Mould for foam forming of high polymer material and forming method

Abstract

The invention discloses a high polymer material foam forming mold which comprises a main body, the main body is provided with a cavity used for containing high polymer fluid, and a plurality of side walls of the main body are arranged; the injection molding opening is formed in the top of the main body and is used for injecting polymer fluid; the backflow component is arranged at the upper part of the side wall of the main body and is used for storing the discharged polymer fluid; the bubbling pipe is installed in the main body through the round openings, the bubbling pipe main body is a hollow pipe with one end opened and the other end closed, the side wall of the hollow pipe is provided with a plurality of round openings, the round openings are provided with elastic closing plates, compressed gas is introduced into the bubbling pipe, and the elastic closing plates can form spherical protrusions. According to the mold for foam molding of the high polymer material, foam holes are formed by a physical method when the high polymer material is molded, and the positions and sizes of the foam holes can be controlled.

Description

Technical Field

[0001] The invention relates to the field of polymer material forming and processing, and in particular to a mold and a forming method for polymer material foaming. Background Art

[0002] Conventional polymer foaming molding methods mainly use foaming agents, including physical foaming agents or chemical foaming agents, to allow polymer materials to foam and mold in a molten state. Physical foaming agents, such as supercritical carbon dioxide or nitrogen foaming, or expandable microsphere foaming agents, chemical foaming agents such as AC foaming agents, etc. However, in these methods, the location of the bubbles is random and the sizes are also distributed in different sizes, which affects the mechanical properties of the foam.

[0003] Therefore, technicians in this field are committed to developing a method for foaming polymer materials, which can obtain cells with controllable position arrangement, and the size of the cells can be adjusted as needed. Summary of the invention

[0004] Under this background, the present invention proposes a polymer foaming molding die and a preparation method thereof, which uses a physical method to mold the polymer foam cells, and can control the position and size of the foam cells.

[0005] In order to overcome at least one of the above disadvantages of the prior art, the present invention provides a mold for foaming a polymer material, the mold comprising A main body, wherein the main body is provided with a cavity for containing a polymer fluid, and a side wall of the main body is provided with a plurality of mounting holes; An injection port, disposed at the top of the main body, for injecting polymer fluid; A backflow component, arranged on the upper part of the side wall of the main body, for storing the discharged polymer fluid; The bubble tube is installed in the main body through the circular opening. The bubble tube main body is a hollow tube with one end open and the other end closed. A plurality of circular openings are arranged on the side wall of the hollow tube. An elastic baffle is arranged on the circular opening. When compressed gas is introduced into the bubble tube, the elastic baffle can form a spherical protrusion.

[0006] Furthermore, the positions on the two opposite side walls are not on the same straight line but are staggered.

[0007] Furthermore, the elastic plate is made of silicone rubber.

[0008] Furthermore, the silicone rubber is cross-linked silicone rubber.

[0009] Furthermore, the diameter of the hollow tube is 0.2-0.25 mm; the spacing of the circular openings is 0.5-3 mm; and the diameter of the circular openings is 0.03-0.1 mm.

[0010] The second aspect of the present invention provides a polymer material foaming molding method using the above mold, specifically: S1 injects polymer fluid into the mold through the injection port; S2 After the polymer fluid is filled, compressed gas is introduced into the bubble tube to form a spherical bulge on the bubble tube, and the backflow component is opened at the same time to discharge the squeezed polymer fluid; S3 After the excess polymer fluid is discharged from the mold, the backflow component is closed, and after heat and pressure are maintained, the temperature is lowered until the polymer fluid cools down to below the thermal deformation temperature; S4 releases the compressed gas in the bubble tube, connects to a vacuum pump, retracts the elastic plate back into the bubble tube, removes the bubble tube, and obtains a polymer foaming material.

[0011] Furthermore, the compressed gas is nitrogen or air.

[0012] Furthermore, the pressure of the compressed gas is 0.2~0.5MPa.

