of the Invention

[0004] In view of this, the present invention provides a polyurethane rigid foaming process for the bottom guard plate of a battery box, optimizes the formula, improves the molding method, and solves the problems of low foaming efficiency and poor foaming quality existing in the traditional process.

[0005] To achieve the above purpose, the technical solution of the present invention is as follows:

[0006] A polyurethane rigid foaming process for a battery box bottom guard plate comprises the following steps:

[0007] Step 1: Pre-masking the foaming contour of the bottom guard plate to isolate the foaming layer beyond the range from the bottom guard plate;

[0008] Step 2: Clean the mold thoroughly, fix the bottom guard plate to be foamed in the upper mold cavity of the mold, set the mold temperature between 50-58℃, and measure the mold temperature between 49-52℃;

[0009] Step 3: Store material A and material B in raw material storage tanks respectively, control the tank temperature at 25-30°C, maintain the material temperature at 32-36°C, and use a stirring device to keep the raw materials uniform;

[0010] Step 4: Transfer material A and material B to a mixing reaction tank in a weight ratio of material A: material B = 100:103 and mix them quickly. Control the temperature in the mixing reaction tank between 32-35°C;

[0011] Step 5: Pour the material in the mixed reaction tank into the lower mold cavity through the robot arm with a pouring time of 4.3-5.8 seconds. After confirming that the injection state is normal, close the mold and maintain the mold temperature at 50-58°C;

[0012] Step 6: After the foam layer is matured, demould it, remove the masking tape, and mill the edges of the foam layer.

[0013] By adopting the above process, the bottom guard plate is placed on the upper template, the foaming layer is free of bubbles, the material temperature is increased and the pouring time is controlled within the time when the foaming material is just in the foaming state, thereby avoiding the premature foaming of the foaming layer and the uneven mucosa phenomenon. The foaming layer is matured and formed at the optimal time, and the raw material ratio is optimized. The surface of the foaming layer is smooth and hard, which improves the foaming quality and foaming efficiency. The bottom plate is masked and pre-treated to facilitate the subsequent trimming of the foaming layer.

[0014] Preferably, in step 1, the masking pretreatment of the foaming range of the bottom guard plate includes the following steps:

[0015] S1: Check the appearance of the bottom guard plate to be foamed to eliminate any defects such as deformation and PVC damage;

[0016] S2: Place the bottom guard plate with the PVC layer facing downwards and use the limit plate to accurately position it. The two long edges of the limit plate should coincide with the inner corrugation line of the bottom guard plate, and the bottom edge should coincide with the edge line of the bottom boss of the bottom guard plate.

[0017] S3: Compact the bottom guard plate and use a marker to draw positioning contour lines on the bottom guard plate along the edges around the limit plate. The contour lines form a closed loop.

[0018] S4: Use 4cm wide tape to mask along the edge of the positioning line. The ends of the tape can extend 3cm beyond the positioning line. After masking, scrape and compact it. There should be no bubbles within 1cm of the inner tape edge. Perform secondary masking on the corners of the concave corner and the bottom of the bottom guard plate.

[0019] S5: Remove any excess tape outside the positioning line and use foam to separate the masked bottom guard plate, overlapping them neatly. This method prevents the material from sticking to the bottom guard plate during foaming, making it easier to adjust the edge of the foam layer.

[0020] As a preference: in step 2, the mold temperature is preferably 50° C. The above process accelerates the demoulding speed and is suitable for continuous production.

[0021] As a preference: in step 3, the material temperature of material A and material B is preferably 35° C. Using the above process, when the material temperature is 35° C., the viscosity of material A and material B is best matched, and the mixing uniformity is improved.

[0022] As a preferred embodiment: in step 5, the pouring pressure is 7-10 MPa. The above process is adopted so that the mixed liquid can fill the groove.

[0023] As a preferred embodiment, the lower mold cavity of the mold is provided with exhaust holes. With the above structure, the layout of the exhaust holes is coordinated with the positioning of the upper mold cavity, which solves the problem of gas retention during foaming.

[0024] Preferably, the material A comprises polyether resin, polyester resin, silica, and additives; and the material B comprises isocyanate polymer, isocyanate adduct, and additives. Using the above process, the flexibility and impact resistance of the foam layer are improved.

[0025] Preferably, the foaming process is carried out on an automated turntable production line with a turntable frequency of 8.5-9.4 Hz, and a robotic arm injects the mixed foaming material into the lower mold cavity of the mold to achieve continuous production. The above method achieves continuous production and ensures stable production efficiency.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. The upper mold cavity foaming design effectively solves the problem of gas gathering in the concave area and being difficult to discharge in the traditional lower mold cavity process, improves the foaming quality, reduces bubble defects in the foaming layer, and reduces surface roughness, meeting the high flatness and sealing requirements of the battery bottom guard plate.

[0028] 2. Increase the material temperature, shorten the milky white period of the polyurethane foaming reaction, significantly reduce the aging time, control the injection time, avoid uneven mold sticking caused by premature foaming of the foaming material, and improve production efficiency.

