Polyvinyl chloride supercritical carbon dioxide foaming mold

Abstract

A polyvinyl chloride supercritical carbon dioxide foaming mold comprises an upper mold plate and a lower mold plate, the upper mold plate is a flat plate, a blind hole for a thermocouple to be inserted is formed in the side face of the upper mold plate, a cavity is formed in the lower mold plate, a blind hole for a thermocouple to be inserted is formed in the side face of the lower mold plate, a sealing groove is formed around the periphery of the cavity, and a trapezoidal sealing strip and a pressing strip corresponding to the trapezoidal sealing strip are arranged in the sealing groove. At least one air passage is arranged between the bottom surface of the lower mold plate and the bottom surface of the cavity, the air passage is connected with an air inlet pipe, 10-20 air holes are formed in the position, corresponding to the air passage, of the bottom surface of the cavity of the lower mold plate and are communicated with the air passage, and the diameter of each air hole is 1-3mm. By reasonably arranging the air inlet holes and optimizing the shape and the number of the air inlet holes, uniform distribution of scCO2 in a mold cavity is ensured, the problem of uneven foaming caused by too high or too low local gas concentration is avoided, the uniformity and the mechanical property of a foam structure of a foaming material are improved, the rejection rate and the rework rate are reduced by improving the air inlet efficiency and the foaming effect, and the production cost is reduced. The production cost and the energy consumption are reduced.

Description

Technical Field

[0001] The utility model relates to a supercritical carbon dioxide foaming mold, in particular to a mold used for supercritical carbon dioxide foaming of polyvinyl chloride. Background Art

[0002] Polyvinyl chloride (PVC), an important thermoplastic, is widely used in various industrial fields due to its excellent processing properties, mechanical properties, and chemical resistance. However, in the field of PVC foaming, traditional foaming technology often uses chemical foaming agents. These foaming agents produce harmful gases during use, which not only pollute the environment but also may affect the quality and safety of the foamed products. In addition, traditional foaming technology has certain limitations in terms of foaming uniformity, cell size control, and production efficiency.

[0003] In recent years, with the improvement of environmental awareness and the development of green manufacturing technology, supercritical carbon dioxide (scCO2) foaming technology has gradually attracted attention. As an environmentally friendly foaming agent, scCO2 has the advantages of being non-toxic, harmless, and recyclable. In addition, it has good solubility and diffusivity in the supercritical state, and can quickly penetrate and dissolve in the polyvinyl chloride mixture. By adjusting the process parameters, efficient foaming of polyvinyl chloride can be achieved. However, when applying scCO2 foaming technology to PVC foaming molds, a series of technical difficulties need to be solved. First, the mold's air intake system needs to be optimized to ensure that scCO2 can enter the mold cavity evenly and stably, avoiding the problem of uneven foaming caused by local gas concentrations that are too high or too low. Secondly, the mold's temperature control system and pressure regulation system also need to be precisely designed to maintain the stability of the temperature and pressure in the mold cavity, ensuring the smooth progress of the foaming process and the quality of the foamed product. The utility model patent with announcement number CN 220548589U discloses a supercritical gas foaming mold. The air intake method it adopts is to open a vent hole connected to the foaming molding cavity on the upper mold body. However, this air intake method is suitable for foaming sheet materials such as EVA, but not for foaming powdered or colloidal materials such as polyvinyl chloride. This is because after the supercritical carbon dioxide gas is introduced from the upper mold plate, the powdered or colloidal material pre-added to the mold cavity will be blown out of the pit at the position where the air flow is directly blown. After foaming, pits will form on the upper surface, and the uniformity of the pore structure and surface smoothness of the polyvinyl chloride foam material cannot be guaranteed. Summary of the Invention

[0004] The purpose of the utility model is to provide a supercritical carbon dioxide foaming mold for polyvinyl chloride, which can achieve uniform air intake of scCO2, efficient foaming and stable molding, thereby improving the uniformity of the pore structure and surface smoothness of the PVC foam material.

[0005] The purpose of this utility model is achieved through the following technical solutions:

[0006] A polyvinyl chloride supercritical carbon dioxide foaming mold includes an upper template and a lower template. The upper template is a flat plate with blind holes for inserting thermocouples on its side. The lower template is provided with a cavity with blind holes for inserting thermocouples on its side. A sealing groove is provided around the periphery of the cavity. A trapezoidal sealing strip and a corresponding pressure strip are provided in the sealing groove. At least one air duct is provided between the bottom surface of the lower template and the bottom surface of the cavity. The air duct is connected to an air inlet pipe. 10-20 air holes are provided on the bottom surface of the lower template cavity corresponding to the air duct, and are connected to the air duct. The air hole diameter is 1mm-3mm.

[0007] In order to further make the scCO2 intake uniform, three air channels are provided, which are evenly arranged at corresponding positions of the lower template cavity, and are connected to the cavity through air holes provided at corresponding positions of the air channels.

[0008] As a further improvement to the above, in order to prevent the pores from being blocked after polyvinyl chloride powder or colloidal material is added to the lower template and foamed, a breathable sheet is provided at the bottom of the lower template cavity to ensure that the pores are not blocked. The breathable sheet is placed at the bottom of the lower template cavity before each addition.