[0013] Furthermore, the heat preservation and pressure holding time is 5 to 10 minutes.

[0014] The beneficial effects of the present invention are as follows: the polymer material foaming molding mold disclosed in the present invention uses a bubble tube as a bubble generating device, and an elastic plate is arranged on the bubble tube, which can ensure that the bubble size is uniform and controllable, facilitates and accurately controls the bubble size, and prevents different small bubbles from merging into large bubbles, thereby affecting the structure and mechanical properties of the foam material. Bubble tubes of different sizes can also be used according to the requirements of the foaming material for the bubble position, size and density, and the elastic plates with different spacings and diameters can be precisely controlled. The pressure in the bubble tube can also be controlled to control the bulging size of the elastic plate, thereby controlling the size of the bubble of the polymer foam material.

[0015] The polymer material foaming molding method disclosed in the present invention does not require the addition of a foaming agent. Conventional foaming agents are very sensitive to temperature, and the decomposition of the foaming agent can only be completed within a certain temperature range. If the temperature is too low, the foaming agent will not decompose. If the temperature is too high, the foaming agent will decompose too quickly, which is inconsistent with the cross-linking, and the foam material will fail to foam. The foaming of the present invention relies on an external air compressor to provide the pressure of the bubbles, which is not limited by temperature. As long as the polymer melt strength is sufficient, the foaming can be carried out. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0017] Figure 1 This is a schematic diagram of the mold structure in an embodiment of the present invention; Figure 2 Schematic diagram of the bubble tube structure in an embodiment of the present invention.

[0018] 100. mold; 1. injection port; 2. body; 21.; 3. backflow component; 4. bubble tube; 41. circular opening; 42. elastic baffle; 43. hollow tube. DETAILED DESCRIPTION

[0019] It should be mentioned before discussing the exemplary embodiments in more detail that some exemplary embodiments are described as processes or methods depicted as flow charts. Although the flow charts describe the operations as sequential processes, many of the operations therein can be implemented in parallel, concurrently or simultaneously. In addition, the order of the operations can be rearranged. The process can be terminated when its operation is completed, but can also have additional steps not included in the accompanying drawings. The process can correspond to a method, function, procedure, subroutine, subprogram, etc.

[0020] It should be understood that, although the terms "first", "second", etc. may be used herein to describe various units, these units should not be limited by these terms. These terms are used only to distinguish one unit from another unit. For example, without departing from the scope of the exemplary embodiments, the first unit may be referred to as the second unit, and similarly the second unit may be referred to as the first unit. The term "and / or" used herein includes any and all combinations of one or more of the listed associated items.

[0021] The present invention provides a polymer fluid foaming mold 100, referring to Figure 1~2 The mold 100 includes a body 2 and a backflow component 3. An injection port 1 is provided on the top surface of the body 2. A connecting pipe connected to the backflow component 3 is provided near the upper part of the side wall of the body 2 away from the injection port 1. One end of the connecting pipe is connected to the body 2, and the other end is connected to the backflow component 3. The injection port 1 is used to inject polymer fluid into the body 2 when starting injection molding, and the backflow component 3 is used to temporarily store the polymer fluid extruded under pressure.

[0022] The body 2 is provided with a cavity inside, and a plurality of mounting holes 21 for inserting the bubble tube 4 are provided on the side wall of the cavity. The bubble tube 4 is an elongated hollow tube 43 with an opening at one end and a closed end at the other end, and the diameter is 0.2-0.25 mm. A plurality of circular openings 41 are provided on the outer surface of the bubble tube 4, and the distance between two adjacent circular openings 41 is 0.5-3 mm, and the diameter of the circular opening 41 is 0.03-0.1 mm. An elastic plate 42 is provided on the circular opening 41. Bubble tubes 4 of different sizes can be used according to the requirements of the foaming material for the position, size and density of the bubble holes, and the circular openings 41 of different spacings and diameters can be precisely controlled. It can ensure that the bubble holes are uniform in size, and the bubble hole size can be conveniently controlled. Compared with the existing foaming mold, it can also prevent different small bubbles from merging into large bubbles, which affects the structure and mechanical properties of the foam material.