[0029] 3. By integrating an automated robot injection system, a continuous production line is constructed to achieve automated operations, which reduces manual intervention compared to traditional processes and significantly increases production capacity.

[0030] 4: Stick the tape along the foaming contour. During foaming, the part of the material that exceeds the tape will not stick to the bottom guard plate, which is convenient for adjusting the edge of the foaming layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a flowchart of the polyurethane rigid foaming process for the bottom guard plate of the battery box;

[0032] Figure 2 Schematic diagram of the shielding pretreatment of the bottom guard plate. DETAILED DESCRIPTION

[0033] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0034] like Figure 1 As shown, a polyurethane rigid foaming process for a battery box bottom guard plate includes the following steps:

[0035] Step 1: Pre-masking the foaming contour of the bottom guard plate 1 to isolate the foaming layer beyond the range from the bottom guard plate 1;

[0036] Step 2: Thoroughly clean the mold. Fix the bottom guard plate 1 to be foamed to the upper mold cavity of the mold. Set the mold temperature between 50-58°C and measure the mold temperature to be between 49-52°C. The mold temperature is preferably 50°C. When cleaning the mold, use a scraper and wire brush to thoroughly remove residual foam from the upper and lower mold cavities. Wipe the yellowed area of the upper mold cavity with alcohol and check whether the sealing strip is loose. The lower mold cavity has a vent. When cleaning the mold, clean the vent and V-groove to ensure smooth flow. Use an air gun to blow the chamfered edges of the lower mold cavity. If there is a large area of foam residue, apply a release agent and let the mold rest for one hour.

[0037] Step 3: Store materials A and B in separate raw material storage tanks. Maintain the tank temperature at 25-30°C and the material temperature at 32-36°C. Use a stirring device to maintain uniformity. Material A includes polyether resin, polyester resin, silica, and additives; Material B includes isocyanate polymer, isocyanate adduct, and additives. The material temperature is preferably 35°C.

[0038] Step 4: Convey material A and material B into a mixing reaction tank in a weight ratio of material A: material B = 100:103 and mix them quickly. Control the temperature in the mixing reaction tank between 32-35°C.

[0039] Step 5: The material in the mixed reaction tank is poured into the lower mold cavity using a robotic arm with a pouring time of 4.3-5.8 seconds. After confirming that the injection state is normal, the mold is closed and the mold temperature is maintained at 50-58°C. The pouring pressure is 7-10MPa. The poured material flows evenly and gradually spreads out from a point in the mold. The normal state is that there are no bubbles in the center and no missing materials.

[0040] Step 6: After the foam layer has matured, it is demolded, masking tape 3 is removed, and the edges of the foam layer are milled and trimmed. The foam layer matures and molds in approximately 14 minutes, significantly improving production efficiency and ensuring production quality.

[0041] like Figure 2 As shown, the masking pretreatment of the foaming range of the bottom guard plate 1 in step 1 includes the following steps:

[0042] S1: Check the appearance of the bottom guard plate 1 to be foamed to eliminate any defects such as deformation and PVC damage;

[0043] S2: Place the bottom guard plate 1 with the PVC layer facing downwards, and place the limit plate 2 on the surface of the bottom guard plate 1. Position it accurately so that the two long edges of the limit plate 2 coincide with the inner corrugation line of the bottom guard plate 1, and the bottom edge coincides and aligns with the edge line of the bottom boss of the bottom guard plate 1.

[0044] S3: Compact the bottom guard plate 1, and use a marker to draw a positioning outline on the bottom guard plate 1 along the edges of the limit plate 2. The outline line should be complete and clear to form a closed loop;

[0045] S4: Use a 4cm wide tape 3 to mask along the edge of the positioning line. The edge of the tape 3 should coincide with the positioning line. Both ends of the tape 3 can extend 3cm beyond the positioning line. After masking, scrape and compact it. There should be no bubbles within a 1cm width of the inner edge of the tape 3. Perform a secondary masking on the corner of the concave corner and the bottom position of the bottom guard plate 1 and press firmly.

[0046] S5: Use a blade to remove excess tape 3 outside the positioning line. Separate the masked bottom guards 1 with foam, overlapping them neatly. The number of overlapping bottom guards 1 should not exceed 20. During foaming, the part of the material that extends beyond the tape 3 will not adhere to the bottom guards 1, making it easier to adjust the edge of the foaming layer.

[0047] In this embodiment, the foaming molding process is carried out on an automated turntable production line. The production line includes a mold closing point, a mold opening point, upper and lower parts positions, a pouring point, etc. The turntable frequency is 8.5-9.4Hz. The mixed foaming material is injected into the lower mold cavity of the mold through a robotic arm to achieve continuous production.