[0009] As a further improvement of the above, the air-permeable sheet at the bottom of the lower template cavity is a melamine foam sheet.

[0010] Beneficial effects

[0011] The utility model ensures uniform distribution of scCO2 in the mold cavity by rationally arranging the air inlet holes and optimizing the shape and number of the air inlet holes, avoids the problem of uneven foaming caused by excessively high or low local gas concentration, improves the uniformity of the pore structure and mechanical properties of the foaming material, reduces the scrap rate and rework rate, and reduces production costs and energy consumption by improving the air intake efficiency and foaming effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The following is a further explanation with reference to the accompanying drawings

[0013] Figure 1 This is the assembly diagram of Example 1;

[0014] Figure 2 It is a partial enlarged view of the assembly diagram of Example 1;

[0015] Figure 3 This is a front view of the lower template of Example 1;

[0016] Figure 4 This is a front view of the lower template of Example 2;

[0017] Figure 5 This is an assembly diagram of Example 3;

[0018] Among them: 1. Upper template; 2. Lower template; 3. Air inlet; 4. Air hole; 5. Thermocouple hole of upper template; 6. Sealing strip; 7. Sealing strip pressure strip; 8. Thermocouple hole of lower template; 9. Breathable sheet DETAILED DESCRIPTION

[0019] Example 1, reference Figure 1 、 Figure 2 、 Figure 3 A polyvinyl chloride supercritical carbon dioxide foaming mold includes an upper template 1 and a lower template 2. The upper template 1 is a flat plate with an upper template thermocouple hole 5 for inserting a thermocouple on the side. The lower template 2 is provided with a cavity and an upper template thermocouple hole 8 for inserting a thermocouple on the side. A sealing groove is provided around the outer periphery of the cavity, and a trapezoidal sealing strip 6 and a corresponding pressure strip 7 are provided in the sealing groove. An air inlet 3 is provided between the bottom surface 2 of the lower template and the bottom surface of the cavity. Ten air holes 4 are provided on the bottom surface of the cavity of the lower template 2 corresponding to the air channel, which are connected to the air inlet 3. The diameter of the air hole 4 is 3 mm.

[0020] Example 2: This example differs from Example 1 in that 20 air holes 4 are provided on the bottom surface of the lower template 2 at positions corresponding to the air inlet 3 and connected to the air inlet 3 , and the diameter of the air holes 4 is 1 mm.

[0021] Example 3: The difference between this example and Example 1 is that 15 air holes 4 are provided on the bottom surface of the lower template 2 at positions corresponding to the air inlet 3 and connected to the air inlet 3. The diameter of the air holes 4 is 2 mm.

[0022] Example 4, with reference to Figure 4 The difference between this embodiment and embodiment 1 is that three air inlet channels 3 are provided between the bottom surface of the lower template 2 and the bottom surface of the cavity, and 10 air holes 4 are provided at positions corresponding to the bottom surface of the cavity of the lower template 2 and the three air channels, respectively connected to the three air inlet channels 3, and the diameter of the air holes 4 is 3 mm.

[0023] Example 5, with reference to Figure 5 , Figure 5 This is the assembly diagram of Example 3.

Claims

1. A polyvinyl chloride supercritical carbon dioxide foaming mold, comprising an upper template and a lower template. The upper template is a flat plate with a blind hole for inserting a thermocouple on its side. The lower template has a cavity with a blind hole for inserting a thermocouple on its side. A sealing groove is provided around the periphery of the cavity. A trapezoidal sealing strip and a corresponding pressure strip are provided in the sealing groove. The following features are provided: At least one air channel is provided between the bottom surface of the lower template and the bottom surface of the cavity, and the air channel is connected to the air inlet pipe. 10-20 air holes are provided at the position corresponding to the air channel on the bottom surface of the lower template cavity, and the air holes are connected to the air channel. The diameter of the air holes is 1mm-3mm.

2. A polyvinyl chloride supercritical carbon dioxide foaming mold according to claim 1, characterized in that An air passage is provided between the bottom surface of the lower template and the bottom surface of the cavity, and is arranged at a position corresponding to the cavity wall on the bottom surface of the lower template cavity. An air hole is provided on the bottom surface of the cavity to communicate with the air passage.

3. A polyvinyl chloride supercritical carbon dioxide foaming mold according to claim 1, characterized in that Three air passages are provided between the bottom surface of the lower template and the bottom surface of the cavity, which are evenly arranged on the bottom surface of the lower template cavity. The bottom surface of the cavity is provided with air holes connected to the air passages.

4. A polyvinyl chloride supercritical carbon dioxide foaming mold according to any one of claims 1 to 3, characterized in that A breathable sheet is provided at the bottom of the lower template cavity, and the thickness of the breathable sheet is 1mm-2mm.

5. A polyvinyl chloride supercritical carbon dioxide foaming mold according to claim 3, characterized in that The air-permeable sheet at the bottom of the lower template cavity is a melamine foam sheet.

Images