[0023] A bubble tube 4 is used as a bubble pore generating device, and an elastic plate 42 is arranged on the bubble tube 4. Compressed gas, such as compressed air or compressed nitrogen, is introduced into the bubble tube 4 to make the elastic plate 42 swell to form a spherical protrusion. The bulging size of the elastic plate 42 can be controlled by controlling the pressure in the bubble tube 4, thereby controlling the size of the bubbles in the polymer foaming material.

[0024] In some embodiments, the position distribution and size of the circular openings 41 on the bubble tube 4 can be determined according to the pore distribution requirements and size of the polymer fluid foaming material.

[0025] In some embodiments, the bubble tube 4 is made of stainless steel, which is corrosion-resistant, not easy to rust, and can also be processed into a smooth surface.

[0026] In some implementations, the elastic plate 42 is made of a corrosion-resistant material, such as silicone rubber, preferably cross-linked silicone rubber, which has strong mechanical properties.

[0027] In some embodiments, the top and bottom of the body 2 are also provided with mounting holes 21 for inserting 4, and the mounting holes 21 on the two opposite side walls are not on the same straight line, so that the bubble tubes 4 inserted in two opposite directions will not interfere with each other.

[0028] In some embodiments, an isolating agent is applied to the surface of the elastic plate 42 to form a protective film to hinder the adhesion between the elastic plate 42 and the polymer foam material, making it easier to remove the bubble tube 4 with the elastic plate 42 installed from the polymer foam material after molding.

[0029] Example 1 The specific components of the polymer fluid in this embodiment are: 59.4 parts of PP resin, 30 parts of LDPE, 10 parts of kaolin (4000 mesh) surface treated with 1% titanate coupling agent, 0.3 parts of cross-linking agent diisopropylbenzene peroxide (DCP), 0.3 parts of antioxidant 1010, and no physical or chemical foaming agent is added.

[0030] First add the above ingredients into the blending equipment and blend them, melt them into a fluid, and set aside.

[0031] S1 Injection molding into the body 2 of the mold 100 through the injection port 1; S2 After the main body 2 is filled with polymer fluid, the injection port is closed, and nitrogen is introduced into the bubble tube 4 through the opening on the bubble tube 4, so that the pressure in the bubble tube 4 reaches 0.4MPa. At this time, the elastic plate 42 installed on the circular opening 41 is pressurized and bulges to form spherical protrusions. At the same time, the valve on the backflow component 3 is opened, so that the polymer fluid pressurized by the bulging of the elastic plate 42 overflows into the backflow component for temporary storage; S3 After the bubbling tube 4 is pressurized, the backflow component 3 is closed to keep the polymer fluid in the body 2 at 240°C for 8 minutes. After the heat preservation is completed, the temperature is lowered to below 50°C; S4: Release the nitrogen in the bubble tube, connect the vacuum pump, retract the elastic plate 42 into the bubble tube 4, pull out the bubble tube 4 from the body 2, and then open the body 2 to obtain the polymer foaming material A.

[0032] After testing, the foam density is 0.36g / cm 3 , tensile strength is 14.5MPa, and elongation at break is 87%.

[0033] Comparative Example 1 The polymer fluid components in this comparative example are: 53.4 parts of PP resin, 30 parts of LDPE, filler: 10 parts of kaolin (4000 mesh) surface treated with 1% titanate coupling agent, 0.3 parts of cross-linking agent diisopropyl peroxide (DCP), 4 parts of AC foaming agent, 1 part of zinc oxide, 1 part of stearic acid, and 0.3 parts of antioxidant 1010.