[0048] In the polyurethane rigid foaming process of the battery box bottom guard plate 1, the design of fixing the bottom guard plate 1 to the upper mold cavity uses gravity-assisted filling and natural exhaust mechanisms, and cooperates with the exhaust holes of the lower mold cavity to completely eliminate bubble defects, so that the density of the foamed layer is uniform and the surface is smooth. Increasing the temperature of material A and material B from 25-30°C in the traditional process to 32-36°C (preferably 35°C) can enhance the fluidity of material A and material B after mixing, and can better fill complex structures such as mold grooves and corners, and can shorten the milky white period and speed up the foaming start-up speed. Through the automated production line, the pouring time is controlled by the robot arm to complete the pouring within 4.3-5.8 seconds. When the pouring is completed, the foaming material is in a state of just rising, which can perfectly control the time and avoid premature bubbling of the foaming layer, resulting in uneven mucosa.

[0049] In this embodiment, the ratio of material A to material B is optimized to a weight ratio of 100:103, which can better avoid residual unreacted monomers compared to the traditional 1:1 ratio. This ratio can increase the cross-linking density of the foaming layer, increase the compressive strength, optimize the pore structure, and reduce the thermal conductivity to . In addition, the 3% excess design of material B can compensate for the effect of ambient humidity on foaming, ensure process stability, and achieve the best viscosity matching when the material temperature is 35°C, which can avoid foaming shrinkage or surface defects caused by ratio deviation, and ultimately achieve a high-strength, lightweight and excellent thermal insulation foaming layer.

[0050] Finally, it should be noted that the above description is only a preferred embodiment of the present invention. Under the guidance of the present invention, ordinary technicians in this field can make various similar expressions without violating the purpose and claims of the present invention. Such changes fall within the scope of protection of the present invention.

Claims

1. A polyurethane rigid foaming process for the bottom guard plate of a battery box, characterized in that: The following steps are involved: Step 1: Pre-masking the foaming contour of the bottom guard plate (1) to isolate the foaming layer beyond the range from the bottom guard plate (1); Step 2: clean the mold thoroughly, fix the bottom guard plate (1) to be foamed in the upper mold cavity of the mold, set the mold temperature between 50-58°C, and measure the mold temperature between 49-52°C; Step 3: Store material A and material B in raw material storage tanks respectively, control the tank temperature at 25-30°C, maintain the material temperature at 32-36°C, and use a stirring device to keep the raw materials uniform; Step 4: Transfer material A and material B to a mixing reaction tank in a weight ratio of material A: material B = 100:103 and mix them quickly. Control the temperature in the mixing reaction tank between 32-35°C; Step 5: Pour the material in the mixed reaction tank into the lower mold cavity through the robot arm with a pouring time of 4.3-5.8 seconds. After confirming that the injection state is normal, close the mold and maintain the mold temperature at 50-58°C; Step 6: After the foam layer is matured, it is demoulded, the masking tape (3) is removed, and the edge of the foam layer is milled and trimmed.

2. The polyurethane rigid foaming process for the bottom guard plate of a battery box according to claim 1, characterized in that: In step 1, the masking pretreatment of the foaming range of the bottom guard plate (1) includes the following steps: S1: Check the appearance of the bottom guard plate (1) to be foamed, and eliminate any defects such as deformation and PVC damage; S2: Place the bottom guard plate (1) with the PVC layer facing downwards and use the limiting plate (2) to accurately position it. The two long edges of the limiting plate (2) are aligned with the inner corrugation line of the bottom guard plate (1), and the bottom edge is aligned with the bottom boss edge line of the bottom guard plate (1); S3: Compact the bottom guard plate (1), and use a marker to draw a positioning contour line on the bottom guard plate (1) along the edges of the limiting plate (2), so that the contour line forms a closed loop; S4: Use a 4cm wide tape (3) to mask along the edge of the positioning line. The two ends of the tape (3) can extend 3cm beyond the positioning line. After masking, scrape and compact it. There should be no bubbles within a 1cm width of the edge of the inner circle of the tape (3). Perform secondary masking on the corner of the concave corner position and the bottom position of the bottom guard plate (1); S5: Remove the excess tape (3) outside the positioning line, and separate the bottom guard plate (1) after masking with foam and overlap them neatly.

3. The polyurethane rigid foaming process for the bottom guard plate of a battery box according to claim 1, characterized in that: In step 2, the mold temperature is preferably 50°C.

4. The polyurethane rigid foaming process for the bottom guard plate of a battery box according to claim 1, characterized in that: In step 3, the material temperature of material A and material B is preferably 35°C.

5. The polyurethane rigid foaming process for the bottom guard plate of a battery box according to claim 1, characterized in that: In step five, the pouring pressure is 7-10 MPa.

6. The polyurethane rigid foaming process for the bottom guard plate of a battery box according to claim 1, characterized in that: The lower mold cavity of the mold is provided with an exhaust hole.

7. The polyurethane rigid foaming process for the bottom guard plate of a battery box according to claim 1, characterized in that: The material A comprises polyether resin, polyester resin, silicon dioxide and auxiliary agents; the material B comprises isocyanate polymer, isocyanate adduct and auxiliary agents.

8. The polyurethane rigid foaming process for the bottom guard plate of a battery box according to claim 1, characterized in that: The foaming process is carried out on an automated turntable production line with a turntable frequency of 8.5-9.4 Hz. The mixed foaming material is injected into the lower mold cavity of the mold by a robotic arm to achieve continuous production.

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