[0034] The preparation steps include: (1) Preparing a pre-foamed blended material: mixing PP resin, LDPE, filler and antioxidant in an internal mixer according to the weight ratio for 5-10 minutes, the internal mixing temperature is 210-230°C, and the internal mixing speed is 30-40 r / min; after internal mixing, the temperature is lowered to 150°C, and a cross-linking agent, AC foaming agent, zinc oxide and stearic acid are added, and the mixture is further internally mixed for 3-6 minutes to obtain a pre-foamed blended material; (2) Preparation of foaming material: The pre-foamed blended material is foamed by molding to obtain modified foaming material B. After testing, the foam density is 0.4 g / cm 3 , tensile strength is 10.3MPa, and elongation at break is 56%.

[0035] By comparison, it is found that the polymer foam material A prepared by the polymer material foaming molding method provided by the present invention has higher tensile strength and greater elongation at break than the modified foam material B prepared in the comparative example, and has stronger mechanical properties when the density difference is not much.

[0036] The above is only an embodiment of the present invention. The common sense such as the known specific structure and characteristics in the scheme is not described in detail here. The ordinary technicians in the relevant field know all the common technical knowledge in the technical field of the invention before the application date or priority date, can know all the existing technologies in the field, and have the ability to apply the conventional experimental means before that date. The ordinary technicians in the relevant field can improve and implement this scheme in combination with their own abilities under the enlightenment given by this application. Some typical known structures or known methods should not become obstacles for ordinary technicians in the relevant field to implement this application. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several deformations and improvements can be made, which should also be regarded as the scope of protection of the present invention, which will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A mold for polymer foaming, characterized in that: The mold includes A main body, wherein the main body is provided with a cavity for containing a polymer fluid, and a side wall of the main body is provided with a plurality of mounting holes; An injection port, disposed at the top of the main body, for injecting polymer fluid; A backflow component, disposed on the upper portion of the side wall of the main body, for storing the discharged polymer fluid; The bubble tube is installed in the main body through the circular opening. The bubble tube main body is a hollow tube with one end open and the other end closed. A plurality of circular openings are arranged on the side wall of the hollow tube. An elastic baffle is arranged on the circular opening. When compressed gas is introduced into the bubble tube, the elastic baffle can form a spherical protrusion.

2. A mold for polymer foaming as claimed in claim 1, characterized in that: The positions of the mounting holes on the two opposite side walls are not on the same straight line, but are staggered.

3. A mold for polymer foaming as claimed in claim 1, characterized in that: The elastic plate is made of silicone rubber.

4. A mold for polymer foaming as claimed in claim 3, characterized in that: The silicone rubber is cross-linked silicone rubber.

5. A mold for polymer foaming as claimed in claim 1, characterized in that: The diameter of the hollow tube is 0.2-0.25 mm; the spacing of the circular openings is 0.5-3 mm; and the diameter of the circular openings is 0.03-0.1 mm.

6. A method for foaming a polymer material, characterized in that: Using the mold described in any one of claims 1 to 5 to foam a polymer material, specifically S1 injects polymer fluid into the mold through the injection port; S2 After the polymer fluid is filled, compressed gas is introduced into the bubble tube to form a spherical bulge on the bubble tube, and the backflow component is opened at the same time to discharge the squeezed polymer fluid; S3 After the excess polymer fluid is discharged from the mold, the backflow component is closed, and after heat and pressure are maintained, the temperature is lowered until the polymer fluid cools down to below the thermal deformation temperature; S4 releases the compressed gas in the bubble tube, connects to a vacuum pump, retracts the elastic plate back into the bubble tube, removes the bubble tube, and obtains a polymer foaming material.

7. The polymer material foaming molding method according to claim 6, characterized in that: The compression The gas is nitrogen or air.

8. The polymer material foaming molding method according to claim 6, characterized in that: The compression The gas pressure is 0.2~0.5MPa.

9. The polymer material foaming molding method according to claim 6, characterized in that: The insulation The holding time is 5~10min.

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